Efeitos da cronicidade da dieta hiperlipídica no remodelamento do tecido adiposo marrom

Abstract

Excessive intake of a diet rich in saturated fat causes an imbalance in energy homeostasis, being one of the main causes for obesity onset, leading to dysfunction of brown adipocytes and, consequently, a decrease in thermogenic capacity, with morphological and functional alterations called whitening. The present study aimed to evaluate the effects of the chronicity of the high-fat diet on brown adipose tissue remodeling, aiming to elucidate the pathways involved in this process. Sixty male C57BL/6 mice (three months old) were randomly assigned to receive a control diet (C, 10% energy as lipids) or a high-fat diet (HF, 50% energy as lipids) for 12, 16 or 20 weeks (C12, HF12, C16, HF16, C20 and HF20). The animals in the HF groups had overweight, oral glucose intolerance, and substantial accumulation of intra-abdominal and subcutaneous fat pads. Furthermore, the animals in the HF groups showed brown adipocyte dysfunction with loss of thermogenic capacity, increased expression of vascular rarefaction, inflammation, and apoptotic markers. These functional changes were accompanied by morphological alterations in brown adipocytes that showed an increase in the lipid droplet size, characterizing the whitening of this tissue. In conclusion, the HF diet caused brown adipocyte dysfunction (whitening) after 12, 16 and 20 weeks. The increase in the size of the lipid droplet caused the brown adipocyte to assume a closer arrangement to the white (unilocular) adipocyte, with a consequent reduction in its thermogenic capacity. Inflammation and endoplasmic reticulum stress appear to mediate structural and functional changes in brown adipose tissue in obesity.