Sulphatoxy melatonin: an index of depression in anorexia nervosa and bulimia nervosa

Melatonin: comprehensive profile

This chapter includes the aspects of melatonin. The drug is synthesized in the pineal gland starting from tryptophane or synthetically by using indole as starting material. Melatonin has been used as an adjunct to interleukin-2 therapy for malignant neoplasms, as contraceptive, in the management of various forms of insomnia, to alleviate jet lag following long flights, and finally as free radical scavenger and hence as an antioxidant and an anti-inflammatory. The chapter discusses the drug metabolism and pharmacokinetics and presents various method of analysis of this drug such as biological analysis, spectroscopic analysis, and chromatographic techniques of separation. It also discusses its physical properties such as solubility characteristics, X-ray powder diffraction pattern, and thermal methods of analysis. The chapter is concluded with a discussion on its biological properties such as activity, toxicity, and safety.

Melatonin excretion with affect disorders over age 60

Numerous studies have reported low melatonin secretion in depression, but other studies have suggested no deficit or an increase. Alterations of circadian phase or duration of melatonin secretion have also been described. Since melatonin secretion decreases as we age, it seemed interesting to examine melatonin and depression in an aging sample. Volunteers who complained of mood or sleep problems were recruited for studies in which fractional urine specimens were collected for 24 h, both at home and in the laboratory. The major metabolite, 6-sulfatoxymelatonin (aMT6s), was determined by radioimmunoassay. Of 72 volunteers aged 60-78 years, seven had current major depression and 55% had a lifetime history of an affective disorder. A 55-fold range of home aMT6s excretion rates was observed. A lifetime history of any affective disorder was significantly associated with greater log(10)[mesor] aMT6s excretion in home collections and laboratory collections, but current affective disorders were neither significantly related to melatonin excretion nor to aMT6s acrophase timing, onset, offset or duration. These results are only weakly consistent with a photoperiodic hypothesis of depression.

The effect of presynaptic catecholamine depletion on 6-hydroxymelatonin sulfate: a double blind study of alpha-methyl-para-tyrosine

Because it is a competitive inhibitor of tyrosine hydroxylase, alpha-methyl-para-tyrosine (AMPT) is used to study psychiatric disorders. Melatonin serves as a biological marker of catecholamine function since its secretion is regulated by noradrenergic neurons via beta-adrenergic receptors in the pineal gland. Ten healthy volunteers were administered AMPT in a double-blind placebo controlled study. When subjects received AMPT, nocturnal 6-hydroxymelatonin sulfate (6-SM) decreased significantly as compared with promethazine (night 1 P=0.002; and night 2 P=0.001). Urinary MHPG also decreased on both study days (DF1,9 F=9.82, GG=0.0121). Nocturnal 6-SM excretion and melatonin secretion correlated highly (r=0.91, P=0.0007). Behavioral ratings did not reveal a difference in symptomatology and did not correlate with changes in 6-SM or MHPG. This study demonstrates in healthy controls that 6-SM reliably reflects presynaptic catecholamine depletion induced by AMPT without the emergence of behavioral symptoms.

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.

Duodenum is not a consistent source of melatonin in rats

Markedly increased melatonin levels in plasma have been observed in response to tryptophan administration. This post-tryptophan melatonin increase has been attributed to the duodenum. Because extra-pineal sources of melatonin may be important in interpreting the meaning of altered melatonin production observed in patient populations, this work was undertaken to confirm whether melatonin is produced in the duodenum and to know whether the duodenum need be considered when investigating the circadian control of melatonin production. We measured melatonin in rat duodenum by HPLC both under basal conditions and following tryptophan load. No melatonin was observed in duodenum under conditions of 2.5 ng/g measurement limits. Neither was there any evidence found for the melatonin precursor N-acetylserotonin. Treatment with N-acetylserotonin resulted in increased melatonin content in the pineal gland, but no evidence for melatonin in the duodenum. In vitro incubation of duodenum tissue with 5-hydroxytryptophan, 5-methoxytryptophan, or N-acetylserotonin revealed no detectable melatonin synthesis, and incubation with melatonin revealed no detectable melatonin degradation. The lack of confirmation of melatonin content and the lack of either synthetic or degradative enzyme activity in duodenum tissue suggest that melatonin production from duodenum need not be considered in human or animal studies of melatonin production.

Low lymphocyte interferon-gamma production and variable proliferative response in anorexia nervosa patients

Interferon-gamma (IFN-gamma) production by peripheral blood mononuclear cells (PBMC) in 14 patients with anorexia nervosa (AN) was significantly lower than in 14 age-matched healthy controls. Follow-up samples in four patients displayed low levels, except in two when they recovered the IFN-gamma production as the hormonal cycles were restored. A large interindividual variation for the lymphocyte proliferative response was observed in 30 AN patients. DNA synthesis of PBMC was normal in 8 patients (27%), significantly increased in 6 (20%) (P < 0.001), and significantly decreased in 16 (53%) (P < 0.001). IFN-gamma inhibition was reversed by culturing a control lymphocyte population with monocytes from patients with AN. This was not observed in cultures of control monocytes and AN lymphocytes. IL-2 receptor (TAC subunit) was assessed and no difference was found in the number of TAC-positive cells between patients and controls. These results point out impaired production of the immunomodulator cytokine IFN-gamma as a major functional defect of AN peripheral lymphocytes.

An oral melatonin replacement regimen that re-establishes the normal circadian levels of urinary 6-sulphatoxymelatonin in functionally pinealectomized rats

Wistar rats maintained on a 12-hr daily photoperiod (LD 12:12 cycle) exhibited a diurnal rhythm in urinary 6-sulphatoxymelatonin (aMT6s) concentrations with peak levels in the scotophase. Light-induced functional pinealectomy (FPX) abolished the nocturnal rise in aMT6s, lowering it to photophase levels. The objective of the study was to formulate an oral melatonin replacement regimen that would restore a normal rhythmic output of urinary aMT6s in functionally pinealectomised rats. Three regimens of sequential doses of melatonin were tested. Of these, the regimen with melatonin concentrations of 4 ng, 12 ng, 65 ng, and 4 ng per ml of drinking water given to rats during the 1st, 2nd, 3rd, and 4th 3-hr periods, respectively, of the 12-hr FPX phase, was found to generate a urinary aMT6s level that closely resembled the natural level and rhythm exhibited under an LD 12:12 cycle. This dose is considered appropriate to restore certain melatonin-mediated physiological functions in Wistar rats subjected to FPX.

Pineal and adrenal function before and after refeeding in anorexia nervosa

Nine female subjects with anorexia nervosa (AN) were studied when emaciated (mean 72% of average body weight), and after refeeding (mean 85% of average body weight). They were compared to 9 individually age-matched female control subjects. On each occasion blood was sampled for serum melatonin and plasma cortisol through the night, and urine was collected over 24 hr to measure sulfatoxy melatonin levels. The AN group did not differ in their level of depression before and after weight gain. There were no significant differences in serum melatonin values among the patient group before or after weight gain and the control group. Levels of urinary sulfatoxy melatonin were also significantly higher in nighttime compared to daytime samples both before and after weight gain. Plasma cortisol values were significantly elevated in the emaciated state and this was accounted for by higher cortisol levels at 9, 10, 11, and 12 PM and at 6 AM compared with the weight restored state and to controls. This study suggests that pineal activity in patients with AN is not altered by chronic changes in weight, and is not closely associated with changes in cortisol.

Urinary 6-sulphatoxymelatonin, an index of pineal function in the rat

The objective of this study was to apply the radioimmunoassay for 6-sulphatoxymelatonin (aMT6s) to rat urine, and use it to study the source of aMT6s. The radioimmunoassay was found to have acceptable within- and between-assay variation, excellent specificity, and good parallelism between the standard and unknown. Because urine is highly contaminated we assessed whether preliminary purification was required and established that it was unnecessary. Using this assay a 24-hr rhythm in 6-sulphatoxymelatonin output was seen in pools of urine harvested at 3-hr intervals from Wistar rats on LD 12:12. The nocturnal rise in aMT6s was abolished by constant light. In contrast pinealectomy lowered aMT6s output significantly throughout both dark and light. This study confirms previous studies indicating that the pineal is the major source of 6-sulphatoxymelatonin. It is concluded that urinary 6-sulphatoxymelatonin as measured by radioimmunoassay is a valid measure of pineal gland activity in the rat.