TNFSF13B and obesity due to melanocortin 4 receptor deficiency: Interestingly, however, despite extreme adiposity, serum BAFF concentration was not altered in ob/ob mice compared to WT controls (Figure 5E), which was distinct from high-fat diet-induced obese mice that exhibited severe obesity and insulin resistance accompanied with a significantly increased serum BAFF level compared to normal diet-fed mice [5].