Effects of fecal microbiota transplantation on serum uric acid levels, 1 symptoms and intestinal barrier function in patients with acute and 2 recurrent gout: a pilot study

1 Background: Gut dysbiosis has been reported to be closely associated with gout. Fecal 2 microbiota transplantation (FMT) has been considered as an effective way to restore 3 the balance of gut microbiota. We aimed to evaluate the effects of FMT on serum uric 4 acid levels, symptoms and the intestinal barrier function in patients with acute and 5 recurrent gout. 6 Methods: We performed a pilot study of FMT for acute and recurrent gout. The primary 7 outcome was the changes in serum uric acid level on day 28 post-FMT and in gout 8 symptoms by one year. The secondary outcomes included the changes in levels of urine 9 uric acid, diamine oxidase (DAO), D-lactic acid and endotoxin on day 28 post-FMT. 10 The levels of DAO, D-lactic acid and endotoxin were assessed by enzyme assay. 11 Results: Eleven patients received FMT treatment. All the patients had a reduction in 12 serum uric acid levels after FMT treatment ( P < 0.05), accompanied with a decrease in 13 the frequency and duration time of acute gout flares. The levels of DAO, D-lactic acid 14 and endotoxin, reflecting the intestinal barrier function, were higher in patients with 15 gout than in healthy donors ( P < 0.05). After FMT treatment, the levels of DAO and 16 endotoxin decreased ( P < 0.05). Conclusions: FMT is effective for reducing serum uric acid levels and improving gout symptoms in patients with gout, and contributes to improve the impaired intestinal barrier function of the patients.

Gout, the most common form of inflammatory arthritis, is a chronic urate crystal 2 deposition disease [1]. Sustained hyperuricemia is the uppermost risk factor for gout, 3 mainly caused by the overproduction and/or underexcretion of urate [1]. 4 Underexcretion of urate is the primary cause of hyperuricemia for most patients with 5 gout. The urate is mainly excreted through the kidney and intestine pathways, 6 accounting for two thirds and one third of the total urate, respectively. In case of renal 7 damage, the intestine pathway will compensatorily become the main pathway to 8 eliminate urate [1]. 9 Gut microbiota, crucial for maintaining the homeostasis of the intestinal 10 environment, is involved in the metabolism of the host [2]. It has been reported that the 11 gut dysbiosis exists in patients with gout [3,4], which leads to the abnormal metabolism 12 of host purine and uric acid [5]. Manipulation of gut dysbiosis with probiotics alleviates 13 fructose-induced hyperuricemia in mice, accompanied with the enhancement of 14 intestinal barrier function [6]. Therefore, a possibility arises that the patients with gout 15 will benefit from restoring a healthy gut microbiota. 16 Fecal microbiota transplantation (FMT) has been regarded as a safe and effective 17 way to restore a healthy gut microbiota, exhibiting remarkable clinical efficacy for 18 Clostridium difficile infection, inflammatory bowel disease and other gut dysbiosis-19 related diseases [7][8][9][10]. Recently, Han et al. conducted FMT in hyperuricemic mice, 20 and found that serum uric acid levels reduced and uric acid excretion increased [11], 21 demonstrating an ameliorating effect of FMT on hyperuricemia. They further found that 22 5 the expression of claudin-1 and occludin in these mice was increased, compared to that 1 in hyperuricemic mice with renal injury [11]. These data indicate that FMT repairs 2 intestinal integrity, which might function as one of the underlying mechanisms by 3 which FMT alleviates hyperuricemia. Although the encouraging results from the animal 4 experiments, whether FMT reduces the serum uric acid levels and improves gout 5 symptoms in patients with gout and improves intestinal integrity in human remains 6 unknown. 7 In this pilot study, we aimed to evaluate the effects of FMT on serum uric acid 8 levels, symptoms and the intestinal barrier function in patients with acute and recurrent 9 gout.  Patients who met the following criteria were included in the study: 1) aged ≥ 18 years; treated with uric-acid-lowering drugs for more than one year, but still with 1 hyperuricemia and suffering from acute gout flares twice or more a year. The exclusion 2 criteria were as follows: 1) pregnancy; 2) gastrointestinal infection, cardiopulmonary 3 failure or serious liver diseases; and 3) rejection to conduct transendoscopic enteral 4 tubing. There was no sex restriction.

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The healthy donors without kinship to patients with gout were included as the  The fresh fecal microbiota suspension was prepared using the automatic purification  Normally distributed data were presented as mean ± standard deviation (SD), while 1 non-normally distributed data were presented as median (interquartile range).

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Comparisons of the differences before and after FMT treatment were performed using 3 paired-samples t-test for the normally distributed data, or Wilcoxon Signed Rank Test, 4 otherwise. Comparisons of the differences between the patients and donors were 5 performed using independent-samples t-test for the normally distributed data with equal 6 variance, or Mann-Whitney U-test, otherwise. SPSS statistical package (version 19.0) 7 was employed to perform all statistical analyses. P < 0.05 was regarded as statistical 8 significance.  After FMT, the serum uric acid levels reduced in eight (72.73%) out of 11 patients. 1 The averaged serum uric acid levels in patients reduced to (481.55 ± 119.77) μmol/L, 2 which was significantly lower than that before FMT (t = 2.513, P = 0.031; Fig. 1), but 3 still significantly higher than that in donors (Mann-Whitney U value = 11.000, P = 4 0.031; Fig. 1).

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Urine uric acid test results before and after FMT were available in four of the 11 6 patients. As shown in Table S1, the urine uric acid levels decreased in three patients but 7 increased in one patient after FMT; there was no significant difference between the  After FMT treatment, the levels of serum DAO and endotoxin in patients with gout 5 were reduced (P < 0.05; Fig. 2A and C). D-lactic acid level decreased slightly, with no 6 significant difference (t = 1.237, P = 0.244; Fig. 2B). In addition, there were no 7 significant differences in the levels of serum DAO and endotoxin between patients with 8 gout after FMT and the donors ( Fig. 2A and C), indicating that the levels of serum DAO 9 and endotoxin return to normal after FMT treatment. However, D-lactic acid levels in 10 patients with gout after FMT was still obviously higher than that in donors (Mann-11 Whitney U value = 3.000, P = 0.003; Fig. 2B).  The primary cause of hyperuricemia for most people with gout is underexcretion of 10 urate [1]. The kidney and intestine are the main excretion pathways of uric acid [2, 18].

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In the present study, the urine uric acid levels in gout patients seemed to be unchanged 12 after FMT treatment, suggesting that FMT might not affect the excretion of uric acid 13 through the kidney, and the reduced serum acid levels after FMT might not be caused 14 by the increased elimination through the kidney, but associated with an increased 15 elimination through the intestine. However, the data on the urine uric acid levels before 16 and after FMT were available only in four patients, and thus our observation needs to 17 be confirmed in studies with more sample sizes.

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In the experiments in mice with hyperuricemia, it has been found that hyperuricemia        Faecal microbiota transplantation alters gut microbiota in patients with irritable bowel 10 syndrome: results from a randomised, double-blind placebo-controlled study. Gut.   Serum uric acid levels of donors (n = 6) and patients with gout (n = 11) before and after 4 FMT. Data are presented as mean ± standard deviation (SD). 5 *, P < 0.05, and **, P <0.01, comparison as shown in the figure.