Sera Of Diabetic Rats Research Articles

Estimation of oxidant, antioxidant and metabolic biomarkers in sera of diabetic rats administrated with parsley leaves extract and its isolated apigenin

Estimation of oxidant, antioxidant and metabolic biomarkers in sera of diabetic rats administrated with parsley leaves extract and its isolated apigenin

Vitamin D-binding protein is required for the protective effects of vitamin D in renal fibroblasts and is phosphorylated in diabetic rats

Serum vitamin D is bound to vitamin D-binding protein (DBP). We studied the roles of DBP in streptozotocin-diabetic rats and high glucose (HG)-cultured cells. In diabetic rat sera, there was one upregulated (with a lower isoelectric point [pI], phosphorylated at S268, S270, S464 and T269) and one downregulated (with a higher pI, phosphorylated at S454 and S457) DBP. DBP levels with lower pI were increased in diabetic rat kidney and liver. HG (30 mM) increased DBP protein expression in NRK-49F cells and Clone-9 hepatocytes. HG decreased pI of DBP in Clone-9 hepatocytes. Moreover, DBP short hairpin ribonucleic acid attenuated 1,25-(OH)2D3-induced attenuation of HG-induced renin (but not collagen IV and fibronectin) protein expression in NRK-49F cells. Thus, DBP level is increased whereas DBP is phosphorylated in diabetic rat serum. HG increased DBP protein expression in renal fibroblasts and hepatocytes. Moreover, DBP is required for vitamin D-induced attenuation of HG-induced renin in NRK-49F cells.

Insulin suppresses the expression and function of breast cancer resistance protein in primary cultures of rat brain microvessel endothelial cells

The aim of this study was to investigate the role of insulin in the regulation of breast cancer resistance protein (BCRP) function and expression using primary cultured rat brain microvessel endothelial cells (rBMECs) as an in vitro model of the blood brain barrier (BBB). The prazosin uptake assay and western blot analysis were used to assess the function and expression of BCRP, respectively. It was noted that the uptake of prazosin by rBMECs was time-, concentration- and temperature-dependent. The BCRP inhibitors novobiocin and imatinib mesylate significantly increased the uptake of prazosin by the cells in a concentration-dependent manner. The cells were also incubated with sera from diabetic rats for 72h, serving as a diabetic in vitro model. We found that the uptake of prazosin by rBMECs incubated in the diabetic rat sera was 39.8% of that in normal rat sera, and insulin treatment reversed this decrease. Further results showed that insulin down-regulated the function and expression of BCRP in rBMECs in a concentration-dependent manner. Treatment with an antibody against the insulin receptor abolished the down-regulation of BCRP function and expression that was induced by insulin. These results indicate that insulin suppressed the function and expression of BCRPs in rBMEC primary cultures.

Antibodies to advanced glycation end products in children with diabetes mellitus

The tissue accumulation of advanced glycation end products (AGE) alters the structure and function of long-lived proteins. A number of studies have shown that tissue accumulation of AGE correlates with the severity of diabetic complications. Proteins containing AGE are highly immunogenic and anti-AGE antibodies were found in sera of diabetic rats and human. Considering the potential use of anti-AGE antibodies as a marker of AGE deposition during diabetes, we have investigated, by competitive ELISA, the presence of anti-AGE antibodies in sera of 58 children with Type 1 diabetes mellitus. The patients were studied for the period of 5 years. Positive for anti-AGE antibodies were 19 children with diabetes. Fourteen of them showed initial data for vascular complications. Anti-AGE antibodies were related to age ( r=.25, P=.024), duration of diabetes ( r=.41, P=.0001), HbA1c ( r=.27, P=.016), microalbuminuria ( r=.41, P=.0001), retinopathy ( r=.35, P=.001), triglycerides ( r=.27, P=.016), and total cholesterol ( r=.19, P=.05). In conclusion, our study showed that the investigation of the levels and dynamics of anti-AGE antibodies might give the possibility for early diagnosis and prognosis of the severity of diabetic late complications.

Roles of advanced glycation endproducts (AGE) and receptor for AGE on vascular smooth muscle cell growth.

Proliferation of vascular smooth muscle cells (VSMC) represents an essential event in the developement of diabetic atherosclerosis. Previous studies suggest that several cytokines and growth factors mediate the proliferation capability in VSMC from diabetic animals. In addition, advanced glycation end products (AGE) and receptor for AGE (RAGE) are important for pathologic features of diabetic complications. In the present study, we attempted to clarify the roles of AGE and RAGE in the proliferation of VSMC using streptozotocin (STZ)-treated rat sera and aortic SMC prepared from non-diabetic rats. AGE levels increased in the diabetic sera, which enhanced the growth of VSMC in proportion to their diabetic periods. AGE-bovine serum albumin (BSA) prepared in vitro also exhibited a stimulatory effect on VSMC growth. The endocytic uptake of AGE and enhanced RAGE expression in VSMC after culture with diabetic sera were observed. In addition, anti-AGE and anti-RAGE antibodies inhibited these stimulatory effects on VSMC growth. These findings suggest that AGE in diabetic rat sera may cause an enhanced effect on VSMC proliferation. However, the concentrations of AGE in diabetic sera were much lower than that of AGE-BSA which demonstrated a significant stimulatory effect on VSMC growth. The magnitude of the VSMC growth-enhancement by the diabetic sera was markedly greater than that by the AGE-BSA solution. In conclusion, the AGE-RAGE interaction in VSMC, in addition to growth factors induced by AGE, contributes to the stimulatory effect of diabetic sera on VSMC proliferation which can accelerate atherosclerosis.

Inhibition of development of peripheral neuropathy in streptozotocin-induced diabetic rats with N-acetylcysteine

N-acetylcysteine (NAC) is a precursor of glutathione (GSH) synthesis, a free radical scavenger and an inhibitor of tumour necrosis factor alpha (TNF). Because these functions might be beneficial in diabetic complications, in this study we examined whether NAC inhibits peripheral neuropathy. Motor nerve conduction velocity (MNCV) was significantly decreased in streptozotocin-induced-diabetic Wistar rats compared to control rats. Oral administration of NAC reduced the decline of MNCV in diabetic rats. Structural analysis of the sural nerve disclosed significant reduction of fibres undergoing myelin wrinkling and inhibition of myelinated fibre atrophy in NAC-treated diabetic rats. NAC treatment had no effect on blood glucose levels or on the nerve glucose, sorbitol and cAMP contents, whereas it corrected the decreased GSH levels in erythrocytes, the increased lipid peroxide levels in plasma and the increased lipopolysaccharide-induced TNF activity in sera of diabetic rats. Thus, NAC inhibited the development of functional and structural abnormalities of the peripheral nerve in streptozotocin-induced diabetic rats.

Nonenzymatic glycation of transferrin: decrease of iron-binding capacity and increase of oxygen radical production.

The total iron-binding capacity (TIBC) and iron contents of diabetic rat serum, as well as the iron-binding capacity of glycated transferrin and oxygen radical production by the glycated proteins were examined. The TIBC and iron content of diabetic rat sera were found to be much lower than those of control rat sera. Incubation of human serum with glucose in vitro resulted in a significant fall of its unsaturated iron-binding capacity (UIBC) with time. When apotransferrin was incubated with glucose, its UIBC significantly decreased. The iron content of holotransferrin was markedly reduced by incubation with bathophenanthroline sulphonic acid (BPSA) in the presence of glucose, although the content was not altered by incubation with BPSA alone. The generation of superoxide radical (O2-) and hydroxyl radical (OH.) by the glycated holotransferrin was much greater than that by glycated apotransferrin. Glycated holotransferrin showed significantly accelerated hydroxyl radical production by the hypoxanthine-xanthine oxidase system, while intact holotransferrin did not. Treatment of holotransferrin with glucose caused the fragmentation of the protein, while the same treatment of apotransferrin did not. These results suggest that iron ions in the glycated transferrin molecule are bound loosely to the protein and are redox-active and the glycated holotransferrin produces oxygen radicals including O2- and OH. efficiently, and that the glycated transferrin does not function as an iron-binding protein.

Alpha 1 acid glycoprotein in streptozotocin diabetic rats. Some aspects of sugar moiety structure and metabolism.

The pure alpha 1 acid glycoprotein (AGP) preparation from streptozotocin diabetic rat sera showed diminished sialic acid content and lower ratios of galactose to mannose and galactose to fucose. In vivo incorporation of 14C-leucine and 3H-galactose into AGP of control and diabetic animals was studied 30, 60 and 120 min after administration of the radioisotopic precursors. The changed 14C/3H ratio in AGP of diabetic rats suggested disturbed glycosylation of AGP in this disease. Similar activity of UDP-galactose 4-epimerase in control and diabetic rat liver was found suggesting that this enzyme has no influence on the decreased level of serum protein bound galactose.

Similarity of somatomedin inhibitor in sera from starved, hypophysectomized, and diabetic rats: distinction from a heat-stable inhibitor of rat cartilage metabolism.

The inhibitory effects of sera from starved, hypophysectomized, and alloxan-diabetic rats on basal and somatomedin-stimulated sulfate incorporation into cartilage from hypophysectomized rats were compared. The somatomedin inhibitory activity in serum from diabetic rats behaved like that in serum from starved rats on heating at 60 C. Both were labile in the native sera (pH 8.3-8.4), but activity was conserved to a large extent by lowering the pH to 7.4 and diluting the sera before heating. In all of these sera the peak of the somatomedin inhibitory activity was eluted from a column of Sephacryl S-200 at pH 7.4 just after albumin, and lesser amounts were eluted with albumin and higher molecular weight components. Activity of this type was undetectable in fractions prepared from sera that had been heated at 60 C. These results indicate the similarity of this inhibitor in starved, hypophysectomized, and diabetic rat sera. Certain fractions of both starved and diabetic rat sera, which were eluted from a column of Sephacryl S-200 beyond the total bed volume, contained heat-stable inhibitory activity. In contrast to the effects of the heat-labile inhibitor, these fractions only inhibited basal sulfate incorporation into hypophysectomized rat cartilage under the assay conditions employed. This heat-stable inhibitor was not detected in fractions of hypophysectomized rat serum, and inhibitory concentrations of corticosterone were present in fractions of starved and diabetic rat sera containing the material. The findings suggest that the heat-stable inhibitor is corticosterone.

INHIBITION OF MUSCLE GLUCOSE UPTAKE BY DIABETIC RAT SERA OF VARYING GLUCOSE AND LIPOPROTEIN CONTENT

INHIBITION OF MUSCLE GLUCOSE UPTAKE BY DIABETIC RAT SERA OF VARYING GLUCOSE AND LIPOPROTEIN CONTENT