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Posted: Sun Nov 07, 2010 10:06 pm
Norepinephrin (NE) signaling via ADRA2 winds up lowering NE release.
Turning up the ADRA2s should serve to lower overall NE release.

Endocrinology. 2010 Jun;151(6):2483-93. Epub 2010 Apr 6.
Adrenoceptor expression and diurnal rhythms of melatonin and its
precursors in the pineal gland of type 2 diabetic goto-kakizaki rats.
Bach AG, Mˆºhlbauer E, Peschke E.

Institute of Anatomy and Cell Biology, Martin Luther University
Halle-Wittenberg, Grosse Steinstrasse 52, 06097 Halle/Saale, Germany.

A decrease in the nighttime release of the pineal hormone melatonin is
associated with aging and chronic diseases in animals an humans.
Melatonin has a protective role in type 2 diabetes; however, its
synthesis itself is affected in the disease. The aim of this study was
to detect crucially impaired steps in the pineal melatonin synthesis of
type 2 diabetic Goto-Kakizaki (GK) rats. Therefore, plasma melatonin
concentrations and the pineal content of melatonin and its precursors
(tryptophan, 5-hydroxytryptophan, serotonin, and N-acetylserotonin) were
quantified in GK rats compared with Wistar rats (each group 8 and 50 wk
old) in a diurnal manner (four animals per group and per time point).
Additionally, the expression of pineal adrenoceptor subtype mRNA was
investigated. We found that in diabetic GK rats, 1) inhibitory
alpha-2-adrenoceptors (ADRA2) are significantly more strongly expressed
than in Wistar rats, 2) the formation of 5-hydroxytryptophan is
crucially impaired, and 3) the pineal gland protein content is
significantly reduced compared with that in Wistar rats. This is the
first time that melatonin synthesis is examined in a type 2 diabetic rat
model in a diurnal manner. The present data unveil several reasons for a
reduced melatonin secretion in diabetic animals and present an important
link in the interaction between melatonin and insulin.

PMID: 20371702
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