Increased Hydrogen Sulfide Production Research Articles

Gut microbiome signatures reflect different subtypes of irritable bowel syndrome

ABSTRACT Irritable bowel syndrome (IBS) is a heterogeneous condition with multifactorial pathogenesis. We studied deeply phenotyped individuals with microbiota sequencing enrolled in the American Gut Project. The IBS subjects were matched by age, gender, body mass index, geography, and dietary patterns with non-IBS controls. A total of 942 subjects with IBS-Diarrhea (IBS-D), IBS-Constipation (IBS-C), unclassified IBS (IBS-U), and 942 non-IBS controls were included. We compared taxonomic and functional composition of gut microbiota based on 16S sequencing data and linked them with clinical characteristics and dietary factors. Subjects with IBS-D or IBS-U but not IBS-C showed significantly reduced bacterial diversity (Shannon; p < .01). Distinct bacterial signatures were associated with different IBS subtypes, and the related functional changes were related to IBS pathogenesis, such as the increased hydrogen sulfide production pathway in IBS-D and the increased palmitoleate biosynthesis pathway in IBS-C. IBS subjects with depression showed lower abundance of Bifidobacterium, Sutterella, Butyricimonas and higher abundance of Proteus than those without depression. The relative abundance of microbial short-chain fatty acid production pathways was significantly lower in IBS patients with depression than those without depression in all three subtypes. Female, younger age in IBS-D, and older age in IBS-C were associated with more severe microbiota dysbiosis, and distinct dietary factors had significant effects on the gut microbiota in different IBS subtypes. Our analysis identified the compositional uniqueness of gut microbiota in different IBS subtypes. Distinct associations of the gut microbiota with depression in IBS provide insights into shared pathways in disease pathogenesis. These findings highlight the importance of personalized gut microbiome modulation approaches in different subtypes for optimal therapeutic effects.

Differential expression of cystathionine beta synthase in adolescents with Down syndrome: impact on adiposity.

Obesity is more prevalent among people with Down Syndrome (DS) compared to general population. In this pilot study, we investigated the effect of cystathionine beta-synthase (CBS) overdosage on the regulation of transsulfuration pathway and the obesity phenotype in fifty adolescents (25 obese/overweight and 25 lean) with trisomy 21. The transcriptional levels of CBS in leukocytes and its translational levels in plasma were quantified using real time polymerase chain reaction and enzyme-linked immunosorbent assay respectively. Meanwhile, ultra performance liquid chromatography tandem mass spectrometry was used to determine the plasma concentrations of methionine, homocysteine, cystathionine and cysteine. Fasting plasma lipid profiles were assessed by colorimetric assays. The anthropometric measurements and indices of all subjects were recorded. Both DS groups had comparable levels of CBS transcripts (p = 0.2734). The plasma levels of the enzyme were significantly higher in the lean DS cases (p = 0.0174) compared to the obese/overweight participants. Total cholesterol, triglycerides, high-density lipoprotein, low-density lipoprotein, methionine, homocysteine, cystathionine and cysteine showed similar plasma levels in both groups. However, the plasma cysteine levels exceeded the normal range in all DS cases. We reported a statistically significant inverse association between CBS enzyme levels and weight (r= - 0.3498, p = 0.0128), hip circumference (r= - 0.3584, p = 0.0106), body mass index (r= - 0.3719, p = 0.0078) and body adiposity index (r= - 0.3183, p = 0.0243). Our data suggests that the high concentrations of CBS enzyme together with cysteine modulate the DS obesity presumably through increased hydrogen sulfide production which has recently showed anti-adiposity effects.

Sulfate assimilation regulates hydrogen sulfide production independent of lifespan and reactive oxygen species under methionine restriction condition in yeast.

Endogenously produced hydrogen sulfide was proposed to be an underlying mechanism of lifespan extension via methionine restriction. However, hydrogen sulfide regulation and its beneficial effects via methionine restriction remain elusive. Here, we identified the genes required to increase hydrogen sulfide production under methionine restriction condition using genome-wide high-throughput screening in yeast strains with single-gene deletions. Sulfate assimilation-related genes, such as MET1, MET3, MET5, and MET10, were found to be particularly crucial for hydrogen sulfide production. Interestingly, methionine restriction failed to increase hydrogen sulfide production in mutant strains; however, it successfully extended chronological lifespan and reduced reactive oxygen species levels. Altogether, our observations suggested that increased hydrogen sulfide production via methionine restriction is not the mechanism underlying extended yeast lifespan, even though increased hydrogen sulfide production occurred simultaneously with yeast lifespan extension under methionine restriction condition.

Short-term preoperative protein restriction attenuates vein graft disease via induction of cystathionine γ-lyase.

Therapies to prevent vein graft disease, a major problem in cardiovascular and lower extremity bypass surgeries, are currently lacking. Short-term preoperative protein restriction holds promise as an effective preconditioning method against surgical stress in rodent models, but whether it can improve vein graft patency after bypass surgery is undetermined. Here, we hypothesized that short-term protein restriction would limit vein graft disease via up-regulation of cystathionine γ-lyase and increased endogenous production of the cytoprotective gaseous signalling molecule hydrogen sulfide. Low-density lipoprotein receptor knockout mice were preconditioned for 1 week on a high-fat high-cholesterol (HFHC) diet with or without protein prior to left common carotid interposition vein graft surgery with caval veins from donor mice on corresponding diets. Both groups were returned to a complete HFHC diet post-operatively, and vein grafts analysed 4 or 28 days later. A novel global transgenic cystathionine γ-lyase overexpressing mouse model was also employed to study effects of genetic overexpression on graft patency. Protein restriction decreased vein graft intimal/media+adventitia area and thickness ratios and intimal smooth muscle cell infiltration 28 days post-operatively, and neutrophil transmigration 4 days post-operatively. Protein restriction increased cystathionine γ-lyase protein expression in aortic and caval vein endothelial cells (ECs) and frequency of lung EC producing hydrogen sulfide. The cystathionine γ-lyase inhibitor propargylglycine abrogated protein restriction-mediated protection from graft failure and the increase in hydrogen sulfide-producing ECs, while cystathionine γ-lyase transgenic mice displayed increased hydrogen sulfide production capacity and were protected from vein graft disease independent of diet. One week of protein restriction attenuates vein graft disease via increased cystathionine γ-lyase expression and hydrogen sulfide production, and decreased early inflammation. Dietary or pharmacological interventions to increase cystathionine γ-lyase or hydrogen sulfide may thus serve as new and practical strategies to improve vein graft durability.

The role of hypoxia-inducible factors in carotid body (patho) physiology.

Hypoxia-inducible factors mediate adaptive responses to reduced O2 availability. In patients with obstructive sleep apnoea, repeated episodes of hypoxaemia and reoxygenation (intermittent hypoxia) are sensed by the carotid body (CB). The ensuing CB chemosensory reflex activates the sympathetic nervous system and increased secretion of catecholamines by the adrenal medulla, resulting in hypertension and breathing abnormalities. In the CB, intermittent hypoxia induces the formation of reactive oxygen species (ROS) and increased intracellular Ca2+ levels, which drive increased expression of hypoxia-inducible factor (HIF) 1α and a decrease in the levels of HIF-2α. Intermittent hypoxia increases HIF-1α-dependent expression of Nox2, encoding the pro-oxidant enzyme NADPH oxidase 2, and decreased HIF-2α-dependent expression of Sod2, encoding the anti-oxidant enzyme superoxide dismutase 2. These changes in gene expression drive persistently elevated ROS levels in the CB, brainstem, and adrenal medulla that are required for the development of hypertension and breathing abnormalities. The ROS generated by dysregulated HIF activity in the CB results in oxidation and inhibition of haem oxygenase 2, and the resulting reduction in the levels of carbon monoxide leads to increased hydrogen sulfide production, triggering glomus cell depolarization. Thus, the pathophysiology of obstructive sleep apnoea involves the dysregulation of O2 -regulated transcription factors, gasotransmitters, and sympathetic outflow that affects blood pressure and breathing.

Oxygen-sensitive mitochondrial accumulation of cystathionine β-synthase mediated by Lon protease

Oxygen-sensitive accumulation and degradation, two opposite but intrinsically linked events, of heme proteins in mitochondria affect mitochondrial functions, including bioenergetics and oxygen-sensing processes. Cystathionine β-synthase (CBS) contains a prosthetic heme group and catalyzes the production of hydrogen sulfide in mammalian cells. Here we show that CBS proteins were present in liver mitochondria at a low level under normoxia conditions. Ischemia/hypoxia increased the accumulation of CBS proteins in mitochondria. The normalization of oxygen partial pressure accelerated the degradation of CBS proteins. Lon protease, a major degradation enzyme in mitochondrial matrix, recognized and degraded mitochondrial CBS by specifically targeting at the oxygenated heme group of CBS proteins. The accumulation of CBS in mitochondria increased hydrogen sulfide production, which prevented Ca(2+)-mediated cytochrome c release from mitochondria and decreased reactive oxygen species generation. Mitochondrial accumulation of heme oxygenase-1, another heme protein, was also regulated by oxygen level and Lon protease in the same mechanism as for CBS. Our findings provide a fundamental and general mechanism for oxygen-sensitive regulation of mitochondrial functions by linking oxygenation level to the accumulation/degradation of mitochondrial heme proteins.

Improved XLT4 Agar: Small Addition of Peptone to Promote Stronger Production of Hydrogen-Sulfide by Salmonellae

Xylose lysine tergitol4 agar (XLT4) is a highly selective plating medium used for isolating salmonellae. Studies have shown that XLT4 increases the recovery of salmonellae found in food, environmental and clinical samples. Further testing demonstrated that the addition of low concentrations of proteose peptone No. 3 (pp3) to XLT4 produced blacker Salmonella colonies in shorter incubation times (increased hydrogen sulfide production), while still maintaining strong inhibition of competing bacteria. The increased black colony formation facilitates prompt recognition of the weaker hydrogen sulfide-producing Salmonella strains. Test concentrations of pp3 at 0.5, 1.2 and 1.8 g/L were added to XLT4 and compared with plain XLT4 using pure bacterial cultures. In addition, these four plating media, plus xylose lysine desoxycholate agar (XLD) were evaluated using nonspiked chicken liver and pork sausage samples. The concentration of 1.2 g/L of pp3 in XLT4 gave the best overall results. In virtually all cases, the Salmonella colonies were larger and more black than on plain XLT4 without pp3. The improved XLT4 is recommended for more reliable detection of salmonellae from food, environmental and clinical samples.

Improved XLT4 Agar: Small Addition of Peptone to Promote Stronger Production of Hydrogen-Sulfide by Salmonellae

Xylose lysine tergitol4 agar (XLT4) is a highly selective plating medium used for isolating salmonellae. Studies have shown that XLT4 increases the recovery of salmonellae found in food, environmental and clinical samples. Further testing demonstrated that the addition of low concentrations of proteose peptone No. 3 (pp3) to XLT4 produced blacker Salmonella colonies in shorter incubation times (increased hydrogen sulfide production), while still maintaining strong inhibition of competing bacteria. The increased black colony formation facilitates prompt recognition of the weaker hydrogen sulfide-producing Salmonella strains. Test concentrations of pp3 at 0.5, 1.2 and 1.8 g/L were added to XLT4 and compared with plain XLT4 using pure bacterial cultures. In addition, these four plating media, plus xylose lysine desoxycholate agar (XLD) were evaluated using nonspiked chicken liver and pork sausage samples. The concentration of 1.2 g/L of pp3 in XLT4 gave the best overall results. In virtually all cases, the Salmonella colonies were larger and more black than on plain XLT4 without pp3. The improved XLT4 is recommended for more reliable detection of salmonellae from food, environmental and clinical samples.