PPARδ agonists have opposing effects on insulin resistance in high fat-fed rats and mice due to different metabolic responses in muscle.
OBJECTIVE
The peroxisome proliferator-activated receptor (PPAR)δ has been considered a therapeutic target for diabetes and obesity through enhancement of fatty acid oxidation. The present study aimed to characterize the effects of PPARδ agonists during insulin resistance of the whole body, muscle and liver.


METHODS
Wistar rats and C57BL/J6 mice were fed a high fat diet (HF) and then treated with PPARδ agonists NNC61-5920 and GW501516. The effects on insulin resistance were evaluated by hyperinsulinaemic clamp or glucose tolerance tests combined with glucose tracers.


RESULTS
In HF rats, 3 weeks of treatment with NNC61-5920 reduced the glucose infusion rate (by 14%, P < 0.05) and glucose disposal into muscle (by 20-30%, P < 0.01) during hyperinsulinaemic clamp. Despite increased mRNA expression of carnitine palmitoyltransferase-1, pyruvate dehydrogenase kinase 4 and uncoupling protein 3 in muscle, plasma and muscle triglyceride levels were raised (P < 0.01). Similar metabolic effects were observed after extended treatment with NNC61-5920 and GW501516 to 6 weeks. However, HF mice treated with NNC61-5920 improved their plasma lipid profile, glucose tolerance and insulin action in muscle. In both HF rats and mice, NNC61-5920 treatment attenuated hepatic insulin resistance and decreased expression of stearoyl-CoA desaturase 1, fatty acid translocase protein CD36 and lipoprotein lipase in liver.


CONCLUSIONS
PPARδ agonists exacerbated insulin resistance in HF rats in contrast to their beneficial effects on metabolic syndrome in HF mice. These opposing metabolic consequences result from their different effects on lipid metabolism and insulin sensitivity in skeletal muscle of these two species.
Diabetes and Obesity Research Program, Garvan Institute of Medical Research, University of New South Wales, Sydney, NSW, Australia. jiming.ye@rmit.edu.au
Ji-Ming
JM
Ye
Jennifer
J
Tid-Ang
Nigel
N
Turner
Xiao-Yi
XY
Zeng
Hai-Yan
HY
Li
Gregory J
GJ
Cooney
Erik Max
EM
Wulff
Per
P
Sauerberg
Edward W
EW
Kraegen
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage*; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D007333:Insulin Resistance; D050356:Lipid Metabolism / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009928:Organ Specificity; D047494:PPAR delta / Q000819:agonists*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013045:Species Specificity; D013844:Thiazoles / Q000494:pharmacology; D014280:Triglycerides / Q000378:metabolism
D015415:Biomarkers; D004041:Dietary Fats; C425931:GW 501516; D047494:PPAR delta; D012333:RNA, Messenger; D013844:Thiazoles; D014280:Triglycerides; D005947:Glucose
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