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APPL1 counteracts obesity-induced vascular insulin resistance and endothelial dysfunction by modulating the endothelial production of nitric oxide and endothelin-1 in mice.

Wang Y, Cheng KK, Lam KS, Wu D, Wang Y, Huang Y, Vanhoutte PM, Sweeney G, Li Y, Xu A - Diabetes (2011)

Bottom Line: However, the cellular mechanisms that control the dual vascular effects of insulin remain unclear.In endothelial cells, APPL1 potentiated insulin-stimulated Akt activation by competing with the Akt inhibitor Tribbles 3 (TRB3) and suppressed ERK1/2 signaling by altering the phosphorylation status of its upstream kinase Raf-1.APPL1 plays a key role in coordinating the vasodilator and vasoconstrictor effects of insulin by modulating Akt-dependent NO production and ERK1/2-mediated ET-1 secretion in the endothelium.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Division of Endocrinology and Metabolism, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.

ABSTRACT

Objective: Insulin stimulates both nitric oxide (NO)-dependent vasodilation and endothelin-1 (ET-1)-dependent vasoconstriction. However, the cellular mechanisms that control the dual vascular effects of insulin remain unclear. This study aimed to investigate the roles of the multidomain adaptor protein APPL1 in modulating vascular actions of insulin in mice and in endothelial cells.

Research design and methods: Both APPL1 knockout mice and APPL1 transgenic mice were generated to evaluate APPL1's physiological roles in regulating vascular reactivity and insulin signaling in endothelial cells.

Results: Insulin potently induced NO-dependent relaxations in mesenteric arteries of 8-week-old mice, whereas this effect of insulin was progressively impaired with ageing or upon development of obesity induced by high-fat diet. Transgenic expression of APPL1 prevented age- and obesity-induced impairment in insulin-induced vasodilation and reversed obesity-induced augmentation in insulin-evoked ET-1-dependent vasoconstriction. By contrast, genetic disruption of APPL1 shifted the effects of insulin from vasodilation to vasoconstriction. At the molecular level, insulin-elicited activation of protein kinase B (Akt) and endothelial NO synthase and production of NO were enhanced in APPL1 transgenic mice but were abrogated in APPL1 knockout mice. Conversely, insulin-induced extracellular signal-related kinase (ERK)1/2 phosphorylation and ET-1 expression was augmented in APPL1 knockout mice but was diminished in APPL1 transgenic mice. In endothelial cells, APPL1 potentiated insulin-stimulated Akt activation by competing with the Akt inhibitor Tribbles 3 (TRB3) and suppressed ERK1/2 signaling by altering the phosphorylation status of its upstream kinase Raf-1.

Conclusions: APPL1 plays a key role in coordinating the vasodilator and vasoconstrictor effects of insulin by modulating Akt-dependent NO production and ERK1/2-mediated ET-1 secretion in the endothelium.

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The insulin-induced ET-1–dependent contraction is suppressed in APPL1-Tg mice on HFD. A: Effect of insulin in mesenteric arteries of 16-week-old WT mice on HFD in the presence of the ERK1/2 inhibitor PD98059 (5 μmol/L) or the ET-1A receptor antagonist BQ123 (1 μmol/L). Data are expressed as percentage of the contraction to U46619. B: Effect of insulin in mesenteric arteries of 16-week-old APPL1-Tg and WT mice fed HFD or STD in the presence of l-NAME (100 μmol/L). Data are shown as area under the curve (AUC). C: The mRNA levels of ET-1 in mesenteric arteries from 16-week-old APPL1-Tg and WT mice fed STD or HFD were quantified by real-time quantitative-PCR and normalized against GAPDH. *P < 0.05, **P < 0.01 (n = 5–8).
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Figure 3: The insulin-induced ET-1–dependent contraction is suppressed in APPL1-Tg mice on HFD. A: Effect of insulin in mesenteric arteries of 16-week-old WT mice on HFD in the presence of the ERK1/2 inhibitor PD98059 (5 μmol/L) or the ET-1A receptor antagonist BQ123 (1 μmol/L). Data are expressed as percentage of the contraction to U46619. B: Effect of insulin in mesenteric arteries of 16-week-old APPL1-Tg and WT mice fed HFD or STD in the presence of l-NAME (100 μmol/L). Data are shown as area under the curve (AUC). C: The mRNA levels of ET-1 in mesenteric arteries from 16-week-old APPL1-Tg and WT mice fed STD or HFD were quantified by real-time quantitative-PCR and normalized against GAPDH. *P < 0.05, **P < 0.01 (n = 5–8).

Mentions: In obesity, insulin promotes vasoconstriction by stimulating the release of ET-1 (19,20). We next investigated the impact of APPL1 overexpression on insulin-stimulated ET-1 expression and vasoconstriction in mice on HFD. Treatment of mesenteric arteries of 16-week-old WT mice on HFD with either the ERK1/2 inhibitor PD98059 (5 μmol/L) or the endothelin type a (ET-1A) receptor antagonist BQ123 (1 μmol/L) blocked insulin-elicited contractions and restored insulin-evoked relaxations (Fig. 3A), confirming that the insulin-induced vasoconstriction was mediated by ET-1 through ERK1/2 activation. In both APPL1-Tg mice and WT littermates on STD, l-NAME (100 μmol/L for 30 min) inhibited the relaxations to insulin (Fig. 3B). Treatment of mesenteric arteries with l-NAME potentiated insulin-elicited contractions in arteries of 16-week-old WT mice on HFD (Fig. 3B). By contrast, l-NAME blocked insulin-induced relaxations but did not unmask contractions to 100 nmol/L insulin in preparations of age-matched APPL1-Tg mice on HFD. These findings suggest that although the NO-mediated relaxation effects were inhibited by l-NAME, insulin-stimulated ET-1 production may not be abundant enough to induce vasoconstriction under STD.


APPL1 counteracts obesity-induced vascular insulin resistance and endothelial dysfunction by modulating the endothelial production of nitric oxide and endothelin-1 in mice.

Wang Y, Cheng KK, Lam KS, Wu D, Wang Y, Huang Y, Vanhoutte PM, Sweeney G, Li Y, Xu A - Diabetes (2011)

The insulin-induced ET-1–dependent contraction is suppressed in APPL1-Tg mice on HFD. A: Effect of insulin in mesenteric arteries of 16-week-old WT mice on HFD in the presence of the ERK1/2 inhibitor PD98059 (5 μmol/L) or the ET-1A receptor antagonist BQ123 (1 μmol/L). Data are expressed as percentage of the contraction to U46619. B: Effect of insulin in mesenteric arteries of 16-week-old APPL1-Tg and WT mice fed HFD or STD in the presence of l-NAME (100 μmol/L). Data are shown as area under the curve (AUC). C: The mRNA levels of ET-1 in mesenteric arteries from 16-week-old APPL1-Tg and WT mice fed STD or HFD were quantified by real-time quantitative-PCR and normalized against GAPDH. *P < 0.05, **P < 0.01 (n = 5–8).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Figure 3: The insulin-induced ET-1–dependent contraction is suppressed in APPL1-Tg mice on HFD. A: Effect of insulin in mesenteric arteries of 16-week-old WT mice on HFD in the presence of the ERK1/2 inhibitor PD98059 (5 μmol/L) or the ET-1A receptor antagonist BQ123 (1 μmol/L). Data are expressed as percentage of the contraction to U46619. B: Effect of insulin in mesenteric arteries of 16-week-old APPL1-Tg and WT mice fed HFD or STD in the presence of l-NAME (100 μmol/L). Data are shown as area under the curve (AUC). C: The mRNA levels of ET-1 in mesenteric arteries from 16-week-old APPL1-Tg and WT mice fed STD or HFD were quantified by real-time quantitative-PCR and normalized against GAPDH. *P < 0.05, **P < 0.01 (n = 5–8).
Mentions: In obesity, insulin promotes vasoconstriction by stimulating the release of ET-1 (19,20). We next investigated the impact of APPL1 overexpression on insulin-stimulated ET-1 expression and vasoconstriction in mice on HFD. Treatment of mesenteric arteries of 16-week-old WT mice on HFD with either the ERK1/2 inhibitor PD98059 (5 μmol/L) or the endothelin type a (ET-1A) receptor antagonist BQ123 (1 μmol/L) blocked insulin-elicited contractions and restored insulin-evoked relaxations (Fig. 3A), confirming that the insulin-induced vasoconstriction was mediated by ET-1 through ERK1/2 activation. In both APPL1-Tg mice and WT littermates on STD, l-NAME (100 μmol/L for 30 min) inhibited the relaxations to insulin (Fig. 3B). Treatment of mesenteric arteries with l-NAME potentiated insulin-elicited contractions in arteries of 16-week-old WT mice on HFD (Fig. 3B). By contrast, l-NAME blocked insulin-induced relaxations but did not unmask contractions to 100 nmol/L insulin in preparations of age-matched APPL1-Tg mice on HFD. These findings suggest that although the NO-mediated relaxation effects were inhibited by l-NAME, insulin-stimulated ET-1 production may not be abundant enough to induce vasoconstriction under STD.

Bottom Line: However, the cellular mechanisms that control the dual vascular effects of insulin remain unclear.In endothelial cells, APPL1 potentiated insulin-stimulated Akt activation by competing with the Akt inhibitor Tribbles 3 (TRB3) and suppressed ERK1/2 signaling by altering the phosphorylation status of its upstream kinase Raf-1.APPL1 plays a key role in coordinating the vasodilator and vasoconstrictor effects of insulin by modulating Akt-dependent NO production and ERK1/2-mediated ET-1 secretion in the endothelium.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Division of Endocrinology and Metabolism, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai, China.

ABSTRACT

Objective: Insulin stimulates both nitric oxide (NO)-dependent vasodilation and endothelin-1 (ET-1)-dependent vasoconstriction. However, the cellular mechanisms that control the dual vascular effects of insulin remain unclear. This study aimed to investigate the roles of the multidomain adaptor protein APPL1 in modulating vascular actions of insulin in mice and in endothelial cells.

Research design and methods: Both APPL1 knockout mice and APPL1 transgenic mice were generated to evaluate APPL1's physiological roles in regulating vascular reactivity and insulin signaling in endothelial cells.

Results: Insulin potently induced NO-dependent relaxations in mesenteric arteries of 8-week-old mice, whereas this effect of insulin was progressively impaired with ageing or upon development of obesity induced by high-fat diet. Transgenic expression of APPL1 prevented age- and obesity-induced impairment in insulin-induced vasodilation and reversed obesity-induced augmentation in insulin-evoked ET-1-dependent vasoconstriction. By contrast, genetic disruption of APPL1 shifted the effects of insulin from vasodilation to vasoconstriction. At the molecular level, insulin-elicited activation of protein kinase B (Akt) and endothelial NO synthase and production of NO were enhanced in APPL1 transgenic mice but were abrogated in APPL1 knockout mice. Conversely, insulin-induced extracellular signal-related kinase (ERK)1/2 phosphorylation and ET-1 expression was augmented in APPL1 knockout mice but was diminished in APPL1 transgenic mice. In endothelial cells, APPL1 potentiated insulin-stimulated Akt activation by competing with the Akt inhibitor Tribbles 3 (TRB3) and suppressed ERK1/2 signaling by altering the phosphorylation status of its upstream kinase Raf-1.

Conclusions: APPL1 plays a key role in coordinating the vasodilator and vasoconstrictor effects of insulin by modulating Akt-dependent NO production and ERK1/2-mediated ET-1 secretion in the endothelium.

Show MeSH
Related in: MedlinePlus