LEP and obesity due to melanocortin 4 receptor deficiency: Additionally, since an increasing evidence has shown a strong link between ER stress and the pathology of obesity and T2DM that may lead to the leptin and insulin resistance, we performed a quantitative assessment of the ER morphometric parameters in the hypothalamus of rats with T2DM and after metformin and propionic acid administration (Figure 2k, 2I).