Liver-specific overexpression of lipoprotein lipase improves glucose metabolism in high-fat diet-fed mice

Figures

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  Fig 1. Hepatic LPL overexpression attenuates lipid accumulation in high-fat diet (HFD)-fed mice liver. Male C57BL/6 mice were intravenously treated with Ad vectors at a dose of 5 × 109 IFU/mouse via the tail vein and were simultaneously fed HFD. PBS-treated mice were fed ND throughout the experimental period. Hepatic LPL (A) mRNA and (B) protein levels determined using quantitative RT-PCR and western blot analysis, respectively, 2 weeks after administration of Ad-LPL, Ad-Luc, or PBS. Hepatic LPL mRNA levels in Ad-Luc-treated mice were set as 1.0. (C) Body weights of mice determined weekly. Liver sections obtained 2 weeks after administration of Ad-LPL, Ad-Luc, or PBS and stained with (D) hematoxylin and eosin, or (E) Oil red O. Arrowheads indicate lipid droplets. Bar = 50 μm. (F) Semi-quantitative analysis of Oil red O staining performed using ImageJ. (G) Fasting serum triglyceride and (H) free fatty acid levels in mice 2 weeks after Ad vector treatment. One-way ANOVA with Dunnett’s post hoc tests was used for multiple comparisons (A, F–H). The Mann–Whitney U test was used to compare the differences between two independent groups (C). The data are expressed as the mean ± standard error…

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  Fig 2. Hepatic LPL overexpression improves glucose metabolism and insulin resistance in HFD-fed mice. Male C57BL/6 mice were intravenously treated with Ad vectors via the tail vein and were simultaneously fed HFD. PBS-treated mice were fed ND throughout the experimental period. (A) Blood glucose levels during the intra-peritoneal glucose tolerance test of mice 2 weeks after administration of Ad-LPL, Ad-Luc, or PBS. (B) Fasting blood glucose levels of mice 1 and 2 weeks after administration of Ad-LPL, Ad-Luc, or PBS. (C) Blood glucose levels during the intra-peritoneal insulin tolerance test of mice 2 weeks after administration of Ad-LPL, Ad-Luc, or PBS. (D) Fasting insulin levels and (E) HOMA-IR of mice 2 weeks after administration of Ad-LPL, Ad-Luc, or PBS. One-way ANOVA with Dunnett’s post hoc tests was used for multiple comparisons (A, B, D, and E). The Mann–Whitney U test was used to compare differences between two independent groups (C). The data are expressed as the mean ± standard error (n = 4–5). *, P < 0.05 in comparison with Ad-Luc.

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  Fig 3. Hepatic LPL overexpression upregulates fatty acid oxidation-related genes and protein in HFD-fed mice. Male C57BL/6 mice were intravenously treated with Ad vectors via the tail vein and were simultaneously fed HFD. PBS-treated mice were fed ND throughout the experimental period. Hepatic (A) PPARα, (B) CPT1, and (D) ACOX1 mRNA levels in male C57BL/6 mice 2 weeks after administration of Ad-LPL, Ad-Luc, or PBS determined using quantitative RT-PCR. The data were normalized to the corresponding value in the Ad-Luc-treated group. One-way ANOVA with Dunnett’s post hoc tests was used for multiple comparisons. The data are expressed as the mean ± standard error (n = 5). Hepatic (C) CPT1 and (E) ACOX1 protein levels in male C57BL/6 mice 2 weeks after administration of Ad-LPL or Ad-Luc determined using western blot analysis. The quantification data were normalized to the corresponding value in the Ad-Luc-treated group. The Mann–Whitney U test was used to compare the differences between two independent groups. The data are expressed as the mean ± standard error (n = 3). *, P < 0.05 vs. Ad-Luc.

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  Fig 4. Hepatic LPL overexpression maintains mitochondrial content in HFD-fed mice. Male C57BL/6 mice were intravenously treated with Ad vectors via the tail vein and were simultaneously fed HFD. PBS-treated mice were fed ND throughout the experimental period. Two weeks after administration of Ad-LPL, Ad-Luc, or PBS, (A, C) expression of mitochondrial genes in the liver determined using quantitative RT-PCR. The data were normalized to the corresponding values in the Ad-Luc-treated group. One-way ANOVA with Dunnett’s post hoc tests was used for multiple comparisons. Hepatic (B) citrate synthase protein levels in male C57BL/6 mice 2 weeks after administration of Ad-LPL or Ad-Luc determined using western blot analysis. The quantification data were normalized to the corresponding value in the Ad-Luc-treated group. The Mann–Whitney U test was used to compare the differences between two independent groups. (D) The area of mitochondria in the liver was assessed via transmission electron microscopy analysis. Arrowheads indicate mitochondria. Bar = 5 μm. (E) The area of mitochondria was determined by measuring the area of mitochondria in the cell using Fig 4D. The Mann–Whitney U test was used to…