Efeito da dieta hipoproteica-hiperglicídica sobre o metabolismo de lipídeos e o processo de browning no tecido adiposo de ratos em crescimento

Abstract

To evaluate the browning and the origin of fatty acids (FAs) in the maintenance of triacylglycerol (TG) storage and/or as fuel for thermogenesis in perirenal adipose tissue (periWAT) and inguinal adipose tissue (ingWAT) of rats treated with a low-protein, highcarbohydrate (LPHC) diet. Methods: LPHC (6% protein, 74% carbohydrate) or control (C; 17% protein, 63% carbohydrate) diets were administered to rats for 15 days. The tissues were stained with H&E for histological analysis. The content of uncoupling protein 1 (UCP1) was determined by immunofluorescence. Levels of T-box transcription factor (TBX1), PR domain containing 16 (PRDM16), adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), lipoprotein lipase (LPL), glycerokinase (GyK), phosphoenolpyruvate carboxykinase (PEPCK), glucose transporter 4 (GLUT4), β3-adrenergic receptor (AR), β1-AR, protein kinase A (PKA), adenosine-monophosphate-activated protein kinase (AMPK), and phospho-AMPK were determined by immunoblotting. Serum fibroblast growth factor 21 (FGF21) was measured using a commercial kit (Student’s t-tests, P < 0.05). Results: The LPHC diet increased FGF21 levels by 150-fold. The presence of multilocular adipocytes, combined with the increased contents of UCP1, TBX1, and PRDM16 in periWAT of LPHC-fed rats, suggested the occurrence of browning. The contents of β1-AR and LPL were increased in the periWAT. The ingWAT showed higher ATGL and PEPCK levels, phosphoAMPK/AMPK ratio, and reduced β3-AR and PKA levels. Conclusion: These findings suggested that browning occurred only in the periWAT and that higher utilization of FAs from blood lipoproteins acted as fuel for thermogenesis. Increased G3P generation by glyceroneogenesis increased FAs re-esterification from lipolysis, explaining the increased TG storage in the ingWAT.