Research: April 2015

Gut Bugs and Obesity

>> Saturday, April 18, 2015

There is a lot of interest and excitement in the research going on about the microscopic organisms that reside in our intestines (called 'gut microbiota'). And so there should be! Did you know that human beings are not actually 100% human, but that we are actually made up of 90% gut microbiota cells and only 10% human cells? Mind boggling, isn't it.

It turns out that we have evolved to welcome gut microbiota into our own personal ecosystems, such that these bugs actually do some work for us behind the scenes. For example, while simple and complex polysaccharides (ie, dietary fiber) escape digestion by our upper gastrointestinal (GI) tracts, they can be transformed by bacteria into digestible substances such as sugars or short chain fatty acids. These short chain fatty acids are involved in regulation of fat storage in the liver and throughout the body via numerous mechanisms that we are only just beginning to understand.

The type of gut bugs we carry is important, but the story is far from clear. In studies of rodents, obesity seems to be associated with carrying more of the Firmicutes phylum and less of the Bacteroides phylum, but the research is quite conflicted on this when it comes to humans. If there is a relationship between the type of bacteria and obesity, it's unclear which is the chicken and which is the egg - in other words, did these bacteria contribute to obesity, or does developing obesity (or eating a poor diet, thus increasing the risk of obesity) change the gut bacteria towards this particular balance?

The gut microbiota also appear to play a role in the production of gut hormones (such as GLP-1) that signal our brains that we are feeling full during a meal, and this response differs depending on what type of bacteria we carry. Certain types of gut bugs may also stimulate production of inflammatory chemicals by our immune systems that contribute to the risk of insulin resistance, type 2 diabetes, metabolic syndrome, and so forth.

There are probably more unanswered questions than answered ones at this point in the area of the gut microbiome and how it plays into obesity, and thankfully, there is a lot of research ongoing in this area. A growing body of evidence supports the possibility of prebiotic or probiotic approaches to changing the composition of the gut microbiota in favor of certain types of gut bugs, thereby having a positive impact on obesity and related diseases. I will be following this area with interest!

Follow me on twitter! @drsuepedersen

Does Metformin Decrease Heart Risk in Polycystic Ovary Syndrome?

>> Friday, April 10, 2015

Metformin is a medication that is considered the first line treatment for type 2 diabetes globally. One of the reasons why is because it is the only diabetes medication that has data to suggest that it decreases the risk of heart disease. Metformin can also be used to regulate menses in women with polycystic ovary syndrome (PCOS)- could metformin help decrease heart risk in these women as well? A recent study has endeavored to answer this question.

The study randomized 50 women with PCOS to receive either the birth control pill, or the birth control pill plus metformin, for 6 months, and they looked at the effect these treatments had on the thickness of the inner wall of the carotid artery (called 'carotid intima media thickness') as well as the ability of arteries to dilate (called 'flow mediated dilatation').

While their findings were not significantly different between groups, numerically, the carotid artery wall grew thicker in the women on the pill, whereas it became thinner in women who were also on metformin. A thicker inner wall is considered a marker for heart disease risk. The ability of arteries to dilate was also a little better numerically on metformin (but again, not statistically significant); arteries that are better able to dilate are healthier and are associated with lower risk of heart disease.

So, while this was technically a 'negative' study in that no statistically significant difference was shown, I agree with the authors that the numbers may have become significant if the number of patients in the study was larger (50 patients is a very small study). There is good reason to think that metformin could decrease heart disease risk in these women, as PCOS is a condition where the body is more resistant to the effects of insulin, and metformin works by decreasing the body's resistance to insulin, thereby improving many metabolic parameters.

The ability of metformin to decrease heart disease risk in women with PCOS now needs to be studies in much larger clinical trials, so that we can get an answer to this important question.

Follow me on twitter: @drsuepedersen

Is Lifespan Shortened By Obesity?

>> Thursday, April 2, 2015

What is the impact of obesity on our lifespan? The answer may be more complicated than you might think.

An interesting study published in Lancet Diabetes & Endocrinology looked at data from nearly 4.000 people, where they built a statistical model to estimate the effect on lifespan of having a body mass index (BMI) in the overweight category (25-29.9), obesity (BMI 30-34.9), 'very obese' (BMI 35 or higher), compared to an ideal BMI of 18.5-25.

They found that the effect of excess body weight on years of life lost was highest in younger individuals. For example, very obese men aged 20-39 lost 8.4 years of life, whereas very obese men aged 60-79 years lost only 0.9 years. Similarly, very obese women aged 20-39 years lost 6.1 years of life, whereas very obese women aged 60-79 lost 0.9 years of life.

The fact that excess body weight has less negative impact on lifespan as we get older may reflect that a little extra body weight may be protective as we age, as we then have more energy supply to sustain us if we become ill with a condition that causes us to lose weight (which could be anything from a bad flu to cancer). It may also be reflective of the obesity paradox - people with certain medical conditions (such as heart disease or kidney failure) with obesity have been found to have better survival than people with these conditions who are lean. This may be because of the benefit of having extra energy stores on board, or could be because thin people with serious medical problems may simply be sicker.

So, while optimum weight management appears to be most important in our younger years, it is still important throughout our lives, with a slight shift in focus over time.