Metabolism of glucose and lipids is essential for nutrient balance and metabolic homeostasis, and is dynamically regulated by adipose tissue and liver. Dysfunction in regulation of these molecules as well as the secreted factors results in metabolic syndrome and insulin resistance (IR), which is a precursor to type 2 diabetes. Studies have shown that as the main site of adaptive thermogenesis, brown adipose tissue (BAT) improves hepatic insulin sensitivity, whereas white adipose tissue (WAT) can induce hepatic IR. However, how these organs communicate to regulate insulin sensitivity is not completely understood due to the lack of representative experimental models. Animals models are useful but suffer from confounding effects from other organs; traditional in vitro models have limited physiological representation.
We have developed an organ-on-chip platform to study the interactions between BAT/WAT and liver under different metabolic states. The adipose-liver organ-chip consists of two interconnected microfluidic devices - brown/white adipocytes were cultured in one device and hepatocytes (insulin sensitive and IR) in the other, both under perfusion. We show that (a) adipocytes exhibited higher intracellular lipid and fatty acid secretion and (b) the hepatocytes secreted higher albumin compared to traditional co-cultures. We found that brown adipocytes secretions restored insulin sensitivity, and improved glucose/lipid metabolism in IR hepatocytes. In contrast, white adipocytes worsened insulin sensitivity and glucose/lipid metabolism. IR hepatocytes lowered Akt-phosphorylation and glucose uptake while upregulated adipocyte fatty acids secretion. Through RNA-seq, we have identified adipose genes responsible for improving hepatic IR.
We have discovered potential new targets for improving hepatic insulin sensitivity. The novel organ-chip platform represented the cells physiologically and will be useful in the discovery and validation of new therapeutic targets for T2D.
N. Tanataweethum: None. A. Trang: None. L. Annepureddy: None. J. Mehta: None. R.N. Cohen: None. A. Bhushan: None.