IDH2 Deficiency Aggravates Fructose-Induced NAFLD by Modulating Hepatic Fatty Acid Metabolism and Activating Inflammatory Signaling in Female Mice - PubMed (original) (raw)

Hoe-Sung Kim 2, Kaleigh Elizabeth Beane 3, Allison Michelle Montalbano 4, Jin Hyup Lee 5, Young Jun Kim 6, Jun Ho Kim 7, Byungwhi Caleb Kong 8, Sangyub Kim 9, Jeen-Woo Park 10, Eui-Cheol Shin 2, Jae Kyeom Kim 11

Affiliations

IDH2 Deficiency Aggravates Fructose-Induced NAFLD by Modulating Hepatic Fatty Acid Metabolism and Activating Inflammatory Signaling in Female Mice

Jeong Hoon Pan et al. Nutrients. 2018.

Abstract

Fructose is a strong risk factor for non-alcoholic fatty liver disease (NAFLD), resulting from the disruption of redox systems by excessive reactive oxygen species production in the liver cells. Of note, recent epidemiological studies indicated that women are more prone to developing metabolic syndrome in response to fructose-sweetened beverages. Hence, we examined whether disruption of the redox system through a deletion of NADPH supplying mitochondrial enzyme, NADP⁺-dependent isocitrate dehydrogenase (IDH2), exacerbates fructose-induced NAFLD conditions in C57BL/6 female mice. Wild-type (WT) and IDH2 knockout (KO) mice were treated with either water or 34% fructose water over six weeks. NAFLD phenotypes and key proteins and mRNAs involved in the inflammatory pathway (e.g., NF-κB p65 and IL-1β) were assessed. Hepatic lipid accumulation was significantly increased in IDH2 KO mice fed fructose compared to the WT counterpart. Neutrophil infiltration was observed only in IDH2 KO mice fed fructose. Furthermore, phosphorylation of NF-κB p65 and expression of IL-1β was remarkably upregulated in IDH2 KO mice fed fructose, and expression of IκBα was decreased by fructose treatment in both WT and IDH2 KO groups. For the first time, we report our novel findings that IDH2 KO female mice may be more susceptible to fructose-induced NAFLD and the associated inflammatory response, suggesting a mechanistic role of IDH2 in metabolic diseases.

Keywords: IDH2; NAFLD; NF-κB; female mice; fructose.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1

Figure 1

IDH2 knockout aggravates fructose-induced NAFLD conditions. (A) IDH2 genotyping was performed using mouse tail DNA; (B) protein and mRNA expression of IDH2 in liver tissue of mice were measured by Western blotting and PCR analyses; (C) body weight was recorded once a week for six weeks; (D) body weight gain was calculated as follows: Final body weight (at sixth week)—Initial body weight (at 0th week). (E) Tissue weights of liver, visceral adipose tissue, and brown adipose tissue were represented as the ratio of tissue weights to final body weights; (F) hepatic lipid accumulation was assessed by Oil Red O staining, and stained area was calculated using ImageJ software (NIH); (G) quantitative PCR analysis of mRNA expressions involved in fatty acid synthesis and β-oxidation (i.e., SREBP-1, SCD1, FAS, DGAT2, AMPKα, SIRT1, and PPAR-α) in liver tissue. All data are presented as the LSM ± SEM and different letters indicate statistically significant at p < 0.05.

Figure 2

Figure 2

IDH2 knockout exacerbates inflammatory responses via hepatic NF-κB pathway in mice fed 34% fructose over six weeks. (A) Morphology of liver tissues was assessed by hematoxylin and eosin staining; (B) inflammatory serum cytokines were analyzed using the Proteome Profiler Mouse Cytokine Array Panel A kit (R&D Systems). Levels of 40 cytokines were compared between the experimental groups. (C) A graph depicting the relative pixel density of selected dot blots out of the 40 cytokines; (D) quantitative PCR analysis of inflammatory mRNA expressions (i.e., IL-1β, TNF-α, Nfkbia, and RelA) in liver tissues; (E) immunoblot analysis of NF-κB p65 and IL-1β protein expression in liver tissue. Actin was examined as the loading control, and a graph depicting the quantification of the relative abundance of the proteins is shown. All data are presented as the LSM ± SEM and different letters indicate statistically significant at p < 0.05.

References

    1. Lim J.S., Mietus-Snyder M., Valente A., Schwarz J.M., Lustig R.H. The role of fructose in the pathogenesis of NAFLD and the metabolic syndrome. Nat. Rev. Gastroenterol. Hepatol. 2010;7:251–264. doi: 10.1038/nrgastro.2010.41. - DOI - PubMed
    1. Miller A., Adeli K. Dietary fructose and the metabolic syndrome. Curr. Opin. Gastroenterol. 2008;24:204–209. doi: 10.1097/MOG.0b013e3282f3f4c4. - DOI - PubMed
    1. Yan H., Harding J.J. Glycation-induced inactivation and loss of antigenicity of catalase and superoxide dismutase. Biochem. J. 1997;328:599–605. doi: 10.1042/bj3280599. - DOI - PMC - PubMed
    1. Lillig C.H., Lonn M.E., Enoksson M., Fernandes A.P., Holmgren A. Short interfering RNA-mediated silencing of glutaredoxin 2 increases the sensitivity of HeLa cells toward doxorubicin and phenylarsine oxide. Proc. Natl. Acad. Sci. USA. 2004;101:13227–13232. doi: 10.1073/pnas.0401896101. - DOI - PMC - PubMed
    1. Jo S.H., Son M.K., Koh H.J., Lee S.M., Song I.H., Kim Y.O., Lee Y.S., Jeong K.S., Kim W.B., Park J.W., et al. Control of mitochondrial redox balance and cellular defense against oxidative damage by mitochondrial NADP+-dependent isocitrate dehydrogenase. J. Biol. Chem. 2001;276:16168–16176. doi: 10.1074/jbc.M010120200. - DOI - PubMed

MeSH terms

Substances

LinkOut - more resources