Endocrine Abstracts

Obesity is thought to be a main risk factor of insulin resistance and diabetes mellitus. Study on concentrations of lipids in the tissues of animals with experimental model of obesity resulting in insulin resistance remains currently central. The work was initiated to study the spectrum of lipids and their concentrations in the tissues of experimental animals with the induced alimentary obesity.

Alimentary obesity with concurrent insulin resistance was induced in the outbred rats by means of a 6-month high-calorie carbohydrate diet. The thin-layer chromatography was used to determine the spectrum of lipids (Kates, 1975); neutral lipids were measured spectrophotometrically (Prokhorova, 1982), while phospholipids were measured by phosphorus (Vaskovsky et al., 1975).

The model of obesity and insulin resistance induced, body mass and body fat mass of rats was found to increase by 62% and 6.2%, respectively. The blood glucose and cholesterol were found to increase, but insulin sensitivity of some tissues declined. As to lipid composition in the skeletal muscle of animals with alimentary obesity, lysophosphatidylcholine (LPC), phosphatidylethanolamine (PE) and cardiolipin were found toincrease by 18%, 17% and 10%, respectively, whilesphingomyelin (SPH), phosphatidylcholine (PC), phosphatidylinositol (PI) and phosphatidylserine (PS) reduced by 41%, 24%, 17% and 39%, respectively; total phospholipids were found to decrease by 16%. In the liver tissues of rats with alimentary obesity, lysophosphatidylcholine (LPC), cardiolipin and phosphatidic acid (PA) were observed to reduce by 280%, 7% and 29%, respectively, while LPC, PC, PI and PS were found to decrease by 31%, 24, 3% and 5%, respectively. The increase in LPC and PA in the tissues under study could be the evidence for activation of phospholipases taking place in alimentary obesity. The neutral lipids, such as cholesterol, non-esterified fatty acids and total lipids were established to increase by 33%, 60% and 22%, respectively, in the skeletal muscle, and by 23%, 49% and 17% in the liver tissues, respectively

Our findings demonstrated that in the alimentary obesity model with the increased blood glucose and cholesterol there are changes in lipid composition of the insulin sensitive tissues. The changes are likely to produce an effect on the receptor sites of insulin in the tissues under study and cause the onset of insulin resistance.