Effects of Folate and Fructose Intakes on Renal Cytokines and Fibrosis in an Adenine-Induced Mouse Model of Chronic Kidney Disease

Dietary pattern characterized by low intake of vegetables and fruits and high consumption of fat, soft drink and desserts are associated with an increased risk of chronic diseases. To investigate the effects of folate status and fructose intake on adenine-induced chronic kidney disease (CKD), seven-week-old C57BL/6 mice were divided into six groups and fed either a control diet (Ctrl), a 26% (<i>w</i>/<i>w</i>) high-fructose diet (Hfru), Ctrl plus 0.15% adenine (Ctrl+ade), Hfru+ade, Hfru with folate deficiency plus adenine (Hfru-f+ade), or Hfru with tenfold folate supplementation plus adenine (Hfru+f10+ade). After 10 weeks on the assigned diets, adenine was administrated to the +ade groups for 7 weeks. The results showed that all adenine-treated mice exhibited increased fasting blood glucose, urinary glucose, and elevated renal expression of collagen 1a1 (<i>Col1a1</i>), fibronectin (<i>Fn1</i>), and smooth muscle α-actin (<i>Acta2</i>). Compared with Ctrl mice, Hfru-fed mice showed significantly higher serum creatinine, increased urinary protein, and reduced creatinine clearance. Adenine induced kidney injury in all +ade groups, with the most severe damage observed in Hfru-f+ade mice, as indicated by elevated blood urine nitrogen (BUN), urinary protein, neutrophil gelatinase-associated lipocalin (NGAL), and renal fibrosis. In contrast, Hfru+f10+ade mice showed the lowest levels of these renal injury markers. The Hfru+ade diets increased renal <i>Hif1α</i> and <i>iNos</i> gene expression, which was further exacerbated by folate deficiency. Secretion of the anti-inflammatory cytokine interleukin (IL-10) by splenocytes was significantly reduced under folate-deficient conditions. Renal IL-10 levels were suppressed in all +ade groups but were significantly increased by folate supplementation. Renal IL-10 levels were negatively correlated with the inflammatory chemokine monocyte chemoattractant protein (MCP-1) and transforming growth factor (TGF)-β, whereas renal MCP-1 levels showed positive correlations with TGF-β and IL-6. Overall, these findings suggest that high fructose consumption in the absence of adequate folate intake may be of concern for CKD progression.