Aging-dependent changes in the effect of daily melatonin supplementation on rat metabolic and behavioral responses.

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J Pineal Res 2001 Aug;31(1):89-94 Related Articles, Books, LinkOut

Aging-dependent changes in the effect of daily melatonin supplementation on rat

metabolic and behavioral responses.

Rasmussen DD, Mitton DR, Larsen SA, Yellon SM.

VA Puget Sound Health Care System, Department of Psychiatry and Behavioral

Sciences, University of Washington, Seattle

98195, USA. drasmuss@...

Pineal melatonin secretion has been reported to commonly decrease with aging,

whereas intra-abdominal adiposity, plasma

insulin and plasma leptin levels tend to increase.

We recently demonstrated that daily melatonin administration starting at middle

age suppressed male rat intra-abdominal

fat, plasma leptin and plasma insulin to youthful levels, suggesting that

aging-related changes in pineal melatonin

secretion and in energy regulation may be functionally related.

Accordingly, we have now investigated the effects of daily melatonin treatment

on energy regulation in young versus

middle-aged male Sprague Dawley rats.

Addition of melatonin to the drinking water (0.2 microg/mL) produced nocturnal

and diurnal plasma melatonin

concentrations in middle-aged rats (12 months) equivalent to those of young

adult (5 months) rats.

Administration of this melatonin dosage every day for 10 wk starting at 10

months of age suppressed (P < 0.01) relative

intra-abdominal fat, non-fasted plasma insulin and plasma leptin by 27, 39, and

51%, respectively (vs. vehicle-treated

controls).

In contrast, administration of melatonin for 10 wk starting at 3 months of age

did not significantly alter (P> 0.10) any

of these parameters.

The melatonin administration stimulated (102%, P < 0.001) behavioral

responsiveness of the middle-aged rats in a test of

response to novelty, restoring youthful levels, but did not significantly alter

behavioral responsiveness of the young

rats.

These results suggest that suppression of intra-abdominal adiposity and plasma

leptin and insulin levels and stimulation

of behavioral responsiveness in response to daily exogenous melatonin begins at

middle age, coincident with and likely

dependent upon the aging-associated decline in endogenous pineal melatonin

secretion.

These results further suggest that appropriate melatonin supplementation may

potentially provide therapy or prophylaxis

not only for the insulin resistance, increased intra-abdominal fat and resulting

pathologies that occur with aging, but

also for some aging-associated behavioral changes.

PMID: 11485011 [PubMed - in process]

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Greg ,

http://www.ozemail.com.au/~gowatson

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