Serotonergic Signaling in Adipocytes is Critical for Insulin Triggering Adipogenesis

Hojin Lee,Soomin Lee,Jung-Mi Oh,Seoyeong Jung,Hye-Young Joung,Sun Young Park,Sungkun Chun,Jaekwang Lee 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10

5-Hydroxytryptamine (5-HT, serotonin), a monoamine neurotransmitter derived from the amino acid tryptophan, is related to body weight and food intake regulation. Although serotonin signaling is important to develop obesity in the central nervous system, however, it is unclear what the role of serotonin signaling to develop adiposity in peripheral system. In this study, we showed that serotonin was synthesized in adipocytes, regulated adipogenesis by increase of ROS which was produced during serotonin metabolism by monoamine oxidases (MAOs) in adipocyte differentiation. Interestingly, we found that among MAOs, MAO-B was upregulated during differentiation in 3T3L1 and primary adipocytes. In the same line, increased ROS production during adipogenesis was blocked by selegiline, MAO-B inhibitor, in 3T3L1 and primary adipocyte. Moreover, the high-fat diet (HFD) fed mice with the administration of selegiline showed weight loss and reduction of fat size. Consequently, these data suggest that adipocyte is serotonergic cell and adipocytes synthesize serotonin and produce ROS during serotonin degradation by MAO enzymes, specially MAO-B, which could be a therapeutic target for anti-obesity.

Therapeutic Potential of Stem Cells Strategy for Cardiovascular Diseases

Lee, Chang Youn,Kim, Ran,Ham, Onju,Lee, Jihyun,Kim, Pilseog,Lee, Seokyeon,Oh, Sekyung,Lee, Hojin,Lee, Minyoung,Kim, Jongmin,Chang, Woochul Hindawi Publishing Corporation 2016 Stem cells international Vol.2016 No.-

<P>Despite development of medicine, cardiovascular diseases (CVDs) are still the leading cause of mortality and morbidity worldwide. Over the past 10 years, various stem cells have been utilized in therapeutic strategies for the treatment of CVDs. CVDs are characterized by a broad range of pathological reactions including inflammation, necrosis, hyperplasia, and hypertrophy. However, the causes of CVDs are still unclear. While there is a limit to the currently available target-dependent treatments, the therapeutic potential of stem cells is very attractive for the treatment of CVDs because of their paracrine effects, anti-inflammatory activity, and immunomodulatory capacity. Various studies have recently reported increased therapeutic potential of transplantation of microRNA- (miRNA-) overexpressing stem cells or small-molecule-treated cells. In addition to treatment with drugs or overexpressed miRNA in stem cells, stem cell-derived extracellular vesicles also have therapeutic potential because they can deliver the stem cell-specific RNA and protein into the host cell, thereby improving cell viability. Here, we reported the state of stem cell-based therapy for the treatment of CVDs and the potential for cell-free based therapy.</P>

Haptic Assistance for Memorization of 2-D Selection Sequences

Hojin Lee,Gabjong Han,In Lee,Sunghoon Yim,Kyungpyo Hong,Hyeseon Lee,Seungmoon Choi IEEE 2013 IEEE transactions on human-machine systems Vol.43 No.6

<P>This paper investigates the effect of haptic feedback on the learning of a 2-D sequential selection task, used as an abstraction of complex industrial manual assembly tasks. This mnemonic-motor task requires memorization of the selection order of points scattered on a 2-D plane and reproduction of this order using entire arm movements. Four information presentation methods, visual information only, visual information + enactment, visual information + haptic guidance, and visual information + haptic disturbance, are considered. The latter three methods provide different levels of haptic kinesthetic feedback to the trainee. We carried out a user study to assess the quantitative performance differences of the four training methods using a custom-built visuo-haptic training system. Experimental results showed the relative advantages and disadvantages of each information presentation method for both short-term and long-term memorization. In particular, training with only visual information was the best option for short-term memory, while training also with haptic disturbance was the most effective for long-term memory. Our findings have implications to designing a training method that is suitable for given training requirements.</P>

POMY: 햅틱 피드백을 적용한 몰입형 영어 학습 시스템

이재봉(Jaebong Lee),이규송(Kyusong Lee),Hoang Minh Phuong,이호진(Hojin Lee),이근배(Gary Geunbae Lee),최승문(Seungmoon Choi) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.8

In this paper, we propose a novel CALL (Computer-Assisted Language Learning) system, which is called POMY (POSTECH Immersive English Study). In our system, students can study English while talking to characters in a computer-generated virtual environment. POMY also supports haptic feedback, so students can study English in a more interesting manner. Haptic feedback is provided by two platforms, a haptic chair and a force-feedback device. The haptic chair, which is equipped with an array of vibrotactile actuators, delivers directional information to the student. The force-feedback device enables the student to feel the physical properties of an object. These haptic systems help the student better understand English conversations and focus on studying. We conducted a user experiment and its results showed that our haptic-enabled English study contributes to better learning of English.

Alternative new mesenchymal stem cell source exerts tumor tropism through ALCAM and N-cadherin via regulation of microRNA-192 and -218

Kim, Ran,Park, Sang In,Lee, Chang Youn,Lee, Jihyun,Kim, Pilseog,Oh, Sekyung,Lee, Hojin,Lee, Min Young,Kim, Jongmin,Chung, Yong-An,Hwang, Ki-Chul,Maeng, Lee-So,Chang, Woochul Springer US 2017 MOLECULAR AND CELLULAR BIOCHEMISTRY - Vol.427 No.1

<P>Gliomas are the most common type of malignant primary brain tumors. Some treatments of gliomas exist, but they are rarely curative. Mesenchymal stem cells (MSCs) are emerging as potential modes of targeted cancer therapy owing to their capacity for homing toward tumor sites. It has been proposed that MSCs derived from various sources, such as bone marrow, adipose tissue and umbilical cord blood, can be used as cell-based therapy for brain tumors. Here, MSCs obtained from the synovial fluid of osteoarthritis or rheumatoid arthritis patients were investigated as therapeutic candidates. Specifically, we compared migratory and adhesive abilities, as well as expression levels of related genes and microRNA in bone marrow derived-MSCs (BMMSCs), adipose derived-MSCs (ADMSCs), and synovial fluid derived-MSCs (SFMSCs) after treatment with conditioned medium from gliomas. Migration and adhesion of SFMSCs increased through upregulation of the activated lymphocyte cell adhesion molecule (ALCAM) and N-cadherin by microRNA-192 and -218 downregulation, similar to BMMSCs and ADMSCs. Migratory capacities of all types of MSCs were evaluated in vivo, and SFMSCs migrated intensively toward gliomas. These results suggest that SFMSCs have potential for use in cell-based antitumor therapies.</P>

A Study on Dynamic Asset Allocation Strategy for Optimal Portfolio Selection

Lee, Hojin Korea Institute for International Economic Policy 2021 East Asian Economic Review Vol.25 No.3

We use iterative numerical procedures combined with analytical methods due to Rapach and Wohar (2009) to solve for the dynamic asset allocation strategy for optimal portfolio demand. We compare different optimal portfolio demands when investors in each country have different access to overseas and domestic investment opportunities. The optimal dynamic asset allocation strategy without foreign investment opportunities leads domestic investors in Korea, Hong Kong, and Singapore to allocate more funds to domestic bonds than to domestic stocks. However, the U.S. investors allocate more wealth to domestic stocks than to domestic bonds. Investors in all countries short bills at a low level of risk aversion. Next, we investigate dynamic asset allocation strategy when domestic investors in Korea have access to foreign markets. The optimal portfolio demand leads investors in Korea to allocate most resources to domestic bonds and foreign stocks. On the other hand, the portfolio weights on foreign bonds and domestic stocks are relatively low. We also analyze dynamic asset allocation strategy for the investors in the U.S., Hong Kong, and Singapore when they have access to the Korean markets as overseas investment opportunities. Compared to the results when the investors only have access to domestic markets, the investors in the U.S. and Singapore increase the portfolio weights on domestic stocks in spite of the overseas investment opportunities in the Korean markets. The investors in the U.S., Hong Kong, and Singapore short domestic bills to invest more than initial funds in risky assets with a varying degree of relative risk aversion coefficients without exception.

Effect of 42 amino acid long amyloid-β peptides on Arabidopsis plants

Lee, HanGyeol,Kim, Ji Woo,Jeong, Sangyun,An, Jungeun,Kim, Young-Cheon,Ryu, Hojin,Lee, Jeong Hwan The Korean Society of Plant Biotechnology 2020 JOURNAL OF PLANT BIOTECHNOLOGY Vol.47 No.4

Although the evolution of Arabidopsis thaliana and humans diverged approximately 1.6 billion years ago, recent studies have demonstrated that protein function and cellular processes involved in disease response remain remarkably conserved. Particularly, γ-secretase, a multisubunit protein complex that participates in intramembrane proteolysis (RIP) regulation, is also known to mediate the cleavage of more than 80 substrates including the amyloid precursor protein (APP) and the Notch receptor. Although the genes (PS1/2, APH-1, PEN-2, and NCT) coding for the γ-secretase complex components are present in plant genomes, their function remains largely uncharacterized. Given that the deposition of 42 amino acid long amyloid-β peptides (hAβ₄₂) is thought to be one of the main causes of Alzheimer's disease, we aimed to examine the physiological effects of hAβ₄₂ peptides on plants. Interestingly, we found that Arabidopsis protoplast death increased after 24 h of exposure to 3 or 5 µM hAβ₄₂ peptides. Furthermore, transgenic Arabidopsis plants overexpressing the hAβ₄₂ gene exhibited changes in primary root length and silique phyllotaxy. Taken together, our results demonstrate that hAβ₄₂ peptides, a metazoan protein, significantly affect Arabidopsis protoplast viability and plant morphology.

Structural Breaks or Long Memory for Stock Market Volatility and Volatility Forecasting

Hojin Lee 한국재무학회 2011 財務硏究 Vol.24 No.3

Semi-parametric Method for Estimating Tail Related Risk Measures in the Stock Market

( Hojin Lee ) 한국경제학회 2016 The Korean Economic Review Vol.32 No.2

The generalized Pareto distribution (GPD) approach for estimating the Value-at-Risk (VaR) and the expected shortfall (ES) is compared to other methods for evaluating extreme risk with normally distributed returns. When the market index returns have a fat-tailed distribution, the risk measures computed from the normal distribution underestimate the tail-related risk. We also compare the computation results of the VaR based on the GPD approximations to those based on the RiskMetrics methodology and GARCH model estimation. The estimates of the VaR are robust to a variety of threshold values. Contrary to this, the VaR values based on the RiskMetrics methodology and the GARCH model are extremely volatile. From a risk manager`s perspective, it would be difficult to adjust capital requirement of a financial institution to conditional market risk. Due to concerns raised for practical and statistical reasons, we can conclude that the GPD method for measuring unconditional market risk is more appropriate for measuring and managing the tail-related risk.

ERAS in Anesthesiologist Perspectives

Hojin Lee 대한외과학회 2022 대한외과학회 학술대회 초록집 Vol.2022 No.11