Nutr Res Pract.  2011 Jun;5(3):219-223.

High fat diet-induced obesity leads to proinflammatory response associated with higher expression of NOD2 protein

• Kim MS
• Choi MS
• Han SN

Abstract

Obesity has been reported to be associated with low grade inflammatory status. In this study, we investigated the inflammatory response as well as associated signaling molecules in immune cells from diet-induced obese mice. Four-week-old C57BL mice were fed diets containing 5% fat (control) or 20% fat and 1% cholesterol (HFD) for 24 weeks. Splenocytes (1 x 10(7) cells) were stimulated with 10 microg/mL of lipopolysaccharide (LPS) for 6 or 24 hrs. Production of interleukin (IL)-1beta, IL-6, and TNF-alpha as well as protein expression levels of nucleotide-binding oligomerization domain (NOD)2, signal transducer and activator of transcription (STAT)3, and pSTAT3 were determined. Mice fed HFD gained significantly more body weight compared to mice fed control diet (28.2 +/- 0.6 g in HFD and 15.4 +/- 0.8 g in control). After stimulation with LPS for 6 hrs, production of IL-1beta was significantly higher (P = 0.001) and production of tumor necrosis factor (TNF)-alpha tended to be higher (P < 0.064) in the HFD group. After 24 hrs of LPS stimulation, splenocytes from the HFD group produced significantly higher levels of IL-6 (10.02 +/- 0.66 ng/mL in HFD and 7.33 +/- 0.56 ng/mL in control, P = 0.005) and IL-1beta (121.34 +/- 12.72 pg/mL in HFD and 49.74 +/- 6.58 pg/mL in control, P < 0.001). There were no significant differences in the expression levels of STAT3 and pSTAT3 between the HFD and the control groups. However, the expression level of NOD2 protein as determined by Western blot analysis was 60% higher in the HFD group compared with the control group. NOD2 contributes to the induction of inflammation by activation of nuclear factor kappaB. These findings suggest that diet-induced obesity is associated with increased inflammatory response of immune cells, and higher expression of NOD2 may contribute to these changes.

Keyword

Obesity; inflammatory cytokines; NOD2; STAT3; high fat diet

MeSH Terms

Animals
Blotting, Western
Body Weight
Cholesterol
Diet
Diet, High-Fat
Inflammation
Interleukin-6
Interleukins
Mice
Mice, Inbred C57BL
Mice, Obese
Obesity
Staphylococcal Protein A
Transducers
Tumor Necrosis Factor-alpha
Cholesterol
Interleukin-6
Interleukins
Staphylococcal Protein A
Tumor Necrosis Factor-alpha

Figure

• 

  Fig. 1 Levels of inflammatory cytokines produced by splenocytes from animals in the control and HFD groups. Levels of (A) IL-6, (B) IL-1β, and TNF-α produced by splenocytes (1 × 107 cells) stimulated with LPS (10 µg/mL) for 6 or 24 hrs. *Significantly different from the control group by Student's t-test at P < 0.05.

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  Fig. 2 NOD2 expression levels in splenocytes from animals in the control and HFD groups stimulated with LPS (10 µg/mL). (A) Representative immunoblots. (B) Densitometric analyses of NOD2 protein expression corrected for Actin expression. Values are means ± SEM (n = 4). *Significantly different from the control group by Student's t-test at P < 0.05.

• 

  Fig. 3 Expression levels of STAT3 and pSTAT3 in splenocytes from animals in the control and HFD groups stimulated with LPS (10 µg/mL). (A) Representative immunoblots of STAT3. (B) Densitometric analyses of STAT3 protein expression corrected for actin expression. (C) Representative immunoblots of pSTAT3. (D) Densitometric analyses of pSTAT3 protein expression corrected for actin expression. Values are means ± SEM (n = 4).

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