Effect of resveratrol treatment on graft revascularization after islet transplantation in streptozotocin-induced diabetic mice

Statistically unbiased prediction enables accurate denoising of voltage imaging data

Here we report SUPPORT (statistically unbiased prediction utilizing spatiotemporal information in imaging data), a self-supervised learning method for removing Poisson-Gaussian noise in voltage imaging data. SUPPORT is based on the insight that a pixel value in voltage imaging data is highly dependent on its spatiotemporal neighboring pixels, even when its temporally adjacent frames alone do not provide useful information for statistical prediction. Such dependency is captured and used by a convolutional neural network with a spatiotemporal blind spot to accurately denoise voltage imaging data in which the existence of the action potential in a time frame cannot be inferred by the information in other frames. Through simulations and experiments, we show that SUPPORT enables precise denoising of voltage imaging data and other types of microscopy image while preserving the underlying dynamics within the scene.

In vivo longitudinal 920 nm two-photon intravital kidney imaging of a dynamic 2,8-DHA crystal formation and tubular deterioration in the adenine-induced chronic kidney disease mouse model

Chronic kidney disease (CKD) is one of the most common renal diseases manifested by gradual loss of kidney function with no symptoms in the early stage. The underlying mechanism in the pathogenesis of CKD with various causes such as high blood pressure, diabetes, high cholesterol, and kidney infection is not well understood. In vivo longitudinal repetitive cellular-level observation of the kidney of the CKD animal model can provide novel insights to diagnose and treat the CKD by visualizing the dynamically changing pathophysiology of CKD with its progression over time. In this study, using two-photon intravital microscopy with a single 920 nm fixed-wavelength fs-pulsed laser, we longitudinally and repetitively observed the kidney of an adenine diet-induced CKD mouse model for 30 days. Interestingly, we could successfully visualize the 2,8-dihydroxyadenine (2,8-DHA) crystal formation with a second-harmonics generation (SHG) signal and the morphological deterioration of renal tubules with autofluorescence using a single 920 nm two-photon excitation. The longitudinal in vivo two-photon imaging results of increasing 2,8-DHA crystals and decreasing tubular area ratio visualized by SHG and autofluorescence signal, respectively, were highly correlated with the CKD progression monitored by a blood test showing increased cystatin C and blood urea nitrogen (BUN) levels over time. This result suggests the potential of label-free second-harmonics generation crystal imaging as a novel optical technique for in vivo CKD progression monitoring.

Anti-Oxidative Therapy in Islet Cell Transplantation

Islet cell transplantation has become a favorable therapeutic approach in the treatment of Type 1 Diabetes due to the lower surgical risks and potential complications compared to conventional pancreas transplantation. Despite significant improvements in islet cell transplantation outcomes, several limitations hamper long-term graft survival due to tremendous damage and loss of islet cells during the islet cell transplantation process. Oxidative stress has been identified as an omnipresent stressor that negatively affects both the viability and function of isolated islets. Furthermore, it has been established that at baseline, pancreatic β cells exhibit reduced antioxidative capacity, rendering them even more susceptible to oxidative stress during metabolic stress. Thus, identifying antioxidants capable of conferring protection against oxidative stressors present throughout the islet transplantation process is a valuable approach to improving the overall outcomes of islet cell transplantation. In this review we discuss the potential application of antioxidative therapy during each step of islet cell transplantation.

An updated pharmacological insight of resveratrol in the treatment of diabetic nephropathy

As one of the most common complications of diabetes, nephropathy develops in approximately 40% of diabetic individuals. Although end stage kidney disease is known as one of the most consequences of diabetic nephropathy, the majority of diabetic individuals might die from cardiovascular diseases and infections before renal replacement treatment. Moreover, the routine medical treatments for diabetes hold undesirable side effects. The explosive prevalence of diabetes urges clinicians and scientists to investigate the complementary or alternative therapies. Phytochemicals are emerging as alternatives with a wide range of therapeutic effects on various pathologies, including diabetic kidney disease. Of those phytochemicals, resveratrol, a natural polyphenolic stilbene, has been found to exert a broad spectrum of health benefits via various signaling molecules. In particular, resveratrol has gained a great deal of attention because of its anti-oxidative, anti-inflammatory, anti-diabetic, anti-obesity, cardiovascular-protective, and anti-tumor properties. In the renal system, emerging evidence shows that resveratrol has already been used to ameliorate chronic or acute kidney injury. This review critically summarizes the current findings and molecular mechanisms of resveratrol in diabetic renal damage. In addition, we will discuss the adverse and inconsistent effects of resveratrol in diabetic nephropathy. Although there is increasing evidence that resveratrol affords great potential in diabetic nephropathy therapy, these results should be treated with caution before its clinical translation. In addition, the unfavorable pharmacokinetics and/or pharmacodynamics profiles, such as poor bioavailability, may limit its extensive clinical applications. It is clear that further research is needed to unravel these limitations and improve its efficacy against diabetic nephropathy. Increasing investigation of resveratrol in diabetic kidney disease will not only help us better understand its pharmacological actions, but also provide novel potential targets for therapeutic intervention.

Role of sirtuin-1 (SIRT1) in hypoxic injury in pancreatic β-cells

Islet transplantation (ITx) is being developed as a treatment for type 1 diabetes mellitus, but hypoxic damage to transplanted islet grafts is an important factor affecting successful transplantation. To investigate the role of sirtuin-1 (SIRT1) under hypoxic injury in INS-1 cells, one type of pancreatic β-cell lines, we used SRT1720 and GW4064 for SIRT1 activation. The small interfering RNA SIRT1 (si-SIRT1) was used to suppress SIRT1 gene expression. We measured cell viability, apoptosis, and the levels of inflammatory cytokines, including tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), and reactive oxygen species (ROS), under hypoxic conditions. Real-time PCR and Western blot analysis were performed. Cell viability was significantly reduced to 71% and 40% after 4 and 6 h of hypoxic conditions, respectively. Apoptosis increased significantly 2.8-fold and 5.3-fold after 4 and 6 h of hypoxia, respectively. SIRT1 expression was significantly reduced at the mRNA and protein levels during hypoxia. Hypoxic damage significantly increased the TNF-α, IL-6 and ROS levels in INS-1 cells. However, the reduced cell viability and increased inflammatory cytokines from hypoxic damage were ameliorated by SIRT1 activation in INS-1 cells. These results suggest that SIRT1 is a potential target for the protection of pancreatic β-cells against hypoxic damage during ITx.

Significant reduction of apoptosis induced via hypoxia and oxidative stress in isolated human islet by resveratrol

BACKGROUND AND AIMS

Successful islet transplantation as a promising treatment of diabetes type 1 is threatened with the loss of islets during the pre-transplant culture due to hypoxia and oxidative stress-induced apoptosis. Therefore, optimization of culture in order to preserve the islets is a critical point. In this study, we investigated the effect of resveratrol, as a cytoprotective agent, on the cultured human islets.

METHODS AND RESULTS

Isolated islets were treated with different concentrations of resveratrol for 24 and 72 h. Islets' viability, apoptosis, apoptosis markers, and insulin and C-peptide secretion, along with the production of reactive oxygen species (ROS), hypoxia inducible factor 1 alpha (HIF-1α), and its target genes in the islets were investigated. Our findings showed that the islets were exposed to hypoxia and oxidative stress after isolation and during culture. This insult induced apoptosis and decreased viability during 72 h. The presence of resveratrol significantly attenuated HIF-1α and ROS production, reduced apoptosis, promoted the VEGF secretion, and increased the insulin and C-peptide secretion. In this regard, resveratrol improved the islet's survival and function in the culture period.

CONCLUSIONS

Using resveratrol can attenuate the stressful condition for the islets in the pre-transplant culture and subsequently ameliorate their viability and functionality that lead to successful outcome after clinical transplantation.

A Novel Pancreatic Imaging Window for Stabilized Longitudinal In Vivo Observation of Pancreatic Islets in Murine Model

Longitudinal imaging of murine pancreas is technically challenging due to the mechanical softness of the tissue influenced by peristalsis. Here, we report a novel pancreatic imaging window for long-term stabilized cellular-level observation of the islets in the pancreas in vivo. By spatially separating the pancreas from the bowel movement and physiologic respiration with a metal plate integrated in the imaging window, we successfully tracked the pancreatic islets up to three weeks and visualized the dumbbell-shape transformation from the single islet. This window can be a useful tool for long-term cellular-level visualization of the microstructure in the pancreas.

Resveratrol reduces liver endoplasmic reticulum stress and improves insulin sensitivity in vivo and in vitro

Purpose: The aim of the study was to examine the effects of resveratrol upon hepatic endoplasmic reticulum stress (ERS) and insulin sensitivity in vivo and in vitro. Material and methods: C57BL/6J mice were fed a high-fat diet (HFD) for 8 weeks, and insulin resistance was evaluated by the intraperitoneal glucose tolerance test (IPGTT). Mice were then treated with resveratrol for 12 weeks and blood and liver samples collected. Blood biochemical indicators were determined by kits, liver protein expression was determined by western blot, and morphological changes were observed by histological staining. Palmitic acid (PA)-induced insulin-resistant HepG2 cells were established. Cells were exposed to 100, 50 or 20 μM resveratrol for 24 hrs, and proliferation/cytotoxicity was determined. Cells were divided into five groups: control, PA, PA + Rev (100 μM), PA + Rev (50 μM) and PA + Rev (20 μM) groups. After 24 hrs of treatment, cellular proteins were analyzed the same way as animal tissues. Results: The IPGTT confirmed that the insulin resistance model was established successfully. After resveratrol treatment, fasting blood glucose and cholesterol levels declined and the quantitative insulin sensitivity check index increased. Western-blot results showed that resveratrol-treated HFD mice had reduced hepatic levels of p-PERK, ATF-4 and TRIB3, and increased the levels of ATF-6, p-AKT and p-GSK3β. In the cell model, resveratrol with 100 and 50 μM enhanced ERS and insulin resistance, whereas 20 μM had beneficial effects, similar to the animal model. Conclusion: Resveratrol reduced hepatic ERS, thereby improving insulin sensitivity and glucose levels. However, high doses of resveratrol had harmful effects on cells, elevating ERS and insulin resistance. The safe dose of resveratrol needs further investigation.