Pharmacological inhibition of myostatin/TGF-β receptor/pSmad3 signaling rescues muscle regenerative responses in mouse model of type 1 diabetes

Abstract

Aim: To study the influence of acute experimental diabetes on the regenerative potential of muscle stem (satellite) cells in mice. Methods: Male C57BL/6 young mice were injected with a single dose of streptozotocin (STZ, 180 mg/kg, ip) to induce diabetes. The diabetic mice were treated with insulin (0.75 U/kg, ip), follistatin (12 μg/kg, im) or Alk5 inhibitor (5 μmol/L per kg, sc) once a day. On the first day when high glucose levels were found, cardiotoxin (CTX) was focally injected into tibialis anterior and gastronemius muscles of the mice. The muscles were harvested 3 d and 5 d after CTX injection, and myofibers and satellite cells were isolated. Quantitative ex-vivo and in-vivo assays of myogenic potential were used to evaluate the muscle regenerative responses. Results: The satellite cells from the diabetic mice 3 d after CTX injection fail to activate, and the repair of muscle deteriorates, resembling that observed in old control mice. Furthermore, the satellite cells have excessive levels of myostatin, TGF-β receptor 1, pSmad3 and the cell cycle inhibitor p15, while the level of TGF-β1 remain unchanged. Treatment of the diabetic mice with insulin rescued muscle regenerative responses, and restored the expression levels of myostatin, TGF-β receptor 1, pSmad3, and p15 to those similar of healthy controls. Treatment of the diabetic mice with the myostatin antagonist follistatin, or with the Alk5 inhibitor of TGF-β receptor 1 (which did not diminish the blood glucose levels) rescued muscle regenerative responses and attenuated the myostatin/ TGFβ receptor/pSmad3 signaling. Conclusion: The muscle regenerative responses are incapacitated and repair of the tissue fails within hours after the initiation of hyperglycemia in a mouse model of type 1 diabetes, but stem cell function is rescued by insulin, as well as follistatin or an Alk5 inhibitor that blocks TGF-β receptor signaling.

Sirt1-Independent Rescue of Muscle Regeneration by Resveratrol in Type I Diabetes

“…Muscle stem cells (also known as satellite cells) are typically quiescent and start dividing in response to injury or attrition of muscle fibers (myofibers); activated satellite cells then differentiate along the myogenic lineage into fusion-competent proliferating myoblasts (expressing Pax7, MyoD and desmin) and postmitotic multinucleated myotubes (expressing eMyHC), which repair the damaged tissue [19]. Based on our work, type I diabetes has a direct negative effect on the ability of muscle stem cells to activate and regenerate muscle, due to intensified myostatin/ TGF-β receptor/pSmad 3 signaling [3]. Both exogenous insulin and inhibitors of the TGF-β receptor rescue the regenerative capacity of muscle stem cells in the diabetic condition to ~80% of healthy controls, and interestingly, as mentioned above, attenuation of TGF-β receptor signaling enables robust muscle repair in the diabetic state [3].…”

“…Based on our work, type I diabetes has a direct negative effect on the ability of muscle stem cells to activate and regenerate muscle, due to intensified myostatin/ TGF-β receptor/pSmad 3 signaling [3]. Both exogenous insulin and inhibitors of the TGF-β receptor rescue the regenerative capacity of muscle stem cells in the diabetic condition to ~80% of healthy controls, and interestingly, as mentioned above, attenuation of TGF-β receptor signaling enables robust muscle repair in the diabetic state [3].…”

“…Millions of people suffer from diabetes mellitus, which manifests as a lack of cell and organ function, poor wound healing and reduced longevity due to dysfunction of many organ systems [1][2][3][4][5]. Type I or insulin-dependent diabetes (IDDM), is called juvenile because it mainly occurs in children, adolescents, or young adults; it is also an autoimmune disease [6].…”

“…despite the ongoing hyperglycemia. Specifically, inhibition of myostatin/TGF-β receptor/ pSmad3 rescues regeneration of skeletal muscle in a mouse model of type I diabetes [3]. When combined with insulin treatment, such additional ways to preserve tissue health might prove invaluable in the treatment of diabetes and other severe chronic metabolic disorders.…”

“…The direct influence of diabetes on the performance of tissue stem cells has just begun to be uncovered, and our recent work in type I diabetes demonstrated that a lack of insulin and resulting high blood glucose levels quickly but reversibly incapacitates the regenerative responses of muscle stem cells [3], which can to some extent explain the phenomenon of muscle wasting in cases of diabetes [17,18]. Muscle stem cells (also known as satellite cells) are typically quiescent and start dividing in response to injury or attrition of muscle fibers (myofibers); activated satellite cells then differentiate along the myogenic lineage into fusion-competent proliferating myoblasts (expressing Pax7, MyoD and desmin) and postmitotic multinucleated myotubes (expressing eMyHC), which repair the damaged tissue [19].…”