MC4R and type 2 diabetes mellitus: A number of scientific reports have suggested that the MC4R rs17782313 and PGC1α rs8192678 polymorphisms are associated with the onset of T2DM and CVD (81–86), which prompted us to conduct this meta-analysis to clarify the relationships of the two polymorphic variants with the indexes of obesity, glucometabolic disorder and dyslipidemia since all of these indexes are closely related to T2DM and CVD.