Accumulation of endoplasmic reticulum stress and lipogenesis in the liver through generational effects of high fat diets Jiong Li 1,2 , Jin Huang 1 , Jian-Shuang Li 1 , Hong Chen 3 , Kun Huang 3,⇑ , Ling Zheng 1,2,⇑ 1 College of Life Sciences, Wuhan University, Wuhan, Hubei, PR China; 2 Diabetes Center, Wuhan University, Wuhan, Hubei, PR China; 3 Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan, Hubei, PR China Background & Aims: The dramatic rise of nonalcoholic fatty liver disease (NAFLD) among children in the past decade cannot be solely explained by the increased high fat diet (HFD) intake in kids. Recent studies suggest that the offspring of HFD-fed moth- ers develop a worse form of NAFLD when weaned on the HFD than when weaned on the normal chow (NC), indicating that a feed-forward circle may exacerbate the syndromes throughout multiple generations. In the present study, the aforementioned feed-forward circle was investigated in mice by employing con- tinuous HFD feeding for three generations. Methods: C57BL/6 mice were fed with either a HFD or NC for three consecutive generations (F0, F1, and F2). Body weight, food intake, hepatic histology; levels of insulin, leptin, and triglycer- ides; expression of factors involved in lipogenesis and endoplas- mic reticulum (ER) stress pathways; and histone methylation status were investigated in male offspring. Results: Obesity occurred earlier, became more severe through generations (F2 >F1 >F0), and was accompanied by a gradual increase of histological scoring of steatosis in male mice with transgenerational HFD feeding. The highest degree of steatosis occurred in HFD-treated F2 mice and was associated with the highest levels of insulin and leptin. The latter mice were charac- terized by enhanced lipogenesis and ER stress with a trend of transgenerational changes was detected for LXRa, ERO1-a, histone methylations, and H3K9 histone methyltransferase. Furthermore, chromatin immunoprecipitation (CHIP) assay dem- onstrated a significantly reduced accumulation of methylated histones in LXRa and ERO1-a gene promoters. Conclusions: Under HFD feeding stress, the male offspring of the F2 generation (derived from both grand-maternal and maternal obesity) are extremely susceptible to developing obesity and hepatic steatosis. This is presumably a consequence of transgen- erational accumulation of epigenetic modifications leading to up- regulation of lipogenesis and ER stress pathways in the liver. Ó 2011 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. Introduction Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver diseases, with a prevalence of 10–31% worldwide [1,2]. NAFLD is usually associated with obesity and type 2 diabetes mellitus (T2DM) [2], and can gradually develop from simple steatosis to steatohepatitis, advanced fibrosis, and eventually cirrhosis [3]. In the past decades, the global prevalence of obesity and NAFLD has dramatically increased in both adults and children [4,5]. The disproportionately early-onset of obesity and NAFLD among children can be partially explained by Baker’s ‘‘Fetal ori- gins of adult disease’’ hypothesis [6], which is supported by the fact that high fat diet (HFD) intake during pregnancy increases the rates of obesity and metabolic disorders, including NAFLD, in offspring [7–10]. To date, most studies on rodent models have focused on the relationships between diet-induced obesity in female rodents (F0) and the development of metabolic diseases in adult offspring (F1) weaned on normal chow (NC). Under this condition, the HFD may impact the F1 generation mostly through developmental over-nutrition. However, a recent study suggests that alterations of neural circuitry in offspring from maternal obesity (F0) may lead to the offspring (F1) preferring HFD or hyperphagia [11]. Under this condition, the effects of a HFD on the F1 generation are through both developmental and adult over-nutrition. In fact, the F1 offspring under both developmental and adult over-nutrition insults (F1 offspring of maternal obesity weaned on a HFD) develop nonalcoholic steatohepatitis, a worse form of NAFLD, when they become adults. However, F1 offspring under only developmental over-nutrition insult (F1 offspring of maternal obesity weaned on NC) develop only NAFLD when they Journal of Hepatology 2012 vol. 56 j 900–907 Keywords: NAFLD; Maternal obesity; Lipogenesis; ER stress; Histone methylation. Received 24 April 2011; received in revised form 12 October 2011; accepted 16 October 2011; available online 13 December 2011 ⇑ Corresponding authors. Addresses: Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, PR China (K. Huang), College of Life Sciences, Wuhan University, Wuhan 430072, PR China. Tel.: +86 27 68755559 (L. Zheng). E-mail addresses: kunhuang2008@hotmail.com (K. Huang), lzheng217@hotmail. com, lzheng@whu.edu.cn (L. Zheng). Abbreviations: NAFLD, nonalcoholic fatty liver disease; T2DM, type 2 diabetes mellitus; HFD, high fat diet; NC, normal chow; HF F0, high fat-fed offspring of normal chow fed mice; HF F1, high fat-fed offspring of HF F0 mice; HF F2, high fat-fed offspring of HF F1 mice; NC F0, normal chow-fed offspring of normal chow fed mice; NC F1, normal chow-fed offspring of NC F0 mice; NC F2, normal chow- fed offspring of NC F1 mice; ER, endoplasmic reticulum; BW, body weight; GTT, glucose tolerance test; ITT, insulin tolerance test; SREBP-1c, sterol regulatory element binding protein 1c; LXR, liver X receptor; PPAR, peroxisome proliferator- activated receptor; FASN, fatty acid synthase; NFBG, non-fasted blood glucose; FBG, fasted blood glucose; pSREBP-1, precursor SREBP-1; mSREBP-1, mature SR- EBP-1; eIF2a, eukaryotic initiation factor 2a; BIP, binding immunoglobulin pro- tein; ERO1-a, oxireductase endoplasmic reticulum oxidoreductin1-a. Research Article