Background: Obesity is associated with hyperleptinemia and endothelial dysfunction. Hyperleptinemia has been reported to induce both oxidative stress

Background: Adolescent mothers may be at increased risk of irreversible bone loss during pregnancy and lactation, particularly when calcium intake is low. Objective: Longitudinal changes in bone mass from lactation to postweaning were evaluated in 10 adolescent mothers aged 15–18 y who habitually consumed <500 mg Ca/d. Design: Total-body bone mineral content (TBBMC), total-body bone mineral density (TBBMD), and lumbar spine bone mineral density (LSBMD) were measured at lactation (6–24 wk postpartum) and after weaning (12–30 mo postpartum). Serum hormones (intact parathyroid hormone, estradiol, and prolactin), serum calcium, and markers of bone turnover [urinary N-telopeptide cross-linking region of type I collagen (NTx) and plasma activity of bone alkaline phosphatase] were measured at lactation. Results: TBBMC, total calcium content, TBBMD, and LSBMD increased from lactation to postweaning (P < 0.01). TBBMD and LSBMD were, respectively, 3.6% and 9.7% lower than predicted at lactation and 0.3% and 4.8% lower than predicted in the postweaning period. The increase in age-matched TBBMD adequacy was correlated with the time after resumption of menses (r = 0.86, P < 0.01). Calcium accretion from lactation to postweaning correlated negatively with estradiol (r = −0.86) and prolactin (r = −0.69) and positively with intact parathyroid hormone (r = 0.72) and NTx (r = 0.84) measured at lactation (P < 0.05). Conclusions: It appears that adolescent mothers with habitually low calcium intakes recover from lactation-associated bone loss after weaning. The rate of bone accretion, however, may not be sufficient to attain peak bone mass at maturity. Hormones regulating bone turnover during lactation may influence bone recovery in adolescent mothers.

Background: Pregnancy and lactation in adolescents with habitually low calcium intake may adversely affect maternal bone mass.

The aim of this study was to evaluate the effect of organic grape juice intake on biochemical variables and microcirculatory parameters in triathlon athletes. The physiological stress that is imposed by a strenuous sport, such as a triathlon, together with an insufficient amount of antioxidants in the diet may cause oxidative imbalance and endothelial dysfunction. Ten adult male triathletes participated in this study. A venous blood sample was drawn before (baseline) and after 20 days of organic grape juice intake (300 ml/day). Serum insulin, plasma glucose and uric acid levels, the total content of polyphenols, and the erythrocyte superoxide dismutase activity were determined. The functional microcirculatory parameters (the functional capillary density, red blood cell velocity at baseline and peak levels, and time required to reach the peak red blood cell velocity during postocclusive reactive hyperemia after a one-min arterial occlusion) were evaluated using nailfold videocapillaroscopy. Compared with baseline levels, the peak levels of serum insulin ( p = 0.02), plasma uric acid ( p = 0.04), the functional capillary density ( p = 0.003), and the red blood cell velocity (p < 0.001) increased, whereas the plasma glucose level (p,0.001), erythrocyte superoxide dismutase activity ( p = 0.04), and time required to reach red blood cell velocity during postocclusive reactive hyperemia ( p = 0.04) decreased after organic grape juice intake. Our data showed that organic grape juice intake improved glucose homeostasis, antioxidant capacity, and microvascular function, which may be due to its high concentration of polyphenols. These results indicate that organic grape juice has a positive effect in endurance athletes.

Physiologic adaptation to the high calcium demand during pregnancy and lactation may be different in adolescents than in adults, particularly at low calcium intake. The aim of this cross-sectional study was to compare biochemical markers of calcium and bone metabolism between adolescent (14–19 y) and adult (21–35 y) women with calcium intake ∼500 mg/d, in three different physiologic states, i.e., control (nonpregnant, nonlactating; NPNL), pregnant and lactating. Markers of calcium metabolism [serum Ca, P and intact parathyroid hormone (iPTH); urinary Ca and P] and of bone turnover [urinary deoxypyridinoline (D-Pyr) and plasma bone alkaline phosphatase (BAP)] were measured in NPNL (adolescents, n = 12 and adults, n = 25), pregnant (adolescents, n = 30 and adults, n = 36) and lactating (adolescents, n = 19 and adults, n = 26) women. In the NPNL women, iPTH, D-Pyr and BAP were higher (P < 0.001) and urinary Ca was lower (P < 0.001) in adolescents than in adults. Serum iPTH was higher (P < 0.001) and urinary Ca was lower (P < 0.01) in adolescents than in adults also in pregnancy and lactation. Compared with NPNL women, serum Ca decreased (P < 0.001) with pregnancy in adolescents but not in adults. The increase in D-Pyr with pregnancy and lactation was very pronounced in adults (∼130%, P < 0.001) but less in adolescents (<25%, P < 0.01). BAP increased (P < 0.001) with pregnancy and lactation in adults (∼60%) but decreased (P < 0.001) with pregnancy in adolescents (∼13%). Pregnancy and lactation appear to affect bone turnover in adolescent and adult women with low calcium intake differently.