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Browsing by Author "Alexander, Brenda M."

Now showing 1 - 3 of 3
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    Changes in Bone Mineral Density and Serum Lipids across the First Postpartum Year: Effect of Aerobic Fitness and Physical Activity
    Kyle, Erin M.; Miller, Hayley B.; Schueler, Jessica; Clinton, Michelle; Alexander, Brenda M.; Hart, Ann Marie; Larson-Meyer, D. Enette (MDPI, 2022-02-08)
    This study evaluated the changes in bone mineral density (BMD) and serum lipids across the first postpartum year in lactating women compared to never-pregnant controls, and the influence of physical activity (PA). The study also explored whether N-telopeptides, pyridinoline, and deoxypyridinoline in urine serve as biomarkers of bone resorption. A cohort of 18 initially lactating postpartum women and 16 never pregnant controls were studied. BMD (dual energy X-ray absorptiometry), serum lipid profiles, and PA (Baecke PA Questionnaire) were assessed at baseline (4–6 weeks postpartum), 6 months, and 12 months. Postpartum women lost 5.2 ± 1.4 kg body weight and BMD decreased by 1.4% and 3.1% in the total body and dual-femur, respectively. Furthermore, BMDdid not show signs of rebound. Lipid profiles improved, with increases in high-density lipoprotein-cholesterol (HDL-C) and decreases in low-density lipoprotein cholesterol (LDL-C) and the cholesterol/HDL-C ratio at 12 months (vs. baseline). These changes were not influenced by lactation, but the fall the Cholesterol/HDL-C ratio was influenced by leisure-time (p = 0.051, time X group) and sport (p = 0.028, time effect) PA. The decrease in BMD from baseline to 12 months in total body and dual femur, however, was greater in those who continued to breastfeed for a full year compared to those who stopped at close to 6 months. Urinary markers of bone resorption, measured in a subset of participants, reflect BMD loss, particularly in the dual-femur, and may reflect changes bone resorption before observed changes in BMD. Results provide support that habitual postpartum PA may favorably influence changes in serum lipids but not necessarily BMD. The benefit of exercise and use of urinary biomarkers of bone deserves further exploration.
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    Reflection of Dietary Iodine in the 24 h Urinary Iodine Concentration, Serum Iodine and Thyroglobulin as Biomarkers of Iodine Status: A Pilot Study
    Hlucny, Katelyn; Alexander, Brenda M.; Gerow, Kenneth G.; Larson-Meyer, D. Enette (MDPI, 2021-07-23)
    Background: The iodine status of the US population is considered adequate, but subpopulations remain at risk for iodine deficiency and a biomarker of individual iodine status has yet to be determined. The purpose of this study was to determine whether a 3 day titration diet, providing known quantities of iodized salt, is reflected in 24 h urinary iodine concentration (UIC), serum iodine, and thyroglobulin (Tg). Methods: A total of 10 participants (31.3 ± 4.0 years, 76.1 ± 6.3 kg) completed three, 3 day iodine titration diets (minimal iodine, US RDA, (United States Recommended Daily Allowance), and 3× RDA). The 24 h UIC, serum iodine, and Tg were measured following each diet. The 24 h UIC and an iodine-specific food frequency questionnaire (FFQ) were completed at baseline. Results: UIC increased an average of 19.3 μg/L for every gram of iodized salt consumed and was different from minimal to RDA (p = 0.001) and RDA to 3× RDA diets (p = 0.04). Serum iodine was different from RDA to 3× RDA (p = 0.006) whereas Tg was not responsive to diet. Baseline UIC was associated with iodine intake from milk (r = 0.688, p = 0.028) and fish/seafood (r = 0.646, p = 0.043). Conclusion: These results suggest that 24 h UIC and serum iodine may be reflective of individual iodine status and may serve as biomarkers of iodine status.
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    Vitamin D Synthesis Following a Single Bout of Sun Exposure in Older and Younger Men and Women
    Chalcraft, Jenna R.; Cardinal, Linda M.; Wechsler, Perry J.; Hollis, Bruce W.; Gerow, Kenneth G.; Alexander, Brenda M.; Keith, Jill F.; Larson-Meyer, D. Enette (MDPI, 2020-07-27)
    Older adults are frequently cited as an at-risk population for vitamin D deficiency that may in part be due to decreased cutaneous synthesis, a potentially important source of cholecalciferol (vitamin D3). Previous studies found that cutaneous D3 production declines with age; however, most studies have been conducted ex vivo or in the photobiology lab. The purpose of this study was to characterize the response of vitamin D metabolites following a 30-min bout of sun exposure (15-min each to the dorsal and ventral sides) at close to solar noon in younger and older adults. Methods: 30 healthy individuals with skin type II/III were recruited; a younger cohort, aged 20–37 (n = 18) and an older cohort (n = 12), age 51–69 years. Exposure was at outer limits of sensible sun exposure designed to enhance vitamin D synthesis without increasing risk of photo ageing and non-melanoma skin cancer. Serum D3 concentration was measured at baseline, 24, 48 and 72 h post-exposure. Serum 25(OH)D was measured at baseline and 72 h post-exposure plus 168 h post-exposure in the older cohort. Results: D3 increased in response to sun exposure (time effect; p = 0.002) with a trend for a difference in D3 between cohorts (time*group; p = 0.09). By regression modeling of continuous data, age accounted for 20% of the variation in D3 production. D3 production decreased by 13% per decade. Despite changes in D3, however, serum 25(OH)D did not change from baseline to 72 or 168 h post exposure (p > 0.10). Conclusions: Serum D3 concentration increased significantly in response to outdoor sun exposure in younger and older adults. While ageing may dampen cutaneous synthesis, sunlight exposure is still a significant source of vitamin D3.