Differential expression of sirtuin 2 and adipocyte maturation restriction: an adaptation process during hypoxia in fish

Abstract

Sirtuins have received wide spread attention due to their diverse physiological role in metabolism. Among sirtuins, SIRT2 is more abundant in adipocytes; exerts effect on adipocyte differentiation, a process involves conversion of preadipocytes to mature adipocytes orchestrated by adipokines and adipogenic transcription factors. Grey mullets (Scientific name: Mugil cephalus) were chosen as study organism due to its excellent serve as a biomonitor. Adipocytes isolated from natural field condition were termed as field hypoxic (Ennore) and normoxic (Kovalam) based on DO level in the estuary. Previous study portrayed the hypoxic instance of Ennore estuary (low DO) and grey mullet (HIF1α in adipocytes, brain EC and hepatocytes) inhabiting this estuary. In this context, fish adipocytes of both conditions were subjected to in vitro hypoxia for 1h (in the pre/trigassed incubator with the supply of 1% O2; 94% N2; 5% CO2) and analyzed the expression of adipokines, adipogenic transcription factors and anti-adipogenic markers in fish adipocytes. Elevation of ADMA, TNFα and leptin along with decreased adiponectin, adipogenic transcription factors and altering sirtuins were observed in test adipocytes and in control adipocytes on in vitro hypoxia. It suggests that adipocytes may follow internal caloric restriction as portrayed from cytomorphological/ultrastructural analysis, limiting adipocyte maturation process, one of the adaptive mechanisms triggered by adipocyte of fish surviving in Ennore estuary. Prolonged exposure to hypoxia (test on in vitro hypoxia for 1h) showed a drastic alteration in these components leading to both structural and biological fluctuation when compared to limited hypoxic condition (field hypoxic and control on in vitro hypoxia). Our study concludes that hypoxia may serve as the chief molecular cue in eliciting adipocyte maturation restriction though metabolic reprogramming and it also emerges the significance of adipocyte maturation restriction in imparting survival mechanism.