Adipocyte-specific Nos2 deletion improves insulin resistance and dyslipidemia through brown fat activation in diet-induced obese mice

OBJECTIVE

Inducible nitric oxide (NO) synthase (NOS2) is a well documented inflammatory mediator of insulin resistance in obesity. NOS2 expression is induced in both adipocytes and macrophages within adipose tissue during high-fat (HF)-induced obesity.

METHODS

Eight week old male mice with adipocyte selective deletion of the Nos2 gene (Nos2^AD-KO) and their wildtype littermates (Nos2^fl/fl) were subjected to chow or high-fat high-sucrose (HFHS) diet for 10 weeks followed by metabolic phenotyping and determination of brown adipose tissue (BAT) thermogenesis. The direct impact of NO on BAT mitochondrial respiration was also assessed in brown adipocytes.

RESULTS

Here, we show that HFHS-fed Nos2^AD-KO mice had improved insulin sensitivity as compared to Nos2^fl/fl littermates. Nos2^AD-KO mice were also protected from HF-induced dyslipidemia and exhibited increased energy expenditure compared to Nos2^fl/fl mice. This was linked to activation of BAT in HFHS-fed Nos2^AD-KO mice as shown by increased Ucp1 and Ucp2 gene expression and augmented respiratory capacity of BAT mitochondria. Furthermore, mitochondrial respiration was inhibited by NO, or upon cytokine-induced NOS2 activation, but improved by NOS2 inhibition in brown adipocytes.

CONCLUSIONS

These results demonstrate a key role for adipocyte NOS2 in the development of obesity-linked insulin resistance and dyslipidemia, partly through NO dependent inhibition of BAT mitochondrial bioenergetics.