Therapies for hyperglycaemia-induced diabetic complications: from animal models to clinical trials

Breakthroughs in road mapping IL-35 mediated immunotherapy for type-1 and autoimmune diabetes mellitus

IL-35 is a recently discovered protein made up of IL-12α and IL-27β chains. It is encoded by IL12A and EBI3 genes. Interest in researching IL-35 has significantly increased in recent years, as evidenced by numerous scientific publications. Diabetes is on the rise globally, causing more illness and death in developing countries. The International Diabetes Federation (IDF) reports that diabetes is increasingly affecting children and teenagers, with varying rates across different regions. Therefore, scientists seek new diabetes treatments despite the growth of drug research. Recent research aims to emphasize IL-35 as a critical regulator of diabetes, especially type 1 and autoimmune diabetes. This review provides an overview of recent research on IL-35 and its link to diabetes and its associated complications. Studies suggest that IL-35 can offer protection against type-1 diabetes and autoimmune diabetes by regulating macrophage polarization, T-cell-related cytokines, and regulatory B cells (Bregs). This review will hopefully assist biomedical scientists in exploring the potential role of IL-35-mediated immunotherapy in treating diabetes. However, further research is necessary to determine the exact mechanism and plan clinical trials.

Pharmacological mechanisms of Taohe Chengqi decoction in diabetic cardiovascular complications: A systematic review, network pharmacology and molecular docking

Background

Diabetic cardiovascular complications are the leading cause of diabetes-related deaths. These complications place an enormous and growing burden on global health systems and economies. The objective of this study was to conduct a systematic review on the therapeutic mechanisms of Taohe Chengqi Decoction (THCQD) in the treatment of diabetic cardiovascular complications. To predict the potential mechanisms of action of THCQD on diabetic cardiovascular complications using network pharmacology, and to validate these predictions through molecular docking analysis.

Methods

To collect relevant animal experiments, we searched a total of 6 databases. Eligibility for the study was determined based on inclusion and exclusion criteria. Data extraction was then performed on the literature. Methodological quality of animal studies was assessed using SYRCLE criteria. Based on network pharmacology, intersecting genes for THCQD and diabetic cardiovascular complications were obtained using Venny, PPI analysis and topology analysis of intersecting genes were performed; GO and KEGG were used for enrichment analysis and prediction of new targets of action. Molecular docking techniques were employed to model the interactions between drug components and target genes, thereby validating the results of network pharmacology predictions.

Results

A total of 16 studies were finally identified that fit the direction of this review. Included 6 studies of the myocardium, 1 study of the aortic arch, 5 studies of the femoral artery, 4 studies of the thoracic aorta. THCQD exhibited anti-inflammatory, anti-fibrotic and anti-atherosclerotic effects on cardiovascular complications in diabetic rats. Network pharmacology results showed that C0363 (Resveratrol), C0041 (Emodin), and C1114 (Baicalein) were the key components in the treatment of diabetic cardiovascular complications by THCQD. PPI results showed that INS, AKT1, TNF, ALB, IL6, IL1B as the genes that interact with the top 6. KEGG enrichment analysis identified the AGE-RAGE signaling pathway in diabetic complications as the most prominent pathway enriched by THCQD for diabetic cardiovascular complications genes. The results of molecular docking showed that the key active components demonstrated favorable interactions with their corresponding target genes.

Conclusion

In conclusion, the results of both basic and web-based pharmacological studies support the beneficial effects of the natural herbal formulation THCQD on diabetic cardiovascular complications. This decoction has anti-inflammatory and antifibrotic properties and is effective in ameliorating diabetic cardiovascular disease. The network pharmacology results further support these ideas and identify the AGE-RAGE signaling pathway in diabetic complications as possibly the most relevant pathway for THCQD in the treatment of diabetic cardiovascular complications. The extent of the therapeutic potential of all-natural herbal components in the treatment of diabetic cardiovascular disease merits further investigation.

Macromolecules from mushrooms, venoms, microorganisms, and plants for diabetes treatment - Progress or setback?

Diabetes is a substantial public health issue, while its prevalence continues to rise worldwide, affecting millions of persons between the ages of 20 and 80, the development of new therapeutic classes improving glycemic control and consequently micro and macrovascular complications are needed. Today, diabetes treatment is daily for life, and should not be interrupted. However, insulin secretagogues medications, and exogenous self-administration of insulin provide efficient antidiabetic effects, but their misuse leads to hypoglycemic complications besides other risks, hence the need to look for other natural products not to use solely but in concert with others types of medications. In this review, we will highlight briefly the pathophysiology of diabetes and its complications, then we will report the main bioactive macromolecules derived from various sources of natural products providing anti-diabetic properties. However, further researches need to be carried out to face the limitations hampering the development of effective natural drugs for diabetes treatment.

The role and mechanism of action of miR-483-3p in mediating the effects of IGF-1 on human renal tubular epithelial cells induced by high glucose

This study aimed to elucidate the influence of miR-483-3p on human renal tubular epithelial cells (HK-2) under high glucose conditions and to understand its mechanism. Human proximal tubular epithelial cells (HK-2) were exposed to 50 mmol/L glucose for 48 h to establish a renal tubular epithelial cell injury model, denoted as the high glucose group (HG group). Cells were also cultured for 48 h in a medium containing 5.5 mmol/L glucose, serving as the low glucose group. Transfection was performed in various groups: HK-2 + low glucose (control group), high glucose (50 mM) (HG group), high glucose + miR-483-3p mimics (HG + mimics group), high glucose +miR-483-3p inhibitor (HG + inhibitor group), and corresponding negative controls. Real-time quantitative polymerase chain reaction (qPCR) assessed the mRNA expression of miR-483-3p, bax, bcl-2, and caspase-3. Western blot determined the corresponding protein levels. Proliferation was assessed using the CCK-8 assay, and cell apoptosis was analyzed using the fluorescence TUNEL method. Western blot and Masson's staining were conducted to observe alterations in cell fibrosis post miR-483-3p transfection. Furthermore, a dual-luciferase assay investigated the targeting relationship between miR-483-3p and IGF-1. The CCK8 assay demonstrated that the HG + mimics group inhibited HK-2 cell proliferation, while the fluorescent TUNEL method revealed induced cell apoptosis in this group. Conversely, the HG + inhibitor group promoted cell proliferation and suppressed cell apoptosis. The HG + mimics group upregulated mRNA and protein expression of pro-apoptotic markers (bax and caspase-3), while downregulating anti-apoptotic marker (bcl-2) expression. In contrast, the HG + inhibitor group showed opposite effects. Collagen I and FN protein levels were significantly elevated in the HG + mimics group compared to controls (P < 0.05). Conversely, in the HG + inhibitor group, the protein expression of Collagen I and FN was notably reduced compared to the HG group (P < 0.05). The dual luciferase reporter assay confirmed that miR-483-3p could inhibit the luciferase activity of IGF-1's 3'-UTR region (P < 0.05). miR-483-3p exerts targeted regulation on IGF-1, promoting apoptosis and fibrosis in renal tubular epithelial cells induced by high glucose conditions.

Effect of Crocus sativus Extract Supplementation in the Metabolic Control of People with Diabetes Mellitus Type 1: A Double-Blind Randomized Placebo-Controlled Trial

Introduction-Background: Data from experimental trials show that Crocus sativus L. (saffron) is considered to improve glycemia, lipid profile, and blood pressure and reduce oxidative stress. So far, clinical trials have been conducted in individuals with metabolic syndrome and Diabetes Mellitus type 2 (DMT-2). The purpose of this study is to assess the effectiveness of saffron in individuals with Diabetes Mellitus type 1 (DMT-1).

PATIENTS-METHODS

61 individuals with DMT-1, mean age 48 years old (48.3 ± 14.6), 26 females (42.6%) were randomized to receive a new oral supplement in sachets containing probiotics, prebiotics, magnesium, and Crocus sativus L. extract or placebo containing probiotics, prebiotics and magnesium daily for 6 months. Glycemic control was assessed with a continuous glucose monitoring system and laboratory measurement of HbA1c and lipid profile was also examined. Blood pressure at baseline and end of intervention was also measured. Individuals were either on a continuous subcutaneous insulin infusion with an insulin pump or in multiple daily injection regimens. Diabetes distress and satiety were assessed through a questionnaire and body composition was assessed with bioelectrical impedance.

RESULTS

At the end of the intervention, the two groups differed significantly only in serum triglycerides (p = 0.049). After 6 months of treatment, a significant reduction in the active group was observed in glycated hemoglobin (p = 0.046) and serum triglycerides (p = 0.021) compared to baseline. The other primary endpoints (glycemic control, lipid profile, blood pressure) did not differ within the groups from baseline to end of intervention, and there was no significant difference between the two groups. Diabetes distress score improved significantly only in the active group (p = 0.044), suggesting an overall improvement in diabetes disease burden in these individuals but that was not significant enough between the two groups.

CONCLUSIONS

A probiotic supplement with saffron extract improves serum triglycerides in well-controlled people with DMT-1 and may potentially be a valuable adjunct for enhancing glycemic control.

Nimbidiol protects from renal injury by alleviating redox imbalance in diabetic mice

Introduction

Chronic hyperglycemia-induced oxidative stress plays a crucial role in the development of diabetic nephropathy (DN). Moreover, adverse extracellular matrix (ECM) accumulation elevates renal resistive index leading to progressive worsening of the pathology in DN. Nimbidiol is an alpha-glucosidase inhibitor, isolated from the medicinal plant, 'neem' (Azadirachta indica) and reported as a promising anti-diabetic compound. Previously, a myriad of studies demonstrated an anti-oxidative property of a broad-spectrum neem-extracts in various diseases including diabetes. Our recent study has shown that Nimbidiol protects diabetic mice from fibrotic renal dysfunction in part by mitigating adverse ECM accumulation. However, the precise mechanism remains poorly understood.

Methods

The present study aimed to investigate whether Nimbidiol ameliorates renal injury by reducing oxidative stress in type-1 diabetes. To test the hypothesis, wild-type (C57BL/6J) and diabetic Akita (C57BL/6-Ins2Akita/J) mice aged 10-14 weeks were used to treat with saline or Nimbidiol (400 μg kg-1 day-1) for 8 weeks.

Results

Diabetic mice showed elevated blood pressure, increased renal resistive index, and decreased renal vasculature compared to wild-type control. In diabetic kidney, reactive oxygen species and the expression levels of 4HNE, p22phox, Nox4, and ROMO1 were increased while GSH: GSSG, and the expression levels of SOD-1, SOD-2, and catalase were decreased. Further, eNOS, ACE2, Sirt1 and IL-10 were found to be downregulated while iNOS and IL-17 were upregulated in diabetic kidney. The changes were accompanied by elevated expression of the renal injury markers viz., lipocalin-2 and KIM-1 in diabetic kidney. Moreover, an upregulation of p-NF-κB and a downregulation of IkBα were observed in diabetic kidney compared to the control. Nimbidiol ameliorated these pathological changes in diabetic mice.

Conclusion

Altogether, the data of our study suggest that oxidative stress largely contributes to the diabetic renal injury, and Nimbidiol mitigates redox imbalance and thereby protects kidney in part by inhibiting NF-κB signaling pathway in type-1 diabetes.

Efficacy of adipose-derived mesenchymal stem cell therapy in the treatment of chronic micro- and macrovascular complications of diabetes

Diabetes mellitus is a highly prevalent disease characterized by hyperglycaemia that damages the vascular system, leading to micro- (retinopathy, neuropathy, nephropathy) and macrovascular diseases (cardiovascular disease). There are also secondary complications of diabetes (cardiomyopathy, erectile dysfunction or diabetic foot ulcers). Stem cell-based therapies have become a promising tool targeting diabetes symptoms and its chronic complications. Among all stem cells, adipose-derived mesenchymal stem cells (ADMSCs) are of great importance because of their abundance, non-invasive isolation and no ethical limitations. Characteristics that make ADMSCs good candidates for cell-based therapy are their wide immunomodulatory properties and paracrine activities through the secretion of an array of growth factors, chemokines, cytokines, angiogenic factors and anti-apoptotic molecules. Besides, after transplantation, ADMSCs show great ex vivo expansion capacity and differentiation to other cell types, including insulin-producing cells, cardiomyocytes, chondrocytes, hepatocyte-like cells, neurons, endothelial cells, photoreceptor-like cells, or astrocytes. Preclinical studies have shown that ADMSC-based therapy effectively improved visual acuity, ameliorated polyneuropathy and foot ulceration, arrested the development and progression of diabetic kidney disease, or alleviated the diabetes-induced cardiomyocyte hypertrophy. However, despite the positive results obtained in animal models, there are still several challenges that need to be overcome before the results of preclinical studies can be translated into clinical applications. To date, there are several clinical trials or ongoing trials using ADMSCs in the treatment of diabetic complications, most of them in the treatment of diabetic foot ulcers. This narrative review summarizes the most recent outcomes on the usage of ADMSCs in the treatment of long-term complications of diabetes in both animal models and clinical trials.

TOX3 deficiency mitigates hyperglycemia by suppressing hepatic gluconeogenesis through FoxO1

BACKGROUND

Excessive hepatic glucose production is a hallmark that contributes to hyperglycemia in type 2 diabetes (T2D). The regulatory network governing this process remains incompletely understood. Here, we demonstrate that TOX3, a high-mobility group family member, acts as a major transcriptional driver for hepatic glucose production.

METHODS

Tox3-overexpressed and knockout mice were constructed to explore its metabolic functions. Transcriptomic and chromatin-immunoprecipitation sequencing (ChIP-seq) were used to identify downstream targets of TOX3. Both FoxO1 silencing and inhibitor approaches were used to assess the contribution of FoxO1. TOX3 expression levels were examined in the livers of mice and human subjects. Finally, Tox3 was genetically manipulated in diet-induced obese mice to evaluate its therapeutic potential.

RESULTS

Hepatic Tox3 overexpression activates the gluconeogenic program, resulting in hyperglycemia and insulin resistance in mice. Hepatocyte-specific Tox3 knockout suppresses gluconeogenesis and improves insulin sensitivity. Mechanistically, integrated hepatic transcriptomic and ChIP-seq analyses identify FoxO1 as a direct target of TOX3. TOX3 stimulates FoxO1 transcription by directly binding to and activating its promoter, whereas FoxO1 silencing abrogates TOX3-induced dysglycemia in mice. In human subjects, hepatic TOX3 expression shows a significant positive correlation with blood glucose levels under normoglycemic conditions, yet is repressed by high glucose during T2D. Importantly, hepatic Tox3 deficiency markedly protects against and ameliorates the hyperglycemia and glucose intolerance in diet-induced diabetic mice.

CONCLUSIONS

Our findings establish TOX3 as a driver for excessive gluconeogenesis through activating hepatic FoxO1 transcription. TOX3 could serve as a promising target for preventing and treating hyperglycemia in T2D.

A Dual Therapeutic Approach to Diabetes Mellitus via Bioactive Phytochemicals Found in a Poly Herbal Extract by Restoration of Favorable Gut Flora and Related Short-Chain Fatty Acids

Diabetes mellitus (DM), a metabolic and endocrine condition, poses a serious threat to human health and longevity. The emerging role of gut microbiome associated with bioactive compounds has recently created a new hope for DM treatment. UHPLC-HRMS methods were used to identify these compounds in a poly herbal ethanolic extract (PHE). The effects of PHE on body weight (BW), fasting blood glucose (FBG) level, gut microbiota, fecal short-chain fatty acids (SCFAs) production, and the correlation between DM-related indices and gut microbes, in rats were investigated. Chebulic acid (0.368%), gallic acid (0.469%), andrographolide (1.304%), berberine (6.442%), and numerous polysaccharides were the most representative constituents in PHE. A more significant BW gain and a reduction in FBG level towards normal of PHE 600 mg/kg treated rats group were resulted at the end of 28th days of the study. Moreover, the composition of the gut microbiota corroborated the study's hypothesis, as evidenced by an increased ratio of Bacteroidetes to Firmicutes and some beneficial microbial species, including Prevotella copri and Lactobacillus hamster. The relative abundance of Bifidobacterium pseudolongum, Ruminococcus bromii, and Blautia producta was found to decline in PHE treatment groups as compared to diabetic group. The abundance of beneficial bacteria in PHE 600 mg/kg treatment group was concurrently associated with increased SCFAs concentrations of acetate and propionate (7.26 nmol/g and 4.13 nmol/g). The findings of this study suggest a promising approach to prevent DM by demonstrating that these naturally occurring compounds decreased FBG levels by increasing SCFAs content and SCFAs producing gut microbiota.

Protein Kinase C (PKC)-mediated TGF-β Regulation in Diabetic Neuropathy: Emphasis on Neuro-inflammation and Allodynia

According to the World Health Organization (WHO), diabetes has been increasing steadily over the past few decades. In developing countries, it is the cause of increased morbidity and mortality. Diabetes and its complications are associated with education, occupation, and income across all levels of socioeconomic status. Factors, such as hyperglycemia, social ignorance, lack of proper health knowledge, and late access to medical care, can worsen diabetic complications. Amongst the complications, neuropathic pain and inflammation are considered the most common causes of morbidity for common populations. This review is focused on exploring protein kinase C (PKC)-mediated TGF-946; regulation in diabetic complications with particular emphasis on allodynia. The role of PKC-triggered TGF-946; in diabetic neuropathy is not well explored. This review will provide a better understanding of the PKC-mediated TGF-946; regulation in diabetic neuropathy with several schematic illustrations. Neuroinflammation and associated hyperalgesia and allodynia during microvascular complications in diabetes are scientifically illustrated in this review. It is hoped that this review will facilitate biomedical scientists to better understand the etiology and target drugs effectively to manage diabetes and diabetic neuropathy.

[The Role of TGF-β1/SMAD in Diabetic Nephropathy: Mechanisms and Research Development]

Diabetic nephropathy (DN) is a common complication of diabetes and a leading cause of end-stage renal disease. Transforming growth factor-β1 (TGF-β1)/SMAD signaling activation plays an important role in the onset and progression of DN. Reported findings suggest that the activation of TGF-β1 (including the latent form, the active form, and the receptors) and its downstream signaling proteins (SMAD3, SMAD7, etc.) plays a critical role in DN. In addition, TGF-β1/SMAD signaling may mediate the pathogenesis and progression of DN via various microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Emerging evidence shows that TGF-β1, SMAD3, and SMAD7 are the main signaling proteins that contribute to the development of DN, and that they can be potential targets for the treatment of DN. However, recent clinical trials have shown that the anti-TGF-β1 monoclonal antibody treatment fails to effectively alleviate DN, which suggests that upstream inhibition of TGF-β1/SMAD signaling does not alleviate clinical symptoms and that this may be related to the fact that TGF-β1/SMAD has multiple biological effects. Targeted inhibition of the downstream TGF-β1 signaling (e.g., SMAD3 and SMAD7) may be an effective approach to attenuate DN. This article discussed the current understanding of the molecular mechanisms and potential targets for the treatment and prevention of DN by focusing on TGF-β1/SMAD signaling.

Precision Medicine in Diabetic Kidney Disease: A Narrative Review Framed by Lived Experience

Purpose of review

Diabetic kidney disease (DKD) is a leading cause of chronic kidney disease (CKD) for which many treatments exist that have been shown to prevent CKD progression and kidney failure. However, DKD is a complex and heterogeneous etiology of CKD with a spectrum of phenotypes and disease trajectories. In this narrative review, we discuss precision medicine approaches to DKD, including genomics, metabolomics, proteomics, and their potential role in the management of diabetes mellitus and DKD. A patient and caregivers of patients with lived experience with CKD were involved in this review.

Sources of information

Original research articles were identified from MEDLINE and Google Scholar using the search terms "diabetes," "diabetic kidney disease," "diabetic nephropathy," "chronic kidney disease," "kidney failure," "dialysis," "nephrology," "genomics," "metabolomics," and "proteomics."

Methods

A focused review and critical appraisal of existing literature regarding the precision medicine approaches to the diagnosis, prognosis, and treatment of diabetes and DKD framed by a patient partner's/caregiver's lived experience.

Key findings

Distinguishing diabetic nephropathy from CKD due to other types of DKD and non-DKD is challenging and typically requires a kidney biopsy for a diagnosis. Biomarkers have been identified to assist with the prediction of the onset and progression of DKD, but they have yet to be incorporated and evaluated relative to clinical standard of care CKD and kidney failure risk prediction tools. Genomics has identified multiple causal genetic variants for neonatal diabetes mellitus and monogenic diabetes of the young that can be used for diagnostic purposes and to specify antiglycemic therapy. Genome-wide-associated studies have identified genes implicated in DKD pathophysiology in the setting of type 1 and 2 diabetes but their translational benefits are lagging beyond polygenetic risk scores. Metabolomics and proteomics have been shown to improve diagnostic accuracy in DKD, have been used to identify novel pathways involved in DKD pathogenesis, and can be used to improve the prediction of CKD progression and kidney failure as well as predict response to DKD therapy.

Limitations

There are a limited number of large, high-quality prospective observational studies and no randomized controlled trials that support the use of precision medicine based approaches to improve clinical outcomes in adults with or at risk of diabetes and DKD. It is unclear which patients may benefit from the clinical use of genomics, metabolomics and proteomics along the spectrum of DKD trajectory.

Implications

Additional research is needed to evaluate the role of the use of precision medicine for DKD management, including diagnosis, differentiation of diabetic nephropathy from other etiologies of DKD and CKD, short-term and long-term risk prognostication kidney outcomes, and the prediction of response to and safety of disease-modifying therapies.

Exploring the Therapeutic Potential of Berberine and Tocopherol in Managing Diabetic Neuropathy: A Comprehensive Approach towards Alleviating Chronic Neuropathic Pain

Diabetic neuropathy (DN) causes sensory dysfunction, such as numbness, tingling, or burning sensations. Traditional medication may not ease pain and discomfort, but natural remedies such as Berberine (BR) and vitamin E or Tocopherol (TOC) have therapeutic potential to reduce inflammation while improving nerve function. Novel substances offer a more potent alternative method for managing severe chronic neuropathic pain that does not react to standard drug therapy by targeting various pathways that regulate it. Rats with diabetic control received oral doses of BR + TOC that showed significant changes in serum insulin levels compared to DN controls after 90 days, suggesting a decrease in sensitivity to painful stimuli partly by modulating the oxidative stress of the inflammatory pathway such as TNF-α suppression or stimulation of TNF-α depending on the amount of dose consumed by them. NF-kB also played its role here. Administering doses of BR and TOC reduced heightened levels of NF-kB and AGEs, effectively counteracting inflammation-targeted key factors in diabetes, promising possibilities for the benefits of these molecules revealed through in vivo investigation. In summary, treating neuropathy pain with a more comprehensive and organic approach can involve harnessing the powerful capabilities of BR and TOC. These compounds have been found to not only considerably decrease inflammation but also provide effective nerve protection while enhancing overall nerve function. With their multifunctional impacts on various neuropathic pain pathways in the body, these naturally occurring substances offer an exciting possibility for those who encounter high levels of neuropathic distress that do not respond well to conventional medication-centred therapies.

Optimizing glycation control in diabetes: An integrated approach for inhibiting nonenzymatic glycation reactions of biological macromolecules

Diabetes is a multifactorial disorder that increases mortality and disability due to its complications. A key driver of these complications is nonenzymatic glycation, which generates advanced glycation end-products (AGEs) that impair tissue function. Therefore, effective nonenzymatic glycation prevention and control strategies are urgently needed. This review comprehensively describes the molecular mechanisms and pathological consequences of nonenzymatic glycation in diabetes and outlines various anti-glycation strategies, such as lowering plasma glucose, interfering with the glycation reaction, and degrading early and late glycation products. Diet, exercise, and hypoglycemic medications can reduce the onset of high glucose at the source. Glucose or amino acid analogs such as flavonoids, lysine and aminoguanidine competitively bind to proteins or glucose to block the initial nonenzymatic glycation reaction. In addition, deglycation enzymes such as amadoriase, fructosamine-3-kinase, parkinson's disease protein, glutamine amidotransferase-like class 1 domain-containing 3A and terminal FraB deglycase can eliminate existing nonenzymatic glycation products. These strategies involve nutritional, pharmacological, and enzymatic interventions that target different stages of nonenzymatic glycation. This review also emphasizes the therapeutic potential of anti-glycation drugs for preventing and treating diabetes complications.

Effect of L-serine on oxidative stress markers in the kidney of streptozotocin-induced diabetic mice

Oxidative stress is critical in the occurrence and development of diabetes and its related complications. L-serine has recently been shown to reduce oxidative stress, the incidence of autoimmune diabetes and improve glucose homeostasis. The aim of this study was to investigate the effects of daily L-serine administration on blood glucose, renal function and oxidative stress markers in the kidney of streptozotocin-induced diabetic mice. Eighteen C57BL/6 male mice were randomly divided into three groups (n = 6 per group). Streptozotocin was used to induce diabetes and a group of diabetic mice was treated with 280 mg/day of L-serine dissolved in drinking water for 4 weeks. The level of blood glucose, biochemical markers of renal function (total protein, urea, creatinine and albumin) and oxidative stress markers (protein carbonyls, malondialdehyde, glutathione peroxidase, superoxide dismutase and catalase) were measured using spectrophotometry. The results indicated that L-serine significantly decreased the glucose level in diabetic mice (188.6 ± 22.69 mg/dL, P = 0.02). Moreover, treatment of diabetic mice with L-serine reduced protein carbonyls (3.249 ± 0.9165 nmol/mg protein, P < 0.05) and malondialdehyde levels (1.891 ± 0.7696 μM/mg protein, P = 0.051). However, L-serine showed no significant effects on renal function, and a slight reduction in histopathological changes was observed in mice receiving L-serine. This study revealed that L-serine effectively ameliorates oxidative stress in kidney tissue and reduces the blood glucose concentration in diabetic mice.

β-Cell Autophagy Pathway and Endoplasmic Reticulum Stress Regulating-Role of Liposomal Curcumin in Experimental Diabetes Mellitus: A Molecular and Morphometric Study

Background: Autophagy can confer protection to pancreatic β-cells from the harmful effects of metabolic stress by delaying apoptosis. Curcumin (CUR) alleviates oxidative and endoplasmic reticulum (ER) stress, activates autophagy, reduces inflammation, and decreases β-cell damage in type I diabetes. Liposomal CUR (LPs-CUR) has a higher therapeutic value and better pharmacokinetics than CUR. Objectives: We determined LPs-CUR’s ability to alleviate stress, reduce β-cell damage and unraveled the mechanism underlying its protective effect using a streptozotocin (STZ)-induced type I diabetic rat model. Methods: Sprague−Dawley rats were grouped into vehicle control, STZ-diabetic (STZ 65 mg/kg), STZ-diabetic-3-MA (3-methyladenine [3-MA] 10 mg/kg b.wt), STZ. diabetic-LPs-CUR (LPs-CUR 10 mg/kg b.wt), and STZ diabetic-LPs-CUR-3-MA (LPs-CUR 10 mg/kg b.wt; 3-MA 10 mg/kg b.wt). Results: LPs-CUR significantly reduced blood glucose, oxidative stress, and cellular inflammation in the pancreatic tissue (p < 0.001). ER stress-dependent genes included ATF-6, eIF-2, CHOP, JNK, BiP, and XBP LPs-CUR significantly suppressed fold changes, while it upregulated the autophagic markers Beclin-1 and LC3-II. Conclusions: LP-CUR ameliorates β-cell damage by targeting the autophagy pathway with the regulatory miRNAs miR-137 and miR-29b, which functionally abrogates ER stress in β-cells. This study presents a new therapeutic target for managing type I diabetes using miR-137 and miR-29b.

Pulsed magnetic field treatment ameliorates the progression of peripheral neuropathy by modulating the neuronal oxidative stress, apoptosis and angiogenesis in a rat model of experimental diabetes

OBJECTIVE

The present study aimed to investigate the possible anti-neuropathic effects of daily pulsed magnetic field treatments (PMF) in streptozotocin (60 mg/kg) induced 4 weeks diabetic (type-1) wistar rats (6-8 months).

MATERIALS AND METHODS

Body mass, blood glucose and thermal and mechanical sensations were evaluated during the PMF or sham-PMF in diabetic or non-diabetic rats (n = 7/group). After the measurements of motor nerve conduction velocities (MNCV), the levels of several biomarkers for oxidative stress, apoptosis and angiogenesis in spinal cord and sciatic nerve were measured.

RESULTS

PMF for 4 weeks significantly recovered the MCNV (96.9% and 63.9%) and almost fully (100%) restored to the latency and threshold. PMF also significantly suppressed the diabetes induced enhances in biochemical markers of both neuronal tissues.

CONCLUSIONS

Findings suggested that PMF might prevent the development of functional abnormalities in diabetic rats due to its anti-oxidative, anti-apoptotic and anti-angiogenic actions in neuronal tissues.

Integrated experimental-computational analysis of a HepaRG liver-islet microphysiological system for human-centric diabetes research

Microphysiological systems (MPS) are powerful tools for emulating human physiology and replicating disease progression in vitro. MPS could be better predictors of human outcome than current animal models, but mechanistic interpretation and in vivo extrapolation of the experimental results remain significant challenges. Here, we address these challenges using an integrated experimental-computational approach. This approach allows for in silico representation and predictions of glucose metabolism in a previously reported MPS with two organ compartments (liver and pancreas) connected in a closed loop with circulating medium. We developed a computational model describing glucose metabolism over 15 days of culture in the MPS. The model was calibrated on an experiment-specific basis using data from seven experiments, where HepaRG single-liver or liver-islet cultures were exposed to both normal and hyperglycemic conditions resembling high blood glucose levels in diabetes. The calibrated models reproduced the fast (i.e. hourly) variations in glucose and insulin observed in the MPS experiments, as well as the long-term (i.e. over weeks) decline in both glucose tolerance and insulin secretion. We also investigated the behaviour of the system under hypoglycemia by simulating this condition in silico, and the model could correctly predict the glucose and insulin responses measured in new MPS experiments. Last, we used the computational model to translate the experimental results to humans, showing good agreement with published data of the glucose response to a meal in healthy subjects. The integrated experimental-computational framework opens new avenues for future investigations toward disease mechanisms and the development of new therapies for metabolic disorders.

Microphysiological systems (MPS) are powerful tools to unravel biological knowledge underlying disease. MPS provide a physiologically relevant, human-based in vitro setting, which can potentially yield better translatability to humans than current animal models and traditional cell cultures. However, mechanistic interpretation and extrapolation of the experimental results to human outcome remain significant challenges. In this study, we confront these challenges using an integrated experimental-computational approach. We present a computational model describing glucose metabolism in a previously reported MPS integrating liver and pancreas. This MPS supports a homeostatic feedback loop between HepaRG/HHSteC spheroids and pancreatic islets, and allows for detailed investigations of mechanisms underlying type 2 diabetes in humans. We show that the computational model captures the complex dynamics of glucose-insulin regulation observed in the system, and can provide mechanistic insight into disease progression features, such as insulin resistance and β-cell dynamics. Furthermore, the computational model can explain key differences in temporal dynamics between MPS and human responses, and thus provides a tool for translating experimental insights into human outcome. The integrated experimental-computational framework opens new avenues for future investigations toward disease mechanisms and the development of new therapies for metabolic disorders.

Rev-erbs agonist SR9009 alleviates ischemia-reperfusion injury by heightening endogenous cardioprotection at onset of type-2 diabetes in rats: Down-regulating ferritinophagy/ferroptosis signaling

The complex progression of type-2 diabetes (T2DM) results in inconsistent findings on myocardial susceptibility to ischemia-reperfusion (IR). IR injuries in multiple organs interconnect with ferroptosis. Targeting Rev-erbs might limit ferroptosis, with increasing attention turning to the application of circadian medicine against IR injuries. However, whether the Rev-erbs agonist SR9009 could mitigate diabetic IR injury remains unknown. Here, we investigated the susceptibility to IR at onset of T2DM in rats and its potential association between SR9009 and ferritinophagy/ferroptosis signaling. Onset of T2DM model was induced with a high-fat diet and the intraperitoneal injection of a low dose of streptozotocin. Myocardial IR model was established as well. Rats' general characteristics, cardiac function, glycolipid profiles, serum biochemistry, apoptosis index (AI) and morphological histology were observed and analyzed. Western blot and immunofluorescence (IF) were employed to evaluate the expression of ferritinophagy/ferroptosis signaling and its co-localization. Glycolipid profiles and cardiac diastolic function were significantly impaired in diabetic rats. CK-MB, AI levels and ferritinophagy/ferroptosis-related proteins expression decreased towards myocardial IR in diabetic rats compared to non-diabetic rats'. The ferroptosis inducer Erastin up-regulated SOD, MDA, and AI levels, as well as the expression of ferritinophagy/ferroptosis-related proteins in diabetic rats towards IR. Treatment with SR9009 down-regulated the degree of myocardial injury and ferritinophagy/ferroptosis-related proteins expression compared to diabetic rats treated with or without Erastin. Onset of T2DM activated endogenous cardioprotection against the susceptibility to myocardial IR injury, and SR9009 exogenously enhanced this endogenous mechanism and alleviated myocardial IR injury at onset of T2DM by down-regulating ferritinophagy/ferroptosis signaling.

Antidiabetic and neuroprotective effects of a novel repaglinide analog

Repaglinide (RPG) is an oral insulin secretagogue used in the treatment of diabetes. In this study, a new RPG analog was synthesized. Its antidiabetic and neuroprotective effects on dorsal root ganglions (DRG) in streptozotocin (STZ)-induced diabetic rats were examined compared to RPG. To assess the effects of 2-methoxy-4-(2-((3-methyl-1-(2-(piperidin-1-yl)phenyl)butyl)amino)-2-oxoethoxy)benzoic acid (OXR), the impact of OXR on oxidative stress biomarkers, motor function, and the expression of the glutamate dehydrogenase 1 (GLUD1), SLC2A2/glucose transporter 2 (GLUT2), and glucokinase (GCK) genes in STZ-induced diabetic rats were assessed. DRGs were examined histologically using hemotoxylin and eosin staining. Molecular docking was used to investigate the interactions between OXR and the binding site of RPG, the ATP-sensitive potassium (KATP) channel. Following 5 weeks of treatment, OXR significantly increased the level of total antioxidant power, decreased reactive oxygen species, and lipid peroxidation in the DRGs of diabetic rats. OXR restored STZ-induced pathophysiological damages in DRG tissues. Administration of OXR improved motor function of rats with diabetic neuropathy. Administration of 0.5 mg/kg OXR reduced blood glucose while promoting insulin, mainly through upregulation of messenger RNA expression of GLUD1, GLUT2, and GCK in the pancreas. Molecular docking revealed a favorable binding mode of OXR to the KATP channel. In conclusion, OXR has neuroprotective effects in diabetic rats by lowering oxidative stress, lowering blood glucose, and stimulating insulin secretion. We report that 0.5 mg/kg OXR administration was the most effective concentration of the compound in this study. OXR may be a promising target for further research on neuroprotective antidiabetic molecules.

Recent Advances of LncRNA H19 in Diabetes LncRNA H19 in Diabetes

Diabetes mellitus (DM) causes damage to major organs, including the heart, liver, brain, kidneys, eyes, and blood vessels, threatening the health of the individuals. Emerging evidence has demonstrated that lncRNAs has important functions in the pathogenesis of human diseases, such as cancers, neurodegenerative diseases, cardiac fibroblast phenotypes, hypertension, heart failure, atherosclerosis and diabetes. Recently, H19, a lncRNA, has been reported to shown to participate in the regulatory process of muscle differentiation, glucose metabolism, and tumor metastasis, as well as endometrial development. However, the roles of H19 in DM were still not completely understood. This review was conducted to summarize the functions of H19 in diabetes and discuss the challenges and possible strategies of H19 in DM.

Vitisin A, a Resveratrol Tetramer, Improves Scopolamine-Induced Impaired Learning and Memory Functions in Amnesiac ICR Mice

Resveratrol has been reported to exhibit neuroprotective activities in vitro and in vivo. However, little is known about resveratrol tetramers of hopeaphenol, vitisin A, and vitisin B with the same molecular mass in the improvement of degenerative disorders. In this study, two 95% ethanol extracts (95EE) from stem parts of Vitis thunbergii Sieb. & Zucc. (VT-95EE) and from the root (R) parts of Vitis thunbergii var. taiwaniana (VTT-R-95EE) showed comparable acetylcholinesterase (AChE) inhibitory activities. It was found that VT-95EE and VTT-R-95EE showed different distribution patterns of identified resveratrol and resveratrol tetramers of hopeaphenol, vitisin A, and vitisin B based on the analyses of HPLC chromatographic profiles. The hopeaphenol, vitisin A, and vitisin B, showed AChE and monoamine oxidase-B inhibitions in a dose-dependent manner, among which vitisin B and vitisin A exhibited much better activities than those of resveratrol, and had neuroprotective activities against methylglyoxal-induced SH-SY5Y cell deaths. The scopolamine-induced amnesiac ICR mice treated with VT-95EE and its ethyl acetate-partitioned fraction (VT-95EE-EA) at doses of 200 and 400 mg/kg, or vitisin A at a dose of 40 mg/kg, but not vitisin B (40 mg/kg), were shown significantly to improve the impaired learning behaviors by passive avoidance tests compared to those in the control without drug treatments (p < 0.05). Compared to mice in the control group, the brain extracts in the vitisin A-treated mice or donepezil-treated mice showed significant reductions in AChE activities and malondialdehyde levels (p < 0.05), and elevated the reduced protein expressions of brain-derived neurotrophic factor (BDNF) and BDNF receptor, tropomyosin receptor kinase B (TrkB). These results revealed that vitisin A was the active constituent in the VT-95EE and VTT-95EE, and the VT medicinal plant and that the endemic variety of VTT has potential in developing functional foods for an unmet medical need for neurodegenerative disorders.

Focus on ferroptosis, pyroptosis, apoptosis and autophagy of vascular endothelial cells to the strategic targets for the treatment of atherosclerosis

Vascular endothelial cells (VECs), which are lined up in the inner surface of blood vessels, are in direct contact with the metabolite-related endogenous danger signals in the circulatory system. Moreover, VECs death impairs vasodilation and increases endothelium-dependent permeability, which is strongly correlated with the development of atherosclerosis (AS). Among several forms of cell death, regulatory death of endothelial cells frequently occurs in AS, mainly including ferroptosis, pyroptosis, apoptosis and autophagy. In this review, we summarize regulatory factors and signaling mechanisms of regulatory death in endothelial cells, discussing their effects in the context of the atherosclerotic procession.

Treatment for Diabetic Peripheral Neuropathy: What have we Learned from Animal Models?

INTRODUCTION

Animal models have been widely used to investigate the etiology and potential treatments for diabetic peripheral neuropathy. What we have learned from these studies and the extent to which this information has been adapted for the human condition will be the subject of this review article.

METHODS

A comprehensive search of the PubMed database was performed, and relevant articles on the topic were included in this review.

RESULTS

Extensive study of diabetic animal models has shown that the etiology of diabetic peripheral neuropathy is complex, with multiple mechanisms affecting neurons, Schwann cells, and the microvasculature, which contribute to the phenotypic nature of this most common complication of diabetes. Moreover, animal studies have demonstrated that the mechanisms related to peripheral neuropathy occurring in type 1 and type 2 diabetes are likely different, with hyperglycemia being the primary factor for neuropathology in type 1 diabetes, which contributes to a lesser extent in type 2 diabetes, whereas insulin resistance, hyperlipidemia, and other factors may have a greater role. Two of the earliest mechanisms described from animal studies as a cause for diabetic peripheral neuropathy were the activation of the aldose reductase pathway and increased non-enzymatic glycation. However, continuing research has identified numerous other potential factors that may contribute to diabetic peripheral neuropathy, including oxidative and inflammatory stress, dysregulation of protein kinase C and hexosamine pathways, and decreased neurotrophic support. In addition, recent studies have demonstrated that peripheral neuropathy-like symptoms are present in animal models, representing pre-diabetes in the absence of hyperglycemia.

CONCLUSION

This complexity complicates the successful treatment of diabetic peripheral neuropathy, and results in the poor outcome of translating successful treatments from animal studies to human clinical trials.

Theories behind the effect of starch‑ and sucrose‑reduced diets on gastrointestinal symptoms in irritable bowel syndrome (Review)

Increased amounts of starch and sugar have been added to the diet in the Western world during the last decades. Undigested carbohydrates lead to bacterial fermentation and gas production with diffusion of water, causing abdominal bloating, pain and diarrhea. Therefore, dietary advice is the first line of treatment of irritable bowel syndrome (IBS), a disease characterized by abdominal pain and altered bowel habits without any organic findings. Recently, a diet with a reduction of starch and sucrose led to a marked effect on gastrointestinal (GI) symptoms. The mechanism is unknown, but three possible mechanisms are presented in the present review. First, functional variants of the enzyme sucrase‑isomaltase (SI) have been described in IBS. A subgroup of patients with IBS may thus suffer from partial SI deficiency with reduced digestion of starch and sucrose. Second, fructose absorption is less efficient than glucose absorption, which may lead to a physiological fructose malabsorption when ingesting high amounts of sucrose. A third mechanism is that high‑sugar diets causing hyperglycemia, hyperinsulinemia and weight gain have led to painful neuropathy in animal models; whereas, improved metabolic control in humans has led to improvement of neuropathy. Starch‑ and sucrose‑reduced diets lead to decreased levels of C‑peptide, insulin, gastric inhibitory peptide, leptin and weight reduction. These metabolic changes may reduce the excitability of the hypersensitive nervous system often found in IBS and, thereby, lead to the reduced symptoms found after the diet. In conclusion, further studies are needed to investigate the pathophysiology behind development of symptoms after starch and sucrose intake, and the mechanisms behind symptom relief after reduced intake.

Aspulvinones Suppress Postprandial Hyperglycemia as Potent α-Glucosidase Inhibitors From Aspergillus terreus ASM-1

Chemical investigation of Aspergillus terreus ASM-1 fermentation resulted in the isolation of three new prenylated aspulvinones V–X (1–3), together with the previously reported analogs, aspulvinone H (4), J-CR (5), and R (6). Their structures were elucidated by various spectroscopic methods including HRESIMS and NMR, and the absolute configurations of 2 and 3 were determined by ECD comparison. Compounds 1–6 were evaluated for α-glucosidase inhibitory effects with acarbose as positive control. As a result, compounds 1 and 4 exhibited potent α-glucosidase inhibitory activities with IC₅₀ values of 2.2 and 4.6 µM in mixed-type manners. The thermodynamic constants recognized the interaction between inhibitors and α-glucosidase was hydrophobic force-driven spontaneous exothermic reaction. The CD spectra also indicate that the compounds 1 and 4 changed the enzyme conformation. Furthermore, compound 4 significantly suppressed the increases in postprandial blood glucose levels in the C57BL/6J mice.

Vitamin D-VDR (vitamin D receptor) regulates defective autophagy in renal tubular epithelial cell in streptozotocin-induced diabetic mice via the AMPK pathway

Diabetic nephropathy (DN) has become a major cause of end-stage renal disease, and autophagy disorder is implicated in the pathogenesis of DN. Our previous studies found that vitamin D (VD) and VDR (vitamin D receptor) played a renoprotective role by inhibiting inflammation and fibrosis. However, whether VD-VDR regulates autophagy disorders in DN remains unclear. In this study, we established a streptozotocin (STZ)-induced diabetic model in vdr knockout (vdr-KO) mice and VDR specifically overexpressed in renal proximal tubular epithelial cells (Vdr-OE) mice. Our results showed that paricalcitol (an activated vitamin D analog) or Vdr-OE could alleviate STZ-induced ALB (albumin) excretion, renal tubule injury and inflammation, while these were worsened in vdr-KO mice. Defective autophagy was observed in the kidneys of STZ mice, which was more pronounced in vdr-KO mice and could be partially restored by paricalcitol or Vdr-OE. In high glucose-induced HK-2 cells, defective autophagy and decreased PRKAA1/AMPK phosphorylation was observed, which could be partially restored by paricalcitol in a VDR-dependent manner. AMPK inhibitor abolished paricalcitol-induced autophagy activation, and AMPK activator restored the defective autophagy in high glucose-induced HK-2 cells. Furthermore, paricalcitol-mediated AMPK activation was abrogated by CAMKK2/CaMKKβ inhibition, but not by STK11/LKB1 knockout. Meanwhile, paricalcitol rescued the decreased Ca²⁺ concentration induced by high glucose. In conclusion, VD-VDR can restore defective autophagy in the kidney of STZ-induced diabetic mice, which could be attributed to the activation of the Ca²⁺-CAMKK2-AMPK pathway in renal tubular epithelial cells.

Abbreviations: ACTB/β-actin: actin beta;AGE: advanced glycation end-products;AMPK: AMP-activated protein kinase;CAMKK2/CaMKKβ: calcium-calmodulin dependent protein kinase kinase 2;CQ: chloroquine;DN: diabetic nephropathy;HG: high levels of glucose;KO: knockout;LG: low levels of glucose;MAP1LC3/LC3: microtubule associated protein 1 light chain 3;NOD2: nucleotide binding oligomerization domain containing 2;OE: overexpression;PAS: periodic acid Schiff; Pari: paricalcitol;PTECs: proximal renal tubule epithelial cells;RT: room temperature;SQSTM1/p62: sequestosome 1;STK11/LKB1: serine/threonine kinase 11;STZ: streptozotocin;TEM: transmission electron microscopy;VD: vitamin D;VDR: vitamin D receptor;WT: wild-type

A review of risk factors associated with insulin omission for weight loss in type 1 diabetes

Research suggests that as many as 60% of people with type 1 diabetes (T1D) admit to misusing insulin. Insulin omission (IO) for the purpose of weight loss, often referred to as diabulimia, is a behaviour becoming increasingly recognised, not least since prolonged engagement can lead to serious vascular complications and mortality. Several risk factors appear to be relevant to the development of IO, most notably gender, anxiety and depression and increased weight concerns and body dissatisfaction. Evidence suggests that women, especially young girls, are more likely to omit insulin as a method of weight loss compared to men. Mental health conditions such as anxiety and depression are increasingly prevalent in people with T1D compared to their peers, and appear to contribute to the risk of IO. Increased weight concerns and body dissatisfaction are further prominent risk factors, especially given increases in weight which often occur following diagnosis and the monitoring of weight by diabetes teams. This review presents evidence examining these risk factors which increase the likelihood of a person with T1D engaging in IO and highlights the complications associated with prolongment of the behaviour. Further research looking at the comorbidities of these risk factors, alongside other factors, would provide greater insight into understanding IO in people with T1D.

Construction of lncRNA-related ceRNA regulatory network in diabetic subdermal endothelial cells

Long non-coding RNAs (lncRNAs) were considered to be involved in vascular complications in diabetes mellitus, but still only limited knowledge in this regard has been obtained. Herein, we further explored the roles of lncRNAs and mRNAs in diabetic vasculopathy (DV) through conducting bioinformatics analysis using data set downloaded from GEO database. The differentially expressed lncRNAs and mRNAs were identified by edge package. GO enrichment analysis and KEGG pathway analysis were performed based on clusterprofiler package. The relationship between lncRNA and miRNA was predicted using starBase database, and the potential mRNAs targeted by miRNAs were predicted by TargetScan, miRTarbase and miRDB database. The string database was used to analyze the protein-protein interaction (PPI). As a result, a total of 12 lncRNAs and 711 mRNAs were found to be differentially expressed in the diabetic subdermal endothelial cells compared with normal controls. A ceRNA network was established, which was composed of seven lncRNA nodes, 49 miRNA nodes, 58 mRNA nodes and 183 edges, and MSC-AS1 and LINC01550 may serve as key nodes. GO function enrichment analysis showed enrichments of epithelial cell proliferation, intercellular junction, and cell adhesion molecule binding. KEGG pathway analysis revealed 33 enriched pathways. PPI protein interaction analysis identified 57 potential ceRNA-related proteins. Overall, this study suggests that multiple lncRNAs, specifically MSC-AS1 and LINC01550, may play an important role in DV development and they are like to be developed as the therapeutic targets for DV. However, further experiments in vitro and in vivo should be conducted to validate our results.

A kinome screen reveals that Nemo-like kinase is a key suppressor of hepatic gluconeogenesis

Antihyperglycemic therapy is an important priority for the treatment of type 2 diabetes (T2D). Excessive hepatic glucose production (HGP) is a major cause of fasting hyperglycemia. Therefore, a better understanding of its regulation would be important to develop effective antihyperglycemic therapies. Using a gluconeogenesis-targeted kinome screening approach combined with transcriptome analyses, we uncovered Nemo-like kinase (NLK) as a potent suppressor of HGP. Mechanistically, NLK phosphorylates and promotes nuclear export of CRTC2 and FOXO1, two key regulators of hepatic gluconeogenesis, resulting in the proteasome-dependent degradation of the former and the inhibition of the self-transcriptional activity and expression of the latter. Importantly, the expression of NLK is downregulated in the liver of individuals with diabetes and in diabetic rodent models and restoring NLK expression in the mouse model ameliorates hyperglycemia. Therefore, our findings uncover NLK as a critical player in the gluconeogenic regulatory network and as a potential therapeutic target for T2D.

Sleeve Gastrectomy Attenuates Diabetic Nephropathy by Upregulating Nephrin Expressions in Diabetic Obese Rats

PURPOSE

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease, and sleeve gastrectomy (SG) is considered to be an effective strategy to improve pre-existing DN. However, the mechanism remains unknown.

MATERIALS AND METHODS

Animal model of DN was induced by high-fat diet (HFD) and streptozotocin (STZ). SG or sham surgery was performed and rats were sacrificed at 4, 8, and 12 weeks after surgery. The basic parameters (blood glucose, body weight, kidney weight), indicators of renal function including serum creatinine (Scr), blood urea nitrogen (BUN), urine microalbumin, urine creatinine (Ucr), microalbumin creatinine ratio (UACR), ultrastructural changes of glomerulus, and the expression of nephrin gene and protein in glomerular podocytes were compared among groups.

RESULTS

Blood glucose and body weight of SG rats were significantly lower than those of the sham-operated rats, and renal function of SG groups were also significantly improved within the postoperative period of 12 weeks. The results of periodic acid-Schiff staining (PAS) and transmission electron microscopy (TEM) showed that glomerular hypertrophy and accumulation of extracellular matrix proteins were significantly alleviated after SG, and the thickness of basement membrane and the fusion or effacement of foot processes were also significantly improved. The mRNA and protein expression of nephrin in SG groups was significantly higher than that in the sham group.

CONCLUSION

These results suggest that SG attenuates DN by upregulating the expression of nephrin and improving the ultrastructure of glomerular filtration membrane. This study indicates that SG can be used as an available therapeutic intervention for DN.

Design, synthesis, and biological evaluation of 1,2,4-oxadiazole-containing pyrazolo[3,4-b]pyridinones as a new series of AMPKɑ1β1γ1 activators

Adenosine monophosphate-activated protein kinase (AMPK) plays a key role in maintaining whole-body homeostasis and has been regarded as a therapeutic target for the treatment of diabetic nephropathy (DN). Herein, a series of 1,2,4-oxadiazole-containing pyrazolo[3,4-b]pyridinone derivatives is reported as AMPKɑ1β1γ1 activators. The in vitro biological assay demonstrated that compounds 12k (EC₅₀ [AMPKα1γ1β1] = 180 nM) and 13q (EC₅₀ [AMPKα1γ1β1] = 2 nM) displayed significant enzyme activation. Mechanism studies indicated that both compounds reduced the levels of reactive oxygen species in a rat kidney fibroblast cell line (NRK-49F) stimulated by transforming growth factor-β and induced early apoptosis of NRK-49F cells at 10 μM. Molecular docking studies suggested that 13q exhibited critical hydrogen-bond interactions with the critical amino acid residues Lys29, Lys31, Asn111, and Asp88 at the binding site of the AMPK protein. These results enrich the structure pool of AMPK activators and provide novel lead compounds for the subsequent development of compounds with a promising therapeutic potential against DN.

Oxy-imino saccharidic derivatives as a new structural class of aldose reductase inhibitors endowed with anti-oxidant activity

Aldose reductase is a key enzyme in the development of long term diabetic complications and its inhibition represents a viable therapeutic solution for people affected by these pathologies. Therefore, the search for effective aldose reductase inhibitors is a timely and pressing challenge. Herein we describe the access to a novel class of oxyimino derivatives, obtained by reaction of a 1,5-dicarbonyl substrate with O-(arylmethyl)hydroxylamines. The synthesised compounds proved to be active against the target enzyme. The best performing inhibitor, compound (Z)-8, proved also to reduce both cell death and the apoptotic process when tested in an in vitro model of diabetic retinopathy made of photoreceptor-like 661w cell line exposed to high-glucose medium, counteracting oxidative stress triggered by hyperglycaemic conditions.

The role and therapeutic potential of Hsp90, Hsp70, and smaller heat shock proteins in peripheral and central neuropathies

Heat shock proteins (Hsps) are molecular chaperones that also play important roles in the activation of the heat shock response (HSR). The HSR is an evolutionary conserved and protective mechanism that is used to counter abnormal physiological conditions, stressors, and disease states, such as those exemplified in cancer and/or neurodegeneration. In normal cells, heat shock factor-1 (HSF-1), the transcription factor that regulates the HSR, remains in a dormant multiprotein complex that is formed upon association with chaperones (Hsp90, Hsp70, etc.), co-chaperones, and client proteins. However, under cellular stress, HSF-1 dissociates from Hsp90 and induces the transcriptional upregulation of Hsp70 to afford protection against the encountered cellular stress. As a consequence of both peripheral and central neuropathies, cellular stress occurs and results in the accumulation of unfolded and/or misfolded proteins, which can be counterbalanced by activation of the HSR. Since Hsp90 is the primary regulator of the HSR, modulation of Hsp90 by small molecules represents an attractive therapeutic approach against both peripheral and central neuropathies.

Cellular and molecular effects of hyperglycemia on ion channels in vascular smooth muscle

Diabetes affects millions of people worldwide. This devastating disease dramatically increases the risk of developing cardiovascular disorders. A hallmark metabolic abnormality in diabetes is hyperglycemia, which contributes to the pathogenesis of cardiovascular complications. These cardiovascular complications are, at least in part, related to hyperglycemia-induced molecular and cellular changes in the cells making up blood vessels. Whereas the mechanisms mediating endothelial dysfunction during hyperglycemia have been extensively examined, much less is known about how hyperglycemia impacts vascular smooth muscle function. Vascular smooth muscle function is exquisitely regulated by many ion channels, including several members of the potassium (K+) channel superfamily and voltage-gated L-type Ca2+ channels. Modulation of vascular smooth muscle ion channels function by hyperglycemia is emerging as a key contributor to vascular dysfunction in diabetes. In this review, we summarize the current understanding of how diabetic hyperglycemia modulates the activity of these ion channels in vascular smooth muscle. We examine underlying mechanisms, general properties, and physiological relevance in the context of myogenic tone and vascular reactivity.

Bioactive Agent Discovery from the Natural Compounds for the Treatment of Type 2 Diabetes Rat Model

Diabetes mellitus is a well-known chronic metabolic disease that poses a long-term threat to human health and is characterized by a relative or absolute lack of insulin, resulting in hyperglycemia. Type 2 diabetes mellitus (T2DM) typically affects many metabolic pathways, resulting in β-cell dysfunction, insulin resistance, abnormal blood glucose levels, inflammatory processes, excessive oxidative reactions, and impaired lipid metabolism. It also leads to diabetes-related complications in many organ systems. Antidiabetic drugs have been approved for the treatment of hyperglycemia in T2DM; these are beneficial for glucose metabolism and promote weight loss, but have the risk of side effects, such as nausea or an upset stomach. A wide range of active components, derived from medicinal plants, such as alkaloids, flavonoids, polyphenol, quinones, and terpenoids may act as alternative sources of antidiabetic agents. They are usually attributed to improvements in pancreatic function by increasing insulin secretions or by reducing the intestinal absorption of glucose. Ease of availability, low cost, least undesirable side effects, and powerful pharmacological actions make plant-based preparations the key player of all available treatments. Based on the study of therapeutic reagents in the pathogenesis of humans, we use the appropriate animal models of T2DM to evaluate medicinal plant treatments. Many of the rat models have characteristics similar to those in humans and have the advantages of ease of genetic manipulation, a short breeding span, and access to physiological and invasive testing. In this review, we summarize the pathophysiological status of T2DM rat models and focus on several bioactive compounds from herbal medicine with different functional groups that exhibit therapeutic potential in the T2DM rat models, in turn, may guide future approach in treating diabetes with natural drugs.

Andrographolide Exerts Antihyperglycemic Effect through Strengthening Intestinal Barrier Function and Increasing Microbial Composition of Akkermansia muciniphila

Accumulating evidence indicates that type 2 diabetes (T2D) is associated with intestinal barrier dysfunction and dysbiosis, implying the potential targets for T2D therapeutics. Andrographolide was reported to have several beneficial effects on diabetes and its associated complications. However, the protective role of andrographolide, as well as its underlying mechanism against T2D, remains elusive. Herein, we reported that andrographolide enhanced intestinal barrier integrity in LPS-induced Caco-2 cells as indicated by the improvement of cell monolayer barrier permeability and upregulation of tight junction protein expression. In addition, andrographolide alleviated LPS-induced oxidative stress by preventing ROS and superoxide anion radical overproduction and reversing glutathione depletion. In line with the in vitro results, andrographolide reduced metabolic endotoxemia and strengthened gut barrier integrity in db/db diabetic mice. We also found that andrographolide appeared to ameliorate glucose intolerance and insulin resistance and attenuated diabetes-associated redox disturbance and inflammation. Furthermore, our results indicated that andrographolide modified gut microbiota composition as indicated by elevated Bacteroidetes/Firmicutes ratio, enriched microbial species of Akkermansia muciniphila, and increased SCFAs level. Taken together, this study demonstrated that andrographolide exerted a glucose-lowering effect through strengthening intestinal barrier function and increasing the microbial species of A. muciniphila, which illuminates a plausible approach to prevent T2D by regulating gut barrier integrity and shaping intestinal microbiota composition.

Melatonin inhibits high glucose-induced ox-LDL/LDL expression and apoptosis in human umbilical endothelial cells

BACKGROUND

Cardiovascular disease (CVD) is one of the major cause of mortality in diabetic patients. Evidence suggests that hyperglycemia in diabetic patients contributes to increased risk of CVD. This study is to investigate the therapeutic effects of melatonin on glucose-treated human umbilical vein endothelial cells (HUVEC) and provide insights on the underlying mechanisms.

MATERIALS AND METHODS

Cell viability was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Reactive oxygen species (ROS) and membrane potential was detected using 2',7'-dichlorofluorescein diacetate and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1) dye staining, respectively. While, cell apoptosis was determined by Annexin-V staining and protein expression was measured using Western blot.

RESULTS

Our results suggested that melatonin inhibited glucose-induced ROS elevation, mitochondria dysfunction and apoptosis on HUVEC. Melatonin inhibited glucose-induced HUVEC apoptosis via PI3K/Akt signaling pathway. Activation of Akt further activated BcL-2 pathway through upregulation of Mcl-1 expression and downregulation Bax expression in order to inhibit glucose-induced HUVEC apoptosis. Besides that, melatonin promoted downregulation of oxLDL/LOX-1 in order to inhibit glucose-induced HUVEC apoptosis.

CONCLUSIONS

In conclusion, our results suggested that melatonin exerted vasculoprotective effects against glucose-induced apoptosis in HUVEC through PI3K/Akt, Bcl-2 and oxLDL/LOX-1 signaling pathways.

Impact of Crocus Sativus L. on Metabolic Profile in Patients with Diabetes Mellitus or Metabolic Syndrome: A Systematic Review

Background: Experimental studies demonstrated a positive effect of administration of Crocus sativus L. (saffron) and its bioactive ingredients on metabolic profile through their antioxidant capacity. Purpose: To determine if the use of saffron in humans is beneficial to patients with diabetes mellitus (DM) or metabolic syndrome (MS). Methods: This systematic review includes 14 randomized control trials that investigated the impact of saffron administration and its bioactive ingredient crocin on the metabolic profile of patients with DM, MS, prediabetes, and coronary artery disease. We documented the following clinical outcomes: fasting blood glucose (FBG), glycated haemoglobin (HbA1c), total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, systolic, and diastolic blood pressure. Results: Eight studies examined the efficacy of saffron in patients with DM, four with the metabolic syndrome, one with prediabetes and one with coronary artery disease. A favorable effect on FBG was observed. The results regarding blood lipids and blood pressure were inconclusive in the current review. Conclusions: According to the available limited evidence, saffron may have a favorable effect on FBG. Many of the studies in the reviewed literature are of poor quality, and more research is needed in this direction to confirm and establish the above findings.

Regulation of TFEB activity and its potential as a therapeutic target against kidney diseases

The transcription factor EB (TFEB) regulates the expression of target genes bearing the Coordinated Lysosomal Expression and Regulation (CLEAR) motif, thereby modulating autophagy and lysosomal biogenesis. Furthermore, TFEB can bind to the promoter of autophagy-associated genes and induce the formation of autophagosomes, autophagosome-lysosome fusion, and lysosomal cargo degradation. An increasing number of studies have shown that TFEB stimulates the intracellular clearance of pathogenic factors by enhancing autophagy and lysosomal function in multiple kidney diseases, such as cystinosis, acute kidney injury, and diabetic nephropathy. Taken together, this highlights the importance of developing novel therapeutic strategies against kidney diseases based on TFEB regulation. In this review, we present an overview of the current data on TFEB and its implication in kidney disease.

Transplantation of adipose-derived mesenchymal stem cell sheets directly into the kidney suppresses the progression of renal injury in a diabetic nephropathy rat model

AIMS/INTRODUCTION

Adipose-derived mesenchymal stem cell (ASC) transplantation is a promising therapy for diabetic nephropathy (DN). However, intravascular administration of ASCs is associated with low engraftment in target organs. Therefore, we considered applying the cell sheet technology to ASCs. In this study, ASC sheets were directly transplanted into the kidneys of a DN rat model, and therapeutic consequences were analyzed.

MATERIALS AND METHODS

Adipose-derived mesenchymal stem cells were isolated from adipose tissues of 7-week-old enhanced green fluorescent protein rats, and ASC sheets were prepared using a temperature-responsive culture dish. A DN rat model was established from 5-week-old Spontaneously Diabetic Torii fatty rats. Seven-week-old DN rats (n = 21) were assigned to one of the following groups: sham-operated (n = 6); ASC suspension (6.0 × 106  cells/mL) administered intravenously (n = 7); six ASC sheets transplanted directly into the kidney (n = 8). The therapeutic effect of the cell sheets was determined based on urinary biomarker expression and histological analyses.

RESULTS

The ASC sheets survived under the kidney capsule of the DN rat model for 14 days after transplantation. Furthermore, albuminuria and urinary tumor necrosis factor-α levels were significantly lower in the ASC sheets transplanted directly into the kidney group than in the sham-operated and ASC suspension administered intravenously groups (P < 0.05). Histologically, the ASC sheets transplanted directly into the kidney group presented mild atrophy of the proximal tubule and maintained the renal tubular structure.

CONCLUSIONS

Transplantation of ASC sheets directly into the kidney improved transplantation efficiency and suppressed renal injury progression. Therefore, the ASC sheet technology might be a promising novel treatment for DN.

Dysregulation of trophic factors contributes to diabetic retinopathy in the Ins2Akita mouse

Diabetic retinopathy (DR) is considered as a diabetes-related complication that can lead to severe visual impairments. By 2030, it is expected that 1 in 5 adults will suffer from the disease. Suitable animal models for chronic DR are essential for a better understanding of the pathophysiology and to further develop new treatments. The Ins2^Akita mouse is a type 1 diabetes model that shows signs of both early and late stages of DR, including pericyte loss, increased vascular permeability, increased acellular capillaries and neovascularization. To further characterize DR in the Ins2^Akita mouse model, we have evaluated the protein levels of the angiogenesis inducers vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) and the angiogenesis inhibitor pigment epithelium-derived factor (PEDF). Additionally, we have analyzed the protein expression profile of the glial markers ionized calcium binding adaptor molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) as well as of the chemokine monocyte chemoattractant protein 1 (MCP-1). In this study we demonstrate that, with disease progression, there is the development of an inflammatory response and an unbalanced expression of pro- and antiangiogenic factors in the neural retina and in the retinal pigment epithelium (RPE) of Ins2^Akita mice. Therefore, our data provide support for the diabetic retinopathy features detected in the Ins2^Akita retina, reflecting what is observed in the human pathology.

Effect of diabetes blood-stasis syndrome and Xuefu Zhuyu decoction on ROS-ERK1/2 signaling pathway in rat retina Müller cells

This research aimed to investigate whether diabetic blood-stasis syndrome had a relationship with ROS-ERK1/2 signaling pathway in rat retina Müller cells and explore the effects of traditional Chinese drugs designed for promoting blood circulation to remove blood stasis on diabetic retinopathy (DR) treatment. Immunofluorescence was applied to determine purity of Müller cells. The diabetes was induced in rats by streptozotocin (STZ). Müller cells were stimulated by blood serum obtained from rats with blood-stasis syndrome and then treated by Xuefu Zhuyu decoction. Kits for reactive oxygen species (ROS), superoxide dismutase (SOD) and glutathione (GSH) were used for corresponding detection. Western blot analysis was used to determine the phosphorylation of ERK1/2. The results indicated that stimulation of Müller cells by blood serum of rats with diabetic blood-stasis syndrome increased the expression of ROS, inhibited SOD and GSH, and activated ERK1/2 signaling pathway. Treatment of Xuefu Zhuyu decoction could weaken this phenomenon. What's more, similar effects of ERK1/2 inhibitor U0126 with Xuefu Zhuyu decoction proved the involvement of ERK1/2 signaling pathway. Therefore, our results suggested that traditional Chinese drugs for promoting blood circulation to remove blood stasis would be an effective therapy to treat DR.

Diet-Induced Rodent Models of Diabetic Peripheral Neuropathy, Retinopathy and Nephropathy

Unhealthy dietary habits are major modifiable risk factors for the development of type 2 diabetes mellitus, a metabolic disease with increasing prevalence and serious consequences. Microvascular complications of diabetes, namely diabetic peripheral neuropathy (DPN), retinopathy (DR), and nephropathy (DN), are associated with high morbidity rates and a heavy social and economic burden. Currently, available therapeutic options to counter the evolution of diabetic microvascular complications are clearly insufficient, which strongly recommends further research. Animal models are essential tools to dissect the molecular mechanisms underlying disease progression, to unravel new therapeutic targets, as well as to evaluate the efficacy of new drugs and/or novel therapeutic approaches. However, choosing the best animal model is challenging due to the large number of factors that need to be considered. This is particularly relevant for models induced by dietary modifications, which vary markedly in terms of macronutrient composition. In this article, we revisit the rodent models of diet-induced DPN, DR, and DN, critically comparing the main features of these microvascular complications in humans and the criteria for their diagnosis with the parameters that have been used in preclinical research using rodent models, considering the possible need for factors which can accelerate or aggravate these conditions.

Biomineralization synthesis of a near-infrared fluorescent nanoprobe for direct glucose sensing in whole blood

A near-infrared (NIR) fluorescent nanoprobe that enables to circumvent the interference of background absorption and fluorescence in whole blood was developed for the direct sensing of blood glucose. Here, NIR fluorescent protein (iRFP) and glucose oxidase (GOx) were collectively deployed as the templates for the biomineralization of Mn2+ to prepare a NIR fluorescent nanoprobe (iRFP-GOx-MnO2 nanoparticles, iRGMs), in which the fluorescence of iRFP was effectively quenched by MnO2via energy transfer. When the iRGMs were mixed with whole blood samples, GOx can convert blood glucose into gluconic acid, as well as H2O2, which will reduce MnO2 and decompose the iRGMs. As a result, the NIR fluorescence of iRFPs was restored, providing a fluorometric assay for the direct detection of blood glucose. Owing to the high efficiency of the cascade reaction and the low background interference of the NIR fluorescence signal, accurate and rapid analysis of the glucose levels in whole blood samples was achieved using the iRGMs. Moreover, an iRGM-based paper device that only requires 5 microliters of samples was also demonstrated in the direct assay of blood glucose without any pretreatment, affording an alternative approach for the accurate monitoring of blood glucose levels.

Role of Transient Receptor Potential Canonical Channel 6 (TRPC6) in Diabetic Kidney Disease by Regulating Podocyte Actin Cytoskeleton Rearrangement

Podocyte injury is an important pathogenesis step causing proteinuric kidney diseases such as diabetic kidney disease (DKD). Actin cytoskeleton rearrangement in podocyte induced by multiple pathogenic factors is believed to be the key process resulting in glomerular injury. Many studies have recently shown that transient receptor potential canonical channel 6 (TRPC6) in podocyte plays a critical role in the development and progression of proteinuric kidney disease by regulating its actin cytoskeleton rearrangement. This review is aimed at summarizing the role of TRPC6 on DKD by regulating the podocyte actin cytoskeleton rearrangement, thereby help further broaden our views and understanding on the mechanism of DKD and provide a theoretic basis for exploring new therapeutic targets for DKD patients.

Lysosome restoration to activate podocyte autophagy: a new therapeutic strategy for diabetic kidney disease

Autophagy, the intracellular lysosomal degradation process plays a pivotal role in podocyte homeostasis in diabetic kidney disease (DKD). Lysosomal function, autophagic activity, and their actions were investigated in vitro and in vivo. We found that LC3-II- and p62-positive vacuoles accumulated in podocytes of patients with DKD. Moreover, we found that advanced glycation end products (AGEs) could increase the protein expression of LC3-II and p62 in a dose- and time-dependent manner in cultured podocytes. However, the mRNA expression of LC3B, Beclin-1 or ATG7, as well as the protein level of Beclin-1 or ATG7 did not change significantly in the AGE-treated cells compared with that in control groups, suggesting that AGEs did not induce autophagy. In addition, AGEs led to an increase in the number of autophagosomes but not autolysosomes, accompanied with a failure in lysosomal turnover of LC3-II or p62, indicating that the degradation of autophagic vacuoles was blocked. Furthermore, we observed a dramatic decrease in the enzymatic activities, and the degradation of DQ-ovalbumin was significantly suppressed after podocytes were treated with AGEs. Plasma-irregular lysosomal-associated membrane protein 1 granules accompanied with the diffusion of cathepsin D expression and acridine orange redistribution were observed in AGE-treated podocytes, indicating that the lysosomal membrane permeability was triggered. Interestingly, we also found that AGEs-induced autophagic inhibition and podocyte injury were mimicked by the specific lysosomotropic agent, l-leucyl-l-leucine methyl ester. The exacerbated apoptosis and Rac-1-dependent actin-cytoskeletal disorganization were alleviated by an improvement in the lysosomal-dependent autophagic pathway by resveratrol plus vitamin E treatment in AGE-treated podocytes. However, the rescued effects were reversed by the addition of leupeptin, a lysosomal inhibitor. It suggests that restoring lysosomal function to activate autophagy may contribute to the development of new therapeutic strategies for DKD.