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Obesity is a major risk factor for chronic renal fibrosis and kidneys’ structural and inflammatory impairments. This study aims to examine the possible therapeutic effects of vitamin D supplementation against renal inflammatory and kidney’s structural fibrosis and degeneration.

Forty male Wistar rats were divided into two groups for 16 weeks: normal diet (ND) and high-fat diet (HFD); then, each group was subdivided into two groups including ND, ND + vitamin D and HFD, HFD + vitamin D. Vitamin D supplementation was done for five weeks at 500 IU/kg dosage. Renal tissue concentrations of tumor necrosis factor (TNF)-α, interleukin 6, interleukin 1 beta, monocyte chemoattractant protein (MCP)-1 and transforming growth factor-beta (TGF-β), serum values of lipids, markers of glucose homeostasis and urea, creatinine and uric acid and renal tissue histological and structural changes were determined.

HFD feeding caused remarkable histological and structural changes including higher TNF-α, MCP-1 and TGF-β concentrations in renal tissues of rats, whereas vitamin D has potent anti-inflammatory effects (P = 0.036, 0.047 and 0.02, respectively). Vitamin D administration also reduced urea and uric acid concentrations (P = 0.023 and 0.049, respectively). Moreover, vitamin D reduced glomerulomegaly, reduced lipid accumulation and limited dilated Bowman’s space in rats and improved glycemic status by increasing insulin (P = 0.04) and reducing insulin resistance (P = 0.006).

The current study has some limitations. It was better to measure the level of inflammatory cytokines’ expression in the kidney tissues. Additionally, the measurement of baseline values of inflammatory cytokines was not possible because of the possibility of animals’ drop-out.

According to the study findings, vitamin D treatment in the current report showed a significant therapeutic role in reducing inflammation, improving glycemic and lipid abnormalities and structural and histological modifications in renal tissues of rats. These findings have a great value because after confirming in a human model, vitamin D can be suggested as a potential therapeutic tool in clinical practice.

After being confirmed by other animal or human researches, the results of the current work could have great social implications by reducing the prevalence of obesity-related renal complications and highlighting the beneficial roles of vitamin D.

To the best of the authors’ knowledge, this is the first study to investigate the histological and inflammatory changes in the kidneys and metabolic parameters in the HFD induced rats and also clarified the therapeutic roles of vitamin D in ameliorating the inflammatory, histological, metabolic and functional changes in the kidneys of obese rats.