Identification of a Membrane Receptor for Retinol-Binding Protein Functioning in the Cellular Uptake of Retinal

Retinol-binding protein (RBP) is the transport protein that carries retinol in the circulation from the liver to its target tissues. The existence of a cell-surface receptor on the target cells, which mediates the uptake of retinol from RBP, has been known since 1975. Recently, it was identified as an integral transmem-brane protein named STRA6 that is inducible by retinoic acid in certain cancer cells. The receptor was found to be highly specific for RBP, with high affinity, and to be localized in all tissues known to require retinol for their function, particularly the pigment epithelium of the eye.     

人体β-胡萝卜素的肠转化和吸收后转化的研究

目的 :为了解部分中国人体内 β 胡萝卜素 ( β carotene ,以下简称 β C)转化维生素A (vitaminA ,以下简称VA)的效率 ,开展了本研究。方法 :使用稳定同位素稀释法对 15名 5 0 60岁健康农村志愿者 (男 9,女6)进行β C人体代谢实验。 2周适应期和 5 6天实验期内 ,志愿者接受常规膳食 ,避免大量VA和 β C摄入以及烟、酒和营养补充剂。实验第 1天 ,给受试者含 6mg氘标记 β C( 2 H8β C)玉米油胶丸 ,随半流质早餐 (脂肪热能比 2 5 % )一起摄入。实验第 4天 ,受试者以同样方法摄入含 3mg氘标记醋酸视黄醇 ( 2 H8RAC)油剂胶丸。实验第 1天和第 4天摄入标记物后 0 ,3 ,5 ,7,9,11,13h时 ,实验第 2 ,3 ,5 ,6,7,8,9,10 ,14,2 1,2 8,3 5 ,42 ,49,5 6天晨空腹时 ,采静脉血。用高效液相色谱仪 (HPLC)分离血清 β C和VA组分 ,再分别使用气相质谱仪(GC MS)和液相质谱仪 (LC MS)测定VA和 β C组分的同位素丰度。根据VA和 β C的浓度和同位素丰度 ,描述标记VA和β C在体内应答的血液动力学曲线。 结果 :所有 15名受试者对2 H8RAC应答明显 ;但是在对2 H8β C的应答方面 ,只有 11名受试者2 H4视黄醇应答曲线明显 ,有 4名受试者血清2 H4视黄醇应答曲线非常微弱。经过对备份血清样品进行的多次重复GC MS测定 ,我们目前初步?     

Zinc and magnesium in liver cirrhosis

Abstract. The Authors determined zinc (Zn) and magnesium (Mg) in the plasma, urine, erythrocytes (RBCs), mono- and polymorphonuclear cells (MNCs and PMNs) of patients with overt alcoholic and nonalcoholic liver cirrhosis. In order to obtain a clearer clinical picture, biochemical and nutritional parameters (retinol, tocopherol, six different carotenoids, creatinine-height index and tricipital skinfold), as well as markers of portal hypertension (spleno-portal size and platelet count) were also evaluated.
The plasma levels of Zn and Mg were found to be reduced, as were the urine levels of Mg. Urine Zn, on the other hand, was higher than normal. Plasma Zn correlated inversely, and urine Zn directly, with the severity of the disease, rather than with alcohol consumption or treatment with diuretics. Protein metabolism impairment would appear to affect the plasma transport of Zn rather than its overall availability in the organism; the opposite was found in the case of Mg, the availability of which appeared to be reduced. Determination of the two elements in RBCs, MNCs and PMNs suggested that a true nutritional deficit cannot be demonstrated. MNCs, rather than RBCs or PMNs seem better to reflect tissue status of trace elements.     

13-cis-retinoic acid (NSC 122758) in the treatment of children with metastatic neuroblastoma unresponsive to conventional chemotherapy: Report from the childrens cancer study group

The Childrens Cancer Study Group evaluated daily oral 13-cis-retinoic acid to determine its therapeutic efficacy in 28 children with advanced neuroblastoma refractory to conventional therapy. Cheilitis and fissured lips were the most common side effects; however, fewer than 50% of the patients experienced any toxicity. Two of twenty-two evaluable children demonstrated positive response to therapy. In one case, a child received the drug for 11 months. Seventeen patients demonstrated progressive disease within 28 days of the start of treatment. Three other patients with stable disease, or removed from study at day 28, were considered nonresponsive. Our data demonstrate that, when given as a single daily oral dose of 100 mg/m², 13-cis-retinoic acid does not have significant activity in children with advanced neuroblastoma. © 1992 Wiley-Liss, Inc.     

视黄醇结合蛋白4与代谢综合征的关系

目的 探讨视黄醇结合蛋白4(RBP4)的血清水平及-G 803 A SNP与代谢综合征的关系.方法 收集116名伴2型糖尿病的代谢综合征患者和93名正常体检者,放射免疫法测定RBP4血清水平,聚合酶链式反应及序列分析检测G 803 A多态性基因型.结果 (1)RBP4水平在所有受试者中与体质指数(BMI)、腰围、空腹胰岛素(FINS)、胰岛素抵抗指数(HOMA-IR)、三酰甘油(TG)正相关,对照组中与TG、TC、LDL-C正相关,男性组中与DBP正相关,女性组中与年龄、FINS、HOMA-IR、TG、SBP正相关,多元逐步回归分析发现腰围、BMI、TG和年龄是独立相关因素;RBP4水平在代谢综合征组和男性组显著升高,在有规律运动组显著降低.(2)代谢综合征组与正常对照组的RBP4-G 803 A多态性基因型分布未见显著差异,按不同基因型分组的代谢指标亦无显著性差异.结论 在中国汉族人群中,RBP4水平与多个代谢参数相关,RBP4基因-G 803 A SNP与代谢综合征没有关联.     

Contrasting in vitro effects of retinol and mononuclear cell factor on young and old human cartilage

Studies with young animal cartilage have shown that retinol and mononuclear cell-factor (MCF) cause in vitro breakdown of the cartilage, mediated by the living chondrocyte (indirect degradation). We studied the effects of retinol and MCF on healthy human articular cartilage of different ages, measuring the effects on proteoglycan (PG) content of the cartilage, and on PG synthesis during 8 days of culture. This study shows: Retinol and MCF induce indirect degradation of young, but not of old human cartilage of the humeral head; Both retinol and MCF suppress PG synthesis of young and stimulate PG synthesis of old cartilage; The effects of retinol and MCF on cartilage PG content and on PG synthesis are related to the metabolic state of the chondrocyte; Therefore mononuclear cell-factor may have a destructive or beneficial effect on cartilage depending on whether proteoglycan synthesizing activity is high or low, respectively.     

Plasma levels of antioxidant vitamins and cholesterol in a large population sample in Central-Northern Italy

Background: In a population-based multicenter case-control study of diet, life-style, and gastric cancer a large series of adults, aged 30–75 years (mean 58.9 yearss), were randomly sampled from the general population in 3 areas of Central-Northern Italy. Aim of the study: To evaluate the relationship between plasma levels of antioxidant vitamins and cholesterol, and sociodemographic characteristics, life-style factors, and dietary intake of selected nutrients in a sample of the Italian population. Methods: A fasting blood sample was available for 945 subjects (553 men, 392 women). The plasma concentrations of ascorbic acid, carotene, retinol, alpha-tocopherol, and cholesterol were determined by a centralized laboratory. All participants answered to a detailed questionnaire collecting information on sociodemographic and anthropometric characteristics, smoking, alcohol drinking, and dietary habits. Covariance analysis models, with post hoc Dunnett tests, including terms for age, sex, study center, and period of blood drawing, were used for selected multiple-way comparisons of mean values of plasma nutrients. Results: Mean plasma values of retinol were higher among men while women had higher levels of plasma carotene, ascorbic acid, alpha-tocopherol, and cholesterol. Plasma carotene levels showed an inverse association with body mass index, alcohol consumption, and smoking and a positive association with social class. Carotene concentrations were higher in plasma samples obtained in spring/summer, while ascorbic acid levels were higher in autumn/winter. Partial correlation coefficients between carotene and ascorbic acid (0.69 in men; 0.74 in women), between carotene and alpha-tocopherol (0.44; 0.37), and between alpha-tocopherol and ascorbic acid (0.45; 0.41). Plasma alpha-tocopherol and retinol correlated with plasma cholesterol. On the other hand, plasma carotene and ascorbic acid were correlated with their estimated dietary intakes, while the intakes of other nutrients, as expected, correlated rather poorly with the respective plasma concentrations. Conclusions: Socio-economic factors, life-style, and specific nutrient intake, in addition to gender, are related to nutrient plasma levels in Italian adults and may provide specific suggestions for the prevention of chronic diseases. Received: 8 December 1998, Accepted: 25 February 1999     

Measurement of albumin and low molecular weight proteins in the urine of newborn infants using a cotton wool ball collection method

Objective : The aim of this study was to investigate the inter-relationship between urinary excretion of alpha-1-microglobulin (AIM), retinol-binding protein (RBP) and albumin in term and premature neonates, with urine collected into cotton wool balls and extracted by a novel method. Subjects and methods : Sixty-four infants were studied on the first day of life; 26 had been born at term (37–42 weeks gestation) and 38 prematurely (24–28 weeks n = 16, 29–36 weeks n = 22). Urine collected into cotton wool balls was analysed following a new detergent extraction method, which resulted in a recovery rate of 94–107% for albumin, AIM, RBP and creatinine. Results : Urinary protein excretion, expressed as a ratio to urinary creatinine, decreased significantly with increasing gestational age (24–28 weeks, 29–36 weeks, 37–42 weeks: albuminxreatinine ratio mg/mmol mean 96.9, 31.7, 19.3; AIM: creatinine ratio mg/mmol mean 99.3, 37.0, 7.8; RBP: creatinine ratio mg/mmol mean 16.2, 3.8, and <0.01, below the limit of detection, respectively). When results were corrected for birthweight, this gestation-associated effect was still present for A1M and RBP, but not for albumin. In premature infants there was a significant positive correlation between AIM: creatinine ratio and RBP: creatinine ratio ( r = 0.85), and also between albumin and both AIM and RBP ( r = 0.82 and 0.77). Conclusion : Increased excretion of AIM, RBP and albumin at earlier gestational ages is probably due to proximal tubular immaturity, although tubular damage and also glomerular dysfunction cannot be excluded as possible explanations.