The prebiotic effects of soluble dietary fiber mixture on renal anemia and the gut microbiota in end-stage renal disease patients on maintenance hemodialysis: a prospective, randomized, placebo-controlled study

BACKGROUND: Renal anemia is caused by end-stage renal disease (ESRD) but has a complex etiology. The application of dietary fiber (DF) to regulate the gut microbiota has shown effective therapeutic effects in some diseases, but its role in renal anemia is not clear. The aim of this study was to explore the effect of DF on renal anemia by regulating the gut microbiota and its metabolite, short-chain fatty acids (SCFAs). METHODS: A total of 162 ESRD patients were enrolled and randomly distributed into a DF or a control group (received oral DF or potato starch, 10 g/day for 8 weeks). Hemoglobin (Hb), serum iron (Fe(2+)), serum ferritin (SF), soluble transferrin receptor (sTfR), hepcidin and the dosage of recombinant human erythropoietin (rhEPO) before and after intervention in patients were analyzed. The gut microbiota and SCFAs in both groups were analyzed by 16S rDNA sequencing and gas chromatography–mass spectrometry, respectively. Spearman’s correlation test was used to analyze the correlation between the gut microbiota, SCFAs and the hematological indicators. RESULTS: Compared with the control group, (1) the patients in the DF group had higher Hb [117.0 (12.5) g/L vs. 94.0 (14.5) g/L, p < 0.001], Fe(2+) [13.23 (4.83) μmol/L vs. 10.26 (5.55) μmol/L, p < 0.001], and SF levels [54.15 (86.66) ng/ml vs. 41.48 (36.60) ng/ml, p = 0.003]. (2) The rhEPO dosage in the DF group was not significantly decreased (p = 0.12). (3) Bifidobacterium adolescentis, Lactobacillus and Lactobacillaceae were increased in the DF group, and Lactobacillus and Lactobacillaceae were positively correlated with Hb (r = 0.44, p < 0.001; r = 0.44, p < 0.001) and Fe(2+) levels (r = 0.26, p = 0.016; r = 0.26, p = 0.016) and negatively correlated with rhEPO dosage (r = − 0.45, p < 0.001; r = − 0.45, p < 0.001). (4) Patients in the DF group had elevated serum butyric acid (BA) levels [0.80 (1.65) vs. 0.05 (0.04), p < 0.001] and BA levels were positively correlated with Hb (r = 0.26, p = 0.019) and Fe(2+) (r = 0.31, p = 0.005) and negatively correlated with rhEPO dosage (r = − 0.36, p = 0.001). Lactobacillus and Lactobacillaceae were positively correlated with BA levels (r = 0.78, p < 0.001; r = 0.78, p < 0.001). CONCLUSION: DF may improve renal anemia in ESRD patients by regulating the gut microbiota and SCFAs. Trial registration This study was registered in the China Clinical Trial Registry (www.chictr.org.cn) on December 20, 2018 (ChiCTR1800020232). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12967-022-03812-x.