Regulation Of Blood Glucose

Question 1

Normal fasting glucose is……., after one hour of meal it is….., post-prandial is…..

Answer 1

70-100 mg%
150 mg%
140 mg%

Question 2

With respect glucose transporters (GLUTs), intestinal is….., hepatic is….., B cells of islets is….., heart/skm/adipose tissue is……& are regulated by………, other tissues is……

Answer 2

4 & SGLT1
2
2
4, insulin
1&3

Question 3

Compare kinetics of Hexokinase & glucokinase

Answer 3

1. H. has high affinity & low Km for glucose, it is saturated in the liver acting at constant rate in all normal conditions. To ensure adequate rate of glycolysis & meet liver needs.
2. G. has low affinity & high Km for glucose. Allows uptake of large amounts of glucose after meal , for glycogen & fatty acid synthesis. Prevents large amounts of glucose from entering systemic circulation & minimizing absorptive hyperglycemia.

Question 4

Describe structure & biosynthesis of insulin

Answer 4

Composed of 51AA consisting of 2 chains A(21) & B linked together by 2 disulphide bridges. Synthesis involves 2 inactive precursors preproinwulin & proinsulin that are seuentially cleaved to form active hormone & C-peptide.

Question 5

…….is a good indicator of insulin production & secretion

Answer 5

C-peptide

Question 6

Describe secretion of insulin

Answer 6

B cells are freely permeable to glucose via GLUT2 & is phosphorylated by glucokinase & there is inc glycolysis & TCA activity producing ATP which causes opening ATP-sensitive K+-channels causing depolarization & Ca++ influx causing exocytosis of insulin.

Question 7

Describe intracellular metabolic effects of insulin

Answer 7

1. Inc glycolysis by inducing glucokinase, PK1, PK
2. Inc glycogenesis by stimulating glycogen synthase & inhibit glycogenolysis by inhibiting glycogen phosphorylase
3. Inhibit gluconeogenesis by repression of pyruvate carboxylase, PEPCK, G6P&F1-6 bisphosphatase
4. Inc HMP by induction of G6PD & 6Pgluconic dehydrogenase

Question 8

List triggers for glucagon release

Answer 8

1. Dec glucose
2. Inc AAs & CAs

Question 9

Describe intracellular metabolic effects of glucagon (epinepherine)

Answer 9

1. Inc glycogenolysis in liver by stimulation of glycogen phosphorylase & inhibition of glycogen synthase
2. Inc gluconeogenesis by induction of pyruvate carboxykase, PEPCK, G6P, F1-6 bisphosphatase

Question 10

GR: Obese people have insulin resistance

Answer 10

Bec adipose tissue occasionally secretes glucocorticoids

Question 11

Describe intracellular metabolic effects of GH

Answer 11

Dec glucose uptake by muscle , may be by indirect effect as it stimulates mobilization of free fatty acids that exert the previous effect.

Question 12

Hypoglycemia is usually considered below……

Answer 12

40mg%

Question 13

List causes of hypoglycemia

Answer 13

1. Neonatal
2. Insulin-dependent hypoglycemia
3. Postprandial hypoglycemia
4. Fasting hypoglycemia
5. Alcohol-related hypoglycemia
6. Inborn errors of metabolsim

Question 14

Causes of fasting hypoglycemia

Answer 14

A. Reduction in the rate of glucose production by hepatic glycogenolysis/gluconeogenesis:
-hepatocellular damage
-renal failure
-adrenal insufficiency
B. Inc rate of glucose used by peripheral tissues due to overproduction of insulin by rare pancreatic tumors.

Question 15

GR: Occurrence of alcohol-related hypoglycemia

Answer 15

Alcohol is metabolized by 2 steps of oxidation, in which NAD+ accepts electrons and becomes NADH. The abundance of NADH leads to shift of pyruvate to lactate, OAA to malate. This causes intermediates of gluconeogenesis to divert to other pathways producing hypoglycemia & behavioural side effects of alcohol.

Question 16

List inborn errors of metabolism causing hypoglycemia

Answer 16

1. Glycogen storage disease type I, Von Geirke, glucose 6-phosphatase def
2. Hereditary Fructose intolerance
3. Galactose 1-P uridyl transferase def
4. Inborn errors of gluconeogenesis
5. Fatty acid oxidation defects (carnitine, CPT-1, medium chain acyl-CoA dehydrogenase deficiency)