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Purpose: The effects of statins on insulin resistance (IR) and type 2 diabetes mellitus (T2DM) are still controversial and its effects on pancreatic fibrosis are poorly defined. The purpose of this study is to examine the effects of atorvastatin on these issues using the Otsuka Long-Evans Tokushima Fatty (OLETF) rat, an animal model of IR, T2DM and pancreatic fibrosis., Methods: Male OLETF rats were divided into 2 groups at 6weeks of age. The first group received a standard diet until the end of experimental period at age 28weeks. The second group was given a diet containing 0.05% atorvastatin from 6weeks of age, before the onset of IR and pancreatic fibrosis. The age-matched Long-Evans Tokushima Otsuka rats without presence of IR, T2DM and pancreatic fibrosis, received a standard diet and were used as a normal control., Results: Atorvastatin slightly decreased serum fasting glucose and insulin levels, but significantly improved index of IR compared with the untreated OLETF rats. In addition, atorvastatin markedly decreased transforming growth factor-β1 mRNA expression, myeloperoxidase activity and proportion of fibrotic area, and elevated superoxide dismutase activity in the pancreas compared with the untreated OLETF rats., Conclusions: These findings suggest that atorvastatin exerts favorable influence on progression of IR and pancreatic inflammation and fibrosis via pleiotropic effect such as anti-oxidative property., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aim: To examine the effects of pancreatic rest, stimulation and rest/stimulation on the natural course of recovery after acute pancreatitis., Methods: Acute hemorrhagic pancreatitis (AP) was induced in male rats by intraductal infusion of 40 μL/100 g body weight of 3% sodium taurocholate. All rats took food ad libitum. At 24 h after induction of AP, rats were divided into four groups: control (AP-C), pancreas rest (AP-R), stimulation (AP-S), and rest/stimulation (AP-R/S). Rats in the AP-C, AP-R and AP-S groups received oral administration of 2 mL/kg body weight saline, cholecystokinin (CCK)-1 receptor antagonist, and endogenous CCK release stimulant, respectively, twice daily for 10 d, while those in the AP-R/S group received twice daily CCK-1 receptor antagonist for the first 5 d followed by twice daily CCK release stimulant for 5 d. Rats without any treatment were used as control group (Control). Biochemical and histological changes in the pancreas, and secretory function were evaluated on day 12 at 24 h after the last treatment., Results: Feeding ad libitum (AP-C) delayed biochemical, histological and functional recovery from AP. In AP-C rats, bombesin-stimulated pancreatic secretory function and HOMA-β-cell score were significantly lower than those in other groups of rats. In AP-R rats, protein per DNA ratio and pancreatic exocrine secretory function were significantly low compared with those in Control rats. In AP-S and AP-R/S rats, the above parameters recovered to the Control levels. Bombesin-stimulated pancreatic exocrine response in AP-R/S rats was higher than in AP-S rats and almost returned to control levels. In the pancreas of AP-C rats, destruction of pancreatic acini, marked infiltration of inflammatory cells, and strong expression of α-smooth muscle actin, tumor necrosis factor-α and interleukin-1β were seen. Pancreatic rest reversed these histological alterations, but not atrophy of pancreatic acini and mild infiltration of inflammatory cells. In AP-S and AP-R/S rats, the pancreas showed almost normal architecture., Conclusion: The favorable treatment strategy for AP is to keep the pancreas at rest during an early stage followed by pancreatic stimulation by promoting endogenous CCK release.

Background/aim: The renin-angiotensin system (RAS) exists in the pancreas, but the role of RAS in the regulation of pancreatic exocrine secretion under physiological conditions has been little known. The present study addressed the RAS's effect on the pancreatic secretion by using valsartan, a specific angiotensin II receptor blocker, in conscious rats., Method: Male Wistar rats prepared with pancreatic, biliary, duodenal and jugular vein cannulas were used. To examine the role of RAS in the pancreatic secretion, valsartan at 1, 5, or 25 mg/kg was administered into the duodenum via cannula, and volume of pancreatic juice and protein concentration were determined. In addition, to examine the role of RAS in hormone-stimulated pancreatic hypersecretion, pancreatic secretion was examined in response to stimulation of secretin or cholecystokinin after intraduodenal infusion of valsartan at 25 mg/kg. Furthermore, to examine the mechanism of action of RAS on pancreatic secretion, intravenous infusion of atropine or perivagal application of capsaicin was conducted and then the pancreatic secretion was examined following intraduodenal infusion of valsartan at 25 mg/kg., Results: Volume of pancreatic juice, but not protein output, significantly decreased after administration of valsartan. However, administration of valsartan did not exert significant effects on secretin- or cholesystokinin-stimulated pancreatic secretion. Treatment with atropine and perivagal application of capsaicin completely abolished the suppressive effect of valsartan on pancreatic juice secretion., Conclusion: Present results suggest that RAS plays a stimulatory role in pancreatic juice secretion via cholinergic afferent pathway without affecting protein secretion and hormonally stimulated pancreatic secretion under physiological conditions., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Objectives: To elucidate the role of transforming growth factor (TGF) beta1 and extracellular matrix (ECM) after acute necrotizing pancreatitis, we studied the regulation of TGF-beta1 and ECM after induction of pancreatitis., Methods: We examined the serial changes of levels of plasma TGF-beta1 by enzyme-linked immunoassay and expression of TGF-beta1 and ECM by Northern and Western blot analyses, respectively, in the pancreas after induction of sodium taurocholate-induced acute pancreatitis., Results: Plasma total (active and inactive) TGF-beta1 levels at 3 hours after induction of pancreatitis were significantly increased compared with baseline values. The levels of TGF-beta1 messenger RNA (mRNA) were unaltered by day 2. Levels of fibronectin mRNA at 3 hours after induction of pancreatitis were already higher than the baseline values. Latency-associated peptide-TGF-beta1 showed a peak on day 7. Thus, the expression of ECM mRNA increased earlier than that of TGF-beta1 mRNA., Conclusions: These results suggest that the increase in plasma TGF-beta1 concentration probably results from the elevated secretion of TGF-beta1 from several cells and/or the redistribution of TGF-beta1 protein and that the increase in expression of ECM probably is associated with the activation of TGF-beta1. It is conceivable that both increased plasma concentration and focal activation of TGF-beta1 play an important role in ECM production during the early stage of acute pancreatitis.

Local tissue pressure is higher in chronic pancreatitis than in the normal pancreas. We reported recently that pressure application induces synthesis of extracellular matrix (ECM) and cytokines in pancreatic stellate cells (PSCs) and that epigallocatechin gallate (EGCG), a potent antioxidant, inhibits the transformation of PSCs from quiescent to activated phenotype and ethanol-induced synthesis of ECM and cytokines in PSCs. These results suggest that oxidative stress and reactive oxygen species (ROS) are important in PSC activation. The aim of this study was to clarify the effects of ROS on activation and functions of pressure-stimulated PSCs. We used freshly isolated rat PSCs and culture-activated PSCs. Pressure was applied on rat cultured PSCs by adding compressed helium gas into a pressure-loading apparatus. PSCs were cultured with or without antioxidants (EGCG and N-acetyl cysteine) under normal or elevated pressure. Externally applied high pressure (80 mmHg) resulted in a gradual decrease of superoxide dismutase activity in PSCs and increased intracellular ROS generation as early as 30 s, reaching a peak level at 1 h. Antioxidants significantly inhibited ROS generation. Pressure increased the expression levels of alpha-smooth muscle actin, alpha(1)(I)-procollagen, and TGF-beta1 in PSCs. EGCG suppressed these alterations, abolished pressure-induced phosphorylation of p38 MAPK, and suppressed pressure-induced PSC transformation to activated phenotype. Our results indicated that ROS is a key player in pressure-induced PSC activation and ECM synthesis. Antioxidants could be potentially effective against the development of pancreatic fibrosis in patients with chronic pancreatitis.

Objective: Hyperglycemia is implicated in fibrosis in many organs. Exocrine and endocrine pancreas are closely linked both anatomically and physiologically, and pathological conditions in the exocrine gland can cause impairment of endocrine function and vice versa. Chronic pancreatitis causes pancreatic fibrosis and sometimes results in diabetes mellitus. Pancreatic stellate cells (PSCs) play a pivotal role in pancreatic fibrogenesis. However, the effects of high glucose concentrations on PSC activation have not been fully elucidated., Methods: Cultured PSCs were incubated in the presence of various concentrations of glucose. Pancreatic stellate cell proliferation, alpha-smooth muscle actin (alpha-SMA) expression, and collagen production were determined by colorimetric conversion assay, Western blot analysis, and Sirius red dye binding assay, respectively., Results: High glucose concentrations significantly increased PSC proliferation, alpha-SMA expression, and collagen type I production in PSCs. High glucose concentrations activated protein kinase C (PKC) in PSCs, and PKC inhibitor GF109203X inhibited glucose-stimulated PSC proliferation, alpha-SMA expression, and collagen secretion. High glucose also activated p38 mitogen-activated protein kinase (MAPK) in PSCs, and p38 MAPK inhibitor SB203580 inhibited glucose-stimulated collagen secretion., Conclusions: Our results indicate that high glucose concentrations stimulate PSC activation via PKC-p38 MAP kinase pathway and suggest that high glucose may aggravate pancreatic fibrosis.

Oral administration of alpha-glucosidase inhibitor reduces postprandial serum glucose and insulin concentrations; thus, alpha-glucosidase inhibitor is used for the treatment of diabetes mellitus worldwide. In our study, we have evaluated the effect of alpha-glucosidase inhibitor, acarbose, on age-related glucose intolerance and pancreatic atrophy in the Long-Evans Tokushima Otsuka (LETO) rat. The first group of rats received a standard rat diet (control). The second group received a diet containing acarbose (150 mg/100 g food) from 12 to 28 weeks and then switched to a standard rat diet until 72 weeks of age (A12-28W). The third group was administered the same diet containing acarbose from 12 to 72 weeks of age (A12-72W). Fasting serum glucose and insulin concentrations gradually increased with increasing age in the control group, but these increases were completely prevented (A12-72W) or delayed (A12-28W) by acarbose treatment. In addition, acarbose treatment prevented the deterioration in insulin resistance with increasing age. At 72 weeks of age, pancreatic wet weight and DNA content in the A12-72W group were significantly higher than those in the control group. Although most islets were enlarged, and some portions of pancreatic tissue contained fatty and connective tissue in the control group, these alterations were mild in the A12-28W group and remained minimal in the A12-72W group. Our study suggests that acarbose is useful in the prevention of age-related glucose intolerance and pancreatic atrophy.

Background and Aims: The imbalance between synthesis and degradation of extracellular matrix (ECM) proteins is a characteristic feature in chronic pancreatitis. We evaluated the relationship between type IV collagen structure in the basement membrane (BM) and the development of acinar atrophy or the regeneration from acinar injury., Methods: Three different models of pancreatitis were induced in rats by repetitive intraperitoneal injections of 500 mg/100 g body weight of arginine (Arg) or 20 microg/kg body weight of caerulein (Cn) or a single retrograde intraductal infusion of 40 microL/100 g body weight of 3% sodium taurocholate (NaTc). We examined the changes in type IV collagen structure by immunostaining, and the serial changes in the gelatinolytic activity of pro- and active matrix metalloproteinase-2 by zymography in these models of pancreatitis., Results: The pancreas appeared to be histologically normal on day 35 after the first intraperitoneal Cn injection and on day 42 after intraductal infusion of NaTc, whereas 85% to 90% of acinar tissue was replaced by fatty tissue and dilated pancreatic ducts on day 54 after the first intraperitoneal Arg injection. Immunoreactivity for type IV collagen appeared as a discontinuous line along the BM of ducts, vessels, tubular complexes, and acinar cells on day 40 in Arg-induced pancreatitis, whereas it was detected as a continuous line along the BM on day 35 in Cn-induced pancreatitis and on day 42 in NaTc-induced pancreatitits. Gelatinolytic activity of active MMP-2 increased significantly from day 13 to day 40 after the first intraperitoneal Arg injection, whereas it decreased to the baseline level on day 35 after the first intraperitoneal Cn injection and on day 42 after intraductal infusion of NaTc., Conclusions: Our findings indicate that a long-term increase in gelatinolytic activity of active MMP-2 in Arg-induced pancreatitis causes continuous disorganization of type IV collagen in the BM and progressive acinar atrophy, whereas a transient increase in gelatinolytic activity of active MMP-2 is involved in the regeneration of type IV collagen structure in the BM and recovery from acinar injury.

Background: Otsuka Long-Evans Tokushima Fatty (OLETF) rat, a model of type 2 diabetes, lacks the expression of cholecystokinin-1 receptor mRNA and exhibits inflammation and degeneration of the pancreas and eventually develops insulinopenic diabetes. Protease inhibitors are known to modulate inflammatory response and fibrosis as well as inhibit proteases activity., Aim: To examine the effects of long-term treatment with camostat, a synthetic protease inhibitor, on metabolic and histopathological changes in the islets of OLETF rats., Method: OLETF rats were fed either camostat-containing food (200 mg/100 g) from 12 or 28 weeks of age to 72 weeks of age, or fed standard rat diet., Results: Camostat-fed rats gained less weight or lost weight, although they consumed more food than the control rat when food intake was adjusted for body weight. Camostat reduced visceral adipose depots and fasting serum concentrations of triglyceride, free fatty acids, cholesterol, glucose, and insulin. Pancreatic insulin content in camostat-treated rats was significantly higher than in control rats. Immunohistochemistry revealed marked suppression of expressions of tumor necrosis factor alpha , interleukin 1 beta , interleukin 6, and alpha-smooth muscle actin in the islets of camostat-treated rats, compared with control rats. Histologically, disruption of the islets and pancreatic fibrosis were noted in control rats but not in camostat-fed rats., Conclusion: Our findings suggest that camostat prevents and reverses obesity, hyperinsulinemia, hyperglycemia, and hyperlipidemia and markedly inhibits inflammation, fibrosis, and disruption of the islets in the genetically obese diabetic OLETF rats.

Pancreatic stellate cells (PSCs) play a central role in development of pancreatic fibrosis. In chronic pancreatitis, pancreatic tissue pressure is higher than that of the normal pancreas. We here evaluate the effects of pressure on the activation of rat PSCs. PSCs were isolated from the pancreas of Wistar rat using collagenase digestion and centrifugation with Nycodenz gradient. Pressure was applied to cultured rat PSCs by adding compressed helium gas into the pressure-loading apparatus to raise the internal pressure. Cell proliferation rate was assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation. MAPK protein levels and alpha-smooth muscle actin (alpha-SMA) expression were evaluated by Western blot analysis. Concentration of activated transforming growth factor-beta1 (TGF-beta1) secreted from PSCs into culture medium was determined by ELISA. Collagen type I mRNA expression and collagen secretion were assessed by quantitative PCR and Sirius red dye binding assay, respectively. Application of pressure significantly increased BrdU incorporation and alpha-SMA expression. In addition, pressure rapidly increased the phosphorylation of p44/42 and p38 MAPK. Treatment of PSCs with an MEK inhibitor and p38 MAPK inhibitor suppressed pressure-induced cell proliferation and alpha-SMA expression, respectively. Moreover, pressure significantly promoted activated TGF-beta1 secretion, collagen type I mRNA expression, and collagen secretion. Our results demonstrate that pressure itself activates rat PSCs and suggest that increased pancreatic tissue pressure may accelerate the development of pancreatic fibrosis in chronic pancreatitis.

Recent studies demonstrated that cholecystokinin (CCK) at physiological levels stimulates pancreatic enzyme secretion via a capsaicin-sensitive afferent vagal pathway. This study examined whether chemical ablation of afferent vagal fibers influences pancreatic growth and secretion in rats. Bilateral subdiaphragmatic vagal trunks were exposed, and capsaicin solution was applied. Pancreatic wet weight and pancreatic secretion and growth in response to endogenous and exogenous CCK were examined 7 days after capsaicin treatment. Perivagal application of capsaicin increased plasma CCK levels and significantly increased pancreatic wet weight compared with those in the control rats. Oral administration of CCK-1 receptor antagonist loxiglumide prevented the increase in pancreatic wet weight after capsaicin treatment. In addition, continuous intraduodenal infusion of trypsin prevented the increase in plasma CCK levels and pancreatic wet weight after capsaicin treatment. There were no significant differences in the expression levels of CCK-1 receptor mRNA and protein in the pancreas in capsaicin-treated and control rats. Intraduodenal administration of camostat or intravenous infusion of CCK-8 stimulated pancreatic secretion in control rats but not in capsaicin-treated rats. In contrast, repeated oral administrations of camostat or intraperitoneal injections of CCK-8 significantly increased pancreatic wet weight in both capsaicin-treated and control rats. Present results suggest that perivagal application of capsaicin stimulates pancreatic growth via an increase in endogenous CCK and that exogenous and endogenous CCK stimulate pancreatic growth not via vagal afferent fibers but directly in rats.

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-alpha (TNFalpha) was expressed in the inflammatory cells, acinar cells, and islets in PxC rats. However, histologic alterations, including expression of TNFalpha, 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.

Pancreatic regeneration involves two pathways; proliferation and differentiation of pancreatic progenitor cells, which probably exist in pancreatic ductal epithelium, and replication of pre-existing differentiated acinar, islet, and ductal epithelial cells. During pancreatic development, differentiated cells arise from the ductal progenitor cells expressing the pancreatic/duodenal homeobox-1 (PDX-1) homeodomain transcription factor. The aims of this study were to characterize cell proliferation and differentiation during regeneration after acute necrotizing pancreatitis and to evaluate the role of PDX-1-positive stem cells. Necrotizing pancreatitis was induced in rats by retrograde intraductal infusion of sodium taurocholate. Cell types were classified into five categories: main, large, and small ductal epithelial cells, tubular complexes and acinar cells. Each category was scored using a 5-bromo-2'-deoxyuridine (BrdU) labelling index (LI) at various time points after induction of pancreatitis. Tissue sections were also immunostained for PDX-1 to determine the source of pancreatic stem cells. Acinar necrosis was observed at 24 h after induction of pancreatitis and most lobules were filled with tubular complexes on day 5. Subsequently, newly formed acinar cells were observed on day 7, but the lobular architecture returned to normal appearance on day 28. Proliferation started in the main and large ducts at 24 h; marked mitotic activity was evident in small ductal epithelial cells and tubular complexes on day 3, and in acinar cells on day 7. At 24 h after induction of pancreatitis, epithelial cells of the main duct with PDX-1-positive nuclei were greatly increased, simultaneously with the peak LI of BrdU. These results suggest that regeneration after necrotizing pancreatitis involves proliferation and differentiation of pancreatic progenitor cells, and that ductal epithelial cells with PDX-1-positive nuclei may contribute to the differentiation of pancreatic stem cells in the main duct., (Copyright 2002 John Wiley & Sons, Ltd.)

Introduction: The pathogenesis and the mechanism of the development of severe acute pancreatitis are not clearly understood., Aims: We performed differential display analysis to find genes that show transcriptional changes in the pancreas during the development of severe acute pancreatitis in the rat., Methodology: Twenty candidate pancreatitis-associated complementary DNA (cDNA) fragments were isolated. cDNA sequencing and subsequent database analysis revealed that one fragment (C18-2) among the 20 cDNA fragments showed no significant sequence similarity to previously reported genes, suggesting that it represented a novel gene. The rapid and high expression of C18-2 during the acute phase of pancreatitis suggested that the gene was involved in the development of acute pancreatitis. Therefore, we used rapid amplification of cDNA ends and identified the full-length cDNA., Results: Analysis of the open reading frame of the cDNA indicated that the deduced protein from the messenger RNA (mRNA) was a polypeptide of 174 amino acids, unexpectedly similar to that of a known gene, rat pancreatitis-associated protein II/regenerating gene III (PAP II/Reg III). However, the length of the identified mRNA (1,467 base pairs) was longer than that of rat PAP II mRNA (885 base pairs), because the elongated mRNA was generated through the different polyadenylation site in the same gene. The elongated mRNA after acute pancreatitis was strongly induced in the restricted early phase, in comparison with the original mRNA., Conclusion: It is considered that the elongated mRNA affects the function of PAP II/Reg III protein because the elongated mRNA with long 3; untranslated regions is known to be involved in the translation efficiency. The identified mRNA may play an important role in the progression of pancreatitis.

Introduction: Dibutyltin dichloride (DBTC) is widely used as a stabilizer for polyvinylchloride plastics and is of particular toxicologic interest., Aim: To examine the effects of DBTC on pancreatic exocrine function in isolated rat pancreatic acini., Methodology: Isolated rat pancreatic acini were incubated with various secretagogues in the presence or absence of DBTC. We investigated the effects of DBTC on amylase release, receptor binding, and protein kinase C (PKC) enzyme activity., Results: DBTC reduced cholecystokinin octapeptide (CCK-8)-stimulated and carbamylcholine-stimulated amylase release and the binding of [(125)I]CCK-8 to isolated rat pancreatic acini. Conversely, DBTC potentiated secretin-stimulated amylase release, although it slightly inhibited [(125)I]secretin binding to its receptors. In addition, DBTC potentiated amylase release stimulated by vasoactive intestinal peptide, 8-bromoadenosine 3', 5'-monophosphate (8Br-cAMP) or calcium ionophore A23187, whereas it had no influence on amylase release stimulated by 12-O-tetradecanoylphorbol 13-acetate. The protein kinase C (PKC) inhibitor calphostin C abolished the DBTC-induced potentiation of amylase release stimulated by 8Br-cAMP or A23187. Moreover, DBTC caused a significant translocation of PKC enzyme activity from cytosol to membrane fraction., Conclusions: These results indicate that DBTC reduces CCK-8- and carbamylcholine-stimulated amylase release by inhibiting their receptor bindings to pancreatic acini, whereas it potentiates cAMP-mediated amylase release by activating PKC in isolated rat pancreatic acini.

Arteriovenous malformation (AVM) of the pancreas is a rare condition that may cause severe gastrointestinal bleeding. We describe a 54-year-old man with a 7-year history of recurrent duodenal ulcer due to AVM in the pancreatic head. We recommended pancreatoduodenectomy because of recurrent haemorrhage from the duodenal ulcer, but the patient refused surgery on several occasions. He was admitted to our hospital complaining of severe upper abdominal pain radiating to the back and was diagnosed with acute pancreatitis. He agreed at that stage to the surgical treatment. The resected specimen contained a highly vascular malformation in the pancreatic head and ulceration in the adjacent descending duodenum. Histopathological examination revealed numerous vascular structures with dilated and tortuous vessels in the pancreatic head, confirming the presence of AVM. Moreover, oedema, inflammatory cell infiltration, haemorrhage and necrosis were evident, confirming the presence of acute pancreatitis.

Introduction: Peroxisome proliferator-activated receptors (PPARs) are a family of ligand-activated nuclear transcription factors belonging to the nuclear hormone receptors. Troglitazone, a specific ligand for PPAR-gamma is shown to regulate not only lipids and glucose metabolism, but also cell cycle, differentiation, and apoptosis., Aim: To examine the effect of chronic oral administration of troglitazone on the age-related changes of insulin resistance, plasma CCK levels, and pancreatic growth in normal rats., Methodology: A troglitazone-rich diet (0.2%) was given from 12 to 28 weeks of age or from 12 or 28 weeks of age to 72 weeks of age., Results: Fasting serum glucose concentrations in control rats increased progressively with age, which was almost completely prevented by troglitazone treatment. Serum insulin concentrations and pancreatic insulin content in the control rat markedly increased at 28 weeks of age but decreased at 72 weeks of age. These parameters in troglitazone-treated rats remained at nearly the same concentrations at all ages. Insulin concentration relative to DNA in the control rats increased with age, whereas in the troglitazone-treated rats it remained at nearly the same concentrations throughout the observation periods and was significantly lower than that in the controls. Insulin resistance in control rats showed a great increase at 72 weeks of age, whereas it was nearly the same at all ages in troglitazone-treated rats and was significantly lower than those in the control rats. Plasma cholecystokinin concentrations in control rats slightly but insignificantly increased with age, whereas pancreatic weight decreased age-dependently when corrected for body weight. Although troglitazone treatment appeared to decrease plasma cholecystokinin concentrations compared with those in the control rats, it significantly increased pancreatic weight and prevented age-dependent decrease. Troglitazone treatment significantly increased pancreatic protein and DNA contents, but the protein per DNA ratio, an indicator of cellular size, remained at nearly the same concentrations at all ages. The contour of the islets in the control rats at 72 weeks of age was somewhat irregular with structural disarrangement and fibrosis. Moreover, the islets were separated into small sections (cluster) by fibrosis. Troglitazone treatment prevented or reversed these age-related changes of the islets to those in rats at 12 weeks of age., Conclusion: Our results indicate that troglitazone stimulates pancreatic growth in the normal rat not only by reducing insulin resistance and improving glucose metabolism, but also by suppressing fibrosis of the islets.

Recently established Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of naturally occurring obesity diabetes, exhibit progressive accumulation of connective tissue in the pancreas. The present study was designed to determine the pathogenic role of transforming growth factor-beta1 (TGF-beta1) in the development of pancreatic fibrosis in OLETF rats by investigating the serial changes in the expression of TGF-beta1 and extracellular matrix (ECM) in the pancreas. Progressive proliferation of connective tissue arose from the interstitial region surrounding islets at 20 wk of age and extended to the exocrine pancreas adjacent to the islets. TGF-beta1 mRNA levels in the pancreas increased at 20 wk of age and reached a peak value at 30 wk of age. Fibronectin (FN) and procollagen types I and III mRNAs peaked at 20 wk of age and remained at higher levels than those in the nondiabetic counterparts Long-Evans Tokushima Otsuka rats until 50 wk of age. Immunoreactivities for TGF-beta1 and FN were found in islets of OLETF rats at 20 wk of age and were seen in acinar and interstitial cells at 50 wk of age. Moreover, alpha-smooth muscle actin was located at interstitial region surrounding the islets. Proliferation of the connective tissue in the pancreas of OLETF rats closely correlated with expression of TGF-beta1 and ECM. Our results suggest that the development of pancreatic fibrosis in OLETF rats extends from endocrine to exocrine pancreas and that TGF-beta1 is involved in pancreatic fibrosis of OLETF rats.

Considered to be an etiologic factor of acute pancreatitis, hypersecretion of pancreatic juice and digestive enzymes is often associated with hyperbilirubinemia. We explored the intracellular mechanisms through which bilirubin affects pancreatic exocrine secretory function by examining the effect of bilirubin on isolated rat pancreatic acini. Bilirubin stimulated amylase release in a concentration- and time-dependent manner, significantly increasing amylase release at concentrations >5 mg/100 ml and after 15 min of incubation. Coincubation of bilirubin with vasoactive intestinal polypeptide, 8-bromo-cAMP, or A-23187 had a synergistic effect on amylase release, whereas coincubation with CCK-8, carbamylcholine, or 12-O-tetradecanoylphorbol 13-acetate had an additive effect. Bilirubin did not affect acinar cAMP content or Ca(2+) efflux. Intracellular Ca(2+) pool depletion had no influence on bilirubin-evoked amylase release. The protein kinase C (PKC) inhibitors staurosporine and calphostin C partially but significantly inhibited bilirubin-stimulated amylase release, whereas the PKA inhibitor H-89 did not. The tyrosine kinase (TK) inhibitor genistein, phospholipase A(2) (PLA(2)) inhibitor indoxam, and PLC inhibitor U-73122 also inhibited amylase release. Bilirubin significantly translocated PKC activity from the cytosol to the membrane fraction and activated TK in cytosol and membrane fractions. These results indicate that bilirubin stimulates amylase release by activating PKC and TK in rat pancreatic acini and that PLC and PLA(2) partly mediate this process.

Presents information on a study which examined the effect of troglitazone treatment on pancreatic growth in the cholecystokinin-A receptor-deficient subject. Methodology; Results of the study; Discussion.