L-carnitine improves metabolic disorders and regulates apelin and apelin receptor genes expression in adipose tissue in diabetic rats

Apelin is a new adipocytokine that acts as an endogenous hormone in various tissues through its receptor (APJ). This study aimed to investigate the effects of oral administration of L-carnitine (LC) on the expression of Apelin and APJ in adipose tissue of experimentally induced insulin-resistant and type 2 diabetic rats. In this experimental study, 60 male rats fed with high fat/high carbohydrate (HF/HC) diet. After 50 mg/kg intraperitoneally injection of streptozotocin (STZ) and confirmation of diabetes (FBS higher than 126 mg/dl), the animals were daily treated with 300 mg/kg LC for 28 days. At days 7, 14, and 28 of posttreatment, the expression of apelin and APJ in adipose tissue were determined using qPCR in diabetic, diabetic + LC treated, control, and control + LC treated groups. Apelin, insulin, TNF-α, and IL1-β were measured by the ELISA method. Results demonstrated that the rats fed with the HF/HC diet for 5 weeks were hyperinsulinemic and normoglycemic, while after STZ injection, they showed hyperinsulinemia and hyperglycemia with higher levels of HOMA-IR. Apelin serum level, APJ and apelin gene expression in adipose tissue increased significantly with the development of diabetes compared to the control group. Treatment with LC for 14 days caused a reduction in apelin and APJ expressions in adipose tissue of diabetic rats. TNF-α and IL1-β levels were reduced in diabetic rats 14 days after their treatment with LC. The study results show that L-carnitine could act as a new regulator in apelin gene expression in adipose tissue, improving the metabolic disorders in diabetic patients.