This looks very promising, directly from Walter Pierpaoli:

http://www.antiaging-systems.com/extract/melatonin.htm

Taka

As a bonus, melatonin prevents atherosclerosis:

J-Pineal-Res. 2002 Apr; 32(3): 179-86

Long-term melatonin administration increases polyunsaturated fatty
acid percentage in plasma lipids of hypercholesterolemic rats.

Pita, M L : Hoyos, M : Martin Lacave, I : Osuna, C : Fernandez Santos,
J M : Guerrero, J M

This study was designed to investigate the effect of melatonin on the
fatty acid composition of plasma and tissue lipids. Melatonin
administration to rats fed with a standard diet only increased long-
chain n-6 polyunsaturated fatty acids (PUFA) in total plasma lipids
and liver phospholipids but induced significant changes in
hypercholesterolemic rats. In plasma, palmitoleic and oleic acids
increased and n-6 and n-3 PUFA decreased in hypercholesterolemic rats;
theses changes were reversed by melatonin administration. The analysis
of lipid fractions revealed that only the cholesteryl ester fraction
was affected by melatonin. Histological studies of the carotid artery
intima revealed the appearance, in hypercholesterolemic rats, of fatty
streaks produced by a mass of foam cells covered by the endothelium
and by a thin layer of mononucleated cells. These changes were
prevented by melatonin. We conclude that long-term melatonin
administration modifies the fatty acid composition of rat plasma and
liver lipids and ameliorates the arterial fatty infiltration induced
by cholesterol.

and slows down the flax seed oil induced mammary carcinogenesis:

Effect of Melatonin and Linolenic Acid on Mammary Cancer in Transgenic
Mice with c-neu Breast Cancer Oncogene

Ghanta N. Rao, Elizabeth Ney and Ronald A. Herbert

Breast cancer is one of the most common cancers and is a leading cause
of mortality in women. The TG.NK transgenic mouse line expresses the c-
neu breast cancer oncogene under the control of a MMTV promoter and
appears to be a useful animal model for evaluation of intervention
strategies to delay/prevent breast cancer. Fiber-rich nonpurified diet
(NTP-2000) and some retinoid analogues have been shown to
significantly delay the development of mammary cancer in the TG.NK
model. Four-week-old hemizygous TG.NK female mice with MMTV/c-neu
oncogene fed NTP-2000 diet were gavaged with 0.05–0.2ml of flaxseed
oil as the source of -3 rich PUFA, or melatonin at 50–200mg/kg or a
combination of 0.10ml flaxseed oil and 50mg/kg melatonin in a gavage
volume of 0.2ml per mouse with corn oil as the vehicle for 30 weeks.
The time course of the mammary tumor incidence pattern was advanced by
flaxseed oil compared to the control. At the high dose (0.2ml) of
flaxseed oil, when the -6: -3 PUFA ratio was closer to 1, there was
some delay in the growth of mammary tumors. Melatonin delayed the
appearance of palpable tumors and the growth of the tumors with a dose-
related statistically significant negative trend for the incidence of
tumors. The combination of flaxseed oil and melatonin caused a
significant decrease in the number of tumors and tumor weight per
mouse compared to the control and to flaxseed oil but not to melatonin
alone. Flaxseed oil may delay the growth of mammary tumors if the
-6:-3 PUFA ratio of fat consumed is closer to 1. Melatonin has the
potential to markedly delay the appearance of palpable mammary tumors.
Studies are in progress with the TG.NK mouse model to understand the
histological and molecular changes associated with the dose-response
pattern of mammary tumor incidence and growth after treatment with a
broad range of doses of melatonin.

SOURCE: http://www.springerlink.com/content/g6126vvj0764283v/