TLR2 and obesity due to melanocortin 4 receptor deficiency: Since obesity is also associated with elevated fatty acid levels, the induction of TLR2 expression by both DHA and EPA individually and additively with peptidoglycan and the additive induction of TLR2 by both linoleic acid and peptidoglycan suggests that fatty acids may be partly responsible for the upregulation of TLR2 in obesity.