쿠싱증후군 환자에서 당 대사 이상 정도에 따른 인슐린 감수성과 인슐린 저항성의 변화

정인경,김성훈,정재훈,민용기,이명식,이문규,유형준,안규정,노정현,김동준,김광원 대한내분비학회 2003 Endocrinology and metabolism Vol.18 No.4

연구배경 당질 코르티코이드는 당 대사에 매우 중요한 호르몬으로 내인성 당질 코르티코이드 과다상태인 쿠싱증후군에서는 말초조직에서 인슐린 저항이 증가하고 이를 보상하고자 인슐린 분비의 증가로 고인슐린혈증이 동반된다고 보고되고 있다. 하지만 생체 내에서와 달리 시험관내에서는 췌도세포에 당질 코르티코이드를 장시간 처리하면, 인슐린 분비 및 생합성이직접적으로 억제됨이 확인된 바 있어 쿠싱증후군 환자에서 당뇨병의 원인으로는 아마도 말초조직에서 증가된 인슐린 저항성 뿐 아니라 이를 충분히 보상하지 못하는 췌장에서의 인슐린 분비 저하가 같이 동반되어있지 않을까 하는 가설을 세우게 되었고, 아직까지 당질코르티코이드가 당대사 이상을 일으키는 기전에 대해 쿠싱증후군을 당대사 정도에 따라 인슐린 감수성과 분비능을 분석한 연구는 없었기에 이를 알아보고자 하였다. 방법: 삼성서울병원에서 쿠싱증후군으로 진단 받은 환자 15명을 대상으로 하였다. 이에 대한 대조군으로는 쿠싱증후군 환자와 같은 성별 그리고 체질량지수를 갖은 15명의 건강한 성인을 대상으로 비교 하였다 쿠싱증후군 환자를 대상으로 경구당부하 검사를 통해 당대사 정도를 정상군, 내당능장애군, 그리고 당뇨병군으로 나눈 후 정맥 당부하 검사를 시행하여 각군의 인슐린 저항성과 인슐린 분비능의 지표를 비교하고, 수술 후 쿠싱증후군이 완치된 상태에서 수술 전후의 당대사 지표의 변화를 조사하였다. 결과: 1) 쿠싱증후군 환자 중 정상인은 20%, 내당능 장애는 27%, 그리고 당뇨병은 53%였다. 체질량지수, 나이, 그리고 발병 기간은 세 군간에 의미 있는 차이가 없었으나, 24시간 소변검사의 코르티솔 농도는 당뇨병군에서 의미있게 높았다. 2) 정맥당부하 검사 결과, 인슐린 감수성 지표인 Sl는쿠싱증추린」서 1.58±0.10[×10^(-4)(min^(-1)(μU/mL)^(-1)]로 정상 대조군의 3.37±0.49[×10^(-4)(min^(-1)(μU/mL)^(-1)]에 비해 의미있게 낮았으나(P=0.024), 쿠싱증후군 환자 중 NGT, IGT, DM 군간에 서로 통계적인 차이는 없었다. 3) SG는 정상 대조군과 쿠싱증후군 환자간에는 의미있는 차이가 없었고, 쿠싱 증후군에 있어서 당대사가 악화될수록 감소하는 경향을 보였으나 의미있는 차이는 없었다. 4) 인슐린 분비능의 지표인 AIRg는 정상인에 비해 전체 쿠싱증후군 환자의 경우 증가하는 경향을 보였으나 의미있는 차이는 없었다. 하지만 쿠싱증후군 환자중에서 당대사 상태에 따라 NGT군은 1299 (1297∼1310)(mu/g/min ×10^(-2))로 정상 대조군(368.9±98.6[mu/g/min ×10^(-2)]) 보다도 의미있게 높았고, DM군{202.2 (91.1~371.4) [mu/g/min ×10^(-2)}은 NGT군에 비해 의미있게 낮았다(P=0.0031). 5) 15명중 현재 완치 상태에 있는 6명에 대해 수술전과 후로 비교하였다. 수술 전 당대사 상태가 1명은정상, 1명은 내당능 장애, 그리고 4명은 당뇨병이었으나 수술 후 시행한 경구 당부하 검사상 모두 정상 당대사 상태를 보였다. 6) 수술 후 완치된 환자 6명에 있어 인슐린 감수성지표인 Sl는 수술전에 중앙값이 1.22[×10^(-4)(min^(-1)(μU/mL)^(-1)]로 대조군에 비해 의미있게 감고』어 있었으나(p.0.05), 수술후 10.95 [×10^(-4)(min^(-1)(μU/mL)^(-1)]로 정상 수준으로 회복되었고(P=0.0022), 인슐린 분비능을 나타내는 AIRg [mu/g/min ×10^(-2)] 값도 정상수준으로 회복되었다. 특히 인슐린 분비능의 회복양상은 혈당농도에 따라 판이하게 나타나서, 정상과 내당능장애 상태에 있던 2명은 수술전에 1201 [mu/g/min ×10^(-2)]로 증가되어 있던 AIRg 값이 수술 후 정상 수준으로 감소하였고, 수술 전에 당뇨병 상태에 있던 4명의 경우 245.9 [mu/g/min ×10^(-2)]로 인슐린 분비능이 감고il어 있었는데 이들은 수술 후 모두 정상 수준으로 증가되었다 (P=0.0286). 결론: 쿠싱증후군 환자에서 당대사 이상은 80%로 높은 유병률을 보였다. 모든 쿠싱증후군환자에서 인슐린 감수성은 정상인에 비해 저하되어 있어 말초조직의 인슐린 저항이 선행됨을 시사하며, 인슐린 분비능은 당대사의 정도에 따라 다르게 나타났는데, 정상 당대사군에서는 인슐린의 저항성을 극복할 만큼 정상 대조군보다 더 많은 양의 인슐린 분비를 하다가 고코르티솔혈증이 심할수록 인슐린 분비능의 감소로 당뇨병으로 진행됨을 확인할 수 있었고, 이런 인슐린 저항성과 인슐린 분비장애는 수술 후 다시 회복되는 가역적인변화를 보였다. Background: Glucocorticoid plays an important role in the control of carbohydrate metabolism. Patients with Cushing's syndrome have been reported to have an increased incidence of carbohydrate intolerance due to peripheral insulin resistance and hyperinsulinemia, although the exact incidence and nature of this disorder have remained unclear. Few results have been published about insulin resistance and insulin secretion according to the level of glucose concentration, or about the reversibility of such defects in patients with Cushing's syndrome. Methods: To assess the effect of glucocorticoid on the insulin sensitivity and insulin secretion in Cushing's syndrome, 15 patients with Cushing's syndrome were classified into 3 groups (normal glucose tolerance: NGT, impaired glucose tolerance: IGT, diabetes: DM) according to the degree of glucose tolerance based on the oral glucose tolerance test (OGTT). Insulin modified, frequently sampled, intravenous glucose tolerance test (FSIGT) was performed before and after curative surgery on these patients and on 15 healthy control subjects. Data were evaluated by non-parametric statistical analysis. Results: 1) Among the 15 patients with Cushing's syndrome, 3 (20%) were NGT, 4 (27%) IGT, and 8 (53%) DM, based on OGTT. Twenty-four hour urinary free cortisol (UFC) was significantly higher in the DM group. 2) Insulin sensitivity index (SI) of Cushing's syndrome was significantly lower than that of the control group p=0.0024), but was not significantly different among the three Cushing's syndrome groups of NGT, IGT and DM. 3) Glucose mediated glucose disposal (SG) (Ed- confirm this abbreviation; it does not seem to match the definition) of Cushing's syndrome was not significantly different from that of the control group. 4) Insulin secretion (AIRg) of Cushing's syndrome tended to be high, but it was not significantly different from that of control. However, according to the level of glucose concentration there was significant difference in AlRg among the three Cushing's syndrome groups p=0.0031); AIRg of DM was significantly lower than that of NGT. 5) After surgical treatment, parameters of insulin sensitivity and insulin secretion were normalized in 6 cured patients; 1 with NGT, 1 with IGT, and 4 with DM, preoperatively. Median SI of all 6 patients was significantly improved up to the normal range postoperatively p=0.0022). Median AIRg of these 6 patients was balanced around that of normal control postoperatively p=0.0286). Conclusion: Eighty percent of patients with Cushing's syndrome had abnormality of carbohydrate metabolism. Insulin sensitivity was significantly decreased in Cushing's syndrome. Insulin secretion was significantly higher only in the NGT and IGT groups of Cushing's syndrome. As the hypercortisolemia is exacerbated, insulin secretion is significantly decreased and causes DM, suggesting that glucocorticoid has a direct or indirect toxic effect on the pancreatic beta cell (J Kor SOC Endocrinol 18:392-403, 2003).

Ultrasonic Degradation of Endocrine Disrupting Compounds in Seawater and Brackish Water

So Young Park,Jong Sung Park,Ha Yoon Lee,Ji Yong Heo,Yeo Min Yoon,Kyung Ho Choi,Nam Guk Her 대한환경공학회 2011 Environmental Engineering Research Vol.16 No.3

In this study, a series of experiments was conducted on the relative degradation of commonly known endocrine-disrupting compounds such as bisphenol A (BPA) and 17α-ethinyl estradiol (Ee₂) in a single-component aqueous solution using 28 and 580 kHz ultrasonic reactors. The experiments were conducted with three different types of model water: deionized water (DI), synthetic brackish water (SBW), and synthetic seawater (SSW) at pH 4, 7.5, and 11 in the presence of inert glass beads and humic acids. Significantly higher sonochemical degradation (93-97% for BPA) occurred at 580 kHz than at 28 kHz (43-61% for BPA), regardless of water type. A slightly higher degradation was observed for Ee₂ compared to that of BPA. The degradation rate of BPA and Ee₂ in DI water, SBW, and SSW after 30 min of ultrasound irradiation at 580 kHz increased slightly with the increase in pH from 4 (0.073-0.091 min-1 for BPA and 0.081-0.094 min-1 for Ee₂) to 7.5 (0.087-0.114 min-1 for BPA and 0.092?0.124 min-1 for Ee₂). In contrast, significant degradation was observed at pH 11 (0.149-0.221 min-1 for BPA and 0.147-0.228 min-1 for Ee₂). For the given frequencies of 28 and 580 kHz, the degradation rate increased in the presence of glass beads (0.1 mm and 25 g) for both BPA and Ee₂: 0.018-0.107 min-1 without beads and 0.052-0.142 min-1 with beads for BPA; 0.021-0.111 min-1 without beads and 0.054-0.136 min-1 with beads for Ee₂. A slight increase in degradation of both BPA and Ee₂ was found as the concentration of dissolved organic carbon (DOC, humic acids) increased in both SBW and SSW: 0.107-0.115 min-1 in SBW and 0.087-0.101 min-1 in SSW for BPA; 0.111-0.111 min-1 in SWB and 0.092-0.105 min-1 in SSW for Ee₂. After 30 min of sonicating the humic acid solution, DOC removal varied depending on the water type: 27% (3 mg L-1) and 7% (10 mg L-1) in SBW and 7% (3 mg L-1) and 4% (10 mg L-1) in SSW.

태연혈(太淵穴)의 유침 시간에 따른 체온 변화 -적외선체열촬영(赤外線體熱撮影)을 중심으로-

이봉효 ( Bong Hyo Lee ),이경민 ( Kyung Min Lee ),박지하 ( Ji Ha Park ),김민서 ( Min Seo Kim ),김산들 ( San Deul Kim ),박병규 ( Byeong Gyu Park ),양현동 ( Hyun Dong Yang ),예성호 ( Sung Ho Yea ),이호정 ( Ho Jung Lee ),최재원 ( Jae 경락경혈학회 2012 Korean Journal of Acupuncture Vol.29 No.2

Objectives: This study was performed to find the desirable remaining time of needle in the acupuncture treatment. Methods: The 21 volunteers were given acupuncture at LU9 vertically and needles were remained for 2 min, 10 min, 15 min, 30 min, respectively. The thermographic change induced by acupuncture was measured with Digital Infrared Thermographic Image at the following acupoints: LU11, LU10, LU9, LU8, LU5, LU1, and PC7. The statistical significance of thermographi change was evaluated using paired t-test and post hoc Wilcoxon test. Results: The most significant changes after acupuncture were produced when needles were remained for 10 min or 15 min. LU11, LU5, LU1, and PC7 were the point at which all of the remaining time produced significant change commonly. At LU11, the biggest change was produced when needle was remained for 15 min, while at LU5, LU1, and PC7, the biggest change was produced when needle was remained for 30 min, and the smallest change was produced when needle was remained for 10 min at all of acupoints of LU11, LU5, LU1, and PC7. The unbalance between left side and right was decreased the most largely in 15 min group. Conclusions: The results of this study suggest that the desirable remaining time of acupuncture needle might be 15 min.

The Effect of Aerobic Exercise Training Versus Resveratrol Supplementation on Mitochondrial Biogenesis in Skeletal Muscle of High-fat Diet-induced Obese Mice

Kyung-Il Kim(김경일),Sang-Min An(안상민),Hee-Geun Park(박희근),Wang-Lok Lee(이왕록) 한국생명과학회 2019 생명과학회지 Vol.29 No.8

본 연구에서는 고지방식이로 유발된 비만 쥐의 골격근에서 유산소 운동과 레스베라트롤 투여가 미토콘드리아 생합성에 미치는 영향을 조사하였다. 4주령 C57BL/6의 수컷 쥐를 이용하여, 일반 식이 그룹(NC, n=10), 고지방식이 그룹(HR, n=10), 레스베라트롤 투여와 고지방식이 그룹(HRe, n=10), 유산소 운동 그룹(HE, n=10)으로 분류하였다. 유산소 운동은 16주 동안 40~60 min/day 동안 10-14m/min, 0% grade의 강도로 주당 4회 트레드밀 운동을 실시하였고, 레스베라트롤은 16주 동안 1일 1회, 주당 4회 체중 당 25 mg/kg을 투여하였다. COX-IV mRNA 발현은 NC와 HC 그룹 간에 유의한 차이가 있었으며(p<0.05), HE 그룹의 SIRT-3, PGC-1α 및 COX-IV mRNA 발현은 HC 및 HRe 그룹에 비해 유의하게 증가하였다(p<0.05). 또한, 오직 HE 그룹의 PGC-1α 및 COX-IV mRNA의 발현만이 HC 그룹에 비해 유의하게 증가하였다(p<0.05). 이상의 결과를 종합해보면, 고지방식이로 유발된 비만 쥐는 골격근에서 미토콘드리아 생합성 유전자 발현에 영향을 나타내지 않는 것으로 보인다. 하지만, 유산소 운동 훈련은 고지방식이로 유발된 비만 쥐의 골격근에서 미토콘드리아 생합성 유전자 발현을 증가시키는 것으로 나타났다. 이러한 연구 결과는 레스베라트롤 투여가 아닌 유산소 운동이 고지방식이로 유도된 쥐의 골격근에서 미토콘드리아 생합성에 긍정적인 영향을 미친다는 것을 시사한다. The purpose of this study was to analyze the effects of aerobic exercise and resveratrol supplementation on mitochondrial biogenesis in skeletal muscle of high-fat diet-induced obese mice. In this study, 4-wk-old C57BL/6 male mice were divided into four groups, with 10 animals in each group: a normal diet group (NC), high-fat diet group (HC), high-fat diet group with resveratrol supplementation (HRe), and high-fat diet GROUP with exercise (HE). Aerobic exercise was performed on a treadmill for 40~60 min/d at 10~14 m/min, 0% grade, 4 d/wk for 16 wk. Resveratrol (25 mg/kg bodyweight) was administrated once a day, 4 d/wk for 16 wk. There was a significance difference in COX-IV mRNA expression in the NC group versus that in the HC group (p<0.05). The expression of the SIRT-3, PGC-1a, and COX-IV mRNA genes in the HE group increased significantly as compared with the expression of these genes in the HC and HRe groups (p<0.05). These results indicated that high- fat diet- induced obesity did not affect mitochondria biogenesis gene expression in skeletal muscle. In contrast, aerobic exercise training increased the expression of mitochondria biogenesis gene expression in skeletal muscle in high-fat diet-induced obese mice. These findings suggested that aerobic exercise but not resveratrol supplementation had a positive effect on mitochondrial biogenesis in skeletal muscle in high-fat diet-induced obese mice.

Pulse Oximetry and Skin Temperature Gradient as Diagnostic Tools of Successful Caudal Block

Duk Kyung Kim,Kyoung Min Lee,Won Kyoung Kwon,Chung Sik Oh,Sung Whan Jang 대한마취과학회 2007 Korean Journal of Anesthesiology Vol.53 No.6

Background: Though caudal block is a relative simple technique, it has not been widely used in adults because of a high failure rate. We assumed that any tests to quantify the changes of sympathetic tone in the affected areas would be excellent indicators of successful block. We tested the usefulness of two candidates (pulse oximetry plethysmographic waveform amplitude measured at 5th toe and calf minus 5th toe skin temperature gradient) as indicators of successful caudal block. Methods: In 45 adult patients undergoing anal surgery with caudal block, these two variables were simultaneously measured at 2-min intervals for 20 min. A two-fold increase in the plethysmographic waveform amplitude from baseline and skin temperature gradient of 0°C were predefined as test criteria of successful block. Results: While the sensitivity, specificity, positive predictive value, and negative predictive value of the skin temperature gradient test were 45.9%, 100%, 100%, and 9.1%, those of the plethysmographic waveform test were 86.5%, 100%, 100%, and 28.6%. The plethysmographic waveform test showed a significantly higher discriminative capacity than the skin temperature gradient test (94.9% vs. 48.7%, P < 0.05) Conclusions: Unlike the skin temperature gradient test, the plethysmographic waveform test showed a considerably high validity in detecting successful block. Considering its simple and real time monitoring potentials together with a high failure rate of caudal block in adults, we cautiously recommend it as a supplemental diagnostic tool to predict successful block, especially when verbal communication with patient is difficult. (Korean J Anesthesiol 2007; 53: S 19∼25)

기계적 자극을 이용한 인체 중간엽줄기세포로부터 유사-섬유모세포로의 분화 유도

최경민 ( Kyung Min Choi ),서영권 ( Young Kwon Seo ),윤희훈 ( Hee Hoon Yoon ),권순용 ( Soon Yong Kwon ),이화성 ( Hwa Sung Lee ),박용순 ( Yong Soon Park ),손영숙 ( Young Sook Son ),송계용 ( Kye Yong Song ),김영진 ( Young Jin Kim 한국조직공학과 재생의학회 2006 조직공학과 재생의학 Vol.3 No.4

Recently, in vitro reconstruction of anterior cruciate ligament(ACL) has been tried using tissue engineering technique, especially mesenchymal stem cell(MSC) is considered as a good cell source. In this study, we tried to find the effect of mechanical stimulus on the differentiation of bone marrow-derived MSC into ACL fibroblastlike cell using a cell training bioreactor imposing cyclic mechanical tension whose parameters were 120 min/day, 1 Hz, and 5% strain. After 2 weeks of culture, MSCs under cyclic tension showed more regularly oriented alignment and lower expression of CD73 and CD105 than control by microscopy and FACS analysis. In transcriptional level, type I collagen, type II collagen, fibronectin, elastin, α-smooth muscle actin mRNA expressions of MSCs under cyclic tension were higher than control and similar to native ACL. In conclusion, it is thought that mechanical cyclic tension induced the loss of stemness of MSC, therefore improved the differentiation into ACL fibroblast-like cell.

Protective Effects of N-acetylcystenine and Selenium against Doxorubicin Toxicity in Rats

Yeo-sung Yoon,Sun-don Kim,Min-hye Lee,Heung-shik S.Lee,In-se Lee,Je-kyung Sung,Eun-sung Park 대한수의학회 2003 Journal of Veterinary Science Vol.4 No.2

Effects of N-acetylcysteine and Selenium against Doxorubicin Toxicity in RatsEun-sung Park, Sun-don Kim1, Min-hye Lee, Heung-shik S. Lee, In-se Lee, Je-kyung Sung and Yeo-sung Yoon*

개의 췌도분리에서 췌장의 팽창과 콜라겐 분해요소

이상훈,김성주,박정환,김종성,오승훈,한진수,정인경,양태영,김동준,김광원,이문규,민용기,이명식,정재훈,함종렬 대한당뇨병학회 2000 Diabetes and Metabolism Journal Vol.24 No.2

Backgrounds: One of the main problems conditioning the outcome of islet transplantation is the ability to separate a sufficient number of viable islets with preserved function. Islet purification is critically affected by all of the isolation stages. Thus, it is necessary to set up the standard isolation method that islets are separate well from acinar without compromising islet yield and viability. Methods: Twenty three adult mongrel dogs were used for the experiment of total pancreatectomy with islet isolation. The islets were properly isolated by a modified Recordi method. The obtained islets were further purified by centrifugation on discontinuous gradients using cell separation system (Model 2991, Cobe, Lakewood Colo). We evaluated islet number (islet equivalent number, 150 um equivalents/kg of recipient body weight, IEq/kg), purity, cell volume, viabilty, recovery rate, and comparison of outcome according to the isolation conditions. Results: 1) The mean of islet numbers before purification were 13543±9431Eq/kg, digestion times were 13.8±2.6 min., digestion temperature was 37.4±0.2℃, purity was 59.7?.0%, viability was 90.0±2.1%, cell volume was 4.7±1.1 mL, islet number after purification were 4064±361 IEq/kg, and recovery rate was 29±2.9%. 2) Isolated islet numbers were different according to the degree of pancreas distension with collagenase, digestion temperature, and digestion time. 3) The best conditions for islet isolation were above 37.5℃ in temperature at recirculation of collagenase, within 12 min in digestion time and well distended pancreas with collagenase. 4) According to multiple regression adjusted by variable factors, the degree of pancreas distension with collagenase and digestion time were independently associated factors for successful islet isolation. Conclusions: In this study, we concluded that the degree of pancreas distension with collagenase and digestion time were independent factors for successful islet isolation and the best conditions for islet isolation were above 37.5℃ in temperature at recirculation of collagenase, within 12 min in digestion time and well distended pancreas with collagenase.

Effects of Mechanical Stimulation on the Proliferation of Bone Marrow-derived Human Mesenchymal Stem Cells

Choi, Kyung-Min,Seo, Young-Kwon,Yoon, Hee-Hoon,Song, Kye-Yong,Kwon, Soon-Yong,Lee, Hwa-Sung,Park, Jung-Keug Korean Society for Biotechnology and Bioengineerin 2007 Biotechnology and Bioprocess Engineering Vol.12 No.6

To support and enhance the in vitro growth and activity of mesenchymal stem cells (MSCs), the cell culture medium may be supplemented with various proteins and factors to mimic the physiological environment in which the cells optimally proliferate and differentiate. In this study, the effects of mechanical factors on cellular metabolic responses were investigated experimentally using a bioreactor. The effects of various chemical factors, such as growth factors, cytokines, and hormones, were also investigated. Based on previous reports demonstrating the important roles of mechanical factors in the growth and activity of MSCs, we sought to evaluate the effects of mechanical stimuli on the proliferation of bone marrow-derived MSCs using a cell training bioreactor that imposed cyclic mechanical stretch, with parameters of 240 min/day, 0.03 Hz, and $5{\sim}15%$ strain. The application of cyclic stretch $(5{\sim}15%\;strain)$ to the MSCs enhanced their proliferation during the early stage(3 days), but not the late stage (14 days), of batch culture. Mechanical stretch did not increase the release of lactate dehydrogenase (LDH) from the MSCs during culture. Appropriate levels of mechanical stretch $(5{\sim}10%\;strain)$ increased collagen synthesis, but did not alter MSC stretch was able to serve as a potent positive modulator of MSC proliferation during the initial stages of culture.

대장직장 종양에 대한 내시경 점막하 절제술의 연대순 임상 결과와 학습 곡선

이상민 ( Sang Min Lee ),김은수 ( Eun Soo Kim ),박경식 ( Kyung Sik Park ),조광범 ( Kwang Bum Cho ),김동춘 ( Dong Choon Kim ),강유진 ( Yu Jin Kang ),이유진 ( Yoo Jin Lee ),이정민 ( Jung Min Lee ),최은성 ( Eun Sung Choi ),최재혁 ( Ja 대한소화기학회 2014 대한소화기학회지 Vol.64 No.4

Background/Aims: Endoscopic submucosal dissection (ESD) is an effective procedure for en-bloc curative resection of the colorectal tumor. As it requires high technical skills and experience in therapeutic endoscopy, it is important to understand learning curve of ESD technique. The aim of this study was to retrospectively describe the clinical results of ESD and to evaluate learning curve for the ESD of colorectal tumors. Methods: A total of 90 patients with 90 colorectal neoplasms, who had undergone ESD at a tertiary referral hospital from July 2009 to December 2012, were enrolled. The ESD was performed by a single endoscopist. All ESD cases were divided into three periods: first, cases 1-30; second, cases 31-60; and third, cases 61-90. Results: The en-bloc resection rates in third period (100%) was significantly higher than that of the first (93.3%) and second period (80%) (p=0.025). The perforation rate in third period (0%) also significantly decreased compared with that of the first (13.3%) and second period (20%) (p=0.032). To calibrate the difference of tumor size among periods, proficiency was calculated, as the procedure time per specimen area (min/cm2). The proficiency in third period (4.3) was significantly shorter than that of the first (16.8) and second period (10.2) (p=0.004). Conclusions: The learning curve of colorectal ESD in our study shows that at least 60 cases of ESD have to be conducted to acquire sufficient skill of degree without perforation. (Korean J Gastroenterol 2014;64:198-205)