Non-target GC-MS analyses of fecal VOCs in NASH-hepatocellular carcinoma model STAM mice.

The increased incidence of obesity in the global population has increased the risk of several chronic inflammation-related diseases, including non-alcoholic steatohepatitis (NASH)-hepatocellular carcinoma (HCC). The progression from NASH to HCC involves a virus-independent liver carcinogenic mechanism; however, we currently lack effective treatment and prevention strategies. Several reports have suggested that fecal volatile organic compounds (VOCs) are strongly associated with NASH-HCC; therefore, we explored the biomarkers involved in its pathogenesis and progression. Fecal samples collected from control and NASH-HCC model STAM mice were subjected to headspace autosampler gas chromatography-electron ionization-mass spectrometry. Non-target profiling analysis identified diacetyl (2,3-butandione) as a fecal VOC that characterizes STAM mice. Although fecal diacetyl levels were correlated with the HCC in STAM mice, diacetyl is known as a cytotoxic/tissue-damaging compound rather than genotoxic or mutagenic; therefore, we examined the effect of bioactivity associated with NASH progression. We observed that diacetyl induced several pro-inflammatory molecules, including tumor necrosis factor-α, cyclooxygenase-2, monocyte chemoattractant protein-1, and transforming growth factor-ß, in mouse macrophage RAW264.7 and Kupffer KPU5 cells. Additionally, we observed that diacetyl induced α-smooth muscle actin, one of the hallmarks of fibrosis, in an ex vivo cultured hepatic section, but not in in vitro hepatic stellate TWNT-1 cells. These results suggest that diacetyl would be a potential biomarker of fecal VOC in STAM mice, and its ability to trigger the macrophage-derived inflammation and fibrosis may partly contribute to NASH-HCC carcinogenesis.

Apigenin Alleviates Endoplasmic Reticulum Stress-Mediated Apoptosis in INS-1 ß-Cells.

The improvement of type 2 diabetes mellitus induced by naturally occurring polyphenols, known as flavonoids, has received considerable attention. However, there is a dearth of information regarding the effect of the trihydroxyflavone apigenin on pancreatic ß-cell function. In the present study, the anti-diabetic effect of apigenin on pancreatic ß-cell insulin secretion, apoptosis, and the mechanism underlying its anti-diabetic effects, were investigated in the INS-ID ß-cell line. The results showed that apigenin concentration-dependently facilitated 11.1-mM glucose-induced insulin secretion, which peaked at 30 µM. Apigenin also concentration-dependently inhibited the expression of endoplasmic reticulum (ER) stress signaling proteins, CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) and cleaved caspase-3, which was elevated by thapsigargin in INS-1D cells, with peak suppression at 30 µM. This was strongly correlated with the results of flow cytometric analysis of annexin V/propidium iodide (PI) staining and DNA fragmentation analysis. Moreover, the increased expression of thioredoxin-interacting protein (TXNIP) induced by thapsigargin was remarkably reduced by apigenin in a concentration-dependent manner. These results suggest that apigenin is an attractive candidate with remarkable and potent anti-diabetic effects on ß-cells, which are mediated by facilitating glucose-stimulated insulin secretion and preventing ER stress-mediated ß-cell apoptosis, the latter of which may be possibly mediated by reduced expression of CHOP and TXNIP, thereby promoting ß-cell survival and function.

Increased Tropism of Extracellular Vesicles Derived from Palmitic Acid-Treated Hepatocytes to Activated Hepatic Stellate Cells.

Myofibroblast-like activated hepatic stellate cells (aHSCs), which produce collagen, a major cause of liver fibrosis, are specific target cells for antifibrotic treatment. Recently, several reports have indicated that extracellular vesicles (EVs) play important roles in cell-to-cell communication through their tropism for specific cells or organs. Therefore, the present study aimed to identify aHSC-directed EVs by focusing on cell-to-cell interactions in the liver under pathological conditions. EVs were derived from the hepatocyte cell line AML12 treated with or without palmitic acid (PA) and evaluated for their physical properties and uptake by the aHSC cell line LX-2. AML12-derived EVs had a mean particle diameter of 110-130 nm, negative charge, and expressed the exosomal makers CD9 and CD63. PA-treated AML12 cells released larger EVs with higher protein levels than those without PA treatment. The intracellular uptake efficacy of EVs derived from PA-treated AML12 cells into activated LX-2 cells was significantly higher than those without PA treatment. Our study revealed that PA treatment induces hepatocytes to release EVs with aHSC-tropism. These findings may contribute to the development of an EV-based drug delivery system (DDS) for aHSC-targeted therapy and provide new insights into the role of steatotic hepatocyte-derived EVs in physiological or pathophysiological functions.

Relationship between preoperative anxiety and onset of delirium after cardiovascular surgery in elderly patients: focus on personality and coping process.

BACKGROUND: Postoperative delirium is associated with increased mortality. Therefore, it is important to manage delirium during the entire perioperative period. Preoperative anxiety is associated with poor prognosis in postoperative patients who have undergone cardiovascular surgery. This study aims to investigate the relationship between preoperative anxiety and onset of delirium after cardiovascular surgery in elderly patients (aged 65 years or older), considering the individual psychological characteristics, such as personality and stress coping skills in response to anxiety, as confounding factors. METHODS: This prospective study included patients aged >65 years in a preoperative state before undergoing cardiovascular surgery. Subjects were divided into two groups based on whether they experienced postoperative delirium, or not. We compared clinical and demographic factors, preoperative psychiatric and psychological factors, and intraoperative and perioperative physical factors between the control and delirium groups. Multiple imputations were used to account for missing data. RESULTS: Out of 168 subjects enrolled in this study, 26 (15.5%) developed postoperative delirium. Univariate analysis showed significant differences in age (P = 0.027), cognitive function (P = 0.007), agreeableness (P = 0.029), and the Acute Physiology and Chronic Health Evaluation-II (APACHE-II) score (P = 0.023) between the delirium and control groups. Multiple logistic regression analysis did not identify a significant association between preoperative anxiety and the onset of postoperative delirium. However, age (odds ratio (OR) = 1.114, P = 0.018), agreeableness (OR = 0.555, P = 0.008), and the APACHE-II score (OR = 1.227, P = 0.008) were identified as risk factors for postoperative delirium. CONCLUSION: Agreeableness, one of the personality traits associated with preoperative anxiety, appears to be involved in the development of postoperative delirium as an independent psychological factor, regardless of age or physical factors.

Caffeine-induced inversion of prostaglandin E2 effects on hepatic stellate cell activation.

BACKGROUND AND AIMS: Liver inflammation leads to the activation of hepatic stellate cells (HSCs), resulting in the development of liver fibrosis. The present study aimed to investigate the effects of prostaglandin E2 (PGE2), which is biosynthesized by Kupffer cells, hepatocytes, and HSCs during inflammation, on HSC activation, including its combinatory effect with caffeine. METHODS: HSCs isolated from mice were activated by culturing in a medium supplemented with 10% fetal bovine serum for 7 days on plastic plates. The activation of HSCs was evaluated by immunofluorescence of α-smooth muscle actin in HSCs. Comprehensive gene expression analysis was performed using mRNA-sequencing to compare HSCs cultured for 1 or 7 days, with or without PGE2, caffeine, or both. RESULTS: PGE2 (1 µM) facilitated the activation of HSCs but inhibited the HSC activation in the presence of caffeine (3 mM). Comprehensive gene expression analysis revealed that HSCs treated with PGE2 in the presence of caffeine were classified in the same class as HSCs cultured for 1 day, i.e., quiescent HSCs. In contrast, PGE2 did not exhibit an inhibitory effect on HSC activation when co-treated with any isoform-specific phosphodiesterase inhibitors. Although the adenylate cyclase inhibitor 2',5'-dideoxyadenosine suppressed the elevation of intracellular cAMP level induced by PGE2 in the presence of caffeine, it had no effect on the inhibition of HSC activation by PGE2 plus caffeine. CONCLUSION: The effect of PGE2 on HSC activation is changed from facilitatory to inhibitory when combined with caffeine, suggesting that caffeine may effectively suppress liver fibrosis during inflammation.

Differentiation-inducing factor-1 prevents hepatic stellate cell activation through inhibiting GSK3ß inactivation.

Differentiation-inducing factor-1 (DIF-1), a morphogen produced by the cellular slime mold Dictyostelium discoideum, is a natural product that has attracted considerable attention for its antitumor properties. Here, we report a novel inhibitory effect of DIF-1 on the activation of hepatic stellate cells (HSCs) responsible for liver fibrosis. DIF-1 drastically inhibited transdifferentiation of quiescent HSCs into myofibroblastic activated HSCs in a concentration-dependent manner, thus conferring an antifibrotic effect against in the liver. Neither SQ22536, an adenylate cyclase inhibitor, nor ODQ, a guanylate cyclase inhibitor, showed any effect on the inhibition of HSC activation by DIF-1. In contrast, TWS119, a glycogen synthase kinase 3ß (GSK3ß) inhibitor, attenuated the inhibitory effect of DIF-1. Moreover, the level of inactive GSK3ß (phosphorylated at Ser9) was significantly reduced by DIF-1. DIF-1 also inhibited nuclear translocation of ß-catenin and reduced the level of non-phospho (active) ß-catenin. These results suggest that DIF-1 inhibits HSC activation by disrupting the Wnt/ß-catenin signaling pathway through dephosphorylation of GSK3ß. We propose that DIF-1 is a possible candidate as a therapeutic agent for preventing liver fibrosis.

Alleviation of mechanical stress-induced allodynia by improving blood flow in chronic constriction injury mice.

Reduced blood flow in the skin is observed in patients with neuropathic pain and in animal models. The aim of the present study was to elucidate the relationship between reduced skin blood flow and neuropathic pain in mice with a chronic constriction injury (CCI). Noradrenaline-induced contraction was enhanced in isolated plantar arteries ipsilateral to the CCI surgery compared to the contralateral arteries. Ten µM hydralazine, a peripheral vasodilator, at improved the enhanced contractile response in the ipsilateral arteries. The plantar blood flow in vivo was lower on the ipsilateral side of the CCI mice than on the contralateral side, and a 50% paw withdrawal threshold, as measured using the von Frey filament test, was lower on the former than on the latter side. An intraperitoneal injection (i.p.) of hydralazine (1 mg/kg) or phentolamine (5 mg/kg) improved blood flow in the skin and hyperalgesia in the ipsilateral plantar. In adrenalectomized CCI mice, plantar blood flow in the skin on the ipsilateral side was increased compared to in sham-operated mice, which was accompanied by alleviation of hyperalgesia. Moreover, the enhanced contractile response to noradrenaline was also observed in the ipsilateral plantar arteries isolated from the adrenalectomized CCI mice. Either hydralazine (1 mg/kg, i.p.) or an adrenalectomy barely affected mean arterial pressure in the CCI mice, whereas phentolamine (5 mg/kg, i.p.) lowered it. These results suggest that reduced blood flow in the skin contributes to neuropathic pain and that improving that blood flow with peripheral vasodilators, such as hydralazine, can alleviate it.

[A case of metastatic uveal melanoma of the liver and digestive tract].

Metastasis of uveal melanoma of the digestive tract is rare. We report a case of a patient with metastatic uveal melanoma of the liver and digestive tract. A 68-year-old man was admitted with primary complaint of appetite loss and fatigue. Abdominal computed tomography revealed a 13-cm diameter tumor in the right lobe of the liver. We diagnosed him with metastatic uveal melanoma. We performed a liver tumor biopsy and diagnosed metastatic melanoma;we found distant metastases in the stomach, duodenum, and rectum on endoscopic biopsy. We administered systemic chemotherapy [DACa-Tam therapy (Dacarbazine, 220mg/m2×3 days;Nimustine, 60mg/m2×1 day;Carboplatin area under the curve (AUC) =4×1 day;Tamoxifen, 40mg/day×3 days)]. Prognosis is unfavorable in approximately half of the patients with liver metastases that occur through blood circulation. The patient died of liver failure two months after the diagnosis.

Caffeine Suppresses the Activation of Hepatic Stellate Cells cAMP-Independently by Antagonizing Adenosine Receptors.

During liver injury, hepatic stellate cells (HSCs) are activated by various cytokines and transdifferentiated into myofibroblast-like activated HSCs, which produce collagen, a major source of liver fibrosis. Therefore, the suppression of HSC activation is regarded as a therapeutic target for liver fibrosis. Several epidemiological reports have revealed that caffeine intake decreases the risk of liver disease. In this study, therefore, we investigated the effect of caffeine on the activation of primary HSCs isolated from mice. Caffeine suppressed the activation of HSC in a concentration-dependent manner. BAPTA-AM, an intracellular Ca2+ chelator, had no effect on the caffeine-induced suppression of HSC activation. None of the isoform-selective inhibitors of phosphodiesterase1 to 5 affected changes in the morphology of HSC during activation, whereas CGS-15943, an adenosine receptor antagonist, inhibited them. Caffeine had no effect on intracellular cAMP level or on the phosphorylation of extracellular signal-regulated kinase (ERK)1/2. In contrast, caffeine significantly decreased the phosphorylation of Akt1. These results suggest that caffeine inhibits HSC activation by antagonizing adenosine receptors, leading to Akt1 signaling activation.

Clinical usefulness of ursodeoxycholic acid for Japanese patients with autoimmune hepatitis.

AIM: To evaluate the therapeutic effects of ursodeoxycholic acid (UDCA) on autoimmune hepatitis (AIH). METHODS: A total 136 patients who were diagnosed with AIH were included in our study. All of the patients underwent a liver biopsy, and had at least a probable diagnosis on the basis of either the revised scoring system or the simplified scores. Initial treatment included UDCA monotherapy (Group U, n = 48) and prednisolone (PSL) monotherapy (Group P, n = 88). Group U was further classified into two subgroups according to the effect of UDCA: Patients who had achieved remission induction with UDCA monotherapy and showed no sign of relapse (Subgroup U1, n = 34) and patients who additionally received PSL during follow-up (Subgroup U2, n = 14). We compared the clinical and histological findings between each groups, and investigated factors contributing to the response to UDCA monotherapy. RESULTS: In Group U, 34 patients (71%) achieved and maintained remission over 49 (range: 8-90) mo (Subgroup U1) and 14 patients (29%) additionally received PSL (Subgroup U2) during follow-up. Two patients in Subgroup U2 achieved remission induction once but additionally required PSL administration because of relapse (15 and 35 mo after the start of treatment). The remaining 12 patients in Subgroup U2 failed to achieve remission induction during follow-up, and PSL was added during 7 (range: 2-18) mo. Compared with Subgroup U2, Subgroup U1 had significantly lower alanine aminotransferase (ALT) levels at onset (124 IU/L vs 262 IU/L, P = 0.023) and a significantly higher proportion of patients with mild inflammation (A1) on histological examination (70.6% vs 35.7%, P = 0.025). When multivariate analysis was performed to identify factors contributing to the response to UDCA monotherapy, only a serum ALT level of 200 IU/L or lower was found to be associated with a significant difference (P = 0.013). CONCLUSION: To prevent adverse events related to corticosteroids, UDCA monotherapy for AIH needs to be considered in patients with a serum ALT level of 200 IU/L or lower.

G-protein coupled estrogen receptor-mediated non-genomic facilitatory effect of estrogen on cooling-induced reduction of skin blood flow in mice.

An enhanced vasoconstrictor activity of cutaneous arteries participates in the reduction of skin blood flow induced by cooling stimulation. Raynaud's phenomenon, which is characterized by intense cooling-induced constriction of cutaneous arteries, is more common in women during the period from menarche to menopause. We thus investigated the effect of 17ß-estradiol (E2) on cooling-induced reduction of plantar skin blood flow (PSBF) in mouse in vivo. Ovariectomized female ddY mice, anaesthetized with pentobarbital, were treated with tetrodotoxin for eliminating the sympathetic nerve tone and artificially ventilated. The PSBF was measured by laser Doppler flowmetry. Cooling air temperature around the foot from 25 to 20, 15, or 10°C decreased the PSBF in a temperature-dependent manner, which was suppressed by the specific α2C-adrenoceptor antagonist MK-912. When E2 was intravenously administered as a bolus followed by a constant infusion for 10min just before the cooling stimulation, the cooling-induced reduction of PSBF was facilitated by E2 in a dose-dependent manner. The facilitatory effect of E2 was not induced after the treatment with MK-912. Similar facilitatory effect was induced by an intravenous application of G-1, an agonist of G protein-coupled estrogen receptor (GPER, also termed GPR30). Moreover, the facilitatory effect of E2 was abolished by the GPER antagonist G15. These results suggest that acute administration of E2 leads to the facilitation of cooling-induced, α2C-adrenoceptor-mediated reduction of skin blood flow via the activation of the non-genomic estrogen receptor GPER.

[Regulation of Lipid Metabolism by Diacylglycerol Kinases in Pancreatic ß-cells].

The appropriate secretion of insulin from pancreatic ß-cells is essential for regulating blood glucose levels. Glucose-stimulated insulin secretion (GSIS) involves the following steps: Glucose uptake by pancreatic ß-cells is metabolized to produce ATP. Increased ATP levels result in the closure of ATP-sensitive K(+) (KATP) channels, resulting in membrane depolarization that activates voltage-dependent Ca(2+) channels to subsequently trigger insulin secretion. In addition to this primary mechanism through KATP channels, insulin secretion is regulated by cyclic AMP and diacylglycerol (DAG), which mediate the effects of receptor agonists such as GLP-1 and acetylcholine. Glucose by itself can also increase the levels of these second messengers. Recently, we have shown an obligatory role of diacylglycerol kinase (DGK), an enzyme catalyzing the conversion of DAG to phosphatidic acid, in GSIS. Of the 10 known DGK isoforms, we focused on type-I DGK isoforms (i.e., DGKα, DGKß, and DGKγ), which are activated by Ca(2+). The protein expression of DGKα and DGKγ was detected in mouse pancreatic islets and the pancreatic ß-cell line MIN6. Depletion of these DGKs by a specific inhibitor or siRNA decreased both [Ca(2+)]i and insulin secretion in MIN6 cells. Similar [Ca(2+)]i responses were induced by DiC8, a membrane-permeable DAG analog. These results suggest that DGKα and DGKγ play crucial roles in insulin secretion, and that their depletion impairs insulin secretion through DAG accumulation. In this article, we review the current understanding of the roles of DAG- and DGK-signaling in pancreatic ß-cells, and discuss their pathophysiological roles in the progression of type-2 diabetes.

Depression of type I diacylglycerol kinases in pancreatic ß-cells from male mice results in impaired insulin secretion.

Diacylglycerol kinase (DGK) catalyzes the conversion of diacylglycerol (DAG) to phosphatidic acid. This study investigated the expression and function of DGK in pancreatic ß-cells. mRNA expression of type I DGK isoforms (α, ß, γ) was detected in mouse pancreatic islets and the ß-cell line MIN6. Protein expression of DGKα and DGKγ was also detected in mouse ß-cells and MIN6 cells. The type I DGK inhibitor R59949 inhibited high K(+)- and glucose-induced insulin secretion in MIN6 cells. Moreover, single knockdown of DGKα or DGKγ by small interfering RNA slightly but significantly decreased glucose- and high K(+)-induced insulin secretions, and the double knockdown further decreased them to the levels comparable with those induced by R59949. R59949 and DiC8, a membrane permeable DAG analog, decreased intracellular Ca(2+) concentration elevated by glucose and high K(+) in MIN6 cells. Real-time imaging in MIN6 cells expressing green fluorescent protein-tagged DGKα or DGKγ showed that the DGK activator phorbol 12-myristate 13-acetate rapidly induced translocation of DGKγ to the plasma membrane, whereas high K(+) slowly translocated DGKα and DGKγ to the plasma membrane. R59949 increased the DAG content in MIN6 cells when stimulated with high KCl, whereas it did not increase the DAG content but decreased the phosphatidic acid content when stimulated with high glucose. Finally, R59949 was confirmed to inhibit high K(+)-induced insulin secretion from mouse islets and glucose-induced insulin secretion from rat islets. These results suggest that DGKα and DGKγ are present in ß-cells and that the depression of these DGKs causes a decrease in intracellular Ca(2+) concentration, thereby reducing insulin secretion.

[A long-term survival case of liver epithelioid hemangioendothelioma with multiple lung metastases that regressed by long-term administration of interleukin-2].

A patient was a 46-year-old man. Multiple lung tumors had been pointed out on a medical examination at age 24. He came to our hospital for further examination. Multiple liver and lung tumors were found out, and epithelioid hemangioendothelioma (EHE) derived from the liver was diagnosed by biopsy. At first we gave recombinant interleukin-2 (rIL-2) by intra-arterial and local injection and then continued it by intramuscular injection for 22 years as maintenance therapy. The tumors have regressed, with partial necrosis. EHE is a rare tumor, but we do not have a standard antitumor therapy except surgical resection. This case suggests that rIL-2 may become a new therapy for EHE. We think that the report of the long-term survival of a case of EHE in which rIL-2 treatment was effective is extremely valuable.

[Case of lymphangioleiomyomatosis associated with protein-losing gastroenteropathy].

A 29-year-old woman was referred to our hospital for the intensive examination of leg edema and hypoproteinemia. CT scan of showed multiple thin-walled cysts in both lungs, suggesting lymphangioleiomyomatosis. CT scan of the abdomen, lymphoscintigraphy showed enlarged abdominal lymph nodes. Protein loss from the gastrointestinal tract was documented by measurement of the clearance of alpha-1 antitrypsin from the plasma using a 72 h stool collection and (99m)Tc human serum albumin scintigraphy. We thought that secondary lymphangiectasia with lymphangioleiomyomatosis caused protein-losing gastroenteropathy. Dietary therapy resulted in symptomatic improvement.

Dual effect of nitric oxide on ATP-sensitive K+ channels in rat pancreatic beta cells.

We have previously shown that NO has stimulatory and inhibitory effects on insulin secretion at low and high concentrations, respectively. The present study investigated effects of NO on K ATP channels of rat beta cells by patch clamp analysis to elucidate the mechanism for the dual effect. NOC7 at 0.5 microM suppressed K ATP channels activated by diazoxide in the cell-attached and perforated whole-cell modes but failed to suppress them in the inside-out mode. The inhibitory effect in the cell-attached mode was abolished by the soluble guanylate cyclase inhibitor ODQ and by the protein kinase G inhibitor KT5823. Moreover, 0.5 microM NOC7 failed to suppress the channel activity in the presence of the mitochondrial uncoupler FCCP. In contrast, 10 microM NOC7 activated K ATP channels in the cell-attached and perforated whole-cell modes, although it had no effect on the channels in the inside-out mode. The K ATP currents evoked by 10 microM NOC7 in the cell-attached mode were not inhibited by ODQ. The dual effect of NOC7 at 0.5 and 10 microM was observed in the same patch. Taken together, these results suggest that low-concentration NO exerts an inhibitory effect on K ATP channels of beta cells, which is induced through the cGMP/protein kinase G pathway, whereas high-concentration NO activates K ATP channels through the mechanism independent of cGMP.

Intrahepatic expression of the co-stimulatory molecules programmed death-1, and its ligands in autoimmune liver disease.

Liver-infiltrating T cells play an essential role in the immunopathogenesis of autoimmune liver disease. Programmed death-1 (PD-1) and its ligands, B7-H1/PD-L1 and B7-DC/PD-L2, are new CD28-B7 family members that are involved in the regulation of immune responses. The ligation of PD-1 inhibits T-cell receptor-mediated T cell proliferation and cytokine production, and PD-1-deficient mice develop various organ-specific autoimmune diseases. To investigate the expressions of PD-1 and its ligands in autoimmune liver disease, in particular autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC), immunohistochemical analysis was performed. Liver biopsy specimens obtained from 17 patients with AIH and PBC were studied. PD-1 was expressed on more than half of the liver-infiltrating T cells within the portal tract. Some of the intrahepatic T cells expressed B7-H1 in patients with AIH and PBC. B7-H1 and B7-DC were mainly expressed on some Kupffer cells (KC) and liver sinusoidal endothelial cells (LSEC) within the sinusoids and their expression was upregulated in autoimmune liver disease. These results suggest that the interaction of PD-1 on T cells with increased expression of B7-H1 and B7-DC on KC and LSEC might be involved in the downregulation of autoreactive lymphocytes and result in the regulation of pathogenesis in autoimmune liver disease.

Passive stretching produces Akt- and MAPK-dependent augmentations of GLUT4 translocation and glucose uptake in skeletal muscles of mice.

Muscle contraction is accompanied by passive stretching or deformation of cells and tissues. The present study aims to clarify whether or not acute passive stretching evokes glucose transporter 4 (GLUT4) translocation and glucose uptake in skeletal muscles of mice. Passive stretching mainly induced GLUT4 translocation from an intracellular membrane-rich fraction (PF5) to a plasma membrane-rich fraction (F2) and accelerated glucose uptake in hindlimb muscles; whereas electrical stimulation, which mimics physical exercise in vivo, and insulin, each induced GLUT4 translocation from an intracellular membrane-rich fraction (PF5) to a fraction rich in plasma membrane (F2), and to one rich in transverse tubules (PF3), along with subsequent glucose uptake. Mechanical stretching increased phosphorylation of Akt and p38 mitogen-activated protein kinase (p38 MAPK), but it had no apparent effect on the activity of AMP-activated protein kinase (AMPK). Electrical stimulation augmented the activity of not only AMPK but also phosphorylation of Akt and p38 MAPK. Our results suggest that passive stretching produces translocation of GLUT4 mainly from the fraction rich in intracellular membrane to that rich in plasma membrane, and that the glucose uptake could be Akt- and p38 MAPK-dependent, but AMPK-independent manners.