Geniposide alleviates diabetic nephropathy of mice through AMPK/SIRT1/NF-κB pathway

Role of Pyroptosis in Diabetes and Its Therapeutic Implications

Pyroptosis is mainly considered as a new pro-inflammatory mediated-programmed cell death. In addition, pyroptosis is described by gasdermin-induced pore formation on the membrane, cell swelling and rapid lysis, and several pro-inflammatory mediators interleukin-1β (IL-1β) and interleukin-18 (IL-18) release. Extensive studies have shown that pyroptosis is commonly involved by activating the caspase-1-dependent canonical pathway and caspase-4/5/11-dependent non-canonical pathway. However, pyroptosis facilitates local inflammation and inflammatory responses. Current researches have reported that pyroptosis promotes the progression of several diabetic complications. Emerging studies have suggested that some potential molecules targeting the pyroptosis and inflammasome signaling pathways could be a novel therapeutic avenue for managing and treating diabetes and its complications in the near future. Our narrative review concisely describes the possible mechanism of pyroptosis and its progressive understanding of the development of diabetic complications.

Pyroptosis: A New Frontier in Kidney Diseases

Pyroptosis is a pattern of programmed cell death that significantly differs from apoptosis and autophagy in terms of cell morphology and function. The process of pyroptosis is characterized predominantly by the formation of gasdermin protein family-mediated membrane perforation, cell collapse, and the release of inflammatory factors, including IL-1β and IL-18. In recent years, with the rise of pyroptosis research, scholars have devoted time to study the mechanism of pyroptosis in kidney-related diseases. Pyroptosis is probably involved in kidney diseases through two pathways: the caspase-1-mediated canonical pathway and the caspase-4/5/11-mediated noncanonical pathway. In addition, some scholars have identified targets for the treatment of kidney-related diseases from the viewpoint of pyroptosis and developed corresponding medicines, which may become a recommendation for prognosis, targeted treatment, and clinical diagnosis of kidney diseases. This paper focuses on the up-to-date advances in the field of pyroptosis, especially on the key pathogenic role of pyroptosis in the development and progression of kidney diseases. It presents a more in-depth understanding of the pathogenesis of kidney diseases and introduces novel therapeutic targets for the prevention and clinical treatment of kidney diseases.

Vitamin A and Daucus carota root extract mitigate STZ-induced diabetic retinal degeneration in Wistar albino rats by modulating neurotransmission and downregulation of apoptotic pathways

The objective of our study was to explore the deleterious effects of diabetes on the visual functions of the retina and to address whether the administration of vitamin A and carrot root extract (CE) confer retinal protection in hyperglycemic rats via modulation of oxidative stress, biochemical alternations, and retinal neurotransmission. Fifty male Wistar albino rats weighing 180 ± 12.41 g were randomized into five groups (n = 10): controls, diabetic group (injected with 40 mg/kg dissolved in 0.1 sodium citrate buffer), diabetic group treated with vitamin A (2,500 IU/kg, low dose), diabetic group treated with vitamin (5,000 IU/kg, high dose), and diabetic groups administered CE (200 mg/kg/every other day). Our findings showed that, compared to controls, diabetic rats showed a significant decrease in their retinal thickness, increased apoptotic ganglion cells, and a noticeable degeneration of their synaptic layers. The inner retina displayed increased activity of neovascularization; however, the outer retina exhibited vacuolar degeneration of the photoreceptor cell layer. Our biochemical assessments showed reduced levels of CAT, SOD, and GST along with increased lipid peroxidation. Concurrently, cellular angiogenic and stress markers were significantly elevated associated with increased apoptotic activities as evidenced by increased expressions of annexin-V and PARP. Furthermore, the neurotransmitter content of the retina was altered in diabetic rats compared to controls and diabetic-treated groups. Paradoxically, vitamin A and CE supplementation attenuate these retinal insults in diabetic animals and normalized aforementioned assayed parameters; evidencing that both treatments exerted ameliorative impacts and restored visual functions by diminishing oxidative stress and neuronal degeneration. PRACTICAL APPLICATIONS: Diabetes is a complex disease that involves various physiological perturbations especially visual functions. In our study, we showed that vitamin A and carrot root extract (CE) confer remarkable protection against retinal degeneration in STZ-induced diabetic rats. Our findings showed that the chemical and phytochemical ingredients of the vitamin A and CE substantially attenuated the histopathological changes, oxidative stress, inflammatory reactions, and cellular death in diabetic rats. These favorable changes are attributable to the high content of retinoic acid, carotenoids, and phenolic compounds that effectively regulates the production of visual pigments, increases the antioxidant defense system, and diminishes the pro-inflammatory and apoptotic pathways. Thus, the nutritional values of vitamin A and CE represent promising therapeutic choices to mitigate the retinal-induced diabetic insults.

Relevance of the Pyroptosis-Related Inflammasome Pathway in the Pathogenesis of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a major cause of chronic kidney disease (CKD) in many developed and developing countries. Pyroptosis is a recently discovered form of programmed cell death (PCD). With progress in research on DKD, researchers have become increasingly interested in elucidating the role of pyroptosis in DKD pathogenesis. This review focuses on the three pathways of pyroptosis generation: the canonical inflammasome, non-canonical inflammasome, and caspase-3-mediated inflammasome pathways. The molecular and pathophysiological mechanisms of the pyroptosis-related inflammasome pathway in the development of DKD are summarized. Activation of the diabetes-mediated pyroptosis-related inflammasomes, such as nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), Toll-like receptor 4 (TLR4), caspase-1, interleukin (IL)-1β, and the IL-18 axis, plays an essential role in DKD lesions. By inhibiting activation of the TLR4 and NLRP3 inflammasomes, the production of caspase-1, IL-1β, and IL-18 is inhibited, thereby improving the pathological changes associated with DKD. Studies using high-glucose-induced cell models, high-fat diet/streptozotocin-induced DKD animal models, and human biopsies will help determine the spatial and temporal expression of DKD inflammatory components. Recent studies have confirmed the relationship between the pyroptosis-related inflammasome pathway and kidney disease. However, these studies are relatively superficial at present, and the mechanism needs further elucidation. Linking these findings with disease activity and prognosis would provide new ideas for DKD research.

Geniposide Improves Diabetic Nephropathy by Enhancing ULK1-Mediated Autophagy and Reducing Oxidative Stress through AMPK Activation

Diabetic nephropathy (DN) is a common pathological feature in patients with diabetes and the leading cause of end-stage renal disease. Although several pharmacological agents have been developed, the management of DN remains challenging. Geniposide, a natural compound has been reported for anti-inflammatory and anti-diabetic effects; however, its role in DN remains poorly understood. This study investigated the protective effects of geniposide on DN and its underlying mechanisms. We used a C57BL/6 mouse model of DN in combination with a high-fat diet and streptozotocin after unilateral nephrectomy and treated with geniposide by oral gavage for 5 weeks. Geniposide effectively improves DN-induced renal structural and functional abnormalities by reducing albuminuria, podocyte loss, glomerular and tubular injury, renal inflammation and interstitial fibrosis. These changes induced by geniposide were associated with an increase of AMPK activity to enhance ULK1-mediated autophagy response and a decrease of AKT activity to block oxidative stress, inflammation and fibrosis in diabetic kidney. In addition, geniposide increased the activities of PKA and GSK3β, possibly modulating AMPK and AKT pathways, efficiently improving renal dysfunction and ameliorating the progression of DN. Conclusively, geniposide enhances ULK1-mediated autophagy and reduces oxidative stress, inflammation and fibrosis, suggesting geniposide as a promising treatment for DN.

Melatonin Attenuates Diabetic Myocardial Microvascular Injury through Activating the AMPK/SIRT1 Signaling Pathway

Cardiac microvascular endothelial cell (CMEC) dysfunction is considered as a major contributor to the cardiovascular complications in diabetes mellitus, with oxidative stress caused by hyperglycemia playing a critical role in the progression of CMEC dysfunction. Melatonin is a kind of hormone well known for its antioxidant properties, which has potential protective effects against diabetes mellitus and its complications. However, the role of melatonin on CMEC dysfunction caused by hyperglycemia and its molecular mechanisms underlying these effects has not been clarified. Herein, we investigate the protective effects of melatonin on high glucose- (HG-) evoked oxidative stress and apoptosis in CMECs and underlying mechanisms. Our results revealed that melatonin ameliorated the injury caused by HG in primary cultured rat CMECs. Injury can be accompanied by reduced reactive oxygen species (ROS) and malondialdehyde (MDA) production, and enhanced superoxide dismutase (SOD) activity. Meanwhile, melatonin treatment significantly inhibited HG-induced CMEC apoptosis. Moreover, melatonin increased the activity of the AMPK/SIRT1 signaling axis in CMECs under HG condition, whereas administration of the AMPK inhibitor compound C or SIRT1 silencing partially abrogated the beneficial effects of melatonin. In streptozotocin- (STZ-) evoked diabetic mice, melatonin notably ameliorated cardiac dysfunction and activated the AMPK/SIRT1 signaling. In conclusion, our findings revealed that melatonin attenuates HG-induced CMEC oxidant stress, apoptosis injury, and STZ-induced cardiac dysfunction through regulating the AMPK/SIRT1 signaling pathway.

Antidiabetic and Nephroprotective Effects of Polysaccharide Extract from the Seaweed Caulerpa racemosa in High Fructose-Streptozotocin Induced Diabetic Nephropathy

BACKGROUND

Nephropathy is a frontline complication of diabetes mellitus (DM) associated with impaired redox-inflammatory networks. The study investigated the antidiabetic and nephroprotective potentials of PCR against diabetic nephropathy (DN) in rats.

METHODS

DN was induced in rats using a combination of a high fructose solution for 4 weeks and an intraperitoneal injection of streptozotocin (35 mg/kg). Diabetic rats were treated with PCR (100 and 400 mg/kg body weight) for 8 weeks. Serum biochemical parameters as well as renal oxidative stress parameters, proinflammatory cytokines, Western blot and histopathological analyses were evaluated.

RESULTS

There were significant increases in fasting blood glucose, urinary albumin, serum creatinine, blood urea nitrogen (BUN), total cholesterol (TC), triglycerides (TG), and low-density lipoproteins (LDL-C) levels in diabetic rats compared to the non-diabetic control rats. DM-induced DN prominently depressed renal superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities, whereas renal malondialdehyde (MDA) level was markedly increased. Furthermore, renal inflammatory cytokines, IL-1β, IL-6, TNF-α and TGF-β, were considerably elevated compared to non-diabetic control rats. Additionally, DN rats showed a significant increase in renal fibrosis, as evidenced by increased expression of TGF-β1, collagen-1, fibronectin and alpha-smooth muscle actin (α-SMA) in the kidneys. Histopathological lesions were consistent with tubule thickening and glomerular hypertrophy. Conversely, PCR treatment exerted significant attenuation of hyperglycemia, dyslipidemia and renal oxidative stress indicators. The increased renal levels of IL-1β, IL-6, TNF-α and TGF-β were also notably reversed dose-dependently with alleviation of nephropathic histology. Furthermore, PCR reduced the expression of α-SMA, fibronectin, collagen-1 and TGF-β1 in the renal tissues.

CONCLUSION

Our results suggest that PCR displayed antidiabetic and nephroprotective effects against DN by impeding oxidative stress and inflammation. As such, PCR has potentials as a food supplement for alleviating renal dysfunction caused by diabetes.

Mini-Review: GSDME-Mediated Pyroptosis in Diabetic Nephropathy

Pyroptosis is a recently identified type of lytic programmed cell death, in which pores form in the plasma membrane, and cells swell, rupture, and then release their contents, including inflammatory cytokines. Molecular studies indicated that pyroptosis may occur via a gasdermin D (GSDMD) and caspase-1 (Casp1) -dependent classical pathway, a GSDMD and Casp11/4/5-dependent non-classical pathway, or a gasdermin E (GSDME) and Casp3-dependent pathway. Studies of animal models and humans indicated that pyroptosis can exacerbate several complications of diabetes, including diabetic nephropathy (DN), a serious microvascular complication of diabetes. Many studies investigated the mechanism mediating the renoprotective effect of GSDMD regulation in the kidneys of patients and animal models with diabetes. As a newly discovered regulatory mechanism, GSDME and Casp3-dependent pyroptotic pathway in the progression of DN has also attracted people's attention. Z-DEVD-FMK, an inhibitor of Casp3, ameliorates albuminuria, improves renal function, and reduces tubulointerstitial fibrosis in diabetic mice, and these effects are associated with the inhibition of GSDME. Studies of HK-2 cells indicated that the molecular and histological features of secondary necrosis were present following glucose stimulation due to GSDME cleavage, such as cell swelling, and release of cellular contents. Therefore, therapies targeting Casp3/GSDME-dependent pyroptosis have potential for treatment of DN. A novel nephroprotective strategy that employs GSDME-derived peptides which are directed against Casp3-induced cell death may be a key breakthrough. This mini-review describes the discovery and history of research in this pyroptosis pathway and reviews the function of proteins in the gasdermin family, with a focus on the role of GSDME-mediated pyroptosis in DN. Many studies have investigated the impact of GSDME-mediated pyroptosis in kidney diseases, and these studies used multiple interventions, in vitro models, and in vivo models. We expect that further research on the function of GDSME in DN may provide valuable insights that may help to improve treatments for this disease.