Lipopolysaccharide inhibits the expression of resistin in adipocytes

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   Figure 1

   Improvement of OGTT by LPS. Acute effect of LPS: 129 male mice were injected (i.p.) with a single high dose (1 mg/kg body weight) (A) or low dose (80 μg/kg body weight) (B) of LPS and OGTT was analyzed 24 h later. Control animals received PBS. n=6, data were expressed as means±s.e.m. and analyzed by two-way ANOVA or unpaired Student's t-test, *P<0.05 vs PBS. Total AUCs were calculated with y values set at zero. Chronic effect of LPS: 129 male mice received a daily i.p. injection of LPS (80 μg/kg body weight per day) for 7 days, and OGTT was examined. Control animals were treated with PBS injection in the same volume amount (C). n=6, data were expressed as means±s.e.m. and analyzed by two-way ANOVA or unpaired Student's t-test, *P<0.05 vs PBS. Total AUCs were calculated with y values set at zero.
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   Figure 2

   Down-regulation of resistin by LPS in adipose tissues. (1) In vivo effects. Expression of resistin mRNA (A) and protein (B) in lean mice treated with LPS (80 μg/kg body weight per day) for 7 days. Resistin mRNA (C) and protein (D) in db/db mice treated with LPS (100 μg/kg body weight per day) for 7 days. Resistin mRNA levels are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by one-way ANOVA. *P<0.05, **P<0.01 compared with PBS group, n=6. (2) Effects in cultured adipocytes and ex vivo adipose tissues. Time-dependent response to 1000 ng/ml LPS in primary adipocytes (E), 3T3-L1 adipocytes (I) and adipose tissue fragments (L). Dose-dependent response to LPS treatment for 24 h in primary adipocytes (F), 3T3-L1 adipocytes (J) and adipose tissue fragments (M). Reversible effect of LPS on resistin expression. Adipocytes (G) and adipose tissues (N) were treated with LPS (300 ng/ml) for 8, 24, or 8 h then withdrawal of LPS for 16 h. Effect on resistin protein levels in primary rat adipocytes (H) and 3T3-L1 cells (K) treated with 1000 ng/ml LPS for 24 h. Resistin mRNA levels are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by one-way ANOVA. *P<0.05, **P<0.01 compared with PBS group; ^#P<0.05, ^##P<0.01 compared with LPS (300 ng/ml) treatment for 24 h, 8 h groups; n=6.
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   Figure 3

   Lipid A moiety-dependent effect. Effects of LPS (300 ng/ml), detoxified LPS (300 ng/ml) or lipid A (300 ng/ml) on resistin levels in adipose tissue fragments (A), primary adipocytes (B) and 3T3-L1 cells (C). Effect of PMB (500 U/ml) in ex vivo culture of adipose tissues (D), primary adipocytes (E) and 3T3-L1 adipocytes (F). Resistin mRNA levels are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by one-way ANOVA. *P<0.01 compared with PBS group; ^#P<0.05, ^##P<0.01, LPS+PMB group compared with LPS group; n=6.
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   Figure 4

   LPS down-regulates resistin expression by a transcriptional mechanism. Effect of LPS (300 ng/ml) on the half-life of resistin mRNA levels in 3T3-L1 adipocytes (A) and in primary rat adipocytes (B) in the presence of 5 μg/ml actinomycin D. Effect of LPS on resistin promoter activity by the luciferase activity of resistin-luc (4137 bp) induced by 24 h treatment with 300 ng/ml LPS relative to the control vehicle (C). Resistin mRNA levels are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by two-way ANOVA or unpaired Student's t-test. *P<0.01 compared with PBS group; n=6.
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   Figure 5

   JNK-dependent effect. Effects of LPS (1000 ng/ml) or lipid A (1000 ng/ml) on JNK phosphorylation in 3T3-L1 adipocytes (A). Blockade of TLR4 by PMB (500 U/ml) completely attenuated the phosphorylation of JNK induced by LPS (1000 ng/ml) in 3T3-L1 adipocytes (B). Inhibition of JNK phosphorylation by SP600125 (20 μM) significantly blocked the effect of LPS (1000 ng/ml) on resistin expression in primary rat adipocytes (C) and 3T3-L1 adipocytes (D). Resistin mRNA levels are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by one-way ANOVA. *P<0.01 compared with PBS group; ^#P<0.01, LPS+PMB group compared with LPS group or LPS+SP600125 group compared with LPS group; n=6.
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   Figure 6

   CHOP-10-dependent effect. Effect of LPS (1000 ng/ml) on CHOP-10 mRNA expression in adipose tissues (A) and in cultured 3T3-L1 adipocytes (B). The protein level of CHOP-10 in the presence of 1000 ng/ml LPS for 24 h in 3T3-L1 adipocytes (C). Blockade of JNK phosphorylation by SP600125 (20 μM) markedly attenuated the decrement of CHOP-10 mRNA (D) and protein (E) in cultured 3T3-L1 adipocytes. Over-expression of CHOP-10 blocked the inhibitory effect of LPS on the resistin mRNA (F). mRNA levels of CHOP-10 and resistin are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by one-way ANOVA. *P<0.05, **P<0.01 compared with PBS group; ^#P<0.05, ^##P<0.01 LPS+SP600125 group compared with LPS group or LPS+antisense CHOP-10 group compared with LPS+missense CHOP-10 group; n=6.
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   Figure 7

   C/EBP-α-dependent modulation. Effect of LPS (1000 ng/ml) on C/EBP-α mRNA expression in adipose tissues (A) and in cultured 3T3-L1 adipocytes (B). The protein level of C/EBP-α in the presence of 1000 ng/ml LPS for 24 h in 3T3-L1 adipocytes (C). Blockade of JNK phosphorylation by SP600125 (20 μM) markedly attenuated the decrement of C/EBP-α mRNA (D) and protein (E) in cultured 3T3-L1 adipocytes. Over-expression of C/EBP-α blocked the inhibitory effect of LPS on the resistin mRNA (F). mRNA levels of C/EBP-α and resistin are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by one-way ANOVA. *P<0.01 compared with PBS group; ^#P<0.01 LPS+SP600125 group compared with LPS group or LPS+C/EBP-α plasmid group compared with LPS+GFP plasmid group; n=6.
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   Figure 8

   PPAR-γ-dependent regulation. Effect of LPS (1000 ng/ml) on PPAR-γ mRNA expression in adipose tissues (A) and in cultured 3T3-L1 adipocytes (B). The protein level of PPAR-γ in 3T3-L1 adipocytes treated with 1000 ng/ml LPS for 24 h (C). Blockade of JNK phosphorylation by SP600125 (20 μM) markedly attenuated the decrement of PPAR-γ mRNA (D) and protein (E) in cultured 3T3-L1 adipocytes. Activation of PPAR-γ by rosiglitazone (1 μM) (F), or by over-expression of PPAR-γ (G) blocked the inhibitory effect of LPS on the resistin mRNA. mRNA levels of PPAR-γ and resistin are normalized to β-actin mRNA levels, and the results are mean±s.e.m. of three independent experiments and analyzed by one-way ANOVA. **P<0.01 compared with PBS group; ^#P<0.05, LPS+rosiglitazone group compared with LPS group, ^##P<0.01 LPS+SP600125 group compared with LPS group or LPS+PPAR-γ adenoviral vectors group compared with LPS+adenoviral vectors group; n=6.
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   Figure 9

   Illustration of signaling pathways. LPS modulates resistin expression through the TLR4-JNK-CHOP-10-C/EBP-α/PPAR-γ signaling.

• © 2013 Society for Endocrinology