A study of connective tissue macromolecules in skin of mice with goldthioglucose-induced obesity.

The effect of obesity on the connective tissue composition of skin was investigated in mice with goldthioglucose (GTG)-induced obesity. Four months after GTG treatment, the obese animals were sacrificed. Acid mucopolysaccharides, glycoproteins, collagen, and elastin were analyzed in the skin and compared to the controls. Total MPS in the skin from obese animals decreased, reflected mostly in hyaluronic acid. Chondroitin showed an increase over controls. The content of soluble glycoproteins varied; total carbohydrate and sialic acid of the glycoprotein tended to increase with obesity. Collagen and elastin both tended to decrease with obesity.     

Hepatic glycoprotein synthesis in streptozotocin diabetic rats

In vitro incorporation of 3H-mannose into dolichol phosphate mannose, dolichol pyrophosphate oligosaccharides, and secretory and membrane glycoproteins was investigated in liver slices from streptozotocin diabetic rats. In addition, 14C-leucine incorporation into glycoproteins was studied. 3H-mannose incorporation was significantly less in secretory glycoproteins from diabetic rat liver slices than from control tissues, but 14C-leucine incorporation in these proteins was similar in both groups. Dolichol-phosphate mannose and dolichol-phosphate oligosaccharide synthesis were significantly down-regulated in diabetes. When incubated with insulin, mannosylation of secretory proteins, dolichol-phosphate mannose and dolichol-phosphate oligosaccharides reached control levels in three hours. Dolichol-phosphate mannosyltransferase activity was significantly less in diabetes, while in the presence of insulin, the enzyme activity reached control levels in three hours. These results indicate that key intermediates in glycoprotein biosynthesis are regulated by insulin.     

Dolichol synthesis in liver slices of streptozotocin diabetic rats

The rate of dolichol synthesis in normal and diabetic liver slices in the presence or absence of insulin was investigated with radiolabeled acetate and mevalonate as substrates. Cholesterol and dolichol syntheses were found low in diabetic rat liver slices when incubated either with 1-14C-acetate or 2-3H-mevalonate. In the presence of insulin, cholesterol and dolichol synthesis in diabetic rat liver slices returned to normal in nine hours when incubated with 1-14C-acetate; however, with 2-3H-mevalonate, synthesis of cholesterol and dolichol normalized in about three hours. These studies show that dolichol synthesis in rat liver slices is dependent on insulin.     

Metabolism of low-density lipoprotein-proteoglycan complex by macrophages: further evidence for a receptor pathway

Earlier, we (Vijayagopal, P., et al. (1985) Biochim. Biophys. Acta 837-251) have shown that complexes of plasma low-density lipoproteins (LDL) and arterial chondroitin sulfate-dermatan sulfate proteoglycan aggregate promote LDL degradation and cholesteryl ester accumulation in mouse peritoneal macrophages. Further studies were conducted to determine whether LDL-proteoglycan complex is metabolized by a receptor-mediated process. Native proteoglycan aggregate was isolated from bovine aorta by associative CsCl isopycnic centrifugation. Complex of 125I-labeled LDL and proteoglycan aggregate formed in the presence of 30 mM Ca2+ was incubated with macrophages, and the binding at 4 degrees C and degradation at 37 degrees C of 125I-labeled LDL in the complex was monitored. Both binding and degradation of the complex were specific and saturable, suggesting that the processes are receptor mediated. The Kd for binding was 23 micrograms LDL protein per ml in the complex. Degradation of 125I-labeled LDL-proteoglycan complex was not suppressed by preincubation of macrophages with excess unlabeled complex, suggesting that the receptor for the complex is not subject to down regulation. Both binding and degradation of the complex and the resultant stimulation of cholesteryl ester synthesis were inhibited by limited treatment of cells with low doses of trypsin and pronase, indicating that the binding sites are protein or glycoprotein in nature. Binding was not inhibited by an excess of native LDL and beta-VLDL and exhibited only partial competition by excess unlabeled acetyl-LDL; however, polyinosinic acid, fucoidin and dextran sulfate, known inhibitors of acetyl-LDL binding and degradation in macrophages, did not affect LDL-proteoglycan complex binding and degradation. Similarly, excess unlabeled LDL-proteoglycan complex produced only partial inhibition of the binding and degradation of 125I-labeled acetyl-LDL by macrophages, suggesting that the binding sites for acetyl-LDL and LDL-proteoglycan complex are probably not identical. These studies provide evidence for a receptor-mediated pathway for the metabolism of LDL-proteoglycan complex in macrophages.     

ABO associations with blood pressure, serum lipids and lipoproteins, and anthropometric measures

Discriminant analysis was used to explore multivariate associations with ABO blood types in a biracial sample of 898 Bogalusa youths. Dependent variables included blood pressure (systolic and diastolic), serum lipid and lipoprotein levels (total cholesterol, alpha-, beta-, and pre-beta-lipoprotein cholesterol, and triglycerides), and anthropometric variables (height, weight, right arm length, triceps skinfold thickness, and a computed ponderal index). Analyses performed within race showed that several variables including beta-lipoprotein cholesterol, systolic blood pressure, and the ponderal index were sufficient to discriminate between individuals possessing the B antigen (B and AB) and those not possessing the B antigen (A and O) in the White subsample. However, height in itself can account for the detected difference, B individuals being taller than non-B individuals by a mean value of 2.4 cm. A concordant, but not significant effect was found in the Black subsample. Further tests support the conclusion that the strongest association is between ABO blood type and height.     

Studies on the mechanism of uptake of low density lipoprotein-proteoglycan complex in macrophages

Earlier, we (Vijayagopal, P. et al. (1988) Biochim. Biophys. Acta 960, 210) showed that mouse peritoneal macrophages metabolize low density lipoprotein (LDL)-proteoglycan complex by a receptor pathway distinct from the acetyl-LDL receptor. Further studies were conducted to probe further into the mechanism of LDL-proteoglycan complex uptake by macrophages. Both 125I-methyl-LDL-proteoglycan complex and 125I-LDL-proteoglycan complex were taken up and degraded by the cells to the same extent. Similarly, the ability of these ligands to stimulate cholesteryl ester synthesis was also indistinguishable. These results rule out the possibility of apoB,E receptor involvement in the uptake of LDL-proteoglycan complex in macrophages. Sodium fluoride, cytochalasin D and aggregated LDL inhibited degradation of the complex by 24%, 26% and 28%, respectively, indicating that phagocytosis is only a minor pathway for the uptake. Both binding and degradation of the complex were not inhibited by excess hyaluronic acid suggesting that ligand recognition was not through hyaluronic acid binding sites. As compared to acetyl-LDL, the cellular degradation of LDL-proteoglycan complex was retarded. Macrophages exhibited a rapid stimulation of [3H]inositol trisphosphate (IP3) release and diacylglycerol production when incubated with LDL-proteoglycan complex. Furthermore, pertussis toxin produced a 62% inhibition of LDL-proteoglycan complex mediated IP3 release, suggesting that LDL-proteoglycan complex metabolism in macrophages is dependent upon the G-protein coupled signal transduction mechanism. These results show that receptor mediated endocytosis plays a major role in the metabolism of LDL-proteoglycan complex in macrophages.     

A multivariate method for detecting genetic linkage, with application to a pedigree with an adverse lipoprotein phenotype.

The robust or model-free method for detecting linkage developed by Haseman and Elston for data from sib pairs is extended to incorporate observations of multiple traits on each individual. A method is proposed that estimates the linear function that results in the strongest correlation between the squared pair differences in the trait measurements and identity by descent at a marker locus. The method is illustrated by the study of apolipoprotein and cholesterol levels in individuals from a large family that had many members diagnosed with coronary heart disease.