Calcium-dependent insulin resistance in hepatocytes: mathematical model.

Hepatocyte insulin resistance is one of the early factors of developing type II diabetes. If insulin resistance is treated early, type II diabetes could be prevented. In recent years, scientists have been conducting extensive research on the underlying issues on a cellular and molecular level. It was found that the modulation of IP-receptors, the mitochondrial ability to form the mitochondria-associated membranes (MAMs) and the endoplasmic reticulum stress during Ca signaling play a key role in hepatocyte being able to maintain euglycemia and provide metabolic flexibility. However, researchers cannot agree on what factor is the key one in resulting in insulin resistance. In this work, we propose a mathematical model of Ca signaling. We included in the model all the major contributors of a proper Ca signaling during both the fasting and the postprandial state. Our modeling results are in good agreement with available experimental data. The analysis of modeling results suggests that MAMs dysfunction alone cannot result in abnormal Ca signaling and the wrong modulation of IP-receptors is a more definite reason. However, both the MAMs dysfunction and the IP signaling dysregulation combined can lead to a robust Ca signal and improper glucose release. In addition, our model results suggest a strong dependence of Ca oscillations pattern on morphological characteristics of the ER and the mitochondria.