Biochemical and Biophysical Research Communications
Regular ArticleVitamin A Regulates the Expression of Apolipoprotein Al and CIII Genes in the Rat
Abstract
The effect of vitamin A on the expression of apoAI and CIII genes in intact rats was studied. In vitamin A-deficient rats, the hepatic level of apoAl mRNA was increased and enhanced by an oral administration of excess retinoic acid(RA). A similar administration to normal rats caused an increase in the apoAI mRNA level in the intestine without affecting that of hepatic mRNA. Though the hepatic level of apo CIII mRNA was not affected by the vitamin A status, the intestinal level was positively regulated by vitamin A. These findings show that vitamin A regulates the expression of apolipoprotein AI and CIII genes in a tissue-specific and complex fashion.
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Specific Milk Composition of miR-30b Transgenic Mice Associated with Early Duodenum Maturation in Offspring with Lasting Consequences for Growth
2023, Journal of NutritionMilk composition is complex and includes numerous components essential for offspring growth and development. In addition to the high abundance of miR-30b microRNA, milk produced by the transgenic mouse model of miR-30b-mammary deregulation displays a significantly altered fatty acid profile. Moreover, wild-type adopted pups fed miR-30b milk present an early growth defect.
This study aimed to investigate the consequences of miR-30b milk feeding on the duodenal development of wild-type neonates, a prime target of suckled milk, along with comprehensive milk phenotyping.
The duodenums of wild-type pups fed miR-30b milk were extensively characterized at postnatal day (PND)-5, PND-6, and PND-15 using histological, transcriptomic, proteomic, and duodenal permeability analyses and compared with those of pups fed wild-type milk. Milk of miR-30b foster dams collected at mid-lactation was extensively analyzed using proteomic, metabolomic, and lipidomic approaches and hormonal immunoassays.
At PND-5, wild-type pups fed miR-30b milk showed maturation of their duodenum with 1.5-fold (P < 0.05) and 1.3-fold (P < 0.10) increased expression of Claudin-3 and Claudin-4, respectively, and changes in 8 duodenal proteins (P < 0.10), with an earlier reduction in paracellular and transcellular permeability (183 ng/mL fluorescein sulfonic acid [FSA] and 12 ng/mL horseradish peroxidase [HRP], respectively, compared with 5700 ng/mL FSA and 90 ng/mL HRP in wild-type; P < 0.001). Compared with wild-type milk, miR-30b milk displayed an increase in total lipid (219 g/L compared with 151 g/L; P < 0.05), ceramide (17.6 μM compared with 6.9 μM; P < 0.05), and sphingomyelin concentrations (163.7 μM compared with 76.3 μM; P < 0.05); overexpression of 9 proteins involved in the gut barrier (P < 0.1); and higher insulin and leptin concentrations (1.88 ng/mL and 2.04 ng/mL, respectively, compared with 0.79 ng/mL and 1.06 ng/mL; P < 0.01).
miR-30b milk displays significant changes in bioactive components associated with neonatal duodenal integrity and maturation, which could be involved in the earlier intestinal closure phenotype of the wild-type pups associated with a lower growth rate.
The factors that bind to the hepatic-specific human apolipoprotein AI (apoAI) 48-bp downstream enhancer (DSE) were identified and characterized by electrophoretic mobility shift assays. A significant homology was shown between the histone 4 (H4) promoters and the hepatic-specific human apoAI DSE at Sp1 and H4TF2 binding sites. Human HepG2 nuclear extracts were used to form four specific complexes with the DSE (referred to as apoAI DSE-1, -2, -3, and -4). The apoAI DSE-1 and -2 complexes showed similar binding specificity to the Sp/H4TF1 consensus site within the apoAI DSE. The apoAI DSE-1 complex was predominantly recognized by anti-Sp1 and Sp3 sera in gel shift assays, indicating that the DSE was recognized by multiple Sp family members. Nuclear extracts that were prepared from retinoic acid treated HepG2 cells showed increased levels of Sp factors in gel shift and Western blot assays. The apoAI DSE-2 complex was identified as H4TF1 and formed in the absence of magnesium chloride. The apoAI DSE-3 complex bound to a consensus GATA element within the DSE that was recognized by recombinant human GATA-6 as well. The apoAI DSE-3 complex was completely disrupted by a GATA-4 antibody in EMSA. GATA-4 and -6 were detected in nuclear extracts prepared from retinoic acid treated HepG2 cells using Western blot assays. The highest apoAI DSE-3 levels were observed with retinoic acid treated HepG2 cell nuclear extracts in EMSA. ApoAI DSE-4 is a multi-factor complex that includes an Sp/H4TF1 factor and either H4TF2 or apoAI DSE-3. Because apoAI DSE mutations revealed transcription defects in transient transfection assays, we conclude that the entire DSE sequence is required for full apoAI transcriptional activity in HepG2 cells.
Regulation of lipid and lipoprotein metabolism by retinoids
2001, Journal of the American Academy of DermatologyRetinoids are small vitamin A-derived lipophilic compounds that influence a wide variety of developmental and metabolic processes. Retinoids exert their action by activating transcription factors belonging to the retinoic acid receptor (RAR) and retinoid X receptor (RXR) subfamilies of nuclear receptors. Therapeutically, retinoids are used for the treatment of dermatological disorders and certain cancers. Dyslipidemia is a common side-effect of therapy with the currently available retinoids. This review summarizes our current understanding of the molecular mechanisms of regulation of lipid and lipoprotein metabolism by retinoids. (J Am Acad Dermatol 2001;45:S158-67.)
Negative regulation of Apo A-I gene expression by retinoic acid in rat hepatocytes maintained in a coculture system
1998, Biochimica et Biophysica Acta - Lipids and Lipid MetabolismRat hepatocytes cocultured with rat liver epithelial cells (RLEC) were used to investigate the influence of all-trans retinoic acid (RA) on the regulation of apolipoproteins (Apo) A-I and A-II gene expression, the major protein constituent of high-density lipoproteins. In contrast to rat hepatocytes in conventional primary culture, Apo A-I and Apo A-II gene expression remained high and stable for several days in parenchymal cells in coculture. Treatment of cocultured rat hepatocytes with RA resulted in a specific decrease in Apo A-I mRNA levels whereas no marked difference in Apo A-II mRNA levels was observed. Such a negative effect of RA was already detected as early as 2 days of treatment and was effective for the entire experimental period (6 days). As controls, RARβ mRNA levels increased whereas those of GAPDH mRNA were not affected by the RA treatment. The decrease in Apo A-I mRNA levels was associated with lower amounts of Apo A-I secreted in the culture medium within day 1 of treatment. This effect required active transcription and protein synthesis. These results show that, contrary to primary pure hepatocyte cultures and hepatoma cell lines, cocultures of rat hepatocytes reproduce the in vivo results suggesting that only well differentiated hepatocytes may correctly respond to RA. Furthermore, they demonstrate that RA can directly act on hepatocytes and differently affect Apo A-I and Apo A-II gene expression.
Vitamin A deficiency increases hepatic apolipoprotein A-I mRNA expression in both euthyroid and hypothyroid rats
1997, Journal of Nutritional BiochemistryWe have examined the effects of chronic thyroid hormone deficiency, vitamin A deficiency, and subsequent acute repletion with thyroid hormone (T3) and/or retinoic acid (RA) on the expression of hepatic apolipoprotein (apo) A-I mRNA. Chronically hypothyroid and/or retinoid-deficient male Lewis rats were treated once or three times with T3, all-trans-RA, or both hormones. The hypothyroid state significantly reduced (P < 0.001) and the vitamin A-deficient state significantly elevated (P < 0.0001) the expression of apo A-I mRNA. A single injection of T3 (10 μg/100 gm body weight) significantly elevated apo A-I mRNA in hypothyroid rats (P < 0.001). A single injection of RA (20 μg/rat) reduced apo A-I mRNA by about 20 to 25% and daily injection of RA for three days reduced apo A-I mRNA abundance further in hypothyroid (P < 0.05), but not euthyroid, rats. There was a significant interaction between T3 hormone treatment and vitamin A status of the rats, as well as between RA and T3 treatment and the thyroid status of the rats. These in vivo results may indicate that nuclear retinoid receptors and thyroid hormone receptors interact in the regulation of the apo A-I gene in liver.
Retinoic acid increases cellular retinol binding protein II mRNA and retinol uptake in the human intestinal Caco-2 cell line
1997, Journal of NutritionCellular retinol binding protein II (CRBPII) is an abundant small intestinal protein that facilitates vitamin A trafficking and metabolism. The magnitude of retinol uptake and metabolism correlate to CRBPII levels in the human intestinal Caco-2 cell line. To investigate the importance of retinoic acid receptor response elements in the promoter of the CRBPII gene, retinoic acid regulation of CRBPII expression and vitamin A absorption was studied in differentiated Caco-2 cells. All-trans- or 9-cis-retinoic acid increased CRBPII mRNA levels two- to threefold. This was associated with a 50% increase in retinol absorption. Retinoic acid receptor β and apolipoprotein A1 regulatory protein-1, two nuclear receptors that bind to the CRBPII promoter, were also induced, whereas other retinoid and orphan receptors were not. Thus, retinoic acid may regulate CRBPII expression directly or by selectively changing levels of nuclear receptors or other factors. These studies are the first to demonstrate that retinoic acid can modulate endogenous CRBPII mRNA levels and retinol absorption in Caco-2 cells and suggest that human intestinal vitamin A absorption may be regulated by retinoids.