Publications

Activation of macrophages by TLR agonists enhances foam cell formation, but the underlying mechanisms are not understood. We examined the effects of TLR agonists on ADRP/ADFP, a protein associated with forming lipid droplets, and Mal1 a fatty acid-binding protein, in two mouse macrophage cell lines and human monocytes. Low doses of LPS, a TLR4 agonist increased both mRNA and protein levels of ADRP/ADFP and Mal1 in RAW 264.7 macrophages. Following pretreatment with Intralipid, fatty acids, or acetyl-LDL to increase triglyceride or cholesterol ester storage, LPS treatment still increased ADRP/ADFP and Mal1 mRNA levels. LPS also induced ADRP/ADFP and Mal1 in J774 macrophages and ADRP/ADFP in human monocytes. Zymosan, a fungal product that activates TLR2, poly-I:C, a viral mimetic that activates TLR3, and imiquimod, a TLR7 agonist, also increased ADRP/ADFP. Zymosan, but not poly-I:C or imiquimod, induced Mal1. In contrast, neither gene was induced by TNFalpha, IL-1beta, IL-6, or interferon-gamma. Thus TLR agonists induce ADRP/ADFP and Mal1, which likely contributes to macrophage triglyceride and cholesterol ester storage leading to foam cell formation.

BACKGROUND

The effects of different HIV protease inhibitors (PIs) on peripheral insulin resistance have been described, but less is known about their effects on insulin suppression of endogenous glucose production (EGP).

METHODS

We tested the acute effects of 3 PIs, indinavir, ritonavir, and amprenavir, on EGP quantified by stable isotope techniques during the hyperinsulinemic, euglycemic clamp in 3 similar placebo-controlled protocols.

RESULTS

EGP was higher with indinavir in the hyperinsulinemic state than with placebo (4.1 +/- 1.3 vs. 2.2 +/- 0.8 microg x kg(-1) x min(-1), P = 0.04). A trend toward higher EGP was seen with ritonavir (3.6 +/- 0.3 vs. 3.0 +/- 0.5 microg x kg(-1) x min(-1), P = 0.08). There was no evidence that amprenavir blunted insulin suppression of EGP compared with placebo (2.9 +/- 0.04 vs. 3.2 +/- 0.7 microg x kg(-1) x min(-1), P = 0.63).

CONCLUSIONS

Some PIs can acutely blunt the ability of insulin to suppress EGP, but, as with insulin resistance, the effects of PIs on EGP are drug-specific, not class-specific.

The acute phase response is characterized by elevations in serum triglyceride levels due to both an increase in hepatic VLDL production and a delay in the clearance of triglyceride rich lipoproteins secondary to a decrease in lipoprotein lipase (LPL) activity. Recently there has been a marked increase in our understanding of factors that regulate LPL activity. GPIHBP1 facilitates the interaction of LPL and lipoproteins thereby allowing lipolysis to occur. Angiopoietin like proteins (ANGPTL) 3 and 4 inhibit LPL activity. In the present study, treatment of mice with LPS, an activator of TLR4 and a model of Gram-negative infections, did not alter the expression of GPIHBP1 in heart or adipose tissue. However, LPS decreased the expression of ANGPTL3 in liver and increased the expression of ANGPTL4 in heart, muscle, and adipose tissue. Serum ANGPTL4 protein levels were markedly increased at 8 and 16h following LPS treatment. Administration of zymosan, an activator of TLR2 and a model of fungal infections, also increased serum ANGPTL4 protein and mRNA levels in liver, heart, muscle, and adipose tissue. Finally, treatment of 3T3-L1 adipocytes with LPS or cytokines (TNF alpha, IL-1 beta, and interferon gamma) stimulated ANGPTL4 expression. These studies demonstrate that ANGPTL4 is a positive acute phase protein and the increase in ANGPTL4 could contribute to the hypertriglyceridemia that characteristically occurs during the acute phase response by inhibiting LPL activity.

BACKGROUND

HIV protease inhibitors have been shown to worsen glucose and lipid metabolism. Recent studies have suggested that protease inhibitors can impair insulin secretion in HIV-infected patients. We studied the effects of the protease inhibitor combination lopinavir and ritonavir on insulin secretion, insulin sensitivity, and lipid metabolism in HIV-negative persons.

METHODS

A combination dose of lopinavir 400 mg and ritonavir 100 mg was given twice daily to eight HIV-seronegative men for 4 weeks. Fasting glucose, insulin, lipid, and lipoprotein profiles; oral glucose tolerance; insulin secretion and insulin-mediated glucose disposal by hyperglycemic clamp; and body composition by dual energy X-ray absorptiometry were determined before and after lopinavir/ritonavir administration.

RESULTS

There was no change in first-phase insulin secretion (2.82 +/- 0.30 versus 2.71 +/- 0.31 nmol/l; P = 0.60), as well as fasting insulin and glucose levels, oral glucose tolerance, or insulin-mediated glucose disposal after 4 weeks administration of lopinavir/ritonavir. However, there were significant increases in fasting triglycerides (1.02 +/- 0.13 versus 2.20 +/- 0.31 mmol/l; P = 0.001), total cholesterol (4.42 +/- 0.30 versus 5.70 +/- 0.60 mmol/l; P = 0.007), and apo B-100 levels (0.86 +/- 0.07 versus 1.07 +/- 0.11 g/l; P = 0.0009). High-density lipoprotein cholesterol decreased (0.99 +/- 0.11 versus 0.82 +/- 0.10 mmol/l; P = 0.005). There were no changes in body composition, weight, or body fat.

CONCLUSION

Although administration of lopinavir/ritonavir to healthy, HIV-seronegative volunteers for 4 weeks resulted in increased triglyceride and decreased high-density lipoprotein cholesterol levels, there was no change in first-phase insulin secretion during the hyperglycemic clamp. The reported effects of protease inhibitor on insulin secretion in HIV-infected individuals may be due to changes in HIV-related factors and not a direct drug effect.

BACKGROUND

Distal coronary artery disease (CAD) is less amenable to surgery or stenting compared with proximal disease. However, little is known about the epidemiology of distal versus proximal CAD.

METHODS

We determined the prevalence and factors associated with proximal, mid, and distally located plaque in the left anterior descending, left circumflex, and right coronary arteries in 418 subjects without prior CAD history who underwent coronary computed tomographic angiography for symptoms or stress test results. Clinical characteristics and coronary artery calcium (CAC) scores were also determined.

RESULTS

Most subjects (88%) had plaque, but only 18% of plaques were associated with stenosis >50%. In subjects with single-vessel plaque, only 7% had distal plaque, whereas 75% had proximal plaque. With 3-vessel plaque, 70% had distal and 100% had proximal plaques. Of subjects with a single location of plaque along a vessel, most had proximal plaque (69%); isolated distal-vessel plaque was rare (2%). Distal plaque was dominantly found in association with both proximal and mid plaque (88%). After multivariable adjustment for demographics, traditional, and nontraditional risk factors, both increasing number of vessels with plaque and clinically significant CAC scores were independently associated with higher odds of distal plaque, whereas associations of traditional risk factors were weaker. Distal plaque was independently associated with stenosis > 50%.

CONCLUSION

These data support the concept that early lesions are most often proximal and that CAC scoring may be a poor screening tool for detecting proximal disease. Furthermore, distal lesions are more associated with advanced disease than with traditional cardiovascular risk factors.

Carbohydrate response element binding protein (ChREBP) is a recently discovered transcription factor whose levels and activity are increased by glucose leading to the activation of target genes, which include acetyl-CoA carboxylase, fatty acid synthase, and liver-type pyruvate kinase. Here, we demonstrate that lipopolysaccharide (LPS) treatment causes a marked decrease in ChREBP mRNA and protein levels in the liver of mice fed a normal chow diet or in mice fasted for 24 h and then re-fed a high carbohydrate diet. This decrease occurs rapidly and is a sensitive response (half-maximal dose 0.1 μg/mouse). The decrease in ChREBP is accompanied by a decrease in the expression of ChREBP target genes. Zymosan and turpentine treatment also decrease hepatic ChREBP levels and the expression of its target genes. Additionally, tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) decrease liver ChREBP expression both in vivo and in Hep3B cells in culture. Finally, LPS decreased ChREBP expression in muscle and adipose tissue. These studies demonstrate that ChREBP is down-regulated during the acute phase response resulting in alterations in the expression of ChREBP regulated target genes. Thus, ChREBP joins a growing list of transcription factors that are regulated during the acute phase response.

BACKGROUND

The role of host genetics in the development of subclinical atherosclerosis in the context of HIV-infected persons who are being treated with highly active antiretroviral therapy (HAART) is not well understood.

METHODS

The present genome-wide association study (GWAS) is based on 177 HIV-positive Caucasian males receiving HAART who participated in the Fat Redistribution and Metabolic Change in HIV Infection (FRAM) Study. Common and internal carotid intima-media thicknesses (cIMT) measured by B-mode ultrasound were used as a subclinical measure of atherosclerosis. Single nucleotide polymorphisms (SNPs) were assayed using the Illumina HumanCNV370-quad beadchip. Copy Number Variants (CNV) were inferred using a hidden Markov Model (PennCNV). Regression analyses were used to assess the association of common and internal cIMT with individual SNPs and CNVs, adjusting for age, duration of antiretroviral treatment, and principal components to account for potential population stratification.

RESULTS

Two SNPs in tight linkage disequilibrium, rs2229116 (a missense, nonsynonymous polymorphism (IIe to Val)) and rs7177922, located in the ryanodine receptor (RYR3) gene on chromosome 15 were significantly associated with common cIMT (P-value < 1.61 x 10). The RYR gene family has been known to play a role in the etiology of cardiovascular disease and has been shown to be regulated by HIV TAT protein.

CONCLUSION

These results suggest that in the context of HIV infection and HAART, a functional SNP in a biologically plausible candidate gene, RYR3, is associated with increased common carotid IMT, which is a surrogate for atherosclerosis.

Systematic differences between readers or equipment in imaging studies are not uncommon; failure to account for such differences when using Carotid Ultrasonography may introduce bias into associations between carotid intima media thickness (cIMT) and outcomes. We demonstrate the impact of this source of systematic measurement error (SME) using data on 5,521 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) and 661 participants from the Study of Fat Redistribution and Metabolic Change in HIV Infection (FRAM). Participants were between 37 and 78 years old. Two outcomes were considered: (1) the effect of HIV infection on cIMT (between study) and (2) the association of cIMT with cardiovascular events (within study). All estimates were adjusted for demographics (age, gender, and ethnicity) and for traditional cardiovascular disease risk factors (smoking, blood pressure, diabetes and cholesterol). When comparing the FRAM and MESA cohorts to estimate the association of HIV infection on common cIMT, accounting for machine and reader variability (between study variability) reduced the difference associated with HIV infection from +0.080 mm (95% Confidence Interval (CI):0.065-0.095) to +0.037 mm (95% CI:0.003 to 0.072) while internal cIMT declined from +0.254 mm (95% CI:0.205-0.303) to +0.192 mm (95% CI:0.076-0.308). Attenuation of the association between cIMT and cardiovascular endpoints occurred when within study reader variability was not accounted for. The effect of SME due to use of multiple readers or machines is most important when comparisons are made between two different study populations. Within-cohort measurement error dilutes the association with events.

CONTEXT

HIV-infected patients on antiretroviral therapy are at increased risk for excess visceral adiposity and insulin resistance. Treatment with GH decreases visceral adiposity but worsens glucose metabolism. IGF-I, which mediates many of the effects of GH, improves insulin sensitivity in HIV-negative individuals.

OBJECTIVE

Our objective was to determine whether IGF-I, complexed to its major binding protein, IGF-binding protein-3 (IGFBP-3), improves glucose metabolism and alters body fat distribution in HIV-infected patients with abdominal obesity and insulin resistance.

METHODS

We conducted a pilot, open-label study in 13 HIV-infected men with excess abdominal adiposity and insulin resistance to assess the effect of 3 months of treatment with IGF-I/IGFBP-3 on glucose metabolism and fat distribution. Glucose metabolism was assessed by oral glucose tolerance test and hyperinsulinemic-euglycemic clamp. Endogenous glucose production (EGP), gluconeogenesis, whole-body lipolysis, and de novo lipogenesis (DNL) were measured with stable isotope infusions. Body composition was assessed by dual-energy x-ray absorptiometry and abdominal computed tomography scan.

RESULTS

Glucose tolerance improved and insulin-mediated glucose uptake increased significantly during treatment. EGP increased under fasting conditions, and suppression of EGP by insulin was blunted. Fasting triglycerides decreased significantly in association with a decrease in hepatic DNL. Lean body mass increased and total body fat decreased, whereas visceral adipose tissue did not change.

CONCLUSIONS

Treatment with IGF-I/IGFBP-3 improved whole-body glucose uptake and glucose tolerance, while increasing hepatic glucose production. Fasting triglycerides improved, reflecting decreased DNL, and visceral adiposity was unchanged.