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.
Animals ; Gene Deletion ; Histones/genetics* ; Insulin ; Insulin Receptor Substrate Proteins/metabolism* ; Insulin Resistance/genetics* ; Membrane Cofactor Protein/genetics* ; Mice ; Mice, Knockout ; Muscles/metabolism* ; Phosphoric Monoester Hydrolases/metabolism* ; Protein Tyrosine Phosphatase, Non-Receptor Type 1/metabolism* ; Proto-Oncogene Proteins c-akt/metabolism* ; RNA, Messenger/metabolism* ; Receptor, Insulin/metabolism* ; Tyrosine/genetics* ; Up-Regulation

Protein tyrosine phosphatase 1B (PTP1B) has led to an intense interest in developing its inhibitors as anti-diabetes, anti-obesity and anti-cancer agents. The fruits of Rubus chingii (Chinese raspberry) were used as a kind of dietary traditional Chinese medicine. The methanolic extract of R. chingii fruits exhibited significant PTP1B inhibitory activity. Further bioactivity-guided fractionation resulted in the isolation of three PTP1B inhibitory ursane-type triterpenes: ursolic acid (1), 2-oxopomolic acid (2), and 2α, 19α-dihydroxy-3-oxo-urs-12-en-28-oic acid (3). Kinetics analyses revealed that 1 was a non-competitive PTP1B inhibitor, and 2 and 3 were mixed type PTP1B inhibitors. Compounds 1-3 and structurally related triterpenes (4-8) were further analyzed the structure-activity relationship, and were evaluated the inhibitory selectivity against four homologous protein tyrosine phosphatases (TCPTP, VHR, SHP-1 and SHP-2). Molecular docking simulations were also carried out, and the result indicated that 1, 3-acetoxy-urs-12-ene-28-oic acid (5), and pomolic acid-3β-acetate (6) bound at the allosteric site including α3, α6, and α7 helix of PTP1B.
Enzyme Inhibitors ; chemistry ; metabolism ; Fruit ; chemistry ; Humans ; Kinetics ; Methanol ; chemistry ; Molecular Docking Simulation ; Molecular Structure ; Plant Extracts ; chemistry ; Protein Binding ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; antagonists & inhibitors ; metabolism ; Protein Tyrosine Phosphatases ; antagonists & inhibitors ; Rubus ; chemistry ; Structure-Activity Relationship ; Triterpenes ; chemistry ; metabolism

Eleven flavonoids were isolated from the twigs of Broussonetia papyrifera by column chromatography over silica gel,ODS,MCI gel,and Sephadex LH-20,as well as RP-HPLC.Their structures were identified by spectroscopic methods including NMR,MS,UV,and IR as broupapyrin A(1),5,7,3',4'-tetrahydroxy-3-methoxy-8-geranylflavone(2),8-prenylquercetin-3-methyl ether(3),broussonol D(4),broussoflavonol B(5),uralenol(6),broussonol E(7),8-(1,1-dimethylallyl)-5'-(3-methylbut-2-enyl)-3',4',5,7-tetrahydroxyflanvonol(8),broussoflavonol E(9),4,2',4'-trihydroxychalcone(10),and butein(11).Compound 1 is a new isoprenylated flavonol.Compounds 3,6,10,and 11 were obtained from the genus Broussonetia for the first time,and 4 and 7 were firstly discovered in B.papyrifera.Compounds 1-5 and 7-9 showed significant inhibitory effects on PTP1 B with IC50 values ranging from(0.83±0.30) to(4.66±0.83) μmol·L-1.
Broussonetia ; chemistry ; Chromatography, High Pressure Liquid ; Flavonoids ; isolation & purification ; pharmacology ; Magnetic Resonance Spectroscopy ; Phytochemicals ; isolation & purification ; pharmacology ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; antagonists & inhibitors

Thyroid diseases, including autoimmune thyroid diseases and thyroid cancer, are known to have high heritability. Family and twin studies have indicated that genetics plays a major role in the development of thyroid diseases. Thyroid function, represented by thyroid stimulating hormone (TSH) and free thyroxine (T4), is also known to be partly genetically determined. Before the era of genome-wide association studies (GWAS), the ability to identify genes responsible for susceptibility to thyroid disease was limited. Over the past decade, GWAS have been used to identify genes involved in many complex diseases, including various phenotypes of the thyroid gland. In GWAS of autoimmune thyroid diseases, many susceptibility loci associated with autoimmunity (human leukocyte antigen [HLA], protein tyrosine phosphatase, non-receptor type 22 [PTPN22], cytotoxic T-lymphocyte associated protein 4 [CTLA4], and interleukin 2 receptor subunit alpha [IL2RA]) or thyroid-specific genes (thyroid stimulating hormone receptor [TSHR] and forkhead box E1 [FOXE1]) have been identified. Regarding thyroid function, many susceptibility loci for levels of TSH and free T4 have been identified through genome-wide analyses. In GWAS of differentiated thyroid cancer, associations at FOXE1, MAP3K12 binding inhibitory protein 1 (MBIP)-NK2 homeobox 1 (NKX2-1), disrupted in renal carcinoma 3 (DIRC3), neuregulin 1 (NRG1), and pecanex-like 2 (PCNXL2) have been commonly identified in people of European and Korean ancestry, and many other susceptibility loci have been found in specific populations. Through GWAS of various thyroid-related phenotypes, many susceptibility loci have been found, providing insights into the pathogenesis of thyroid diseases and disease co-clustering within families and individuals.
Autoimmunity ; Genes, Homeobox ; Genetics ; Genome-Wide Association Study* ; Graves Disease ; Hashimoto Disease ; Humans ; Leukocytes ; Neuregulin-1 ; Phenotype ; Protein Tyrosine Phosphatase, Non-Receptor Type 22 ; Receptors, Interleukin-2 ; T-Lymphocytes, Cytotoxic ; Thyroid Diseases* ; Thyroid Gland* ; Thyroid Neoplasms* ; Thyrotropin ; Thyroxine

Cyclic ADP-ribose (cADPR) releases Ca²⁺ from ryanodine receptor (RyR)-sensitive calcium pools in various cell types. In cardiac myocytes, the physiological levels of cADPR transiently increase the amplitude and frequency of Ca²⁺ (that is, a rapid increase and decrease of calcium within one second) during the cardiac action potential. In this study, we demonstrated that cADPR levels higher than physiological levels induce a slow and gradual increase in the resting intracellular Ca²⁺ ([Ca²⁺](i)) level over 10 min by inhibiting the sarcoendoplasmic reticulum Ca²⁺ ATPase (SERCA). Higher cADPR levels mediate the tyrosine-dephosphorylation of α-actin by protein tyrosine phosphatase 1B (PTP1B) present in the endoplasmic reticulum. The tyrosine dephosphorylation of α-actin dissociates phospholamban, the key regulator of SERCA, from α-actin and results in SERCA inhibition. The disruption of the integrity of α-actin by cytochalasin B and the inhibition of α-actin tyrosine dephosphorylation by a PTP1B inhibitor block cADPR-mediated Ca²⁺ increase. Our results suggest that levels of cADPR that are relatively higher than normal physiological levels modify calcium homeostasis through the dephosphorylation of α-actin by PTB1B and the subsequent inhibition of SERCA in cardiac myocytes.
Action Potentials ; Adenosine Diphosphate* ; Adenosine Triphosphatases ; Calcium ; Cyclic ADP-Ribose ; Cytochalasin B ; Endoplasmic Reticulum ; Homeostasis ; Muscle Cells* ; Myocytes, Cardiac ; Protein Tyrosine Phosphatase, Non-Receptor Type 1* ; Protein Tyrosine Phosphatases* ; Reticulum ; Ryanodine Receptor Calcium Release Channel ; Tyrosine

To investigate the effects of 2-(4-methoxycarbonyl-2-tetradecyloxyphenyl)carbamoylbenzoic acid (CX09040) on protecting pancreatic β cells, the β cell dysfunction model mice were induced by injection of alloxan into the caudal vein of ICR mice, and were treated with compound CX09040. Liraglutide was used as the positive control drug. The amount and the size of islets observed in pathological sections were calculated to evaluate the β cell mass; the glucose stimulated insulin secretion (GSIS) test was applied to estimate the β cell secretary function; the oral glucose tolerance test (OGTT) was taken to observe the glucose metabolism in mice; the expressions of protein in pancreas were detected by Western blotting. The effects on the target protein tyrosine phosphatase 1B (PTP1B) were assessed by the PTP1B activities of both recombinant protein and the intracellular enzyme, and by the PTP1B expression in the pancreas of mice, separately. As the results, with the treatment of CX09040 in alloxan-induced β cell dysfunction mice, the islet amount (P<0.05) and size (P<0.05) increased significantly, the changes of serum insulin in GSIS (P<0.01) and the values of acute insulin response (AIR, P<0.01) were enhanced, compared to those in model group; the impaired glucose tolerance was also ameliorated by CX09040 with the decrease of the values of area under curve (AUC, P<0.01). The activation of the signaling pathways related to β cell proliferation was enhanced by increasing the levels of p-Akt/Akt (P<0.01), p-FoxO1/FoxOl (P<0.001) and PDX-1 (P<0.01). The effects of CX09040 on PTP1B were observed by inhibiting the recombinant hPTP1B activity with IC50 value of 2.78x 10(-7) mol.L-1, reducing the intracellular PTP1B activity of 72.8% (P<0.001), suppressing the PTP1B expression (P<0.001) and up-regulating p-IRβ/IRβ (P<0.01) in pancreas of the β cell dysfunction mice, separately. In conclusion, compound CX09040 showed significant protection effects against the dysfunction of β cell of mice by enlarging the pancreatic β cell mass and increasing the glucose-induced insulin secretion; its major mechanism may be the inhibition on target PTP1B and the succedent up-regulation of β cell proliferation.
Alloxan ; Animals ; Benzoates ; pharmacology ; Biological Assay ; Disease Models, Animal ; Glucose ; metabolism ; Glucose Tolerance Test ; Insulin ; secretion ; Insulin Resistance ; Insulin-Secreting Cells ; drug effects ; Liraglutide ; pharmacology ; Mice ; Mice, Inbred ICR ; Molecular Weight ; Pancreas ; drug effects ; enzymology ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; antagonists & inhibitors ; Signal Transduction

Protein tyrosine phosphatase (PTP) 1B is a potential target for the treatment of diabetes and obesity. We have previously identified the benzoyl sulfathiazole derivative II as a non-competitive PTP1B inhibitor with in vivo insulin sensitizing effects. Preliminary SAR study on this compound series has been carried out herein, and thirteen new compounds have been designed and synthesized. Among them, compound 10 exhibited potent inhibition against human recombinant PTP1B with the IC50 value of 3.97 micromol x L(-1), and is comparable to that of compound II.
Humans ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; antagonists & inhibitors ; Structure-Activity Relationship ; Sulfathiazoles ; chemistry ; pharmacology

OBJECTIVEChromium is an essential mineral that is thought to be necessary for normal glucose homeostasis. Numerous studies give evidence that chromium picolinate can modulate blood glucose and insulin resistance. The main ingredient of Tianmai Xiaoke (TMXK) Tablet is chromium picolinate. In China, TMXK Tablet is used to treat type 2 diabetes. This study investigated the effect of TMXK on glucose metabolism in diabetic rats to explore possible underlying molecular mechanisms for its action.

METHODSDiabetes was induced in rats by feeding a high-fat diet and subcutaneously injection with a single dose of streptozotocin (50 mg/kg, tail vein). One week after streptozotocin-injection, model rats were divided into diabetic group, low dose of TMXK group and high dose of TMXK group. Eight normal rats were used as normal control. After 8 weeks of treatment, skeletal muscle was obtained and was analyzed using Roche NimbleGen mRNA array and quantitative polymerase chain reaction (qPCR). Fasting blood glucose, oral glucose tolerance test and homeostasis model assessment of insulin resistance (HOMA-IR) index were also measured.

RESULTSThe authors found that the administration of TMXK Tablet can reduce the fasting blood glucose and fasting insulin level and HOMA-IR index. The authors also found that 2 223 genes from skeletal muscle of the high-dose TMXK group had significant changes in expression (1 752 increased, 471 decreased). Based on Kyoto encyclopedia of genes and genomes pathway analysis, the most three significant pathways were "insulin signaling pathway", "glycolysis/gluconeogenesis" and "citrate cycle (TCA)". qPCR showed that relative levels of forkhead box O3 (FoxO3), phosphoenolpyruvate carboxykinase 2 (Pck2), and protein tyrosine phosphatase 1B (Ptp1b) were significantly decreased in the high-dose TMXK group, while v-akt murine thymoma viral oncogene homolog 1 (Akt1) and insulin receptor substrate 2 (Irs2) were increased.

CONCLUSIONOur data show that TMXK Tablet reduces fasting glucose level and improves insulin resistance in diabetic rats. The mechanism may be linked to the inactivation of PTP1B and PCK enzymes, or through intracellular pathways, such as the insulin signaling pathway.

Animals ; Blood Glucose ; analysis ; Chromium ; administration & dosage ; Diabetes Mellitus, Type 2 ; drug therapy ; metabolism ; Insulin ; physiology ; Insulin Resistance ; Male ; Medicine, Chinese Traditional ; Phosphoenolpyruvate Carboxykinase (ATP) ; antagonists & inhibitors ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; antagonists & inhibitors ; Rats ; Rats, Sprague-Dawley ; Real-Time Polymerase Chain Reaction ; Signal Transduction ; drug effects ; Tablets

OBJECTIVE: To investigate the expression pattern of adapter protein with a Src-homology 2 domain (SH2B1), the suppressor of cytokine signaling-3 (SOCS3), protein-tyrosine phosphatase 1B (PTP1B) and neturopetide Y (NPY) in obese and normal mice hypothalamus and its relation with serum leptin and insulin levels. METHODS: The obesity animal model was prepared with healthy C57/bl6 mice. Lee's index and Homeostasis model assessment-insulin resistance (HOMA-IR) were calculated. The mRNA levels of SH2B1, SOCS3, PTP1B and NPY were measured by fluorescent quantitation RT-PCR. The SH2B1 and NPY protein expressions were detected by Western blot. RESULTS: Compared with the normal mice of the same age, SH2B1 mRNA expression in the obese mice hypothalamus decreased. SOCS3 and PTP1B mRNA expression increased. Western blot showed that SH2B1 protein expression decreased, while NPY protein expression increased in the obese mice. Linear correlation analysis showed that the serum leptin and fasting insulin levels were negatively correlated with SH2B1mRNA expression and positively correlated with SOCS3 and PTP1B mRNA expression. CONCLUSION SH2B1, SOCS3, PTP1B and NPY are key factors for obesity development.
Adaptor Proteins, Signal Transducing ; metabolism ; Animals ; Hypothalamus ; metabolism ; Insulin ; blood ; Insulin Resistance ; Leptin ; blood ; Mice ; Mice, Inbred C57BL ; Neuropeptide Y ; metabolism ; Obesity ; metabolism ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; metabolism ; RNA, Messenger ; Suppressor of Cytokine Signaling 3 Protein ; Suppressor of Cytokine Signaling Proteins ; metabolism

Animals ; Cell Survival ; radiation effects ; Light ; adverse effects ; Mice ; Mice, Knockout ; Protein Tyrosine Phosphatase, Non-Receptor Type 1 ; antagonists & inhibitors ; metabolism ; Retinal Rod Photoreceptor Cells ; cytology ; enzymology ; radiation effects