Contribution of CTCF binding to transcriptional activity at the HOXA locus in NPM1-mutant AML cells.

Transcriptional regulation of the HOXA genes is thought to involve CTCF-mediated chromatin loops and the opposing actions of the COMPASS and Polycomb epigenetic complexes. We investigated the role of these mechanisms at the HOXA cluster in AML cells with the common NPM1c mutation, which express both HOXA and HOXB genes. CTCF binding at the HOXA locus is conserved across primary AML samples, regardless of HOXA gene expression, and defines a continuous chromatin domain marked by COMPASS-associated histone H3 trimethylation in NPM1-mutant primary AML samples. Profiling of the three-dimensional chromatin architecture in primary AML samples with the NPM1c mutation identified chromatin loops between the HOXA cluster and loci in the SNX10 and SKAP2 genes, and an intergenic region located 1.4 Mbp upstream of the HOXA locus. Deletion of CTCF binding sites in the NPM1-mutant OCI-AML3 AML cell line reduced multiple long-range interactions, but resulted in CTCF-independent loops with sequences in SKAP2 that were marked by enhancer-associated histone modifications in primary AML samples. HOXA gene expression was maintained in CTCF binding site mutants, indicating that transcriptional activity at the HOXA locus in NPM1-mutant AML cells may be sustained through persistent interactions with SKAP2 enhancers, or by intrinsic factors within the HOXA gene cluster.

HIV protease inhibitors that block GLUT4 precipitate acute, decompensated heart failure in a mouse model of dilated cardiomyopathy.

The clinical use of HIV protease inhibitors is associated with insulin resistance and other metabolic changes that increase long-term cardiovascular risk. Since the failing heart has increased reliance on glucose, the influence of drug exposure on glucose homeostasis, myocardial glucose uptake, cardiac function, and survival was determined in TG9 mice, an established transgenic model of dilated cardiomyopathy generated by cardiac-specific overexpression of Cre-recombinase, as these animals progressed to overt heart failure. Beginning on day of life 75, TG9 mice and nontransgenic littermate controls were given a daily 10 mg/kg intraperitoneal injection of HIV protease inhibitors (ritonavir, lopinavir/ritonavir 4:1, atazanavir, atazanavir/ritonavir 4:1) or vehicle. Glucose tolerance testing, measurement of in vivo myocardial 2-deoxyglucose uptake, and echocardiography were performed before and 30 min following drug administration. The progression of dilated cardiomyopathy in TG9 animals was accompanied by impaired glucose tolerance, which was acutely exacerbated by exposure to ritonavir. Ritonavir and lopinavir precipitated acute, decompensated heart failure and death from pulmonary edema in TG9 mice. However, atazanavir, which does not inhibit glucose transport, had no effect. These studies demonstrate that, in the presence of dilated cardiomyopathy, HIV protease inhibitors that impair glucose transport induce acute, decompensated heart failure. The potential for HIV protease inhibitors to contribute to or exacerbate cardiomyopathy in human patients warrants further investigation.

Sitagliptin Reduces Inflammation and Chronic Immune Cell Activation in HIV+ Adults With Impaired Glucose Tolerance.

CONTEXT: HIV infection is associated with a greater risk for fasting hyperinsulinemia, impaired glucose tolerance, and higher incidence rates for vascular disease, myocardial infarction, or stroke despite effective combination antiretroviral therapy (cART). The underlying mechanism(s) may involve chronic low-grade systemic inflammation and immune cell activation. Dipeptidyl peptidase-4 inhibitors (sitagliptin) improve glucose tolerance and may possess immunomodulatory effects because leukocyte CD26 cell surface receptors express dipeptidyl peptidase-4 activity. OBJECTIVE: Sitagliptin will reduce inflammatory and immune cell activation markers known to be elevated in cART-treated HIV-infected (HIV+) adults with impaired glucose tolerance. DESIGN: This was designed as a prospective, randomized, placebo-controlled, double-blind trial of sitagliptin in HIV+ adults. SETTING: The setting was an academic medical center. PATIENTS: Patients were cART-treated HIV+ men and women (n = 36) with stable HIV disease and impaired glucose tolerance. INTERVENTIONS: Interventions included sitagliptin 100 mg/d or placebo for 8 weeks. MAIN OUTCOME MEASURES: At baseline and week 8, plasma high-sensitivity C-reactive protein and C-X-C motif chemokine 10 concentrations (ELISA), oral glucose tolerance, and abdominal sc adipose mRNA expression for M1 macrophage markers (monocyte chemotactic protein-1, EGF-like module-containing, mucin-like hormone receptor 1). RESULTS: Sitagliptin reduced glucose area under the curve (P = .002) and improved oral glucose insulin sensitivity index (P = .04) more than placebo. Sitagliptin reduced plasma high-sensitivity C-reactive protein and C-X-C motif chemokine 10 levels more than placebo (P < .009). Adipose tissue monocyte chemotactic protein-1 mRNA abundance declined significantly more (P = .01), and adipose EGF-like module-containing, mucin-like hormone receptor 1 mRNA expression tended to decline more (P = .19) in sitagliptin than placebo. CONCLUSION: Sitagliptin had beneficial systemic and adipose anti-inflammatory effects in cART-treated HIV+ adults with impaired glucose tolerance. Large-scale, long-term studies should determine whether sitagliptin reduces cardiovascular risk and events in HIV+ adults.

Dipeptidyl peptidase IV inhibition does not adversely affect immune or virological status in HIV infected men and women: a pilot safety study.

CONTEXT: People infected with HIV have a higher risk for developing insulin resistance, diabetes, and cardiovascular disease than the general population. Dipeptidyl peptidase IV (DPP4) inhibitors are glucose-lowering medications with pleiotropic actions that may particularly benefit people with HIV, but the immune and virological safety of DPP4 inhibition in HIV is unknown. OBJECTIVE: DPP4 inhibition will not reduce CD4+ T lymphocyte number or increase HIV viremia in HIV-positive adults. DESIGN: This was a randomized, placebo-controlled, double-blind safety trial of sitagliptin in HIV-positive adults. SETTING: The study was conducted at an academic medical center. PARTICIPANTS: Twenty nondiabetic HIV-positive men and women (9.8 ± 5.5 years of known HIV) taking antiretroviral therapy and with stable immune (625 ± 134 CD4+ T cells per microliter) and virological (<48 copies HIV RNA per milliliter) status. INTERVENTION: The intervention included sitagliptin (100 mg/d) vs matching placebo for up to 24 weeks. MAIN OUTCOME MEASURES: CD4+ T cell number and plasma HIV RNA were measured every 4 weeks; fasting serum regulated upon activation normal T-cell expressed and secreted (RANTES), stromal derived factor (SDF)-1α, Soluble TNF receptor II, and oral glucose tolerance were measured at baseline, week 8, and the end of study. ANOVA was used for between-group comparisons; P < .05 was considered significant. RESULTS: Compared with placebo, sitagliptin did not reduce CD4+ T cell count, plasma HIV RNA remained less than 48 copies/mL, RANTES and soluble TNF receptor II concentrations did not increase. SDF1α concentrations declined (P < .0002) in the sitagliptin group. The oral glucose tolerance levels improved in the sitagliptin group at week 8. CONCLUSIONS: Despite lowering SDF1α levels, sitagliptin did not adversely affect immune or virological status, or increase immune activation, but did improve glycemia in healthy, nondiabetic HIV-positive adults. These safety data allow future efficacy studies of sitagliptin in HIV-positive people with cardiometabolic complications.

A structural basis for the acute effects of HIV protease inhibitors on GLUT4 intrinsic activity.

Human immunodeficiency virus (HIV) protease inhibitors (PIs) act as reversible noncompetitive inhibitors of GLUT4 with binding affinities in the low micromolar range and are known to contribute to alterations in glucose homeostasis during treatment of HIV infection. As aspartyl protease inhibitors, these compounds all possess a core peptidomimetic structure together with flanking hydrophobic moieties. To determine the molecular basis for GLUT4 inhibition, a family of related oligopeptides containing structural elements found in PIs was screened for their ability to inhibit 2-deoxyglucose transport in primary rat adipocytes. The peptide oxybenzylcarbonyl-His-Phe-Phe-O-ethyl ester (zHFFe) was identified as a potent inhibitor of zero-trans glucose flux with a K(i) of 26 mum. Similar to PIs, transport inhibition by this peptide was acute, noncompetitive, and reversible. Within a Xenopus oocyte expression system, zHFFe acutely and reversibly inhibited GLUT4-mediated glucose uptake, whereas GLUT1 activity was unaffected at concentrations as high as 1 mm. The related photoactivatable peptide zHFF-p-benzoylphenylalanine-[(125)I]Tyr-O-ethyl ester selectively labeled GLUT4 in rat adipocytes and indinavir effectively protected against photolabeling. Furthermore, GLUT4 bound to a peptide affinity column containing the zHFF sequence and was eluted by indinavir. These data establish a structural basis for PI effects on GLUT4 activity and support the direct binding of PIs to the transport protein as the mechanism for acute inhibition of insulin-stimulated glucose uptake.