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Scientists discover new obesity gene

Researchers have discovered that the obesity-associated elements within the gene FTO interact with IRX3, a distant gene on the genome that appears to be the functional obesity gene.

Senior study author Marcelo Nobrega, PhD, associate professor of human genetics at the University of Chicago, said that their data strongly suggest that IRX3 controls body mass and regulates body composition, asserting that any association between FTO and obesity appears due to the influence of IRX3.

Hoping to explain these observations, Nobrega and his team mapped the behavior of promoters—regions of DNA that activate gene expression—located within one million base pairs on either side of the FTO gene. In adult mice brains, where FTO was thought to affect metabolic function, they discovered that the promoter that turns on FTO did not interact with obesity-associated FTO introns.

Co-author Jose Luis Gomez-Skarmeta, PhD, a geneticist at the Andalusian Center of Developmental Biology in Sevilla, Spain, said that instead they found that the promoter for IRX3, a gene several hundred thousand base pairs away, did interact with these introns, as well as a large number of other elements across the vast genetic distance we studied. The researchers found a similar pattern of interactions in humans after analysing data from the ENCODE project, which they confirmed with experiments on human cells.

Using data from 153 brain samples from individuals of European ancestry, they discovered that the mutations to FTO introns that affected body weight are associated with IRX3 expression, but not FTO. Obesity-related FTO introns enhanced the expression of IRX3, functioning as regulatory elements. The FTO gene itself did not appear to play a role in this interaction.

Genetic factors that help humans break down milk identified

Researchers have found that the beginning and successive spread of cattle domestication in Africa is behind humans’ ability to digest milk sugar lactose.

The findings provide strong evidence that lactase persistence evolved in human populations as a dietary adaptation.

Study author Sarah Tishkoff of the University of Pennsylvania, said that the study sheds light on both the genetic basis and evolutionary history of a biologically relevant trait in humans and the origins of pastoralism in Africa. Individuals with northern European ancestry, as well as African, Arabian, and Central Asian pastoral populations with a tradition of fresh-milk production and consumption, retain high levels of lactase into adulthood.

Tishkoff, along with co-researcher Alessia Ranciaro, performed a large-scale sequencing analysis of all of the genomic regions thought to influence the activity of the lactase-encoding LCT gene in 819 individuals from 63 diverse African populations and in 154 non-Africans from nine different populations in Europe, the Middle East, and Central and East Asia.

They identified several single-nucleotide variants—DNA sequence variations affecting a single nucleotide—associated with lactase persistence.
Moreover, their genetic analysis revealed strong evidence of recent positive selection affecting several variants associated with this trait in African populations, most likely in response to the cultural development of pastoralism.

Diet-rich meat and fish boost health in older men

A new study from Japan suggests that older men could gain a boost physically, mentally and socially, if they eat a diet rich in meat and fish.

This study of more than 1,000 older adults suggested that men who ate the most meat and fish reduced their odds of mental and physical decline by 39 percent, compared with men who ate the least animal protein, CBS News reported.

But the same association was not seen in women. Nor were the same benefits linked to proteins from plants, the researchers found.

However, the study doesn’t actually prove that eating meat and fish caused the men’s health improvements, or that low animal protein intake contributes to early decline.
Lona Sandon, an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas, said that it is an observational study that simply shows a relationship between protein and
functional decline.

It does not prove cause and effect, Sandon said.

Still, research indicates adequate protein intake is important as people age, Sandon noted.

The ability to process protein may decline in old age. As a result, protein requirements may increase, the study suggested.

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