It has been long noted that abdominal obesity, elevated blood pressure, elevated triglycerides, reduced high-density lipoprotein (HDL, “good”) cholesterol, and elevated blood sugar all seem to happen in many of the same people and when they do they are labeled the metabolic syndrome by many, like the World Health Organization. Some research suggests that central obesity and/or insulin resistance are the most likely causative factors underlying the rest of metabolic syndrome. But many questions remain about how these things are tied together. For example you can have high blood pressure and not be obese or be obese and not have insulin resistance or diabetes etc.. If we could find an underlying causative thread for this constellation of the metabolic syndrome it might inform better treatment. Finding genes that connect these pieces provides an avenue of finding root causes.
One way to try and find a genetic link between the components of the metabolic syndrome is with twin studies. An ongoing registry of 1,237 twin pairs, 330 identical and 233 fraternal, is the Vietnam Era Twin Study of Aging. This is an all male collection of data on mostly white guys who are now 62 years old. They probably represent average white American men of this age. When they started out passing their army physical at age 20 they were 75-80% not overweight or obese, by middle age they were 75-80% overweight or obese.
The components of the metabolic syndrome were recently analyzed in these twins using multivariate biometrical modeling, whatever that is, and reported in the December issue of the journal Obesity. (1) Finding correlations using this method does not tell you what the genes are, only that there must be some. Whatever is left after genetic correlation is assessed must be attributed non-specifically to environment, maybe things like diet and exercise. They found that the metabolic syndrome components seem to come from two genetic factors. Blood pressure was genetically unrelated to insulin resistance and triglycerides and cholesterol. Obesity was the only characteristic genetically and environmentally related to all the other factors. This could mean that we need to reform the constellation that we call the metabolic syndrome or that we need to treat some pieces of it separately because fixing those parts may not automatically fix other parts.
1. Panizzon MS et al. A new look at the genetic and environmental coherence of metabolic syndrome components. Obesity. 2015; 23: 2499-2507.
John DiTraglia M.D. is a Pediatrician in Portsmouth. He can be reached by e-mail- [email protected] or phone-354-6605.