Exercise training increases hepatic endoplasmic reticulum (er) stress protein expression in MTP-inhibited high-fat fed rats.
The purpose of the study was: (1) to determine the effects of microsomal triglyceride transfer protein (MTP) inhibition on endoplasmic reticulum (ER) stress in liver, and (2) to determine if this response is altered in exercise-trained rats. Female Sprague-Dawley rats (6 weeks) fed either a standard (SD) or a high-saturated fat (HF; 43% as energy) diet were trained (Tr) or kept sedentary (Sed) for 6 week. Exercise training consisted of continuous running on a motor-driven rodent treadmill 5 times/week. Ten days before the end of these interventions, rats were administrated (ip) daily a MTP inhibitor (MTPX) or a placebo (P). MTPX injection resulted in a large (p < 0.01) liver triacylglycerol (TAG) accumulation in SD and HF-fed rats (approximately 200 mg g(-1)), irrespective of the training status, while plasma TAG levels were largely (approximately 80%) decreased (p < 0.01). MTPX injection in HF but not in SD-fed animals resulted in an increase in BiP/GRP78, ATF6, PERK, and XBP-1 mRNA levels, (p < 0.01) indicating an increase in the unfolding protein response (UPR) to ER stress. Interestingly, exercise training in rats fed the HF diet resulted in a further increase in BiP/GRP78 and XBP-1 mRNA levels in MTPX animals (p < 0.01). It is concluded that: (1) ER stress induced by MTPX occurs only in HF-fed rats despite the fact that liver TAG levels were largely increased in both dietary models; (2) the increase in gene expression of UPR markers with training may constitute a protective mechanism against ER stress in liver.
Chapados
Natalie Ann
NA
Department of Kinesiology, University of Montreal, Montréal, Québec, Canada. n.chapados@gmail.com
Lavoie
Jean-Marc
JM
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001823:Body Composition; D002352:Carrier Proteins / Q000037:antagonists & inhibitors*; D004032:Diet; D004041:Dietary Fats; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004734:Energy Metabolism; D005260:Female; D015870:Gene Expression; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010919:Placebos; D051381:Rats; D017207:Rats, Sprague-Dawley; D014280:Triglycerides / Q000097:blood; D056811:Unfolded Protein Response
D015415:Biomarkers; D002352:Carrier Proteins; D004041:Dietary Fats; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D010919:Placebos; D014280:Triglycerides; C106092:microsomal triglyceride transfer protein