Role of insulin in lipid metabolism:

Fat cells responds to insulin with in minutes of its administration. There will be reduction in the release of fatty acids from fat stores. At the same time there will be increase in the synthesis of triacylglycerol to increase fat esterification and storage. So overall effect is decrease in fatty acids in blood.

Insulin inhibits an enzyme called ‘lipase’ in fat cells. Lipase function is to breakdown fat and release free fatty acids in to the blood. Once it’s activity is inhibited by insulin, it  no longer releases fatty acids from stored fat. Insulin also increases the activity of another enzyme called ‘lipo protein lipase’ in blood vessel endothelial cells. The function of lipoprotein lipase is to synthesize triacylglycerol using free fatty acids. So fatty acid levels are decreased.

So what happens in diabetes?

Type 1 -

In diabetes there is deficiency of insulin. The chylomicrons and VLDL (both are types of lipoproteins in blood that carry triglycerides from intestinal food and liver respectively) are released in to blood waiting for the enzyme lipoprotein lipase to act. Because of insulin deficiency which is needed by it, the enzyme can not function to its full extent. This increases triglycerides in blood causing ‘Hypertriglyceridemia’, a type of high cholesterol state.

Type 2 -

The above mechanism also operates in type 2 diabetes. In addition there will be some other mechanisms are responsible for hypertriglyceridemia in type 2. In type 2 there is insulin resistance state which is not an ideal condition for the enzyme lipoprotein lipase. And also the type 2 diabetics are obese, where there will be excess VLDL, related to obesity. VLDL is not metabolized completely increasing the levels of ‘Intermediate density lipoproteins’ in the blood. (IDL carries very high cholesterol in them)

Complications of excess cholesterol:

Most important complication is atherosclerosis. Atherosclerosis is deposition of lipid in the inner layers of arteries causing thickening and plaque like formation. The plaque can further develop to cause weakening of the artery wall leading to dilatation and rupture of the artery, clot forms on it’s surface which dislodges and cause embolism. These emboli may block the small arteries and cause ischemia of the organ.

When coronary arteries which supply the heart are involved, patient will suffer from heart attacks due to myocardial infarction. When artery is blocked by the growing plaque, which occludes the lumen, then also myocardial infarction may occur.

Management:

* Fat restriction. (cholesterol levels are determined accurately before starting the treatment)

* Exercise. 30 - 60 minutes of aerobic exercise, walking etc will be done. Exercise reduce body weight and decrease insulin resistance.

* Controlling blood sugar.

* Avoiding alcohol.

* Drugs like niacin, Gemfibrozil. Good cholesterol and hypertension control is advised in diabetes as the risk of atherosclerosis increased.

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