ADIPOR1 and obesity due to melanocortin 4 receptor deficiency: A series of studies have indicate that AdipoR1 expression is downregulated in various organs under pathological conditions, such as in the pancreas and liver of ob-/ob- and db-/db- mice [24], in the adipose tissue of obese diabetic KKAy mice and patients with obesity [25], [26], in the soleus muscle of obese Zucker rats [27], and in hyperglycemia- and hyperinsulinemia- stimulated L6 myoblasts [28].