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PURPOSE OF REVIEW - This narrative review summarizes recent data on factors associated with insulin resistance (IR) in adults with HIV, including contemporary antiretroviral therapy (ART).
RECENT FINDINGS - IR remains common in persons with HIV, even those receiving contemporary ART. Generalized and abdominal obesity and ectopic fat are correlates of IR, and emerging data have identified associations with biomarkers of inflammation and immune activation. Small studies suggest associations between mitochondria and IR. In ART-naïve individuals, IR increased within 4 weeks of starting ART in persons receiving contemporary boosted protease inhibitors or an integrase inhibitor. The importance of IR in non-diabetic persons with HIV will continue to grow as the population ages and obesity increases. Non-invasive estimates of IR appear to perform well in persons with HIV, but clinically relevant cutoffs are uncertain. Unexpected metabolic effects of newer HIV integrase inhibitors have been reported; thus, careful observation for and studies of IR are still warranted.
Notch signaling largely determines intestinal epithelial cell fate. High Notch activity drives progenitors toward absorptive enterocytes by repressing secretory differentiation programs, whereas low Notch permits secretory cell assignment. Myeloid translocation gene-related 1 (MTGR1) is a transcriptional corepressor in the myeloid translocation gene/Eight-Twenty-One family. Given that Mtgr1(-/-) mice have a dramatic reduction of intestinal epithelial secretory cells, we hypothesized that MTGR1 is a key repressor of Notch signaling. In support of this, transcriptome analysis of laser capture microdissected Mtgr1(-/-) intestinal crypts revealed Notch activation, and secretory markers Mucin2, Chromogranin A, and Growth factor-independent 1 (Gfi1) were down-regulated in Mtgr1(-/-) whole intestines and Mtgr1(-/-) enteroids. We demonstrate that MTGR1 is in a complex with Suppressor of Hairless Homolog, a key Notch effector, and represses Notch-induced Hairy/Enhancer of Split 1 activity. Moreover, pharmacologic Notch inhibition using a γ-secretase inhibitor (GSI) rescued the hyperproliferative baseline phenotype in the Mtgr1(-/-) intestine and increased production of goblet and enteroendocrine lineages in Mtgr1(-/-) mice. GSI increased Paneth cell production in wild-type mice but failed to do so in Mtgr1(-/-) mice. We determined that MTGR1 can interact with GFI1, a transcriptional corepressor required for Paneth cell differentiation, and repress GFI1 targets. Overall, the data suggest that MTGR1, a transcriptional corepressor well characterized in hematopoiesis, plays a critical role in intestinal lineage allocation.
BACKGROUND - Nonnucleoside reverse transcriptase inhibitor-based antiretroviral therapy is not suitable for all treatment-naive HIV-infected persons.
OBJECTIVE - To evaluate 3 nonnucleoside reverse transcriptase inhibitor-sparing initial antiretroviral regimens to show equivalence for virologic efficacy and tolerability.
DESIGN - A phase 3, open-label study randomized in a 1:1:1 ratio with follow-up for at least 96 weeks. (ClinicalTrials.gov: NCT00811954).
SETTING - 57 sites in the United States and Puerto Rico.
PATIENTS - Treatment-naive persons aged 18 years or older with HIV-1 RNA levels greater than 1000 copies/mL without resistance to nucleoside reverse transcriptase inhibitors or protease inhibitors.
INTERVENTION - Atazanavir, 300 mg/d, with ritonavir, 100 mg/d; raltegravir, 400 mg twice daily; or darunavir, 800 mg/d, with ritonavir, 100 mg/d, plus combination emtricitabine, 200 mg/d, and tenofovir disoproxil fumarate, 300 mg/d.
MEASUREMENTS - Virologic failure, defined as a confirmed HIV-1 RNA level greater than 1000 copies/mL at or after 16 weeks and before 24 weeks or greater than 200 copies/mL at or after 24 weeks, and tolerability failure, defined as discontinuation of atazanavir, raltegravir, or darunavir for toxicity. A secondary end point was a combination of virologic efficacy and tolerability.
RESULTS - Among 1809 participants, all pairwise comparisons of incidence of virologic failure over 96 weeks showed equivalence within a margin of equivalence defined as -10% to 10%. Raltegravir and ritonavir-boosted darunavir were equivalent for tolerability, whereas ritonavir-boosted atazanavir resulted in a 12.7% and 9.2% higher incidence of tolerability discontinuation than raltegravir and ritonavir-boosted darunavir, respectively, primarily because of hyperbilirubinemia. For combined virologic efficacy and tolerability, ritonavir-boosted darunavir was superior to ritonavir-boosted atazanavir, and raltegravir was superior to both protease inhibitors. Antiretroviral resistance at the time of virologic failure was rare but more frequent with raltegravir.
LIMITATION - The trial was open-label, and ritonavir was not provided.
CONCLUSION - Over 2 years, all 3 regimens attained high and equivalent rates of virologic control. Tolerability of regimens containing raltegravir or ritonavir-boosted darunavir was superior to that of the ritonavir-boosted atazanavir regimen.
PRIMARY FUNDING SOURCE - National Institute of Allergy and Infectious Diseases.
RATIONALE - We recently reported two novel biomarkers for acute kidney injury (AKI), tissue inhibitor of metalloproteinases (TIMP)-2 and insulin-like growth factor binding protein 7 (IGFBP7), both related to G1 cell cycle arrest.
OBJECTIVES - We now validate a clinical test for urinary [TIMP-2]·[IGFBP7] at a high-sensitivity cutoff greater than 0.3 for AKI risk stratification in a diverse population of critically ill patients.
METHODS - We conducted a prospective multicenter study of 420 critically ill patients. The primary analysis was the ability of urinary [TIMP-2]·[IGFBP7] to predict moderate to severe AKI within 12 hours. AKI was adjudicated by a committee of three independent expert nephrologists who were masked to the results of the test.
MEASUREMENTS AND MAIN RESULTS - Urinary TIMP-2 and IGFBP7 were measured using a clinical immunoassay platform. The primary endpoint was reached in 17% of patients. For a single urinary [TIMP-2]·[IGFBP7] test, sensitivity at the prespecified high-sensitivity cutoff of 0.3 (ng/ml)(2)/1,000 was 92% (95% confidence interval [CI], 85-98%) with a negative likelihood ratio of 0.18 (95% CI, 0.06-0.33). Critically ill patients with urinary [TIMP-2]·[IGFBP7] greater than 0.3 had seven times the risk for AKI (95% CI, 4-22) compared with critically ill patients with a test result below 0.3. In a multivariate model including clinical information, urinary [TIMP-2]·[IGFBP7] remained statistically significant and a strong predictor of AKI (area under the curve, 0.70, 95% CI, 0.63-0.76 for clinical variables alone, vs. area under the curve, 0.86, 95% CI, 0.80-0.90 for clinical variables plus [TIMP-2]·[IGFBP7]).
CONCLUSIONS - Urinary [TIMP-2]·[IGFBP7] greater than 0.3 (ng/ml)(2)/1,000 identifies patients at risk for imminent AKI. Clinical trial registered with www.clinicaltrials.gov (NCT 01573962).
BACKGROUND - Atazanavir-associated hyperbilirubinemia can cause premature discontinuation of atazanavir and avoidance of its initial prescription. We used genomewide genotyping and clinical data to characterize determinants of atazanavir pharmacokinetics and hyperbilirubinemia in AIDS Clinical Trials Group protocol A5202.
METHODS - Plasma atazanavir pharmacokinetics and indirect bilirubin concentrations were characterized in HIV-1-infected patients randomized to atazanavir/ritonavir-containing regimens. A subset had genomewide genotype data available.
RESULTS - Genomewide assay data were available from 542 participants, of whom 475 also had data on estimated atazanavir clearance and relevant covariates available. Peak bilirubin concentration and relevant covariates were available for 443 participants. By multivariate analysis, higher peak on-treatment bilirubin levels were found to be associated with the UGT1A1 rs887829 T allele (P=6.4×10(-12)), higher baseline hemoglobin levels (P=4.9×10(-13)), higher baseline bilirubin levels (P=6.7×10(-12)), and slower plasma atazanavir clearance (P=8.6×10(-11)). For peak bilirubin levels greater than 3.0 mg/dl, the positive predictive value of a baseline bilirubin level of 0.5 mg/dl or higher with hemoglobin concentrations of 14 g/dl or higher was 0.51, which increased to 0.85 with rs887829 TT homozygosity. For peak bilirubin levels of 3.0 mg/dl or lower, the positive predictive value of a baseline bilirubin level less than 0.5 mg/dl with a hemoglobin concentration less than 14 g/dl was 0.91, which increased to 0.96 with rs887829 CC homozygosity. No polymorphism predicted atazanavir pharmacokinetics at genomewide significance.
CONCLUSION - Atazanavir-associated hyperbilirubinemia is best predicted by considering UGT1A1 genotype, baseline bilirubin level, and baseline hemoglobin level in combination. Use of ritonavir as a pharmacokinetic enhancer may have abrogated genetic associations with atazanavir pharmacokinetics.
Small molecule docking predicts the interaction of a small molecule ligand with a protein at atomic-detail accuracy including position and conformation the ligand but also conformational changes of the protein upon ligand binding. While successful in the majority of cases, docking algorithms including RosettaLigand fail in some cases to predict the correct protein/ligand complex structure. In this study we show that simultaneous docking of explicit interface water molecules greatly improves Rosetta's ability to distinguish correct from incorrect ligand poses. This result holds true for both protein-centric water docking wherein waters are located relative to the protein binding site and ligand-centric water docking wherein waters move with the ligand during docking. Protein-centric docking is used to model 99 HIV-1 protease/protease inhibitor structures. We find protease inhibitor placement improving at a ratio of 9:1 when one critical interface water molecule is included in the docking simulation. Ligand-centric docking is applied to 341 structures from the CSAR benchmark of diverse protein/ligand complexes . Across this diverse dataset we see up to 56% recovery of failed docking studies, when waters are included in the docking simulation.
OBJECTIVES - To estimate the incidence of and risk factors for modifications to first antiretroviral therapy (ART) regimen, treatment interruption and death.
METHODS - A total of 21 801 patients from 18 cohorts in Europe and North America starting ART on regimens including at least two nucleoside reverse transcriptase inhibitors and boosted protease inhibitor or non-nucleoside reverse transcriptase inhibitor during 2002-2009 were included. Incidence of modifications (change of drug class, substitution/addition within class, or switch to nonstandard regimen), interruption or death and associations with patient characteristics were estimated using competing-risks methods.
RESULTS - During median 28 months follow-up, 8786 (40.3%) patients modified first ART, 2346 (10.8%) interrupted and 427 (2.0%) died before changing regimen. Three-year cumulative percentages of modification, interruption and death were 47, 12 and 2%, respectively. After adjustment, rates of interruption were highest for IDUs and lowest for MSM, and higher for patients starting ART with CD4 cell count above 350 cells/μl than other patients. Compared to efavirenz, patients on lopinavir and other protease inhibitors had higher rates of modification and interruption, on atazanavir had lower rates of class change, and on nevirapine higher rates of interruption. Those on tenofovir/emtricitabine backbone had lowest rates of substitutions and switches to nonstandard regimen, and on abacavir/lamivudine lowest rates of interruption. Rates of substitution and switches to nonstandard regimen were lower in 2006-2009.
CONCLUSION - Rates of modification and interruption were high, particularly in the first year of ART. Decreased rates of substitutions or switches to nonstandard regimen in recent years may be linked to greater use of well tolerated once-daily drugs.
PURPOSE - Bortezomib, a first-generation proteasome inhibitor, induces an endoplasmic reticulum (ER) stress response, which ultimately leads to dysregulation of intracellular Ca(2+) and apoptotic cell death. This study investigated the role of the Ca(2+)-dependent enzyme, calpain, in bortezomib cytotoxicity. A novel therapeutic combination was evaluated in which HIV protease inhibitors were used to block calpain activity and enhance bortezomib cytotoxicity in myeloma cells in vitro and in vivo.
METHODS - Bortezomib-mediated cell death was examined using assays for apoptosis (Annexin V staining), total cell death (trypan blue exclusion), and growth inhibition (MTT). The effects of calpain on bortezomib-induced cytotoxicity were investigated using siRNA knockdown or pharmaceutical inhibitors. Enzyme activity assays and immunofluorescence analysis were used to identify mechanistic effects.
RESULTS - Inhibition of the Ca(2+)-dependent cysteine protease calpain, either by pharmacologic or genetic means, enhances or accelerates bortezomib-induced myeloma cell death. The increase in cell death is not associated with an increase in caspase activity, nor is there evidence of greater inhibition of proteasome activity, suggesting an alternate, calpain-regulated mechanism of bortezomib-induced cell death. Bortezomib initiates an autophagic response in myeloma cells associated with cell survival. Inhibition of calpain subverts the cytoprotective function of autophagy leading to increased bortezomib-mediated cell death. Combination therapy with bortezomib and the calpain-blocking HIV protease inhibitor, nelfinavir, reversed bortezomib resistance and induced near-complete tumor regressions in an SCID mouse xenograft model of myeloma.
OBJECTIVE - Among HIV-positive patients prescribed ritonavir-boosted lopinavir, SLCO1B1 521T→C (rs4149056) is associated with increased plasma lopinavir exposure. Protease inhibitors (PIs) are also substrates for cytochrome P450 (CYP) 3A and ABCB1, which are induced by NR1I2. We characterized relationships between ABCB1, CYP3A4, CYP3A5, NR1I2, and SLCO1B1 polymorphisms and trough PI concentrations among AIDS Clinical Trials Group study A5146 participants.
METHODS - At study entry, subjects with virologic failure on PI-containing regimens initiated new ritonavir-boosted PI regimens. We studied associations between week 2 PI plasma trough concentrations and 143 polymorphisms in these genes, including 4 targeted polymorphisms.
RESULTS - Among 275 subjects with both drug concentrations and genetic data, allelic frequencies of SLCO1B1 521T→C were 15%, 1%, and 8% in whites, blacks, and Hispanics, respectively. Further analyses were limited to 268 white, black, or Hispanic subjects who initiated ritonavir-boosted lopinavir (n = 98), fosamprenavir (n = 69), or saquinavir (n = 99). Of targeted polymorphisms, SLCO1B1 521T→C tended to be associated with higher lopinavir concentrations, with a 1.38-fold increase in the mean per C allele (95% confidence interval, 0.97-1.96; n = 98; P = 0.07). With fosamprenavir, SLCO1B1 521T→C was associated with lower amprenavir concentrations, with a 35% decrease in the mean per C allele (geometric mean ratio 0.65; 95% confidence interval, 0.44-0.94; n = 69; adjusted P = 0.02). There was no significant association with saquinavir concentrations, and none of the remaining 139 exploratory polymorphisms were statistically significant after correcting for multiple comparisons.
CONCLUSIONS - With ritonavir-boosted PIs, a SLCO1B1 polymorphism that predicts higher lopinavir trough concentrations seems to predict lower amprenavir trough concentrations. The mechanism underlying this discordant association is uncertain.
To discover promising sulfated allosteric modulators (SAMs) of glycosaminoglycan-binding proteins (GBPs), such as human factor XIa (FXIa), we screened a library of 26 synthetic, sulfated quinazolin-4(3H)-ones (QAOs) resulting in the identification of six molecules that reduced the Vmax of substrate hydrolysis without influencing the KM. Mutagenesis of residues of the heparin-binding site (HBS) of FXIa introduced a nearly 5-fold loss in inhibition potency supporting recognition of an allosteric site. Fluorescence studies showed a sigmoidal binding profile indicating highly cooperative binding. Competition with a positively charged, heparin-binding polymer did not fully nullify inhibition suggesting importance of hydrophobic forces to binding. This discovery suggests the operation of a dual-element recognition process, which relies on an initial Coulombic attraction of anionic SAMs to the cationic HBS of FXIa that forms a locked complex through tight interaction with an adjacent hydrophobic patch. The dual-element strategy may be widely applicable for discovering SAMs of other GBPs.