TRPV1 and obesity due to melanocortin 4 receptor deficiency: In addition, by using a TRPV1 knockout mouse model, previous studies yielded seemingly contradictory findings that TRPV1 exerts protective (Lee et al., 2015), deleterious (Motter and Ahern, 2008), or no effects (Marshall et al., 2013) on high-fat diet-induced obesity.