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Articles by D Zheng
Total Records ( 20 ) for D Zheng
  D Zheng , X Li , H Xu , X Lu , Y Hu and W. Fan

Docetaxel (Doc) has extraordinary activities against a variety of solid tumors. However, the clinical efficacy of Doc is limited due to its poor solubility, low selective distribution, fast elimination in vivo, etc. In the present study, Doc was incorporated into the core-shell structure of nanoparticles prepared based on our previous work. The obtained docetaxel-loaded nanoparticles (DOCNP) were characterized with various biophysical methodologies, and its antitumor efficacy against malignant melanoma was evaluated both in vitro and in vivo. Our results indicated that Doc could be incorporated into the nanoparticles with high encapsulation efficiency (>90%). The incorporated Doc can be released from DOCNP in a sustained manner. In vitro cytotoxicity studies indicated that DOCNP could effectively kill B16 cells and show a dose- and time-dependent efficacy. Furthermore, intratumoral administration revealed that DOCNP has significantly higher antitumor effect and lower toxicity to normal cells and tissues than free Doc. These results suggest that DOCNP may be a promising drug delivery system in therapy for malignant melanoma.

  Q Wang , J Li , J Gu , B Huang , Y Zhao , D Zheng , Y Ding and L. Zeng

The green tea constituent, (–)-epigallocatechin-3-gallate (EGCG), has chemopreventive and anticancer effects. This is partially because of the selective ability of EGCG to induce apoptosis and death in cancer cells without affecting normal cells. In the present study, the activity of EGCG against the myeloma cell line, KM3, was examined. Our results demonstrated, for the first time, that the treatment of the KM3 cell line with EGCG inhibits cell proliferation and induces apoptosis, and there is a synergistic effect when EGCG and bortezomib are combined. Further experiments showed that this effect involves the NF-B pathway. EGCG inhibits the expression of the P65 mRNA and P65/pP65 protein, meanwhile it downregulates pIB expression and upregulates IB expression. EGCG also activates caspase-3, -8, cleaved caspase-9, and poly-ADP-ribose polymerase (PARP) and subsequent apoptosis. These findings provided experimental evidence for efficacy of EGCG alone or in combination with bortezomib in multiple myeloma therapy.

  J. M Richey , O. O Woolcott , D Stefanovski , L. N Harrison , D Zheng , M Lottati , I. R Hsu , S. P Kim , M Kabir , K. J Catalano , J. D Chiu , V Ionut , C Kolka , V Mooradian and R. N. Bergman

We investigated whether rimonabant, a type 1 cannabinoid receptor antagonist, reduces visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in dogs maintained on a hypercaloric high-fat diet (HHFD). To determine whether energy expenditure contributed to body weight changes, we also calculated resting metabolic rate. Twenty male dogs received either rimonabant (1.25 mg·kg–1·day–1, orally; n = 11) or placebo (n = 9) for 16 wk, concomitant with a HHFD. VAT, SAT, and nonfat tissue were measured by magnetic resonance imaging. Resting metabolic rate was assessed by indirect calorimetry. By week 16 of treatment, rimonabant dogs lost 2.5% of their body weight (P = 0.029), whereas in placebo dogs body weight increased by 6.2% (P < 0.001). Rimonabant reduced food intake (P = 0.027), concomitant with a reduction of SAT by 19.5% (P < 0.001). In contrast with the VAT increase with placebo (P < 0.01), VAT did not change with rimonabant. Nonfat tissue remained unchanged in both groups. Body weight loss was not associated with either resting metabolic rate (r2 = 0.24; P = 0.154) or food intake (r2 = 0.24; P = 0.166). In conclusion, rimonabant reduced body weight together with a reduction in abdominal fat, mainly because of SAT loss. Body weight changes were not associated with either resting metabolic rate or food intake. The findings provide evidence of a peripheral effect of rimonabant to reduce adiposity and body weight, possibly through a direct effect on adipose tissue.

  V Ionut , H Liu , V Mooradian , A. V. B Castro , M Kabir , D Stefanovski , D Zheng , E. L Kirkman and R. N. Bergman

Human type 2 diabetes mellitus (T2DM) is often characterized by obesity-associated insulin resistance (IR) and β-cell function deficiency. Development of relevant large animal models to study T2DM is important and timely, because most existing models have dramatic reductions in pancreatic function and no associated obesity and IR, features that resemble more T1DM than T2DM. Our goal was to create a canine model of T2DM in which obesity-associated IR occurs first, followed by moderate reduction in β-cell function, leading to mild diabetes or impaired glucose tolerance. Lean dogs (n = 12) received a high-fat diet that increased visceral (52%, P < 0.001) and subcutaneous (130%, P < 0.001) fat and resulted in a 31% reduction in insulin sensitivity (SI) (5.8 ± 0.7 x 10–4 to 4.1 ± 0.5 x 10–4 µU·ml–1·min–1, P < 0.05). Animals then received a single low dose of streptozotocin (STZ; range 30–15 mg/kg). The decrease in β-cell function was dose dependent and resulted in three diabetes models: 1) frank hyperglycemia (high STZ dose); 2) mild T2DM with normal or impaired fasting glucose (FG), 2-h glucose >200 mg/dl during OGTT and 77–93% AIRg reduction (intermediate dose); and 3) prediabetes with normal FG, normal 2-h glucose during OGTT and 17–74% AIRg reduction (low dose). Twelve weeks after STZ, animals without frank diabetes had 58% more body fat, decreased β-cell function (17–93%), and 40% lower SI. We conclude that high-fat feeding and variable-dose STZ in dog result in stable models of obesity, insulin resistance, and 1) overt diabetes, 2) mild T2DM, or 3) impaired glucose tolerance. These models open new avenues for studying the mechanism of compensatory changes that occur in T2DM and for evaluating new therapeutic strategies to prevent progression or to treat overt diabetes.

  D Zheng , V Ionut , V Mooradian , D Stefanovski and R. N. Bergman

The full impact of the liver, through both glucose production and uptake, on systemic glucose appearance cannot be readily studied in a classical glucose clamp because hepatic glucose metabolism is regulated not only by portal insulin and glucose levels but also portal glucose delivery (the portal signal). In the present study, we modified the classical glucose clamp by giving exogenous glucose through portal vein, the "portal glucose infusion (PoG)-glucose clamp", to determine the net hepatic effect on postprandial systemic glucose supply along with the measurement of whole body glucose disposal. By comparing systemic rate of glucose appearance (Ra) with portal glucose infusion rate (PoGinf), we quantified "net hepatic glucose addition (NHGA)" in the place of endogenous glucose production determined in a regular clamp. When PoG-glucose clamps (n = 6) were performed in dogs at basal insulinemia and hyperglycemia (~150 mg/dl, portal and systemic), we measured consistently higher Ra than PoGinf (4.2 ± 0.6 vs. 2.9 ± 0.6 mg·kg–1·min–1 at steady state, P < 0.001) and thus positive NHGA at 1.3 ± 0.1 mg·kg–1·min–1, identifying net hepatic addition of glucose to portal exogenous glucose. In contrast, when PoG-glucose clamps (n = 6) were performed at hyperinsulinemia (~250 pmol/l) and systemic euglycemia (portal hyperglycemia due to portal glucose infusion), we measured consistently lower Ra than PoGinf (13.1 ± 2.4 vs. 14.3 ± 2.4 mg·kg–1·min–1, P < 0.001), and therefore negative NHGA at –1.1 ± 0.1 mg·kg–1·min–1, identifying a switch of the liver from net production to net uptake of portal exogenous glucose. Steady-state whole body glucose disposal was 4.1 ± 0.5 and 13.0 ± 2.4 mg·kg–1·min–1, respectively, determined as in a classical glucose clamp. We conclude that the PoG-glucose clamp, simulating postprandial glucose entry and metabolism, enables simultaneous assessment of the net hepatic effect on postprandial systemic glucose supply as well as whole body glucose disposal in various animal models (rodents, dogs, and pigs) with established portal vein catheterization.

  E. B Jensen , D Zheng , R. A Russell , R Bassel Duby , R. S Williams , A. L Olson and G. L. Dohm
  Denervation by sciatic nerve resection causes decreased muscle glucose transporter 4 (GLUT4) expression, but little is known about the signaling events that cause this decrease. Experiments were designed to test the hypothesis that decreased GLUT4 expression in denervated muscle occurs because of decreased calcium/CaMK activity, which would then lead to decreased activation of the transcription factors myocyte enhancer factor 2 (MEF2) and GLUT4 enhancer factor (GEF), which are required for normal GLUT4 expression. GLUT4 mRNA was elevated in mice expressing constitutively active CaMK isoform IV (CaMKIV) and decreased by denervation. Denervation decreased GEF binding to the promoter and the content of GEF in the nucleus, but there was no change in either MEF2 binding or MEF2 protein content. Expression of a MEF2-dependent reporter gene did not change in denervated skeletal muscle. To determine the domains of the GLUT4 promoter that respond to denervation, transgenic mice expressing the chloramphenicol acetyl transferase (CAT) reporter gene driven by different lengths of the human GLUT4 promoter were denervated. Using several different promoter/reporter gene constructs, we found that all areas of the GLUT4 promoter were truncated or missing, except for the MEF2 binding domain and the basal promoter. All of the GLUT4 promoter/CAT reporter constructs evaluated responded normally to denervation. Our data lead us to conclude that decreased CaMK activity is not the reason for decreased GLUT4 content in denervated muscle and that negative control of GLUT4 expression is not mediated through the MEF2 or GEF-binding domains. These findings indicate that withdrawal of a GEF- or MEF2-dependent signal is not likely a major determinant of the denervation effect on GLUT4 expression. Thus, the response to denervation may be mediated by other elements present in the basal promoter of the GLUT4 gene.
  N Dong , S Chen , J Yang , L He , P Liu , D Zheng , L Li , Y Zhou , C Ruan , E Plow and Q. Wu

Background— Corin is a transmembrane protease that processes natriuretic peptides in the heart. Like many membrane proteins, corin is shed from the cell surface.

Methods and Results— In this study, we obtained plasma samples from healthy controls and patients with heart failure (HF) and acute myocardial infarction. Soluble corin levels in plasma were measured by an ELISA method. In healthy adults (n=198), plasma corin levels were 690 pg/mL (SD, 260 pg/mL). The corin levels did not differ significantly among different age groups. In patients with HF (n=291), plasma corin levels were significantly lower compared with that of healthy controls (365 pg/mL [SD, 259]; P<0.001). The reduction in plasma corin levels seemed to correlate with the severity of HF. In patients of New York Heart Association classes II, III, and IV, plasma corin levels were 450 pg/mL (SD, 281 pg/mL; n=69), 377 pg/mL (SD, 270 pg/mL; n=132), and 282 pg/mL (SD, 194 pg/mL; n=90), respectively (P<0.001 class II vs class IV; P<0.05 class III vs class IV). In contrast, plasma corin levels in patients with acute myocardial infarction (n=73) were similar to that of healthy controls (678 pg/mL [SD, 285 pg/mL]; P>0.05).

Conclusions— Soluble corin was detected in human plasma. Plasma corin levels were reduced significantly in patients with HF but not in those with acute myocardial infarction. Our results indicate that corin deficiency may contribute to the pathogenesis of HF and that plasma corin may be used as a biomarker in the diagnosis of HF.

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