Retinol Research Today is a free monthly online journal that collates and summarizes the latest research about Retinol, including details on vitamin a, uses, wrinkle treatment, anti-aging.

Retinoic acid reduces glucocorticoid sensitivity in C2C12 myotubes by decreasing 11beta-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor activities.

Aubry EM, Odermatt A

Department of Pharmaceutical Sciences, Division of Molecular and Systems Toxicology, University of Basel, Basel, Switzerland.

Vitamin A is a nutrient with remarkable effects on adipose tissue and skeletal muscles, and plays a role in controlling energy balance. Retinoic acid (RA), the carboxylic form of vitamin A, has been associated with improved glucose tolerance and insulin sensitivity. In contrast, elevated glucocorticoids have been implicated in the development of insulin resistance and impaired glucose tolerance. Here, we investigated whether RA might counteract glucocorticoid effects in skeletal muscle cells by lowering 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1)-dependent local glucocorticoid activation and/or activation of glucocorticoid receptor (GR). We found a dose-dependent down-regulation of 11beta-HSD1 mRNA expression and activity upon incubation of fully differentiated mouse C2C12 myotubes with RA. In addition, RA inhibited GR transactivation by an 11beta-HSD1-independent mechanism. The presence of RA during myogenesis did not prevent myotube formation but resulted in relatively glucocorticoid-resistant myotubes, exhibiting very low 11beta-HSD1 expression and GR activity. The use of selective retinoic acid receptor (RAR) and retinoid X receptor ligands provided evidence that these effects were mediated through RARgamma. Importantly, short hairpin RNA against RARgamma abolished the effect of RA on 11beta-HSD1 and GR. In conclusion, we provide evidence for an important role of RA in the control of glucocorticoid activity during myogenesis and in myotubes. Disturbances of the nutrient and hormonal regulation of glucocorticoid action in skeletal muscles might be relevant for metabolic diseases.

Published 21 May 2009 in Endocrinology, 150(6): 2700-8.
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Articles on Retinol published 21 May 2009:

Retinoic acid is present in the postnatal rat olfactory organ and persists in vitamin A--depleted neural tissue.   J Nutr, 139(6): 1067-72.

Vitamin A (VA), all-trans-retinol (at-ROL), and its derivative, all-trans-retinoic acid (at-RA), are required for neuron development. The effects of these retinoids are dependent upon the nutritional status of the rat and tissue-specific dynamics of retinoid access and utilization. The purpose of this study was to determine the status of at-ROL and at-RA in the peripheral olfactory organ of postnatal rats fed a normal diet and rats fed a VA-deficient (VAD) diet. Extracted retinoids were ... [Abstract] [Full-text]

Golden Rice is an effective source of vitamin A.   Am J Clin Nutr, 89(6): 1776-83.

BACKGROUND: Genetically engineered "Golden Rice" contains up to 35 microg beta-carotene per gram of rice. It is important to determine the vitamin A equivalency of Golden Rice beta-carotene to project the potential effect of this biofortified grain in rice-consuming populations that commonly exhibit low vitamin A status. OBJECTIVE: The objective was to determine the vitamin A value of intrinsically labeled dietary Golden Rice in humans. DESIGN: Golden Rice plants were grown ... [Abstract] [Full-text]

Localized Th1-, Th2-, T regulatory cell-, and inflammation-associated hepatic and pulmonary immune responses in Ascaris suum-infected swine are increased by retinoic acid.   Infect Immun, 77(6): 2576-87.

Pigs infected with Ascaris suum or controls were given 100 microg (low-dose) or 1,000 microg (high-dose) all-trans retinoic acid (ATRA)/kg body weight in corn oil or corn oil alone per os on days after inoculation (DAI) -1, +1, and +3 with infective eggs. Treatment with ATRA increased interleukin 4 (IL4) and IL12p70 in plasma of infected pigs at 7 DAI and augmented bronchoalveolar lavage (BAL) eosinophilia observed at 7 and 14 DAI. To explore potential molecular mechanisms underlying these ... [Abstract] [Full-text]

Articles on Retinol published 11 May 2009:

The effect of high-dose vitamin A supplementation administered with BCG vaccine at birth may be modified by subsequent DTP vaccination.   Vaccine, 27(21): 2891-8.

Unexpectedly, we found no overall beneficial effect on mortality in a randomised trial of vitamin A supplementation (VAS) or placebo administered with BCG vaccine at birth in Guinea-Bissau. We conducted an explorative analysis to examine whether subsequent diphtheria-tetanus-pertussis (DTP) vaccinations had modified the effect of VAS at birth. VAS was associated with a weak tendency for decreased mortality as long as BCG was the most recent vaccination, the mortality rate ratio being 0.86 ... [Abstract] [Full-text]

Articles on Retinol published 28 April 2009:

Retinoic acid effects on thyroid function of female rats.   Life Sci, 84(19): 673-7.

AIMS: Retinoic acid is widely used in dermatological treatment and thyroid cancer management; however its possible side-effects on normal thyroid function remains unknown. We aimed to determine the effects of retinoic acid on thyroid function of adult female rats. MAIN METHODS: Female Wistar rats were treated with all-trans-retinoic acid and 13-cis retinoic acid for 14 and 28 days. Then, rats were killed and thyroid function was evaluated. KEY FINDINGS: Serum T4 and thyrotropin levels remained ... [Abstract] [Full-text]

Articles on Retinol published 27 April 2009:

The Ski protein can inhibit ligand induced RARalpha and HDAC3 degradation in the retinoic acid signaling pathway.   Biochem Biophys Res Commun, 383(1): 119-24.

Recent data has implicated the Ski protein as being a physiologically relevant negative regulator of signaling by retinoic acid (RA). The mechanism by which Ski represses RA signaling is unknown. Co-immunoprecipitation and immunofluorescence assay showed that Ski and RARalpha are in the same complex in both the absence and presence of RA, which makes Ski different from other corepressors. We determined that Ski can stabilize RARalpha and HDAC3. These results suggest that Ski represses RA ... [Abstract] [Full-text]

Articles on Retinol published 22 April 2009:

All-trans retinoic acid induces Thrombospondin-1 expression in acute promyelocytic leukemia cells though down-regulation of its transcription repressor, c-MYC oncoprotein.   Biochem Biophys Res Commun, 382(4): 790-4.

Thrombospondin-1 (TSP-1) was found to mediate the therapeutic effects of all-trans retinoic acid (ATRA) for leukemia. The aim of the present study was to evaluate the role of c-MYC, a key transcription factor that contributes to the genesis of many human tumors, in TSP-1 induction by ATRA in acute promyelocytic leukemia (APL). ATRA treatment markedly increased TSP-1 level and inhibited c-MYC expression in NB4 APL leukemic cells compared with controls. Promoter assays indicated that c-MYC ... [Abstract] [Full-text]

Articles on Retinol published 21 April 2009:

Divergent functions for airway epithelial matrix metalloproteinase 7 and retinoic acid in experimental asthma.   Nat Immunol, 10(5): 496-503.

The innate immune response of airway epithelial cells to airborne allergens initiates the development of T cell responses that are central to allergic inflammation. Although proteinase allergens induce the expression of interleukin 25, we show here that epithelial matrix metalloproteinase 7 (MMP7) was expressed during asthma and was required for the maximum activity of interleukin 25 in promoting the differentiation of T helper type 2 cells. Allergen-challenged Mmp7(-/-) mice had less airway ... [Abstract] [Full-text]

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