Magnetic resonance imaging of experimental mouse colitis and association with inflammatory activity

BACKGROUND: Ulcerative colitis and Crohn's disease are the major chronic inflammatory bowel diseases affecting the gastrointestinal tract in humans. Imaging techniques such as endoscopy and computed tomography are used to monitor disease activity. Magnetic resonance imaging (MRI) is emerging as a diagnostic modality, and studies have shown that MRI can be used in the diagnostic procedure of patients with inflammatory bowel disease. The aim of the present study was to investigate the role of MRI in quantitatively reflecting inflammation in an experimental mouse colitis model. METHODS: Colonic inflammation was induced by exposing mice to dextran sulfate sodium. MRI was used to assess colon wall thickness, T2-weighted (T2w) signal, and contrast-enhanced T1-weighted (T1w) signal in inflamed and healthy animals in vivo. Haptoglobin and interleukin-1beta served as systemic and local inflammatory markers, and macroscopic ex vivo scoring of the colon was performed to assess colonic inflammation. RESULTS: Dextran sulfate sodium-exposed animals displayed increased levels of inflammatory markers and higher inflammatory score compared with healthy animals. Colon wall thickness and contrast-enhanced T1w signal were significantly increased in dextran sulfate sodium-exposed compared with healthy animals. In addition, the T2w signal was positively correlated with haptoglobin levels and colon wall thickness in the inflamed animals. CONCLUSIONS: Our results show that MRI can be used to depict healthy and inflamed mouse colon and that the T2w signal, contrast-enhanced T1w signal, and colon wall thickness may be used to characterize inflammation in experimental colitis. These potential biomarkers may be useful in the evaluation of putative drugs in longitudinal studies in both mice and humans.     

Neurotensin induces IL-6 secretion in mouse preadipocytes and adipose tissues during 2,4,6,-trinitrobenzensulphonic acid-induced colitis

Mesenteric fat is known to undergo inflammatory changes after 2,4,6,-trinitrobenzensulphonic acid (TNBS)–induced colitis. Neurotensin (NT) and neurotensin receptor 1 (NTR1) have been shown to play a major role in the pathogenesis of intestinal inflammation. This led us to explore whether NT and NTR1 are expressed in the mesenteric fat depots during TNBS-induced colitis and whether NT participates in the increased interleukin (IL)–6 secretion in this inflammatory response. TNBS-induced inflammation in the colon increases NT and NTR1 expression in mesenteric adipose tissues, including mesenteric preadipocytes. Compared with wild-type mice, NT knockout (KO) mice have reduced TNBS-induced colitis accompanied by diminished inflammatory responses in mesenteric adipose tissue. Specifically, IL-6 and p65 phosphorylation levels in mesenteric fat of NT KO mice are also reduced compared with wild-type mice. Mouse 3T3-L1 preadipocytes express NTR1 and its expression is increased after stimulation of preadipocytes with proinflammatory cytokines. NT stimulation of 3T3-L1 preadipocytes overexpressing NTR1 causes PKCδ phosphorylation and IL-6 secretion in a time- and dose-dependent fashion. Moreover, NT-mediated IL-6 expression is nuclear factor–κB and PKCδ dependent. We also found that supernatants from NT-exposed 3T3-L1-NTR1 preadipocytes and mesenteric fat obtained from wild-type mice 2 days after TNBS administration stimulate an IL-6–dependent macrophage migration measured by a macrophage migration assay, whereas this response is reduced when mesenteric fat from NT KO mice is used. These results demonstrate an important role for NT in acute colitis and adipose tissue inflammation associated with experimental colitis that involves direct NT proinflammatory responses in preadipocytes.     

IL-1 beta -converting enzyme (caspase-1) in intestinal inflammation

IL-1 beta-converting enzyme (ICE; caspase-1) is the intracellular protease that cleaves the precursors of IL-1 beta and IL-18 into active cytokines. In the present study, the effect of ICE deficiency was evaluated during experimental colitis in mice. In acute dextran sulfate sodium-induced colitis, ICE-deficient (ICE KO) mice exhibited a greater than 50% decrease of the clinical scores weight loss, diarrhea, rectal bleeding, and colon length, whereas daily treatment with IL-1 receptor antagonist revealed a modest reduction in colitis severity. To further characterize the function of ICE and its role in intestinal inflammation, chronic colitis was induced over a 30-day time period. During this chronic time course, ICE KO mice exhibited a near complete protection, as reflected by significantly reduced clinical scores and almost absent histological signs of colitis. Consistently, colon shortening occurred only in dextran sulfate sodium-exposed wild-type mice but not in ICE KO mice. Protection was accompanied by reduced spontaneous release of the proinflammatory cytokines IL-18, IL-1 beta, and IFN-gamma from total colon cultures. In addition, flow cytometric analysis of isolated mesenteric lymph node cells revealed evidence of reduced cell activation in ICE KO mice as evaluated by surface expression of CD3 CD69 and CD4 CD25. We conclude that inhibition of ICE represents a novel anti-inflammatory strategy for intestinal inflammation.     

Dietary cholesterol, rather than liver steatosis, leads to hepatic inflammation in hyperlipidemic mouse models of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) involves liver lipid accumulation (steatosis) combined with hepatic inflammation. The transition towards hepatic inflammation represents a key step in pathogenesis, because it will set the stage for further liver damage, culminating in hepatic fibrosis, cirrhosis, and liver cancer. The actual risk factors that drive hepatic inflammation during the progression to NASH remain largely unknown. The role of steatosis and dietary cholesterol in the etiology of diet-induced NASH was investigated using hyperlipidemic mouse models fed a Western diet. Livers of male and female hyperlipidemic (low-density lipoprotein receptor-deficient [ldlr(-/-)] and apolipoprotein E2 knock-in [APOE2ki]) mouse models were compared with livers of normolipidemic wild-type (WT) C57BL/6J mice after short-term feeding with a high-fat diet with cholesterol (HFC) and without cholesterol. Whereas WT mice displayed only steatosis after a short-term HFC diet, female ldlr(-/-) and APOE2ki mice showed steatosis with severe inflammation characterized by infiltration of macrophages and increased nuclear factor kappaB (NF-kappaB) signaling. Remarkably, male ldlr(-/-) and APOE2ki mice developed severe hepatic inflammation in the absence of steatosis after 7 days on an HFC diet compared with WT animals. An HFC diet induced bloated, "foamy" Kupffer cells in male and female ldlr(-/-) and APOE2ki mice. Hepatic inflammation was found to be linked to increased plasma very low-density lipoprotein (VLDL) cholesterol levels. Omitting cholesterol from the HFC diet lowered plasma VLDL cholesterol and prevented the development of inflammation and hepatic foam cells. CONCLUSION: These findings indicate that dietary cholesterol, possibly in the form of modified plasma lipoproteins, is an important risk factor for the progression to hepatic inflammation in diet-induced NASH.     

Paracellular entry of interleukin-10 producing Lactococcus lactis in inflamed intestinal mucosa in mice

BACKGROUND: Genetically modified Lactococcus lactis secreting interleukin-10 (IL-10) has been demonstrated to provide localized delivery of a therapeutic agent through active in situ synthesis in murine colitis. At present, many aspects of the exact mechanism by which the beneficial effect of the IL-10-producing L. lactis on the mucosa is mediated remain to be clarified. METHODS: Our aim was to determine the interaction of L. lactis with the intestinal mucosa. Therefore, we administered IL-10-producing L. lactis to healthy mice and in 2 mouse models of chronic colitis. Paraffin sections of ileum and colon samples were examined with confocal and transmission electron microscopy. Ileum and colon homogenates were prepared after flushing and after removal of mucus layer and epithelium. These homogenates and homogenates of mesenteric lymph nodes and spleen were plated on agar and immunoblotting for L. lactis and IL-10 was performed. RESULTS: Both confocal and electron microscopy showed the presence of lactococci in inflamed intestinal mucosa of mice with colitis. We recovered viable bacteria that could still produce IL-10 from homogenates of inflamed ileum and colon of which mucous and epithelial layers were removed. We did not find lactococci in mesenteric lymph nodes or in the spleen of mice with colitis. CONCLUSIONS: This study demonstrates uptake of IL-10-secreting L. lactis by the paracellular route in inflamed mucosal tissue. We suggest that IL-10 production by L. lactis residing inside the mucosa in the vicinity of responsive cells can improve the local action of interleukin-10 in inflamed tissue and the efficiency of the treatment.     

Colonic inflammation accelerates the progression of liver disease: A protective role of dipotassium glycyrrhizate

BackgroundThe incidence of non-alcoholic fatty liver disease (NAFLD) and its more severe and progressive form, non-alcoholic steatohepatitis (NASH) is increasing worldwide. Gut inflammation seems to concur to the pathogenesis of NASH. No drugs are currently approved for NASH treatment.AimsTo investigate if inflamed gut directly contributes to the progression of NASH through gut epithelial and vascular barrier impairment and to evaluate the efficacy of dipotassium glycyrrhizate (DPG) to improve the liver disease.MethodsA NASH model was set up by feeding mice, for 8 and 13 weeks, with high fat diet with high fructose and glucose (HFD-FG) supplemented periodically with dextran sulfate sodium (DSS) in drinking water. A group was also treated with DPG by gavage. Histological, immunohistochemical and molecular analysis were performed.ResultsDSS-induced colitis increased steatosis, inflammatory (IL-6, TNFα, NLRP3, MCP-1) as well as fibrotic (TGF-β, α-SMA) mediator expression in HFD-FG mice. Beneficial effect of DPG was associated with restoration of intestinal epithelial and vascular barriers, evaluated respectively by ZO-1 and PV-1 expression, that are known to limit bacterial translocation.ConclusionColonic inflammation strongly contributes to the progression of NASH, likely by favouring bacterial translocation. DPG treatment could represent a novel strategy to reduce liver injury.     

R-spondin1, a novel intestinotrophic mitogen, ameliorates experimental colitis in mice

BACKGROUND & AIMS: R-spondin 1 (Rspo1) is a novel epithelial mitogen that stimulates the growth of mucosa in both the small and large intestine. METHODS: We investigated the therapeutic potential of Rspo1 in ameliorating experimental colitis induced by dextran sulfate sodium (DSS) or trinitrobenzene sulfonic acid (TNBS) as well as nonsteroidal anti-inflammatory drug-induced colitis in interleukin (IL)-10-deficient mice. RESULTS: Therapeutic administration of recombinant Rspo1 protein reduced the loss of body weight, diarrhea, and rectal bleeding in a mouse model of acute or chronic DSS-induced colitis. Histologic evaluation revealed that Rspo1 improved mucosal integrity in both villus and/or crypt compartments in the small intestine and colon by stimulating crypt cell growth and mucosal regeneration in DSS-treated mice. Moreover, Rspo1 significantly reduced DSS-induced myeloperoxidase activity and inhibited the overproduction of proinflammatory cytokines, including tumor necrosis factor-alpha, IL-1alpha, IL-6, interferon-gamma, and granulocyte-macrophage colony-stimulating factor, in mouse intestinal tissue, indicating that Rspo1 may reduce DSS-induced inflammation by preserving the mucosal barrier function. Likewise, Rspo1 therapy also alleviated TNBS-induced interstitial inflammation and mucosal erosion in the mouse colon. Furthermore, Rspo1 substantially decreased the histopathologic severity of chronic enterocolitis by repairing crypt epithelium and simultaneously suppressing inflammatory infiltration in piroxicam-exposed IL-10(-/-) mice. Endogenous Rspo1 protein was localized to villus epithelium and crypt Paneth cells in mouse small intestine. CONCLUSIONS: Our results show that Rspo1 may be clinically useful in the therapeutic treatment of inflammatory bowel disease by stimulating crypt cell growth, accelerating mucosal regeneration, and restoring intestinal architecture.     

Epicardial fat, cardiac dimensions, and low-grade inflammation in young adult monozygotic twins discordant for obesity

Epicardial fat with its close proximity to coronary arteries has been suggested to be a significant predictor of cardiovascular disease. We studied the relations among acquired obesity, low-grade inflammation, and genetic factors in the accumulation of epicardial fat. A rare sample (n = 15) of healthy monozygotic (MZ) twin pairs discordant for obesity (intrapair difference in body mass index ≥3 kg/m(2)) and 9 concordant MZ pairs 23 to 33 years old were examined for cardiac structure, function, epicardial fat thickness (echocardiography), abdominal subcutaneous tissue, and visceral adipose tissue (VAT), liver fat (magnetic resonance imaging/spectroscopy), and serum high-sensitivity C-reactive protein. In the entire sample, MZ cotwins were remarkably similar in most echocardiographic measurements including epicardial fat (intraclass correlation 0.63, p = 0.0004). However, in the discordant pairs, the obese cotwins (16.5 kg, 23% heavier) had 26% more epicardial fat (p = 0.0029) than nonobese cotwins. They also had significantly larger atrial and left ventricular dimensions. Epicardial fat correlated with VAT (r = 0.49, p = 0.02) in individual twins and when using intrapair differences of measurements within pairs (r = 0.39, p = 0.06). In multiple regression analyses including abdominal subcutaneous tissue, VAT, and liver fat, high-sensitivity C-reactive protein was the only factor that remained significantly associated with epicardial fat in individual twins and within pairs. In conclusion, subjects who share the same genes seem to have similar cardiac dimensions. However, acquired obesity increases epicardial fat independent of genetic factors. The close relation between epicardial fat and low-grade inflammation is likely to contribute to the development of cardiovascular disease in obesity.     

Heligmosmoides polygyrus fourth stages induce protection against DSS‐induced colitis and change opioid expression in the intestine

Primary exposure of mice to the nematode Heligmosomoides polygyrus infection reduces inflammation in an experimental model of colitis. The aim of the present investigation was to evaluate whether the reduced inflammation provoked by H. polygyrus L4 larvae in BALB/c mice treated with dextran sulphate sodium is associated with changed expression of opioids in the small intestine and colon. Colitis was induced by 5% Dextran sulphate sodium (DSS) oral administration for 3 days before oral infection with 200 infective larvae (L3) H. polygyrus until the end of the experiment, 6 days post‐infection. Clinical disease symptoms were monitored daily. The expressions of proopiomelanocortin POMC1, MOR1 (Oprm1) – opioid receptor and β‐endorphin were determined by RT‐PCR, Western blot and immunoassay, respectively, in the colon and small intestine of mice. RT‐PCR analysis of colon tissues showed up‐regulation of the expression of POMC and MOR1 opioid‐dependent genes in mice with DSS‐induced colitis. H. polygyrus L4 larvae inhibited DSS‐induced colitis symptoms that were correlated with increased IL‐1β, TNF‐α, IL‐6, myeloperoxidase (MPO) concentration, macrophages infiltration and MOR1, POMC and β‐endorphin increased expression in the small intestine and inhibition of those in the colon.     

Visceral adipose tissue area is an independent risk factor for hepatic steatosis

Background and Aim:  Recent data indicate that hepatic steatosis is associated with insulin resistance, dyslipidemia and obesity (especially central body fat distribution). There have been few studies on the correlation between biopsy-proven hepatic steatosis and the above factors in a disease-free population. The aim of the present study was to evaluate the relation between hepatic steatosis assessed by biopsy and clinical characteristics including regional fat distribution measured by computed tomography (CT) in living liver donors.
Methods:  Laboratory data, liver/spleen Hounsfield ratio (L/S ratio), regional fat distribution by CT and liver status by biopsy were evaluated retrospectively in a total of 177 living liver donors without a history of alcohol intake.
Results:  The unpaired t -test showed that age, triglycerides (TG), high density lipoprotein, total cholesterol, alanine aminotransferase, body mass index, L/S ratio, visceral adipose tissue area (VAT) and subcutaneous adipose tissue area (SAT) were associated with hepatic steatosis. In the multiple logistic regression analysis, VAT (odds ratio 1.031, 95% CI 1.013–1.048, P  < 0.01) and TG (odds ratio 1.012, 95% CI 1.004–1.020, P  < 0.01) were independent risk factors of hepatic steatosis. Subgroup analysis also showed that VAT was an independent risk factor in men (odds ratio 1.022, 95% CI 1.003–1.041, P  < 0.05) and women (odds ratio 1.086, 95% CI 1.010–1.168, P  < 0.05).
Conclusion:  Our results suggest that visceral abdominal adiposity is correlated with hepatic steatosis in healthy living liver donors.     

Increased expression of HIP/PAP and regenerating gene III in human inflammatory bowel disease and a murine bacterial reconstitution model

Although microorganisms play a role in gut inflammation, it remains uncertain which epithelial genes are expressed in response to luminal flora and whether these molecules are also involved in pathologic mucosal inflammation. Germ-free mice were orally challenged with a bacterial suspension prepared from conventionally housed mice (bacterial reconstitution). Thereafter, the differential gene expression in gut epithelial cells was identified by differential display. The expression of the identified genes was also examined in dextran sulfate sodium (DSS)-induced colitis and human inflammatory bowel disease (IBD) epithelial cells. Regenerating gene III (Reg III) was strongly induced in gut epithelial cells following bacterial reconstitution, as well as in the colitis initiated by DSS. The mRNA expression of hepatocarcinoma-intestine-pancreas/pancreatic associated protein (HIP/PAP), a human counterpart of Reg III, was enhanced in colonic epithelial cells of patients with IBD. Reg III mRNA expression was localized in the epithelial cells including goblet cells and columnar cells in mice; on the other hand, HIP/PAP-expressing cells were correlated with Paneth cell metaplasia in human colon. Epithelial expression of Reg III or HIP/PAP was induced under mucosal inflammation initiated by exposure to commensal bacteria or DSS as well as inflamed IBD colon.     

Cross-organ sensitization of lumbosacral spinal neurons receiving urinary bladder input in rats with inflamed colon

BACKGROUND & AIMS: Clinical studies show that patients with irritable bowel syndrome and colonic diseases frequently experience sensory and motor dysfunctions of the urinary bladder. The aim of this study was to investigate the spinal neuronal mechanisms responsible for potential cross talk between these visceral organs. METHODS: Colonic inflammation was induced by dextran sulfate sodium (5%) in drinking water for 7-12 days (n = 12); another group of rats without dextran sulfate sodium (n = 12) was used as control. Extracellular potentials of single L6 to S2 spinal neurons were recorded in pentobarbital-anesthetized and paralyzed rats with dextran sulfate sodium-induced colitis or normal colon. Urinary bladder distention (0.5-2.0 mL; 20 seconds) was produced with saline inflation, and colorectal distention was induced by inflation of an air balloon (80 mm Hg; 20 seconds). RESULTS: A total of 58 of 153 (38%) and 55 of 152 (36%) spinal neurons responded to urinary bladder distention in dextran sulfate sodium-treated and control animals, respectively. The mean background activity of neurons excited by urinary bladder distention in rats with dextran sulfate sodium-induced colitis was significantly higher than in the control group. The threshold volume for excitatory responses to urinary bladder distention in rats with inflamed colon (0.024 +/- 0.09 mL; n = 30) was significantly lower than for control rats (0.062 +/- 0.016 mL; n = 31; P < .05). The stimulus-response curves of excitatory responses to graded urinary bladder distention were significantly increased for both viscerovisceral (urinary bladder distention and colorectal distention) convergent neurons and urinary bladder distention-receptive neurons in rats with colitis compared with control animals. CONCLUSIONS: Acute colitis sensitized lumbosacral spinal neurons receiving input from the urinary bladder. Thus, spinal neuronal hyperexcitability may be involved in central cross-organ sensitization of visceral nociception between the colon and urinary bladder.     

Conventional dendritic cells regulate the outcome of colonic inflammation independently of T cells

We explored the physiological role of conventional dendritic cells (cDCs) in acute colitis induced by a single cycle of dextran sodium sulfate administration. Depending on their mode of activation and independently of T cells, cDCs can enhance or attenuate the severity of dextran sodium sulfate-induced colitis. The latter beneficial effect was achieved, in part, by IFN-1 induced by Toll-like receptor 9-activated cDCs. IFN-1 inhibits colonic inflammation by regulating neutrophil and monocyte trafficking to the inflamed colon and restraining the inflammatory products of tissue macrophages. These data highlight a novel role of cDCs in the regulation of other innate immune cells and position them as major players in acute colonic inflammation.     

Anti-interferon-inducible chemokine, CXCL10, reduces colitis by impairing T helper-1 induction and recruitment in mice

BACKGROUND: Colitis in interleukin (IL)-10 mice is a CD4 T helper 1 (TH1)-mediated disease characterized by intermittent, transmural inflammation reminiscent of human Crohn's disease. In this study, we investigated the hypothesis that production of the CXC chemokine CXCL10 (interferon [IFN]gamma-inducible protein 10) enhances induction of inflammatory responses in draining lymph nodes (LNs) and promotes colonic TH1 cell recruitment. METHODS: Colitis was induced in B6 IL-10 mice. Mice were given anti-CXCL10 mAb in 2-week intervals before and after peak colitis. Colitis severity was graded and cytokine/chemokine levels were analyzed by real-time polymerase chain reaction. Cell yields were quantitated and effector cell recruitment was assessed by recovery of transferred D011.10 TH1 cells shortly (72 h) after transfer. RESULTS: Treatment with anti-CXCL10 during colitis development decreased clinical and histologic disease severity as well as cytokine/chemokine mRNA and accumulation of mononuclear cells in LNs and colon. Treatment of mice with severe colitis reduced colitis scores and cell yields to lesser degrees. Anti-CXCL10 specifically decreased recruitment of transferred TH1 cells into mesenteric LNs (MLNs) and colon of IL-10 mice by 75% (P<0.05). CONCLUSION: These results suggest that CXCL10 plays a dual role in colitis development by enhancing TH1 cell generation in inductive sites and promoting effector cell recruitment to inflamed tissue. Blockade of CXCL10 may be a useful adjunct to remission-inducing therapies in inflammatory bowel disease (IBD) by impairing disease recurrence through selective inhibition of effector cell generation and trafficking in vivo.     

Blocking MAdCAM-1 in vivo reduces leukocyte extravasation and reverses chronic inflammation in experimental colitis

Background Leukocyte recruitment to sites of intestinal inflammation is a crucial multi-step process, leading ultimately to the accumulation of cells in the inflamed tissue. These interactions in the gut are critically dependent on the mucosal addressin cell adhesion molecule-1 (MAdCAM-1), which is expressed on endothelial cells within the mesenteric lymph nodes and the lamina propria of the intestine. Here, we investigate the pathophysiologic role of MAdCAM-1 in the intestinal microcirculation in vivo.Methods Using a standard mouse model, chronic colitis was established after four cycles of dextran sodium sulfate (DSS) application. MAdCAM-1 expression was investigated by immunohistochemistry and Western blotting, as well as real-time polymerase chain reaction (PCR). Intravital microscopy was used to study the role of MAdCAM-1 on leukocyte-endothelium interactions and leukocyte extravasation.Results Significant changes in MAdCAM-1 were observed in mice with chronic DSS-induced colitis. Upregulation of MAdCAM-1 expression in chronic colitis was demonstrated on a protein and messenger ribonucleic acid (mRNA) level. Anti-MAdCAM-1 treatment lead to a marked reduction (>60%) of leukocyte sticking and extravasation in vivo, compared to the controls. This was parallelled by a significant reduction (45%) of intestinal inflammation, as measured by the histologic grading score.Conclusion These in vivo results demonstrate a distinct role of MAdCAM-1 in inflammatory intestinal diseases, and suggest that therapeutic strategies targeting this adhesion molecule could be useful in the treatment of chronic colitis.S. Farkas and M. Hornung contributed equally to this work.     

Down-regulation of endothelial adhesion molecules and leukocyte adhesion by treatment with superoxide dismutase is beneficial in chronic immune experimental colitis

Modulation of adhesion molecule expression that govern trafficking of leukocytes into the inflamed intestine is envisioned as a new strategy for treatment of inflammatory bowel disease (IBD). This study was designed to determine the impact of reducing oxidative stress on adhesion molecules expression and leukocyte recruitment in experimental chronic colitis. For that purpose, colitic interleukin-10 knockout and wild-type mice were studied. Groups of animals were treated with Cu/Zn superoxide dismutase (SOD1) 13 mg/kg/d or vehicle for either 7 or 14 days. Expression of vascular cell adhesion molecule-1 and mucosal addressin cell adhesion molecule-1 were determined; leukocyte-endothelial cell interactions in colonic venules were studied with intravital microscopy; and changes in colon pathology and biomarkers of colitis severity were determined. Development of colitis was associated with a marked increase in endothelial vascular cell adhesion molecule-1 and mucosal addressin cell adhesion molecule-1 expression, which were significantly reduced by treatment with SOD1. The increase in leukocyte rolling and adhesion in colonic venules of colitic mice were significantly reduced by administration of SOD1. This treatment markedly reduced colonic lipid hydroperoxidation, myeoloperoxidase activity, and plasma levels of serum amyloid A protein and resulted in significant, although modest, reductions in histologic damage score. The therapeutic value of SOD1 when administered prophylactically was assessed in the dextran sulfate sodium model of colitis with similar positive results. These results indicate that SOD1 affords significant amelioration of colonic inflammatory changes in experimental colitis. Down-regulation of adhesion molecule expression, reduction of lipid hydroperoxidation, and recruitment of leukocytes into the inflamed intestine contribute to this beneficial effect.     

Experimental evidence of obstructive sleep apnea syndrome as a second hit accomplice in nonalcoholic steatohepatitis pathogenesis

Obstructive sleep apnea (OSA) causes chronic intermittent hypoxia (CIH) during sleep. OSA is associated with nonalcoholic steatohepatitis (NASH) in obese individuals and may contribute to progression of nonalcoholic fatty liver disease from steatosis to NASH. The purpose of this study was to examine whether CIH induces inflammatory changes in the liver in mice with diet-induced hepatic steatosis. C57BL/6J mice (n = 8) on a high-fat, high-cholesterol diet were exposed to CIH for 6 mo and were compared with mice on the same diet exposed to intermittent air (control; n = 8). CIH caused liver injury with an increase in serum ALT (461 ± 58 U/l vs. 103 ± 16 U/l in the control group; p < 0.01) and AST (637 ± 37 U/l vs. 175 ± 13 U/l in the control group; p < 0.001), whereas alkaline phosphatase and total bilirubin levels were unchanged. Histology revealed hepatic steatosis in both groups, with mild accentuation of fat staining in the zone 3 hepatocytes in mice exposed to CIH. Animals exposed to CIH exhibited lobular inflammation and fibrosis in the liver, which were not evident in control mice. CIH caused significant increases in lipid peroxidation in serum and liver tissue; significant increases in hepatic levels of myeloperoxidase and proinflammatory cytokines IL-1P, IL-6, and CXC chemokine MIP-2; a trend toward an increase in TNF-α; and an increase in α1(I)-collagen mRNA. We conclude that CIH induces lipid peroxidation and inflammation in the livers of mice on a high-fat, high-cholesterol diet.Abstract published under the permission of the editor of Am J Physiol Gastrointest Liver Physiol     

Intestinal blood flow in murine colitis induced with dextran sulfate sodium

The aim of this study was to assess whether colitis induced by dextran sulfate sodium (DSS; 10% in tap water for 7 days) in BALB/c mice is associated with changes in intestinal blood flow. After anaesthesia, systemic hemodynamic variable and regional blood flows and resistances in various organs were measured in both control and DSS-treated mice. Mean arterial blood pressure was significantly lower in DSS-treated mice than in controls (56 ± 4 vs 66 ± 3 mm Hg; P < 0.05), but no differences were found in regional blood flows to or vascular resistances in the lungs, liver, stomach, small intestine (upper, middle, and lower part), cecum, mesentery + pancreas, spleen, kidneys, brain, and skin. However, compared to the control mice, blood flows in the middle (0.88 ± 0.13 vs 0.55 ± 0.09 ml/min/g; P < 0.05) and distal (0.69 ± 0.11 vs 0.29 ± 0.05 ml/min/g; P < 0.05) colon were significantly higher, and vascular resistances in the proximal (0.87 ± 0.21 vs 1.36 ± 0.21 mm Hg min/ml/100 g; P < 0.05), middle (0.60 ± 0.10 vs 1.46 ± 0.35 mm Hg min/ml 100 g; P < 0.05) as well as distal (0.90 ± 0.25 vs 2.67 ± 0.49 mm Hg min/ml/100 g; P < 0.05) colon were significantly lower in mice with experimental colitis. Interestingly, there was a gradient in the intestinal blood flow in control mice from the upper small intestine (2.79 ± 0.72 ml/min/g) down to the distal colon (0.29 ± 0.05 ml/min/g); such a gradient was also present in the colitis mice. It is concluded that DSS-induced colitis in mice is associated with microcirculatory disturbances in the colon, mainly in its middle and distal parts.     

Oestrogen alters adipocyte biology and protects female mice from adipocyte inflammation and insulin resistance

Aims: Obesity is associated with insulin resistance, liver steatosis and low‐grade inflammation. The role of oestrogen in sex differences in the above co‐morbidities is not fully understood. Our aim was to assess the role oestrogen has in modulating adipocyte size, adipose tissue oxidative stress, inflammation, insulin resistance and liver steatosis. Methods: To determine the role oestrogen has in the above co‐morbidities related to obesity, we randomized C57BL/6J mice into four groups (15 mice per group): (i) male, (ii) non‐ovariectomized female (novx), (iii) ovariectomized female (ovx) and (iv) ovariectomized female mice supplemented with 17β estradiol (ovx‐E). Mice received either a low‐fat (LF) or a high‐fat (HF) diet for 10 weeks. Outcomes measured were bodyweight, body fat, adipocyte diameter, adipose tissue lipolysis markers, adipose tissue oxidative stress, inflammation, insulin resistance and liver steatosis. Results: Male and ovx‐female mice consuming the HF diet had a higher propensity of gaining weight, specifically in the form of body fat. Oestrogen protected female mice from adipocyte hypertrophy and from developing adipose tissue oxidative stress and inflammation. Moreover, novx‐female and ovx‐female+E mice had higher phosphorylated levels of protein kinase A and hormone sensitive lipase, markers associated with lipolysis. Additionally, male and ovx female mice had a higher propensity of developing liver steatosis and insulin resistance. In contrast, oestrogen protected female mice from developing liver steatosis and from becoming insulin resistant. Conclusion: We show that oestrogen protects female mice from adipocyte hypertrophy and adipose tissue oxidative stress and inflammation. Furthermore, oestrogen prevented female mice from developing liver steatosis and from becoming insulin resistant.     

Sitagliptin attenuates methionine/choline-deficient diet-induced steatohepatitis

Aims

Accumulating evidence suggests that inhibitors of dipeptidyl peptidase-4 (DPP-4), such as sitagliptin, may play an important role in the prevention of non-alcoholic steatohepatitis (NASH). This study was conducted to elucidate whether sitagliptin could prevent steatohepatitis by inhibiting pathways involved in hepatic steatosis, inflammation, and fibrosis.

Methods

C57BL/6 mice were fed a methionine/choline-deficient (MCD) diet with or without supplement with sitagliptin for 5 weeks. Liver and adipose tissue from mice were examined histologically and immunohistochemically to estimate the effect of sitagliptin on the development of NASH.

Results

Supplementation with sitagliptin resulted in significant improvement of MCD diet-induced fat accumulation in the liver. In addition, sitagliptin treatment lowered fatty acid uptake, expression of VLDL receptor and hepatic triglyceride content. Sitagliptin also effectively attenuated MCD diet-induced hepatic inflammation, endoplasmic reticulum (ER) stress, and liver injury, as evidenced by reduced proinflammatory cytokine levels, ER stress markers, and TUNEL staining. Expression of CYP2E1 and 4NHE were strongly increased by the MCD diet, but this effect was successfully prevented by sitagliptin treatment. Furthermore, sitagliptin significantly decreased levels of MCD diet-induced fibrosis-associated proteins such as fibronectin and α-SMA in the liver. Inflammatory and atrophic changes of adipose tissue by MCD diet were restored by sitagliptin treatment.

Conclusions

Sitagliptin attenuated MCD diet-induced hepatic steatosis, inflammation, and fibrosis in mice through amelioration of mechanisms responsible for the development of NASH, including CD36 expression, NF-κB activation, ER stress, CYP2E1 expression, and lipid peroxidation. Treatment with sitagliptin may represent an effective approach for the prevention and treatment of NASH.