Gut microbes and body fat

First seen at Dish.  The eye catching graphics opening this post are one of my pet peeves, of course.  Correlation?  Causation?  Close enough.  Lots of confounding factors here.  Just saying.  But the links in the post are much better, and even acknowledge the correlation/causation issue in relation to these specific graphs, and discuss some of those confounding factors.

This article by Moises Velasquez-Manoff is the best one I have seen yet on our intestinal microbes.  Fascinating.  It’s a long article, but filled with all kinds of facts.  I didn’t verify any of them, and after all, it is from the internet, so who knows if this is all true, but food for thought (haha!).  Here are some highlights, but there is a lot more in the article:

Chronic, low-grade inflammation has long been recognized as a feature of metabolic syndrome, a cluster of dysfunctions that tends to precede full-blown diabetes and that also increases the risk of heart disease, stroke, certain cancers, and even dementia…

…………

…along with their two-sandwich, two-hash-brown, 910-calorie breakfast, one-third of his volunteers—10 in total—quaffed a glass of fresh OJ. The non-juice drinkers, half of whom drank sugar water, and the other half plain water, had the expected response—inflammation and elevated blood sugar. But the OJ drinkers had neither elevated blood sugar nor inflammation. The juice seemed to shield their metabolism. “It just switched off the whole damn thing,” Dandona says. Other scientists have since confirmed that OJ has a strong anti-inflammatory effect.

…………..

Here’s the traditional understanding of metabolic syndrome: You ate too much refined food sopped in grease. Calories flooded your body. Usually, a hormone called insulin would help your cells absorb these calories for use. But the sheer overabundance of energy in this case overwhelms your cells. They stop responding to insulin. To compensate, your pancreas begins cranking out more insulin. When the pancreas finally collapses from exhaustion, you have diabetes. In addition, you develop resistance to another hormone called leptin, which signals satiety, or fullness. So you tend to overeat. Meanwhile, fat cells, which have become bloated and stressed as they try to store the excess calories, begin emitting a danger signal—low-grade inflammation.

But new research suggest another scenario: Inflammation might not be a symptom, it could be a cause. According to this theory, it is the immune activation caused by lousy food that prompts insulin and leptin resistance. Sugar builds up in your blood. Insulin increases. Your liver and pancreas strain to keep up. All because the loudly blaring danger signal—the inflammation—hampers your cells’ ability to respond to hormonal signals. Maybe the most dramatic evidence in support of this idea comes from experiments where scientists quash inflammation in animals. If you simply increase the number of white blood cells that alleviate inflammation—called regulatory T-cells—in obese mice with metabolic syndrome, the whole syndrome fades away. Deal with the inflammation, it seems, and you halt the dysfunction.

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A DECADE AGO, microbiologists at Washington University in St. Louis noticed that mice raised without any microbes, in plastic bubbles with positive air pressure, could gorge on food without developing metabolic syndrome [15] or growing obese. But when colonized with their native microbes, these mice quickly became insulin resistant and grew fat, all while eating less food than their germ-free counterparts.

The researchers surmised that the microbes helped the rodents harvest energy from food. The mice, which then had more calories than they needed, stored the surplus as fat. But across the Atlantic, Patrice Cani [16] at the Catholic University of Louvain in Brussels, Belgium, suspected that inflammation contributed, and that the inflammation emanated from native microbes.

To prove the principle, he gave mice a low dose of endotoxin [17], that molecule that resides in the outer walls of certain bacteria. The mice’s livers became insulin resistant; the mice became obese and developed diabetes. A high-fat diet alone produced the same result: Endotoxin leaked into circulation; inflammation took hold; the mice grew fat and diabetic. Then came the bombshell. The mere addition of soluble plant fibers [18] called oligosaccharides, found in things like bananas, garlic, and asparagus, prevented the entire cascade—no endotoxin, no inflammation, and no diabetes.

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Oligosaccharides are one form of what’s known as a “prebiotic”: fibers that, because they make it all the way to the colon intact, feed, as it were, the bacteria that live there. One reason we’ve evolved to house microbes at all is because they “digest” these fibers by fermenting them, breaking them down and allowing us to utilize their healthful byproducts, like acetic acid, butyric acid, B vitamins, and vitamin K.

Cani had essentially arrived at the same place as Dandona with his freshly squeezed orange juice

…………..

Then one day in 2008, a morbidly obese man walked into Zhao’s lab in China [19]. The 26-year-old was diabetic, inflamed, had high bad cholesterol, and elevated blood sugar. No one in his immediate family was heavy, but he weighed 385 pounds.

Zhao noticed something odd about the man’s microbes. Thirty-five percent belonged to a single, endotoxin-producing species called Enterobacter cloacae. So he put the man on a version of his own regimen—whole grains supplemented with other prebiotics. As treatment progressed, the Enterobacter cloacae declined, as did circulating endotoxin and markers of inflammation.

After 23 weeks, the man had lost 113 pounds. That bacterial bloom had receded to the point of being undetectable. Counts of anti-inflammatory bacteria—microbes that specialize in fermenting nondigestible fibers—had increased. But could Zhao prove that these microbial changes caused anything? After all, the regimen may have simply contained far fewer calories than the patient’s previous diet.

So Zhao introduced the Enterobacter into mice. They developed endotoxemia, fattened up and became diabetic—but only when eating a high fat diet. Mice colonized with bifidobacteria and fed a high fat diet, meanwhile, remained lean, as did germ-free mice. The enterobacter was evidently unique, an opportunist. Aided by a high fat diet, the microbe appeared able to hijack the metabolism of both mice and man.

Zhao, who related his own story to Science [20] last year, has repeated a version of this regimen in at least 90 subjects, achieved similar improvements, and has more than 1,000 patients in ongoing trials.

 

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