MRS studies of muscle and heart in obesity and diabetes

Type 2 diabetes (T2D) has reached epidemic proportions and is a major threat to global public health. In vivo magnetic resonance spectroscopy (MRS) allows the noninvasive study of tissuemetabolism and hasmade major contributions to our understanding of the etiology of insulin resistance and T2D. Moreover, MRS has proved extremely useful in the evaluation of the effects of life-style interventions and drug therapies on tissue metabolism and function. In this article, we review MRS studies of glucose transport and phosphorylation, glycogen synthesis, lipid metabolism, energy metabolism, and ion homeostasis in skeletal muscle and heart in the setting of obesity and T2D. Studies of obesity and T2D both in humans and in animal models are included. The main findings can be summarized as follows. In obesity, both skeletal muscle and the heart are faced with lipid overload. In skeletal muscle, this leads to lipid-induced insulin resistance and mitochondrial dysfunction, which can be alleviated by lowering muscle lipid content. In the heart, lipid accumulation in obesity and T2D is associated with impairments in cardiac energetics and function.