Metabolic clues regarding the enhanced performance of elite endurance athletes from orchiectomy-induced hormonal changes

Development of Classification Models for the Prediction of Alzheimer's Disease Utilizing Circulating Sex Hormone Ratios

BACKGROUND

While sex hormones are essential for normal cognitive health, those individuals with greater endocrine dyscrasia around menopause and with andropause are more likely to develop cognitive loss and Alzheimer's disease (AD).

OBJECTIVE

To assess whether circulating sex hormones may provide an etiologically significant, surrogate biomarker, for cognitive decline.

METHODS

Plasma (n = 152) and serum (n = 107) samples from age- and gender-matched AD and control subjects from the Wisconsin Alzheimer's Disease Research Center (ADRC) were analyzed for 11 steroids and follicle-stimulating hormone. Logistic regression (LR), correlation analyses, and recursive partitioning (RP) were used to examine the interactions of hormones and hormone ratios and their association with AD. Models generated were then tested on an additional 43 ADRC samples.

RESULTS

The wide variation and substantial overlap in the concentrations of all circulating sex steroids across control and AD groups precluded their use for predicting AD. Classification tree analyses (RP) revealed interactions among single hormones and hormone ratios that associated with AD status, the most predictive including only the hormone ratios identified by LR. The strongest associations were observed between cortisol, cortisone, and androstenedione with AD, with contributions from progesterone and 17β-estradiol. Utilizing this model, we correctly predicted 81% of AD test cases and 64% of control test cases.

CONCLUSION

We have developed a diagnostic model for AD, the Wisconsin Hormone Algorithm Test for Cognition (WHAT-Cog), that utilizes classification tree analyses of hormone ratios. Further refinement of this technology could provide a quick and cheap diagnostic method for screening those with AD.

A meta-analysis of fat intake, reproduction, and breast cancer risk: an evolutionary perspective

OBJECTIVES

This study is a systematic review of literature published up to May of 2010 aimed to identify relationships between dietary fat, and fat subtypes, with risk of breast cancer in women.

METHODS

Descriptive data, estimates of relative risk and associated 95% confidence interval (CI) were extracted from relative studies and analyzed using the random effects model of DerSimonian and Laird.

RESULTS

Cohort study results indicated significant summary relative risks between polyunsaturated fat and breast cancer (1.091, 95% CI: 1.001; 1.184). In case-control studies no association between fat and breast cancer was observed. Post-menopausal women indicated a significant association between total fat (1.042, 95%CI: 1.013; 1.073), PUFA intake (1.22, 95% CI: 1.08; 1.381), and breast cancer. A non-significant inverse relation between intake of all fat types and breast cancer was identified in premenopausal women.

CONCLUSIONS

These results support the idea that possible elevations in serum estrogen levels by an adult exposure to a high-fat diet would increase breast cancer risk. Furthermore, menopausal status was observed to affect women's risk of breast cancer. Higher risks of breast cancer were found in post-menopausal women consuming diets high in total fat and polyunsaturated fats. Conversely, dietary fat appears to have preventative effects in pre-menopausal women. This study takes a transformative approach combining epidemiological, biomedical, and evolutionary theory to evaluate how biocultural variations in risk factors (i.e., diet and reproduction) affect the evolution of breast cancers.

Evolution of lactation: nutrition v. protection with special reference to five mammalian species

The evolutionary origin of the mammary gland has been difficult to establish because little knowledge can be gained on the origin of soft tissue organs from fossil evidence. One approach to resolve the origin of lactation has compared the anatomy of existing primitive mammals to skin glands, whilst another has examined the metabolic and molecular synergy between mammary gland development and the innate immune system. We have reviewed the physiology of lactation in five mammalian species with special reference to these theories. In all species, milk fulfils dual functions of providing protection and nutrition to the young and, furthermore, within species the quality and quantity of milk are highly conserved despite maternal malnutrition or illness. There are vast differences in birth weight, milk production, feeding frequency, macronutrient concentration, growth rate and length of lactation between rabbits, quokkas (Setonix brachyurus), pigs, cattle and humans. The components that protect the neonate against infection do so without causing inflammation. Many protective components are not unique to the mammary gland and are shared with the innate immune system. In contrast, many of the macronutrients in milk are unique to the mammary gland, have evolved from components of the innate immune system, and have either retained or developed multiple functions including the provision of nourishment and protection of the hatchling/neonate. Thus, there is a strong argument to suggest that the mammary gland evolved from the inflammatory response; however, the extensive protection that has developed in milk to actively avoid triggering inflammation seems to be a contradiction.

A multi-hit endocrine model of intrinsic adult-onset asthma

Epidemiological studies indicate that adult-onset asthma is initiated by stress (anxiety and depression), obesity and menopause. Ironically, despite our understanding of the various stressors that promote chronic adult-onset asthma, most of which are known to elevate cortisol production via the hypothalamic-pituitary-adrenal (HPA) axis, inhaled and systemic corticosteroids are the mainstay for the treatment of chronic asthma. This implicates other endocrine or cellular changes independent of cortisol synthesis in non-allergic adult-onset asthma. The mechanism by which corticosteroids are thought to modulate bronchial tone in relieving asthma is via corticosteroid-responsive genes that increase PGE(2) and cAMP production which promote muscle relaxation. Therefore, any physiological condition that suppresses intracellular PGE(2) and cAMP production would counter cortisol-induced muscle relaxation and potentially trigger non-allergic adult-onset asthma. Stress, obesity and menopause act on three interrelated endocrine pathways, the serotonergic, leptinergic and hypothalamic pathways, all of which operate through receptors to modulate cAMP and Ca(2+) metabolism in smooth muscle cells (SMCs). We propose that the level of SMC cAMP, as determined by overall signaling through corticosteroid receptors, leptin receptors and the GPCRs of the HPG and serotonergic pathways, will regulate bronchial tone (i.e. the 'Multi-Hit Endocrine Model of Adult-Onset Asthma'). Thus, decreases in HPG (menopause) and serotonergic (depression) signaling and increases in leptinergic (obesity) signaling relative to HPA signaling would decrease cellular SMC cAMP and promote muscle contraction. This model can explain the discrepant epidemiological data associating stress, obesity, depression and menopause with adult-onset asthma and is supported by basic and clinical data. Treatment of depressed or menopausal asthmatics with selective serotonin reuptake inhibitors or hormone replacement therapy, respectively, alleviates bronchoconstriction. Future therapeutic strategies might therefore target the serotonergic, leptinergic and hypothalamic pathways in regulating cellular cAMP production and bronchoconstriction for the treatment of adult-onset asthma.