Scientists have found a strong correlation between climate and several of the genetic variations that appear to influence the risk of metabolic syndrome, consistent with the idea that these variants played a crucial role in adaptations to the cold. The researchers report that some genes associated with cold tolerance have a protective effect against the disease, while others increase disease risk.
The researchers set out to look for correlations between the frequency of genetic variations linked to metabolic syndrome and climate variables in worldwide population samples. They selected 82 genes associated with energy metabolism – many of them previously implicated in disease risk – and looked for climate-related variations in those genes. They studied genetic variation in 1,034 people from 54 populations, finding widespread correlations between the frequencies of certain genetic variations and colder climates, as measured by latitude as well as summer and winter temperatures.
One of the strongest signals of selection came from the leptin receptor, a gene involved in the regulation of appetite and energy balance. One version of this gene is increasingly common in locales with colder winters. This version of the leptin receptor is associated with increased respiratory quotient – the ability to take up oxygen and release carbon dioxide – which plays an important role in heat production. This allele also has been linked to lower BMI, less abdominal fat and lower blood pressure, and is thus protective against metabolic syndrome.
Not all cold-tolerance-related gene variants protect against metabolic syndrome. Increased blood glucose levels, for example, could protect someone from the cold by making fuel more readily available for heat production, yet it raises the risk of type 2 diabetes. The authors suggest that the search for genes that vary according to climate could provide additional clues about the onset of metabolism related diseases.
MEDICA.de; Source: University of Chicago Medical Center