- Enlisting Gut Bacteria And Fiber To Fight Diabetes
- Eating fiber helps your gut bacteria fight diabetes
- High-Fiber Generates Gut Bacteria Good for Type 2 Diabetes
- Certain Fibers Could Become Part of the Treatment for Type 2 Diabetes
- For diabetics, a high-fiber diet feeds gut microbes, lowering blood sugar
- Fiber-fermenting bacteria improve health of type 2 diabetes patients: Dietary fibers promote gut bacteria that benefit blood glucose control
- A high fiber diet may promote specific short-chain fatty acid producers to achieve better metabolic control in type 2 diabetes
- High fiber diet may help with management of type 2 diabetes
Enlisting Gut Bacteria And Fiber To Fight Diabetes
From the WebMD Archives
March 9, 2018 — Scientists say they’ve found a direct connection between blood sugar and gut bacteria. By exploiting that connection with a very high-fiber diet, they’ve successfully treated a small group of people with type 2 diabetes.
The finding could be important not only for the 100 million American adults with diabetes or prediabetes, but also for anyone who’s trying to manage their weight.
Doctors and nutritionists have long known that fiber is important for good health. Studies have shown that people who eat diets high in fiber and low in saturated fat have lower risks for many chronic diseases, including heart disease, diabetes, and some intestinal problems constipation and diverticulitis.
What hasn’t been well-understood is exactly how fiber gives you these benefits.
Evidence has been mounting that fiber plays a key role in the types of bacteria that thrive in our guts and how they work.
Last year, new research from the Finnish Diabetes Prevention Study showed that people who ate more fiber had more of an anti-inflammatory chemical in their blood called indolepropionic acid, which is made by gut bacteria. They were also less ly to go on to get type 2 diabetes.
The new study builds on that by showing how fiber helps grow bacteria in the gut that produce chemical signals that help to regulate appetite and blood sugar.
“Overall, this study adds to what we know about how important the gut microbiota is when it comes to the development of some chronic diseases, type 2 diabetes,” says Vanessa de Mello Laaksonen, PhD, an assistant professor in nutrigenomics at the University of Eastern Finland, who was not involved in the research.
About 1 in 11 Americans has diabetes. Type 2 diabetes is the most common form and is on the rise in the U.S. in both children and adults.
For the study, a team of scientists in China put 27 people with type 2 diabetes on a very high-fiber diet and followed them for 12 weeks, measuring changes to their blood sugar, and also to their gut bacteria.
They compared this group with 16 others who also had type 2 diabetes who got standard advice on exercise and eating right for diabetes along with a diet for the study that racked up roughly same number of calories, but had a lot less fiber.
The high-fiber group was getting a whopping 37 grams of fiber a day, while the group getting the average, healthy diet was eating about 16 grams of fiber a day — which, by chance, is about what American adults average.
Both groups were also taking a medication called acarbose to help manage their blood sugar. Acarbose acts a bit fiber in that it prevents some carbohydrates from being digested in the gut for energy. Before the study, all participants were weaned off any other medications to manage their blood sugar. If they used insulin, it was adjusted as needed throughout the study.
Both groups improved, but by the end of the experiment, the group on the very high-fiber diet was healthier than the group getting standard care. They had better control of their blood sugar, and they’d lost a bit more weight.
About 90% of the high-fiber group achieved good control of their blood sugar — keeping their hemoglobin A1c under 7%, the target recommended by the American Diabetes Association — compared with just 50% of the group on a standard diabetes diet.
Here’s why that could be true.
All that fiber, which came from a wide variety of food sources, fertilized the growth of 15 strains of bacteria that produce certain short-chain fatty acids. Those acids act as both a fuel source for cells and as messengers.
In the new study, these short-chain fatty acids signaled the gut to make more glucagon- peptide-1 (GLP-1) and peptide YY (PYY).
GLP-1 is a hormone that tells the body to make more insulin, while PYY dials down appetite. The two are critical in keeping blood sugar and weight under control.
Some diabetes drugs also work by increasing GLP-1. The increase in short-chain fatty acids also made the gut walls unfriendly to other kinds of bacteria that block GLP-1, boosting the effect.
“This is one benefit, one reason why high-fiber diets work,” says study researcher Liping Zhao, PhD, a professor of applied microbiology at both Rutgers University in New Brunswick, NJ, and Shanghai Jiao Tong University in Shanghai, China.
To make sure it was the change in gut bacteria that was driving the results — and not something else — the scientists then transferred the gut bacteria from their study participants to mice that were bred to be germ-free. Because they were bred not to have any of their own gut bacteria, scientists could later introduce bacteria and watch what happened as they started growing.
The mice that got the bacteria from the humans on the high-fiber diets had better fasting blood sugar levels than mice that got bacteria from people on the usual diabetes diet, even though they were eating the same chow.
The study was published in the journal Science.
The study authors say it would be difficult for the average person to copy their high-fiber diet.
People in the high-fiber part of the study ate a specially prepared gruel made from oats, white beans, yellow corn, red beans, yams, peanuts, and lotus seeds, along with two whole grains that are unfamiliar to Westerners — green buckwheat and adlay, or Job’s tears. They also got more fiber in the form of powders that included bitter melon, kudzu starch, inulin, and resistant dextrin.
What’s important, researchers say, is the principle of all this: The good bacteria in our guts, the ones that keep us healthy, need a lot more fiber than we’re now giving them to thrive.
The U.S. Department of Agriculture recommends that healthy adults eat somewhere between 22 and 34 grams of fiber every day, according to the government’s dietary guidelines.
Most of us only get about half that much.
Kids and adults are so short on fiber in the U.S. that the expert panel that put together the most recent version of the dietary guidelines singled out fiber as one of four “nutrients of public health concern.”
Lacking fiber, the study suggests that the bacteria that help us regulate our appetite and control our blood sugar get out-competed by other bacteria that actually suppress those all-important signals.
The researchers who are leading the Finnish Diabetes Prevention Study think high-fiber diets are doable with a little planning.
“We think that some 30-40 grams per day may not be unrealistic if you use whole-grain products, fruit and vegetables several times a day, instead of low-fiber bread, sugar-containing juices, and meat,” says Laaksonen.
Sources of fiber in their healthy Nordic Diet focuses on whole grains rye, barley and oats, berries, and beans and peas.
The study also shows something else that’s important to understand about gut bacteria: They’re already there, and they change in response to our diets.
Most studies have shown that probiotic supplements, which promise to deliver millions or billions of helpful bacteria to our guts, have few effects that usually don't last long. That’s because the bacteria that live inside us are there because of what we eat.
The best way to change them in a lasting way is to change their food source — our diets.
“When you introduce a large amount of diverse fibers into the gut, it’s just you threw some new nutrition into a pond. You disturb the system. Some members will take advantage of that to grow and increase their population levels. Some others may decline,” Zhao says.
“That’s exactly what happens in the gut ecosystem,” he says.
Gut bacteria, he says, live off two food sources — the food we can’t digest, which is fiber, and the products of digestion that are made locally in our intestines.
Lacking fiber, he says, this enormous ecosystem in our intestines, made up of an estimated 100 trillion cells, can become underfed in ways that encourage disease instead of health.
If you decide to boost the fiber in your diet, Zhao cautions that it takes some time for the bacteria to adjust — about a month. That period of adjustment can come with some uncomfortable side effects bloating and gas.
Liping Zhao, PhD, professor of applied microbiology, Rutgers University, New Brunswick, NJ; professor, Shanghai Jiao Tong University, Shanghai, China.
Vanessa de Mello Laaksonen, PhD, assistant professor in nutrigenomics, the University of Eastern Finland, Kuopio, Finland.
Science, March 8, 2018.
Scientific Reports: “Indolepropionic acid and novel lipid metabolites are associated with a lower risk of type 2 diabetes in the Finnish Diabetes Prevention Study.”
Nutrients: “Ten-Year Trends in Fiber and Whole Grain Intakes and Food Sources for the United States Population: National Health and Nutrition Examination Survey 2001-2010.”
American Diabetes Association, Statistics About Diabetes, accessed March 8, 2018.
U.S. Department of Agriculture, Dietary Guidelines for Americans, 2015-2020, 8th Edition.
© 2018 WebMD, LLC. All rights reserved.
Eating fiber helps your gut bacteria fight diabetes
New research finds that a shift in diet to incorporate more fiber could encourage specific types of gut bacteria, reducing the symptoms of diabetes and aiding weight loss.
Share on PinterestIncreasing fiber intake might help to reduce the symptoms of type 2 diabetes.
Type 2 diabetes is often referred to as a lifestyle disease; in many cases, it can be prevented by changing habits such as diet and activity levels.
However, modern society seems powerless to halt its onward march.
Diabetes now affects almost 1 in 10 people in the United States. Currently, more than 100 million adults in the U.S. have diabetes or prediabetes.
The condition impacts levels of glucose in the body, meaning they can no longer be regulated correctly, leading to damage of tissues and organs.
The hormone at the root of this dysfunction is insulin. People with type 2 diabetes either produce too little or their bodies do not respond adequately to it.
Because the type 2 juggernaut does not appear to be slowing, uncovering new ways to intervene is of paramount importance. Of course, prevention is the end goal where possible, but for those living with the condition, controlling it is also vital.
In recent years, gut bacteria have been brought in for questioning. Could they hold some answers?
The human gut contains billions of bacteria — some good for health, some not so good. Overall, they are essential to the proper functioning of the digestive system, and, as it is slowly being revealed, they are influential across many of the body’s systems.
Previous studies have shown that people who consume more fiber have a lower risk of developing type 2 diabetes. A diet rich in fiber can also help to reduce fasting glucose levels in those already living with diabetes. However, individual responses to this type of dietary intervention have been variable.
Recently, Liping Zhao — who is a professor at Rutgers University-New Brunswick in New Jersey — studied the fiber-gut bacteria-diabetes relationship in more detail. He wanted to understand how a fiber-rich diet might influence gut flora and reduce symptoms; once the mechanism is understood, it will be easier to design tailored anti-diabetes diets.
The study, which ran for 6 years, is published this week in the journal Science.
Many gut bacteria types break down carbohydrates into short-chain fatty acids, including acetate, butyrate, and propionate. These fatty acids help to nourish the cells that line the gut, reduce inflammation, and regulate hunger.
Earlier studies have found an association between reduced levels of short-chain fatty acids and diabetes, among other conditions.
In the new study, the team put the participants on one of two diets. Half received standard dietary recommendations, and the others consumed a similar diet but with the inclusion of high levels of several dietary fibers, including whole grains and traditional Chinese medicinal foods.
The experimental diet also included prebiotics, which encourage the growth of gut bacteria that make short-chain fatty acids. Both groups were controlling blood sugar with the help of a drug called acarbose.
After 12 weeks, participants on the high-fiber diet demonstrated a larger reduction in their 3-month average blood glucose levels. Also, their fasting blood glucose levels dropped quicker, and they lost significantly more weight than the control group.
Next, Zhao and colleagues wanted to distinguish which strains of bacteria were responsible for this positive effect. Of the 141 gut bacteria strains capable of making short-chain fatty acids, just 15 are promoted by the consumption of fiber. Levels of these were found to correlate with the level of healthy changes.
“Our study lays the foundation and opens the possibility that fibers targeting this group of gut bacteria could eventually become a major part of your diet and your treatment.”
When these strains became the dominant species in the gut, they increased levels of the short-chain fatty acids butyrate and acetate. The researchers believe that these compounds create a more acidic environment in the gut, which reduces the numbers of unwanted bacterial species, leading to an increase in insulin production and “better blood glucose control.”
These new findings lay the groundwork for designing innovative diets that could help people with diabetes to manage their condition through the food that they eat.
As the number of U.S. individuals with diabetes steadily grows, this type of simple, relatively cheap intervention could make a huge difference to people’s quality of life.
High-Fiber Generates Gut Bacteria Good for Type 2 Diabetes
A select “guild” of gut bacteria responsible for the benefits of high-fiber diets in type 2 diabetes has been identified in a study in which those patients on the high-fiber diet showed improved control of HbA1c.
Effectively, eating the right dietary fibers may rebalance the gut microbiome and lead to reduced blood sugar and body weight, and may pave the way for a new nutritional approach to preventing and managing type 2 diabetes, say the researchers.
The specific bacteria thought to be effective produce short chain fatty acids (SCFAs).
“Targeted promotion of the active SCFA producers…via personalized nutrition may present a novel ecological approach for manipulating the gut microbiota to manage type 2 diabetes and potentially other dysbiosis-related diseases,” write the authors led by Liping Zhao, PhD, from the School of Environmental and Biological Sciences, Rutgers University-New Brunswick, New Jersey.
The research was conducted in China, and was published in the March 9 issue of Science.
However, separately, in an article published online November 1, 2017, in Gut, a whole-grain diet failed to alter insulin sensitivity and the gut microbiome in healthy individuals at risk for development of metabolic syndrome. But the high-fiber diet did lead to lower body weight and less systemic low-grade inflammation.
Certain Fibers Could Become Part of the Treatment for Type 2 Diabetes
In their paper, Zhao and colleagues explain that gut microbes play a range of roles in response to food intake, and they suggest that chronic diseases, such as type 2 diabetes, may in part result from a deficiency in SCFA production from carbohydrate fermentation in the gut.
Prior clinical trials have shown that increased intake of nondigestible but fermentable carbohydrates (dietary fibers) helps alleviate type 2 diabetes, but treatment responses vary considerably. The authors note that improved understanding of how gut bacteria respond, both as individual species and via interactions with each other, may improve clinical outcomes of dietary interventions.
In this study, patients with type 2 diabetes were randomly assigned to either a control group, in which they received usual care comprising patient education and dietary recommendations (n = 16), or the high-fiber diet treatment group, in which they were prescribed a diet composed of whole grains, traditional Chinese medicinal foods, and prebiotics (n = 27).
Next, the researchers characterized the dynamics of the gut microbiota and its effect on patients' glucose levels, including cataloging bacterial genes to see how the increased dietary fibers altered the overall composition of the gut microbiota. Specifically, they examined the genes involved in the production of glucose metabolites.
HbA1c levels, the primary outcome measure, fell significantly from baseline in a time-dependent manner in both groups. However, from day 28 onward, there was a greater reduction in the high-fiber treatment group.
The proportion of participants who achieved adequate glycemic control (HbA1c < 7%) at the end of the intervention (12 weeks) was significantly higher in the treatment group (89% vs 50% in the control group; P = .005).
Of 141 strains of SCFA-producing gut bacteria identified, only 15 were promoted by consumption of the high-fiber diet, and these are the ones most ly to be involved in driving the health benefits seen. These 15 formed the so-called guild that boosts deficient SCFA production (mainly butyrate and acetate) from the gut ecosystem, say the researchers.
“[P]romoting this active group of SCFA producers not only enhanced a beneficial function but also maintained a gut environment that keeps detrimental bacteria at bay,” Zhao and colleagues observe.
They add that considered as a functional group, the abundance and evenness of this guild of SCFA producers correlates with host clinical outcomes.
“Our clinical data indicate that increased availability of nondigestible but fermentable carbohydrates is sufficient to induce clinically relevant metabolic improvements in patients with type 2 diabetes.”
In a news release from Rutgers University, Zhao points out that their study opens the possibility that, for patients with type 2 diabetes, “Fibers targeting this group of gut bacteria could eventually become a major part of your diet and your treatment.”
Meanwhile, in the research published in Gut, 60 Danish adults at risk of developing metabolic syndrome were randomly assigned, in a crossover trial, to two 8-week dietary intervention periods comprising a whole-grain diet (mean, 179 g whole grain/day) and a refined grain diet (13 g/day), separated by a washout period of more than 6 weeks.
Intake of a diet rich in whole grains was associated with lower energy intake and body weight and a significant reduction in circulating markers of inflammation, such as interleukin 6 and C-reactive protein, report Henrik Munch Roager, PhD, from the National Food Institute, Technical University of Denmark, Kongens lyngby, and colleagues.
However, “in contrast to our hypothesis,” compared with the refined grain diet, the whole-grain-rich diet did not significantly modify fecal microbiome composition, nor did it affect glucose homeostasis. So the health benefits of this specific diet rich in whole grains “appeared to be independent of changes in the gut microbiome composition within an 8-week diet study,” they observe.
Nevertheless, “Whole grain consumption has beneficial effects on blood markers of subclinical inflammation in adults at risk of developing metabolic syndrome, and higher intake of whole grains should be encouraged in those at risk of inflammation-related diseases,” they conclude.
One of the authors of the Gut paper was partly supported by an unrestricted grant from cereal Partners Worldwide, a joint venture between Nestlé Sa and General Mills Ltd. The other authors have disclosed no relevant financial relationships.
Gut. Published online November 1, 2017. Abstract
Science. 2018;359:1151-1156. Abstract
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For diabetics, a high-fiber diet feeds gut microbes, lowering blood sugar
Plenty of fiber: That’s long been the recommendation for a healthy diet. But why?
The main rationale has been that fiber is made up of undigestible bulk that prevents people from eating unhealthy food — and helps keep the digestive tract regular.
But new research suggests that dietary fibers actually play a critical role in feeding the trillions of microbes that reside in our bodies, known collectively as the microbiome. And that specifically for people with type 2 diabetes, a high-fiber diet along with a favorable gut microbiome can keep patients’ blood sugar and body weight under control.
Researchers in China were able to pinpoint the specific “good” bacteria that ferment fiber into acids, and ultimately improves insulin regulation.
These bugs, according to lead investigator Liping Zhao, chair of applied microbiology at Rutgers University, create an acidic microenvironment in the gut that helps beneficial, blood-sugar-lowering bacteria proliferate — and might even keep pathogens at bay.
The research was published Thursday in Science.
“The study really gets at the mechanistic reasons of why these fiber-rich, plant-based diets may be helpful, especially in patients with type 2 diabetes,” said Dr. Clare Lee, an endocrinologist at Johns Hopkins University who also studies the link between diabetes and the microbiome. She was not involved in the study.
“It’s an exciting step towards understanding potential mechanisms that can help us prevent and treat diabetes,” she said.
Fiber, of course, has long been shown to improve blood sugar, and diabetics are encouraged to eat plenty of it. But the benefits of fiber may be much more complex than scientists previously understood.
“Leafy greens, whole grains, fruits with fibers: There’s lots of evidence that microbes will digest foods our bodies can’t,” said Dr. Lynn Bry, director of the Massachusetts Host-Microbiome Center at Harvard University, who was also not involved in the research. “When you eat, you’re not only feeding yourself, you’re feeding your microbiota.”
In a randomized, controlled trial, 27 participants with diabetes were given large quantities of dietary fibers — including whole grains, traditional Chinese medicinal foods, and prebiotics. The 16 participants in the control group had about the same caloric and nutrient intake, but not the supplemental fiber. Both sets took the diabetes drug acarbose.
Study participants on the fiber-rich diet saw a substantial decrease in their HbA1c levels (the metric that gauges a person’s blood sugar levels over several months) and lost more weight. Because the only difference between the two groups was their level of fiber intake, the benefits can be solely attributed to diet, Zhao said.
His team then delved deeper — examining the microbial ecosystem of the participants’ guts before and after the dietary intervention. They found that as bacteria fermented the dietary fiber, the composition of the gut microbiome changed.
When bacteria from a person on a fiber-rich diet was transplanted into a mouse’s gut, its ability to control its blood sugar actually improved. But when that same person’s pre-treatment gut bacteria was transplanted to a mouse’s gut, its blood sugar worsened.
The gut microenvironment changed, too: Dozens of gut bacteria are able to digest dietary fibers, and produce short-chain fatty acetic acids and butyric acids as a byproduct. But only 15 strains can actually survive in the newly acidic environment that they create. Zhao dubs these “foundation species” that might have some therapeutic use.
The study also affirms a long-standing hypothesis that short-chain fatty acids acetate and butyrate do indeed play a role in regulating blood sugar in humans. It’s been shown to some degree in animals, particularly cows — but the study marked the first time this mechanism has been shown in humans.
The study, while small, was still sufficiently robust, Bry and Lee said — and suggests that changes to the microbiome could substantially impact diseases diabetes. Zhao, for his part, thinks the next step for this research is to see if changes to the microbiome could even reverse the course of diabetes.
“There are many ways to alter microbiota,” Bry said. “But the easiest way is your diet.”
Fiber-fermenting bacteria improve health of type 2 diabetes patients: Dietary fibers promote gut bacteria that benefit blood glucose control
The fight against type 2 diabetes may soon improve thanks to a pioneering high-fiber diet study led by a Rutgers University-New Brunswick professor.
Promotion of a select group of gut bacteria by a diet high in diverse fibers led to better blood glucose control, greater weight loss and better lipid levels in people with type 2 diabetes, according to research published today in Science.
The study, underway for six years, provides evidence that eating more of the right dietary fibers may rebalance the gut microbiota, or the ecosystem of bacteria in the gastrointestinal tract that help digest food and are important for overall human health.
“Our study lays the foundation and opens the possibility that fibers targeting this group of gut bacteria could eventually become a major part of your diet and your treatment,” said Liping Zhao, the study's lead author and a professor in the Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences at Rutgers University-New Brunswick.
Type 2 diabetes, one of the most common debilitating diseases, develops when the pancreas makes too little insulin — a hormone that helps glucose enter cells for use as energy — or the body doesn't use insulin well.
In the gut, many bacteria break down carbohydrates, such as dietary fibers, and produce short-chain fatty acids that nourish our gut lining cells, reduce inflammation and help control appetite. A shortage of short-chain fatty acids has been associated with type 2 diabetes and other diseases.
Many clinical studies also show that increasing dietary fiber intake could alleviate type 2 diabetes, but the effectiveness can vary due to the lack of understanding of the mechanisms, according to Zhao, who works in New Jersey Institute for Food, Nutrition, and Health at Rutgers-New Brunswick.
In research based in China, Zhao and scientists from Shanghai Jiao Tong University and Yan Lam, a research assistant professor in Zhao's lab at Rutgers, randomized patients with type 2 diabetes into two groups.
The control group received standard patient education and dietary recommendations. The treatment group was given a large amount of many types of dietary fibers while ingesting a similar diet for energy and major nutrients.
Both groups took the drug acarbose to help control blood glucose.
The high-fiber diet included whole grains, traditional Chinese medicinal foods rich in dietary fibers and prebiotics, which promote growth of short-chain fatty acid-producing gut bacteria. After 12 weeks, patients on the high-fiber diet had greater reduction in a three-month average of blood glucose levels. Their fasting blood glucose levels also dropped faster and they lost more weight.
Surprisingly, of the 141 strains of short-chain fatty acid-producing gut bacteria identified by next-generation sequencing, only 15 are promoted by consuming more fibers and thus are ly to be the key drivers of better health.
Bolstered by the high-fiber diet, they became the dominant strains in the gut after they boosted levels of the short-chain fatty acids butyrate and acetate.
These acids created a mildly acidic gut environment that reduced populations of detrimental bacteria and led to increased insulin production and better blood glucose control.
The study supports establishing a healthy gut microbiota as a new nutritional approach for preventing and managing type 2 diabetes.
Materials provided by Rutgers University. Note: Content may be edited for style and length.
- Liping Zhao, Feng Zhang, Xiaoying Ding, Guojun Wu, Yan Y. Lam, Xuejiao Wang, Huaqing Fu, Xinhe Xue, Chunhua Lu, Jilin Ma, Lihua Yu, Chengmei Xu, Zhongying Ren, Ying Xu, Songmei Xu, Hongli Shen, Xiuli Zhu, Yu Shi, Qingyun Shen, Weiping Dong, Rui Liu, Yunxia Ling, Yue Zeng, Xingpeng Wang, Qianpeng Zhang, Jing Wang, Linghua Wang, Yanqiu Wu, Benhua Zeng, Hong Wei, Menghui Zhang, Yongde Peng, Chenhong Zhang. Gut bacteria selectively promoted by dietary fibers alleviate type 2 diabetes. Science, 2018; 359 (6380): 1151 DOI: 10.1126/science.aao5774
A high fiber diet may promote specific short-chain fatty acid producers to achieve better metabolic control in type 2 diabetes
Gut bacterial communities ferment non-digestible carbohydrates and as a metabolic output produce short-chain fatty acids (SCFAs) that are involved in fiber’s beneficial effects.
Activities of SCFAs include not only providing an energy substrate to colonocytes, but also mitigating inflammation, regulating weight through increasing satiety and balancing blood sugar, among others.
Although deficiency in SCFA production has been related to chronic diseases including type 2 diabetes mellitus (T2DM), it is unknown whether gut microbiota-mediated mechanisms could actively mediate dietary fiber’s metabolic effects.
A new randomized clinical trial, led by Dr.
Chenhong Zhang from the State Key Laboratory of Systems Biomedicine, School of Life Sciences and Biotechnology at Shanghai Jiao Tong University (Shanghai, China), has found that promotion of a select group of gut bacteria by a diet high in diverse fibers may lead to better blood glucose and lipid control and greater weight loss in people with T2DM.
The researchers randomized patients with clinically diagnosed T2DM into two groups: the treatment group (n = 27) was given a large amount of diverse fibers from dietary sources and the control group (n = 16) received standard patient education and dietary recommendations the 2013 Chinese Diabetes Society Guidelines for T2DM. The daily energy and macronutrient intake were similar across groups. Both groups took the drug acarbose to help control blood glucose. Dynamics of the gut microbiota and subjects’ glucose homeostasis were characterized at days 0, 28, 56, and 84.
A greater reduction in the level of haemoglobin A1c (HbA1c) was achieved in the intervention group from day 28 until the end of the study.
Besides this, the proportion of participants who achieved adequate glycemic control (HbA1c < 7%) at the end of the intervention at 3 months was also higher in the intervention group.
The treatment group also showed greater reduction in body weight and better blood lipid profiles when compared to the control group. These data show that a high-fiber diet improves clinical outcomes related to glucose homeostasis in participants with T2DM.
In order to determine causality between the gut microbiota and fiber-induced improvement of host glycemic control, pre- and postintervention gut microbiota from participants was transplanted into germ-free mice.
Although mice transplanted with the postintervention gut microbiota from either the intervention or control group showed better metabolic health parameters than those with the preintervention gut microbiota, mice that received postintervention gut microbiota from the intervention group had the lowest fasting and postprandial blood glucose levels.
Regarding the impact of increased dietary fibers on the global structure of the gut microbiota, both groups had a significant reduction in gene richness along with significant clinical improvements from day 0 to day 28, which contradicts the current concept that greater overall diversity implies better health. After day 28, gene richness tended to be higher in the intervention group and this trend was related with better clinical outcomes related to glucose homeostasis.
When exploring functional changes in the gut microbiota involved in improved clinical outcomes, carbohydrate-active enzyme (CAZy)-encoding gene richness was decreased in both groups compared with the baseline but remained higher in the intervention group after day 28.
Specifically, the intervention group showed changes in the capacity for carbohydrate metabolism, such as an enrichment of specific genes encoding a multienzyme complex for plant cell wall degradation.
These results highlight that the abundance distribution of specific functional genes rather that global gene richness may be more relevant as a health-related gut microbiota profile.
Besides this, different responses of SCFA-functional genes to the high-fiber intervention were detected: faecal acetic acid concentrations were similar in both groups during the whole study, whereas butyric acid concentrations increased significantly only in the intervention group.
Of the 141 strains of SCFA-producing gut bacteria identified by next-generation sequencing, only 15 strains belonging to Firmicutes, Actinobacteria and Proteobacteria phyla were promoted by consuming a high fiber diet and the response was strain-specific.
All 15 positive responders in the intervention group harboured genes for acetate production and butyrate production, whereas in the control group only 3 acetate producing strains among the 15 positive responders were promoted.
The effect of the high-fiber diet on promoting the butyrate production pathway and inducing butyrate production was observed only in the intervention group.
When the fiber-promoted SCFA producers were present in greater diversity and abundance, participants had better improvement in HbA1c levels, partly through increased glucagon- peptide-1 production. Furthermore, positive responders diminished the bacterial production of metabolically detrimental compounds such as indole and hydrogen sulphide.
Seven positive responders in the intervention group of active producers for SCFA production showed at least one significant correlation with clinical parameters. The acetate-producing Bifidobacterium pseudocatenulatum was one of the most significant promoted SCFA producers and it alleviated high-fat diet-induced dysregulation of glucose homeostasis in mice.
To sum up, dietary fiber is able to promote specific SCFA producing bacteria that may present a novel approach for managing T2DM. These results open the possibility that targeting specific gut microbial communities through dietary fiber could become an important part of T2DM treatment.
Zhao L, Zhang F, Ding X, et al. Gut bacteria selectively promoted by dietary fibers alleviate type 2 diabetes. Science. 2018; 359(6380):1151-6. doi: 10.1126/science.aao5774.
30 Mar 2020
by GMFH Editing Team
23 Mar 2020
by Patrice D. Cani
16 Mar 2020
by GMFH Editing Team
High fiber diet may help with management of type 2 diabetes
March 9 (UPI) — A high-fiber diet has previously been recommended for type 2 diabetes, but researchers have now discovered exactly why it improves health.
The diet helps promote gut bacteria, leading to better blood glucose control, greater weight loss and better lipid levels in people with type 2 diabetes, according to research published Friday in the journal Science.
The six-year study, led by Rutgers University, shows that these dietary fibers may rebalance the gut microbiota, the ecosystem of bacteria in the gastrointestinal tract that help digest food.
“Our study lays the foundation and opens the possibility that fibers targeting this group of gut bacteria could eventually become a major part of your diet and your treatment,” lead author Liping Zhao, a professor in the Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences at Rutgers University-New Brunswick, said in a press release.RELATED Genetic link to heart failure found in African-Americans
In research based in China, Zhao and scientists from Shanghai Jiao Tong University and Yan Lam, a research assistant professor in Zhao's lab at Rutgers, studied patients with type 2 diabetes in two groups.
In a 27-person treatment group, participants were was given a large amount of many types of dietary fibers, along with a similar diet for energy and major nutrients. A control group of 16, meanwhile, received standard patient education and dietary recommendations. Both groups also took the drug acarbose to help control blood glucose.
“Leafy greens, whole grains, fruits with fibers: There's lots of evidence that microbes will digest foods our bodies can't,” Dr.
Lynn Bry, director of the Massachusetts Host-Microbiome Center at Harvard University, who was also not involved in the research, told STAT.
“When you eat, you're not only feeding yourself, you're feeding your microbiota.”RELATED Primary care doctors should loosen type 2 diabetes goals, ACP says
Twelve weeks after the study started, participants on the high-fiber diet had greater reduction in a three-month average of blood glucose levels than participants receiving standard care. In addition, their fasting blood glucose levels dropped faster and they lost more weight than the standard care group.
Only 15 of the 141 identifiable strains of short-chain fatty acid-producing gut bacteria are ly to be the key drivers of better health, researchers say, but they became the dominant strains in the gut after boosting short-chain fatty acids butyrate and acetate. They also led to increased insulin production and better blood glucose control.
Many bacteria break down carbohydrates, such as dietary fibers, and produce short-chain fatty acids that nourish cells lining the gut. In turn, they reduce inflammation and help control appetite.RELATED Researchers identify five distinct types of diabetes
But in diabetes and other diseases, there a shortage of bacteria's short-chain fatty acids.
Researchers say they plan further studies to determine if greater changes to the gut microbiota could do more to help treat type 2 diabetes — possibly even curing it — in addition to the current study's suggestion that increasing health of the microbiota as a way of managing the condition.
RELATED Low-carb diets boost risk for serious birth defects