Moreover, collagen XVIII synthesis in VAT is associated with circulating free fatty acids in obesity, and a genetic linkage analysis shows an association between chromosome 21, where COL18A1 is located, and the familial combined hyperlipidemia-triglyceride trait, as well as increased serum triglycerides in hypertensive pedigrees [127,160]. Here, COL18A1 is linked to obesity due to melanocortin 4 receptor deficiency.