New Insights on the Role of SERCA During Vessel Remodeling in Metabolic Syndrome

Role of Insulin-Like Growth Factor Receptor 2 across Muscle Homeostasis: Implications for Treating Muscular Dystrophy

The insulin-like growth factor 2 receptor (IGF2R) plays a major role in binding and regulating the circulating and tissue levels of the mitogenic peptide insulin-like growth factor 2 (IGF2). IGF2/IGF2R interaction influences cell growth, survival, and migration in normal tissue development, and the deregulation of IGF2R expression has been associated with growth-related disease and cancer. IGF2R overexpression has been implicated in heart and muscle disease progression. Recent research findings suggest novel approaches to target IGF2R action. This review highlights recent advances in the understanding of the IGF2R structure and pathways related to muscle homeostasis.

Astragaloside IV Attenuates Podocyte Apoptosis Mediated by Endoplasmic Reticulum Stress through Upregulating Sarco/Endoplasmic Reticulum Ca2+-ATPase 2 Expression in Diabetic Nephropathy

Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) plays a central role in the pathogenesis of diabetes. This protein has been recognized as a potential target for diabetic therapy. In this study, we identified astragaloside IV (AS-IV) as a potent modulator of SERCA inhibiting renal injury in diabetic status. Increasing doses of AS-IV (2, 6, and 18 mg kg^-1 day^-1) were administered intragastrically to db/db mice for 8 weeks. Biochemical and histopathological approaches were conducted to evaluate the therapeutic effects of AS-IV. Cultured mouse podocytes were used to further explore the underlying mechanism in vitro. AS-IV dose-dependently increased SERCA activity and SERCA2 expression, and suppressed ER stress-mediated and mitochondria-mediated apoptosis in db/db mouse kidney. AS-IV also normalized glucose tolerance and insulin sensitivity, improved renal function, and ameliorated glomerulosclerosis and renal inflammation in db/db mice. In palmitate stimulated podocytes, AS-IV markedly improved inhibitions of SERCA activity and SERCA2 expression, restored intracellular Ca²⁺ homeostasis, and attenuated podocyte apoptosis in a dose-dependent manner with a concomitant abrogation of ER stress as evidenced by the downregulation of GRP78, cleaved ATF6, phospho-IRE1α and phospho-PERK, and the inactivation of both ER stress-mediated and mitochondria-mediated apoptotic pathways. Furthermore, SERCA2b knockdown eliminated the effect of AS-IV on ER stress and ER stress-mediated apoptotic pathway, whereas its overexpression exhibited an anti-apoptotic effect. Our data obtained from in vivo and in vitro studies demonstrate that AS-IV attenuates renal injury in diabetes subsequent to inhibiting ER stress-induced podocyte apoptosis through restoring SERCA activity and SERCA2 expression.