Obesity Villain b29

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In a healthy microbiome, overgrowth doesn’t happen because enough species are present to enforce nature’s system of checks and balances. Childhood Obesity News discussed Prof. Liping Zhao’s discovery of a bacterial strain that can get out of control and expand its population to as much as one-third of the entire microbiome.

He contends that the right prebiotic diet can police this harmful bug. The resulting change in the microbiome’s composition apparently facilitates massive weight loss, even for patients who expend no energy in workouts.

It truly does sound “too good to be true.” Yet, who would bother to claim such extraordinary results on behalf of substances that have been available to the public for centuries? It’s not as if anyone can own the patent on traditional Chinese foods.

In what way is b29 villainous?

Obesity-wise, the trouble starts when endotoxins produced by bacteria hit the bloodstream. Studies of germ-free rodents, specially raised for lab experimentation, show that they are “resistant to high-fat diet induced obesity.” So, ingested fat alone isn’t enough to make them obese.

Prof. Zhao showed that even when endotoxin-producing bacteria live in the gut, their presence alone isn’t enough to cause obesity, because the endotoxin doesn’t get into the bloodstream. It turns out that both are necessary, but not sufficient, conditions.

Prof. Zhao, whose accomplishments, offices, and publication credits form an extensive list, isolated a strain of enterobacter cloacae called b29 and introduced it into the bodies of sterile mice. Here’s what happened:

When the guts of germ-free mice were colonized with the endotoxin-producing bacterium, the mice became obese, insulin resistant, had fatty liver, inflammation and they also experienced inhibition of the gene required for burning stored fat in the gut, along with several genes in the liver for synthesizing fat… If you switch to a high fat diet, endotoxin enters the bloodstream and all of the health issues ensue.

All this is ecology-dependent. The environmental conditions need to be right for the bug to beat the competition and achieve dominance. Prof. Zhao and his colleagues admit that they are far from understanding the ecological factors, though it does seem clear that b19 deactivates the gene that switches on fat-burning and conversely, getting rid of b29 allows the gene to operate correctly and supervise fat-burning.

Disturbing the peace

Among other activities, the microbiota both produce and regulate bile acids; synthesize vitamins; regulate dietary lipids; and influence the absorptive abilities of the epithelium. They also practice “competitive exclusion,” or as Dr. Billi Gordon puts it, the micro-thugs “hijack our bodies and behaviors for personal gain,” waging constant warfare for their slice of the “turf,” which is our colons.

Faced with bugs they don’t want to be friends with, the already established tenants will react with hostility, eat anything they find consumable, and leave no food for the invaders. If the existing microbiota feel threatened by newcomers, they will hog any available attachment sites, much like able-bodied drivers taking up disability spaces. They will whip up some antimicrobial peptides and engage in chemical warfare.

Like any other creature, b29 has its natural enemies, and a quite unfair way of engineering its victory over them. It takes advantage of a weakness in the host’s immune system, which for some reason seems to tolerate b29, rather than recognizing it as an enemy. But why do some people’s immune systems have that security flaw? By taking detailed patient histories, Prof. Zhao discovered a commonality:

When during the first few days or months of life, their test subjects had serious infections, diarrhea and fever, from which they recovered. From there, they quickly became obese. So there might be something about this early infection that makes the immune system tolerate this bacterium.

Your responses and feedback are welcome!

Source: “#123: Liping Zhao, PhD: Changing Gut Bacteria Ecology w/ Chinese Medicines and Berberine,” HighIntensityHealth.com, 12/08/15
Source: “The Interplay of the Gut Microbiome, Bile Acids, and Volatile Organic Compounds,” NIH.gov, 03/03/15
Photo credit: Grey World via Visualhunt/CC BY

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