Physiological and pathological
biochemistry of carbohydrates
Digestion and absorption of carbohydrates and its disorders
Basic metabolic pathways of carbohydrates and its disorders
Metabolic disorders of fructose and galactose
Glycogenoses
Regulation of glycemia and its disorders
Complex carbohydrates
mucopolysaccharidoses
Diabetes mellitus as a complex metabolic disease – diabetes
biochemistry
Molecular interpretation of late consequences of diabetes
1Pathobiochemistry carbohydrates-
2018
Carbohydrates
2Pathobiochemistry carbohydrates-
2018
Carbohydrates
• also saccharides (from lat. saccharum)
• Organic compound belonging to group of
polyhydroxyderivates - aldehydes or ketones Low
molecular weight carbohydrates are soluble in water
and taste sweet
• Macromolecular carbohydrates are mostly
flavourless, their solubility in water is limited (starch,
agar) or are totally insoluble (cellulose)
3Pathobiochemistry carbohydrates-
2018
Carbohydrates
• Consists of carbon, hydrogen and oxygen, they differ in
structure and size of molecule
• Basic structural unit - monosaccharide
• Glycosidic bond
• Source of energy for function of brain and muscles
• Primary source of energy in intensive training
• In plants, carbohydrates are formed by assimilation of air CO2
in presence of water and daylight - photosynthesis
• Daily intake 50 - 60% of overall energetic intake
• Amount of energy in 1g = 4 kcal = 17 kJ
• Storage glykogen (liver and muscles)
4Pathobiochemistry carbohydrates-
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Classification of carbohydrates
• Simple carbohydrates
– Monosaccharides 1 x 6C
– Disaccharides 2 x 6C
• Complex carbohydrates
– Polysaccharides 10 and more C
5Pathobiochemistry carbohydrates-
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Simple carbohydrates
• Monosaccharides
– Occurence: fruit (10 – 12%), honey (35%G,
35%F), vegetable, juices…
– Sweet taste
• Glucose (grape, starch sugar, dextrose)
» Fastest source of energy
» Essential for brain and erytrocytes (150 g/day)
• Fructose (fruit sugar, levulose)
• Galactose (constituent of milk sugar)
,
6Pathobiochemistry carbohydrates-
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Simple carbohydrates
• Disaccharides
• Maltose (malt sugar) – grain and malt shoots
glucose + glucose
• Saccharose (beet, reed sugar) – sugar beet, sugarcane,
maple syrup
- consumption 100 – 120 g/person/day
- daily intake 10% max. 10
glucose + fructose
• Lactose (milk sugar) – milk and milk products
- consumption 10 – 30 g/person/day
glucose + galactose
7Pathobiochemistry carbohydrates-
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Complex carbohydrates
• Polysaccharides
– Digestible (amylose + amylopectin)
– Consisting of glu units
– Starch – plant
– Glycogen - animal
– Main sources in food: grains and their products
(flour, bread, rice, pasta, corn, oat..), potatoes,
legumes, vegetable
8Pathobiochemistry carbohydrates-
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Complex carbohydrates
• Polysaccharides
– Indigestible (fibre)
– Partial to complete resistence to hydrolysis by
digestive juices
– Except for soluble fibre they pass unaltered
through small intestine
– Fermentation by enzymes of large intestine
microflora → FA
– 1 g of fibre = 3 kJ
• DDD 25 – 30g ratio R:N 1:3
– Division
» Soluble – pectins, inulin, fructooligosaccharides, slimes,
gums, hemicelluloses …
fruit, oat, malt, legumes, potatoes
» Insoluble – cellulose. Lignin, hemicelluloses…
vegetable, bran, whole grain products 9Pathobiochemistry carbohydrates-
2018
Significance of fibre
• Soluble
– Partial cleavage in small intestine → gels → slowdown in
upper part of GIT → elevation of viscosity of intestinal
content→ ↓ access of digestive juices to substrates, binding
of mineral compounds → ↓ absorption of nutrients and bile
acids, velocity slowdown of glu resorption, prebiotic
• Insoluble
– ↑ stool contain (dilution and binding of toxic compounds),
shortening of transit time → reduction of resorption of toxic
compounds, ↓ absorption of some nutrients
– Fermentation => FA with short chain (acetate, propionate,
butyrate) = sources of energy for colonocytes (80%), lower pH
=> Preventive x bowel obstruction, polyps
and large intestine tumours, bilestones, reduce blood cholesterol
10Pathobiochemistry carbohydrates-
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Digestion of starch
• Oral cavity
• Starch – salivary α-amylase (ptyalin)
• pH optimum 6,7
• Stomach
• Decreased activity of ptyalin
11Pathobiochemistry carbohydrates-
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Digestion of starches
• Small intestine
• Pancreatic enzymes–
pancreatic α-amylase
– Hydrolysis of 1,4 α-bond
=> maltose, maltotriose, glu polymers,
α-limit dextrines (8 glu)
• Mucous membranes of small intestine –
oligosaccharidases
– The outside of the brush border
– α-limit dextrinase – α-limit dextrines
– Glucoamylase – maltose => glu
- maltotriose => glu
- polymers of glu => glu
12Pathobiochemistry carbohydrates-
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Digestion of
disaccharides
• Small intestine
– Mucous membrane of small intestine – disaccharidases
» Laktose → lactase => glu and gal
» Maltose → maltase => glu and glu
» Saccharose → saccharase => glu and fru
– Lack of disaccharidases => diarrhea, flatulence
» Increased amount of osmotically active molecules
of oligosaccharides and formation of gases
– Lactase – activity declines with age
» lactase intolerance
– Digestion and resorption malfunctions in inflammations
13Pathobiochemistry carbohydrates-
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Absorption of carbohydrates
• Fast – through the wall of small intestine => v. Portae
• Resorption – before the rests of food get into terminal ileum
• Max. speed 120 g/day.
• Site of absorption – the duodenum and proximal jejunum
• Effect of Na+ on carbohydrates transport
– ↑ c Na+ at mucosal surface of cells → facilitates glu entry into the
cell and the other way around
– Common contransport
– Na+ - transport down concentration gradient + glu = secondary
active transport into ICT, facilitated or simple diffusion into ECT
– Gal – the mechanism is the same
– Fru – absorption independent on Na+
- slower resorption
- facilitated diffusion
- part of fru → glu (mucosal cells)
14Pathobiochemistry carbohydrates-
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15Pathobiochemistry carbohydrates-
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Summary of digestion- saccharides
16
Beginning of carbohydrates digestion mouth
- salivary α-amylase cleaves
starches into dextrins, maltotriose,
maltose, digestion continues through the
esophagus and in the stomach before
acidic gastric juice is secreted and
salivary amylase is inactivated by its low
pH.
pancreatic α-amylase is secreted in
duodenum - dextrins to disaccharides
which are digested by specific intestinal
disaccharidases of intestinal juice into
monosaccharides in small intestine
sucrose (by sucrase) = glucose and
fructose
lactose (by lactase) = galactose and
glucose
maltose (by maltase) = glucose and
glucose
Simple carbohydrates are actively
absorbed into enterocytes - secondary
active cotransport of Na+ and delivered
down the gradient using a carrier
(facilitated diffusion) from cells to
portal blood. In case of fructose, only
passive transport had been proven and
its absorption is faster than of other
monosaccharides.
Simple sugars can be resorbed to portal blood and transported to the
liver and to other tissues where they serve as a source of energy or
storage of energy (glycogen) in liver. Excess intake of carbohydrates is
stored in form of fat.
Pathobiochemistry carbohydrates-
2018
Carbohydrate metabolism
• Monosaccharides → portal circulation → liver
• 1. step in metabolism of glu,fru, gal – phosphorylation
• Galactose → gal-1-P→ glu-1-P (→ glucose)
– Share on glycogen synthesis, reversible reactions
– Gal – formation of glycolipids, mucoproteins
• Fructose → fru-6-P → fru-1,6-diP →
→ fru-1-P → dihydroxyacetone and glyceraldehyde → metabolic
pathways of glu
• glucose, synthesis of glycogen and TAG
» Liver - high ability to synthesizeTAG
• Use of hexose phosphates
– Cleavage as an energy substrate in tissues
– conversion to glycogen (liver, skeletal muscle)
– conversion to FA and triacylglycerols (TAG) (liver, adipose tissue) –
energy reserve
– Minority part - metabolization in pentose cycle, synthesis of
glycoproteins, glycolipids 17Pathobiochemistry carbohydrates-
2018
Glucose metabolism
• Glycolysis -anaerobic
– degradation of glu under anaerobic conditions to
pyruvate or lactate
– Gain of energy 2 ATP/1 mol of Glu
– Process consists of several steps
– Does not take place in mitochondria but in
cytoplasm
• Pyruvate => acetyl-CoA (irreversible reaction)
=> lactate
=> alanine => proteins
18Pathobiochemistry carbohydrates-
2018
Aerobic glycolysis and Citric
acid cycle
• Acetyl-CoA => fats
=> Krebs cycle
• Krebs cycle– oxidation of carbohydrates, fats and
some AA
• Krebs cycle => Acetyl-CoA => reduced cofactors, CO2,
water and energy
• Aerobic oxidation- respiratory chain– 36-38 mol
ATP/1 mol glu
• Process of CC – mitochondria
• Requires O2 delivery
• It doesn‘t work under anaerobic conditions!!!!!
19Pathobiochemistry carbohydrates-
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Glycogen metabolism
• Glycogenesis
• Starage glycogen formation from Glu-1-P
• When? - In excess of glucose
• Store - liver (100 g), muscle (300-400 g)
• Glycogen - holds water
• Glycogenolysis
• Glycogen decomposition
• When? - In lack of Glu
• Adrenalin (activation of phosphorylase)
20Pathobiochemistry carbohydrates-
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The physiological importance
of glucose
• Glu - the fastest source of energy
essential for Ery and brain, nerve cells.
• Min. need 150 g/24 h.
– < 150 g/24 h => glukoneogenesis, ketogenesis (energy from FA,
formation of ketone bodies in case that production exceeds
utilization => ketosis - disturbance of acid-base balance,
prevention min. 50 – 100 g sacch./day)
• Blood glucose level – glycemia (3,9 – 6,1 mmol/l)
– hepatic glucose- liver maintains constant level of glu
• Hypoglycemia => ↑ glucagon, adrenaline => mobilization of Glu
formation (glycogenolysis)
• Glu - can not be sythesized from fat only from small amount of
glycerol 21Pathobiochemistry carbohydrates-
2018
Hormonal regulation
• Insulin
– Produced by B-cells of Langerhans pankreatic islets
– Stimulatory effect on glu utilization
– Secretion regulator – glycemia (gly) level
– ↑ gly level => ↑ insulin => ↑ utilization of glu to cells => normalization
of gly level
– Is stimulated also by fructose, AA (Arg), glucagon
• Glucagon
– Produced by A-cells of Langerhans pankreatic islets
– Activates hepatic phosphorylase => glykogenolysis => ↑ gly
level
• Corticosteroids, catecholamines, thyroid hormones,
growth hormone 22Pathobiochemistry carbohydrates-
2018
Gain of glucose under physiological
conditions
• Supply from external environment - simple or
complex carbohydrates
• from storage – glycogen
• Glukoneogenesis – from AA
– When? - starvation, low carbohydrate intake, DM,
stress
– Also in reverse order – transamination of glu
metabolism products → AA
23Pathobiochemistry carbohydrates-
2018
Resorption phase Postresorption phase,
starving
Saccharides
from food
Glycogenolysis
(liver)
Gluconeogenesis
(livers, kidneys)
3,1-5,0 mmol/l
Blood glucose level
Pathobiochemistry carbohydrates-
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24
Glucose in blood
One of basic priorities of metabolic
regulation:
Hormonal regulation:
insulin (decreases glu level)
glucagon
adrenalin
kortisol
(increases glu level)
blood glucose level can´t drop under 3 mmol/l
Pathobiochemistry carbohydrates-
2018
25
Factors determining the glucose
level
• The balance between the amount of glu
entering the blood and amount of glu that
leaves blood
– Intake of carbohydrates from food
– The speed of glu entry into muscle cells., adipose
tissue cells and other organs
– 5% glu → glycogen
– 30 – 40 % glu → fat (when filled stocks with glycogen)
– The rest → metabolism in muscle and other tissues
– Liver glycogen during starvation→ glucosa
» Prolonged starvation → glykogenu depletion =>
glukoneogenesis
26Pathobiochemistry carbohydrates-
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Glucose level determining factors
• Balance between amounts of glu entering the
blood and glu leaving the blood
– Intake of saccharides from food
– Velocity of glu entry to muscle cells, adipocyte
cells and other organs
– 5% of glu → glycogen
– 30 – 40 % of glu → fat (if glycogen supplies are full)
– The rest → metabolisation in muscles and other
tissues
– Liver glycogen in starving→ glucose
» Long-lasting starving → drawing out of glycogen =>
gluconeogenesis
27Pathobiochemistry carbohydrates-
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Homeostasis of carbohydrates
during exercise
• At rest and after exertion
• Consumption of FA by skeletal muscle
• Consumption of glu – brain
• Physical exertion => glycogenolysis => ↑ gly level,
gradual reduction during
exercise
=> ↑ gluconeogenesis↓ insulin level, ↑
glucagon and adrenalin level
• After physical exertion=> gluconeogenesis, decline
in output of glu from liver
(for liver glycogen refill)
=> ↑ insulin level => Support of
glycogen storage
28Pathobiochemistry carbohydrates-
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Entry of glucose to the cells
Glucose transporters
-transmembrane proteins facilitate
transport of glucose to the cells
- type GLUT (1-14)* or SGLT**
* glucose transporter
** sodium-coupled glucose transporter
Glu molecules are strongly polar, can´t diffuse
through hydrophobic lipid bilayer membrane
(hydrogen bonds between OH groups and water)
Pathobiochemistry carbohydrates-
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29
GLUT 1-GLUT 14, identical traits:
 500 AA, 12 transmembrane helixes
mechanism:
Facilitated diffusion through membrane (down the
concentration gradient, no energy required)
Pathobiochemistry carbohydrates-
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30
Why so many types of transporters ?
• they differ in affinity to glucose
• they can by regulated differently
• they occur in different tissues
Pathobiochemistry carbohydrates-
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Glucose transporters of GLUT type
Type characteristics
GLUT 1 Majority of cells (Ercs, muscle cells under
resting conditions, blood vessels in brain and
elsewhere)
GLUT 2 livers, -cells of pancreas, kidneys
GLUT 3 Nerve cells, placenta and elsewhere
GLUT 4 Muscle, adipocytes – dependent on insuline
GLUT 5 Transport of fructose – small intestine and
elsewhere
GLUT 7 Intracellular transport in livers
Pathobiochemistry carbohydrates-
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Transport of glucose by GLUT
Mechanism of facilitated diffusionPathobiochemistry carbohydrates-
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33
Pathobiochemistry carbohydrates-
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34
Pathobiochemistry carbohydrates-
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35
Receptors GLUT 4 is dependent of insulin
insulin
receptor
vesicles
insulin
Pathobiochemistry carbohydrates-
2018
36
insulin
receptor
insulin
Transport on membrane
Binding of insulin on receptor
Pathobiochemistry carbohydrates-
2018
37
insulin
receptor
Glu transporters on
membrane
Transport glu in cell
Pathobiochemistry carbohydrates-
2018
38
Glucose transport into the cells of
the intestinal mucosa and the renal
tubule (SGLT)
Mechanism: co-transport with sodium secondary active
transport
at two specific sites linked
transporter of glucose and
Na + transport thereof
coincides (no energy) Na + is
then pumped from the cell
ATPase (consumption of
ATP), glucose is then
transported out of the cell
via GLUT2
Pathobiochemistry carbohydrates-
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39
Liver
Other tissue
CNS ERYTROCYTS
Glu
Distribution of Glu to tissue
dependent of Glu
Pathobiochemistry carbohydrates-
2018
40
therefore, decreases if the uptake of glucose, the
body begins to save glucose and preferably only supplies
the CNS and erythrocytes
Glucose is distributed into the tissues as a source of
energy
for red blood cells and the CNS glucose is practically
the sole and irreplaceable source of energy
Other cells may also metabolize fatty acids
(or amino acids and ketone bodies)
Pathobiochemistry carbohydrates-
2018
41
Metabolism of glucose
Glycolysis
•the energy
gain profit
acetyl CoA
occurs in most
cells
glycogen
synthesis
storage
form of
glucose
it occurs
mostly in the
liver and
muscles
pentose cycle
profit pentose
Profit NADPH
synthetic
reactions
obtains energy
takes place in
most c.
Pathobiochemistry carbohydrates-
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42
Phase glucose metabolism and
hormonal regulation
Pathobiochemistry carbohydrates-
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43
4 8 12 16 20 24 28 2 8 16 24 32 40
Hodiny Dny
Využití glukosy
(g/h)
40
30
20
10
0
I II III IV V
Exogenní
Glykogen (jaterní)
Glukoneogeneze
Sources of glucose metabolism in various stages
Pathobiochemistry carbohydrates-
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44
hours
days
Metabolism of glucose after a meal (resorptive
phase)
Characteristics:
metabolism controlled insulin most tissues uses
glucose as an energy source, runs glycolysis glucose is
stored "rainy day" (liver, muscle) - the synthesis of
glycogen in liver and muscle acetyl CoA generated by
glycolysis can be used for the synthesis of fatty
acids and consequently lipids ( "fatter after sweet")
Pathobiochemistry carbohydrates-
2018
45
Glucose metabolism for longer after a meal or
in fasted
Characteristics:
metabolic control glucagon (a hormone) organism
"saves" glucose, glucose is used mainly CNS and
erythrocytes other tissues metabolize other
nutrients, especially MK glucose level is replenished
glycogen breakdown and gluconeogenesis in the liver
Pathobiochemistry carbohydrates-
2018
46
Glucose metabolism in short-term stress
•metabolic control stress hormones (adrenaline,
noradrenaline) preparation for fight or flight
(fight or flight) priority is to supply the muscle
glucose in the liver glycogenolysis, glukoneogenze
muscle lipolysis, glycogenolysis and glycolysis
Pathobiochemistry carbohydrates-
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47
Glucose in bloodSources of glucose metabolism in various stages
In describing the metabolism of the two basic
metabolic state called absorption (resorptive) and
post absorption phase (postresorpční) phase.
Absorption phase lasts approximately 4 hours and
includes a meal and after. Post absorption phase is
the state during and after an overnight fast.
Starvation: when food intake is stopped for more
than 12 to 14 hours, pass metabolism in starvation
phase (= short-from tens of hours to several days,
to long = more than two to three weeks). Blood
glucose levels in healthy humans is maintained within
a very narrow range. In postresorpční stage, blood
glucose is maintained in the range of 4.5 to 5.2 mmol
/ l.
After a meal containing carbohydrates blood glucose
levels rise. After 0.5-1 h, reaches the level of
glucose in the blood of healthy people 8-10 mmol / l.
Glucose at this stage serves as the main source of
energy for
most tissues and is stored as glycogen in the liver.
After about 1 hour after meals level begins
glucose to drop, because glucose is consumed
catabolism and storage. normoglycemia is
re-established after about 2-4 hours. After this time,
the liver, the process of glycogenolysis and glucose
It is released from the liver into the blood. Once
glycogen decreases, begin to be dismantled also
lipids
in adipose tissue of hormone-sensitive lipase, and in
blood they are supplied fatty acids and glycerol.
Fatty acids are used as an alternative fuel for
certain tissues and glycerol is used for
gluconeogenesis. 48
TEST
During the night of fasting is glukosemie maintained both
processes - glycogenolysis and gluconeogenesis.
After approximately 30 hours of fasting, the glycogen
stores in the liver practically exhausted.
Gluconeogenesis becomes the sole source of glucose in the
blood. Changes in glucose metabolism occurring during the
transition from phase to phase saturation starvation are
regulated mainly hormones insulin and
glucagon. Insulin is increased after a meal, glucagon
increases during starvation.
Pathobiochemistry carbohydrates-
2018
• 1. To the liver. Here excess sugar
from meals is stored to cover sugar
shortages between meals and to
make fat from excess sugar.
• Transport of sugar goes both to and
from the liver. The liver fills the
"Sugar Central" between meals.
• 2. To the brain. The brain is
completely dependent upon sugar
combustion for its supply of energy,
in any case under normal
conditions. It uses really huge
amounts of sugar.
• 3. To muscles and fat tissue. At
least 40% of the body is comprised of
skeletal muscles. These can use both
fats and sugar to supply energy. The
rate of sugar uptake and burning
follows physical activity; more work;
more sugar burned. Muscles do take
up and store glucose to cover future
activity but they cannot release sugar
back to the blood stream or "Sugar
Central". Fat tissue stores surplus
sugar as fat. About half of this comes
from the liver, the rest is made by fat
itself.
Pathobiochemistry carbohydrates-
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49
Sources glu in various stages of
metabolism
Sources of Glu
in phase
I II III IV V
Duration of
phase
0-4 h 4-16 h 16-32 h to 24 days longer than 24 days
Main source of
Glc
Diet Glycogen Glycogen,
Gluconeogenesis
Gluconeogenesis Gluconeogenesis
Source of Glc in
blood
Diet Glycogenolysis
(gluconeogeneze)
Gluconeogenesis,
(glycogenolysis)
Gluconeogenesis
(liver, kidney)
Gluconeogenesis
(liver, kidney)
Tissue-Glc from
blood
all All,no liver
Limitation:
muscle,adipose t.
All,no liver
Limitation:
muscle,adipose t.
CNS, Ercs, kidney
Limitation:
muscle,
Ercs, ledviny
Limitation: CNS,
Main source of
E for CNS
Glc Glc Glc, ketone bodies Glc, ketone bodies Ketone bodies, Glc
50Pathobiochemistry carbohydrates-
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TEST
Disorders of carbohydrate metabolism
Blood sugar and hormones
The glucose concentration in the blood (glucose) under physiological conditions is maintained
within a narrow range of values from 3.9 to 5.6 mmol / l in fasting and postprandial less than
10 mmol / l. It is strictly regulated by a variety of mechanisms: insulin, which lowers blood
glucose and antiinzulin acting hormones - glucagon, catecholamines, glucocorticoids and growth
hormone that increases blood glucose. On the regulation of glucose homeostasis is a major part
liver. Maintaining constant values of glucose is essential for the activity of the CNS and other
tissues and cells (e.g. erythrocytes).
increase in blood glucose levels above 7.77 mmol / l -
hyperglycaemia
reduction below 2.5 mmol / l - hypoglycemia
enzymopathies or regulatory disorders (diabetes)
Hypoglycemia - insufficient energy supply to the brain (neuroglycopenia), increased
secretion of catecholamines (palpitation, anxiety, tremor, sweating)
Formation: 1. insufficient supply of glucose into the blood circulation
Second from too rapid uptake of circulation
Hypoglycaemia during fasting - sugar metabolism disorders, tumors, endocrine,
hepatic cirrhosis, pregnancy, newborns, drug-induced
Hyperglycemia - Diabetes mellitus, endocrine disorders, diseases of the pancreas,
liver, severe acute diseases (infection)
51Pathobiochemistry carbohydrates-
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TEST
Hereditary disorders of carbohydrate
metabolism
• Disorders of carbohydrate metabolism („small molecules“)
• Fructose
• Galactose
• Disorders of metabolism polysaccharides („big molecules“)
• Glycogenosis (also product deficiency)
• Disorders of protein glykosylation (and lipids)
• product deficiency
• Diabetes mellitus as a complex metabolic disease - diabetes
biochemistry
• Molecular interpretation of late effects of diabetes
52Pathobiochemistry carbohydrates-
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TEST
Diabetes mellitus
• (Insulin deficiency - increase in plasma glucose concentration, glucose excretion in the
urine)
• Type 1 (insulin-dependent, juvenile type IDDM)
polygenic autoimmune disease, the absolute lack of insulin
genetic predisposition combined with: viral infection, toxins, stress
(Several years, 5-10% undiagnosed diabetics)
slow destruction of β-islet cell mediated
activated T lymphocytes and cytokines - insulitis (lymphocytic infiltration of islet cells,
inflammation). Insulitis reduces the number of functional β-cells in the pancreatic
buňkáchdisorders
of synthesis and secretion of insulin.
Type 2 (non-insulin dependent, or adult type, NIDDM)
combination of hereditary factors and environment
a combination of insulin resistance and relative deficiency of insulin (abnormal insulin
receptor antibodies, anti-insulin)
resistance to the action of insulin: reduced number of plasma membrane receptors on
target cells, postrecep. blockade of intracellular glucose metabolism (decreased number
of receptors, reduced affinity, decreased activity of the complex; abnormal signal
transduction or abnormal phosphorylation reaction for the formation of excessive TNF).
gradual loss of the ability of β-cells to respond to glucose, insulin resistance,
dysregulation of glucose production in the liver
53Pathobiochemistry carbohydrates-
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TEST
Diabetes mellitus (DM) is a chronic disease with high
morbidity and mortality, in the last decade was
recorded a strong growth of this disease. Currently
in the Czech Republic recorded more than 800,000
diabetics. DM includes a heterogeneous group of
chronic metabolic diseases whose primary symptom is
hyperglycemia. Is due to lack of insulin, its lack of
efficacy (some talk about the relative scarcity), or a
combination of both.
The lack of insulin results in a distortion glucose
transport from blood into the cells of the cell membrane,
which leads to hyperglycemia and lack of glucose
intracellularly. Inadequate utilization of glucose by the
cells is replaced by other energy sources. Stimulates
gluconeogenesis and glycogenolysis, further increased
lipolytic cleavage of triglycerides into fatty acids and
glycerol in adipocytes. By degrading fatty acid in βoxidation
is formed acetyl-CoA excess, from that ketone
bodies are formed in the liver - acetoacetate, 3hydroxybutyrate
and acetone. Acetoacetate can serve as
a source of energy for muscle activity and brain instead
of glucose. If the formation of ketone bodies exceeds
their utilization by peripheral tissues, ketoacidosis
develops. Given that the ketones are soluble and
excreted in the urine, occurs ketonuria.
Excess of glucose also receives into urine and glucosuria develops. Because glucose and ketone bodies are osmotically
active, pull down with him larger amounts of water into the urine, which is the basis of polyuria.
From the above result and the characteristic symptoms of DM as thirst and polyuria; It also identified lack of
appetite and weight loss.
Chronic hyperglycemia associated with impaired function of many internal organs, especially the kidneys, eyes, vascular
and nervous system.
54Pathobiochemistry carbohydrates-
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Differences between types of diabetes
Type 1 Type 2
Age usually below 30 usually above 30
Frequency (% of all diabetics) 10−20 % 80−90 %
The emergence of symptoms acute or subacute slow
Obesity Not usual very common
Inducing factors
altered immune response after viral
infection
obesity, pregnancy, stress
Pancreatic insulin content absent or trace amount low, normal, high
Glucagon in plasma high, but resumable insulin high, but resistant to insulin
Antibodies against pancreatic islets Present in 85 % cases less than 5 %
Primary insulin resistance minimal usually pronounced
Response to the insulin treatment +++ + until Response
to dietary treatment slight
always present, but various
degrees
Response to treatment with oral
antidiabetic agents
absent present
Typical acute complications ketoacidosis hyperosmolar coma
Association with HLA yes no
Complications: Diabetic ketoacidosis, hypoglycemia, diabetic nephropathy, periodontitis
55Pathobiochemistry carbohydrates-
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TEST
PATHOGENESIS OF DIABETES MELLITUS
Insulin insufficiency
Fatty acids 
Ketone bodies 
 - hydroxybutirate,
acetoacetate accumulation in
blood
Metabolic
acidosis
Ketonuria
Kussmaul's
respiration
CNS depression
Blood glucose level 
glucosuria
polyuri
a
dehydration
 thirst 
Hypovolemia
SHOCK
Poly-
dipsia
Pathobiochemistry carbohydrates-
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56
IMPAIRMENT OF LIPID METABOLISM IN DIABETES MELLITUS
Decreased glucose utilization
Decreased lipogenesis
Mobilization of fats to depoes
Hyperlipidemia
Metabolic acidosis
Increased ketogenesis and cholesterol
productoin
Ketonemia and
hypercholesterolemi
a
Ketonuria
Loss of Na+
Keto-acidotic coma
Insulin deficiency
57
Decreased glucose utilization
Increase in proteolysis
Aminacidemia, increased uptake of aminoacids by the
liver
1. Activation of gluconeogenesis
2. Increased removal of nitrogen via urea
Loss of potassium and other ions by the cells
Dehydration of the
cells
Potassium loss by
the organism
Insulin deficiency
IMPAIRMENT OF PROTEIN METABOLISM IN DIABETES MELLITUS
Pathobiochemistry carbohydrates-
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Symptoms of diabetes mellitus
Major symptoms are:
• hyperglycemia,
• glucosuria and
• polyuria.
Pathobiochemistry carbohydrates-
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59
Evaluation of glycemia -fasting
deciding value
Interpretation Glu in plasma - fasting
exclusion of diabetes < 5,6 mmol/l
Prediabetes (increase glycemia) 5,6 – 6,9 mmol/l
Diabetes mellitus ≥ 7,0 mmol/l
The reference interval glucose
fasting plasma adults: 3.9 to 5.6 mmol / l
Glycemia was determined in venous plasma. Glucose values are for the adult population.
Diabetes diagnosis must be confirmed by repeated measurements.
Evaluations are carried out on the basis of the Czech Society of Clinical Biochemistry
and the Czech Diabetes Society (2012) as recommended by WHO www.čskb.cz
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Determination of glucose concentration in blood
• the examination, that provides basic information on carbohydrate metabolism. Picked up
capillary or venous blood, and glucose is determined in whole blood, plasma or serum.
• For determination of glucose in whole blood values are 10-15% lower (depending on
hematocrit) in arterial blood is about 10% higher than in venous (arteriovenous difference).
To prevent glycolysis added NaF (2.5 mg per 1 ml of whole blood) into containers .
• Examination of glucose concentration in blood has the necessary information value only
if it´s known the time interval between collection of blood and food intake.
• Examination of glycemia is performed:
• Fasting (blood is drawn at least 8 hours after ingestion) - indicated when searching
diabetics and diagnosis of DM;
• randomly measured glycemia (blood is collected without giving a time relation to food intake)
- is carried out in suspected hypoglycemia or hyperglycemia;
• after a meal - post-prandial glycemia (1 hour after a meal containing carbohydrates) indicated
to check the effectiveness of DM treatments;
• as the glycemic profile - glycemia is determined several times a day, usually before the main
meals, sometimes after meals and at night.
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Methods for glycemia determination
• Glycemia determination in laboratory conditions
• To determine the concentration of glucose used different methods.
• Advanced methods are coupled with an enzyme enzyme.
• Glucose may be determined by each enzyme,
• that it metabolizes.
•
• The glucose oxidase reaction
• Recommended routine method utilizes enzymatic reactions coupled glucose oxidase (GOD, EC
1.1.3.4) and peroxidase (POD, EC 1.11.1.7). In the first reaction the enzyme glucose oxidase
catalyzes the oxidation of glucose by atmospheric oxygen to give gluconic acid, which passes the
internal ester gluconolactone. It is known that in solution is 36% of glucose in the form of α-anomer
and 64% in the form of β-anomer. GOD is highly specific for β-D-glucopyranose. In order to oxidize
both anomers, is necessary mutarotation α- to β-anomer, that occurs spontaneously during a
sufficiently long incubation. As a byproduct of the reaction, glucose oxidase produces equimolar
amounts of hydrogen peroxide.
• In a further reaction catalysed by peroxidase, formed hydrogen peroxide reacts with a suitable
chromogen, which is oxidized to a reactive intermediate, and one with another agent coupled to a
constant-soluble dye. An example may be the oxidative coupling of phenol derivative with 4aminoantipyrine
to a red dye, whose absorbance after stabilization of the reaction equilibrium is
measured.
• Other methods use measurements of oxygen depletion that occurs during the reaction catalyzed
by glucose oxidase and that we can monitor electrochemically by the oxygen or enzyme electrode.
62Pathobiochemistry carbohydrates-
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Hexokinase reaction
• Hexokinase method is characterized by the high specificity . Hexokinase (EC 2.7.1.1) phosphorylates glucose
in the presence of ATP to glucose-6-phosphate. In the next step, the glucose-6-phosphate is oxidized by
glucose-6-phosphate dehydrogenase versus NADP + into 6-phosphogluconolactone. Reduction of NADP +
into NADPH can be evaluated by direct UV photometry area on the principle of Warburg optical test.
• Determination of glycemia in the outside of laboratory conditions
• Glycemia amongs the parameters that are often examined without laboratory facilities. Fast approximate
determination of glycemia is common in emergency care. Patients treated with insulin are also preferably
regularly monitored using a personal glycemia meter and then by using the measured values therapy is
adjusted. Blood glucose concentrations are among the most common parameters determined examination
techniques at the point of patient care (point of care testing, POCT). It should be borne in mind, however, that
POCT methods, however improve the quality of care and patient comfort, not replace regular medical
examination or laboratory control.
• Methods for rapid determination of glycemia use several principles. The starting material is usually a drop of
capillary blood which is applied to the test strip.
• The oldest, but still used strips are based on the same reactions as the photometric measuring glucose
concentration. Capillary blood migrates several layers of different materials, which makes it separates blood
cells and zone only the plasm penetrates into the reaction. The reaction zone contains glucose oxidase,
peroxidase and a suitable chromogen. Depending on the concentration of glucose develops differently intense
color. The evaluation is done either by visually comparing the color chart or using a glucometer - a dedicated
reflective photometer. The advantage of the visual evaluation is its independence from any instrumentation.
Determination of glycemia using this method is only approximate, however, is quite sufficient especially in
emergency care. Glucometers based on reflective photometry are currently pushed reliable electrochemical
analyzers.
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Oral glucose tolerance test (OGTT)
G l ucose tolerance
Glu in plasma after 2 hours
after load
Normal (exclusion of diabetu mellitu)  7,8 mmol/l
Impaired glucose tolerance 7,8 - 11 mmol/l
Diabetes mellitus ≥ 11,1 mmol/l
Glucose values are for the adult population.
For expressing a diagnosis result must be confirmed repeatedly.
The finding of impaired glucose tolerance OGTT is repeated every two years.
Evaluations are carried out on the basis of the Czech Society of Clinical Biochemistry
and the Czech Diabetes Society (2012) as recommended by WHO www.čskb.cz
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1) Glycogenosis (glycogen storage disease, GSD)
• are inherited metabolic disorders with a deficiency of an enzyme
or transport protein, which result in either abnormal glycogen
structure, or an abnormal content in the tissues. Inheritance of
all types of GSD is an autosomal recessive, except there are only
two subtypes of GSD IX for which inheritance is bound to the X-
chromosome.
• Etiopatogenesis
• The cause of these diseases is zero or insufficient synthesis of
functional proteins (enzymes and transporters) participating in
either glycogenolysis or glycogen synthesis. Depending on the
enzyme, glycogenosis can be divided into several types, that differ
both clinical course and the biochemical findings and prognosis
• biochemical image
• Most often found in laboratory tests
dominate these symptoms:. hypoglycemia
• hyperlactatemia
• metabolic acidosis
• hyperlipidemia
• hyperuricemia 65Pathobiochemistry carbohydrates-
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66Pathobiochemistry carbohydrates-
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Classification and basic characteristics of glycogenosis
Classification:
Depending accumulation
•by the storage in the cytosol - all except GSD II
•by the storage in lysosomes - GSD II
According to organ damage
•generalized: II, IV
•liver: Ia, Ib, III, VI, IX, 0
•muscle: V, VII; red muscle cells may be
component type II, III, IX
•with myocard impairment : II, III, one of the subtypes IX
•with renal impairment: Ia, Ib
•muscle glycogen storage disease
symptoms: muscle weakness and slackness, fatigue, increased exertion pain
muscles and attacks myolysis (ev. i hemolysis)
Usually occur after the 20th year of life
Laboratory findings: increased level of CK-MM, AST, ALT, LDH;
urine myoglobinuria; since muscular tissue does not influence glucose homeostasis, for the type V,
VII (only muscle GSD) hyperlactacidaemia and dyslipidemia aren´t in the results of blood analysis
treatment: symptomatic; demonstrated a beneficial effect of increased protein intake
•Liver glycogen storage disease
symptoms : hepatomegalie, menší vzrůst
Laboratory findings: hyperlactacidaemia, dyslipidemia, ketotic hypoglycemia, hyperuricemia
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Overview glycogenosis type I-V[1]
Type of glycogenosis Defective enzyme
Place of
accumulation
main clinical signs
I – von Gierk
glucose-6-
phosphatase
liver, kidney
slow growth,
hypoglycemia,
hepatomegaly
II – Pompe
lysosomal α-
glucosidase
muscles, liver
heart failure,
hypotonia
III – Corri
glycogen
unbranching enzyme
liver, muscles
Slow growth, muscle
weakness,
hypoglycemia
IV – Andersen
glycogen branching
enzyme
liver, muscles
failure to thrive, liver
failure, muscle
weakness
V – McArdle phosphorylase muscles
muscle weakness,
cramps
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69Pathobiochemistry carbohydrates-
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Glycogenosis type 0 (aglycogenosis)
• Lack of the enzyme glycogen synthase in the liver (muscle, leukocytes
and enterocytes doesn´t missing). Liver glycogen is reduced below 2%
normal.
• clinical picture
• Conditions severe hypoglycemia with cramps - lead to brain damage and
mental retardation. They occur mainly in the morning, after overnight
fasting, are accompanied by ketonemia. After administration of
glucose observed prolonged hyperglycemia and increased lactate in
serum (liver constitutes glycogen, glucose is metabolised to lactate).
• Urgent diagnosis is essential to child survival.
• Episodes of hypoglycemia can be prevented by frequent
administration of protein-rich
• meals 70Pathobiochemistry carbohydrates-
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Glykogenose type Ia (von Gierke‘s disease)
Impaired activity of glucose-6-phosphatase (converts glucose-6-P into glucose, that is if necessary released from the liver into the blood).
AR inherited disease gene on the 17th chromosome.
Clinical picture
It begins in infancy, progressive hepatomegaly (liver function is normal, it does not develop cirrhosis) and
hypoglycemic convulsions fasting.
During febrile conditions, hypoglycemia is more frequent and is accompanied by lactic acidosis (hyperlactacidemia is consequence of an excess
of glucose-6-phosphate, which is in case of inability to hydrolyse to glucose, further metabolized by glycolysis, whose products are lactate and
pyruvate) with Kussmaul breathing.
•Characteristic facies "doll face"
•Organism adapts to hypoglycemia - insulin secretion decreases, lipase in adipose tissue is activated → hyperlipoproteinemia occurs →
ketone bodies are formed, caused by increased degradation. Ketone bodies and lactate are then involved in acidosis.
•Glucagon administration does not increase glucose but lactate..
•Galactose, fructose and glycerol, also require hepatic G-6-Pase for conversion to glucose → ingestion of sucrose and lactose leads
• to hyperlactacidaemia with only a small rise of blood glucose level.
•Slows the growth and puberty is lagging behind.
•In adulthood xanthomas and nephromegaly may appear, and associated renal failure with hypertension, gout, liver adenomas.
•Laboratory
•fasting hypoglycemia (often only in infants and toddlers)
•hyperlipidemia and hyperlactacidaemia that blocks the secretion of uric acid and makes hyperuricemia
Diagnostics
•UZ: hepatomegaly and nephromegaly, hepatic adenomas may occur
•Liver biopsy: steatosis and multiplication of glycogen
Therapy
•The aim is to prevent states of severe hypoglycemia and MAc
•Diet therapy - The frequent feeding with a restriction of animal fats, lactose, sucrose and fructose
•Calorie requirement is mainly replaced by starches and maltodextrins.
•From toddler age, corn starch is served after every meal.
•At night continuous nutrition through a nasogastric tube is suitable, so as to administrate 30% of daily intake at night.
•In acute metabolic disorder associated with lactic acidosis, i.v. glucose must be administered during infection.
Supportive pharmacotherapy: administration of an xantinoxidase inhibitor to prevent gout and uric acid nephropathy
• (but since the uric acid is a powerful antioxidant, the efforts are to keep her blood levels at the upper limit of the normal range);
• when severe hypertriacylglycerolemia – nicotinic acid and fibrates (to reduce the risk of cholelithiasis and pancreatitis).
Complications
•Hepatic adenomas, osteopenia, anemia, polycystic ovaries, pulmonary hypertension, depression (exhaustive treatment).
Prognosis
•In childhood is good, in adulthood hepatic, renal and cardiovascular complications may develop.
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Glycogenosis type I – Girke’s disease.
• Girke’s disease cause deficit of
glucose-6-phosphatase. This
enzyme provides 90 % of glucose
which disengages in liver from
glycogen. It play central role in normal
glucose homeostasis. Glucose which
disengages attached to disintegration
of glycogen or is derivated in process
of gluconeogenesis obligatory goes
over stage of glucose-6-phosphate.
Enzyme glucose-6-phosphatase tears
away a phosphate group from glucose.
There free glucose is formed it goes
out in blood. Attached to Girke’s
disease stage of tearing phosphate
group is blocked. There are no free
glucose hypoglycemia occur.
Hypoglycemia arises. Attached to
Girke’s disease glycogen is deponed
in liver and kidneys. Pathobiochemistry carbohydrates-
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Glycogenose type Ib
• Defect of glc-6-P translocase (transporter of glucose-6-phosphate
across the ER membrane).
• Clinical picture
• It is indistinguishable from Ia.
• Symptoms include - neutropenia with neutrophil dysfunction → frequent
respiratory tract infections, urinary tract and skin.
• Most patients have symptoms of inflammatory bowel disease (prolonged
diarrhea).
• Pharmacotherapy
• Prophylaxis with cotrimoxazol; administration of GCSF (granulocyte
colony-stimulating factor, factor stimulating the creation of
granulocytes) → long term leads to hypersplenism, renal cancer, AML.
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77Pathobiochemistry carbohydrates-
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Glycogenose type II (generalized, Pompe‘s Disease)
• In 1932, Dutch pathologist dr. J. C. Pompe [2] described this disease. This is a AR hereditary disease
caused by the AR gene mutation. This gene encodes acidic lysosomal
α-1,4-glucosidase (GAA).
• Gene for GAA was localized on the long arm of the 17th chromosome (17q23) [2].
• Due to a deficiency or lack of GAA enzyme activity, lysosomal glycogen accumulation occurs in many
tissues, particularly in skeletal muscle and in the myocardium (infants) and to a lesser extent also in
endothelial vascular system in the CNS (in particular astrocytes) in the liver and kidneys [2] .
• Incidence: 1:40 000. In the Czech Republic 4 patients are currently diagnosed (assuming considerable
underdiagnosis of this disease due to the lack of neonatal screening) [2].
• Prenatal diagnosis is possible - finding of abnormal lysosomes in amniocytes.
• Clinical picture
• The classic infantile form (IIa)
• Affects infants (enzymopathies) - always lethal.
• During the weeks and months the child becomes completely hypotonic - weakly sucks (→ unthrifty),
breathing shallowly (→ susceptibility to respiratory infections and sleep apnea).
• Distinct cardiomegaly, high P at EKG, abbreviated PQ and transmission failure.
• Liver slightly enlarged, also described macroglossia.
• Consciousness is not infringed, so does intellect.
• Frequent aspiration pneumonia with atelectasis
• Death of 2 years from respiratory failure.
• Laboratory finding
• Elevated liver and muscle enzyme levels in blood (ALT, AST, LDH, CK). The presence of oligosaccharides
in urine.
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79Pathobiochemistry carbohydrates-
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80Pathobiochemistry carbohydrates-
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Late type - juvenile and adult form (IIb)
• It affects older children and adults (enzymopenia)
• Clinically heterogeneous (given by a number of different mutations that can occur in GAA gene, there
have been already described over 200) → severity is determined by the residual enzyme activity.
• cardiomegaly is smaller, normal ECG, arrhythmias frequently.
• Death usually around the 30th to 40th year of life (according to age manifestation). It may not
shorten life expectancy, allows a sedentary job.
• Symptoms
• Dominated disability of muscles (muscle weakness, hypotonia) pelvic girdle (difficult standing up) and
pharynx (problems with food intake), respiratory muscles are also affected (sleep apnea, dyspnea) →
most common cause of death is respiratory failure; however myocardium is not usually affected.
• Diagnosis, Clinical examination
• Laboratory findings of GAA reduced activity in leukocytes or fibroblasts.
• Molecular-biological identified mutation for a given enzyme.
• Demonstration of glycogen deposits in biopsy specimens (muscle).
• Skin biopsy - electron microscope detectable abnormality of lysosomes.
• Treatment
• Only slows the progression; enzyme replacement therapy (ERT - enzyme replacement therapy) by
Myozyme® preparation (by infusion), contains GAA α-glucosidase precursor, which is by the acidic
environment in lysosomes converted to the active enzyme; symptomatic therapy (physiotherapy,
medication support, balneotherapy).
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Type ІІ glycogenosis – Pompe’s disease.
• Illness is related to
deficit of lysosomal
enzyme – sour
maltase, or α-1,4glucosidase.
This
enzyme slits
glycogene to glucose
in digestive vacuoles.
Attached to it’s deficit
glycogen
accumulates at first in
lysosomes and
then in cytosole of
hepatocytes and
myocytes.
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Glycogen Storage Disorders:
• Type 2- Pompe’s disease:
• Normal Glucose
• Do to an accumulation of glycogen in
lysosomes.
• **Ancient city of Pompeii was destroyed by Mt. Vesuvius- 79 AD**
• Manifested by massive Cardiomegaly,
Hepatomegaly, Macroglossia.
• Fatal If results in CHF.
• Limited therapies in Neonatal Variant.
– Attempts at enzyme replacement ongoing.
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Glycogenose disease type III (Cori‘s
disease, Forbes disease)
• Rare AR hereditary disease. This is a disorder of
enzymes degrading the branching of glycogen
(debrancher amylo-1,6-glucosidase and oligo-1,4glukantransferase).
Produces a similar clinical picture
as GSD I, but has a milder course.
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Type ІІІ glycogenosis – Cori’s
disease, Forbs’ disease
This illness is named
limited ecstrinosis. In
it’s base lies a deficit
of amylo-1,6-
glucosidase.
Degradation of
glycogen pauses in
sites of branching.
Glycogen
accumulates in liver
and muscles. Cure is
diet with big proteins
maintenance.
Glycogen in the Liver (left stained
to show glycogen, right normal)
Glycogen in Muscle Cells
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Glykogenose type IV (Andersen‘s disease)
• Rare AR hereditary disease, previously about 10 cases have been described.
Defective enzyme is amylopektinose (branching enzyme) → accumulation of
polysaccharide without branching points.
• Infantile type, Symptoms:
• Severe heart and liver diseases (cirrhosis, hepatosplenomegaly, portal
hypertension), ascites; rapidly progressive, with the desperate prognosis (death
usually occurs due to heart or liver failure in the first year of life)
• Juvenile, adult form
• Atypical;
• manifestations are generalized.
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Type ІV glycogenosis – Anderson’s disease.
• It is called by deficit of amilo-
1,4,1,6-transglucosidase (branching
enzyme).
• As result of this there is derivated
anomalous glycogen with very long
branches and rare points of
branching.
• It is not exposed to degradation and
accumulates in liver, heart, kidneys,
spleen, lymphatic nods, skeletal
muscles.
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Glykogenose type V (McArdler‘s syndrome)
• Deficiency of myophosphorylase → muscles have an increased glycogen
content that forms vacuoles
(up to 4%). Symptoms. Reduced tolerance of physical exertion.
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• Glykogenose type VI (Hers' disease)
Deficit in liver phosphorylase.
• Illness arises as result of insufficiency of hepatic
phosphorylase complex. Glycogen accumulates in liver.
Typical sign is hepatomegalia.
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• Glykogenose type VII (Taruis'
disease)
• Deficit in phosphofructokinase in muscle and
erythrocytes.
• Symptoms
• Reduced tolerance of physical exertion, increased muscle
glycogen content. There can also occur hemolytic anemia.
• Illness essence is in oppression of muscle
phosphofrutkinase. Symptoms are similar to McArdles
disease.
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Disorders of Fructose Metabolism
Ingestion of large amounts of sucrose
(beet or cane sugar) causes, after
subsequent decomposition, the
increased level of fructose. Fructose
is in the liver decomposed
significantly faster by glycolysis than
glucose, resulting in rapid flow
through certain liver metabolic
pathways, and consequently there is
an increased formation of fatty acids,
their esterification and secretion of
VLDL - may cause a rise of
triglycerides in serum. Excess of
contained glucose amplifies this
phenomenon.
Fructose derived from sucrose can be
converted in humans to glucose and
lactate prior to entering the portal
circulation. Together with glucitol,
fructose is contained in the human
lens, where it can accumulate in
diabetes and can cause a diabetic
cataract. It is also found in seminal
plasma and secreted into the fetal
circulation of ungulates and
cetaceans, where it acts as an
important source of energy.
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Initially, the degradation of fructose is not glucose dependent, subsequent metabolic steps can enter glycolysis. A possible
complication is hereditary fructose intolerance which is caused by the absence of liver aldolase B, which metabolizes
fructose-1-phosphate to glyceral and glyceron-3-phosphate, or defect fructose-1,6-bisphosphatase, which causes
accumulation of fructose-1-phosphate, leading to inhibition of glycolysis and glycogenolysis, subsequently leads to
hypoglycemia. Although there is phosphorylation of fructose, cell lacks ATP and phosphate and can not further degrade.
Chronic intake of fructose may cause irreversible destruction of the liver. Treatment consists of reduced fructose diet.
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1) Essential Benign fructosuria
fructokinase deficiency, fructose resorbed by intestine
in the organism, can‘t be metabolically used and is
excreted in the urine without clinical symptoms
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96
2) Hereditary fructose intolerance
AR inherited disease, 1:40 000, deficiency of E fructose-6-P aldolase in the liver
pathogenesis: fructose-6-P accumulates in the liver, causes competitive inhibition
of phosphorylase and prevents glycogen breakdown to glucose, which causes severe
hypoglycemia symptoms at birth are consistent with the classical galactosaemia
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3) Hereditary fructose 1,6bisphosphatase deficiency
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Disorders of Galactose Metabolism
• Galactosemia is an
increase in the
concentration of
galactose in the
blood serum.
Galactosemia may
be caused by
defects in these
enzymes:
• galactose-1-
phosphate,
• uridyltransferase,
• uridyldiphosphate
galaktose-4epimerase
and
• galactokinase.
98Pathobiochemistry carbohydrates-
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Disorders of Galactose Metabolism summary
Galactosemia - increased concentration of galactose in serum - defects:
galactose-1-phosphate uridyltransferase, uridyldiphosphatgalaktose-
4-epimerase galactokinase.
1) Classical galactosemia
AR hereditary disease, 1:50 000, deficiency of galactose-1-phosphate uridyltransferase,
which metabolizes galactose-1-phosphate
Pathogenesis: galactose-1-phosphate accumulates in the liver, kidneys, brain
and in the lens of the eye; it is metabolised by alternative way to galactitol, which
is toxic, symptoms after birth, hepatomegaly, progressing jaundice,
lethargy, convulsions, acute septic symptoms resemble disease with liver
and renal failure, untreated - brain edema and often bilateral cataracts
2) Galactokinase deficit
AR hereditary disease, 1: 200,000, deficiency of galactokinase, which catalyzes the
conversion of galactose to galactose-1-phosphate
Pathogenesis: galactose and galactitol accumulates in the lens and cause its osmotic edema,
bilateral cataracts, pseudotumor cerebri
3) Uridyldiphosphatgalaktose-4-epimerase deficit
AR inherited disease, uridyldiphosphatgalaktose-4-epimerase deficit, reminiscent of classic
galactosemia, psychomotor retardation
99Pathobiochemistry carbohydrates-
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1) Classical galactosemia
• Serious AR hereditary disease, incidence of 1:50 000
• Cause: lack of galactose-1-phosphate-uridyltransferase which metabolizes
galactose-1-phosphate
• Pathogenesis: galactose-1-phosphate accumulates in the liver, kidney, brain and
the eye lens; in alternative way is metabolised to galactitol, which is toxic
• Clinical picture: symptoms begin between 4.-9. day
• Vomiting, hepatomegaly, progressing jaundice, lethargy or convulsions
• Symptoms resemble acute septic disease with hepatic and renal failure
• If untreated, brain edema and often bilateral cataracts develop
• In NNPH the symptoms appear after conversion to dairy diet
• Diagnosis: proving of elevated concentrations of galactitol in urine and galactose-
1-phosphate in erythrocytes
• Confirmation is always necessary on the enzymatic and molecular level
• Therapy: at the first suspicion it is necessary to immediately discontinue dairy
diet
• In case of confirmation of the diagnosis, lactose lifelong diet is indicated
• Prognosis: may not be favorable even if detected in time, because the child has
been exposed to galactosis intrauterinary
• Most often speech disorder and hypogonadotropic hypogonadism at girls arises.
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101Pathobiochemistry carbohydrates-
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Galactosemia
• This is hereditary
illness. In it’s base lies
an blockade of
galactose
metabolism. In
organism intermediate
metabolits
accumulate. There are
two the main forms of
galactosemia on base
of transferase
insufficiency and on
base of galactokinase
insufficiency. Pathobiochemistry carbohydrates-
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Deficit of glucose-1-
phosphaturidyltransferase.
• This enzyme converts galactose-1-phosphate in glucose-1-phosphate.
Attached to it’s insufficiency galactose-1-phosphate and sugar alcohol
of galactose (galactit) accumulates in tissues lens of the eye, liver,
brain, kidneys. Mammal and cow milk contains lactose.
• Therefore the illness symptoms appear with first days of child life.
• Diarrhea, vomiting, dehydrotation occur.
• Liver increases (splenomegalia). Hepatocytes lose ability to conjugate
bilirubine. Children become yellowish.
• Affection of kidneys displays in proteinuria, aminoaciduria and
acidosis.
• For galactosemia cataract is very typical. Their beginnings related to
accumulation of osmotic active galactite in vitreous bodies of eyes.
Galactite absorb in water, and water breaks tissues.
• Dangerous consequences arise in the brain. This foremost is delay of
mental development.
• Mortal end is possible.
• Cure method is diet without galactose.
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2) Galactokinase deficit
• Rare AR inherited disease, incidence 1: 200 000
• Cause: Lack of galactokinase, which catalyzes the conversion of
galactose to galactose-1-phosphate
• Pathogenesis: galactose and galactitol accumulates in the lens and cause
the osmotic edema
• Clinical picture: usually bilateral cataracts, pseudotumor cerebri
• Therapy: The disease is treatable with diet restricting lactate,
cataracts may disappear [1]
104
Attached to this illness variant a
process of phosphorilation of
galactose is blocked, that is
transformation of galactose in
galactose-1-phosphat. Illness
displays in cataracts. Other
symptoms are absent or minor.
Cure is diet without galactose.
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3) Uridyldiphosphategalaktose-4-epimerase deficit
• Rare AR hereditary disease
• Cause: Lack of uridyldiphosphategalaktose-4-epimerase
• Clinical picture:
– Mild form: partial enzyme deficiencies, benign
– Severe form: vomiting, deprivation, hepatopathy neonates reminiscent
of classic galactosemia, psychomotor retardation
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Hereditary metabolic disorders of complex molecules[1]
• [2] are genetically determined disorders of synthesis, transport
and catabolism of macromolecules. They affect cell organelles,
where their synthesis or degradation occurs, such as lysosomes
and peroxisomes, or transport proteins and then manifest as
disturbances of cell transport and processing. It is often
cumulative diseases.
• Among macromolecules whose metabolism may be affected
belong [1]: sphingolipids, glycosaminoglycans
(mucopolysaccharides), oligosaccharides, myelin, fatty acid with
a long chain etherphospholipides (plasmalogens), phytates and
others.
• Glycoproteinoses
• Mucopolysaccharidoses 106Pathobiochemistry carbohydrates-
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Mucopolysaccharidosis
• Hereditary disorders of lysosomal enzymes activity
(partial degradation of cellular metabolites, which
accumulate intracellularly + are toxic to the organ
systems: CNS, eye, bone, visceral organs)
• Typical disproportionate growth failure with skeletal
deformities
• mucopolysaccharides are stored in hepatocytes and
Kupffer cells, enlarged liver
• Mucopolysaccharidoses are metabolic disorders of mucopolysaccharides[1]. They are
hereditary disorders of lysosomal enzymes activity (partial degradation of cellular
metabolites, which accumulate intracellularly + are toxic to the organ systems: CNS,
eye, bone, visceral organs). [2]
• All mucopolysaccharidoses are characterized by disproportionate disorder of growth
with skeletal deformities. [1] Various mucopolysaccharides are stored in hepatocytes
and Kupffer cells. The liver is enlarged. Fibrosis or cirrhosis are not rare. [3]
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Mucopolysaccharidosis type I. (Hurler syndrome, gargoylism)
deficiency of α-L-iduronidase, exoglycosidase, which cleaves IdUA from non-reducing end of
dermatansulphate, heparasulphate, accumulation of dermatansulphate, AR heredity, enlargement of
the skull, thick hair, the term "Gargoyles" (low brow, broad nose, enlarged lips), blindness, deafness,
severe mental retardation, deformity of the chest, hepatosplenomegaly,
Mucopolysaccharidosis type II. (Hunter syndrome)
deficiency of L-iduronosulphatesulphatase enzyme, accumulation of heparansulphate (GR
inheritance, men)
severe form: faster progression and mortality in 15. year of life, heart failure, macrocephalus,
malformed teeth, hepatosplenomegaly, hearing disorders, dementia, cardiomegaly, narrowing of the
coronary arteries
lightweight form: handicapped can live up to 50 years, slowed growth, flexed posture of the fingers,
retinitis pigmentosa, normal intellect, frequent impaired hearing
Mucopolysaccharidosis type III. (Sanfilippo syndrome)
accumulation of heparansulphate, dominates the affection of CNS, mental retardation, hyperactivity,
aggression
Mucopolysaccharidosis type IV. (Morquio syndrome)
keratansulphate and chondroitinsulphate accumulation
significant affection of the skeleton
Mucopolysaccharidosis type V. (formerly Scheie syndrome)
mild skeletal manifestations
Mucopolysaccharidosis type VI. (Maroteaux–Lamy syndrome)
accumulation of dermatansulphate, short stature, systemic organ impairment, skeletal deformity
Mucopolysaccharidosis type VII.
AR inheritance, mutation of β-glucuronidase
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Glycoproteinoses
• usually AR heredity
• Symptoms are similar to mucopolysaccharidoses, but
there neither cummulation of mucopolysaccharides
neither nor mucopolysachariduria
• fragments of glycoproteins are present in urine
• leads to lysosomal distention and secondarily induced
increased activity of lysosomal enzymes
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Glycoproteins
• are proteins that have a central chain with
covalently bound oligosaccharides
• the weight proportion of carbohydrates in the
molecule is from 1% to 85%
• saccharide units unlike glycosaminoglycans do not
alternate regularly
• have predominantly neutral character
• very frequent saccharides are fucose and sialic
acid
• have different functions, such as antigens,
enzymes
• are a standard part of membranes, have catalytic
functions, are carriers of immunological
specificity, are part of the mucus and also
extracellular matrix
•
carrier protein is synthesized on the rough ER, in the GA saccharides are bound to it
in two ways:
O-glycosidic bond to OH group of serine or threonine protein by N-acetylglucosamine
saccharide chain
N-glycosidic bond to NH2 group of asparagine protein by N-acetylglucosamine, to
which saccharide chain has been transferred from dolicholpyrophosphte carrier
degradation in lysosomes by endoglycosidases (fucosidase, aspartylglukosaminidase) and
exoglycosidases (galactosidase, neuraminidase, hexosaminidasa, mannosidase)
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Selective disorders of N-glycosylation
CDG-Ia, phosphomannomutase 2 deficiency
Retracted (inverted) nipples, an abnormal distribution of fat, strabismus, cerebellar hypoplasia,
facial dysmorphia, convulsions and some level of psychomotor retardation
Stroke-like episodes, peripheral neuropathy, skeletal abnormalities
Clinical course in three stages
1. multisystem disease in infancy
2. ataxia and mental retardation in late infancy and childhood
3. stable disability in adulthood
CDG-Ib, phosphomannose isomerase deficiency
Phosphomannose isomerase: step in the synthesis of GDP-mannose: fructose-6-P mannose-6-P
diarrhea and cyclical vomiting, severe hypoglycemia, failure to thrive, hepatic fibrosis, enteropathy
with proteins losses, coagulation disorders, without neurological impairment
Treatment: mannose 1g/kg/day (hexokinase: mannose  mannose-6-P)
CDG-Ic
Symptoms of CDG-Ic are similar to those of CDG-Ia but much less severe. Patients have frequent
seizures, psychomotor retardation that is milder than in CDG-Ia, pronounced axial hypotonia, and
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• Mucolipidosa I (Sialidosa)
• deficit of sialidase (neuraminidase)
• Normosomatic form
• massive myoclonus (spasmodic twitching of muscles) induced by emotion and
movement, red stains on the fundus
• Dysmorphic form
• dysmorphia with Hurleroid features
• Mucolipidose II (Inclusion Disease, I-cell disease)
• GlcNAc-phosphotransferase mutations
• abnormal transfer of GlcNAc-1-phosphate into newly synthesized lysosomal enzymes, and thus these enzymes are
missing Man-6-phosphate, which would send them to the lysosomes
• hydrolases missing in lysosomes, material accumulates therein, which gives rise to an inclusion bodies
• Clinical manifestations as dysmorphia of Hurleroid type
• Mannosidosa
• deficit of acid α-mannosidase
• expressive facial dysmorphia
• opacity of the lens, cataracts of the lens
• skeletal disorders
• Fukosidose
• deficiency of α-L-fucosidase
• clinically manifests after the first year by the initial hypotonia, mental and motor retardation
• often ends by Abnormal decerebral rigidity before 6 years of age
• mild facial dysmorphia
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Hereditary disorders of sugar metabolism
Diseases caused by defects in the synthesis of N-glycans
Congenital disorders of glycosylation Congenital disorders of glycosylation (CDG)
are diseases, whose cause lies in defective enzymes that are involved in the synthesis of
oligosaccharide chains of glycoproteins. These diseases include diseases with impaired
N- glycosylation, O- glycosylation, combined disorders N-a O- glycosylation, and disorder of lipid glycosylation.
The most common cause CDG is defective synthesis of N-glycan. So far is known 21 enzymes in the synthesis of N-glycan
that may be defective. The term N-glycan is used for N-linked oligosaccharides and polysaccharides.
• There was discovered over 20 types of congenital disorders of glycosylation.
• It is expected that most CDG will have been discovered.
• Congenital disorders of glycosylation are divided into two groups– I a II, by defect pathways.
• Each of these two groups includes a subset of another, by a defective enzyme.
• Type I CDG – assembly disorder including disorders of dolicholphosphate producing
• Type II CDG – disrorder of transport (processing)
Glucosa-6-phosphate dehydrogenase deficiency
Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency) or fabismus or favismus
worldwide are among the most common enzyme defects.
G6PD deficiency increases the sensitivity of erythrocytes to oxidative stress.
Clinically, it manifests neonatal jaundice, acute hemolysis and rarely chronic hemolytic anemia.
People with this disease may be asymptomatic in some cases.
It is an X-linked inherited disease that occurs primarily in Africa, Asia, Mediterranean and Middle East.
The number affected is estimated at 400 million people.
There are known various types of genetic mutations in the G6PD gene (Xq28, OMIM: 305900)
responsible for different types of G6PD with differently severe clinical manifestations.[1][2]
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