Acute pancreatitis in obesity: adipokines and dietary fish oil.

BACKGROUND: Acute pancreatitis is a substantial clinical problem accounting for 240,000 hospital admissions yearly in the United States. Obesity is epidemic and is clearly an independent risk factor for increased severity of acute pancreatitis (AP). Adipose tissue is an endocrine organ that secretes a variety of metabolically active substances termed adipokines. However, the role of adipokines in modulating acute pancreatitis severity remains incompletely understood. Dietary fish oil is rich in omega-3 free fatty acids and attenuates adipose tissue-induced inflammation. Therefore, we hypothesized that feeding obese mice diets rich in fish oil would alter the adipokine milieu and attenuate the severity of pancreatitis. METHODS: Lean (C57BL/6 J) and obese (LepDb) mice were fed either a soybean oil- or fish oil-rich diet for 4 weeks. AP was induced by six hourly intraperitoneal injections of cerulein (50 µg/kg). Serum adipokine levels were measured, and pancreatitis severity was assessed histologically and by measuring pancreatic concentrations of interleukin-1 beta (IL-1ß), interleukin-6 (IL-6), myleoperoxidase (MPO), and monocyte chemoattractant protein-1 (MCP-1). RESULTS: Obese mice developed more severe pancreatitis than lean mice. Fish oil significantly decreased serum leptin (lean and obese) and increased serum adiponectin (lean only). Fish oil did not alter the baseline pancreatic inflammatory milieu, nor did it change histologic or biochemical pancreatitis severity. CONCLUSION: These data demonstrate that a diet rich in fish oil altered the adipokine milieu in lean and congenitally obese mice; however, fish oil did not improve pancreatitis severity induced with cerulein hyperstimulation.

Adipokines and cytokines in human pancreatic juice: unraveling the local pancreatic inflammatory milieu.

BACKGROUND: Differential adipokine expression in obesity influences the inflammatory milieu, and may explain in part obesity's negative impact on pancreatic disease. Pancreatic juice analysis may provide a good means to evaluate the local pancreatic inflammatory milieu. The presence of adipokines in pancreatic juice is unknown. AIMS: This proof-of-concept study was designed to determine the presence of adipokines and cytokines in human pancreatic juice. METHODS: With institutional review board approval, pancreatic juice was obtained from ten patients with a broad range of diagnoses at the time of endoscopic retrograde cholangiopancreatography. Pancreatic juice was assayed using enzyme-linked immunosorbent assay (ELISA) for insulin, the proinflammatory adipokine leptin, the anti-inflammatory adipokine adiponectin, and the inflammatory mediators interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and monocyte chemoattractant protein-1 (MCP-1). Correlation between adipokine and inflammatory mediator expression was determined by linear regression analysis. Data are presented as mean +/- standard error of the mean (SEM); P < 0.05 was considered statistically significant. RESULTS: Leptin (0.16 +/- 0.05 ng/ml) and adiponectin (0.63 +/- 0.02 microg/ml) were both present, as were the inflammatory mediators IL-6 (112.6 +/- 28.1 pg/ml), TNF-alpha (49.0 +/- 18.8 pg/ml), and MCP-1 (32.2 +/- 0.9 pg/ml). Paradoxically, the expression of the anti-inflammatory adipokine adiponectin correlated strongly with that of the proinflammatory cytokine IL-6 (R(2) = 0.98, P < 0.001). CONCLUSIONS: This report is the first to describe adipokine expression in human pancreatic juice. Human pancreatic juice inflammatory mediators and adipokines may provide an important measurement of the local pancreatic inflammatory milieu.

Nuclear magnetic resonance spectroscopy-based metabolomics of the fatty pancreas: implicating fat in pancreatic pathology.

BACKGROUND: Obesity is a worldwide epidemic and a significant risk factor for pancreatic diseases including pancreatitis and pancreatic cancer; the mechanisms underlying this association are unknown. Metabolomics is a powerful new analytical approach for describing the metabolome (compliment of small molecules) of cells, tissue or biofluids at any given time. Our aim was to analyze pancreatic fat content in lean and congenitally obese mice using both metabolomic analysis and conventional chromatography. METHODS: The pancreatic fat content of 12 lean (C57BL/6J), 12 obese leptin-deficient (Lep(ob)) and 12 obese hyperleptinemic (Lep(db)) mice was evaluated by metabolomic analysis, thin-layer and gas chromatography. RESULTS: Pancreata of congenitally obese mice had significantly more total pancreatic fat, triglycerides and free fatty acids, but significantly less phospholipids and cholesterol than those of lean mice. Metabolomic analysis showed excellent correlation with thin-layer and gas chromatography in measuring total fat, triglycerides and phospholipids. CONCLUSIONS: Differences in pancreatic fat content and character may have important implications when considering the local pancreatic proinflammatory milieu in obesity. Metabolomic analysis is a valid, powerful tool with which to further define the mechanisms by which fat impacts pancreatic disease.

Adiponectin receptor-1 expression is decreased in the pancreas of obese mice.

BACKGROUND: Obesity is epidemic in the 21st century and has been shown to be a risk factor for developing severe acute pancreatitis. Adipose tissue produces small molecules called adipokines, which are important in modulating metabolism and inflammation. The anti-inflammatory adipokine adiponectin is decreased in obesity and inversely mirrors the severity of pancreatitis in a murine experimental model. Adiponectin acts through two receptors, AdipoR1 and AdipoR2; no data are currently available regarding adiponection receptor expression in the obese murine pancreas. MATERIALS AND METHODS: Immunohistochemical and reverse transcription-polymerase chain reaction analysis were undertaken to determine expression of adiponectin receptors AdipoR1 and AdipoR2 in the pancreas and liver of lean (C57BL/6J) and congenitally obese (Lep(Ob) and Lep(Db)) mice. RESULTS: Immunohistochemistry confirmed expression of both AdipoR1 and AdipoR2 in the pancreas of all three murine strains. Staining was positive in acinar cells and to a lesser extent in islet cells. Pancreatic gene expression of AdipoR2 was similar among lean and obese mice. AdipoR1 gene expression, however, was significantly (P < 0.001) decreased in the pancreas of both Lep(Ob) and Lep(Db) mice compared to wild-type lean animals. Gene expression of both AdipoR1 and AdipoR2 was significantly less in the liver of obese (Lep(Ob) and Lep(Db)) mice compared to wild-type lean animals (P < 0.001). CONCLUSIONS: These data show for the first time that the adiponectin receptors AdipoR1 and AdipoR2 are expressed in the obese murine pancreas. The paucity of AdipoR1 receptors may be important when considering the role played by adipokines in the genesis of severe pancreatitis in obesity.

High dietary carbohydrates decrease gallbladder volume and enhance cholesterol crystal formation.

BACKGROUND: Animal and human data suggest that a diet high in refined carbohydrates leads to gallstone formation. However, no data are available on the role of dietary carbohydrates on gallbladder volume or on cholesterol crystal formation. Therefore, we tested the hypothesis that a high carbohydrate diet would alter gallbladder volume and enhance cholesterol crystal formation. METHODS: At 8 weeks of age, 60 lean and 36 obese leptin-deficient female mice were fed a 45% carbohydrate diet while an equal number of lean and obese mice were fed a 75% carbohydrate diet for 4 weeks. All animals then underwent cholecystectomy, and gallbladder bile volume was recorded. Bile was pooled, filtered, and maintained in a water bath at 37 degrees C for 14 days. Birefringent cholesterol crystals in bile were counted daily; crystal observation time and crystal mass were determined. RESULTS: The crystal observation time was significantly shortened in both lean and obese mice on the 75% diet compared with their counterparts on the 45% diet. The crystal mass was significantly increased in the lean mice on the 75% diet compared with the 45% diet. Gallbladder volumes were significantly reduced in both lean and obese mice on the 75% diet compared with their counterparts on the 45% diet. CONCLUSIONS: These data suggest that a high carbohydrate diet decreases gallbladder volume, shortens cholesterol crystal observation time, and increases crystal mass. We conclude that dietary carbohydrates may play a role in cholesterol gallstone formation by altering biliary motility and by enhancing crystal formation.

Ezetimibe ameliorates cholecystosteatosis.

BACKGROUND: Cholecystosteatosis is the accumulation of gallbladder wall fats leading to decreased gallbladder emptying. Ezetimibe inhibits intestinal fat absorption and prevents murine gallstone formation. However, the influence of ezetimibe on gallbladder emptying and cholecystosteatosis has not been studied. Therefore, we tested the hypothesis that ezetimibe would improve gallbladder motility by preventing the buildup of fats in the gallbladder wall. METHODS: Forty lean female mice were fed either a control diet or a lithogenic diet for 6 weeks. Half of the mice on each diet received ezetimibe. At 11 weeks of age, all mice were fasted overnight and underwent gallbladder ultrasonography to determine ejection fraction. One week later, the mice were fasted and underwent cholecystectomy. Bile was examined for cholesterol crystals. The gallbladders were snap-frozen for lipid analysis. RESULTS: The lithogenic diet significantly (P < 0.05) increased serum cholesterol, biliary crystals, gallbladder wall cholesterol and cholesterol/phospholipid ratio, and decreased gallbladder ejection fraction. All of these abnormalities were reversed (P < 0.05) by the addition of ezetimibe to the diet. CONCLUSIONS: These data suggest that ezetimibe lowers serum cholesterol, prevents biliary crystals, and normalizes gallbladder wall fat and function. We conclude that ezetimibe ameliorates cholecystosteatosis and may be an effective agent for gallstone prevention.

Resistin-like molecule alpha reduces gallbladder optimal tension.

INTRODUCTION: Insulin resistance is associated with increased gallbladder volume and impaired gallbladder emptying. Resistin and resistin-like molecule alpha (RELM-alpha) are adipose-derived hormones that are believed to mediate insulin resistance. Therefore, we tested the hypothesis that administration of resistin or RELM-alpha would cause insulin resistance and diminish gallbladder contractility. METHODS: In two sequential studies 40 eight-week-old nondiabetic lean mice were fed a chow diet for 4 weeks. In Study A, 10 mice received 20 microg of resistin IP, while in Study B 10 mice received 20 microg of RELM-alpha IP for seven days. In each study, 10 control mice received an equal volume of saline IP for seven days. At 12 weeks animals were fasted and underwent cholecystectomy, and in vitro gallbladder response to neurotransmitters was determined. Serum resistin, RELM-alpha, glucose, and insulin levels were measured. HOMA index, a measure of insulin resistance, was calculated. RESULTS: RELM-alpha significantly increased HOMA index. RELM-alpha decreased gallbladder optimal tension, but did not alter responses to neurotransmitters. Resistin had no effect on HOMA index or on gallbladder optimal tension or response. CONCLUSION: These data suggest that in nondiabetic lean mice: 1) resistin does not alter insulin resistance or gallbladder optimal tension, but 2) RELM-alpha increases insulin resistance and reduces gallbladder optimal tension. Therefore, we concluded that RELM-alpha may play a role in insulin-resistance mediated gallbladder dysmotility.

Nonalcoholic Fatty gallbladder disease: the influence of diet in lean and obese mice.

The obesity epidemic has contributed to an increased prevalence of gallstones and a higher percentage of chronic acalculous cholecystitis. Obesity is associated with Type II diabetes and hyperlipidemia in murine models. In addition, we have previously demonstrated that serum glucose, insulin, cholesterol, and triglycerides correlated with gallbladder contractility in murine models. However, the relative role of insulin resistance and gallbladder fat infiltration in this phenomenon remain unclear. Therefore, we tested the hypothesis that gallbladder wall lipids are related to obesity and diet and are inversely correlated with gallbladder contractility. One hundred lean control (C7BL/6J) and 36 obese leptin-deficient (Lep(ob)) 8-week-old female mice were fed either a chow diet or a 1.0% cholesterol, 15% butterfat (high-lipid) diet for four weeks. Pooled gallbladders were then analyzed for free fatty acids (FFA), phospholipids (PL), total cholesterol (TC), and triglycerides (TG). Cholesterol/phospholipid ratios were then calculated. The Lep(ob) mice fed a chow diet had significantly higher (P < 0.01) gallbladder lipids than the three other groups. The lean mice that were fed a high-lipid diet had increased (P < 0.05) gallbladder TC compared to the lean mice on a chow diet. In addition, the cholesterol/phospholipid ratio was significantly increased (P < 0.01) in the lean mice fed a high-lipid diet compared to the other three groups. Finally, the high-lipid diet decreased gallbladder FFA (P < 0.01), PL (P = 0.08), and TC (P < 0.05) in Lep(ob) mice. These data suggest that (1) obese mice have increased gallbladder lipids; (2) a high-cholesterol, high-fat diet increases gallbladder lipids and the cholesterol/phospholipid ratio in lean mice; but (3) decreases gallbladder fatty acids, phospholipids, and cholesterol in obese mice. Prior studies have documented similarly decreased gallbladder response to neurotransmitters in obese mice on a chow diet, as well as lean and obese mice on a high-lipid diet. Therefore, we conclude that leptin-deficient obesity and/or a high-fat diet causes nonalcoholic fatty gallbladder disease, which is manifested by diminished gallbladder contractility.

Adipocytes enhance murine pancreatic cancer growth via a hepatocyte growth factor (HGF)-mediated mechanism.

INTRODUCTION: Obesity accelerates the development and progression of pancreatic cancer, though the mechanisms underlying this association are unclear. Adipocytes are biologically active, producing factors such as hepatocyte growth factor (HGF) that may influence tumor progression. We therefore sought to test the hypothesis that adipocyte-secreted factors including HGF accelerate pancreatic cancer cell proliferation. MATERIAL AND METHODS: Murine pancreatic cancer cells (Pan02 and TGP-47) were grown in a) conditioned medium (CM) from murine F442A preadipocytes, b) HGF-knockdown preadipocyte CM, c) recombinant murine HGF at increasing doses, and d) CM plus HGF-receptor (c-met) inhibitor. Cell proliferation was measured using the MTT assay. ANOVA and t-test were applied; p < 0.05 considered significant. RESULTS: Wild-type preadipocyte CM accelerated Pan02 and TGP-47 cell proliferation relative to control (59 ± 12% and 34 ± 12%, p < 0.01, respectively). Knockdown of preadipocyte HGF resulted in attenuated proliferation vs. wild type CM in Pan02 cells (35 ± 5% vs. 68 ± 14% greater than control; p < 0.05), but proliferation in TGP-47 cells remained unchanged. Recombinant HGF dose-dependently increased Pan02, but not TGP-47, proliferation (p < 0.05). Inhibition of HGF receptor, c-met, resulted in attenuated proliferation versus control in Pan02 cells, but not TGP-47 cells. CONCLUSIONS: These experiments demonstrate that adipocyte-derived factors accelerate murine pancreatic cancer proliferation. In the case of Pan02 cells, HGF is responsible, in part, for this proliferation.

Impaired intestinal cell proliferation and cell death in leptin-deficient obese mice.

BACKGROUND: After massive small-bowel resection and loss of absorptive capacity, residual intestine has compensatory ability to adapt by cellular hyperplasia and increased absorptive function. Growth factors have been shown to enhance intestinal adaptation, but the mechanisms involved are not well defined. Leptin has been shown to function as a trophic factor in the intestine and enhances carbohydrate absorption after small-bowel resection. Therefore, we hypothesized that leptin deficiency may impair the adaptive response by modulating cellular proliferation or cell death after small-bowel resection. METHODS: Twelve-week-old male lean control (C57BL/6J, n = 28) and leptin-deficient (Lep(ob), n = 24) obese mice underwent sham laparotomy, intestinal transection, or 50% proximal small-bowel resection. Mice were killed at 48 hours postresection, and remnant intestine was harvested. Phenotypic analysis to assess adaptation included characterization of cell proliferation (percentage BrdU incorporation), apoptosis (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nickend labeling assay), and morphometric response (villus height, crypt depth). RESULTS: The percentage S-bromodeoxyuridine (BrdU) incorporation and apoptotic indices of obese transected mice were significantly lower than lean transected mice (7.3 vs 21.9% and 0.70 vs 1.53% respectively, p < .05). In resected animals, the percentage BrdU incorporation and apoptotic indices of obese resected mice were significantly lower than for lean resected (6.1 vs 22.0% and 0.93 vs 1.80% respectively, p < .05). No differences between groups, regardless of surgery, were identified in villus height or crypt depth. CONCLUSIONS: Therefore, we conclude that leptin deficiency impairs both cell proliferation and cell death in the early adaptive period after either small-bowel transection or resection.

Leptin-resistant obese mice have paradoxically low biliary cholesterol saturation.

BACKGROUND: Human obesity is associated with leptin resistance, elevated serum glucose and lipids, hepatic steatosis, and cholesterol gallstone formation. These gallstones are thought to result from hypersecretion of biliary cholesterol as well as biliary stasis. Leptin-resistant Lep(db) obese mice, which are known to have elevated serum leptin, glucose, and lipids, as well as hepatic steatosis, should be an appropriate model for human gallstone formation. Therefore, we tested the hypothesis that leptin-resistant mice would have increased gallbladder volume, biliary cholesterol saturation, and cholesterol crystal formation. METHODS: Sixty lean control mice and 60 Lep(db) obese mice on a low cholesterol chow diet were studied. Gallbladder volumes were measured and bile was pooled to calculate cholesterol saturation index. Serum cholesterol, glucose, and leptin levels were determined from pooled serum. Hepatic fat vacuoles were counted. Bile from a second group of 90 lean control and 59 obese mice was observed microscopically for cholesterol crystal formation. RESULTS: Leptin-resistant obese mice have significantly higher serum cholesterol, glucose, and leptin levels, hepatic fat vacuoles, and gallbladder volume than lean control mice. However, biliary cholesterol saturation index and cholesterol crystal formation were significantly diminished in the obese mice. CONCLUSIONS: These data suggest that leptin-resistant Lep(db) obese mice have (1) increased gallbladder volume, (2) decreased biliary cholesterol saturation despite elevated serum cholesterol and hepatic steatosis, and (3) decreased in vitro cholesterol crystal formation. We conclude that the link between obesity and gallstone formation does not require hypersecretion of biliary cholesterol.

Decreased gallbladder response in leptin-deficient obese mice.

Obesity is a major risk factor for gallstone formation, but the pathogenesis of this phenomenon remains unclear. Human data on gallbladder emptying are conflicting, and no animal data exist on the effect of obesity on gallbladder motility. Leptin, a hormone produced by adipocytes, is known to have central effects on neuropeptide Y and cholecystokinin, but the influence of leptin on the biliary effects of these hormones is unknown. Therefore we tested the hypothesis that leptin-deficient C57BL/6J-lep(ob) obese mice would have decreased gallbladder responses to excitatory stimuli. Twelve-week-old lean control (C57BL/6J) (n = 22) and C57BL/6J-lep(ob) obese (n = 20) female mice were fed a nonlithogenic diet. The mice were fasted overnight and underwent cholecystectomy. Whole gallbladders were placed in 3 ml muscle baths. After optimal length was determined with acetylcholine (10(-5) mol/L, responses to increasing doses of neuropeptide Y (10(-8) to 10(-6) mol/L) and cholecystokinin-8 (10(-10) to 10(-7) mol/L) were measured. Student's t test and two-way analysis of variance were used where appropriate. Results were expressed as Newtons per cross-sectional area. The lean control mice had significantly greater excitatory responses to acetylcholine than the obese mice (0.37 +/- 0.05 vs. 0.16 +/- 0.02, P < 0.01). The gallbladder responses were also greater when mice were treated with neuropeptide Y (10(-8) mol/L: 0.00 +/- 0.00 vs. 0.00 +/- 0.00, NS; 10(-7) mol/L: 0.12 +/- 0.02 vs. 0.05 +/- 0.01, P < 0.01; 10(-6) mol/L: 0.26 +/- 0.08 vs. 0.06 +/- 0.01, P < 0.01) and cholecystokinin (10(-10) mol/L: 0.27 +/- 0.04 vs. 0.13 +/- 0.02, P < 0.01; 10(-9) mol/L: 0.59 +/- 0.08 vs. 0.27 +/- 0.04, P < 0.01; 10(-8) mol/L: 0.80 +/- 0.11 vs. 0.37 +/- 0.05, P < 0.01; 10(-7) mol/L: 0.86 +/- 0.11 vs. 0.44 +/- 0.06, P < 0.01). These data suggest that genetically obese, leptin-deficient mice have decreased responses to acetylcholine, neuropeptide Y, and cholecystokinin. We conclude that decreased gallbladder motility contributes to the increased incidence of gallstones associated with obesity.

Diabetes and hyperlipidemia correlate with gallbladder contractility in leptin-related murine obesity.

Obesity is associated with many comorbid conditions including diabetes, hyperlipidemia, and gallstones. However, the interaction among these modalities remains unclear. We recently demonstrated that both leptin-deficient and leptin-resistant obese mice have impaired biliary motility. These obese mice also are diabetic and hyperlipidemic. Therefore, we tested the hypothesis that serum glucose, insulin, cholesterol, and triglyceride levels would correlate with gallbladder contractility. Thirty-four lean control, 10 lean heterozygous leptin-deficient, 18 obese homozygous leptin-deficient, and 12 obese homozygous leptin-resistant mice were fed a nonlithogenic chow diet while nine lean control and nine obese homozygous leptin-deficient mice were fed a high-cholesterol diet for 4 weeks. In vitro gallbladder responses to cholecystokinin (CCK; 10(-8) mol/L), acetylcholine (ACh; 10(-5) mol/L), and neuropeptide Y (NPY; 10(-6) mol/L) were measured. Serum glucose, insulin, cholesterol, and triglyceride levels were measured from pooled serum from an additional 704 animals. Gallbladder responses were greatest for CCK, intermediate for ACh, and least for NPY. Serum glucose, insulin, cholesterol, and triglyceride levels and body weight all correlated similarly, negatively, and significantly (P<0.001) with gallbladder contractility. Hyperglycemia, insulin-resistance, hyperlipidemia, and body weight in obese mice with leptin dysfunction are associated with poor gallbladder contractility, which in turn may contribute to the association between obesity and gallstone formation.

Obesity, but not high-fat diet, promotes murine pancreatic cancer growth.

BACKGROUND: Obesity accelerates pancreatic cancer growth; the mechanisms underlying this association are poorly understood. This study evaluated the hypothesis that obesity, rather than high-fat diet, is responsible for accelerated pancreatic cancer growth. METHODS: Male C57BL/6J mice were studied after 19 weeks of high-fat (60 % fat; n = 20) or low-fat (10 % fat; n = 10) diet and 5 weeks of Pan02 murine pancreatic cancer growth (flank). RESULTS: By two-way ANOVA, diet did not (p = 0.58), but body weight, significantly influenced tumor weight (p = 0.01). Tumor weight correlated positively with body weight (R (2) = 0.562; p < 0.001). Tumors in overweight mice were twice as large as those growing in lean mice (1.2 ± 0.2 g vs. 0.6 ± .01 g, p < 0.01), had significantly fewer apoptotic cells than those in lean mice (0.8 ± 0.4 vs 2.4 ± 0.5; p < 0.05), and greater adipocyte volume (3.7 vs. 2.2 %, p < 0.05). Apoptosis (R (2) = 0.472; p = 0.008) and serum adiponectin correlated negatively with tumor weight (R = 0.45; p < 0.05). CONCLUSIONS: These data suggest that body weight, and not high-fat diet, is responsible for accelerated murine pancreatic cancer growth observed in this model of diet-induced obesity. Decreased tumor apoptosis appears to play an important mechanistic role in this process. The concept that decreased apoptosis is potentiated by hypoadiponectinemia (seen in obesity) deserves further investigation.

Validation of a novel, physiologic model of experimental acute pancreatitis in the mouse.

BACKGROUND: Many experimental models of acute pancreatitis suffer from lack of clinical relevance. We sought to validate a recently reported murine model of acute pancreatitis that more closely represents the physiology of human biliary pancreatitis. METHODS: Mice (C57BL/6J n=6 and CF-1 n=8) underwent infusion of 50µl of 5% sodium taurocholate (NaT) or 50µl of normal saline (NaCl) directly into the pancreatic duct. Twenty-four hours later, pancreatitis severity was graded histologically by three independent observers, and pancreatic tissue concentration of interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) were determined by ELISA. RESULTS: Twenty four hours after retrograde injection, the total pancreatitis score was significantly greater in mice infused with NaT than in those infused with NaCl (6.3 ± 1.2 vs. 1.2 ± 0.4, p<0.05). In addition, the inflammatory mediators IL-6 and MCP-1 were increased in the NaT group relative to the NaCl group. DISCUSSION: Retrograde pancreatic duct infusion of sodium taurocholate induces acute pancreatitis in the mouse. This model is likely representative of human biliary pancreatitis pathophysiology, and therefore provides a powerful tool with which to elucidate basic mechanisms underlying the pathogenesis of acute pancreatitis.

Does adiponectin upregulation attenuate the severity of acute pancreatitis in obesity?

INTRODUCTION: Obesity is an independent risk factor for severe acute pancreatitis, though the mechanisms underlying this association are unknown. The powerful anti-inflammatory adipokine adiponectin is decreased in obesity. We recently showed that the severity of pancreatitis in obese mice is inversely related to circulating adiponectin levels, and therefore hypothesized that adiponectin upregulation would attenuate the severity of pancreatitis in obese mice. METHODS: Forty congenitally obese mice were studied. Seven days prior to study, 20 mice received a single tail vein injection of adenovirus expressing recombinant murine adiponectin (APN; 2 × 108 plaque forming unit (pfu)), and the remainder received a control adenoviral vector expressing ß-galactosidase (ß-gal; 2 × 108 pfu). Half of the mice in each group had pancreatitis induced by cerulein injection (50 mcg/kg IP hourly for 6 h). The other half received saline on the same schedule. Serum APN concentration and pancreatic tissue concentrations of interleukin (IL)-6, IL-1ß, and MCP-1 were measured by ELISA. Histologic pancreatitis score was calculated based on the degree of inflammation (0-4), edema (0-4), and vacuolization (0-4). Data were analyzed by ANOVA and Tukey's tests; p < 0.05 was considered significant. RESULTS: No difference in body weight was observed between groups. Serum APN was significantly upregulated in the APN group compared with the ß-gal group. Pancreatic tissue concentration of IL-6 was significantly decreased in the APN group compared with the ß-gal group. No change either in pancreatic tissue concentration of IL-1ß and MCP-1 or in the severity of histologic pancreatitis were observed. CONCLUSION: Adiponectin upregulation modulates the pancreatic cytokine milieu but does not attenuate pancreatitis in this model of mild acute pancreatitis.

Insulin, leptin, and tumoral adipocytes promote murine pancreatic cancer growth.

BACKGROUND: Obesity accelerates development and growth of human pancreatic cancer. We recently reported similar findings in a novel murine model of pancreatic cancer in congenitally obese mice. The current experiments were designed to evaluate the effects of diet-induced obesity on pancreatic cancer growth. METHODS: Thirty C57BL/6J female mice were fed either control 10% fat (n = 10) or 60% fat diet (n = 20) starting at age 6 weeks. At 11 weeks, 2.5 × 10(5) PAN02 murine pancreatic cancer cells were inoculated. After 6 weeks, tumors were harvested. Serum adiponectin, leptin, insulin, and glucose concentrations were measured. Tumor proliferation, apoptosis, adipocyte content, and tumor-infiltrating lymphocytes were evaluated. RESULTS: The diet-induced obesity diet led to significant weight gain (control 21.3 ± 0.6 g; diet-induced obesity 23.1 ± 0.5 g; p = 0.03). Mice heavier than 23.1 g were considered "Overweight." Tumors grew significantly larger in overweight (1.3 ± 0.3 g) compared to lean (0.5 ± 0.2 g; p = 0.03) mice; tumor size correlated positively with body weight (R = 0.56; p < 0.02). Serum leptin (3.1 ± 0.7 vs. 1.4 ± 0.2 ng/ml) and insulin (0.5 ± 0.2 vs. 0.18 ± 0.02 ng/ml) were significantly greater in overweight mice. Tumor proliferation, apoptosis, and tumor adipocyte volume were similar. T and B lymphocytes were observed infiltrating tumors from lean and overweight mice in similar number. CONCLUSION: These data show that diet-induced obesity accelerates the growth of murine pancreatic cancer.

Obesity potentiates the growth and dissemination of pancreatic cancer.

BACKGROUND: Obesity is an independent risk factor for pancreatic cancer development and progression, although the mechanisms underlying this association are completely unknown. The aim of the current study was to investigate the influence of obesity on pancreatic cancer growth using a novel in vivo model. METHODS: Lean (C57BL/6 J) and obese (Lep(Db) and Lep(Ob)) mice were inoculated with murine pancreatic cancer cells (PAN02), and studied after 5 weeks of tumor growth. Tumor histology was evaluated by hematoxylin and eosin staining, cellular proliferation was assessed by 5-bromodeoxyuridine, and apoptosis was measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay. Serum adiponectin, leptin, and insulin levels were assayed. RESULTS: Obese mice developed larger tumors, and a significantly greater number of mice developed metastases; mortality was also greater in obese mice. Tumor apoptosis did not differ among strains, but tumors from both obese strains had greater proliferation relative to those growing in lean animals. Serum adiponectin concentration correlated negatively and serum insulin concentration correlated positively with tumor proliferation. Intratumoral adipocyte mass in tumors from both obese strains was significantly greater than that in tumors of lean mice. CONCLUSION: Data from this novel in vivo model suggest that the altered adipokine milieu and insulin resistance observed in obesity may lead directly to changes in tumor microenvironment, thereby promoting pancreatic cancer growth and dissemination.

Cannabinoid receptor-1 blockade attenuates acute pancreatitis in obesity by an adiponectin mediated mechanism.

BACKGROUND: Obesity is a risk factor for increased severity of acute pancreatitis. Adipocytes produce adiponectin, an anti-inflammatory molecule that is paradoxically decreased in the setting of obesity. We have shown that adiponectin concentration inversely mirrors the severity of pancreatitis in obese mice. Cannabinoid receptor CB-1 blockade increases circulating adiponectin concentration. We, therefore, hypothesize that blockade of CB-1 would increase adiponectin and attenuate pancreatitis severity. METHODS: Forty lean (C57BL/6J) and 40 obese (Lep(Db)) mice were studied. Half of the mice in each strain received intraperitoneal injection of the CB-1 antagonist rimonabant (10 mg/kg daily for 7 days); the others received vehicle. Pancreatitis was induced by intraperitoneal injection of cerulein (50 microg/g hourly x 6). Pancreatitis severity was determined by histology. Pancreatic chemokine and proinflammatory cytokine concentrations were measured by ELISA. RESULTS: Rimonabant treatment significantly increased circulating adiponectin concentration in obese mice (p < 0.03 vs. vehicle). After induction of pancreatitis, obese mice treated with rimonabant had significantly decreased histologic pancreatitis (p < 0.001), significantly lower pancreatic tissue levels of monocyte chemoattractant protein-1 (p = 0.03), tumor necrosis factor-alpha (p < 0.001), interleukin-6 (p < 0.001), and myeloperoxidase (p = 0.006) relative to vehicle-treated animals. CONCLUSIONS: In obese mice, cannabinoid receptor CB-1 blockade with rimonabant attenuates the severity of acute pancreatitis by an adiponectin-mediated mechanism.

Leptin regulates gallbladder genes related to gallstone pathogenesis in leptin-deficient mice.

BACKGROUND: Little is known about the genetic factors that cause alterations in gallbladder motility, cholesterol crystal nucleation, biliary lipids, and, ultimately, cholesterol gallstones. Obese, leptin-deficient (Lep(ob)) mice have large gallbladder volumes with decreased contraction in vitro and are predisposed to cholesterol crystal formation. Leptin administration to these mice causes weight loss and restores gallbladder function. We hypothesize that administration of leptin to Lep(ob) mice would cause weight loss, decrease gallbladder volume, and change gallbladder genes related to gallbladder motility, nucleating factors, and lipid metabolism. STUDY DESIGN: Twenty-four 8-week-old Lep(ob) mice were fed a nonlithogenic diet for 4 weeks. Twelve mice received daily IP saline injections, and 12 received 5 mug/g recombinant leptin. Gallbladder mRNA was pooled and analyzed on murine genome microarray chips. Selected genes were confirmed by real-time polymerase chain reaction (PCR) in a second group of mice treated by the same protocol. RESULTS: Leptin-deficient mice given leptin had significant weight loss and reductions in gallbladder volume. These mice had upregulation of the leptin receptor (p = 0.007; PCR = 1.1-fold increase) but downregulation of leptin (p = 0.003; PCR = 13.5-fold decrease). Leptin upregulated the cholecystokinin A receptor (p < 0.001; PCR = 3.1-fold increase), acetylcholine beta2 receptor (p = 0.005), and the Ca+-calmodulin-dependent protein kinase (p = 0.002) genes. Leptin also altered immunoglobulin heavy chain 4 (p = 0.005; PCR = 17.7-fold increase), mucin 3 (p = 0.006), and carboxylesterase (p = 0.016; PCR = 2.5-fold decrease) genes. Leptin downregulated 3-hydroxy 3-methylglutaryl coenzyme A reductase (p = 0.006; PCR = 2.5-fold decrease) and LDL receptor (p = 0.003). CONCLUSIONS: Leptin modulates obesity and regulates gallbladder genes related to cholesterol gallstone pathogenesis.