Insulin‐dependent mitochondrial Ca 2+ uptake in skeletal muscle is quickly disrupted in high‐fat diet fed mice (572.3)

The mitochondrial function quickly responds to energy‐dense food supply in order to deal with the demand but the role of mitochondrial Ca2+ in these processes has not been understood. Male C57BL/6J mice were fed a normal chow diet (NCD) or a high fat diet (HFD) for 1 week. The insulin resistance was evaluated by IPGTT, fasting glucose and insulin, and HOMA‐IR. GLUT4myc‐eGFP was electroporated in the Flexor digitorum brevis muscle (FDB). Insulin induces an increase in cytoplasmic and mitochondrial Ca2+ signal in adult fibers. The uncoupler FCCP, releases Ca2+ from mitochondria to cytoplasm. Insulin‐dependent mitochondrial Ca2+ uptake is decreased in fibers from short‐term HFD fed mice while insulin‐dependent cytoplasmic Ca2+ increase appear to be faster and stronger. In fibers from NCD fed mice, insulin‐dependent mitochondrial Ca2+ uptake was inhibited by xestospongin B, a specific IP3R inhibitor. Using TMRE+ in the non‐quenching mode (5 nM), we found that the ΔΨm was larger in fibers from short‐term HFD fed mice v/s NCD derived fibers. Using TMRE+ in quenching mode (100 nM), we found that the TMRE+ released after uncoupler stimuli was higher in fibers from short‐term HFD fed mice v/s NCD fed mice. The glucose analogue (2‐NBDG) uptake and the redistribution of GLUT4myceGFP induced by insulin were decreased in presence of xestospongin or ruthenium red (MCU inhibitor). This effect suggest a retrograde regulation of insulin signaling by mitochondrial Ca2+ uptake. Grant Funding Source : Supported by FONDECYT 11130267 and ACT1111