Tomohisa Ishikawa

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.

Although an aberrant reduction in pancreatic β‐cell mass contributes to the pathogenesis of diabetes, the mechanism underlying the regulation of β‐cell mass is poorly understood. Here, we show that diacylglycerol kinase δ (DGKδ) is a key enzyme in the regulation of β‐cell mass. DGKδ expression was detected in the nucleus of β‐cells. We developed β‐cell‐specific DGKδ knockout (βDGKδ KO) mice, which showed lower blood glucose, higher plasma insulin levels, and better glucose tolerance compared to control mice. Moreover, an increased number of small islets and Ki‐67‐positive islet cells, as well as elevated cyclin B1 expression in the islets, were detected in the pancreas of βDGKδ KO mice. DGKδ knockdown in the β‐cell line MIN6 induced significant increases in bromodeoxyuridine (BrdU) incorporation and cyclin B1 expression. Finally, we confirmed that streptozotocin‐induced hyperglycemia and β‐cell loss were alleviated in βDGKδ KO mice. Thus, suppressing the expression or enzymatic activity of DGKδ that functions as a suppressor of β‐cell proliferation could be a novel therapeutic approach to increase β‐cell mass for the treatment of diabetes.

Objectives We aimed to investigate the association between the digit symbol test (DST) and clinical characteristics, including the nutritional status of LC patients. Methods Fifty-nine cirrhotic patients without a history of overt hepatic encephalopathy were retrospectively evaluated. We examined neuropsychological abnormalities (NPAs) using the DST. We also estimated the detailed nutritional status using the Food Frequency Questionnaire (FFQ). The patients were divided into two groups according to their DST status: patients with normal DST scores (DST-Nor group, n=45) and those with abnormal DST scores (DST-Abn group, n=14). The clinical and nutritional findings of the two groups were compared. Results Overall, 14 (23.7%) patients had a DST abnormality. There were significant differences between the two groups in serum albumin (Alb; p=0.0043), valine (Val; p=0.0016), leucine (Leu; p=0.0078), isoleucine (Ile; p=0.0022), the molar ratio of total branched-chain amino acids to tyrosine (BTR; p=0.00025), total-bilirubin (T-Bil; p=0.0071), prothrombin time (%) (PT; p=0.028), and serum sodium (Na; p=0.035). A multivariate analysis found the BTR to be the only independent predictor of a DST abnormality (hazard ratio, 9.24; p<0.031). An FFQ analysis, revealed that the nutritional findings of patients with and without a DST abnormality, were similar. Conclusion The BTR was useful for predicting the risk of NPAs, as defined by a DST abnormality. The risk of NPAs may be estimated by monitoring the BTR.

Sialidase cleaves sialic acid residues from a sialoglycoconjugate: oligosaccharides, glycolipids and glycoproteins that contain sialic acid. Histochemical imaging of the mouse pancreas using a benzothiazolylphenol-based sialic acid derivative (BTP3-Neu5Ac), a highly sensitive histochemical imaging probe used to assess sialidase activity, showed that pancreatic islets have intense sialidase activity. The sialidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (DANA) remarkably enhances glutamate release from hippocampal neurons. Since there are many similar processes between synaptic vesicle exocytosis and secretory granule exocytosis, we investigated the effect of DANA on insulin release from β-cells. Insulin release was induced in INS-1D cells by treatment with 8.3 mM glucose, and the release was enhanced by treatment with DANA. In a mouse intraperitoneal glucose tolerance test, the increase in serum insulin levels was enhanced by intravenous injection with DANA. However, under fasting conditions, insulin release was not enhanced by treatment with DANA. Calcium oscillations induced by 8.3 mM glucose treatment of INS-1D cells were not affected by DANA. Blood insulin levels in sialidase isozyme Neu3-deficient mice were significantly higher than those in WT mice under ad libitum feeding conditions, but the levels were not different under fasting conditions. These results indicate that DANA is a glucose-dependent potentiator of insulin secretion. The sialidase inhibitor may be useful for anti-diabetic treatment with a low risk of hypoglycemia.

During liver injury, quiescent hepatic stellate cells (qHSCs) are activated by various cytokines and transdifferentiated into myofibroblast-like activated HSCs (aHSCs), which produce collagen, leading to liver fibrosis. Accordingly, the reversion of aHSC is expected to be a therapeutic target for liver fibrosis. Several epidemiological reports have suggested that the intake of caffeine decreases the risk of liver fibrosis. In the present study, therefore, we investigated the effect of caffeine on the reversion of aHSCs into qHSC. We used aHSC which was isolated from mice as qHSC and activated by culturing in DMEM supplemented with 10% FBS for 7 days. Caffeine (0.1–10 mM) decreased the expression of α-smooth muscle actin (α-SMA) and type I collagen a1 (COLIa1), an index of aHSC, in a concentration-dependent manner. Caffeine also increased the expression of matrix metalloproteinase-9 (MMP-9), an index of qHSC. Similarly to caffeine, the adenosine receptor inhibitor CGS-15943 had also significant effects on the expression of α-SMA, COLIa1 and MMP-9. These results suggest that caffeine induces the reversion of aHSC in a concentration-dependent manner via antagonizing adenosine receptors.