Dietary Fiber Promotes Beneficial Bacteria, Improving Glucose Control in Diabetes Interview with:

Liping Zhao PhD, Professor Department of Biochemistry and Microbiology School of Environmental and Biological Sciences Rutgers University-New Brunswick NJ

Dr. Zhao

Liping Zhao PhD, Professor
Department of Biochemistry and Microbiology
School of Environmental and Biological Sciences
Rutgers University-New Brunswick NJ What is the background for this study?

Response: Microbes in the human gut (collectively known as the gut microbiota) provide many functions that are important for human health. A notable example is that some gut bacteria are able to ferment non-digestible carbohydrates in our diet, e.g. dietary fibers, to produce short-chain fatty acids (SCFAs). These SCFAs nourish our gut epithelial cells, reduce inflammation, and play a role in appetite control. Deficiency of SCFAs has been associated with many diseases including type 2 diabetes. Many gut bacteria have the genes (and therefore the capacity) to produce SCFAs from carbohydrate fermentation. However, we know little about how these bacteria, as individual strains and as a group, actually respond to an increased supply of carbohydrates. This is key to improve clinical efficacy of dietary fiber interventions to improve human health. What are the main findings?

Response: We randomized patients to treatment or control group. The control group received standard patient education and dietary recommendations; the intervention group was provided with a diet similar to the controls, plus a large amount of dietary fibers with diverse structures and properties. Throughout the 12-week treatment, the intervention group experienced more significant and faster improvement in blood glucose control, greater weight loss, and better lipid profile compared to the controls. Importantly, the study showed that these beneficial effects of the high fiber diet were directly contributed by changes in the gut microbiota. We further identified a small group of bacterial strains that were likely to be the key drivers of patients’ clinical improvements: these bacteria all possess the ability to produce SCFAs, and by taking advantage of the increased dietary fibers, they out-competed the others and became dominant members of the gut microbial community.

Their activity increased the production of butyrate and acetate (two major beneficial sub-types of SCFAs) that benefited the human host:

1) by promoting the secretion of gut hormones and subsequently increasing insulin production that led to improved blood glucose control; and

2) by maintaining a mildly acidic gut environment which is unfavorable for known detrimental bacteria. Overall, when members of this group of bacteria reached greater abundance and diversity, the patients had lower acetylated hemoglobin levels which indicated better blood glucose regulation. What should readers take away from your report?

Response: Our findings open a new avenue for nutrition therapy of type 2 diabetes. In addition to managing acute glycemic control by limiting carbohydrate intake, physicians and dietitians may include dietary fibers to improve glycemic control by encouraging the growth of short-chain fatty acid-producing bacteria in the gut. What recommendations do you have for future research as a result of this work?

Response: If we help a patient establish a new gut microbiota with the best possible profile of such guild of positive responders, how much of his/her health can be restored if they keep the new microbiota for long-term? In other words, can we reverse T2D by restoring and keeping a healthy gut microbiota with this group of SCFA producers as targets? 

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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 

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