Research news from the Friedman School of Nutrition Science and Policy at Tufts University

(1) Genetics Research and Obesity
(2) Osteoporosis Prevention and Vitamin B12

Genetics Research Unlocks a Key Regulator of Weight in Women

“He can eat like a horse.” “She eats like a bird.”

Recently, Jose Ordovas, PhD, and colleagues shed some light on a genetic factor in obesity. Ordovas, director of the Nutrition and Genomics Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University uncovered two variants in the perilipin gene that influence body weight in white women.

The perilipin gene determines how much perilipin protein is produced and perilipin protein, in turn, controls the breakdown of fat within the cell. More perilipin means more fat is stored in the cells. Research to date has shown that people with more perilipin protein store more fat. Ordovas and his colleagues have identified two variations at the perilipin gene locus which appear to affect the expression or activity of the perilipin proteins.

“Our findings show that variations in the perilipin gene locus may play a role in determining obesity risk in women,” said Ordovas, a leading nutrigenomics scientist. “Perilipin is the guardian of the fat cell, a kind of moat that determines how frequently the drawbridge is used to release fat – if the drawbridge isn’t used, fat stays stored.”

Ordovas compared four common variants found at the perilipin gene site with measurements of body fat percentage and waist circumference in over 700 white men and women. Women with two of the genetic variations tended to have higher body fat and greater waist circumference than women with the other variants. Men’s body shape and size did not appear to be affected by the same variants in the gene. The researchers think that this may be due to hormonal differences between men and women .

“Our data show that the perilipin gene locus may be a significant genetic determinant for obesity risk in white women,” continued Ordovas, who is also a professor at the Friedman School of Nutrition Science and Policy at Tufts. “Understanding more about these genetic variations will contribute to our ability to create effective treatments for obesity.”

Qi, L., Shen, H., Larson, I., Schaefer, E., Greenberg, A., Tregouet, D., Corella, D., Ordovas, J., Obesity Research, 2004 Nov: 12 (11): 1758-1765 “Gender-Specific Association of a Perilipin Gene Haplotype with Obesity Risk in a White Population.”

Qi, L, Corella, D., Sorlí, J.V., Portolés, O., Shen, H., Coltell, O., Godoy, D., Greenberg, A.S., Ordovas, J.M. Clinical Genetics, 2004 Oct;66 (4):299-310, “Genetic variation at the perilipin (PLIN) locus is associated with obesity-related phenotypes in White women.”

Researchers In Quest of Osteoporosis Prevention Find Benefits In Vitamin B12

It can’t be said enough: an ounce of prevention is worth a pound of bone. An estimated 40% of women and 13% of men are at high risk of an osteoporotic fracture in their lifetime. When these fractures occur in older individuals, quality of life can decrease, sometimes dramatically. Osteoporosis is also associated with higher mortality. New research conducted by Katherine Tucker, PhD, director of the Dietary Assessment and Epidemiology Research Program at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, examined dietary factors in relation to osteoporosis and uncovered a positive association between vitamin B12 and bone health. In other words, the authors conclude that vitamin B12 deficiency may be an important modifiable risk factor for osteoporosis.

“Osteoporosis is becoming a much greater issue now that people are living so much longer,” said lead author Tucker, also a professor at the Friedman School of Nutrition Science and Policy at Tufts. “Our study provides support for a way in which people can actively lower their risk of osteoporosis and help to preserve quality of life.”

Tucker and her colleagues measured bone mineral density–a measure of bone quality–and vitamin B12 level in more than 2,500 men and women participating in the Framingham Osteoporosis Study. They found that both men and women with low vitamin B12 levels had on average lower bone mineral densities–putting them at greater risk of osteoporosis–than men and women with higher levels. The men exhibiting low vitamin B12 levels had significantly lower bone density in several areas of the hip, and the women exhibiting low vitamin B12 levels had particularly low bone density in the spine.

“This is the first large scale study of its kind to show an association between low vitamin B12 and low bone mineral density in men and it confirms other reports of this association in women,” said Tucker, “It shows that getting enough vitamin B12 from meats, poultry, fish and dairy products may be important for both men and women in maintaining strong bones. Some individuals, particularly older people, have difficulty absorbing vitamin B12 from foods, however, and inclusion of breakfast cereals fortified with vitamin B12 or use of vitamin B12 supplements offers additional protection.”

Tucker K., et al, Journal of Bone and Mineral Research, 2005 Jan;20(1):152-8. “Low plasma vitamin B12 is associated with lower bone mineral density: the Framingham Osteoporosis Study.”