• Nutrition Research and Practice
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• 제12권3호
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• pp.183-190
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• 2018

BACKGROUND/OBJECTIVE: This study was designed to investigate how a Portulaca oleracea L. extract (POE) stimulates insulin secretion in INS-1 pancreatic ${\beta}-cells$. MATERIALS/METHOD: INS-1 pancreatic ${\beta}-cells$ were incubated in the presence of various glucose concentrations: 1.1 or 5.6, 16.7 mM glucose. The cells were treated with insulin secretagogues or insulin secretion inhibitor for insulin secretion assay using an insulin ELISA kit. In order to quantify intracellular influx of $Ca^{2+}$ caused by POE treatment, the effect of POE on intracellular $Ca^{2+}$ in INS-1 pancreatic ${\beta}-cells$ was examined using Fluo-2 AM dye. RESULTS: POE at 10 to $200{\mu}g/mL$ significantly increased insulin secretion dose-dependently as compared to the control. Experiments at three glucose concentrations (1.1, 5.6, and 16.7 mM) confirmed that POE significantly stimulated insulin secretion on its own as well as in a glucose-dependent manner. POE also exerted synergistic effects on insulin secretion with secretagogues, such as L-alanine, 3-isobutyl-1-methylxanthine, and especially tolbutamide, and at a depolarizing concentration of KCl. The insulin secretion caused by POE was significantly attenuated by treatment with diazoxide, an opener of the $K{^+}_{ATP}$ channel (blocking insulin secretion) and by verapamil (a $Ca^{2+}$ channel blocker). The insulinotropic effect of POE was not observed under $Ca^{2+}$-free conditions in INS-1 pancreatic ${\beta}-cells$. When the cells were preincubated with a $Ca^{2+}$ fluorescent dye, Fluo-2 (acetoxymethyl ester), the cells treated with POE showed changes in fluorescence in red, green, and blue tones, indicating a significant increase in intracellular $Ca^{2+}$, which closely correlated with increases in the levels of insulin secretion. CONCLUSIONS: These findings indicate that POE stimulates insulin secretion via a $K{^+}_{ATP}$ channel-dependent pathway in INS-1 pancreatic ${\beta}-cells$.

• 대한의생명과학회지
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• 제18권3호
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• pp.193-200
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• 2012

We examined the effects of polyamines such as putrescine and cadaverine on the biosynthesis and secretion of insulin in the mouse pancreatic ${\beta}$-cell line, MIN-6. Basal insulin secretion (BIS) and glucose-stimulated insulin secretion (GSIS) from the MIN-6 cells were significantly increased by 20 min- or 24 h-treatment with micromolar concentrations of polyamines. To determine whether the enhancement was due to increase of insulin production by polyamines, we investigated the insulin mRNA and protein production. Both insulin mRNA and protein production were found to be not significantly affected by the polyamine treatment. Next, we examined the expression of several transcription factors (TFs) related to insulin synthesis and secretion in order to identify upstream events responsible for the promotion of insulin secretion of MIN6 cells by polyamines. Of the 6 TFs tested, MafA was induced by treatment of polyamines. MafA mRNA and protein expressions increased with treatment of polyamines. Overall results suggest that cadaverine and putrescine promote the insulin secretion process rather than the insulin biosynthesis from MIN6 cells. Also MafA may be involved in the enhanced insulin secretion process. Further studies are needed to elucidate the underlying mechanisms for promotion of insulin secretion by polyamines.

• 대한한방내과학회지
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• 제31권1호
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• pp.25-39
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• 2010

Background : At high glucose levels in $\beta$-cells, cell viability and insulin secretion are decreased by glucotoxicity. Sopyung-tang(SPT) had an effect on blood glucose level decrease and antioxidant enzyme activities in streptozotocin-induced diabetic rats. Objectives : This study performed a series of experiment to verify the effects of SPT extract on the cell viability, antioxidant enzyme activities, insulin secretion and insulin mRNA expression at hyperglycemic states of RIN-m5F. Methods : After treatment at various concentrations of SPT added to the RIN-m5F cells, cell viability by MTT assay, free radical-scavenging activity, SOD activity and insulin secretion were measured. Additionally, insulin-related gene expression was measured using real-time RT-PCR. Results : Compared to the control group, SPT extract showed considerable effects on RIN-m5F cell viability, DPPH radical-scavenging activity, superoxide dismutase (SOD) activity, insulin secretion and insulin-related gene expression. Conclusions : This study showed that SPT extract has an effect on $\beta$-cell cell viability, insulin secretion and insulin-related gene expression. Thus, SPT extract may be used for treatment of diabetes and its complications. Further mechanism studies of SPT seem to be necessary on the glucotoxicity and oxidative stress.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1998년도 춘계학술대회
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• pp.1-4
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• 1998

Impaired insulin action in Type 2 diabetes is thought to lead to hyperglycemia, with both environmental and complex genetic factors playing key roles. Although the primary lesion in Type 2 diabetes is unknown, a number of studies suggest that metabolic defects in the liver, skeletal muscle and fat, and pancreatic ${\beta}$-cells contribute to the disease. These metabolic abnormalities are characterized by the overproduction of hepatic glucose, impaired insulin secretion, and peripheral insulin resistance. In current pharmacological treatment of Type 2 diabetes, sulfonylurea (SU) drugs have mainly been used as oral hypoglycemic drugs to stimulate endogenous insulin secretion from ${\beta}$ cells. SU drugs, however, sometimes aggravate the disease by causing fatigue of the pancreatic ${\beta}$ cells, which leads to reduced drug efficacy after long-term treatment. This class of drugs also leads to enhanced obesity arising from the stimulation of endogenous insulin secretion in obese Type 2 diabetic patients, plus an increased incidence of SU-induced hypoglycemia. Since 1980, a major challenge has been made by us to develop a potential pharmacological therapy for the treatment of insulin resistance in peripheral tissues and/or suppression of abnormal hepatic glucose production in Type 2 diabetic patients. Such a drug would be expected to have fewer side effects and retain long-term efficacy.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2001년도 학술 발표회 진행표 및 논문초록
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• pp.47-47
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• 2001

Opening of $Ca^{2＋}$ -channels represents the final common pathway for insulin secretion in pancreatic beta-cells and related cell lines. We investigated voltage-sensitive calcium channels (VSCCs) and insulin secretion in RINm5F, an insulinoma cell line derived from rat pancreatic beta-cells. Several types of VSCCs were identified in RINm5f cells： dihydropyridine-sensitive L-type, $\omega$-conotoxin GVIA-sensitive N-type, $\omega$-agatoxin IVA-sensitive P-type channels, and $\omega$-conotoxin MVIIC sensitive Q-type channels.(omitted)

• BMB Reports
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• 제52권5호
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• pp.295-303
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• 2019

Breakthroughs in stem cell technology have contributed to disease modeling and drug screening via organoid technology. Organoid are defined as three-dimensional cellular aggregations derived from adult tissues or stem cells. They recapitulate the intricate pattern and functionality of the original tissue. Insulin is secreted mainly by the pancreatic ${\beta}$ cells. Large-scale production of insulin-secreting ${\beta}$ cells is crucial for diabetes therapy. Here, we provide a brief overview of organoids and focus on recent advances in protocols for the generation of pancreatic islet organoids from pancreatic tissue or pluripotent stem cells for insulin secretion. The feasibility and limitations of organoid cultures derived from stem cells for insulin production will be described. As the pancreas and gut share the same embryological origin and produce insulin, we will also discuss the possible application of gut organoids for diabetes therapy. Better understanding of the challenges associated with the current protocols for organoid culture facilitates development of scalable organoid cultures for applications in biomedicine.

• Preventive Nutrition and Food Science
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• 제9권4호
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• pp.367-373
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• 2004

The prevalence of type-2 diabetes increases remarkably in post-menopausal women, possibly because insulin secretion fails to compensate for the insulin resistance induced in various tissues by estrogen insufficiency. However, this has not been fully defined. Therefore, the present study investigated whether an ovariectomy (OVX) would increase insulin resistance and decrease the $\beta$-cell function and mass in female rats with and without a $90\%$ pancreatectomy (Px). Female rats aged 15 weeks were divided into four groups: 1) OVX + Px, 2) SOVX (sham operation of OVX) + Px, 3) OVX + SPx (sham operation of Px), and 4) SOVX + SPx, and given a $30\%$ fat diet for 8 weeks. At the end of the experimental period, the islet function and insulin resistance were determined using a hyperglycemic clamp and a euglycemic hyperinsulinemic clamp, respectively. The OVX only increased the body weight in the SPx rats, which was partially related to the food intake. Yet, the OVX did increase the peripheral insulin resistance, while the Px increased this resistance further. The OVX and Px both exacerbated the islet function, as measured by the insulin secretion pattern, while delaying and decreasing the first-phase insulin secretion. The OVX only decreased the proliferation of $\beta$-cells in the Px rats, while increasing apoptosis in both the Px and SPx rats. As a result, the OVX decreased the $\beta$-cell mass in the Px rats, but increased the mass in the SPx rats. In conclusion, an OVX was found to accelerate the development and progression of diabetes by increasing the insulin resistance and decreasing the $\beta$-cell mass. Therefore, menopause can be a risk factor for type-2 diabetes, mainly due to a deceased proliferation of $\beta$-cells.

• Journal of the Korean Wood Science and Technology
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• 제47권4호
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• pp.498-508
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• 2019

This study was carried out to investigate the potential of Korean red pine (Pinus densiflora) inner bark extracts as an antidiabetic agent. The ethyl acetate soluble fraction of the bark extracts was chromatographed on a Sephadex LH-20 column to yield five compounds, which structures were elucidated by NMR spectroscopy. The isolated compounds were (+)-catehin, (-)-epicatechin, taxifolin, taxifolin-3'-O-${\beta}$-D-(+)-glucose and $\tilde{n}$-courmaric acid. The antidiabetic activity of the different fractions, including the crude extracts and isolated compounds, was evaluated by ${\beta}$-cells insulin secretion and glucose uptake in skeletal muscle cells. The insulin secretion was 128% for taxifolin at $25{\mu}g/mL$. However, the other samples had no effect on this test. For the glucose uptake activity assay, $1{\mu}M$ insulin and 2 mM metformin were used as controls. Both the crude extract and taxifolin showed relatively low activity values, but the other samples yielded glucose uptake values over 260%. ${\rho}$-courmaric acid showed the highest uptake (270%). The results confirmed that Korean red pine extracts may be used as a hypoglycemic agent.

• 한국수정란이식학회지
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• 제20권1호
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• pp.71-77
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• 2005

Relaxin과 insulin이 돼지 난포 과립막세포의 스테로이드 호르몬 분비에 미치는 영향을 연구하기위하여 체외에서 황체화된 과립막세포에서 prosesterone과 $17{\beta}-estradiol$의 생산을 조사하였다. 돼지난포 과립막세포를 혈청 존재하에 배양접시에 부착 후 48시간 동안 체외배양하고 무혈청 배지에서 24시간 배양하였다. Relaxin과 insulin의 용량의존성을 확인하기 위하여 다양한 농도 (10, 100, 1,000 ng/ml)를 각각 무혈청 배지에 첨가하였다. 병합 효과를 알아보기 위하여 100 ng/ml relaxin과 100 ng/ml insulin을 단독 혹은 병합하여 처리하였는데 황체호르몬 (100 ng/ml)을 처리한 경우와 처리하지 않은 경우 모두를 조사, 분석하였다. 최종 배양이 끝난 배양액을 수집하여 RIA법으로 proses-terone과 $17{\beta}-estradiol$의 농도를 조사하였다. Relaxin과 insulin은 용량이 증가될수록 progesterone의 생산을 증가시켰으나 $17{\beta}-estradiol$의 생산에는 아무런 영향이 없었다. 병합실험에서는 relaxin과 insulin 단독 또는 병합시 황체호르몬 존재 하에서 progesterone의 생산을 증가시켰으나 $17{\beta}-estradiol$의 생산에는 아무런 영향이 없었다. 결론적으로 relaxin과 insulin은 돼지 황체화 과립막세포의 progesterone 분비를 증가시키지만 $17{\beta}-estradiol$의 생산에는 효과가 없었으며 병합에 의한 상승효과는 없었다. Progesterone 생산에 미치는 relaxin과 insulin의 효과는 황체호르몬의 존재에 의해 증대되었다.

• BMB Reports
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• 제51권10호
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• pp.538-543
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• 2018

Pancreatic beta cell destruction and dysfunction induced by cytokines is a major cause of type 1 diabetes. Paraoxonase 1 (PON1), an arylesterase with antioxidant activity, has been shown to play an important role in preventing the development of diabetes in transgenic mice. However, no studies have examined the anti-diabetic effect of PON1 delivered to beta cells using protein transduction. In this study, we expressed the cell-permeable PON1 fused with PEP-1 protein transduction domain (PEP-1-PON1) to investigate whether transduced PEP-1-PON1 protects beta cells against cytokine-induced cytotoxicity. PEP-1-PON1 was effectively delivered to INS-1 cells and prevented cytokine-induced cell destruction in a dose-dependent manner. Transduced PEP-1-PON1 significantly reduced the levels of reactive oxygen species (ROS) and nitric oxide (NO), DNA fragmentation, and expression of inflammatory mediators, endoplasmic reticulum (ER) stress proteins, and apoptosis-related proteins in cytokine-treated cells. Moreover, transduced PEP-1-PON1 restored the decrease in basal and glucose-stimulated insulin secretion induced by cytokines. These data indicate that PEP-1-PON1 protects beta cells from cytokine-induced cytotoxicity by alleviating oxidative/nitrosative stress, ER stress, and inflammation. Thus, PEP-1-mediated PON1 transduction might be an effective method to reduce the extent of destruction and dysfunction of pancreatic beta cells in autoimmune diabetes.