Vitamin D3 potentiates the nephroprotective effects of metformin in a rat model of metabolic syndrome: role of AMPK/SIRT1 activation and DPP-4 inhibition

The effect of short-term vitamin D on the antioxidant capacity following exhaustive aerobic exercise

Background

Exhaustive Aerobic Exercise (EAE) increases the production of free radicals and oxidative stress in the body. One of the most effective approaches to reduce EAE-induced oxidative stress is antioxidant supplementation.

Objectives

Therefore, the present study investigated the effect of short-term Vitamin D (Vit D) supplementation on antioxidant capacity in inactive men following an EAE session.

Methods

In this clinical trial, 24 non-athlete men were randomly divided into Experimental (Exp; n = 12) and Control (C; n = 12) groups. Exp received 2,000 IU of Vit D daily for six weeks (42 days), while C received a lactose placebo daily with the same color, shape, and warmth percentage. EAE sessions were performed on a treadmill before and after six weeks of supplementation.

Results

The results showed that EAE increased antioxidant capacity and Vit D (P<0.05). Compared with C, six weeks of Vit D supplementation significantly increased superoxide dismutase (P=0.001), glutathione peroxidase (P=0.011), catalase (P=0.018), peroxidase (P=0.001), and Vit D (P=0.001), in the Exp at the Post 2 stage.

Conclusion

Finally, short-term Vit D supplementation could be recommended to non-athlete men deciding to participate in EAE to prevent oxidative damage.

Concurrent alteration in inflammatory biomarker gene expression and oxidative stress: how aerobic training and vitamin D improve T2DM

Background

Vitamin D (Vit D) supplementation and Aerobic Training (AT) exert several beneficial effects such as antioxidant and anti-inflammatory actions. The literature on the effects of AT and Vit D supplementation on the oxidative stress biomarkers and gene expression of inflammatory cytokines in patients with Type 2 Diabetes Mellitus (T2DM) is limited. The present study aimed to examine the effects of AT and Vit D supplementation on inflammation and oxidative stress signaling pathways in T2DM patients.

Materials and methods

In this single-blinded, randomized, placebo-controlled trial, 48 men with T2DM (aged 35–50 years with Body Mass Index (BMI) of 25–30 kg/m2) were randomly allocated into four groups: AT+Vit D (n = 10); AT + placebo (AT; n = 10); Vit D (n = 10), and Control + placebo (C; n = 10). The eight-week AT program was executed for 20–40 min/day, at 60–75% of heart rate maximum (HRmax), for 3 days/wks. The Vit D group received 50,000 IU of Vit D supplement capsules per week for 8 weeks. The serum levels of oxidative stress biomarkers and gene expression of inflammatory cytokines in the Peripheral Blood Mononuclear Cells (PBMCs) were evaluated using the RT-PCR method. To analyze the data, paired t-tests and one-way analysis of variance and Tukey’s post hoc test were used at the significance level of P < 0.05.

Results

The result shows that serum 25-OH-Vit D, total nitrite, Total Glutathione (GSH), Total Antioxidant Capacity (TAC), Superoxide Dismutase (SOD), Catalase (CAT), and Glutathione Peroxidase (GPX) increased; and insulin, Fasting Blood Glucose (FBG), Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), High Sensitivity C-Reactive Protein (hs-CRP), Malondialdehyde (MDA), glycated albumin, and Urinary 8-hydroxydeoxyguanine (8-OHdG) decreased significantly in all groups after 8 weeks, except for C. In addition, results of RT-PCR showed that AT+Vit D, Vit D, and AT significantly downregulated the gene expression of Tumor Necrosis Factor-Alpha (TNF-α), Interleukin-1 Beta (IL-1β), Mitogen-Activated Protein Kinases 1 (MAPK1), Nuclear Factor Kappa B (NF-κB) 1 (p50). It also upregulated Interleukin-4 (IL-4) gene expression, Peroxisome Proliferator-Activated Receptor Gamma (PPAR-γ) in T2DM patients compared to the C.

Conclusion

Additionally, the AT+Vit D group showed significantly lower insulin, FBG, HOMA-IR, hs-CRP, MDA, glycated albumin, urinary 8-OHdG, IL-1β, TNF-α, MAPK1, and NF-κB1 (p50) levels and significantly higher serum 25-OH-Vit D, total nitrite, GSH, TAC, CAT, SOD, GPX, IL-4, and PPAR-γ levels compared to the AT and Vit D groups. In T2DM patients, 8 weeks of AT+Vit D had a more significant impact on certain gene expressions related to inflammation and oxidative stress than Vit D or AT alone.

Vitamin D3 potentiates the nephroprotective effects of vildagliptin-metformin combination in a rat model of metabolic syndrome

The current study was conducted to investigate the nephroprotective effects of vildagliptin-metformin combination in an experimental model of fructose/salt-induced metabolic syndrome (MetS). A major aim was to evaluate the potential capacity of vitamin D3 to potentiate the pleiotropic nephroprotective effects of vildagliptin-metformin combination. MetS was induced in adult male Wistar rats by adding fructose (10%) to everyday drinking water and salt (3%) to the diet for 6 weeks. Along with the same concentrations of fructose/salt feeding, MetS rats were then treated orally with either vildagliptin (10 mg/kg/day)-metformin (200 mg/kg/day) combination, vitamin D3 (10 μg/kg/day), or the triple therapy for a further 6 weeks. The incidence of MetS was confirmed 6 weeks after fructose/salt consumption, when the rats exhibited significant weight gain, dyslipidemia, hyperuricemia, insulin resistance, hyperinsulinemia, and impaired glucose tolerance. At the end of the 12-week experimental period, MetS rats displayed significantly deteriorated renal function, enhanced intrarenal oxidative stress and inflammation together with exaggerated renal histopathological damages and interstitial fibrosis. The study has corroborated antioxidant, anti-inflammatory, and antifibrotic effects of vildagliptin-metformin combination, vitamin D3, and the triple collaborative therapy, conferring renoprotection in the setting of MetS. Due attention has been paid to the crucial role of dipeptidyl peptidase-4 inhibition and sirtuin-1/5' adenosine monophosphate-activated protein kinase activation as novel therapeutic targets to optimize renoprotection. The apparent potentiating effect, evoked upon coadministration of vitamin D3 with vildagliptin-metformin combination, may provide a cornerstone for further clinical investigations.

Renoprotective Effects of DPP-4 Inhibitors

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) worldwide. Dipeptidyl peptidase (DPP)-4 inhibitors are widely used in the treatment of patients with type 2 diabetes (T2D). DPP-4 inhibitors reduce glucose levels by inhibiting degradation of incretins. DPP-4 is a ubiquitous protein with exopeptidase activity that exists in cell membrane-bound and soluble forms. It has been shown that an increased renal DPP-4 activity is associated with the development of DKD. A series of clinical and experimental studies showed that DPP-4 inhibitors have beneficial effects on DKD, independent of their glucose-lowering abilities, which are mediated by anti-fibrotic, anti-inflammatory, and anti-oxidative stress properties. In this review article, we highlight the current understanding of the clinical efficacy and the mechanisms underlying renoprotection by DPP-4 inhibitors under diabetic conditions.