Aminoguanidine pyridoxal adduct is superior to aminoguanidine for preventing diabetic nephropathy in mice.

Aminoguanidine inhibits the formation of advanced glycation end-products, and has been extensively examined in animals. However, administration of aminoguanidine decreases the hepatic content of pyridoxal phosphate. In order to avoid this problem, we developed an aminoguanidine pyridoxal Schiff base adduct and examined its efficacy in vitro as well as in a model of diabetic nephropathy. Mice with streptozotocin-induced diabetes were treated with aminoguanidine or aminoguanidine pyridoxal adduct for 9 weeks. An in vitro study was also performed to assess the antioxidant activity of aminoguanidine and its pyridoxal adduct. Neither drug altered glycemic control. Aminoguanidine pyridoxal adduct significantly improved urinary albumin excretion by 78.1 % compared with the diabetic control, and also had a better preventive effect on the progression of renal pathology than aminoguanidine did. Inhibition of glycation by both drugs was similar, but the antioxidant activity of the pyridoxal adduct was far superior. These findings suggest that aminoguanidine pyridoxal adduct may be superior to aminoguanidine, as it not only prevents vitamin B6 deficiency but is also better at controlling diabetic nephropathy, as this adduct inhibits oxidation as well as glycation.     

Amylin is more potent and more effective than glucagon in raising plasma glucose concentration in fasted, anesthetized rats.

Amylin is a 37 amino-acid peptide secreted from the pancreatic beta-cells. It has actions on carbohydrate metabolism in vivo, including elevation of blood glucose. In this study, the hyperglycemic effect of intravenous bolus injections of amylin was compared with similar injections of glucagon in 20-hour fasted rats lightly anesthetized with halothane. Administered doses ranged from 0.01 micrograms to 1000 micrograms (about 7 pmol/kg--750 nmol/kg for amylin and 8 pmol/kg--800 pmol/kg for glucagon). Control animals received an equal volume of saline. A single intravenous injection of amylin or glucagon led to an increase of plasma glucose levels, which peaked approximately at 1 hour after treatment. The calculated ED50 for amylin was 1.48 nmol whereas that for glucagon was 7.46 nmol; the maximum glucose increment was 4.3 mM for amylin, and 2.9 mM for glucagon. These results show that amylin is a more potent and more effective hyperglycemic agent than glucagon under these experimental conditions.     

Syzygium cumini is more effective in preventing the increase of erythrocytic ADA activity than phenolic compounds under hyperglycemic conditions in vitro

Syzygium cumini (S. cumini) is a plant known for its antidiabetic properties. The aim of this study was to evaluate the effect of Sc aqueous leaf extract (ASc) on adenosine deaminase (ADA) activity in erythrocytes (RBCs) exposed to high glucose concentrations (30 mM) in vitro. We also investigated the effects of the main phenolic compounds found in ASc (gallic acid, rutin, and chlorogenic acid) and the effects of insulin, caffeine, and dipyridamole, which are substances involved in the adenosine metabolism, on ADA activity in vitro. Blood samples were obtained from healthy volunteers and a suspension of RBCs was used for the determination of ADA activity. The results showed that: (1) the effect of ASc on ADA activity was more significant than the combination of phenolic compounds; (2) insulin, caffeine, or dipyridamole prevented high glucose increase of ADA activity at doses as low as 50 μU/mL, 25 μM, and 1 μM, respectively; (3) the inhibitory effect caused by ASc on erythrocyte ADA activity remained practically the same after the combination of the extract with insulin or caffeine; (4) when RBCs were exposed to ASc plus dipyridamole, this chemical attenuated the effect of ASc on ADA activity, suggesting an antagonism or a competition with ASc by the same site of action. Therefore, ASc was more effective in preventing the increase in ADA activity than phenolic compounds, suggesting that ASc may collaborate to improve endothelial dysfunction, antioxidant, anti-inflammatory, and antithrombotic properties of adenosine by affecting its metabolism. The results of this study help to provide evidence of the empirically supported benefits of the use of S. cumini in diabetes.     

Hepatocyte-derived ApoE is more effective than non-hepatocyte-derived ApoE in remnant lipoprotein clearance

The importance of hepatocyte-derived apolipoprotein (apo) E in the clearance of remnant lipoproteins in the liver is controversial. To address this controversy, we compared remnant clearance in two mouse models in which apoE is primarily derived either from hepatocytes or from an extrahepatic source. Hypomorphic apoE mice universally express reduced levels of apoE in all tissues, with the liver remaining the primary source of apoE. This mouse model of hepatocyte-derived apoE was compared with Apoe(-/-) mice transplanted with mouse bone marrow as a model of primarily non-hepatocyte-derived apoE. Immunohistochemical analysis of liver sections revealed that only the hepatocyte-derived apoE model had detectable levels of apoE on hepatic sinusoidal surfaces. The non-hepatocyte-derived apoE model with plasma apoE levels similar to those in the hepatocyte-derived model had 2-fold more total plasma cholesterol, 4-fold more total plasma triglycerides, and 8-fold higher levels of apoB48, similar to Apoe(-/-) mice. Both the hepatocyte-derived and the non-hepatocyte-derived apoE models had delayed clearance of an infused bolus of (125)I-labeled remnants compared with wild-type mice. However, after 3 h, plasma remnants reached wild-type levels only in the hepatocyte-derived apoE model, which had accumulated 70 +/- 5% of wild-type levels of remnants in the liver while the non-hepatocyte-derived apoE model had accumulated only 38 +/- 4%. These results demonstrate the existence of a role for both hepatically derived and localized apoE in remnant clearance. This role likely represents the enrichment of remnants sequestered on hepatocyte, with hepatocyte-derived apoE, facilitating their receptor-mediated internalization.     

The effects of aminoguanidine on retinopathy in STZ-induced diabetic rats

BackgroundThe accumulation of advanced glycated end products (AGEs) in retinal blood vessels is one of the major etiological factors contributing to diabetic retinopathy. Aminoguanidine (AG) is one of the most extensively used inhibitors of AGEs formation. The aim of this study was to investigate whether AG could protect the development of diabetic retinopathy through inhibition of AGEs.MethodsRat diabetes was induced by intraperitoneal injection with streptozotocin (STZ). AG was given to rats in drinking water. Retina was extracted 3 and 6 months following STZ and AG administration. Immunochemistry and transmission electron microscope were used to detect the expression of AGEs and retina morphology.ResultsExtensive staining of AGEs was detected in retinal blood vessels of 3- and 6-month diabetic rats, while no significant staining was found in the control non-diabetic retina or AG treated groups. Pericyte loss, endothelial cell proliferation, increased ratio of endothelial cells/pericytes, acellular capillaries and capillary occlusion were observed in the retina of 6-month diabetic rats. The increased electron density of retinal capillary basement membrane, mitochondrial swelling in pericytes and endothelial cells were also found in 6-month diabetic rats. The 3-month diabetic rats and the AG-treated rats did not have similar morphological changes compared to control group. The AGEs staining in AG-treated rats was still weakly positive.ConclusionsAGEs plays pivotal roles in diabetic retinopathy. AGE deposition occurs prior to retinal microvasculature changes. AG could prevent the onset and development of diabetic retinopathy through inhibition of AGEs.     

Power training is more effective than strength training for maintaining bone mineral density in postmenopausal women.

Physical exercise has a favorable impact on bones, but optimum training strategies are still under discussion. In this study, we compared the effect of slow and fast resistance exercises on various osteodensitometric parameters. Fifty-three postmenopausal women were randomly assigned to a strength training (ST) or a power training group (PT). Both groups carried out a progressive resistance training, a gymnastics session, and a home training over a period of 12 mo. During the resistance training, the ST group used slow and the PT group fast movements; otherwise there were no training differences. All subjects were supplemented with Ca and vitamin D. At baseline and after 12 mo, bone mineral density (BMD) was measured at the lumbar spine, proximal femur, and distal forearm by dual-energy X-ray absorptiometry. We also measured anthropometric data and maximum static strength. Frequency and grade of pain were assessed by questionnaire. After 12 mo, significant between-group differences were observed for BMD at the lumbar spine (P < 0.05) and the total hip (P < 0.05). Whereas the PT group maintained BMD at the spine (+0.7 +/- 2.1%, not significant) and the total hip (0.0 +/- 1.7%, not significant), the ST group lost significantly at both sites (spine: -0.9 +/- 1.9%; P < 0.05; total hip: -1.2 +/- 1.5%; P < 0.01). No significant between-group differences were observed for anthropometric data, maximum strength, BMD of the forearm, or frequency and grade of pain. These findings suggest that power training is more effective than strength training in reducing bone loss in postmenopausal women.     

T4 DNA ligase is more than an effective trap of cyclized dsDNA

T4 DNA ligase is used in standard cyclization assays to trap double-stranded DNA (dsDNA) in low-probability, cyclic or highly bent conformations. The cyclization probability, deduced from the relative yield of cyclized product, can be used in conjunction with statistical mechanical models to extract the bending stiffness of dsDNA. By inserting the base analog 2-aminopurine (2-AP) at designated positions in 89bp and 94bp dsDNA fragments, we find that T4 DNA ligase can have a previously unknown effect. Specifically, we observe that addition of T4 ligase to dsDNA in proportions comparable to what is used in the cyclization assay leads to a significant increase in fluorescence from 2-AP. This effect is believed to originate from stabilization of local base-pair opening by formation of transient DNA-ligase complexes. Non-specific binding of T4 ligase to dsDNA is also confirmed using fluorescence correlation spectroscopy (FCS) experiments, which reveal a systematic reduction of dsDNA diffusivity in the presence of ligase. ATP competes with regular DNA for non-covalent binding to the T4 ligase and is found to significantly reduce DNA-ligase complexation. For short dsDNA fragments, however, the population of DNA-ligase complexes at typical ATP concentrations used in DNA cyclization studies is determined to be large enough to dominate the cyclization reaction.     

Gamma-tocopherol is less effective than alpha-tocopherol in preventing oxidant-induced sister chromatid exchanges in Chinese hamster V79 cells.

Although alpha-tocopherol (alpha-TOC) is the most biologically active form of vitamin E and is found at high levels in plasma, gamma-tocopherol (gamma-TOC) has also been found to be a powerful antioxidant in vitro and constitutes up to 70% of the dietary intake of TOC. Low plasma levels of gamma-TOC and a high alpha-TOC:gamma-TOC ratio may be associated with coronary heart disease, suggesting that there may be a positive protective role for the gamma-form of TOC. In this study the ability of different forms of vitamin E to protect against sister chromatid exchanges (SCE) induced by either hydrogen peroxide or menadione was investigated. Chinese hamster V79 cells were pre-treated with 10 microM TOC for 24 h, and then challenged with a genotoxin. After a 24 h pre-treatment, there was a greater incorporation of gamma-TOC (319.8 +/- 66.2 ng/10(6) cells) into V79 cells compared to alpha-TOC (66.9 +/- 6.4 ng/10(6) cells). Gamma-TOC did not protect the cells against SCE induced by either hydrogen peroxide or menadione, alpha-TOC acetate was partially protective against both genotoxins, whereas alpha-TOC completely abolished the oxidant induced SCE. These results demonstrate that, despite a greater incorporation of gamma-TOC into V79 cells, alpha-TOC but not gamma-TOC was more effective at inhibiting oxidatively-induced SCE in V79 cells.     

Glycoconjugates with NeuAc-NeuAc-Gal-Glc are more effective at preventing adhesion of Helicobacter pylori to gastric epithelial cells than glycoconjugates with NeuAc-Gal-Glc.

Helicobacter pylori (H. pylori) adheres to human gastric epithelial cells, eliciting various gastroduodenal diseases. Gangliosides play a critical role in bacterial adhesion to cell surfaces. The present study examined how residues of gangliosides are important for inhibition of adhesion of H. pylori to MKN-45 cells. We measured adhesion or detachment effects of gangliosides on the interaction between MKN-45 cells and H. pylori, as well as interleukin-8 production. Among the gangliosides, O-Ac-GD3, GT(1b), GD(1a), GD(1b), GT(1a), and GD3 had potent dose dependent inhibitory effects on adhesion of H. pylori to MKN-45 cells, interleukin-8 production, and vacuole formation induced by H. pylori toxin binding to Vero cells. GD3 also accelerated bacterial detachment of MKN-45 cells with adherent H. pylori in a dose dependent manner. Such results strongly suggest that the mechanism involved in the inhibition of H. pylori adhesion is mediated by the variations of the residues of the NeuAc-NeuAc-Gal-Glc chain of gangliosides. NeuAc-NeuAc-Gal-Glc exhibits a more inhibitory effect on adhesion than the NeuAc-Gal-Glc chain. Such gangioside and oligosaccrharide sequences appear to have therapeutic importance for prevention of H. pylori adhesion, as well as reduction of both inflammation and gastric mucosal injuries.     

Enhancing pollination is more effective than increased conventional agriculture inputs for improving watermelon yields

Agricultural practices to improve yields in small‐scale farms in Africa usually focus on improving growing conditions for the crops by applying fertilizers, irrigation, and/or pesticides. This may, however, have limited effect on yield if the availability of effective pollinators is too low. In this study, we established an experiment to test whether soil fertility, soil moisture, and/or pollination was limiting watermelon (Citrullus lanatus) yields in Northern Tanzania. We subjected the experimental field to common farming practices while we treated selected plants with extrafertilizer applications, increased irrigation and/or extra pollination in a three‐way factorial experiment. One week before harvest, we assessed yield from each plant, quantified as the number of mature fruits and their weights. We also assessed fruit shape since this may affect the market price. For the first fruit ripening on each plant, we also assessed sugar content (brix) and flesh color as measures of fruit quality for human consumption. Extra pollination significantly increased the probability of a plant producing a second fruit of a size the farmer could sell at the market, and also the fruit sugar content, whereas additional fertilizer applications or increased irrigation did not improve yields. In addition, we did not find significant effects of increased fertilizer or watering on fruit sugar, weight, or color. We concluded that, insufficient pollination is limiting watermelon yields in our experiment and we suggest that this may be a common situation in sub‐Saharan Africa. It is therefore critically important that small‐scale farmers understand the role of pollinators and understand their importance for agricultural production. Agricultural policies to improve yields in developing countries should therefore also include measures to improve pollination services by giving education and advisory services to farmers on how to develop pollinator‐friendly habitats in agricultural landscapes.     

Inferior retinal light exposure is more effective than superior retinal exposure in suppressing melatonin in humans

Illumination of different areas of the human retina elicits differences in acute light-induced suppression of melatonin. The aim of this study was to compare changes in plasma melatonin levels when light exposures of equal illuminance and equal photon dose were administered to superior, inferior, and full retinal fields. Nine healthy subjects participated in the study. Plexiglass eye shields were modified to permit selective exposure of the superior and inferior halves of the retinas of each subject. The Humphrey Visual Field Analyzer was used both to confirm intact full visual fields and to quantify exposure of upper and lower visual fields. On study nights, eyes were dilated, and subjects were exposed to patternless white light for 90 min between 0200 and 0330 under five conditions: (1) full retinal exposure at 200 lux, (2) full retinal exposure at 100 lux, (3) inferior retinal exposure at 200 lux, (4) superior retinal exposure at 200 lux, and (5) a dark-exposed control. Plasma melatonin levels were determined by radioimmunoassay. ANOVA demonstrated a significant effect of exposure condition (F = 5.91, p < 0.005). Post hoc Fisher PLSD tests showed significant (p < 0.05) melatonin suppression of both full retinal exposures as well as the inferior retinal exposure; however, superior retinal exposure was significantly less effective in suppressing melatonin. Furthermore, suppression with superior retinal exposure was not significantly different from that of the dark control condition. The results indicate that the inferior retina contributes more to the light-induced suppression of melatonin than the superior retina at the photon dosages tested in this study. Findings suggest a greater sensitivity or denser distribution of photoreceptors in the inferior retina are involved in light detection for the retinohypothalamic tract of humans.     

Docosahexaenoic acid and 17 beta-estradiol co-treatment is more effective than 17 beta-estradiol alone in maintaining bone post-ovariectomy

Bone-protective effects of combined treatment with long chain polyunsaturated fatty acids (LCPUFAs) and estrogenic compounds following ovariectomy have previously been reported. Recent evidence suggests the n-3 LCPUFA docosahexaenoic acid (DHA, 22:6n-3) is particularly bone-protective. The aim of this study was to determine whether combined treatment with DHA and estrogenic compounds has a beneficial effect on bone mass in ovariectomized (OVX) rats. Rats were randomized into 9 groups and either ovariectomized (8 groups) or sham-operated (1 group). Using a 2 x 4 factorial design approach, OVX animals received either no estrogenic compound, genistein (20 mg/kg body weight/day), daidzein, (20 mg/kg body weight/day) or 17 beta-estradiol (1 microg/day) with or without DHA (0.5 g/kg body weight/day) for 18 weeks. Bone mineral content (BMC), area (BA), and density (BMD), plasma osteocalcin and IL-6 concentrations, and red blood cell (RBC) fatty acid composition were measured. Femur BMC was significantly greater in animals treated with DHA or 17 beta-estradiol than in ovariectomized controls. Plasma carboxylated osteocalcin was significantly higher in DHA-treated animals and total osteocalcin significantly lower in 17 beta-estradiol-treated animals compared with ovariectomized controls. There were significant interactions between treatment with estrogenic compounds and DHA for femur BMC, plasma IL-6 concentration, and RBC fatty acid composition. Combined treatment with 17beta-estradiol+DHA was more effective than either treatment alone at preserving femur BMC and lowering circulating concentrations of pro-inflammatory IL-6. The percentage of n-3 LCPUFAs in RBCs was significantly greater in animals receiving 17 beta-estradiol+DHA compared with either treatment alone. There was no beneficial effect of combined DHA and phytoestrogen treatment on bone. Results from this study raise the possibility that co-treatment with 17 beta-estradiol and DHA may allow a lower dose of 17 beta-estradiol to be used to provide the same bone-protective effects as when 17 beta-estradiol is administered alone.     

Characterization of a novel hemoglobin-glutathione adduct that is elevated in diabetic patients.

BACKGROUND: Typically, a diagnosis of diabetes mellitus is based on elevated circulating blood glucose levels. In an attempt to discover additional markers for the disease and predictors of prognosis, we undertook the characterization of HbA1d3 in diabetic and normal patients. MATERIAL AND METHODS: PolyCAT A cation exchange chromatography and liquid chromatography-mass spectroscopy was utilized to separate the alpha- and beta-globin chains of HbA1d3 and characterize their presence in normal and diabetic patients. RESULTS: We report the characterization of HbA1d3 as a glutathionylated, minor hemoglobin subfraction that occurs in higher levels in diabetic patients (2.26 +/- 0.29%) than in normal individuals (1.21 +/- 0.14%, p < 0.001). The alpha-chain spectrum displayed a molecular ion of m/z 15126 Da, which is consistent with the predicted native mass of the HbA0 alpha-globin chain. By contrast, the mass spectrum of the beta-chain showed a mass excess of 307 Da (m/z = 16173 Da) versus that of the native HbA0 beta-globin chain (m/z = 15866 Da). The native molecular weight of the modified beta-globin chain HbA0 was regenerated by treatment of HbA1d3 with dithiothreitol, consistent with a glutathionylated adduct. CONCLUSIONS: We propose that HbA1d3 (HbSSG) forms normally in vivo, and may provide a useful marker of oxidative stress in diabetes mellitus and potentially other pathologic situations.     

Intracisternal sauvagine is more potent than corticotropin-releasing factor to decrease gastric vagal efferent activity in rats.

Consecutive intracisternal (ic) injections of corticotropin-releasing factor (CRF) (21, 63, and 126 pmol, ic) or sauvagine (2.1, 6.3, and 21 pmol, ic) decreased gastric vagal efferent multiunit discharge (GVED) to 82%, 75% and 69% and 71%, 40% and 21%, respectively, from preinjection basal levels (taken as 100%). The inhibitory action was dose related (magnitude and duration of the response, 7-45 min). The CRF antagonist, [D-Phe12,Nle21,38,Calpha-MeLeu37]-rCRF12-4 1 (6.25 nmol, ic) increased GVED by 43.5+/-4.3% and blocked the decrease in GVED induced by CRF (21 pmol, ic) for >90 min with a complete recovery after 3 h. Vehicles (injected intracisternally) had no effect. These data indicate that: 1) CRF injected intracisternally decreases GVED through the activation of CRF receptors and sauvagine is more potent than CRF to inhibit GVED; and 2) endogenous CRF exerts an inhibitory tone on basal GVED in urethane-anesthetized rats undergoing surgery.