Question

Write one to two paragraphs describing the role of insulin in the metabolism of glucose, fat, and protein. Also, discuss how insulin is related to the manifestations of diabetes.

Answer 1

On Carbohydrate Metabolism.
Insulin is the only antidiabetic hormone secreted in the body, i.e. it is the only hormone in the body that reduces blood glucose level. Insulin reduces the blood glucose level by its following actions on carbohydrate metabolism:
i. Increases transport and uptake of glucose by the cells.   
ii. Promotes peripheral utilization of glucose
iii. Promotes storage of glucose – glycogenesis
iv. Inhibits glycogenolysis
v. Inhibits gluconeogenesis.
Thus, insulin decreases the blood glucose level by: i. Facilitating transport and uptake of glucose by
the cells
ii. Increasing the peripheral utilization of glucose
iii. Increasing the storage of glucose by converting it into glycogen in liver and muscle
iv. Inhibiting glycogenolysis
v. Inhibiting gluconeogenesis.
On Protein Metabolism
Insulin facilitates the synthesis and storage of proteins and inhibits the cellular utilization of proteins by the following actions:
i. Facilitating the transport of amino acids into the cell from blood, by increasing the permeability of cell membrane for amino acids
ii. Accelerating protein synthesis by influencing the transcription of DNA and by increasing the translation of mRNA
iii. Preventing protein catabolism by decreasing the activity of cellular enzymes which act on proteins
iv. Preventing conversion of proteins into glucose.
Thus, insulin is responsible for the conservation
and storage of proteins in the body.
. On Fat Metabolism
Insulin stimulates the synthesis of fat. It also increases the storage of fat in the adipose tissue.
Actions of insulin on fat metabolism are:
i. Synthesis of fatty acids and triglycerides
Insulin promotes the transport of excess glucose into cells, particularly the liver cells. This glucose is utilized for the synthesis of fatty acids and triglycerides. Insulin promotes the synthesis of lipids by activating the enzymes which convert:
a. Glucose into fatty acids
b. Fatty acids into triglycerides.
ii. Transport of fatty acids into adipose tissue
Insulin facilitates the transport of fatty acids into the
adipose tissue.
iii. Storage of fat
Insulin promotes the storage of fat in adipose tissue by inhibiting the enzymes which degrade the triglycerides.

insulin is related to the manifestations of diabetes

Type I Diabetes Mellitus
Type I diabetes mellitus is due to deficiency of insulin because of destruction of β-cells in islets of Langerhans. This type of diabetes mellitus may occur at any age of life. But, it usually occurs before 40 years of age and the persons affected by this require insulin injection. So it is also called insulin-dependent diabetes mellitus (IDDM). When it develops at infancy or childhood, it is called juvenile diabetes.
Type I diabetes mellitus develops rapidly and pro- gresses at a rapid phase. It is not associated with obesity, but may be associated with acidosis or ketosis.

Type II diabetes mellitus is due to insulin resistance (failure of insulin receptors to give response to insulin). So, the body is unable to use insulin. About 90% of diabetic patients have type II diabetes mellitus. It usually occurs after 40 years. Only some forms of Type II diabetes require insulin. In most cases, it can be controlled by oral hypoglycemic drugs. So it is also called noninsulin- dependent diabetes mellitus (NIDDM).