Endocrine Abstracts

Obesity is considered as a major factor of insulin resistance and diabetes mellitus risk. Study on lipid composition of tissues in obesity is relevant in understanding of mechanisms underlying insulin resistance.

Aim: The work was initiated to study lipid composition of liver and skeletal muscles tissues in rats with alimentary obesity.

Materials and methods: Obesity was induced in rats leading an inactive lifestyle with prolonged high calorie diet (standard diet + fat, sugar and margarine). After the animals’ weight of 400–500g was achieved they were sacrificed; their liver and skeletal muscles were removed for study. Lipids were extracted by Kates (1975) and fractionated by thin layer chromatography.

Results: In livers of rats with induced alimentary obesity cholesterol and triglycerides were found to increase by 23% and 48%, respectively, total phospholipids were found to decrease from 1039±37.2 μg of phosphorus per gram of tissue to 878.6±32.1 μg of phosphorus per gram of tissue documented in the control animals. Changes in the fraction composition of liver phospholipids were found in rats with the induced alimentary obesity too. Thus, lysophospholipids, cardiolipin and phosphatidic acid were found increased by 280%, 7.1% and 29%, respectively, while phosphatidylcholines, phosphatidylethanolamines and sphingomyelins were found to decrease by 9%, 34% and 31%, respectively. In the skeletal muscles of rats with alimentary obesity cholesterol and triglycerides were found to increase, while total phospholipids decreased; changes in some phospholipid fractions were oppositely directed.

Conclusions: Changes in concentrations of neutral lipids, total phospholipids and some of their fractions registered in rats with the induced alimentary obesity are thought to be caused by fluctuations in lipid metabolism and activation of lipolytic enzymes. The changes in lipid composition of tissues under study could underlie insulin resistance in alimentary obesity.