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The genetic architecture of NAFLD among inbred strains of mice.

Hui ST, Parks BW, Org E, Norheim F, Che N, Pan C, Castellani LW, Charugundla S, Dirks DL, Psychogios N, Neuhaus I, Gerszten RE, Kirchgessner T, Gargalovic PS, Lusis AJ - Elife (2015)

Bottom Line: Genome-wide association studies revealed three loci associated with hepatic TG accumulation.We hypothesize that Gde1 expression increases TG production by contributing to the production of glycerol-3-phosphate.Our multi-level data, including transcript levels, metabolite levels, and gut microbiota composition, provide a framework for understanding genetic and environmental interactions underlying hepatic steatosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine/Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States.

ABSTRACT
To identify genetic and environmental factors contributing to the pathogenesis of non-alcoholic fatty liver disease, we examined liver steatosis and related clinical and molecular traits in more than 100 unique inbred mouse strains, which were fed a diet rich in fat and carbohydrates. A >30-fold variation in hepatic TG accumulation was observed among the strains. Genome-wide association studies revealed three loci associated with hepatic TG accumulation. Utilizing transcriptomic data from the liver and adipose tissue, we identified several high-confidence candidate genes for hepatic steatosis, including Gde1, a glycerophosphodiester phosphodiesterase not previously implicated in triglyceride metabolism. We confirmed the role of Gde1 by in vivo hepatic over-expression and shRNA knockdown studies. We hypothesize that Gde1 expression increases TG production by contributing to the production of glycerol-3-phosphate. Our multi-level data, including transcript levels, metabolite levels, and gut microbiota composition, provide a framework for understanding genetic and environmental interactions underlying hepatic steatosis.

No MeSH data available.


Related in: MedlinePlus

Effects of Gde1 overexpression in mice by adenoviral transduction.C57BL/6 mice were injected with Ad-Gde1 (1 × 109 pfu per mouse, i.v.) and fed with a HF/HS diet for 7 days. Control group received the same dose of Ad-LacZ. (A) Western-blot of liver homogenate using anti-GDE1 or anti-tubulin antibody. (B) Comparison of liver weight between Gde1-overexpressing mice and the control mice. (C) Differences in plasma triglyceride (TG), TC, and free fatty acids levels between Gde1-overexpressing mice (filled bars) and the control mice (empty bars). (D) Hepatic fat percentage in the two groups of mice was determined by MRI. (E–G) Liver lipids were extracted and quantified: triglyceride (TG), TC, and phospholipids (PL). (H) Expression of lipogenic genes was measured by qPCR and normalized to the level of the housekeeping gene 36B4. Ad-LacZ (empty bars) and Ad-Gde1 (filled bars) Results are presented as mean + SD (n = 7–8) * denotes p < 0.05 and ** denotes p < 0.01.DOI:http://dx.doi.org/10.7554/eLife.05607.019
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fig8: Effects of Gde1 overexpression in mice by adenoviral transduction.C57BL/6 mice were injected with Ad-Gde1 (1 × 109 pfu per mouse, i.v.) and fed with a HF/HS diet for 7 days. Control group received the same dose of Ad-LacZ. (A) Western-blot of liver homogenate using anti-GDE1 or anti-tubulin antibody. (B) Comparison of liver weight between Gde1-overexpressing mice and the control mice. (C) Differences in plasma triglyceride (TG), TC, and free fatty acids levels between Gde1-overexpressing mice (filled bars) and the control mice (empty bars). (D) Hepatic fat percentage in the two groups of mice was determined by MRI. (E–G) Liver lipids were extracted and quantified: triglyceride (TG), TC, and phospholipids (PL). (H) Expression of lipogenic genes was measured by qPCR and normalized to the level of the housekeeping gene 36B4. Ad-LacZ (empty bars) and Ad-Gde1 (filled bars) Results are presented as mean + SD (n = 7–8) * denotes p < 0.05 and ** denotes p < 0.01.DOI:http://dx.doi.org/10.7554/eLife.05607.019

Mentions: The finding of positive correlation between hepatic Gde1 expression and steatosis suggests that increased expression of Gde1 would promote hepatic TG accumulation. To directly assess the effect of Gde1 on hepatic TG in vivo, Gde1 was overexpressed in 8-week-old C57BL/6 mice (Ad-Gde1, 1 × 109 pfu per mouse, i.v.) by adenoviral transduction (Figure 8A). The control group (Ad-LacZ) received the same dose of adenovirus expressing LacZ. Mice were fed a HF/HS diet for 7 days after adenovirus injection and their hepatic lipids were measured. This regimen was chosen because gene expression by adenoviral transduction is only sustained for a short period of time (a few weeks or less). Preliminary studies in mice showed that HF/HS diet induced a threefold increase in hepatic TG accumulation in 1 week (data not shown). While there was no significant difference in body weight, the weight of livers from Gde1-overexpressing mice was 40% higher than that of the control (Figure 8B, p = 4.7 × 10−5). In addition, plasma TG, TC, and FFA were all elevated in Ad-Gde1 mice (Figure 8C). MRI analysis showed that livers from Gde1-overexpressing mice contained significantly higher fat content (Figure 8D, p = 0.0002). Lipid analyses revealed that the increase in hepatic fat content was primarily due to increased accumulation of TG (Figure 8E, p = 0.014), as hepatic TC and phospholipid content were not significantly different from the control group (Figure 8F,G). Hepatic genes involved in TG biosynthesis (Fasn, Dgat2, and Gpd1) were down-regulated in mice overexpressing Gde1 (Figure 8H).10.7554/eLife.05607.019Figure 8.Effects of Gde1 overexpression in mice by adenoviral transduction.


The genetic architecture of NAFLD among inbred strains of mice.

Hui ST, Parks BW, Org E, Norheim F, Che N, Pan C, Castellani LW, Charugundla S, Dirks DL, Psychogios N, Neuhaus I, Gerszten RE, Kirchgessner T, Gargalovic PS, Lusis AJ - Elife (2015)

Effects of Gde1 overexpression in mice by adenoviral transduction.C57BL/6 mice were injected with Ad-Gde1 (1 × 109 pfu per mouse, i.v.) and fed with a HF/HS diet for 7 days. Control group received the same dose of Ad-LacZ. (A) Western-blot of liver homogenate using anti-GDE1 or anti-tubulin antibody. (B) Comparison of liver weight between Gde1-overexpressing mice and the control mice. (C) Differences in plasma triglyceride (TG), TC, and free fatty acids levels between Gde1-overexpressing mice (filled bars) and the control mice (empty bars). (D) Hepatic fat percentage in the two groups of mice was determined by MRI. (E–G) Liver lipids were extracted and quantified: triglyceride (TG), TC, and phospholipids (PL). (H) Expression of lipogenic genes was measured by qPCR and normalized to the level of the housekeeping gene 36B4. Ad-LacZ (empty bars) and Ad-Gde1 (filled bars) Results are presented as mean + SD (n = 7–8) * denotes p < 0.05 and ** denotes p < 0.01.DOI:http://dx.doi.org/10.7554/eLife.05607.019
© Copyright Policy
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4493743&req=5

fig8: Effects of Gde1 overexpression in mice by adenoviral transduction.C57BL/6 mice were injected with Ad-Gde1 (1 × 109 pfu per mouse, i.v.) and fed with a HF/HS diet for 7 days. Control group received the same dose of Ad-LacZ. (A) Western-blot of liver homogenate using anti-GDE1 or anti-tubulin antibody. (B) Comparison of liver weight between Gde1-overexpressing mice and the control mice. (C) Differences in plasma triglyceride (TG), TC, and free fatty acids levels between Gde1-overexpressing mice (filled bars) and the control mice (empty bars). (D) Hepatic fat percentage in the two groups of mice was determined by MRI. (E–G) Liver lipids were extracted and quantified: triglyceride (TG), TC, and phospholipids (PL). (H) Expression of lipogenic genes was measured by qPCR and normalized to the level of the housekeeping gene 36B4. Ad-LacZ (empty bars) and Ad-Gde1 (filled bars) Results are presented as mean + SD (n = 7–8) * denotes p < 0.05 and ** denotes p < 0.01.DOI:http://dx.doi.org/10.7554/eLife.05607.019
Mentions: The finding of positive correlation between hepatic Gde1 expression and steatosis suggests that increased expression of Gde1 would promote hepatic TG accumulation. To directly assess the effect of Gde1 on hepatic TG in vivo, Gde1 was overexpressed in 8-week-old C57BL/6 mice (Ad-Gde1, 1 × 109 pfu per mouse, i.v.) by adenoviral transduction (Figure 8A). The control group (Ad-LacZ) received the same dose of adenovirus expressing LacZ. Mice were fed a HF/HS diet for 7 days after adenovirus injection and their hepatic lipids were measured. This regimen was chosen because gene expression by adenoviral transduction is only sustained for a short period of time (a few weeks or less). Preliminary studies in mice showed that HF/HS diet induced a threefold increase in hepatic TG accumulation in 1 week (data not shown). While there was no significant difference in body weight, the weight of livers from Gde1-overexpressing mice was 40% higher than that of the control (Figure 8B, p = 4.7 × 10−5). In addition, plasma TG, TC, and FFA were all elevated in Ad-Gde1 mice (Figure 8C). MRI analysis showed that livers from Gde1-overexpressing mice contained significantly higher fat content (Figure 8D, p = 0.0002). Lipid analyses revealed that the increase in hepatic fat content was primarily due to increased accumulation of TG (Figure 8E, p = 0.014), as hepatic TC and phospholipid content were not significantly different from the control group (Figure 8F,G). Hepatic genes involved in TG biosynthesis (Fasn, Dgat2, and Gpd1) were down-regulated in mice overexpressing Gde1 (Figure 8H).10.7554/eLife.05607.019Figure 8.Effects of Gde1 overexpression in mice by adenoviral transduction.

Bottom Line: Genome-wide association studies revealed three loci associated with hepatic TG accumulation.We hypothesize that Gde1 expression increases TG production by contributing to the production of glycerol-3-phosphate.Our multi-level data, including transcript levels, metabolite levels, and gut microbiota composition, provide a framework for understanding genetic and environmental interactions underlying hepatic steatosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine/Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, United States.

ABSTRACT
To identify genetic and environmental factors contributing to the pathogenesis of non-alcoholic fatty liver disease, we examined liver steatosis and related clinical and molecular traits in more than 100 unique inbred mouse strains, which were fed a diet rich in fat and carbohydrates. A >30-fold variation in hepatic TG accumulation was observed among the strains. Genome-wide association studies revealed three loci associated with hepatic TG accumulation. Utilizing transcriptomic data from the liver and adipose tissue, we identified several high-confidence candidate genes for hepatic steatosis, including Gde1, a glycerophosphodiester phosphodiesterase not previously implicated in triglyceride metabolism. We confirmed the role of Gde1 by in vivo hepatic over-expression and shRNA knockdown studies. We hypothesize that Gde1 expression increases TG production by contributing to the production of glycerol-3-phosphate. Our multi-level data, including transcript levels, metabolite levels, and gut microbiota composition, provide a framework for understanding genetic and environmental interactions underlying hepatic steatosis.

No MeSH data available.


Related in: MedlinePlus