Atherosclerosis and diabetes – payment for resistance to cold?
Scientists at the University of Chicago, working under the guidance of Professor Anna Di Rienzo, have found that many of the mutations that provided a person's ability to tolerate low temperatures increase predisposition to metabolic syndrome – a complex of interrelated pathologies: obesity, high blood cholesterol, cardiovascular diseases and diabetes.
More than a hundred years ago, scientists noticed that the population of the northern regions is characterized by a more massive physique and shorter limbs. In the 1950s, the relationship between a cold climate and a high body mass index was revealed.
According to the results of the new work, a pronounced correlation exists between climate and several genetic variations that increase the risk of developing metabolic syndrome. This confirms the theory that these genetic variants played a key role in adapting to the cold. The authors state that some genes associated with cold resistance prevent the development of metabolic syndrome, while others increase the risk of its development.
Early human ancestors lived in a humid hot climate, so the evolutionary process contributed to the selection of traits that provide cooling of the body. As individual populations migrated to cooler climate zones, the evolutionary pressure began to increase in the direction of adaptation to new conditions by increasing the efficiency of processes aimed at generating and preserving heat.
Thousands of years later, in the era of central heating and food abundance, these genetic variations take on a completely different meaning. They determine our predisposition to a whole set of diseases, including obesity, cardiovascular diseases and type 2 diabetes.
The authors identified 82 genes associated with energy metabolism, many of which cause the risk of developing diseases, and studied climate-related variants of these genes. To do this, they analyzed the genetic variations of 1,034 people from 54 populations and identified a number of reliable associations between the frequency of occurrence of certain variations and the cold climate.
One of the most pronounced indicators of evolutionary selection was the leptin receptor gene involved in the regulation of appetite and energy balance. One of the versions of this gene, often found in residents of cold regions, is associated with a high respiratory coefficient, reflecting the efficiency of oxygen absorption and carbon dioxide release and playing an important role in heat production. This variant of the gene is also associated with a low body mass ratio, less belly fat and low blood pressure, and thus with a minimal risk of developing metabolic syndrome.
Other genes, whose occurrence varies depending on the climate, are involved in heat production, cholesterol metabolism, energy use and regulation of blood glucose levels.
Many gene variants that increase resistance to low temperatures also increase the likelihood of developing a metabolic syndrome. For example, a high level of glucose in the blood can protect against cold by increasing the availability of raw materials for the production of thermal energy, but it increases the risk of developing type 2 diabetes. A version of the FABP2 gene, the frequency of which increases as the average annual temperature decreases, increases the body mass coefficient, promotes fat accumulation and increases cholesterol levels. It also protects against the cold, but at the same time increases the risk of developing cardiovascular diseases and diabetes.
Apparently, such gene variants spread rapidly in human populations as the cold regions of high latitudes were populated, but in modern conditions, when a huge amount of calories enters the body and the need to generate heat is minimized, they have acquired a completely new role. The authors believe that the search and study of genes, the frequency of occurrence of which depends on the climate, will help shed light on the mechanisms of development of many metabolic disorders.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
19.02.2008