Insulin protects liver cells from saturated fatty acid-induced apoptosis via inhibition of c-Jun NH2 terminal kinase activity.
Hepatocyte apoptosis is increased in patients with nonalcoholic steatohepatitis and correlates with disease severity. Long-chain saturated fatty acids, such as palmitate and stearate, induce apoptosis in liver cells. The present study examined insulin-mediated protection against saturated fatty acid-induced apoptosis in the rat hepatoma cell line, H4IIE, and primary rat hepatocytes. Cells were provided a control media (no fatty acids) or the same media containing 250 micromol/liter of albumin-bound oleate or palmitate for 16 h. Insulin concentrations were 0, 1, 10, or 100 nmol/liter (n=4-6/treatment). Palmitate, but not oleate, activated caspase-3 and induced DNA fragmentation in the absence of insulin. Insulin reduced palmitate-mediated activation of caspase-3 and DNA fragmentation in a dose-dependent manner. Phosphatidylinositol 3-kinase inhibitors abolished these effects of insulin. Insulin-mediated inhibition of palmitate-induced apoptosis was not due to an augmentation in the unfolded protein response or increased expression of genes encoding the inhibitor of apoptosis proteins, inhibitor of apoptosis protein-2 and X-linked mammalian inhibitor of apoptosis protein. Palmitate, but not oleate, increased c-Jun NH2 terminal kinase activity in the absence of insulin. Insulin or SP600125, a chemical inhibitor of c-Jun NH2 terminal kinase, blocked palmitate-mediated activation of c-Jun NH2 terminal kinase and reduced apoptosis. These data suggest that insulin is an important determinant of saturated fatty acid-induced apoptosis in liver cells and may have implications for fatty acid-mediated liver cell injury in insulin-deficient and/or -resistant states.
Pagliassotti
M J
MJ
Department of Food Science and Human Nutrition, Colorado State University, Campus Deliver 1571, Fort Collins, Colorado 80526, USA. pagliasm@cahs.colostate.edu
Wei
Y
Y
Wang
D
D
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005227:Fatty Acids / Q000494:pharmacology*; D005260:Female; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015151:Immunoblotting; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D010168:Palmitates / Q000494:pharmacology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019284:Thapsigargin / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D000873:Anthracenes; D002867:Chromones; D005227:Fatty Acids; D051034:Inhibitor of Apoptosis Proteins; D007328:Insulin; D009025:Morpholines; D010168:Palmitates; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; C432165:pyrazolanthrone; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019284:Thapsigargin; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3; D000077191:Wortmannin