This article shows that melatonin protects against breast cancer and inhibits linoleic acid (omega-6) uptake and metabolism to 13-HODE by cancer cells. I think that enough sleep may also decrease the AA incorporation into cells in the people immune to the omega-6 overload syndromes ...
Cancer Res. 2005 Dec 1;65(23):11174-84.
Melatonin-depleted blood from premenopausal women exposed to light at night stimulates growth of human breast cancer xenografts in nude rats.
Blask DE, Brainard GC, Dauchy RT, Hanifin JP, Davidson LK, Krause JA, Sauer LA, Rivera-Bermudez MA, Dubocovich ML, Jasser SA, Lynch DT, Rollag MD, Zalatan F.
Laboratory of Chrono-Neuroendocrine Oncology, Bassett Research Institute, The Mary Imogene Bassett Hospital, Cooperstown, New York 13326, USA. [email protected]
The increased breast cancer risk in female night shift workers has been postulated to result from the suppression of pineal melatonin production by exposure to light at night. Exposure of rats bearing rat hepatomas or human breast cancer xenografts to increasing intensities of white fluorescent light during each 12-hour dark phase (0-345 microW/cm2) resulted in a dose-dependent suppression of nocturnal melatonin blood levels and a stimulation of tumor growth and linoleic acid uptake/metabolism to the mitogenic molecule 13-hydroxyoctadecadienoic acid. Venous blood samples were collected from healthy, premenopausal female volunteers during either the daytime, nighttime, or nighttime following 90 minutes of ocular bright, white fluorescent light exposure at 580 microW/cm2 (i.e., 2,800 lx). Compared with tumors perfused with daytime-collected melatonin-deficient blood, human breast cancer xenografts and rat hepatomas perfused in situ, with nocturnal, physiologically melatonin-rich blood collected during the night, exhibited markedly suppressed proliferative activity and linoleic acid uptake/metabolism. Tumors perfused with melatonin-deficient blood collected following ocular exposure to light at night exhibited the daytime pattern of high tumor proliferative activity. These results are the first to show that the tumor growth response to exposure to light during darkness is intensity dependent and that the human nocturnal, circadian melatonin signal not only inhibits human breast cancer growth but that this effect is extinguished by short-term ocular exposure to bright, white light at night. These mechanistic studies are the first to provide a rational biological explanation for the increased breast cancer risk in female night shift workers.
PMID: 16322268
QUOTE: The suppression of
circadian melatonin production by ocular exposure to bright white
light at night, leading to augmented nocturnal tumor uptake of
dietary linoleic acid and its conversion to mitogenically active 13-
HODE, can now be afforded serious consideration as a new risk
factor for human breast cancer (4, 5) and a significant public health
issue (55). The high nocturnal dietary intake of fat, particularly
linoleic acid, reported for night shift workers (56, 57), coupled with
melatonin suppression by exposure to light at night provide a firm
mechanistic basis upon which to explain, in part, the increased risk
of breast cancer in some women who work night shifts for many
years (9�?1). Thus, strategies to preserve the integrity of the
circadian melatonin signal (i.e., avoidance of bright light at night,
intelligent lighting design, circadian-timed physiologic melatonin
supplementation) coupled with modifications in nocturnal dietary
fat intake may offer a unique approach to the prevention of breast
cancer, and perhaps other melatonin-sensitive cancers, in our
increasingly 24-hour society. UNQUOTE. |
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