Dapagliflozin and metformin in combination ameliorates diabetic nephropathy by suppressing oxidative stress, inflammation, and apoptosis and activating autophagy in diabetic rats

Considering the effects of sodium-glucose cotransporter inhibitors and metformin on the kidneys, a combination of both agents is postulated to provide protection against diabetic nephropathy (DN). We examined the potential protective effects of dapagliflozin, metformin, and their combination on kidney injury in rats with type 2 diabetes. Diabetic (DM) rats were administered dapagliflozin (1.0 mg/kg/day), metformin (100 mg/kg/day), or a combination (dapagliflozin 0.5 mg/kg/day plus metformin 50 mg/kg/day) by oral gavage for 4 weeks. Dapagliflozin monotherapy or in combination with metformin was more effective than metformin monotherapy in attenuating renal dysfunction, improving renal organic anion transporter 3 expression, and activating renal autophagy by modulating the AMPK/mTOR/SIRT1 axis in DM rats. Interestingly, dapagliflozin monotherapy exhibited greater efficacy in suppressing renal oxidative stress in DM rats than metformin or the combination treatment. Renal and pancreatic injury scores decreased in all treatment groups. Apoptotic markers were predominantly reduced in dapagliflozin monotherapy and combination treatment groups. The low-dose combination treatment, through synergistic coordination, appeared to modulate oxidative, autophagic, and apoptotic signaling and confer significant renoprotective effects against DM-induced complications. In addition, a low dose of the combination might be beneficial to patients by avoiding the risk of side effects of the medication. Future clinical trials are necessary to study the nephroprotective effects of the combined treatment at a low dosage in patients with diabetes.

Metformin mitigates renal dysfunction in obese insulin-resistant rats via activation of the AMPK/PPARα pathway

Insulin signaling and lipid metabolism are disrupted by long-term consumption of a high-fat diet (HFD). This disruption can lead to insulin resistance, dyslipidemia and subsequently renal dysfunction as a consequence of the inactivation of the AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor-α (PPARα) or AMPK/PPARα pathways. We investigated the impact of metformin on the prevention of renal dysfunction through the modulation of AMPK-regulated PPARα-dependent pathways in insulin-resistant rats induced by a HFD. Male Wistar rats were fed a HFD for 16 weeks to induce insulin resistance. After insulin resistance had been confirmed, metformin (30 mg/kg) or gemfibrozil (50 mg/kg) was given orally for 8 weeks. Evidence of insulin resistance, dyslipidemia, lipid accumulation and kidney injury were observed in HF rats. Impairment of lipid oxidation, energy metabolism and renal organic anion transporter 3 (Oat3) expression and function were demonstrated in HF rats. Metformin can stimulate the AMPK/PPARα pathways and suppress sterol regulatory element-binding transcription factor 1 (SREBP1) and fatty acid synthase (FAS) signaling (SREBP1/FAS) to enable the regulation of lipid metabolism. Renal inflammatory markers and renal fibrosis expression induced by a HFD were more effectively reduced after metformin treatment than after gemfibrozil treatment. Interestingly, renal Oat3 function and expression and kidney injury were improved following metformin and gemfibrozil treatment. Renal cluster of differentiation 36 (CD36) or sodium glucose cotransporter type 2 (SGLT2) expression did not differ after treatment with metformin or gemfibrozil. Metformin and gemfibrozil could reduce the impairment of renal injury in obese conditions induced by a HFD through the AMPK/PPARα-dependent pathway. Interestingly, metformin demonstrated greater efficacy than gemfibrozil in attenuating renal lipotoxicity through the AMPK-regulated SREBP1/FAS signaling pathway.

Resistant starch from black rice, Oryza sativa L. var. ameliorates renal inflammation, fibrosis and injury in insulin resistant rats

It has recently been reported that black rice (BR) extract has anti-obesity, anti-diabetic, and anti-osteoporosis effects. It has been shown to reduce obese-related kidney dysfunction in animal models. This study aimed to investigate the effect of resistant starch from BR (RS) on renal inflammation, oxidative stress, and apoptosis in obese insulin resistant rats. Male Wistar rats were divided into six groups: normal diet (ND), ND treated with 150 mg of RS (NDRS150), high-fat (HF) diet, HF treated with 100 and 150 mg of RS (HFRS100), (HFRS150), and HF treated with metformin as a positive control. Insulin resistance was shown in the HF rats by glucose intolerance, increased insulin, total area under the curve of glucose and homeostasis model assessment of insulin resistance and dyslipidemia. The resulting metabolic disturbance in the HF rats caused renal inflammation, fibrosis and apoptosis progressing to kidney injury and dysfunction. Prebiotic RS including anthocyanin from BR at doses of 100 and 150 mg ameliorated insulin resistance, dyslipidemia and liver injury. Treatment with RS reduced TGF-β fibrotic and apoptotic pathways by inhibition of NF-κB and inflammatory cytokines which potentially restore kidney damage and dysfunction. In conclusion, prebiotic RS from BR ameliorated obesity induced renal injury and dysfunction by attenuating inflammatory, fibrotic, and apoptotic pathways in insulin resistant rats induced by HF.

Chitosan oligosaccharide mitigates kidney injury in prediabetic rats by improving intestinal barrier and renal autophagy

Consumption of a high-fat diet (HFD) not only increases the risk of metabolic syndrome but also initiates kidney injury. Lipid accumulation-induced systemic low-grade inflammation is an upstream mechanism of kidney injury associated with prediabetes. Chitosan oligosaccharide (COS) provides potent anti-obesity effects through several mechanisms including fecal lipid excretion. In this study, we investigated the effects of COS on the prevention of obesity-related complications and its ability to confer renoprotection in a prediabetic model. Rats fed on a HFD developed obesity, glucose intolerance and kidney dysfunction. COS intervention successfully ameliorated these conditions (p < 0.05) by attenuating intestinal lipid absorption and the renal inflammation-autophagy-apoptosis axis. A novel anti-inflammatory effect of COS had been demonstrated by the strengthening of intestinal barrier integrity via calcium-sensing receptor (p < 0.05). The use of COS as a supplement may be useful in reducing prediabetic complications especially renal injury and the risk of type 2 diabetes.

The impact of prebiotic fructooligosaccharides on gut dysbiosis and inflammation in obesity and diabetes related kidney disease

Obesity is an extensive health problem worldwide that is frequently associated with diabetes. It is a risk factor for the development of several diseases including diabetic nephropathy. Recent studies have reported that gut dysbiosis aggravates the progression of obesity and diabetes by increasing the production of uremic toxins in conjunction with gut barrier dysfunction which then leads to increased passage of lipopolysaccharides (LPS) into the blood circulatory system eventually causing systemic inflammation. Therefore, the modification of gut microbiota using a prebiotic supplement may assist in the restoration of gut barrier function and reduce any disturbance of the inflammatory response. In this review information has been compiled concerning the possible mechanisms involved in an increase in obesity, diabetes and kidney dysfunction via the exacerbation of the inflammatory response and its association with gut dysbiosis. In addition, the role of fructooligosaccharides (FOS), a source of prebiotic widely available commercially, on the improvement of gut dysbiosis and attenuation of inflammation on obese and diabetic conditions has been reviewed. The evidence confirms that FOS supplementation could improve the pathological changes associated with obesity and diabetes related kidney disease, however, knowledge concerning the mechanisms involved is still limited and needs further elucidation.

The combination of dapagliflozin and statins ameliorates renal injury through attenuating the activation of inflammasome-mediated autophagy in insulin-resistant rats

Long-term use of a high-fat diet with high-fructose (HFF) intake could promote insulin resistance and induce lipid accumulation leading to kidney injury possibly via impairment of the autophagy process and enhancement of the inflammasome pathway. We investigated whether dapagliflozin as a monotherapy or combined with atorvastatin could restore kidney autophagy impairment and reduce inflammasome activation associated with kidney injury induced by HFF consumption. Male Wistar rats were given an HFF for 16 weeks and then treated with dapagliflozin with or without atorvastatin for 4 weeks. Impaired glucose tolerance, dyslipidemia, renal lipid accumulation along with impaired renal autophagy and activated inflammasome pathway promoted renal injury were exhibited in HFF rats. Dapagliflozin with or without atorvastatin treatment could partially restore disrupted metabolic parameters and reduce kidney injury. In particular, the combination treatment group showed significant amelioration of inflammasome activation and autophagy impairment. In conclusion, the combination therapy of dapagliflozin and atorvastatin has a positive effect on renal injury associated with autophagy and inflammasome activation induced by HFF in insulin-resistant rats. This study is the first report demonstrating the underlying mechanism associated with a combination treatment of dapagliflozin and atorvastatin on autophagy and inflammasome pathways in an insulin-resistant condition. Therefore, dapagliflozin in combination with atorvastatin may be a further preventive or therapeutic strategy for chronic kidney disease in an insulin-resistant or diabetic condition.

Agomelatine protects against obesity-induced renal injury by inhibiting endoplasmic reticulum stress/apoptosis pathway in rats

Obesity is recognized as a risk for the development of chronic kidney disease. Excessive fat accumulation in obesity is associated with the overproduction of reactive oxygen species with the underproduction of antioxidant mechanisms generating oxidative stress together with chronic low-grade inflammation which subsequently leads to the development of several obesity-related complications. It has been suggested that the abnormal lipid accumulation can induce endoplasmic reticulum (ER) stress and cellular apoptosis in several tissue types. Agomelatine is a relatively new antidepressant which is a synthetic agonist of melatonin. Previous study reported the antioxidant and anti-inflammatory effects of agomelatine. In this study, we investigated the therapeutic effects of agomelatine in obesity-related renal injury. Male Wistar rats were fed with normal diet or high-fat diet (HF) for 16 weeks. After that, vehicle or agomelatine or vildagliptin was orally administered to HF rats for 4 weeks. Our results indicated that HF rats demonstrated insulin resistance which was accompanied by an impairment of renal function and renal organic anion transporter 3 (Oat3) function as well as renal oxidative stress, ER stress, and apoptosis. Interestingly, agomelatine treatment not only improved the metabolic parameters, renal function and renal Oat3 function but also attenuated renal oxidative stress, ER stress and subsequent apoptosis. Therefore, agomelatine exerted renoprotective effects in obese insulin-resistant condition. These results suggested that agomelatine could be used as a drug to improve metabolic disturbance and prevent kidney dysfunction in obese condition.

Atorvastatin attenuates obese-induced kidney injury and impaired renal organic anion transporter 3 function through inhibition of oxidative stress and inflammation

An excessive consumption of high-fat diet can lead to the alterations of glucose and lipid metabolism, impaired insulin signaling and increased ectopic lipid accumulation resulting in renal lipotoxicity and subsequent renal dysfunction. Atorvastatin is a lipid-lowering drug in clinical treatment. Several studies have reported that atorvastatin has several significant pleiotropic effects including anti-inflammatory, antioxidant, and anti-apoptotic effects. However, the effects of atorvastatin on metabolic disturbance and renal lipotoxicity in obesity are not fully understood. In this study, obesity in rat was developed by high-fat diet (HFD) feeding for 16 weeks. After that, the HFD-fed rats were received either a vehicle (HF), atorvastatin (HFA) or vildagliptin (HFVIL), by oral gavage for 4 weeks. We found that HF rats showed insulin resistance, visceral fat expansion and renal lipid accumulation. Impaired renal function and renal organic anion transporter 3 (Oat3) function and expression were also observed in HF rats. The marked increases in MDA level, renal injury and NF-κB, TGF-β, NOX-4, PKC-α expression were demonstrated in HF rats. Atorvastatin or vildagliptin treatment attenuated insulin resistance and renal lipid accumulation-induced lipotoxicity in HFA and HFVIL rats. Moreover, the proteins involved in renal inflammation, fibrosis, oxidative stress and apoptosis were attenuated leading to improved renal Oat3 function and renal function in the treated groups. Interestingly, atorvastatin showed higher efficacy than vildagliptin in improving insulin resistance, renal lipid accumulation and in exerting renoprotective effects in obesity-induced renal injury and impaired renal Oat3 function.