Differential responses of hepatic endoplasmic reticulum stress and inflammation in diet-induced obese rats with high-fat diet rich in lard oil or soybean oil.
METHODS
To investigate the effects of high-fat diet enriched with lard oil or soybean oil on liver endoplasmic reticulum (ER) stress and inflammation markers in diet-induced obese (DIO) rats and estimate the influence of following low-fat diet feeding.


RESULTS
Male SD rats were fed with standard low-fat diet (LF, n = 10) and two isoenergentic high-fat diets enriched with lard (HL, n = 45) or soybean oil (HS, n = 45) respectively for 10 weeks. Then DIO rats from HL and HS were fed either high-fat diet continuously (HL/HL, HS/HS) or switched to low-fat diet (HL/LF, HS/LF) for another 8 weeks. Rats in control group were maintained with low-fat diet. Body fat, serum insulin level, HOMA-IR and ectopic lipid deposition in liver were increased in HL/HL and HS/HS compared to control, but increased to a greater extent in HL/HL compared to HS/HS. Markers of ER stress including PERK and CHOP protein expression and phosphorylation of eIF2α were significantly elevated in HL/HL group while phosphorylation of IRE1α and GRP78 protein expression were suppressed in both HL/HL and HS/HS. Besides, inflammatory signals (OPN, TLR2, TLR4 and TNF-α) expressions significantly increased in HL/HL compared to others. Switching to low-fat diet reduced liver fat deposition, HOMA-IR, mRNA expression of TLR4, TNF-α, PERK in both HL/LF and HS/LF, but only decreased protein expression of OPN, PERK and CHOP in HL/LF group. In addition, HL/LF and HS/LF exhibited decreased phosphorylation of eIF2α and increased phosphorylation of IRE1α and GRP78 protein expression when compared with HL/HL and HS/HS respectively.


CONCLUSIONS
Lard oil was more deleterious in insulin resistance and hepatic steatosis via promoting ER stress and inflammation responses in DIO rats, which may be attributed to the enrichment of saturated fatty acid. Low-fat diet was confirmed to be useful in recovering from impaired insulin sensitivity and liver fat deposition in this study.
Department of Nutrition and Food Hygiene, Hubei Key Laboratory of Food Nutrition and Safety, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China ; Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China.
Min
M
Zhao
Baocai
B
Zang
Mengjie
M
Cheng
Yan
Y
Ma
Yanhong
Y
Yang
Nianhong
N
Yang
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D018752:Diet, Fat-Restricted; D059305:Diet, High-Fat / Q000009:adverse effects; D004041:Dietary Fats / Q000008:administration & dosage*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects* / Q000235:genetics; D004722:Endoribonucleases / Q000235:genetics / Q000276:immunology; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000276:immunology; D015870:Gene Expression / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000276:immunology; D007249:Inflammation / Q000178:diet therapy / Q000209:etiology / Q000276:immunology / Q000378:metabolism; D007328:Insulin / Q000097:blood; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D009097:Multienzyme Complexes / Q000235:genetics / Q000276:immunology; D009765:Obesity / Q000178:diet therapy / Q000209:etiology / Q000276:immunology* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013024:Soybean Oil / Q000008:administration & dosage*; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology; D051742:Transcription Factor CHOP / Q000235:genetics / Q000276:immunology; D019892:eIF-2 Kinase / Q000235:genetics / Q000276:immunology; D000091342:Endoplasmic Reticulum Chaperone BiP
D004041:Dietary Fats; D004722:Endoribonucleases; D015852:Eukaryotic Initiation Factor-2; D006360:Heat-Shock Proteins; D007328:Insulin; D009097:Multienzyme Complexes; D017346:Protein Serine-Threonine Kinases; D013024:Soybean Oil; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051742:Transcription Factor CHOP; D019892:eIF-2 Kinase; C497251:Ddit3 protein, rat; C575026:Ern1 protein, rat; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; C495343:Tlr2 protein, rat; C495347:Tlr4 protein, rat; C029310:lard