Jornada Baiana de neurocirurgia

Sessão Cirúrgica do Colégio Brasileiro de Cirugiões Capítulo Bahia

Participem....

Suplemento de Vitamina K reduz a progressão da resistencia a insulina em idosos

Vitamin K Supplements Reduce Progression of Insulin Resistance in Older Men  CME

News Author: Laurie Barclay, MD
CME Author: Laurie Barclay, MD 

 

October 29, 2008 — Vitamin K supplementation for 36 months at doses attainable in the diet may reduce progression of insulin resistance in older men, according to the results of a randomized controlled trial reported in the November issue of Diabetes Care.

"Vitamin K has a potentially beneficial role in insulin resistance, but evidence is limited in humans," write Makiko Yoshida, PhD, from the Jean Mayer US Department of Agriculture Human Nutrition Research Center, Tufts University in Boston, Massachusetts, and colleagues. "We tested the hypothesis that vitamin K supplementation for 36 months will improve insulin resistance in older men and women."

This was an ancillary study of a 36-month, randomized, double-blind, controlled trial evaluating the effect on bone loss of supplementation with 500 µg/day of phylloquinone in 355 older nondiabetic men and women. Age range was 60 to 80 years, and 60% were women. The main endpoint of this ancillary study was insulin resistance at 36 months, measured by homeostasis model assessment of insulin resistance (HOMA-IR). Secondary endpoints were fasting plasma insulin and glucose levels.

There was a significant interaction between sex and treatment (P = .02), with HOMA-IR significantly lower at the 36-month visit among men in the supplement group vs men in the control group (P = .01), after adjustment for baseline HOMA-IR, body mass index (BMI), and change in body weight. For women, outcome measures did not differ significantly between intervention groups.

Limitations of this study include failure to test the effect of this intervention on postglucose challenge measures of insulin resistance, overweight or obesity more prevalent in women who received vitamin K supplementation vs those who did not, and possibly insufficient statistical power to detect statistically significant differences in HOMA-IR in response to vitamin K supplementation in women.

Other limitations include analyses of data obtained from a study designed to determine the effect of vitamin K supplementation on changes in bone mineral density and vascular calcification in older men and women; findings possibly not representative of the general population; use of HOMA-IR, which only provides an indirect estimate of insulin resistance vs the hyperinsulinemic euglycemic clamp; body composition evaluation limited to BMI and percent body fat; and predominantly Caucasian sample.

"Vitamin K supplementation for 36 months at doses attainable in the diet may reduce progression of insulin resistance in older men...but not in older women," the study authors write. "As the parent study was not designed to test this hypothesis, these findings need to be replicated in a study designed specifically to test the hypothesis that vitamin K plays a protective role in insulin resistance in older adults."

The US Department of Agriculture, the National Institutes of Health, and the American Heart Association supported this study. Dr. Yoshida was supported by a Graduate Student Scholarship from the Ministry of Education, Culture, Sports and Technology of Japan. Another study author was supported by a Career Development Award from the American Diabetes Association and by the National Institute of Diabetes and Digestive and Kidney Diseases. Hermes Arznemittel, Munich, Germany, donated the supplements used for this study.

Diabetes Care. 2008;31:2092-2096.