A xanthene derivative, DS20060511, attenuates glucose intolerance by inducing skeletal muscle-specific GLUT4 translocation in mice

Design, Synthesis, and Biological Evaluation of 1,4-Dihydropyridine-Indole as a Potential Antidiabetic Agent via GLUT4 Translocation Stimulation

In the quest for the discovery of antidiabetic compounds, a series of 27 1,4-dihydropyridine-indole derivatives were synthesized using a diversity approach. These compounds were systematically evaluated for their antidiabetic activity, starting with an in vitro assessment for GLUT4 translocation stimulation in L6-GLUT4myc myotubes, followed by in vivo antihyperglycemic activity evaluation in a streptozotocin (STZ)-induced diabetic rat model. Among the synthesized compounds, 12, 14, 15, 16, 19, 27, and 35 demonstrated significant potential to stimulate GLUT4 translocation in skeletal muscle cells. Compound 19 exhibited the highest potency and was selected for in vivo evaluation. A notable reduction of 21.6% (p < 0.01) in blood glucose levels was observed after 5 h of treatment with compound 19 in STZ-induced diabetic rats. Furthermore, pharmacokinetic studies affirmed that compound 19 was favorable to oral exposure with suitable pharmacological parameters. Overall, compound 19 emerged as a promising lead compound for further structural modification and optimization.

Critical Signaling Transduction Pathways and Intestinal Barrier: Implications for Pathophysiology and Therapeutics

The intestinal barrier is a sum of the functions and structures consisting of the intestinal mucosal epithelium, mucus, intestinal flora, secretory immunoglobulins, and digestive juices. It is the first-line defense mechanism that resists nonspecific infections with powerful functions that include physical, endocrine, and immune defenses. Health and physiological homeostasis are greatly dependent on the sturdiness of the intestinal barrier shield, whose dysfunction can contribute to the progression of numerous types of intestinal diseases. Disorders of internal homeostasis may also induce barrier impairment and form vicious cycles during the response to diseases. Therefore, the identification of the underlying mechanisms involved in intestinal barrier function and the development of effective drugs targeting its damage have become popular research topics. Evidence has shown that multiple signaling pathways and corresponding critical molecules are extensively involved in the regulation of the barrier pathophysiological state. Ectopic expression or activation of signaling pathways plays an essential role in the process of shield destruction. Although some drugs, such as molecular or signaling inhibitors, are currently used for the treatment of intestinal diseases, their efficacy cannot meet current medical requirements. In this review, we summarize the current achievements in research on the relationships between the intestinal barrier and signaling pathways. The limitations and future perspectives are also discussed to provide new horizons for targeted therapies for restoring intestinal barrier function that have translational potential.

Lean nonalcoholic fatty liver disease and sarcopenia

Nonalcoholic fatty liver disease (NAFLD) has become one of the most common chronic liver diseases in the world. The risk factor for NAFLD is often considered to be obesity, but it can also occur in people with lean type, which is defined as lean NAFLD. Lean NAFLD is commonly associated with sarcopenia, a progressive loss of muscle quantity and quality. The pathological features of lean NAFLD such as visceral obesity, insulin resistance, and metabolic inflammation are inducers of sarcopenia, whereas loss of muscle mass and function further exacerbates ectopic fat accumulation and lean NAFLD. Therefore, we discussed the association of sarcopenia and lean NAFLD, summarized the underlying pathological mechanisms, and proposed potential strategies to reduce the risks of lean NAFLD and sarcopenia in this review.

Proteomic analysis of skeletal muscle in Chinese hamsters with type 2 diabetes mellitus reveals that OPLAH downregulation affects insulin resistance and impaired glucose uptake

Type 2 diabetes mellitus (T2DM) is a metabolic disease controlled by a combination of genetic and environmental factors. The Chinese hamster, as a novel animal model of spontaneous T2DM with high phenotypic similarity to human disease, is of great value in identifying potential therapeutic targets for T2DM. Here, we used tandem mass tag (TMT) quantitative proteomics based on liquid chromatography-tandem mass spectrometry to assess the skeletal muscles of a Chinese hamster diabetes model. We identified 38 differentially abundant proteins, of which 14 were upregulated and 24 were downregulated. Further analysis of the differentially abundant proteins revealed that five of them (OPLAH, GST, EPHX1, SIRT5, ALDH1L1) were associated with oxidative stress; these were validated at the protein and mRNA levels, and the results were consistent with the proteomic analysis results. In addition, we evaluated the role of OPLAH in the pathogenesis of T2DM in human skeletal muscle cells (HSKMCs) by silencing it. The knockdown of OPLAH caused an increase in reactive oxygen species content, decreased the GSH content, inhibited the PI3K/Akt/GLUT4 signaling pathway, and reduced glucose uptake. We propose that OPLAH downregulation plays a role in insulin resistance and glucose uptake disorders in HSKMCs possibly via oxidative stress, making it a new therapeutic target for T2DM.

Post-translational Modifications: The Signals at the Intersection of Exercise, Glucose Uptake, and Insulin Sensitivity

Diabetes is a global epidemic, of which type 2 diabetes makes up the majority of cases. Nonetheless, for some individuals, type 2 diabetes is eminently preventable and treatable via lifestyle interventions. Glucose uptake into skeletal muscle increases during and in recovery from exercise, with exercise effective at controlling glucose homeostasis in individuals with type 2 diabetes. Furthermore, acute and chronic exercise sensitizes skeletal muscle to insulin. A complex network of signals converge and interact to regulate glucose metabolism and insulin sensitivity in response to exercise. Numerous forms of post-translational modifications (eg, phosphorylation, ubiquitination, acetylation, ribosylation, and more) are regulated by exercise. Here we review the current state of the art of the role of post-translational modifications in transducing exercise-induced signals to modulate glucose uptake and insulin sensitivity within skeletal muscle. Furthermore, we consider emerging evidence for noncanonical signaling in the control of glucose homeostasis and the potential for regulation by exercise. While exercise is clearly an effective intervention to reduce glycemia and improve insulin sensitivity, the insulin- and exercise-sensitive signaling networks orchestrating this biology are not fully clarified. Elucidation of the complex proteome-wide interactions between post-translational modifications and the associated functional implications will identify mechanisms by which exercise regulates glucose homeostasis and insulin sensitivity. In doing so, this knowledge should illuminate novel therapeutic targets to enhance insulin sensitivity for the clinical management of type 2 diabetes.