Pineal and adrenal function before and after refeeding in anorexia nervosa

Adaptive thermogenesis in humans

The increasing prevalence of obesity and its comorbidities reflects the interaction of genes that favor the storage of excess energy as fat with an environment that provides ad libitum availability of energy-dense foods and encourages an increasingly sedentary lifestyle. Although weight reduction is difficult in and of itself, anyone who has ever lost weight will confirm that it is much harder to keep the weight off once it has been lost. The over 80% recidivism rate to preweight loss levels of body fatness after otherwise successful weight loss is due to the coordinate actions of metabolic, behavioral, neuroendocrine and autonomic responses designed to maintain body energy stores (fat) at a central nervous system-defined 'ideal'. This 'adaptive thermogenesis' creates the ideal situation for weight regain and is operant in both lean and obese individuals attempting to sustain reduced body weights. Much of this opposition to sustained weight loss is mediated by the adipocyte-derived hormone 'leptin'. The multiple systems regulating energy stores and opposing the maintenance of a reduced body weight illustrate that body energy stores in general and obesity in particular are actively 'defended' by interlocking bioenergetic and neurobiological physiologies. Important inferences can be drawn for therapeutic strategies by recognizing obesity as a disease in which the human body actively opposes the 'cure' over long periods of time beyond the initial resolution of symptomatology.

Leptin-mediated neuroendocrine alterations in anorexia nervosa: somatic and behavioral implications

Hypoleptinemia is a key endocrinological feature of anorexia nervosa (AN). Several symptoms in acute AN are related to the low circulating leptin levels including amenorrhea and semi-starvation-induced hyperactivity. The drop in leptin levels results from the loss of fat mass; once leptin levels fall below specific thresholds the hypothalamic-pituitary-gonadal and -thyroid axes are down-regulated; in contrast, the hypothalamic-pituitary-adrenal axis is up-regulated. Hypoleptinemia is the major signal underlying both somatic and behavioral adaptations to starvation. Because the mechanisms involved in this adaptation are similar in rodents and humans, rodent models can be used to investigate the relevant central pathways which underly the respective starvation-induced symptoms. During therapeutically induced weight gain, leptin levels can intermittently increase above normal concentrations. This hyperleptinemia could predispose to renewed weight loss.

Identification of molecular targets for dietary energy restriction prevention of skin carcinogenesis: An idea cultivated by Edward Bresnick

Dietary energy restriction (DER) has long been known to strikingly inhibit carcinogenesis in many animal models. The animal data has been corroborated by recent and ongoing epidemiological studies demonstrating the importance of energy balance, physical exercise and obesity in human cancer. Dr. Edward Bresnick provided key insights into this important area of research and pivotal direction for the author's research while he served as Director of the Eppley Institute for Research in Cancer, Omaha, NE. These insights moved this research toward demonstrating that DER reduced the expression of key protein kinase C isoforms in mouse skin. More recent studies have uncovered downstream events that are inhibited by DER including blockage of tumor promoter activation of Raf-1, ERK 1,2 and AP-1 expression. Parallel studies have demonstrated the DER inhibition of these key cellular signaling events in mouse skin carcinogenesis are dependent upon an intact adrenal gland because adrenalectomized mice fed DER diet did not have reduced tumor burden or inhibited signaling and blocked AP-1 activation as was observed in DER mice with intact adrenal glands. In addition, the DER inhibition of tumorigenesis and AP-1 signaling was restored in adrenalectomized mice that were given corticosterone in the drinking water. This showed that in mice in the chemical carcinogenesis protocol glucocorticoid hormone plays a major role in mediating DER prevention of cancer. Studies are ongoing to further assess the mechanism of DER modulation of skin cancer by assessing impacts on transcriptional regulation and expression of genes that are critical in skin carcinogenesis.

Pain modulation role of melatonin in eating disorders

The objective of this study was to test the effect of melatonin on thermal pain threshold in female patients with eating disorders. Fourteen patients were included in the study. We found a parabolic relation between pain threshold and the content of urine sulfatoxymelatonin (r = 0.6299, P < 0.05). We can speculate that increase in severity of eating disorder pathology may decrease both the melatonin level and pain sensitivity. In contrast with expected melatonin analgesic effect, our results showed its possible normalizing influence as well on pathologically decreased pain sensitivity.

Obesity and cortisol

Cortisol in obesity is a much-studied problem. Previous information indicates that cortisol secretion is elevated but that circulatory concentrations are normal or low, suggesting that peripheral disappearance rate is elevated. These studies have usually not taken into account the difference between central and peripheral types of obesity. Recent studies using saliva cortisol have indicated that the problem is complex with both high and low secretion of cortisol, perhaps depending on the status of the function of the hypothalamic-pituitary-adrenal gland axis. A significant background factor seems to be environmental stress. The results also suggest that the pattern of cortisol secretion may be important. Other neuroendocrine pathways are also involved, including the central sympathetic nervous system, the gonadal and growth hormone axes, and the leptin system. In concert, these abnormalities seem to be responsible for the abnormal metabolism often seen in central obesity. Several associated polymorphisms of candidate genes may provide a genetic background. Cortisol conversion to inactive metabolites may be a factor increasing central signals to secretion and may add to the increased secretion of cortisol induced by centrally acting factors. Perinatal factors have been found to be involved in the pathogenesis of obesity and its complications. The mechanism involved is not known, but available information suggests that programming of the hypothalamic-pituitary-adrenal axis may be responsible.

The hypothalamic-pituitary-adrenal axis in anorexia nervosa

Studies examining the function of the hypothalamic-pituitary-adrenal (HPA) axis in anorexia nervosa are reviewed. A principal finding is that of hypercortisolism, associated with increased central corticotropin-releasing hormone levels and normal circulating levels of adrenocorticotropic hormone. Similarities between neuroendocrine findings in anorexia nervosa and in affective disorder are reviewed. The contribution of circadian rhythm disturbances and malnutrition to observed HPA axis abnormalities in anorexia nervosa is also considered. Directions for future research are discussed.

Cultured peripheral blood mononuclear leukocytes from anorexia nervosa patients are refractory to visible light

Cultured human peripheral blood mononuclear leukocytes [PBML] from patients with anorexia nervosa [AN] did not respond to light stimulation as PBML of normal controls [NC] did. During winter, visible light increased [3H]thymidine incorporation into DNA of NC-PBML stimulated with phytohemagglutinin [PHA]. This effect was enhanced by 10(-7) M melatonin. PHA-stimulated DNA synthesis of PBML from AN patients failed to respond to photic stimulation during winter, and their proliferative response to melatonin was significantly blunted. In vitro photic stimulation of NC-PBML reduced melatonin while increasing both serotonin and 5-hydroxyindole 3-acetic acid [HIAA] production in both basal and PHA-stimulated conditions. In contrast AN-PBML, that in darkness enhanced the oxidative deamination of serotonin into HIAA more than NC-PBML, did not switch their indole metabolism in response to light. Light did not inhibit the binding of both melatonin and serotonin to AN-PBML as occurred in NC-PBML. The present data suggest that AN-PBML do not respond to light in vitro, because of a failure in the regulation of serotonin and melatonin metabolism.

Melatonin disturbances in anorexia nervosa and bulimia nervosa

The pineal gland releases melatonin into the blood stream in response to sympathetic noradrenergic stimulation of pinealocytes. This process is inhibited by light via the retino-hypothalamic-pineal pathway. Hence melatonin is predominantly released in darkness. Because serotonin is a precursor of melatonin, the intake of dietary tryptophan may also influence melatonin levels. Although the exact physiological role of melatonin in humans is unclear, it appears to be implicated in reproductive physiology, especially in terms of the onset of menarche. Low levels of melatonin also occur in depression. In this review, studies of melatonin in patients with anorexia nervosa and bulimia nervosa are considered in relation to potential abnormalities of noradrenergic function and circadian rhythm. The influence of weight loss, binging and purging, and depression on melatonin is discussed. Other studies involving the assessment of melatonin in relation to menstrual function are required.