The role of a VGF derived peptide in the regulation of food intake in a seasonal rodent

The Siberian hamster has evolved a strategy to promote winter survival whereby decreasing photoperiod induces both catabolization of fat reserves and a reduction in food intake, resulting in bodyweight loss of 30–40%. We have recently observed that VGF (nonacronymic) mRNA in the dorsomedial posterior hypothalamic nucleus (dmpArc) of the Siberian hamster is photoperiodically regulated with significantly higher expression associated with weight loss in short photoperiod. This suggests a potential role for VGF in the regulation of metabolism. Our aim was to determine whether VGF peptide(s) may be involved in the reduction of food intake and bodyweight in Siberian hamsters during exposure to winter photoperiod. Recently, Bartolomucci et al. (2005) described a metabolic role for the VGF derived peptide TLQP-21 in rats (Society of Neuroscience, 2005). Thus, we investigated the acute and chronic effects of this VGF derived peptide in hamsters maintained on long photoperiod. In the first study, hamsters received a single infusion of saline or VGF into the 3rd ventricle. A reduction in food intake was observed at 1 h post-injection, an effect which persisted for 24 h post-injection. A decrease in bodyweight was also observed 24 h post-injection. No hyperactivity or sedation was observed at any time point. In the second study, hamsters were sub-chronically infused into the 3rd ventricle with either saline or VGF for 7 days. A significant decrease in food intake and bodyweight was occurred throughout the study. This decrease in bodyweight reflected by a reduction in adiposity. Epidiymal white adipose tissue weight at day 7 was significantly decreased in VGF-treated hamsters when compared to controls (Day 7: saline, 1.4 ± 0.2 g; VGF, 0.6 ± 0.1 g; p < 0.005). These data demonstrate that the VGF derived peptide, TLQP-21, has catabolic effects. However more importantly, these data are consistent with the hypothesis that increased VGF peptide synthesis in the dmpArc may contribute to the catabolization of fat reserves and the reduction in food intake observed in Siberian hamsters maintained in short photoperiod. (Supported by BBSRC/SEERAD project Grant BBS/B/10765.)