Comparison of patient characteristics between East Asian and non-East Asian patients with insulin autoimmune syndrome

OBJECTIVE

Insulin autoimmune syndrome (IAS) is the third most common cause of spontaneous hypoglycaemia in Japan but very rare in the rest of the world. We aimed to identify factors, which are associated with the occurrence of IAS and which may differ between East Asian and non-East Asian patients.

DESIGN

A PubMed search using the search terms 'insulin autoimmune syndrome' and 'Hirata disease' revealed a total of 287 reports of IAS cases, including one previously unpublished own case.

RESULTS

Mean age (±standard deviation) was 52 ± 19 years in East Asian and 54 ± 21 years in non-East Asian patients (p > .05). In both groups, there were more females. Mean body mass index was lower in East Asian than in non-East Asian patients (23.0 ± 4.3 vs. 27.1 ± 5.6 kg/m² , p < .0001). Postprandial hypoglycaemia was more common in non-East Asian patients (p < .05). East Asian patients took more frequently antithyroid medications and non-East Asian patients angiotensin-converting enzyme (ACE) inhibitors (both p < .0001). Graves' disease and other autoimmune diseases were more frequently observed in East Asian patients (both p < .01). Parameters of glucose metabolism were comparable in both groups, independent of diabetes diagnosis (p > .05), except for insulin that was higher in East Asian compared to non-East Asian metabolically healthy patients (p < .01). Human leukocyte antigen (HLA)-DRB1*0406 was the most frequent HLA-type in East Asian patients (p < .0001), whereas DRB1*0403 and *0404 were more frequent in non-East Asian patients (both p < .05). Non-East Asian patients received more secondary treatments, including plasmapheresis and rituximab, whereas medication discontinuation was more common in East Asian patients (all p < .05). Outcome was similar in both groups (p > .05).

CONCLUSIONS

Factors associated with IAS markedly differ between East Asian and non-East Asian patients, with autoimmune disorders, particularly Graves' disease, antithyroid medications, and HLA-DRB1*0406 more prevalent in East Asian patients and cardiovascular and plasma cell diseases, ACE inhibitors and HLA-DRB1*0403 more prevalent in non-East Asian patients.

Influence of pH, Temperature and Protease Inhibitors on Kinetics and Mechanism of Thermally Induced Aggregation of Potato Proteins

Understanding aggregation in food protein systems is essential to control processes ranging from the stabilization of colloidal dispersions to the formation of macroscopic gels. Patatin rich potato protein isolates (PPI) have promising techno-functionality as alternatives to established proteins from egg white or milk. In this work, the influence of pH and temperature on the kinetics of PPI denaturation and aggregation was investigated as an option for targeted functionalization. At a slightly acidic pH, rates of denaturation and aggregation of the globular patatin in PPI were fast. These aggregates were shown to possess a low amount of disulfide bonds and a high amount of exposed hydrophobic amino acids (S₀). Gradually increasing the pH slowed down the rate of denaturation and aggregation and alkaline pH levels led to an increased formation of disulfide bonds within these aggregates, whereas S₀ was reduced. Aggregation below denaturation temperature (T_d) favored aggregation driven by disulfide bridge formation. Aggregation above T_d led to fast unfolding, and initial aggregation was less determined by disulfide bridge formation. Inter-molecular disulfide formation occurred during extended heating times. Blocking different protein interactions revealed that the formation of disulfide bond linked aggregation is preceded by the formation of non-covalent bonds. Overall, the results help to control the kinetics, morphology, and interactions of potato protein aggregation for potential applications in food systems.

Diallyl Trisulfide Inhibits Platelet Aggregation through the Modification of Sulfhydryl Groups

Diallyl trisulfide (DATS) is a secondary metabolite of allicin, a volatile organosulfur flavoring compound generated by the crushing of garlic. These compounds have various medicinal effects such as antiplatelet activity. In this study, we demonstrated for the first time the cellular mechanism involved in the inhibition of platelet aggregation by DATS and dipropyl trisulfide (DPTS), which is a saturated analogue of DATS. Washed murine platelets were incubated with these sulfides, and platelet aggregation was evaluated by light transmission aggregometry. The amount of reaction products produced by DATS, DPTS, and glutathione (GSH) was measured using liquid chromatography-mass spectrometry. Compared with DPTS, DATS potently inhibited platelet aggregation induced by thrombin, U46619, and collagen. N-Ethylmaleimide (NEM), which is commonly used to modify sulfhydryl groups, also suppressed platelet aggregation. The reactivity of DATS with GSH was higher than that of DPTS. These data suggested that DATS inhibited platelet aggregation through the reaction of sulfhydryl groups.

2,3-Dimethoxy-5-methyl-p-benzoquinone (Coenzyme Q0) Disrupts Carbohydrate Metabolism of HeLa Cells by Adduct Formation with Intracellular Free Sulfhydryl-Groups, and Induces ATP Depletion and Necrosis

2,3-Dimethoxy-5-methyl-p-benzoquinone is a common chemical structure of coenzyme Q (CoQ) that conjugates different lengths of an isoprenoid side chain at the 6-position of the p-benzoquinone ring. In a series of studies to explore the cytotoxic mechanism of CoQ homologues with a short isoprenoid side chain, we found that a CoQ analogue without an isoprenoid side chain, CoQ₀, showed marked toxicity against HeLa cells in comparison with cytotoxic homologues. Therefore, we examined the cytotoxic mechanism of CoQ₀. Different from the cytotoxic CoQ homologues that induced apoptosis, 100 µM CoQ₀ induced necrosis of HeLa cells. The CoQ₀-induced cell death was accompanied by a decrease in endogenous non-protein and protein-associated sulfhydryl (SH)-groups, but this improved with the concomitant addition of compounds with SH-groups but not antioxidants without SH-groups. In addition, UV-spectrum analysis suggested that CoQ₀ could rapidly form S-conjugated adducts with compounds with SH-groups by Michael addition. On the other hand, enzyme activities of both glyceraldehyde-3-phosphate dehydrogenase, which has a Cys residue in the active site, and α-ketoglutarate dehydrogenase complex, which requires cofactors with SH-groups, CoA and protein-bound α-lipoic acid, and CoA and ATP contents in the cells were significantly decreased by the addition of CoQ₀ but not CoQ₁. Furthermore, the decrease of an endogenous antioxidant, glutathione (GSH), by CoQ₀ treatment was much greater than the predicted increase of endogenous GSH disulfide. These results suggest that CoQ₀ rapidly forms S-conjugate adducts with these endogenous non-protein and protein-associated SH-groups of HeLa cells, which disrupts carbohydrate metabolism followed by intracellular ATP depletion and necrotic cell death.

Coptisine-induced inhibition of Helicobacter pylori: elucidation of specific mechanisms by probing urease active site and its maturation process

In this study, we examined the anti-Helicobactor pylori effects of the main protoberberine-type alkaloids in Rhizoma Coptidis. Coptisine exerted varying antibacterial and bactericidal effects against three standard H. pylori strains and eleven clinical isolates, including four drug-resistant strains, with minimum inhibitory concentrations ranging from 25 to 50 μg/mL and minimal bactericidal concentrations ranging from 37.5 to 125 μg/mL. Coptisine’s anti-H. pylori effects derived from specific inhibition of urease in vivo. In vitro, coptisine inactivated urease in a concentration-dependent manner through slow-binding inhibition and involved binding to the urease active site sulfhydryl group. Coptisine inhibition of H. pylori urease (HPU) was mixed type, while inhibition of jack bean urease was non-competitive. Importantly, coptisine also inhibited HPU by binding to its nickel metallocentre. Besides, coptisine interfered with urease maturation by inhibiting activity of prototypical urease accessory protein UreG and formation of UreG dimers and by promoting dissociation of nickel from UreG dimers. These findings demonstrate that coptisine inhibits urease activity by targeting its active site and inhibiting its maturation, thereby effectively inhibiting H. pylori. Coptisine may thus be an effective anti-H. pylori agent.

Identification of a metabolic disposal route for the oncometabolite S-(2-succino)cysteine in Bacillus subtilis

Cellular thiols such as cysteine spontaneously and readily react with the respiratory intermediate fumarate, resulting in the formation of stable S-(2-succino)-adducts. Fumarate-mediated succination of thiols increases in certain tumors and in response to glucotoxicity associated with diabetes. Therefore, S-(2-succino)-adducts such as S-(2-succino)cysteine (2SC) are considered oncometabolites and biomarkers for human disease. No disposal routes for S-(2-succino)-compounds have been reported prior to this study. Here, we show that Bacillus subtilis metabolizes 2SC to cysteine using a pathway encoded by the yxe operon. The first step is N-acetylation of 2SC followed by an oxygenation that we propose results in the release of oxaloacetate and N-acetylcysteine, which is deacetylated to give cysteine. Knockouts of the genes predicted to mediate each step in the pathway lose the ability to grow on 2SC as the sulfur source and accumulate the expected upstream metabolite(s). We further show that N-acetylation of 2SC relieves toxicity. This is the first demonstration of a metabolic disposal route for any S-(2-succino)-compound, paving the way toward the identification of corresponding pathways in other species.

Correlations between skin hydration parameters and corneocyte-derived parameters to characterize skin conditions

BACKGROUND

Skin hydration is generally assessed using the parameters of skin surface water content (SWC) and trans-epidermal water loss (TEWL). To date, few studies have characterized skin conditions using correlations between skin hydration parameters and corneocyte parameters.

AIMS

The parameters SWC and TEWL allow the classification of skin conditions into four distinct Groups. The purpose of this study was to assess the characteristics of skin conditions classified by SWC and TEWL for correlations with parameters from corneocytes.

METHODS

A human volunteer test was conducted that measured SWC and TEWL. As corneocyte-derived parameters, the size and thick abrasion ratios, the ratio of sulfhydryl groups and disulfide bonds (SH/SS) and CP levels were analyzed.

RESULTS

Volunteers were classified by their median SWC and TEWL values into 4 Groups: Group I (high SWC/low TEWL), Group II (high SWC/high TEWL), Group III (low SWC/low TEWL), and Group IV (low SWC/high TEWL). Group IV showed a significantly smaller size of corneocytes. Groups III and IV had significantly higher thick abrasion ratios and CP levels. Group I had a significantly lower SH/SS value. The SWC/TEWL value showed a decline in order from Group I to Group IV.

CONCLUSION

Groups classified by their SWC and TEWL values showed characteristic skin conditions. We propose that the SWC and TEWL ratio is a comprehensive parameter to assess skin conditions.

Biochemical Mechanism of Rhododendrol-Induced Leukoderma

RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol (RD))-a skin-whitening ingredient-was reported to induce leukoderma in some consumers. We have examined the biochemical basis of the RD-induced leukoderma by elucidating the metabolic fate of RD in the course of tyrosinase-catalyzed oxidation. We found that the oxidation of racemic RD by mushroom tyrosinase rapidly produces RD-quinone, which gives rise to secondary quinone products. Subsequently, we confirmed that human tyrosinase is able to oxidize both enantiomers of RD. We then showed that B16 cells exposed to RD produce high levels of RD-pheomelanin and protein-SH adducts of RD-quinone. Our recent studies showed that RD-eumelanin-an oxidation product of RD-exhibits a potent pro-oxidant activity that is enhanced by ultraviolet-A radiation. In this review, we summarize our biochemical findings on the tyrosinase-dependent metabolism of RD and related studies by other research groups. The results suggest two major mechanisms of cytotoxicity to melanocytes. One is the cytotoxicity of RD-quinone through binding with sulfhydryl proteins that leads to the inactivation of sulfhydryl enzymes and protein denaturation that leads to endoplasmic reticulum stress. The other mechanism is the pro-oxidant activity of RD-derived melanins that leads to oxidative stress resulting from the depletion of antioxidants and the generation of reactive oxygen radicals.

Dehomocysteinylation is catalysed by the sirtuin-2-like bacterial lysine deacetylase CobB

Hyperhomocysteinemia, which is characterized by elevated blood levels of the non-protein amino acid homocysteine (Hcy), is an independent risk factor for many diseases, including cardiovascular diseases, neurodegenerative diseases and birth defects. The incorporation of homocysteine into proteins, known as protein N-homocysteinylation, has been considered a major mechanism that contributes to hyperhomocysteinemia. However, the process of dehomocysteinylation, the N-homocysteinylation substrates and the regulatory enzyme(s) remain largely unknown. In this study, we observed that the dehomocysteinylation reaction is a spontaneous process that can be inhibited by blocking -SH groups, which have been demonstrated to be critical for non-enzymatic dehomocysteinylation reactions. We also report that CobB, a known Sir2-like bacterial lysine deacetylase, catalyzes lysine dehomocysteinylation reactions both in vitro and in vivo. Our work provides insight into how this non-enzymatic modification might be removed from affected proteins, supplies potential targets for developing identification methods for N-homocysteine proteins, and identifies CobB as the first prokaryotic dehomocysteinylation enzyme.

Andrographolide sodium bisulphite-induced inactivation of urease: inhibitory potency, kinetics and mechanism

BACKGROUND

The inhibitory effect of andrographolide sodium bisulphite (ASB) on jack bean urease (JBU) and Helicobacter pylori urease (HPU) was performed to elucidate the inhibitory potency, kinetics and mechanism of inhibition in 20 mM phosphate buffer, pH 7.0, 2 mM EDTA, 25 °C.

METHODS

The ammonia formations, indicator of urease activity, were examined using modified spectrophotometric Berthelot (phenol-hypochlorite) method. The inhibitory effect of ASB was characterized with IC50 values. Lineweaver-Burk and Dixon plots for JBU inhibition of ASB was constructed from the kinetic data. SH-blocking reagents and competitive active site Ni2+ binding inhibitors were employed for mechanism study. Molecular docking technique was used to provide some information on binding conformations as well as confirm the inhibition mode.

RESULTS

The IC50 of ASB against JBU and HPU was 3.28±0.13 mM and 3.17±0.34 mM, respectively. The inhibition proved to be competitive and concentration- dependent in a slow-binding progress. The rapid formation of initial ASB-JBU complex with an inhibition constant of Ki=2.86×10(-3) mM was followed by a slow isomerization into the final complex with an overall inhibition constant of Ki*=1.33×10(-4) mM. The protective experiment proved that the urease active site is involved in the binding of ASB. Thiol reagents (L-cysteine and dithiothreithol) strongly protect the enzyme from the loss of enzymatic activity, while boric acid and fluoride show weaker protection, indicating that the active-site sulfhydryl group of JBU was potentially involved in the blocking process. Moreover, inhibition of ASB proved to be reversible since ASB-inactivated JBU could be reactivated by dithiothreitol application. Molecular docking assay suggested that ASB made contacts with the important sulfhydryl group Cys-592 residue and restricted the mobility of the active-site flap.

CONCLUSIONS

ASB was a competitive inhibitor targeting thiol groups of urease in a slow-binding manner both reversibly and concentration-dependently, serving as a promising urease inhibitor for the treatment of urease-related diseases.

Mechanisms of gastroprotection of methanol extract of Melastoma malabathricum leaves

BACKGROUND

Melastoma malabathricum L. (Melastomaceae) is a small shrub with various medicinal uses. The present study was carried out to determine the gastroprotective mechanisms of methanol extract of M. malabathricum leaves (MEMM) in rats.

METHODS

The extract's mechanisms of gastroprotection (50, 250, 500 mg/kg) were studied using the pylorus-ligation in rat model wherein volume, pH, free and total acidity of gastric juice, and gastric wall mucus content were determined. The involvement of endogenous nitric oxide (NO) and sulfhydryl (SH) compounds in the gastroprotective effect of MEMM were also measured. MEMM was subjected to the antioxidant, anti-inflammatory and phytochemical analysis and HPLC profiling.

RESULTS

MEMM contained various phyto-constituents with quercitrin being identified as part of them. MEMM and quercitrin: i) significantly (p < 0.05) reduced the volume and acidity of gastric juice while increasing the pH and gastric wall mucus content.; ii) significantly (p < 0.05) increased the level of SOD, GTP and GTR while significantly (p < 0.05) reduced the level of CAT, MPO and TBARS activities.; iii) exerted gastroprotective activity when assessed using the ethanol-induced gastric ulcer assay, which was reversed by N(G)-nitro-L-arginine methyl esters (L-NAME; an inhibitor of NO synthase) and N-ethylmaleimide (NEM; a sulfhydryl (SH) blocker). MEMM inhibited the lipoxygenase (LOX) and xanthine oxidase (XO) activities with the highest affinity for the former while quercitrin showed high affinity for XO activity.

CONCLUSIONS

MEMM exhibited a gastroprotective activity due partly to the presence of quercitrin, its antioxidant and anti-inflammatory activities, and via the modulation of NO and SH groups.

Tyrosinase-catalyzed metabolism of rhododendrol (RD) in B16 melanoma cells: production of RD-pheomelanin and covalent binding with thiol proteins

RS-4-(4-Hydroxyphenyl)-2-butanol (rhododendrol, RD) was reported to induce leukoderma of the skin. To explore the mechanism underlying that effect, we previously showed that oxidation of RD with mushroom tyrosinase produces RD-quinone, which is converted to secondary quinone products, and we suggested that those quinones are cytotoxic because they bind to cellular proteins and produce reactive oxygen species. We then confirmed that human tyrosinase can oxidize both enantiomers of RD. In this study, we examined the metabolism of RD in B16F1 melanoma cells in vitro. Using 4-amino-3-hydroxy-n-butylbenzene as a specific indicator, we detected moderate levels of RD-pheomelanin in B16F1 cells exposed to 0.3 to 0.5 mM RD for 72 h. We also confirmed the covalent binding of RD-quinone to non-protein thiols and proteins through cysteinyl residues. The covalent binding of RD-quinone to proteins was 20- to 30-fold greater than dopaquinone. These results suggest that the tyrosinase-induced metabolism of RD causes melanocyte toxicity.

The effect of heavy metals on nicotinamideN-methyltransferase activityin vitro relating to Parkinson's disease

OBJECTIVE

The aims of this study were to determine the effects of heavy metals such as manganese on nicotinamideN-methyltransferase (EC 2.1.1.1) (NNMT) activity and to consider the possibility of involvement of NNMT activation in the pathogenesis of heavy metal induced Parkinson's disease.

METHODS

NNMT activity in supernatants separated from brain, liver and kidney homogenates of 5 elderly male Wistar rats by centrifugation were measured by high performance liquid chromatography system with fluorescence. NNMT activity under the conditon of 0.5 or 5.0 mM Mn(2+), Fe(2+), Cu(2+) or Cd(2+) was compared with control (no metal ion existence).

RESULTS

NNMT activities in rat brain, liver and kidneys were significantly decreased by Cu(2+), and those in the liver and kidneys were significantly decreased by Cd(2+). Mn(2+) reduced NNMT activity only in the liver. Fe(2+) had no effect on NNMT activity.

CONCLUSIONS

No metal increased NNMT activity in this study, contrary to our hypothesis. Further study is needed to clarify the reason why the effects of Mn(2+) and Fe(2+) which have a high relevance to Parkinson's disease on NNMT activity differ from those of Cu(2+) and Cd(2+).

Interaction between cysteines introduced into each transmembrane domain of the rat P2X2 receptor

1 ATP-gated ion channels (P2X receptors) contain two hydrophobic segments that are presumed to span the plasma membrane (TM1 and TM2). Pairs of cysteines were introduced by mutagenesis into the rat P2X(2) receptor, one in TM1 one in TM2, at positions where single substitutions have previously been shown to confer sensitivity to methanethiosulfonates. The receptors were expressed in HEK293 cells; interactions between the cysteines were sought by measuring the effects on ionic currents of dithiothreitol and methanethiosulfonates. 2 Nine pairs gave normally functioning channels: F44C/I328C, F44C/N333C, F44C/L338C, Q37C/I328C, Q37C/N333C, Q37C/T336C, Q37C/L338C, G30C/I328C, G30C/N333C. None formed functionally detectable disulfide bonds. 3 Currents at the F44C/L338C receptor had time course and ATP-sensitivity similar to those for the F44C mutation alone. Methyl-methanethiosulfonate bound to L338C but did not inhibit ionic current. Methyl-methanethiosulfonate inhibited currents at F44C, but not at F44C/L338C. 4 Ethylammonium-methylthiosulfonate inhibited currents at both F44C and L338C, but not at F44C/L338C. It reversed the rapid current deactivation at F44C/L338C. 5 The results suggest that a methanethiosulfonate binding to L338C prevents binding to F44C; this might indicate proximity of these two residues.

The thiol group in the catalytic chains of aspartate transcarbamoylase

The allosteric enzyme aspartate transcarbamoylase (EC 2.1.3.2) was previously shown to consist of two functionally distinct types of polypeptide chains. X-ray diffraction and chemical studies showed that there are six copies of both catalytic (C) and regulatory (R) chains, and that the intact molecular complex (C(6)R(6)) has D(3) symmetry. Organomercurials react preferentially with the four thiol groups on each R chain, dissociating the molecular complex. We show that 2-chloromercuri-4-nitrophenol reacts specifically and rapidly with the single C-chain thiol, which is believed to be near the catalytic site. This reaction inactivates the enzyme in solution and does not dissociate the molecular complex. Spectrophotometric titration and mercury analysis indicates that six molecules of this mercurial are firmly bound to the enzyme (R(6)C(6)), and crystallographic studies establish that only six sites, related by D(3) symmetry, are modified. The known low reactivity of this C-chain thiol with other sulfhydryl reagents, the unusual structural requirements in the reaction with 2-chloromercuri-4-nitrophenol, and the spectral properties of the resulting derivative provide insight into the environment of this thiol. Probably, at least one positively charged group of the enzyme is nearby, and the environment of this thiol is at least partially hydrophobic.

Contact regions for dinitrophenyl and menadione haptens in an immunoglobulin binding more than one antigen

Protein 460 is a mouse myeloma gamma A(2) protein that competitively binds two small haptens, 2,4-epsilon-dinitrophenyl-L-lysine (Dnp-Lys) and 2-methyl-1:4-naphthaquinone thioglycollate (MenTG), to the antibody-combining region. The intact protein has a relatively inaccessible sulfhydryl group on each heavy chain. When it is substituted with a bulky reagent the binding affinity for MenTG decreases, while the binding of Dnp-Lys remains the same. Guanidine.HCl selectively reduces binding of Dnp-Lys; dimethylsulfoxide selectively reduces binding of MenTG. Papain digestion of protein 460 followed by column chromatography gave two fractions: one contained both binding activities and the other contained the sulfhydryl group. The affinity for Dnp-Lys of the first fraction is the same as that of the whole molecule, while affinity for MenTG is decreased. Since selective alteration of one or the other binding activity can occur in different ways, it seems likely that even though the haptens compete with each other, there is some spatial separation between the groups of contact amino-acid residues involved in the binding of these two haptens. These findings do not support the hypothesis that an immunoglobulin molecule carries combining sites complementary only to a single hapten or to a structurally related series of haptens, but rather suggests that the antibody-combining site may be a polyfunctional region capable of binding several structurally dissimilar haptens. We discuss a mechanism whereby polyfunctional combining sites can give rise to an antibody population (immune serum) that has a high degree of specificity to a single hapten.