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Articles by Xia Xu
Total Records ( 2 ) for Xia Xu
  Michael H. Davidson , Nicola Abate , Christie M. Ballantyne , Alberico L. Catapano , Xia Xu , Jianxin Lin , Elizabeth Rosenberg and Andrew M. Tershakovec


Recent evidence suggests that in addition to low-density lipoprotein cholesterol (LDL-C), apolipoprotein B (Apo-B), non-high-density lipoprotein cholesterol (non-HDL-C), some lipoprotein ratios, and C-reactive protein (CRP) are predictive of coronary heart disease (CHD) risk. This post-hoc analysis of two trials comparing single-tablet ezetimibe/simvastatin (EZE/SIMVA) to atorvastatin (ATORVA) or rosuvastatin (ROSUVA) evaluates the proportion of patients attaining LDL-C <70 mg/dL and specific levels of these emerging risk factors.


These were double-blind, 6-week, parallel group trials of hypercholesterolemic patients randomized to milligram equivalent doses of ATORVA versus EZE 10 mg/SIMVA, or to usual starting, next higher, and maximum doses of ROSUVA versus EZE/SIMVA. This analysis examined the percent of patients in prespecified dose comparisons and overall achievement of LDL-C <70 mg/dL and/or Apo-B <90 mg/dL, total cholesterol (TC)/HDL-C <4.0, or Apo-B/Apo-A-I <0.7 among all treated patients, non-HDL-C <100 mg/dL among patients with baseline triglycerides ≥200 mg/dL, or CRP <2.0 mg/L among patients with baseline CRP ≥2.0 mg/L.


Within each trial, baseline characteristics were similar among groups. At all dose comparisons, significantly more patients receiving EZE/SIMVA reached LDL-C <70 mg/dL and achieved both LDL-C <70 mg/dL and either Apo-B <90 mg/dL, TC/HDL-C <4.0, or Apo-B/Apo-A-I <0.7 (EZE/SIMVA versus ATORVA) compared to ATORVA and ROSUVA. For most dose comparisons, significantly more patients receiving EZE/SIMVA attained both LDL-C <70 mg/dL and either non-HDL-C <100 mg/dL or CRP <2 mg/L compared to ATORVA or ROSUVA.


The greater efficacy related to changes in blood lipids of EZE/SIMVA compared with both ATORVA and ROSUVA extends to changes in many emerging risk factors. Ultimate clinical implications of these findings still need to be defined.

  Helena I. M. Boshoff , Xia Xu , Kapil Tahlan , Cynthia S. Dowd , Kevin Pethe , Luis R. Camacho , Tae- Ho Park , Chang- Soo Yun , Dirk Schnappinger , Sabine Ehrt , Kerstin J. Williams and Clifton E. Barry
  Despite the presence of genes that apparently encode NAD salvage-specific enzymes in its genome, it has been previously thought that Mycobacterium tuberculosis can only synthesize NAD de novo. Transcriptional analysis of the de novo synthesis and putative salvage pathway genes revealed an up-regulation of the salvage pathway genes in vivo and in vitro under conditions of hypoxia. [14C]Nicotinamide incorporation assays in M. tuberculosis isolated directly from the lungs of infected mice or from infected macrophages revealed that incorporation of exogenous nicotinamide was very efficient in in vivo-adapted cells, in contrast to cells grown aerobically in vitro. Two putative nicotinic acid phosphoribosyltransferases, PncB1 (Rv1330c) and PncB2 (Rv0573c), were examined by a combination of in vitro enzymatic activity assays and allelic exchange studies. These studies revealed that both play a role in cofactor salvage. Mutants in the de novo pathway died upon removal of exogenous nicotinamide during active replication in vitro. Cell death is induced by both cofactor starvation and disruption of cellular redox homeostasis as electron transport is impaired by limiting NAD. Inhibitors of NAD synthetase, an essential enzyme common to both recycling and de novo synthesis pathways, displayed the same bactericidal effect as sudden NAD starvation of the de novo pathway mutant in both actively growing and nonreplicating M. tuberculosis. These studies demonstrate the plasticity of the organism in maintaining NAD levels and establish that the two enzymes of the universal pathway are attractive chemotherapeutic targets for active as well as latent tuberculosis.
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