Supplementary Material for: Increased Energy Expenditure, Lipolysis and Hyperinsulinemia Confer Resistance to Central Obesity and Type 2 Diabetes in Mice Lacking Alpha2α-Adrenoceptors
2018-11-02T10:47:04Z (GMT) by
The alpha2A-adrenoceptors (α<sub>2A</sub>-ARs) are Gi-coupled receptors, which prejunctionally inhibit the release of norepinephrine (NE) and epinephrine (Epi), and postjunctionally inhibit insulin secretion and lipolysis. We have earlier shown that α<sub>2A</sub><sup>–/–</sup> mice display sympathetic hyperactivity, hyperinsulinemia and improved glucose tolerance. Here we employed α<sub>2A</sub><sup>–/–</sup> mice and placed the mice on a high-fat diet (HFD) to test the hypothesis that lack of α<sub>2A</sub>-ARs protects from diet-induced obesity and type 2 diabetes (T2D). In addition, a high-caloric diet was combined with running wheel exercise to test the interaction of diet and exercise. HFD was obesogenic in both genotypes, but α<sub>2A</sub><sup>–/–</sup> mice accumulated less visceral fat than the wild-type controls, were protected from T2D, and their insulin secretion was unaltered by the diet. Lack of α<sub>2A</sub>-ARs is associated with an increased sympatho-adrenal tone, which resulted in increased energy expenditure and fat oxidation rate potentiated by HFD. Fittingly, α<sub>2A</sub><sup>–/–</sup> mice displayed enhanced lipolytic responses to Epi, and increased faecal lipids suggesting altered fat mobilization and absorption. Subcutaneous white fat appeared to be thermogenically more active (measured as <i>Ucp1</i> mRNA expression) in α<sub>2A</sub><sup>–/–</sup> mice, and brown fat showed an increased response to NE. Exercise was effective in reducing total body adiposity and increasing lean mass in both genotypes, but there was a significant diet-genotype interaction, as even modestly increased physical activity combined with lack of α<sub>2A</sub>-AR signalling promoted weight loss more efficiently than exercise with normal α<sub>2A</sub>-AR function. These results suggest that blockade of α<sub>2A</sub>-ARs may be exploited to reduce visceral fat and to improve insulin secretion.