Many effect measures used in clinical trials are problematic because they are differentially understood by patients and physicians. The emergence of novel methods such as accelerated failure-time models and quantile regression has shifted the focus of effect measurement from probability measures to time-to-event measures. Such modeling techniques are rapidly evolving, but matching non-parametric descriptive measures are lacking. We propose such a measure, the delay of events, demonstrating treatment effect as a gain in event-free time. We believe this measure to be of value for shared clinical decision-making. The rationale behind the measure is given, and it is conceptually explained using the Kaplan–Meier estimate and the quantile regression framework. A formula for calculation of the delay of events is given. Hypothetical and empirical examples are used to demonstrate the measure. The measure is discussed in relation to other measures highlighting the time effects of preventive treatments. There is a need to further investigate the properties of the measure as well as its role in clinical decision-making.
Clinical trials; Randomized; Kaplan–Meier survival curves; Preventive measures; Treatment Outcome
In 2010, more than 45 years after the initial discovery of lipoprotein(a) [Lp(a)] by Kare Berg, an European Atherosclerosis Society Consensus Panel recommended screening for elevated Lp(a) in people at moderate to high risk of atherosclerotic cardiovascular disease (CVD). This recommendation was based on extensive epidemiological findings demonstrating a significant association between elevated plasma Lp(a) levels and coronary heart disease, myocardial infarction, and stroke. In addition to those patients considered to be at moderate to high risk of heart disease, statin-treated patients with recurrent heart disease were also identified as targeted for screening of elevated Lp(a) levels. Taken together, recent findings have significantly strengthened the notion of Lp(a) as a causal risk factor for CVD. It is well established that Lp(a) levels are largely determined by the size of the apolipoprotein a [apo(a)] gene; however, recent studies have identified several other LPA gene polymorphisms that have significant associations with an elevated Lp(a) level and a reduced copy number of K4 repeats. In addition, the contribution of other genes in regulating Lp(a) levels has been described. Besides the strong genetic regulation, new evidence has emerged regarding the impact of inflammation as a modulator of Lp(a) risk factor properties. Thus, oxidized phospholipids that possess a strong proinflammatory potential are preferentially carried on Lp(a) particles. Collectively, these findings point to the importance of both phenotypic and genotypic factors in influencing apo(a) proatherogenic properties. Therefore, studies taking both of these factors into account determining the amount of Lp(a) associated with each individual apo(a) size allele are valuable tools when assessing a risk factor role of Lp(a).
The formation of hybrids of nanofibrillated cellulose and titania nanoparticles in aqueous media has been studied. Their transparency and mechanical behavior have been assessed by spectrophotometry and nanoindentation. The results show that limiting the titania nanoparticle concentration below 16 vol% yields homogeneous hybrids with a very high Young’s modulus and hardness, of up to 44 GPa and 3.4 GPa, respectively, and an optical transmittance above 80%. Electron microscopy shows that higher nanoparticle contents result in agglomeration and an inhomogeneous hybrid nanostructure with a concomitant reduction of hardness and optical transmittance. Infrared spectroscopy suggests that the nanostructure of the hybrids is controlled by electrostatic adsorption of the titania nanoparticles on the negatively charged nanocellulose surfaces.
Levels of acute phase reactants are impacted by age. To what extent cardiovascular risk associated with aging is due to an increase in the inflammatory burden is not known. We assessed the relationship with age of inflammatory markers, representing a) systemic (C-reactive protein [CRP], fibrinogen and serum amyloid-A [SAA]) and b) vascular (lipoprotein-associated phospholipase A2 [Lp-PLA2] and pentraxin-3 [PTX-3]) inflammation.
Methods and Results
We determined Lp-PLA2 mass and activity, CRP, fibrinogen, SAA, and PTX-3 levels and other CVD risk factors in 336 Caucasians and 224 African Americans. Levels of systemic inflammatory markers increased significantly with age in both ethnic groups (P<0.05 for all), while trend patterns of vascular inflammatory markers did not change significantly with age for either group. In multivariate regression models adjusting for confounding variables, age remained independently associated with a composite z-score for systemic, but not vascular inflammation (β=0.250, P<0.001 and (β=0.276, P<0.001, for Caucasians and African Americans respectively).
We report an increase in the systemic, but not vascular, inflammatory burden over age. Levels of both categories of inflammatory markers over age were similar across ethnicity after adjustment for confounders. Our results underscore the importance of age in evaluating inflammatory markers to assess cardiovascular risk.
Inflammation; aging; cardiovascular disease; epidemiology
Lipoprotein(a) [Lp(a)] is a CVD risk factor, where inflammation impacts levels differentially across ethnicity. We investigated the effect of systemic [serum amyloid A (SAA)] and vascular [pentraxin-3 (PTX-3)] inflammation on Lp(a) levels across different apo(a) sizes in a bi-ethnic population. Lp(a) and allele-specific apo(a) levels, apo(a) sizes, SAA and PTX-3 levels were determined in 336 Caucasians and 224 African Americans. We dichotomized subjects into 2 groups using the respective median SAA (29.8 and 41.5 mg/dl for Caucasians and African Americans, respectively) or PTX-3 levels (1.6 and 1.1 ng/ml for Caucasians and African Americans, respectively). Among African Americans, but not in Caucasians, Lp(a) levels were increased (146 vs. 117 nmol/l, P=0.024) in the high vs. low SAA group. No difference was seen across PTX-3 groups. Further, among African Americans with smaller (<26 K4 repeats) apo(a) sizes, allele-specific apo(a) levels (111 vs. 79 nmol/l, P=0.020) were increased in the high vs. low SAA group. Again, no difference was seen for PTX-3. We did not find any significant associations between allele-specific apo(a) and SAA or PTX-3 levels among Caucasians with smaller (<26 K4) apo(a) sizes. In conclusion, elevated levels of SAA, but not PTX-3, were significantly associated with higher Lp(a) levels for smaller (<26 K4) apo(a) sizes in African Americans. Our results implicate that a pro-inflammatory stimulus may result in an increased cardiovascular risk through a selective increase in Lp(a) levels among African Americans carrying smaller apo(a) size.
The results of short-term studies in humans suggest that, compared with glucose, acute consumption of fructose leads to increased postprandial energy expenditure and carbohydrate oxidation and decreased postprandial fat oxidation. The objective of this study was to determine the potential effects of increased fructose consumption compared to isocaloric glucose consumption on substrate utilization and energy expenditure following sustained consumption and under energy-balanced conditions.
As part of a parallel arm study, overweight/obese male and female subjects, 40–72 y, consumed glucose- or fructose-sweetened beverages providing 25% of energy requirements for 10 weeks. Energy expenditure and substrate utilization were assessed using indirect calorimetry at baseline and during the 10th week of intervention.
Consumption of fructose, but not glucose, led to significant decreases of net postprandial fat oxidation and significant increases of net postprandial carbohydrate oxidation (P < 0.0001 for both). Resting energy expenditure decreased significantly from baseline values in subjects consuming fructose (P = 0.031) but not in those consuming glucose.
Increased consumption of fructose for 10 weeks leads to marked changes of postprandial substrate utilization including a significant reduction of net fat oxidation. In addition, we report that resting energy expenditure is reduced compared to baseline values in subjects consuming fructose-sweetened beverages for 10 weeks.
fructose; fat oxidation; carbohydrate oxidation; energy expenditure; metabolic rate; humans
Random errors in measurement of a risk factor will introduce downward bias of an estimated association to a disease or a disease marker. This phenomenon is called regression dilution bias. A bias correction may be made with data from a validity study or a reliability study.
Aims and methods
In this article we give a non-technical description of designs of reliability studies with emphasis on selection of individuals for a repeated measurement, assumptions of measurement error models, and correction methods for the slope in a simple linear regression model where the dependent variable is a continuous variable. Also, we describe situations where correction for regression dilution bias is not appropriate.
The methods are illustrated with the association between insulin sensitivity measured with the euglycaemic insulin clamp technique and fasting insulin, where measurement of the latter variable carries noticeable random error. We provide software tools for estimation of a corrected slope in a simple linear regression model assuming data for a continuous dependent variable and a continuous risk factor from a main study and an additional measurement of the risk factor in a reliability study. Also, we supply programs for estimation of the number of individuals needed in the reliability study and for choice of its design.
Our conclusion is that correction for regression dilution bias is seldom applied in epidemiological studies. This may cause important effects of risk factors with large measurement errors to be neglected.
Correction methods; measurement errors; regression dilution bias; SAS and R programs
Prospective studies in humans examining the effects of fructose consumption on biological markers associated with the development of metabolic syndrome are lacking. Therefore we investigated the relative effects of 10 wks of fructose or glucose consumption on plasma uric acid and RBP-4 concentrations, as well as liver enzyme (AST, ALT, and GGT) activities in men and women.
As part of a parallel arm study, older (age 40–72), overweight and obese male and female subjects (BMI 25–35 kg/m2) consumed glucose- or fructose-sweetened beverages providing 25% of energy requirements for 10 wks. Fasting and 24-h blood collections were performed at baseline and following 10 wks of intervention and plasma concentrations of uric acid, RBP-4 and liver enzyme activities were measured.
Consumption of fructose, but not glucose, led to significant increases of 24-h uric acid profiles (P < 0.0001) and RBP-4 concentrations (P = 0.012), as well as plasma GGT activity (P = 0.04). Fasting plasma uric acid concentrations increased in both groups; however, the response was significantly greater in subjects consuming fructose (P = 0.002 for effect of sugar). Within the fructose group male subjects exhibited larger increases of RBP-4 levels than women (P = 0.024).
These findings suggest that consumption of fructose at 25% of energy requirements for 10 wks, compared with isocaloric consumption of glucose, may contribute to the development of components of the metabolic syndrome by increasing circulating uric acid, GGT activity, suggesting alteration of hepatic function, and the production of RBP-4.
Hypertriglyceridemia may be associated with important complications. The aim of this study is to estimate the magnitude of association and quality of supporting evidence linking hypertriglyceridemia to cardiovascular events and pancreatitis.
We conducted a systematic review of multiple electronic bibliographic databases and subsequent meta-analysis using a random effects model. Studies eligible for this review followed patients longitudinally and evaluated quantitatively the association of fasting hypertriglyceridemia with the outcomes of interest. Reviewers working independently and in duplicate reviewed studies and extracted data.
35 studies provided data sufficient for meta-analysis. The quality of these observational studies was moderate to low with fair level of multivariable adjustments and adequate exposure and outcome ascertainment. Fasting hypertriglyceridemia was significantly associated with cardiovascular death (odds ratios (OR) 1.80; 95% confidence interval (CI) 1.31-2.49), cardiovascular events (OR, 1.37; 95% CI, 1.23-1.53), myocardial infarction (OR, 1.31; 95% CI, 1.15-1.49), and pancreatitis (OR, 3.96; 95% CI, 1.27-12.34, in one study only). The association with all-cause mortality was not statistically significant.
The current evidence suggests that fasting hypertriglyceridemia is associated with increased risk of cardiovascular death, MI, cardiovascular events, and possibly acute pancreatitis.
Précis: hypertriglyceridemia is associated with increased risk of cardiovascular death, MI, cardiovascular events, and possibly acute pancreatitis
Hypertriglyceridemia; Cardiovascular disease; Pancreatitis; Systematic reviews and meta-analysis
Seasonal variations in hemoglobin-A1c have been reported in diabetic patients, but the underlying mechanisms have not been elucidated.
To study if insulin sensitivity, insulin secretion, and fasting plasma glucose showed seasonal variations in a Swedish population-based cohort of elderly men.
Altogether 1117 men were investigated with a euglycemic insulin clamp and measurements of fasting plasma glucose and insulin secretion after an oral glucose tolerance test. Values were analyzed in linear regression models with an indicator variable for winter/summer season and outdoor temperature as predictors.
During winter, insulin sensitivity (M/I, unit = 100 × mg × min-1 × kg-1/(mU × L-1)) was 11.0% lower (4.84 versus 5.44, P = 0.0003), incremental area under the insulin curve was 16.4% higher (1167 versus 1003 mU/L, P = 0.007). Fasting plasma glucose was, however, not statistically significantly different (5.80 versus 5.71 mmol/L, P = 0.28) compared to the summer season. There was an association between outdoor temperature and M/I (0.57 units increase (95% CI 0.29–0.82, P < 0.0001) per 10°C increase of outdoor temperature) independent of winter/summer season. Adjustment for life-style factors, type 2 diabetes, and medication did not alter these results.
Insulin sensitivity showed seasonal variations with lower values during the winter and higher during the summer season. Inverse compensatory variations of insulin secretion resulted in only minor variations of fasting plasma glucose. Insulin sensitivity was associated with outdoor temperature. These phenomena should be further investigated in diabetic patients.
Insulin secretion; insulin sensitivity; seasonal variation
Lipoprotein (a) [Lp(a)], is present only in humans, Old World nonhuman primates, and the European hedgehog. Lp(a) has many properties in common with low-density lipoprotein (LDL) but contains a unique protein, apo(a), which is structurally different from other apolipoproteins. The size of the apo(a) gene is highly variable, resulting in the protein molecular weight ranging from 300 to 800 kDa; this large variation may be caused by neutral evolution in the absence of any selection advantage. Apo(a) influences to a major extent metabolic and physicochemical properties of Lp(a), and the size polymorphism of the apo(a) gene contributes to the pronounced heterogeneity of Lp(a). There is an inverse relationship between apo(a) size and Lp(a) levels; however, this pattern is complex. For a given apo(a) size, there is a considerable variation in Lp(a) levels across individuals, underscoring the importance to assess allele-specific Lp(a) levels. Further, Lp(a) levels differ between populations, and blacks have generally higher levels than Asians and whites, adjusting for apo(a) sizes. In addition to the apo(a) size polymorphism, an upstream pentanucleotide repeat (TTTTAn) affects Lp(a) levels. Several meta-analyses have provided support for an association between Lp(a) and coronary artery disease, and the levels of Lp(a) carried in particles with smaller size apo(a) isoforms are associated with cardiovascular disease or with preclinical vascular changes. Further, there is an interaction between Lp(a) and other risk factors for cardiovascular disease. The physiological role of Lp(a) is unknown, although a majority of studies implicate Lp(a) as a risk factor.
atherosclerosis; genetics; blacks; lipids
Lipoprotein (a), Lp(a), has many properties in common with low density lipoprotein, LDL, but contains a unique protein apolipoprotein(a), linked to apolipoprotein B-100 by a single disulfide bond. There is a substantial size heterogeneity of apo(a), and generally smaller apo(a) sizes tend to correspond to higher plasma Lp(a) levels, but this relation is far from linear, underscoring the importance to assess allele-specific apo(a) levels. The presence of apo(a), a highly charged, carbohydrate-rich, hydrophilic protein may obscure key features of the LDL moiety and offer opportunities for binding to vessel wall elements. Recently, interest in Lp(a) has increased because studies over the past decade have confirmed and more robustly demonstrated a risk factor role of Lp(a) for cardiovascular disease. In particular, levels of Lp(a) carried in particles with smaller size apo(a) isoforms are associated with CAD. Other studies suggest that pro-inflammatory conditions may modulate risk factor properties of Lp(a). Further, Lp(a) may act as a preferential acceptor for pro-inflammatory oxidized phospholipids transferred from tissues or from other lipoproteins. However, at present only a limited number of agents (e.g. nicotinic acid and estrogen) has proven efficacy in lowering Lp(a) levels. Although Lp(a) has not been definitely established as a cardiovascular risk factor and no guidelines presently recommend intervention, Lp(a)-lowering therapy might offer benefits in subgroups of patients with high Lp(a) levels.
Lipoprotein(a); apo(a) size; allele-specific apo(a) levels; risk factors; ethnicity
Apolipoprotein E (ApoE) plays a major role in lipoprotein metabolism and genetic variability of ApoE confers susceptibility to coronary artery disease (CAD). Beyond variability in the coding region, promoter polymorphisms in the ApoE gene impact on ApoE transcription.
We determined the ApoE − 491 A/T promoter polymorphism, ApoE isoforms, lipid and lipoprotein levels, and CAD risk factors in 313 Caucasians and 215 African Americans.
Caucasians had a lower ApoE T allele frequency compared to African Americans (18.1% vs. 32.3%, P < 0.05). Among T/* carriers, ApoB levels were significantly lower in Caucasians, but significantly higher among African Americans, in both cases compared to A/A homozygotes (P = 0.017, and P = 0.012). For a given −491A/T genotype, levels of atherogenic lipoproteins differed across ApoE2/E3/E4 isoforms among African Americans, but not Caucasians, as T/* carriers with ApoE4 had significantly higher ApoB levels compared to T/* carriers with ApoE2 (P = 0.010). Among patients with CAD, Caucasian A/A homozygotes and African American T/* carriers had higher ApoB levels compared to the same genotype without CAD (P = 0.007, P = 0.049, respectively).
We observed an ethnicity-specific variability in ApoB levels across the ApoE − 491 A/T polymorphism and a modulatory impact on this pattern by ApoE2/E3/E4 isoforms.
Studies demonstrate that the apolipoprotein B/apolipoprotein A-I (ApoB/apoA-I) ratio predicts cardiovascular risk better than any of the cholesterol indexes. A number of factors that define the metabolic syndrome (MS) differ across African-American and European-American ethnicities. We assessed relationship of the apoB/apoA-I ratio to MS and coronary artery disease (CAD) in 224 African-Americans and 304 European-Americans. The MS was defined by the revised NCEP-ATP III criteria and CAD was assessed as ≥50% stenosis or a continuous cardiovascular score (0–75). European-Americans had higher apoB/apoA-I ratio compared with African-Americans (1.15 vs. 1.07, P=0.008). The apoB/apoA-I ratio was associated with presence of the MS in both European-Americans (OR=5.9; 95% confidence interval (CI), 2.53–13.57; P<0.001) and African-Americans (OR=8.3; 95% CI, 3.52–19.25; P<0.001), and was higher in subjects with MS compared to those without MS (1.21 vs. 1.04, P<0.001 for European-Americans and 1.20 vs. 0.94, P<0.001 for African-Americans). There was a stepwise increase in the prevalence of MS across apoB/apoA-I ratio tertiles in both ethnic groups (χ2=13.1, P<0.001 for European-Americans and χ2=19.6, P<0.001 for African-Americans). In multiple regression analyses, the apoB/apoA-I ratio independently predicted CAD in African-Americans (β=0.242, P=0.011). The cardiovascular score was significantly increased across apoB/apoA-I ratio tertiles in European-American subjects with MS (P=0.001), whereas this association was seen in African-American subjects without MS (P=0.023). In conclusion, the apoB/apoA-I ratio differed across ethnicities and was associated with presence of the MS in both groups. Among African-Americans, elevated apoB/apoA-I ratio independently predicted higher risk for CAD.
apoB/apoA-I ratio; cardiovascular disease; ethnicity
Purpose of review
To review the current scientific literature and recent clinical trials on HIV protease inhibitors (PIs) and their potential role in the pathogenesis of lipodystrophy and metabolic disorders.
HIV PI treatment may affect the normal stimulatory effect of insulin on glucose and fat storage. Further, chronic inflammation from HIV infection and PI treatment trigger cellular homeostatic stress responses with adverse effects on intermediary metabolism. The physiologic outcome is such that total adipocyte storage capacity is decreased, and the remaining adipocytes resist further fat storage. This process leads to a pathologic cycle of lipodystrophy and lipotoxicity, a pro-atherogenic lipid profile, and a clinical phenotype of increased central body fat distribution similar to the metabolic syndrome.
PIs are a key component of antiretroviral therapy and have dramatically improved the life expectancy of HIV-infected individuals. However, they are also associated with abnormalities in glucose/lipid metabolism and body fat distribution. Further studies are needed to better define the pathogenesis of PI-associated metabolic and body fat changes and their potential treatment.
HIV; protease inhibitors; metabolic disorders; lipodystrophy
Lipoprotein-associated phospholipase A2 (Lp-PLA2) and lipoprotein(a) [Lp(a)] have been implicated as cardiovascular disease risk factors, and are differentially regulated across ethnicity. We investigated the association between Lp-PLA2 activity and allele-specific apolipoprotein(a) [apo(a)] levels in a bi-ethnic population.
Lp-PLA2 activity, Lp(a) and allele-specific apo(a) levels were determined in 224 African Americans and 336 Caucasians.
Lp-PLA2 activity level was higher among Caucasians compared to African Americans (173 ± 41 vs. 141 ± 39 nmol/min/ml, P<0.001), and positively associated with Lp(a), total and LDL cholesterol, triglyceride, apolipoprotein B-100, and negatively with HDL cholesterol levels in both ethnic groups. The association between Lp-PLA2 activity and Lp(a) was stronger among African Americans compared to Caucasians (R=0.238, β1=3.48, vs. R=0.111, β1=1.93, respectively). The Lp-PLA2 activity level was significantly associated with allele-specific apo(a) levels for smaller (<26 K4 repeats) apo(a) sizes in both ethnic groups (P=0.015 for African Americans, P=0.038 for Caucasians). In contrast, for larger (>26 K4 repeats) apo(a) sizes, high Lp-PLA2 activity levels were associated with higher allele-specific apo(a) levels in African Americans (P=0.009), but not in Caucasians.
The association between Lp-PLA2 activity and allele-specific apo(a) levels differs across African American-Caucasian ethnicity.
lipoprotein; allele-specific apo(a); K4 repeats; vascular inflammation marker; ethnicity
Elevated lipoprotein(a) [Lp(a)] is associated with ischemic stroke (IS) among Whites, but data is sparse for non-White populations.
Using a population-based case-control study design with subjects from the Northern Manhattan Stroke Study, we assessed whether Lp(a) levels were independently associated with IS risk among Whites, Blacks and Hispanics.
Design and Setting
Lp(a) levels were measured in 317 IS cases (mean age 69 ± 13 years; 56% women; 16% Whites, 31% Blacks and 52% Hispanics) and 413 community-based controls, matched by age, race/ethnicity and gender. In-person assessments included demographics, socioeconomic status, presence of vascular risk factors and fasting lipid levels. Logistic regression was used to determine the independent association of Lp(a) and IS. Stratified analyses investigated gender and race/ethnic differences.
Mean Lp(a) levels were greater among cases than controls (46.3 ± 41.0 vs. 38.9 ± 38.2 mg/dl; p < 0.01). After adjusting for stroke risk factors (hypertension, diabetes mellitus, coronary artery disease, cigarette smoking), lipid levels, and socioeconomic status, Lp(a) levels ≥30 mg/dl were independently associated with an increased stroke risk in the overall cohort (adjusted odds ratio, OR, 1.8, 95% confidence interval, CI, 1.20–2.6; p = 0.004). There was a significant linear dose-response relationship between Lp(a) levels and IS risk. The association between IS risk and Lp(a) ≥30 mg/dl was more pronounced among men (adjusted OR 2.0, 95% CI 1.1–3.5; p = 0.02) and among Blacks (adjusted OR 2.7, 95% CI 1.2–6.2; p = 0.02).
Elevated Lp(a) levels were significantly and independently associated with increased stroke risk, suggesting that Lp(a) is a risk factor for IS across White, Black and Hispanic race/ethnic groups.
Lipoprotein(a); Northern Manhattan Stroke Study; Ischemic stroke
The aim of this study was to investigate the association of C-reactive protein (CRP) with the metabolic syndrome (MS) and its components, and their association with coronary artery disease (CAD) in African-Americans (AA) and European-Americans (EA). MS was defined using revised National Cholesterol Education Program Adult Treatment Panel III criteria in 224 AA and 304 EA undergoing coronary angiography; CAD was defined as ≥50% stenosis in any segment or as a composite cardiovascular score (0–75). The relative frequency of MS and CAD was significantly higher among AA subjects with high (≥3 mg/L) vs. low (<3 mg/L) CRP levels (76% vs. 24%, P<0.001 for MS; 70% vs. 30%, P=0.001 for CAD). The composite score was higher in subjects with high (≥3 mg/L) vs. low (<3 mg/L) CRP levels in both AA (16.9 vs. 11.2, P=0.038) and EA (18.5 vs. 14.5, P=0.002). Further, in both ethnic groups the cardiovascular score was higher among subjects with MS, irrespective of CRP levels. Adjusting for other risk factors, multiple regression analysis demonstrated an association of MS, but not CRP, with CAD among EA, but not AA (r2=0.533, P<0.001). In conclusion, MS was independently associated with CAD in both EA and AA, whereas CRP did not add prognostic information beyond established cardiovascular risk factors in either ethnic group.
CRP; Metabolic syndrome; Risk factors; Ethnicity
Advances in human health require the efficient and rapid translation of scientific discoveries into effective clinical treatments; this process in turn depends upon observational data gathered from patients, communities, and public-health research that can be used to guide basic scientific investigation. Such bidirectional translational science, however, faces unprecedented challenges due to the rapid pace of scientific and technological development, as well as the difficulties of negotiating increasingly complex regulatory and commercial environments that overlap the research domain. Further, numerous barriers to translational science have emerged among the nation’s academic research centers, including basic structural and cultural impediments to innovation and collaboration, shortages of trained investigators, and inadequate funding.
To address these serious and systemic problems, in 2006, the National Institutes of Health created the Clinical and Translational Science Awards (CTSA) program, which aims to catalyze the transformation of biomedical research at a national level, speeding the discovery and development of therapies, fostering collaboration, engaging communities, and training succeeding generations of clinical and translational researchers. The authors report in detail on the planning process, begun in 2008, that was used to engage stakeholders and to identify, refine, and ultimately implement the CTSA program’s overarching strategic goals. They also discuss the implications and likely impact of this strategic planning process as it is applied among the nation’s academic health centers.
Diabetes mellitus is associated with increased risk for atherosclerotic cardiovascular disease (CVD). Recent prospective studies in healthy individuals suggest that the postprandial triglyceride (TG) level is a better independent predictor for assessing future CVD events than fasting TG levels. In contrast, results have been more controversial among diabetic patients, as some studies report a positive association between postprandial TG and CVD. This raises the issue of to what extent postprandial TG levels may be of predictive value in the diabetic population. One possibility impacting on the predictive power of postprandial TG in identifying CVD risk may be the presence of other risk factors, including alterations in lipid and lipoprotein metabolism, which could make it more difficult to identify the impact of postprandial lipemia on cardiovascular risk. The findings provide a challenge to develop a better approach to assess the impact of postprandial lipemia on CVD risk under diabetic conditions.
Diabetic dyslipidemia; Postprandial triglyceride; Cardiovascular risk; Diabetic and non diabetic population
The successful introduction of highly active antiretroviral therapy (HAART), a combination of potent antiretroviral agents, including protease inhibitors, nucleoside reverse transcriptase inhibitors, and nonnucleoside reverse transcriptase inhibitors, has impacted positively on morbidity and mortality among human immunodeficiency virus (HIV)-positive patients. Over time, HAART has been associated with a number of metabolic and anthropometric abnormalities, including dyslipidemia and insulin resistance as well as subcutaneous fat loss and abdominal obesity, potentially contributing to cardiovascular risk. Recent studies have more firmly established that both HIV infection and HAART might increase the risk of clinical cardiovascular events. Furthermore, whereas HIV/HAART is associated with multiple aspects of endocrine dysfunction, there has been less focus on bone disease, although some studies indicate a higher prevalence of osteoporosis among HIV-positive subjects compared to HIV-negative controls. The relationship between bone and fat metabolism under HIV-positive conditions deserves further attention, and available data suggest the possibility of an intriguing connection. In the future, an increasing population of aging HIV-positive patients with a spectrum of antiretroviral therapies and accumulation of endocrine abnormalities and conventional cardiovascular risk factors will present preventive and therapeutic challenges to our health-care system.
Vitamin D is not only important for bone health but can also affect the development of several non-bone diseases. The definition of vitamin D insufficiency by serum levels of 25-hydroxyvitamin D depends on the clinical outcome but might also be a consequence of analytical methods used for the definition. Although numerous 25-hydroxyvitamin D assays are available, their comparability is uncertain. We therefore aim to investigate the precision, accuracy and clinical consequences of differences in performance between three common commercially available assays.
Serum 25-hydroxyvitamin D levels from 204 twins from the Swedish Twin Registry were determined with high-pressure liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS), a radioimmunoassay (RIA) and a chemiluminescent immunoassay (CLIA). High inter-assay disagreement was found. Mean 25-hydroxyvitamin D levels were highest for the HPLC-APCI-MS technique (85 nmol/L, 95% CI 81–89), intermediate for RIA (70 nmol/L, 95% CI 66–74) and lowest with CLIA (60 nmol/L, 95% CI 56–64). Using a 50-nmol/L cut-off, 8% of the subjects were insufficient using HPLC-APCI-MS, 22% with RIA and 43% by CLIA. Because of the heritable component of 25-hydroxyvitamin D status, the accuracy of each method could indirectly be assessed by comparison of within-twin pair correlations. The strongest correlation was found for HPLC-APCI-MS (r = 0.7), intermediate for RIA (r = 0.5) and lowest for CLIA (r = 0.4). Regression analyses between the methods revealed a non-uniform variance (p<0.0001) depending on level of 25-hydroxyvitamin D.
There are substantial inter-assay differences in performance. The most valid method was HPLC-APCI-MS. Calibration between 25-hydroxyvitamin D assays is intricate.
The separate roles of inflammation and insulin resistance (IR) in the pathogenesis of cardiovascular disease (CVD) are well recognized. We investigated whether presence of inflammation would modify coronary artery disease (CAD) risk prediction in subjects with or without IR. Insulin, glucose, CRP and fibrinogen levels were determined in 317 Caucasians and 222 African Americans undergoing diagnostic coronary angiography. Extent of CAD was defined by a composite score (0–75). The overall prevalence of IR (HOMA-IR≥3.0) in Caucasians and African Americans was 32.5% and 22.9%, respectively (P<0.05). The degree of CAD (composite score) was higher in subjects with IR (20.7 vs. 14.5, P=0.014 and 20.1 vs. 13.1, P=0.031 for Caucasians and African Americans, respectively), and in a multiple regression model IR was an independent predictor for CAD in both groups. In both ethnic groups, subjects with a combination of IR and high CRP (≥3 mg/L) had significantly higher composite score compared to those with no IR and low CRP (<3 mg/L) (21.2 vs. 13.9, P<0.05 and 20.9 vs. 10.2, P<0.05 for Caucasians and African Americans respectively). Similarly, the composite score was significantly higher in subjects with IR and high fibrinogen (≥340 mg/dl) compared to those with no IR and low fibrinogen. In conclusion, elevated levels of inflammatory markers were positively associated with IR. Further, a combination of IR and inflammation resulted in a higher degree of CAD in both Caucasians and African Americans. The results suggest that inflammation may potentiate the cardiovascular risk factor role of IR.
Insulin resistance; inflammation; CRP; fibrinogen; ethnicity
Metabolic derangements are common in human immunodeficiency virus (HIV)-positive subjects undergoing antiretroviral therapy, but little is known about postprandial conditions.
We investigated the relationship between leptin, adiponectin, nonesterified fatty acids (NEFA), and insulin in response to a day-long meal pattern and evaluated gender differences in HIV-positive men (n = 12) and women (n = 13) undergoing highly active antiretroviral therapy (HAART).
For both men and women, a significant decrease in postprandial NEFA levels was observed following breakfast (0.53 vs. 0.22 mmol/L, P < 0.001, baseline and at 3 hours, respectively), whereas day-long postprandial leptin and adiponectin levels showed small nonsignificant oscillations. In contrast to NEFA and adiponectin, postprandial leptin levels were significantly higher among women compared to men (P < 0.05). Postprandial NEFA levels correlated positively with fasting insulin levels (r2 = 0.25, P = 0.016), and the postbreakfast decrease in NEFA levels correlated significantly with the postbreakfast increase in insulin levels (r2 = 0.17, P = 0.038). No significant association between postprandial adipokines and insulin was observed.
In HAART-treated, HIV-infected men and women, levels of NEFA, but not adipokines, showed significant postprandial variation. Furthermore, food intake resulted in significant NEFA suppression in proportion to the food-stimulated insulin increase.