The relationship between obesity and serum 1,25-dihydroxy vitamin D concentrations in healthy adults.
Several previous reports of small cohorts have found significantly higher serum 1,25-dihydroxy vitamin D (1,25-vit D) in obese compared with nonobese whites. Based on these reports and on recent in vitro studies of adipocytes which suggest that administration of 1,25-vit D can stimulate lipogenesis and inhibit lipolysis, some investigators have proposed that high 1,25-vit D may play a role in promoting or maintaining adipocyte triglyceride stores in obese adults. To test the hypothesis that obesity is commonly associated with increased 1,25-vit D, we examined the relationships between calciotropic hormones and body adiposity in a large cohort of healthy adults. Serum intact PTH, 25-hydroxy vitamin D, and 1,25-vit D were measured in the postabsorptive state in 302 healthy adults who were Caucasian (n = 190; 71% female), African-American (n = 84; 89% female), and of other race/ethnicity (n = 28; 61% female). Results from the 154 obese subjects [body mass index (BMI) 37.3 +/- 5.8 kg/m(2); range, 30.1-58.2 kg/m(2)] were compared with those from 148 nonobese (BMI 25.6 +/- 2.9 kg/m(2); range, 18.0-29.9 kg/m(2)) age-, race-, and sex-matched participants. Body composition was measured by dual energy x-ray absorptiometry. Serum intact PTH was positively correlated with both BMI (r = 0.42; P < 0.0001) and body fat mass (r = 0.37; P < 0.0001). Serum 25-hydroxy vitamin D was negatively correlated with BMI (r = -0.4; P < 0.0001) and body fat mass (r = -0.41; P < 0.0001). Serum 1,25-vit D was also negatively correlated with BMI (r = -0.26; P < 0.0001) and body fat mass (r = -0.25; P = 0.0001). Serum 1,25-vit D was significantly lower in obese than nonobese subjects (105.7 +/- 41.1 vs. 124.8 +/- 36.7 pmol/liter; P < 0.0001) in both Caucasian and African-American adults. We conclude that, because 1,25-vit D concentrations fall with increasing adiposity, it appears unlikely that elevation in 1,25-vit D is an important hormonal mechanism causing or maintaining obesity in adults.
GlaxoSmithKline Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA. shamik.j.parikh@gsk.com
Shamik J
SJ
Parikh
Marni
M
Edelman
Gabriel I
GI
Uwaifo
Renee J
RJ
Freedman
Mariama
M
Semega-Janneh
James
J
Reynolds
Jack A
JA
Yanovski
D000293:Adolescent; D000328:Adult; D000368:Aged; D002118:Calcium / Q000378:metabolism; D015331:Cohort Studies; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*; D012044:Regression Analysis; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood*
D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D002118:Calcium