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Normal eight month old beagle dogs were fed a diet of 30% galactose for a period of two weeks. One group of dogs was untreated while three other groups were orally dosed with 0.25, 1.0, and 5.0 mg/kg of the aldose reductase inhibitor (ARI), AL01576. No visible changes were observed in the lens but glutathione (GSH) and inositol were depleted while dulcitol was elevated. These biochemical changes closely parallel those found in the (two week) streptozotocin induced diabetic rat. In contrast with the diabetic rat model, retina and nerve inositol was not found to differ from normal in spite of significant dulcitol accumulation. Plasma AL01576 was found to be inversely correlated with lens dulcitol concentration. When plasma AL0P1576 concentration was greater than 1 microgram/mL (5 mg/kg), there was a 95% reduction in dulcitol concentration (relative to untreated), while concentrations of 0.2 to 0.2 mg/mL (1 mg/kg) of AL01576 resulted in a dulcitol reduction of at least 70%. Retina and nerve dulcitol concentrations of galactosemic dogs were similarly diminished by AL01576 treatment. The dog model exhibits a biochemical profile of change and responsiveness to ARI therapy similar to that observed in hyperglycemic rats. Changes in retina morphology in diabetic and galactosemic dogs has been shown to closely resemble those occurring in human diabetics; these early biochemical events may also parallel.

Depletion of lens glutathione (GSH) occurs quickly and drastically following induction of diabetes or galactosemia in rats as well as in lens culture. The explanation for this dramatic loss of GSH has been investigated by many laboratories but the solution has been elusive. There are several possible causes for the change in the reducing power of the lens under hyperglycemia. (a) The enzyme glutathione reductase which reduces oxidized glutathione to GSH is inhibited. (b) The cofactor NADPH which both the aldose reductase of polyol pathway and glutathione reductase require becomes depleted under hyperglycemia to the point that there is an insufficient amount for glutathione reduction. (c) Membrane permeability is increased, due to osmotic-induced lens hydration. We explored all the above possibilities in the mechanism of GSH depletion and studied the effect of aldose reductase inhibitor (ARI) on osmotic change. We found that under hyperglycemic condition, there was no change in the enzyme glutathione reductase activity. There was an initial drop in NADPH level but there was sufficient remaining for glutathione reductase use. Both NADPH and glutathione depletion could be prevented completely by ARI. In addition, ARI could also prevent any hyperglycemic-induced abnormal transport and leakage of amino acids. We have therefore concluded that only the decreased membrane transport of amino acids which are needed for glutathione biosynthesis and the simultaneous loss of GSH through leaky membrane as initiated by the polyol pathway can be responsible for the drastic GSH depletion.

Phosphorylcholine (P-choline) is a precursor of the phospholipids in the lens membrane. A human lens normally contains approx. 1 mM P-choline but this is significantly lowered in some cataractous lenses. A normal rat lens contains a very high concentration (11 mM). We found that rat lens P-choline was depleted drastically when the lenses were exposed to hyperglycemic conditions either in culture, with galactose or xylose, or in vivo by streptozotocin-induced diabetes. The lens P-choline level was measured by fractionating the organic phosphates in the lens homogenate using an ion exchange column, or by quantitating the P-choline 31P NMR intensity in intact lenses. The results of both the chemical method and the noninvasive method agreed remarkably well. Besides the change in P-choline, the choline influx was also drastically reduced both in lenses from diabetic rats and in lenses incubated with 30 mM xylose. In addition, the ATP concentration was greatly diminished under similar conditions. The changes in P-choline, choline, and ATP could all be prevented in the presence of an aldose reductase inhibitor (ARI). It is thus concluded that these changes in phospholipid precursors may result from lenticular membrane defects caused by hyperglycemic stress. The effect of the lowered precursors on lipid biosynthesis was observed, and surprisingly showed a more rapid phospholipid-biosynthesis in the 2-week diabetic rat lens than in the 3-day diabetic rat lens.

Floral chemical defence strategies remain under-investigated, despite the significance of flowers to plant fitness. We used cyanogenic glycosides (CNglycs)—constitutive secondary metabolites that deter herbivores by releasing hydrogen cyanide, but also play other metabolic roles—to ask whether more apparent floral tissues and those most important for fitness are more defended as predicted by optimal defence theories, and what fine-scale CNglyc localisation reveals about function(s)? Florets of eleven species from the Proteaceae family were dissected to quantitatively compare the distribution of CNglycs within flowers and investigate whether distributions vary with other floral/plant traits. CNglycs were identified and their localisation in florets was revealed by matrix-assisted laser desorption ionisation mass spectrometry imaging (MALDI-MSI). We identified extremely high CNglyc content in floral tissues of several species (>1% CN), highly tissue-specific CNglyc distributions within florets, and substantial interspecific differences in content distributions, not all consistent with optimal defence hypotheses. Four patterns of within-flower CNglyc allocation were identified: greater tissue-specific allocations to (1) anthers, (2) pedicel (and gynophore), (3) pollen presenter, and (4) a more even distribution among tissues with higher content in pistils. Allocation patterns were not correlated with other floral traits (e.g. colour) or taxonomic relatedness. MALDI-MSI identified differential localisation of two tyrosine-derived CNglycs, demonstrating the importance of visualising metabolite localisation, with the diglycoside proteacin in vascular tissues, and monoglycoside dhurrin across floral tissues. High CNglyc content, and diverse, specific within-flower localisations indicate allocations are adaptive, highlighting the importance of further research into the ecological and metabolic roles of floral CNglycs. [ABSTRACT FROM AUTHOR]

Background: Neuropathic pain, a chronic debilitating painful condition, is frequently difficult to manage with the conventional analgesics. Emerging evidence indicates potential role of peroxisome proliferator-activated receptor (PPAR)-γ, a subfamily of nuclear receptors, in regulating inflammation and oxidative stress at transcription level. Therefore, we investigated whether activation of PPAR-γ attenuate established neuropathic pain and to delineate underlying mechanisms. Methods: Neuropathy was induced by chronic constriction injury of sciatic nerve in rats. Behavioral tests were performed to assess pain hypersensitivity and the markers of inflammation and nitroso-oxidative stress were estimated in sciatic nerve. Results: Chronic administration of pioglitazone (10 and 30 mg/kg, i.p.) for 2 weeks starting 14 days after nerve injury did not induce hypoalgesia in contralateral paws and had no effect on locomotor activity. However, pioglitazone significantly mitigated cold allodynia and thermal hyperalgesia in ipsilateral paws after nerve injury. In addition, pioglitazone reduced plasma extravasation and pro-inflammatory cytokines, TNF-α and IL-1β, following nerve injury. These effects of pioglitazone are parallel with the significant reduction in lipid peroxidation, protein carbonyls, nitrite levels as well as marked improvement in GSH and activities of SOD, catalase in injured nerves. BADGE, a PPAR-γ antagonist (30 mg/kg, i.p.) reversed the effects of pioglitazone in chronic constriction injury (CCI) rats. Conclusion: Together, the present results demonstrate that activation of PPAR-γ receptor-dependently exerted antiallodynic and antihyperalgesic effects through inhibition of inflammation and nitroso-oxidative stress in mononeuropathic rats and supporting a key role of PPAR-γ activation in extenuating existing neuropathic pain. [ABSTRACT FROM AUTHOR]

Background and Aims Floral chemical defence strategies remain understudied despite the significance of flowers to plant fitness, and the fact that many flowers contain secondary metabolites that confer resistance to herbivores. Optimal defence and apparency theories predict that the most apparent plant parts and/or those most important to fitness should be most defended. To test whether within-flower distributions of chemical defence are consistent with these theories we used cyanogenic glycosides (CNglycs), which are constitutive defence metabolites that deter herbivores by releasing hydrogen cyanide upon hydrolysis. Methods We used cyanogenic florets of the genus Lomatia to investigate at what scale there may be strategic allocation of CNglycs in flowers, what their localization reveals about function, and whether levels of floral CNglycs differ between eight congeneric species across a climatic gradient. Within-flower distributions of CNglycs during development were quantified, CNglycs were identified and their localization was visualized in cryosectioned florets using matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). Key Results Florets of all congeneric species studied were cyanogenic, and concentrations differed between species. Within florets there was substantial variation in CNglyc concentrations, with extremely high concentrations (up to 14.6 mg CN g−1 d. wt) in pollen and loose, specialized surface cells on the pollen presenter, among the highest concentrations reported in plant tissues. Two tyrosine-derived CNglycs, the monoglycoside dhurrin and diglycoside proteacin, were identified. MALDI-MSI revealed their varying ratios in different floral tissues; proteacin was primarily localized to anthers and ovules, and dhurrin to specialized cells on the pollen presenter. The mix of transient specialized cells and pollen of L. fraxinifolia was ~11 % dhurrin and ~1.1 % proteacin by mass. Conclusions Tissue-specific distributions of two CNglycs and substantial variation in their concentrations within florets suggests their allocation is under strong selection. Localized, high CNglyc concentrations in transient cells challenge the predictions of defence theories, and highlight the importance of fine-scale metabolite visualization, and the need for further investigation into the ecological and metabolic roles of CNglycs in floral tissues. [ABSTRACT FROM AUTHOR]

Background: Cataract is a major cause of visual impairment in diabetic patients. Due to increasing numbers of type 1 and type 2 diabetics worldwide, the incidence of diabetic cataracts steadily rises. Cataract surgery is the best possible cure for patients suffering from this ailment. However, the elucidation of pathomechanisms to delay or prevent the development of cataract in diabetic patients remains a challenge. Objective: The aim of the present study was to develop a polyherbal eyedrops containing potent antioxidant herbal extract and study the effectiveness as prophylactic treatment against galactose-induced diabetic cataract. Materials and Methods: Formulations were prepared by using extracts of Ginkgo biloba leaves, beet root (Beta vulgaris), and amla (Emblica officinalis) fruits. The viscosity enhancers were used to increase the retention time. Formulations (F1–F5) were prepared by using carboxy methyl cellulose and poly ethylene glycol-400 as thickening agents and propylene glycol as a solubilizer. Preliminary evaluation showed that formulations have passed clarity, sterility, and eye irritancy tests. Viscosity and pH of formulation were within the normal range. Diabetic cataract was induced in Wistar rats by 10% galactose drink (for 30 days) and anticataract activity was evaluated. Formulation was installed in eye as a prophylactic treatment from day 1 of galactose drinking and continued for 30 days. Results: Slit-lamp photography of eyes of rats showed clear lens of rats without any trace of opacity. On the other hand, galactose-treated rats developed dense nuclear opacity in lens as an indication of diabetic cataract. Rats which received prophylactic treatment showed less percent opacity as compared to that of cataract control group and decreased vacuoles. Conclusion: We may conclude that polyherbal formulation containing extracts of Ginkgo biloba leaves, beet root (Beta Vulgaris), and amla (Emblica officinalis) fruits may prevent the development of cataract in diabetic patients. Abbreviations used: ARI: Aldose reductase inhibitors; GPx: Glutathione peroxidase; GR: Glutathione reductase; DTNB: Dithio-bis-nitrobenzoic acid; GSH: Thiol. [ABSTRACT FROM AUTHOR]

Prolonged glucocorticoids (GCs) treatment may lead to the formation of posterior subcapsular cataracts. The present study aimed to investigate differential gene expression in lens epithelial cells (LECs) in response to GCs using DNA microarray profiling. The gene expression profile of GSE13040 was downloaded from the Gene Expression Omnibus database, which includes 12 human LECs treated with vehicle or dexamethasone (Dex) for 4 or 16 h with six samples at each time period, of which three samples were treated with vehicle (control group) and three samples were treated with Dex (Dex group) at each time point. The differentially expressed genes (DEGs) were identified between the control group and the Dex group at each time period with the thresholds of P<0.05 and |logFC|>1. The DEGs were further analyzed using bioinformatics methods. Firstly, DEGs were subject to a hierarchical cluster analysis. Subsequently, the functional enrichment analysis was performed for the common DEGs between the two time periods. Finally, the transcription factors and binding sites of DEGs associated with response to GC stimulus were analyzed. A total of 696 and 949 DEGs were identified at 4 h and 16 h, respectively. Hierarchical cluster analysis revealed that DEG expression was higher in the Dex group than in the control group (P<0.05). A total of 13 significant functions were enriched for the 72 common DEGs at the two time periods. Chemokine (C-C motif) ligand 2 (CCL2), dual-specificity phosphatase-1 (DUSP1) and FAS were associated with the response to GC stimulus and the transcription factor c-Jun bound to promoter regulation regions of CCL2, DUSP1 and FAS. In conclusion, the transcription factors and binding sites of DEGs associated with the response of LECs to GCs may provide potential gene targets for designing and developing drugs to protect against GC-induced cataract formation. [ABSTRACT FROM AUTHOR]

Purpose Refractive changes in diabetic eyes have long been reported but with equivocal results. The lens has been a more recent focus as the source of any change but it is possible that multiple sources of variation have made it difficult to demonstrate a systematic change clinically. The aim of this study was therefore to use a bovine lens model to investigate the optical changes in hyperglycaemia and when lenses are returned to normal glucose levels as would occur following commencement of treatment. Method Bovine eyes were obtained and their lenses excised under sterile conditions before placing them in culture medium within an incubator using standard tissue culture techniques. In the first experiment, lenses were transferred into culture medium containing 5 m m ( n = 12), 15 m m ( n = 12) and 30 m m ( n = 12) glucose. Measurements were made of the change in back vertex focusing distance with equatorial lens diameter using the ScanTox™ measurement system. From these measurements, the back vertex focal length and primary longitudinal spherical aberration were derived. In a second experiment, lenses maintained at 30 m m glucose ( n = 7) were stepped down to 5 m m glucose to simulate starting diabetic therapy and measured in the same way. Changes over time were assessed with a linear regression model. Results A trend towards myopia was observed with increasing hyperglycaemia, this was not statistically significant. When lenses were stepped-down from hyperglycaemia to normal physiological levels of glucose, a hyperopic shift was observed in line with published clinical studies that again failed to reach statistical significance. High variability in the measurement on longitudinal spherical aberration prevented any significant trends being measured. Conclusions Our results suggest that there are no consistent crystalline lens-induced refractive changes following exposure to hyperglycaemia for time-periods up to 5 days used in the current study. It is possible that bovine lenses are able to offset the raised osmotic pressure from high glucose levels in the short-term by a process of osmoregulation and that repeated osmotic stress or longer term exposure may be required to induce the changes in refraction that are seen clinically. [ABSTRACT FROM AUTHOR]

Background: The role of osmotic and oxidative stress has been strongly implicated in the pathogenesis of cataract. Nigerloxin, a fungal metabolite, has been shown to possess aldose reductase inhibition and improved antioxidant defense system in lens of diabetic rats. In the present study, the beneficial influence of nigerloxin was investigated in galactose-induced cataract in experimental animals. Methods: Cataract was induced in Wistar rats by feeding 30% galactose in diet. Groups of galactose-fed rats were orally administered with nigerloxin (25 and 100 mg/kg body weight/day) for 24 days. Results: Lens aldose reductase activity was increased significantly in galactose-fed animals. Lens lipid peroxides and advanced glycation end products were also significantly increased. Antioxidant molecule - reduced glutathione, total thiols and activities of antioxidant enzymes superoxide dismutase and glutathione peroxidase were decreased in the lens of galactose-fed animals. Oral administration of nigerloxin once a day for 24 days at a dose of 100 mg/kg body weight, significantly decreased lens lipid peroxides and advanced glycation end products in galactose-fed rats. Lens aldose reductase activity was reduced and lens antioxidant molecules and antioxidant enzyme activities were elevated significantly by nigerloxin administration. Conclusions: The results suggest that alteration in polyol pathway and antioxidant defense system were countered by nigerloxin in the lens of galactose-fed animals, suggesting the potential of nigerloxin in ameliorating the development of galactose-induced cataract in experimental animals. [ABSTRACT FROM AUTHOR]

Diabetes mellitus is associated with a 5-fold higher prevalence of cataracts, which remains a major cause of blindness in the world. Typical diabetic cataracts contain cortical and/or posterior subcapsular opacities. Adult onset diabetic cataracts also often contain nuclear opacities. Mechanisms of diabetic cataractogenesis have been studied in less detail than those of other diabetic complications. Both animal and human studies support important contribution of increased aldose reductase activity. Surgical extraction is the only cure of diabetic cataract today. An improved understanding of pathogenetic mechanisms, together with finding effective therapeutic agents, remain highest priority for diabetic cataract-related research and pharmaceutical development. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Classical galactosaemia is an inherited inborn error of the major galactose assimilation pathway, caused by galactose-1-phosphate uridyltransferase (GALT) deficiency. Many GALT mutations have been described, with different clinical consequences. In severe forms, newborns present with a life-threatening, acute toxic syndrome that rapidly regresses under a galactose-restricted diet. However, long-term complications, particularly cognitive and motor abnormalities, as well as hypergonadotrophic hypogonadism in female patients are still unavoidable. The pathogenesis of galactose-induced ovarian toxicity remains unclear but probably involves galactose itself and its metabolites such as galactitol and UDP-galactose. Possible mechanisms of ovarian damage include direct toxicity of galactose and metabolites, deficient galactosylation of glycoproteins and glycolipids, oxidative stress and activation of apoptosis. As there is no aetiological treatment, clinical management of ovarian failure in galactosaemic patients principally relies on hormonal replacement therapy to induce pubertal development and to prevent bone loss and other consequences of estrogen deprivation. Further investigations will be necessary to better understand the metabolic flux of galactose through its biochemical pathways and the mechanisms of these secondary complications. The aim of this article is to present an extensive review on the pathogenesis and clinical management of galactose-induced premature ovarian failure. [ABSTRACT FROM AUTHOR]

• Background and Aims Plant cyanogenesis is the release of toxic cyanide from endogenous cyanide-containing compounds, typically cyanogenic glycosides. Despite a large body of phytochemical, taxonomic and ecological work on cyanogenic species, little is known of their frequency in natural plant communities. This study aimed to investigate the frequency of cyanogenesis in Australian tropical rainforests. Secondary aims were to quantify the cyanogenic glycoside content of tissues, to investigate intra-plant and intra-population variation in cyanogenic glycoside concentration and to appraise the potential chemotaxonomic significance of any findings in relation to the distribution of cyanogenesis in related taxa.• Methods All species in six 200 m2 plots at each of five sites across lowland, upland and highland tropical rainforest were screened for cyanogenesis using Feigl–Anger indicator papers. The concentrations of cyanogenic glycosides were accurately determined for all cyanogenic individuals.• Key Results Over 400 species from 87 plant families were screened. Overall, 18 species (4·5 %) were cyanogenic, accounting for 7·3 % of total stem basal area. Cyanogenesis has not previously been reported for 17 of the 18 species, 13 of which are endemic to Australia. Several species belong to plant families or orders in which cyanogenesis has been little reported, if at all (e.g. Elaeocarpaceae, Myrsinaceae, Araliaceae and Lamiaceae). A number of species contained concentrations of cyanogenic glycosides among the highest ever reported for mature leaves—up to 5·2 mg CN g−1 d. wt, for example, in leaves of Elaeocarpus sericopetalus. There was significant variation in cyanogenic glycoside concentration within individuals; young leaves and reproductive tissues typically had higher cyanogen content. In addition, there was substantial variation in cyanogenic glycoside content within populations of single species.• Conclusions This study expands the limited knowledge of the frequency of cyanogenesis in natural plant communities, includes novel reports of cyanogenesis among a range of taxa and characterizes patterns in intra-plant and intra-population variation of cyanogensis. [ABSTRACT FROM AUTHOR]

Neotyphodium spp. fungal endophytes form symbiotic associations with agronomic grasses with expression ranging from mutualistic to parasitic. In general, endophyte infection frequencies seem more variable in natural compared to pastoral situations, suggesting that expression and benefits attributable to endophyte infection depend on the resource environment in which the host–endophyte complex was formed and the conditions under which it is being grown. Emerging evidence suggests that expression is not always mutualistic or beneficial to the host in terms of productivity and persistence in resource-limited environments. Expression of host–endophyte associations will vary depending on resource availability and environmental conditions that influence host physiology and growth, and herbivore behavior. New research suggest alkaloids and secondary metabolites produced by host–endophyte associations can have physiological functions in addition to acting as herbivore deterrents. Novel host–endophyte associations are being created that maintain insect and disease resistance, while having minimal detrimental impact on mammalian herbivores. The influence of host–endophyte associations on sward composition and soil food webs is only now coming to light. While novel endophyte associations and their attendant mechanisms can be considered beneficial in some respect, the associations may not be as adaptable to stressful or marginal resource environments and could have long-term ecological impacts measured in terms of persistence and total productivity of the sward. We review the extensive published work on host–endophyte interactions and illustrate the complexity of host–endophyte associations and their interactions with environment, and the range of responses that occur. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of aldose reductase inhibition on diabetes-induced oxidative-nitrosative stress and poly(ADP-ribose) polymerase (PARP) activation. In animal experiments, control and streptozotocin-induced diabetic rats were treated with or without the aldose reductase inhibitor (ARI) fidarestat (16 mg . kg(-1) . day(-1)) for 6 weeks starting from induction of diabetes. Sorbitol pathway intermediate, but not glucose, accumulation in sciatic nerve and retina was completely prevented in diabetic rats treated with fidarestat. Sciatic motor nerve conduction velocity, hindlimb digital sensory nerve conduction velocity, and sciatic nerve concentrations of two major nonenzymatic antioxidants, glutathione and ascorbate, were reduced in diabetic versus control rats, and these changes were prevented in diabetic rats treated with fidarestat. Fidarestat prevented the diabetes-induced increase in nitrotyrosine (a marker of peroxynitrite-induced injury) and poly(ADP-ribose) immunoreactivities in sciatic nerve and retina. Fidarestat counteracted increased superoxide formation in aorta and epineurial vessels and in in vitro studies using hyperglycemia-exposed endothelial cells, and the DCF test/flow cytometry confirmed the endothelial origin of this phenomenon. Fidarestat did not cause direct inhibition of PARP activity in a cell-free system containing PARP and NAD(+) but did counteract high-glucose-induced PARP activation in Schwann cells. In conclusion, aldose reductase inhibition counteracts diabetes-induced nitrosative stress and PARP activation in sciatic nerve and retina. These findings reveal the new beneficial properties of fidarestat, thus further justifying the ongoing clinical trials of this specific, potent, and low-toxic ARI. [ABSTRACT FROM AUTHOR]

Diabetes is known to affect cataract formation by means of osmotic stress induced by activated aldose reductase in the sorbitol pathway. In addition, alterations in the bioavailability of numerous extralenticular growth factors has been reported and shown to result in various consequences. We have found that the basic fibroblast growth factor (bFGF) accumulates in the vitreous humor of 3- and 8-week diabetic rats. Consequently, the associating signal transduction cascades were severely disrupted, including upregulated phosphorylation of extracellular signal-regulated kinase (ERK) and the common stress-associated mitogen-activated protein kinases p38 and SAPK/JNK. Conversely, under diabetic condition, we observed a dramatic inhibition of phosphatidylinositol-3 kinase activity in lenses obtained from the same animal. Rats treated with the aldose reductase inhibitor AL01576 for the duration of the diabetic condition showed that the diabetes-induced lenticular signaling alterations were normalized, comparable to controls. However, treatment of AL01576 in vitro was ineffective at normalizing the altered constituents in extracted diabetic vitreous after the onset of diabetes. The effect of AL01576 in the high galactose-induced cataract model in vitro was also examined. Administration of AL01576 to lens organ culture normalized the aberrant signaling effects and morphological characteristics associated with in vitro sugar cataract formation. In conclusion, our findings demonstrate diabetes-associated alterations in the lens signal transduction parameters and the effectiveness of AL01576 at normalizing such alterations. The causes for these alterations can be attributed to elevated vitreal bFGF in conjunction with osmotic stress and associated attenuation in redox status of the lens. [ABSTRACT FROM AUTHOR]

The study addressed the role for aldose reductase (AR) in 1) retinal oxidative stress and vascular endothelial growth factor (VEGF) overexpression in early diabetes, and 2) high glucose-induced oxidative stress in retinal endothelial cells. In vivo experiments were performed on control rats and diabetic rats treated with or without low or high dose of the AR inhibitor (ARI) fidarestat (2 or 16 mg. kg(-1). day(-1)). In vitro studies were performed on bovine retinal endothelial cells (BREC) cultured in either 5 or 30 mmol/l glucose with or without 1 micro mol/l fidarestat. Intracellular reactive oxygen species were assessed using the 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (H(2)DCFDA) probe and flow cytometry. Both low and high doses of fidarestat (i.e., the doses that partially and completely inhibited sorbitol pathway hyperactivity) arrested diabetes-induced retinal lipid peroxidation. This was achieved due to upregulation of the key antioxidative defense enzyme activities rather than changes in reduced glutathione, oxidized glutathione, ascorbate and dehydroascorbate concentrations, and the glutathione and ascorbate redox states. Diabetes-associated 2.1-fold VEGF protein overexpression (enzyme-linked immunosorbent assay; ELISA) was dose-dependently prevented by fidarestat, whereas total VEGF mRNA and VEGF-164 mRNA (RT-PCR) abundance were not affected by either diabetes or the ARI. In BREC, fidarestat corrected hyperglycemia-induced increase in H(2)DCFDA fluorescence but not oxidative stress caused by three different pro-oxidants in normoglycemic conditions. In conclusion, increased AR activity contributes to retinal oxidative stress and VEGF protein overexpression in early diabetes. The findings justify the rationale for evaluation of fidarestat on diabetic retinopathy. [ABSTRACT FROM AUTHOR]

Nutritional supplementation with dehydroepiandrosterone (DHEA) may be a candidate for treating diabetes-induced vascular and neural dysfunction. DHEA is a naturally occurring adrenal androgen that has antioxidant properties and is reportedly reduced in diabetes. Using a prevention protocol, we found that dietary supplementation of streptozotocin-induced diabetic rats with 0.1, 0.25, or 0.5% DHEA caused a concentration-dependent prevention in the development of motor nerve conduction velocity and endoneurial blood flow impairment, which are decreased in diabetes. At 0.25%, DHEA significantly prevented the diabetes-induced increase in serum thiobarbituric acid-reactive substances and sciatic nerve conjugated diene levels. This treatment also reduced the production of superoxide by epineurial arterioles of the sciatic nerve. DHEA treatment (0.25%) significantly improved vascular relaxation mediated by acetylcholine in epineurial vessels of diabetic rats. Sciatic nerve Na[SUP+]-K[SUP+]ATPase activity and myoinositol content was also improved by DHEA treatment, whereas sorbitol and fructose content remained elevated. These studies suggest that DHEA, by preventing oxidative stress and perhaps improving sciatic nerve Na[SUP+]-K[SUP+]-ATPase activity, may improve vascular and neural dysfunction in diabetes. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: A strong positive correlation has been found between lipid peroxidation product and vascular endothelial growth factor concentrations in the vitreous of patients with proliferative diabetic retinopathy. To establish a causal relation between diabetes-associated enhanced oxidative stress and vascular endothelial growth factor production, we evaluated two antioxidants, dl-α-lipoic acid and taurine, on retinal vascular endothelial growth factor protein and mRNA expression and on parameters of oxidative stress in streptozotocin-diabetic rats. Methods: Our experiments were on control rats and streptozotocin-diabetic rats with a 6-week duration of diabetes, treated with or without dl-α-lipoic acid (100 mg · kg–1· d–1, i. p.) or taurine (1 % in the diet) starting from induction of diabetes. Vascular endothelial growth factor protein in retinal homogenates was assessed by sandwich ELISA with an affinity-purified polyclonal antibody and vascular endothelial growth factor mRNA by ribonuclease protection assay. Retinal lipid peroxidation products i. e. malondialdehyde plus 4-hydroxyalkenals were quantified with n-methyl-2-phenylindole. Retinal reduced and oxidized glutathione, ascorbate, dehydroascorbate, and sorbitol pathway intermediates were measured spectrofluorometrically, and taurine by reverse-phase HPLC. Results: Vascular endothelial growth factor protein concentration (means ± SD) was increased in diabetic rats compared with control rats (33 ± 7 vs 19 ± 5 pg/mg total protein, p < 0.01) This increase was attenuated by taurine (26 ± 8, p < 0.05) and prevented by dl-α-lipoic acid (21 ± 4, p < 0.01). Vascular endothelial growth factor mRNA abundance was reduced by 1.4-fold in diabetic rats compared with control rats and this decrease was attenuated but not completely prevented by both antioxidants. Malondialdehyde plus 4-hydroxyalkenal concentration was increased in diabetic rats compared with control rats, and both antioxidants arrested accumulation of lipid peroxidation products. Taurine, reduced glutathione, oxidized glutathione, ascorbate, dehydroascorbate and sorbitol pathway intermediate concentrations as well as oxidized glutathione/reduced glutathione and dehydroascorbate/ascorbate ratios were similar in control and diabetic rats treated with or without taurine. Conclusion/interpretation: Oxidative stress is directly involved in up regulation of vascular endothelial growth factor protein in the retina during early diabetes. [Diabetologia (2001) 44: 1102–1110] [ABSTRACT FROM AUTHOR]

We have shown that diabetes-induced reduction in endoneurial blood flow (EBF) and impaired endothelium-dependent vascular relaxation precede slowing of motor nerve conduction velocity (MNCV) and decreased sciatic nerve Na(+)/K(+) ATPase activity. Furthermore, vascular dysfunction was accompanied by an accumulation of superoxide in arterioles that provide circulation to the sciatic nerve. In the present study, we examined the effect that treatment of streptozotocin-induced diabetic rats with antioxidants has on vascular and neural function. Diabetic rats were treated with 0.5% alpha-lipoic acid as a diet supplement or with hydroxyethyl starch deferoxamine (HES-DFO) by weekly intravenous injections at a dose of 75 mg/kg. The treatments significantly improved diabetes-induced decrease in EBF, acetylcholine-mediated vascular relaxation in arterioles that provide circulation to the region of the sciatic nerve, and MNCV. The treatments also reduced the production of superoxide by the aorta and superoxide and peroxynitrite by arterioles that provide circulation to the region of the sciatic nerve. Treating diabetic rats with alpha-lipoic acid prevented the diabetes-induced increase in thiobarbituric acid-reactive substances in serum and significantly improved lens glutathione levels. In contrast, treating diabetic rats with HES-DFO did not prevent diabetes-induced changes of either of these markers of oxidative stress. Diabetes-induced increase in sciatic nerve conjugated diene levels was not improved by treatment with either alpha-lipoic acid or HES-DFO. Treating diabetic rats with alpha-lipoic acid but not HES-DFO partially improved sciatic nerve Na(+)/K(+) ATPase activity and myo-inositol content. The increase in sciatic nerve sorbitol levels in diabetic rats was unchanged by either treatment. These studies suggest that diabetes-induced oxidative stress and the generation of superoxide may be partially responsible for the development of diabetic vascular and neural complications. [ABSTRACT FROM AUTHOR]

Aims/hypothesis. The protein kinase C (PKC), platelet-derived growth factor (PDGF) and polyol pathway play important parts in the hyperproliferation of smooth muscle cells, a characteristic feature of diabetic macroangiopathy. The precise mechanism, however, remains unclear. This study investigated the relation between polyol pathway, protein kinase C and platelet-derived growth factor in the development of diabetic macroangiopathy. Methods. Smooth muscle cells were cultured with 5.5 or 20 mmol/l glucose with or without an aldose reductase inhibitor, epalrestat, or a PKC-β specific inhibitor, LY333 531. Protein kinase C activities, the expression of PKC-βII isoform and PDGF-β receptor protein, free cytosolic NAD+:NADH ratio, the contents of reduced glutathione, and proliferation activities were measured. Results. Smooth muscle cells cultured with 20 mmol/l glucose showed statistically significant increases in protein kinase C activities, the expression of PKC-βII isoform and PDGF-β receptor protein, and proliferation activities, compared with smooth muscle cells cultured with 5.5 mmol/l glucose. Although epalrestat and LY333 531 inhibited protein kinase C activation induced by glucose to the same degree, the effects of epalrestat on proliferation activities and expression of the PDGF-β receptor were more prominent than those of LY333 531. Epalrestat improved the glucose-induced decrease in free cytosolic NAD+:NADH ratio and reduced glutathione content, but LY333 531 did not. The increased expression of membranous PKC-βII isoform was normalized by epalrestat. Conclusion/interpretation. These observations suggest that polyol pathway hyperactivity contributes to the development of diabetic macroangiopathy through protein kinase C, PDGF-β receptor, and oxidative stress, and that an aldose reductase inhibitor has a therapeutic value for this complication. [Diabetologia (2001) 44: 480–487] [ABSTRACT FROM AUTHOR]

Aims/hypothesis. Aldose reductase inhibitors (ARIs) prevent biochemical abnormalities associated with diabetic complications. We evaluated whether a short-term intervention with an adequate dose of ARI, introduced at the very early, precataractous stage, reversed diabetes-induced metabolic imbalances, down-regulation of ATPases and oxidative stress in the lens. Methods. The groups included mature control and streptozotocin-diabetic rats treated with or without ARI sorbinil (65 mg · kg–1· day–1, in the diet, for 2 weeks after 4 weeks of untreated diabetes). Free cytosolic NAD+:NADH and NADP+:NADPH ratios were calculated from the lactate dehydrogenase and malic enzyme systems. Concentrations of metabolites and adenine nucleotides, Na+/K+-ATPase, H+-ATPase and Ca++-independent Mg++-ATPase activities and variables of oxidative stress were measured in individual lenses. Results. Sorbinil treatment essentially corrected diabetes-induced sorbitol and fructose accumulation, myo-inositol depletion, decrease in free cytosolic NAD+:NADH ratio and energy deficiency. Malondialdehyde accumulation, reduced glutathione depletion and the increase in oxidized glutathione:reduced glutathione ratio were partially corrected. Free cytosolic NADP+:NADPH ratio and 4-hydroxyalkenal concentrations were similarly increased in diabetic rats treated with or without ARI. Sorbinil did not counteract diabetes-induced down-regulation of the three ATPase activities. Conclusion/interpretation. All biochemical changes assessed in our study are known to be prevented by ARIs. Despite the essential normalization of the sorbitol pathway activity, only part of them were, however, reversed by the ARI treatment introduced at the very early, i. e. precataractous, stage of diabetes. Therefore, intervention studies can easily underestimate the importance of aldose reductase in the pathogenesis of diabetic complications and should be interpreted with caution. [Diabetologia (2000) 43: 1048–1055] [ABSTRACT FROM AUTHOR]

To clarify whether or not tolerance to nitroglycerin is developed more easily in a diabetic than in a non-diabetic state, the effects of nitroglycerin on aortic preparations isolated from diabetic and nondiabetic rats were examined and compared with those of nicorandil, which has been known to develop less tolerance than does nitroglycerin. Contractile responses to norepinephrine, relaxant responses to nitroglycerin and nicorandil, and the tolerance development to nitroglycerin were found to be no different between diabetic and non-diabetic aortic preparations. N-Acetylcysteine preincubated together with nitroglycerin prevented the tolerance development to nitroglycerin in non-diabetic but not in diabetic aortic preparations. The results suggest that the tolerance to nitroglycerin is developed in the diabetic as well as in the non-diabetic state. [ABSTRACT FROM AUTHOR]

The study was aimed at evaluating changes in lens antioxidant status, glucose utilization, redox state of free cytosolic NAD(P)-couples and adenine nucleotides in rats with 6-week streptozotocin-induced diabetes, and to assess a possibility of preventing them by dl-α-lipoic acid. Rats were divided into control and diabetic groups treated with and without dl-α-lipoic acid (100 mg · kg body weight–1· day–1, i. p.). The concentrations of glucose, sorbitol, fructose, myo-inositol, oxidized glutathione, glycolytic intermediates, malate, α-glycerophosphate, and adenine nucleotides were assayed in individual lenses spectrofluorometrically by enzymatic methods, reduced glutathione and ascorbate – colorimetrically, and taurine by HPLC. Free cytosolic NAD+:NADH and NADP+:NADPH ratios were calculated from the lactate dehydrogenase and malic enzyme systems. Sorbitol pathway metabolites were found to increase, and antioxidant concentrations were reduced in diabetic rats compared with controls. The profile of glycolytic intermediates (increase in glucose 6-phosphate and fructose 6-phosphate, decrease in fructose1,6-diphosphate, increase in dihydroxyacetone phosphate, 3-phosphoglycerate, phosphoenolpyruvate, pyruvate, and no change in lactate), and 5.9-fold increase in α-glycerophosphate suggest diabetes-induced inhibition of glycolysis. Free cytosolic NAD+:NADH ratios, ATP levels, ATP/ADP × inorganic phosphate (Pi), and adenylate charge were reduced in diabetic rats while free cytosolic NADP+:NADPH ratios were elevated. Diabetes-induced changes in the concentrations of antioxidants, key glycolytic intermediates, free cytosolic NAD+:NADH ratios, and energy status were partially prevented by dl-α-lipoic acid, while sorbitol pathway metabolites and free cytosolic NADP+:NADPH ratios remained unaffected. In conclusion, diabetes-induced impairment of lens antioxidative defense, glucose intermediary metabolism via glycolysis, energy status and redox changes are partially prevented by dl-α-lipoic acid. The findings support the important role of oxidative stress in lens metabolic imbalances in diabetes. [Diabetologia (1998) 41: 1442–1450] [ABSTRACT FROM AUTHOR]

Previous studies demonstrating reduced plasma concentrations of ascorbic acid (AA) in diabetes and interactions between this vitamin and biochemical mechanisms such as synthesis of structural proteins, oxidative stress, polyol pathway and non-enzymatic glycation of proteins suggest that disturbed AA metabolism may be important in the pathogenesis of diabetic microangiopathy. However, limited information is available on the concentration of AA in tissues which develop diabetic complications. This study demonstrates reduced renal but not sciatic nerve or plasma AA concentration in two animal models of insulin-dependent diabetes mellitus, namely the STZ-diabetic rat and the spontaneously diabetic BB rat. Decreased lens AA concentration was also observed in STZ-diabetic rats. Improvement of glycaemic control by insulin treatment (albeit insufficient to achieve normoglycaemia) partially corrected lens and renal AA concentration in STZ-diabetic rats. AA treatment increased kidney and lens AA concentrations of STZ-diabetic and non-diabetic rats and corrected the abnormalities observed for untreated diabetic rats. Sciatic nerve AA concentration was not increased by AA treatment in any group. Tissue ratios of dehydroascorbic acid (DHAA)/AA, one index of oxidative stress, were not different between the diabetic and non-diabetic groups and were unaltered by AA supplementation. AA treatment of STZ-diabetic rats had no effect on elevated tissue concentrations of glucose, sorbitol and fructose or reduced myo-inositol concentration. The effect of reduced tissue AA levels in diabetes on either collagen synthesis or ability to combat increased free radical production is not known. However, correction of abnormal kidney and lens AA concentrations in experimental diabetes by AA supplementation suggests that if AA does have a role in the development or progression of the renal and ocular complications of diabetes, this treatment could be beneficial. [Diabetologia (1998) 41: 516–523] [ABSTRACT FROM AUTHOR]

Marine allelochemicals generally are present in greater quantity and diversity in tropical than in temperate regions. Marine algal polyphenolics have been reported as an apparent exception to this biogeographic trend, with literature values for phenolic concentrations significantly higher in temperate than in tropical brown algae. In contrast, our results, the first reported for Caribbean brown algae (orders Dictyotales and Fucales), show that many species have high phenolic levels. In addition, both our study and previous studies with north temperate and tropical species demonstrate that there is marked variation in algal phenolic levels within species from different locations. We conclude that high phenolic concentrations occur in species from both temperate and tropical regions, indicating that latitude alone is not a reasonable predictor of plant phenolic concentrations. [ABSTRACT FROM AUTHOR]

Mature leaves of trees and shrubs from sub-humid tropical regions ofBenin (Acioa barteri, Cassia sieberiana, Dialium guineense, Dichrostachys cinerea, Guiera senegalensis, Milletia thonningii, Piliostigma reticulatum) and arid and semiarid regions of Zimbabwe and Niger (Acacia holosericea, A. nilotica, Dichrostachys cinerea, Securidaca longepedunculata, Parinari cuvetelio, Ziziphus mucronata) in Africa, and from sub-tropical region in foot-hills of North-West Humid Himalayan range (Albizia stipulata, Bauhenia variegata, Cedrela toona, Celtis australis, Dendrocalamus hamiltonii, Grewia optiva, Leucocephala leucocephala, Morus alba, Papulus ciliata, Quercus incana, Q. semecarpifolia, Q. glauca, Q. serrata, Q. ilex, Robinia pseudoacacia, Salix tetrasperma) were analysed for crude protein, total phenols (TP), protein precipitation capacity (PPC) and operational activity of tannins (values are as mean +/- SE). There was no significant difference in the crude protein values of forages obtained from the Himalayan and Africanregion (15.2 +/- 1.16 and 14.1 +/- 1.19%, respectively), however thelevels of TP and biological value of tannins as PPC were significantly higher for the African forages (TP 15.7 +/- 4.27 vs 6.0 +/- 1.0%; PPC 327.2 +/- 113.6 vs 56 +/- 15.9 mg bovine serum albumin precipitated/g). The operational activity of tannins expressed as mg protein precipitated per unit of phenols was also significantly higher in forages from the African regions (1.97 +/- 0.47 vs 0.66 +/- 0.17). For a small set of leaves from arid and semiarid zones of Middle East (Syria, A. cyanophylla; Israel, A. saligna) and India (Eugenia jambolana, Eucalyptus punctata, Prosopis cineraria and Shorea robusta) TP, PPC and tannin activity were closer to those for the African forages. [ABSTRACT FROM AUTHOR]