Associations between disease activity, markers of HDL functionality and arterial stiffness in patients with rheumatoid arthritis.

BACKGROUND AND AIMS: Rheumatoid arthritis (RA) is a chronic, inflammatory disease associated with increased risk of cardiovascular disease (CVD). Measures of HDL metabolism/function were shown to be altered in RA patients with high disease activity. We aimed at evaluating the effect of HDL characteristics on arterial stiffness in RA patients classified according to the inflammatory disease activity. METHODS: RA patients were classified according to disease activity (DAS-28) into active RA (n = 27; DAS-28 > 3.2) and inactive RA patients (n = 17; DAS-28 < 3.2). A control group of healthy individuals was also studied (n = 33). Clinical and biochemical characteristics, cholesteryl ester transfer protein (CETP) and paraoxonase 1 (phenylacetate and paraoxonase) activities and carotid-femoral pulse wave velocity (cf-PWV) were determined. RESULTS: Anthropometric characteristics were similar in all groups. In accordance with the inflammatory status, active RA patients presented elevated hsCRP levels (p < 0.001). There were no differences in the lipid profile between groups. Similarly, features of insulin resistance were absent in RA patients (p = non-significant). Active RA patients presented higher CETP activity than the other two groups (p = 0.026). Phenylacetate and paraoxonase activities were altered in active RA patients in comparison with the other groups (p = 0.034 and p = 0.041, respectively). Cf-PWV was significantly higher in active RA patients in comparison with controls, following adjustment by age (p = 0.030). Age (ßst = 0.468, p = 0.013) and apo A-I levels (ßst = -0.405, p = 0.029) were independent predictors of cf-PWV in a model including hsCRP, HOMA-IR, and phenylacetate activity (r(2) = 0.42). CONCLUSIONS: High DAS-28 identifies patients with alterations in HDL characteristics. Plasma levels of apo A-I can be used as a marker of arterial stiffness in RA.

Dyslipidemia, but not hyperglycemia and insulin resistance, is associated with marked alterations in the HDL lipidome in type 2 diabetic subjects in the DIWA cohort: impact on small HDL particles.

In this study we have used mass spectrometry in order to characterize the HDL lipidome in three groups of women from the DIWA cohort; one control group, plus two groups with type 2 diabetes with insulin resistance; one dyslipidemic and one normolipidemic. The aim was to investigate whether dyslipidemia is required in addition to insulin resistance for the occurrence of an altered HDL lipidome, which in turn might impact HDL functionality. The dyslipidemic type 2 diabetic subjects were distinguished by obesity, hypertriglyceridemia with elevated apoC3, low HDL-cholesterol and chronic low grade inflammation. In a stepwise multivariate linear regression analysis, including biomarkers of dyslipidemia and insulin resistance as independent variables, only dyslipidemia showed a significant correlation with HDL lipid classes. Small HDL-particles predominated in dyslipidemic subjects in contrast to the normolipidemic diabetic and control groups, and were enriched in lysophosphatidylcholine (+13%), a product of proinflammatory phospholipases, and equally in two core lipids, palmitate-rich triacylglycerols and diacylglycerols (+77 %), thereby reflecting elevated CETP activity. Dyslipidemic small HDL particles were further distinguished not only as the primary carrier of ceramides, which promote inflammation and insulin resistance, but also by a subnormal plasmalogen/apoAI ratio, consistent with elevated oxidative stress typical of type 2 diabetes. From these data we conclude that in type 2 diabetes, dyslipidemia predominates relative to hyperglycemia for the occurrence of an altered HDL lipidome. Furthermore, dyslipidemia alters the cargo of bioactive lipids, with implications for HDL function.

Low density lipoproteins as circulating fast temperature sensors.

BACKGROUND: The potential physiological significance of the nanophase transition of neutral lipids in the core of low density lipoprotein (LDL) particles is dependent on whether the rate is fast enough to integrate small (+/-2 degrees C) temperature changes in the blood circulation. METHODOLOGY/PRINCIPAL FINDINGS: Using sub-second, time-resolved small-angle X-ray scattering technology with synchrotron radiation, we have monitored the dynamics of structural changes within LDL, which were triggered by temperature-jumps and -drops, respectively. Our findings reveal that the melting transition is complete within less than 10 milliseconds. The freezing transition proceeds slowly with a half-time of approximately two seconds. Thus, the time period over which LDL particles reside in cooler regions of the body readily facilitates structural reorientation of the apolar core lipids. CONCLUSIONS/SIGNIFICANCE: Low density lipoproteins, the biological nanoparticles responsible for the transport of cholesterol in blood, are shown to act as intrinsic nano-thermometers, which can follow the periodic temperature changes during blood circulation. Our results demonstrate that the lipid core in LDL changes from a liquid crystalline to an oily state within fractions of seconds. This may, through the coupling to the protein structure of LDL, have important repercussions on current theories of the role of LDL in the pathogenesis of atherosclerosis.