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Endothelial NO/cGMP/VASP signaling attenuates Kupffer cell activation and hepatic insulin resistance induced by high-fat feeding.

Tateya S, Rizzo NO, Handa P, Cheng AM, Morgan-Stevenson V, Daum G, Clowes AW, Morton GJ, Schwartz MW, Kim F - Diabetes (2011)

Bottom Line: We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Washington, Seattle, Washington, USA.

ABSTRACT

Objective: Proinflammatory activation of Kupffer cells is implicated in the effect of high-fat feeding to cause liver insulin resistance. We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.

Research design and methods: Effect of NO/cGMP signaling on hepatic inflammation and on isolated Kupffer cells was examined in C57BL/6 mice, eNos(-/-) mice, and Vasp(-/-) mice fed a low-fat or high-fat diet.

Results: We show that high-fat feeding induces proinflammatory activation of Kupffer cells in wild-type mice coincident with reduced liver endothelial nitric oxide synthase activity and NO content while, conversely, enhancement of signaling downstream of endogenous NO by phosphodiesterase-5 inhibition protects against high fat-induced inflammation in Kupffer cells. Furthermore, proinflammatory activation of Kupffer cells is evident in eNos(-/-) mice even on a low-fat diet. Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.

Conclusions: These results collectively imply a physiological role for endothelial NO to limit obesity-associated inflammation and insulin resistance in hepatocytes and support a model in which Kupffer cell activation during high-fat feeding is dependent on reduced NO signaling. Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

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The effect of high-fat (HF) feeding on liver NO, hepatic inflammation, and Kupffer cell activation. Wild-type (WT) mice were fed either a low-fat (LF) or HF diet for 2, 4, or 8 weeks. A: Hepatic NO content during HF and LF feeding as measured by electron spin resonance spectroscopy (n = 9). B: Liver eNOS phosphorylation of Ser 1177 as measured by Western blot (n = 9). C: Liver phospho–IκB-α as measured by Western blot, normalized to total GAPDH levels (n = 9). D: Liver IL-6. E: TNF-α mRNA (n = 9). F: ICAM mRNA levels (n = 9). G: Relative mRNA levels from isolated Kupffer cells as measured by RT-PCR after 2, 4, and 8 weeks of LF or HF diet (n = 5 mice). H: In parallel experiments in WT mice, hepatic insulin signaling was assessed following intraperitoneal injection of insulin or saline vehicle (n = 5 per group). Liver protein lysates were analyzed for IRS-1 tyrosine phosphorylation (p–IRS-1), IRS-1, pAkt, and Akt levels by enzyme-linked immunosorbent assay. *P < 0.05.
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Figure 1: The effect of high-fat (HF) feeding on liver NO, hepatic inflammation, and Kupffer cell activation. Wild-type (WT) mice were fed either a low-fat (LF) or HF diet for 2, 4, or 8 weeks. A: Hepatic NO content during HF and LF feeding as measured by electron spin resonance spectroscopy (n = 9). B: Liver eNOS phosphorylation of Ser 1177 as measured by Western blot (n = 9). C: Liver phospho–IκB-α as measured by Western blot, normalized to total GAPDH levels (n = 9). D: Liver IL-6. E: TNF-α mRNA (n = 9). F: ICAM mRNA levels (n = 9). G: Relative mRNA levels from isolated Kupffer cells as measured by RT-PCR after 2, 4, and 8 weeks of LF or HF diet (n = 5 mice). H: In parallel experiments in WT mice, hepatic insulin signaling was assessed following intraperitoneal injection of insulin or saline vehicle (n = 5 per group). Liver protein lysates were analyzed for IRS-1 tyrosine phosphorylation (p–IRS-1), IRS-1, pAkt, and Akt levels by enzyme-linked immunosorbent assay. *P < 0.05.

Mentions: We found that compared with low fat–fed control mice, liver NO content and phosphorylation of eNOS were reduced after 4 weeks of high-fat feeding (Fig. 1A and B). Markers of liver NF-κB activation—hepatic IκB-α phosphorylation (Fig. 1C), interleukin (IL)-6 (Fig. 1D) and tumor necrosis factor (TNF)-α mRNA expression, TNF-α (Fig. 1E), and intracellular adhesion molecule (ICAM) (Fig. 1F)—were also increased by high-fat feeding, but this did not occur until 8 weeks on the high-fat diet. During high-fat feeding, liver NO content falls prior to the onset of high fat–induced NF-κB signaling.


Endothelial NO/cGMP/VASP signaling attenuates Kupffer cell activation and hepatic insulin resistance induced by high-fat feeding.

Tateya S, Rizzo NO, Handa P, Cheng AM, Morgan-Stevenson V, Daum G, Clowes AW, Morton GJ, Schwartz MW, Kim F - Diabetes (2011)

The effect of high-fat (HF) feeding on liver NO, hepatic inflammation, and Kupffer cell activation. Wild-type (WT) mice were fed either a low-fat (LF) or HF diet for 2, 4, or 8 weeks. A: Hepatic NO content during HF and LF feeding as measured by electron spin resonance spectroscopy (n = 9). B: Liver eNOS phosphorylation of Ser 1177 as measured by Western blot (n = 9). C: Liver phospho–IκB-α as measured by Western blot, normalized to total GAPDH levels (n = 9). D: Liver IL-6. E: TNF-α mRNA (n = 9). F: ICAM mRNA levels (n = 9). G: Relative mRNA levels from isolated Kupffer cells as measured by RT-PCR after 2, 4, and 8 weeks of LF or HF diet (n = 5 mice). H: In parallel experiments in WT mice, hepatic insulin signaling was assessed following intraperitoneal injection of insulin or saline vehicle (n = 5 per group). Liver protein lysates were analyzed for IRS-1 tyrosine phosphorylation (p–IRS-1), IRS-1, pAkt, and Akt levels by enzyme-linked immunosorbent assay. *P < 0.05.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198085&req=5

Figure 1: The effect of high-fat (HF) feeding on liver NO, hepatic inflammation, and Kupffer cell activation. Wild-type (WT) mice were fed either a low-fat (LF) or HF diet for 2, 4, or 8 weeks. A: Hepatic NO content during HF and LF feeding as measured by electron spin resonance spectroscopy (n = 9). B: Liver eNOS phosphorylation of Ser 1177 as measured by Western blot (n = 9). C: Liver phospho–IκB-α as measured by Western blot, normalized to total GAPDH levels (n = 9). D: Liver IL-6. E: TNF-α mRNA (n = 9). F: ICAM mRNA levels (n = 9). G: Relative mRNA levels from isolated Kupffer cells as measured by RT-PCR after 2, 4, and 8 weeks of LF or HF diet (n = 5 mice). H: In parallel experiments in WT mice, hepatic insulin signaling was assessed following intraperitoneal injection of insulin or saline vehicle (n = 5 per group). Liver protein lysates were analyzed for IRS-1 tyrosine phosphorylation (p–IRS-1), IRS-1, pAkt, and Akt levels by enzyme-linked immunosorbent assay. *P < 0.05.
Mentions: We found that compared with low fat–fed control mice, liver NO content and phosphorylation of eNOS were reduced after 4 weeks of high-fat feeding (Fig. 1A and B). Markers of liver NF-κB activation—hepatic IκB-α phosphorylation (Fig. 1C), interleukin (IL)-6 (Fig. 1D) and tumor necrosis factor (TNF)-α mRNA expression, TNF-α (Fig. 1E), and intracellular adhesion molecule (ICAM) (Fig. 1F)—were also increased by high-fat feeding, but this did not occur until 8 weeks on the high-fat diet. During high-fat feeding, liver NO content falls prior to the onset of high fat–induced NF-κB signaling.

Bottom Line: We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Washington, Seattle, Washington, USA.

ABSTRACT

Objective: Proinflammatory activation of Kupffer cells is implicated in the effect of high-fat feeding to cause liver insulin resistance. We sought to determine whether reduced endothelial nitric oxide (NO) signaling contributes to the effect of high-fat feeding to increase hepatic inflammatory signaling and if so, whether this effect 1) involves activation of Kupffer cells and 2) is ameliorated by increased NO signaling.

Research design and methods: Effect of NO/cGMP signaling on hepatic inflammation and on isolated Kupffer cells was examined in C57BL/6 mice, eNos(-/-) mice, and Vasp(-/-) mice fed a low-fat or high-fat diet.

Results: We show that high-fat feeding induces proinflammatory activation of Kupffer cells in wild-type mice coincident with reduced liver endothelial nitric oxide synthase activity and NO content while, conversely, enhancement of signaling downstream of endogenous NO by phosphodiesterase-5 inhibition protects against high fat-induced inflammation in Kupffer cells. Furthermore, proinflammatory activation of Kupffer cells is evident in eNos(-/-) mice even on a low-fat diet. Targeted deletion of vasodilator-stimulated phosphoprotein (VASP), a key downstream target of endothelially derived NO, similarly predisposes to hepatic and Kupffer cell inflammation and abrogates the protective effect of NO signaling in both macrophages and hepatocytes studied in a cell culture model.

Conclusions: These results collectively imply a physiological role for endothelial NO to limit obesity-associated inflammation and insulin resistance in hepatocytes and support a model in which Kupffer cell activation during high-fat feeding is dependent on reduced NO signaling. Our findings also identify the NO/VASP pathway as a novel potential target for the treatment of obesity-associated liver insulin resistance.

Show MeSH
Related in: MedlinePlus