Potential Trimethylamine (TMA)-Producing Bacteria in patients with chronic kidney disease undergoing hemodialysis.

Trimethylamine (TMA), produced by gut microbiota, is the precursor of trimethylamine-N-oxide (TMAO), a uremic toxin that accumulates in patients with chronic kidney disease (CKD). Elevated TMAO plasma levels are associated with cardiovascular complications and CKD progression. To evaluate the association between gut microbiota composition and TMAO plasma levels in CKD patients undergoing hemodialysis (HD). This is a cross-sectional study with 25 patients evaluated (60% female, 53 (18) years, body mass index (BMI) 25.8 (6.75) Kg/m2). They were divided into two groups according to their TMAO plasma levels: normal (≤ 7.4 μM) and high (> 7.4 μM). Uremic toxins such as indoxyl sulfate (IS), p-cresyl sulfate (pCS), and indol acetic acid (IAA) were measured with RP-HPLC, and TMAO plasma levels were quantified using LC-MS/MS. Fecal DNA was extracted with a commercial kit, PCR amplified the V4 region of the 16S rRNA gene, and short-read sequencing was performed on the Illumina platform. Dietary intake, anthropometric measurements, and inflammation markers were also evaluated. Nrf2, NF-κB, IL-1β, and NLRP3 mRNA expressions were measured from peripheral blood mononuclear cells (PBMC) using quantitative real-time polymerase chain reaction (qPCR). There were significant positive correlations between TMAO and plasma levels of pCS, NLPR3 inflammasome mRNA expression, serum phosphorus levels, and negative correlations with dietary lipid intake. The group with TMAO > 7.4 μM showed an increase in the microbiome abundance of Saccharibacteria (genus incertae sedis), Colidextribacter, Dorea, and Staphylococci genera, and a decrease in abundance in the genera Lachnospira, Lactobacilli, and Victivallis. TMAO plasma level was positively correlated with the abundance of bacteria of the genera Colidextribacter and Helicobacter and was negatively correlated with Sphingomanos, Lachnospira, Streptomyces, and Bacillus genera. Saccharibacteria (genus incertae sedis), Colidextribacter, Dorea, and Staphylococci genera showed higher abundance in patients with high TMAO levels. In addition, we observed that elevated plasma TMAO levels are associated with inflammation markers, dietary lipid intake, and serum phosphorus levels in patients undergoing HD.

Alvarenga L ，Kemp JA ，Schultz J ，Cardozo LFMF ，Nakao LS ，Ribeiro-Alves M ，Rosado A ，Mafra D ... -  《-》

The associations between nutrition and circulating gut microbiota-derived uremic toxins in patients undergoing kidney replacement therapy: An observational, cross-sectional study.

Gut microbiota generates a series of bioactive metabolites that can be converted into uremic toxins such as trimethylamine-N-oxide (TMAO), p-cresyl sulfate (pCS), and indoxyl sulfate (IS). The aim of the study was to examine the association between diet and the concentrations of the mentioned gut microbiota-derived uremic toxins. An observational cross-sectional study was conducted involving 210 participants: 84 hemodialysis (HD) patients, 44 peritoneal dialysis (PD) patients, 52 kidney transplant recipients (KTR), and 30 healthy controls. Dietary intake was assessed using a 3-day food diary and a food frequency questionnaire with 6 answers (FFQ-6). The alternate Mediterranean diet (aMED) score was calculated based on data obtained from the 3-day food diary and FFQ-6. Blood samples were analyzed for TMAO, pCS, and IS concentrations using liquid chromatography-mass spectrometry (LC-MS/MS). Significant differences in TMAO, pCS, and IS concentrations were observed among the study groups. HD and PD patients exhibited higher levels of these metabolites compared to KTR and healthy controls. The median aMED score was 4 (3-5) points in the HD group, 4.5 (4-6) points in the PD group, 5 (4-6) points in the KTRs, and 6 (5-7) points in the control group. Higher adherence to the Mediterranean diet (aMED score) was associated with lower pCS levels in dialysis patients. Vegetable intake several times a day was found to mitigate the effects of phenylalanine and tyrosine intake on pCS concentration among dialysis patients. The diet of patients undergoing kidney replacement therapy (KRT) significantly affects the concentrations of gut microbiota-derived uremic toxins. These findings highlight the importance of dietary management in mitigating the adverse effects of these toxins in patients with chronic kidney disease (CKD).

Czaja-Stolc S ，Potrykus M ，Ruszkowski J ，Styburski D ，Dębska-Ślizień A ，Małgorzewicz S ... -  《Clinical Nutrition ESPEN》

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

《Jove-Journal of Visualized Experiments》

Association of trimethylamine N-oxide and metabolites with kidney function decline in patients with chronic kidney disease.

Trimethylamine N-oxide (TMAO) is a gut microbial metabolite derived from dietary l-carnitine and choline. High plasma TMAO levels are associated with cardiovascular disease and overall mortality, but little is known about the associations of TMAO and related metabolites with the risk of kidney function decline among patients with chronic kidney disease (CKD). We prospectively followed 152 nondialysis patients with CKD stages 3-5 and measured plasma TMAO and related metabolites (trimethylamine [TMA], choline, carnitine, and γ-butyrobetaine) via liquid chromatography‒mass spectrometry. An estimated glomerular filtration rate (eGFR) slope >3 ml/min/per 1.73 m2 per year was defined as a rapid decline. We performed logistic regression to determine the probability of rapid or slow eGFR decline, with each metabolite as the main predictor. The gut microbiota was profiled via whole metagenomic sequencing. The participants had a median age of 66 years, 41.4 % were women, 39.5 % had diabetes, and the median eGFR was 23 mL/min/1.73 m2. A rapid decrease in the eGFR occurred in 65 patients (42.8 %) over a median follow-up of 3.3 years. After adjustment for baseline eGFR, proteinuria, and clinical factors, plasma TMAO levels were independently associated with increased odds of rapid eGFR decline (odds ratio, 2.42; 95 % CI, 1.36-4.32), whereas plasma TMA, choline, carnitine, and γ-butyrobetaine levels were not. Patients who exhibited rapid eGFR decline had a distinct gut microbial composition characterized by increased α-diversity and an abundance of TMA-producing bacteria, including those of the genera Desulfovibrio and Collinsella tanakaei, as well as increased expression of the TMA-producing enzymes bbuA and cutC. Our findings suggest the relevance of plasma TMAO in the progression of kidney disease among patients with CKD.

Cheng E ，Hung SC ，Lin TY 《-》

Interactions between the gut microbiome, associated metabolites and the manifestation and progression of heart failure with preserved ejection fraction in ZSF1 rats.

Heart failure with preserved ejection fraction (HFpEF) is associated with systemic inflammation, obesity, metabolic syndrome, and gut microbiome changes. Increased trimethylamine-N-oxide (TMAO) levels are predictive for mortality in HFpEF. The TMAO precursor trimethylamine (TMA) is synthesized by the intestinal microbiome, crosses the intestinal barrier and is metabolized to TMAO by hepatic flavin-containing monooxygenases (FMO). The intricate interactions of microbiome alterations and TMAO in relation to HFpEF manifestation and progression are analyzed here. Healthy lean (L-ZSF1, n = 12) and obese ZSF1 rats with HFpEF (O-ZSF1, n = 12) were studied. HFpEF was confirmed by transthoracic echocardiography, invasive hemodynamic measurements, and detection of N-terminal pro-brain natriuretic peptide (NT-proBNP). TMAO, carnitine, symmetric dimethylarginine (SDMA), and amino acids were measured using mass-spectrometry. The intestinal epithelial barrier was analyzed by immunohistochemistry, in-vitro impedance measurements and determination of plasma lipopolysaccharide via ELISA. Hepatic FMO3 quantity was determined by Western blot. The fecal microbiome at the age of 8, 13 and 20 weeks was assessed using 16s rRNA amplicon sequencing. Increased levels of TMAO (+ 54%), carnitine (+ 46%) and the cardiac stress marker NT-proBNP (+ 25%) as well as a pronounced amino acid imbalance were observed in obese rats with HFpEF. SDMA levels in O-ZSF1 were comparable to L-ZSF1, indicating stable kidney function. Anatomy and zonula occludens protein density in the intestinal epithelium remained unchanged, but both impedance measurements and increased levels of LPS indicated an impaired epithelial barrier function. FMO3 was decreased (- 20%) in the enlarged, but histologically normal livers of O-ZSF1. Alpha diversity, as indicated by the Shannon diversity index, was comparable at 8 weeks of age, but decreased by 13 weeks of age, when HFpEF manifests in O-ZSF1. Bray-Curtis dissimilarity (Beta-Diversity) was shown to be effective in differentiating L-ZSF1 from O-ZSF1 at 20 weeks of age. Members of the microbial families Lactobacillaceae, Ruminococcaceae, Erysipelotrichaceae and Lachnospiraceae were significantly differentially abundant in O-ZSF1 and L-ZSF1 rats. In the ZSF1 HFpEF rat model, increased dietary intake is associated with alterations in gut microbiome composition and bacterial metabolites, an impaired intestinal barrier, and changes in pro-inflammatory and health-predictive metabolic profiles. HFpEF as well as its most common comorbidities obesity and metabolic syndrome and the alterations described here evolve in parallel and are likely to be interrelated and mutually reinforcing. Dietary adaption may have a positive impact on all entities.

Guivala SJ ，Bode KA ，Okun JG ，Kartal E ，Schwedhelm E ，Pohl LV ，Werner S ，Erbs S ，Thiele H ，Büttner P ... -  《Cardiovascular Diabetology》