Journal of Nutrition and Health

The Korean Nutrition Society (한국영양학회)
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Effect of Different Amount of Dietary n-3 PUFA on Colon Carcinogenesis in DMH-treated Rats

쥐에서 식이에 첨가한 n-3 PUFA함량에 따라 대장 암화과정에 미치는 영향

  • Park, Hyun-Suh (Department of Food & Nutrition, Kyung Hee University) ;
  • Kwak, Hye-Kyoung (Department of Food & Nutrition, Kyung Hee University) ;
  • Kim, Min-Seok (Department of Food & Nutrition, Kyung Hee University)
  • 박현서 (경희대학교 생활과학대학 식품영양학과) ;
  • 곽혜경 (경희대학교 생활과학대학 식품영양학과) ;
  • 김민석 (경희대학교 생활과학대학 식품영양학과)
  • Published : 2005.12.01
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Abstract

The objective of the study was to observe the effect of n-3 PUFA on cell proliferation and apoptosis by determining mRNA and protein of COX-2 and eicosanoid product and the mRNA and protein of Bu and Bcl-2 related to apoptosis in colon carcinogenesis of 1,2- dimethylhydrazine (DMH)-treated rats. Ninety male Sprague Dawley rats weighing about 170g were divided into 3 groups, control and n-3 PUFA supplemented groups (FO group: 6.2 mmoles n-3 PUFA; 2FO group: 12.4 mmoles n-3 PUFA) and fed experimental diet for 14 weeks. All rats were intramuscularly injected with DMH 15 mg/kg twice a week for 6 weeks to deliver total dose of 180 mg/kg body weight. Compared with the control group, 6.2 mmoles n-3 PUFA significantly reduced the levels of mRNA and protein expression of COX-2 and 2-series eicosanoids ($TXB_{2}$ and $PGE_{2}$) and decreased cell proliferation in colonic mucosa. However, high levels of n-3 PUFA supplementation significantly increased the levels of mRNA and protein expression of COX-2, TXB2 and PGE2. and increased cell proliferation which was similar level to that of control group. Compared with the control group, n-3 PUFA, regardless of the amount, significantly increased apoptotic index in colonic mucosa. Western blot and RT-PCR analyses showed that the levels of mRNA and protein expression of Bax were significantly increased by 6.2 mmoles n-3 PUFA, but decreased by 12.4 mmoles n-3 PUFA. The analyses also showed the levels of mRNA and protein expression of Bcl-2 were significantly reduced by 6.2 mmoles n-3 PUFA, but increased by 12.4 mmoles n-3 PUFA. The ratio of Bcl-2/Bax in mRNA and protein was significantly reduced by 6.2 mmoles n-3 PUFA but increased by 12.4 mmoles n-3 PUFA. Overall, these results indicate that n-3 PUFA could be effective in preventing colon carcinogenesis by reducing cell proliferation with lower level of COX-2 and 2-series eicosanoid, and increasing apoptosis by inducing pro-apoptotic gene, Bax and inhibiting anti-apoptotic gene, Bcl-2 in the colonic mucosa of DMH-treated rats. However, high level of n-3 PUFA supplementation could stimulate colon carcinogenesis by increasing cell proliferation and inhibiting apoptosis. (Korean J Nutrition 38(10): 807$\sim$816,2005)

본 연구에서는 Sprague Dawley종 수컷 쥐에서 DHM로 대장암을 유발시킨 후 식이에 첨가한 n-3 RUFA 함량에 따라 대장의 암화과정에 어떤영향을 미치는지 생화학적인 기전을 검토하여 다음과 같은 결과를 얻었다. 1) 식이에 n-3 RUFA를 6.2 mmole 첨가하여 먹인 경우에는 COX-2의 mRNA와 단백질의 발현 및 TBX2와 PGE2 합성이 유의하게 감소 되었으며, 이에 따라 세포증식도 억제되었다. 그러나 n-3 RUFA를 12.4 mmole 첨가한 식이로 사육한 경우에는 오히려 COX-2의 mRNA와 단백질의 발현 및 $TXB_2$ 와 $PGE_2$ 합성이 대조군 보다도 더 많이 증가되었고 세포증식도 대조군과 같은 수준으로 증가하여 암화과정을 촉진하였다. 2) 식이에 n-3 PUFA를 6.2 mmole 첨가한 경우 대장 점막의 인지질의 지방산조성중 arachidonic 함량은 유의하게 낮았고, EPA와 DHA 함량은 유의하게 높았으며 n-3 PUFA를 12.4 mmole 첨가한 경우에는 EPA와 DHA 함량은 2배 이상 유의하게 더 높았다. 3) 대장 상피세포의 apoptosis는 식이에 n-3 PUFA를 첨가한 함량과는 관계없이 대조군에 비해 유의하게 약 34$\sim$$42\%$ 증가하였다. 4) 식이에 n-3 PUFA를 6.2 mmole 첨가하였을 때 Bax의 mRNA와 단백질 발현은 각각 유의하게 증가되었으나 n-3 PUFA를 12.4mmole 첨가한 경우에는 유의하게 감소되었다. 반면에Bcl-2의 mRNA와 단백질 발현은 n-3 PUFA 6.2 mmole 첨가한 경우에는 오히려 증가하였다. 총괄해서 본 연구결과에 의하면 항암효과가 있가도 알려진 n-3 PUFA는 식이에 첨가한 함량에 따라 암화과정에 미치는 효과가 다르게 나타났다, 그러므로 앞으로 대장의 암화과정을 억제시키는 n-3 PUFA의 적절량 또는 섭취의 한계치를 정하는 연구가 필요하다고 본다.

Keywords

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