Role of IL-6 in the resolution of pancreatitis in obese mice.
ABSTRACT: Obesity increases severity of acute pancreatitis and risk of pancreatic cancer. Pancreatitis and obesity are associated with elevated IL-6, a cytokine involved in inflammation and tumorigenesis. We studied the role of IL-6 in the response of lean and obese mice to pancreatitis induced by IL-12 + IL-18. Lean and diet-induced obese (DIO) WT and IL-6 KO mice and ob/ob mice pretreated with anti-IL-6 antibodies were evaluated at Days 1, 7, and 15 after induction of pancreatitis. Prolonged elevation of IL-6 in serum and visceral adipose tissue was observed in DIO versus lean WT mice, whereas circulating sIL-6R declined in DIO but not lean mice with pancreatitis. The severe inflammation and lethality of DIO mice were also observed in IL-6 KO mice. However, the delayed resolution of neutrophil infiltration; sustained production of CXCL1, CXCL2, and CCL2; prolonged activation of STAT-3; and induction of MMP-7 in the pancreas, as well as heightened induction of serum amylase A of DIO mice, were blunted significantly in DIO IL-6 KO mice. In DIO mice, production of OPN and TIMP-1 was increased for a prolonged period, and this was mediated by IL-6 in the liver but not the pancreas. Results obtained in IL-6 KO mice were confirmed in ob/ob mice pretreated with anti-IL-6 antibodies. In conclusion, IL-6 does not contribute to the increased severity of pancreatitis of obese mice but participates in delayed recovery from acute inflammation and may favor development of a protumorigenic environment through prolonged activation of STAT-3, induction of MMP-7, and sustained production of chemokines.
Project description:Tryptophan is reportedly the most potent agonist for GPR142. Glucose-stimulated insulin secretion (GSIS) from pancreatic beta cells are enhanced by GPR142-mediated signal. It is not clear, however, if GPR142-mediated signals is solely attributable to GSIS enhancement after tryptophan load in various pathophysiological settings. This study aims to reveal the significance of GPR142 signaling in tryptophan-mediated GSIS enhancement in normal and obese mice. Tryptophan significantly improved glucose tolerance in both lean and DIO mice, but the extent of improvement was bigger in DIO mice with augmented glucose-stimulated insulin secretion (GSIS) enhancement. The same results were obtained in ob/ob mice. GPR142 deletion almost completely blocked tryptophan actions in lean mice, suggesting that GPR142 signaling was solely responsible for the GSIS enhancement. In obese GPR142KO mice, however, a significant amount of tryptophan effects were still observed. Calcium-sensing receptors (CaSR) are also known to recognize tryptophan as ligand. Expression levels of CaSR were significantly elevated in the pancreas of DIO mice, and CaSR antagonist further blocked tryptophan's actions in DIO mice with GPR142 deletion. Although GPR142 signaling had a major role in tryptophan recognition for the enhancement of GSIS in lean mice, other pathways including CaSR signaling also had a significant role in obese mice, which seemed to contribute to the augmented enhancement of GSIS by tryptophan in these animals.
Project description:Galectins (Gal) exert many activities, including regulation of inflammation and adipogenesis. We evaluated modulation of Gal-1, -3, -9 and -12 in visceral (VAT) and subcutaneous (SAT) adipose tissue in mice.We used two mouse models of obesity, high-fat diet induced obesity (DIO) and ob/ob mice. We also evaluated the response of Gal-1 KO mice to DIO.Both age and diet modulated expression of galectins, with DIO mice having higher serum Gal-1 and Gal-3 versus lean mice after 13-17 weeks of high-fat diet. In DIO mice there was a progressive increase in expression of Gal-1 and Gal-9 in SAT, whereas Gal-3 increased in both VAT and SAT. Expression of Gal-12 declined over time in VAT of DIO mice, similar to adiponectin. Obesity lead to increased production of Gal-1 in adipocytes, whereas the increased Gal-3 and Gal-9 of obesity mostly derived from the stromovascular fraction. Expression of Gal-12 was restricted to adipocytes. There was increased production of Gal-3 and Gal-9, but not Gal-1, in CD11c(-) and CD11c(+) macrophages from VAT of DIO versus lean mice. Expression of Gal-1, -3 and -12 in VAT and SAT of ob/ob mice followed a trend comparable to DIO mice. Rosiglitazone reduced serum Gal-1, but not Gal-3 and modulated expression of Gal-3 in VAT and Gal-9 and Gal-12 in SAT of DIO mice. High-fat feeding lead to increased adiposity in Gal-1 KO versus WT mice, with loss of correlation between leptin and adiposity and no alterations in glucose and insulin levels.Obesity leads to differential modulation of Gal-1, 3, 9 and 12 in VAT and SAT, with Gal-1 acting as a modulator of adiposity.
Project description:OBJECTIVE:Obesity increases morbidity and resource utilization in sepsis patients. Sepsis transitions from early/hyper-inflammatory to late/hypo-inflammatory phase. Majority of sepsis-mortality occurs during the late sepsis; no therapies exist to treat late sepsis. In lean mice, we have shown that sirtuins (SIRTs) modulate this transition. Here, we investigated the role of sirtuins, especially the adipose-tissue abundant SIRT-2 on transition from early to late sepsis in obese with sepsis. METHODS:Sepsis was induced using cecal ligation and puncture (CLP) in ob/ob mice. We measured microvascular inflammation in response to lipopolysaccharide/normal saline re-stimulation as a "second-hit" (marker of immune function) at different time points to track phases of sepsis in ob/ob mice. We determined SIRT-2 expression during different phases of sepsis. We studied the effect of SIRT-2 inhibition during the hypo-inflammatory phase on immune function and 7-day survival. We used a RAW264.7 (RAW) cell model of sepsis for mechanistic studies. We confirmed key findings in diet induced obese (DIO) mice with sepsis. RESULTS:We observed that the ob/ob-septic mice showed an enhanced early inflammation and a persistent and prolonged hypo-inflammatory phase when compared to WT mice. Unlike WT mice that showed increased SIRT1 expression, we found that SIRT2 levels were increased in ob/ob mice during hypo-inflammation. SIRT-2 inhibition in ob/ob mice during the hypo-inflammatory phase of sepsis reversed the repressed microvascular inflammation in vivo via activation of endothelial cells and circulating leukocytes and significantly improved survival. We confirmed the key finding of the role of SIRT2 during hypo-inflammatory phase of sepsis in this project in DIO-sepsis mice. Mechanistically, in the sepsis cell model, SIRT-2 expression modulated inflammatory response by deacetylation of NF?Bp65. CONCLUSION:SIRT-2 regulates microvascular inflammation in obese mice with sepsis and may provide a novel treatment target for obesity with sepsis.
Project description:Drug pharmacokinetics can be altered in obese and diabetic subjects. In consideration of the prevalence of obesity and diabetes, characterization of transporter expression in mouse models of diabetes and obesity may be a useful tool to aid in prediction of altered drug pharmacokinetics or adverse drug reactions. It has been reported that ob/ob mice, which display a severe obesity and diabetes phenotype, exhibit multiple changes in drug transporter expression in liver and kidney. In the present study, the mRNA and protein expression of major drug transporters was determined in livers and kidneys of diet-induced obese (DIO) C57BL/6J male mice. The mice were fed a high-fat diet (HFD) (60% fat) from 6 weeks of age and display obesity, fatty liver, and mild hyperglycemia. The HFD diet increased expression of multidrug resistance-associated proteins Abcc3 and 4 mRNA and protein in liver by 3.4- and 1.4-fold, respectively, compared with that detected in control mice fed a low-fat diet (LFD). In contrast, Abcc1 mRNA and protein decreased by 50% in livers of DIO mice compared with those in livers to lean mice. The HFD did not alter transporter expression in kidney compared with the LFD. In summary, unlike ob/ob and db/db mice, DIO mice exhibited a selective induction of efflux transporter expression in liver (i.e., Abcc3 and 4). In addition, diet-induced obesity affects transporter expression in liver but not kidney in the C57BL/6J mouse model. These data indicate that hepatic transporter expression is only slightly altered in a model of mild diabetes and nonalcoholic fatty liver disease and obesity.
Project description:The arcuate nucleus (ARC) of the hypothalamus plays a key role in sensing metabolic feedback and regulating energy homeostasis. Recent studies revealed activation of microglia in mice with high-fat diet (HFD)-induced obesity (DIO), suggesting a potential pathophysiological role for inflammatory processes within the hypothalamus. To further investigate the metabolic causes and molecular underpinnings of such glial activation, we analyzed the microglial activity in wild-type (WT), monogenic obese ob/ob (leptin deficient), db/db (leptin-receptor mutation), and Type-4 melanocortin receptor knockout (MC4R KO) mice on either a HFD or on standardized chow (SC) diet. Following HFD exposure, we observed a significant increase in the total number of ARC microglia, immunoreactivity of ionized calcium binding adaptor molecule 1 (iba1-ir), cluster of differentiation 68 (CD68-ir), and ramification of microglial processes. The ob/ob mice had significantly less iba1-ir and ramifications. Leptin replacement rescued these phenomena. The db/db mice had similar iba1-ir comparable with WT mice but had significantly lower CD68-ir and more ramifications than WT mice. After 2 weeks of HFD, ob/ob mice showed an increase of iba1-ir, and db/db mice showed increase of CD68-ir. Obese MC4R KO mice fed a SC diet had comparable iba1-ir and CD68-ir with WT mice but had significantly more ramifications than WT mice. Intriguingly, treatment of DIO mice with glucagon-like peptide-1 receptor agonists reduced microglial activation independent of body weight. Our results show that diet type, adipokines, and gut signals, but not body weight, affect the presence and activity levels of hypothalamic microglia in obesity.
Project description:Obesity, and in particular visceral obesity, has been associated with an increased risk of developing cancers as well as higher rates of mortality following diagnosis. The impact of obesity on adipose-derived stromal cells (ASC), which contribute to the formation of tumor stroma, is unknown. Here we hypothesized that visceral source and diet-induced obesity (DIO) changes the ASC phenotype, contributing to the tumor promoting effects of obesity. We found that ASC isolated from subcutaneous (SC-ASC) and visceral (V-ASC) white adipose tissue(WAT) of lean(Le) and obese(Ob) mice exhibited similar mesenchymal cell surface markers expression, and had comparable effects on ovarian cancer cell proliferation and migration. Obese and visceral derived ASC proliferated slower and exhibited impaired differentiation into adipocytes and osteocytes in vitro as compared to ASC derived from subcutaneous WAT of lean mice. Intraperitoneal co-injection of ovarian cancer cells with obese or visceral derived ASC, but not lean SC-ASC, increased growth of intraperitoneal ID8 tumors as compared to controls. Obese and V-ASC increased stromal infiltration of inflammatory cells, including CD3+ T cells and F4/80+ macrophages. Obese and visceral derived ASC, but not lean SC-ASC, increased expression of chemotactic factors IL-6, MIP-2, and MCP-1 when cultured with tumor cells. Overall, these results demonstrate that obese and V-ASC have a unique phenotype, with more limited proliferation and differentiation capacity but enhanced expression of chemotactic factors in response to malignant cells which support infiltration of inflammatory cells and support tumor growth and dissemination.
Project description:While adipose tissue-associated macrophages contribute to development of chronic inflammation and insulin resistance of obesity, little is known about the role of hepatic Kupffer cells in this environment. Here we address the impact of Kupffer cell ablation using clodronate-encapsulated liposome depletion in a diet-induced obese (DIO) and insulin resistant mouse model. Hepatic expression of macrophage markers measured by realtime RT-PCR remained unaltered in DIO mice despite characteristic expansion of adipose tissue-associated macrophages. DIO mouse livers displayed increased expression of alternative activation markers but unaltered proinflammatory cytokine expression when compared to lean mice. Kupffer cell ablation reduced hepatic anti-inflammatory cytokine IL-10 mRNA expression in lean and DIO mice by 95% and 84%, respectively. Despite decreased hepatic IL-6 gene expression after ablation in lean and DIO mice, hepatic STAT3 phosphorylation, Socs3 and acute phase protein mRNA expression increased. Kupffer cell ablation in DIO mice resulted in additional hepatic triglyceride accumulation and a 30-40% reduction in hepatic insulin receptor autophosphorylation and Akt activation. Implicating systemic loss of IL-10, high-fat-fed IL-10 knockout mice also displayed increased hepatic STAT3 signaling and hepatic triglyceride accumulation. Insulin signaling was not altered, however. In conclusion, Kupffer cells are a major source of hepatic IL-10 expression, the loss of which is associated with increased STAT3-dependent signaling and steatosis. One or more additional factors appear to be required, however, for the Kupffer cell-dependent protective effect on insulin receptor signaling in DIO mice.
Project description:Previous studies have proposed roles for hypothalamic reactive oxygen species (ROS) in the modulation of circuit activity of the melanocortin system. Here we show that suppression of ROS diminishes pro-opiomelanocortin (POMC) cell activation and promotes the activity of neuropeptide Y (NPY)- and agouti-related peptide (AgRP)-co-producing (NPY/AgRP) neurons and feeding, whereas ROS-activates POMC neurons and reduces feeding. The levels of ROS in POMC neurons were positively correlated with those of leptin in lean and ob/ob mice, a relationship that was diminished in diet-induced obese (DIO) mice. High-fat feeding resulted in proliferation of peroxisomes and elevated peroxisome proliferator-activated receptor ? (PPAR-?) mRNA levels within the hypothalamus. The proliferation of peroxisomes in POMC neurons induced by the PPAR-? agonist rosiglitazone decreased ROS levels and increased food intake in lean mice on high-fat diet. Conversely, the suppression of peroxisome proliferation by the PPAR antagonist GW9662 increased ROS concentrations and c-fos expression in POMC neurons. Also, it reversed high-fat feeding-triggered elevated NPY/AgRP and low POMC neuronal firing, and resulted in decreased feeding of DIO mice. Finally, central administration of ROS alone increased c-fos and phosphorylated signal transducer and activator of transcription 3 (pStat3) expression in POMC neurons and reduced feeding of DIO mice. These observations unmask a previously unknown hypothalamic cellular process associated with peroxisomes and ROS in the central regulation of energy metabolism in states of leptin resistance.
Project description:Recent research links diet-induced obesity (DIO) with impaired immunity, although the underlying mechanisms remain unclear. We find that the induction of inducible NO synthase (iNOS) and cytokines is suppressed in mice with DIO and in bone marrow macrophages (BMMPhi) from mice with DIO exposed to an oral pathogen, Porphyromonas gingivalis. BMMPhi from lean mice pre-treated with free fatty acids (FFAs) and exposed to P. gingivalis also exhibit a diminished induction of iNOS and cytokines. BMMPhi from lean and obese mice exposed to P. gingivalis and analyzed by a phosphorylation protein array show a reduction of Akt only in BMMPhi from mice with DIO. This reduction is responsible for diminished NF-kappaB activation and diminished induction of iNOS and cytokines. We next observed that Toll-like receptor 2 (TLR2) is suppressed in BMMPhi from DIO mice whereas carboxy-terminal modulator protein (CTMP), a known suppressor of Akt phosphorylation, is elevated. This elevation stems from defective TLR2 signaling. In BMMPhi from lean mice, both FFAs and TNF-alpha--via separate pathways--induce an increase in CMTP. However, in BMMPhi from DIO mice, TLR2 can no longer inhibit the TNF-alpha-induced increase in CTMP caused by P. gingivalis challenge. This defect can then be restored by transfecting WT TLR2 into BMMPhi from DIO mice. Thus, feeding mice a high-fat diet over time elevates the CTMP intracellular pool, initially via FFAs activating TLR2 and later when the defective TLR2 is unable to inhibit TNF-alpha-induced CTMP. These findings unveil a link between obesity and innate immunity.
Project description:Associations between modifiable factors and the efficacy of cancer immunotherapies remain uncertain. We found previously that diet-induced obesity (DIO) reduces the efficacy of an immunotherapy consisting of adenovirus-encoded TRAIL plus CpG oligonucleotide (AdT/CpG) in mice with renal tumors. To eliminate confounding effects of diet and determine whether outcomes could be improved in DIO mice, we evaluated AdT/CpG combined with anti-CTLA-4 in diet-matched, obese-resistant (OB-RES) versus DIO tumor-bearing mice. Therapy-treated OB-RES mice displayed effective renal tumor control and sustained CD4<sup>+</sup> and CD8<sup>+</sup> T cell responses. In contrast, therapy-treated DIO mice exhibited progressive tumor outgrowth and blunted T cell responses, characterized by reduced intratumoral frequencies of IFNγ<sup>+</sup> CD4<sup>+</sup> and CD8<sup>+</sup> T cells. Weak effector T cell responses in therapy-treated DIO mice were accompanied by low intratumoral concentrations of the T cell chemoattractant CCL5, heightened concentrations of pro-tumorigenic GM-CSF, and impaired proliferative capacity of CD44<sup>+</sup>CD8<sup>+</sup> T cells in tumor-draining lymph nodes. Our findings demonstrate that in lean mice with renal tumors, combining in situ T cell priming upstream of anti-CTLA-4 enhances outcomes versus anti-CTLA-4 alone. However, host obesity is associated with heightened immunotherapy resistance, characterized by multi-factorial deficiencies in effector CD4<sup>+</sup> and CD8<sup>+</sup> T cell responses that extend beyond the tumor microenvironment.