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Food restriction differentially affects mRNAs encoding the major anterior pituitary tropic hormones
1Department of Physiology, University of Texas Health Science Center, San Antonio, USA. han@uthscsa.edu
Abstract:
Chronic food restriction (FR) leads to adaptive cellular changes, some of which retard aging. Moreover, some of these changes occur within weeks after onset of FR. Because neuroendocrine mechanisms may mediate these effects, we measured the effect of FR on the messenger ribonucleicacids (mRNAs) encoding all of the tropic hormones of the anterior pituitary (AP). Slot blot and solution hybridization were conducted on AP ribonucleicacid (RNA) samples obtained at 0500 h (AM) and 1500 h (PM) from 3-month-old male Fischer 344 rats fed ad libitum (AL) or FR (60% of AL calories) since 6 weeks of age. PolyA RNA/microgram total RNA was similar in AL and FR rats, indicating that there was no overall effect of FR on mRNA levels. The level of proopiomelanocortin (POMC) mRNA was not reduced by FR when expressed per microgram of RNA or as total AP content. By contrast, the total AP content of the mRNAs encoding LH beta, FSH beta, TSH beta, GH, and PRL was markedly reduced by FR. When expressed per microgram of RNA, however, only GH (AM and PM), FSH beta (AM), TSH beta (PM), and PRL (PM) were reduced by FR. These results reveal that FR differentially affects pituitary tropic hormone mRNA levels within weeks after onset of FR, and are consistent with a role for neuroendocrine alterations in the initiation of adaptive cellular responses to FR.
Insights
Chronic food restriction (FR) rapidly alters pituitary hormone messenger RNA (mRNA) levels in rats. These neuroendocrine changes suggest a role in the adaptive cellular responses that may slow aging.
Area of Science:
- Endocrinology
- Molecular Biology
- Aging Research
Background:
- Chronic food restriction (FR) induces adaptive cellular changes that can retard aging.
- These adaptive changes can manifest within weeks of initiating FR.
- Neuroendocrine mechanisms are hypothesized to mediate these FR-induced effects.
Purpose of the Study:
- To investigate the impact of FR on the messenger ribonucleic acids (mRNAs) encoding anterior pituitary (AP) tropic hormones.
- To determine if FR differentially affects the expression of specific pituitary hormone mRNAs.
Main Methods:
- Measurement of AP tropic hormone mRNA levels in Fischer 344 rats using slot blot and solution hybridization.
- Comparison of mRNA levels between ad libitum (AL) fed rats and rats subjected to 60% calorie FR since 6 weeks of age.
- Analysis of mRNA levels at two time points (0500 h and 1500 h) to account for diurnal variations.
Main Results:
- FR did not alter the overall polyA RNA content per microgram of total RNA.
- Proopiomelanocortin (POMC) mRNA levels remained unchanged by FR.
- FR significantly reduced the total AP content of mRNAs for LH beta, FSH beta, TSH beta, GH, and PRL.
- Specific reductions in GH, FSH beta, TSH beta, and PRL mRNA levels per microgram of RNA were observed at specific time points.
Conclusions:
- Food restriction differentially impacts pituitary tropic hormone mRNA levels within weeks.
- These findings support a role for neuroendocrine alterations in initiating adaptive cellular responses to FR.
- The study highlights the rapid onset of molecular adaptations to caloric restriction.