The role of adiponectin in atherosclerosis: do lipids tip the scales?

Adiponectin is associated with abnormal lipid profile and coronary microvascular dysfunction in patients with dilated cardiomyopathy without overt heart failure

Reduced plasma adiponectin has been associated with abnormal lipid profile, reduced left ventricle (LV) function, and the extent of coronary atherosclerosis in coronary artery disease. The aim of this study was to assess these relationships in patients with dilated cardiomyopathy (DCM) without overt heart failure. Plasma adiponectin was measured in 55 DCM patients (age, 59 ± 12 years; male, 36; body mass index [BMI], 26.9 ± 0.49 kg/m²; LV ejection fraction, 39.8% ± 1.3%; New York Heart Association class I-II) and in 40 age- and BMI-matched healthy controls. In a subset of 25 patients, myocardial blood flow (MBF) was measured at rest and during intravenous dipyridamole (0.56 mg/kg in 4 minutes) by positron emission tomography and ¹³N-ammonia as a flow tracer. Adiponectin was 6.6 ± 0.34 μg/mL in controls and 10.9 ± 0.85 μg/mL in DCM patients (P < .001), where it was related inversely with BMI (P = .009) and directly with brain natriuretic peptide (P = .017), high-density lipoprotein (HDL) cholesterol (P = .002), and MBF dipyridamole (P = .020). Adiponectin lesser than median value in patients was associated with higher total to HDL cholesterol ratio (4.8 ± 0.24 vs 3.9 ± 0.18, P = .009) and lower MBF reserve (1.76 ± 0.16 vs 2.43 ± 0.19, P = .01). These results could suggest that down-regulation of the adiponectin levels and reduced HDL cholesterol have a key role in causing impaired coronary function and myocardial perfusion in DCM.

Retinol-binding protein-4 in experimental and clinical metabolic disease

Retinol-binding protein-4 (RBP4), a 21-kDa protein synthesized in the liver and adipose tissue, has recently been described as a murine adipokine involved in the development of insulin resistance. The expression of the gene encoding RBP4 was increased in the adipose tissue, but not in the liver, of insulin-resistant adipose GLUT4(-/-) mice and five other mouse models of obesity and insulin resistance. In addition, intraperitoneal injection or transgenic overexpression of RBP4 in mice induced insulin resistance. While experimental clinical approaches (mostly applying clamp techniques) in humans confirmed correlations of RBP4 with insulin resistance, studies in larger groups out of clinical routine failed to demonstrate a connection with alternative measures of insulin sensitivity. Yet, significant associations of RBP4 with atherogenic lipids were found and a focus of future studies should be the influence on atherosclerosis and related complications. Based on current data, the function of RBP4 as an adipokine exerting metabolic effects in glucose metabolism in humans remains uncertain and might be restricted to rodent models.

Relationship of adiponectin with markers of systemic inflammation, atherogenic dyslipidemia, and heart failure in patients with coronary heart disease

BACKGROUND

Adiponectin, an adipocyte-derived hormone, appears to be a modulator of lipid metabolism and systemic inflammation and is present in particularly low concentrations in patients with coronary heart disease (CHD). However, the clinical importance of adiponectin in individuals at markedly high risk for future cardiovascular morbidity and mortality has not been fully elucidated. We examined the associations between serum adiponectin and several biomarkers related to cardiovascular disease and heart failure in a large high-risk population comprising patients with prevalent CHD.

METHODS

We measured fasting adiponectin, interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP), N-terminal pro-B-type natriuretic peptide (NT-proBNP), and markers of lipoprotein metabolism in 1174 patients with CHD.

RESULTS

After adjustment for age and sex, adiponectin was associated with HDL-cholesterol (HDL-C; r = 0.25; P <0.0001), NT-proBNP (r = 0.17; P <0.0001), and plasma triglyceride (r = -0.21; P <0.0001) concentrations. There was, however, no statistically significant association between adiponectin and markers of systemic inflammation. In partial correlation analyses further adjusted for body mass index, alcohol intake, smoking status, presence of diabetes and/or hypertension, lipid-lowering drug therapy, and fasting plasma glucose, adiponectin remained significantly associated with HDL-C (r = 0.21; P <0.0001), NT-proBNP (r = 0.15; P <0.0001), and plasma triglycerides (r = -0.16; P <0.0001).

CONCLUSIONS

Serum adiponectin is associated with the presence of atherogenic dyslipidemia and with NT-proBNP concentration but not with markers of systemic inflammation in patients with manifest CHD. Thus, atherogenic dyslipidemia may link adiponectin with the progression of atherosclerosis. Moreover, serum adiponectin may be related to BNP in patients with CHD.