Ken-Ichiro Fukumitsu

Metabolic abnormalities in the genetically obese and diabetic Otsuka Long-Evans Tokushima fatty rat can be prevented and reversed by α-glucosidase inhibitor

The recently developed Otsuka Long-Evans Tokushima Fatty (OLETF) rat is known to develop insulinopenic diabetes after a prolonged period in a condition resembling non-insulin-dependent diabetes mellitus (NIDDM). We examined the effect of pharmacological intervention with a potent intestinal alpha-glucosidase inhibitor, acarbose, on the metabolic and histopathologic changes in this rat model. The first two groups of rats received an acarbose-rich diet (150 mg/100 g normal chow) from 12 weeks of age (ie, before the onset of diabetes) or from 28 weeks of age (ie, after the onset of diabetes), while a third group received the acarbose-rich diet for the initial 16 weeks only (from 12 to 28 weeks of age). A control group received standard rat chow. Acarbose-fed rats gained less weight or lost weight despite increased food intake when switched to the acarbose-rich diet. Acarbose also reduced visceral adipose depots and fasting triglyceride (TG), glucose, and insulin levels. At the end of the study at 72 weeks, the pancreatic wet weight and insulin content were significantly higher in the treated groups versus control rats. The morphological changes observed in control rats, such as atrophy of the pancreas and reduced number and size of islets, were not present in acarbose-treated rats. Rats fed acarbose from 12 to 28 weeks of age gradually gained weight after switching to standard chow, and hyperinsulinemia, hyperglycemia, and hyperlipidemia appeared (in that order). The pancreatic insulin content in these rats was significantly higher and the visceral adipose depot was significantly smaller than in control rats. Our study demonstrates that acarbose prevented and reversed the metabolic derangement and histopathological changes in genetically diabetic rats. Moreover, treatment with acarbose even for a short period produced a marked delay in the development of insulin insensitivity and frank diabetes.

Defects of cholecystokinin (CCK)-A receptor gene expression and CCK-A receptor-mediated biological functions in Otsuka Long-Evans Tokushima Fatty (OLETF) rats.

Abstract: Recent studies in genetically obese and diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats suggest defects of cholecystokinin (CCK)-A receptor gene expression and CCK-A receptor-mediated biological functions such as pancreatic juice, protein, and gastric acid secretion. The present studies were undertaken to further examine CCK-A receptor gene expression and CCK-A receptor-mediated biological functions in the pancreas, stomach, and brain of OLETF rats. Expression of the CCK-A receptor gene could not be detected in the stomach, pancreas and brain by the reverse-transcription polymerase chain reaction (RT-PCR) method and Southern blotting of the PCR products. Southern blot analysis of genomic DNA from OLETF and control Long-Evans Tokushima Otsuka (LETO) rats with CCK-A receptor fragment as a probe revealed different restriction bands. Expression of the CCK-B receptor gene was observed in the stomach, pancreas, and brain in both OLETF and LETO rats by the RT-PCR method, with expression of the CCK-B receptor gene markedly enhanced in OLETF rats compared with that in LETO rats. Consistent with the defect of CCK-A receptor gene expression, CCK-A receptor-mediated biological functions were not observed in these organs. Perfused exocrine and endocrine pancreas of OLETF rats were insensitive to CCK stimulation but not to carbamylcholine stimulation. Basal gastric acid and pepsinogen secretions in OLETF rats were higher than in LETO rats. OLETF rats showed a significantly higher average daily food intake, gained body weight faster, and were heavier than LETO rats. The present study confirmed that OLETF rats have CCK-A receptor gene anomalies and demonstrated deficient CCK-A receptor-mediated biological function in the pancreas, stomach, and brain.

Oleic acid-induced Pancreatitis alters expression of transforming growth factor-β1 and Extracellular matrix components in rats

Introduction and Aims Extracellular matrix (ECM) components participate in the process of tissue repair and development of fibrosis in the pancreas. We studied the production kinetics of ECM components and transforming growth factor (TGF)–&bgr;1 and identified their production sites in the pancreas following pancreatitis. Methodology Pancreatitis was induced in rats by a single intraductal infusion of oleic acid. Gene expression of TGF-&bgr;s and ECM components was studied by northern blotting. Pancreatic stellate cell activation was assessed by immunostaining for &agr;-smooth muscle actin (&agr;SMA) and desmin. Results Gene expression of TGF-&bgr;s and ECM components was increased in association with pancreatic fibrosis after 1–2 weeks and remained higher than the control levels for the ensuing 12 weeks. Both &agr;SMA and desmin were strongly immunostained around small vessels and faintly stained in mesenchymal cells and tubular complexes at 1 week. The combination of staining for &agr;SMA plus in situ hybridization for procollagen type III mRNA revealed that procollagen type III mRNA was expressed in both &agr;SMA-positive and &agr;SMA-negative cells in the mesenchyma. Conclusions Our findings demonstrate that expression of genes for both TGF-&bgr;s and ECM components was increased and that both &agr;SMA-positive myofibroblasts and mesenchymal cells are the major sources of ECM components after pancreatitis.

Treatment for Hyperglycemia Promotes Pancreatic Regeneration in Rats Without CCK-1 Receptor Gene Expression

Introduction and Aim Recent studies have suggested that CCK is not essential for normal pancreatic growth in mice. We examined whether the treatment of hyperglycemia participates in a non-CCK-1-receptor–mediated mechanism of pancreatic regeneration after partial (30%) pancreatectomy (Px) with use of Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an animal model for type 2 diabetes mellitus without CCK-1 receptor gene expression. Methodology Male OLETF rats were divided into five groups at 24 weeks of age. The first group was killed to examine the pancreas at 24 weeks of age (PrePx). The second group underwent a midline laparotomy and received a standard rat chow (ShamPx). The remaining three groups of rats received one of the following three treatments after Px: a standard rat chow (PxC), a diet containing acarbose (PxA), or a standard rat chow and once-daily subcutaneous injection of insulin (PxI) for 8 weeks. Results PxC rats had significantly higher serum glucose levels than did PxA and PxI rats. Pancreatic weight and pancreatic contents of protein in PxA and PxI rats were significantly higher than in PxC rats. The pancreas in PxC rats was atrophic, and marked inflammatory cell infiltration was observed in the pancreas. In addition, tumor necrosis factor-&agr; (TNF&agr;) was expressed in the inflammatory cells, acinar cells, and islets in PxC rats. However, histologic alterations, including expression of TNF&agr;, remained at a minimum in PxA and PxI rats. Conclusion We conclude that the control of serum glucose levels plays an important role in preventing pancreatic atrophy and participates in the non-CCK-1-receptor–mediated mechanisms of pancreatic growth in rats.

Chronic Oral Administration of Protease Inhibitor Decreases CCK-A Receptor mRNA Expression but Increases Pancreatic Growth in Rats

It is well-known that chronic oral administration of trypsin inhibitors induces pancreatic hypertrophy and hyperplasia via stimulation of endogenous cholecystokinin (CCK) release. Because the growth-promoting effect of CCK on the pancreas is specifically mediated by the CCK-A receptor, we examined the plasma CCK concentrations, the expression of CCK mRNA in the intestine and CCK-A receptor mRNA in the pancreas, and pancreatic growth in rats after chronic oral administration of synthetic protease inhibitor (PI). PI at a dose of 100 mg/kg body weight was administered via an orogastric tube once daily for 20 days. Plasma CCK concentrations at 24 hours after the first PI administration were significantly higher than those in randomly fed rats (6.57 ± 0.67 pmol/L vs 4.31 ± 0.51 pmol/L;p < 0.001), and further increased to 14.24 ± 1.63 pmol/L after PI for 10 days and decreased to 10.05 ± 0.72 pmol/L after 15 days of PI administration. Treatment with PI for 20 days significantly increased the pancreatic weight, and the total pancreatic protein and DNA content by 190%, 290%, and 170%, respectively, when compared to the control rats. Chronic oral administration of PI, however, reduced CCK-A receptor mRNA expression in the pancreas by 60%. These findings suggest that chronic oral administration of PI induces an elevation of endogenous CCK release and stimulates pancreatic growth, but down-regulates the biosynthesis of CCK-A receptor at the transcriptional level in the pancreas.

Cholecystokinin‐1 receptor protein up‐regulation during pancreatic regeneration after acute haemorrhagic pancreatitis in rats

Background  Cholecystokinin (CCK) plays an important role in regeneration after acute pancreatitis in rats. The present study was aimed to elucidate the role of CCK‐1 receptor (CCK‐1R) in acute pancreatitis. We investigated the serial changes in CCK‐1R mRNA and protein levels and their immunolocalization after acute haemorrhagic pancreatitis induced in male Wistar rats by retrograde intraductal infusion of 4% sodium taurocholate (100 µL 100 g−1 body weight).