SIRT1: a promising therapeutic target in type 2 diabetes mellitus

Melatonin promotes diabetic wound healing by mediating mitochondrial function in endothelial cells through the AMPK/SIRT1/HIF-1α pathway

OBJECTIVE

Diabetic wounds are open lesions that can develop on any part of the body of diabetic patients. Importantly, melatonin (Mel) exerts promotional effects on wound healing. Accordingly, this study explored the mechanism of Mel in diabetic wound healing by mediating mitochondrial function in endothelial cells.

METHODS

Human umbilical vein vascular endothelial cells (HUVECs) were exposed to high glucose (HG) to mimic a diabetic environment in vitro, followed by Mel treatment. Cell viability, invasion and angiogenic capacity were evaluated with CCK-8, Transwell, and tube formation assays, respectively. CD31 protein expression was determined with Western blot. Wound healing ability was evaluated in vitro, and the levels of adenosine triphosphate (ATP), reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and apoptosis-related proteins (Bcl-2/Bax/CytC) were also detected. To verify the role of the AMPK/SIRT1/HIF-1α pathway in diabetic wound healing, HG-induced HUVECs treated with Mel were subjected to treatment with sh-HIF-1α, AMPK inhibitor (compound c), or SIRT1 inhibitor (Nicotinamide).

RESULTS

HG impaired the proliferation, invasion, angiogenesis, and wound healing ability of HUVEC, increased ROS, Bax, and CytC levels, and decreased MMP and the levels of ATP and Bcl-2. Mel facilitated viability, angiogenesis, and wound healing ability while ameliorating mitochondrial dysfunction in HG-treated HUVECs. Mel activated the AMPK/SIRT1 pathway to upregulate HIF-1α in HG-treated HUVECs. HIF-1α knockdown, CC, or Nicotinamide negated the effect of Mel on HG-treated HUVECs.

CONCLUSIONS

Mel fosters angiogenesis and represses mitochondrial dysfunction in endothelial cells by activating the AMPK/SIRT1/HIF-1α pathway, thereby promoting diabetic wound healing.

Sodium-Glucose Transporter-2 Inhibitors (SGLT2i) and Myocardial Ischemia: Another Compelling Reason to Consider These Agents Regardless of Diabetes

In recent years, the introduction of sodium-glucose transporter-2 inhibitors (SGLT2is) marked a significant advancement in the treatment of cardiovascular disease (CVD). Beyond their known effects on glycemic control and lipid profile, SGLT2is demonstrate notable benefits for cardiovascular morbidity and mortality, regardless of diabetic status. These agents are currently recommended as first-line therapies in patients with heart failure, both with reduced and preserved ejection fraction, as they improve symptoms and reduce the risk of hospitalization. While several studies have demonstrated that SGLT2is can reduce the incidence of major adverse cardiovascular events (MACEs), the true impact of these agents on atherosclerosis progression and myocardial ischemia remains to be fully understood. A global beneficial effect related to improved glycemic and lipid control could be hypothesized, even though substantial evidence shows a direct impact on molecular pathways that enhance endothelial function, exhibit anti-inflammatory properties, and provide myocardial protection. In this context, this narrative review summarizes the current knowledge regarding these novel anti-diabetic drugs in preventing and treating myocardial ischemia, aiming to define an additional area of application beyond glycemic control and heart failure.

Association of SIRT1 rs3758391 Polymorphism With T2DM in Bangladeshi Population: Evidence From a Case-Control Study and Meta-Analysis

Background and Aim

Type 2 diabetes mellitus (T2DM) remains one of the major causes of morbidity and mortality worldwide, including Bangladesh. SIRT1, an NAD-dependent deacetylase, is involved in energy homeostasis and protects β-cells of the pancreas from oxidative stress. Single nucleotide polymorphisms (SNPs) in the SIRT1 gene have been found to be associated with T2DM in several populations, however, with conflicting results. The aim of this present case-control study, along with the meta-analysis, was to elucidate the association of rs3758391 polymorphism with the susceptibility to T2DM in Bangladeshi population.

Methods

72 T2DM patients and 90 healthy controls were enrolled in our study and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was employed for genotyping the SNP. Odds ratio (OR) with 95% confidence interval (95% CI) was used to represent the association of SIRT1 polymorphism with T2DM. For the meta-analysis six studies were included and pooled odds ratio with 95% CI were calculated for six genetic models using the random effects model. Heterogeneity and publication bias was also calculated for each study.

Results

A significant association was found between rs3758391 polymorphism and increased risk of T2DM under codominant TT versus CC (OR = 3.88, 95% CI = 1.34-11.25, p = 0.012), recessive TT versus CC + CT (OR = 2.83, 95% CI = 1.12-7.09, p = 0.027) and allelic T versus C (OR = 1.67, 95% CI = 1.07-2.60, p = 0.024) genetic models. However, no significant association between rs3758391 and other biochemical and anthropometric parameters were found. Our meta-analysis showed no statistically significant association of this polymorphism.

Conclusion

We conclude that, polymorphism at rs3758391 of SIRT1 gene conferred an increased risk of T2DM in Bangladeshi population.

Sirtuins and Their Implications in the Physiopathology of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) imposes serious short- and long-term health problems for the mother and her child. An effective therapeutic that can reduce the incidence of GDM and improve long-term outcomes is a major research priority and is very important for public health. Unfortunately, despite numerous studies, the molecular mechanisms underlying GDM are not fully defined and require further study. Chronic low-grade inflammation, oxidative stress, and insulin resistance are central features of pregnancies complicated by GDM. There is evidence of the involvement of sirtuins, which are NAD+-dependent histone deacetylases, in energy metabolism and inflammation. Taking these facts into consideration, the role of sirtuins in the pathomechanism of GDM will be discussed.

Emodin alleviates lung injury via the miR-217-5p/Sirt1 axis in rats with severe acute pancreatitis

Acute lung injury (ALI) is closely related to high mortality in severe acute pancreatitis (SAP). This study unveils the therapeutic effect and mechanism of miR-217-5p on SAP-associated ALI. The miR-217-5p RNA expression was significantly up-regulated in lipopolysaccharide (LPS)-stimulated primary rat alveolar epithelial type II cells (AEC II) and sodium taurocholate-treated pancreas and lung in SAP rats. miR-217 inhibition protected AEC II from LPS-induced damage by inhibiting apoptosis and reducing the TNF-α, IL-6, and ROS levels. miR-217 inhibition suppressed apoptosis and alleviated mitochondrial damage through mitochondria-mediated apoptotic pathway in vitro. Sirt1 is a direct target of miR-217-5p. Dual-luciferase reporter assay confirmed the binding of miR-217-5p to Sirt1 mRNA 3'-UTR. The rescue experiment identified that the anti-apoptotic, anti-inflammatory, and anti-oxidative effects of miR-217 inhibition were mediated by Sirt1 in vitro. Emodin (EMO) protected AEC II from LPS-induced damage and alleviated pancreatic and lung tissue injuries. EMO exerted similar effects as miR-217 inhibition in vitro and in vivo. The effects of EMO were abolished by miR-217 overexpression. In conclusion, miR-217-5p inhibition exerts protective effects on SAP-ALI in vitro and in vivo by repressing apoptosis, inflammation, and oxidative stress through Sirt1 activation. EMO protects against lung injuries in SAP-associated ALI rats through miR-217-5p/Sirt1 axis.

LncRNA LYPLAL1, miR-204-5p, and SIRT1: novel signatures for risk assessment of diabetic macrovascular complications

Long-term, uncontrolled diabetes mellitus can lead to micro- and macrovascular problems. The protective function of lncRNA LYPLAL1 is to reduce endothelium cell inflammation by upregulating sirtuin 1 (SIRT1) and reducing microRNA (miR)-204-5p. This work attempted to examine the lncRNA LYPLAL1/miR-204-5p/SIRT1 molecules as diagnostic biomarkers for diabetic MVC and to assess their clinical correlations. The study enrolled 32 controls, 32 patients with diabetes alone, and 32 patients with diabetic MVC. RT-qPCR, or quantitative real-time PCR, was utilized to determine the expression levels of lncRNA and miR. SIRT1 was measured by ELISA. When comparing cases with MVC to those without MVC, the lncRNA LYPLAL1 and SIRT1 values were significantly lower. Conversely, patients with MVC had significantly higher miR-204-5p levels than those without MVC. The LncRNA LYPLAL1 performed best in terms of detecting MVC. It attained 90.6% specificity and 96.9% sensitivity. A combination of three markers (lncRNA LYPLAL1, miR-204-5p, and SIRT1) yielded the best accuracy at 98.4%. LYPLAL1 expression appeared to be an independent MVC predictor. Adjusted OR for LYPLAL1 expression was 405 (95% CI: 1.4-1200) (p = 0.039). When we compared cases with MVC to those without MVC, the lncRNA LYPLAL1 and SIRT1 values were significantly lower. Patients with MVC had significantly higher miR-204-5p levels than those without MVC. LYPLAL1 LncRNA demonstrated the best performance characteristics. LncRNA LYPLAL1 expression is an independent predictor of MVC.

Protective Effects of Berberine on Nonalcoholic Fatty Liver Disease in db/db Mice via AMPK/SIRT1 Pathway Activation

OBJECTIVE

Berberine (BBR) has emerged as a promising therapeutic agent for nonalcoholic fatty liver disease (NAFLD). This study aims to elucidate the underlying molecular mechanisms.

METHODS

In this study, db/db mice were chosen as an animal model for NAFLD. A total of 10 healthy C57BL/6J mice and 30 db/db mice were randomly allocated to one of 4 groups: the normal control (NC) group, the diabetic control (DC) group, the Metformin (MET) therapy group, and the BBR therapy group. The total cholesterol (TC), triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in the serum were measured. The glutathione peroxidase (GSH-Px), glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), interleukin (IL)-1β, tumor necrosis factor (TNF)-α and monocyte chemotactic protein 1 (MCP-1) levels in liver tissue were measured. Hematoxylin and eosin (H&E), acid-Schiff (PAS) and TUNEL stanning was performed for histopathological analysis. Western blotting and immunohistochemistry were conducted to detect the expression levels of key proteins in the AMPK/SIRT1 pathway.

RESULTS

BBR could improve lipid metabolism, attenuate hepatic steatosis and alleviate liver injury significantly. The excessive oxidative stress, high levels of inflammation and abnormal apoptosis in db/db mice were reversed after BBR intervention. BBR clearly changed the expression of AMP-activated protein kinase (AMPK)/Sirtuin 1 (SIRT1), and their downstream proteins.

CONCLUSION

BBR could reverse NAFLD-related liver injury, likely by activating the AMPK/SIRT1 signaling pathway to inhibit oxidative stress, inflammation and apoptosis in hepatic tissue.

Exploring the Significance of Gut Microbiota in Diabetes Pathogenesis and Management-A Narrative Review

Type 2 diabetes is a disease with significant health consequences for the individual. Currently, new mechanisms and therapeutic approaches that may affect this disease are being sought. One of them is the association of type 2 diabetes with microbiota. Through the enteric nervous system and the gut-microbiota axis, the microbiota affects the functioning of the body. It has been proven to have a real impact on influencing glucose and lipid metabolism and insulin sensitivity. With dysbiosis, there is increased bacterial translocation through the disrupted intestinal barrier and increased inflammation in the body. In diabetes, the microbiota's composition is altered with, for example, a more abundant class of Betaproteobacteria. The consequences of these disorders are linked to mechanisms involving short-chain fatty acids, branched-chain amino acids, and bacterial lipopolysaccharide, among others. Interventions focusing on the gut microbiota are gaining traction as a promising approach to diabetes management. Studies are currently being conducted on the effects of the supply of probiotics and prebiotics, as well as fecal microbiota transplantation, on the course of diabetes. Further research will allow us to fully develop our knowledge on the subject and possibly best treat and prevent type 2 diabetes.

Bisphenol A accelerates the vascular complications in patients with Type 2 diabetes mellitus through vascular calcification-a molecular approach

PURPOSE

Environmental pollutant Bisphenol A (BPA) strongly interacts with insulin resistance, which leads to type 2 diabetes mellitus (T2DM). Uncontrolled glucose levels in both blood and urine develops vascular complications in T2DM patients. However, glucose-controlled diabetic patients are also affected by vascular complications due to vascular calcification, and there is a lack of clinically relevant data on BPA levels available in patients with T2DM-associated vascular complications due to vascular calcification. Therefore, we measured BPA levels in T2DM-associated vascular complications and correlated systemic BPA levels with vascular calcification-related gene expression.

METHODS

This study included 120 participants with T2DM and its associated vascular complications. Serum and urinary BPA were estimated using an ELISA kit, and gene expression of the study participants in peripheral blood mononuclear cells (PBMCs) was studied with quantitative real-time PCR.

RESULTS

Serum and urinary BPA levels were higher in T2DM and its associated vascular complications with CVD and DN patients compared to control. Both Serum and urinary BPA had higher significance with Sirt1 (p < 0.001, p < 0.001), Runx2 (p < 0.01, p < 0.001) and IL-1beta (p < 0.001, p < 0.02) gene expression in the study groups, but, TNF-alpha significant with Serum BPA (p < 0.04), not urinary BPA (p < 0.31).

CONCLUSION

BPA levels were positively correlated with lower Sirt1 and increased Runx2 in T2DM-associated vascular complications patients. Also, higher expression of IL-1beta and TNF-alpha was observed in T2DM-associated vascular complications patients. Our study is the first to associate BPA levels with vascular calcification in patients with T2DM and its associated vascular complications.

Tanshinone IIA ameliorates experimental diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress in cardiomyocytes via SIRT1

Diabetic cardiomyopathy (DCM) is a common complication in patients with diabetes, and ultimately leads to heart failure. Endoplasmic reticulum stress (ERS) induced by abnormal glycolipid metabolism is a critical factor that affects the occurrence and development of DCM. Additionally, the upregulation/activation of silent information regulation 2 homolog-1 (SIRT1) has been shown to protect against DCM. Tanshinone II A (Tan IIA), the main active component of Salviae miltiorrhizae radix et rhizome (a valuable Chinese medicine), has protective effects against cardiovascular disease and diabetes. However, its role and mechanisms in diabetes-induced cardiac dysfunction remain unclear. Therefore, we explored whether Tan IIA alleviates ERS-mediated DCM via SIRT1 and elucidated the underlying mechanism. The results suggested that Tan IIA alleviated the pathological changes in the hearts of diabetic mice, ameliorated the cytopathological morphology of cardiomyocytes, reduced the cell death rate, and inhibited the expression of ERS-related proteins and mRNA. The SIRT1 agonist inhibited the activities of glucose-regulated protein 78 (GRP78). Furthermore, the opposite results under the SIRT1 inhibitor. SIRT1 knockdown was induced by siRNA-SIRT1 transfection, and the degree of GRP78 acetylation was increased. Cumulatively, Tan IIA ameliorated DCM by inhibiting ERS and upregulating SIRT1 expression.

Integration of network pharmacology, transcriptomics and molecular docking reveals two novel hypoglycemic components in snow chrysanthemum

Our previous studies uncovered the glucose-lowering properties of snow chrysanthemum tea, however, the active ingredients and underlying mechanisms were yet to be uncovered. Flavonoids are the most active and abundant components in snow chrysanthemum tea. In this study, we treated leptin-deficient diabetic ob/ob or high-fat diet (HFD)-induced C57BL/6 J obese mice with or without total flavonoids of snow chrysanthemum (TFSC) for 14 weeks. Results indicated that TFSC ameliorated dyslipidemia and fatty liver, thereby reducing hyperlipidemia. Further mechanism experiments, including RNA-seq and experimental validation, revealed TFSC improved glycolipid metabolism primarily by activating the AMPK/Sirt1/PPARγ pathway. Additionally, by integrating UPLC, network pharmacology, transcriptomics, and experimental validation, we identified two novel hypoglycemic compounds, sulfuretin and leptosidin, in TFSC. Treatment with 12.5 μmol/L sulfuretin obviously stimulated cellular glucose consumption, and sulfuretin (3.125, 6.25 and 12.5 μmol/L) significantly mitigated glucose uptake damage and reliably facilitated glucose consumption in insulin-resistant HepG2 cells. Remarkably, sulfuretin interacted with the ligand-binding pocket of PPARγ via three hydrogen bond interactions with the residues LYS-367, GLN-286 and TYR-477. Furthermore, a concentration of 12.5 μmol/L sulfuretin effectively upregulated the expression of PPARγ, exhibiting a comparable potency to a renowned PPARγ agonist at 20 μmol/L. Taken together, our findings have identified two new hypoglycemic compounds and revealed their mechanisms, which significantly expands people's understanding of the active components in snow chrysanthemum that have hypoglycemic effects.

The Combination of Natural Molecules Naringenin, Hesperetin, Curcumin, Polydatin and Quercetin Synergistically Decreases SEMA3E Expression Levels and DPPIV Activity in In Vitro Models of Insulin Resistance

Type 2 diabetes mellitus (T2DM) is a disease characterized by a prolonged hyperglycemic condition caused by insulin resistance mechanisms in muscle and liver, reduced insulin production by pancreatic β cells, and a chronic inflammatory state with increased levels of the pro-inflammatory marker semaphorin 3E. Phytochemicals present in several foods have been used to complement oral hypoglycemic drugs for the management of T2DM. Notably, dipeptidyl peptidase IV (DPPIV) inhibitors have demonstrated efficacy in the treatment of T2DM. Our study aimed to investigate, in in vitro models of insulin resistance, the ability of the flavanones naringenin and hesperetin, used alone and in combination with the anti-inflammatory natural molecules curcumin, polydatin, and quercetin, to counteract the insulin resistance and pro-inflammatory molecular mechanisms that are involved in T2DM development. Our results show for the first time that the combination of naringenin, hesperetin, curcumin, polydatin, and quercetin (that mirror the nutraceutical formulation GliceFen^®, Mivell, Italy) synergistically decreases expression levels of the pro-inflammatory gene SEMA3E in insulin-resistant HepG2 cells and synergistically decreases DPPIV activity in insulin-resistant Hep3B cells, indicating that the combination of these five phytochemicals is able to inhibit pro-inflammatory and insulin resistance molecular mechanisms and could represent an effective innovative complementary approach to T2DM pharmacological treatment.

Nutraceutical Prevention of Diabetic Complications—Focus on Dicarbonyl and Oxidative Stress

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.

Protective effect of Astragaloside IV on chronic intermittent hypoxia-induced vascular endothelial dysfunction through the calpain-1/SIRT1/AMPK signaling pathway

Vascular endothelial dysfunction (VED) is linked with the pathogenesis of obstructive sleep apnea (OSA) comorbidities, such as cardiovascular disease. Astragaloside IV (As-IV) has exhibited significant improvement for endothelial dysfunction. Nonetheless, the protective mechanism is not clear. Therefore, the present study investigated the potential mechanism of As-IV on VED. Calpain-1 knockout and wild-type C57BL/6 mice exposed to chronic intermittent hypoxia (CIH) were established and treated with As-IV (40, 80 mg/kg) for 4 weeks. Human coronary artery endothelial cells (HCAECs) subjected to CIH exposure were pretreated with As-IV, MDL-28170 (calpain-1 inhibitor) and SRT1720 (SIRT1 activator) for 48 h in vitro. The endothelial function, inflammation, oxidative stress and mitochondrial function were measured to evaluate VED. Our data revealed that As-IV treatment ameliorated CIH-induced endothelial-dependent vasomotion and augmented nitric oxide (NO) production. As-IV administration suppressed the secretion of inflammation, oxidative stress and mitochondrial dysfunction. As-IV treatment reduced the expression of calpain-1 and restored the downregulated expression of SIRT1 and Thr¹⁷² AMPK and Ser¹¹⁷⁷ eNOS phosphorylation. The effects of calpain-1 knockout and SRT1720 were similar to the effect of As-IV on VED. These findings demonstrated that As-IV ameliorated VED induced by chronic intermittent hypoxia via the calpain-1/SIRT1/AMPK signaling pathway.

New Advances on Pathophysiology of Diabetes Neuropathy and Pain Management: Potential Role of Melatonin and DPP-4 Inhibitors

Pre-diabetes and diabetes are growing threats to the modern world. Diabetes mellitus (DM) is associated with comorbidities such as hypertension (83.40%), obesity (90.49%), and dyslipidemia (93.43%), creating a substantial burden on patients and society. Reductive and oxidative (Redox) stress level imbalance and inflammation play an important role in DM progression. Various therapeutics have been investigated to treat these neuronal complications. Melatonin and dipeptidyl peptidase IV inhibitors (DPP-4i) are known to possess powerful antioxidant and anti-inflammatory properties and have garnered significant attention in the recent years. In this present review article, we have reviewed the recently published reports on the therapeutic efficiency of melatonin and DPP-4i in the treatment of DM. We summarized the efficacy of melatonin and DPP-4i in DM and associated complications of diabetic neuropathy (DNP) and neuropathic pain. Furthermore, we discussed the mechanisms of action and their efficacy in the alleviation of oxidative stress in DM.

Sirtuins Modulation: A Promising Strategy for HIV-Associated Neurocognitive Impairments

HIV-Associated neurocognitive disorder (HAND) is one of the major concerns since it persists in 40% of this population. Nowadays, HAND neuropathogenesis is considered to be caused by the infected cells that cross the brain-blood barrier and produce viral proteins that can be secreted and internalized into neurons leading to disruption of cellular processes. The evidence points to viral proteins such as Tat as the causal agent for neuronal alteration and thus HAND. The hallmarks in Tat-induced neurodegeneration are endoplasmic reticulum stress and mitochondrial dysfunction. Sirtuins (SIRTs) are NAD+-dependent deacetylases involved in mitochondria biogenesis, unfolded protein response, and intrinsic apoptosis pathway. Tat interaction with these deacetylases causes inhibition of SIRT1 and SIRT3. Studies revealed that SIRTs activation promotes neuroprotection in neurodegenerative diseases such Alzheimer's and Parkinson's disease. Therefore, this review focuses on Tat-induced neurotoxicity mechanisms that involve SIRTs as key regulators and their modulation as a therapeutic strategy for tackling HAND and thereby improving the quality of life of people living with HIV.