"Diabetes Genes Decline out of Africa"

A November 4^th article in Science magazine by Ann Gibbons described a presentation on genetics and diabetes at a recent poster session. A current Stanford graduate student, Erik Corona, explained his research on the SNPs that are connected with type II diabetes and their prevalence throughout the world. Type II diabetes results when either the body does not produce enough insulin or the cells of the body stop responding to the insulin that is produced. This causes too little glucose being removed from the bloodstream, leading to other symptoms and problems such as kidney or vision failure and heart attack or stroke. This form of diabetes is thought to be produced by a combination of environmental and lifestyle factors, preexisting conditions, and genetics.

In the United States 8.3% of the population has diabetes, with African Americans and Native Americans being the two groups with the highest rates within them. Diabetes is currently uncommon in Sub-Saharan Africa, where only 3% of the population has the disease. However, rates of diabetes have been increasing as more Africans adopt an urban and western lifestyle and diet.

Corona’s research showed that the SNPs associated with diabetes are extremely prevalent in Africa and become rarer as one moves outward from there. There is a resurgence of the SNPs in North America, possibly due to a different lifestyle and diet that migrants there may have encountered. Corona suspects that as early humans left Africa, the genes for diabetes were gradually lost. In Africa, it is likely they served a role in better blood sugar and energy use when humans had a diet that was not rich in sugar or fat and when they did not live as long. At this time, these genes would have benefitted fitness levels, unlike their role today. This could present a problem for Africans in the future as they adopt a different, more fat and sugar rich lifestyle.

The question for researchers now is how large a role these genes actually play in predisposing people to diabetes. It may turn out that environmental and lifestyle influences are exponentially more important. Corona and his associates hope to use this type of gene analysis for more diseases in the future and to have that information available to doctors.

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The OXTR Gene and Human Behavior

OXTR has a remarkable effect on the way we interact with and relate to our fellow man. This oxytocin receptor gene codes for a protein which acts as a receptor for oxytocin, a hormone and neurotransmitter. The OXTR gene may govern behavioral modulation and induce emotions almost immediately detectable by humans. On human chromosomes at the 3p25 location, the OXTR gene encodes these proteins.

So why are OXTR genes so special?

There are two types of OXTR, the A and G, which designate how the OXTR affects our social behavior. With two G-type OXTR genes, a human tends to exude more empathy and sensitive behavior. Those with one or more A-copies are less likely to exhibit these empathic or sociable tendencies. Aleksandr Kogan's study at the University of Toronto has found that the difference between these two types of OXTR genes is what constitutes the difference between two very different dispositions among people-- which strangers can sense within just minutes of meeting or watching an individual.

It's fascinating to consider that our behavior is so closely determined by our genome. Kogan's work filming individuals talking to a partner about suffering has revealed that, when volunteers watch the footage on mute for just 20 seconds, those volunteers responded almost precisely according to whether they had A or G-type OXTR genes. G-owners tended to respond more empathically, while A-owners, as expected, did not respond as emotionally. 

In addition, independent viewers of the clips with two G-copies responded to the footage with a more physical empathy: eye contact, open arms, nodding heads, etc. As a result, these viewers may be perceived as more trustworthy, social, or emotionally in-touch than others. This shows that people are incredibly sensitive to behavior as a social cue. A tiny genetic difference actually manifests in human behavior, even for mere seconds, as a huge effect on personality and sociability.

Kogan worked with a strikingly small sample size, which is why his paper has been largely criticized by other scientific scholars. However, it provides an exciting window onto the genetic underpinnings of human behavior.