Limits...
Impaired LDL receptor-related protein 1 translocation correlates with improved dyslipidemia and atherosclerosis in apoE-deficient mice.

Gordts PL, Bartelt A, Nilsson SK, Annaert W, Christoffersen C, Nielsen LB, Heeren J, Roebroek AJ - PLoS ONE (2012)

Bottom Line: Postprandial lipoprotein improvement was explained by increased hepatic clearance of triglyceride-rich remnant lipoproteins and accompanied by a compensatory 1.6-fold upregulation of LDLR expression in hepatocytes.These findings demonstrate that the NPxYxxL motif in LRP1 is important for insulin-mediated translocation and slow perinuclear endosomal recycling.These LRP1 impairments correlated with reduced atherogenesis and cholesterol levels in apoE-deficient mice, likely via compensatory LDLR upregulation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Experimental Mouse Genetics, Center for Human Genetics, KU Leuven, Leuven, Belgium.

ABSTRACT

Objective: Determination of the in vivo significance of LDL receptor-related protein 1 (LRP1) dysfunction on lipid metabolism and atherosclerosis development in absence of its main ligand apoE.

Methods and results: LRP1 knock-in mice carrying an inactivating mutation in the NPxYxxL motif were crossed with apoE-deficient mice. In the absence of apoE, relative to LRP1 wild-type animals, LRP1 mutated mice showed an increased clearance of postprandial lipids despite a compromised LRP1 endocytosis rate and inefficient insulin-mediated translocation of the receptor to the plasma membrane, likely due to inefficient slow recycling of the mutated receptor. Postprandial lipoprotein improvement was explained by increased hepatic clearance of triglyceride-rich remnant lipoproteins and accompanied by a compensatory 1.6-fold upregulation of LDLR expression in hepatocytes. One year-old apoE-deficient mice having the dysfunctional LRP1 revealed a 3-fold decrease in spontaneous atherosclerosis development and a 2-fold reduction in LDL-cholesterol levels.

Conclusion: These findings demonstrate that the NPxYxxL motif in LRP1 is important for insulin-mediated translocation and slow perinuclear endosomal recycling. These LRP1 impairments correlated with reduced atherogenesis and cholesterol levels in apoE-deficient mice, likely via compensatory LDLR upregulation.

Show MeSH

Related in: MedlinePlus

Reduced atherosclerosis development in ApoE−/−LRP1n2/n2 mice.A–B, Spontaneous atherosclerosis development in 26- (A) and 52-week (A–B) old mice. C–E, Different cholesterol levels in lipoprotein fractions (VLDL, LDL and HDL) separated via sequential ultracentrifugation in mice at 52-weeks of age (C), total triglyceride levels (D) and correlation plot between atherogenesis and total cholesterol for individual mice (E). Statistical analysis via determination of the Pearson’s correlation coefficient (Rp) revealed a significant positive correlation between atherosclerosis load in the aorta and circulating cholesterol levels. F, Total plasma cholesterol levels in mice at 12-, 26- or 52-weeks of age. G, Immunoblot analyses of hepatic LDLR and β-actin expression levels in 8- and 52-week old mice. ApoE−/− (□ or ○) and apoE−/−LRP1n2/n2 (▪ or •) mice, n = 7–12 on a chow diet, data are mean±SEM. *P<0.005, **P<0.0005.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3368875&req=5

pone-0038330-g005: Reduced atherosclerosis development in ApoE−/−LRP1n2/n2 mice.A–B, Spontaneous atherosclerosis development in 26- (A) and 52-week (A–B) old mice. C–E, Different cholesterol levels in lipoprotein fractions (VLDL, LDL and HDL) separated via sequential ultracentrifugation in mice at 52-weeks of age (C), total triglyceride levels (D) and correlation plot between atherogenesis and total cholesterol for individual mice (E). Statistical analysis via determination of the Pearson’s correlation coefficient (Rp) revealed a significant positive correlation between atherosclerosis load in the aorta and circulating cholesterol levels. F, Total plasma cholesterol levels in mice at 12-, 26- or 52-weeks of age. G, Immunoblot analyses of hepatic LDLR and β-actin expression levels in 8- and 52-week old mice. ApoE−/− (□ or ○) and apoE−/−LRP1n2/n2 (▪ or •) mice, n = 7–12 on a chow diet, data are mean±SEM. *P<0.005, **P<0.0005.

Mentions: The impact of inefficient insulin-mediated translocation on spontaneous atherosclerosis development was evaluated in 26 week old mice. At this age, there was only minor development of early lesions. Nevertheless, apoE−/−LRP1n2/n2 mice had significantly less plaque load compared to apoE−/− mice (2×n = 8; Figure 5A). For advanced plaques analysis mice were allowed to age up to 52 weeks. At this age, just 8% of the aortic surface of apoE−/−LRP1n2/n2 mice (n = 7) had Sudan IV positive lesions in comparison to 30% in the control apoE−/− group (n = 12; Figure 5B). Analyzing plaque volume in ascending aortas confirmed that plaques in apoE−/− mice (n = 6) were 1.6-fold larger compared to plaques in apoE−/−LRP1n2/n2 mice (n = 8) (data not shown). Plasma cholesterol levels in 52-weeks of age apoE−/− mice were significantly 2-fold higher compared to apoE−/−LRP1n2/n2 mice (resp. 836±80 mg/dl vs. 411±66 mg/dl) due to higher VLDL- and LDL-cholesterol levels (Figure 5C). Assessment of the total TG levels indicated higher levels for the apoE−/− mice compared to apoE−/−LRP1n2/n2 mice; however, not significantly (Figure 5D). There was a significant correlation between plaque load and cholesterol levels (Figure 5E). The observed higher cholesterol levels in apoE−/−mice of 52 weeks were age-dependent (Figure 5F) and associated with a significant age-dependent decrease in total hepatic LDLR levels (Figure 5G). Still despite this decrease, the LDLR expression levels of aged apoE−/−LRP1n2/n2 mice were 1.5-fold higher than aged-matched apoE−/−mice (data not shown). The data suggest that in the absence of apoE impaired LRP1 function correlates with improved atherosclerosis outcome.


Impaired LDL receptor-related protein 1 translocation correlates with improved dyslipidemia and atherosclerosis in apoE-deficient mice.

Gordts PL, Bartelt A, Nilsson SK, Annaert W, Christoffersen C, Nielsen LB, Heeren J, Roebroek AJ - PLoS ONE (2012)

Reduced atherosclerosis development in ApoE−/−LRP1n2/n2 mice.A–B, Spontaneous atherosclerosis development in 26- (A) and 52-week (A–B) old mice. C–E, Different cholesterol levels in lipoprotein fractions (VLDL, LDL and HDL) separated via sequential ultracentrifugation in mice at 52-weeks of age (C), total triglyceride levels (D) and correlation plot between atherogenesis and total cholesterol for individual mice (E). Statistical analysis via determination of the Pearson’s correlation coefficient (Rp) revealed a significant positive correlation between atherosclerosis load in the aorta and circulating cholesterol levels. F, Total plasma cholesterol levels in mice at 12-, 26- or 52-weeks of age. G, Immunoblot analyses of hepatic LDLR and β-actin expression levels in 8- and 52-week old mice. ApoE−/− (□ or ○) and apoE−/−LRP1n2/n2 (▪ or •) mice, n = 7–12 on a chow diet, data are mean±SEM. *P<0.005, **P<0.0005.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368875&req=5

pone-0038330-g005: Reduced atherosclerosis development in ApoE−/−LRP1n2/n2 mice.A–B, Spontaneous atherosclerosis development in 26- (A) and 52-week (A–B) old mice. C–E, Different cholesterol levels in lipoprotein fractions (VLDL, LDL and HDL) separated via sequential ultracentrifugation in mice at 52-weeks of age (C), total triglyceride levels (D) and correlation plot between atherogenesis and total cholesterol for individual mice (E). Statistical analysis via determination of the Pearson’s correlation coefficient (Rp) revealed a significant positive correlation between atherosclerosis load in the aorta and circulating cholesterol levels. F, Total plasma cholesterol levels in mice at 12-, 26- or 52-weeks of age. G, Immunoblot analyses of hepatic LDLR and β-actin expression levels in 8- and 52-week old mice. ApoE−/− (□ or ○) and apoE−/−LRP1n2/n2 (▪ or •) mice, n = 7–12 on a chow diet, data are mean±SEM. *P<0.005, **P<0.0005.
Mentions: The impact of inefficient insulin-mediated translocation on spontaneous atherosclerosis development was evaluated in 26 week old mice. At this age, there was only minor development of early lesions. Nevertheless, apoE−/−LRP1n2/n2 mice had significantly less plaque load compared to apoE−/− mice (2×n = 8; Figure 5A). For advanced plaques analysis mice were allowed to age up to 52 weeks. At this age, just 8% of the aortic surface of apoE−/−LRP1n2/n2 mice (n = 7) had Sudan IV positive lesions in comparison to 30% in the control apoE−/− group (n = 12; Figure 5B). Analyzing plaque volume in ascending aortas confirmed that plaques in apoE−/− mice (n = 6) were 1.6-fold larger compared to plaques in apoE−/−LRP1n2/n2 mice (n = 8) (data not shown). Plasma cholesterol levels in 52-weeks of age apoE−/− mice were significantly 2-fold higher compared to apoE−/−LRP1n2/n2 mice (resp. 836±80 mg/dl vs. 411±66 mg/dl) due to higher VLDL- and LDL-cholesterol levels (Figure 5C). Assessment of the total TG levels indicated higher levels for the apoE−/− mice compared to apoE−/−LRP1n2/n2 mice; however, not significantly (Figure 5D). There was a significant correlation between plaque load and cholesterol levels (Figure 5E). The observed higher cholesterol levels in apoE−/−mice of 52 weeks were age-dependent (Figure 5F) and associated with a significant age-dependent decrease in total hepatic LDLR levels (Figure 5G). Still despite this decrease, the LDLR expression levels of aged apoE−/−LRP1n2/n2 mice were 1.5-fold higher than aged-matched apoE−/−mice (data not shown). The data suggest that in the absence of apoE impaired LRP1 function correlates with improved atherosclerosis outcome.

Bottom Line: Postprandial lipoprotein improvement was explained by increased hepatic clearance of triglyceride-rich remnant lipoproteins and accompanied by a compensatory 1.6-fold upregulation of LDLR expression in hepatocytes.These findings demonstrate that the NPxYxxL motif in LRP1 is important for insulin-mediated translocation and slow perinuclear endosomal recycling.These LRP1 impairments correlated with reduced atherogenesis and cholesterol levels in apoE-deficient mice, likely via compensatory LDLR upregulation.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Experimental Mouse Genetics, Center for Human Genetics, KU Leuven, Leuven, Belgium.

ABSTRACT

Objective: Determination of the in vivo significance of LDL receptor-related protein 1 (LRP1) dysfunction on lipid metabolism and atherosclerosis development in absence of its main ligand apoE.

Methods and results: LRP1 knock-in mice carrying an inactivating mutation in the NPxYxxL motif were crossed with apoE-deficient mice. In the absence of apoE, relative to LRP1 wild-type animals, LRP1 mutated mice showed an increased clearance of postprandial lipids despite a compromised LRP1 endocytosis rate and inefficient insulin-mediated translocation of the receptor to the plasma membrane, likely due to inefficient slow recycling of the mutated receptor. Postprandial lipoprotein improvement was explained by increased hepatic clearance of triglyceride-rich remnant lipoproteins and accompanied by a compensatory 1.6-fold upregulation of LDLR expression in hepatocytes. One year-old apoE-deficient mice having the dysfunctional LRP1 revealed a 3-fold decrease in spontaneous atherosclerosis development and a 2-fold reduction in LDL-cholesterol levels.

Conclusion: These findings demonstrate that the NPxYxxL motif in LRP1 is important for insulin-mediated translocation and slow perinuclear endosomal recycling. These LRP1 impairments correlated with reduced atherogenesis and cholesterol levels in apoE-deficient mice, likely via compensatory LDLR upregulation.

Show MeSH
Related in: MedlinePlus