VITAMIN D RECEPTOR FOKI GENOTYPE INFLUENCES BONE MINERAL DENSITY RESPONSE TO STRENGTH TRAINING

Authors: RABON-STITH, KARMA - UNIV MD, KINESIOLOGY; HAGBERG, JAMES - UNIV MD, KINESIOLOGY; PHARES, DANA - UNIV MD, KINESIOLOGY; KOSTEK, MATTHEW - UNIV MD, KINESIOLOGY; DELMONICO, MATTHEW - UNIV MD, KINESIOLOGY; ROTH, STEPHEN - UNIV MD, KINESIOLOGY; FERRELL, ROBERT - U PITTSBRG, GENETICS; CONWAY, JOAN; RYAN, ALICE - UMD,BALTIMORE, GRECC; HURLEY, BEN - UNIV MD, KINESIOLOGY

Submitted to: Experimental Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2005
Publication Date: 5/12/2005
Citation: Rabon-Stith, K.M., Hagberg, J.M., Phares, D.B., Kostek, M.C., Delmonico, M.J., Roth, S.M., Ferrell, R.E., Conway, J.M., Ryan, A.S., & Hurley, B.F. 2005. Vitamin D receptor (VDR) FOKI genotype influences bone mineral density response to strength training, but not aerobic training. Experimental Physiology. 90: 653-661.

Interpretive Summary: Earlier studies have shown that the bone mineral density response to exercise varies with type of exercise. To determine the influence of the vitamin D receptor (VDR) gene FokI genotype on bone mineral density response to two exercise training modalities, 206 healthy men and women were studied before and after four to six months of either aerobic exercise training (AT) or strength training (ST). One hundred and twenty-three older (50-85 years) adults completed AT and 83 subjects completed ST. DNA was extracted from blood samples of all subjects and genetic typing was performed at a specific gene locus, the VDR FokI, to determine its association to training response. Total body, greater trochanter, and femoral neck bone mineral density (BMD) was measured before and after AT and ST exercise programs using dual-energy x-ray absorptiometry. The VDR FokI genotype was significantly related to ST- but not AT - induced changes in femoral neck BMD (P less than 0.05). The heterozygotes (Ff) in the ST group approached a significantly greater increase in femoral neck BMD (P = 0.058) compared to ff homozygotes. There were no significant genetic relationships in the AT group. These data indicate that VDR FokI genotype may influence femoral neck BMD response to ST, but not AT. These findings will have impact on the design of exercise regimens for older Americans who are desirous of increasing bone mineral density and are of interest to health professionals, physical therapists and exercise physiologists.

Technical Abstract: To determine the influence of the vitamin D receptor (VDR) gene FokI genotype on bone mineral density response to two exercise training modalities, 206 healthy men and women (50-85 yrs) were studied before and after about four to six months of either aerobic exercise training (AT) or strength training (ST). One hundred and twenty-three subjects completed AT (n = 51 men & 72 women) and 83 subjects completed ST (n = 40 men & 43 women). DNA was extracted from blood samples of all subjects and genotyping was performed at the VDR FokI locus to determine its association to training response. Total body, greater trochanter, and femoral neck bone mineral density (BMD) was measured before and after both training programs using dual-energy x-ray absorptiometry. VDR FokI genotype was significantly related to ST- but not AT - induced changes in femoral neck BMD (P less than 0.05). The heterozygotes (Ff) in the ST group approached a significantly greater increase in femoral neck BMD (P = 0.058) compared to f homozygotes. There were no significant genotype relationships in the AT group. These data indicate that VDR FokI genotype may influence femoral neck BMD response to ST, but not AT.