Qualitative and quantitative changes of melatonin levels in physiological and pathological aging and in centenarians

Abstract

Melatonin secretion is an endogenous synchronizer, and it may possess some anti-aging properties. Thus we examined melatonin levels in physiological aging, in extreme senescence and in senile dementia. In healthy old (age 66-94 yr) and young subjects (age 23-39 yr) and in demented patients (age 68-91 yr) plasma melatonin was measured by radioimmunoassay in eight serial blood samples. In centenarians (age 100-107 yr) melatonin levels were estimated by assaying urinary 6-hydroxymelatonin sulfate (aMT6s) in two different urine samples collected from 08:00 to 20:00 hours and from 20:00 to 08:00 hours. These data were compared with the aMT6s excretion of old and young controls. Elderly subjects, demented or not, exhibited a flattened circadian profile of plasma melatonin, because of the suppression of the nocturnal peak. An age-related decline of the circadian amplitude of the melatonin rhythm occurred in old subjects, especially in demented individuals. Furthermore, the melatonin nocturnal peak was significantly correlated with the severity of the cognitive impairment. aMT6s urinary excretion also declined with age. However, as in young controls, in centenarians the aMT6s excretion was significantly higher at night than during the day. In conclusion, pineal melatonin secretion is affected by age and by the degree of cognitive impairment. In centenarians the maintenance of the circadian organization of melatonin secretion may suggest that the amplitude of the nocturnal peak and/or the persistence of a prevalent nocturnal secretion may be an important marker of biological age and of health status.

Circadian Rhythms of Melatonin Secretion in Peri- and Postmenopausal Women with Insomnia

“…(6,16,17) This fact indicates a decrease in those epiphysis functions that produce melatonin, which is a consequence of functional changes in the pineal gland and other links of the circadian system of the organism in the process of aging. (18) An age-related decrease in melatonin secretion is indicative of impaired pineal and pituitary control over ovarian rhythm and a progressive decline in fertility function.…”

“…(5) The agerelated decrease in melatonin secretion is a well-known fact; not only its level but also its production curve changes. (6)(7)(8) These changes could be the cause of various diseases, including SDs. (9) Results of our pilot research show that there is a relationship between the chronobiological rhythms of melatonin secretion and SDs in women of perimenopausal age.…”

Formation of S-Nitrosothiols from Regiospecific Reaction of Thiols with N-Nitrosotryptophan Derivatives

“…Because N-nitroso compounds were found in aortic rat tissues (26) and proline can be nitrosated only at acidic pH values (27,28), one may conclude that N-nitrosotryptophan derivatives represent the major amount of the experimentally identified N-nitroso compounds in vivo. The major amount of N-nitrosotryptophan derivatives would be located in proteins, because the concentrations of low molecular weight, N-terminal blocked tryptophan derivatives like melatonin are very low in plasma (ϳ0.2 nM) (29). The main mass thiols circulating in blood are albumin (680 M) (6), cysteine (ϳ10 M) (30), homocysteine (5-15 M) (31), and glutathione (7 M) (30).…”

Circadian Typology: A Comprehensive Review

“…The maintenance of the melatonin circadian rhythm is considered as a biological marker associated with successful ageing, while the flattening of the rhythm is related to the appearance of neurodegenerative diseases and the concomitant presence of psychiatric pathology (Magri et al, 2005;Wu et al, 2005).…”