Yonsei Med J.  2011 May;52(3):495-501. 10.3349/ymj.2011.52.3.495.

Peroxisome Proliferator-Activated Receptor-Gamma Expression in the Lung Tissue of Obese Rats

• Hwang SJ
• Kim JH
• Shim JW
• Kim DS
• Jung HL
• Park MS
• Lee WY
• Kim SY
• Shim JY

• KMID: 1777023
• DOI: http://doi.org/10.3349/ymj.2011.52.3.495

Abstract

PURPOSE
Obesity is a risk factor for asthma and type II diabetes. Peroxisome proliferator-activated receptor (PPAR)-gamma has been suggested to regulate inflammatory responses in diabetes and asthma. We investigated whether PPAR-alpha, PPAR-gamma, adiponectin receptors (AdipoR1, AdipoR2), leptin, and tumor necrosis factor (TNF)-alpha are expressed in rat lung tissues and whether the expression differs between obese Otsuka Long-Evans Tokushima Fatty (OLETF) and lean Long Evans Tokushima Otsuka (LETO) rats.
MATERIALS AND METHODS
Obese and lean rats were given with a high fat diet or a 30% restricted diet for 32 weeks, and their blood glucose levels and weights were monitored. After 32 weeks, mRNA levels of PPAR-alpha, PPAR-gamma, AdipoR1, AdipoR2, leptin, and TNF-alpha in lung tissues were measured using real time PCR.
RESULTS
PPAR-alpha, PPAR-gamma, AdipoR1, AdipoR2, leptin, and TNF-alpha were expressed in both obese and lean rat lung tissues. Increased serum glucose levels on intraperitoneal glucose tolerance testing and a higher weight gain at 32 weeks were observed in OLETF control rats compared to OLETF diet restricted rats. PPAR-gamma expression was markedly elevated in obese control and diet restricted rats compared to lean rats, although PPAR-gamma expression in obese rats was not affected by diet restriction. Leptin was highly expressed in OLETF rats compared to LETO rats. TNF-alpha expression was enhanced in OLETF control rats compared LETO diet restricted rats, and decreased by diet restriction. PPAR-alpha, AdipoR1, and AdipoR2 expression were not significantly different between obese and lean rats.
CONCLUSION
PPAR-gamma was highly expressed in the lung tissues of obese rats and may be a novel treatment target for regulating lung inflammation associated with obesity.

Keyword

Obesity; peroxisome proliferator activated receptor; adiponectin receptor; lung; leptin; TNF-alpha

MeSH Terms

Animals
Body Weight
Glucose Tolerance Test
Leptin/genetics/metabolism
Lung/*metabolism
Male
Obesity/genetics/*metabolism
PPAR gamma/genetics/*metabolism
RNA, Messenger/metabolism
Rats
Rats, Long-Evans
Receptors, Adiponectin/genetics/metabolism
Tumor Necrosis Factor-alpha/genetics/metabolism

Figure

• 

  Fig. 1 Body weight changes between control rats and rats with 30% diet restriction. The weight gain of the OLETF control group was significantly higher than the other groups (p<0.05). The LETO control group showed a higher weight gain than the LETO diet restricted group. The OLETF diet restricted group had a greater weight gain than the LETO diet restricted group. *p<0.01 compared to the other groups. †p<0.05 compared to LETO (30% diet-restriction). OLETF, Otsuka Long-Evans Tokushima Fatty; LETO, Long-Evans Tokushima Otsuka; C, control.

• 

  Fig. 2 Intraperitoneal glucose tolerance testing in obese and lean rats at 32 weeks of treatment. The OLETF control rats showed higher serum glucose levels than the other groups at 30, 60, 90 and 120 minutes after an intraperitoneal glucose challenge. *p<0.05 compared to the other groups. OLETF, Otsuka Long-Evans Tokushima Fatty; LETO, Long-Evans Tokushima Otsuka; C, control.

• 

  Fig. 3 Adiponectin receptor 1, adiponectin receptor 2, PPAR-α, and PPAR-γ mRNA expressions in lung tissue of OLETF rats and LETO rats: each mRNA expression was measured by real time PCR. (A) AdipoR1 mRNA levels did not show significant differences among all groups. (B) AdipoR2 mRNA levels were not different in the four groups. (C) PPAR-α mRNA levels in the four groups showed no significant differences. (D) PPAR-γ mRNA levels showed marked increases in the OLETF control rats compared to the LETO control and diet restricted rats. However, PPAR-γ was not affected by diet restriction. *p<0.05. OLETF, Otsuka Long-Evans Tokushima Fatty; LETO, Long-Evans Tokushima Otsuka.

• 

  Fig. 4 Leptin and TNF-α mRNA expressions in lung tissue of OLETF rats and LETO rats: each mRNA expression was measured by real time PCR. (A) Leptin mRNA levels showed marked increase in the OLETF control rats compared to the LETO control and diet restricted rats. However, leptin was not affected by diet restriction. (B) TNF-α mRNA levels increased significantly in the OLETF control rats compared to the OLETF and LETO diet restricted rats. *p<0.05. OLETF, Otsuka Long-Evans Tokushima Fatty; LETO, Long-Evans Tokushima Otsuka.

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