Search Results (195)

Insulin-regulated glucose uptake is a central mechanism in maintaining systemic glucose homeostasis, primarily occurring in skeletal muscle and adipose tissue. This process relies on the insulin-stimulated translocation of the glucose transporter, GLUT4, from specialized intracellular compartments, known as GLUT4 storage vesicles (GSVs), to the plasma membrane. Disruption of this pathway is a hallmark of insulin resistance and a key contributor to the pathogenesis of type 2 diabetes. Recent advances have provided critical insights into both the insulin signalling cascades and the complex biogenesis, as well as the trafficking and fusion dynamics of GSVs. This review synthesizes the current understanding of the molecular mechanisms governing GSV mobilization and membrane fusion, highlighting key regulatory nodes that may become dysfunctional in metabolic disease. By elucidating these pathways, we propose new therapeutic avenues targeting GSV trafficking to improve insulin sensitivity and combat type 2 diabetes. Full article

Background: There is growing evidence suggesting that SARS-CoV-2 may contribute to metabolic dysfunction. SARS-CoV-2 infection is associated with systemic inflammation, oxidative stress, and metabolic dysregulation, all of which may impair liver function and promote glucose intolerance. This study investigated the role of SARS-CoV-2, specifically its Main Protease (M^pro), in accelerating insulin resistance and metabolic dysfunction in HepG2 cells in vitro. Methods: HepG2 cells were treated with varying concentrations of M^pro (2.5, 5, 10, 20, 40, 80, and 160 nmol/mL) for 24 h to assess cytotoxicity and glucose uptake. Based on initial findings, subsequent assays focused on higher concentrations (40, 80, and 160 nmol/mL). The effects of M^pro on cell viability, protein kinase B (AKT) expression, matrix metallopeptidase-1 (MMP1), dipeptidyl peptidase 4 (DPP4), interleukin-6 (IL-6) expression, and lipid peroxidation were investigated. Results: Our findings reveal that the SARS-CoV-2 M^pro treatment led to a concentration-dependent reduction in glucose uptake in HepG2 cells. Additionally, the M^pro treatment was associated with reduced insulin-stimulated AKT activation, particularly at higher concentrations. Inflammatory markers such as IL-6 were elevated in the extracellular medium, while DPP4 expression was decreased. However, extracellular soluble DPP4 (sDPP4) levels did not show a significant change. Despite these changes, cell viability remained relatively unaffected, suggesting that the HepG2 cells were able to maintain overall metabolic functions under M^pro exposure. Conclusions: This study demonstrated the concentration-dependent impairment of hepatic glucose metabolism, insulin signaling, and inflammatory pathways in HepG2 cells acutely exposed to the SARS-CoV-2 M^pro. These findings warrant further investigation to explore the long-term metabolic effects of SARS-CoV-2 and its proteases in the liver and to develop potential therapeutic approaches for post-viral metabolic complications. Full article

Background: Obesity is associated with insulin resistance (IR) and characterized by impaired activation of the PI3K/AKT route and glucose uptake. Elevated plasma levels of palmitic acid (PA) diminish insulin signaling in vitro and in vivo. Origanum vulgare L. essential oil (OVEO) is rich in monoterpenes with protective effects against IR. Objective: The study aimed to assess total phenols content and antioxidant activity of OVEO and its cytotoxicity, as well as its effect on insulin signaling and glucose uptake in PA-treated adipocytes. Methods: The quantification of total phenolic content was determined using the Folin–Ciocalteu method, while the antioxidant capacity of OVEO was assessed by DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) methods. The cytotoxicity of OVEO (0.1–10 µg/mL) was assessed using the MTS assay. SW872 adipocytes were incubated with 0.4 mM PA for 24 h, with or without a 2 h preincubation of OVEO, and then stimulated with insulin (100 nM, 10 min) or a vehicle. Phosphorylation of Tyr-IRS-1, Ser-AKT, and Thr-AS160 was analyzed by Western blot, and glucose uptake was measured using 2-NBDG. Results: OVEO contained phenols and exhibits antioxidant capacity. All the concentrations of OVEO assessed were not cytotoxic on SW872 adipocytes. PA decreased basal phospho-AS160 as well as insulin-stimulated phospho-IRS1, phospho-AKT, phospho-AS160 and glucose uptake, while OVEO co-treatment enhanced these markers. Conclusions: These findings suggest a beneficial effect of OVEO on the PA-impaired insulin pathway and glucose uptake, which might be explained by its phenolic content and antioxidant capacity, highlighting its potential as a complementary therapeutic agent for IR and related metabolic disorders. Full article

Thai fermented soybeans (TFSs) contain phytochemicals with anti-diabetic benefits. In this study, an initial non-optimized TFS extract (TFSE) was prepared using a conventional triplicate 80% ethanol extraction method and evaluated for its biological activity. TFSE effectively reversed TNF-α-induced insulin resistance in 3T3-L1 adipocytes by enhancing insulin-stimulated glucose uptake, indicating anti-diabetic potential. TFSE also upregulated the phosphorylation of AKT (a key insulin signaling mediator) and the expression of adipogenic proteins (PPARγ, CEBPα) in TNF-α-exposed 3T3-L1, suggesting the mitigation of adipocyte dysfunction; however, the results did not reach statistical significance. The conventional extraction process was labor-intensive and time-consuming, and to enhance extraction efficiency and bioactivity, the process was subsequently optimized using environmentally friendly microwave-assisted extraction (MAE) in combination with the Box–Behnken design (BBD) and response surface methodology (RSM). The optimized extract (O-TFSE) was obtained over a significantly shorter extraction time and exhibited higher levels of total flavonoids and antioxidant activity in comparison to TFSE, while showing reduced levels of isoflavones (daidzein, genistein, and glycitein) in relation to TFSE. Interestingly, O-TFSE retained similar efficacy in reversing TNF-α-induced insulin resistance and demonstrated significantly stronger α-glucosidase and α-amylase inhibitory activities, indicating its enhanced potential for diabetes management. These results support the use of MAE as an efficient method for extracting functional compounds from TFS for functional foods targeting insulin resistance and type 2 diabetes mellitus. Full article

Quercetin (QE) is a naturally occurring flavonoid found in many fruits, vegetables, and other plant-based foods. It is recognized for its diverse pharmacological activities. Among its many therapeutic potentials, its antidiabetic properties are of particular interest due to the growing worldwide prevalence of diabetes mellitus. QE improves glycemic control by enhancing insulin sensitivity, stimulating glucose uptake, and preserving pancreatic beta cell function. These effects are mediated by the modulation of key molecular pathways, including AMPK, PI3K/Akt, and Nrf2/ARE, as well as by the suppression of oxidative stress and pro-inflammatory cytokines, such as TNF-α and IL-6. Furthermore, QE mitigates the progression of diabetic complications such as nephropathy, retinopathy, and vascular dysfunction, reducing lipid peroxidation and protecting endothelial function. However, the clinical application of quercetin is limited by its low water solubility, poor bioavailability, and extensive phase II metabolism. Advances in formulation strategies, including the use of nanocarriers, co-crystals, and phospholipid complexes, have shown promise in improving its pharmacokinetics. This review elucidates the mechanistic basis of QE quercetin antidiabetic action and discusses strategies to enhance its therapeutic potential in clinical settings. Full article

Neuroinflammation is a key process in Alzheimer’s disease (AD). We aimed to examine the development and evaluation of a comprehensive in vitro model that captures the complex interplay between neurons and immune cell types. Retinoic acid-differentiated SH-SY5Y neuroblastoma cells exposed to LPS-conditioned media (CM) from RAW264.7 macrophages, BV2 microglia, and HL60 promyelocytic cells differentiated into neutrophil- or monocyte-like phenotypes were analyzed. The effects of CM containing inflammatory factors on neuronal viability and function were systematically evaluated. Neuronal oxidative stress, mitochondrial function, autophagy and protein aggregates were analyzed. The involvement of insulin resistance was studied by assaying glucose uptake and determining its IC₅₀ values for cell viability improvement and GSK3β phosphorylation. After short-term exposure (3 h), most inflammatory CMs induced peroxide production in neurons, with the strongest effect observed in media from DMSO- or RA-differentiated HL60 cells. Mitochondrial membrane potential was markedly reduced by LPS-stimulated BV2 and HL60-derived CMs. Prolonged exposure (72 h) revealed partial normalization of oxidative stress and mitochondrial membrane potential. Glucose uptake was significantly impaired in cells treated with LPS-activated RAW264.7, BV2, and DMSO-differentiated HL60 cell media, while insulin partially rescued this effect, except for the CM of BV2 cells. Notably, insulin IC₅₀ increased dramatically under LPS-treated BV2 cells induced inflammation (35 vs. 198 pM), confirming the development of insulin resistance. Immune cell-specific inflammation causes distinct effects on neuronal oxidative stress, mitochondrial function, protein aggregation, insulin signaling and viability. LPS-activated BV2-derived CM best recapitulates AD-related pathology, offering a relevant in vitro model for further studies. Full article

Glucagon-like peptide-1 (GLP-1) has emerged as a pivotal regulator in the management of glucose homeostasis, glycogen metabolism, and energy balance, positioning it as a critical therapeutic target for addressing obesity, metabolic syndrome, and type 2 diabetes mellitus (T2DM). GLP-1 receptor agonists (GLP-1RAs) have shown promise for improving glycemic control and reducing weight through appetite regulation, delayed gastric emptying, and energy expenditure modulation. This narrative review explores the mechanisms of GLP-1-mediated glycogen metabolism and energy expenditure, particularly in key tissues—pancreas, liver, skeletal muscle, and adipose tissue. In the pancreas, GLP-1 enhances insulin secretion and beta-cell function. In the liver, it promotes glycogen synthesis via insulin-dependent and potential insulin-independent pathways, involving protein kinase B (AKT) and AMP-activated protein kinase (AMPK) signaling. Skeletal muscle benefits from GLP-1 through increased glucose uptake, AMPK activation, and mitochondrial function, facilitating glycogen storage. In adipose tissue, GLP-1 stimulates brown adipose tissue (BAT) thermogenesis and energy expenditure, contributing to weight loss. This increase in energy expenditure, along with enhanced glycogen metabolism, is a plausible mechanism for the weight loss observed with GLP-1RAs. Despite these advances, significant knowledge gaps remain, particularly regarding the direct hepatic effects of GLP-1, the extent to which it modulates glycogen metabolism in vivo, and its impact on thermogenesis in humans. Future research focusing on both the tissue-specific actions of GLP-1 and its systemic role in energy homeostasis and metabolic regulation will be essential for optimizing its therapeutic potential. Full article

Three-dimensional (3D) in vitro adipocyte models provide physiologically relevant platforms for studying adipogenesis and obesity-related metabolic dysfunction. However, long-term adipocyte culture is often hindered by limited cell–matrix adhesion and spheroid detachment. Previously, we demonstrated that elastin-like polypeptide (ELP)–polyethyleneimine (PEI) coatings functionalized with a trivalent RGD motif enhanced spheroid retention during frequent media changes. The present study investigates the long-term functional consequences of RGD incorporation over a 28-day culture period. 3T3-L1 preadipocytes were seeded, differentiated, and matured on ELP-PEI or ELP-(RGD)₃-PEI coatings. Spheroid morphology, triglyceride content, expression of PPAR-γ, adiponectin, HIF-1α genes, and insulin-stimulated glucose uptake were assessed. Both coatings supported initial spheroid formation, but only ELP-PEI maintained the 3D architecture and supported adipogenic maturation and insulin responsiveness. ELP-(RGD)₃-PEI promoted early retention but led to spheroid disassembly by mid-culture; notably, by day 28, cells reaggregated into abnormally large spheroids with impaired metabolic function, likely due to continued proliferation. These findings highlight the critical role of extracellular matrix-mediated cell–cell versus cell–substrate interactions in maintaining 3D culture fidelity. While RGD enhances adhesion, it disrupts spheroid integrity and compromises adipogenic and metabolic maturation. Taken together, ELP-PEI coatings offer a more conducive microenvironment for long-term 3D adipocyte culture and hold promise for modeling obesity-associated metabolic dysfunction in vitro. Full article

Aging is a significant risk factor for various conditions, including neurodegeneration, cardiovascular disease, and type 2 diabetes. The accumulation of reactive oxygen species (ROS) and a decline in antioxidant defense are mechanisms that are widely acknowledged as causing the acceleration of both aging and the onset of age-related diseases. To promote longevity and reduce the risk of the development of aging-related disorders, it is essential to prevent or minimize oxidative stress and enhance antioxidant defense. It has been shown that Anoectochilus burmannicus (AB), a jewel orchid rich in phenolic compounds, can impact various biological activities associated with aging prevention. These activities include antioxidant, anti-inflammation, anti-insulin resistance, and anti-obesity effects. The aim of this study was to explore whether AB extract (ABE) could serve as an anti-aging agent using a Sod1-deficient Drosophila model, which accelerates the process of aging through ROS production. The results demonstrated that ABE, at a concentration of 2.5 mg/mL, significantly extended the lifespan of the flies and helped maintain their locomotor activity as they aged. ABE also reduced the age-related accumulation of damaged proteins in the muscle of the flies by inhibiting the expression of Gstd1, a genetic marker for oxidative stress. This finding agrees with those from in vitro experiments, which have shown the potential for ABE to reduce the production of ROS induced by H₂O₂ in myoblasts. ABE has been shown to attenuate insulin resistance, an age-related disorder, by inhibiting the pro-inflammatory cytokine TNF-α, which in turn increased insulin-stimulated glucose uptake in adipocytes. These findings suggest a promising role of ABE as an ingredient in functional foods or nutraceuticals aimed at promoting health, preventing oxidative stress, and potentially managing age-associated diseases. Full article

The rising demand for alternative solutions to diabetes mellitus has prompted significant interest in the exploration of plant-derived anti-diabetic compounds, especially within a circular economy framework that seeks sustainable and profitable reuse options. In this context, red (RSGO) and white (WGSO) grape seed oils, by-products of Sicilian vineyards, were prepared, analyzed for their fatty acid, polyphenol, carotenoid, and chlorophyll content, and evaluated for their glucose-lowering ability on HepG2 cells. Utilizing cytochemical techniques, flow cytometry, and protein blotting, we explored the effects of non-toxic oil dilutions on (i) glycogen storage, (ii) glucose consumption/uptake, (iii) GLUT-2, GLUT-4, and hepatocyte nuclear factor-1α (HNF1α) expression levels, and (iv) AMP-activated protein kinase (AMPK), insulin receptor substrate-1 (IRS-1), AKT, and PKCζ phosphorylation states, which are involved in insulin-mediated and -independent regulation of GLUT-4 membrane exposure. RGSO and WGSO, despite adopting slightly varying molecular strategies, were both proven to be effective stimulators of glucose absorption and glycogenesis. Specifically, RSGO promoted GLUT-2 and GLUT-4 up-regulation, whereas the WGSO-induced effect was associated with an increase in GLUT-4 levels alone. Moreover, the oils activated both pathways responsible for GLUT-4 translocation. Therefore, these wine-making residues have substantial potential as anti-diabetic solutions, holding promise for integration into the biomedical and food sectors. Full article

Background: Vitiligo is featured by the manifestation of white maculae and primarily results from inflammatory/immune-selective aggression to melanocytes. The trigger mechanism leading to the activation of resident immune cells in the skin still lacks a molecular description. There is growing evidence linking altered mitochondrial metabolism to vitiligo, suggesting that an underlying metabolic defect may enable a direct activation of the immune system. Recent evidence demonstrated the association of vitiligo with disorders related to systemic metabolism, including insulin resistance (IR) and lipid disarrangements. However, IR, defined as a cellular defect in the insulin-mediated control of glucose metabolism, and its possible role in vitiligo pathogenesis has not been proven yet. Methods: In this study, we compared the Ins/IGF-1 intracellular signaling of dermal and epidermal cells isolated from non-lesional vitiligo skin to that belonging to cells obtained from healthy donors. Results: We demonstrated that due to the intensified glucose uptake, S6, and insulin receptor substrate 1 (IRS1) chronic phosphorylation, their inducibilities were downsized, a condition that coincides with the definition of insulin resistance at the cellular level. Correspondingly, the mitogenic and metabolic activities normally provoked by Ins/IGF-1 exposure resulted in significantly compromised vitiligo cells (p ≤ 0.05). Besides all the vitiligo-derived skin cells manifesting an energetic disequilibrium consisting of a low ATP, catabolic processes activation, and chronic oxidative stress, the functional consequences of this state appear amplified in the keratinocyte lineage. Conclusion: The presented data argue for insulin and IGF-1 resistance collocating dysfunctional glucose metabolism in the mechanisms of vitiligo pathogenesis. In vitiligo keratinocytes, the intrinsic impairment of intracellular metabolic activities, particularly when associated with stimulation with Ins/IGF-1, converges into an aberrant pro-inflammatory phenotype that may initiate immune cell recruitment. Full article

Background: Phytochemicals possess diverse therapeutic potential; however, the impact of arene substitutions on the pharmacological properties of the bibenzyl compounds batatasin III and gigantol, derived from Dendrobium venustum, remains unexplored. Objectives: This study examines how structural differences between these compounds affect cellular glucose uptake and lipid metabolism during adipocyte differentiation. Methods: The effects of both bibenzyl compounds on cytotoxicity and glucose uptake were assessed in mouse and human pre-adipocytes and rat skeletal muscle myoblasts using colorimetric assays. Lipid metabolism was evaluated through Oil Red O staining and quantification of triglyceride and glycerol levels, while protein and gene expression during adipocyte differentiation were analyzed via western blotting and RT-qPCR. Results: At the highest non-cytotoxic concentration (25 µM), gigantol significantly enhanced glucose uptake (up to 2-fold) under both basal and insulin-stimulated conditions, whereas batatasin III showed a similar effect only under basal conditions. Gigantol upregulated GLUT1 and GLUT4 in myotubes but downregulated them in adipocytes, whereas batatasin III had minimal impact on these transporters. Both compounds suppressed lipid accumulation in mouse and human adipocytes by decreasing intracellular triglyceride content and promoting extracellular glycerol release. However, batatasin III did not affect extracellular glycerol release during early adipocyte differentiation, as evidenced by the marked downregulation of key lipogenic proteins (PLIN1, LPL, FABP4) observed only with gigantol. Molecular docking analyses suggest that gigantol’s greater bioactivity may result from its higher number of arene substitutions. Conclusions: This study provides the first evidence that differences in arene substitutions among orchid-derived bibenzyls influence their pharmacological properties. Our findings support the strategic modification of natural products as a potential approach for managing metabolic disorders. Full article

Introduction: Metabolic age (MA) is the difference between an individual’s actual age and the age of their body based on physiological and biological factors. It is an indicator that reflects a person’s physical and biological state, regardless of chronological age. Insulin resistance (IR) is a health disorder in which tissues exhibit a reduced response to the circulating glucose uptake stimulated by insulin. Objective: The aim of this study is to evaluate the association between MA, determined through bioelectrical impedance analysis, and the risk of IR, assessed using validated scales, in a cohort of Spanish workers. Methodology: A descriptive cross-sectional study was conducted on 8590 Spanish workers to assess the association between MA and a set of sociodemographic variables, health habits, and IR risk scales such as the Triglyceride–Glucose Index (TyG Index), Metabolic Score for Insulin Resistance (METS-IR), and Single Point Insulin Sensitivity Estimator (SPISE). Results: All analyzed variables were associated with MA values, with the strongest associations observed for IR risk scale values (OR 4.88 [95% CI 4.12–5.65] for METS-IR, 4.42 [95% CI 3.70–5.15] for SPISE, and 3.42 [95% CI 2.97–3.87] for the TyG Index) and physical activity. Conclusions: Metabolic age is influenced by sociodemographic variables such as age, sex, and social class; health habits such as smoking, physical activity, and adherence to the Mediterranean diet; and by IR risk scale values. Full article

Gestational diabetes mellitus (GDM) is characterized by an inadequate pancreatic β-cell response to pregnancy-induced insulin resistance, resulting in hyperglycemia. The pathophysiology involves reduced incretin hormone secretion and signaling, specifically decreased glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), impairing insulinotropic effects. Pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), impair insulin receptor substrate-1 (IRS-1) phosphorylation, disrupting insulin-mediated glucose uptake. β-cell dysfunction in GDM is associated with decreased pancreatic duodenal homeobox 1 (PDX1) expression, increased endoplasmic reticulum stress markers (CHOP, GRP78), and mitochondrial dysfunction leading to impaired ATP production and reduced glucose-stimulated insulin secretion. Excessive gestational weight gain exacerbates insulin resistance through hyperleptinemia, which downregulates insulin receptor expression via JAK/STAT signaling. Additionally, hypoadiponectinemia decreases AMP-activated protein kinase (AMPK) activation in skeletal muscle, impairing GLUT4 translocation. Placental hormones such as human placental lactogen (hPL) induce lipolysis, increasing circulating free fatty acids which activate protein kinase C, inhibiting insulin signaling. Placental 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) overactivity elevates cortisol levels, which activate glucocorticoid receptors to further reduce insulin sensitivity. GDM diagnostic thresholds (≥92 mg/dL fasting, ≥153 mg/dL post-load) are lower than type 2 diabetes to prevent fetal hyperinsulinemia and macrosomia. Management strategies focus on lifestyle modifications, including dietary carbohydrate restriction and exercise. Pharmacological interventions, such as insulin or metformin, aim to restore AMPK signaling and reduce hepatic glucose output. Emerging therapies, such as glucagon-like peptide-1 receptor (GLP-1R) agonists, show potential in improving glycemic control and reducing inflammation. A mechanistic understanding of GDM pathophysiology is essential for developing targeted therapeutic strategies to prevent both adverse pregnancy outcomes and the progression to overt diabetes in affected women. Full article

Postnatally, glucagon acutely lowers plasma amino acid (AA) concentrations by stimulating hepatic AA catabolism, but its fetal actions remain unclear. This study tested whether a 2 h fetal glucagon infusion would stimulate hepatic AA catabolism and inhibit placental AA transfer. Late-gestation pregnant sheep (0.9 gestation) underwent surgical, vascular catheterization and received fetal glucagon (n = 8) or vehicle infusions (n = 8) in a crossover design with a 48 h washout period. Nutrient uptake and utilization were assessed during each infusion, and fetal liver and placental tissue were collected post-infusion under hyperglucagonemic (n = 4) or vehicle (n = 4) conditions. Glucagon receptor was identified in fetal hepatocyte and trophoblast cells. Glucagon reduced fetal plasma AA concentrations by 20% (p = 0.0103) and increased plasma glucose by 47% (p = 0.0152), leading to a three-fold rise in fetal plasma insulin (p = 0.0459). Hepatic gene expression associated with AA catabolism and gluconeogenesis increased (p < 0.0500) following glucagon infusion, and hepatic metabolomic analysis showed enrichment in AA metabolism pathways. However, placental AA transfer was unaffected by 2 h fetal glucagon infusions. In conclusion, a 2 h glucagon infusion stimulates hepatic glucose production and enhances AA catabolism in the fetal liver, lowering plasma AA concentrations. The primary acute effects of fetal glucagon are hepatic, as placental AA transfer is unchanged. Full article