OB-RGRP regulates the phosphorylation of JAK2 and STAT3 in primary rat adipocytes.

This study aimed to explore the role of obestatin R gene-related protein (OB-RGRP) in autocrine signal transduction of adipocytes. Primary rat adipocytes were isolated and verified by microscopic observation and oil red O staining. OB-RGRP expression vector and OB-RGRP siRNA (si-OB-RGRP) were constructed and transfected into adipocytes. Adipocytes were then divided into five groups: (1) Control; (2) Vector (empty expression vector); (3) OB-RGRP (OB-RGRP expression vector); (4) si-OB-RGRP NC (si-OB-RGRP negative control); (5) si-OB-RGRP. mRNA and protein levels of OB-RGRP, JAK2, phosphorylated JAK2 (p-JAK2), STAT3 and phosphorylated STAT3 (p-STAT3) were examined using RT-PCR and western blot, respectively. Results showed that mRNA and protein levels of OB-RGRP in the Vector and si-OB-RGRP NC groups were similar to those in the Control group. Their levels in the si-OB-RGRP and OB-RGRP groups were significantly down-regulated and up-regulated (p < .05), respectively, in comparison with the control cells. There was no significant difference in the mRNA and protein levels of JAK2 and STAT3 among various groups. Moreover, the si-OB-RGRP NC and Vector groups induced similar ratios of p-JAK2 to JAK2 (p-JAK2/JAK2) and p-STAT3 to STAT3 (p-STAT3/STAT3) to the Control group. However, these two ratios in the si-OB-RGRP and OB-RGRP groups were significantly reduced and elevated (p < .05), respectively, in comparison with the Control group. These results suggested that OB-RGRP overexpression enhanced the levels of p-JAK2 and p-STAT3 while OB-RGRP silencing lowered their levels. In conclusion, OB-RGRP regulated the phosphorylation of JAK2 and STAT3 in primary rat adipocytes.

Endospanin1 affects oppositely body weight regulation and glucose homeostasis by differentially regulating central leptin signaling.

The hypothalamic arcuate nucleus (ARC) is a major integration center for energy and glucose homeostasis that responds to leptin. Resistance to leptin in the ARC is an important component of the development of obesity and type 2 diabetes. Recently, we showed that Endospanin1 (Endo1) is a negative regulator of the leptin receptor (OBR) that interacts with OBR and retains the receptor inside the cell, leading to a decreased activation of the anorectic STAT3 pathway. Endo1 is up-regulated in the ARC of high fat diet (HFD)-fed mice, and its silencing in the ARC of lean and obese mice prevents and reverses the development of obesity. OBJECTIVE: Herein we investigated whether decreased Endo1 expression in the hypothalamic ARC, associated with reduced obesity, could also ameliorate glucose homeostasis accordingly. METHODS: We studied glucose homeostasis in lean or obese mice silenced for Endo1 in the ARC via stereotactic injection of shRNA-expressing lentiviral vectors. RESULTS: We observed that despite being leaner, Endo1-silenced mice showed impaired glucose homeostasis on HFD. Mechanistically, we show that Endo1 interacts with p85, the regulatory subunit of PI3K, and mediates leptin-induced PI3K activation. CONCLUSIONS: Our results thus define Endo1 as an important hypothalamic integrator of leptin signaling, and its silencing differentially regulates the OBR-dependent functions.