Health for life

The results of two studies published in Diabetes Care, one in 2006¹, and one in 2007², both led by Dr. Duk-Hee Lee, reveal a significant association between environmental pesticides and type 2 diabetes.

The first study was a cross sectional analysis involving 2,016 adult participants from the National Health and Nutrition Examination Survey of 1999–2000. It examined the relationship between toxic persistent organic pollutants (POPs) and diabetes.

After adjusting for age, sex, race/ethnicity, poverty income ratio, BMI, and waist circumference, the odds ratios (ORs) were 1.0, 16.9, 15.8, 36.7, and 38.0 (P for trend < 0.001), for five categories of exposure. That means there was a 38-fold greater odds of having diabetes for those in the highest exposure group compared to those in the lowest exposure group.*

Another interesting finding of this study was that being obese was not associated with having diabetes if the subjects blood levels of POPs were low. So, being thin but having high levels of POPs could place you at greater risk for diabetes than being overweight but having low levels.


* This study cited the source of many of these toxins: "Greater than 90% of POPs comes from animal foods in the general population without occupational or accidental exposures."
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The second study was a cross-sectional analysis involving 749 nondiabetic adults. It examined the relationship between POPs and insulin resistance.

The adjusted odds ratios were 1.8 for being equal to or above the 50th percentile for insulin resistance, 4.4 for the 75th percentile, and 7.5 for the 90th percentile. So, there was almost an 8-fold greater odds of having insulin resistance for those in the highest exposure group than the lowest.

The strongest associations were found for organochlorine (OC) pesticides or nondioxin-like polychlorinated biphenyls (PCBs).

An interesting finding of this study was that the association between OC pesticides and insulin resistance strengthened as waist circumference increased, suggesting that POPs may interact with obesity to increase the risk of type 2 diabetes.
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Finally, a commentary that appeared in the January 26th edition of The Lancet³ drew attention to Dr. Lees findings:

"This result was a surprise for many people working in diabetes research, because most studies to date have focused on the effects of genetics and the westernisation of dietary habits and lifestyle, while ignoring the potential effect of xenobiotics."

And note that:

"... an increasing number of reports suggest that chronic dietary exposure to, and accumulation of, low concentrations of environmental pollutants within the body might also be associated with diabetogenesis."

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¹ A Strong Dose-Response Relation Between Serum Concentrations of Persistent Organic Pollutants and Diabetes

² Association Between Serum Concentrations of Persistent Organic Pollutants and Insulin Resistance Among Nondiabetic Adults

³ Environmental Pollution And Diabetes: A Neglected Association, The Lancet, Vol. 371, No. 9609, 26 January 2008.

"Use it or lose it." The saying could apply especially to the brain when it comes to protecting against Alzheimers disease. Previous studies have shown that keeping the mind active, exercising and social interactions may help delay the onset of dementia in Alzheimers disease.

Now, a new study led by Dennis Selkoe, MD, co-director of the Center for Neurologic Diseases in the BWH Department of Neurology, provides specific pre-clinical scientific evidence supporting the concept that prolonged and intensive stimulation by an enriched environment, especially regular exposure to new activities, may have beneficial effects in delaying one of the key negative factors in Alzheimers disease.

The study will be published online on March 6, 2013 in Neuron.

Alzheimers disease occurs when a protein called amyloid beta accumulates and forms "senile plaques" in the brain. This protein accumulation can block nerve cells in the brain from properly communicating with one another. This may gradually lead to an erosion of a persons mental processes, such as memory, attention, and the ability to learn, understand and process information.

The BWH researchers used a wild-type mouse model when evaluating how the environment might affect Alzheimers disease. Unlike other pre-clinical models used in Alzheimers disease research, wild-type mice tend to more closely mimic the scenario of average humans developing the disease under normal environmental conditions, rather than being strongly genetically pre-disposed to the disease.

Selkoe and his team found that prolonged exposure to an enriched environment activated certain adrenalin-related brain receptors which triggered a signaling pathway that prevented amyloid beta protein from weakening the communication between nerve cells in the brains "memory center," the hippocampus. The hippocampus plays an important role in both short- and long-term memory.

The ability of an enriched, novel environment to prevent amyloid beta protein from affecting the signaling strength and communication between nerve cells was seen in both young and middle-aged wild-type mice.

"This part of our work suggests that prolonged exposure to a richer, more novel environment beginning even in middle age might help protect the hippocampus from the bad effects of amyloid beta, which builds up to toxic levels in one hundred percent of Alzheimer patients," said Selkoe.

Moreover, the scientists found that exposing the brain to novel activities in particular provided greater protection against Alzheimers disease than did just aerobic exercise. According to the researchers, this observation may be due to stimulation that occurred not only physically, but also mentally, when the mice moved quickly from one novel object to another.

"This work helps provide a molecular mechanism for why a richer environment can help lessen the memory-eroding effects of the build-up of amyloid beta protein with age," said Selkoe. "They point to basic scientific reasons for the apparent lessening of AD risk in people with cognitively richer and more complex experiences during life."