Abstract
Epidemiological studies have shown that obesity and cigarette smoking (CS) are major cardiovascular (CV) risk factors and when coexisting in the same individuals have additive/synergistic effects upon CVD development. We have shown that stable compounds of CS (ATVB 2004) as well as nicotine, in concentrations found in smoker’s plasma, promote atherosclerotic CVD (AJP 2013). Here we studied in Sprague Dawley (SD) rats with diet -induced obesity the mechanisms involved in nicotine enhancement of CVD. SD rats (N=6-7 each group) were fed either a high fat (HF) or a standard chow (SCH) diet with or without nicotine (100 mg/kg/day in the drinking water) for 20 weeks. The HF rats developed central obesity, characterized by increased body weight gain (22%) and abdominal fat weight (53%), increased plasma levels of cholesterol (33%), non-esterified free fatty acids (68%), insulin (15%) glucose (12%)and systolic blood pressure (SBP: 146 ± 5 vs. 131 ± 5 mmHg SCH rats, p<0.05). Nicotine further increased SBP in obese HF rats (158 ± 4 mmHg, p<0.05) but not in lean SCH rats. Nicotine significantly increased O2- production in both obese (1689 ± 87 count/min/mg) and lean rats (1074 ± 105 count/min/mg) and further impaired EDR (Emax: 74 ± 5%) in obese HF rats. Nicotine also increased the expression of the macrophage marker ED1 in the aortas of obese HF rats. In peritoneal macrophages from obese HF rats TNFα, IL1β and CD36 were increased, and were further significantly increased in nicotine-treated obese HF rats. Using PCR array for inflammatory cytokines and receptor signaling pathway we found that the aortas from obese HF rats showed 2-4 fold increases in expression of several chemokines and interleukin genes expression; nicotine further increased the expression of 11 pro-inflammatory genes in the aortas from obese HF rats. Our results suggest that nicotine dramatically aggravates the CV effects of diet -induced obesity by increasing oxidative stress, vascular inflammation and endothelial dysfunction. Clinically chronic inhalation of nicotine, as that delivered by E-cigarettes, by individuals unable to quit the habit may have an important pro-atherogenic effect, particularly in obese subjects.