Cyanidin-3-O-glucoside ameliorates palmitate-induced inflammation and insulin resistance in 3T3-L1 hypertrophic adipocytes

Obesity, one of the most common worldwide health disease, is a metabolic disorder correlated with an elevated morbidity and mortality rates, and increased risk of numerous pathologies, such as cardiovascular diseases and type 2 diabetes (Kaufer et al., 2001). It is associated with increased free fatty acids accumulation, alteration of adipokine levels and adaptive immune system that promote lipotoxicity and cause oxidative stress, inflammation, and insulin resistance in adipose tissue (McLaughlin et al., 2014). Several studies suggest that anthocyanins, natural polyphenols commonly present in food and vegetables from Mediterranean Diet, exert significant cardiovascular health-promoting effects probably through the modulation of specific cellular signalling pathways (Cimino et al., 2013). The aim of this work was to evaluate the in vitro protective effect exerted by cyanidin-3-O-glucoside (C3G), a widely distributed anthocyanin, on inflammation and insulin resistance induced by Palmitic Acid (PA) in mouse adipocytes (3T3-L1). Fully differentiated 3T3-L1 adipocytes were pretreated with different concentrations of C3G (5-10μM) for 24 h and then exposed to high concentrations of PA (1 mM) for 24 h in order to induce cellular hypertrophy. To evaluate the insulin-resistance condition, cells were subsequently treated with insulin 100 nM. NF-kB and insulin pathways were evaluated by means of Western blot and Real-time PCR techniques. Our results confirmed that PA was able to induce NF-κB proinflammatory pathway through the activation of IKK and the increase of nuclear accumulation of p65/NF-κB. Furthermore, PA induced mRNA up-regulation of NF-κB-modulated proinflammatory cytokines, such as IL-6 and TNF-α. Interestingly, C3G pretreatment was able to prevent the activation of NF-κB pathway and downstream cytokines mRNA levels. Moreover, PA induced insulin-resistance by the specific impairment of insulin IRS1/P3K/Akt signaling pathway, followed by a downstream reduction of the glucose transporter GLUT-1 and adiponectin. Interestingly, C3G pretreatment effectively reversed the effects of PA on IRS1/PI3K/Akt axis. In particular, we observed that C3G restored AdipoQ and GLUT1 expression altered by PA so improving insulin sensibility from hypertrophic adipocytes. These findings demonstrate that C3G ameliorates inflammation and insulin-resistance conditions induced by PA, thus suggesting new potential roles for this molecule in the prevention and treatment of pathological conditions linked to obesity. Bibliographic References 1. Cimino, F., Speciale, A., Anwar, S., Canali, R., Ricciardi, E., Virgili, F., Trombetta, D.,and Saija, A. (2013). Anthocyanins protect human endothelial cells from mild hyperoxia damage through modulation of Nrf2 pathway. Genes Nutr 8, 391-399 2. Kaufer, M.; Tavano, L.; Ávila, H. Obesidad en el adulto. In Nutriología Médica, 1st ed.; Casanueva, E., Kaufer, M., Pérez, A., Arroyo, P., Eds.; Editorial Médica Panamericana: México, México, (2001) 3. McLaughlin, Tracey, et al. T-cell profile in adipose tissue is associated with insulin resistance and systemic inflammation in humans. Arteriosclerosis, thrombosis, and vascular biology (2014): ATVBAHA-114.