The Effect of PR and Exercise on Fatty Acid Transporters Expression in OVX Rats Skeletal Muscles

Abstract

Most of postmenopausal women are suffering from the various symptoms, which are caused by estrogen deficiency. Especially, due to impaired lipid metabolism, the level of LDL cholesterol and triacylglycerol (TG) are increased that are major reasons of diverse diseases such as metabolic syndrome, cardiovascular diseases and myocardial infarction. In recently, PR (PR) and exercise have been receiving the great deal of attention as an alternative of estrogen replacement therapy (ERT), which is reported that has side effects, for reducing the symptoms of postmenopausal women. From previous studies, PR and exercise were identified that have effects on reducing fat mass in postmenopausal women. However, the effects of PR and exercise on fatty acid transporters, which play essential roles in fatty acid transports, have not been studied well. Accordingly, the purpose of this study was to examine the effects of PR and exercise on fatty acid transporters expression, which affect fatty acid transports on OVX (OVX) rats skeletal muscles. Ovary removed sixty female SD rats, 8 weeks old, were given a high fat diet. After 1 week of recovery period, rats were randomly divided into 6 groups: (1) high fat diet + sedentary + vehicle (HSV), (2) high fat diet + sedentary + PR (complex of PR by 3 to 1) (HSP), (3) high fat diet + sedentary + hormone (17β-extradiol treat) (HSH), (4) high fat diet + exercise + vehicle (HEV), (5) high fat diet + exercise + PR (HEP), (6) high fat diet + exercise + hormone (HEH). Exercise was consisted of low intensity treadmill exercise for 8 weeks (1-4th week: 15m/min for 30min, 5-8th week: 18m/min for 40min, 5times/week). Real-Time qPCR Analysis and immunohistochemistry were used to determine the effects of PR and exercise on fatty acid transporters expression in OVX rats soleus and plantaris muscles. As a result, there were no significant differences on FATP1 and FAT/CD36 mRNA expression between exercise groups and sedentary groups in OVX rats soleus and plantaris muscles. However in both muscles, FABPpm mRNA expression was significantly up-regulated by exercise. However, there were no synergic effects of exercise combined with PR on FABPpm mRNA expression. Immuno-staining results showed that, in all exercise groups except estradiol intake groups, FATP1 proteins expressed higher and translocated from intracellular depot to the plasma membrane in OVX rats soleus muscles. FABPpm and FAT/CD36 proteins expression were also increased and localized at plasma membrane in all exercise groups compared with sedentary groups in OVX rats soleus muscles. In addition, in OVX rats plantaris muscles, all three fatty acid transporters proteins were expressed higher and translocated to plasma membrane in exercise groups in comparison with sedentary groups. In this study, though there were no effects on FATP1 and FAT/CD36 mRNA expression, exercise induce to up-regulate FABPpm mRNA expression rather than exercise combined with PR. This implies that exercise might be the greatest stimulator of up-regulation of FABPpm mRNA expression. Aerobic exercise may induce to increase fatty acid uptake in OVX rats skeletal muscles through up-regulation of FABPpm mRNA expression, which are known as muscle specific and play important roles in fatty acid uptake into skeletal muscles. In addition, the results of this study showed that PR and exercise induce fatty acid transporters proteins to express higher and to translocate from cytosol to plasma membrane. Accordingly, the results of this study suggest that PR and exercise have effects on decreasing fat mass by up-regulation of fatty acid transporters expression in OVX rats skeletal muscles.;대다수의 폐경기 여성들은 에스트로겐 감소로 인한 지질대사의 불균형에 의해 대사증후군, 심혈관계 질환 등 여러 합병증의 위험에 노출되어있다. 갈근/지황과 운동은 부작용이 나타나는 에스트로겐 보충 요법(ERT)의 대안으로써, 폐경기 여성들의 지방 감소에 효과가 있는 것으로 알려져 있다. 그러나 갈근/지황과 운동이 지방산 수송에 있어 중요한 역할을 하는 지방산 수송체에 미치는 영향에 관한 연구는 많이 진행되지 않았다. 따라서 본 연구에서는 갈근/지황과 운동이 난소절제 쥐의 골격근에서 대표적인 지방산 수송체인FATP1, FABPpm, FAT/CD36 발현에 미치는 영향을 알아보았다. 고지방 식이를 유도한 총 60 마리의 쥐를 6 집단으로 무선 배정하였다: (1)HSV; 고지방식이+비운동+물, (2)HSP; 고지방식이+비운동+갈근/지황, (3)HSH; 고지방식이+비운동+에스트로겐 호르몬, (4)HEV; 고지방식이+운동+물, (5)HEP; 고지방식이+운동+갈근/지황, (6)HEH; 고지방식이+운동+에스트로겐 호르몬. 운동은 저강도의트레드밀 운동으로 진행되었으며, 1-4주차는 15m/min의 속도로 30분간, 5-8주차는 18m/min의 속도로 40분간 일주일에 5번씩 총 8주간 진행하였다. 실험 결과, FATP1 와 FAT/CD36 mRNA 발현은 변화가 없었지만, FABPpm mRNA 발현은 운동그룹의 가자미근과 족저근에서 모두 유효하게 증가하였다. 이는 운동이 근육 특이적 유전자이며 지방산 수송에 중요한 역할을 하는 FABPpm의 발현을 상향 조절함으로써 난소절제 쥐의 골격근 내의 지방산 흡수를 증가시킨다고 볼 수 있다. 그러나 지방산 수송체의 mRNA발현에 있어 갈근/지황과 운동의 복합 상승효과는 나타나지 않았다. 면역화학염색 결과, 갈근/지황과 운동은 세 지방산 수송체 단백질 발현의 증가와 세포막으로 이동을 유도하였음을 알 수 있었다. 이러한 결과를 바탕으로, 본 연구의 결과는 갈근/지황과 운동이 난소절제 쥐의 골격근에서 지방산 수송체의 발현의 상향조절을 유도함으로써 지방산 산화를 증가시키고, 지방을 감소시키는 효과를 가진다고 제안할 수 있다.