Oral Presentation ANZOS-OSSANZ-AOCO Joint Annual Scientific Meeting 2017

AMPK in ghrelin receptor-expressing ventromedial hypothalamic neurons controls body weight gain. (#168)

Sasha Rawlinson 1 , Romana Stark 1 , Zane Andrews 1
  1. Monash University, Clayton, VIC, Australia

Obesity is a leading health problem and its prevalence is increasing worldwide at an alarming rate. It is currently estimated that 1 in 10 people in the world are obese. Ghrelin is an orexigenic peptide hormone that drives an increase in food intake and body weight by acting on growth hormone secretagogue receptors (GHSRs), expressed in many regions of the brain. However, the exact sites and mechanisms of actions of the hormone remain unknown. The GHSR is highly expressed in the ventromedial hypothalamus (VMH), a crucial region involved in energy homeostasis. AMP-activated protein kinase (AMPK) is required to convey the ghrelin signal, such as in the arcuate nucleus to ultimately increase food intake, but the role of AMPK in GHSR-expressing VMH neurons is yet to be explored. We thus hypothesise that AMPK in GHSR-expressing neurons of the VMH contributes to the control food intake, energy expenditure, and regulates body weight gain. We knocked down AMPK activity in GHSR-expressing VMH neurons via stereotaxic injections of cre-dependent adeno-associated viruses in the GHSR cre mouse line, rendering the AMPK α2 subunit inactive. Injections sites were verified using immunohistochemistry for mCherry expression in the VMH. Down-regulation of AMPK activity in GHSR VMH neurons resulted in an increase in body weight on a chow diet over 8 weeks compared to controls, but no significant change in food intake. Energy expenditure was analysed using calorimetry. AMPK knock down impaired glucose tolerance, while no differences were observed during an insulin tolerance test and a 2-Deoxy-D-Glucose challenge test. Our data thus suggests that AMPK in GHSR VMH neurons is important to regulate glucose and energy homeostasis. Future studies are required to test whether these neurons are important for regulating responses to fasting and ghrelin administration.