고 콜레스테롤혈증을 유발한 마우스에서 수수 추출물의 투여가 콜레스테롤 대사 조절기전에 미치는 효과

Abstract

Sorghum has many phytochemical such as tannins, phenolic acids, anthocyanins, phytosterol and polycosanol. Sorghum has been suggested to have hypocholesterolemic effect, but the mechanism is unknown. Thus, we investigated the effects of oral administration of sorghum extract (SE) on hepatic cholesterol metabolism related protein expression and blood lipid profiles in high cholesterol diet fed mice for eight weeks. Male C57BL/6 mice were fed either a modified AIN-93G diet (normal control group, NC) or a modified AIN-93G diet with 2% cholesterol (high cholesterol group, HC) for 8 weeks. During the last 4 weeks of diets, NC group was orally administered saline, and 2% cholesterol diet groups were received either saline (HC) or 600 mg sorghum extract per kg body weight (HC-SE). There were no significant differences in dietary intake, body weight, and weights of organ except for liver. Liver weight was significantly higher in mice fed HC than in NC and HC-SE groups. Levels of serum total- and LDL-cholesterol were significantly lower in NC and HC-SE groups than in HC group, while HDL-cholesterol was significantly higher in NC group than in HC and HC-SE groups. Serum level of triglyceride was not significantly different, but hepatic triglyceride and total-cholesterol levels were significantly lower in HC-SE and NC groups than in HC group. The expression of 3-hydroxy methyl glutaryl-coenzyme A reductase, sterol regulatory elementary binding protein2 and fatty acid synthase were significantly lower in HC-SE group than in HC group, while phosphorylated AMP-activated protein kinase/ AMP-activated protein kinase ratio and cholesterol 7-α hydroxylasewere significantly higher in HC-SE group than in HC group. However, there were no significant differences in the expression of 12-α hydroxylase between HC and HC-SE groups. In conclusion, our results suggested that sorghum extract significantly reduced blood levels of cholesterol by down-regulation of the hepatic cholesterol biosynthesis and degradation.|수수는 전 세계적으로 많이 생산되는 주요 5대 주요 곡물의 하나이며 다른 잡곡류에 비해 tannin, phenolic acid, anthocyanin, phytosterol과 polycosanol 등의 생리활성 물질을 다량 함유하고 있다. 현재까지 수수의 이러한 생리활성 물질들이 체내 콜레스테롤 농도에 영향을 미친다는 다양한 연구결과들이 보고되고 있지만 이런 현상들이 어떠한 기전으로 이뤄지는지는 아직 명확하지 않다. 따라서 본 연구는 고 콜레스테롤혈증을 유도한 쥐에서 수수추출물의 투여가 나타내는 효과 및 작용 기전을 규명하기 위하여 수행하였다. C57BL/6 마우스 21마리를 7마리씩 3군으로 나누어 한 군은 AIN-93G 식이(NC 군)를, 다른 두 군은 AIN-93G식이에 2% 콜레스테롤이 함유된 식이(HC 군)를 총 8주간 공급하였다. 식이 공급 개시 후 5주차에 NC 군과 HC 군 중 한 군은 생리 식염수를, 다른 HC 군은 생리식염수에 수수추출물을 체중 kg당 600 mg의 농도로 용해하여 4주간 경구 투여하였다(HC-SE 군). 8주 후 실험동물을 희생시켜 혈액 및 간의 지질 농도와 콜레스테롤 대사 관련 단백질의 발현을 측정하여 군간의 차이를 비교한 결과 HC-SE 군에서 혈중 총 콜레스테롤과 LDL 콜레스테롤이 HC 군에 비하여 유의하게 감소하는 반면에 HDL 콜레스테롤은 NC 군에 비하여 HC 군과 HC-SE 군이 유의적으로 낮았고 HC 군과 HC-SE 군은 유의적인 차이가 없었다. 혈중 중성지방 농도는 군간에 유의적인 차이가 없었지만 간의 중성지방과 총 콜레스테롤 수치는 HC-SE 군이 HC 군에 비하여 유의적으로 감소하였다. 콜레스테롤 합성의 속도조절 효소인 3-hydroxy methyl glutaryl-coenzyme A reductase(HMGCR)와 HMGCR의 유전자 합성을 조절하는 sterol regulatory elementary binding protein2(SREBP2)는 HC-SE 군이 HC 군에 비하여 유의적으로 감소하였다. HMGCR의 활성은 AMP-activated protein kinase(AMPK) 인산화가 많이 될수록 감소하는데 이 인산화 정도를 나타내는 phosphorylated AMP-activated protein kinase(phospho-AMPK)/ AMPK ratio가 HC-SE 군이 HC 군에 비하여 유의적으로 증가하여 수수추출물의 투여가 콜레스테롤 생합성 기전에 영향을 주어 총 콜레스테롤 및 LDL 콜레스테롤을 유의적으로 낮추는 것으로 나타났다. 또한 지방산 사슬을 연장해 주는 fatty acid synthase(FAS)의 발현은 HC-SE 군이 HC 군보다 유의적으로 낮아져 간의 중성지방을 낮춘 것으로 사료되었다. 콜레스테롤 항상성 조절에서 필수인 담즙산 염 생성의 속도조절 효소인 cholesterol 7-α hydroxylase(CYP7A1)은 HC-SE 군이 HC 군에 비하여 유의적으로 증가하였으나 12-α hydroxylase(CYP8B1)의 단백질 발현은 HC-SE와 HC 군간에 유의적인 차이가 없었다. 따라서 본 연구 결과 수수추출물이 고 콜레스테롤 혈증 마우스에서 혈중 콜레스테롤과 LDL 콜레스테롤의 농도를 감소시키며 이 효과는 콜레스테롤의 생합성과 분해 기전 대한 수수추출물의 영향에 의한 것으로 사료되었다.; Sorghum has many phytochemical such as tannins, phenolic acids, anthocyanins, phytosterol and polycosanol. Sorghum has been suggested to have hypocholesterolemic effect, but the mechanism is unknown. Thus, we investigated the effects of oral administration of sorghum extract (SE) on hepatic cholesterol metabolism related protein expression and blood lipid profiles in high cholesterol diet fed mice for eight weeks. Male C57BL/6 mice were fed either a modified AIN-93G diet (normal control group, NC) or a modified AIN-93G diet with 2% cholesterol (high cholesterol group, HC) for 8 weeks. During the last 4 weeks of diets, NC group was orally administered saline, and 2% cholesterol diet groups were received either saline (HC) or 600 mg sorghum extract per kg body weight (HC-SE). There were no significant differences in dietary intake, body weight, and weights of organ except for liver. Liver weight was significantly higher in mice fed HC than in NC and HC-SE groups. Levels of serum total- and LDL-cholesterol were significantly lower in NC and HC-SE groups than in HC group, while HDL-cholesterol was significantly higher in NC group than in HC and HC-SE groups. Serum level of triglyceride was not significantly different, but hepatic triglyceride and total-cholesterol levels were significantly lower in HC-SE and NC groups than in HC group. The expression of 3-hydroxy methyl glutaryl-coenzyme A reductase, sterol regulatory elementary binding protein2 and fatty acid synthase were significantly lower in HC-SE group than in HC group, while phosphorylated AMP-activated protein kinase/ AMP-activated protein kinase ratio and cholesterol 7-α hydroxylasewere significantly higher in HC-SE group than in HC group. However, there were no significant differences in the expression of 12-α hydroxylase between HC and HC-SE groups. In conclusion, our results suggested that sorghum extract significantly reduced blood levels of cholesterol by down-regulation of the hepatic cholesterol biosynthesis and degradation.