Alendronate reduces osteoclast precursors in osteoporosis.

UNLABELLED: This study evaluates the effect of alendronate on osteoclastogenesis, cytokine production, and bone resorption in postmenopausal women. We suggest that it acts on mature bone resorbing osteoclasts after 3 months of treatment, whereas, after 1 year, it diminishes their formation by reducing their precursors and serum RANKL. INTRODUCTION: Osteoclasts are the target cells of bisphosphonates, though the most drug-sensitive steps of their formation and activity have not been determined. The present study evaluates the effect of alendronate on osteoclastogenesis, cytokine production, and bone resorption in postmenopausal women. METHODS: The study was conducted on 35 osteoporotic women; 15 were pretreated with alendronate 70 mg/week, whereas, 20 were treated with calcium 1 g/day and vitamin D 800 IU/day. After 3 months, 30 received alendonate 70/mg, vitamin D 2800 IU/week, and calcium 1 g/day for 12 months (combined therapy), whereas, the other five patients remained on calcium 1 g/day and vitamin D 800 IU/day. The following parameters were assessed before and after therapy: changes in bone resorption markers, circulating osteoclast precursors, formation of osteoclasts in peripheral blood mononuclear cell cultures, their viability, and variations in cytokines production. RESULTS: After 3 months of alendronate, there was no significant reduction in the number of osteoclast precursors, osteoclast formation and viability, and cytokine levels, whereas, there was a significant reduction of bone resorption markers. One year of the combined therapy, on the other hand, reduced osteoclast precursors, osteoclast formation, and serum RANKL, whereas, calcium plus vitamin D alone had no effect. CONCLUSIONS: We suggest that alendronate mainly acts on mature bone resorbing osteoclasts in the short term, whereas, its long-term administration diminishes their formation by reducing their precursors and serum RANKL.

Hypoparathyroidism and co-existing celiac disease.

A 62-yr-old woman with idiopathic hypoparathyroidism was admitted to our hospital for severe anemia (Hb 5.6 gr/dl) and hypoalbuminemia (3.2 gr/dl). Hypoparathyroidism was diagnosed when she was 33 yr old, because of repeated hypocalcemic tetanic crises, low calcium and high phosphate levels. Since then she has been treated with oral calcium gluconate and calcitriol, with satisfactory clinical balance and normalization of calcium serum levels. After menopause, despite this therapy, the patient still had frequent hypocalcemic tetanic crises, resolving with iv administration, in high doses, of calcium gluconate. The anemia, for which the patient came to our attention, was hypochromic microcytic and in the past she had been treated with iron and transfusion therapy. The patient's recent history also revealed recurrent long lasting episodes of diarrhea, hyporexia and weight loss. The clinical presentation seemed related to a malabsorption syndrome: a celiac disease (CD) diagnosis was confirmed, based upon the finding, at duodenal biopsy, of a severe villous atrophy. A bone mineral density (BMD) evaluation showed a limited reduction of femoral values classified as osteopenia according to the World Health Organization (WHO) criteria. Thereafter, the patient was instructed to follow a gluten-free diet which rapidly led to an improvement of the nutritional parameters and to a reduction of calcium and vitamin D requirements. Difficult clinical and metabolic control in hypoparathyroidism patients may suggest the possible co-existence of both endocrine and extra-endocrine autoimmune diseases, such as CD. Moreover, bone density, normally reduced in celiac patients, seems to be preserved (maintained) by the lack of parathyroid secretion.

Intracellular protein glycation in cultured retinal capillary pericytes and endothelial cells exposed to high-glucose concentration.

There is now increasing evidence suggesting that non-enzymatic glycation (NEG) of proteins is involved in the pathogenesis of chronic diabetic complication. In this study we demonstrate that chronic exposure to high-glucose concentration leads to intracellular protein glycation in cultured bovine retinal capillary pericytes and endothelial cells. The level of intracellular protein glycation, as measured using a competitive enzyme-linked immunoabsorbant assay (ELISA), was found to increase in both pericytes and endothelial cells as function of time. As expected products of NEG were only detected when the Schiff base and the Amadori products were chemically reduced to glucitollysine by sodium borohydride. Despite the accumulation of early glycation products on cellular proteins there was no further rearrangement reaction into advanced glycation endproducts (AGEs), even after 12 days of incubation in high-glucose medium. Immunofluorescence microscopy demonstrated that the monoclonal antibody reacting with glucitollysine stains the cytoplasm of both pericytes and endothelial cells in a finely punctate pattern. Further studies using Western blot analysis suggested that a number of cellular proteins, including smooth muscle actin in pericytes, become rapidly glycated. The results from this in vitro study suggest that excessive accumulation of early products of non-enzymatic glycation in pericytes and endothelial cells may play an important role in the pathogenesis of diabetic retinopathy.

Dehydroepiandrosterone protects bovine retinal capillary pericytes against glucose toxicity.

Pericyte loss is an early feature of diabetic retinopathy and represents a key step in the progression of this disease. This study aimed to evaluate the effect of dehydroepiandro-sterone (DHEA) on glucose toxicity in retinal capillary pericytes. Bovine retinal pericytes (BRP) were cultured in a high glucose concentration, with or without DHEA. After 4 days of incubation the number of BRP was significantly reduced by the high glucose concentration. The addition of DHEA to the medium reversed the adverse effect of high glucose: BRP proliferation partially recovered in the presence of 10 nmol/l DHEA, and completely recovered in the presence of DHEA at concentrations equal to or greater than 100 nmol/l. At physiological glucose concentrations, DHEA had no effect on BRP growth. Data show that DHEA, at concentrations similar to those found in human plasma, protects BRP against glucose toxicity. This effect seems specific for DHEA, since its metabolites, 5-en-androstene-3 beta, 17 beta-diol, dihydrotestosterone and estradiol did not alter BRP growth in normal or high glucose media. Various pieces of evidence link the antioxidant properties of DHEA to its protective effect on glucose-induced toxicity in BRP.

Toxic action of advanced glycation end products on cultured retinal capillary pericytes and endothelial cells: relevance to diabetic retinopathy.

The toxic effects of advanced glycation end products (AGEs) on bovine retinal capillary pericytes (BRP) and endothelial cells (BREC) were studied. AGE-modified bovine serum albumin (AGE-BSA) was toxic to BRP. At a concentration of 500 micrograms/ml it reduced the BRP number to 48 +/- 3% (p < 0.05) of untreated controls, as determined by cell counting with haemocytometer. AGE-BSA was also toxic to bovine aortic endothelial cells (BAEC) reducing cell number to 84 +/- 3.1% of untreated controls. Under similar conditions, low concentrations (62.5 micrograms/ml) of AGE-BSA were mitogenic to BREC increasing the cell proliferation to 156 +/- 11% (p < 0.05) above that of untreated controls. At a higher dose of 500 micrograms/ml AGE-BSA decreased the proliferation of BREC to 85 +/- 6% of untreated controls. Immunoblot analysis demonstrated that BRP and BREC express the p60 AGE-receptor. Retinal capillary bed from the human also stained positively for the p60 AGE-receptor. Addition of 0.25 micrograms/ml of p60 AGE-receptor antibody was able to block the effects of AGE-BSA on BRP and BREC. The level of binding of [125I]-labelled AGE-BSA to the cell surface was small but significant among the three cell types. There was also an increase in the internalized pool of radioligand in BRP and BREC but this was very much lower than in BAEC. In all the cell types the internalized pool of [125I]-labelled AGE-BSA was much larger than the amount associated with the cell surface. Degradation products were not detected in the media over the 24-h incubation of the cells with [125I]AGE-BSA. The binding of [125I]-labelled AGE-BSA to the cell surface was prevented by the addition of p60 AGE-receptor. These results suggest that the interaction of AGE-modified proteins with the membrane-bound AGE-receptor may play an important role in the pathogenesis of diabetic retinopathy.

Thiamine corrects delayed replication and decreases production of lactate and advanced glycation end-products in bovine retinal and human umbilical vein endothelial cells cultured under high glucose conditions.

This study aimed at verifying whether thiamine, a co-enzyme which decreases intracellular glycolysis metabolites by allowing pyruvate and glyceraldheyde 3-phosphate to enter the Krebs cycle and the pentose-phosphate shunt, respectively, corrects delayed replication caused by high glucose concentrations in cultured human umbilical vein (HUVEC) and bovine retinal endothelial cells (BREC). After incubation in physiological (5.6 mmol/l) or high (28.0 mmol/l) glucose with or without 150 mumol/l thiamine, cells were counted and proliferation assessed by mitochondrial dehydrogenase activity. Lactate was measured in both cell types as an index of glycolytic activity and fluorescent advanced glycosylation end-products (AGE) concentration was determined in the HUVEC lysate. Both cell counts and proliferation assays in either of the cell types confirmed the impairment to cell replication induced by high glucose. When thiamine was added to cells kept under high glucose conditions, the number of surviving cells was significantly increased and the reduced cell proliferation appeared to be corrected. Lactate assays confirmed the increased production of this metabolite by BREC and HUVEC in high glucose, which was reduced by thiamine. Fluorescent AGE determination showed that thiamine may prevent non-enzymatic glycation in HUVEC. Thiamine restores cell replication, decreases the glycolytic flux and prevents fluorescent AGE formation in endothelial cells cultured in high glucose, suggesting that abnormal levels of glycolytic metabolite(s) may damage cells.

Levels of vascular endothelial growth factor are elevated in the vitreous of patients with subretinal neovascularisation.

BACKGROUND: Vascular endothelial growth factor (VEGF) has been shown to play a major role in intraocular neovascularisation in ischaemic retinal diseases. Subretinal neovascularisation is an important cause of central visual loss, but little is known about the role of this growth factor in its pathogenesis. The aim of this study was to investigate the possible role of VEGF in the development of subretinal neovascularisation. METHODS: Undiluted vitreous samples were obtained from patients undergoing vitrectomy for removal of non-age-related subfoveal neovascular membranes (SFNM). For comparison vitreous from patients undergoing vitrectomy for idiopathic full thickness macular holes (FTMH) and proliferative diabetic retinopathy (PDR) was used. Indirect enzyme linked immunosorbent assay (ELISA), with an antibody directed against the conserved N-terminal region of human VEGF165, was used to determine vitreous levels of VEGF. The growth factor was also localised in the vitreous of patients with SFNM by western blot analysis. RESULTS: The mean (SE) VEGF concentration in the vitreous of patients with SFNM was 27.78 (2.22) ng/ml (n = 8), FTMH was 16.62 (0.9) ng/ml (n = 18), and PDR was 37.77 (3.28) ng/ml (n = 16). The differences between the PDR group and SFNM group versus the FTMH group were both significant (p = 0.0001 and p = 0.0015) as analysed by the Wilcoxon rank sum test). CONCLUSIONS: Vitreous levels of VEGF are significantly elevated in eyes with non-age-related subretinal neovascularisation compared with eyes with FTMH but not as elevated as in PDR. This suggests that VEGF is involved in subretinal angiogenesis.

The effect of aminoguanidine and tolrestat on glucose toxicity in bovine retinal capillary pericytes.

Cultured bovine retinal capillary pericytes (BRP) were used to investigate the effect of an aldose reductase inhibitor, tolrestat, and an inhibitor of advanced glycation end products (AGE) formation, aminoguanidine, on glucose toxicity. Glucose at high concentration reduced the replicative activity of pericytes in a dose-dependent manner. Tolrestat completely inhibited the production of sorbitol in cells exposed to a high concentration of glucose but failed to protect the cells from glucose toxicity. These results suggest that sorbitol accumulation in cells is probably not the major mechanism for glucose toxicity. In contrast, the addition of aminoguanidine at 10 mM concentration to the culture media protected pericytes from glucose toxicity. The degree of protected pericytes from glucose toxicity. The degree of protection was dose-dependent and evident at aminoguanidine concentration as low as 1 mM. The drug was only slightly toxic to BRP but induced morphological changes in pericytes with the loss of cellular processes and decreased cell spreading. This may suggest some action of aminoguanidine on the pericyte cytoskeleton. High concentration of glucose significantly increased the level of early glycation but not fluorescent AGE formation on BRP proteins. This was inhibited by the addition of aminoguanidine suggesting that glycation of cellular/membrane proteins and other mechanisms may play an important role in the toxic action of high glucose levels in cultured pericytes.

Growth of bovine retinal pericytes and endothelial cells in high hexose concentrations.

Selective loss of capillary pericytes occurs early in diabetic and galactosemic retinopathies, at a stage when endothelial cells are still spared. To ascertain whether such loss is directly related to high hexose concentrations, the replication of bovine retinal pericytes and endothelial cells was studied by culturing them in media containing 5.6 mmol/l glucose alone and enriched with extra glucose, mannitol or galactose to achieve final concentrations of 16.7, 27.8 and 50.0 mmol/l. At the end of the incubation there were significantly less pericytes/culture cell in 16.7 mmol/l glucose (341 +/- 78 x 10(3), mean +/- SEM, p = 0.027) and galactose (304 +/- 55 x 10(3), p = 0.046) than in 5.6 mmol/l glucose (417 +/- 98 and 355 +/- 75 x 10(3) for separate experiments, respectively). Mannitol had no such effect (343 +/- 52 vs. 337 +/- 52 x 10(3). Endothelial cells did not change in number, except in 50.0 mmol/l glucose (533 +/- 66 vs. 629 +/- 67 x 10(3) at 5.6 mmol/l; p = 0.026) and 50.0 mmol/l galactose (440 +/- 48 vs. 592 +/- 51 x 10(3); p = 0.013). To verify if these effects are due to decreased replication, the uptake of 3H-thymidine was measured in pericytes and endothelial cells subjected to the same concentrations of glucose, mannitol and galactose. In pericytes, thymidine uptake was reduced in the presence of 16.7 mmol/l glucose (p = 0.003, compared to 5.6 mmol/l) and galactose (p = 0.027) but not mannitol. Pericyte counts and thymidine uptake was reduced for concentrations of glucose, galactose and mannitol higher than 16.7 mmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of the effects of human blood derivatives and individual growth factors on [3H]thymidine uptake in bovine retinal pericytes and endothelial cells.

Pericytes disappear early, selectively and specifically from retinal capillaries in diabetic microangiopathy, but little is known of their growth and turnover in health and disease. We have studied the effects of human blood derivatives and of a panel of individual growth factors on [3H]thymidine incorporation in bovine retinal pericytes and endothelial cells. Human serum and platelet-rich plasma stimulated incorporation of the nucleotide in a dose-dependent manner in both cell types, and did so more potently than platelet-free plasma. Consistent and significant stimulation of DNA synthesis in pericytes was observed with basic fibroblast growth factor (ED50 = 1.8 x 10(-13) mol/l), acidic fibroblast growth factor (7.4 x 10(-12) mol/l), insulin-like growth factor 1 (8.6 x 10(-10) mol/l), insulin (158 microU/ml) and endothelin-1 (6.1 x 10(-10) mol/l). Transforming growth factor beta 1 inhibited DNA synthesis (ID50 = 3.6 x 10(-10) mol/l) and so did heparin (1.4 x 10(-6) mol/l) and low molecular weight heparin (2.9 x 10(-6) mol/l). Retinal endothelial cells were stimulated by basic fibroblast growth factor (3.2 x 10(-13) mol/l) and acidic fibroblast growth factor (1.3 x 10(-9) mol/l), and inhibited by transforming growth factor beta 1 (1.6 x 10(-12) mol/l). Neither cell type was stimulated by platelet-derived growth factor (A + B chain heterodimer), epidermal growth factor, growth hormone, or nerve growth factor (7S complex). The characteristics and active concentrations of the above growth factors suggest that none is solely responsible for the pericyte mitogenic activity of platelets, serum or plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed replication of human umbilical vein endothelial cells in high glucose is corrected by L-tyrosine.

Human umbilical vein endothelial cells (HUVEC) cultured in high glucose exhibit delayed replication and colchicine-resistant microtubules. Tubulin dysfunction and stabilization, brought about by acetylation of the NH2-terminal residues, loss of the C-terminal tyrosine and binding of microtubular-associated proteins (MAPs) may be involved in the above phenomenon. The effects of L-tyrosine on HUVEC replication in high glucose were tested and the hypothesis that non-enzymatic glycosylation might impair tubulin depolymerization was also checked by growing the cells in the presence of L-glucose, which binds to intracellular proteins but remains metabolically inactive. After 18 days in culture, the number (mean +/- SEM, n = 7) of HUVEC grown in 28.0 mmol/l D-glucose (435.7 +/- 59.1 x 10(3)) was lower than in 5.6 mmol/l D-glucose (818.3 +/- 75.2 x 10(3)), p < 0.0001. The addition of L-tyrosine 1.7 mmol/l corrected such growth inhibition (623.3 +/- 81.7 x 10(3)), p < 0.0001 vs. D-glucose 28.0 mmol/l, but the cells recovered were less numerous than in physiological glucose alone (p = 0.016). The addition of L-tyrosine to D-glucose 5.6 mmol/l (731.0 +/- 63.2 x 10(3)) did not modify the cell number significantly. HUVEC in extra L-glucose (687.4 +/- 72.0 x 10(3)) were less numerous than in 5.6 mmol/l D-glucose, p = 0.028, but more than in D-glucose 28 mmol/l, p < 0.0001, and were not modified by the addition of L-tyrosine (729.4 +/- 67.1 x 10(3)). HUVEC grown in physiologic and high glucose exhibited specific immunofluorescence for acetylated tubulin and MAPs.(ABSTRACT TRUNCATED AT 250 WORDS)

von Willebrand factor and endothelial abnormalities in diabetic microangiopathy.

We briefly summarize current knowledge on 1) the abnormalities of von Willebrand factor (vWF) as an indicator of endothelial cell (EC) dysfunction in diabetes and 2) the modifications induced in the growth of cultured ECs by high glucose in the incubation media. A MEDLINE search (1986 through Sept. 1989) was performed to update previous relevant references on vWF and ECs in healthy and diabetic subjects. Main data in the literature and personal contributions were scrutinized. Study quality, information, and relevance to the subject were assessed. vWF is synthesized and stored mainly in ECs. Its plasma levels are increased in diabetic microangiopathy but are not influenced by circulating glucose, insulin, or growth hormone, nor do they acutely affect platelet function in diabetes. Supraphysiological concentrations of glucose inhibit the replication of cultured ECs from large vessels via different possible mechanisms but appear to stimulate pathways involved in the activation of capillary ECs. vWF is a possible marker of EC damage in diabetes, and prospective studies will ascertain its role as a predictor for the development of microangiopathy. The possible dichotomy in the response of cultured ECs from large and small vessels to high glucose in the culture media may help explain some of the lesions observed in the walls of arteries and capillaries in diabetes.

Metastasis to pituitary adenoma.

Neoplasm to neoplasm metastasis is a medical curiosity. We report two cases of adenocarcinoma metastatic to pituitary adenoma. In both, abrupt progression of symptoms referable to the sellar region was noted and followed by the death of the patient.