CARBOHYDRATE TOLERANCE
Post on 02-Jan-2016
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CARBOHYDRATE TOLERANCE Glucose tolerance is the ability to regulate the
blood glucose concentration after the administration of a test dose of glucose (normally 1 g/kg body weight) Diabetes Mellitus decrease glucose tolerance.
Normal blood glucose levels are 50-100 mg per desi liter (500/180 - 1000/180 mmol / l).
Depend on the intake of food before the test. Patients do not febrile, not in stress.
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8 am 8 am6 pmnoon midnight
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Glucose
Insulinmeals
Blood glucose levels are relatively constant
There is also an opinion that under the normal curve160 mg/100 ml one hour and120 mg/100 ml two hours after administration of glucose.
BLOOD GLUCOSE LEVELS
Sources:1) Food2) Gluconeogenesis3) Glycogenolysis
Maintenance of blood glucose by the liver with glycogenolysis and gluconeogenesis, is under hormonal control (glucagon or if blood glucose drops very promptly epinephrine)
Coordination between organs is needed to control blood glucose
levels
Glucose
GlycogenGluconeogenesis
adipocytesliver
muscle
Food consumption
Carbohydrate metabolism Glucose turnover (basal state)
55% Oxidation
20% Glycolysis (muscle)
25% Re-uptake
(liver, gut)
10% Muscle
45% Brain
Glucose
75% Glycogenolysis
25% Gluconeogenesis
60% from lactate
If blood glucose ↓ pancreatic glucagon released, glucagon activates adenylyl cyclase, an enzyme catalyzes formation of cAMP from ATP, cAMP activates the cAMP-dependent protein kinase, which in turn will converts phosphorylase kinase b to phosphorylase kinase a (ATP as phosphate donors). Active phosphorylase kinase catalyzes phosphorylase b to phosphorylase a. Phosphorylase a break down glycogen and generate G 1P. With glucantransferase and debranching enzyme glycogenolysis will proceed until the liver depleted with glycogen. G-1P converted to G-6P and G-6Pase splits the phosphate. Glucose then enters the circulation.
Glycogenn
Glycogenn -1
G-1P G-6P G ( in the Liver ) +
Other hormones (in addition to glucagon and epinephrine)affecting blood glucose levels:InsulinGHACTHCortisolThyroid
INSULIN Secreted in inactive form
Proinsulin C peptide + insulin C peptide is more easily measuredSubstances or chemicals which stimulates insulin secretion:glucose, amino acids, free fatty acids, ketone bodies, glucagon, tolbutamide and secretine.In contrast epinephrine inhibits Insulin secretion
Insulin entrance of G into cells except liver, erythrocytes and neuronal cells.
C peptideProinsulinInsulinMW
Ca2+-dependent endopeptidases
A Chain
B Chain
PC2(PC3)
PC3
Growth Hormone:
Growth hormone may affect levels blood glucose by activating Hormone Sensitive Lipase. The resulting fatty acids, and derivatives (acetyl-CoA and ketone compounds) causes inhibition of glucose consumption by peripheral tissues
ACTH (Adreno Cortico Tropic Hormone)
Affect the metabolism of carbohydrates together with GH increase gluconeogenesis
Cortisol: enhance gluconeogenesis
Renal function in Carbohydrate Metabolism
As a “safety clap“. If blood glucose ↑ , some will be excreted through the kidneys (renal threshold)Renal threshold: 170 - 180 mg / dl.Glucosuria occurredTubule reabsorption capability350 mg / min.
Carbohydrate metabolism Glucose turnover (basal state)
55% Oxidation
20% Glycolysis (muscle)
25% Re-uptake
(liver, gut)
10% Muscle
45% Brain
→ Glucose
75% Glycogenolysis
25% Gluconeogenesis
60% from lactate
Biomedical importance
Normal metabolism: hunger if not prolonged, sports, pregnancy and lactation
Abnormal metabolism: lack of certain foodstuffs, as well as enzyme deficiencies or because of abnormal hormone secretion. The most interesting disease to study is diabetes mellitus ( DM ).
Glycolysis: Pyruvate kinase enzyme hemolytic anemia.Malignant tumor ↑ lactic acidHeart can not tolerance unaerobic glycolysis
Glycogen: abnormal accumulation of I VIII
Oxidation of pyruvic acid: vitamin deficiency vit. B1 beri-beri
MP Shunt: G6PD deficiency hemolytic
Fructose: Essential Fructosuria, "hereditary" fructose intoleranceSorbitol: ↑ peristalsis
Diabetes Mellitus: ↓ glucose utilization
Hemolytic can be caused by deficiency of thefollowing enzymes:PFK-1 (phosphofructo kinase-1)Pyruvate kinaseG6PD (glucose 6 phosphate dehydrogenase)
High dietary fructose or fructose infusioncan cause:↓ inorganic phosphate (Pi) ↓ ATP synthesisDecreases in inhibition of Purine synthesisby ATP ↑ Uric acid (uric acid)
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