Endoplasmic reticulum (ER) stress has been causatively linked to the onset of various pathologies. However, if and how inherent variations in the resulting unfolded protein response (UPR) affect the predisposition to ER stress-associated metabolic conditions remains to be established. By using genetically diverse deer mice (Peromyscus maniculatus) as a model, we show that the profile of tunicamycin-induced UPR in fibroblasts isolated at puberty varies between individuals and predicts deregulation of lipid metabolism and diet-induced hepatic steatosis later in life. Among the different UPR targets tested, CHOP more consistently predicted elevated plasma cholesterol and hepatic steatosis. Compared to baseline levels or inducibility, the maximal intensity of the UPR following stimulation best predicts the onset of pathology. Differences in the expression profile of the UPR recorded in cells from different populations of deer mice correlate with the varying response to ER stress in altitude adaptation. Our data suggest that the response to ER stress in cultured cells varies among individuals and its profile early in life may predict the onset of ER stress-associated disease in the elderly.
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Coordination of the unfolded protein response during hepatic steatosis identifies CHOP as a specific regulator of hepatocyte ballooning
The unfolded protein response (UPR) is an adaptive response that is implicated in multiple metabolic pathologies, including hepatic steatosis. In the present study we analyzed publicly available RNAseq data to explore how the execution of the UPR is orchestrated in specimens that exhibit hepatocyte ballooning, a landmark feature of steatosis. By focusing on a panel of well-established UPR genes we assessed how the UPR is coordinated with the whole transcriptome in specimens with or without hepatocyte ballooning. Our analyses showed that neither average levels nor correlation in expression between major UPR genes such as HSPA5 (BiP/GRP78), HSP90b1 (GRP94) or DDIT3 (CHOP), is altered in different groups. However, a panel of transcripts that depending on the stringency of the analysis ranged from 16 to 372, lost its coordination with HSPA5, the major UPR chaperone, when hepatocyte ballooning occurred. In 13 genes the majority of which is associated with metabolic processes, the coordination with the HSPA5 was reversed from positive to negative in livers with ballooning hepatocytes. In order to examine if during ballooning, UPR genes abolish established and acquire novel functionalities we performed gene ontology analyses. These studies showed that among the various UPR genes interrogated, DDIT3 was the only that during ballooning was not associated with conventional functions linked to endoplasmic reticulum stress while HSPA90b1 exhibited the highest function retention between the specimens with or without ballooning. Our results challenge conventional notions on the impact of specific genes in disease and suggest that besides abundance, the mode of coordination of UPR may be more important for disease development.
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- Award ID(s):
- 1736150
- NSF-PAR ID:
- 10164411
- Date Published:
- Journal Name:
- Cell Stress and Chaperones
- ISSN:
- 1355-8145
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)Abstract Background Deregulation in lipid metabolism leads to the onset of hepatic steatosis while at subsequent stages of disease development, the induction of inflammation, marks the transition of steatosis to non-alcoholic steatohepatitis. While differential gene expression unveils individual genes that are deregulated at different stages of disease development, how the whole transcriptome is deregulated in steatosis remains unclear. Methods Using outbred deer mice fed with high fat as a model, we assessed the correlation of each transcript with every other transcript in the transcriptome. The onset of steatosis in the liver was also evaluated histologically. Results Our results indicate that transcriptional reprogramming directing immune cell engagement proceeds robustly, even in the absence of histologically detectable steatosis, following administration of high fat diet. In the liver transcriptomes of animals with steatosis, a preference for the engagement of regulators of T cell activation and myeloid leukocyte differentiation was also recorded as opposed to the steatosis-free livers at which non-specific lymphocytic activation was seen. As compared to controls, in the animals with steatosis, transcriptome was subjected to more widespread reorganization while in the animals without steatosis, reorganization was less extensive. Comparison of the steatosis and non-steatosis livers showed high retention of coordination suggesting that diet supersedes pathology in shaping the transcriptome’s profile. Conclusions This highly versatile strategy suggests that the molecular changes inducing inflammation proceed robustly even before any evidence of steatohepatitis is recorded, either histologically or by differential expression analysis.more » « less
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null (Ed.)ABSTRACT The unfolded protein response (UPR) is involved in the pathogenesis of metabolic disorders, yet whether variations in the UPR among individuals influence the propensity for metabolic disease remains unexplored. Using outbred deer mice as a model, we show that the intensity of UPR in fibroblasts isolated early in life predicts the extent of body weight gain after high-fat diet (HFD) administration. Contrary to those with intense UPR, animals with moderate UPR in fibroblasts and therefore displaying compromised stress resolution did not gain body weight but developed inflammation, especially in the skin, after HFD administration. Fibroblasts emerged as potent modifiers of this differential responsiveness to HFD, as indicated by the comparison of the UPR profiles of fibroblasts responding to fatty acids in vitro, by correlation analyses between UPR and proinflammatory cytokine-associated transcriptomes, and by BiP (also known as HSPA5) immunolocalization in skin lesions from animals receiving HFD. These results suggest that the UPR operates as a modifier of an individual's propensity for body weight gain in a manner that, at least in part, involves the regulation of an inflammatory response by skin fibroblasts. This article has an associated First Person interview with the first author of the paper.more » « less
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Graca Almeida-Porada, MD3 1Fetal Research and Therapy Program, Wake Forest Institute for Regenerative Medicine, Winston Salem, NC 2Massachusetts Institute of Technology, Cambridge, MA 3Fetal Research and Therapy Program, Wake Forest Institute For Regenerative Medicine, Winston-Salem, NC Clinical trials employing AAV vectors for hemophilia A have been hindered by unanticipated immunological and/or inflammatory responses in some of the patients. Also, these trials have often yielded lower levels of transgene expression than were expected based upon preclinical studies, highlighting the poor correlation between the transduction efficiency observed in traditional 2D cultures of primary cells in vitro, and that observed in those same cell types in vivo. 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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s12192-020-01132-x
