A species of gut bacteria called\u00a0Roseburia inulinivorans\u00a0is specifically associated with human muscle strength and improved muscular performance in mice, finds research published online in the journal\u00a0Gut.\u00a0<\/p>\n
R inulinivorans\u00a0changes certain metabolic processes in muscle, and converts muscle fibres to ‘fast-twitch (type II)—designed for short intensive movement, such as sprinting and weights-the findings show.\u00a0<\/p>\n
R inulinivorans\u00a0holds promise as a nutraceutical probiotic for treating age-related muscle wasting disease, suggest the Dutch and Spanish researchers.\u00a0<\/p>\n
Dwindling muscle mass and strength are major contributors to frailty, reduced mobility and functionality, and poor health, particularly as people age and among those with long term conditions, they explain.\u00a0<\/p>\n
Gut bacteria have been implicated in a wide range of health conditions, including metabolic, neurodegenerative, and cardiovascular diseases, and an emerging body of evidence suggests that they may also influence muscle mass and function, add the researchers.\u00a0<\/p>\n
They therefore wanted to find out whether specific gut microbial species might be associated with muscle strength and, if so, what the underlying mechanisms might be.\u00a0<\/p>\n
To do this, they analysed stool samples from 90 healthy young (18-25 year olds) and 33 older (65+) adults for the presence of bacteria.\u00a0<\/p>\n
\u00a0Their hand grip strength, leg press and bench press performance, and VO2 max (maximal oxygen consumption during exertion) which is an indicator of cardiorespiratory fitness, were used to assess physical fitness.\u00a0<\/p>\n
Among all the bacteria found in the stool samples, the Roseburia group (genus) was the only one that was positively associated with muscle mass and strength.\u00a0\u00a0<\/p>\n
R faecis\u00a0and\u00a0R intestinalis\u00a0species weren’t significantly associated with hand grip strength or VO\u2082 max in either age group.\u00a0<\/p>\n
But the older adults with detectable\u00a0R inulinivorans\u00a0in their stool sample had 29% higher handgrip strength than those without, and without a concomitant increase in peak oxygen uptake, indicating better fitness.\u00a0\u00a0<\/p>\n
In young adults, greater abundance of\u00a0R inulinivorans\u00a0was positively associated with both handgrip strength and VO\u2082 max. And the relative abundance of both\u00a0R inulinivorans\u00a0and\u00a0R intestinalis\u00a0was positively associated with leg press and bench press strength as well.\u00a0<\/p>\n
The relative abundance of\u00a0R faecis\u00a0and\u00a0R hominis\u00a0wasn’t associated with any of the indicators of muscle strength, which suggests that different Roseburia species may influence different aspects of muscle strength, say the researchers.\u00a0<\/p>\n
Roseburia was also more abundant in the young adults, among whom the proportion of\u00a0R faecis\u00a0ranged from 0% to 3.3%; that of\u00a0R intestinalis\u00a0ranged from 0% to 5.5%; while that of\u00a0R inulinivorans\u00a0ranged from 0% to 6.6%.\u00a0<\/p>\n
Among the older adults, the proportion of\u00a0R faecis\u00a0ranged from 0% to 2.2%; that of\u00a0R intestinalis ranged from 0%-0.7%, while that of\u00a0R inulinivorans\u00a0ranged from 0% to 1.3%.\u00a0\u00a0<\/p>\n
In a bid to identify a causal role for Roseburia in muscle strength, the researchers fed Roseburia species once a week for 8 weeks to 32 mice that had previously been given a cocktail of antibiotics for a fortnight to deplete their gut microbiome<\/a>.\u00a0\u00a0<\/p>\n The mice were randomly assigned to one of 4 groups, 3 of which received a different strain of Roseburia, and one of which received no Roseburia (control group).\u00a0<\/p>\n None of the Roseburia species enhanced running time to exhaustion. But compared with the control group,\u00a0R inulinivorans\u00a0induced a noticeable increase of around 30% in forelimb grip strength-a proxy for muscle function-after 4, 6, and 8 weeks of treatment.\u00a0<\/p>\n What’s more, mice treated with\u00a0R inulinivorans\u00a0had larger muscle fibre size and a significantly higher proportion of type II (‘fast twitch’) fibres in the soleus muscle located in the calf, compared with the other groups, although not when compared with the mice treated with\u00a0R intestinalis.\u00a0<\/p>\n Further analysis of fibre size distribution revealed that this was relatively evenly distributed in the control group, whereas mice treated with\u00a0R inulinivorans\u00a0had higher levels of larger fibres than those treated with the other Roseburia species or mice in the control group.\u00a0\u00a0<\/p>\n These changes were also accompanied by metabolic changes in the proteins and enzymes key to muscle energy production.\u00a0<\/p>\n The researchers acknowledge various limitations to their findings. In the animal study, none of the human Roseburia species colonised the mouse gut. And specific pathways related to inflammation<\/a> or neuromuscular signalling weren’t directly assessed and these might have been influential.\u00a0<\/p>\n Long term studies are needed to determine whether changes in the abundance of\u00a0R inulinivorans\u00a0are a cause or consequence of muscle function change, they emphasise.\u00a0\u00a0<\/p>\n Nevertheless, they suggest: “Collectively, our findings provide robust evidence supporting a gut-muscle axis in which\u00a0R inulinivorans\u00a0positively modulates muscle metabolism and muscle strength.”\u00a0\u00a0<\/p>\n And they conclude: “Additionally, we observed that the relative abundance of\u00a0R inulinivorans\u00a0is lower in older adults than in young adults. Its abundance appears to decline with advancing age, a period during which the prevalence of sarcopenia [muscle loss] increases, suggesting a potential role for\u00a0R inulinivorans\u00a0as a probiotic candidate for preserving muscle strength.”\u00a0<\/p>\n Source:<\/p>\n Journal reference:<\/p>\n