Publications

Angiopoietin like protein 4 (ANGPTL4) inhibits lipoprotein lipase (LPL) activity. Previous studies have shown that Toll-like Receptor (TLR) activation increases serum levels of ANGPTL4 and expression of ANGPTL4 in liver, heart, muscle, and adipose tissue in mice. ANGPTL4 is expressed in macrophages and is induced by inflammatory saturated fatty acids. The absence of ANGPTL4 leads to the increased uptake of pro-inflammatory saturated fatty acids by macrophages in the mesentery lymph nodes due to the failure of ANGPTL4 to inhibit LPL activity, resulting in peritonitis, intestinal fibrosis, weight loss, and death. Here we determined the effect of TLR activation on the expression of macrophage ANGPTL4. LPS treatment resulted in a 70% decrease in ANGPTL4 expression in mouse spleen, a tissue enriched in macrophages. In mouse peritoneal macrophages, LPS treatment also markedly decreased ANGPTL4 expression. In RAW cells, a macrophage cell line, LPS, zymosan, poly I:C, and imiquimod all inhibited ANGPTL4 expression. In contrast, neither TNF, IL-1, nor IL-6 altered ANGPTL4 expression. Finally, in cholesterol loaded macrophages, LPS treatment still decreased ANGPTL4 expression. Thus, while in most tissues ANGPTL4 expression is stimulated by inflammatory stimuli, in macrophages TLR activators inhibit ANGPTL4 expression, which could lead to a variety of down-stream effects important in host defense and wound repair.

LPS treatment of macrophages induces TG accumulation, which is accentuated by TG-rich lipoproteins or FFA. We defined pathways altered during macrophage activation that contribute to TG accumulation. Glucose uptake increased with activation, accompanied by increased GLUT1. Oxidation of glucose markedly decreased, whereas incorporation of glucose-derived carbon into FA and sterols increased. Macrophage activation also increased uptake of FFA, associated with an increase in CD36. Oxidation of FA was markedly reduced, whereas the incorporation of FA into TGs increased, associated with increased GPAT3 and DGAT2. Additionally, macrophage activation decreased TG lipolysis; however, expression of ATGL or HSL was not altered. Macrophage activation altered gene expression similarly when incubated with exogenous FA or AcLDL. Whereas activation with ligands of TLR2 (zymosan), TLR3 (poly I:C), or TLR4 (LPS) induced alterations in macrophage gene expression, leading to TG accumulation, treatment of macrophages with cytokines had minimal effects. Thus, activation of TLRs leads to accumulation of TG in macrophages by multiple pathways that may have beneficial effects in host defense but could contribute to the accelerated atherosclerosis in chronic infections and inflammatory diseases.

Caspase-14 is an enzyme that is expressed predominantly in cornifying epithelia and catalyses the degradation of profilaggrin. Additionally, caspase-14 plays an important role in the terminal differentiation of keratinocytes. However, how caspase-14 expression is regulated remains largely unknown. Here we demonstrate that ceramides (C(2) -Cer and C(6) -Cer), but not other sphingolipids (C(8) -glucosylceramides, sphinganine, sphingosine-1-phosphate or ceramide-1-phosphate), increase caspase-14 expression (mRNA and protein) in cultured human keratinocytes in a dose- and time-dependent manner. Inhibitors of glucosylceramide synthase and ceramidase increase endogenous ceramide levels and also increase caspase-14 expression, indicating an important regulatory role for ceramides and suggesting that the conversion of ceramides to other metabolites is not required. The increase in caspase-14 expression induced by ceramides is first seen at 16 h and requires new protein synthesis, suggesting that the ceramide-induced increase is likely an indirect effect. Furthermore, ceramides increase caspase-14 gene expression primarily by increasing transcription. Blocking de novo synthesis of ceramides does not affect caspase-14 expression, suggesting that basal expression is not dependent on ceramide levels. These studies show that ceramides, an important structural lipid, stimulate caspase-14 expression providing a mechanism for coordinately regulating the formation of lipid lamellar membranes with the formation of corneocytes.

OBJECTIVES

To compare asymmetric dimethylarginine (ADMA) among HIV-infected and uninfected individuals and to evaluate predictors of ADMA in HIV infection.

BACKGROUND

HIV-infected individuals have high rates of atherosclerosis. Endothelial dysfunction is central to atherogenesis and is one possible mechanism underlying this increased cardiovascular risk. ADMA is an endogenous inhibitor of endothelial nitric oxide synthase. Among uninfected individuals, higher ADMA levels predict cardiovascular events and mortality. The association between HIV infection, HIV-related factors, and ADMA has not been well described.

METHODS

We compared ADMA in 248 HIV-infected individuals and 50 uninfected controls. We performed multivariable analysis using traditional cardiovascular and HIV-specific factors as covariates to identify factors associated with ADMA.

RESULTS

HIV-infected men were older, less often Caucasian, more hypertensive, and had lower HDL than uninfected men. The median duration of HIV infection was 13 years, median CD4+ count was 592 cells/μL, 76% had an undetectable viral load, and 76% were on antiretroviral therapy. ADMA levels were modestly higher in HIV-infected individuals than controls [median (IQR): 0.46 μM (0.41-0.52) vs. 0.44 μM (0.38-0.46), p = 0.019], but the association lost statistical significance after controlling for cardiovascular risk factors (+0.028 μM, p = 0.054). Lower CD4+ count and both detectable and higher viral load were independently associated with increased ADMA.

CONCLUSIONS

ADMA levels were modestly elevated in the setting of HIV infection. Notably, a greater HIV-associated inflammatory burden, as evidenced by lower CD4+ counts and higher viral loads, was associated with increased ADMA levels. Our findings suggest that HIV infection impairs endothelial function and predisposes to atherosclerosis through chronic inflammation and subsequent accumulation of ADMA.

Atherosclerosis is consistently higher among the HIV-positive patients, with or without treatment, than among the HIV-negative population. Risk factors linked to atherosclerotic cardiovascular disease in HIV infection are both traditional and HIV specific although the underlying mechanisms are not fully delineated. Three key sequential biological processes are postulated to accelerate progression of atherosclerosis in the context of HIV: (1) inflammation, (2) transformation of monocytes to macrophages and then foam cells, and (3) apoptosis of foam cells leading to plaque development through Ca(2+)-dependent endoplasmic reticulum stress. These proatherogenic mechanisms are further affected when HIV interacts with the genes involved in various phases within this network.

BACKGROUND

HIV infection has been associated with dyslipidemia, insulin resistance, and changes in body composition, including loss of subcutaneous fat and skeletal muscle, with relative sparing of upper trunk and visceral fat. Because of its resemblance to Cushing's syndrome, caused by glucocorticoid excess, we hypothesized that variations in the glucocorticoid receptor (GR) gene, associated with changes in sensitivity to glucocorticoids, may be associated with such abnormalities in HIV-infected patients.

DESIGN

This was a cross-sectional genetic association study.

MATERIALS AND METHODS

GR polymorphisms were determined in HIV-infected participants from the study of Fat Redistribution and Metabolic Change in HIV Infection (FRAM). We created haplotypes in 754 participants and assessed the associations with fasting metabolic parameters and body composition by MRI.

RESULTS

After stratification for ethnicity, we found no consistent pattern of associations between the described GR haplotypes and body composition or metabolic parameters in HIV-infected patients. However, we found a new haplotype comprising the Tth111I polymorphism in African-Americans. Heterozygous carriers of this haplotype (n=24) had significantly higher levels of high-density lipoprotein cholesterol compared with age-matched and sex-matched noncarriers (n=96) (median 55 vs. 44 mg/dl, P=0.026) and a tendency toward lower glucose (-5 mg/dl) and triglyceride (-21 mg/dl) levels and lower visceral adipose tissue mass (-0.22 l). CD4 count as well as skeletal muscle mass were also lower in carriers of this haplotype (-154 cells/μl and -1.6 l, respectively).

CONCLUSION

Although our cohort included only a small number of carriers of the new Tth111I haplotype, these results are suggestive that this GR haplotype may be associated with a healthier metabolic profile in African-Americans with HIV infection.

Atherosclerosis is an inflammatory disease that is accelerated in human immunodeficiency virus (HIV) infection. Individuals with HIV infection have an activated type I interferon (IFN) monocyte phenotype, which may enhance uptake of modified low-density lipoprotein (LDL) thereby initiating a prefoam cell pathology and recruitment into atherosclerotic plaques. In a sampling of HIV-infected subjects, an increase in monocyte activation genes, MX1 and CXCL10, correlated with monocyte expression of the scavenger receptor A (SR-A), a major receptor for lipid uptake and foam cell formation. Monocytes from HIV-infected subjects accumulated more lipid than control uninfected subjects. We modeled increased activation in HIV infection by priming human monocytes with IFNα followed by exposure to acetylated LDL (acLDL). Exposure to IFNα increased acLDL uptake, which generated increased cellular reactive oxygen species (ROS). We posit that HIV infection augments formation of arterial plaques by triggering monocyte activation with a type I IFN profile, which induces SR-A expression, lipid uptake, and subsequent ROS production. These findings may explain in part why HIV-infected individuals with chronic immune activation have an increased risk of atherosclerosis.

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with a 2-4 fold increased risk of developing Type 2 diabetes mellitus. However, detailed assessments of glucose metabolism and insulin secretion in a study designed to minimize confounders are lacking. Furthermore, few studies examine potential mechanisms involved. We analyzed data from a case-control study of medically healthy, medication-free adults to determine whether individuals with PTSD had abnormal glucose or insulin response to oral glucose tolerance test (OGTT) compared to controls. Secondarily, we assessed potential mediators such as sleep, cortisol and adiponectin.

METHODS

Data was analyzed from 92 age and gender-matched subjects (44 PTSD, 48 controls). Chronic PTSD was diagnosed using the Structured Clinical Interview for DSM-IV and Clinician Administered PTSD Scale. Subjects underwent 75-g OGTT, actigraphy and sleep diary (to quantify sleep duration), polysomnography (to assess slow wave sleep [SWS] and delta power), and overnight blood sampling (for cortisol and adiponectin).

RESULTS

At baseline, individuals with PTSD had mildly increased insulin levels (by 19%, compared to controls, p=0.048) that was mediated primarily by weight. In response to OGTT, the PTSD group had higher levels of insulin at 120 min (by 44%, p=0.03) and insulin AUC (by 43%, p=0.015) compared to controls, after adjusting for confounders. Glucose levels were similar in the two groups. Although self-reported sleep duration, SWS, and delta power differed between PTSD subjects and controls, they did not mediate the effects of PTSD status on insulin response.

CONCLUSION

In this case-control study, individuals with PTSD had a hyperinsulinemic response to oral glucose challenge compared to controls, suggestive of insulin resistance.