title: Glucolipotoxicity alters lipid partitioning and causes mitochondrial dysfunction, cholesterol, and ceramide deposition and reactive oxygen species production in INS832/13 ss-cells.
abstract: Elevated glucose and saturated fatty acids synergize in inducing apoptosis in INS832/13 cells and in human islet cells. In order to gain insight into the molecular mechanism(s) of glucolipotoxicity (Gltox), gene profiling and metabolic analyses were performed in INS832/13 cells cultured at 5 or 20 mm glucose in the absence or presence of palmitate. Expression changes were observed for transcripts involved in mitochondrial, lipid, and glucose metabolism. At 24 h after Gltox, increased expression of lipid partitioning genes suggested a promotion of fatty acid esterification and reduced lipid oxidation/detoxification, whereas changes in the expression of energy metabolism genes suggested mitochondrial dysfunction. These changes were associated with decreased glucose-induced insulin secretion, total insulin content, ATP levels, AMP-kinase activity, mitochondrial membrane potential and fat oxidation, unchanged de novo fatty acid synthesis, and increased reactive oxygen species, cholesterol, ceramide, and triglyceride levels. However, the synergy between elevated glucose and palmitate to cause ss-cell toxicity in term of apoptosis and reduced glucose-induced insulin secretion only correlated with triglyceride and ceramide depositions. Overexpression of endoplasmic reticulum glycerol-3-phosphate acyl transferase to enhance lipid esterification amplified Gltox at intermediate glucose (11 mm), whereas reducing acetyl-coenzyme A carboxylase 1 expression by small interfering RNA to shift lipid partitioning to fat oxidation reduced Gltox. The results suggest that Gltox entails alterations in lipid partitioning, sterol and ceramide accumulation, mitochondrial dysfunction, and reactive oxygen species production, all contributing to altering ss-cell function. The data also suggest that the early promotion of lipid esterification processes is instrumental in the Gltox process.
authors.affiliation: Molecular Nutrition Unit and the Montreal Diabetes Research Center, the Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montreal, Quebec, Canada H1W 4A4.
authors.forename: Wissal
authors.initials: W
authors.lastname: El-Assaad
authors.forename: Erik
authors.initials: E
authors.lastname: Joly
authors.forename: Annie
authors.initials: A
authors.lastname: Barbeau
authors.forename: Robert
authors.initials: R
authors.lastname: Sladek
authors.forename: Jean
authors.initials: J
authors.lastname: Buteau
authors.forename: Isabel
authors.initials: I
authors.lastname: Maestre
authors.forename: Emilie
authors.initials: E
authors.lastname: Pepin
authors.forename: Shangang
authors.initials: S
authors.lastname: Zhao
authors.forename: José
authors.initials: J
authors.lastname: Iglesias
authors.forename: Enrique
authors.initials: E
authors.lastname: Roche
authors.forename: Marc
authors.initials: M
authors.lastname: Prentki
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D050356:Lipid Metabolism / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D009713:Nucleotidyltransferases / Q000235:genetics / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis; D010168:Palmitates / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D002518:Ceramides; D010168:Palmitates; D017382:Reactive Oxygen Species; D002784:Cholesterol; D000123:Acetyltransferases; C055210:aminoglycoside N1-acetyltransferase; D009713:Nucleotidyltransferases; C020675:glycerol-3-phosphate cytidylyltransferase; D005947:Glucose