Investigation of effects of centrally administration of FGF21 on hypothalamus-pituitary-thyroid axis and UCP1 gene expression

Aim: Fibroblast growth factor 21 (FGF21) is a protein which predominantly expressed by the liver, is also expressed in adipose tissue and the pancreas. FGF21 and thyroid hormones have similar effects to the regulation of energy homeostasis suggest a possible relationship between FGF21 and thyroid hormones. The present study was designed to investigate the effects of chronic intracerebroventricular (icv) administration of FGF21 on hypothalamus-hypophysis-thyroid axis and energy metabolism. Material and Method: In this study, thirty Wistar Albino male rats were used, and were divided randomly into 3 groups (n=10, in each group). No operation was applied to the rats in the control group. Rats in the experimental groups, FGF21 (0.72µg/day), and rats in sham group, intracerebroventriculary artificial cerebrospinal fluid was injected for seven days (10 µl/h). During experimental period, food intake and body weights were recorded daily. After seven days, animals were decapitated and their brain, blood, white and brown adipose tissues were taken. TRH mRNA levels in hypothalamus, uncoupling protein 1 (UCP1) mRNA levels in white and brown adipose tissues of the groups were determined by RT-PCR method. Serum T3 and T4 levels were measured by using ELISA method. Results: Groups are compared in terms of hypothalamic TRH mRNA expression, serum T3 and T4 levels, according to sham and control groups, FGF21 administration was determined to statistically increased TRH mRNA expression, serum T3 (p<0.05) and serum T4 (p<0.001). According to sham and control groups, while FGF21 infusion was significantly increased UCP1 mRNA levels in white adipose tissue (p<0.05), UCP1 mRNA levels was not changed in brown adipose tissue. Groups were compared in terms of body weight and food intake, despite FGF21 infusion increased food intake, it was not found to change the body weight (p<0.05). Conclusion: Our results suggest that icv FGF21 administration affects white adipose tissue over hypothalamic-pituitary-thyroid axis and while food intake is increased, it is not cause to increase body weight.