Nipsnap1 – A Novel Thermogenic Regulator

Abstract Objectives We aim to discover molecular treatment options to combat obesity by studying a process known as non-shivering thermogenesis (NST). The major objective is to determine if Nipsnap1 can regulate NST in brown adipose tissue (BAT) and evaluate its potential for obesity treatment. Methods 1. Identification of Nipsnap1 and loss-of-function study•Unbiased proteomic analysis is performed on BAT isolated mitochondria samples from 6-week-old mice exposed to cold to activate NST (n = 3). •siRNA-mediated knockdown of Nipsnap1 is performed on primary brown adipocytes isolated from mice. Seahorse Bioanalyzer is used for Mitochondria Respiration Test. •Thermogenic tissue-specific Nipsnap1 knockout mice (N1-KO) are generated by crossing floxed Nipsnap1 (N1-Flox) transgenic mice with UCP1-Cre mice. 2. Role of Nipsnap1 in thermogenesis•Phenotypical studies in vivo are performed on 6-week-old N1-KO and N1-Flox mice (n = 8). Mice are acclimated in 30°C followed by cold exposure in 4°C for ten days. Rectal temperature is measured. •N1-KO mice metabolism level and locomotive movement are monitored by the Sable Promethion Metabolic Cage system (n = 8). Results Nipsnap1 displays potent thermogenic properties. By unbiased proteomic analysis, we identify Nipsnap1, which is highly induced when NST is activated and strongly correlates with the NST key protein Uncoupling Protein 1 (UCP1). Nipsnap1 ablation in primary brown adipocytes reveals significant reductions in thermogenic adipose function. siNipsnap1 causes complete ablation of UCP1 protein levels. Moreover, it causes a 50% reduction (P < 0.001) of mitochondrial oxidative capacity and a 40% reduction (P < 0.05) of glycolytic capacity in cells. Nipsnap1 KO mice have impaired NST and reduced energy expenditure in vivo. Under prolonged cold exposure (day 7–10), N1-KO mice exhibit significant defects (day 10, P < 0.05) to maintain body temperature by NST. We demonstrated that the N1-KO mice had a 10% (P < 0.01) reduction in energy expenditure during the active night period after prolonged cold (day 5–8) treatment compared to controls. Conclusions Nipsnap1 plays an essential role in regulating NST. Targeting Nipsnap1 to increase energy expenditure at the molecular level will provide new insights into developing a safe and effective method to combat obesity and metabolic disease. Funding Sources Agency: NIH; Institute: NIDDK.