The hepatic ectonucleotide pyrophosphatase/phosphodiesterase 1 gene mRNA abundance is reduced by insulin and induced by dexamethasone

Hormones regulate hepatic gene expressions to maintain metabolic homeostasis. Ectonucleotide pyrophosphatase/phosphodiesterase 1 has been thought to interfere with insulin signaling. To determine its potential role in the regulation of metabolism, we analyzed its gene (Enpp1) expression in the liver of rats experiencing fasting and refeeding cycles, and in primary rat hepatocytes and human hepatoma HepG2 cells treated with insulin and dexamethasone using northern blot and real-time PCR techniques. Hepatic Enpp1 expression was induced by fasting and reduced by refeeding in the rat liver. In primary rat hepatocytes and HepG2 hepatoma cells, insulin reduced Enpp1 mRNA abundance, whereas dexamethasone induced it. Dexamethasone disrupted the insulin-reduced Enpp1 expression in primary hepatocytes. This is in contrast to the responses of the expression of the cytosolic form of phosphoenolpyruvate carboxykinase gene to the same hormones, where insulin reduced it significantly in the process. In addition, the dexamethasone-induced Enpp1 gene expression was attenuated in the presence of 8-Br-cAMP. In conclusion, we demonstrated for the first time that hepatic Enpp1 is regulated in the cycle of fasting and refeeding, a process that might be attributed to insulin-reduced Enpp1 expression. This insulin-reduced Enpp1 expression might play a role in the development of complications in diabetic patients.

Pharmacogenetic research progress of inosine triphosphate pyrophosphatase / 国际儿科学杂志

Purine drugs are for the treatment of autoimmune diseases,organ transplantation,acute lymphoblastic leukemia.The adverse reaction rate is 15％ ～ 28％,which impacts on the clinical application in recent years.Studies have shown that inosine triphosphate pyrophosphatase (ITPA) are different between individuals,and there are adverse reactions in patients with defects of ITPA when purine drugs are used.This paper reviewes the ITPA pharmacogenetic research progresses.

Study on the association between gene polymorphism of ENPP1 and left ventricular hypertrophy: A Guangzhou Biobank Cohort Study-CVD / 中华流行病学杂志

Objective To examine the association between genetic polymorphism of rs1409181 in ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) and left ventricular hypertrophy (LVH) among older Chinese in Guangzhou. Methods 390 subjects aged ≥50 years were randomly selected from the Guangzhou Biobank Cohort Study-CVD. Information on personal history, blood pressure, fasting plasma glucose and lipids were collected. Color Doppler ultrasound was used to measure the indicators of LVH, including left ventricular internal diastolic diameter (LVIDD) , thickness of the interventricular septum diastolic wall (IVSD) and the posterior wall diastolic diameter (LVPWD). LVIDD was calculated using Devereux ventricular mass (LVM)equation while the Left ventricular mass index (LVMI) equation was used to estimate LVH. The genotype of rs1409181 was determined by Taqman SNP genotyping kits using the ABI 7900HT real time PCR system. Results In the GG, CG and CC genotype groups, the proportions of LVH were 21.5%, 28.2% and 37.5% respectively. Compared with GG, the adjusted odds ratios (95% confidence interval) for the LVH were 1.39(0.78-2.50) and 2.36(1.21-4.60) for CG genotype and CC genotype of ENPP1 respectively (P for trend=0.01). Conclusion Polymorphism of ENPP1 gene rs1409181 was associated with LVH in the older Chinese people in Guangzhou.

ENPP1 K121Q Genotype Not Associated with Coronary Artery Calcification in Korean Patients with Type 2 Diabetes Mellitus / 당뇨병

BACKGROUND: Ectonucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1) generates inorganic pyrophosphate, a solute that serves as an essential physiological inhibitor of calcification. Inactivating mutations of ENPP1 are associated with generalized calcification in infancy and an increased risk of developing type 2 diabetes mellitus (T2DM). We hypothesized that the ENPP1 K121Q variant may be associated with increased coronary artery calcification in T2DM patients. METHODS: The study subjects were aged 34 to 85 years and showed no evidence of clinical cardiovascular disease prior to recruitment. A total of 140 patients with T2DM were assessed for their coronary artery calcium (CAC) scores and ENPP1 K121Q polymorphisms were identified. RESULTS: The prevalence of subjects carrying the KQ genotype was 12.9% (n = 18). There were no 121QQ homozygotes. Patients with the KQ genotype did not show a significantly higher CAC score (122 vs. 18; P = 0.858). We matched each patient with the KQ genotype to a respective control with the KK genotype by gender, age, and duration of diabetes. When compared to matched controls, we observed no significant difference in CAC score (P = 0.959). CONCLUSIONS: The ENPP1 K121Q polymorphism does not appear to be associated with coronary artery calcification in patients with T2DM.

The K121Q Polymorphism in ENPP1 (PC-1) Is Not Associated with Type 2 Diabetes or Obesity in Korean Male Workers

Type 2 diabetes is characterized by insulin resistance, and ENPP1 plays an important role in insulin resistance. We investigated the association of the ENPP1 K121Q polymorphism with both diabetes and obesity (body mass index [BMI]) in Korean male workers. The study design was case-control. Subjects were 1,945 male workers (type 2 diabetes, 195; non-diabetes, 1,750) of nuclear power plants who received examinations from March to October in 2004. We collected venous blood samples under fasting (> or =8 hr) conditions, calculated BMI by height and weight, and assessed relevant biochemical factors. The results of this study demonstrated that the ENPP1 121Q genotype (KQ+QQ types) was not associated with type 2 diabetes (odds ratios [OR], 0.854; 95% confidence interval [CI], 0.571-1.278) or obesity (OR, 0.933; 95% CI, 0.731-1.190). In addition, the frequency of the Q allele was not related to type 2 diabetes (OR, 0.911; 95% CI, 0.630-1.319) or obesity (OR, 0.962; 95% CI, 0.767-1.205). We concluded that the ENPP1 121Q allele is not a critical determinant for either diabetes or obesity in Korean males. The discordance between the results of this study and those derived from studies of Dominican, South Asian, Caucasian, Finnish, and French populations might be due to differences in genetic backgrounds between these populations.

Effect of Nitric Oxide on ADP-ribose Pyrophosphatase Activity

BACKGROUND: ADP-ribosyl pyrophosphatases (ADPRase) has been known to catalyze the hydrolysis of ADP-ribose to ribose-5-phosphate and AMP. The role of ADPRase has been suggested to sanitize the cell by removing potentially toxic ADP-ribose. In this study, we examined the effect of nitric oxide on ADPRase activity in macrophages. METHODS: ADPRase activity was measured in NO-inducing J774 cells. For in vitro experiments, recombinant human ADPRase was prepared in bacteria. RESULTS: ADPRase activity was increased by the treatment of exogenous NO generating reagent, sodium nitroprusside (SNP), in J774 cells. The increased ADPRase activity was mediated by the post-translational modification, likely to cause cADP-ribosylation via nitrosylation of cysteine residue on the enzyme. The stimulation with endogeneous NO inducers, TNF-alpha/IFN-gamma, also increased ADPRase activity through NO synthesis. Futhermore, ADPRase activity may be mediated by the post-translational modification of ADPRase, ADP-ribosylation. CONCLUSION: These results indicate that NO synthesized by macrophage activation plays a critical role in the increase in ADPRase activity following ADP-ribose metabolism.

Non-identity of reaction centres for pyrophosphatase and toxic actions of cardiotoxin II: The status of cardiotoxin II as a metalloprotein.

Cardiotoxin II of the Indian cobra (Naja naja) contains approximately four Mg2+ per mol. Complete demetallation of the toxin is achieved by three cycles of treatment with ethylenediamine tetraacetate and gel filtration. Reconstitution of toxin by treatment of the apo-protein with Mg2+ restores metal content and inorganic pyrophosphatase activity only to the extent of two atoms/mol and 65%, respectively. Use of Mg (II)-EDTA in the reconstitution experiment yields restoration of half the original enzyme activity. Mg2+ is required for the inorganic pyrophosphatase action of the toxin. A definitive statement on the non-essentiality of Mg2+ for the lethal toxicity of the toxin is not possible at present, although experimental observations indicate that demetallated toxin is as toxic as the native toxin. Based on this and the differing sensitivities of the enzyme and toxic activities of the toxin to heat, it is suggested that the reaction centres in the toxin for the two activities are different and that the pyrophosphatase activity is not causally connected with the lethal toxicity of the toxin.

Cardiotoxin of the Indian cobra (Naja naja) is a pyrophosphatase.

An inorganic pyrophosphatase has been purified to apparent homogeniety from Indian cobra (Naja naja) venom, with a ten fold increase in specific activity. The enzyme activity is intrinsic to a protein fraction in the venom which is normally termed cardiotoxin, cobramine, cytotoxin and so on. The enzyme shows a low Km (70 μΜ) and high heat stability. The enzyme was active against sodium pyrophosphate; it also hydrolyses a few mononucletides and sugar phosphates at much lower rates. The physiological significance of inorganic pyro phosphatase in venom is discussed.

Comparison of the conformation and stability of the native dimeric, monomelic, tetrameric and the desensitized forms of the nucleotide pyrophosphatase from mung bean (Phaseolus aureus) seedlings.

A homogenous and crystalline form of nucleotide pyrophosphatase (EC 3.6.1.9) from Phaseolus aureus (mung bean) seedlings was used for the study of the regulation of enzyme activity by adenine nucleotides. The native dimeric form of the enzyme had a helical content of about 65% which was reduced to almost zero values by the addition of AMP. In addition to this change in the helical content, AMP converted the native dimer to a tetramer. Desensitization of AMP regulation, without an alteration of the molecular weight, was achieved either by reversible denaturation with 6 Μ urea or by passage through a column of Blue Sepharose but additionof phydroxymercuribenzoate desensitized the enzyme by dissociating the native dimer to a monomer. The changes in the quaternary structure and conformation of the enzyme consequent to AMP interaction or desensitization were monitored by measuring the helical content, EDTA inactivation and Zn2+ reactivation, stability towards heat denaturation, profiles of urea denaturation and susceptibility towards proteolytic digestion. Based on these results and our earlier work on this enzyme, we propose a model for the regulation of the mung bean nucleotide pyrophosphatase by association-dissociation and conformational changes. The model emphasizes that multiple mechanisms are operative in the desensitization of regulatory proteins.

EXPRESSION OF ECTONUCLEOTIDE PYROPHOSPHATASE/PHOSPHODIESTERASE 1 IN HUMAN OVARY AND ITS RELATIONSHIP WITH POLYCYSTIC OVARY SYNDROME / 解剖学报

Objective Insulin resistance is a possible cause of polycystic ovary syndrome(PCOS).It is presumed that ectonucleotide pyrophosphatase/phosphodiesterase 1(ENPP1) is associated with insulin resistance.The purpose of this study is to explore the expression of ENPP1 in granulosa cells of the ovary and its relationship with PCOS. Methods Twelve aliquots of follicular granulosa cells were isolated from 12 samples of the patients with PCOS and 22 aliquots from 22 samples of the patients without PCOS,respectively.ENPP1 expression was analyzed by reverse transcription polymerase chain reaction(RT-PCR) and in situ hybridization.The relative expression of ENPP1 mRNA was detected by real-time quantitative polymerase chain reaction(real-time PCR). Results ENPP1 was expressed in granulosa cells of the ovary.ENPP1 expression's 2~(-?Ct) in granulosa cells of PCOS was significantly higher than non-PCOS(1.67?0.89 vs.0.94?0.76,P=0.017).Conclusion ENPP1 expression plays a role in ovary function and may be closely associated with the development of PCOS.

LIGHT AND ELECTRON MICROSCOPY OBSERVATION ON ACTIVITIES AND LOCALIZATION OF 5'-NUCLEOTIDASE AND THIAMINE PYROPHOSPHATASE IN THE HUMAN PROSTATE HYPERPLASIA / 解剖学报

The epithelial cells of human prostatic hyperplasia had been studied cytochemically for 5'-nucleotidase and thiamine pyrophosphatase activity with light and electron microscopy. The 5'-nucleotidase (5'-Nase) activities were present in the epithelial cells at lysosomes, Golgi vacuoles, vesicles, secretory vacuoles and free surface of plasmic membrane, the secretion material within the acinar lumina of the prostate gland also showed 5'-nucleotidase reaction product. The activity of 5'-nucleotidase has not markedly changed by the actinomyces globispores treatment, but slightly decreased after estrogen treatment. It was no enzyme reaction after treated by testectomy.Activities of thiamine pyrophosphatase (TPPase) were restricted to the Golgi area, and there were heavy deposits of reaction products in concave face of Golgi saccule. The activities of TPPase were not markedly changed by estrogen and actinomyces globispores treatments but none of enzyme activities could be seen after testectomy.