Tag: Science Daily

West African genes lower the risk of obesity in men, suggests study

Selected coverage: Medical Daily, Milwaukee Community Journal, Science Daily

African American men with a high degree of West African genetic ancestry have less central adiposity

The obesity epidemic affects women and men of every ethnic group in the United States, but strong gender and racial disparities in the risk of overweight and obesity exist. African American women are currently more at risk than any other group in the United States: 82.1% of African American women are overweight or obese (defined as having a BMI of 25 or higher), compared to 76.2% of Hispanic women and 64.6% of Caucasian women, according to the 2011-2012 National Health and Nutrition Examination Survey (NHANES). Socioeconomic factors, such as inequalities in access to healthcare, healthy food, and safe places to exercise, are known to be important causes of these and other racial disparities in health characteristics.

In contrast, “only” 69.1% of African American men are overweight or obese – a percentage that is still alarmingly high in absolute terms, but lower than the percentages for Caucasian men (73.2%), and Hispanic men (77.9%), according to the NHANES data. A similar pattern has been reported for type-2 diabetes, a disease strongly associated with overweight and obesity: according to a 2007 study in The American Journal of Public Health, the incidence of diabetes is higher among African American women (24.5%) than among Caucasian women (20.7%), but lower among African American men (16.7%) than among Caucasian men (19.6%).

Why do African American men have a relatively low risk of overweight, obesity, and diabetes, despite facing many of the same socioeconomic disadvantages as African American women? A new study in the open-access journal Frontiers in Genetics suggests that the cause may be partly genetic.

“Here we show that West-African genetic ancestry may afford protection against central adiposity in African American men, but not in African American women,” says Yann Klimentidis, Assistant Professor at the Epidemiology and Biostatistics Department of the University of Arizona, the study’s lead author.

Central adiposity (“belly fat”), the build-up of excess fat under the skin of the lower torso and around the internal organs, is a strong risk factor for obesity and diabetes, as well as for high blood pressure, high blood sugar, disease of the heart, liver, and pancreas, and some cancers.

In the new study, Klimentidis and colleagues analyze genetic data from 4,425 volunteers, all healthy African American women and men between the ages of 45 and 85. These data had been collected in the course of two prospective studies sponsored by the National Heart Lung and Blood Institute of the NIH: the Atherosclerosis Risk in Communities Study (ARIC) and the Multi-Ethnic Study of Atherosclerosis (MESA).

Klimentidis et al. focused on approximately 3,500 nucleotides (“letters” in the genome) that often differ between people from West Africa and Europe. In this way, they could estimate the degree of West African genetic ancestry – the fraction of the genome inherited from West African ancestors – for each participant in the study. A 2015 study in The American Journal of Human Genetics has shown that this fraction varies considerably among African Americans, due to differences in genetic contributions from ancestors from other ethnic groups, especially Europeans and Native Americans.

The new results show that the Waist Circumference and Waist-Hip Ratio tends to be lower in African American men with a high degree of West African genetic ancestry, indicating that they have less central adiposity than African American men with a lower degree of West African genetic ancestry. In contrast, there was no association between Waist Circumference and Waist-Hip Ratio and the degree of West African genetic ancestry in African American women.

The researchers conclude that the gene pool of the African American population contains one or more gene variants – originally inherited from West African ancestors — that give partial protection against central adiposity, but only when present in men. Further research is needed to identify these gene variants and the physiological mechanisms through which they operate, to help prevent and treat central obesity.

“There are still many unanswered questions, including: What are the specific genes that afford protection against central adiposity in men of West African ancestry, or conversely, What are the genes that predispose individuals of other ancestries to greater central adiposity? What cultural, socio-economic, or other factors might explain the lack of protection in African American women?” says Klimentidis.

“The reasons for group differences in multifactorial traits like obesity remain difficult to understand, especially when simplistic explanations do not easily explain complex patterns, like group differences which are not constant across sexes. We believe these new analyses begin to shed light on the factors underpinning the some ethnic disparities in obesity,” says David Allison, Distinguished Professor of Public Health and Director of the Nutrition Obesity Research Center at University of Alabama at Birmingham, a coauthor on the study.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2016-06/f-wag052316.php

Study: http://journal.frontiersin.org/article/10.3389/fgene.2016.00089/full

Re-energizing the aging brain

Selected Coverage: Science Daily

The human brain has a prodigious demand for energy — 20 to 30% of the body’s energy budget. In the course of normal aging, in people with neurodegenerative diseases or mental disorders, or in periods of physiological stress, the supply of sugars to the brain may be reduced. This leads to a reduction in the brain’s energy reserves, which in turn can lead to cognitive decline and loss of memory.

But new research on mice shows that the brain’s energy reserves can be increased with a daily dose of pyruvate, a small energy-rich molecule that sits at the hub of most of the energy pathways inside the cell. These results need to be replicated in human subjects, but could ultimately lead to clinical applications.

“In our new study, we show that long-term dietary supplementation with pyruvate increases the energy reserves in the brain, at least in mice, in the form of the molecules glycogen, creatine and lactate,” says lead author Heikki Tanila, Professor of Molecular Neurobiology at the A. I. Virtanen Institute of the University of Eastern Finland.

What’s more, dietary supplementation with pyruvate didn’t only increase the brain’s energy stores: it also changed the behavior of the mice in positive ways, show the researchers.

“The mice became more energetic and increased their explorative activity. It appears that these behavioral changes are directly due to the effect of pyruvate on brain function, since we didn’t find that these mice had developed greater muscle force or endurance,” says Tanila.

For example, chronic supplementation with pyruvate facilitated the spatial learning of middle-aged (6- to 12-months-old) mice, made them more interested in the odor of unfamiliar mice, and stimulated them to perform so-called “rearing”, an exploratory behavior where mice stand on their hind legs and investigate their surroundings (photo).

The dose necessary to achieve these effects was about 800 mg pyruvate per day – which corresponds to about 10 g per day in humans — given to the mice in normal chow over a period of 2.5 to 6 months. A single large dose of pyruvate injected directly into the blood stream had no detectable effect.

Interestingly, the positive response to dietary supplementation with pyruvate was also found in a strain of transgenic mice called APPswe/PS1dE9, often used as an animal model for the study of Alzheimer’s disease. These mice exhibit many of the same symptoms as people with Alzheimer’s, such as the deposition of protein plaques in the brain, neurodegeneration, and cognitive decline. These results raise hopes that pyruvate might also benefit people with neurodegenerative disorders such as Alzheimer’s and Parkinson’s.

“Pyruvate supplementation may prove beneficial as an activating treatment for the elderly and in therapies for alleviating cognitive decline due to aging, neurodegenerative disease, or mental disorders. It is well tolerated and warrants further studies in humans,” says Tanila.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2016-03/f-rta031016.php

Study: http://journal.frontiersin.org/article/10.3389/fnagi.2016.00041/full