Diane D. Stadler

Conflicting indicators of biotin status from a cross-sectional study of normal pregnancy.

OBJECTIVE To assess biotin nutritional status during normal human gestation. METHODS Urine samples were obtained in a cross-sectional design from 16 women in early pregnancy (17 +/- 1 weeks, mean +/- 1 SD) and from 13 women in late pregnancy (36 +/- 1 weeks). The urinary excretion of biotin, two metabolites bisnorbiotin (BNB) and biotin sulfoxide (BSO), and the organic acid 3-hydroxyisovaleric acid (3-HIA) were measured by HPLC/avidin-binding assay and GC/MS, respectively. Excretion rates were expressed as concentration ratios to urinary creatinine. RESULTS In both early and late pregnancy, 3-HIA excretion was increased compared to controls (p < 0.0001), suggesting decreased activity of a biotin-dependent enzyme caused by tissue biotin depletion. In early pregnancy, urinary excretion of biotin was normal; in late pregnancy, excretion was increased (p < 0.0002), suggesting biotin status was not decreased. In late pregnancy, urinary excretion of BNB and BSO were increased (p < 0.009). CONCLUSION The apparent conflict in the indices of biotin status is not explained by this study but could be resolved by two alternate explanations: 1) Pregnancy caused an impairment of renal reclamation of biotin, BNB, and BSO leading to a paradoxical increase in biotin excretion 2) Pregnancy caused metabolic or renal effects that increased 3-HIA excretion nonspecifically; hence, the increased 3-HIA excretion did not reflect biotin deficiency. We speculate that some of the women studied were marginally biotin deficient and that renal wasting and accelerated breakdown of biotin contributed to the deficiency.

Familial resemblance of bone mineralization, calcium intake, and physical activity in early-adolescent daughters, their mothers, and maternal grandmothers

OBJECTIVE To describe familial relationships among bone mineral density (BMD), calcium intake, and physical activity in early-adolescent daughters, their premenopausal mothers, and postmenopausal maternal grandmothers. SUBJECTS Healthy, early-adolescent daughter and premenopausal mother pairs (n=72) were enrolled in the study. In addition, a cohort of 22 postmenopausal maternal grandmothers were measured for comparison of related triads (n=22). DESIGN Cross-sectional measurements of hip (three sites) and lumbar spine BMD by dual energy x-ray absorptiometry (DXA), body height and weight, menstrual function, current calcium intake, and current and past physical activity patterns were assessed using recalls and questionnaires. STATISTICAL ANALYSIS Correlational analysis was used to establish relationships between bone characteristics and body size, menstrual function, calcium intake, and physical activity. Multiple regression analyses with backward elimination were used to examine heritability of bone characteristics in daughter-mother and mother-grandmother pairs and daughter-mother-grandmother triads. Quick cluster analysis and cross-tabulation with Pearsons chi(2) were used to evaluate familial patterns for bone characteristics and lifestyle practices. RESULTS Height, weight, and lumbar spine BMD were significantly correlated within mother-daughter pairs. Current and past calcium intakes were not related within pairs or triads or to BMD in the daughters or the grandmothers. A weak inverse relationship between calcium intake and the hip trochanter and lumbar spine BMD was observed in the mothers (R(2)=-0.25; P=.05). Physical activity, independent of calcium intake, was strong predictor of BMD for daughters and mothers. Among the daughters, the hertiability estimates for trochanter and lumbar spine BMD were 0.56 and 0.70, respectively (P<.01). The heritability estimate for premenopausal mothers were significant for lumbar spine BMD (h(2)=0.66; P<.01). Daughter-mother-grandmother triads with low physical activity had low femoral neck BMD whereas those with high physical activity had high femoral neck BMD (P<.001). APPLICATIONS Making physical activity a part of the daily routine, in addition to an adequate intake of calcium and bone-related nutrients, is an important goal for maintaining or improving bone health for women of all ages.

Predictors of bone mass by peripheral quantitative computed tomography in early adolescent girls

This cross-sectional study used peripheral quantitative computed tomography (pQCT) to evaluate the influences of age, body size, puberty, calcium intake, and physical activity on bone acquisition in healthy early adolescent girls. The pQCT technique provides analyses of volumetric bone mineral density (vBMD) (mg/cm(3)) for total as well as cortical and trabecular bone compartments and bone strength expressed as polar strength strain index (mm(2)). Bone mass of the nondominant distal and midshaft tibia by pQCT and lumbar spine and hip by dual X-ray absorptiometry (DXA) were measured in 84 girls ages 11-14 yr. Pubertal stage, menarche status, anthropometrics, and 3-d food intake and physical activity records were collected. Total and cortical bone mineral content and vBMD measurements by pQCT were significantly related to lumbar spine and femoral neck BMD measurements by DXA. We did not note any significant determinants or predictors for trabecular bone mass. Body weight was the most important predictor and determinant of total and cortical bone density and strength in healthy adolescent girls. Menarche, calcium intake, height, body mass index, and weight-bearing physical activity level age were also identified as minor but significant predictors and determinants of bone density and strength. Bone measurements by the pQCT technique provide information on bone acquisition, architecture, and strength during rapid periods of growth and development. Broader cross-sectional studies using the pQCT technique to evaluate the influence of age, gender, ethnicity, puberty, body size, and lifestyle factors on bone acquisition and strength are needed.

Effect of Long-Term Valproic Acid Administration on the Efficiency of Carnitine Reabsorption in Humans

To elucidate the etiology of valproic acid-induced carnitine deficiency, we tested the hypothesis that long-term valproic acid administration decreases the rate of carnitine reabsorption. Thirteen healthy men participated in a 34-day protocol in which carnitine clearance was measured before and after 28 days of valproic acid administration. During valproic acid administration (days 6 to 33), plasma free and total carnitine concentrations decreased (18% and 12%, respectively, P<.05) by 16 days, but returned to pretreatment concentrations by 28 days. From day 14 to day 30, the rate of free carnitine excretion was 50% lower than at baseline (day 4, P<.05). Free and total carnitine clearance, indexed to the glomerular filtration rate, was lower after valproic acid administration (P<.01). Contrary to our hypothesis, after 28 days of valproic acid administration, the rate of carnitine reabsorption was enhanced independent of the glomerular filtration rate and filtered load. Changes in the plasma concentration, rate of excretion, and clearance were specific for carnitine and were not generalized in magnitude or direction to the other amino acids. We conclude that the kidney adapts to conserve carnitine during valproic acid administration and therefore does not cause valproic acid-induced carnitine depletion in adults.

Effect of Breastfeeding Peer Counseling on Initiation and Duration of Breastfeeding among Adolescent Mothers

Abstract A breastfeeding initiation rate of 75% is a goal established by Healthy People 2000. Adolescent mothers are among the least likely to breastfeed their infants, thereby reducing their chance of meeting this goal. Peer counseling is an effective way to correct misinformation and to encourage breastfeeding among adolescent mothers. This study tested the hypothesis that peer counseling increases the rate at which breastfeeding is initiated and maintained to 6 weeks postpartum among adolescent mothers. Fifty-eight pregnant adolescents were recruited from the Teen Mother and Child Program (TMCP) to participate in a prospective randomized intervention trial. Informed consent was obtained from all teens who were considering breastfeeding. Women were randomly assigned to either a peer counselor intervention group (n=29) or control group (n=29). Peer counselors (n=6) ranging in age from 17 to 24 were trained through the WIC Program. Intervention group participants met individually with peer counselors during a prenatal clinic visit and received education and support for breastfeeding. They were contacted by telephone at least weekly after the birth of their baby. Breastfeeding was initiated by 100% and 96% of the intervention and control participants respectively, and maintained to 6 weeks postpartum by 54% and 40% of intervention and control group participants, respectively. Overall, TMCP initiation rates of 86% were reported. Compared to TMCP data collected between 1991-1996 which reported a 70% initiation rate, these results suggest a 16% increase in overall initiation rate. Exclusive breastfeeding was practiced by 75% and 42% of intervention and control participants, (p