Sex dimorphism in the aged metabolic phenotype of smoothelin-like 1 (SMTNL1) deficient mice

Smoothelin-like 1 (SMTNL1) is expressed in smooth and skeletal muscle tissues as well as a variety of steroid hormone-sensitive tissues. SMTNL1 can play a sex-dependent regulatory role in skeletal muscle metabolism in mice. Previous studies have documented appreciable changes in muscle morphology and metabolic function of young male mice with genetic deletion of Smtnl1 . SMTNL1 can also impact the energy metabolism and insulin sensitivity of female mice during pregnancy. Therefore, we investigated the metabolic outcome of global SMTNL1 knockout (KO) in male and female mice with advancing age using a comprehensive lab animal monitoring system (CLAMS). With ageing, body weight gain was markedly higher with a concomitant increase in whole body adiposity as well as specific white adipose depots in the absence of SMTNL1. Moreover, this genotypic difference in whole body adiposity was greater in the female cohort. The deletion of SMTNL1 was also associated with delayed satiety in mice fed a high fat diet, which was more pronounced in the female mice. A significant genotypic difference was also revealed for the metabolic energy balance in 12 month old animals of both sexes. The KO animals were metabolically less efficient and displayed a preference for carbohydrate catabolism. However, reduced glucose tolerance was observed only in the female group with the deletion of SMTNL1. Taken together, the current findings establish a novel role for SMTNL1 in modulating adiposity and energy metabolism with ageing in a sex dimorphic way. ### Competing Interest Statement J.A.M. is cofounder and has an equity position in Arch Biopartners Inc. All other authors declare no conflicts of interest.