Inger Stallmann-Jorgensen

A 16-week randomized clinical trial of 2000 international units daily vitamin D3 supplementation in black youth: 25-hydroxyvitamin D, adiposity, and arterial stiffness.

CONTEXT Vitamin D insufficiency/deficiency is commonly observed in black youth. OBJECTIVE The aim was to determine 25-hydroxyvitamin D [25(OH)D] in response to 2000 IU vitamin D supplementation over time; to evaluate the relation between 25(OH)D concentrations and total body fat mass by dual-energy x-ray absorptiometry; and to determine whether vitamin D supplementation improves arterial stiffness measured by pulse wave velocity (PWV). DESIGN We conducted a randomized, blinded, controlled clinical trial. SETTING AND PARTICIPANTS Forty-nine normotensive black boys and girls, aged 16.3 ± 1.4 yr, were randomly assigned to either the control group (400 IU/d; n = 24) or the experimental group (2000 IU/d; n = 25). RESULTS Plasma 25(OH)D values at baseline and at 4, 8, and 16 wk were 34.0 ± 10.6, 44.9 ± 9.4, 51.2 ± 11.1, and 59.8 ± 18.2 nmol/liter, respectively, for the control group; and 33.1 ± 8.7, 55.0 ± 11.8, 70.9 ± 22.0, and 85.7 ± 30.1 nmol/liter, respectively, for the experimental group. The experimental group vs. the control group reached significantly higher 25(OH)D concentrations at 8 and 16 wk, respectively. Partial correlation analyses indicated that total body fat mass at baseline was significantly and inversely associated with 25(OH)D concentrations in response to the 2000-IU supplement across time. Furthermore, carotid-femoral PWV increased from baseline (5.38 ± 0.53 m/sec) to posttest (5.71 ± 0.75 m/sec) in the control group (P = 0.016), whereas in the experimental group carotid-femoral PWV decreased from baseline (5.41 ± 0.73 m/sec) to posttest (5.33 ± 0.79 m/sec) (P = 0.031). CONCLUSION Daily 2000 IU vitamin D supplementation may be effective in optimizing vitamin D status and counteracting the progression of aortic stiffness in black youth. Plasma 25(OH)D concentrations in response to the 2000 IU/d supplementation are negatively modulated by adiposity.

Low 25-Hydroxyvitamin D Levels in Adolescents: Race, Season, Adiposity, Physical Activity, and Fitness

OBJECTIVES: The objectives were to characterize the vitamin D status of black and white adolescents residing in the southeastern United States (latitude: ∼33°N) and to investigate relationships with adiposity. METHODS: Plasma 25-hydroxyvitamin D levels were measured with liquid chromatography-tandem mass spectroscopy for 559 adolescents 14 to 18 years of age (45% black and 49% female). Fat tissues, physical activity, and cardiovascular fitness also were measured. RESULTS: The overall prevalences of vitamin D insufficiency (<75 nmol/L) and deficiency (≤50 nmol/L) were 56.4% and 28.8%, respectively. Black versus white subjects had significantly lower plasma 25-hydroxyvitamin D levels in every season (winter, 35.9 ± 2.5 vs 77.4 ± 2.7 nmol/L; spring, 46.4 ± 3.5 vs 101.3 ± 3.5 nmol/L; summer, 50.7 ± 4.0 vs 104.3 ± 4.0 nmol/L; autumn, 54.4 ± 4.0 vs 96.8 ± 2.7 nmol/L). With adjustment for age, gender, race, season, height, and sexual maturation, there were significant inverse correlations between 25-hydroxyvitamin D levels and all adiposity measurements, including BMI percentile (P = .02), waist circumference (P < .01), total fat mass (P < .01), percentage of body fat (P < .01), visceral adipose tissue (P = .015), and subcutaneous abdominal adipose tissue (P = .039). There were significant positive associations between 25-hydroxyvitamin D levels and vigorous physical activity (P < .01) and cardiovascular fitness (P = .025). CONCLUSIONS: Low vitamin D status is prevalent among adolescents living in a year-round sunny climate, particularly among black youths. The relationships between 25-hydroxyvitamin D levels, adiposity, physical activity, and fitness seem to be present in adolescence.

Vitamin D3 Supplementation for 16 Weeks Improves Flow-Mediated Dilation in Overweight African-American Adults

BACKGROUND A growing body of evidence has linked vitamin D deficiency to increased risk of cardiovascular disease. Vitamin D deficiency is also more common in African Americans for whom an increased cardiovascular disease risk exists. This study sought to test the hypothesis that 16 weeks of 60,000 IU monthly supplementation of oral vitamin D(3) would improve flow-mediated dilation (FMD) in African Americans, whereas no change would be observed in the placebo group. METHODS A randomized, double-blind, placebo-controlled clinical trial was conducted. Fifty-seven African-American adults were randomly assigned to either the placebo group or vitamin D group. RESULTS Following 16 weeks of placebo (n = 23; mean age 31 ± 2 years) or 60,000 IU monthly oral vitamin D(3) (n = 22; mean age 29 ± 2 years), serum concentrations of 25-hydroxyvitamin D (25(OH)D) increased from 38.2 ± 3.0 to 48.7 ± 3.2 nmol/l and 34.3 ± 2.2 to 100.9 ± 6.6 nmol/l, respectively. No changes in serum parathyroid hormone (PTH), serum calcium, or urine calcium/creatinine were observed following either treatment. Following 16 weeks of treatment, significant improvements in FMD were only observed in the vitamin D group (1.8 ± 1.3%), whereas the placebo group had no change (-1.3 ± 0.6%). Similarly, the vitamin D group exhibited an increase in absolute change in diameter (0.005 ± 0.004 cm) and FMD/shear (0.08 ± 0.04 %/s(-1), area under the curve (AUC) × 10(3)) following treatment, whereas no change (-0.005 ± 0.002 cm and -0.02 ± 0.02 %/s(-1), AUC, respectively) was observed following placebo. CONCLUSION Supplementation of 60,000 IU monthly oral vitamin D(3) (~2,000 IU/day) for 16 weeks is effective at improving vascular endothelial function in African-American adults.

Leukocyte Telomere Length in Healthy Caucasian and African-American Adolescents: Relationships with Race, Sex, Adiposity, Adipokines, and Physical Activity

OBJECTIVE To examine the relationships of race, sex, adiposity, adipokines, and physical activity to telomere length in adolescents. STUDY DESIGN Leukocyte telomere length (T/S ratio) was assessed cross-sectionally in 667 adolescents (aged 14-18 years; 48% African-Americans; 51% girls) using a quantitative polymerase chain reaction method. Generalized estimating equations analyses were performed. RESULTS Telomere length was greater in the African-American adolescents than in the Caucasian adolescents (age- and sex-adjusted T/S ratio ± SE, 1.32 ± 0.01 vs 1.27 ± 0.01: P = .014) and greater in girls than in boys (age- and race-adjusted T/S ratio ± SE, 1.31 ± 0.01 vs 1.27 ± 0.01; P = .007). None of the adiposity or adipokine measures explained a significant proportion of the variance in telomere length. Vigorous physical activity was positively associated with telomere length (adjusted R(2) = 0.019; P = .009) and accounted for 1.9% of the total variance only in girls. CONCLUSIONS This study, conducted in a biracial adolescent cohort, demonstrated that (1) race and sex differences in telomere length have already emerged during adolescence; (2) adiposity and adipokines are not associated with telomere length at this age; and (3) the antiaging effect of vigorous physical activity may begin in youth, especially in girls.

FTO variant rs9939609 is associated with body mass index and waist circumference, but not with energy intake or physical activity in European- and African-American youth

BackgroundGenome-wide association studies found common variants in the fat mass and obesity-associated (FTO) gene associated with adiposity in Caucasians and Asians but the association was not confirmed in African populations. Association of FTO variants with insulin resistance and energy intake showed inconsistent results in previous studies. This study aimed to assess the influence of FTO variant rs9939609 on adiposity, insulin resistance, energy intake and physical activity in European - (EA) and African-American (AA) youth.MethodsWe conducted a cross-sectional study in EA and AA youths. One thousand, nine hundred and seventy-eight youths (48.2% EAs, 47.1% male, mean age 16.5 years) had measures of anthropometry. Percent body fat (%BF) was measured by dual-energy X-ray absorptiometry, visceral adipose tissue (VAT) and subcutaneous abdominal adipose tissue (SAAT) by magnetic resonance imaging. Energy intake and physical activity were based on self report from up to 7 24-hour recalls. Physical activity was also measured by accelerometry.ResultsFTO rs9939609 was significantly associated with body mass index (BMI) (P = 0.01), weight (P = 0.03) and waist circumference (P = 0.04), with per-allele effects of 0.4 kg/m2, 1.3 kg and 0.8 cm, respectively. No significant association was found between rs9939609 and %BF, VAT, SAAT or insulin resistance (P > 0.05), or between rs9939609 and energy intake or vigorous physical activity (P > 0.05). No significant interactions of rs9939609 with ethnicity, gender, energy intake or physical activity were observed (P > 0.05).ConclusionsThe FTO variant rs9939609 is modestly associated with BMI and waist circumference, but not with energy intake or physical activity. Moreover, these effects were similar for EAs and AAs. Improved understanding of the effect of the FTO variant will offer new insights into the etiology of excess adiposity.

General and visceral adiposity in black and white adolescents and their relation with reported physical activity and diet.

Background:Excess body fat accumulation may begin in youth and is linked with increased risk of cardiovascular disease. Examination of physical activity (PA) and diet behaviours predictive of adiposity may help target efforts to reduce chronic disease risk.Objective:We hypothesized that energy intake (EI) from fat, vigorous PA (VPA), and their interaction would predict body fat percentage (%BF) and visceral adipose tissue (VAT) in youth and that sedentary behaviours and intake of dairy, fruit, vegetable and whole grain foods would be related to adiposity.Design:A cross-sectional, observational study of reported PA and diet behaviours and objective adiposity measures.Subjects:Six-hundred sixty-one healthy black and white adolescents aged 14–18 years.Measurements:Diet by 24-h recalls using Nutrition Data Systems for Research (Minneapolis, MN, USA), VPA by previous day physical activity recalls (PAR), and %BF with dual-energy X-ray absorptiometry. VAT by magnetic resonance imaging for 434 subjects.Results:Reported EI and VPA were positively correlated with each other and were negative predictors of %BF. Time spent watching television or movies and %EI from protein were positive predictors of %BF. Adjusted for EI, none of the independent variables predictive of %BF retained their significance. %BF and VAT were highly correlated (r=0.73, P<0.0001). EI was the sole and negative predictor of VAT.Conclusions:Higher energy ‘throughput’, not energy restriction, characterize leaner youths. Youths should be advised to engage in VPA so that they can eat sufficient calories to obtain the nutrients required for optimal health while remaining lean.

Increased telomerase activity and vitamin D supplementation in overweight African Americans

Objective:We aimed to investigate whether vitamin D supplementation modulates peripheral blood mononuclear cell (PBMC) telomerase activity in overweight African Americans.Design:A double blind, randomized and placebo-controlled clinical trial (#NCT01141192) was recently conducted.Subjects And Methods:African-American adults were randomly assigned to either the placebo, or the vitamin D group (60 000 IU per month (equivalent to ∼2000 IU per day) oral vitamin D3 supplementation). Fresh PBMCs were collected from 37 subjects (18 in the placebo group and 19 in the vitamin D group), both at baseline and 16 weeks. PBMC telomerase activity was measured by the telomeric repeat amplification protocol.Results:Serum 25 hydroxyvitamin D levels increased from 40.7±15.7 at baseline to 48.1±17.5 nmol l–1 at posttest (P=0.004) in the placebo group, and from 35.4±11.3 at baseline to 103.7±31.5 nmol l–1 at posttests (P<0.0001) in the vitamin D group. In the vitamin D group, PBMC telomerase activity increased by 19.2% from baseline (1.56±0.29 absorbance reading unit (AU)) to posttest (1.86±0.42 AU, P<0.0001). The significance persisted after controlling for age, sex and body mass index (P=0.039). PBMC telomerase activity in the placebo group did not change from baseline (1.43±0.26 AU) to posttest (1.46±0.27 AU, P=0.157).Conclusion:Vitamin D supplementation significantly increased PBMC telomerase activity in overweight African Americans. Our data suggest that vitamin D may improve telomere maintenance and prevent cell senescence and counteract obesity-induced acceleration of cellular aging.

Lifestyle and Socioeconomic‐Status Modify the Effects of ADRB2 and NOS3 on Adiposity in European‐American and African‐American Adolescents

The aim of the study is to investigate the influence of and interaction between lifestyle behaviors (diet and physical activity (PA)) and single‐nucleotide polymorphisms (SNPs) in obesity‐candidate genes (ADRB2, APOB and NOS3) on general and central adiposity. Six‐hundred‐and‐twenty‐one European‐American (EA) and African‐American (AA) youths aged 13–19 years were classified by ethnicity (49% AA), gender (45% male), and socioeconomic status (SES). PA and dietary intake with up to seven 24‐h recalls were reported for all subjects. Percent body fat (%BF) was measured by dual‐energy X‐ray absorptiometry, visceral adipose tissue (VAT), and subcutaneous abdominal adipose tissue (SAAT) by magnetic resonance imaging. Reported energy intake (EI) and vigorous PA (VPA) were negative predictors of %BF and SAAT. Carriers of the NOS3 Asp298 allele had higher %BF only in the presence of an adverse environment (low SES). Compared to the most common NOS3 haplotype, homozygotes for haplotype A‐non4r‐Asp had 6.1% higher %BF. Significant interactions were revealed between the ADRB2 Arg16Gly SNP and VPA on VAT, SAAT and waist circumference (WC) such that Gly16 homozygotes may benefit less from increased VPA to reduce their weight. Genetic susceptibility to increased general and central adiposity is dependent on several factors, such as SES and vigorous exercise. Improved understanding of the joint effect of genes and lifestyle on adiposity will offer new insights into obesity and may provide new avenues for personalized prevention and treatment.

URINARY PROSTASIN: A POSSIBLE BIOMARKER FOR RENAL PRESSURE NATRIURESIS IN BLACK ADOLESCENTS

Prostasin is a membrane-bound/secretive serine protease interacting with aldosterone and the epithelial sodium channel in the kidney. We and others have previously proposed the concept of stress-induced pressure natriuresis (SIPN) where increased urinary sodium excretion (UNaV) is coupled with elevated blood pressure (BP) in response to behavioral stress in normotensive adolescents. This study thus aimed to test the relationship between prostasin and pressure natriuresis using the SIPN model. A cohort of 102 normotensive black adolescents (mean age: 17.0 ± 1.2 y; 56% females) were placed on a controlled sodium (4000 ± 200 mg/d) and potassium (2600 ± 200 mg/d) diet for three days before testing. The SIPN protocol consisted of a 1-h baseline period, a 1-h stress period (competitive video game), and a 1-h recovery period. During the stress period, BP elevation was coupled with an increase in UNaV. Urinary prostasin concentration had more than a 2-fold reduction from baseline (38.4 ± 32.7 ng/mL) to stress (17.2 ± 16.0 ng/mL), and further declined during recovery (12.1 ± 16.2 ng/mL) (p < 0.001). Urinary prostasin was inversely correlated with UNaV during stress (r = −0.43, p = 0.0001), even after being normalized by urinary creatinine. Our data suggest that urinary prostasin could be a novel biomarker and/or mechanism for renal pressure natriuresis in normotensive black adolescents.

High sodium intake is associated with short leukocyte telomere length in overweight and obese adolescents

Background/objectives:Telomere shortening has an important role in cellular aging. However, the impact of high sodium intake, an important risk factor of age-related diseases, on telomere shortening remains unknown. Therefore, we examined the relationship between high dietary sodium intake and leukocyte telomere length (LTL), particularly in the context of obesity, as obesity increases salt sensitivity.Subjects/methods:LTL was determined by a quantitative polymerase chain reaction method in 766 adolescents aged 14–18 years (50% females, 49% African Americans). Dietary sodium intake was assessed by seven independent 24-h dietary recalls. We divided the sample into low sodium (mean 2388±522 mg per day) or high sodium groups (mean 4142±882 mg per day) based on the median value (3280.9 mg per day).Results:In the entire cohort, there was no significant association between sodium intake and LTL (r=−0.05, P=0.24). However, there was a significant interaction between sodium intake and obesity status (P=0.049). Further multiple linear regression analyses revealed that higher dietary sodium intake was associated with shorter LTL in the overweight/obese group (body mass index ⩾85th percentile, β=−0.37, P=0.04), but not in the normal-weight group (β=0.01, P=0.93) after adjusting for multiple confounding factors. In the overweight/obese group, LTL was significantly shorter in the high sodium intake subjects vs low sodium intake subjects (1.24±0.22 vs. 1.32±0.20, P=0.02), but not the normal-weight group (1.29±0.24 vs 1.30±0.24, P=0.69).Conclusions:Higher dietary sodium intake is associated with shorter telomere length in overweight and obese adolescents.