Anti-osteoporosis effects of mammalian lignans and their precursors from flaxseed and safflower seed using zebrafish model.

Secoisolariciresinol diglucoside (SDG) and tracheloside (TCL) are the main lignan components of flaxseed cake and safflower seed cake, which are by-products of oil extraction. Both SDG and TCL are metabolized into mammalian lignan enterolactone (EL) with the involvement of intestinal bacteria. In this research, we evaluated the anti-osteoporosis effects of SDG and the in vivo metabolites EL and enterodiol (ED) prepared in our previous work, as well as the newly isolated chemical constituents from safflower seed, including TCL, the lactone ring opening product of TCL (OTCL) and two alkaloids on the alloxan-induced zebrafish model. All the compounds showed significant anti-osteoporosis effects at 80 µM, with p < 0.05 for EL and p < 0.001 for other compounds compared with the model. SDG and TCL showed the most significant and concentration-dependent effects, with p < 0.001 compared with model at 20 µM. The alkaloids, N-coumaroylserotonin glucoside and N-feruloylserotonin glucoside, also showed anti-osteoporosis at 20 µM with p < 0.01, whereas EL, ED, and OTCL showed no significant effects. Quantitative real-time polymerase chain reaction revealed that SDG and TCL upregulated the expression of osteogenic genes Runx2, SP7, OPG, Col1a1a, Alp, ON, OPN, and OCN in alloxan-treated zebrafish. The in vivo metabolite of lignans, EL, showed significant anti-inflammatory effect (p < 0.01) at 20 µM, which might also help to combat osteoporosis and other complications caused by excessive immune response in the body. The results provided scientific data for using the oil extraction by-products as sources of anti-osteoporosis compounds. PRACTICAL APPLICATION: This study found that lignans in flaxseed cake and safflower seed cake exhibited anti-osteoporosis effects by upregulating the expression of osteogenic genes, making the oil extraction by-products sources of anti-osteoporosis compounds.

(-)-Epigallocatechin gallate (EGCG) pharmacokinetics and molecular interactions towards amelioration of hyperglycemia, hyperlipidemia associated hepatorenal oxidative injury in alloxan induced diabetic mice.

Diabetes mellitus has become a serious problem associated with health complications, such as metabolism disorders and liver-kidney dysfunction. The inadequacies associated with conventional medicines have led to a determined search for alternative natural therapeutic agents. The present study was conducted to evaluate the hypoglycemic, antilipidemic, and antioxidant effects of EGCG in surviving diabetic mice. Alloxan diabetic mice were treated with EGCG. Their bloods were collected and submitted to various biochemical measurements, including blood glucose, cholesterol, triglycerides, urea, creatinine, and transaminases. Their livers and kidneys were isolated to assess oxidative damage and to perform histological analysis. Both EGCG and insulin treatment of diabetic mice resulted in a significant reduction in fasting blood glucose levels. EGCG supplementation also ameliorated hepatic as well as renal toxicity indices. Moreover, diabetic mice injected with EGCG exhibited significant changes in antioxidant enzyme activities in the liver and kidney. Histological analyses also showed that it exerted an ameliorative action on these organs and efficiently protected the liver-kidney functions of diabetic mice. EGCG was found to bind α-amylase, PTP1B, and α-glucosidase with good affinities ranging from -6.1 to -8.4 kcal/mol. The findings revealed that EGCG administration induced attractive curative effects on diabetic mice, particularly in terms of liver-kidney function. EGCG can, therefore, be considered as a potential strong candidate for future applications to treat and alleviate diabetic burden. Its pharmacokinetics, high affinities, and molecular interactions with the targeted receptors satisfactory explain the in vivo findings.

Maternal alloxan exposure induces damage in rat offspring lumbar vertebrae and protective role of arachidonic acid.

BACKGROUND: Vertebral abnormalities in offspring of diabetic mothers make major challenges worldwide and were not sufficiently studied before. AIM: To investigate the effects of alloxan-induced diabetes on rats' lumbar vertebrae, and to assess the potential beneficial impact of arachidonic acid. MATERIALS AND METHODS: Pregnant rats were randomly equally divided into four groups: control, alloxan-induced diabetes received alloxan injection 150 mg∕kg, alloxan + arachidonic acid group received arachidonic acid 10 µg∕animal then given alloxan injection, and arachidonic acid group received it, until offspring age of three weeks. Six male offspring from each group were included in this study at ages of newborn, three-week-old, two-month-old, and their body measurements were recorded. Lumbar vertebrae and pancreas specimens were examined by light microscopy, morphometry, transmission electron microscopy (TEM), and immunohistochemistry for insulin expression. RESULTS: In alloxan-induced diabetes newborn, three-week-old, and two-month-old rats, body measurements were significantly declined, histomorphometry of 6th lumbar vertebrae revealed disorganized chondrocytes, with vacuolated cytoplasm, empty lacunae, diminished matrix staining, with areas devoid of cells. TEM showed shrunken reserve and proliferative cells, with irregular nuclei, and damaged mitochondria. In contrast, alloxan + arachidonic acid group had cytoarchitecture of lumbar vertebrae that were like control group. Histomorphometry of pancreas in alloxan-induced diabetes group showed significant reduction in pancreatic islets number and surface area, damaged pancreatic islet cells appeared atrophied with apoptotic nuclei, and very weak insulin immunostaining. Whereas alloxan + arachidonic acid group displayed healthy features of pancreatic islets, which resembled control group, with strong insulin immunostaining. CONCLUSIONS: Arachidonic acid mitigated alloxan-induced diabetes by its antidiabetic activity.

Synthesis, physico-chemical properties and effect of adenosine thiamine triphosphate on vitamin B1 metabolism in the liver of alloxan diabetic rats.

BACKGROUND: Adenosine thiamine triphosphate (AThTP) is a nucleotide discovered in bacteria and some other living organisms more than a decade ago. No biochemical function for AThTP has been established yet, however, experimental data available indicate its possible involvement in metabolic regulation or cell signaling. Metabolism of AThTP in mammals, as well as the feasibility of its pharmacological application, is essentially unstudied. METHODS: Preparative low-pressure chromatography was employed to purify chemically synthesized AThTP with its further analysis by mass spectrometry, HPLC, UV and fluorescence spectroscopy. Enzyme activity assays along with HPLC were used to examine the effects of AThTP and thiamine on vitamin B1 metabolism in the liver of alloxan-induced diabetic rats. RESULTS: An improved procedure for AThTP synthesis and purification is elaborated. Solution stability, optical spectral properties and the molar absorption coefficient for AThTP were determined. The levels of thiamine compounds were found to be increased in the liver of diabetic rats. Neither AThTP nor thiamine treatment affected hepatic vitamin B1 metabolism. Fasting blood glucose concentration was also unchangeable after AThTP or thiamine administration. GENERAL SIGNIFICANCE: Contrast to the widespread view about thiamine deficiency in diabetes, our results clearly shows an adaptive increase in the level of B1 vitamers in the liver of alloxan diabetic rats with no further rising after AThTP or thiamine treatment at a moderate dose. Neither AThTP nor thiamine is effective in glycaemic control. These findings are to be considered in future studies dealing with thiamine or its analogues application to correct metabolic disturbances in diabetes.

Metformin and Bee Venom: a Comparative Detection of Histological Alteration of the Pancreas and Systemic Inflammatory Markers in Diabetic Mice.

Metformin is the approved medication for managing global health issues concerning type 2 diabetes mellitus (T2DM). Using natural bioactive compounds as an alternative therapy is crucial to managing several metabolic diseases. Therefore, due to recent limited studies that detected the role of bee venom (BV) in improving diabetic conditions in Iraq, the current study was designed to identify the potential therapeutic role of BV and metformin in diabetic mice. Twenty male mice (Balb/c) aged about 60 days with an average weight of 26.55±2.70 g were randomly divided into four groups (n=5). The animals were placed in plastic cages for acclimatization for one week of access to food and water ad libitum. Overnight fasting was applied to 15 mice which were then injected with 95 mg/kg body weight of prepared alloxan. The mice were supplemented with glucose fluid for 3 days. On day 4, the blood was collected from the tail to measure the circulating glucose level. When blood glucose levels exceed 200 mg/dl, the animals are considered diabetic. After induction of diabetes, the animals were divided as follows: Control group: included five mice that were not subjected to diabetes induction; the animals in this group: did not receive any medications. Diabetic group: including five mice confirmed with diabetes without receiving any treatments. Metformin group: including five diabetic mice exposed to a single oral dose of 150 mg/kg of metformin for 30 days. Bee Venom group: including five diabetic mice exposed to a single intraperitoneal dose of 1 mg/kg Bee Venom for 30 days. After 30 days of treatment, blood was drained, and serum was obtained to detect the levels of glucose, insulin, TNFα, IL6, and IL10 by using precise enzyme-linked immunosorbent assay (ELIZA) kits. Also, the pancreas was collected from all mice for histopathological investigation. The result displayed significantly elevated glucose concentration in diabetic mice, while metformin and BV significantly reversed these increases. A significant decline in insulin concentration was seen in diabetic mice, whereas metformin and BV significantly enhanced this reduction in insulin concentration. Furthermore, mice treated with alloxan exhibited remarkable increases in TNFα and IL6 compared to control mice, while supplemented metformin and BV significantly reduced these high concentrations. Moreover, the level of IL10 markedly declined in diabetic mice, which was reversed significantly in response to metformin and BV. Histological detection of the pancreas in diabetic mice showed significant changes in the shape and size of islets associated with the arrangement and number of beta cells with a reduction of islets covering connective tissue. Metformin slightly restored these alterations; however, significant and remarkable restoring of histological changing was promoted by BV. Thus, BV could be a potential agent for managing metabolic disorders including diabetes.

[MORPHOLOGICAL ALTERATIONS IN THE INTERNAL ORGANS OF RATS WITH ALLOXAN DIABETES].

The aim of our study was to assess morphological changes in internal organs in a redox-induced model of alloxan diabetes in rats.According to the results of the study, the blood glucose level in rats began to increase 24 hours after the of alloxan administration, reached the maximum level on the 15th day of observation, and decreased on the 25-35 day, to the control level. In parallel with the increase in blood glucose level, an increase in the malondialdehyde (MDA) content in the blood serum was observed.Severe hyperemia, edema, and focal fibrotic changes were revealed morphologically in the kidneys, liver and myocardium. The degree of morphological changes was increased (lymphocytic-cell infiltration, degenerative changes (dystrophy), small necrotic areas) with an increase in the level of glucose and MDA in the blood. It can be assumed that the damage to the tissues of the kidneys, heart, liver and blood vessels in diabetes is largely due to the intensification of oxidative stress in the body.

Hyperglycemic condition influence on mineral trioxide aggregate biocompatibility and biomineralization.

This study aimed to investigate in vitro and in vivo the influence of hyperglycemic condition on biocompatibility and biomineralization of gray mineral trioxide aggregate (GMTA) and white mineral trioxide aggregate (WMTA). For the in vitro study, fibroblast-like cells L929 were cultured under high or normal glucose concentration to investigate the effects of both MTA's on cell proliferation and inflammatory cytokines production IL-1ß, IL-6, and TNF-α. For the in vivo study, polyethylene tubes containing MTA materials and empty tubes were implanted into dorsal connective tissues of Wistar rats previously assigned normal and hyperglycemic. After 7 and 30 days, the tubes with surrounding tissues were removed and subjected to histological, fluorescence and immunohistochemical analyzes of IL-1ß, IL-6, and TNF-α. In vitro study showed that, under high glucose condition, GMTA reduced cell proliferation and IL-6 production compared with WMTA. Moreover, in vivo study revealed that hyperglycemic condition did not modify the inflammatory response and cytokines production in the tissue close to both materials. Independently of hyperglycemic status, mineralized areas were observed with both materials, but the fluorescence intensity of WMTA was diminished on 14 days in hyperglycemic animals. It is possible to conclude that GMTA was able to inhibit the proliferation rate and IL-6 production under high glucose concentration in vitro. Furthermore, cytokines production and inflammatory response were not upregulated in hyperglycemic animals; however, a decrease in the calcium deposition was observed in presence of WMTA, suggesting a delay in the mineralization process.

All-trans retinoic acid improves pancreatic cell proliferation on induced type 1 diabetic rats.

All-trans retinoic acid (ATRA) has been extensively studied as an integrating component of endocrine functions in the pancreas. The aim of this study was to evaluate the effects of ATRA on physiopathological biomarkers in an experimental model of rat with type 1 diabetes induced by alloxan (T1D). Twenty Wistar rats were divided equally into five groups, each receiving a different treatment: a control group (CG), a diabetic group without T1D treatment, a diabetic group treated with ATRA, a diabetic group supplemented with vitamin E (VIT E), and a group that was given olive oil (V). The administration of ATRA for 17 days produced a significant reduction in weight and glucose levels, compared to the T1D and VIT E groups. The evaluation of total antioxidant capacity (TAC) and lipoperoxidation showed no relevant difference among the groups. The results of the histological analysis showed similarities both in the size and in the number of islets of Langerhans in the pancreatic tissue obtained from the ATRA group and the CG. ATRA displayed a significant reduction of glycemic values in diabetic rats. Ultrastructurally, ß-cells, acinar, and ductal cells restored their normal appearance. ATRA can contribute to the recovery of pancreatic damage due to alloxan induction. It seems that the antioxidant effect of ATRA is not responsible for the differences observed.

Alloxan Disintegrates the Plant Cytoskeleton and Suppresses mlo-Mediated Powdery Mildew Resistance.

Recessively inherited mutant alleles of Mlo genes (mlo) confer broad-spectrum penetration resistance to powdery mildew pathogens in angiosperm plants. Although a few components are known to be required for mlo resistance, the detailed molecular mechanism underlying this type of immunity remains elusive. In this study, we identified alloxan (5,5-dihydroxyl pyrimidine-2,4,6-trione) and some of its structural analogs as chemical suppressors of mlo-mediated resistance in monocotyledonous barley (Hordeum vulgare) and dicotyledonous Arabidopsis thaliana. Apart from mlo resistance, alloxan impairs nonhost resistance in Arabidopsis. Histological analysis revealed that the chemical reduces callose deposition and hydrogen peroxide accumulation at attempted fungal penetration sites. Fluorescence microscopy revealed that alloxan interferes with the motility of cellular organelles (peroxisomes, endosomes and the endoplasmic reticulum) and the pathogen-triggered redistribution of the PEN1/SYP121 t-SNARE protein. These cellular defects are likely the consequence of disassembly of actin filaments and microtubules upon alloxan treatment. Similar to the situation in animal cells, alloxan elicited the temporary accumulation of reactive oxygen species (ROS) in cotyledons and rosette leaves of Arabidopsis plants. Our results suggest that alloxan may destabilize cytoskeletal architecture via induction of an early transient ROS burst, further leading to the failure of molecular and cellular processes that are critical for plant immunity.

Chamomile and oregano extracts synergistically exhibit antihyperglycemic, antihyperlipidemic, and renal protective effects in alloxan-induced diabetic rats.

The bio-activities of separate Matricaria chamomilla (chamomile) and Origanum vulgare (oregano) are well studied; however, the combined effects of both natural products in animal diabetic models are not well characterized. In this study, alloxan-induced male albino rats were treated with single dose aqueous suspension of chamomile or oregano at dose level of either 150 or 300 mg/kg body mass or as equal parts as combination by stomach tube for 6 weeks. After treatment, blood samples were assessed for diabetic, renal, and lipid profiles. Insulin, amylase activity, and diabetic renal apoptosis were further evaluated. Treatment with higher dose of the extracts (300 mg/kg) as individual or as mixture of low doses (150 mg/kg of both the extracts) had significant mass gain, hypoglycemic effect (p ≤ 0.05) with decreased amylase activity and increased serum insulin levels. Restoration of renal profile, lipid profile with increase in HDL-c (p ≤ 0.05) along with reversal of pro-apoptotic Bax and anti-apoptotic Bcl-2 were well observed with 300 mg/kg mixture, showing synergistic activity of the extracts compared with individual low dose of 150 mg/kg. Collectively, our results indicate that combination of chamomile and oregano extracts will form a new class of drugs to treat diabetic complications.

Improved antioxidative defence protects insulin-producing cells against homocysteine toxicity.

Homocysteine (HC) is considered to play an important role in the development of metabolic syndrome complications. Insulin-producing cells are prone to HC toxicity and this has been linked to oxidative stress. However, the exact mechanisms remain unknown. Therefore it was the aim of this study to determine the nature of reactive oxygen species responsible for HC toxicity. Chronic exposure of RINm5F and INS1E insulin-producing cells to HC decreased cell viability and glucose-induced insulin secretion in a concentration-dependent manner and led to a significant induction of hydrogen peroxide generation in the cytosolic, but not the mitochondrial compartment of the cell. Cytosolic overexpression of catalase, a hydrogen peroxide detoxifying enzyme, provided a significant protection against viability loss and hydrogen peroxide generation, while mitochondrial overexpression of catalase did not protect against HC toxicity. Overexpression of CuZnSOD, a cytosolic superoxide dismutating enzyme, also protected against HC toxicity. However, the best protection was achieved in the case of a combined overexpression of CuZnSOD and catalase. Incubation of cells in combination with alloxan resulted in a significant increase of HC toxicity and an increase of hydrogen peroxide generation. Overexpression of CuZnSOD or catalase protected against the toxicity of HC plus alloxan, with a superior protection achieved again by combined overexpression. The results indicate that HC induces oxidative stress in insulin-producing cells by stimulation of superoxide radical and hydrogen peroxide generation in the cytoplasm. The low antioxidative defence status makes the insulin-producing cells very vulnerable to HC toxicity.

Insights into the complex formed by matrix metalloproteinase-2 and alloxan inhibitors: molecular dynamics simulations and free energy calculations.

Matrix metalloproteinases (MMP) are well-known biological targets implicated in tumour progression, homeostatic regulation, innate immunity, impaired delivery of pro-apoptotic ligands, and the release and cleavage of cell-surface receptors. Hence, the development of potent and selective inhibitors targeting these enzymes continues to be eagerly sought. In this paper, a number of alloxan-based compounds, initially conceived to bias other therapeutically relevant enzymes, were rationally modified and successfully repurposed to inhibit MMP-2 (also named gelatinase A) in the nanomolar range. Importantly, the alloxan core makes its debut as zinc binding group since it ensures a stable tetrahedral coordination of the catalytic zinc ion in concert with the three histidines of the HExxHxxGxxH metzincin signature motif, further stabilized by a hydrogen bond with the glutamate residue belonging to the same motif. The molecular decoration of the alloxan core with a biphenyl privileged structure allowed to sample the deep S(1)' specificity pocket of MMP-2 and to relate the high affinity towards this enzyme with the chance of forming a hydrogen bond network with the backbone of Leu116 and Asn147 and the side chains of Tyr144, Thr145 and Arg149 at the bottom of the pocket. The effect of even slight structural changes in determining the interaction at the S(1)' subsite of MMP-2 as well as the nature and strength of the binding is elucidated via molecular dynamics simulations and free energy calculations. Among the herein presented compounds, the highest affinity (pIC(50) = 7.06) is found for BAM, a compound exhibiting also selectivity (>20) towards MMP-2, as compared to MMP-9, the other member of the gelatinases.

Determination of alloxan by fluorometric high-performance liquid chromatography.

A fluorometric, reversed-phase high-performance liquid chromatography (RP-HPLC) method that allows quantitation of low levels of alloxan has been described. The method involved derivatization of alloxan with 500-200,000-fold excess of 1, 2-phenylenediamine (PD) in 0.1 M acetate buffer, pH 4.5 for 15 min at room temperature. The fluorescent product alloxazine (excitation: 382 nm; emission: 435 nm) was then analyzed by RP-HPLC using an Eclipse XDB-C18 (4.6 x 150 mm) column and a mobile phase consisting of 0.1% trifluoroacetic acid in 15/85 (v/v) acetonitrile/water at a flow of 1 mL/min (injection volume: 20 microL). The method is robust, and as low as 0.1 pmol of the analyte could be successfully detected and quantified. Following a minimal pre-treatment such as ultrafiltration (molecular weight cut-off 5000 Da) or protein precipitation using perchloric acid, acetonitrile, or phosphotungstic acid, the method is suitable for analysis of alloxan in complex physiological fluids (e.g. fetal bovine serum) and tissue homogenates (e.g. heart and kidney). The method has been rigorously evaluated and adapted in the laboratory for routine analysis and determination of alloxan added to cell cultures.

Low catalase activity in blood is associated with the diabetes caused by alloxan.

BACKGROUND: Hydrogen peroxide is enzymatically processed by catalase, and catalase deficiency in blood is known as acatalasemia. We examined whether low catalase activity is a risk factor for diabetes mellitus. METHODS: Blood glucose, insulin and glucose tolerance test were examined in acatalasemic and normal mice under non-stress and oxidative stress conditions. Alloxan administration was used as oxidative stress. RESULTS: Alloxan, which was a drug that caused diabetes mellitus, mostly generated hydrogen peroxide by the reaction of alloxan and reduced glutathione, in vitro. Incidence of hyperglycemia in alloxan-untreated acatalasemic mice was as low as that in the normal mice. However, the incidence of acatalasemia mice treated with alloxan was higher than that in normal mice, and the number of pancreatic beta-cells in the acatalasemic mice was less than that in normal mice. CONCLUSION: These results indicate that low catalase activity in the blood is associated with the diabetes mellitus caused by alloxan administration.

Efeitos do treinamento de natação em aspectos metabólicos e morfológicos de ratos diabéticos / Effects of swimming training on metabolic and morphologic aspects in diabetic rats

Fundamento: O exercício físico aeróbio influencia vários aspectos da patologia diabética, incluindo o desenvolvimento de cardiomiopatias. O modelo de diabetes induzido experimentalmente em ratos tem contribuído para avanços nesta linha de pesquisa. Objetivo: Estudar os efeitos de um protocolode treinamento físico aeróbio moderado em meio aquático sobre alguns aspectos metabólicos, histológicos e ultra-estruturais do miocárdio de ratos diabéticos experimentais. Métodos: Ratos da linhagem Wistar foram distribuídos em 4 grupos; controle sedentário (CS), controle treinado (CT), diabético sedentário (DS) e diabético treinado (DT). Para indução do diabetes experimental, os animais receberam Aloxana monoidratada Sigma (35mg/Kg de peso corporal i.v.). O programa de treinamento aeróbio consistiu em natação por 60 minutos diários, 5 dias/semana, durante 4 semanas consecutivas, com cargas equivalentes à 2,5% do peso corporal. Após o sacrifício dos animais, o sangue foi utilizado para dosagem de glicose e ácidos graxos livres (AGL). Amostras do miocárdio foram coletadas para análises histológicas, histoquímicas e ultra-estruturais. Resultados: O diabetes experimental causou aumento da glicemia e AGL séricos e redução da insulinemia. Os ratos diabéticos apresentaram aumento da glicose e da concentração de AGL séricos e alterações histológicas e histoquimicas no miocárdio. Por outro lado, o treinamento físico aeróbio restaurou algumas destas alterações. Conclusão: A análise dos resultados mostrou que a indução do diabetes por meio da droga aloxana promove alterações metabólicas, histoquímicas e ultra-estruturais no miocárdio de ratos e que o treinamento físico aeróbio moderado em meio aquático restaurou algumas destas alterações.

Background: Aerobic physical exercise influences several aspects of diabetic pathology, including cardiomyopathy development. The experimentally-induced diabetic rat model has contributed to advances in this line of research. Objective: The aim of the present study was to examine the effects of moderate aerobic physical training on the metabolic, histological and ultra structural aspects of myocardium in experimental diabetic rats. Methods: Wistar rats were divided into 4 groups, sedentary control (SC), trained control (TC), sedentary diabetic (SD) and trained diabetic (TD). Diabetes was induced by Alloxan (35 mg/kg b.w. i.v.). The aerobic training program consisted by swimming 5 days/week, 1 h/day, supportinga load of 2.5 % body weight for 4 weeks. At the end of the training period, the rats were sacrificed and theblood was collected for determinations of serum glucose and free fat acids (FFA). The myocardium wascollected for determinations of histological, histochemistry and ultra structural aspects. Results: Diabetes increased glucose and FFA concentrations in blood and induced histological and histoquimical alterations in myocardium. In the other hand, aerobic physical training was able to restore this alterations. Conclusion: Inconclusion experimental alloxan-induced diabetes promoted some metabolic, histological and ultra structural alterations in myocardium of rats and moderate aerobic physical training recuperates some ofthese alterations.

Commonalities of genetic resistance to spontaneous autoimmune and free radical--mediated diabetes.

ALR/Lt, a NOD-related mouse strain, was selected for resistance to alloxan free radical-mediated diabetes (ALD). Despite extensive genomic identity with NOD (>70%), ALR mice display strong resistance to autoimmune type 1 diabetes (T1D) due to both an unusual elevation in systemic antioxidant defenses and a reduction in cellular ROS production that extends to the beta cell level. Reciprocal backcross to NOD previously linked the ALR-derived T1D resistance to Chr. 3, 8, and 17 as well as to the ALR mt-Nd2(a) allele encoded by the mitochondrial genome (mtDNA). To determine whether any of the ALR-derived loci protecting against T1D also protected against ALD, 296 six-week-old F2 mice from reciprocal outcrosses were alloxan-treated and assessed for diabetes onset, and a genome-wide scan (GWS) was conducted. GWS linked mt-Nd2 as well as three nuclear loci with alloxan-induced diabetes. A dominant ALR-derived ALD resistance locus on Chr. 8 colocalized with the ALR-derived T1D resistance locus identified in the previous backcross analysis. In contrast, whereas ALR contributed a novel T1D resistance locus on Chr. 3 marked by Susp, a more proximal ALR-derived region marked by Il-2 contributed ALD susceptibility, not resistance. In addition, a locus was mapped on Chr. 2, where heterozygosity provided heightened susceptibility. Tests for alloxan sensitivity in ALR conplastic mice encoding the NOD mt-Nd2(c) allele and NOD mice congenic for the protective Chr. 8 locus supported our mapping results. Alloxan sensitivity was increased in ALR.mt(NOD) mice, whereas it was decreased by congenic introduction of ALR genome on Chr. 8 into NOD. These data demonstrate both similarities and differences in the genetic control of T1D versus ROS-induced diabetes.

O-GlcNAc modulation at Akt1 Ser473 correlates with apoptosis of murine pancreatic beta cells.

O-GlcNAc transferase (OGT)-mediated modification of protein Ser/Thr residues with O-GlcNAc influences protein activity, similar to the effects of phosphorylation. The anti-apoptotic Akt1 is both activated by phosphorylation and modified with O-GlcNAc. However, the nature and significance of the Akt1 O-GlcNAc modification is unknown. The relationship of O-GlcNAc modification and phosphorylation at Akt1 Ser473 was examined with respect to apoptosis of murine beta-pancreatic cells. Glucosamine treatment induced apoptosis, which correlated with enhanced O-GlcNAc modification of Akt1 and concomitant reduction in Ser473 phosphorylation. Pharmacological inhibition of OGT or O-GlcNAcase revealed an inverse correlation between O-GlcNAc modification and Ser473 phosphorylation of Akt1. MALDI-TOF/TOF mass spectrometry analysis of Akt1 immunoprecipitates from glucosamine-treated cells, but not untreated controls, showed a peptide containing S473/T479 that was presumably modified with O-GlcNAc. Furthermore, in vitro O-GlcNAc-modification analysis of wildtype and mutant Akt1 revealed that S473 was targeted by recombinant OGT. A S473A Akt1 mutant demonstrated reduced basal and glucosamine-induced Akt1 O-GlcNAc modification compared with wildtype Akt1. Furthermore, wildtype Akt1, but not the S473A mutant, appeared to be associated with OGT following glucosamine treatment. Together, these observations suggest that Akt1 Ser473 may undergo both phosphorylation and O-GlcNAc modification, and the balance between these may regulate murine beta-pancreatic cell fate.

Monitoring diet effects via biofluids and their implications for metabolomics studies.

The effect of diet on metabolites found in rat urine samples has been investigated using nuclear magnetic resonance (NMR) and a new ambient ionization mass spectrometry experiment, extractive electrospray ionization mass spectrometry (EESI-MS). Urine samples from rats with three different dietary regimens were readily distinguished using multivariate statistical analysis on metabolites detected by NMR and MS. To observe the effect of diet on metabolic pathways, metabolites related to specific pathways were also investigated using multivariate statistical analysis. Discrimination is increased by making observations on restricted compound sets. Changes in diet at 24-h intervals led to predictable changes in the spectral data. Principal component analysis was used to separate the rats into groups according to their different dietary regimens using the full NMR, EESI-MS data or restricted sets of peaks in the mass spectra corresponding only to metabolites found in the urea cycle and metabolism of amino groups pathway. By contrast, multivariate analysis of variance from the score plots showed that metabolites of purine metabolism obscure the classification relative to the full metabolite set. These results suggest that it may be possible to reduce the number of statistical variables used by monitoring the biochemical variability of particular pathways. It should also be possible by this procedure to reduce the effect of diet in the biofluid samples for such purposes as disease detection.

Mechanistic aspects of alloxan diabetogenic activity: a key role of keto-enol inversion of dialuric acid on ionization.

The inversion of the keto-enol stability order of dialuric acid on ionization was calculated and verified experimentally. The radical cations in both forms were characterized. The spectrum of the keto form was observed upon direct ionization of dialuric acid under matrix conditions, whereas the enol form was formed upon a sequential electron-proton-proton attachment to alloxan under acidic aqueous condition. Facilitation of the one-electron oxidation of dialuric acid upon its enolization can result in a more effective formation of superoxide radical anion in the process of its auto-oxidation. This process is discussed in reference to the alloxan diabetogenic action. Both neutral keto and enol forms are energetically close, and under favorable conditions, the auto-oxidation of dialuric acid could involve participation of the enol form.

Role of O-linked beta-N-acetylglucosamine modification in the subcellular distribution of alpha4 phosphoprotein and Sp1 in rat lymphoma cells.

The mTOR alpha4 phosphoprotein is a prolactin (PRL)-downregulated gene product that is found in the nucleus of PRL-dependent rat Nb2 lymphoma cells. Alpha4 lacks a nuclear localization signal (NLS) and the mechanism of its nuclear targeting is unknown. Post-translational modification by O-linked beta-N-acetylglucosamine (O-GlcNAc) moieties has been implicated in the nuclear transport of some proteins, including transcription factor Sp1. The nucleocytoplasmic enzymes O-beta-N-acetylglucosaminyltransferase (OGT) and O-beta-N-acetylglucosaminidase (O-GlcNAcase) adds or remove O-GlcNAc moieties, respectively. If O-GlcNac moieties contribute to the nuclear targeting of alpha4, a decrease in O-GlcNAcylation (e.g., by inhibition of OGT) may redistribute alpha4 to the cytosol. The present study showed that alpha4 and Sp1 were both O-GlcNAcylated in quiescent and PRL-treated Nb2 cells. PRL alone or PRL + streptozotocin (STZ; an O-GlcNAcase inhibitor) significantly (P