Nature article: Dieting and its effect on the gut microbiome

IMAGE: Colorized scanning electron microscope picture of the intestine bacterium Clostridioides difficile.
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Credit: © CDC | Janice Carr

Researchers from Charité – Universitätsmedizin Berlin and the University of California in San Francisco had been capable of present for the primary time {that a} very low calorie weight loss program considerably alters the composition of the microbiota current within the human intestine. In a present Nature* publication, the researchers report that weight-reduction plan leads to a rise of particular micro organism – notably Clostridioides difficile, which is related to antibiotic-induced diarrhea and colitis. These micro organism apparently have an effect on the physique’s power stability by exerting an affect on the absorption of vitamins from the intestine.

The human intestine microbiome consists of trillions of microorganisms and differs from one individual to the following. In individuals who’re obese or overweight, as an illustration, its composition is understood to be totally different to that present in people with a standard physique weight. Many of us will, sooner or later in our lives, attempt weight-reduction plan with a purpose to reduce weight. But what impact does such a drastic change in weight loss program have on our our bodies? An worldwide crew of researchers co-led by Charité has addressed this query. “For the primary time, we had been capable of present {that a} very low calorie weight loss program produces main adjustments within the composition of the intestine microbiome and that these adjustments have an effect on the host’s power stability,” says Prof. Dr. Joachim Spranger, Head of Charité’s Department of Endocrinology and Metabolic Diseases and one of many examine’s lead authors.

To discover the consequences of weight-reduction plan, the crew studied 80 older (post-menopausal) ladies whose weight ranged from barely obese to severely overweight for a period of 16 weeks. The ladies both adopted a medically supervised meal alternative regime, consuming shakes totaling lower than 800 energy a day, or maintained their weight at some stage in the examine. The members had been examined on the Experimental and Clinical Research Center (ECRC), a facility collectively operated by Charité and the Max Delbrück Center for Molecular Medicine (MDC). Regular stool pattern evaluation confirmed that weight-reduction plan diminished the variety of microorganisms current within the intestine and adjusted the composition of the intestine microbiome. “We had been capable of observe how the micro organism tailored their metabolism with a purpose to take up extra sugar molecules and, by doing so, make them unavailable to their human host. One would possibly say we noticed the event of a ‘hungry microbiome’,” says the examine’s first writer, Dr. Reiner Jumpertz von Schwartzenberg, a researcher and clinician on the Department of Endocrinology and Metabolic Diseases whose work on the examine was funded by the Clinician Scientist program operated by Charité and the Berlin Institute of Health (BIH).

Stool samples, which had been collected earlier than and after weight-reduction plan, had been then transferred into mice which had been saved beneath germ-free circumstances and, consequently, lacked all intestine microbiota. The outcomes had been staggering: Animals which acquired post-dieting stools misplaced greater than 10 p.c of their physique mass. Pre-diet stools had no impact in anyway. “Our outcomes present that this phenomenon is primarily defined by adjustments within the absorption of vitamins from the animals’ guts,” says Prof. Spranger. He provides: “This highlights the truth that intestine micro organism have a significant affect on the absorption of meals.”

When the researchers studied stool composition in better element, they had been significantly struck by indicators of elevated colonization by a selected bacterium – Clostridioides difficile. While this microorganism is usually discovered within the pure atmosphere and within the guts of wholesome human beings and animals, its numbers within the intestine can improve in response to antibiotic use, doubtlessly leading to extreme irritation of the intestine wall. It is also called one of the crucial widespread hospital-associated pathogens. Increased portions of the bacterium had been discovered each in members who had accomplished the load loss routine and in mice which had acquired post-dieting intestine micro organism. “We had been capable of present that C. difficile produced the toxins usually related to this bacterium and that this was what the animals’ weight reduction was contingent upon,” explains Prof. Spranger. He provides: “Despite that, neither the members nor the animals confirmed related indicators of intestine irritation.”

Summing up the outcomes of the analysis, Prof. Spranger says: “A really low calorie weight loss program severely modifies our intestine microbiome and seems to cut back the colonization-resistance for the hospital-associated bacterium Clostridioides difficile. These adjustments render the absorption of vitamins throughout the intestine wall much less environment friendly, notably with out producing related medical signs. What stays unclear is whether or not or to which extent such a asymptomatic colonization by C. difficile would possibly impair or doubtlessly enhance an individual’s well being. This needs to be explored in bigger research.” Results from the present examine, which additionally acquired funding from the German Center for Cardiovascular Disease (DZHK), would possibly even give rise to remedy choices for metabolic problems resembling weight problems and diabetes. For this cause, the researchers will now discover how intestine micro organism is perhaps influenced with a purpose to produce useful results on the load and metabolism of their human hosts.

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*Jumpertz von Schwartzenberg R et al. Caloric restriction disrupts the microbiota and colonization resistance. Nature (2021), doi: 10.1038/s41586-021-03663-4.

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