Bhandaru Radhakrishnamurthy

Connective Tissue Macromolecular Changes in Rats with Experimentally Induced Diabetes and Hyperinsulinism

A study of connective tissue components from skin of rats with induced diabetes and hyperinsulinism was performed. Diabetes was induced in rats by a single injection of streptozotocin (50 to 75 mg./kg. body weight) and hyperinsulinism by daily injection of NPH insulin (½ to 2½ U.). Serum was analyzed for protein-bound carbohydrates and free sugars. A decrease in serum protein-bound sugars was observed in the diabetic animals. These slightly increased in hyperinsulin state. Acid mucopolysaccharides (MPS), glycoproteins (GP) and collagen were isolated from skin of experimental animals and compared with the controls. The contents of total MPS and GP decreased in diabetic skin; these increased in hyperinsulin state, similar to that observed in human diabetes. Diabetic rat skin had more soluble collagen, while less soluble collagen was observed in hyperinsulin state. It is suggested from these observations that insulin is a driving force toward the synthesis and accumulation of these compounds in connective tissue in experimental hyperinsulinism and, perhaps, in human diabetes with prolonged insulin treatment.

Low-density lipoprotein binding affinity of arterial chondroitin sulfate proteoglycan variants modulates cholesteryl ester accumulation in macrophages

Proteoglycans are considered to facilitate lipid accumulation in the arterial wall, as part of the injury and repair process in atherogenesis. The present study determined (1) characteristics of arterial tissue chondroitin sulfate proteoglycan (CS-PG) monomers of versican type that vary in binding affinity to low-density lipoproteins (LDL), and (2) the ability of these variants to modulate LDL metabolism by macrophages. A large CS-PG devoid of dermatan sulfate (DS) was isolated and purified from bovine aorta intima-media under dissociative conditions. The proteoglycan was further subfractionated by LDL affinity chromatography into CS-PGI and CS-PGII variants, the former eluting at 0.1 M NaCl and the latter at 1.0 M NaCl. The core protein of both variants had a similar molecular mass (1.7 x 10(5). However, CS-PGII contained more glycosaminoglycan (GAG) chains (30 vs. 25) with higher average molecular mass (4.2 x 10(4) vs. 3.8 x 10(4)) than CS-PGI. Furthermore, CS-PGII contained a relatively higher proportion of CS6-sulfate to CS4-sulfate (65: 35 vs. 52: 48). Sulfate-to-hexosamine molar ratio of GAG measured approximately 1 in both variants. In terms of metabolism by macrophages, when compared to complex of LDL and CS-PGI, complex of LDL and CS-PGII produced consistent increase in degradation (10.3-fold vs. 8.4-fold over native LDL) and cell association (16.3-fold vs. 10.2-fold over native LDL) of the ligand, and stimulation of cholesteryl ester synthesis (8.4-fold vs. 6.4-fold over native LDL). CS-PGII was as potent as native CS/DS-PG aggregate, which is a complex made of proteoglycan monomers, hyaluronate, and link protein(s), in stimulating the above activities in macrophages. Thus, variations in LDL-binding affinity of CS-PG can potentially modulate the lipid accumulation in atherogenesis.

Injury to the arterial wall of rabbits produces proteoglycan variants with enhanced low-density lipoprotein-binding property.

The effect of arterial injury on proteoglycans (PG) and their ability to bind low-density lipoprotein (LDL) were studied in rabbits 12 weeks after balloon injury. Following biosynthetic labeling in an organ culture system, PG were isolated under dissociative conditions from deendothelialized areas (DEA), reendothelialized areas (REA), and uninjured areas (control) of the aortic tissue. DEA and REA tissues yielded 42-52% more PG and incorporated 39-67% more 35S-label into proteoglycans than control tissues. Ion-exchange chromatography of PG from DEA and REA tissues yielded PG-I, PG-II, and PG-III, while from control tissue only PG-I and PG-II. PG-II formed major portion (74-84%) of the isolated PG in all three tissue types. PGI preparations comprised entirely of heparan sulfate (HS)-PG of similar hydrodynamic size (Kav = 0.45-0.47). PG-II from DEA and REA tissues consisted of PGII-A (Kav = 0.02-0.04) and PGII-B (Kav = 0.32), while PG-II from control tissue contained only PGII-B with relatively smaller hydrodynamic size (Kav = 0.40). PGII-A preparations contained predominantly chondroitin sulfate (CS)-PG with no dermatan sulfate (DS); whereas PGII-B consisted mainly of CS/DS-PG, with relatively high proportion of DS in DEA and REA tissues vs. control tissue (50-54% vs. 43%). Further, the glycosaminoglycan chains of CS/DS-PG from DEA and REA tissues were 1.7-fold longer than those from control tissue. PG-III contained about 80% CS/DS-PG and 20% HS-PG; CS/DS-PG was similar to those found in PGII-B from DEA and REA tissues. HS-PG from PG-II and PG-III, unlike those from PG-I, was enriched with N-sulfated residues. PGI from all the three tissue types bound poorly to LDL. On the other hand, PGII-A, PGII-B, and PG-III from DEA and REA tissues showed enhanced ability to bind LDL, in that order. For example, the LDL-binding ability of PGII-B from DEA and REA was 2.9- to 3.1-fold above that from control tissue. Thus, arterial injury with or without regenerated endothelium produces proteoglycan variants with altered characteristics and enhanced LDL-binding ability.

Urinary N-Acetyl-β-D-Glucosaminidase Changes in Relation to Age, Sex, Race, and Diastolic and Systolic Blood Pressure in a Young Adult Biracial Population the Bogalusa Heart Study

Increased urinary activity of N-acetyl-β-d-glucosaminidase (NAG) has been reported in many clinical conditions, including essential hypertension. Since hypertension is increasingly recognized as beginning in childhood, we hypothesized that urinary NAG changes with increasing blood pressure may start early in life and may also be the evidence of the existence of early hypertensive disease. We analyzed the urinary NAG changes in 980 young adults, ages between 18 to 32, in relation to age, race, sex, and systolic and diastolic blood pressure. We observed that black women had the highest level of NAG, with or without adjustment for creatinine. With aging, urinary NAG significantly increased in men. As blood pressure increased, urinary NAG excretion appeared to increase, and this was more apparent in black women (P < .05). Significant correlations between NAG excretion and systolic (r = 0.12, P = .04) and diastolic (r = 0.18, P = .003) blood pressures existed in the oldest age group, 28 to 32 years old. These findings show that a significant association between urinary NAG and blood pressure exists in normal young adults and changes in urinary NAG may be evidence of early hypertensive disease.

Does Adult-Onset Diabetes Mellitus Begin in Childhood?: The Bogalusa Heart Study

Children and young adults (N = 52, age 7-31, average 15.3 years) from parents with or without a history of onset of diabetes mellitus after the age of 30 years were studied for anthropometric and metabolic parameters related to diabetes. An oral glucose tolerance test was performed and blood samples were collected fasting and 15, 30, and 60 minutes after a standard glucose load. Offspring of diabetic parents were significantly heavier and more obese, although not uniformly overweight. Blood pressure, fasting insulin, glucagon, and triglycerides were significantly higher in offspring of diabetic parents. Approximately one-half of the offspring and siblings of diabetic parents had 30-minute blood glucose levels greater than 161 mg/dL, whereas none of the controls exceeded this level. These observations suggest abnormalities consistent with diabetes mellitus are already present in children and young adults, and may be detected by a response to glucose load.

Phylogenetic Variability of Serum Lipids and Lipoproteins in Nonhuman Primates Fed Diets with Different Contents of Dietary Cholesterol

The response of serum lipids and lipoproteins to different levels of dietary cholesterol (0.05% to 1.5% w/w) was measured in six nonhuman primate species. Relative response of serum cholesterol in different species, measured in terms of response, index, varied with dietary cholesterol concentration. The overall response for the different diets allowed ranking of the species as follows: Squirrel is greater than green is greater then spider is approximately thesus is approximately patas is greater than chimpanzee The serum cholesterol response was reflected not only in an increase in beta + pre-beta-lipoprotein cholesterol but also in alpha-lipoprotein cholesterol, with significant differences among species in the amount of cholesterol transported in the lipoprotein classes.

Fibronectin Synthesis by Aorta Explants from Rabbits Fed High Cholesterol Diets

Abstract Fibronectin synthesis was studied in aorta explants in culture from rabbits fed a high fat-high cholesterol diet. [3H]Mannose and [14C]leucine were used to label oligosaccharide side chains and the protein core, respectively. The synthesis was followed by monitoring immunoprecipitable fibronectin from the culture medium using polyclonal goat anti-rabbit fibronectin antibody. Synthesis of fibronectin increased by [14C]leucine (81%) and [3H]mannose (29%) incorporation over controls. On gel filtration, fibronectin synthesized by controls and cholesterol-fed rabbit resolved into four fractions. Pulse-chase experiment with [3H]glucosamine or [3H]leucine showed that fibronectin secreted by the aorta explants from rabbits fed high fat-high cholesterol diets incorporated an increased amount of radioactivity. Pulsing with [3H]mannose showed decreased incorporation of the label. During the chase period, the rate of secretion of fibronectin into the media by the hypercholesterolemic rabbit aorta explants was increased. The fibronectin that bound to the gelatin or heparin columns from cholesterol-fed rabbit aorta media had lower levels of [3H]mannose incorporated into the glycoprotein than the control. These results indicate that there is an alteration in carbohydrate composition of the fibronectin synthesized by the aorta explants from rabbits fed a high cholesterol diet. High fat-cholesterol intake could play a causative role in matrix dysfunction during atherogenesis by altering glycoprotein synthesis.