According to researchers from the University of Chicagoa strong association exists between metabolic syndrome and cold tolerance.
In the study, the researchers found that many of the genetic variations that have enabled human populations to tolerate colder climates might also affect their susceptibility to metabolic syndrome, a cluster of related abnormalities such as obesity, elevated cholesterol levels, heart disease, and diabetes.
They reported that some genes linked to cold tolerance have a protective effect against the disease, while others increase disease risk.
The research team 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 linked to energy metabolism, many of them previously implicated in disease risk, and looked for climate-related variations in those genes.
They examined 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.
The authors found that 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 associated with lower BMI, less abdominal fat and lower blood pressure, and is thus protective against metabolic syndrome.
Other genes that varied according to climate included several involved in heat production, cholesterol metabolism, energy use, and blood glucose regulation.
The researchers found that not all cold-tolerance-related gene variants protect against metabolic syndrome.
The version of a gene called FABP2 that became more common as temperatures fell causes increased BMI, promotes fat storage and elevates cholesterol levels. This would protect against the cold, but increase susceptibility to heart disease and diabetes.
"All these genes are likely to be involved in metabolic adaptations to cold climates, but they have opposing effects on metabolic syndrome risk," said Anna Di Rienzo, professor of human genetics at the University of Chicago.
The study is published in the February issue of the open-access journal PLoS Genetics.