Serum 25-hydroxyvitamin D (25-OH-D) in obese adolescents.

Endokrynol Pol. 2011;62(6):506-11.
Garanty-Bogacka B, Syrenicz M, Goral J, Krupa B, Syrenicz J, Walczak M, Syrenicz A.
Independent Laboratory of Propaedeutics of Children’s Diseases, Pomeranian Medical University, Szczecin, Poland. propedeutyka1 at wp.pl

BACKGROUND:
There is increasing evidence that vitamin D deficiency is common and has been associated with several non-bone related outcomes, including insulin resistance, type 2 diabetes and cardiovascular disease. The influences of gender, puberty, and adiposity on serum hydroxyvitamin D (25-OH-D) levels and the relationship between 25-OH-D and insulin resistance in obese children were studied.

MATERIAL AND METHODS:
Age, gender, pubertal stage, weight status (standard deviation score of body mass index: BMI-SDS, percentage body fat, waist circumference), 25-OH-D levels, and insulin resistance index calculated by homeostasis model assessment (HOMA-IR) were evaluated in 64 obese adolescents. Multivariable linear regression was used to determine factors associated with decreased serum 25-OH-D levels and to study the relationship between 25-OH-D and HOMA-IR.

RESULTS:
Median serum 25-OH-D level was 10.1 ng/mL (25.2 nmol/L).

• 14% of patients were vitamin D-sufficient (25-OH-D ? 20 ng/mL),
• 36% had intermediate values (11-19 ng/mL), and
• 50% were deficient (25-OH-D ? 10 ng/mL).

In the multivariable model, older age, puberty, higher value of percentage of body fat, and the presence of acanthosis nigricans (AN) were all negatively associated with 25-OH-D. Lower 25-OH-D levels were also associated with higher blood glucose, insulin and HOMA-IR after adjustment for puberty and SDS-BMI. Summer positively correlated with 25-OH-D level.

CONCLUSION:
Our study confirms that obesity is a risk factor for vitamin D deficiency. Hypovitaminosis D, common in obese adolescents at risk for type 2 diabetes (older age, puberty, acanthosis nigricans) is associated with worse insulin resistance.

PMID: 22144216

Table extracted from PDF file at the bottom of this page

The lower the value of p, the more probable the association.
p = 0 is extremely probable

	Endokrynologia Polska/Polish Journal of Endocrinology 2011; 62 (6)
	Table III. Clinical and biochemical characteristics of subjects based on vitamin D status Tabela III. Kliniczna i biochemiczna charakterystyka grupy badanej w zaleznosci od stezenia witaminy D w surowicy
	Sufficient > 20 ng/mL Insufficient < 20 ng/mL Deficient < 10 ng/ml p value n (%) 9 (14) 23 (36) 32 (50) Age, years (mean ± SD) 13.3 ± 2.5 14.8 ± 1.6 16.2 ± 2.3 0.025 Studied in winter, n (%) 1 (4) 9 (36) 16 (60) 0.078 Male/female, n (%) 7(21) / 2(7) 10(30) / 13(42) 16(49) /16(51) 0.450 Body mass, kg (mean ± SD) 67.5 ± 15.4 81.4 ± 15.6 87.8 ± 20.6 0.017 BMI-SDS (mean ± SD) 2.9 ± 0.6 3.5 ± 1.3 4.1 ± 1.7 0.086 Percentage of fat (mean ± SD) 29.3 ± 4.2 32.6 ± 4.3 36.9 ± 4.1 0.000 Waist-SDS [cm] (mean ± SD) 2.7 ± 1.0 3.4 ± 1.3 4.7 ± 1.7 0.001 Acanthosis nigricans, n (%) 1 (3) 5 (15) 27 (82) 0.000 SBP [mm Hg] (mean ± SD) 114.8 ± 8.2 119.4 ± 10.3 127.7 ± 8.9 0.000 DBP [mm Hg] (mean ± SD) 70.4 ± 8.3 74.4 ± 10.0 84.5 ± 8.9 0.000 25-OH-D [ng/mL] (mean ± SD) 24.1 ± 1.9 14.1 ± 2.9 6.8 ± 1.7 0.000 Glucose [mmol/L] (mean ± SD) 5.1 ± 0.2 5.3 ± 0.4 5.3 ± 0.4 0.286 Insulin [uU/mL] (mean ± SD) 13.5 ± 5.4 13.8 ± 5.5 25.7 ± 9.9 0.000 HOMA-IR median (min, max) 3.0 ± 1.3 3.1 ± 1.4 5.9 ± 2.2 0.000 HbA1c (%) (mean ± SD) 5.3 ± 0.2 5.4 ± 0.3 5.7 ± 0.3 0.000 T-chol [mg/dL] (mean ± SD) 159.2 ± 38.5 168.7 ± 24.5 183.2 ± 21.0 0.019 HDL-chol [mg/dL] (mean ± SD) 50.8 ± 9.1 54.2 ± 9.2 41.2 ± 9.2 0.000 LDL-chol [mg/dL] (mean ± SD) 87.6 ± 37.2 95.7 ± 45.4 113.0 ± 27.2 0.027 TG, mg/dL [mg/mL] (mean ± SD) 71.4 ± 38.7 93.7 ± 45.4 162.4 ± 43.0 0.003
	(Table III). Table III displays differences in clinical characteristics and results of biochemical investigations by vitamin D status. The risk of vitamin D deficiency/insufficiency was greater in winter (25/26) than in summer (30/38; p = 0.078). Sex was not associated with vitamin D sta­tus, although boys had higher mean serum 25-OH-D levels compared to girls (13.3 ± 7.2 vs. 10.4 ± 5.4 ng/mL; p = 0.07; data not shown). Pubertal stage (2-5 accord­ing to Tanner's scale) was not associated with vitamin D status (p = 0.126; data not shown). Both vitamin D deficiency and insufficiency were associated with higher body mass, (but not with BMI-SDS), higher content of fat tissue, greater waist cir­cumference (waist-SDS), and the presence of acanthosis nigricans, which was found in 97% of vitamin D deficient / insufficient patients. Adolescents with vitamin D defi-
	509

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