Resveratrol bidirectionally regulates insulin effects in skeletal muscle through alternation of intracellular redox homeostasis

Physicochemical properties, health benefits, and applications of the polysaccharides from Rosa rugosa Thunb.: A review

Rosa rugosa Thunb. (R. rugosa) has been used as food and medicine and not just as ornamental plant for nearly a thousand years, its nutritional and medicinal value have been recognized by people. It contains a variety of biological active ingredients that are beneficial to the human body. R. rugosa polysaccharides are also one of the main bioactive ingredients, which have many health benefits such as anti-diabetes, antioxidation, anti-inflammation, anti-tumour, moisture-preserving and anti-alcoholic liver disease. This review summarizes the extraction, purification, structural characteristics, health benefits, and structure-activity relationships of R. rugosa polysaccharides. In addition, current and potential applications of R. rugosa polysaccharides are analyzed and supplemented, hoping to provide some valuable insights for further research and development of functional food additives, nutritional supplements, additives for daily chemical products, and even pharmaceuticals.

Resveratrol relieves HFD-induced insulin resistance in skeletal muscle tissue through antioxidant capacity enhancement and the Nrf2-Keap1 signaling pathway

BACKGROUND

Resveratrol has received much attention due to its beneficial effects including antioxidant activity. The purpose of this study was to investigate the therapeutic effects of resveratrol treatment on oxidative stress and insulin resistance in the skeletal muscle of high-fat diet (HFD)-fed animals.

METHODS AND RESULTS

A total of 30 six-week-old C57BL/6J mice were randomly allocated to three groups (10 animals in each group): The control group in which mice were fed a normal chow diet (NCD); the HFD group in which mice were fed an HFD for 26 weeks; and the HFD-resveratrol group in which HFD was replaced by a resveratrol supplemented-HFD (400 mg/kg diet) after 10 weeks of HFD feeding. At the end of this period, gastrocnemius muscle samples were examined to determine insulin resistance and the oxidative status in the presence of HFD and resveratrol. Resveratrol supplementation in HFD-fed mice reduced body and adipose tissue weight, improved insulin sensitivity, and decreased oxidative stress as indicated by lower malonaldehyde (MDA) levels and higher total antioxidant capacity. The supplement also increased the expression and activity of antioxidative enzymes in gastrocnemius muscle and modulated Nrf2 and Keap1 expression levels.

CONCLUSIONS

These results suggest that resveratrol is effective in improving the antioxidant defense system of the skeletal muscle in HFD-fed mice, indicating its therapeutic potential to combat diseases associated with insulin resistance and oxidative stress.

Resveratrol as a potential protective compound against skeletal muscle insulin resistance

The increasing prevalence of type 2 diabetes has become a major global problem. Insulin resistance has a central role in pathophysiology of type 2 diabetes. Skeletal muscle is responsible for the disposal of most of the glucose under conditions of insulin stimulation, and insulin resistance in skeletal muscle causes dysregulation of glucose homeostasis in the whole body. Despite the current pharmaceutical and non-pharmacological treatment strategies to combat diabetes, there is still a need for new therapeutic agents due to the limitations of the therapeutic agents. Meanwhile, plant polyphenols have attracted the attention of researchers for their use in the treatment of diabetes and have gained popularity. Resveratrol, a stilbenoid polyphenol, exists in various plant sources, and a growing body of evidence suggests its beneficial properties, including antidiabetic activities. The present review aimed to provide a summary of the role of resveratrol in insulin resistance in skeletal muscle and its related mechanisms. To achieve the objectives, by searching the PubMed, Scopus and Web of Science databases, we have summarized the results of all cell culture, animal, and human studies that have investigated the effects of resveratrol in different models on insulin resistance in skeletal muscle.

Perturbated glucose metabolism augments epithelial cell proinflammatory function in chronic rhinosinusitis

BACKGROUND

Glucose concentrations are increased in nasal secretions in chronic rhinosinusitis (CRS). However, the glucose metabolism and its contribution to disease pathogenesis in CRS remain unexplored.

OBJECTIVES

We sought to explore the glucose metabolism and its effect on the function of nasal epithelial cells in CRS with and without nasal polyps (CRSwNP and CRSsNP).

METHODS

Glucose metabolites were detected with mass spectrometry. The mRNA levels of glucose transporters (GLUTs), metabolic enzymes, and inflammatory mediators were detected by quantitative RT-PCR. The protein expression of GLUTs was studied by immunofluorescence staining, Western blotting, and flow cytometry. Glucose uptake was measured by using fluorescent glucose analog. Human nasal epithelial cells (HNECs) were cultured. Bioenergetic analysis was performed with Seahorse XF analyzer. Gene expression in HNECs was profiled by RNA sequencing.

RESULTS

Increased glucose concentrations in nasal secretions was confirmed in both CRSsNP and CRSwNP. GLUT4, GLUT10, and GLUT11 were abundantly expressed in HNECs, whose expression was upregulated by inflammatory cytokines and D-glucose and was increased in CRS. Glucose uptake, glycolysis and tricarboxylic acid cycle metabolites, metabolic enzymes, and extracellular acidification rate and oxygen consumption rates were increased in HNECs in CRSsNP and CRSwNP, with a predominant shift to glycolysis. HNECs treated with high-level apical D-glucose showed enhanced glucose uptake, predominant glycolysis, and upregulated production of IL-1α, IL-1β, TNF-α, CCL20, and CXCL8, which was suppressed by 2-deoxy-D-glucose, an inhibitor of glycolysis.

CONCLUSIONS

Increased glucose in nasal secretions promotes glucose uptake and predominant glycolysis in epithelial cells, augmenting the proinflammatory function of epithelial cells in CRS.

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.

Bioactive Components in Whole Grains for the Regulation of Skeletal Muscle Function

Skeletal muscle plays a primary role in metabolic health and physical performance. Conversely, skeletal muscle dysfunctions such as muscular dystrophy, atrophy and aging-related sarcopenia could lead to frailty, decreased independence and increased risk of hospitalization. Dietary intervention has become an effective approach to improving muscle health and function. Evidence shows that whole grains possess multiple health benefits compared with refined grains. Importantly, there is growing evidence demonstrating that bioactive substances derived from whole grains such as polyphenols, γ-oryzanol, β-sitosterol, betaine, octacosanol, alkylresorcinols and β-glucan could contribute to enhancing myogenesis, muscle mass and metabolic function. In this review, we discuss the potential role of whole-grain-derived bioactive components in the regulation of muscle function, emphasizing the underlying mechanisms by which these compounds regulate muscle biology. This work will contribute toward increasing awareness of nutraceutical supplementation of whole grain functional ingredients for the prevention and treatment of muscle dysfunctions.

Silibinin improves L-cell mass and function through an estrogen receptor-mediated antioxidative mechanism

BACKGROUND

Silibinin, a major component of milk thistle extract silymarin, promotes hypoglycemia by activating estrogen receptor (ER) α and β-mediated pathways in pancreatic β-cells. Glucagon-like peptide-1 (GLP-1) is the enteroendocrine peptide produced in L-cells, and it controls glucose homeostasis through multiple pathways. The effect of silibinin on L-cell mass and function is still unknown.

PURPOSE

The protective effect of silibinin on palmitate (PA)-treated intestinal L-cell line GLUTag cells and the SHRSP•Z-Leprfa/Izm-Dmcr (SP•ZF) diabetic rat model was investigated in current study.

METHODS

After pre-incubation with 50 μM silibinin for 4 h, GLUTag cells were treated with 0.125 mM PA. MTT, Annexin V/PI apoptosis, Hoechst 33342 staining, western blot, DCFH-DA, GLP-1 ELISA, qRT-PCR and immunofluorescence analyses were undertaken to determine ER-dependent protection of silibinin against PA-induced cellular damage. The differential protein expression of GLUTag cells under different treatments was examined by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). The SP•ZF diabetic rat model was chosen for in vivo study. After 4 weeks of gastric gavage with 100 or 300 mg kg-1 of silibinin, the physiological indexes of the rats were measured. Cells expressing GLP-1, 8‑hydroxy-2'-deoxyguanosine (8-OHdG), ERα, and/or ERβ in duodenum tissues were detected by immunofluorescence.

RESULTS

The current study showed that the GLUTag cells preincubated with silibinin activated the transcription factor nuclear erythroid-2 like factor-2 (Nrf2)-antioxidant pathway, reduced reactive oxygen species (ROS) generation, and improved cell survival and GLP-1 content, while the antioxidative effect of silibinin was blocked by the selective ERα antagonist MPP or ERβ antagonist PHTPP in GLUTag cells. Our proteomics data further revealed that ERα or β inactivation reduced glutathione peroxide and proteins associated with endocytosis and reproduction, thus at least partially reversing the protective effect of silibinin. SP•ZF rats received silibinin treatment showed increased serum GLP-1 content and improved glucose homeostasis. Furthermore, silibinin upregulated ERα and β levels and reduced the level of 8-OHdG in GLP-1-positive cells.

CONCLUSIONS

Our study showed that silibinin improved L-cell mass and function through an ER-mediated antioxidant pathway, and the proteomics analysis revealed for the first time the differential regulation of proteins by PA and silibinin in GLUTag cells.

Resveratrol Alleviates Skeletal Muscle Insulin Resistance by Downregulating Long Noncoding RNA

Long noncoding RNA (lncRNA) is a crucial factor in the progression of insulin resistance (IR). Resveratrol (RSV) exhibits promising therapeutic potential for IR. However, there are few studies on whether RSV improves IR through lncRNA. This study aimed to determine whether RSV could influence the expression of lncRNA and to elucidate the underlying mechanism. Mice were divided into three groups: control group, high-fat diet (HFD) group, and HFD + RSV group. We conducted a high-throughput sequencing analysis to detect lncRNA and mRNA expression signatures and the ceRNA-network in the skeletal muscles of mice that were fed an HFD to induce IR. Hierarchical clustering, gene enrichment, and gene ceRNA-network analyses were subsequently conducted. Differentially expressed lncRNAs were selected and validated via reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The biological functions of the selected lncRNAs were investigated by silencing the target genes via lentivirus transfection of C2C12 mouse myotube cells. RSV treatment reversed the expression of 338 mRNAs and 629 lncRNAs in the skeletal muscles of mice with HFD-induced IR. The results of the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes database analyses indicated that the differentially expressed mRNAs modulated type II diabetes mellitus. After validating randomly selected lncRNAs via RT-qPCR, we identified a novel lncRNA, NONMMUT044897.2, which was upregulated in the HFD group and reversed with RSV treatment. Additionally, NONMMUT044897.2 was proven to function as a ceRNA of microRNA- (miR-) 7051-5p. Suppressor of Cytokine Signaling 1 (SOCS1) was confirmed as a target of miR-7051-5p. We further performed lentivirus transfection to knock down NONMMUT044897.2 in vitro and found that NONMMUT044897.2 silenced SOCS1 and potentiated the insulin signaling pathway. Hence, RSV mimicked the silencing effect of lentivirus transfection on NONMMUT044897.2. Our study revealed that RSV reduced IR in mouse skeletal muscles via the regulation of NONMMUT044897.2.

The regulatory role of dietary factors in skeletal muscle development, regeneration and function

Skeletal muscle plays a crucial role in motor function, respiration, and whole-body energy homeostasis. How to regulate the development and function of skeletal muscle has become a hot research topic for improving lifestyle and extending life span. Numerous transcription factors and nutritional factors have been clarified are closely associated with the regulation of skeletal muscle development, regeneration and function. In this article, the roles of different dietary factors including green tea, quercetin, curcumin (CUR), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and resveratrol (RES) in regulating skeletal muscle development, muscle mass, muscle function, and muscle recovery have been summarized and discussed. We also reviewed the potential regulatory molecular mechanism of these factors. Based on the current findings, dietary factors may be used as a potential therapeutic agent to treat skeletal muscle dysfunction as well as its related diseases.

Effects of Early Resveratrol Intervention on Skeletal Muscle Mitochondrial Function and Redox Status in Neonatal Piglets with or without Intrauterine Growth Retardation

Skeletal muscle mitochondrial malfunction of offspring induced by intrauterine growth retardation (IUGR) may be a contributor to growth restriction and metabolic disorder at various periods of life. This study explored the effects of IUGR and resveratrol (RSV) on mitochondrial function and redox status in the longissimus dorsi muscle (LM) of piglets during the sucking period. A total of 36 pairs of IUGR and normal birth weight male piglets were orally fed with either 80 mg RSV/kg body weight/d or 0.5% carboxymethylcellulose sodium during days 7-21 after birth. The results showed that RSV treatment improved anomalous mitochondrial morphology, increased adenosine triphosphate and glycogen contents, and enhanced nicotinamide adenine dinucleotide/reduced form of nicotinamide-adenine dinucleotide ratio in the LM of IUGR piglets. Moreover, the IUGR-induced increased malondialdehyde and protein carbonyl concentrations, abnormal mtDNA number, and suppressed genes expression of mitochondrial biogenesis such as nuclear respiratory factor 1, estrogen-related receptor alpha, and polymerase gamma in the LM were restored to some extent by RSV treatment. Additionally, RSV increased mitochondrial complex V activity in the LM of piglets. Collectively, RSV administration alleviated the LM mitochondrial dysfunction and oxidative damage of IUGR piglets.