Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups

Surviving prolonged fasting implies closely regulated alterations in fuel provisioning to meet metabolic requirements, while preserving homeostasis. Little is known, however, of the endocrine regulations governing such metabolic adaptations in naturally fasting free-ranging animals. The hormonal responses to natural prolonged fasting and how they correlate to the metabolic adaptations observed, were investigated in subantarctic fur seal (Arctocephalus tropicalis) pups, which, because of the intermittent pattern of maternal attendance, repeatedly endure exceptionally long fasting episodes throughout their development (1–3 mo). Phase I fasting was characterized by a dramatic decrease in plasma insulin, glucagon, leptin, and total L-thyroxine (T4) associated with reductions in mass-specific resting metabolic rate (RMR), plasma triglycerides, glycerol, and urea-to-creatine ratio, while nonesterified fatty acids (NEFA) and β-OHB increased. In contrast, the metabolic steady-state of phase II fasting reached within 6 days was associated with minimal concentrations of insulin, glucagon, and leptin; unchanged cortisol and triiodothyronine (T3); and moderately increased T4. The early fall in insulin and leptin may mediate the shift to the strategy of energy conservation, protein sparing, and primary reliance on body lipids observed in response to the cessation of feeding. In contrast to the typical mammalian starvation response, nonelevated cortisol and minimal glucagon levels may contribute to body protein preservation and downregulation of catabolic pathways, in general. Furthermore, thyroid hormones may be involved in a process of energy conservation, independent of pups' nutritional state. These original hormonal settings might reflect an adaptation to the otariid repeated fasting pattern and emphasize the crucial importance of a tight physiological control over metabolism to survive extreme energetic constraints.

Prevention of aromatase inhibitor-induced bone loss with alendronate in postmenopausal women: the BATMAN trial

Abstract:
Postmenopausal women on aromatase inhibitors (AI) are at risk of aromatase inhibitor-associated bone loss (AIBL) and fractures.

In 2005 Osteoporosis Australia proposed an algorithm for bisphosphonate intervention. Three hundred and three postmenopausal women with early breast cancer (EBC) were enrolled (osteoporotic, n=25; osteopaenic, n=146; normal bone mineral density (BMD), n=126). Weekly alendronate (70 mg) treatment efficacy as triggered by the algorithm in preventing bone loss was evaluated. All patients received anastrozole (1 mg daily), calcium and vitamin D.

Results:
All osteoporotic patients received alendronate at baseline. Eleven out of the 146 (7.5%) osteopaenic patients commenced alendronate within 18 months of participation and eleven commenced after. One hundred and twenty four out of the 146 (84.9%) osteopaenic patients and all 126 with normal baseline BMD did not trigger the algorithm.

At three years, lumbar spine mean BMD increased (15.6%, p<0.01) in the osteoporotic group. BMD in the osteopaenic group with early intervention significantly increased at three years (6.3%, p=0.02). No significant change was seen in the late intervention group. No change was observed in those with osteopaenia without alendronate.

There was a significant drop in lumbar spine (−5.4%) and hip (−4.5%) mean BMD, in the normal BMD group, none of whom received alendronate.

Fracture data will be presented.

Conclusion:
In postmenopausal women with endocrine-responsive EBC, BMD improved over time when a bisphosphonate is administered with anastrozole in osteoporotic patients using an osteoporosis schedule. Subjects with normal baseline BMD experienced the greatest BMD loss, although none became osteoporotic.

Study protocol: the childhood to adolescence transition study (CATS)

Background
Puberty is a multifaceted developmental process that begins in late-childhood with a cascade of endocrine changes that ultimately lead to sexual maturation and reproductive capability. The transition through puberty is marked by an increased risk for the onset of a range of health problems, particularly those related to the control of behaviour and emotion. Early onset puberty is associated with a greater risk of cancers of the reproductive tract and cardiovascular disease. Previous studies have had methodological limitations and have tended to view puberty as a unitary process, with little distinction between adrenarche, gonadarche and linear growth. The Childhood to Adolescence Transition Study (CATS) aims to prospectively examine associations between the timing and stage of the different hormonally-mediated changes, as well as the onset and course of common health and behavioural problems that emerge in the transition from childhood to adolescence. The initial focus of CATS is on adrenarche, the first hormonal process in the pubertal cascade, which begins for most children at around 8 years of age.

Methods/Design
CATS is a longitudinal population-based cohort study. All Grade 3 students (8–9 years of age) from a stratified cluster sample of schools in Melbourne, Australia were invited to take part. In total, 1239 students and a parent/guardian were recruited to participate in the study. Measures are repeated annually and comprise student, parent and teacher questionnaires, and student anthropometric measurements. A saliva sample was collected from students at baseline and will be repeated at later waves, with the primary purpose of measuring hormonal indices of adrenarche and gonadarche.

Discussion
CATS is uniquely placed to capture biological and phenotypic indices of the pubertal process from its earliest manifestations, together with anthropometric measures and assessment of child health and development. The cohort will provide rich detail of the development, lifestyle, external circumstances and health of children during the transition from childhood through to adolescence. Baseline associations between the hormonal measures and measures of mental health and behaviour will initially be examined cross-sectionally, and then in later waves longitudinally. CATS will make a unique contribution to the understanding of adrenarche and puberty in children’s health and development.

Differential effects of exercise on tibial shaft marrow density in young female athletes

Context:
Increased mechanical loading can promote the preferential differentiation of bone marrow mesenchymal stem cells to osteoblastogenesis, but it is not known whether long-term bone strength-enhancing exercise in humans can reduce marrow adiposity.

Objective:
Our objective was to examine whether bone marrow density (MaD), as an estimate of marrow adiposity 1) differs between young female athletes with contrasting loading histories and bone strengths and 2) is an independent predictor of bone strength at the weight-bearing tibia.

Design:
Mid-tibial MaD, cortical area (CoA), total area, medullary area, strength strain index (SSI), and cortical volumetric bone mineral density (vBMD) (total, endocortical, midcortical, and pericortical) was assessed using peripheral quantitative computed tomography in 179 female athletes involved in both impact and nonimpact loading sports and 41 controls aged 17–40 years.

Results:
As we have previously reported CoA, total area, and SSI were 16% to 24% greater in the impact group compared with the controls (all P < .001) and 12% to 18% greater than in the nonimpact group (all P < .001). The impact group also had 0.5% higher MaD than the nonimpact and control groups (both P < .05). Regression analysis further showed that midtibial MaD was significantly associated with SSI, CoA, endocortical vBMD, and pericortical vBMD (P < .05) in all women combined, after adjusting for age, bone length, loading groups, medullary area, muscle cross-sectional area, and percent fat.

Conclusion:
In young female athletes, tibial bone MaD was associated with loading history and was an independent predictor of tibial bone strength. These findings suggest that an exercise-induced increase in bone strength may be mediated via reduced bone marrow adiposity and consequently increased osteoblastogenesis.

Role of intensive training in the growth and maturation of artistic gymnasts

Short stature and later maturation of youth artistic gymnasts are often attributed to the effects of intensive training from a young age. Given limitations of available data, inadequate specification of training, failure to consider other factors affecting growth and maturation, and failure to address epidemiological criteria for causality, it has not been possible thus far to establish cause–effect relationships between training and the growth and maturation of young artistic gymnasts. In response to this ongoing debate, the Scientific Commission of the International Gymnastics Federation (FIG) convened a committee to review the current literature and address four questions: (1) Is there a negative effect of training on attained adult stature? (2) Is there a negative effect of training on growth of body segments? (3) Does training attenuate pubertal growth and maturation, specifically, the rate of growth and/or the timing and tempo of maturation? (4) Does training negatively influence the endocrine system, specifically hormones related to growth and pubertal maturation? The basic information for the review was derived from the active involvement of committee members in research on normal variation and clinical aspects of growth and maturation, and on the growth and maturation of artistic gymnasts and other youth athletes. The committee was thus thoroughly familiar with the literature on growth and maturation in general and of gymnasts and young athletes. Relevant data were more available for females than males. Youth who persisted in the sport were a highly select sample, who tended to be shorter for chronological age but who had appropriate weight-for-height. Data for secondary sex characteristics, skeletal age and age at peak height velocity indicated later maturation, but the maturity status of gymnasts overlapped the normal range of variability observed in the general population. Gymnasts as a group demonstrated a pattern of growth and maturation similar to that observed among short-, normal-, late-maturing individuals who were not athletes. Evidence for endocrine changes in gymnasts was inadequate for inferences relative to potential training effects. Allowing for noted limitations, the following conclusions were deemed acceptable: (1) Adult height or near adult height of female and male artistic gymnasts is not compromised by intensive gymnastics training. (2) Gymnastics training does not appear to attenuate growth of upper (sitting height) or lower (legs) body segment lengths. (3) Gymnastics training does not appear to attenuate pubertal growth and maturation, neither rate of growth nor the timing and tempo of the growth spurt. (4) Available data are inadequate to address the issue of intensive gymnastics training and alterations within the endocrine system.

n-3 LC-PUFA deposition efficiency and appetite regulating hormones are modulated by the dietary lipid source during rainbow trout grow-out and finishing periods

Largely attributable to concerns surrounding sustainability, the utilisation of omega-3 long-chain polyunsaturated fatty acid-rich (n-3 LC-PUFA) fish oils in aquafeeds for farmed fish species is an increasingly concerning issue. Therefore, strategies to maximise the deposition efficiency of these key health beneficial fatty acids are being investigated. The present study examined the effects of four vegetable-based dietary lipid sources (linseed, olive, palm and sunflower oil) on the deposition efficiency of n-3 LC-PUFA and the circulating blood plasma concentrations of the appetite-regulating hormones, leptin and ghrelin, during the grow-out and finishing phases in rainbow trout culture. Minimal detrimental effects were noted in fish performance; however, major modifications were apparent in tissue fatty acid compositions, which generally reflected that of the diet. These modifications diminished somewhat following the fish oil finishing phase, but longer-lasting effects remained evident. The fatty acid composition of the alternative oils was demonstrated to have a modulatory effect on the deposition efficiency of n-3 LC-PUFA and on the key endocrine hormones involved in appetite regulation, growth and feed intake during both the grow-out and finishing phases. In particular, n-6 PUFA (sunflower oil diet) appeared to ‘spare’ the catabolism of n-3 LC-PUFA and, as such, resulted in the highest retention of these fatty acids, ultimately highlighting new nutritional approaches to maximise the maintenance of the qualitative benefits of fish oils when they are used in feeds for aquaculture species.

Retracted: Experimental evidence that maternal corticosterone controls adaptive offspring sex ratios

1. Sex allocation theory has received considerable attention, yet the mechanism(s) by which mothers skew offspring sex ratios remain unknown. In birds, females are the heterogametic sex, which potentially gives them control of whether gametes will be male or female. How females might control the sex of the gamete is unclear, but one possibility is that variation in steroid hormones may mediate this process. 2. We experimentally altered circulating levels of corticosterone in female Gouldian finches (Erythrura gouldiae), a species that demonstrates both extreme stress responses and extreme offspring sex ratio biases when breeding with a low-quality (genetically incompatible) partner. 3. During egg production, individual females received both corticosterone and metyrapone (a corticosterone-synthesis inhibitor) implants, in random order, to induce both high and low levels of circulating stress hormones (within physiological limits). 4. We found that females with elevated corticosterone levels produced male-biased sex ratios, but when the same females were treated with metyrapone they produced female-biased offspring sex ratios. 5. These stress responses are adaptive because females constrained to breeding with low-quality males can substantially increase their fitness by overproducing sons. Changes in maternal corticosterone levels during stressful situations, such as the quality of a breeding partner, may provide an endocrine mechanism that can be exploited for strategic sex allocation.

Female body condition affects foetal growth in a capital breeding mysticete

1.Sex allocation theory has received considerable attention, yet the mechanism(s) by which mothers skew offspring sex ratios remain unknown. In birds, females are the heterogametic sex, which potentially gives them control of whether gametes will be male or female. How females might control the sex of the gamete is unclear, but one possibility is that variation in steroid hormones may mediate this process. 2.We experimentally altered circulating levels of corticosterone in female Gouldian finches (Erythrura gouldiae), a species that demonstrates both extreme stress responses and extreme offspring sex ratio biases when breeding with a low-quality (genetically incompatible) partner. 3.During egg production, individual females received both corticosterone and metyrapone (a corticosterone-synthesis inhibitor) implants, in random order, to induce both high and low levels of circulating stress hormones (within physiological limits). 4.We found that females with elevated corticosterone levels produced male-biased sex ratios, but when the same females were treated with metyrapone they produced female-biased offspring sex ratios. 5.These stress responses are adaptive because females constrained to breeding with low-quality males can substantially increase their fitness by overproducing sons. Changes in maternal corticosterone levels during stressful situations, such as the quality of a breeding partner, may provide an endocrine mechanism that can be exploited for strategic sex allocation.