INS and obesity due to melanocortin 4 receptor deficiency: In addition, B6 mice do not develop overt type 2 diabetes when fed with an HFD, but they are a model for early stages of the disease with phenotypes that include obesity, mildly elevated non-fasting blood glucose, increased serum glucose, glucose intolerance with advancing age and elevated triglycerides, glucose, HDL, LDL, insulin, and leptin (Collins et al., 2004)6.