Differential regulation of cGMP pools during brown adipocyte differentiation

Obesity is characterized by an abnormal expansion in white adipose tissue (WAT) mass, which results in comorbidities such as, type 2 diabetes mellitus and cardiovascular disease. Brown adipose tissue (BAT), on the other hand, is distinguished by its ability to dissipate energy in the form of heat through a process called non-shivering thermogenesis, making it a promising target to combat obesity. Previous research has shown that cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) play a major role in BAT function. They enhance brownadipocyte(BA) differentiation, lipolysis, thermogenesis, mitochondrial biogenesis, energy expenditure and are able to induce browning of WAT. While the downstream effects of cGMP on BA differentiation have been investigated, the differences between the function and characteristics of local cGMP pools derived from either soluble guanylate cyclase (sGC) or particulate GCs (natriuretic peptide receptor A and B; NPRA and NPRB) remain unclear. BA were isolated from transgenic mice expressing the cytosolic cGMP FRET biosensor cGi-500 as well as BA obtained from human donor using the intensiometric green-cGull biosensor to probe the dynamics of cGMP production and degradation by the GCs and phosphodiesterases (PDEs) in real-time. Our results demonstrate that, depending on which GC produces cGMP, different subsets of PDEs are involved in its degradation, thereby locally confining the distinct cGMP pools. Furthermore, we show that during maturation in both human and murine BA, both the primary GC responsible for cGMP production as well as the distinct subsets of PDEs involved in its degradation change.