Type 2 diabetes mellitus (DM2) is a chronic pathology characterized by peripheral insulin resistance in tissues such as skeletal muscle, adipose tissue and liver. It develops when the β cells fail to compensate for this peripheral resistance. Insulin resistance is associated with other pathologies and may be related to obesity, cardiovascular disease, nonalcoholic fatty liver disease, metabolic syndrome, and polycystic ovary syndrome. But does diabetes affect muscle mass?
How does diabetes affect muscle mass?
The loss of muscle mass results from the negative balance between the rate of synthesis and protein degradation. In an individual with diabetes, a number of proteolytic reactions (protein-breaking reactions) increase due to insulin resistance, worsening the rate of muscle breakdown.
Insulin is often only related to the transport of plasma glucose to the skeletal muscle and liver. However, this hormone performs several functions, such as regulation in protein metabolism, decreasing the rate of protein degradation. Insulin also transports amino acids (from the so-called pool of amino acids in the blood) to other tissues, such as the skeletal muscle itself.
In addition to all the papers mentioned above, insulin has an important role in protein synthesis. Insulin stimulates IGF-1 (insulin-dependent growth factor), IGF-1 plays a vital role in activating the mTOR pathway (positive regulator of protein synthesis and muscle hypertrophy). In addition, IGF-1 inhibits pathways that catabolis proteins.
As exposed, insulin resistance can alter protein metabolism, attenuating protein synthesis and optimizing protein degradation, making muscle mass loss more conducive.
Clinical practice
Physical exercise has been reported as a non-pharmacological tool for the treatment of diabetes mellitus 2, evidence suggests the combination of aerobic exercise with resistance training. Aerobic exercises improve insulin sensitivity due to mitochondrial biogenesis, and resistance training seems to optimize muscle glucose uptake due to increased glut-4 translocation due to the influence of adrenaline.
In addition, resistance training increases mTOR activation. MTOR is the main signaling pathway through which training stimulates muscle hypertrophy and protein synthesis. Mechanical stimuli, such as resistance training, have the potential to activate muscle mTOR complex 1 (mTORC1).
Thereby physical exercise seems to be a great ally in the treatment of type 2 diabetes mellitus. Both for glycemic control, as well as to prevent loss of muscle mass.
References:
PERRY, Ben D. et al. Muscle atrophy in patients with Type 2 Diabetes Mellitus: roles of inflammatory pathways, physical activity and exercise. Exercise immunology review, v. 22, p. 94, 2016. https://pubmed.ncbi.nlm.nih.gov/26859514/.
NEWSHOLME, E. A.; DIMITRIADIS, G. Integration of biochemical and physiologic effects of insulin on glucose metabolism. Experimental and Clinical Endocrinology & Diabetes, v. 109, n. Suppl 2, p. S122-S134. Available in: https://doi.org/10.1055/s-2001-18575.
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