Folic acid supplementation alleviates high-salt diet-induced renal fibrosis in mice

doi:10.12122/j.issn.1673-4254.2026.03.24

Abstract

Abstract:

Objective To investigate the protective effect of 2-week dietary folic acid (FA) supplementation against renal fibrosis induced by high-salt (HS) diet in mice. Methods Twenty-eight mice were randomly divided into control, HS (8% NaCl) diet group, HS+low-dose FA (FA: 0.56 mg/kg) group and HS+high-dose FA (5.6 mg/kg) group. The changes in body weight, food intake, water consumption, tail artery systolic pressure, and heart rate of the mice were monitored, and serum levels of creatinine (SCr) and inflammatory cytokines (IL-1β, IL-6, and TNF-α) were measured. Renal histopathology of the mice was assessed using HE, periodic acid-Schiff (PAS), Masson, and Sirius red staining. Renal expressions of Kim1, vimentin, α-Sma, and E-cadherin mRNAs and E-cadherin, vimentin, and α‑SMA proteins were detected using RT-qPCR and immunohistochemistry. Results In mice feeding a HS diet, FA supplementation significantly reduced their water intake, lowered tail artery systolic pressure, heart rate, renal index and serum SCr levels, reducing also serum levels of TNF‑α , IL-1β, and IL-6. Masson and Sirius red staining revealed markedly reduced glomerular and interstitial fibrosis indices in HS+low-dose FA group, while the mice in HS+high-dose FA group showed mixed fibrotic improvements. Immunohistochemical results demonstrated that FA significantly upregulated E-cadherin protein expression and suppressed vimentin expression in renal tissues. Both FA doses inhibited HS-induced mRNA and protein expressions of fibrosis markers (Vimentin, Kim1 and α-Sma), attenuated interstitial collagen deposition, and alleviated renal fibrosis. FA also upregulated renal E-cadherin mRNA expression, contributing to fibrosis mitigation. Conclusion FA intervention ameliorates renal inflammation and delays fibrosis progression in HS-fed mice. Low-dose FA supplementation produces better protective effect than high-dose FA, likely mediated by regulation of renal E-cadherin, Kim1, vimentin, and α-Sma expressions.

Key words: short-term high salt, renal damage, folic acid intervention, renal fibrosis

Fang TANG, Yongyi WANG, Tingting LIANG, Weiying HE, Huilv LAO, Jiale SONG. Folic acid supplementation alleviates high-salt diet-induced renal fibrosis in mice[J]. Journal of Southern Medical University, 2026, 46(3): 707-714.

Figures/Tables 8

Tab.1 Primer sequences used in this study

Gene	Forward primer (5'→3')	Revise primer (5'→3')
Ecadherin	GGGACAAAGAAACAAAGGT	TGACACGGCATGAGAATAG
Vimentin	AGCCTCTATTCCTCATCCC	TAGTTGGCAAAGCGGTCAT
αSma	AGCATCCGACCTTGCTAACG	CCAGAGTCCAGCACAATACCAG
Kim1	ATGGCACTGTGACATCCTC	CCAACATAGAAGCCCTTAG

Fig.1 Effect of folic acid (FA) supplementation on body weight, food intake and water consumption in mice fed a high-salt (HS) diet (n=7). *P<0.05, **P<0.01 vs CON, #P<0.05 vs HS.

Fig.2 Effect of FA on blood pressure and heart rate in mice fed a HS diet (n=7). *P<0.05 vs CON, #P<0.05 vs HS.

Fig.3 Effect of FA on kidney index and renal function parameters in mice fed a HS diet. *P<0.05 vs CON, #P<0.05, ##P<0.01 vs HS.

Fig.4 Effect of FA on serum levels of inflammatory cytokines in mice fed a HS diet. *P<0.05 vs CON, #P<0.05 vs HS.

Fig.5 Effect of FA on histopathology of the renal cortex and medulla in mice fed a HS diet (HE/PAS staining, original magnification: ×400). A: HE staining (Scale bar=50 μm). B: PAS staining (Scale bar=50 μm).

Fig.6 Effect of FA on histopathology of the renal cortex and medulla fibrosis in mice fed a HS diet (Masson/Sirius Red staining, ×400). A: Masson staining(Scale bar=50 μm); B: Sirius Red staining (Scale bar=50 μm). *P<0.05,**P<0.01, ***P<0.001 vs CON; #P<0.05, ##P<0.01 vs HS.

Fig.7 Effect of FA on protein and mRNA levels of E-cadherin, vimentin,Kim-1 and α-SMA in the kidneys of mice fed a HS diet (Immunohistochemical staining, ×400). A: Protein levels of E-cadherin (Scale bar=50 μm). B: Protein levels of Vimentin (Scale bar=50 μm). C: Protein and mRNA levels of vimentin, Kim-1 and α-SMA. *P<0.05, **P<0.01 vs CON; #P<0.05, ##P<0.01, ###P<0.001 vs HS.

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