Combination of lipid metabolism alterations and their sensitivity to inflammatory cytokines in human lipin-1-deficient myoblasts.
Lipin-1 deficiency is associated with massive rhabdomyolysis episodes in humans, precipitated by febrile illnesses. Despite well-known roles of lipin-1 in lipid biosynthesis and transcriptional regulation, the pathogenic mechanisms leading to rhabdomyolysis remain unknown. Here we show that primary myoblasts from lipin-1-deficient patients exhibit a dramatic decrease in LPIN1 expression and phosphatidic acid phosphatase 1 activity, and a significant accumulation of lipid droplets (LD). The expression levels of LPIN1-target genes [peroxisome proliferator-activated receptors delta and alpha (PPARδ, PPARα), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), acyl-coenzyme A dehydrogenase, very long (ACADVL), carnitine palmitoyltransferase IB and 2 (CPT1B and CPT2)] were not affected while lipin-2 protein level, a closely related member of the family, was increased. Microarray analysis of patients' myotubes identified 19 down-regulated and 51 up-regulated genes, indicating pleiotropic effects of lipin-1 deficiency. Special attention was paid to the up-regulated ACACB (acetyl-CoA carboxylase beta), a key enzyme in the fatty acid synthesis/oxidation balance. We demonstrated that overexpression of ACACB was associated with free fatty acid accumulation in patients' myoblasts whereas malonyl-carnitine (as a measure of malonyl-CoA) and CPT1 activity were in the normal range in basal conditions accordingly to the normal daily activity reported by the patients. Remarkably ACACB invalidation in patients' myoblasts decreased LD number and size while LPIN1 invalidation in controls induced LD accumulation. Further, pro-inflammatory treatments tumor necrosis factor alpha+Interleukin-1beta(TNF1α+IL-1ß) designed to mimic febrile illness, resulted in increased malonyl-carnitine levels, reduced CPT1 activity and enhanced LD accumulation, a phenomenon reversed by dexamethasone and TNFα or IL-1ß inhibitors. Our data suggest that the pathogenic mechanism of rhabdomyolysis in lipin-1-deficient patients combines the predisposing constitutive impairment of lipid metabolism and its exacerbation by pro-inflammatory cytokines.
Inserm U781, Imagine Institut des Maladies Génétiques, Université Paris Descartes et Centre de Référence des Maladies Héréditaires du Métabolisme, Hôpital Necker, AP-HP, Paris, France.
Caroline
C
Michot
Asmaa
A
Mamoune
Joseph
J
Vamecq
Mai Thao
MT
Viou
Lu-Sheng
LS
Hsieh
Eric
E
Testet
Jeanne
J
Lainé
Laurence
L
Hubert
Anne-Frédérique
AF
Dessein
Monique
M
Fontaine
Chris
C
Ottolenghi
Laetitia
L
Fouillen
Karim
K
Nadra
Etienne
E
Blanc
Jean
J
Bastin
Sophie
S
Candon
Mario
M
Pende
Arnold
A
Munnich
Asma
A
Smahi
Fatima
F
Djouadi
George M
GM
Carman
Norma
N
Romero
Yves
Y
de Keyzer
Pascale
P
de Lonlay
D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D016022:Case-Control Studies; D002453:Cell Cycle; D049109:Cell Proliferation; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000494:pharmacology*; D059865:Endoplasmic Reticulum Stress; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D018836:Inflammation Mediators / Q000494:pharmacology*; D052439:Lipid Metabolism Disorders / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D008055:Lipids; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009154:Mutation / Q000235:genetics; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D020411:Oligonucleotide Array Sequence Analysis; D000073718:Pancreatitis-Associated Proteins; D010711:Phosphatidate Phosphatase / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012206:Rhabdomyolysis / Q000209:etiology / Q000378:metabolism / Q000473:pathology
D015415:Biomarkers; D016207:Cytokines; D018836:Inflammation Mediators; D008055:Lipids; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D012333:RNA, Messenger; C485999:LPIN1 protein, human; D010711:Phosphatidate Phosphatase
ACACB; CPT; DAG; FAO; FFA; IL-1β; Inflammation; Interleukin-1beta; LD; Lipid droplet; Lipin-1; PA; PAP; PAP1; PL; Poly(I:C); Rhabdomyolysis; TAG; TNFα; acetyl-coenzyme A carboxylase beta; carnitine palmitoyl transferase; diacylglycerol; fatty acid oxidation; free fatty acid; lipid droplets; mRC; mitochondrial respiratory chain; phosphatidic acid; phosphatidic acid phosphatase; phospholipids; polyinosinic-polycytidylic acid; triacylglycerides; tumor necrosis factor alpha