7 research outputs found
Daily Melatonin Administration to Middle-Aged Male Rats Suppresses Body Weight, Intraabdominal Adiposity, and Plasma Leptin and Insulin Independent of Food Intake and Total Body Fat
Pineal melatonin secretion declines with aging, whereas visceral
fat, plasma insulin, and plasma leptin tend to increase. We have
previously demonstrated that daily melatonin administration at middle
age suppressed male rat intraabdominal visceral fat, plasma leptin,
and plasma insulin to youthful levels; the current study was
designed to begin investigating mechanisms that mediate these responses.
Melatonin (0.4 mg/ml) or vehicle was administered in the
drinking water of 10-month-old male Sprague Dawley rats (18/treatment)
for 12 weeks. Half (9/treatment) were then killed, and the other
half were submitted to cross-over treatment for an additional 12
weeks. Twelve weeks of melatonin treatment decreased (P , 0.05)
body weight (BW; by 7% relative to controls), relative intraabdominal
adiposity (by 16%), plasma leptin (by 33%), and plasma insulin (by
25%) while increasing (P , 0.05) locomotor activity (by 19%), core
body temperature (by 0.5 C), and morning plasma corticosterone (by
154%), restoring each of these parameters toward more youthful
levels. Food intake and total body fat were not changed by melatonin
treatment. Melatonin-treated rats that were then crossed over to
control treatment for a further 12 weeks gained BW, whereas control
rats that were crossed to melatonin treatment lost BW, but food
intake did not change in either group. Feed efficiency (grams of BW
change per g cumulative food intake), a measure of metabolic function,
was negative in melatonin-treated rats and positive in control
rats before cross-over (P,0.001); this relationship was reversed after
cross-over (P , 0.001). Thus, melatonin treatment in middle age
decreased BW, intraabdominal adiposity, plasma insulin, and plasma
leptin, without altering food intake or total adiposity. These results
suggest that the decrease in endogenous melatonin with aging may
alter metabolism and physical activity, resulting in increased BW,
visceral adiposity, and associated detrimental metabolic consequences.
(Endocrinology 141: 487–497, 2000