The blood glucose level must be maintained between the normal range of 70-100mg/dL, Level above this range are known as hyperglycemia; and levels below this range are known as hypoglycemia. Just after the meal which includes a lot of carbohydrates, the level of blood glucose reaches 120-140mg/dl. The factors which maintains the blood glucose level are:

1. hormones
2. metabolic processes
3. renal mechanism

The liver controls the blood glucose level in the body. it can easily increase or decrease the concentration of blood glucose according to the need of the body. This easy uptake or release by liver is regulated by two hormones:

• Insulin (hypoglycemic hormone)
• Glucagon (hyperglycemic hormone)

Maintenance of glucose in well-fed condition (hyperglycemic condition)

Normally there is an increased blood glucose level just after the meal which is known as postprandial hyperglycemia. Increased level of glucose increases the release of insulin. This hormone reduces the blood glucose level in following ways

• By stimulating the active the active transport of glucose across cell membranes of muscle and adipose tissue by stimulating GLUT-4 transporter.
• In liver, insulin increases the use of glucose by glycolysis and by inducing the synthesis of main enzymes for glycolysis which are: glucokinase, phosphofructokinase, pyruvate kinase. Glucokinase is important in regulating the blood glucose level after meal
• In muscle and liver, the insulin stimulates the glycogenesis (formation of glycogen) by stimulating glycogen synthase enzyme
• Insulin also inhibits the gluconeogenesis to stop the further formation of glucose.
• Insulin increases protein synthesis and decreases the catabolism of protein which in turn increases the release of amino acids.

Maintenance of blood glucose in fasting state (hypoglycemic condition)

Hypoglycemic condition causes the release of hyperglycemic hormones

Glucagon:- Glucagon produces the opposite effect to that of insulin. It performe ollowing functions

1. In liver it stimulates the glycogenolysis and inhibits the glycogen synthesis
2. It also exert its effect on metabolic processes through the generation of cAMP.
3. It enhances the gluconeogenesis from amino acids and lactate

Epinephrine or Adrenaline:- It is secreted by adrenal medulla and performs two functions:

1. It stimulates glycogenolysis in the liver and muscle by stimulating the phosphorylase activity
2. In muscle, glycogenolysis occurs with formation of lactate

Glucocorticoids:- This hormone is secreted by adrenal cortex which increases gluconeogenesis, protein catabolism, hepatic uptake amino acids.

Thyroxine:- t is secreted by thyroid gland. thyroxine stimulates the hepatic glycogenolysis. It also increase the absorption of hexoses from intestine.

Renal control Mechanism

When blood glucose level rises to high level, the kidney also shows the regulatory effect. Glucose is continuously filtered by the glomeruli and is reabsorbed completely by the renal tubules. The capacity of the renal tubules to reabsorb the glucose is 350mg/min which is known as tubular maximum for glucose(TmG).

If the blood glucose level is above 180mg/100ml, the tubular reabsorption of glucose does not occur completely and the extra amount of glucose is then excreted through the urine. This is known as glucosuria.

The 180mg/100ml is the limiting level of glucose in the blood. If the blood glucose rises this level, the the reabsorption does not occur completely. This is known as renal threshold value of glucose.

Multiple choice question

(MCQs)

1. What is the normal range of blood glucose level?
   A. 80-120mg/dl B. 70-100mg/dl
   C. 120-180mg/dl D. 120-350mg/dl
2. which factor controls the blood glucose level?
   A. renal mechanism B. hormones
   C. metabolic processes D. all of the above
3. Which hormone is known as hyperglycemic hormone?
   A. insulin B. growth hormone
   C. glucagon D. aldosterone
4. Which hormone is known as hypoglycemic hormone?
   A. insulin B. growth hormone
   C. glucagon D. aldosterone
5. Match the following-
   a. insulin 1. Secreted by adrenal medulla
   b. glucagon 2. Secreted by beta cells of pancreatic islets
   c. glucocorticoids 3. Secreted by alpha cells of pancreatic islets
   d. epinephrine 4. Secreted by adrenal cortex
6. During a well fed condition, which cycle is mostly stimulated?
   A. glycolysis B. HMP shunt
   C. glycogenolysis D. TCA cycle
7. During a fasting condition, which cycle is mostly stimulated?
   A. glycolysis B. HMP shunt
   C. glycogenolysis D. TCA cycle
8. Which of the following statement is NOT true?
   A. insulin is a hyperglycemic hormone
   B. glucagon is a hyperglycemic hormone
   C. insulin inhibits gluconeogenesis
   D. thyroxine increases the absorption of hexoses from intestine
9. What is the tubular maximum for glucose?
   A. 200mg/min B. 350mg/min
   C. 120mg/min D. 150mg/dl
10. Which of the following hormones are necessary in regulating the hyperglycemic condition?
    A. glucagon B. adrenaline
    C. thyroxine D. none of the above
11. What is the renal threshold value for glucose?
    A. 180mg/100ml B. 150mg/200ml
    C. 70mg/100ml D. 100mg/100ml
12. Thyroxine is secreted by which gland?
    1. Adrenal gland B. pituitary gland
       C. thyroid gland D. parathyroid gland
13. Which of the following is not the function of glucocorticoids?
    A. uptake of amino acid B. protein anabolism
    C. protein catabolism D. stimulates gluconeogenesis
14. Which enzyme regulates the blood glucose level after meal?
    A. glucokinase B. phosphofructokinase
    C. glycogen synthase D. branching enzyme
15. Which tissue converts the glucose to glycerol-3-phosphate ?
    A. adipose tissue B. areolar tissue
    C. epithelium D. elastic tissue

ANSWERS:

1. 70-100mg/dl

2. all of the above

3. glucagon

4. insulin

5. a – 3 b – 2 c – 4 d – 1

6. glycolysis

7. glycogenolysis

8. insulin is a hyperglycemic hormone

9. 350mg/min

10. none of the above

11. 180mg/100ml

12. thyroid gland

13. protein anabolism

14. glucokinase

15. adipose tissue

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REFERENCE: Pankaja Naik- Biochemistry; 4^th edition; page no:- 195-197