Overexpression of Apolipoprotein A-I Alleviates Insulin Resistance in MASLD Mice Through the PPARα Pathway

Figures

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  Figure 1. ApoA-I alleviates OA-induced insulin resistance and lipid accumulation. (A) Glucose uptake at different concentrations of OA. (B) HepG2 cells were transfected with either the pcDNA3.0 or pcDNA3.0/apoA-I plasmid. The transfected cells were incubated for 24 h in DMEM supplemented with 5% BSA in the presence or absence of 500 μM OA. The level of glucose uptake was measured via bioluminescence assay after 20 min of insulin treatment. (C) HepG2 cells were transfected with either the pcDNA3.0/apoA-I plasmid. The transfected cells were incubated for 24 h in DMEM supplemented with 5% BSA in the presence or absence of 500 μM OA. After 24 h, oil red O was added to detect lipid accumulation in the cells. Scale bar, 200 μm. (D) Oil red O quantification. The data are reported as the means ± SEMs, n = 3. ** p < 0.01, *** p < 0.001, and **** p < 0.0001.

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  Figure 2. ApoA-I promotes the expression and transcriptional activity of PPARα. Isolation of cytoplasmic and nuclear proteins. (A,B) Cytoplasmic and nuclear PPARα were detected and quantified with PPARα antibodies. (C,D) Total cellular protein was isolated and analysed for FABP1 by Western blotting. (E) HEK293T cells were transfected with either the pcDNA3.0/apoA-I plasmid. After 24 h of transfection, the positive control group was treated with pirinixic acid for 24 h. PPARα transcriptional activity was detected via a luciferase reporter assay. (F) HepG2 cells were transfected with either the pcDNA3.0 or pcDNA3.0/apoA-I plasmid. The transfected cells were incubated for 24 h in DMEM supplemented with 5% BSA in the absence of 500 μM OA and/or 1 μM PPARα antagonists GW6471. The data are reported as the means ± SEMs, n = 3, * p < 0.05, ** p < 0.01, **** p < 0.0001, and ns: non-significant.

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  Figure 3. ApoA-I attenuates insulin resistance in HFCFD mice. (A) Body weights of the mice in each group. (B) Liver index of the mice in each group. (C) Intraperitoneal insulin tolerance test (IPITT). (D) The area under the curve (AUC). (E) Glucose tolerance test (IPGTT) of mice. (F) The area under the curve (AUC). (G) Fasting blood glucose levels of the mice. (H) Fasting serum insulin levels of the mice. (I) Homeostasis model of insulin resistance (HOMA-IR). The data are reported as the means ± SEMs, n = 5–7, * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001.

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  Figure 4. ApoA-I alleviates diet-induced lipid accumulation and liver injury. Hepatic triglyceride (A) and cholesterol (B) levels. Oil red O (C) and H&E (D) staining. Scale bar, 100 μm. The data are reported as the means ± SEMs, n = 5–7, * p < 0.05, ** p < 0.01, and *** p < 0.001.

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  Figure 5. ApoA-I promotes the expression of PPARα. (A,B) Separation of the nucleus and cytoplasm from liver tissue. Cytoplasmic and nuclear PPARα were detected and quantified with a PPARα antibody. (C) mRNA was isolated from the liver, and the mRNA levels of PPARα target genes were quantified via real-time quantitative PCR. (D–G) Tissue proteins were isolated and analysed for FABP1 and HMGCS2 expression via Western blotting. The data are reported as the means ± SEMs, n = 5–7, * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001.