Insulin-induced acetylcholine release and the central regulation of adipose tissue thermogenesis

• Grant number: 14/01294-0
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: July 07, 2014
• End date: July 06, 2015
• Field of knowledge: Biological Sciences - Physiology - General Physiology
• Principal Investigator: Mario Jose Abdalla Saad
• Grantee: Luiz Osório Silveira Leiria
• Supervisor: Yu-Hua Tseng
• Host Institution: Faculdade de Ciências Médicas (FCM). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Institution abroad: Harvard University, Boston, United States
• Associated to the scholarship: 13/02503-0 - Insulin resistance and the central regulation of bronchial reactivity, BP.PD

Abstract

Brown adipose tissue (BAT), have an inherent capacity to convert excess food energy into thermal energy instead ATP. BAT is important for both basal and inducible energy expenditure in the form of thermogenesis mediated by the expression of the tissue specific uncoupling protein 1 (UCP1). Clusters of UCP1-expressing adipocytes with thermogenic capac¬ity also develop in white adipose tissue (WAT) in response to vari¬ous stimuli. These adipocytes have been named beige or recruitable WAT (rWAT). BAT and rWAT affects whole-body metabolism and may alter insulin sensitivity and modify susceptibility to weight gain. This is why BAT are attractive target to promote weight loss and has become a focus of biomedical research worldwide as a means to counteract the spread of obesity. Despite fat depots receives cholinergic innervation, the role of acetylcoline in the for the BAT thermogeneses is misunderstood. Our preliminary data suggests that central insulin increases parasympathetic outflow into the lungs. As these cholinergic neurons are sensitive to insulin modulation, we hypothesized that central insulin may regulate BAT and rWAT thermogenesis. Our results also shows that vesicle acetylcholine transporter knockdown mice (VAChT-/-), that have ~70% reduction in the acetylcholine release, have reduced weight gain in comparison with wild type mice when fed with high-fat diet (HFD). In addition, VAChT-/- mice had increased VO2 consumption and a higher brown color intensity of BAT in comparison with wild type mice. We aim to investigate whether insulin modulates adiposity and energy expenditure through central activation of cholinergic neurons and understand how acetylcholine regulate BAT and WAT thermogenesis. For this purpose we will use C57/N3 and VAChT-/- mice fed with either high-fat diet or standard chow diet and also will use immortalized pre-adipocytes cell culture to access cell differentiation in vitro. General metabolic measurements will be done in all groups. Indirect measure of energy expenditure will be done through respirometry, where we will measure VO2 and VCO2 consumption, in a basal state or after application of intracerebroventricular (ICV) insulin microinjection and after intraperitoneal (i.p.) application of norepinephrine, acetylcholinesterases inhibitors or muscarinic antagonists. Acetylcholine levels in the BAT and WAT will be measured under basal condition and after ICV insulin microinjection through fluorescence kit assay. Direct thermal measurement will be done through thermal imaging of skin-surface temperature. Hystological analysis and imunohistochemistry for UCP1 and for the cholinergic neurons marker, cholineacetyl transferase (ChAT), will be done on BAT and WAT. qPCR for the main markers of BAT and rWAT differentiation will be performed in the adipose tissues and in the cell culture treated or not with acetylcholine. Notwithstanding, western blot to insulin signalling pathway-involved proteins on BAT, rWAT, muscle and liver will also be done. Depending on the obtained results, more experiments may also be planned and performed. (AU)