CD36 gene deletion reduces muscle insulin sensitivity in mice by up-regulating PTP1B expression / 南方医科大学学报

OBJECTIVE@#To investigate the effect CD36 deficiency on muscle insulin signaling in mice fed a normal-fat diet and explore the possible mechanism.@*METHODS@#Wild-type (WT) mice and systemic CD36 knockout (CD36-/-) mice with normal feeding for 14 weeks (n=12) were subjected to insulin tolerance test (ITT) after intraperitoneal injection with insulin (1 U/kg). Real-time PCR was used to detect the mRNA expressions of insulin receptor (IR), insulin receptor substrate 1/2 (IRS1/2) and protein tyrosine phosphatase 1B (PTP1B), and Western blotting was performed to detect the protein expressions of AKT, IR, IRS1/2 and PTP1B in the muscle tissues of the mice. Tyrosine phosphorylation of IR and IRS1 and histone acetylation of PTP1B promoter in muscle tissues were detected using co-immunoprecipitation (Co-IP) and chromatin immunoprecipitation (ChIP), respectively.@*RESULTS@#CD36-/- mice showed significantly lowered insulin sensitivity with obviously decreased area under the insulin tolerance curve in comparison with the WT mice (P < 0.05). CD36-/- mice also had significantly higher serum insulin concentration and HOMA-IR than WT mice (P < 0.05). Western blotting showed that the p-AKT/AKT ratio in the muscle tissues was significantly decreased in CD36-/- mice as compared with the WT mice (P < 0.01). No significant differences were found in mRNA and protein levels of IR, IRS1 and IRS2 in the muscle tissues between WT and CD36-/- mice (P>0.05). In the muscle tissue of CD36-/- mice, tyrosine phosphorylation levels of IR and IRS1 were significantly decreased (P < 0.05), and the mRNA and protein levels of PTP1B (P < 0.05) and histone acetylation level of PTP1B promoters (P < 0.01) were significantly increased as compared with those in the WT mice. Intraperitoneal injection of claramine, a PTP1B inhibitor, effectively improved the impairment of insulin sensitivity in CD36-/- mice.@*CONCLUSION@#CD36 is essential for maintaining muscle insulin sensitivity under physiological conditions, and CD36 gene deletion in mice causes impaired insulin sensitivity by up-regulating muscle PTP1B expression, which results in detyrosine phosphorylation of IR and IRS1.

IRF2-INPP4B-mediated autophagy suppresses apoptosis in acute myeloid leukemia cells

BACKGROUND: The present study aimed to investigate the underlying role of interferon-regulatory factor 2 (IRF2)-inositol polyphosphate-4-phosphatase, type-II (INPP4B) axis in the regulation of autophagy in acute myeloid leukemia (AML) cells. METHODS: Quantitative real time PCR (QRT-PCR) and western blot were performed to determine the expression levels of IRF2, INPP4B and autophagy-related markers in AML cell lines. Autophagy was assessed by elevated Beclin-1 expression, the conversion of light chain 3 (LC3)-I to LC3-II, downregulated p62 expression and green fluorescent protein (GFP)-LC3 puncta formation. The colony formation and apoptosis assays were performed to determine the effects of IRF2 and INPP4B on the growth of AML cells. RESULTS: IRF2 and INPP4B were highly expressed in AML cell lines, and were positively correlated with autophagy-related proteins. Overexpression of IRF2 or INPP4B stimulated autophagy of AML cells, whereas inhibition of IRF2 or INPP4B resulted in the attenuation of autophagy. More importantly, IRF2 or INPP4B overexpression reversed autophagy inhibitor, 3-methyladenine (3-MA)-induced proliferation-inhibitory and pro-apoptotic effects, while IRF2 or INPP4B silencing overturned the proliferation-promoting and anti-apoptotic effects of autophagy activator rapamycin. CONCLUSION: IRF2-INPP4B signaling axis attenuated apoptosis through induction of autophagy in AML cells.

Dissolving mechanism of strain P17 on insoluble phosphorus of yellow-brown soil

Strain P17 was a bacterial strain identified as Bacillus megaterium isolated from ground accumulating phosphate rock powder. The fermentation broth of strain P17 and the yellow-brown soil from Nanjing Agricultural University garden were collected to conduct this study. The simulation of fixed insoluble phosphorous forms after applying calcium superphosphate into yellow-brown soil was performed in pots, while available P and total P of soil were extremely positive correlative with those of groundwater. Then the dissolving effect of strain P17 on insoluble P of yellow-brown soil was studied. Results showed that Bacillus megaterium strain P17 had notable solubilizing effect on insoluble phosphates formed when too much water-soluble phosphorous fertilizer used. During 100 days after inoculation, strain P17 was dominant. Until the 120th day, compared with water addition, available P of strain P17 inoculation treated soil increased by 3 times with calcium superphosphate addition. Besides available P, pH, activity of acid and alkaline phosphatase and population of P-solubilizing microbes were detected respectively. P-solubilizing mechanism of P-solubilizing bacteria strain P17 seems to be a synergetic effect of pH decrease, organic acids, phosphatase, etc.

Immobilization of organophosphate hydrolase on biocompatible gelatin pads and its use in removal of organophosphate compounds and nerve agents.

Bacterial organophosphate hydrolases (OPH) have been shown to hydrolyze structurally diverse group of organophosphate (OP) compounds and nerve agents. Due to broad substrate range and unusual catalytic properties, the OPH has successfully been used to develop eco-friendly strategies for detection and decontamination of OP compounds. However, their usage has failed to gain necessary acceptance, due to short half-life of the enzyme and loss of activity during process development. In the present study, we report a simple procedure for immobilization of OPH on biocompatible gelatin pads. The covalent coupling of OPH using glutaraldehyde spacer has been found to dramatically improve the enzyme stability. There is no apparent loss of OPH activity in OPH-gelatin pads stored at room temperature for more than six months. As revealed by a number of kinetic parameters, the catalytic properties of immobilized enzyme are found to be comparable to the free enzyme. Further, the OPH‑gelatin pads effectively eliminate OP insecticide methyl parathion and nerve agent sarin.

Caveolin-1 is involved in reactive oxygen species-induced SHP-2 activation in astrocytes

Recent evidence supports a neuroprotective role of Src homology 2-containing protein tyrosine phosphatase 2 (SHP-2) against ischemic brain injury. However, the molecular mechanisms of SHP-2 activation and those governing how SHP-2 exerts its function under oxidative stress conditions are not well understood. Recently we have reported that reactive oxygen species (ROS)-mediated oxidative stress promotes the phosphorylation of endogenous SHP-2 through lipid rafts, and that this phosphorylation strongly occurs in astrocytes, but not in microglia. To investigate the molecules involved in events leading to phosphorylation of SHP-2, raft proteins were analyzed using astrocytes and microglia. Interestingly, caveolin-1 and -2 were detected only in astrocytes but not in microglia, whereas flotillin-1 was expressed in both cell types. To examine whether the H2O2-dependent phosphorylation of SHP-2 is mediated by caveolin-1, we used specific small interfering RNA (siRNA) to downregulate caveolin-1 expression. In the presence of caveolin-1 siRNA, the level of SHP-2 phosphorylation induced by H2O2 was significantly decreased, compared with in the presence of control siRNA. Overexpression of caveolin-1 effectively increased H2O2-induced SHP-2 phosphorylation in microglia. Lastly, H2O2 induced extracellular signal-regulated kinase (ERK) activation in astrocytes through caveolin-1. Our results suggest that caveolin-1 is involved in astrocyte-specific intracellular responses linked to the SHP-2-mediated signaling cascade following ROS-induced oxidative stress.

Process of rock phosphate solubilization by Aspergillus sp PS 104 in soil amended medium.

Aspergillus sp PS 104, a soil isolate had excellent potential to solubilize rock phosphate in vitro. The process was influenced by the presence of various concentrations of local loess (red soil). The simultaneous occurrence, in our experiment, of high levels of solubilized phosphate and synthesized citric acid, together with the lowest reached pH values, confirmed the role of citric acid in the phosphate solubilization mechanism. When the soil was present, phosphate release was better correlated than citrate synthesis with H+ concentration. Changes in soluble phosphate concentration did not follow a sigmoid pattern. The ability of organism to release phosphatase was also studied. An interesting relationship was observed between the two processes of phosphate mobilization: citric acid synthesis and phosphatase production.

Root-surface phosphatase activity in shrublands across a European gradient: effects of warming.

Root-surface phosphatase activities were measured in natural and semi-natural shrublands across an European climatic gradient of temperature and rainfall including Wales (WL), Denmark (DK), Netherlands (NL), Hungary (HU), Italy (IT) and Spain (SP). In each site a warming experiment was conducted since 1999 or 2001 by means of passive night-time warming using reflective curtains that covered the vegetation at night. The treatments increased yearly average soil temperatures around 0. 8 degrees C in most of sites. Root-surface phosphatase activity values ranged between 56 mg PNP g(-1) h(-1) in IT and 3.5 mg PNP g(-1) h(-1) in HU. Warming had no effect on root-surface phosphatase activity across the sites and only in Hungary a slight increase was detected. Plants at Mediterranean sites (IT, SP) showed a higher root-surface phosphatase activity than plants at temperate sites (WL, NL, DK). We suggest it might be an adaptation of plant species evolved under Mediterranean climate that allows them a) to compensate in wet period for the decrease in phosphatase activity, and thus P uptake, during drought periods, and/or b) to benefit from soluble organic P flushes following the frequent drying-rewetting episodes experienced by soils in Mediterranean ecosystems.

Hydrolysis of organophosphorus compounds by an esterase isozyme from insecticide resistant pest Helicoverpa armigera.

Esterase activity of resistant and susceptible H. armigera were compared in gels with different substrate such as naphthyl acetate, naphthyl phosphate, paraoxon and monocrotophos. Whole body extract of resistant H. armigera hydrolyzed paraoxon, monocrotophos and naphthyl phosphate in gels. Resistant H. armigera showed high esterase, phosphatase and paraoxon hydrolase activity compared to susceptible ones.

Soil microbial population and enzyme activity related to grazing pressure in alpine meadows of Nanda Devi Biosphere Reserve.

The present study aims to analyze the interaction of prevailing biotic pressure on soil environment with emphasis on its physicochemical and microbiological characteristics determining soil fertility status and thus supporting plant and animal biodiversity in Nanda Devi Biosphere Reserve (NDBR) which is located in northern part of Uttaranchal hills between 79 degrees 40'E to 80 degrees 05'E longitude and 30 degrees 17'N to 30 degrees 41'E latitude. The experimental results revealed that the physico-chemical characteristics (viz., moisture, pH, EC, C, N, P, K, CEC) of soil were maximum in moderately grazed meadow and minimum in intensively grazed meadow. Soil microbial analysis measured in terms of total viable count (TVC) exhibited grazing sensitivity trend being maximum population of bacteria > fungi > actinomycetes. The soil microbial population was positively correlated with soil respiration, dehydrogenase activity, acid phosphatase and microbial biomass, which exhibited uneven trend with grazing pressure. Soil from moderately grazed meadow showed highest microbial count and enzyme activities, whilst intensively grazed meadow showed lowest microbial count and enzyme activities. This depicts the beneficial role of prescribed grazing up to limited extent in management of soil fertility, which might have supported luxuriant growth of a variety of grasses.

Bioregulation of carbohydrate metabolism in relation to source-sink operation during grain-filling phase of growth in wheat.

Mobilization of free sugars from vegetative tissues to grain and their transformation to starch in relation to activities of some relevant enzymes during growth and development were investigated in wheat (Triticum aestivum L.). Vegetative tissues, viz. flag-leaf, flag-leaf sheath, nodes and internodes contained high concentration of free sugars from 70 DAS to 18 DPA and that was in the order of accumulation--flag-leaf sheath> flag-leaf and internodes > nodes. In these tissues, major portion of 14C appeared in endogenous sucrose, irrespective of the nature of (U-14C]-sugars supplied. In photosynthetic structures above flag-leaf node, namely peduncle, rachis and bracts, the free sugar make-up was maximum at anthesis (90 DAS). Activity of soluble acid invertase (EC 3.2.1.26) was high in these tissues during early stages of grain growth but reverse was true for soluble neutral invertase (EC 3.2.1.27) activity. In apical and basal portions of grain, free sugars were more or less similarly distributed in concentration. Linear and rapid accumulation of starch in endosperm paralleled with a decline in accumulation of this polymer in pericarp-aleurone. In the latter tissue, the activities of starch hydrolyzing enzymes, i.e alpha- and beta-amylases (3.2.1.1 and 3.2.1.2) were high during initial stages of grain growth. During active grain-filling, alkaline inorganic pyrophosphatase (EC 3.6.1.1) seemed to play a vital role during starch accumulation in endosperm, whereas the involvement of 3-PGA phosphatase (EC 3.1.3.38) was almost confined to pericarp-aleurone. Impairement of ear head photosynthesis by shading depressed starch synthesis (approximately 50%) indicating, thereby, the significant role of current photosynthates during grain-filling. The results suggested that grain growth in wheat was influenced by an efficient operation of source as well as regulatory factors, including enzymes, constituting intrinsic potential of grain sink.

Temporal oscillations of phosphatases in N-phthaloyl gamma-aminobutyric acid treated rats.

N-pathaloyl gamma-aminobutyric acid (P-GABA) was administered to Wistar and 24 hr rhythms of acid and alkaline phosphatases were studied under light-dark conditions. P-GABA administration advanced the peak times of phosphatases. Since GABA is being involved in conveying dark information to the clock, exogenous administration of P-GABA might reduce the photic information received by the clock. The results could be explained by slight daily advances which would bring the peak times to the points 21 days after the start of administration.

Factores de riesgo de coledocolitiasis / Choledocholithiasis risk factors

El tratamiento de la coledocolitiasis asociada a colelitiasis es aún motivo de controversia. La capacidad para predecir la presencia de coledocolitiasis asociada a colelitiasis en pacientes candidatos a cirugía permite dirigir el manejo en forma selectiva. Con este objetivo se analizaron las fichas clínicas de 1137 pacientes sometidos a colecistectomía laparoscópica entre enero de 1993 y abril de 1994, seleccionando 681 pacientes con estudio colangiográfico. Se analizaron parámetros clínicos como ictericia y coluria, bioquímicos como elevación de fosfatasas alcalinas y bilirrubina total y dilatación de la vía biliar en la ecografía. Las variables se analizaron en forma individual (chi cuadrado) y en conjunto (regresión logística paso a paso). En el análisis univariado los parámetros con mejor correlación fueron la ictericia al ingreso, la elevación de fosfatasas alcalinas y la dilatación de la vía biliar. La combinación de las tres arrojó una concordancia del 72 por ciento

Activity of bacterial phosphomonoesterases in batch culture.

The phosphomonoesterases catalyse the hydrolysis of primary esters of phosphoric acid which help the bacteria to survive in phosphate stressed environment. Ninety-five bacterial isolates were obtained from domestic sewage and industrial effluents of gelatine and soap factories at Jabalpur on a medium enriched with phosphate and were screened for phosphatase production. The phosphatase producers were tentatively identified as Escherichia coli, Vibrio vulnificus, Aeromonas hydrophila, Staphylococcus aureus, Pseudomonas maltophilia and Micrococcus varians. The in vitro studies on the production of phosphomonoesterases by bacteria was conducted. The maximum alkaline phosphatase production was recorded on 8th day of incubation by E.coli and P.maltophilia, on 10th day of incubation by V.vulnificus while M.varians and P.maltophilia produced higher acid phosphatase on 4th and 10th day of incubation respectively. The detailed investigations were done to find out the effect of various physical and chemical factors on phosphomonoesterases activity and the optimum conditions required for enzyme activity.

Effect of dexamethasone and corticosterone on activity levels of ATPase, phosphomonoesterases and phosphodiesterase in liver, muscle and testis of post-hatched White Leghorn chicks.

Muscle ATPase activity did not show much change with any of the treatments, while hepatic total and Ca(2+)-Mg(2+)-ATPase activities were decreased with low dose of dexamethasone (DXM(L) and enzyme activity in general was increased with both high dose of DXM(H) and corticosterone. Total and Ca(2+)-Mg(2+)-ATPases were increased in testis of corticosterone treated chicks. Acid phosphatase activity of testis was increased with DXM(H) and decreased with DXM(L) while the enzyme activity in all the three tissues was increased with corticosterone. Muscle alkaline phosphatase activity was decreased with DXM treatments while that of testis was decreased with both DXM(H) and corticosterone treatments. Hepatic PDE activity was decreased with DXM and increased with corticosterone while muscle PDE activity was decreased under both DXM(H) and corticosterone treatments. The results suggest that both hypo. and hypercorticalism can induce tissue specific differential alterations in phosphomonoesterases, ATPases and PDE during early phases of post-natal development of chicks.

Circadian rhythms of renal phosphohydrolases analysed by Cosinor method.

Rhythmometric analysis of hydrolytic enzymes of mouse kidney has been performed on circadian time scale using the F test. Significant rhythms were detected in glucose-6-phosphatase (G6Pase), inorganic pyrophosphatase (InPPase) and alkaline phosphatase (AlPase) on protein and fresh weight basis. Acrophase (time for peak activity) of G6Pase, InPPase and AlPase per mg protein was at 9.9 degrees (1.0 hr), 88.5 degrees (6.0 hr) and at 342.3 degrees (20 hr) respectively. ATPase, which did not show significant rhythm (mean +/- SD = 4.51 +/- 0.30), had a peak value at 32.1 degrees (2.14 hr) with an amplitude of 0.31 units on protein basis. However, G6Pase and AlPase oscillated with high amplitudes (0.18 and 0.71) across the mean value (mesor) of 0.68 +/- 0.3 and 1.43 +/- 0.46 units respectively and with a phase shift of 5 hr. Since G6Pase is a multicomponent and multifunctional enzyme having several overlapping enzyme activities (viz. InPPase), coordinated events of G6Pase, InPPase and ATPase in the regulation of daily renal functions have been mapped in the intact animals, along a physiologic time scale.

Dorsolateral prostatic phosphomonoesterases and adenosine triphosphatases in hypo- and hyperthyroid rats.

Specific activities of phosphomonoesterases (acid and alkaline phosphatases) and adenosine triphosphatases (Mg2+, Ca2+ and Na+/K+ dependent ATPases) of dorsolateral prostate were studied in albino rats, under altered thyroid hormone status. Thyroidectomy induced hypothyroidism and thyroxine administered hyperthyroidism (25 micrograms/100 g body wt/day for 60 days, im) showed no impact on the activity of acid phosphatase. Three fold decrease in the activity of alkaline phosphatase was observed in hyperthyroid group. Ca2+ and Mg2+ dependent ATPases were significantly decreased in hypo- and hyperthyroid status whereas Na+/K+ ATPase was decreased in hyperthyroidism and showed an opposite trend in hypothyroid group.

Specific activities of seminal vesicular phosphomonoesterases and Mg2+-,Ca2+- and Na+/K(+)-adenosine triphosphatases in hypo- and hyperthyroid albino rats.

Hypothyroidism (surgical thyroidectomy) inhibited the activities of acid phosphatase and Mg(2+)-ATPase in seminal vesicular tissue and fluid and that of Ca(2+)- and Na+/K(+)-ATPases in fluid alone, and T4 supplementation restored normalcy in all, except acid phosphatase. Hyperthyroidism (T4 25 micrograms/100g body weight/day for 60 days, im) enhanced the activities of alkaline phosphatase and ATPases in seminal vesicular tissue and fluid, and decreased acid phosphatase activity in tissue alone. Withdrawal of T4 treatment from hyperthyroid rats (after 30 days) augmented the activity of ATPases in tissue and impaired the same in fluid, while phosphomonoesterases remained at hyperthyroid level. The results suggest specific responses of various seminal vesicular phosphatases to altered thyroid hormone status. Modification in the specific threshold of androgen/estrogen action on different phosphatases in seminal vesicles appears to be the plausible mechanism underlying these changes in hypo- and hyperthyroid conditions.

Ventral prostatic phosphomonoesterases and adenosine triphosphatases in hypo- and hyperthyroid albino rats.

Specific activities of prostatic phosphomonoesterases (acid and alkaline phosphatases) and adenosine triphosphatases (Mg2+, Ca2+ and Na+/K+ dependent ATPases) were studied in albino rats, under altered thyroid hormone status. Thyroidectomy induced hypothyroidism decreased the specific activities of acid and alkaline phosphatases, Na+/K+ and Ca2+ dependent ATPases in ventral prostate. Hyperthyroidism (25 micrograms thyroxine/100g body weight/day for 60 days, im) enhanced the activities of acid phosphatase and Na+/K+ dependent ATPase, while Ca2+ dependent ATPase decreased. The altered thyroid status had no effect on the activity of ventral prostatic Mg2+ dependent ATPase. The data obtained in the present study showed differential and specific responses of various ventral prostatic phosphatases to the hypo or hyperthyroid status. The study also shows the necessity of an optimum level of thyroid hormones to maintain the normal activities of these enzymes and their secretory function in ventral prostate.

Effects of cadmium salt on phosphomonoesterases activity and fertilizing ability of fowl spermatozoa.

Daily administration of cadmium salt for 25 days (2.5 mg per Kg body weight) in the male domestic fowl caused the end of treatment period. An increased incidences of concentration. Fertility dropped to zero at the end of the treatment period. Activity of acid and alkaline phosphomonoesterases were also drastically reduced by the end of treatment period. An increased incidences of morphological abnormalities of spermatozoa were noticed in the treated birds. After 46 days cessation of the treatment, full recovery of the above measures was found. These alterations suggest the reversible type of effect of cadmium chloride on the spermatozoa of male domestic fowl.