Publications

BACKGROUND

Some HIV protease inhibitors (PIs), including full-dose ritonavir (800 mg) and ritonavir-boosted lopinavir, acutely induce insulin resistance in the absence of HIV infection and changes in body composition. Boosting dose ritonavir (100-200 mg) is the most commonly prescribed PI, yet its effects on glucose metabolism have not been described in the absence of another PI.

METHODS

In this randomized, double-blind, cross-over study, a single dose of ritonavir 200 mg or placebo was given to healthy HIV-seronegative volunteers before assessment of insulin sensitivity by euglycemic hyperinsulinemic clamp.

RESULTS

Boosting dose ritonavir had no effect on insulin-mediated glucose disposal (M/I, placebo: 8.59 ± 0.83 vs. ritonavir: 8.51 ± 0.64 mg/kg per minute per μU/mL insulin, P = 0.89).

CONCLUSIONS

A single boosting dose of ritonavir does not alter insulin sensitivity, suggesting lopinavir is likely responsible for the induction of insulin resistance demonstrated in prior short-term studies of lopinavir/ritonavir. There is a dose-dependent effect of ritonavir on insulin sensitivity.

OBJECTIVE

to assess the associations between nucleoside reverse transcriptase inhibitors (NRTIs) and change in lipid levels among a large cohort of HIV-infected patients in routine clinical care initiating their first potent antiretroviral regimen.

DESIGN

longitudinal observational cohort study from the Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) cohort.

METHODS

we used generalized estimating equations to examine the association between NRTIs and lipids accounting for within-patient correlations between repeated measures and key clinical and demographic characteristics including other antiretroviral medications.

RESULTS

among 2267 individuals who started their first antiretroviral regimen, tenofovir with emtricitabine or lamivudine was associated with lower levels for total cholesterol, low-density lipoprotein (LDL), triglycerides, non-high-density lipoprotein (HDL), and HDL, compared with other NRTI pairs in adjusted analyses. LDL levels were highest among patients receiving didanosine/lamivudine. Triglyceride levels were highest in stavudine/lamivudine users. HDL levels were highest among patients receiving didanosine/stavudine. Hepatitis C infection and younger age were also associated with lower lipid levels.

CONCLUSION

we found clinically important heterogeneity within the NRTI class of antiretroviral medications regarding their effect on lipid levels over time. Although the lipid profile of tenofovir with emtricitabine or lamivudine appeared to be less pro-atherogenic in this large longitudinal study of HIV-infected patients in routine clinical care, there was no association with beneficial HDL levels. In general, the change in lipid levels associated with most antiretroviral agents, particularly those NRTI combinations currently in common use, are relatively modest. Additional studies are needed to understand the long-term implications of these findings on cardiovascular disease risk.

OBJECTIVE

Patients with RA have systemic inflammation and increased risk of cardiovascular (CV) events, including thrombosis. Levels of fibrinogen, a pro-thrombotic protein with predictive value for CV disease (CVD), are elevated during systemic inflammation. We compared circulating fibrinogen levels in patients with RA with healthy controls and evaluated the relationship with measures of disease activity.

METHODS

Patients with RA and controls were recruited at the University of California, San Francisco (UCSF). Disease activity was evaluated using standard composite indices. Fibrinogen, ESR, serum CRP, acute-phase serum amyloid A and levels of selected cytokines were quantified.

RESULTS

A total of 105 RA patients and 62 controls were studied. Among patients with RA, disease activity ranged from quiescent to highly active disease. Circulating fibrinogen levels were significantly higher in RA than in controls [median (interquartile range) 466 (391-575) vs 367 (309-419) mg/dl, respectively, P < 0.0001]. This difference remained highly statistically significant after adjustment for demographic variables and BMI. Although fibrinogen correlated significantly with clinical measures of disease activity, significantly elevated levels were observed at low levels of activity, even in RA patients with no detectable swollen or tender joints. In multivariable models, ~ 80% of the increased fibrinogen in RA was accounted for by increases in CRP and ESR.

CONCLUSION

Circulating levels of fibrinogen are elevated in RA and correlated with markers of inflammation, but only modestly correlate with clinical assessments of disease activity. Even RA patients with excellent clinical disease control exhibit elevated levels compared with controls.

Inhibition of adipocyte triglyceride biosynthesis is required for fatty acid mobilization during inflammation. Triglyceride biosynthesis requires glycerol 3-phosphate and phosphoenolpyruvate carboxykinase (PEPCK) plays a key role. We demonstrate that LPS, zymosan, and TNF-α decrease PEPCK in liver and fat. Turpentine decreases PEPCK in liver, but not in fat. The LPS-induced decrease in PEPCK does not occur in TLR4 deficient animals, indicating that this receptor is required. The LPS-induced decrease in hepatic PEPCK does not occur in TNF receptor/IL-1 receptor knockout mice, but occurs in fat, indicating that TNF-α/IL-1 is essential for the decrease in liver but not fat. In 3T3-L1 adipocytes TNF-α, IL-1, IL-6, and IFNγ inhibit PEPCK indicating that there are multiple pathways by which PEPCK is decreased in adipocytes. The binding of PPARγ and RXRα to the PPARγ response element in the PEPCK promoter is markedly decreased in adipose tissue nuclear extracts from LPS treated animals. Lipopolysaccharide and zymosan reduce PPARγ and RXRα expression in fat, suggesting that a decrease in PPARγ and RXRα accounts for the decrease in PEPCK. Thus, there are multiple cytokine pathways by which inflammation inhibits PEPCK expression in adipose tissue which could contribute to the increased mobilization of fatty acids during inflammation.

OBJECTIVE AND DESIGN

The aim of this study was to examine the expression of G protein-coupled receptor 81 (GPR81) in mouse adipose tissue in response to inflammatory stimuli. GPR81 is activated by lactate resulting in the inhibition of lipolysis.

MATERIALS AND TREATMENT

Mice were injected with saline, lipopolysaccharide (LPS), zymosan, or turpentine, N = 5 per group. 3T3-L1 adipocytes were treated with tumor necrosis factor alpha, interleukin (IL)-l beta, IL-6, or interferon gamma.

METHODS

GPR81 expression levels were measured by real-time PCR and statistical significance was determined by Student's t test.

RESULTS

LPS resulted in a marked decrease in GPR81 mRNA level in mouse adipose tissue in C57BL/6 and OuJ mice, an effect that was not observed in HeJ mice, which have a mutation in TLR4. Zymosan and turpentine also decreased adipose tissue GPR81 expression. Cytokine treatment of 3T3-L1 adipocytes had no effect on GPR81 expression. GPR81 expression was decreased in ob/ob mice, an animal model of type 2 diabetes that is characterized by inflammation.

CONCLUSION

Inflammation decreases the expression of GPR81 in adipose tissue.

OBJECTIVE

Genetic studies may help explain abnormalities of fat distribution in HIV-infected patients treated with antiretroviral therapy (ARV).

METHODS

Subcutaneous adipose tissue (SAT) volume measured by MRI in the leg, the lower trunk, the upper trunk, and the arm was examined in 192 HIV-infected White men, ARV-treated from the Fat Redistribution and Metabolic Change in HIV infection study. Single-nucleotide polymorphisms were assayed using the Illumina Human CNV370-quad beadchip. Multivariate and univariate genome-wide association analyses of the four SAT depots were implemented in PLINK software adjusted for age and ARV duration. Functional annotation analysis using Ingenuity Systems Pathway Analysis tool was carried out for markers with P lower than 10(-3) near known genes identified by multivariate analysis.

RESULTS

Loci (rs10504906, rs13267998, rs921231) in or near the anion exchanger solute carrier family 26, member 7 isoform a (SLC26A7) were strongly associated with the upper trunk and the arm SAT (9.8×10(-7) ≤P<7.8×10(-6)). Loci (rs193139, rs7523050, rs1761621) in and near a gene-rich region including G-protein-signaling modulator 2 (GPSM2) and syntaxin-binding protein 3 (STXBP3) were significantly associated with the lower body SAT depots (9.9×10(-7) ≤P<9.5×10(-6)). GPSM2 is associated with cell division and cancer whereas STXBP3 is associated with glucose metabolism in adipoctyes. Ingenuity Systems Pathway Analysis identified atherosclerosis, mitochondrial function, and T-cell-mediated apoptosis as processes related to SAT volume in HIV-infected individuals (P<5×10(-3)).

CONCLUSION

Our results are limited by the small sample size and replication is needed; however, this genomic scan uncovered new genes associated with metabolism and inflammatory pathways that may affect SAT volume in ARV-treated HIV-infected patients.

CONTEXT

An increasing number of studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Our previous study of Caucasian women demonstrated that there is an inverse relationship between BMAT and whole-body bone mineral density (BMD). It is unknown whether visceral adipose tissue (VAT), sc adipose tissue (SAT), and skeletal muscle had an effect on the relationship between BMAT and BMD.

OBJECTIVE

In the present study we investigated the relationship between pelvic, hip, and lumbar spine BMAT with hip and lumbar spine BMD in the population-based Coronary Artery Risk Development in Young Adults (CARDIA) sample with adjustment for whole-body magnetic resonance imaging (MRI)-measured VAT, SAT, and skeletal muscle.

DESIGN

T1-weighted MRI was acquired for 210 healthy African-American and Caucasian men and women (age 38-52 yr). Hip and lumbar spine BMD were measured by dual-energy x-ray absorptiometry.

RESULTS

Pelvic, hip, and lumbar spine BMAT had negative correlations with hip and lumbar spine BMD (r = -0.399 to -0.550, P < 0.001). The inverse associations between BMAT and BMD remained strong after adjusting for demographics, weight, skeletal muscle, SAT, VAT, total adipose tissue (TAT), menopausal status, lifestyle factors, and inflammatory markers (standardized regression coefficients = -0. 296 to -0.549, P < 0.001). Among body composition measures, skeletal muscle was the strongest correlate of BMD after adjusting for BMAT (standardized regression coefficients = 0.268-0.614, P < 0.05), with little additional contribution from weight, SAT, VAT, or total adipose tissue.

CONCLUSION

In this middle-aged population, a negative relationship existed between MRI-measured BMAT and hip and lumbar spine BMD independent of demographics and body composition. These observations support the growing evidence linking BMAT with low bone density.

BACKGROUND

Excess risk of cardiovascular disease occurs in effectively treated individuals with human immunodeficiency virus (HIV) infection. Although elevated plasma D-dimer levels are associated with increased morbidity and mortality, the impact of HIV infection on coagulation in vivo has not been well studied.

METHODS

We measured D-dimers, antithrombin, endogenous thrombin potential (ETP; a functional measure of thrombin generation in vitro), thrombin/antithrombin complexes (TAT; a measure of thrombin generation in vivo), tissue factor, prothrombin fragment 1 + 2 (F1+2), and normalized APC sensitivity ratio (nAPCsr) in 199 HIV-positive men who were receiving antiretroviral therapy and had an undetectable HIV RNA level, in 79 HIV-positive untreated men, and in 39 uninfected controls.

RESULTS

Median antithrombin levels were higher while the ETP was lower among HIV-infected adults (treated and untreated), compared with controls. There were few differences between coagulation markers in the 2 HIV groups. Compared with controls, the nAPCsr was lower in treated men and the TAT level was lower in untreated individuals. We observed little difference among measured levels of D-dimer, tissue factor, or F1+2 between HIV-infected individuals and controls. Antiretroviral therapy exposure was associated with a lower antithrombin level, a lower nAPCsr, and a lower ETP, while history of opportunistic infection was associated with a higher nAPCsr.

CONCLUSIONS

HIV infection is associated with decreased thrombin generation, as measured by the ETP, and an increased antithrombin level. These data suggest that HIV infection may not be associated with increased propensity toward clotting, as has been suggested on the basis of isolated measures of D-dimer levels.

The acute phase response (APR) produces marked alterations in lipid and carbohydrate metabolism including decreasing plasma ketone levels. Fibroblast growth factor 21 (FGF21) is a recently discovered hormone that regulates lipid and glucose metabolism and stimulates ketogenesis. Here we demonstrate that lipopolysaccharide (LPS), zymosan, and turpentine, which induce the APR, increase serum FGF21 levels 2-fold. Although LPS, zymosan, and turpentine decrease the hepatic expression of FGF21, they increase FGF21 expression in adipose tissue and muscle, suggesting that extrahepatic tissues account for the increase in serum FGF21. After LPS administration, the characteristic decrease in plasma ketone levels is accentuated in FGF21-/- mice, but this is not due to differences in expression of carnitine palmitoyltransferase 1α or hydroxymethyglutaryl-CoA synthase 2 in liver, because LPS induces similar decreases in the expression of these genes in FGF21-/- and control mice. However, in FGF21-/- mice, the ability of LPS to increase plasma free fatty acid levels is blunted. This failure to increase plasma free fatty acid could contribute to the accentuated decrease in plasma ketone levels because the transport of fatty acids from adipose tissue to liver provides the substrate for ketogenesis. Treatment with exogenous FGF21 reduced the number of animals that die and the rapidity of death after LPS administration in leptin-deficient ob/ob mice and to a lesser extent in control mice. FGF21 also protected from the toxic effects of cecal ligation and puncture-induced sepsis. Thus, FGF21 is a positive APR protein that protects animals from the toxic effects of LPS and sepsis.