(R)-ketamine restores anterior insular cortex activity and cognitive deficits in social isolation-reared mice.

Chronic social isolation increases the risk of mental health problems, including cognitive impairments and depression. While subanesthetic ketamine is considered effective for cognitive impairments in patients with depression, the neural mechanisms underlying its effects are not well understood. Here we identified unique activation of the anterior insular cortex (aIC) as a characteristic feature in brain-wide regions of mice reared in social isolation and treated with (R)-ketamine, a ketamine enantiomer. Using fiber photometry recording on freely moving mice, we found that social isolation attenuates aIC neuronal activation upon social contact and that (R)-ketamine, but not (S)-ketamine, is able to counteracts this reduction. (R)-ketamine facilitated social cognition in social isolation-reared mice during the social memory test. aIC inactivation offset the effect of (R)-ketamine on social memory. Our results suggest that (R)-ketamine has promising potential as an effective intervention for social cognitive deficits by restoring aIC function.

Long-lasting anti-despair and anti-anhedonia effects of (S)-norketamine in social isolation-reared mice.

Alternatives to ketamine without psychotomimetic properties for the treatment of depression have attracted much attention. Here, we examined the anti-despair and anti-anhedonia effects of the ketamine metabolites (S)-norketamine ((S)-NK), (R)-NK, (2S,6S)-hydroxynorketamine, and (2R,6R)-hydroxynorketamine in a mouse model of depression induced by social isolation. All ketamine metabolites examined had acute (30 min after administration) anti-despair-like effects in the forced swim test, but only (S)-NK showed a long-lasting (1 week) effect. Additionally, only (S)-NK improved reduced motivation both 30 min and 24 h after injection in the female encounter test. These results suggest that (S)-NK has potent and long-lasting antidepressant-like effects.

Impact of S-1 adjuvant chemotherapy longer than 6 months on survival in patients with resected pancreatic cancer: a nationwide survey by the Japan Pancreas Society based on real-world data.

BACKGROUND: Based on the Japan Adjuvant Study Group of Pancreatic Cancer 01 study, the standard duration of adjuvant chemotherapy with S-1 (an oral 5-fluorouracil prodrug consisting of tegafur, gimeracil, and oteracil) in patients with resected pancreatic ductal adenocarcinoma (PDAC) was considered to be 6 months, but the impact of increasing its duration on postoperative survival was unknown. Here, the authors investigated this question by reviewing real-world data from a large cohort of patients with PDAC. METHODS: In total, 3949 patients who underwent surgery for PDAC during the study period followed by S-1 adjuvant chemotherapy in board-certified institutions were included. Based on the duration of S-1 chemotherapy, two subgroups were defined: a standard-duration group that included patients who were treated for 180 ± 30 days and a longer duration group that included patients who received treatment for >210 days. RESULTS: The median duration of S-1 chemotherapy was 167 days, with a mean ± standard deviation of 200 ± 193 days. After excluding patients who had a recurrence within 210 days after the initiation of adjuvant chemotherapy, postoperative recurrence-free survival (RFS) and overall survival (OS) in the standard-duration group (n = 1473) and the longer duration group (n = 975) were compared. RFS and OS did not differ significantly between the standard-duration and longer duration groups (5-year RFS: 37.8% vs. 36.2% respectively; p = .6186; 5-year OS: 52.8% vs. 53.4%, respectively; p = .5850). The insignificant difference was verified by multivariate analysis and propensity-score matching analysis. CONCLUSIONS: The current findings suggest that extending S-1 adjuvant chemotherapy beyond 6 months has no significant additional effect on survival in patients with PDAC. This could be useful in determining whether to extend S-1 chemotherapy in patients who have completed the standard 6-month treatment.

Phase I/II study of streptozocin monotherapy in Japanese patients with unresectable or metastatic gastroenteropancreatic neuroendocrine tumors.

BACKGROUND: This phase I/II study was conducted to evaluate the efficacy, safety and pharmacokinetics of streptozocin (STZ) in Japanese patients with unresectable or metastatic gastroenteropancreatic neuroendocrine tumors. METHODS: Twenty-two patients received up to 4 cycles of intravenous STZ at either 500 mg/m2 once daily for 5 consecutive days every 6 weeks (daily regimen) or at 1000-1500 mg/m2 once weekly for 6 weeks (weekly regimen). Tumor response was evaluated using the modified RECIST criteria ver. 1.1, and adverse events were assessed by grade according to the National Cancer Institute CTCAE (ver. 4.0). RESULTS: Fourteen (63.6%) patients completed the study protocol. No patients had complete response; partial response in 2 (9.1%), stable disease in 17 (77.3%), non-complete response/non-progressive disease in 2 (9.1%) and only 1 (4.5%) had non-evaluable disease. Excluding the latter, the response rate in the daily and weekly regimens was 6.7% (1/15) and 16.7% (1/6), respectively, with an overall response rate of 9.5% (2/21). However, the best overall response in each patient showed that the disease control rate was 100%.Adverse events occurred in all 22 patients, including 17 grade 3 adverse events in 11 patients; however, no grade 4 or 5 adverse events were reported. Prophylactic hydration and antiemetic treatment reduced the severity and incidence of nephrotoxicity, nausea and vomiting. Plasma STZ concentrations decreased rapidly after termination of infusion, with a half-life of 32-40 min. Neither repeated administration nor dose increases affected pharmacokinetic parameters. CONCLUSIONS: STZ may be a useful option for Japanese patients with unresectable or metastatic gastroenteropancreatic neuroendocrine tumors.

Claustrum mediates bidirectional and reversible control of stress-induced anxiety responses.

The processing of stress responses involves brain-wide communication among cortical and subcortical regions; however, the underlying mechanisms remain elusive. Here, we show that the claustrum (CLA) is crucial for the control of stress-induced anxiety-related behaviors. A combined approach using brain activation mapping and machine learning showed that the CLA activation serves as a reliable marker of exposure to acute stressors. In TRAP2 mice, which allow activity-dependent genetic labeling, chemogenetic activation of the CLA neuronal ensemble tagged by acute social defeat stress (DS) elicited anxiety-related behaviors, whereas silencing of the CLA ensemble attenuated DS-induced anxiety-related behaviors. Moreover, the CLA received strong input from DS-activated basolateral amygdala neurons, and its circuit-selective optogenetic photostimulation temporarily elicited anxiety-related behaviors. Last, silencing of the CLA ensemble during stress exposure increased resistance to chronic DS. The CLA thus bidirectionally controls stress-induced emotional responses, and its inactivation can serve as a preventative strategy to increase stress resilience.

JNETS clinical practice guidelines for gastroenteropancreatic neuroendocrine neoplasms: diagnosis, treatment, and follow-up: a synopsis.

Neuroendocrine neoplasms (NENs) are rare neoplasms that occur in various organs and present with diverse clinical manifestations. Pathological classification is important in the diagnosis of NENs. Treatment strategies must be selected according to the status of differentiation and malignancy by accurately determining whether the neoplasm is functioning or nonfunctioning, degree of disease progression, and presence of metastasis. The newly revised Clinical Practice Guidelines for Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs) comprises 5 chapters-diagnosis, pathology, surgical treatment, medical and multidisciplinary treatment, and multiple endocrine neoplasia type 1 (MEN1)/von Hippel-Lindau (VHL) disease-and includes 51 clinical questions and 19 columns. These guidelines aim to provide direction and practical clinical content for the management of GEP-NEN preferentially based on clinically useful reports. These revised guidelines also refer to the new concept of "neuroendocrine tumor" (NET) grade 3, which is based on the 2017 and 2019 WHO criteria; this includes health insurance coverage of somatostatin receptor scintigraphy for NEN, everolimus for lung and gastrointestinal NET, and lanreotide for GEP-NET. The guidelines also newly refer to the diagnosis, treatment, and surveillance of NEN associated with VHL disease and MEN1. The accuracy of these guidelines has been improved by examining and adopting new evidence obtained after the first edition was published.

Collision of a pancreatic ductal adenocarcinoma and a pancreatic neuroendocrine tumor associated with multiple endocrine neoplasm type 1.

A 54-year-old man with pancreatic head tumor had undergone pancreaticoduodenectomy and was diagnosed with pancreatic neuroendocrine tumor (P-NET) associated with sporadic multiple endocrine neoplasm type 1. Five years after the resection, P-NET recurred and liver metastases were observed. He was treated with a somatostatin analog. Eleven years after the resection, computed tomography revealed a new pancreatic hypodense and hypovascular mass adjacent to the P-NET that was diagnosed as pancreatic adenocarcinoma via endoscopic ultrasound-guided fine-needle aspiration. He underwent a total remnant pancreatectomy. Pathological examination showed that the lesion was constituted by a pancreatic ductal adenocarcinoma (PDAC) and a neuroendocrine tumor. Additionally, the invasive ductal carcinoma collided with the neuroendocrine tumor. Both PDAC and P-NET cells were observed in the collision area. We could observe the onset of PDAC during the treatment of P-NET. Moreover, we are the first to report the case of a collision of pancreatic endocrine and exocrine tumors diagnosed preoperatively.

Optimal Treatment for Octogenarians With Resectable and Borderline Resectable Pancreatic Ductal Adenocarcinoma: A Multicenter Retrospective Study.

OBJECTIVES: The objective of this study was to clarify the role of pancreatectomy for patients with resectable and borderline resectable pancreatic ductal adenocarcinoma aged 80 years or older using a nationwide audit by the Japan Pancreas Society. METHODS: Data were collected from 39 institutions from 2007 to 2014. The primary endpoint was overall survival, and secondary endpoints were surgical outcomes and predictive factors for prognosis. RESULTS: Data were obtained from 556 octogenarians who underwent pancreatectomy (n = 369, 66%), chemo(radio)therapy (n = 99, 18%), and palliative therapy (n = 88, 16%). Median survival times were 20.6, 18.6, and 8.8 months in each group, respectively. Even after propensity score matching, median survival time in the surgery group (22.8 months) was significantly higher than that in the chemotherapy group (18.5 months; hazard ratio, 0.64 [95% confidence interval, 0.44-0.93]; P = 0.020). Significant independent prognostic factors were body mass index, lymph node metastasis, and tumor diameter in the surgery group, and serum albumin level, American Society of Anesthesiologists classification, body mass index, modified Glasgow prognostic score, second-line chemotherapy, and tumor diameter in the chemotherapy group. CONCLUSIONS: Octogenarians with resectable/borderline resectable pancreatic ductal adenocarcinoma can be recommended for pancreatectomy according to mental and physical fitness for surgical procedures.

Natural history and clinical outcomes of pancreatic neuroendocrine neoplasms based on the WHO 2017 classification; a single-center experience of 30 years.

BACKGROUND/OBJECTIVES: This single-center study aimed to evaluate treatment outcomes and long-term prognosis of patients with pancreatic neuroendocrine neoplasms (PanNENs) based on the World Health Organization (WHO) 2017 classification. METHODS: We enrolled 245 patients with PanNENs treated at Kyushu University Hospital between January 1987 and March 2018. PanNENs were categorized according to the WHO 2017 classification or further subdivisions of Ki-67 index. Clinicopathological features, median survival time (MST), and prognostic factors were retrospectively analyzed. RESULTS: The number of PanNENs, especially non-functioning PanNENs, has increased over the last decade. The mean MST of all patients was 202 months; which was longest in patients with NET G1 (n = 145, MST = 261 months) relative to NET G2 (n = 72, 132 months), NET G3 (n = 3, 34 months) and NEC G3 (n = 17, 9 months). Prognosis in patients with surgery as the first-line treatment was significantly better than in those with drug therapy. However, 26% of patients who underwent curative resection developed recurrence after a median time of 28.7 months. In unresectable PanNENs (n = 97), the MST and 5-year survival rate were 78 months and 55.8%, respectively. Poor differentiation, Ki-67 index of >10% and presence of liver metastasis were significant unfavorable predictors. Response to first-line therapy (stable disease/partial response) and three or more treatment regimens were significant favorable predictors for unresectable PanNENs according to multivariate analyses (p < 0.01). CONCLUSIONS: We demonstrated the utility of the WHO 2017 classification for PanNENs in the real clinical setting. For better prognosis in PanNENs, the use of three or more regimens should be considered.

Pathogenic POGZ mutation causes impaired cortical development and reversible autism-like phenotypes.

Pogo transposable element derived with ZNF domain (POGZ) has been identified as one of the most recurrently de novo mutated genes in patients with neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD), intellectual disability and White-Sutton syndrome; however, the neurobiological basis behind these disorders remains unknown. Here, we show that POGZ regulates neuronal development and that ASD-related de novo mutations impair neuronal development in the developing mouse brain and induced pluripotent cell lines from an ASD patient. We also develop the first mouse model heterozygous for a de novo POGZ mutation identified in a patient with ASD, and we identify ASD-like abnormalities in the mice. Importantly, social deficits can be treated by compensatory inhibition of elevated cell excitability in the mice. Our results provide insight into how de novo mutations on high-confidence ASD genes lead to impaired mature cortical network function, which underlies the cellular pathogenesis of NDDs, including ASD.

[Factors related to Work-Family Conflicts of employees in small and medium-sized businesses].

Objectives　This study elucidated the relationship between work and family conflicts of employees working in small and medium-sized businesses in Japan and its association with their lifestyle and working conditions.Methods　A self-report questionnaire survey was conducted with 294 employees of four small and medium-sized businesses that agreed to participate in the study. The survey included items on demographics, working conditions, lifestyle, the Japanese version of the multidimensional Work-Family Conflict Scale (WFCS), and subjective health and stress. Based on the scores of both the subscales of the WFCS, Work Interference with Family (WIF), and Family Interference with Work (FIW), participants were divided into two groups (high and low score groups). Using these scores as dependent variables, a logistic regression analysis was performed to examine factors related to the WIF and FIW.Results　Of the 227 collected responses, 185 responses with no missing values were determined as valid for the analysis. Participants were 146 men (78.9%) and 39 women (21.1%) with an average age of 43.6±11.2 years. The proportion of spouses and children was about 60%. The median values of WIF and FIW were 3.0 and 2.3, respectively. There were statistically significant differences in "average working hours per day," "ease of taking vacations," "skipping or not skipping meals," and others, between the two groups of WIF, and in "ease of taking vacations" and "subjective health" between the two groups of FIW. A significant difference was found in "subjective stress." Logistic regression analysis showed that the WIF was related to "skipping or not skipping meals," "subjective stress," "average working hours per day," "age," "subjective health," and "ease of taking vacations." FIW was related to "subjective health" only and different factors were extracted.Conclusions　The results of this study suggest that an acceptable lifestyle and better workplace environment is essential to reduce the WIF. Thus, employees should work fewer hours and feel comfortable to take vacations. Additionally, it is necessary to deal with stress skillfully and improve mental and subjective health to reduce FIW.

Prognostic importance of peritoneal washing cytology in patients with otherwise resectable pancreatic ductal adenocarcinoma who underwent pancreatectomy: A nationwide, cancer registry-based study from the Japan Pancreas Society.

BACKGROUND: The importance of peritoneal washing cytology status both as a sign of irresectability and as a prognostic factor for pancreatic ductal adenocarcinoma remains controversial. The purpose of this nationwide, cancer registry-based study was to clarify the clinical implications of operative resection in patients who had positive cytology status. METHODS: Clinical data from 1,970 patients who underwent tumor resection were collected from the Pancreatic Cancer Registry in Japan. Clinicopathologic factors and overall survival curves were analyzed, and multivariate Cox proportional hazard models were evaluated. RESULTS: Among the 1,970 patients analyzed, positive cytology status was found in 106 patients and negative cytology status was found in 1,864 patients. The positive cytology status group had a greater frequency of pancreatic body and tail cancer and greater preoperative serum carbohydrate antigen 19-9 levels than the negative cytology status group (P < .001 each). The ratio of peritoneal recurrence tended to be greater in the positive cytology status group (14% vs 43%; P < .001). Overall median survival times were less in the positive cytology status group (17.5 months vs 29.4 months; P < .001). The 5-year survival rates were 13.7% and 31.1% in the positive cytology status and negative cytology status groups, respectively. Multivariate analysis of positive cytology status patients revealed that adjuvant chemotherapy was an independent prognostic factor. CONCLUSION: Positive cytology status was an adverse prognostic factor in patients who underwent resection for pancreatic ductal adenocarcinoma but did not preclude attempted curative resection. Curative resection followed by adjuvant chemotherapy may contribute to long-term prognosis in patients with positive cytology status.

(R)-Ketamine Induces a Greater Increase in Prefrontal 5-HT Release Than (S)-Ketamine and Ketamine Metabolites via an AMPA Receptor-Independent Mechanism.

BACKGROUND: Although recent studies provide insight into the molecular mechanisms of the effects of ketamine, the antidepressant mechanism of ketamine enantiomers and their metabolites is not fully understood. In view of the involvement of mechanisms other than the N-methyl-D-aspartate receptor in ketamine's action, we investigated the effects of (R)-ketamine, (S)-ketamine, (R)-norketamine [(R)-NK], (S)-NK, (2R,6R)-hydroxynorketamine [(2R,6R)-HNK], and (2S,6S)-HNK on monoaminergic neurotransmission in the prefrontal cortex of mice. METHODS: The extracellular monoamine levels in the prefrontal cortex were measured by in vivo microdialysis. RESULTS: (R)-Ketamine and (S)-ketamine acutely increased serotonin release in a dose-dependent manner, and the effect of (R)-ketamine was greater than that of (S)-ketamine. In contrast, (S)-ketamine caused a robust increase in dopamine release compared with (R)-ketamine. Both ketamine enantiomers increased noradrenaline release, but these effects did not differ. (2R,6R)-HNK caused a slight but significant increase in serotonin and noradrenaline but not dopamine release. (S)-NK increased dopamine and noradrenaline but not serotonin release. Differential effects between (R)-ketamine and (S)-ketamine were also observed in a lipopolysaccharide-induced model of depression. An α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor antagonist, 2,3-dioxo-6-nitro-1,2,3,4- tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), attenuated (S)-ketamine-induced, but not (R)-ketamine-induced serotonin release, whereas NBQX blocked dopamine release induced by both enantiomers. Local application of (R)-ketamine into the prefrontal cortex caused a greater increase in prefrontal serotonin release than that of (S)-ketamine. CONCLUSIONS: (R)-Ketamine strongly activates the prefrontal serotonergic system through an AMPA receptor-independent mechanism. (S)-Ketamine-induced serotonin and dopamine release was AMPA receptor-dependent. These findings provide a neurochemical basis for the underlying pharmacological differences between ketamine enantiomers and their metabolites.

Whole-brain block-face serial microscopy tomography at subcellular resolution using FAST.

Here, we describe an optimized and detailed protocol for block-face serial microscopy tomography (FAST). FAST enables high-speed serial section fluorescence imaging of fixed brains at an axonal spatial resolution and subsequent image data processing. It renders brain-wide anatomical and functional analyses, including structural profiling of nuclear-stained brain at the single-cell level, cell-type-specific mapping with reporter animal brains and neuronal tracing with anterograde/retrograde labeling. Light-sheet fluorescence microscopy of cleared brains is advantageous in regard to imaging speed, but its spatial resolution is generally limited, whereas the opposite is true for conventional confocal microscopy. FAST offers a solution to overcome these technical limitations. This protocol describes detailed procedures for assembling the FAST hardware, sample preparation, imaging and image processing. A single imaging session takes as little as 2.4 h per mouse brain, and sample preparation requires 1 to several days, depending on pretreatments; however, multiple samples can be prepared simultaneously. We anticipate that FAST will contribute to unbiased and hypothesis-free approaches for a better understanding of brain systems.

Correction to: Phase II study of sunitinib in Japanese patients with unresectable or metastatic, well-differentiated pancreatic neuroendocrine tumor.

In the original publication of this article, the license subtype should be CC BY and not CC BY-NC.

An Advanced Well-differentiated Pancreatic Neuroendocrine Carcinoma (NET-G3) Associated with Von Hippel-Lindau Disease.

A 45-year old woman who underwent several surgeries for tumors associated with von Hippel-Lindau disease (VHL) was referred to our hospital due to a pancreatic tumor and liver tumors. She was diagnosed with pancreatic neuroendocrine tumor (NET) with a Ki67 index of 40% based on the examination of a biopsy specimen of the liver tumors. She was treated with everolimus for 6 months and sunitinib for 6 weeks as first- and second-line therapies. She survived for 13 months. At autopsy the diagnosis of pancreatic neuroendocrine tumor (NET)-G3 was confirmed. We herein report an aggressive clinical course of VHL-related NET G3. The further accumulation of cases is required to reach a consensus on treatment for this disease.

Dose and schedule modification are required for long-term continuation of sunitinib in Japanese patients with advanced pancreatic neuroendocrine tumors.

PURPOSE: This study aimed to clarify the efficacy and safety of sunitinib in Japanese patients with pancreatic neuroendocrine tumors (PNET), especially by focusing on dose and schedule modification. METHODS: Sixteen patients with advanced PNET treated with sunitinib were reviewed retrospectively. Efficacy was evaluated by progression-free survival (PFS) and objective tumor response. Toxicity profile was assessed regularly. Correlation between relative dose intensity (RDI) and treatment period was also evaluated. RESULTS: The median PFS was 25.8 months, and the probability of PFS at 1-year was 92%. The objective response rate and clinical benefit rate were 44% and 69%, respectively. The common adverse drug reactions (ADRs) were hand-foot syndrome (88%), neutropenia (75%), leucopenia (75%), and diarrhea (63%). Due to the development of severe ADRs, 81% required dose reduction and 31% discontinued sunitinib treatment, respectively. Prolonged treatment period was significantly correlated with decreased RDI (Spearman r = - 0.57, P = 0.022). The median RDI among 9 patients whom continued sunitinib more than 1 year was 49%. CONCLUSIONS: Sunitinib showed significant clinical benefit in Japanese patients with advanced PNET in the real-world clinical setting. Successful management of ADRs with appropriate dose reduction and interruption can enable long-term continuation of sunitinib.

High-Speed and Scalable Whole-Brain Imaging in Rodents and Primates.

Subcellular resolution imaging of the whole brain and subsequent image analysis are prerequisites for understanding anatomical and functional brain networks. Here, we have developed a very high-speed serial-sectioning imaging system named FAST (block-face serial microscopy tomography), which acquires high-resolution images of a whole mouse brain in a speed range comparable to that of light-sheet fluorescence microscopy. FAST enables complete visualization of the brain at a resolution sufficient to resolve all cells and their subcellular structures. FAST renders unbiased quantitative group comparisons of normal and disease model brain cells for the whole brain at a high spatial resolution. Furthermore, FAST is highly scalable to non-human primate brains and human postmortem brain tissues, and can visualize neuronal projections in a whole adult marmoset brain. Thus, FAST provides new opportunities for global approaches that will allow for a better understanding of brain systems in multiple animal models and in human diseases.

Diagnostic Performance of 48-Hour Fasting Test and Insulin Surrogates in Patients With Suspected Insulinoma.

OBJECTIVES: This study aimed to evaluate the usefulness of the 48-hour fasting test and insulin surrogates followed by a glucagon stimulatory test (GST) for the diagnosis of insulinoma. METHODS: Thirty-five patients with suspected insulinoma who underwent 48-hour fasting test and GST were retrospectively included in our study: 15 patients with surgically proven insulinomas and 20 patients in whom insulinoma was clinically ruled out. We determined the duration of the fasting test, plasma glucose levels, serum levels of immunoreactive insulin and C-peptide, and insulin surrogates (serum levels of ß-hydroxybutyrate, free fatty acid, and response of plasma glucose to intravenous glucagon [ΔPG]) at the end of the fast. RESULTS: The sensitivity and specificity of the 48-hour fasting test were 100.0% and 80.0%, respectively, for the diagnosis of insulinoma. When the 48-hour fasting test and immunoreactive insulin, C-peptide, or insulin surrogates were combined, the combination with GST showed the best results. The sensitivity, specificity, and accuracy rate were 93.3%, 95.0%, and 94.3%, respectively, with 1 false-negative case and 1 false-positive case occurring. CONCLUSIONS: A more accurate and less invasive diagnosis of insulinoma was possible by combining the 48-hour fasting test with the GST, compared with the existing method.

Antifibrotic Effect of Saturated Fatty Acids via Endoplasmic Reticulum Stress Response in Rat Pancreatic Stellate Cells.

OBJECTIVES: We investigated the effect of saturated fatty acids on chronic pancreatitis pathogenesis by elucidating the endoplasmic reticulum (ER) stress response in pancreatic stellate cells (PSCs), which are major effector cells in pancreatic fibrosis. METHODS: Wistar Bonn/Kobori rats were fed either control diet or high-fat diet (HFD) for 4 weeks. Meanwhile, cultured rat PSCs were stimulated with thapsigargin, an ER stress inducer, or palmitic acid (PA). Pancreatic fibrosis, expressions of fibrosis-related and ER stress-related proteins and mRNA, cell viability, and apoptosis were examined. RESULTS: The HFD reduced fibrosis and α-smooth muscle actin expression (ie, activated PSCs) but upregulated ER stress-related mRNA expression in the pancreas of young HFD-fed Wistar Bonn/Kobori rats. Induction of ER stress response in PSCs with thapsigargin or PA induced apoptosis, activated the protein kinase-like ER kinase (PERK) pathway, inhibited cell viability, and downregulated fibrosis-related protein and mRNA expression. The PERK inhibitor negated PA-induced ER stress response. CONCLUSIONS: Saturated fatty acids can inhibit but may not promote the fibrogenesis of chronic pancreatitis, at least in the early stage, via an ER stress response (ie, the PERK pathway) in PSCs. Moreover, induction of an apoptotic ER stress response in PSCs might be a novel therapeutic strategy for pancreatic fibrosis.