No abstract

No abstract

RIEDT, CLAUDIA S., ROBERT E. BROLIN, ROBERT M. SHERRELL, M. PAUL FIELD, AND SUE A. SHAPSES. True fractional calcium absorption is decreased after Roux-en-Y gastric bypass surgery. Obesity. 2006;14: 1940 -1948. Objective: Roux-en-Y gastric bypass (RYGB) is considered to be the gold standard alternative treatment for severe obesity. Weight loss after RYGB results primarily from decreased food intake. Inadequate calcium (Ca) intake and metabolic bone disease can occur after gastric bypass. To our knowledge, whether malabsorption of Ca contributes to an altered Ca metabolism in the RYGB patient has not been addressed previously. Research Methods and Procedures:We recruited 25 extremely obese women in order to study true fractional Ca absorption (TFCA) before and 6 months after RYGB surgery, using a dual stable isotope method ( 42 Ca and 43 Ca) and test load of Ca (200 mg). Hormones regulating Ca absorption and markers of bone turnover were also measured. Results: In 21 women (BMI 52.7 Ϯ 8.3 kg/m 2 , age 43.9 Ϯ 10.4 years) who successfully completed the study, TFCA decreased from 0.36 Ϯ 0.08 to 0.24 Ϯ 0.09 (p Ͻ 0.001) after RYGB. Bone turnover markers increased significantly (p Ͻ 0.01). TFCA correlated with estradiol levels (r ϭ 0.512, p Ͻ 0.02) and tended to correlate with 1,25 (OH) 2 D (r ϭ 0.427, p Ͻ 0.06) at final measurement. Stepwise linear regression indicated that estradiol explained 62% of the variance for TFCA at 6 months post-surgery (p Ͻ 0.01). Discussion: TFCA decreases (0.12 Ϯ 0.08) after RYGB surgery but remains within normal range. Although only some patients were estimated to have low Ca absorption after surgery, all of the patients showed a dramatic increase in markers of bone resorption. The alteration in Ca metabolism after RYGB-induced weight loss appears to be regulated primarily by estradiol levels and might ultimately affect bone mass.

No abstract

As paleoceanographic archives, deep sea coral skeletons offer the potential for high temporal resolution and precise absolute dating, but have not been fully investigated for geochemical reconstructions of past ocean conditions. Here we assess the utility of skeletal P/Ca, Ba/Ca and U/Ca in the deep sea coral D. dianthus as proxies of dissolved phosphate (remineralized at shallow depths), dissolved barium (trace element with silicate-type distribution) and carbonate ion concentrations, respectively. Measurements of these proxies in globally distributed D. dianthus specimens show clear dependence on corresponding seawater properties. Linear regression fits of mean coral Element/Ca ratios against seawater properties yield the equations: P/Ca coral (lmol/ mol) = (0.6 ± 0.1) P/Ca sw (lmol/mol) -(23 ± 18), R 2 = 0.6, n = 16 and Ba/Ca coral (lmol/mol) = (1.4 ± 0.3) Ba/Ca sw (lmol/ mol) + (0 ± 2), R 2 = 0.6, n = 17; no significant relationship is observed between the residuals of each regression and seawater temperature, salinity, pressure, pH or carbonate ion concentrations, suggesting that these variables were not significant secondary dependencies of these proxies. Four D. dianthus specimens growing at locations with O arag 6 0.6 displayed markedly depleted P/Ca compared to the regression based on the remaining samples, a behavior attributed to an undersaturation effect. These corals were excluded from the calibration. Coral U/Ca correlates with seawater carbonate ion: U/Ca coral (lmol/ mol) = (À0.016 ± 0.003) ½CO 2À 3 (lmol/kg) + (3.2 ± 0.3), R 2 = 0.6, n = 17. The residuals of the U/Ca calibration are not significantly related to temperature, salinity, or pressure. Scatter about the linear calibration lines is attributed to imperfect spatialtemporal matches between the selected globally distributed specimens and available water column chemical data, and potentially to unresolved additional effects. The uncertainties of these initial proxy calibration regressions predict that dissolved phosphate could be reconstructed to ±0.4 lmol/kg (for 1.3-1.9 lmol/kg phosphate), and dissolved Ba to ±19 nmol/kg (for 41-82 nmol/ kg Ba sw ). Carbonate ion concentration derived from U/Ca has an uncertainty of ±31lmol/kg (for 60-120 lmol=kg CO 2À 3 ). The effect of microskeletal variability on P/Ca, Ba/Ca, and U/Ca was also assessed, with emphasis on centers of calcification, Fe-Mn phases, and external contaminants. Overall, the results show strong potential for reconstructing aspects of water mass mixing and biogeochemical processes in intermediate and deep waters using fossil deep-sea corals.

No abstract

We suggest that WL is associated with elevated calcium requirements that, if not met, could activate the calcium-parathyroid hormone axis to absorb more calcium. Normal intakes of calcium during energy restriction result in inadequate total calcium absorption and could ultimately compromise calcium balance and bone mass.

No abstract