AHA Conference Report on Cholesterol. Diagnosis, evaluation, and treatment: current status and issues.
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American Heart Association↗
Biomedical subjects
D S Goodman
Publications and source records attributed to D S Goodman.
Regulation of the cellular retinoid-binding proteins and their messenger ribonucleic acids during P19 embryonal carcinoma cell differentiation induced by retinoic acid.
P19 embryonal carcinoma (EC) cells can be induced to differentiate in vitro into a variety of cell types by treatment with different concentrations of retinoic acid (RA). A study was conducted to explore the regulation of expression of the genes for cellular retinoic acid-binding protein (CRABP) and cellular retinol-binding protein (CRBP) in P19 cells induced to differentiate by RA. For each retinoid-binding protein, both the level of specific mRNA and of immunoreactive protein were measured, respectively, by RNase protection assay and by a specific RIA. Dramatic increases in CRABP and CRBP were seen, at both the mRNA and protein levels, during the RA-induced differentiation. CRBP induction differed from that of CRABP in several major ways. 1) Induction of CRBP occurred at lower concentrations of RA (10(-9) M) than did that of CRABP (10(-8)-10(-7) M). 2) CRBP induction was an early response (within 3 h) to RA treatment, whereas CRABP induction occurred at a later time (12-24 h). 3) Induction of CRABP mRNA by RA was blocked by the protein synthesis inhibitor cycloheximide, whereas induction of CRBP mRNA was not. 4) Several differentiation inducers were tested for their effects on the expression of CRABP and CRBP in P19 cells. CRBP induction occurred with a wider spectrum of inducers than did that of CRABP. 5) In addition, the induction of CRABP and CRBP mRNAs by RA was examined in six different cell lines, including three EC lines. CRBP induction occurred in a wider spectrum of cell lines than did that of CRABP. The induction of CRABP in EC cells seems, in general, to correlate with their differentiation into neuron-like cells. Taken together, our results suggest that CRBP induction may be a direct response to RA and represent a general event in RA-induced cell differentiation, whereas CRABP induction may be an indirect response and represent a later event restricted to only certain differentiation pathways. CRBP may be an early response gene induced by RA.
Animals↗
Localization of retinol-binding protein messenger RNA in the rat kidney and in perinephric fat tissue.
The cellular localization of retinol-binding protein (RBP) messenger RNA (mRNA) in the kidney, and the developmental pattern of the renal expression of the RBP gene, were studied in the Sprague-Dawley rat. In situ hybridization studies were conducted with single-stranded cRNA probes, using sections of adult and young rat kidneys. These studies revealed specific localization of RBP mRNA in the outer stripe of the medulla, specifically localized in the S3 segment of the proximal tubules. Northern blot analysis demonstrated that RBP mRNA was not detectable in the kidney before birth or during the first week postpartum, but was clearly detected by the end of the second week of age. No RBP mRNA was observed in the kidney by in situ hybridization at 12 days of age. At 26 days of age, however, RBP mRNA was clearly detected by the in situ hybridization technique, localized in the same anatomic region as that observed in the adult kidney. Transthyretin mRNA was not detected in the adult kidney. Previous studies have shown that immunoreactive RBP is localized in the convoluted segment of the proximal tubules of the rat kidney. The present results demonstrate that RBP mRNA in the kidney is localized in an anatomic region (the S3 segment of the proximal tubules) different from that of immunoreactive RBP. In addition, an intense RBP mRNA hybridization signal was detected in the perinephric fat tissue of 26- and 40-day-old and adult rats. Further analysis of RNA from epididymal fat showed a level of RBP mRNA approximately 20% of that of liver. The function of RBP synthesized in the kidney and adipose tissue remains to be determined. We have previously hypothesized that RBP synthesized in extrahepatic tissue may function in the recycling of retinol back to the liver or to other target tissues.
Adipose Tissue↗
New guidelines for lowering blood cholesterol.
An expert panel of the National Cholesterol Education Program issued a report that presents new, detailed guidelines for cholesterol treatment. The report provides specific recommendations for classifying patients according to their cholesterol levels. By using these guidelines, physicians dealing with individual patients will be able to determine who should be treated to lower blood cholesterol and to decide how such patients should be treated.
Algorithms↗
Retinol-binding protein is synthesized in the mammalian eye.
As the chromophoric component of the visual pigment, retinol plays an essential role in vision. In the plasma, retinol is transported by retinol-binding protein (RBP) in complex with transthyretin (TTR, prealbumin). In previous work we demonstrated intraocular synthesis of TTR. To determine whether RBP is also synthesized in the eye, we performed Northern and Western blot analysis of rat eye, and detected both RBP mRNA and immunoreactive RBP. Regional Northern analysis of bovine eye localized RBP mRNA to ciliary body/iris and retina/RPE. Preliminary immunohistochemical studies revealed a widespread but heterogeneous distribution of RBP in rat eye. We postulate that ocular RBP and TTR are involved in the intraocular translocation of retinol.
Animals↗
Induction of the expression of retinol-binding protein and transthyretin in F9 embryonal carcinoma cells differentiated to embryoid bodies.
Studies were conducted to determine if the expression of the gene for retinol-binding protein (RBP) and/or transthyretin (TTR) could be induced upon differentiation of F9 teratocarcinoma cells to either visceral endoderm or parietal endoderm. Both TTR mRNA and RBP mRNA were undetectable in the undifferentiated F9 stem cells and in F9 cells differentiated to parietal endoderm. However, TTR mRNA and RBP mRNA were both detected in F9 cell aggregates differentiated to embryoid bodies (which contain visceral endoderm-like cells) by treatment of the aggregates in suspension with retinoic acid. TTR mRNA was observed at 3 days, and RBP mRNA at 5 days, after treatment of the F9 cell aggregates with retinoic acid. Both TTR mRNA and RBP mRNA were found to be specifically localized by in situ hybridization in the outer layer of cells (the visceral endoderm-like cells) of the embryoid bodies. Finally, synthesis and secretion of both RBP and TTR by F9 cell embryoid bodies was demonstrated by specific immunoprecipitation of each newly synthesized protein from the culture medium. These data thus demonstrate the production and presence of RBP mRNA and TTR mRNA, and the synthesis and secretion of RBP and TTR, by F9 cell embryoid bodies (specifically by visceral endoderm-like cells). This finding suggests that these two proteins may be synthesized by rodent embryos extremely early in embryonic development.
Animals↗
Plasma transthyretin. Tissue sites of degradation and turnover in the rat.
Transthyretin (TTR) is involved in the plasma transport of both retinol and thyroid hormones. TTR is synthesized in the liver and choroid plexus, and in small amounts in several other tissues. A study was conducted to determine the tissue sites of degradation and turnover of TTR in the rat. The study employed TTR labeled with tyramine cellobiose (TC) and the trapped ligand method. Samples of purified rat TTR were labeled either with 125I-TC or directly with 131I. A mixture of the two labeled TTRs was injected intravenously into six rats. Blood samples were collected via a venous catheter for kinetic (turnover) analysis. After 24 or 48 h, the rats were killed, and 23 different tissues/organs were assayed as possible sites of TTR degradation. Derivatization of TTR with TC did not appreciably alter TTR plasma kinetics. Plasma turnover data were best fit by a three-pool model. The mean fractional turnover of plasma TTR was 0.15/h, and of total body TTR 0.04/h. The major sites of TTR degradation were the liver (36-38% of total body TTR degradation, almost all in hepatocytes), muscle (12-15%), and skin (8-10%). Tissues that were sites of 1-8% of body TTR degradation included kidneys, adipose tissue, testes, and the gastrointestinal tract. Less than 1% of total TTR degradation occurred in the other tissues examined. A second study was conducted in which labeled TTR was injected intraventricularly into the cerebrospinal fluid in order to explore the degradation of TTR of choroid plexus origin. The kinetics of the appearance and disappearance of such labeled TTR in plasma were physiologically reasonable, with an estimated turnover of cerebrospinal fluid TTR of the order of 0.33/h. The major tissue sites of degradation of labeled TTR injected into cerebrospinal fluid and into plasma were approximately the same. No specific degradation of TTR was found in the nervous system tissues. The most active organs of TTR catabolism, per gram wet weight, were liver and kidneys. These studies demonstrate that many tissues participate in TTR turnover and degradation; the studies provide quantitative information about the tissue sites of TTR catabolism.
Animals↗
Retinol-binding protein synthesis and secretion by the rat visceral yolk sac. Effect of retinol status.
Studies were conducted to explore in rats the role of retinol in the regulation of the synthesis and secretion of retinol-binding protein (RBP) by the visceral yolk sac compared to the liver. Previous studies have shown that in retinol deficiency, hepatic RBP secretion is specifically inhibited, whereas hepatic RBP synthesis rate is unchanged. Retinol-depleted, retinoic acid-supplemented female rats were mated, and maternal liver, fetal liver, and visceral yolk sac were obtained at 14 days of gestation (retinol-depleted group). A group of identically treated, retinol-depleted rats were repleted with retinol on the 14th day of gestation, and the same tissues were collected 6 h later (retinol-repleted group). Normal female rats were used as controls. RBP was assayed by radioimmunoassay and RBP mRNA levels by RNase protection assay using a rat RBP cDNA clone. RBP levels in the visceral yolk sac were elevated 10-fold in the retinol-depleted as compared to the control rats and had declined to near normal values in the retinol-repleted animals. The relative levels of RBP mRNA in the visceral yolk sac were very similar in all three groups of rats. Thus, as in the liver, in the visceral yolk sac retinol deficiency inhibits RBP secretion without altering RBP mRNA levels. In the visceral yolk sac, as in the liver, retinol status appears to regulate RBP secretion specifically, without affecting the rate of RBP biosynthesis.
Animals↗
Distributions of retinoids, retinoid-binding proteins and related parameters in different types of liver cells isolated from young and old rats.
The levels of retinoids, retinol-binding protein, cellular retinol-binding protein, cellular retinoic-acid-binding protein, transthyretin and the activities of retinyl palmitate hydrolase and cholesteryl oleate hydrolase were determined in purified parenchymal, fat-storing, endothelial and Kupffer cell preparations, and in liver homogenates from young adult (6-month-old) and old (36-month-old) rats. Retinoid levels were also determined in the plasma from young and old rats. Retinoid contents were determined by HPLC. The binding proteins and transthyretin were measured by specific radioimmunoassays; retinyl palmitate and cholesterol oleate hydrolases were measured by sensitive microassays. The retinoid content of both the liver homogenates and of the fat-storing, and parenchymal cell preparations increased between 6 months and 36 months of age. The cellular distribution of retinoids was similar for the two age groups analyzed with the fat-storing cells being the main retinoid storage sites in the rat liver. Concentrations of retinol-binding protein and transthyretin were high in parenchymal cell preparations. Cellular retinol-binding protein was enriched both in parenchymal and in fat-storing cell preparations; the highest concentrations of cellular retinoic-acid-binding protein were present in fat-storing cell preparations. No major differences were observed between the two age groups in the cellular concentrations and distributions of any of these binding proteins. High activity of cholesterol oleate hydrolase was measured in parenchymal and in Kupffer cell preparations; endothelial cell preparations also contained considerable activities. The distribution of this activity over the various cell types reflects their role in lipoprotein metabolism. Retinyl palmitate hydrolase activity was specifically enriched in parenchymal and in fat-storing cell preparations, consistent with the roles of these cells in retinoid metabolism. No major differences were observed between the two age groups in the cellular distributions of the two hydrolase activities. This study indicates that no major changes occur in the retinoid-related parameters analyzed with age, suggesting that rat liver retinoid metabolism does not change dramatically with age and that retinoid homeostasis is maintained.
Aging↗
Effects of dietary retinoid and triglyceride on the lipid composition of rat liver stellate cells and stellate cell lipid droplets.
Hepatic stellate cells store the majority of the liver's retinoid (vitamin A) reserves as retinyl esters in stellate cell lipid droplets. A study was conducted to explore the effects of differences in dietary retinoid and triglyceride intake on the composition of the stellate cell lipid droplets. Weanling rats were placed on one of five diets that differed in retinoid or triglyceride contents. The dietary groups were: 1) control (2.4 mg retinol (as retinyl acetate)/kg diet and 20.5% of the calories supplied by triglyceride (as peanut oil]; 2) low retinol (0.6 mg retinol/kg diet and control triglyceride levels); 3) high retinol (24 mg retinol/kg diet and control triglyceride levels); 4) low triglyceride (2.4 mg retinol/kg diet and 5% of the calories supplied by triglyceride); and 5) high triglyceride (2.4 mg retinol/kg diet and 45% of the calories supplied by triglyceride). Stellate cells were isolated using the pronase-collagenase method and stellate cell lipid droplets were isolated by differential centrifugation. The levels of retinoids and other lipids were measured by high performance liquid chromatography. The stellate cells from control rats contained 113 micrograms total lipid/10(6) cells. Control stellate cell lipid droplets had the following mean percent lipid composition: 39.5% retinyl ester; 31.7% triglyceride; 15.4% cholesteryl ester; 4.7% cholesterol; 6.3% phospholipids; and 2.4% free fatty acids. Both the concentration of stellate cell lipids and the composition of stellate cell lipid droplets were markedly altered by changes in dietary retinoid. The low and high retinol groups contained, respectively, 82 and 566 micrograms total lipid/10(6) cells, with retinyl ester representing, respectively, 13.6% and 65.4% of the lipid present in the stellate cell lipid droplets. Low and high triglyceride groups were similar to controls in both stellate cell lipid content and the composition of the stellate cell lipid droplets. These findings indicate that the composition of stellate cell lipid droplets is strongly regulated by dietary retinoid status but not by dietary triglyceride intake.
Animals↗
Transthyretin (prealbumin) in familial amyloidotic polyneuropathy: genetic and functional aspects.
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Amyloidosis↗
Studies on the in vivo transfer of retinoids from parenchymal to stellate cells in rat liver.
Studies were conducted to examine the in vivo transfer of chylomicron (dietary) retinoid from rat liver parenchymal to stellate cells. We specifically addressed the question of whether chylomicron retinyl ester is transferred directly from hepatic parenchymal to stellate cells without first undergoing hydrolysis. [14C]Retinyl palmitate and its non-hydrolyzable ether analog, retinyl [3H]hexadecyl ether, were utilized to answer this question. Chylomicrons labeled with these retinoids were injected intravenously into rats. Liver cell fractions, highly enriched in parenchymal or in stellate cells, were isolated 0.5 h, 4.5 h and 24 h after chylomicron injection. The ratio of 3H: 14C found in parenchymal cell preparations 4.5 h after injection was 1.8 times the ratio for the injected chylomicrons, and 24 h postinjection the ratio had increased to 2.5 times that of the chylomicrons. In the stellate-cell-enriched preparations the 3H: 14C ratio was found to be 0.39, 0.29, and 0.23 times the ratio found in the injected labeled chylomicrons at 0.5 h, 4.5 h and 24 h after injection respectively. From the levels of 14C observed in the isolated stellate cells, it is estimated that 0.5 h postinjection the stellate cells contained approximately 34% of the 14C (i.e. the retinol injected as chylomicron retinyl ester) present in the liver. By 4.5 h the 14C present in isolated stellate cells had risen to approximately 41% of that present in the total liver, and 24 h after injection approximately 55% of hepatic total 14C was found in the stellate cells. These findings suggest that chylomicron retinyl ester is not transferred directly from the parenchymal to stellate cells without first undergoing hydrolysis to retinol.
Animals↗
Effects of nutritional and hormonal factors on the metabolism of retinol-binding protein by primary cultures of rat hepatocytes.
Studies were conducted to explore hormonal and nutritional factors that might be involved in the regulation of retinol-binding protein (RBP) synthesis and secretion by the liver. The studies employed primary cultures of hepatocytes from normal rats. When cells were cultured in Dulbecco's modified Eagle's medium alone, a high rate of RBP secretion was observed initially, which declined and became quite low by 24 hr. Supplementing the medium with amino acids maintained RBP and albumin secretion at moderate (but less than initial) rates for at least 3 days. Further addition of dexamethasone maintained the production and secretion rates of RBP, transthyretin, and albumin close to the initial rates for up to 3-5 days in culture. The effects of dexamethasone were not rapid and were not specific for RBP; half-maximal effects were seen at 10(-9) to 10(-8) M levels. Hormonally treated hepatocytes produced and secreted RBP, transthyretin, and albumin at both absolute and relative rates similar to physiological values, as estimated from rates reported by others from studies in vivo (with both rats and humans) and with perfused livers. Glucagon addition partially maintained the secretion rates of these 3 proteins, but less effectively than did dexamethasone. A number of other hormones, added singly or in combination, did not affect RBP production or secretion. Addition of retinol to the cultured normal hepatocytes was without effect upon RBP secretion. These studies show that supplementing the culture medium of hepatocytes with amino acids and dexamethasone maintains RBP production and secretion for several days. In normal hepatocytes, with ample supply of retinol available within the cell, addition of exogenous retinol does not appear to influence RBP metabolism or secretion by the cells.
Animals↗
Studies on the metabolism of retinol-binding protein by primary hepatocytes from retinol-deficient rats.
Studies were conducted to explore the regulation of retinol-binding protein (RBP) metabolism in cultured primary hepatocytes from retinol-deficient rats. Newly isolated hepatocytes from retinol-deficient rats contained elevated levels (3.4-fold) of RBP, compared to hepatocytes from normal (retinol-adequate) rats. Addition of retinol to retinol-depleted hepatocytes stimulated RBP secretion by the cells in a concentration-dependent manner. Maximal stimulation of RBP secretion was seen with a retinol level of 0.3 micrograms/ml. The effect of retinol was quite rapid, and was evident by 20 minutes after addition of retinol to the medium. Stimulation of RBP secretion was only seen during the first few hours after retinol addition. The effect of retinol was specific for RBP; thus, retinol had no effect on the secretion rates of transthyretin or albumin. Addition of retinoic acid also stimulated RBP secretion by retinol-deficient hepatocytes. Addition of dexamethasone to retinol-deficient cells did not maintain the initial rate of RBP secretion. Dexamethasone also had no effect on the secretion of transthyretin or albumin by these cells. The effects of retinol and of dexamethasone seen here with retinol-depleted cells differed dramatically from effects seen in other studies with normal (retinol-adequate) hepatocytes. Thus, with normal cells, dexamethasone maintains RBP, TTR, and albumin production and secretion rates close to initial rates. Also in normal hepatocytes, with ample retinol available within the cell, addition of exogenous retinol does not appear to influence RBP secretion. In contrast, and as shown previously in intact rats, in retinol deficiency the availability of retinol specifically regulates the secretion of RBP by hepatocytes.
Animals↗
Prevalence of cutaneous disease in patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex.
Ninety adult patients with acquired immunodeficiency syndrome (AIDS) and 27 with AIDS-related complex were seen consecutively, when available, either as inpatients or in AIDS clinics and given complete cutaneous examinations. Skin disease was common both in patients with AIDS and in those with AIDS-related complex. The most common cutaneous findings were candidiasis in 55 patients (47.0%), dermatophytosis in 35 (30%), herpes simplex infections in 26 (22%), molluscum contagiosum in 11 (9%), seborrheic dermatitis in 37 (32%), and acquired ichthyosis or xerosis in 36 (30%). Several cutaneous conditions previously reported in association with AIDS were infrequently seen: Psoriasis was seen in only one patient, and deep fungal infections and basal and squamous cell carcinomas were seen in none. No significant differences were noted in the prevalence of skin disease between patients with AIDS and those with AIDS-related complex, although xerosis and ichthyosiform skin changes tended to be more common in those with AIDS. The yellow nail syndrome and "a papular eruption" associated with AIDS were seen. Skin diseases also tended to be widespread and severe in the patients studied.
AIDS-Related Complex↗
Pityrosporum, ketoconazole, and seborrheic dermatitis.
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AIDS-Related Complex↗
Distribution and levels of cellular retinol- and cellular retinoic acid-binding protein in various types of rat testis cells.
The distribution and levels of cellular retinol-binding protein (CRBP) and cellular retinoic acid-binding protein (CRABP) were measured in rat testicular peritubular and Sertoli cells and in isolated rat pachytene spermatocytes and spermatids. Two Sertoli cell preparations, one containing some germ cells and another that had been osmotically shocked to destroy germ cells, were examined. CRBP and CRABP levels were measured by specific and sensitive radioimmunoassays. Testicular peritubular cell cytosol preparations were found to contain high levels of CRBP (1.48 +/- 0.87 microgram CRBP/mg protein) but CRABP could not be detected. The mean CRBP level in Sertoli cell preparations that contained some germ cells was 0.93 +/- 0.24 microgram CRBP/mg protein; this value was similar to the level of 1.11 +/- 0.20 microgram CRBP/mg protein measured for Sertoli cells free of germ cells. The level of CRABP found in Sertoli cell preparations containing germ cells (0.81 +/- 0.32 microgram CRABP/mg protein) was approximately five times greater than was observed in Sertoli cells free of germ cells (0.16 +/- 0.03 microgram CRABP/mg protein). CRBP and CRABP levels in cultured Sertoli cells were not affected by time in culture for up to five days of culture. Pachytene spermatocytes and spermatids were very enriched in CRABP (0.72 +/- 0.26 microgram CRABP/mg protein for spermatocytes and 0.65 +/- 0.21 microgram CRABP/ml protein for spermatids). A search for a high molecular weight retinol-binding protein did not demonstrate the existence of such a protein in Sertoli cell-conditioned medium. In summary, these studies provide quantitative information about the distribution of the cellular retinoid-binding proteins in the cell types that compose the rat testis.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Cellular retinoic acid- and cellular retinol-binding proteins: complementary deoxyribonucleic acid cloning, chromosomal assignment, and tissue specific expression.
Both cellular retinoic acid-binding protein (CRABP) and cellular retinol-binding protein (CRBP) are widely distributed in mammalian tissues and display different patterns of tissue distribution. We have isolated cDNA clones for bovine CRABP and for human CRBP from a bovine adrenal gland cDNA library and from a human liver cDNA library, respectively, by probing with synthetic oligonucleotides. The primary structures of the two proteins inferred from the DNA sequences were identical to the previously reported amino acid sequences. The cDNA probes were used to obtain some information about the genes for CRABP and CRBP, including their chromosomal localization, and about the tissue specific expression of these two genes. Southern blot analyses under highly stringent conditions, of genomic DNA from both the bovine and the mouse, showed that for each retinoid-binding protein, specific DNA sequences are sufficiently conserved across species to allow cross-hybridization to occur. Under the same conditions, however, the DNA sequences for CRABP and CRBP within each species appear to be sufficiently different that cross-hybridization was not observed between the two cDNA probes. Using mouse-hamster somatic cell hybrids, it was demonstrated that these genes map to mouse chromosome 9 or 10. Northern blot analyses of RNA from six tissues from both the bovine and the mouse showed marked differences in the levels of the specific transcript for each binding protein among the different tissues, and in the tissue distribution of CRABP mRNA as compared to that of CRBP mRNA. In both species, CRBP mRNA was detected in more tissues than was CRABP mRNA. For both proteins, the relative tissue distribution of the mRNAs appeared to both resemble and to differ from the reported distribution of the binding proteins themselves. The factors that regulate the tissue specific expression of the genes for CRABP and CRBP remain to be determined.
Amino Acid Sequence↗