Ischemic post-conditioning attenuates renal ischemic reperfusion injury via down-regulation of toll-like receptor 4 in diabetic rats

Vitamin D is involved in the effects of the intestinal flora and its related metabolite TMAO on perirenal fat and kidneys in mice with DKD

BACKGROUND

Vitamin D was shown to directly exert a protective effect on diabetic kidney disease (DKD) in our previous study. However, whether it has an effect on perirenal adipose tissue (PRAT) or the intestinal flora and its metabolites (trimethylamine N-oxide, TMAO) is unclear.

METHODS

DKD mice were received different concentrations of 1,25-(OH)2D3 for 2 weeks. Serum TNF-α levels and TMAO levels were detected. 16S rRNA sequencing was used to analyze gut microbiota. qPCR was used to detect the expression of TLR4, NF-Κb, PGC1α, and UCP-1 in kidney and adipose tissue. Histological changes in kidney and perirenal adipose tissue were observed using HE, PAS, Masson and oil red staining. Immunofluorescence and immunohistochemistry were used to detect the expression of VDR, PGC1α, podocin, and UCP-1 in kidney and adipose tissue. Electron microscopy was used to observe the pathological changes in the kidney. VDR knockout mice were constructed to observe the changes in the gut and adipose tissue, and immunofluorescence and immunohistochemistry were used to detect the expression of UCP-1 and collagen IV in the kidney.

RESULTS

1,25-(OH)2D3 could improve the dysbiosis of the intestinal flora of mice with DKD, increase the abundance of beneficial bacteria, decrease the abundance of harmful bacteria, reduce the pathological changes in the kidney, reduce fat infiltration, and downregulate the expression of TLR4 and NF-κB in kidneys. The serum TMAO concentration in mice with DKD was significantly higher than that of the control group, and was significantly positively correlated with the urine ACR. In addition, vitamin D stimulated the expression of the surface markers PGC1α, UCP-1 and VDR in the PRAT in DKD mice, and TMAO downregulated the expression of PRAT and renal VDR.

CONCLUSIONS

The protective effect of 1,25-(OH)2D3 in DKD mice may affect the intestinal flora and its related metabolite TMAO on perirenal fat and kidneys.

Remote ischemic per-conditioning protects against renal ischemia-reperfusion injury via suppressing gene expression of TLR4 and TNF-α in rat model

The pathogenesis of renal ischemia-reperfusion injury (IRI) involves both inflammatory processes and oxidative stress in the kidney. This study determined whether remote ischemic per-conditioning (RIPerC) is mediated by toll-like receptor 4 (TLR4) signaling pathway in rats. Renal IR injury was induced by occluding renal arteries for 45 min followed by 24 h of reperfusion. RIPerC included 4 cycles of 2 min of ischemia of the left femoral artery followed by 3 min of reperfusion performed at the start of renal ischemia. Rats were divided into sham, IR, and RIPerC groups. At the end of the reperfusion period, urine, blood and tissue samples were gathered. IR created kidney dysfunction, as ascertained by a significant decrease in creatinine clearance and a significant increase in sodium fractional excretion. These changes occurred in concert with a decrease in the activities of glutathione peroxidase, catalase, and superoxide dismutase with an increment in malondialdehyde levels, mRNA expression levels of TLR4 and tumor necrosis factor α (TNF-α), and histological damage in renal tissues. RIPerC treatment diminished all these changes. This study demonstrates that RIPerC has protective effects on the kidney after renal IR, which might be related to the inhibition of the TLR4 signaling pathway and augmentation of antioxidant systems.