In vitro interactions of adipocytes and macrophages : potential roles of vegetal extracts in obesity prevention

Obesity and overweight are a plague that concerns more than 20 % of the world population. People suffering from these states present excessive fat accumulation that could impair health. The main causes are an increased intake of energy-dense food and an increased physical inactivity. The energy excess is stored in the adipose tissue whose functions are deregulated, which induces obesity linked metabolic complications. Indeed, most of the time, obesity is accompanied by metabolic disorders, i.e. type 2 diabetes, cardiovascular disease… Medical interventions are possible but they often appear ineffective, this is why preventive actions need to be set up. This study aimed at investigating the potential beneficial effects of fruit derivatives (i.e., pomegranate husk extract and three apple extracts) on the development of obesity and its metabolic disorders by focusing on the adipose tissue functions. In case of weight gain, the adipose tissues, responsible for the energy storage, have to increase their storage capacity by increasing the size of the adipocytes as well as their number by inducing the differentiation of preadipocytes (adipogenesis). This leads to an increasing body fat mass associated with the obesity complications. In order to identify potential natural candidates that could reduce the adipose tissue expansion linked to obesity development, we have studied the effect of a pomegranate husk extract and three apple extracts on adipogenesis and fat accumulation in vitro. Thanks to fluorescence microscopy technics, we have shown that the pomegranate husk and apple extracts could partially inhibit the adipogenesis and the lipid accumulation. These first results make of these extracts interesting candidates for additional investigations. The second part of this work was focused on the adipose tissue inflammation. Indeed, the adipose tissue of obese people is characterized by a chronic low grade inflammation that could spread throughout the body and induce metabolic disorders. This inflammation is mainly due to an interaction between hypertrophied adipocytes and inflamed macrophages found in the adipose tissues. This condition has been simulated in vitro in order to investigate the potential anti-inflammatory effect of the extracts of interest (i.e., the pomegranate husk extract and three apple extracts). The expression and secretion of pro-inflammatory markers were followed, i.e. IL-6, TNF and CCL-2 as well as the anti-inflammatory adipokine, i.e. adiponectin. Although the pomegranate husk extract was able to reduce the inflammatory secretions of adipocytes or macrophages cultivated independently, the extract was no more able to decrease the inflammation maintained by the both cell types cultivated together. Nevertheless, the three apple extracts have revealed interesting anti-inflammatory effects on the cells monocultivated and cocultivated by reducing the secretion, as well as the expression, of pro-inflammatory mediators. Taken as a whole, the results reported in this work allow to highlighte that natural derivatives such as the pomegranate husk extract or apple extracts could be interesting candidate to prevent obesity development and/or complications by acting on adipose tissue functions. However, additional research has to be done to investigate the bioavailability of these extracts as well as their residual effects in vivo.(SC - Sciences) -- UCL, 201