Background: The therapeutic potential of faecal microbiota transplantation (FMT) is under investigation for a range of inflammatory conditions. While mechanisms of benefit are poorly understood, most models rely on the viability of transplanted microbes. We hypothesised that protocols commonly used in the preparation of faecal transplants will substantially reduce the number, diversity and functional potential of viable microbes. Methods: Stools from eight screened donors were processed under strict anaerobic conditions, in ambient air, and freeze-thawed. Propidium monoazide (PMA) sample treatment was combined with quantitative PCR, 16S rRNA gene amplicon sequencing and short-chain fatty acid (SCFA) analysis to define the viable microbiota composition and functional potential. Findings: Approximately 50% of bacterial content of stool processed immediately under strict anaerobic conditions was non-viable. Homogenisation in ambient air or freeze-thaw reduced viability to 19% and 23% respectively. Processing of samples in ambient air resulted in up to 12-fold reductions in the abundance of important commensal taxa, including the highly butyrogenic species Faecalibacterium prausnitzii, Subdoligranulum variable, and Eubacterium hallii. The adverse impact of atmospheric oxygen exposure on the capacity of the transplanted microbiota to support SCFA biosynthesis was demonstrated by significantly reduced butyrate and acetate production by faecal slurries processed in ambient air. In contrast, while reducing overall levels of viable bacteria, freeze-thaw did not significantly alter viable microbiota composition. Interpretation: The practice of preparing material for faecal transplantation in ambient air profoundly affects viable microbial content, disproportionately reducing the abundance of anaerobic commensals and the capacity for biosynthesis of important anti-inflammatory metabolites.

The physiological cholesterol-lowering benefits of β-glucan have been well documented, however, whether modulation of gut microbiota by β-glucan is associated with these physiological effects remains unknown. The objectives of this study were therefore to determine the impact of β-glucan on the composition of gut microbiota in mildly hypercholesterolemic individuals and to identify if the altered microbiota are associated with bioactivity of β-glucan in improving risk factors of cardiovascular disease (CVD). Using a randomized, controlled crossover study design, individuals received for 5-week either a treatment breakfast containing 3 g high molecular weight (HMW), 3 g low molecular weight (LMW), 5 g LMW barley β-glucan, or wheat and rice. The American Heart Association (AHA) diet served as the background diet for all treatment groups. Phases were separated by 4-week washout periods. Fecal samples were collected at the end of each intervention phase and subjected to Illumina sequencing of 16S rRNA genes. Results revealed that at the phylum level, supplementation of 3 g/d HMW β-glucan increased Bacteroidetes and decreased Firmicutes abundances compared to control (P < 0.001). At the genus level, consumption of 3 g/d HMW β-glucan increased Bacteroides (P < 0.003), tended to increase Prevotella (P < 0.1) but decreased Dorea (P < 0.1), whereas diets containing 5 g LMW β-glucan and 3 g LMW β-glucan failed to alter the gut microbiota composition. Bacteroides, Prevotella, and Dorea composition correlated (P < 0.05) with shifts of CVD risk factors, including body mass index, waist circumference, blood pressure, as well as triglyceride levels. Our data suggest that consumption of HMW β-glucan favorably alters the composition of gut microbiota and this altered microbiota profile associates with a reduction of CVD risk markers. Together, our study suggests that β-glucan induced shifts in gut microbiota in a MW-dependent manner and that might be one of the underlying mechanisms responsible for the physiological benefits of β-glucan.

Chronic disruption of the intestinal microbiota in adult cystic fibrosis (CF) patients is associated with local and systemic inflammation, and has been linked to the risk of serious comorbidities. Supplementation with high amylose maize starch (HAMS) might provide clinical benefit by promoting commensal bacteria and the biosynthesis of immunomodulatory metabolites. However, whether the disrupted CF gut microbiota has the capacity to utilise these substrates is not known. We combined metagenomic sequencing, in vitro fermentation, amplicon sequencing, and metabolomics to define the characteristics of the faecal microbiota in adult CF patients and assess HAMS fermentation capacity. Compared to healthy controls, the faecal metagenome of adult CF patients had reduced bacterial diversity and prevalence of commensal fermentative clades. In vitro fermentation models seeded with CF faecal slurries exhibited reduced acetate levels compared to healthy control reactions, but comparable levels of butyrate and propionate. While the commensal genus Faecalibacterium was strongly associated with short chain fatty acid (SCFA) production by healthy microbiota, it was displaced in this role by Clostridium sensu stricto 1 in the microbiota of CF patients. A subset of CF reactions exhibited enterococcal overgrowth, resulting in lactate accumulation and reduced SCFA biosynthesis. The addition of healthy microbiota to CF faecal slurries failed to displace predominant CF taxa, or substantially influence metabolite biosynthesis. Despite significant microbiota disruption, the adult CF gut microbiota retains the capacity to exploit HAMS. Our findings highlight the potential for taxa associated with the altered CF gut microbiotato mediate prebiotic effects in microbial systems subject to ongoing perturbation, irrespective of the depletion of common commensal clades. ARTICLE HISTORY

Underlying mechanisms responsible for the cholesterol-lowering effect of β-glucan have been proposed, yet have not been fully demonstrated. The primary aim of this study was to determine whether the consumption of barley β-glucan lowers cholesterol by affecting the cholesterol absorption, cholesterol synthesis or bile acid synthesis. In addition, this study was aimed to assess whether the underlying mechanisms are related to cholesterol 7α hydroxylase (CYP7A1) SNP rs3808607 as proposed by us earlier. In a controlled, randomised, cross-over study, participants with mild hypercholesterolaemia (n 30) were randomly assigned to receive breakfast containing 3 g high-molecular weight (HMW), 5 g low-molecular weight (LMW), 3 g LMW barley β-glucan or a control diet, each for 5 weeks. Cholesterol absorption was determined by assessing the enrichment of circulating 13C-cholesterol over 96 h following oral administration; fractional rate of synthesis for cholesterol was assessed by measuring the incorporation rate of 2H derived from deuterium oxide within the body water pool into the erythrocyte cholesterol pool over 24 h; bile acid synthesis was determined by measuring serum 7α-hydroxy-4-cholesten-3-one concentrations. Consumption of 3 g HMW β-glucan decreased total cholesterol (TC) levels (P=0·029), but did not affect cholesterol absorption (P=0·25) or cholesterol synthesis (P=0·14). Increased bile acid synthesis after consumption of 3 g HMW β-glucan was observed in all participants (P=0·049), and more pronounced in individuals carrying homozygous G of rs3808607 (P=0·033). In addition, a linear relationship between log (viscosity) of β-glucan and serum 7α-HC concentration was observed in homozygous G allele carriers. Results indicate that increased bile acid synthesis rather than inhibition of cholesterol absorption or synthesis may be responsible for the cholesterol-lowering effect of barley β-glucan. The pronounced TC reduction in G allele carriers of rs3808607 observed in the previous study may be due to enhanced bile acid synthesis in response to high-viscosity β-glucan consumption in those individuals.

The cholesterol-lowering effect of barley β-glucan has been proposed to be the result of a pleiotropic effect, which involves several biological mechanisms such as gut fermentation, inhibition of intestinal cholesterol absorption and increased bile acid excretion and its synthesis. However, one of the recent studies from our laboratory indicated that increased bile acid excretion and subsequent increase in its synthesis, but not the inhibition of cholesterol absorption or synthesis might be responsible for the cholesterol-lowering effect of barley β-glucan. Accordingly, the primary objective of the present study was to investigate the concentration of bile acids (BA), neutral sterols (NS) and short chain fatty acids (SCFA) excreted through the feces by mildly hypercholesterolemic subjects who consumed diets containing barley β-glucan with varying molecular weights (MW) and concentrations. In a controlled, four phase, crossover trial, 30 mildly hypercholesterolemic but otherwise healthy subjects were randomly assigned to receive breakfast containing 3 g high MW (HMW), 5 g low MW (LMW), 3 g LMW barley β-glucan or a control diet for 5 weeks. The concentrations of BA, NS and SCFA in the feces were measured at the end of each treatment phase. Compared to the other treatment groups, 3 g day-1 HMW barley β-glucan consumption resulted in increased lithocholic acid (LCA) excretion (P < 0.001) but not LMW β-glucan, even at the high dose of 5 g day-1. Increased fermentability of fibre was also evident from a significant increase in fecal total SCFA concentrations in response to the 3 g HMW β-glucan diet compared to the 3 g LMW barley β-glucan and control diet (P = 0.0015). In summary, the current results validate our previous report on the role of fecal bile acid excretion in cholesterol lowering through the consumption of barley β-glucan. In addition, increased SCFA concentrations indicate that an increase in β-glucan molecular weight promotes hindgut fermentation, which might also be playing a role in attenuating cholesterol levels.

Aging is characterized by systemic chronic inflammation, which is accompanied by cellular senescence, immunosenescence, organ dysfunction, and age-related diseases. Given the multidimensional complexity of aging, there is an urgent need for a systematic organization of inflammaging through dimensionality reduction. Factors secreted by senescent cells, known as the senescence-associated secretory phenotype (SASP), promote chronic inflammation and can induce senescence in normal cells. At the same time, chronic inflammation accelerates the senescence of immune cells, resulting in weakened immune function and an inability to clear senescent cells and inflammatory factors, which creates a vicious cycle of inflammation and senescence. Persistently elevated inflammation levels in organs such as the bone marrow, liver, and lungs cannot be eliminated in time, leading to organ damage and aging-related diseases. Therefore, inflammation has been recognized as an endogenous factor in aging, and the elimination of inflammation could be a potential strategy for anti-aging. Here we discuss inflammaging at the molecular, cellular, organ, and disease levels, and review current aging models, the implications of cutting-edge single cell technologies, as well as anti-aging strategies. Since preventing and alleviating aging-related diseases and improving the overall quality of life are the ultimate goals of aging research, our review highlights the critical features and potential mechanisms of inflammation and aging, along with the latest developments and future directions in aging research, providing a theoretical foundation for novel and practical anti-aging strategies.

The HMW β-glucan rather than LMW β-glucan reduced circulating TC effectively in mildly hypercholesterolemic adults. The cholesterol-lowering effect of β-glucan may also be determined by the genetic characteristics of an individual. These data show that individuals carrying theCYP7A1SNP rs3808607-G allele are more responsive to the cholesterol-lowering effect of β-glucan with HMW than TT carriers. This trial was registered atclinicaltrials.govasNCT01408719.

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