Gut Microbiota in Older People: Metabolism and Composition
Gut Microbiota in Older People: Metabolism and Composition
Background Ageing can result in major changes in the composition and metabolic activities of bacterial populations in the large gut and an impaired immune system.
Aim To investigate the effects of synbiotic consumption on the colonic microbiota, immune function and health status in older people.
Methods A randomised, double-blind placebo-controlled, 4-week crossover study was carried out, involving 43 older volunteers, using a synbiotic comprising the probiotic Bifidobacterium longum and an inulin-based prebiotic Synergy 1 (SudZucker, Mannheim, Germany). Faecal and blood samples were collected, and clinical status scored at the start, and at 2- and 4-week intervals, with a 4-week washout between each feeding period. Faecal bacteria were determined by fluorescent in situ hybridisation. Short-chain fatty acid concentrations, cytokine production, bowel habit and a range of clinical parameters were measured.
Results The synbiotic increased bifidobacterial numbers by 1.4 log units (P < 0.0001) and also increased members of the phyla Actinobacteria and Firmicutes (P = 0.0004, P < 0.0001). Proteobacteria were reduced by 1.0 log units (P < 0.0001). Synbiotic feeding was associated with increased butyrate production (P = 0.0399). The pro-inflammatory response was modified by the synbiotic, with significantly reduced pro-inflammatory cytokine TNF-α in peripheral blood after 2 and 4 weeks of synbiotic consumption (P = 0.02, P = 0.0406). The synbiotic had no effect on bowel habit or any clinical parameters.
Conclusion Short-term synbiotic use can be effective in improving the composition and metabolic activities of colonic bacterial communities and immune parameters in older people. This study was registered at clinicaltrials.gov as NCT01226212.
Numbers of older people in western industrialised countries are steadily increasing, together with associated costs to healthcare systems. The colonic microbiota is generally viewed as being stable during adult life, where it plays a key role in host physiology, immune regulation and metabolism, and provides a natural defence against invading pathogens, in processes known collectively as colonisation resistance. However, while good nutrition is important in maintaining the microbiota and its regulatory effects on gut function, poor diet is one of the main factors responsible for changes in the composition and metabolic activities of the colonic microbiota and immunosenescence in older people.
In the stomach, hypochlorhydria due to atrophic gastritis is associated with small bowel bacterial overgrowth and lowered absorption of calcium, ferric iron and vitamin B12, reducing micronutrient intake. Reduced colonic motility resulting from low intake of nondigestible carbohydrates, such as nonstarch polysaccharides and resistant starch, lower bacterial growth and short-chain fatty acid (SCFA) formation can lead to faecal impaction and constipation, and is a significant problem in older people. Many studies in older people indicate that the microbiota differs from that in younger adults, and that increases in putatively pathogenic enterobacteria and putrefactive clostridia occur, together with reductions in species diversity and the loss of bacteria considered to be beneficial to health, such as bifidobacteria and lactobacilli. Ageing can also result in a reduction in the TH1:TH2 ratio and increased production of pro-inflammatory cytokines, including IL-6 and TNF-α. These changes can lead to greater susceptibility to diseases such as gastroenteritis, reduced efficiency of vaccinations and increased susceptibility to infections by Clostridium difficile.
The reduced bifidobacterial numbers and species diversity often reported in older people are of interest, as these organisms are believed to play a significant role in host health and the eco-physiology of the colon. They have been linked to increased resistance to infection and diarrhoeal disease, modulation of immune system activity and protection against cancer, as well other indirect interactions with host metabolism. Consequently, there is a convincing case for maintaining colonic bifidobacterial communities in older people.
Functional foods are increasingly being used to modulate the intestinal microbiota and immune system, and to improve bowel function, particularly through the use of probiotics, prebiotics and synbiotics (synergistic combinations of a probiotic and prebiotic). However, relatively few trials have been carried out to investigate their effects in older people,
We have previously shown that a synbiotic comprising the probiotic Bifidobacterium longum and the prebiotic (Synergy 1, SudZucker, Mannheim, Germany), a preferential inulin and oligofructose growth substrate for the probiotic, was beneficial in increasing mucosal bifidobacteria and reducing mucosal TNF-α in two clinical trials in patients with inflammatory bowel disease. The aims of the present investigation were to determine whether short-term ingestion of this synbiotic could be effective in improving intestinal bacterial community structure, selected immune parameters and gut health in a double-blind, randomised, placebo-controlled crossover study in older people.
Abstract and Introduction
Abstract
Background Ageing can result in major changes in the composition and metabolic activities of bacterial populations in the large gut and an impaired immune system.
Aim To investigate the effects of synbiotic consumption on the colonic microbiota, immune function and health status in older people.
Methods A randomised, double-blind placebo-controlled, 4-week crossover study was carried out, involving 43 older volunteers, using a synbiotic comprising the probiotic Bifidobacterium longum and an inulin-based prebiotic Synergy 1 (SudZucker, Mannheim, Germany). Faecal and blood samples were collected, and clinical status scored at the start, and at 2- and 4-week intervals, with a 4-week washout between each feeding period. Faecal bacteria were determined by fluorescent in situ hybridisation. Short-chain fatty acid concentrations, cytokine production, bowel habit and a range of clinical parameters were measured.
Results The synbiotic increased bifidobacterial numbers by 1.4 log units (P < 0.0001) and also increased members of the phyla Actinobacteria and Firmicutes (P = 0.0004, P < 0.0001). Proteobacteria were reduced by 1.0 log units (P < 0.0001). Synbiotic feeding was associated with increased butyrate production (P = 0.0399). The pro-inflammatory response was modified by the synbiotic, with significantly reduced pro-inflammatory cytokine TNF-α in peripheral blood after 2 and 4 weeks of synbiotic consumption (P = 0.02, P = 0.0406). The synbiotic had no effect on bowel habit or any clinical parameters.
Conclusion Short-term synbiotic use can be effective in improving the composition and metabolic activities of colonic bacterial communities and immune parameters in older people. This study was registered at clinicaltrials.gov as NCT01226212.
Introduction
Numbers of older people in western industrialised countries are steadily increasing, together with associated costs to healthcare systems. The colonic microbiota is generally viewed as being stable during adult life, where it plays a key role in host physiology, immune regulation and metabolism, and provides a natural defence against invading pathogens, in processes known collectively as colonisation resistance. However, while good nutrition is important in maintaining the microbiota and its regulatory effects on gut function, poor diet is one of the main factors responsible for changes in the composition and metabolic activities of the colonic microbiota and immunosenescence in older people.
In the stomach, hypochlorhydria due to atrophic gastritis is associated with small bowel bacterial overgrowth and lowered absorption of calcium, ferric iron and vitamin B12, reducing micronutrient intake. Reduced colonic motility resulting from low intake of nondigestible carbohydrates, such as nonstarch polysaccharides and resistant starch, lower bacterial growth and short-chain fatty acid (SCFA) formation can lead to faecal impaction and constipation, and is a significant problem in older people. Many studies in older people indicate that the microbiota differs from that in younger adults, and that increases in putatively pathogenic enterobacteria and putrefactive clostridia occur, together with reductions in species diversity and the loss of bacteria considered to be beneficial to health, such as bifidobacteria and lactobacilli. Ageing can also result in a reduction in the TH1:TH2 ratio and increased production of pro-inflammatory cytokines, including IL-6 and TNF-α. These changes can lead to greater susceptibility to diseases such as gastroenteritis, reduced efficiency of vaccinations and increased susceptibility to infections by Clostridium difficile.
The reduced bifidobacterial numbers and species diversity often reported in older people are of interest, as these organisms are believed to play a significant role in host health and the eco-physiology of the colon. They have been linked to increased resistance to infection and diarrhoeal disease, modulation of immune system activity and protection against cancer, as well other indirect interactions with host metabolism. Consequently, there is a convincing case for maintaining colonic bifidobacterial communities in older people.
Functional foods are increasingly being used to modulate the intestinal microbiota and immune system, and to improve bowel function, particularly through the use of probiotics, prebiotics and synbiotics (synergistic combinations of a probiotic and prebiotic). However, relatively few trials have been carried out to investigate their effects in older people,
We have previously shown that a synbiotic comprising the probiotic Bifidobacterium longum and the prebiotic (Synergy 1, SudZucker, Mannheim, Germany), a preferential inulin and oligofructose growth substrate for the probiotic, was beneficial in increasing mucosal bifidobacteria and reducing mucosal TNF-α in two clinical trials in patients with inflammatory bowel disease. The aims of the present investigation were to determine whether short-term ingestion of this synbiotic could be effective in improving intestinal bacterial community structure, selected immune parameters and gut health in a double-blind, randomised, placebo-controlled crossover study in older people.
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