Chinese scientists identify gene that may help protect against obesity

A 2022 study published in The Lancet ranked Chinese women 190th globally in terms of obesity prevalence, and Chinese men 149th.

While factors such as diet and levels of development are obviously important, a recent study led by Professor Jin Li and Associate Professor Zheng Hongxiang from Fudan University suggests genetics may also be a factor.

The team analysed 2,877 samples from three independent populations in the southwestern region of Guangxi, the eastern province of Jiangsu and Henan in central China for the study, which was published in the peer-reviewed Journal of Genetics and Genomics.

It identified a type of mitochondrial DNA known to be prevalent in southern China and Southeast Asia that appears to act as a protective factor against obesity.

“Mitochondria are often referred to as the cell’s powerhouses, generating 80 to 90 per cent of the energy needed for various human behaviours. Mitochondrial function has long been associated with obesity,” Jin wrote.

Unlike DNA in the cell nucleus, which comes from both parents, DNA in mitochondria is generally inherited only from the mother. Compared with nuclear DNA, it is more likely to accumulate genetic mutations, which are often used in evolutionary analysis.

Jin and his colleagues conducted association analyses of 16 basal mitochondrial DNA haplogroups, genetic families that trace back to a common ancestor.

They found that a specific variant group named M7 was consistently associated with a decreased risk of obesity. Further analysis identified a subgroup named M7b1a1 as the most likely source.

A 2019 study, by Professor Kong Qingpeng from the Chinese Academy of Sciences, published in Molecular Biology and Evolution, found that this specific subgroup “was mainly distributed in southern China and mainland Southeast Asia and exhibited considerable frequencies in southern Han Chinese individuals – about 5 to 14 per cent”.

Jin said a decreased mitochondrial function may be the reason why M7b1a1 reduces the risk of obesity.

“Decreased mitochondrial functions represent less energy conservation and more heat production, which could result in less weight gain,” he wrote in the paper.

The researchers also found that M7b1a1 appears to have undergone population expansion approximately 15,000 years ago.

Jin said this further supports their hypothesis, adding: “M7b1a1 carriers with greater heat generation may have adapted to the cold climate in the Ice Age well, which may have been evolutionarily advantageous for positive natural selection.

“Our findings … offer new insights into the genetic basis of obesity-related traits, enhancing our understanding of how genetics can influence body fat distribution and obesity risk.”