Trimethylamine N-oxide and kidney diseases: what do we know? / N-óxido de trimetilamina e doenças renais: o que sabemos?

Abstract In the human gut, there is a metabolically active microbiome whose metabolic products reach various organs and are used in the physiological activities of the body. When dysbiosis of intestinal microbial homeostasis occurs, pathogenic metabolites may increase and one of them is trimethyl amine-N-oxide (TMAO). TMAO is thought to have a role in the pathogenesis of insulin resistance, diabetes, hyperlipidemia, atherosclerotic heart diseases, and cerebrovascular events. TMAO level is also associated with renal inflammation, fibrosis, acute kidney injury, diabetic kidney disease, and chronic kidney disease. In this review, the effect of TMAO on various kidney diseases is discussed.

Resumo No intestino humano, existe um microbioma metabolicamente ativo cujos produtos metabólicos alcançam diversos órgãos e são utilizados nas atividades fisiológicas do corpo. Quando ocorre disbiose da homeostase microbiana intestinal, os metabólitos patogênicos podem aumentar, e um deles é o N-óxido de trimetilamina (TMAO). Acredita-se que o TMAO tenha um papel na patogênese da resistência à insulina, diabetes, hiperlipidemia, doenças cardíacas ateroscleróticas e eventos cerebrovasculares. O nível de TMAO também está associado à inflamação renal, fibrose, lesão renal aguda, doença renal diabética e doença renal crônica. Nesta revisão, discute-se o efeito do TMAO em diversas doenças renais.

Unexpectedly High Prevalence of Low Alpha-Galactosidase A Enzyme Activity in Patients with Focal Segmental Glomerulosclerosis

OBJECTIVES: Fabry disease (FD) is a rare disease associated with sphingolipid accumulation. Sphingolipids are components of plasma membranes that are important in podocyte function and accumulate in various glomerular diseases such as focal segmental glomerulosclerosis (FSGS). Both FD and FSGS can cause podocyte damage and are classified as podocytopathies. In this respect, FD and FSGS share the same pathophysiologic pathways. Previous screening studies have shown that a significant proportion of end-stage renal disease (ESRD) patients receiving hemodialysis (HD) have unsuspected FD, and the prevalence of low alpha-galactosidase A (αGLA) enzyme activity in these patients is higher than that in the normal population. We aimed to compare αGLA enzyme activity in patients with biopsy-proven FSGS and ESRD receiving HD. METHODS: The records of 232 patients [62 FSGS (F/M: 33/29); 170 HD (M/F: 93/79)] were evaluated retrospectively. The screening was performed based on the αGLA enzyme activity on a dried blood spot, with the confirmation of plasma LysoGb3 levels, and the known GLA mutations were tested in patients with low enzyme activities. The two groups were compared using these parameters. RESULTS: The mean level of αGLA enzyme activity was found to be lower in FSGS patients than in the HD group (2.88±1.2 μmol/L/h versus 3.79±1.9 μmol/L/h, p<0.001). There was no significant relationship between the two groups with regard to the plasma LysoGb3 levels (2.2±1.22 ng/ml versus 1.7±0.66 ng/ml, p: 0.4). In the analysis of GLA mutations, a D313Y mutation [C(937G>T) in exon p] was found in one patient from the FSGS group. CONCLUSIONS: We found that αGAL activity in patients with FSGS is lower than that in patients undergoing HD. The low enzyme activity in patients with FSGS may be explained by considering the similar pathogenesis of FSGS and FD, which may also lead to sphingolipid deposition and podocyte injury.

Pentraxin-2 is associated with renal fibrosis in patients undergoing renal biopsy

OBJECTIVES: Progressive renal disease is characterized by histological changes in the kidney and fibrosis is a common outcome. Renal biopsy is the only diagnostic tool to evaluate these histopathological changes. Pentraxin-2 (PTX-2) is an anti-inflammatory constitutive plasma protein associated with the innate immune system. Recently, as a biomarker, the circulating level of PTX-2 is shown to be decreased in chronic fibrotic diseases. In this study, we aimed to investigate the relationship between renal fibrosis severity and serum PTX-2 levels in patients undergoing renal biopsy. METHODS: This cross-sectional study included 45 patients and 16 healthy individuals (HIs). The severity of renal fibrosis was evaluated according to the Banff and Sethi scoring systems by the same pathologist. PTX-2 was measured by an enzyme-linked immunosorbent assay and compared with the demographical, clinical, biochemical, and histopathological data of the patients and HIs. RESULTS: PTX-2 levels were lower in the biopsy group than in the HI group (p=0.12). Patients with moderate renal fibrosis had significantly lower serum PTX-2 levels than those in patients with minimal and mild fibrosis (p=0.017 and p=0.010, respectively). PTX-2 concentrations were correlated with serum albumin (r=0.30, p=0.016), and were negatively correlated with serum creatinine levels (rho=-0.42, p=0.01) and body mass index (r=-0.32, p=0.011). CONCLUSIONS: The results indicated that PTX-2 levels are significantly lower in patients with renal fibrosis than HIs, and declining further in patients with severe fibrosis.