Elevated plasma levels of TNF-alpha and interleukin-6 in patients with diastolic dysfunction and glucose metabolism disorders

Insulin resistance and glycemic abnormalities are associated with deterioration of left ventricular diastolic function: a cross-sectional study

BACKGROUND

Left ventricular diastolic dysfunction (LVDD) is considered a precursor of diabetic cardiomyopathy, while insulin resistance (IR) is a precursor of type 2 diabetes mellitus (T2DM) and independently predicts heart failure (HF). We assessed whether IR and abnormalities of the glucose metabolism are related to LVDD.

METHODS

We included 208 patients with normal ejection fraction, 57 (27%) of whom had T2DM before inclusion. In subjects without T2DM, an oral glucose tolerance test (oGTT) was performed. IR was assessed using the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). The lower limit of the top quartile of the HOMA-IR distribution (3.217) was chosen as threshold for IR. LVDD was verified according to current guidelines.

RESULTS

IR was diagnosed in 38 (18%) patients without a history of diabetes. The prevalence of LVDD was 92% in subjects with IR vs. 72% in patients without IR (n = 113), respectively (p = 0.013). In the IR group, the early diastolic mitral inflow velocity (E) in relation to the early diastolic tissue Doppler velocity (averaged from the septal and lateral mitral annulus, E'av) ratio (E/E'av) was significantly higher compared to those without IR (9.8 [8.3-11.5] vs. 8.1 [6.6-11.0], p = 0.011). This finding remains significant when patients with IR and concomitant T2DM based on oGTT results were excluded (E/E'av ratio 9.8 [8.2-11.1)] in IR vs. 7.9 [6.5-10.5] in those without both IR and T2DM, p = 0.014). There were significant differences among patients with and without LVDD regarding the HOMA-IR (1.71 [1.04-3.88] vs. 1.09 [0.43-2.2], p = 0.003). The HOMA-IR was independently associated with LVDD on multivariate logistic regression analysis, a 1-unit increase in HOMA-IR value was associated with an odds ratio for prevalent LVDD of 2.1 (95% CI 1.3-3.1, p = 0.001). Furthermore, the E/E'av ratio increases along the glucose metabolism status from normal glucose metabolism (7.6 [6.2-10.1]) to impaired glucose tolerance (8.8 [7.4-11.0]) and T2DM (10.5 [8.1-13.2]), respectively (p < 0.001).

CONCLUSIONS

Insulin resistance is independently associated with LVDD in subjects without overt T2DM. Patients with IR and glucose metabolism disorders might represent a target population to prevent the development of HF. Screening programs for glucose metabolism disturbances should address the assessment of diastolic function and probably IR.

The ubiquitous interleukin-6: a time for reappraisal

Interleukin-6 (IL-6) is a multifunctional cytokine regulating humoral and cellular responses and playing a central role in inflammation and tissue injury. Its effects are mediated through interaction with its receptor complex, IL-6Rβ (also known as gp130). It plays an important role in the pathogenesis of coronary artery disease and large quantities of IL-6 are found in human atherosclerotic plaques. IL-6 levels positively correlate with higher all-cause mortality, unstable angina, left ventricular dysfunction, propensity to diabetes and its complications, hypertension, obesity and several types of cancer. IL-6 levels augmentation demonstrates a remarkable parallel with another biomarkers reflecting harmful processes, like tumor necrosis factor alpha, interleukins 8 and 18, YKL-40, C reactive protein and resistin. Due to these facts, IL-6 was classified as a noxious interleukin. Nonetheless, there are several facts that challenge this usually accepted point of view. Since IL-6 has also anti-inflammatory activity, it seems reasonable to assume that favorable aspects exist. These aspects are two: 1. protection against bacterial infections, inactivating proinflammatory mediators, mitigating the course of septic shock and inducing the production of cortisol; and 2. influence on insulin sensitivity during exercise; this aspect is even more important. During exercise IL-6 is synthesized and released by muscles, with enhanced insulin action immediately at early recovery. Skeletal muscle may be considered as an endocrine organ; contracting muscles produce IL-6 and release it into the blood exerting its effects on other organs. The increase in circulating levels of IL-6 after exercise is consistent and proportional to exercise duration, intensity, muscle mass involved and endurance capacity. Thus, the fascinating possibility that the plenteous beneficial health effects of exercise could be ultimately mediated by IL-6 merits further elucidation. Interleukins were termed "good" or "bad", probably due to a tendency to see things in black and white, with no gray area in between. Calling IL-6 "a molecule with both beneficial and destructive potentials" would be a more equitable approach. In the literary creatures of Dr. Jekyll and Mr. Hyde, a good and an evil personality are found in the same individual. IL-6 playing the role of Dr. Jekyll is emerging; the time for IL-6 reappraisal is coming.

Eicosapentaenoic acid suppresses ocular inflammation in endotoxin-induced uveitis

PURPOSE

To investigate the effect of eicosapentaenoic acid (EPA) on acute ocular inflammation in an animal model of endotoxin-induced uveitis (EIU).

METHODS

C57Bl/6 mice (6-week-old males) were orally treated with EPA at a dose of 50 mg/kg/day for 5 days. EIU was then induced in the animals by intraperitoneal injection of 160 microg lipopolysaccharide (LPS). Twenty-four hours after LPS injection, leukocyte adhesion to the retinal vasculature was evaluated by the concanavalin A lectin perfusion-labeling technique, and leukocyte infiltration into the vitreous cavity was quantified. Furthermore, the protein levels of monocyte chemotactic protein (MCP)-1, interleukin (IL)-6, intercellular adhesion molecule-1 and phospholyrated nuclear factor (NF)-kappaB p65 in the retina and retinal pigment epithelium (RPE)-choroid complex were examined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

At 24 h after LPS injection, the EIU animals treated with oral EPA administration showed a significant decrease in leukocyte adhesion to the retinal vessels by 43.4% (p<0.01) and leukocyte infiltration into the vitreous cavity by 49.2% (p<0.05). In addition, EPA significantly reduced the protein levels of MCP-1 and IL-6 in the retina and the RPE-choroid complex. Furthermore, phosphorylation of NF-kappaB was suppressed by EPA treatment.

CONCLUSIONS

Our data suggest that EPA inhibits multiple inflammatory molecules in vivo. EPA may become a novel strategy in the prevention and/or treatment of ocular inflammatory diseases.

Diastolic function is strongly and independently associated with cardiorespiratory fitness in central obesity

Cardiorespiratory fitness [maximal O2 consumption (V̇o2max)] is an independent risk factor for type 2 diabetes; but in individuals at risk, factors influencing V̇o2max are poorly understood. We tested the hypothesis that V̇o2max is associated with diastolic function [subendocardial variability ratio (SEVR), %], as diastolic function influences myocardial perfusion. We studied 47 men and women with central obesity without diabetes. We measured fitness (V̇o2max) by treadmill testing and diastolic function (SEVR%) by pulse-wave analysis. We measured other factors influencing this relationship: insulin sensitivity [whole body glucose uptake-to-insulin concentration ratio (M/I)] by hyperinsulinemic euglycemic clamp, fatness by MR imaging and dual-energy X-ray absorptiometry, physical activity energy expenditure (metabolic equivalents of tasks) by the Sensewear Pro2 device, and muscle microvascular exchange capacity (capillary filtration coefficient) by venous plethysmography. Mean age of the subjects was 51 ± 9 (SD) yr. V̇o2max was associated with SEVR% ( r = 0.50, P = 0.001), fatness ( r = −0.39, P = 0.008), and HbA1c ( r = −0.35, P = 0.018), but not with whole body glucose uptake-to-insulin concentration ratio, metabolic equivalents of tasks, or capillary filtration coefficient. In regression modeling with age, sex, fatness, and SEVR% as explanatory variables, only age, sex, and SEVR% were independently associated with V̇o2max (SEVR% − standardized B coefficient = 0.37, 95% confidence interval = 0.003–0.18, P = 0.007). This model identified 46% of the variance in V̇o2max ( R2 = 0.46, P = 0.0001). There was a strong, independent association between V̇o2max and a measure of diastolic function in sedentary individuals with central obesity.