Pyruvate dehydrogenase kinase 4: regulation by thiazolidinediones and implication in glyceroneogenesis in adipose tissue.
OBJECTIVE
Pyruvate dehydrogenase complex (PDC) serves as the metabolic switch between glucose and fatty acid utilization. PDC activity is inhibited by PDC kinase (PDK). PDC shares the same substrate, i.e., pyruvate, as glyceroneogenesis, a pathway controlling fatty acid release from white adipose tissue (WAT). Thiazolidinediones activate glyceroneogenesis. We studied the regulation by rosiglitazone of PDK2 and PDK4 isoforms and tested the hypothesis that glyceroneogenesis could be controlled by PDK.


METHODS
Rosiglitazone was administered to Zucker fa/fa rats, and then PDK4 and PDK2 mRNAs were examined in subcutaneous, periepididymal, and retroperitoneal WAT, liver, and muscle by real-time RT-PCR. Cultured WAT explants from humans and rats and 3T3-F442A adipocytes were rosiglitazone-treated before analyses of PDK2 and PDK4 mRNA and protein. Small interfering RNA (siRNA) was transfected by electroporation. Glyceroneogenesis was determined using [1-(14)C]pyruvate incorporation into lipids.


RESULTS
Rosiglitazone increased PDK4 mRNA in all WAT depots but not in liver and muscle. PDK2 transcript was not affected. This isoform selectivity was also found in ex vivo-treated explants. In 3T3-F442A adipocytes, Pdk4 expression was strongly and selectively induced by rosiglitazone in a direct and transcriptional manner, with a concentration required for half-maximal effect at 1 nmol/l. The use of dichloroacetic acid or leelamine, two PDK inhibitors, or a specific PDK4 siRNA demonstrated that PDK4 participated in glyceroneogenesis, therefore altering nonesterified fatty acid release in both basal and rosiglitazone-activated conditions.


CONCLUSIONS
These data show that PDK4 upregulation in adipocytes participates in the hypolipidemic effect of thiazolidinediones through modulation of glyceroneogenesis.
Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche-S 747, Université Paris Descartes, Centre Universitaire des Saints-Pères, Paris, France.
Thomas
T
Cadoudal
Emilie
E
Distel
Sylvie
S
Durant
Françoise
F
Fouque
Jean-Marc
JM
Blouin
Martine
M
Collinet
Sylvie
S
Bortoli
Claude
C
Forest
Chantal
C
Benelli
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D052436:Adipose Tissue, White / Q000166:cytology; D000328:Adult; D000818:Animals; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D005990:Glycerol / Q000378:metabolism*; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008875:Middle Aged; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051381:Rats; D017207:Rats, Sprague-Dawley; D011924:Rats, Zucker; D000077154:Rosiglitazone; D050151:Subcutaneous Fat / Q000166:cytology; D045162:Thiazolidinediones / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D005227:Fatty Acids; D007004:Hypoglycemic Agents; C000631430:PDK2 protein, human; C000631432:PDK4 protein, human; C000631435:Pdk2 protein, mouse; C000631436:Pdk2 protein, rat; C000631439:Pdk4 protein, mouse; C000631440:Pdk4 protein, rat; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D045162:Thiazolidinediones; D000077154:Rosiglitazone; D017346:Protein Serine-Threonine Kinases; D005990:Glycerol