Why do arteries age? Study explores link to gut bacteria, diet
July 1, 2020
Science Daily/University of Colorado at Boulder
Eat a slab of steak and your resident gut bacteria get to work immediately to break it down. But new research shows that a metabolic byproduct, called TMAO, produced in the process can be harmful to the lining of arteries, making them age faster.
A compound produced in the gut when we eat red meat damages our arteries and may play a key role in boosting risk of heart disease as we get older, according to new University of Colorado Boulder research.
The study, published this month in the American Heart Association journal Hypertension, also suggests that people may be able to prevent or even reverse such age-related decline via dietary changes and targeted therapies, like novel nutritional supplements.
"Our work shows for the first time that not only is this compound directly impairing artery function, it may also help explain the damage to the cardiovascular system that naturally occurs with age," said first author Vienna Brunt, a postdoctoral researcher in the Department of Integrative Physiology.
Eat a slab of steak or a plate of scrambled eggs, and your resident gut bacteria get to work immediately to break it down. As they metabolize the amino acids L-carnitine and choline, they churn out a metabolic byproduct called trimethylamine, which the liver converts to trimethylamine-N-Oxide (TMAO) and sends coursing through your bloodstream.
Previous studies have shown that people with higher blood levels of TMAO are more than twice as likely to have a heart attack or stroke and tend to die earlier.
But to date, scientists haven't completely understood why.
Drawing on animal and human experiments, Brunt and her team set out to answer three questions: Does TMAO somehow damage our vascular system? If so, how? And could it be one reason why cardiovascular health gets worse -- even among people who exercise and don't smoke -- as we get older?
The researchers measured the blood and arterial health of 101 older adults and 22 young adults and found that TMAO levels significantly rise with age. (This falls in line with a previous study in mice, showing the gut microbiome -- or your collection of intestinal bacteria -- changes with age, breeding more bacteria that help produce TMAO).
Adults with higher blood levels of TMAO had significantly worse artery function, the new study found, and showed greater signs of oxidative stress, or tissue damage, in the lining of their blood vessels.
When the researchers fed TMAO directly to young mice, their blood vessels swiftly aged.
"Just putting it in their diet made them look like old mice," said Brunt. She noted that 12-month-old mice (the equivalent of humans about 35 years old) looked more like 27-month-old mice (age 80 in people) after eating TMAO for several months.
Preliminary data also show that mice with higher levels of TMAO exhibit decreases in learning and memory, suggesting the compound could also play a role in age-related cognitive decline.
On the flip side, old mice that ate a compound called dimethyl butanol, (found in trace amounts in olive oil, vinegar and red wine) saw their vascular dysfunction reverse. Scientists believe that this compound prevents the production of TMAO.
Brunt notes that everyone -- even a young vegan -- produces some TMAO. But over time, eating a lot of animal products may take a toll.
"The more red meat you eat, the more you are feeding those bacteria that produce it," she said.
Senior author Doug Seals, director of the Integrative Physiology of Aging Laboratory, said the study is an important breakthrough because it sheds light on why our arteries erode with age, even in the healthiest people.
"Aging is the single greatest risk factor for cardiovascular disease, primarily as a result of oxidative stress to our arteries," said Seals. "But what causes oxidative stress to develop in our arteries as we age? That has been the big unkown. This study identifies what could be a very important driver."
The research team is now further exploring compounds that might block production of TMAO to prevent age-related vascular decline.
For now, they said, a plant-based diet may also keep levels in check.
https://www.sciencedaily.com/releases/2020/07/200701100019.htm
Your stools reveal whether you can lose weight
September 12, 2017
Science Daily/Faculty of Science - University of Copenhagen
Something as simple as a feces sample reveals whether you can lose weight by following dietary recommendations characterized by a high content of fruit, vegetables, fibers and whole grains. This is a finding of a new study conducted at the Department of Nutrition, Exercise and Sports at the University of Copenhagen, Denmark.
The bacteria we all have in our gut may play a decisive role in personalized nutrition and the development of obesity. This is shown by several studies that have delved into the significance of these bacteria.
"Human intestinal bacteria have been linked to the increasing prevalence of overweight and obesity, and scientists have started to investigate whether the intestinal bacteria can play a role in the treatment of overweight. But it is only now that we have a breakthrough demonstrating that certain bacterial species play a decisive role in weight regulation and weight loss" says Professor Arne Astrup, Head of the Department of Nutrition, Exercise and Sports at the University of Copenhagen, Denmark.
The ratio between the two groups of intestinal bacteria is crucial
A relationship between two groups of intestinal bacteria is decisive for whether overweight people lose weight on a diet that follows the Danish national dietary recommendations and contains a lot of fruit, vegetables, fiber and whole grains. In the study 31 subjects ate the New Nordic Diet for 26 weeks and lost an average of 3.5 kg, whereas the 23 subjects eating an Average Danish Diet lost an average of 1.7 kg. Thus weight loss was on average 1.8 kilos greater in the subjects on the New Nordic Diet.
High proportion of Prevotella bacteria lead to weight loss
When the subjects were divided by their level of intestinal bacteria, it was found that people with a high proportion of Prevotella bacteria in relation to Bacteroides bacteria lost 3.5 kg more in 26 weeks when they ate a diet composed by the New Nordic Diet principles compared to those consuming an Average Danish Diet. Subjects with a low proportion of Prevotella bacteria in relation to Bacteroides did not lose any additional weight on the New Nordic Diet. Overall, approximately 50 percent of the population has a high proportion of Prevotella-bacteria in relation to Bacteroides-bacteria.
"The study shows that only about half of the population will lose weight if they eat in accordance with the Danish national dietary recommendations and eat more fruit, vegetables, fibers and whole grains. The other half of the population doesn't seem to gain any benefit in weight from this change of diet," says Assistant Professor Mads Fiil Hjorth at the Department of Nutrition, Exercise and Sports at the University of Copenhagen. He continues: "These people should focus on other diet and physical activity recommendations until a strategy that works especially well for them is identified."
The researchers emphasize that they have already confirmed the results in two independent studies, so they are certain that these results are credible.
Personalized weight loss guidance
The results show that biomarkers, e.g. faecal samples, blood samples, or other samples from our body, which says something about our state of health, should play a far greater role in nutritional guidance. Simply because biomarkers allow us to adapt the guidance to the individual.
"This is a major step forward in personalized nutritional guidance. Guidance based on this knowledge of intestinal bacteria will most likely be more effective than the "one size fits all" approach that often characterises dietary recommendations and dietary guidance," says Assistant Professor Mads Fiil Hjorth.
At present it is primarily research units at universities and other academic institutions that examine the composition of intestinal bacteria, but as an effect of this breakthrough the University of Copenhagen has licensed a company in Boston, USA, to develop and publish a concept based on this research, that will be of benefit to obese people.
https://www.sciencedaily.com/releases/2017/09/170912093122.htm