Aim: 

Aquaporin-9 (AQP9) and glycerol kinase (GlyK) are involved in the initial hepatic handling of glycerol, a precursor for gluconeogenesis and lipogenesis. The aim of this study was to evaluate the influence of gender upon regulation of hepatic AQP9 and GlyK expression in starved rats.

Methods: 

The effect of starvation was evaluated in male and female rats as well as in ovariectomized (ovx) rats. AQP9 and GlyK expression levels were evaluated by immunoblotting and immunohistochemistry. In addition, stopped flow light scattering measurement on hepatocyte membrane vesicles was used to evaluate glycerol transport.

Results: 

Starved males demonstrated a more than 2-fold increase in hepatic AQP9 abundance whereas no effect upon hepatic AQP9 expression was observed in female rats. Coordinately, plasma glycerol levels were unchanged in male rats whereas it was increased in starved females. In addition, hepatocyte membrane glycerol transport from starved males showed higher permeability when compared to females. The hepatic GlyK expression was not affected by starvation, however in the fed state, the abundance was ~ 2-fold higher in males as compared to females. Starvation of ovx rats resulted in an increased expression of AQP9 similar to what was observed in starved males when compared to fed ovx rats, whereas GlyK abundance remained unchanged. Like in starved males, no increase in plasma glycerol was observed in the starved ovx females.

Conclusion: 

These results demonstrate that sexual dimorphism exists in the initial hepatic handling of glycerol in starved rats and our data suggest that female gender is involved in preventing the increased hepatic AQP9 abundance observed in starved males.