Muscle atrophy is characterized by a decrease in the mass of the muscle. With an increase in life expectancy and chronic illnesses, the incidence of muscle atrophy is increasing and the quality of life of patients is decreasing. Thus, reducing muscle atrophy is of high clinical and socio-economic importance. Mistletoe is a semi-parasitic plant that has been used as a traditional medicine in many countries to treat various human illnesses. It has been reported that Korean mistletoe extract (KME) has diverse biological functions including anti-tumor, anti-oxidant, anti-diabetic, anti-obesity properties, and extension of lifespan. Especially, we have recently reported that KME improves exercise endurance in mice, indicating its beneficial roles in enhancing the capacity of skeletal muscle. In this study, we investigated whether KME could activate the signaling pathway related to protein synthesis in a mouse model of muscle atrophy. Interestingly, KME efficiently activated the Akt/mTOR pathway, and Akt and mTOR are important signaling hub molecules for the acceleration of protein synthesis in muscle cells. In addition, KME also increased the activity of S6 kinase which is involved in the regulation of muscle cell size. Moreover, the ERK activity, required for transcription of ribosomal RNA for protein synthesis, was also enhanced in KME-treated mouse muscle. These data support the idea that KME increases muscle mass via increased protein synthesis. Our findings also suggest that Korean mistletoe might be a promising candidate for the development of functional foods that are beneficial for preventing muscle atrophy.

Bitter melon (Momordica charantia) is used in traditional herbal medicine in many Asian countries for the treatment of several diseases such as diabetes, eczema, night blindness, psoriasis, and rheumatism. Especially, most reports concerning the biological activities of bitter melon have focused on its effects on diabetes and hyperglycemia. Also, bitter melon is regarded as a longevity food, suggesting that it has several beneficial effects on anti-aging and the maintenance of a healthy state. Thus, we investigated whether bitter melon could increase the capacity of exercise in this study. Interestingly, bitter melon fruit extract activated AMP-activated protein kinase (AMPK), which is important for regulating glucose homeostasis, mitochondrial content and exercise capacity. In addition, bitter melon extract increased the expression of enzymes involved in fatty acid oxidation such as mitochondrial uncoupling protein 3 (UCP3), carnitine palmitoyl transferase 1b (CPT1b), and pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4). Moreover, exercise tolerance was much more enhanced in bitter melon treated animals compared to the non-treated control group. These results suggest that bitter melon is a promising candidate for the development of functional foods beneficial for physical strength and the enhancement of exercise capacity.

Traditionally, mistletoe is known as an effective anti-cancer medicinal plant, and lectin is recognized as a major component with cytotoxic and immuno-stimulant activity in mistletoe. A Korean mistletoe lectin (KML) has specificity to galactose and galactosamine and is distinguish from European mistletoe lectin (EML). When we examined the concentration of lectin in mistletoe originated from five different types of host trees, the result indicate that the lectin concentration is variable depending on the host tree. Noticeably, mistletoe from chestnut tree contains ten folds higher lectins than that of an oak tree. We also tested the concentration of KML and crude extract (KM-110) of Korean mistletoe that shows 90% cytotoxicity in L5178Y-ML25 lymphoma cell. In addition, the cells show 90% and 70% viability by the treatment of two neutralizing antibodies of KML, 9H7-D10 and 8B11-2C5 neutralization effect with two monoclonal antibodies of KML, 9H7-D10 and 8B11-2C5. Therefore, the result expected that the mistletoe contain some other cytotoxic components except lectin. Finally, the production of TNF-α and IL-6 by RAW 264.7 cells stimulated with lectin free-crude extract (LFKM-110) following neutralization by 9H7-D10 monoclonal antibody shows higher than that of lectin containing-crude extract (KM-110). These results suggest that the Korean mistletoe lectin ha a great potential to be developed as therapeutic agent of cancer.

본 연구에서는 겨우살이 열수 추출물인 미슬로 C의 안전성을 검토하고자 유전 독성 및 실험동물을 이용한 안전성 검사를 실시하였다. 미슬로 C의 미생물 돌연변이 실험을 S. typhimurium의 히스티딘 요구성 균주와 E. coli의 트립토판 요구성 균주를 이용하여 대사 활성계 적용 및 비적용 하에서 복귀돌연변이 시험을 실시한 바, 5,000 ㎍/plate의 처리 농도까지 복귀돌연변이 집락은 나타나지 않았다. ICR 마우스에게 500, 1,000 및 2,000 ㎎/㎏를 경구 투여하고, 골수세포를 수집하여 소핵을 측정한 결과, 정상마우스의 경우와 비교하여 유의한 소핵은 관찰되지 않았기에 미슬로 C는 유전독성을 유발하지 않는 것으로 판단되었다. 식품의약안전청의 의약품 등의 독성시험기준에 따라 암․수 SD 계열의 랫드에 시험물질을 0, 500, 1,000 및 2,000 ㎎/㎏/day의 용량으로 1회 경구 투여한 후, 14일간의 체중 변화 및 사망률을 조사한 결과, 대조군과 비교하여 유의한 체중 변화는 없었으며, LD50은 2,000 ㎎/㎏ 이상인 것으로 사료된다. 또한 0, 250, 500 및 1,000 ㎎/㎏/day의 용량으로 13주간 반복 투여하면서 실험동물의 일반증상, 체중변화, 혈액 및 혈액생화학적 변화, 부검소견, 조직학적인 변화를 관찰하였다. 시험기간 중 암․수 모든 군에서 시험물질 투여에 기인한 일반적인 증상 변화는 관찰되지 않았고, 시험물질의 반복 투여로 인한 사망 마우스 역시 관찰되지 않았다. 따라서 미슬로 C를 13주간의 랫드에 대한 13주 반복 경구투여 결과, 무독성량은 최소한 1,000 ㎎/㎏ 이하인 결과를 나타냈으며, 이 농도에서 독성을 유발하는 표적장기는 관찰되지 않았다.