To examine the hypothesis that insulin resistance (IR) decreases circulating concentrations of NT-pro brain natriuretic peptide (BNP).
Obesity, despite being a risk factor for heart failure (HF), is paradoxically associated with lower concentrations of BNP, a marker of myocardial stress. Low BNP in obesity is postulated to be due to IR; however, it has been difficult to define the role of IR independent of obesity. IR in rheumatoid arthritis (RA) is increased, independent of obesity, thus allowing potential mechanistic insights into the relationship between IR and BNP.
We measured demographic factors, traditional cardiovascular risk factors, body mass index (BMI), markers of inflammation (interleukin-6 (IL-6), C-reactive protein (CRP), tumor necrosis factor α (TNFα)), NT-pro-BNP, and IR by the homeostatic model assessment (HOMA) in 140 patients with RA and 82 control subjects. Patients with heart failure and coronary artery disease were excluded. We used multiple linear regression models to examine the relationship between HOMA and NT-pro-BNP in RA and controls, and in RA alone, the additional effect of inflammation.
As previously reported, NT-pro-BNP concentrations were higher in RA (median 80.49 pg/mL, IQR (23.67–167.08 pg/mL) than controls (17.84 pg/mL (3.28–36.28 pg/mL)) (P<0.001), and the prevalence of IR, defined by HOMA>2.114, was higher among RA than controls (53% vs. 15%, P>0.001). HOMA was positively correlated with NT-pro-BNP (rho=0.226, P=0.007) in RA, but not in controls (rho=−0.154, P=0.168). In a multivariable model adjusted for age, race and sex, we found that increasing HOMA was statistically associated with increasing NT-pro-BNP concentrations in RA (P=0.001), but not controls (P=0.543) (P for interaction = 0.036). In RA subjects, when IL-6 was further included in the model, IL-6 (P=0.0014), but not HOMA (P=0.43), remained significantly associated with NT-pro-BNP, suggesting that IL-6 may be mechanistically involved in the relationship between IR and NT-pro-BNP in RA.
We conclude that in patients with RA, insulin resistance is associated with higher, rather than the expected lower, concentrations of NT-pro-BNP and that this may be related to increased IL-6.
We tested the hypothesis that initiation of TNFα antagonists reduced the risk of fractures compared to nonbiologic comparator in patients with autoimmune diseases.
Using four large administrative databases, we assembled retrospective cohorts of patients with autoimmune diseases who initiated either a TNFα antagonist or a nonbiologic medication. We identified 3 mutually exclusive disease groups: rheumatoid arthritis (RA); inflammatory bowel disease (IBD); and psoriasis, psoriatic arthritis or ankylosing spondylitis (PsO-PsA-AS). We used baseline covariate data to calculate propensity scores (PS) for each disease group and used Cox regression to calculate hazard ratios (HR) and 95% confidence intervals (95%CI). We compared the risk of combined hip, radius/ulna, humerus, or pelvic fractures between PS-matched cohorts of new users of TNFα antagonists and nonbiologic comparator.
We identified 9,020, 2,014 and 2,663 new PS matched episodes of TNFα antagonist and nonbiologic comparator use in RA, IBD and PsO-PsA-AS cohorts, respectively. The risk of combined fractures was similar between new users of TNFα antagonists and nonbiologic comparators for each disease (HR: 1.17, 95%CI [0.91, 1.51]; HR: 1.49, 95%CI [0.72, 3.11]; and HR: 0.92, 95%CI [0.47, 1.82] for RA, IBD and PsO-PsA-AS, respectively). In RA, the risk of combined fractures was associated with an average daily dose of prednisone equivalents >10 mg/day at baseline compared with no glucocorticoid (HR: 1.54, 95%CI [1.03, 2.30]).
The risk of fractures did not differ between initiators of a biologic and a nonbiologic comparator for any disease studied. Among RA patients, use of >10mg/day of prednisone equivalents at baseline increased the fracture risk.
Our aims were to evaluate the effects of polymorphisms in the hepatic drug uptake transporter organic anion transporting polypeptide 1B1 (OATP1B1, SLCO1B1) and efflux transporters multidrug resistance-associated protein 2 (MRP2, ABCC2), bile salt export pump (BSEP, ABCB11), and breast cancer-related protein (BCRP, ABCG2) on single-dose pravastatin pharmacokinetics in healthy European- and African-American participants.
The pharmacokinetics of a single oral 40mg dose of pravastatin was determined in 107 participants (69 European-Americans and 38 African-Americans). Participants were genotyped for known OATP1B1, MRP2, BSEP, and BCRP polymorphisms. Baseline serum total and unconjugated plasma bilirubin concentrations were also determined.
OATP1B1 genotypes were ethnicity-dependent with a 521C allele frequency of ~15% in European-Americans and ~1% in African-Americans. SLCO1B1 521TC genotype was associated with significantly higher pravastatin area under the curve [AUC(0–5)] (P =0.01) and Cmax values (P< 0.05). When analyzed by diplotype, SLCO1B1*1a/*15 (N =8) participants exhibited 45 and 80% higher AUC values than SLCO1B1*1a/*1a (N=29) (P=0.013) and SLCO1B1*1b/*1b (N=34) (P=0.001) carriers, respectively. SLCO1B1*15/*15 (N=2) participants exhibited 92 and 149% higher AUC values than SLCO1B1*1a/*1a (P=0.017) and SLCO1B1*1b/*1b (P= 0.011) carriers, respectively. European-Americans had significantly higher plasma pravastatin AUC(0–5) (P =0.01) and Cmax values (P=0.009) than African-Americans. Neither ABCC2, ABCB11, nor ABCG2 genotypes were associated with differences in pravastatin pharmacokinetics. We did not observe an effect of SLCO1B1 genotype on baseline total or unconjugated bilirubin levels.
SLCO1B1 genotype, in particular the 521C allele, had a significant effect on the pharmacokinetics of pravastatin. Even when adjusted for the presence of the SLCO1B1 521C or 388G variant allele, European-Americans demonstrated significantly higher pravastatin AUC and Cmax values than African-Americans.
ABCB11; ABCC2; ABCG2; BCRP; bilirubin; BSEP; MRP2; OATP1B1; pharmacokinetics; pravastatin; SLCO1B1; transporter
Oxidative stress may play a role in the pathogenesis of depression. We tested the hypothesis that urinary F2 isoprostane, a robust marker of oxidative stress, was increased in patients with depression and associated with symptoms and response to treatment. Urinary F2 isoprostane was compared in 18 patients with depression and 36 age and sex matched control subjects. In patients, we tested the association between oxidative stress, depression questionnaires and antidepressant treatment. Urinary F2 isoprostane excretion was significantly higher in patients with depression than in control subjects. This association remained significant after adjustment for age, sex and BMI. Depression symptom severity scores were not correlated with F2 isoprostane excretion. Nine patients were treated with sertraline or bupropion for eight weeks. Depression severity rating scale scores decreased significantly and F2 isoprostane excretion increased. The increase in F2 isoprostane excretion was inversely correlated with the improvement in Hamilton Depression Rating 17 items. In conclusion, oxidative stress is increased in patients with depression. However, although treatment with either bupropion or sertraline reduces the symptoms of depression, it may increase F2 isoprostane excretion. These results suggest that alternative mechanisms, beyond oxidative stress, may be involved in the development of depression and subsequent responses to treatment.
depression; oxidative stress; F2 isoprostanes; antidepressants; sertraline; bupropion
African Americans have increased hemodynamic responses to both physiologic and pharmacologic adrenergic stimulation compared to Caucasians, and this may contribute to the greater prevalence of hypertension in this ethnic group. A small study suggested enhanced α1-adrenoreceptor-mediated arterial vasoconstriction in the forearm vasculature of African Americans compared to Caucasians, but it is unknown whether this reflects a generalized vascular phenomenon. The objective of this study was to examine the hypothesis that there are ethnic differences in venous α1-adrenoreceptor responsiveness. Using a linear variable differential transformer, we measured local dorsal hand vein responses to increasing doses of the selective α1-adrenoreceptor agonist, phenylephrine, in 106 subjects (64 Caucasians and 42 African Americans). There was wide interindividual variability in responses to phenylephrine. The dose that produced 50% of maximal constriction (ED50) ranged from 11 to 5442 ng/min, and maximal venoconstriction (Emax) ranged from 13.5% to 100%. African Americans (geometric mean ED50=172 ng/min; 95% CI, 115 to 256 ng/min) were more sensitive to phenylephrine than Caucasians (310 ng/min; 95% CI, 222 to 434 ng/min; unadjusted P=0.026; adjusted P=0.003). Median Emax was slightly higher in African Americans (89%; IQR, 82% to 98%) compared to Caucasians (85%; IQR, 75% to 95%; P=0.07). Taken together with previous findings in arterial vessels, our results suggest a generalized increased sensitivity to α1-adrenoreceptor-mediated vasoconstriction in African Americans. Increased vascular α-adrenoreceptor sensitivity could predispose to hypertension, and future studies addressing this mechanism’s contribution to ethnic differences in the prevalence of hypertension will be of interest.
Alpha-1 adrenergic receptor; vasoconstriction; phenylephrine; ethnicity; hypertension
The opioid analgesic propoxyphene was withdrawn from the U.S. market in 2010, motivated by concerns regarding fatality in overdose and adverse cardiac effects, including prolongation of the QT interval. These concerns were based on case reports, summary vital statistics, and surrogate endpoint studies.
Using the linked Tennessee Medicaid database (1992–2007), we conducted a retrospective cohort study that compared risk of sudden cardiac, medication toxicity, and total out-of-hospital death for propopxyphene users with that for comparable nonusers of any prescribed opioid analgesic and users of hydrocodone, an opioid with similar indications. Cohort members had 1,873,500 propoxyphene prescriptions, 1,873,500 matched nonuser control periods and 936,750 matched hydrocodone prescriptions.
Current propoxyphene users had no increased risk for sudden cardiac death (versus nonusers: HR = 1.00 [0.81–1.23]; versus current hydrocodone users: HR = 0.91 [0.68–1.21]) but did have increased risk for medication toxicity deaths (versus nonusers: HR = 1.85 [1.07–3.19], p= 0.027; versus current hydrocodone users: HR = 2.10 [0.87–5.10], p = 0.100). Because toxicity deaths were a small proportion of study deaths, total out-of-hospital mortality differed by less than 10% between the study groups and was not significantly elevated for propoxyphene (versus nonusers: HR = 1.09[0.95–1.25]; versus current hydrocodone users: HR = 1.06 [0.87–1.29]).
Our findings support the concern that propoxyphene has greater toxicity in overdose but do not provide evidence that it increases the risk of sudden cardiac death.
To determine the relationship between foot ulcers, arterial calcification, and peripheral occlusive disease in patients with type 2 diabetes.
We performed a cross-sectional study on 162 patients with type 2 diabetes who underwent assessment of tibial artery calcification (TAC) by non-contrasted CT scan. Peripheral artery occlusive disease was assessed by angiography. Foot status including the presence or absence of ulcers was documented at presentation. A multivariable logistic regression model was used to evaluate the association between foot ulcers, arterial calcification, and the extent of peripheral atherosclerotic occlusive disease.
Patients with foot ulcers (n= 31) were more likely to be older and have a history of tobacco use. They were also more likely to have higher TAC scores (median [IQR]: 4324.6 [609.9, 11163.6] vs. 9.4 [0.0, 343.9], P < 0.001) and more advanced peripheral artery occlusive disease (occlusion index 5.5 [4.8, 6.4] vs. 2.2 [1.0, 3.6], P < 0.001. Foot ulcer was strongly associated with elevated TAC scores in a multivariable regression model (Odds ratio [95% CI] =2.76 [1.61, 4.75], P=0.0002).
There is a strong association between arterial calcification and diabetic foot ulcers that persists after adjusting for the extent of atherosclerosis in patients with type 2 diabetes.
diabetes; foot ulcer; artery calcification; atherosclerosis
α2-Adrenoceptors (α2-AR) mediate both constriction and dilatation of blood vessels. There is substantial inter-individual variability in dorsal hand vein (DHV) constriction responses to α2-AR agonist activation. Genetic factors appear to contribute significantly to this variation. The present study was designed to identify genetic factors contributing to the inter-individual variability in α2-AR-mediated vascular constriction induced by the selective α2-AR agonist dexmedetomidine.
DHV constriction responses to local infusion of dexmedetomidine were assessed by measuring changes in vein diameter with a linear variable differential transformer. The outcome variable was log-transformed dexmedetomidine ED50 for constriction. A genome-wide association study (GWAS) of 433,378 single nucleotide polymorphisms (SNPs) was performed for the sensitivity of DHV responses in 64 healthy Finnish subjects. 20 SNPs were selected based on the GWAS results and their associations with the ED50 of dexmedetomidine were tested in an independent North American study population of 68 healthy individuals.
In both study populations (GWAS and replication samples), the SNP rs9922316 in the gene for protein kinase C type β was consistently associated with dexmedetomidine ED50 for dorsal hand vein constriction (unadjusted p = 0.00016 for the combined population).
Genetic variation in protein kinase C type β may contribute to the inter-individual variation in dorsal hand vein constriction responses to α2-AR activation by the agonist dexmedetomidine.
receptors, adrenergic, alpha; dorsal hand vein; GWAS; candidate genes; dexmedetomidine
Genetic variants of the enzyme that metabolizes warfarin, cytochrome P-450 2C9 (CYP2C9), and of a key pharmacologic target of warfarin, vitamin K epoxide reductase (VKORC1), contribute to differences in patients’ responses to various warfarin doses, but the role of these variants during initial anticoagulation is not clear.
In 297 patients starting warfarin therapy, we assessed CYP2C9 genotypes (CYP2C9 *1, *2, and *3), VKORC1 haplotypes (designated A and non-A), clinical characteristics, response to therapy (as determined by the international normalized ratio [INR]), and bleeding events. The study outcomes were the time to the first INR within the therapeutic range, the time to the first INR of more than 4, the time above the therapeutic INR range, the INR response over time, and the warfarin dose requirement.
As compared with patients with the non-A/non-A haplotype, patients with the A/A haplotype of VKORC1 had a decreased time to the first INR within the therapeutic range (P = 0.02) and to the first INR of more than 4 (P = 0.003). In contrast, the CYP2C9 genotype was not a significant predictor of the time to the first INR within the therapeutic range (P = 0.57) but was a significant predictor of the time to the first INR of more than 4 (P = 0.03). Both the CYP2C9 genotype and VKORC1 haplotype had a significant influence on the required warfarin dose after the first 2 weeks of therapy.
Initial variability in the INR response to warfarin was more strongly associated with genetic variability in the pharmacologic target of warfarin, VKORC1, than with CYP2C9.
Free fatty acids (FFAs) are implicated in the pathogenesis of insulin resistance and atherosclerosis. Inflammatory cytokines promote lipolysis and increase FFAs, a cause of endothelial dysfunction and increased atherosclerosis risk. We hypothesized that increased inflammation is associated with increased FFAs, resulting in insulin resistance and atherosclerosis in patients with systemic lupus erythematosus (SLE). We measured clinical variables, serum FFAs, homeostasis model assessment for insulin resistance (HOMA), inflammatory cytokines, markers of endothelial activation, cholesterol concentrations, and coronary artery calcium in 156 patients with SLE and 90 controls. We compared FFAs in patients with SLE and controls using Wilcoxon rank sum tests and further tested for the independent association between FFAs and disease status with adjustment for age, race, and sex using multivariable regression models. We assessed the relationship between FFA and continuous variables of interest using Spearman correlation and multivariable regression analysis. FFAs levels were higher in patients with SLE than controls (0.55 mmol/l [0.37- 0.71] vs. 0.44 mmol/l [0.32- 0.60], P=0.02). FFAs remained significantly higher among patients with SLE after adjustment for age, race, and sex (P=0.03), but not after further adjustment for BMI (P=0.13). FFA levels did not differ according to current immunosuppressive medication use in univariate and adjusted analysis (all P>0.05). Among patients with SLE, concentrations of FFAs were higher among those with metabolic syndrome compared to those without (0.66 mmol/l [0.46-0.81] vs. 0.52 mmol/l [0.35- 0.66], P<0.001). FFAs were positively correlated with insulin resistance (HOMA) (rho=0.23, P=0.004, P adjusted=0.006) and triglyceride levels (rho=0.22, P=0.01, P adjusted=0.004). FFAs were not associated with inflammatory cytokines (IL-6, TNF-α) (all P>0.05), but were positively associated with levels of E-selectin (rho=0.33, P=<0.001, P adjusted=0.001) and ICAM-1 (rho=0.35, P<0.001, P adjusted=0.001). FFAs were correlated with coronary artery calcium score (rho=0.20, P=0.01), but this was attenuated after adjustment for age, race and sex (P=0.33). FFAs are elevated in patients with SLE, particularly those with metabolic syndrome. FFAs in SLE are not associated with markers of generalized inflammation but are associated with insulin resistance and markers of endothelial activation.
cardiovascular disease; systemic lupus erythematosus; free fatty acids; metabolic syndrome; endothelial activation; insulin resistance
Even mild renal impairment is associated with increased atherosclerosis and cardiovascular mortality. Cystatin C, a novel measure of renal function, is more sensitive than conventional creatinine-based measures for the detection of subtle renal impairment. Increased cystatin concentrations are also associated with cardiovascular risk, independent of conventional measures of renal function. We examined the hypothesis that cystatin C is elevated in systemic lupus erythematosus (SLE) and is associated with coronary atherosclerosis.
We measured serum cystatin C, creatinine, TNF-α, IL-6, coronary artery calcium score (CACS), Framingham risk score (FRS), Modified Diet in Renal Disease estimated glomerular filtration rate (MDRD-eGFR) and other clinical parameters in 118 patients with SLE and 83 control subjects. The independent association between concentrations of cystatin C and SLE was evaluated using multivariable linear regression models, and the relationship between renal measures and coronary calcium was assessed with multivariable proportional odds logistic regression models.
Cystatin C, but not other measures of renal function, was significantly higher in patients with SLE than controls (1.09[Interquartile range, IQR: 0.85–1.28]mg/L vs. 0.89 [IQR: 0.76–0.99]mg/L; P<0.001 after adjusting for age, race and sex and MDRD-eGFR). Cystatin C was significantly associated with SLICC (P=0.04), ESR (P<0.001), CRP (P=0.04), TNF-α (P=0.008) and IL-6 (P=0.01) after adjustment for age, race and sex. Cystatin C was not significantly correlated with coronary calcium score in SLE (rho=0.096, P= 0.31) and the association remained non-significant after adjustment for age, race, sex and Framingham risk score (P=0.99).
Cystatin C was higher in patients with SLE than control subjects even after adjustment for conventional measures of renal function. Cystatin C was significantly correlated with several markers of inflammation in SLE but was not associated with coronary atherosclerosis. Subtle renal dysfunction does not appear to be directly associated with accelerated atherosclerosis in SLE.
cystatin C; systemic lupus erythematosus; renal function; atherosclerosis; Inflammation
Rheumatoid arthritis (RA), a chronic inflammatory disease, is associated with insulin resistance. Experimental evidence indicates that the relationship between insulin resistance and inflammation is bidirectional: Inflammation promotes insulin resistance, and insulin resistance promotes inflammation. Therefore, we examined the hypothesis that pioglitazone, a thiazolidinedione peroxisome proliferator-activated receptor γ agonist, would decrease inflammation and disease activity and improve insulin resistance in patients with RA.
In a single-center, randomized, double-blind, placebo-controlled crossover study patients with RA (N = 34) receiving stable therapy were randomized to also receive either pioglitazone 45 mg daily (n = 17) or matching placebo (n = 17) for eight weeks. This was followed by a four-week washout period and alternative treatment for eight weeks. Outcomes included change in Disease Activity Score in 28 joints (DAS28) score, individual components of the DAS28 score and homeostatic model assessment for insulin resistance (HOMA). Intention-to-treat analysis and linear mixed-effects models were used.
Patients had a mean (±SD) age of 51 (±14.2) years, 82.4% were female and baseline DAS28 high-sensitivity C-reactive protein (DAS28-CRP) was 4.58 (±1.1) units. Addition of pioglitazone was associated with a 9.3% reduction (95% confidence interval (CI) = 0.17% to 17.6%) in DAS28-CRP (P = 0.046), but no significant change in DAS28 erythrocyte sedimentation rate (DAS28-ESR) (P = 0.92). There was a 10.7mm (95% CI = 0.4 to 20.9 mm) improvement in patient-reported global health (P = 0.042), a 48.6% decrease (95% CI = 27.6% to 63.5%) in CRP (P < 0.001) and a 26.4% decrease (95% CI = 3.7% to 43.8%) in insulin resistance as measured by HOMA (P = 0.025), but no significant reduction in swollen or tender joint count or in ESR (all P > 0.05). Lower-extremity edema was more common during pioglitazone treatment (16%) than placebo (0%).
Addition of pioglitazone to RA therapy improves insulin resistance and modestly reduces RA disease activity measured by DAS28-CRP and two of its components, including patient-reported global health and CRP, but not DAS28-ESR or ESR.
Purpose of the review
TNF inhibitors are effective for achieving disease control in several inflammatory diseases. Although anti-TNF agents can inhibit bone loss in vitro, their role in the prevention of clinically relevant outcomes such as osteoporosis and fractures has not been clearly established.
There are many studies of the effects of TNF inhibitors on markers of bone turnover; however few have measured bone mineral density (BMD) or fractures. Most of these studies have small sample sizes and a minority had a placebo control group. Overall these studies suggest that the anti-resorptive effects of anti-TNF therapy are related to control of disease activity.
The antiresorptive effects of TNF inhibitors are likely related to their anti-inflammatory properties. Studies to date have not demonstrated any advantages of TNF inhibitors over traditional non biologic therapies in the prevention of bone loss and fractures.
Anti-TNF; bone loss; rheumatoid arthritis; spondyloarthropaties
Morbidity and mortality secondary to premature cardiovascular disease (CVD) in systemic lupus erythematosus (SLE) remain significant issues. The pathogenesis of CVD in SLE patients has not been fully explored. Epicardial adipose tissue (EAT) is believed to contribute to atherosclerosis development, through a paracrine and systemic inflammatory effect. We measured EAT volume in 162 SLE patients and 86 matched controls to assess the association of EAT with markers of atherosclerosis, cardiovascular risk and immunoactivation.
Clinical and laboratory characteristics collected included anthropomorphic measures, disease activity and damage indices, blood pressure measurement, lipid profile, inflammatory indices, adipokine levels and measures of adiposity. Coronary artery calcium (CAC) and EAT volume were measured using non-contrast cardiac computed tomography.
EAT volume was greater in patients with SLE [(mean± SD) 96.8±45.9cm3] than controls (78.2±40.7 cm3; P=0.001). The EAT volume was 31% larger (95% CI, 16.5% – 47.4%) in SLE patients than controls (P<0.001 adjusted for age, sex, and race; after additional adjustment for waist circumference P=0.007). Within SLE patients, after adjusting for age, race, sex, and waist circumference, EAT volume was associated with cumulative corticosteroid dose (P=0.007), current corticosteroid use (P<0.001), HDL cholesterol (P=0.033), and triglycerides (P=0.005). EAT was significantly correlated with CAC score (P<0.001), but the association was attenuated after adjustment for Framingham risk score (P=0.051).
The increased EAT volume seen in SLE patients is associated with corticosteroid use. Corticosteroids could have adverse cardiovascular effects in SLE via an increase in EAT volume, a marker of risk in the general population.
epicardial adipose tissue; systemic lupus erythematosus; atherosclerosis; coronary calcium score; corticosteroids
Women with systemic lupus erythematosus (SLE) have increased risk for coronary heart disease (CHD) which is underestimated by the Framingham risk score (FRS). We hypothesized that new risk scores that include inflammation or vascular age in the risk calculation would better identify women with SLE at risk for CHD, particularly in those with subclinical coronary atherosclerosis. We calculated the FRS and Reynolds risk score (RRS) in 121 women with SLE and 65 age-matched female controls; coronary age-modified risk scores (camFRS, camRRS) were calculated using coronary age derived from the coronary artery calcium (CAC) score. Risk scores were compared in SLE and controls, and in SLE patients with and without CAC. Although CAC was present in 21 SLE patients (17%) and 4 controls (6%) (P=0.033); the FRS, camFRS, RRS, and camRRS, did not differ significantly among SLE and controls (P>0.05), but were all significantly higher in SLE patients with CAC compared to those without (P< 0.001 for all). The cam-FRS (8%, P=0.016) but not cam-RRS (5%, P=0.221) assigned significantly more SLE patients to a category of ≥10% risk than conventional FRS (1%) and RRS (2%). The RRS was of limited use but coronary age may improve CHD risk prediction in SLE.
SLE; cardiovascular risk; atherosclerosis
We examined the hypothesis that cystatin C, a novel marker of renal function, is elevated in rheumatoidarthritis (RA) and associated with inflammation and coronary atherosclerosis.
We measured serum cystatin C, creatinine, TNF-α and IL-6 concentrations, coronary artery calcium score (CACS), and Modified Diet in Renal Disease estimated GFR (MDRD-eGFR) in 167 patients with RA and 91 controls.
Cystatin C was higher in RA (median [IQR]: 1.16 [0.99–1.35] mg/L) than controls (1.01 [0.90–1.19] mg/L), (P<0.001) and positively correlated with ESR (P<0.001), CRP (P=0.01), DAS28 (P=0.006), and Framingham risk score (FRS)(P=0.02). Cystatin C was correlated with CACS (P<0.001) in RA, but this was not significant after adjustment for age, race, sex and FRS (P =0.44).
Cystatin C concentrations are higher in RA than controls and may reflect inflammation and undetected subclinical renal dysfunction. Cystatin C provides information regarding the risk of atherosclerosis in RA, but this is linked to conventional cardiovascular risk factors.
cystatin; rheumatoid arthritis; renal function; atherosclerosis
There is a large interindividual variability in dexmedetomidine dose requirements for sedation of patients in intensive care units (ICU). Cytochrome P450 2A6 (CYP2A6) mediates an important route of dexmedetomidine metabolism, and genetic variation in CYP2A6 affects the clearance of other substrate drugs. We examined whether CYP2A6 genotypes affect dexmedetomidine disposition.
In 43 critically ill ICU patients receiving dexmedetomidine infusions adjusted to achieve the desired level of sedation, we determined a median of 5 plasma dexmedetomidine concentrations each. Forty subjects were genotyped for five common CYP2A6 alleles and grouped into normal (n=33), intermediate (n=5), and slow metabolizers (n=2).
Using a Bayesian hierarchical nonlinear mixture model, estimated dexmedetomidine clearance was 49.1 L/hr (posterior mean; 95% credible interval, 41.4 to 57.6 L/hr). There were no significant differences in dexmedetomidine clearance among normal, intermediate, and slow CYP2A6 metabolizer groups.
Genetic variation in CYP2A6 is not an important determinant of dexmedetomidine clearance in ICU patients.
CYP2A6; Dexmedetomidine; Pharmacogenetics; Bayesian Modeling
To examine the hypothesis that genetic variation in enzymes and transporters associated with synthesis, storage, release, and metabolism of catecholamines contributes to the interindividual variability in plasma catecholamine concentrations at rest and after exercise.
We measured plasma NE and epinephrine concentrations at rest and after a standardized exercise protocol in 165 healthy subjects (60% Caucasian, 40% African-American) and examined 29 functional or common variants in 14 genes involved in synthesis, transport, or metabolism of catecholamines. We examined the relationship among genotypes and NE concentrations at rest, and the increase after exercise (ΔNE), by multiple linear regression with adjustment for covariates (age, race, sex, BMI, fitness, and, for Δ NE, resting NE). As a secondary outcome, we performed similar analyses for epinephrine concentrations.
There was large interindividual variability in resting NE (mean, 204±102 pg/mL; range, 39 to 616 pg/mL) and ΔNE (mean, 256±206 pg/mL; range, −97 to 953 pg/mL). Resting NE was significantly associated with variants in 4 genes: CYB561 (P<0.001), VMAT2 (P=0.016), CHGA (P=0.039), and PNMT (P=0.038). ΔNE after exercise was associated with 3 variants in PNMT (P=0.041) and COMT (P=0.033 and 0.035), and resting and exercise epinephrine concentrations with 2 variants each.
The findings of this exploratory study suggest that variation in catecholamine pathway genes contributes to the interindividual variability in plasma NE and epinephrine concentrations at rest and after exercise.
Sympathetic Nervous System; Catecholamines; Exercise; Genetics; Polymorphism
Activation of macrophages may contribute to increased atherosclerosis and coronary artery disease in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Neopterin, a pteridine derivative, is a novel marker of monocyte and macrophage activation that is associated with atherosclerosis and cardiovascular risk in the general population. We examined the hypothesis that macrophage activation is associated with accelerated atherosclerosis in SLE and RA.
We compared serum neopterin concentrations, adjusted for age, race, sex and serum creatinine concentration, in patients with SLE (n=148), RA (n=166) and control subjects (n=177). In patients with SLE or RA, serum neopterin concentrations were then tested for association (adjusted for age, race, sex, serum creatinine and medication use) with measures of disease activity or damage, inflammatory markers and mediators, and coronary artery calcium measured by electron beam computed tomography.
Neopterin concentrations were significantly higher in patients with SLE (median 8.0, IQR [6.5–9.8] nmol/l) and RA (6.7[5.3–8.9] nmol/l) than controls (5.7[4.8–7.1] nmol/l), and were higher in SLE than RA (all p<0.001). In SLE, neopterin was significantly correlated with higher ESR (p=0.001), TNF-α (p<0.001), MCP-1 (p=0.005) and homocysteine concentrations (p=0.01), but in RA only with ESR (p=0.01). Neopterin was not associated with coronary calcium in either SLE (p=0.65) or RA (p=0.21).
Macrophage activation, reflected by increased serum neopterin concentrations, was increased in both SLE and RA. Neopterin was more robustly associated with atherogenic mediators of inflammation and homocysteine in SLE than RA but was not associated with coronary atherosclerosis in either disease.
Systemic Lupus Erythematosus; Rheumatoid Arthritis; Neopterin; Homocysteine; Atherosclerosis
α2A-Adrenoceptors (α2A-ARs) have important roles in sympathetic cardiovascular regulation. Variants of ADRA2A affect gene transcription and expression and are associated with insulin release and risk for type 2 diabetes. We examined whether ADRA2A variants are also associated with cardiovascular responses to the selective α2-AR-agonist, dexmedetomidine.
Methods and Results
73 healthy subjects participated in a placebo-controlled single-blind study. After 3 infusions of placebo, subjects received 3 incremental infusions of dexmedetomidine (cumulative dose, 0.4 mcg/kg). Primary outcomes were changes in systolic blood pressure (SBP) and plasma norepinephrine concentrations, measured as difference of the area-under-the-curve during placebo and dexmedetomidine infusions (ΔAUC). We used multiple linear regression analysis to examine the associations between 9 ADRA2A tagging variants and 5 inferred haplotypes and ΔAUC after adjustment for covariates. Homozygous carriers of rs553668, and the corresponding haplotype 4, previously associated with increased α2A-AR expression, had a 2.2-fold greater decrease in AUCSBP after dexmedetomidine (adjusted P=0.006); similarly, the maximum decrease in SBP was 24.7±8.1 mmHg compared to 13.6±5.9 mmHg in carriers of the wildtype allele (P=0.007). Carriers of haplotype 3, previously associated with reduced α2A-AR expression, had a 44% smaller decrease in AUCSBP (P=0.013). Haplotype information significantly improved the model predicting the decrease in SBP (P<0.001). There were similar but non-significant trends for diastolic blood pressure and heart rate. Genotypes were not significantly associated with norepinephrine responses.
Common ADRA2A variants are associated with the hypotensive response to dexmedetomidine. Effects of specific variants/haplotypes in vivo are compatible with their known effects on gene expression in vitro.
receptors; adrenergic; alpha; genetic polymorphism; pharmacogenetics; receptor; variability in drug response
Vascular α1- and α2-adrenergic receptors (ARs) mediate vasoconstriction and are major determinants of peripheral vascular tone. There is wide variability in vasoconstrictor sensitivity to α1- and α2AR-agonists among individuals. In previous studies this variability was not explained by identified α1- and α2-AR genetic variants. Thus, we hypothesized that adrenergic vasoconstrictor sensitivity is determined by shared constrictor mechanisms downstream of the individual receptors and that α1- and α2-AR-mediated vasoconstrictor sensitivity would therefore be correlated.
Dorsal hand vein responses to increasing doses of the α1-AR agonist phenylephrine (12 ng/min –12,000 ng/min) and the α2-AR agonist dexmedetomidine (0.01 ng/min – 100 ng/min) were measured in healthy subjects using a linear variable differential transformer. From individual dose-response curves we calculated the dose of phenylephrine and dexmedetomidine that produced 50% (ED50) of maximum venoconstriction (Emax) for each subject. We examined the correlation between phenylephrine and dexmedetomidine ED50 and Emax before and after adjustment for covariates (age, gender, ethnicity, BMI, blood pressure, heart rate, and baseline plasma norepinephrine concentrations).
In 62 subjects (36 males, 34 African American, 28 Caucasians) the median ED50 for dexmedetomidine was 1.32 ng/min (IQR, 0.45–5.37 ng/min), and for phenylephrine 177.8 ng/min (IQR, 40.7– 436.5 ng/min). The Emax for phenylephrine was 90.8% (82.2–99.6%) and for dexmedetomidine 80.0% (64.7–95.2%). There was no correlation between individual sensitivities (ED50) to phenylephrine and dexmedetomidine, before and after adjustment for covariates (p>0.30).
Phenylephrine and dexmedetomidine both produce strong venoconstriction in the dorsal hand vein; however, there is no significant correlation between vascular sensitivity to an α1-AR and α2-AR agonist. These findings suggest independent regulation of vascular α1- and α2-AR-mediated responses.
α1 adrenoceptors; α2 adrenoceptors; vasoconstriction
The metabolic syndrome is an independent risk factor for ischaemic heart disease. Patients with systemic lupus erythematosus (SLE) have accelerated atherosclerosis; however, there are no controlled studies of the metabolic syndrome in patients with SLE.
To compare the prevalence of the metabolic syndrome in patients with SLE and controls and to evaluate its relationship to other cardiovascular risk factors and inflammation.
102 patients with SLE and 101 controls were studied. The prevalence of the metabolic syndrome was compared in patients and controls using the National Cholesterol Education Program Adult Treatment Panel III (NCEP) and the World Health Organization (WHO) definitions, and associations with cardiovascular risk factors and lupus characteristics were examined.
The metabolic syndrome was present in 32.4% of patients and in 10.9% of controls subjects (p<0.001) using the WHO definition that requires direct determination of insulin resistance, and in 29.4% of patients with SLE and in 19.8% of controls (p = 0.14) using the NCEP definition. Among patients with SLE, both definitions were significantly associated with higher concentrations of C reactive protein (p = 0.001) and the NCEP definition was significantly associated with higher concentrations of homocysteine (p<0.001), lipoprotein (a) (p = 0.02) and cholesterol (p = 0.04). Neither lupus disease activity nor damage scores were associated with the metabolic syndrome.
Patients with SLE have a higher prevalence of insulin resistance and consequently of the WHO‐defined metabolic syndrome than controls. In patients with SLE, the metabolic syndrome was associated with higher levels of inflammation and may provide a link between inflammation and increased cardiovascular risk.
Insulin resistance is increased by inflammation, but the mechanisms are unclear. The present study was undertaken to test the hypothesis that decreased insulin sensitivity is differentially associated with mediators of inflammation by studying 2 chronic inflammatory diseases of different pathogenesis, systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).
We measured fasting insulin, glucose, and lipid levels, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor α (TNFα), and coronary artery calcification in 103 patients with SLE and in 124 patients with RA. Insulin sensitivity was measured using the homeostasis model assessment (HOMA) index.
The HOMA value was higher in RA patients (median 2.05 [interquartile range (IQR) 1.05–3.54]) than in SLE patients (1.40 [0.78–2.59]) (P = 0.007). CRP and ESR did not differ significantly in RA and SLE patients. Body mass index (BMI) was significantly correlated with the HOMA index in both RA (ρ = 0.20) and SLE (ρ = 0.54), independently of age, sex, race, and current use of corticosteroids. In RA patients, the HOMA index was also significantly positively correlated with IL-6 (ρ = 0.63), TNFα (ρ = 0.50), CRP (ρ = 0.29), ESR (ρ = 0.26), coronary calcification (ρ = 0.26), and Disease Activity Score in 28 joints (ρ = 0.21); associations adjusted for age, sex, race, BMI, and current use of corticosteroids remained significant (P < 0.05). In SLE patients, the HOMA index was also significantly correlated with ESR (ρ = 0.35) and CRP (ρ = 0.25), but not with other variables. The association between the ESR and the HOMA value in patients with SLE remained significant after adjustment for confounding covariates (P = 0.008). In multivariable models, the major contributing factors to the HOMA index were the BMI in SLE patients, and IL-6 and TNFα levels in RA patients.
The pathogenesis of insulin resistance and its contribution to atherogenesis varies in different inflammatory settings.
Tacrolimus, an immunosuppressive drug widely prescribed in kidney transplantation, requires therapeutic drug monitoring due to its marked interindividual pharmacokinetic variability and narrow therapeutic index. Previous studies have established that CYP3A5 rs776746 is associated with tacrolimus clearance, blood concentration, and dose requirement. The importance of other drug absorption, distribution, metabolism, and elimination (ADME) gene variants has not been well characterized.
We used novel DNA biobank and electronic medical record resources to identify ADME variants associated with tacrolimus dose requirement. Broad ADME genotyping was performed on 446 kidney transplant recipients who had been dosed to steady state with tacrolimus. The cohort was obtained from Vanderbilt's DNA biobank, BioVU, which contains linked, de-identified electronic medical record data. Genotyping included Affymetrix DMET Plus (1936 polymorphisms), custom Sequenom MassARRAY iPLEX Gold assay (95 polymorphisms), and ancestry-informative markers. The primary outcome was tacrolimus dose requirement defined as blood concentration-to-dose ratio.
In analyses that adjusted for race and other clinical factors, we replicated the association of tacrolimus blood concentration-to-dose ratio with CYP3A5 rs776746 (p = 7.15 × 10−29), and identified associations with nine variants in linkage disequilibrium with rs776746, including eight CYP3A4 variants. No NR1/2 variants were significantly associated. Age, weight, and hemoglobin were also significantly associated with the outcome. In final models, rs776746 explained 39% of variability in dose requirement, and 46% was explained by the model containing clinical covariates.
This study highlights the utility of DNA biobanks and electronic medical records for tacrolimus pharmacogenomic research.
pharmacogenomics; pharmacokinetics; calcineurin inhibitor; tacrolimus; electronic medical records; kidney transplant; cytochrome P4503A5; genetic polymorphism; dosing
We tested the hypothesis that oxidative stress is increased in patients with rheumatoid arthritis (RA) due to increased inflammation and contributes to the pathogenesis of atherosclerosis.
The independent association between urinary F2-isoprostane excretion, a measure of oxidative stress, and RA was tested using multiple linear regression models in 169 patients with RA and 92 control subjects frequency-matched for age, race and sex. The relationship between F2-isoprostane excretion and coronary calcium, a marker of atherosclerosis, was examined in multivariable proportional odds logistic regression models that also assessed the interactions between oxidative stress and LDL and HDL cholesterol.
F2-isoprostane excretion (median [IQR]) was significantly higher in patients with RA (median 2.75 [interquartile range: 1.60-4.06] ng/mg creatinine (Cr)) than control subjects (1.86 [1.25-2.62] ng/mg Cr, adjusted p=0.006). In patients with RA, F2-isoprostanes were positively correlated with BMI (p<0.001) but not with disease activity or mediators of inflammation, such as DAS28 or serum TNF-α, IL-6 and CRP concentrations in adjusted multivariable models (all P>0.05). In patients with RA, F2-isoprostanes significantly modified the effect of HDL cholesterol on coronary calcification (p-value for interaction=0.02) after adjustment for age, sex and race. As F2-isoprostane levels increased, HDL lost its protective effect against coronary calcification.
Oxidative stress measured as F2-isoprostane excretion was higher in patients with RA than control subjects. Among patients with RA, higher F2-isoprostane excretion and HDL cholesterol concentrations interacted significantly and were positively associated with the severity of coronary calcification.
Rheumatoid Arthritis; Oxidative Stress; F2-Isoprostanes; Atherosclerosis; HDL