BACKGROUND: Altered glomerular production of nitric oxide (NO) may be involved in hyperfiltration in early diabetic nephropathy. However little is known as to the role of glomerular endothelial cells (GECs) in diabetic hyperfiltration and their ability to release NO in response to hyperglycemia. METHODS: Using an established cell line, we directly monitored NO release from GECs in response to various concentrations of D-glucose, D-mannitol, and L-arginine, an NO synthase (NOS) agonist. L-Arginine-induced NO release was examined in the cells pretreated for different periods up to 24 h with 10 or 30 mM D-glucose. We also measured serially the accumulation of nitrite, the stable metabolite of NO, produced by the cells incubated for up to 24 h under 10 or 30 mM D-glucose conditions in the presence or absence of the NOS inhibitor, L-NAME. RESULTS: Direct measurement of NO demonstrated that D-glucose, but not D-mannitol, stimulation resulted in a rapid and dose-dependent increase in NO release by the cells. However, L-arginine-induced NO release was attenuated significantly in the cells preincubated for more than 12 h with 30 mM D-glucose compared to 10 mM D-glucose. The L-NAME-inhibitable production of nitrite in the media was significantly increased 1.5--2.0-fold until 6 h after incubation with 30 mM D-glucose compared to 10 mM D-glucose. CONCLUSIONS: We conclude that D-glucose, but not D-mannitol, produces a rapid and dose-dependent increase in NO release, whereas exposure to high D-glucose for more than 12 h may blunt NOS activity and/or NO stability in the GECs. These observations may therefore be important for glomerular endothelial dysfunction induced by hyperglycemia that is still tentative and may have a role in diabetic nephropathy.

Analysis of Variance↗

PubMedDate not supplied

Increased bone formation by intermittent parathyroid hormone administration is due to the stimulation of proliferation and differentiation of osteoprogenitor cells in bone marrow.

In order to examine the mechanism of the anabolic effect of parathyroid hormone (PTH) on bone formation, human PTH(1-34) [hPTH(1-34)] (30 micrograms/kg) was injected subcutaneously to 9-week-old rats 5 times a week for 1 or 3 weeks. Trabecular bone volume (BV/TV) in the tibial metaphysis was not significantly different between the PTH- and vehicle-treated groups, but the parameters related to bone formation, including osteoid surface (OS/BS), mineralizing surface (MS/BS), mineral apposition rate (MAR), and bone formation rate (BFR/BS), were significantly increased as early as 1 week after PTH treatment. And the parameters related to bone resorption including eroded surface (ES/BS) and osteoclast number (N.Oc/BS) were also significantly increased as early as 1 week after PTH treatment. Treatment with PTH for 1 week induced no significant increase in bone mineral density at the femoral metaphysis, whereas the same treatment for 3 weeks induced a significant increase. When bone marrow cells isolated from femora and tibiae of either PTH- or vehicle-treated rats were cultured at a high density (2 x 10(7) cells/one well of 24-multiwell plate), cellular alkaline phosphatase (ALP) activity was significantly increased in the cells isolated from PTH-treated rats compared with vehicle-treated rats. When bone marrow cells were cultured at a low density (4 x 10(6) cells/a one well of 6-multiwell plate) to generate colonies (colony forming unit-fibroblastic, CFU-F), PTH induced apparent increases in both the total number of CFU-F and the number of ALP-positive CFU-F.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗

PubMedDate not supplied

Effect of doxazosin on the size of LDL particle in the type 2 diabetic patients with hypertension.

Hypertension is common in patients with type 2 diabetes mellitus (DM), and contributes to the progression of its complications in patients with diabetes. Doxazosin is a selective alpha1-adrenoceptor-blocking anti-hypertensive agent and has a favorable impact upon lipid metabolism. We investigated the effect of doxazosin on the lipid metabolism in hypertensive patients with type 2 diabetes, especially low-density lipoprotein (LDL) particle size that is associated with many elements of the insulin resistance syndrome. Cross-sectional study (n=19) was designed to determine whether doxazosin, administered with an angiotensin II-converting enzyme inhibitor (ACEI) and a Ca antagonist, affects LDL particle size. As a follow-up study (n=6), lipid and glucose metabolism and LDL particle size were followed for 12 weeks before and after the initiation of doxazosin administration (1-4 mg/day). The average size of LDL particle was significantly larger in the patients treated with doxazosin (LDL-migration index (LDL-MI): 0.348+/-0.027) than those in the patient treated without doxazosin (0.378+/-0.035), although LDL cholesterol levels did not differ between the two groups. The plasma glucose and HbA1c levels remained unchanged. Lipid profile showed normolipemia throughout the period of the study. However, LDL particle size was demonstrated to become larger during the following period. Small LDL fraction (LDL3-7) diminished remarkably and large LDL (LDL1-2) increased on the polyacrylamide gel electrophoresis (PAGE) LDL system (LipoPrint). From this pilot study, it was concluded that doxazosin is a useful anti-hypertensive agent for hypertensive type 2 diabetic patients in improving the size of LDL particle.

Angiotensin-Converting Enzyme Inhibitors↗

PubMedDate not supplied

Effects of advanced glycation endproducts on the generation of macrophage-mediated oxidized low-density lipoprotein.

Macrophages have a receptor that recognizes advanced glycation endproducts (AGE). In this study, we evaluated the effect of AGEs on the generation of macrophage-mediated oxidized low-density lipoprotein (LDL) by measuring the electrophoretic mobilities and lipid hydroperoxide (LHPO) levels of LDL. In the absence of the macrophage monolayer, the differences of the electrophoretic mobilities or LHPO levels of native (n) LDL did not differ significantly between control (c) bovine serum albumin (BSA) and those with AGE-BSA. In the presence of the macrophage monolayer, however, the difference was significant with higher levels after the incubation with AGE-BSA than with c-BSA. In the case of cLDL and glycated (g) LDL, the electrophoretic mobilities and LHPO levels of LDL after 20 h incubation with AGE-BSA in the presence of the macrophage monolayer were significantly higher than those with c-BSA. There were no significant differences, however between the electrophoretic mobilities and LHPO levels of cLDL and of gLDL. These results suggest that AGEs stimulate the generation of macrophage-mediated oxidized LDL, but do not directly stimulate the oxidative modification of gLDL.

Animals↗