The Long-Term Effects of High-Fat and High-Protein Diets on the Metabolic and Endocrine Activity of Adipocytes in Rats

Abstract

The increasing prevalence of overweight and obesity and the rising awareness of their negative consequences are forcing researchers to take a new view of nutrition and its consequences for the metabolism of whole organisms as well as the metabolism of their individual systems and cells. Despite studies on nutrition having been carried out for a few decades, not many of them have focused on the impacts of these diets on changes in the metabolism and endocrine functions of isolated adipocytes. Therefore, we decided to investigate the effects of the long-term use (60 and 120 days) of a high-fat diet (HFD) and of a high-protein diet (HPD) on basic metabolic processes in fat cells—lipogenesis, lipolysis, and glucose uptake—and endocrine function, which was determined according to the secretion of adipokines into the incubation medium. Our results proved that the HPD diet improved insulin sensitivity, increased the intracellular uptake of glucose (p < 0.01) and its incorporation into lipids (p < 0.01) and modulated the endocrine function of these cells (decreasing leptin secretion; p < 0.01). The levels of biochemical parameters in the serum blood also changed in the HPD-fed rats. The effects of the HFD were inverse, as expected. We observed a decrease in adiponectin secretion and a diminished rate of lipogenesis (p < 0.01). Simultaneously, the secretion of leptin and resistin (p < 0.01) from isolated adipocytes increased. In conclusion, we noted that the long-term use of HPD and HFD diets modulates the metabolism and endocrine functions of isolated rat adipocytes. We summarize that an HFD had a negative effect on fat tissue functioning, whereas an HPD had positive results, such as increased insulin sensitivity and an improved metabolism of glucose and lipids in fat tissue. Moreover, we noticed that negative metabolic changes are reflected more rapidly in isolated cells than in the metabolism of the whole organism.