Endocrine Abstracts

Background: The pathophysiological base of metabolic syndrome is insulin resistance. According to Scott E.M., Grant P.J., insulin resistance is supposed to be formed during the evolution and connected by circadian rhythms. Melatonin is synchronizer of circadian rhythms. The modern lifestyle leads to the breach of melatonin synthesis because of absence of season changes in the length of a light day due to the using of artificial lighting.

Aim: The aim was studied influence of melatonin on the development of MS in inversion of the cycle ‘day/night’.

Design: Group ‘A’ (n=25), patients with MetS (the National Cholesterol Education Programs Adult Treatment Panel) and inversion of the cycle ‘day/night’ (at least two night shift a week for 6 and more years), group ‘C’ (n=23), healthy people, working in day shifts. Blood pressure (BP) has been monitored for 24 years. It is determined waist circumference (WC), high-density lipoproteins (HDL) fasting triglycerides (TG), fasting glucose. The melatonin secretion has been determined according to excretion 6-sulfatoxymelatonin (MT6S) in urine.

Results: Total MT6S in both groups was equal, P=0.077. MT6S at 0400 h in group ‘A’ (25.3 95% CI: 17.8–32.8 ng/ml) was less P<0.014. Night MT6S in group ‘A’ (10.2 95% CI: 7.3–13 ng/ml) was higher P<0.001. MT6S at 0400 h was connected with BP(r=−0.34), TG (r=−0.34), HDL (r=0.26), glucose (r=−0.38), P<0.05. Correlation has been determined between the day MT6S and WC (r=−0.28, P<0.05). When the peak secretion of melatonin decreases, it is determined increasing the risk of abdominal obesity (OR 1.8, 95% CI: 0.8–3.7; P<0.05), hypertension OR 1.6 (95% CI: 0.8–3.4; P<0,05) risk of nocturnal hypertension (OR 1.6, 95% CI: 0.8–3.4; P<0.05, hypertriglycerides (OR 1.4, 95% CI: 0.7–2.1; P<0.05), HDL decreasing (OR 1.7, 95% CI 0.9–2.6, P<0.05)

Conclusions: During the long inversion of the cycle ‘day/night’, disturbance of melatonin secretion leads to the development of metabolic syndrome.