Lupenone attenuates thapsigargin-induced endoplasmic reticulum stress and apoptosis in pancreatic beta cells possibly through inhibition of protein tyrosine kinase 2 activity.

AIMS: Prolonged high levels of cytokines, glucose, or free fatty acids are associated with diabetes, elevation of cytosolic Ca2+ concentration ([Ca2+]C), and depletion of Ca2+ concentration in the endoplasmic reticulum (ER) of pancreatic beta cells. This Ca2+ imbalance induces ER stress and apoptosis. Lupenone, a lupan-type triterpenoid, is beneficial in diabetes; however, its mechanism of action is yet to be clarified. This study evaluated the protective mechanism of lupenone against thapsigargin-induced ER stress and apoptosis in pancreatic beta cells. MATERIALS AND METHODS: MIN6, INS-1, and native mouse islet cells were used. Western blot for protein expressions, measurement of [Ca2+]C, and in vivo glucose tolerance test were mainly performed. KEY FINDINGS: Thapsigargin increased the protein levels of cleaved caspase 3, cleaved PARP, and the phosphorylated form of JNK, ATF4, and CHOP. Thapsigargin increased the interaction between stromal interaction molecule1 (Stim1) and Orai1, enhancing store-operated calcium entry (SOCE). SOCE is further activated by protein tyrosine kinase 2 (Pyk2), which is Ca2+-dependent and phosphorylates the tyrosine residue at Y361 in Stim1. Lupenone inhibited thapsigargin-mediated Pyk2 activation, suppressed [Ca2+]C, ER stress, and apoptosis. Lupenone restored impaired glucose-stimulated insulin secretion effectuated by thapsigargin and glucose intolerance in a low-dose streptozotocin-induced diabetic mouse model. SIGNIFICANCE: These results suggested that lupenone attenuated thapsigargin-induced ER stress and apoptosis by inhibiting SOCE; this may be due to the hindrance of Pyk2-mediated Stim1 tyrosine phosphorylation. In beta cells that are inevitably exposed to frequent [Ca2+]C elevation, the attenuation of abnormally high SOCE would be beneficial for their survival.

Whole body mass estimates and error propagation in countermovement jump: a simulated error study.

High-velocity actions are central to clinical and athletic performance, with jumping used to assess outcomes in sports medicine. Ground reaction force (GRF)-based methods are the standard for computing jump characteristics, but require mass estimation and GRF integration, potentially resulting in mass errors which influence outcomes. This study investigated how simulated mass errors influenced the centre of mass (CoM) trajectory during a countermovement jump. The mass was estimated from the static GRF, and simulated errors were added or subtracted to the mass. The CoM trajectory with simulated mass errors was computed using the GRF-based method to investigate mass mis-estimation's influence on jump height. A regression model indicated that, for a 1 kg mass change, there was a 7.7 cm jump height change, and the jump height differed by 11.5 ± 0.4 cm from the maximum to minimum error. A 2-way ANOVA identified significant height differences between the starting position, and landing, or final position with mass errors of ± 0.2 or ± 0.4 kg. These results reveal that small mass errors may produce inaccurate conclusions regarding performance changes, and that errors may propagate throughout the jump trajectory. Caution may be necessary when using GRF-based methods to compute jump height as a power proxy.

Beneficial effects of intermittent fasting: a narrative review.

Caloric restriction is a popular approach to treat obesity and its associated chronic illnesses but is difficult to maintain for a long time. Intermittent fasting is an alternative and easily applicable dietary intervention for caloric restriction. Moreover, intermittent fasting has beneficial effects equivalent to those of caloric restriction in terms of body weight control, improvements in glucose homeostasis and lipid profiles, and anti-inflammatory effects. In this review, the beneficial effects of intermittent fasting are discussed.

The Smart Soil Organism Detector: An instrument and machine learning pipeline for soil species identification.

Understanding the diversity of soil organisms is complicated by both scale and substrate. Every footprint we leave in the soil covers hundreds to millions of organisms yet we cannot see them without extremely laborious extraction and microsopy endeavors. Studying them is also challenging. Keeping them alive so that we can understand their lifecycles and ecological roles ranges from difficult to impossible. Functional and taxonomic identification of soil organisms, while possible, is also challenging. Here we present the Smart Soil Organism Detector, an instrument and machine learning pipeline that combines high-resolution imaging, multi-spectral sensing, large-bore flow cytometry, and machine learning to extract, isolate, count, identify, and separate soil organisms in a high-throughput, high-resolution, non-destructive, and reproducible manner. This system is not only capable of separating alive nematodes, dead nematodes, and nematode cuticles from soil with 100% out-of-sample accuracy, but also capable of identifying nematode strains (sub-species) with 95.5% out-of-sample accuracy and 99.4% specificity. Soil micro-arthropods were identified to class with 96.1% out-of-sample accuracy. Broadly applicable across soil taxa, the Smart SOD system is a tool for understanding global soil biodiversity.

Peroxiredoxin 2 deficiency does not affect insulin resistance and oxidative stress in high-fat diet-fed obese mice.

OBJECTIVE: To examine if peroxiredoxin 2 (Prx2) deficiency aggravates high-fat diet-induced insulin resistance. MATERIAL AND METHODS: Insulin sensitivity was measured in Prx2 knockout (KO) and wild-type (WT) littermates using the hyperinsulinemic-euglycemic clamp. RESULTS: Whole body glucose turnover, glucose uptake, and levels of glucose transporter 4 (Glut4) protein in the skeletal muscle were found to be lower. This was followed by increased expression of oxidative stress markers in Prx2 KO mice than that in WT mice in the control diet group. Although, a 12-week high-fat diet induced insulin resistance and enhanced oxidative stress in both genotypes, there was no difference between WT and Prx2 KO mice with respect to insulin sensitivity and the level of oxidative stress markers. Accordingly, the levels of phosphorylated Akt and Glut4 were similar between the two genotypes. CONCLUSION: These results suggest that Prx2 does not affect high-fat diet-induced oxidative stress and insulin resistance in mice.

Single-Cell Sorting of Non-human Primate Adipocytes with Large-particle Flow Cytometry.

Fluorescence-activated cell sorting enables separation and analysis of heterogeneous cell populations based on size, granularity, and fluorescence intensity. Cell sorting has been widely used for isolation of cells that are ∼10 to 25 µm in diameter. By contrast, cell sorting of unilocular adipocytes isolated from white adipose tissue imposes a significant technological challenge. The combination of their large size (up to 200 µm) and the fragile nature of lipid-laden adipocytes requires the use of specialized flow cytometers equipped with a large nozzle and capable of using low pressure to reduce shear forces during the cell sorting process. Furthermore, isolation of single adipocytes is rarely performed due to the lack of specialized cell sorters that can dispense single adipocytes into individual wells. Conducting cell sorting on single adipocytes would enable analyses of the cell-autonomous heterogeneity in nutrient uptake and metabolism observed in white adipose tissue. In this protocol, we describe single-cell sorting of rhesus macaque adipocytes labeled with fluorescent fatty acid and live-cell indicators using large-particle flow cytometry. This methodology represents a valuable resource for basic and translational studies aimed at understanding the development and function of adipocytes. © 2021 Wiley Periodicals LLC. Basic Protocol: Single-cell flow sorting of adipocytes.

Mitochondrial TFAM as a Signaling Regulator between Cellular Organelles: A Perspective on Metabolic Diseases.

Tissues actively involved in energy metabolism are more likely to face metabolic challenges from bioenergetic substrates and are susceptible to mitochondrial dysfunction, leading to metabolic diseases. The mitochondria receive signals regarding the metabolic states in cells and transmit them to the nucleus or endoplasmic reticulum (ER) using calcium (Ca2+) for appropriate responses. Overflux of Ca2+ in the mitochondria or dysregulation of the signaling to the nucleus and ER could increase the incidence of metabolic diseases including insulin resistance and type 2 diabetes mellitus. Mitochondrial transcription factor A (Tfam) may regulate Ca2+ flux via changing the mitochondrial membrane potential and signals to other organelles such as the nucleus and ER. Since Tfam is involved in metabolic function in the mitochondria, here, we discuss the contribution of Tfam in coordinating mitochondria-ER activities for Ca2+ flux and describe the mechanisms by which Tfam affects mitochondrial Ca2+ flux in response to metabolic challenges.

Portrait Segmentation Using Ensemble of Heterogeneous Deep-Learning Models.

Image segmentation plays a central role in a broad range of applications, such as medical image analysis, autonomous vehicles, video surveillance and augmented reality. Portrait segmentation, which is a subset of semantic image segmentation, is widely used as a preprocessing step in multiple applications such as security systems, entertainment applications, video conferences, etc. A substantial amount of deep learning-based portrait segmentation approaches have been developed, since the performance and accuracy of semantic image segmentation have improved significantly due to the recent introduction of deep learning technology. However, these approaches are limited to a single portrait segmentation model. In this paper, we propose a novel approach using an ensemble method by combining multiple heterogeneous deep-learning based portrait segmentation models to improve the segmentation performance. The Two-Models ensemble and Three-Models ensemble, using a simple soft voting method and weighted soft voting method, were experimented. Intersection over Union (IoU) metric, IoU standard deviation and false prediction rate were used to evaluate the performance. Cost efficiency was calculated to analyze the efficiency of segmentation. The experiment results show that the proposed ensemble approach can perform with higher accuracy and lower errors than single deep-learning-based portrait segmentation models. The results also show that the ensemble of deep-learning models typically increases the use of memory and computing power, although it also shows that the ensemble of deep-learning models can perform more efficiently than a single model with higher accuracy using less memory and less computing power.

PPARδ Attenuates Alcohol-Mediated Insulin Resistance by Enhancing Fatty Acid-Induced Mitochondrial Uncoupling and Antioxidant Defense in Skeletal Muscle.

Alcohol consumption leads to the dysfunction of multiple organs including liver, heart, and skeletal muscle. Alcohol effects on insulin resistance in liver are well evidenced, whereas its effects in skeletal muscle remain controversial. Emerging evidence indicates that alcohol promotes adipose tissue dysfunction, which may induce organ dysregulation. We show that consumption of ethanol (EtOH) reduces the activation of 5'AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) as well as the protein of carnitine palmitoyltransferase 1 (CPT1) and glucose transporter type 4 (GLUT4) in C2C12 myotube. We observed that chronic EtOH consumption increases free fatty acid levels in plasma and triglyceride (TG) accumulation in skeletal muscle and that these increases induce insulin resistance and decrease glucose uptake. Hence, ethanol dysregulates metabolic factors and induces TG accumulation. We found peroxisome proliferator-activated receptor ß/δ (PPARδ) activation recovers AMPK activation and increases carnitine-acylcarnitine translocase (CACT) protein. These effects may contribute to enhance mitochondrial activation via uncoupling protein 3 (UCP3) when fatty acids are used as a substrate, thus reduces EtOH-induced increases in TG levels in skeletal muscle. In addition, PPARδ activation recovered EtOH-induced loss of protein kinase B (AKT) phosphorylation at serine 473 via rapamycin-insensitive companion of mammalian target of rapamycin (Rictor) activation. Importantly, PPARδ activation enhanced mitochondrial uncoupling via UCP3. Taken together, the study shows PPARδ enhances fatty acid utilization and uncoupled respiration via UCP3 and protects against EtOH-induced lipotoxicity and insulin resistance in skeletal muscle.

Alginate-Derived Elicitors Enhance ß-Glucan Content and Antioxidant Activities in Culinary and Medicinal Mushroom, Sparassis latifolia.

This study aimed to investigate the elicitation effects of alginate oligosaccharides extracted from brown algae (Sargassum species) on ß-glucan production in cauliflower mushroom (Sparassis latifolia). Sodium alginate was refined from Sargassum fulvellum, S. fusiforme, and S. horneri, and characterized by proton nuclear magnetic resonance spectroscopy (1H NMR), resulting mannuronic acid to guluronic acid (M/G) rationes from 0.64 to 1.38. Three oligosaccharide fractions, ethanol fraction (EF), solid fraction (SF), and liquid fraction (LF), were prepared by acid hydrolysis and analyzed by Fourier transform infrared (FT-IR) spectra and high-performance anion-exchange chromatography with a pulsed amperometric detector (HPAEC-PAD). The samples of S. fusiforme resulted in the highest hydrolysate in SF and the lowest in LF, which was consistent with its highest M/G ratio. The SF of S. fusiforme and LF of S. horneri were chosen for elicitation on S. latifolia, yielding the highest ß-glucan contents of 56.01 ± 3.45% and 59.74 ± 4.49% in the stalk, respectively. Total polyphenol content (TPC) and antioxidant activities (2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging and Superoxide dismutase (SOD)-like activity) of aqueous extracts of S. latifolia were greatly stimulated by alginate elicitation. These results demonstrate that alginate oligosaccharides extracted from brown algae may be useful as an elicitor to enhance the nutritional value of mushrooms.

Transthyretin Maintains Muscle Homeostasis Through the Novel Shuttle Pathway of Thyroid Hormones During Myoblast Differentiation.

Skeletal muscle, the largest part of the total body mass, influences energy and protein metabolism as well as maintaining homeostasis. Herein, we demonstrate that during murine muscle satellite cell and myoblast differentiation, transthyretin (TTR) can exocytose via exosomes and enter cells as TTR- thyroxine (T4) complex, which consecutively induces the intracellular triiodothyronine (T3) level, followed by T3 secretion out of the cell through the exosomes. The decrease in T3 with the TTR level in 26-week-old mouse muscle, compared to that in 16-week-old muscle, suggests an association of TTR with old muscle. Subsequent studies, including microarray analysis, demonstrated that T3-regulated genes, such as FNDC5 (Fibronectin type III domain containing 5, irisin) and RXRγ (Retinoid X receptor gamma), are influenced by TTR knockdown, implying that thyroid hormones and TTR coordinate with each other with respect to muscle growth and development. These results suggest that, in addition to utilizing T4, skeletal muscle also distributes generated T3 to other tissues and has a vital role in sensing the intracellular T4 level. Furthermore, the results of TTR function with T4 in differentiation will be highly useful in the strategic development of novel therapeutics related to muscle homeostasis and regeneration.

Selenoprotein W deficiency does not affect oxidative stress and insulin sensitivity in the skeletal muscle of high-fat diet-fed obese mice.

Selenoprotein W (SelW) is a selenium-containing protein with a redox motif found abundantly in the skeletal muscle of rodents. Previous in vitro studies suggest that SelW plays an antioxidant role; however, relatively few in vivo studies have addressed the antioxidant role of SelW. Since oxidative stress is a causative factor for the development of insulin resistance in obese subjects, we hypothesized that if SelW plays a role as an antioxidant, SelW deficiency could aggravate the oxidative stress and insulin resistance caused by a high-fat diet. SelW deficiency did not affect insulin sensitivity and H2O2 levels in the skeletal muscle of control diet-fed mice. SelW levels in the skeletal muscle were decreased by high-fat diet feeding for 12 wk. High-fat diet induced obesity and insulin resistance and increased the levels of H2O2 and oxidative stress makers, which were not affected by SelW deficiency. High-fat diet feeding increased the expression of antioxidant enzymes; however, SelW deficiency did not affect the expression levels of antioxidants. These results suggest that SelW does not play a protective role against oxidative stress and insulin resistance in the skeletal muscle of high-fat diet-fed obese mice.

Clusterin deficiency induces lipid accumulation and tissue damage in kidney.

Clusterin is a secretory glycoprotein that is involved in multiple physiopathological processes, including lipid metabolism. Previous studies have shown that clusterin prevents hepatic lipid accumulation via suppression of sterol regulatory element-binding protein (SREBP) 1. In this study, we examined the role of clusterin in renal lipid accumulation in clusterin-knockout mice and NRK52e tubular epithelial cells. Clusterin deficiency increased the expression of SREBP1 and its target genes and decreased malonyl-CoA decarboxylase protein levels in the kidney. Expression of the endocytic receptor, megalin, and scavenger receptor class A was increased in clusterin-deficient mice. Functional analysis of lipid metabolism also revealed that lipid uptake and triglyceride synthesis were increased and fatty acid oxidation was reduced, leading to increased lipid accumulation in clusterin-deficient mice. These phenomena were accompanied by mesangial expansion, fibrosis and increased urinary protein-to-creatinine ratio. High-fat feeding aggravated these clusterin deficiency-induced pathological changes. Clusterin knockdown in NRK52e cells increased lipogenic gene expression and lipid levels, whereas overexpression of clusterin by treatment with adenovirus or recombinant clusterin protein suppressed lipogenic gene expression and lipid levels. Transforming growth factor-beta 1 (TGFB1) expression increased in the kidney of clusterin-deficient mice and suppression of TGFB1 in NRK52e cells suppressed lipid accumulation. These results suggest that clusterin deficiency induces renal lipid accumulation by dysregulating the expression of lipid metabolism-related factors and TGFB1, thereby leading to chronic kidney disease. Hence, clusterin may serve as a therapeutic target for lipid-induced chronic kidney disease.

Trends in Research on the Security of Medical Information in Korea: Focused on Information Privacy Security in Hospitals.

OBJECTIVES: Information technology involves a risk of privacy violation in providing easy access to confidential information,such as personal information and medical information through the Internet. In this study, we investigated medical information security to gain a better understanding of trends in research related to medical information security. METHODS: We researched papers published on '의료정보' and 'medical information' in various Korean journals during a 10-year period from 2005 to 2015. We also analyzed these journal papers for each fiscal year; these papers were categorized into the areas of literature research and empirical research, and were further subdivided according to themes and subjects. RESULTS: It was confirmed that 48 papers were submitted to 35 academic journals. There were 33 (68.8%) literature review articles, and analysis of secondary data was not carried out at all. In terms of empirical research, 8 (16.7%) surveys and 7 (14.6%) program developments were studied. As a result of analyzing these papers according to the research theme by research method, 17 (35.4%) papers on laws, systems, and policies were the most numerous. It was found that among the literature research papers on medical personnel were the most common, and among the empirical research papers, research on experts in information protection and medical personnel were the most common. CONCLUSIONS: We suggest that further research should be done in terms of social perception, human resource development, and technology development to improve risk management in medical information systems.

Nutritional regulation of renal lipogenic factor expression in mice: comparison to regulation in the liver and skeletal muscle.

Regulation of lipogenesis by pathophysiological factors in the liver and skeletal muscle is well understood; however, regulation in the kidney is still unclear. To elucidate nutritional regulation of lipogenic factors in the kidney, we measured the renal expression of lipogenic transcriptional factors and enzymes during fasting and refeeding in chow-fed and high-fat-fed mice. We also examined the regulatory effect of the liver X receptor (LXR) on the expression of lipogenic factors. The renal gene expression of sterol regulatory element-binding protein (SREBP)-1c and fatty acid synthase (FAS) was reduced by fasting for 48 h and restored by refeeding, whereas the mRNA levels of forkhead box O (FOXO)1/3 were increased by fasting and restored by refeeding. Accordingly, protein levels of SREBP-1, FAS, and phosphorylated FOXO1/3 were reduced by fasting and restored by refeeding. The patterns of lipogenic factors expression in the kidney were similar to those in the liver and skeletal muscle. However, this phasic regulation of renal lipogenic gene expression was blunted in diet-induced obese mice. LXR agonist TO901317 increased the lipogenic gene expression and the protein levels of SREBP-1 precursor and FAS but not nuclear SREBP-1. Moreover, increases in insulin-induced gene mRNA and nuclear carbohydrate-responsive element binding protein (ChREBP) levels were observed in the TO901317-treated mice. These results suggest that the kidney shows flexible suppression and restoration of lipogenic factors following fasting and refeeding in lean mice, but this is blunted in obese mice. LXR is involved in the renal expression of lipogenic enzymes, and ChREBP may mediate the response.

Transthyretin: A Transporter Protein Essential for Proliferation of Myoblast in the Myogenic Program.

Irregularities in the cellular uptake of thyroid hormones significantly affect muscle development and regeneration. Herein, we report indispensable role of transthyretin (TTR) in maintaining cellular thyroxine level. TTR was found to enhance recruitment of muscle satellite cells to the site of injury, thereby regulating muscle regeneration. Fluorescence-activated cell sorting (FACS) and immunofluorescence analysis of TTRwt (TTR wild type) and TTRkd (TTR knock-down) cells revealed that TTR controlled cell cycle progression by affecting the expression of Cyclin A2. Deiodinase 2 (D2) mediated increases in triiodothyronine levels were found to regulate the expression of myogenic marker, myogenin (MYOG). Moreover, use of a coumarin derivative (CD) revealed a significant reduction in cellular thyroxine, thereby indicating that TTR play a role in the transport of thyroxine. Taken together, these findings suggest that TTR mediated transport of thyroxine represents a survival mechanism necessary for the myogenic program. The results of this study will be highly useful to the strategic development of novel therapeutics to combat muscular dystrophies.

Effect of High Glucose on MUC5B expression in Human Airway Epithelial Cells.

OBJECTIVES: Excessive production of mucus results in plugging of the airway tract, which can increase morbidity and mortality in affected patients. In patients with diabetes, inflammatory airway disease appears with more frequent relapse and longer duration of symptoms. However, the effects of high glucose (HG) on the secretion of mucin in inflammatory respiratory diseases are not clear. Therefore, this study was conducted in order to investigate the effect and the brief signaling pathway of HG on MUC5B expression in human airway epithelial cells. METHODS: The effect and signaling pathway of HG on MUC5B expression were investigated using reverse transcriptase-polymerase chain reaction (RT-PCR), real-time PCR, enzyme immunoassay, and immunoblot analysis with specific inhibitors and small interfering RNA. RESULTS: HG increased MUC5B expression and epidermal growth factor receptor (EGFR) expression, and activated the phosphorylation of EGFR and p38 mitogen-activated protein kinase (MAPK). Pretreatment with EGFR inhibitor significantly attenuated the HG-induced phosphorylation of p38 MAPK, and pretreatments with p38 inhibitor or EGFR inhibitor significantly attenuated HG-induced MUC5B expression. In addition, knockdown of p38 MAPK by p38 MAPK siRNA significantly blocked HG-induced MUC5B expression. CONCLUSION: These findings suggest that HG induces MUC5B expression via the sequential activations of the EGFR/p38 MAPK signaling pathway in human airway epithelial cells.

Metformin prevents glucotoxicity by alleviating oxidative and ER stress-induced CD36 expression in pancreatic beta cells.

AIM/HYPOTHESIS: Cluster determinant 36 (CD36), a fatty acid transporter, was reported to have a pivotal role in glucotoxicity-induced beta cell dysfunction. However, little is known about how glucotoxicity influences CD36 expression, and it is unknown whether this action can be counteracted by metformin. In the present study, we showed that metformin counteracts glucotoxicity by alleviating oxidative and endoplasmic reticulum (ER) stress-induced CD36 expression. METHODS: We used primary rat islets as well as INS-1 cells for 72h to 24h with 30mM glucose, respectively. Thapsigargin was used as strong ER stressor, and Sulfo-N-succinimidyl oleate (SSO) and RNA interference were chosen for CD36 inhibition. Free fatty acid uptake was measured by radioisotope tracing technique. RESULTS: Exposure of isolated rat islets to high glucose (HG) for 3days decreased insulin and pancreatic duodenal homeobox1 (Pdx1) mRNA expression, with the suppression of glucose-stimulated insulin secretion (GSIS) along with elevation of reactive oxygen species (ROS) levels. Incubation with metformin restored insulin and Pdx1 mRNA expression with significant improvements in GSIS and decrease in ROS production. HG exposure in INS-1 cells increased free fatty acid uptake via induction of CD36 along with impaired insulin and Pdx1 mRNA expression. Moreover, thapsigargin also increased the induction of CD36 expression. Metformin blocked HG- and thapsigargin-induced CD36 expression. In addition, the simultaneous inhibition of intracellular ROS production by metformin or CD36 activation by SSO or CD36 siRNA significantly decreased the apoptotic response in HG-treated INS-1 cells. CONCLUSION/INTERPRETATION: In conclusion, metformin conferred protection against HG-induced apoptosis of pancreatic beta cells, largely by interfering with ROS production, and inhibited the CD36-mediated free fatty acid influx. This report provides evidence that the inhibition of CD36 may have potential therapeutic effects against hyperglycemia-induced beta cell damage in diabetes.

Methionine sulfoxide reductase B1 deficiency does not increase high-fat diet-induced insulin resistance in mice.

Methionine-S-sulfoxide reductase (MsrA) protects against high-fat diet-induced insulin resistance due to its antioxidant effects. To determine whether its counterpart, methionine-R-sulfoxide reductase (MsrB) has similar effects, we compared MsrB1 knockout and wild-type mice using a hyperinsulinemic-euglycemic clamp technique. High-fat feeding for eight weeks increased body weights, fat masses, and plasma levels of glucose, insulin, and triglycerides to similar extents in wild-type and MsrB1 knockout mice. Intraperitoneal glucose tolerance test showed no difference in blood glucose levels between the two genotypes after eight weeks on the high-fat diet. The hyperglycemic-euglycemic clamp study showed that glucose infusion rates and whole body glucose uptakes were decreased to similar extents by the high-fat diet in both wild-type and MsrB1 knockout mice. Hepatic glucose production and glucose uptake of skeletal muscle were unaffected by MsrB1 deficiency. The high-fat diet-induced oxidative stress in skeletal muscle and liver was not aggravated in MsrB1-deficient mice. Interestingly, whereas MsrB1 deficiency reduced JNK protein levels to a great extent in skeletal muscle and liver, it markedly elevated phosphorylation of JNK, suggesting the involvement of MsrB1 in JNK protein activation. However, this JNK phosphorylation based on a p-JNK/JNK level did not positively correlate with insulin resistance in MsrB1-deficient mice. Taken together, our results show that, in contrast to MsrA deficiency, MsrB1 deficiency does not increase high-fat diet-induced insulin resistance in mice.

The Glucotoxicity Protecting Effect of Ezetimibe in Pancreatic Beta Cells via Inhibition of CD36.

Inhibition of CD36, a fatty acid transporter, has been reported to prevent glucotoxicity and ameliorate high glucose induced beta cell dysfunction. Ezetimibe is a selective cholesterol absorption inhibitor that blocks Niemann Pick C1-like 1 protein, but may exert its effect through suppression of CD36. We attempted to clarify the beneficial effect of ezetimibe on insulin secreting cells and to determine whether this effect is related to change of CD36 expression. mRNA expression of insulin and CD36, intracellular peroxide level and glucose stimulated insulin secretion (GSIS) under normal (5.6 mM) or high glucose (30 mM) condition in INS-1 cells and primary rat islet cells were compared. Changes of the aforementioned factors with treatment with ezetimibe (20 µM) under normal or high glucose condition were also assessed. mRNA expression of insulin was decreased with high glucose, which was reversed by ezetimibe in both INS-1 cells and primary rat islets. CD36 mRNA expression was increased with high glucose, but decreased by ezetimibe in INS-1 cells and primary rat islets. Three-day treatment with high glucose resulted in an increase in intracellular peroxide level; however, it was decreased by treatment with ezetimibe. Decrease in GSIS by three-day treatment with high glucose was reversed by ezetimibe. Palmitate uptake following exposure to high glucose conditions for three days was significantly elevated, which was reversed by ezetimibe in INS-1 cells. Ezetimibe may prevent glucotoxicity in pancreatic ß-cells through a decrease in fatty acid influx via inhibition of CD36.