Contents lists available at ScienceDirect Environmental Toxicology and Pharmacology journal homepage: www.elsevier.com/locate/etap Research Paper Combined oral contraceptive and nitric oxide synthesis inhibition synergistically causes cardiac hypertrophy and exacerbates insulin resistance in female rats Lawrence A. Olatunji a, ⁎ , Kehinde S. Olaniyi a , Taofeek O. Usman a,b , Bilikis A. Abolarinwa a , Caleb J. Achile a , In-kyeom Kim c a Cardiovascular Research Laboratory, Department of Physiology, College of Health Sciences, University of Ilorin, Ilorin, Nigeria b Cardiovascular Unit, Department of Physiology, College of Health Sciences, Osun State University, Osogbo, Nigeria c Department of Pharmacology & Cardiovascular Research Institute, Kyungpook National University School of Medicine, Daegu 700-842, Republic of Korea ARTICLE INFO Keywords: Cardiac hypertrophy Inflammation Nitric oxide Oral contraceptive Profibrotic biomarker ABSTRACT Combined oral contraceptive (COC) use or inhibition of nitric oxide (NO) synthesis has been shown to cause hypertension and insulin resistance. However, the concomitant effects of COC and NO deficiency on the heart and glucose regulation are not well known. We therefore hypothesized that COC treatment during NO deficiency would lead to the development of cardiac hypertrophy that is associated with aggravated glucose deregulation, pro-inflammatory and pro-fibrotic biomarkers. Eight-week-old female Wistar rats were randomly allotted into control, NO deficient (N G -nitro-L-arginine methyl ester: L-NAME; 20.0 mg/kg b.w.), COC-treated (1.0 μg ethinylestradiol + 5.0 μg levonorgestrel, p.o) and L-NAME + COC-treated groups. The animals were treated daily for 6 weeks. Systolic blood pressure was estimated by tail-cuff plethysmography, insulin resistance (IR) and β-cell function were estimated by homeostatic model of assessment (HOMA-IR and HOMA-β). Pro-inflammatory (C-reactive protein; CRP and uric acid) and pro-fibrotic (plasminogen activator inhibitor-1; PAI-1) biomarkers were estimated in the plasma. Cardiac histological examination was also done. Results show that COC or L- NAME treatments led to increased blood pressure, HOMA-IR, impaired β-cell function, PAI-1, CRP and uric acid, without significant effect on cardiac mass. L-NAME + COC-treated group had significantly higher blood pressure, HOMA-IR, impaired β-cell function, PAI-1, CRP and cardiac mass than COC- or L-NAME-treated groups. Histological examination validated that COC use during NO deficiency causes cardiac hypertrophy. The present study demonstrates that COC treatment and NO deficiency synergistically causes cardiac hypertrophy that is associated with aggravated glucose deregulation, atherogenic dyslipidemia, pro-inflammatory and pro- fibrotic markers. 1. Introduction In spite of increasing efforts to reduce cardiovascular disease (CVD) risk factors, cardiac and vascular diseases remain an enormous global burden, both in terms of health and costs (Heidenreich et al., 2011; Bhatnagar et al., 2015). The global rise in cardiovascular morbidity and mortality are attributable to increasing incidence of inflammatory CVD risk factors, perhaps due to poor early detection/prognosis (Canto et al., 2011). Cardiac hypertrophy (CH) is a compensatory asymptomatic independent CVD risk factor, which is strongly associated with hyper- tension, increased risk of heart failure, myocardial infarction and sudden cardiac death (Maulik and Kumar, 2012). The complex and dynamic pathophysiological mechanisms of cardiac hypertrophy has been the focus of intense scientific investigation, in an effort to design preventive and curative measures (Nishimura and Ommen, 2007). Elevated inflammatory CVD risk factors that are associated with metabolic disturbances (Tanno et al., 2012) have been identified as a key contributing factor in the development of cardiac hypertrophy (Maulik and Kumar, 2012; Kudo et al., 2009). Insulin resistance (IR) has been shown to be a major metabolic disturbance among hypertension, dyslipidemia, type 2 diabetes, obe- sity, and attendant inflammatory CVD (Fonseca 2010). Also, the compensatory hyperinsulinemia is associated with inflammatory CVD and mortality independent of other risk factors such as obesity or diabetes (Abdul-Ghani et al., 2006). Considerable clinical evidence has suggested a role for IR in the pathogenesis of cardiac hypertrophy http://dx.doi.org/10.1016/j.etap.2017.03.012 Received 30 August 2016; Received in revised form 18 February 2017; Accepted 18 March 2017 ⁎ Corresponding author at: Department of Physiology, University of Ilorin, P.M.B. 1515 Ilorin, 240001, Nigeria. E-mail address: tunjilaw@unilorin.edu.ng (L.A. Olatunji). Environmental Toxicology and Pharmacology 52 (2017) 54–61 Available online 20 March 2017 1382-6689/ © 2017 Elsevier B.V. All rights reserved. MARK