Human Bacteria

Human Bacteria Mapped; Gut Bacteria Linked To Happiness, Inflammatory Bowel Disease, Rheumatoid Arthritis, And Body Weight / Obesity

MONDAY, JUNE 18, 2012 AT 9:56AM

Campylobacter, a bacteria found in the human gut

Researchers recently completed an extensive, 5-year Human Microbiome Project (HMP)identifying more than 10,000 bacterial species living in and on our bodies.  The goal of HMP was to “map the normal microbial make-up of healthy humans.”[I]  Many believe the Human Microbiome Project will allow scientists and physicians to prevent and treat diseases in the future.  Researcher and pediatric gastroenterologist Dr. Phillip Tarr commented “This is really a new vista in biology.  This opens up many, many new opportunities to improve the health of our population.”

Coincidentally, the conclusion of the Human Microbiome Project coincided with the publication of several fascinating articles about gut bacteria and human health.[Ii]   For example, researchers recently linked gut bacteria with:

• Happiness 
• Inflammatory Bowel Disease
• Rheumatoid Arthritis
• Body weight / obesity

Happiness

Scientists at the University College Cork in Ireland recently discovered that an Absence Of Bacteria In Early Life May Decrease Levels Of Brain Serotonin later in life (serotonin is an important neurotransmitter implicated in depression).   This expounds upon previous research investigating potential Mind-Microbe Links.  

Inflammatory Bowel Disease (IBD)

Researchers also believe they may have identified why Western Diet Changes Gut Bacteria And May Trigger Immune-Mediated Diseases Like Inflammatory Bowel Disease (IBD).  Westernized countries tend to consume foods high in saturated fats, and researchers at the University of Chicago found that concentrated milk fats (common in processed foods and confectionary foods) alter the composition of bacteria in our digestive systems.  One bacteria in particular, Bilopha wadsworthia, thrives in the presence of saturated milk fats.  Interestingly, this same bacteria has been found in elevated levels in patients with inflammatory bowel conditions like IBD and appendicitis. 

Rheumatoid Arthritis

Researchers at the Mayo Clinic Linked Gut Bacteria To The Autoimmune Disease Rheumatoid Arthritis.  Rheumatoid arthritis is caused by the body’s immune system attacking its own tissue (like our joints). 

Through clever manipulation of genetic susceptibility to rheumatoid arthritis and introduction of different gut bacteria in mice, researchers concluded that gut bacteria may play an important role in developing rheumatoid arthritis and other autoimmune diseases like type I diabetes and multiple sclerosis (MS).  The researchers noted that changes related to aging (such as hormonal changes) may modulate gut bacteria and contribute to autoimmune disorders.   Specifically, the researchers believe autoimmune disorders may actually begin as an immune system attack on gut bacteria that have penetrated our intestinal walls. [Iii]

Body Weight / Obesity

Interestingly, researchers also recently summarized Evidence That Gut Bacteria Might Modify Body Weight.  Researchers at Arizona State University recently noted that bacteria play an important role in helping our body extract and synthesize important nutrients.  In fact, the body is unable to digest some carbohydrates without gut bacteria (the bacteria digest these carbs for us), and gut bacteria also produce important vitamins like biotin and folate and help us absorb other nutrients like magnesium, calcium, and iron. 

The researchers noted that obese individuals frequently have distinct gut bacteria.  For example, obese individuals typically have a greater proportion of bacteria from the phylum Bacteroidetes, while lean individuals have a greater proportion of bacteria from the phylulm Firmucutes.  Correlation does not imply causation.[Iv]  However, researchers are beginning to identify some compelling mechanisms by which gut bacteria may contribute to obesity.[V]  The researchers at Arizona State believe that we may be able to manipulate or exploit our gut bacteria in order to control weight. 

Future Implications

In an article titled Gut Check: Future Of Drugs May Rest With Your Microbes, Henry Haiser and Peter Tumbaugh of Harvard University note that “The trillions of microbes associated with the human body are a key part of a comprehensive view of pharmacology.”  In other words, future treatment of diseases (such as those noted above) and optimization of health will likely take into account our gut bacteria to a greater extent.  Once fairly obscure, gut bacteria (and the manipulation of gut bacteria) will likely play a greater role in maintaining health and preventing disease in the future. 

What Do You Think?

• Do you know of ways to optimize gut bacteria in order to optimize health?
• What role do you think gut bacteria will play in managing health and preventing disease in the future? 

Related:

• Irritable Bowel Syndrome (IBS) And Gut Bacteria Definitively Linked [vi]
• Additional relevant articles tagged 'Microorganisms' or 'Medicine'

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[I] The human “microbiome” refers to microscopic bacteria, yeasts, protozoa, small parasitic worms, and viruses. However, most microbes in the human microbiome are bacteria; therefore, the terms human “microbiome” or “microbe” are often used to refer specifically to bacteria.    

[Ii] Note that most of our human microbiome resides in our gut.

[Iii] Gut bacteria typically do not penetrate the intestine’s walls and enter the body.  However, researchers believe that under certain conditions (such as certain hormonal conditions and other conditions related to aging), the gut bacteria may penetrate the intestinal wall stimulating an immune response that manifests as rheumatoid arthritis or possibly other autoimmune disease like type I diabetes or MS.  

[Iv] In other words, just because an increase in Bacteroidetes is correlated (or related) to an increase in body weight (obesity), this does not necessarily mean that an increase of Bacteroidetes causes obesity. 

[v] For example, researchers have noted that obesity and insulin-resistance (which could lead to Type II diabetes) are often accompanied by inflammation.  One marker of inflammation that has been associated with obesity and insulin-resistance is blood lipopolysaccharides (LPS).  Interestingly, LPS primarily comes from bacteria such as those that live in our gut. 

Additionally, scientists found that “germ free mice” (literally mice with no germs on or in them) experienced a 60% increase in body fat content and insulin resistance when gut bacteria from obese mice were transplanted to their guts.  Scientists also found that these same mice transplanted with gut bacteria from obese mice experienced a decreased production of a compound called Fiaf (“fasting-induced adipocyte factor).  Fiaf is produced in intestinal tissue and promotes leanness (in other words, opposes obesity).  Therefore, researchers believe that the gut bacteria of obese mice may suppress Fiaf production which in turn promotes obesity.

[vi] If you're curious, here's an excellent reference on the Difference Between Irritable Bowel Syndrome (IBS) And Inflammatory Bowel Disease (IBD)