ER stress markers such as GRP78-BiP, ATF6, P-IRE1α, P-PERK, and P-eIF2α were found to be elevated in several in vitro myoblast models of human obesity [56,57] as well as in the SKM from both sexes of obese and diabetic rodents [58,59] and obese and/or diabetic women [60]. This evidence concerns the gene ATF6 and obesity due to melanocortin 4 receptor deficiency.