leptin and Hypertrophy--Right-Ventricular

Leptin is a neuroendocrine peptide released by adipose tissue that enhances metabolism and acts on the hypothalamus to suppress appetite. Leptin also regulates aspects of cardiovascular function and low serum leptin has been associated with increased mortality in humans. We hypothesized that leptin deficiency alters the structure and function of the pulmonary vasculature.. We examined two groups of C57BL/6 male mice aged 12 weeks: five ob/ob (B6.VLepob/ob) leptin-deficient and five wild type (WT) (C57BL/6) control mice. As expected, weight was significantly greater in ob/ob mice relative to WT mice [weight (g), Mean±SD): ob/ob 52±2.5 g, wild type 30±2.5 g; p<0.001]. The pulmonary vasculature of ob/ob mice and WT control animals was examined by histology, immunohistochemistry and immunofluorescence staining.. Pulmonary arterial wall thickness was significantly increased in ob/ob mice relative to WT littermates [median (interquartile range) distance in pixels: ob/ob 0.13 (0.05-0.18), wild type 0.03 (0.02-0.04); p=0.001]. The ob/ob mice also exhibited significant right ventricular hypertrophy in comparison to control animals [RV thickness (Mean±SD): ob/ob 0.75±0.19, wild type; 0.58±0.13 p<0.001]. We observed substantial macrophage infiltration and abundant proliferation of myofibroblasts and fibroblasts in histological sections of pulmonary arterioles of ob/ob mice. In addition, we noted increased hyaluronan deposition, colocalizing with SMC-actin in the pulmonary vasculature of ob/ob mice relative to WT controls.. The pulmonary pathology of leptin deficiency in ob/ob mice recapitulates many of the histological features of pulmonary vascular diseases, including pulmonary hypertension, suggesting that leptin deficiency is associated to the pathogenesis of pulmonary vascular disease.

Topics: Actins; Animals; Cell Proliferation; Disease Models, Animal; Hyaluronic Acid; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Leptin; Macrophages; Male; Mice, Inbred C57BL; Mice, Knockout; Myofibroblasts; Pulmonary Artery; Vascular Remodeling

The traditionally accepted mechanism for ventricular adaptation to obesity suggests that cavity dilatation in response to increased blood volume and elevated filling pressure results in ventricular hypertrophy as a compensatory mechanism. Our hypothesis was that, instead, initiation of ventricular hypertrophy in obesity may be explained by changes in hormonal milieu and not by cavity dilatation.. 88 female subjects without identifiable cardiovascular risk factors, covering a wide range of body mass indices (BMI), from normal (21.2 ± 1.6 kg/m(2)) to severely obese (45.0 ± 4.6 kg/m(2)), underwent cardiovascular MRI to determine left ventricular (LV) and right ventricular (RV) mass and volumes.. BMI correlated positively with LV and RV mass and end-diastolic volumes (EDV). However overweight is associated with a significant LV and RV hypertrophy (LV: 78 ± 11 g vs 103 ± 16 g, p<0.01; RV: 26 ± 7 g vs 40 ± 11 g, p<0.01) was observed in the absence of differences in LV and RV volumes (LV: EDV 119 ± 15 vs 121 ± 21 ml, p>0.99, RV: 131 ± 17 vs 130 ± 24 ml; p>0.99). Furthermore, significant increases of serum leptin occurred at this pre-obese stage (15.6 ± 19 vs 36.5 ± 22 ng/ml; p=0.013).. In a cohort of healthy female subjects with a wide range of BMIs, ventricular hypertrophy occurs without associated cavity dilatation in overweight individuals, while in manifest obesity, both cavity dilatation and ventricular hypertrophy occur. Elevated leptin levels may have a role in this effect on ventricular mass.

Topics: Adult; Body Mass Index; Cardiomegaly; Cohort Studies; Female; Humans; Hypertrophy, Left Ventricular; Hypertrophy, Right Ventricular; Insulin; Insulin Resistance; Leptin; Magnetic Resonance Imaging; Middle Aged; Obesity; Ventricular Function, Left; Ventricular Function, Right