Abstract 467: The Role of Obesity and Aging in Cardiovascular Remodeling in Monosodium Glutamate Treated Rats
The monosodium glutamate (MSG)-induced obese rat is a model associated with insulin resistance and dyslipidemia. The aim of this study was to evaluate the interaction of obesity and aging in cardiovascular remodeling. Male Wistar rats received subcutaneous injections of MSG (4.0g/kg) from the second to the sixth day after birth. The first sacrifice was done at week 16, when insulin resistance of the MSG group was established, and at week 30 we did the second sacrifice, obtaining four groups: control 16-week (CON-16); monosodium glutamate 16-week (MSG-16); control 30-week (CON-30); monosodium glutamate 30-week (MSG-30). Systolic blood pressure (BP) was measured weekly by tail-cuff plethysmography. The myocardium tissue was fixed and stained with Sirius red. The lumen diameter, media thickness and media cross-sectional area (CSA) of the intramyocardial arteries were measured. Cardiac collagen density was estimated with optical microscopy using the Image Pro Plus analysis system. The Lee index was significantly higher in MSG groups (30.43±0.34 and 31.2±0.2 vs 29.5±0.22 and 29.7±1.0 g/cm, p<0.001). The systolic BP was significantly increased in the MSG-30 group (135±2 mmHg, p<0.001) comparing to CON-16 (113±2 mmHg), CON-30 (115±1 mmHg) and MSG-16 (108±2 mmHg). The morphological analyses show similar diameter at the intramyocardial arteries but media thickness was significantly greater in MSG-30 rats (16.3±0.2 μm2, p < 0.01) when compared to CON-16(12.5±0.5 μm2) and CON-30(13.±0.4 μm2) groups. Vascular remodeling was evident in obese groups observing an adverse effect of aging when measuring media-to-lumen ratio: 30.2±2.0% (CON-16), 39.9±3.7% (MSG-16), 39.3±1.2% (CON-30), 51.2±1.3% (MSG-30) (MSG-30 vs MSG-16 and CON-30 p< 0.05; MSG-30 vs CON-16, p< 0.001). Media CSA was also increased in MSG groups compared to control group resulting in an elevated growth index suggesting a hypertrophic vascular remodeling in these animals. Myocardial collagen density was significantly greater in obese (4.0±0.5 and 5.1±0.5 %) than in control rats (2.1±1.3% and 2.6±0.6%, p<0.01). We concluded that in this experimental model, the presence of obesity promoted the increase of blood pressure and accelerated the adverse cardiovascular remodeling observed in aging.
- © 2012 by American Heart Association, Inc.