Glucose and Fatty Acid Metabolism in a 3 Tissue In-Vitro Model Challenged with Normo- and Hyperglycaemia

Nutrient balance in the human body is maintained through systemic signaling between different cells and tissues. Breaking down this circuitry to its most basic elements and reconstructing the metabolic network in-vitro provides a systematic method to gain a better understanding of how cross-talk between the organs contributes to the whole body metabolic profile and of the specific role of each different cell type. To this end, a 3-way connected culture of hepatocytes, adipose tissue and endothelial cells representing a simplified model of energetic substrate metabolism in the visceral region was developed. The 3-way culture was shown to maintain glucose and fatty acid homeostasis in-vitro. Subsequently it was challenged with insulin and high glucose concentrations to simulate hyperglycaemia. The aim was to study the capacity of the 3-way culture to maintain or restore normal circulating glucose concentrations in response to insulin and to investigate the effects these conditions on other metabolites involved in glucose and lipid metabolism. The results show that the system’s metabolic profile changes dramatically in the presence of high concentrations of glucose, and that these changes are modulated by the presence of insulin. Furthermore, we observed an increase in E-selectin levels in hyperglycaemic conditions and increased IL-6 concentrations in insulin-free-hyperglycaemic conditions, indicating, respectively, endothelial injury and proinflammatory stress in the challenged 3-way system

Study of the crosstalk between hepatocytes and endothelial cells using a novel multicompartmental bioreactor: a comparison between connected cultures and cocultures

The liver and other organs are connected to each other through the bloodstream. Therefore, the connection between tissues is generally mediated by soluble molecules able to cross the endothelial wall of capillaries. We developed a multicompartmental device, multicompartmental bioreactor (MCB), designed to mimic the connection between different tissues in which crosstalk is mediated by soluble molecules transported through the blood. A comparative study of the crosstalk between hepatocytes (HepG2) and endothelial cells (human umbilical vein endothelial cells) in connected culture in the MCB and in a traditional static coculture system was performed by analyzing glucose consumption and secretion of albumin, urea, and nitric oxide. When hepatocytes and endothelial cells were cultured together, the production of albumin and urea increased, and the increase was higher in the MCB than in traditional static coculture. In spite of this enhanced metabolic activity, the crosstalk between hepatocytes and endothelial cell leads to decreased glucose consumption with respect to hepatocytes alone, both in static and in dynamic conditions. However, the dynamic connected culture has a higher rate of metabolite synthesis and secretion with respect to cocultures. This means a more efficient use of energetic substrates and enhanced hepatocyte function in the MCB

Metabolic control through hepatocyte and adipose tissue cross-talk in a multicompartmental modular bioreactor

Physiological processes involve a complex network of signaling molecules that act through paracrinal or endocrinal pathways; however, traditional in vitro models cannot mimic these interactions because of the lack of a dynamic cross-talk between cells belonging to different tissues. The multicompartmental modular bioreactor is a novel cell culture system where hepatocytes and adipose tissue are shown to interact in a more physiological manner. In the multicompartmental modular bioreactor, cells and tissues can be cultured in a common medium, which flows through the system acting as the bloodstream. Primary rat hepatocytes and adipose tissue were cultured separately and together in conventional conditions and in the bioreactor. Urea synthesis, albumin secretion, glycerol, free fatty acid, and glucose concentrations were analyzed and compared. The dynamic connected culture of adipose tissue and hepatocytes led to a significant enhancement of hepatic function in terms of increase of albumin and urea production with respect to conventional cultures. Interestingly, the glycerol gradually released from adipose tissue was buffered in the dynamic connected culture, manifesting a homeostatic-like control. These data show that the dynamic culture not only improves hepatocyte function, but also allows a cross-talk between tissues, leading to enhanced metabolic regulation in vitro