A family of tissue-specific resistin-like molecules

Epithelial-derived IL-33 promotes intestinal tumorigenesis in Apc Min/+ mice

Increased expression of Interleukin (IL)-33 has been detected in intestinal samples of patients with ulcerative colitis, a condition associated with increased risk for colon cancer, but its role in the development of colorectal cancer has yet to be fully examined. Here, we investigated the role of epithelial expressed IL-33 during development of intestinal tumors. IL-33 expression was detected in epithelial cells in colorectal cancer specimens and in the Apc^Min/+ mice. To better understand the role of epithelial-derived IL-33 in the intestinal tumorigenesis, we generated transgenic mice expressing IL-33 in intestinal epithelial cells (V33 mice). V33 Apc^Min/+ mice, resulting from the cross of V33 with Apc^Min/+ mice, had increased intestinal tumor burden compared with littermate Apc^Min/+ mice. Consistently, Apc^Min/+ mice deficient for IL-33 receptor (ST2), had reduced polyp burden. Mechanistically, overexpression of IL-33 promoted expansion of ST2⁺ regulatory T cells, increased Th2 cytokine milieu, and induced alternatively activated macrophages in the gut. IL-33 promoted marked changes in the expression of antimicrobial peptides, and antibiotic treatment of V33 Apc^Min/+ mice abrogated the tumor promoting-effects of IL-33 in the colon. In conclusion, elevated IL-33 signaling increases tumor development in the Apc^Min/+ mice.

Increased expression of resistin in ectopic endometrial tissue of women with endometriosis

PROBLEM

Inflammation is a key process in the establishment and progression of endometriosis. Resistin, an adipocytokine, has biological properties linked to immunologic functions, but its role in endometriosis is unclear.

METHOD OF STUDY

Resistin gene expression was examined in eutopic and ectopic endometrial tissues from women with (n=25) or without (n=25) endometriosis. Resistin mRNA and protein levels were determined in endometrial tissue using quantitative real-time reverse transcription PCR and Western blotting, following adipokine profiling arrays.

RESULTS

Resistin protein was detected in human endometrial tissues using an adipokine array test. Resistin mRNA and protein levels were significantly higher in ectopic endometrial tissue of patients with endometriosis than in normal eutopic endometrial tissue.

CONCLUSION

Our results indicate that resistin is differentially expressed in endometrial tissues from women with endometriosis and imply a role for resistin in endometriosis-associated pelvic inflammation.

Corticoids synergize with IL-1 in the induction of LCN2

OBJECTIVE

Lipocalin-2 (LCN2) is an adipokine that was first identified in neutrophil granules. In the last years it was recognized as a factor that could impair chondrocyte phenotype, cartilage homeostasis as well as growth plate development. Both pro-inflammatory cytokines and glucocorticoids (GCs) modulate LCN2 expression. Actually, GCs were found to be LCN2 inducers, suggesting that part of the negative actions exerted by these anti-inflammatory drugs at cartilage level could be mediated by this adipokine. So, in this study we wanted to investigate whether corticoids were able to act in synergy with IL-1 in the induction of LCN2 and the signaling pathway involved in this process.

MATERIALS AND METHODS

For the realization of this work, ATDC5 mouse chondrogenic cell line was used. We determined the mRNA and protein expression of LCN2 by real-time reverse transcription-polymerase chain reaction (RT-qPCR) and western blot respectively, after GC or mineralcorticoid treatment. Different signaling pathways inhibitors were also used.

RESULTS

GC and mineralcorticoid were able to induce the expression of LCN2 in ATDC5 cells. Interestingly, both corticoids synergized with IL-1 in the induction of LCN2. The effect of these corticoids on the expression of LCN2 occurred through GC or mineralcorticoid receptors and the kinases PI3K, ERK1/2 and JAK2.

CONCLUSIONS

Prolonged use of corticoids may have detrimental effects on cartilage homeostasis. Based on our results, we conclude that corticoids could increase the negative actions exerted by IL-1 by increasing the expression of LCN2.

Adipokine Contribution to the Pathogenesis of Osteoarthritis

Recent studies have shown that overweight and obesity play an important role in the development of osteoarthritis (OA). However, joint overload is not the only risk factor in this disease. For instance, the presence of OA in non-weight-bearing joints such as the hand suggests that metabolic factors may also contribute to its pathogenesis. Recently, white adipose tissue (WAT) has been recognized not only as an energy reservoir but also as an important secretory organ of adipokines. In this regard, adipokines have been closely associated with obesity and also play an important role in bone and cartilage homeostasis. Furthermore, drugs such as rosuvastatin or rosiglitazone have demonstrated chondroprotective and anti-inflammatory effects in cartilage explants from patients with OA. Thus, it seems that adipokines are important factors linking obesity, adiposity, and inflammation in OA. In this review, we are focused on establishing the physiological mechanisms of adipokines on cartilage homeostasis and evaluating their role in the pathophysiology of OA based on evidence derived from experimental research as well as from clinical-epidemiological studies.

Adipose tissue: an endocrine organ playing a role in metabolic regulation

Adipose tissue is a complex endocrine organ with an intricate role in whole body homeostasis. Beyond storing energy, adipose tissue is fundamental in numerous processes including, but not limited to, metabolism, food intake and immune cell function. Adipokines and cytokines are the signaling factors from adipose tissue. These factors play a role in maintaining health, but are also candidates for pathologies associated with obesity. Indeed excessive adiposity causes dysregulation of these factors which negatively affect health and contribute to numerous obesity-induced co-morbidities. In particular, adipokines are fundamental in regulation of glucose homeostasis and insulin signaling, thus aberrant production of these adipose derived hormones correlates with the development and progression of type 2 diabetes. Therefore, elucidation of adipose regulation is crucial for understanding the pathophysiological basis of obesity and metabolic diseases such as type 2 diabetes. In the present review, we summarize current data on the relation between adipokines and adipose depot derived cytokines in the maintenance of glucose homeostasis. Specifically, physiological and molecular functions of several adipokines are defined with particular focus on interactions within the insulin-signaling pathway and subsequent regulation of glucose uptake in both standard and obesity-induced dysregulated conditions. This same relation will be discussed for cytokines and inflammation as well.

Adipokines: Potential Therapeutic Targets for Vascular Dysfunction in Type II Diabetes Mellitus and Obesity

Adipokines are bioactive molecules that regulate several physiological functions such as energy balance, insulin sensitization, appetite regulation, inflammatory response, and vascular homeostasis. They include proinflammatory cytokines such as adipocyte fatty acid binding protein (A-FABP) and anti-inflammatory cytokines such as adiponectin, as well as vasodilator and vasoconstrictor molecules. In obesity and type II diabetes mellitus (DM), insulin resistance causes impairment of the endocrine function of the perivascular adipose tissue, an imbalance in the secretion of vasoconstrictor and vasodilator molecules, and an increased production of reactive oxygen species. Recent studies have shown that targeting plasma levels of adipokines or the expression of their receptors can increase insulin sensitivity, improve vascular function, and reduce the risk of cardiovascular morbidity and mortality. Several reviews have discussed the potential of adipokines as therapeutic targets for type II DM and obesity; however, this review is the first to focus on their therapeutic potential for vascular dysfunction in type II DM and obesity.

The Enigmatic Gut in Cystic Fibrosis: Linking Inflammation, Dysbiosis, and the Increased Risk of Malignancy

PURPOSE OF REVIEW

Intestinal inflammation, dysbiosis, and increased gastrointestinal malignancy risks are well-described in patients with cystic fibrosis (CF). However, there is limited understanding of their pathophysiology. This review aims to discuss these issues and assess potential links between them.

RECENT FINDINGS

Evidence of links between intestinal inflammation and dysbiosis (an imbalance in intestinal microbial populations) exist. Recent studies have demonstrated reduction in intestinal inflammation with probiotic administration. Both bacterial dysbiosis and gut inflammation contribute to the suboptimal nutritional status seen in children with CF. Short-chain fatty acids may be reduced in the gut lumen as a result of bacterial imbalances and may promote inflammation. Inflammation and bacterial dysbiosis in CF may also contribute to emerging adult complications such as gastrointestinal malignancy. An increase in carcinogenic microbes and reduction in microbes protective against cancer have been found in CF, linking bacterial dysbiosis and cancer. Murine studies suggest the CF gene, cystic fibrosis transmembrane conductance regulator (CFTR) gene, itself may be a tumour suppressor gene. The pathophysiology of interactions among intestinal inflammation, dysbiosis, and malignancy in CF is not clearly understood and requires further research.

Chronic Pancreatitis Associated Acute Respiratory Failure

Pancreatitis is a condition characterized by parenchymal inflammation of the pancreas, which is often associated with lung injury due to low level of oxygen and the condition is termed as acute pancreatitis-associated lung injury (APALI). Clinical reports indicated that ~ 20% to 50% of patients from low oxygen levels in blood with acute respiratory distress syndrome (ARDS). ARDS is a severe form of acute lung injury (ALI), a pulmonary disease with impaired airflow making patients difficult to breathe. ALI is frequently observed in patients with severe acute pancreatitis. Approximately one third of severe pancreatitis patients develop acute lung injury and acute respiratory distress syndrome that account for 60% of all deaths within the first week. The major causes of ALI and ARDS are sepsis, trauma, aspiration, multiple blood transfusion, and most importantly acute pancreatitis. The molecular mechanisms of ALI and ARDS are still not well explored, but available reports indicate the involvement of several pro-inflammatory mediators including cytokines (TNF-α, IL-1β, IL-6) and chemokines [like interleukin-8 (IL-8) and macrophage inhibitory factor (MIF)], as well as macrophage polarization regulating the migration and pulmonary infiltration of neutrophils into the pulmonary interstitial tissue, causing injury to the pulmonary parenchyma. Acute lung injury and acute respiratory distress syndrome in acute pancreatitis remains an unsolved issue and needs more research and resources to develop effective treatments and therapies. However, recent efforts have tested several molecules in an experimental model and showed promising results as a treatment option. The current review summarized the mechanism that is operational in pancreatitis-associated acute respiratory failure and respiratory distress syndrome in patients and current treatment options.

High serum resistin associates with intrahepatic inflammation and necrosis: an index of disease severity for patients with chronic HBV infection

BACKGROUND

Studies have revealed that resistin plays a role as an intrahepatic cytokine with proinflammatory activities. This study investigated the association between serum resistin and fibrosis severity and the possible marker role of resistin in the inflammatory process of chronic hepatitis B.

METHODS

In this study, 234 subjects with HBV infection were retrospectively selected, including 85 patients with chronic hepatitis B (CHB), 70 patients with HBV-related liver cirrhosis (LC-B), and 79 patients with HBV-related liver failure (LF-B). Serum levels of resistin, IL-1, IL-6, IL-17, IL-23, TNF-α, and TGF-β1 were assayed by ELISA. Demographic and clinical characteristics of patients were extracted from clinical databases of Taihe Hospital, Hubei University of Medicine, including serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBil), and liver stiffness (LS).

RESULTS

All the selected patients with HBV infection showed significantly increased levels of serum resistin, which was rarely detectable in the healthy controls. Serum resistin levels in patients with CHB, LC-B, and LF-B were 4.119 ± 5.848 ng/mL, 6.370 ± 6.834 ng/mL, and 6.512 ± 6.076 ng/mL, respectively. Compared with the CHB group, patients with LC-B or LF-B presented with significantly higher serum levels of resistin (p < 0.01). On the other hand, all of the enrolled patients had high serum levels of IL-1, IL-6, IL-17, TNF-α, and TGF-β1, but not IL-23. Interestingly, serum levels of resistin was significantly positively correlated with serum levels of TGF-β1 in LC-B patients (R = 0.3090, p = 0.0290), with IL-17 in LC-B (R = 0.4022, p = 0.0038) and LF-B patients (R = 0.5466, p < 0.0001), and with AST (R = 0.4501, p = 0.0036) and LS (R = 0.3415, p = 0.0310) in CHB patients.

CONCLUSIONS

High serum resistin associates with intrahepatic inflammation and necrosis and may be used as an index of disease severity for patients with chronic HBV infection.

Obesity-associated cancer risk: the role of intestinal microbiota in the etiology of the host proinflammatory state

Obesity increases the risks of many cancers. One important mechanism behind this association is the obesity-associated proinflammatory state. Although the composition of the intestinal microbiome undoubtedly can contribute to the proinflammatory state, perhaps the most important aspect of host-microbiome interactions is host exposure to components of intestinal bacteria that stimulate inflammatory reactions. Systemic exposures to intestinal bacteria can be modulated by dietary factors through altering both the composition of the intestinal microbiota and the absorption of bacterial products from the intestinal lumen. In particular, high-fat and high-energy diets have been shown to facilitate absorption of bacterial lipopolysaccharide (LPS) from intestinal bacteria. Biomarkers of bacterial exposures that have been measured in blood include LPS-binding protein, sCD14, fatty acids characteristic of intestinal bacteria, and immunoglobulins specific for bacterial LPS and flagellin. The optimal strategies to reduce these proinflammatory exposures, whether by altering diet composition, avoiding a positive energy balance, or reducing adipose stores, likely differ in each individual. Biomarkers that assess systemic bacterial exposures therefore should be useful to (1) optimize and personalize preventive approaches for individuals and groups with specific characteristics and to (2) gain insight into the possible mechanisms involved with different preventive approaches.

Adipose tissue in control of metabolism

Adipose tissue plays a central role in regulating whole-body energy and glucose homeostasis through its subtle functions at both organ and systemic levels. On one hand, adipose tissue stores energy in the form of lipid and controls the lipid mobilization and distribution in the body. On the other hand, adipose tissue acts as an endocrine organ and produces numerous bioactive factors such as adipokines that communicate with other organs and modulate a range of metabolic pathways. Moreover, brown and beige adipose tissue burn lipid by dissipating energy in the form of heat to maintain euthermia, and have been considered as a new way to counteract obesity. Therefore, adipose tissue dysfunction plays a prominent role in the development of obesity and its related disorders such as insulin resistance, cardiovascular disease, diabetes, depression and cancer. In this review, we will summarize the recent findings of adipose tissue in the control of metabolism, focusing on its endocrine and thermogenic function.

Obesity, Inflammation, and Periodontal Disease

The prevalence of obesity has increased substantially over the past decades in most industrialized countries. Obesity is a systemic disease that predisposes to a variety of co-morbidities and complications that affect overall health. Cross-sectional studies suggest that obesity is also associated with oral diseases, particularly periodontal disease, and prospective studies suggest that periodontitis may be related to cardiovascular disease. The possible causal relationship between obesity and periodontitis and potential underlying biological mechanisms remain to be established; however, the adipose tissue actively secretes a variety of cytokines and hormones that are involved in inflammatory processes, pointing toward similar pathways involved in the pathophysiology of obesity, periodontitis, and related inflammatory diseases. We provide an overview of the definition and assessment of obesity and of related chronic diseases and complications that may be important in the periodontist’s office. Studies that have examined the association between obesity and periodontitis are reviewed, and adipose-tissue-derived hormones and cytokines that are involved in inflammatory processes and their relationship to periodontitis are discussed. Our aim is to raise the periodontist’s awareness when treating obese individuals.

Relevance Study on Cerebral Infarction and Resistin Gene Polymorphism in Chinese Han Population

Recent research on genome-wide associations has implicated that the serum resistin level and its gene polymorphism are associated with cerebral infarction (CI) morbidity and prognosis, and could thereby regulate CI. This study aimed to investigate the association between the resistin single nucleotide polymorphism (SNP) and the susceptibility to CI in the Chinese Han population. A total of 550 CI patients and 313 healthy controls were genotyped. Nine SNPs of the resistin gene previously shown were sequenced and assessed for an association with CI. The numbers of GG genotype carriers of rs3219175 and rs3486119 in the CI group were significantly higher than those in the control group among the middle-aged group (aged 45-65), at 76% vs 67.9% (P=0.025) and 75.5% vs 67.9% (P=0.031). rs3219175 and rs34861192 were associated with CI in the dominant and superdominant models according to the genetic model analysis (P<0.05). Meanwhile, there was strong linkage disequilibrium among the rs34124816, rs3219175, rs34861192, rs1862513, rs3745367, 180C/G and rs3745369 sites. In a haplotype analysis, the occurrence rate of the haplotype AGGCAGC was 1.97 times (P<0.05) higher in the patient group than in the control group. In addition, the numbers of GG genotype carriers of rs3219175 and rs3486119 in the middle-aged male CI patients and the middle-aged small artery occlusion (SAO) CI patients were higher than those in the control group (P<0.05). In the Chinese Han middle-aged population, the GG gene type carriers of the resistin gene sites rs3219175 and rs34861192 had a high risk for CI onset, especially in middle-aged male patients and SAO CI in all middle-aged patients.

The goblet cell-derived mediator RELM-β drives spontaneous colitis in Muc2-deficient mice by promoting commensal microbial dysbiosis

Intestinal goblet cells are potentially key players in controlling susceptibility to ulcerative colitis (UC). Although impaired mucin (Muc2) production by goblet cells increases microbial stimulation of the colonic mucosa, goblet cells secrete other mediators that may influence or promote UC development. Correspondingly, Muc2-deficient ((-/-)) mice develop spontaneous colitis, concurrent with the dramatic upregulation of the goblet cell mediator, resistin-like molecule-beta (RELM-β). Testing RELM-β's role, we generated Muc2(-/-)/Retnlb(-/-) mice, finding that RELM-β deficiency significantly attenuated colitis development and symptoms compared with Muc2(-/-) mice. RELM-β expression in Muc2(-/-) mice strongly induced the production/secretion of the antimicrobial lectin RegIIIβ, that exerted its microbicidal effect predominantly on Gram-positive Lactobacillus species. Compared with Muc2(-/-)/Retnlb(-/-) mice, this worsened intestinal microbial dysbiosis with a selective loss of colonic Lactobacilli spp. in Muc2(-/-) mice. Orally replenishing Muc2(-/-) mice with murine Lactobacillus spp., but not with a probiotic formulation containing several human Lactobacillus spp. (VSL#3), ameliorated their spontaneous colitis in concert with increased production of short-chain fatty acids. These studies demonstrate that the goblet cell mediator RELM-β drives colitis in Muc2(-/-) mice by depleting protective commensal microbes. The ability of selective commensal microbial replacement to ameliorate colitis suggests that personalized bacterial therapy may prove beneficial for treatment of UC.

Circulating Resistin Levels and Risk of Colorectal Cancer: A Meta-Analysis

Objectives. Published data on resistin levels in patients with colorectal cancer (CRC) were conflicting and heterogeneous. We conducted a meta-analysis of observational studies to examine the association of circulating resistin levels with carcinogenesis of the CRC. Methods. Potentially eligible studies published up to November 2015 were searched through MEDLINE, EMBASE, Science Citation Index Expanded database, CNKI, and WanFang database. The pooled weighted mean differences (WMDs) with 95% confidence intervals (CIs) calculated by fixed- or random-effect model were used to estimate the effects. Results. A total of 11 studies involving 965 patients were admitted in our meta-analysis. The pooled effects indicated that resistin levels were higher in CRC patients compared to healthy controls (WMD: 1.47 ng/mL; 95% CI: 0.78 to 2.16), with significant heterogeneity across the studies (I² = 72%, p < 0.0001). Subgroup analyses and sensitivity analyses revealed that study quality, design, sample type, and resistin assays may account for this heterogeneity. No publication bias was observed. Conclusions. Our meta-analysis suggests that increased circulating resistin levels are associated with greater risk of colorectal cancer. Given the limited number of available studies and significant heterogeneity, larger well-designed randomized studies are warranted.

CD301b(+) Mononuclear Phagocytes Maintain Positive Energy Balance through Secretion of Resistin-like Molecule Alpha

Mononuclear phagocytes (MNPs) are a highly heterogeneous group of cells that play important roles in maintaining the body's homeostasis. Here, we found CD301b (also known as MGL2), a lectin commonly used as a marker for alternatively activated macrophages, was selectively expressed by a subset of CD11b(+)CD11c(+)MHCII(+) MNPs in multiple organs including adipose tissues. Depleting CD301b(+) MNPs in vivo led to a significant weight loss with increased insulin sensitivity and a marked reduction in serum Resistin-like molecule (RELM) α, a multifunctional cytokine produced by MNPs. Reconstituting RELMα in CD301b(+) MNP-depleted animals restored body weight and normoglycemia. Thus, CD301b(+) MNPs play crucial roles in maintaining glucose metabolism and net energy balance.

E74-like factor 3 and nuclear factor-κB regulate lipocalin-2 expression in chondrocytes

KEY POINTS

E74-like factor 3 (ELF3) is a transcription factor regulated by inflammation in different physio-pathological situations. Lipocalin-2 (LCN2) emerged as a relevant adipokine involved in the regulation of inflammation. In this study we showed for the first time the involvement of ELF3 in the control of LCN2 expression and its cooperation with nuclear factor-κB (NFκB). Our results will help to better understand of the role of ELF3, NFκB and LCN2 in the pathophysiology of articular cartilage.

ABSTRACT

E74-like factor 3 (ELF3) is a transcription factor induced by inflammatory cytokines in chondrocytes that increases gene expression of catabolic and inflammatory mediators. Lipocalin 2 (LCN2) is a novel adipokine that negatively impacts articular cartilage, triggering catabolic and inflammatory responses in chondrocytes. Here, we investigated the control of LCN2 gene expression by ELF3 in the context of interleukin 1 (IL-1)-driven inflammatory responses in chondrocytes. The interaction of ELF3 and nuclear factor-κB (NFκB) in modulating LCN2 levels was also explored. LCN2 mRNA and protein levels, as well those of several other ELF3 target genes, were determined by RT-qPCR and Western blotting. Human primary chondrocytes, primary chondrocytes from wild-type and Elf3 knockout mice, and immortalized human T/C-28a2 and murine ATDC5 cell lines were used in in vitro assays. The activities of various gene reporter constructs were evaluated by luciferase assays. Gene overexpression and knockdown were performed using specific expression vectors and siRNA technology, respectively. ELF3 overexpression transactivated the LCN2 promoter and increased the IL-1-induced mRNA and protein levels of LCN2, as well as the mRNA expression of other pro-inflammatory mediators, in human and mouse chondrocytes. We also identified a collaborative loop between ELF3 and NFκB that amplifies the induction of LCN2. Our findings show a novel role for ELF3 and NFκB in the induction of the pro-inflammatory adipokine LCN2, providing additional evidence of the interaction between ELF3 and NFκB in modulating inflammatory responses, and a better understanding of the mechanisms of action of ELF3 in chondrocytes.

Serum levels of resistin and interleukin-17 are associated with increased cartilage defects and bone marrow lesions in patients with knee osteoarthritis

OBJECTIVES

To investigate cross-sectional associations between serum levels of resistin and interleukin-17 (IL-17) and cartilage defects and bone marrow lesions (BMLs) in patients with knee symptomatic osteoarthritis (OA).

METHODS

One hundred and ninety-four consecutively-selected patients with knee symptomatic OA (mean 55.4 years, range 34-74, 87% females) were included in Anhui Osteoarthritis (AHOA) Study. Knee cartilage defects and BMLs were determined at different sites using T2-weighted fat-suppressed fast spin echo MRI. Serum resistin, IL-17, and high-sensitivity C-reactive protein (hs-CRP) levels were measured using ELISA.

RESULTS

In multivariable analyses, serum resistin was positively associated with cartilage defects at lateral femoral, lateral tibial, and medial tibial (all p < 0.05) sites. The significant associations were also present with BMLs at lateral femoral and tibial sites (ORs: 1.13-1.19, both p < 0.05). In patients with the highest quartile of hs-CRP (>2.45 pg/ml), IL-17 was positively and significantly associated with cartilage defect score at nearly all sites (ORs: 1.33-1.44, all p < 0.05), and BMLs at lateral and medial femoral sites (ORs: 1.26-1.51, both p < 0.05).

CONCLUSIONS

Serum levels of resistin were positively and independently associated with cartilage defects and BMLs in patients with knee OA. Serum IL-17 was significantly associated with cartilage defects and BMLs in patients with an increased inflammatory status. These suggest that metabolic and inflammatory mechanisms may have a role to play in knee OA.

Pathological Type-2 Immune Response, Enhanced Tumor Growth, and Glucose Intolerance in Retnlβ (RELMβ) Null Mice: A Model of Intestinal Immune System Dysfunction in Disease Susceptibility

Resistin, and its closely related homologs, the resistin-like molecules (RELMs) have been implicated in metabolic dysregulation, inflammation, and cancer. Specifically, RELMβ, expressed predominantly in the goblet cells in the colon, is released both apically and basolaterally, and is hence found in both the intestinal lumen in the mucosal layer as well as in the circulation. RELMβ has been linked to both the pathogenesis of colon cancer and type 2 diabetes. RELMβ plays a complex role in immune system regulation, and the impact of loss of function of RELMβ on colon cancer and metabolic regulation has not been fully elucidated. We therefore tested whether Retnlβ (mouse ortholog of human RETNLβ) null mice have an enhanced or reduced susceptibility for colon cancer as well as metabolic dysfunction. We found that the lack of RELMβ leads to increased colonic expression of T helper cell type-2 cytokines and IL-17, associated with a reduced ability to maintain intestinal homeostasis. This defect leads to an enhanced susceptibility to the development of inflammation, colorectal cancer, and glucose intolerance. In conclusion, the phenotype of the Retnlβ null mice unravels new aspects of inflammation-mediated diseases and strengthens the notion that a proper intestinal barrier function is essential to sustain a healthy phenotype.

Comparison of RELMα and RELMβ Single- and Double-Gene-Deficient Mice Reveals that RELMα Expression Dictates Inflammation and Worm Expulsion in Hookworm Infection

Resistin-like molecules (RELMs) are highly expressed following helminth infection, where they impact both the host and helminth. While RELMα (Retnla) impairs helminth expulsion by inhibiting protective Th2 immunity, RELMβ (Retnlb) can promote its expulsion. We employed Retnla(-/-) and Retnlb(-/-) mice to delineate the function of both proteins following infection with Nippostrongylus brasiliensis, a hookworm that infects the lung and intestine. Whereas wild-type (WT) and Retnlb(-/-)mice exhibited equivalent infection-induced inflammation, Retnla(-/-) mice suffered a heightened inflammatory response, including increased mortality, weight loss, and lung inflammation. In the intestine, Retnla(-/-)mice had low parasite egg burdens compared to those of WT mice, while Retnlb(-/-) mice exhibited high egg burdens, suggesting that RELMα and RELMβ have functionally distinct effects on immunity and inflammation to N. brasiliensis To test the importance of both proteins, we generated Retnla(-/-) Retnlb(-/-) mice. Infected Retnla(-/-)Retnlb(-/-) mice exhibited similar responses to Retnla(-/-) mice, including increased mortality and lung inflammation. This inflammatory response in Retnla(-/-) Retnlb(-/-) mice negatively impacted N. brasiliensis fitness, as demonstrated by significantly lower worm ATP levels and decreased intestinal worm burden and fecundity. Lung cytokine analysis revealed that Retnla(-/-) and Retnla(-/-) Retnlb(-/-) mice expressed significantly increased levels of interleukin-4 (IL-4). Finally, we generated Retnla(-/-) mice on the Rag(-/-) background and observed that the effects of RELMα were abrogated in the absence of adaptive immunity. Together, these data demonstrate that RELMα but not RELMβ significantly impacts the immune response toN. brasiliensis infection by downregulating the Th2 adaptive immune response in the lung, which protects the host but allows improved parasite fitness.

Omentin-1 rs2274907 and resistin rs1862513 polymorphisms influence genetic susceptibility to nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is an obesity-associated disease and dysregulation of adipokines has an important role in its development. Omentin-1 (ITLN1 protein) and resistin are two adipokine secreted from adipose tissue. Single nucleotide polymorphisms in the adipokine genes may affect expression and activity of the adipokine, and thus play a contributory role in NAFLD pathogenesis. The aim of the present study was to investigate the association between omentin-1 rs2274907 (326A/T) and resistin rs1862513 (-420 C/G) polymorphisms and risk of NAFLD in Iranian patients. This case-control study was done on 282 subjects included 94 patients with NAFLD and 188 healthy peoples. The genotypes were determined using PCR-RFLP method. The frequency of omentin-1 AT genotype in patients with NAFLD was significantly different from that in the control (OR=2.3, 95% CI: 1.3-3.8, P=0.003). A significant association was observed between NAFLD and the GG genotype regarding resistin rs1862513 polymorphism (OR=2.3, 95% CI: 1.1-4.8, P=0.03). In conclusion, Omentin-1 rs2274907 and resistin rs1862513 polymorphisms might be a candidate genetic factor for susceptibility to NAFLD.

Resistin-like molecule-β (RELM-β) targets airways fibroblasts to effect remodelling in asthma: from mouse to man

BACKGROUND

RELM-β has been implicated in airways inflammation and remodelling in murine models. Its possible functions in human airways are largely unknown. The aim was to address the hypothesis that RELM-β plays a role in extracellular matrix deposition in asthmatic airways.

METHODS

The effects of RELM-β gene deficiency were studied in a model of allergen exposure in mice sensitised and challenged with Aspergillus fumigatus (Af). RELM-β expression was investigated in bronchial biopsies from asthmatic patients. Direct regulatory effects of RELM-β on human lung fibroblasts were examined using primary cultures and the MRC5 cell line in vitro.

RESULTS

Sensitisation and challenge of wild-type mice with Af-induced release of RELM-β with a time course coincident with that of procollagen in the airways. Af-induced expression of mRNA encoding some, but not all ECM in the lung parenchyma was attenuated in RELM-β-/- mice. RELM-β expression was significantly increased in the bronchial submucosa of human asthmatics compared with controls, and its expression correlated positively with that of fibronectin and α-smooth muscle actin. In addition to epithelial cells, macrophages, fibroblasts and vascular endothelial cells formed the majority of cells expressing RELM-β in the submucosa. Exposure to RELM-β increased TGF-β1, TGF-β2, collagen I, fibronectin, smooth muscle α-actin, laminin α1, and hyaluronan and proteoglycan link protein 1 (Hapl1) production as well as proliferation by human lung fibroblasts in vitro. These changes were associated with activation of ERK1/2 in MRC5 cells.

CONCLUSION

The data are consistent with the hypothesis that elevated RELM-β expression in asthmatic airways contributes to airways remodelling at least partly by increasing fibroblast proliferation and differentiation with resulting deposition of extracellular matrix proteins.

Resistin-Like Molecule α in Allergen-Induced Pulmonary Vascular Remodeling

Resistin-like molecule α (RELMα) has mitogenic, angiogenic, vasoconstrictive, and chemokine-like properties and is highly relevant in lung pathology. Here, we used RELMα knockout (Retnla(-/-)) mice to investigate the role of RELMα in pulmonary vascular remodeling after intermittent ovalbumin (OVA) challenge. We compared saline- and OVA-exposed wild-type (WT) mice and found that OVA induced significant increases in right ventricular systolic pressure, cardiac hypertrophy, pulmonary vascular remodeling of intra-alveolar arteries, goblet cell hyperplasia in airway epithelium, and intensive lung inflammation, especially perivascular inflammation. Genetic ablation of Retnla prevented the OVA-induced increase in pulmonary pressure and cardiac hypertrophy seen in WT mice. Histological analysis showed that Retnla(-/-) mice exhibited less vessel muscularization, less perivascular inflammation, reduced medial thickness of intra-alveolar vessels, and fewer goblet cells in upper airway epithelium (250-600 μm) than did WT animals after OVA challenge. Gene expression profiles showed that genes associated with vascular remodeling, including those related to muscle protein, contractile fibers, and actin cytoskeleton, were expressed at a lower level in OVA-challenged Retnla(-/-) mice than in similarly treated WT mice. In addition, bronchoalveolar lavage from OVA-challenged Retnla(-/-) mice had lower levels of cytokines, such as IL-1β, -1 receptor antagonist, and -16, chemokine (C-X-C motif) ligand 1, -2, -9, -10, and -13, monocyte chemoattractant protein-1, macrophage colony-stimulating factor, TIMP metallopeptidase inhibitor-1, and triggering receptor expressed on myeloid cells-1, than did that from WT mice when analyzed by cytokine array dot blots. Retnla knockout inhibited the OVA-induced T helper 17 response but not the T helper 2 response. Altogether, our results suggest that RELMα is involved in immune response-induced pulmonary vascular remodeling and the associated increase in inflammation typically observed after OVA challenge.

Hypoxia-Inducible Factor 1α Is a Critical Downstream Mediator for Hypoxia-Induced Mitogenic Factor (FIZZ1/RELMα)-Induced Pulmonary Hypertension

OBJECTIVE

Pulmonary hypertension (PH) is characterized by progressive elevation of pulmonary vascular resistance, right ventricular failure, and ultimately death. We have shown that in rodents, hypoxia-induced mitogenic factor (HIMF; also known as FIZZ1 or resistin-like molecule-β) causes PH by initiating lung vascular inflammation. We hypothesized that hypoxia-inducible factor-1 (HIF-1) is a critical downstream signal mediator of HIMF during PH development.

APPROACH AND RESULTS

In this study, we compared the degree of HIMF-induced pulmonary vascular remodeling and PH development in wild-type (HIF-1α(+/+)) and HIF-1α heterozygous null (HIF-1α(+/-)) mice. HIMF-induced PH was significantly diminished in HIF-1α(+/-) mice and was accompanied by a dysregulated vascular endothelial growth factor-A-vascular endothelial growth factor receptor 2 pathway. HIF-1α was critical for bone marrow-derived cell migration and vascular tube formation in response to HIMF. Furthermore, HIMF and its human homolog, resistin-like molecule-β, significantly increased interleukin (IL)-6 in macrophages and lung resident cells through a mechanism dependent on HIF-1α and, at least to some extent, on nuclear factor κB.

CONCLUSIONS

Our results suggest that HIF-1α is a critical downstream transcription factor for HIMF-induced pulmonary vascular remodeling and PH development. Importantly, both HIMF and human resistin-like molecule-β significantly increased IL-6 in lung resident cells and increased perivascular accumulation of IL-6-expressing macrophages in the lungs of mice. These data suggest that HIMF can induce HIF-1, vascular endothelial growth factor-A, and interleukin-6, which are critical mediators of both hypoxic inflammation and PH pathophysiology.

Mouse Resistin (mRetn): cloning, expression and purification in Escherichia coli and the potential regulative effects on murine bone marrow hematopoiesis

Background

Resistin (Retn) is a cytokine which has a controversial physiological role regarding its involvement with obesity and type II diabetes mellitus. Recently, murine Retn was found to be a possibly potential regulator of hematopoiesis in mice shown in the screening results of a set of gene chips which mapped the expression level of murine genes during regeneration of impaired bone marrow (BM) by 5-fluorouracil.

Results

Recombinant mice Retn was expressed in Escherichia coli and purified using ion exchange chromatography. Totally 11.4 mg rmRetn was obtained from 500 ml culture with endotoxin level less than 1.0 EU/ug. The purity of recombinant murine Resistin reached to at least 97.6 % via SDS-PAGE analysis and HPLC. The protein possessed chemotaxis effects in the mouse aortic endothelial cells in vitro in transwell analysis. In vitro, rmRetn could up regulate the CFU number of mice BM and after rmRetn was administered, the cell number of murine bone marrow was significantly increased in vivo after chemotherapy. Finally, rmRetn was found able to protect mice from the chemotoxicity of 5-fluorouracil.

Conclusions

The discovery demonstrated a new function of murine Retn and suggested that it could potentially accelerate bone marrow regeneration post chemotherapy.

Possible Involvement of Serum and Synovial Fluid Resistin in Knee Osteoarthritis: Cartilage Damage, Clinical, and Radiological Links

BACKGROUND

Resistin is an adipocytokine associated with inflammation and insulin resistance. Recent studies have shown that resistin plays an important role in the pathogenesis and progression in osteoarthritis (OA) patients. The current study was aimed at investigating the relationship between resistin in serum and synovial fluid (SF) and disease severity in patients with knee osteoarthritis.

METHOD

Seventy-four patients diagnosed with knee OA and 79 healthy controls receiving regular body check in our hospital were recruited in the study. The Noyes score method was used to assess articular cartilage damage arthroscopically. The symptomatic severity was evaluated according to the Western Ontario McMaster University Osteoarthritis (WOMAC) scores. The radiographic disease severity of OA was assessed by the Kellgren-Lawrence (K-L) grading system. The resistin levels in serum and SF were determined by enzyme-linked immunosorbent assay. Cartilage degradation marker CTX-II in SF was also examined.

RESULTS

SF but not serum resistin levels are positively associated with Noyes scores, K-L grading scores WOMAC pain scores, physical functional scores and WOMAC total scores. In addition, SF resistin correlated positively with CTX-II.

CONCLUSION

Resistin in SF might serve as a potential biomarker for reflecting the disease severity and cartilage degenerative extent of knee OA.

Inflammation, oxidative stress and renin angiotensin system in atherosclerosis

Atherosclerosis is a chronic inflammatory disease associated with cardiovascular dysfunction including myocardial infarction, unstable angina, sudden cardiac death, stroke and peripheral thromboses. It has been predicted that atherosclerosis will be the primary cause of death in the world by 2020. Atherogenesis is initiated by endothelial injury due to oxidative stress associated with cardiovascular risk factors including diabetes mellitus, hypertension, cigarette smoking, dyslipidemia, obesity, and metabolic syndrome. The impairment of the endothelium associated with cardiovascular risk factors creates an imbalance between vasodilating and vasoconstricting factors, in particular, an increase in angiotensin II (Ang II) and a decrease in nitric oxide. The renin-angiotensin system (RAS), and its primary mediator Ang II, also have a direct influence on the progression of the atherosclerotic process via effects on endothelial function, inflammation, fibrinolytic balance, and plaque stability. Anti-inflammatory agents [statins, secretory phospholipase A2 inhibitor, lipoprotein-associated phospholipase A2 inhibitor, 5-lipoxygenase activating protein, chemokine motif ligand-2, C-C chemokine motif receptor 2 pathway inhibitors, methotrexate, IL-1 pathway inhibitor and RAS inhibitors (angiotensin-converting enzyme inhibitors)], Ang II receptor blockers and ranin inhibitors may slow inflammatory processes and disease progression. Several studies in human using anti-inflammatory agents and RAS inhibitors revealed vascular benefits and reduced progression of coronary atherosclerosis in patients with stable angina pectoris; decreased vascular inflammatory markers, improved common carotid intima-media thickness and plaque volume in patients with diagnosed atherosclerosis. Recent preclinical studies have demonstrated therapeutic efficacy of vitamin D analogs paricalcitol in ApoE-deficient atherosclerotic mice.

Goblet Cell Derived RELM-β Recruits CD4+ T Cells during Infectious Colitis to Promote Protective Intestinal Epithelial Cell Proliferation

Enterohemorrhagic Escherichia coli and related food and waterborne pathogens pose significant threats to human health. These attaching/effacing microbes infect the apical surface of intestinal epithelial cells (IEC), causing severe diarrheal disease. Colonizing the intestinal luminal surface helps segregate these microbes from most host inflammatory responses. Based on studies using Citrobacter rodentium, a related mouse pathogen, we speculate that hosts rely on immune-mediated changes in IEC, including goblet cells to defend against these pathogens. These changes include a CD4⁺ T cell-dependent increase in IEC proliferation to replace infected IEC, as well as altered production of the goblet cell-derived mucin Muc2. Another goblet cell mediator, REsistin-Like Molecule (RELM)-β is strongly induced within goblet cells during C. rodentium infection, and was detected in the stool as well as serum. Despite its dramatic induction, RELM-β’s role in host defense is unclear. Thus, wildtype and RELM-β gene deficient mice (Retnlb^-/-) were orally infected with C. rodentium. While their C. rodentium burdens were only modestly elevated, infected Retnlb^-/- mice suffered increased mortality and mucosal ulceration due to deep pathogen penetration of colonic crypts. Immunostaining for Ki67 and BrDU revealed Retnlb^-/- mice were significantly impaired in infection-induced IEC hyper-proliferation. Interestingly, exposure to RELM-β did not directly increase IEC proliferation, rather RELM-β acted as a CD4⁺ T cell chemoattractant. Correspondingly, Retnlb^-/- mice showed impaired CD4⁺ T cell recruitment to their infected colons, along with reduced production of interleukin (IL)-22, a multifunctional cytokine that directly increased IEC proliferation. Enema delivery of RELM-β to Retnlb^-/- mice restored CD4⁺ T cell recruitment, concurrently increasing IL-22 levels and IEC proliferation, while reducing mucosal pathology. These findings demonstrate that RELM-β and goblet cells play an unexpected, yet critical role in recruiting CD4⁺ T cells to the colon to protect against an enteric pathogen, in part via the induction of increased IEC proliferation.

Food and water-borne bacterial pathogens such as enterohemorrhagic Escherichia coli (EHEC) target the epithelial cells that line the inner surface of their host’s intestines, causing inflammation and diarrhea. While professional immune cells including T lymphocytes are well known for promoting host defense, we hypothesized that as the cells in closest contact with these bacterial pathogens, intestinal epithelial cells also play an active and essential role in protecting the host during infection. Infecting mice with Citrobacter rodentium, a mouse specific relative of EHEC, we noted a dramatic upregulation in the expression and secretion of the mediator RELM-β by a subset of epithelial cells called goblet cells. Compared to wildtype mice, mice lacking RELM-β showed less epithelial cell proliferation and suffered significantly more intestinal damage during infection. Rather than directly causing epithelial cell proliferation, we found RELM-β instead recruited T lymphocytes to the infected intestine. Upon reaching the intestine, the T lymphocytes produced the cytokine interleukin-22, which directly increased epithelial cell proliferation. Taken together, these findings indicate that epithelial/goblet cells play a critical role in orchestrating the host response to an intestinal pathogen, by recruiting T lymphocytes and by promoting epithelial proliferation to limit the intestinal damage suffered during infection.

FIZZ1-induced myofibroblast transdifferentiation from adipocytes and its potential role in dermal fibrosis and lipoatrophy

Subcutaneous lipoatrophy characteristically accompanies dermal fibrosis with de novo emergence of myofibroblasts such as in systemic sclerosis or scleroderma. Recently dermal adipocytes were shown to have the capacity to differentiate to myofibroblasts in an animal model. Transforming growth factor β can induce this phenomenon in vitro; however its in vivo significance is unclear. Because found in inflammatory zone 1 (FIZZ1) is an inducer of myofibroblast differentiation but an inhibitor of adipocyte differentiation, we investigated its potential role in adipocyte transdifferentiation to myofibroblast in dermal fibrosis. FIZZ1 caused significant and rapid suppression of the expression of fatty acid binding protein 4 and peroxisome proliferator-activated receptor-γ in adipocytes, consistent with dedifferentiation with loss of lipid and Oil Red O staining. The suppression was accompanied subsequently with stimulation of α-smooth muscle actin and type I collagen expression, indicative of myofibroblast differentiation. In vivo FIZZ1 expression was significantly elevated in the murine bleomycin-induced dermal fibrosis model, which was associated with significant reduction in adipocyte marker gene expression and subcutaneous lipoatrophy. Finally, FIZZ1 knockout mice exhibited significantly reduced bleomycin-induced dermal fibrosis with greater preservation of the subcutaneous fat than wild-type mice. These findings suggested that the FIZZ1 induction of adipocyte transdifferentiation to myofibroblast might be a key pathogenic mechanism for the accumulation of myofibroblasts in dermal fibrosis.

The AMPK pathway mediates an anti-adipogenic effect of fruits of Hovenia dulcis Thunb

Hovenia dulcis Thunb. is well known as a treatment for liver disease. Several studies have demonstrated that extracts of Hovenia dulcis Thunb. or its purified compounds can serve as detoxifying agents for alcohol poisoning. However, its anti-obesity effect has not been reported thus far. In this study, the anti-obesity effect of water extracts from the fruits or stems of Hovenia dulcis Thunb. was examined in 3T3-L1 preadipocytes. The cellular lipid contents in 3T3-L1 adipocytes were assessed by Oil Red O staining. Fruits of Hovenia dulcis Thunb. (FHD) significantly inhibit lipid accumulation during adipogenesis in a dose-dependent manner, but not stems of Hovenia dulcis Thunb. FHD (100 μg ml(-1)) significantly down-regulates the expression of the peroxisome proliferator-activated receptor-γ, CCAAT/enhancer-binding protein-α, adipocyte fatty acid-binding protein 2, adiponectin, and resistin, and the inhibition rates were 29.33%, 54.36%, 34.5%, 55.69%, and 60.39%, respectively. In addition, FHD (100 μg ml(-1)) also up-regulates the phosphorylation of AMP-activated protein kinase (AMPK)-α, liver kinase B1 as a major AMPK kinase, and the downstream substrate acetyl-CoA carboxylase, and the inhibition rates were 43.52%, 38.25%, and 20.39%, respectively. These results indicate that FHD has a significant anti-obesity effect through the modulation of the AMPK pathway, suggesting that FHD has a potential benefit in preventing obesity.

Resistin is a survival factor for porcine ovarian follicular cells

Previously, we demonstrated the expression of resistin in the porcine ovary, the regulation of its expression and its direct effect on ovarian steroidogenesis. The objective of this study was to examine the effect of resistin on cell proliferation and apoptosis in a co-culture model of porcine granulosa and theca cells. First, we analysed the effect of resistin at 1 and 10  ng/ml alone or in combination with FSH- and IGF1 on ovarian cell proliferation with an alamarBlue assay and protein expression of cyclins A and B using western blot. Next, the mRNA and protein expression of selected pro-apoptotic and pro-survival regulators of cell apoptosis, caspase-9, -8 and -3 activity and DNA fragmentation using real time PCR, western blot, fluorescent assay and an ELISA kit, respectively, were analysed after resistin treatment. Furthermore, we determined the effect of resistin on the protein expression of ERK1/2, Stat and Akt kinase. Using specific inhibitors of these kinases, we also checked caspase-3 activity and protein expression. We found that resistin, at both doses, has no effect on cell proliferation. The results showed that resistin decreased pro-apoptotic genes, which was confirmed on protein expression of selected factors. We demonstrate an inhibitory effect of resistin on caspase activity and DNA fragmentation. Finally, resistin stimulated phosphorylation of the ERK1/2, Stat and Akt and kinases inhibitors reversed resistin action on caspase-3 activity and protein expression to control. All of these results showed that resistin has an inhibitory effect on porcine ovarian cell apoptosis by activation of the MAPK/ERK, JAK/Stat and Akt/PI3 kinase signalling pathways.

Validity of adiponectin-to-leptin and adiponectin-to-resistin ratios as predictors of polycystic ovary syndrome

OBJECTIVE

To evaluate the association of changes in adipokine ratios with polycystic ovary syndrome (PCOS) and related features as altered levels of the adipokines adiponectin, leptin, and resistin were linked with the pathogenesis of PCOS.

DESIGN

Case-control retrospective study.

SETTING

Outpatient obstetrics/gynecology and adult endocrinology clinics.

PATIENT(S)

Unrelated women with PCOS (n = 211) and age-matched control women (n = 215).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Utility of adiponectin/leptin and adiponectin/resistin ratios as potential biomarkers of PCOS and associated features.

RESULT(S)

Significant differences in adiponectin but not leptin or resistin serum levels were seen between women with PCOS and control women. Ratios of adiponectin/leptin and adiponectin/resistin, but not leptin/resistin ratios, were statistically significantly different between PCOS cases and control women. Receiver operated characteristics area under the curve demonstrated sensitivity and specificity for adiponectin/leptin and adiponectin/resistin but not leptin/resistin ratios or individual adipokines as predictors of PCOS. Adiponectin/leptin and adiponectin/resistin ratios negatively correlated with body mass index, homeostatic model assessment, insulin resistance, and free insulin, testosterone, and sex hormone-binding globulin. In addition, adiponectin/resistin ratio negatively correlated with menarche.

CONCLUSION(S)

Ratios of adiponectin/leptin and adiponectin/resistin constitute novel predictor factors to explain PCOS and associated features and thus may present target for novel therapeutics in PCOS.

Adipokines, Vascular Wall, and Cardiovascular Disease

Epidemiological evidence has shown that abdominal obesity is closely associated with the development of cardiovascular (CV) disease, suggesting that it might be considered as an independent CV risk factor. However, the pathophysiological mechanisms responsible for the association between these 2 clinical entities remain largely unknown. Adipocytes are considered able to produce and secrete chemical mediators known as “adipokines” that may exert several biological actions, including those on heart and vessels. Of interest, a different adipokine profile can be observed in the plasma of patients with obesity or metabolic syndrome compared with healthy controls. We consider the main adipokines, focusing on their effects on the vascular wall and analyzing their role in CV pathophysiology.

Human resistin and the RELM of Inflammation in diabesity

The initial discovery of resistin and resistin-like molecules (RELMs) in rodents suggested a role for these adipocytokines in molecular linkage of obesity, Type 2 Diabetes mellitus and metabolic syndrome. Since then, it became apparent that the story of resistin and RELMs was very much of mice and men. The putative role of this adipokine family evolved from that of a conveyor of insulin resistance in rodents to instigator of inflammatory processes in humans. Structural dissimilarity, variance in distribution profiles and a lack of corroborating evidence for functional similarities separate the biological functions of resistin in humans from that of rodents. Although present in gross visceral fat deposits in humans, resistin is a component of inflammation, being released from infiltrating white blood cells of the sub-clinical chronic low grade inflammatory response accompanying obesity, rather than from the adipocyte itself. This led researchers to further explore the functions of the resistin family of proteins in inflammatory-related conditions such as atherosclerosis, as well as in cancers such as endometrial and gastric cancers. Although elevated levels of resistin have been found in these conditions, whether it is causative or as a result of these conditions still remains to be determined.

On the function and homeostasis of PCSK9: reciprocal interaction with LDLR and additional lipid effects

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a circulatory ligand that terminates the lifecycle of the low-density lipoprotein (LDL) receptor (LDLR) thus affecting plasma LDL-cholesterol (LDL-C) levels. Recent evidence shows that in addition to the straightforward mechanism of action, there are more complex interactions between PCSK9, LDLR and plasma lipoprotein levels, including: (a) the presence of both parallel and reciprocal regulation of surface LDLR and plasma PCSK9; (b) a correlation between PCSK9 and LDL-C levels dependent not only on the fact that PCSK9 removes hepatic LDLR, but also due to the fact that up to 40% of plasma PCSK9 is physically associated with LDL; and (c) an association between plasma PCSK9 production and the assembly and secretion of triglyceride-rich lipoproteins. The effect of PCSK9 on LDLR is being successfully utilized toward the development of anti-PCSK9 therapies to reduce plasma LDL-C levels. Current biochemical research has uncovered additional mechanisms of action and interacting partners for PCSK9, and this opens the way for a more thorough understanding of the regulation, metabolism, and effects of this interesting protein.

Effects of resistin on ovarian folliculogenesis and steroidogenesis in the vespertilionid bat, Scotophilus heathi

The bat Scotophilus heathi exhibit prolonged anovulatory condition known as delayed ovulation coinciding with the period of extensive fat accumulation. The present study was undertaken to find out whether extensive accumulation of fat in S. heathi is responsible for suppression of ovarian activity by increasing production of adipokine resistin in the bat. This was achieved by (a) investigating variation in serum resistin level in relation to the changes in the body fat mass and (b) evaluating the effect of resistin treatment on ovarian activity with reference to steroid synthesis. An attempt was also made to determine whether resistin mediate its effects on ovary through signal transducer and activator of transcription 3 (STAT3) signaling mechanism. The results showed significant seasonal variation in serum resistin level with the peak level coinciding with the period of maximum fat accumulation, high circulating androgen level and period of anovulation. The treatment with resistin to the bat caused increase in androstenedione due to stimulatory effects on 3β-hydroxysteroid dehydrogenase, but decrease in estradiol level due to inhibitory effect on aromatase. Resistin treatment increased androgen receptor protein together with increased insulin receptor but not through conventional luteinizing hormone receptor and steroidogenic acute regulatory protein mediated pathways. This study further showed that resistin treatment increases androstenedione synthesis and up-regulates insulin receptor in the ovary through STAT3 mediated pathways. These findings suggest that obese women through increased resistin synthesis may causes development of non-ovulatory antral follicles through insulin receptor signaling cascade.

The adipokine Retnla modulates cholesterol homeostasis in hyperlipidemic mice

Hyperlipidemia is a well-recognized risk factor for atherosclerosis and can be regulated by adipokines. Expression of the adipokine resistin-like molecule alpha (Retnla) is regulated by food intake; whether Retnla has a role in the pathogenesis of hyperlipidemia and atherosclerosis is unknown. Here we report that Retnla has a cholesterol-lowering effect and protects against atherosclerosis in low-density lipoprotein receptor-deficient mice. On a high-fat diet, Retnla deficiency promotes hypercholesterolaemia and atherosclerosis, whereas Retnla overexpression reverses these effects and improves the serum lipoprotein profile, with decreased cholesterol in the very low-density lipoprotein fraction concomitant with reduced serum apolipoprotein B levels. We show that Retnla upregulates cholesterol-7-α-hydroxylase, a key hepatic enzyme in the cholesterol catabolic pathway, through induction of its transcriptional activator liver receptor homologue-1, leading to increased excretion of cholesterol in the form of bile acids. These findings define Retnla as a novel therapeutic target for treating hypercholesterolaemia and atherosclerosis.

Polymorphisms in RETN gene and susceptibility to colon cancer in Saudi patients

BACKGROUND AND OBJECTIVES

Resistin is an adipocytokine, which has been studied for its role in insulin resistance and recently in inflammation. Several single-nucleotide polymorphisms (SNPs) have been identified in the human resistin gene (RETN). This study aims to investigate the association of RETN rs1862513 (C-420G) and rs3745367 (G+299A) SNPs with the colon cancer risk in Saudi patients.

DESIGN AND SETTING

This is a case-control study conducted among Saudi adult colon cancer patients recruited from King Abdulaziz Hospital and Oncology Center in Jeddah, Saudi Arabia.

SUBJECTS AND METHODS

In this study, 120 Saudi volunteers (60 colon cancer patients and 60 disease-free controls) were studied. The SNPs were determined by polymerase chain reaction (PCR) and genotyping using PCR- restriction fragment length polymorphism analysis.

RESULTS

In comparing the result obtained for the patient group with that of the controls, colon cancer group displayed different genotype distribution of the RETN C-420G and G+299A SNPs. The study indicated that the SNP-420 heterozygous (CG) genotype (odds ratio [OR]=2.48, 95% CI 1.07-5.74, P=.03) and the SNP +299 heterozygous (GA) genotype (OR=6.5, 95% CI 1.77-24.18, P=.002) significantly increased the risk of colon cancer. A further analysis of the genotype combination of SNPs RETN C-420G and G+299A showed a larger increase in the colon cancer risk.

CONCLUSION

These preliminary results suggested a potential role for RETN C-420G and G+299A polymorphisms in the genetic predisposition to colon cancer disease.

Serum levels of resistin, adiponectin, and apelin in gastroesophageal cancer patients

The aim of the study was the investigation of relationship between cachexia syndrome and serum resistin, adiponectin, and apelin in patients with gastroesophageal cancer (GEC). Material and Methods. Adipocytokines concentrations were measured in sera of 85 GEC patients and 60 healthy controls. They were also evaluated in tumor tissue and appropriate normal mucosa of 38 operated cancer patients. Results. Resistin and apelin concentrations were significantly higher in GEC patients than in the controls. The highest resistin levels were found in cachectic patients and in patients with distant metastasis. Serum adiponectin significantly decreased in GEC patients with regional and distant metastasis. Serum apelin was significantly higher in cachectic patients than in the controls. Apelin was positively correlated with hsCRP level. Resistin and apelin levels increased significantly in tumor tissues. Weak positive correlations between adipocytokines levels in serum and in tumor tissue were observed. Conclusions. Resistin is associated with cachexia and metastasis processes of GEC. Reduction of serum adiponectin reflects adipose tissue wasting in relation to GEC progression. Correlation of apelin with hsCRP can reflect a presumable role of apelin in systemic inflammatory response in esophageal and gastric cancer.

Elevated resistin levels induce central leptin resistance and increased atherosclerotic progression in mice

AIMS/HYPOTHESIS

Resistin was originally identified as an adipocyte-derived factor upregulated during obesity and as a contributor to obesity-associated insulin resistance. Clinically, resistin has also been implicated in cardiovascular disease in a number of different patient populations. Our aim was to simultaneously address these phenomena.

METHODS

We generated mice with modest adipocyte-specific resistin overexpression. These mice were crossed with mice deficient in the LDL receptor (Ldlr (-/-)) to probe the physiological role of resistin. Both metabolic and atherosclerotic assessments were performed.

RESULTS

Resistin overexpression led to increased atherosclerotic progression in Ldlr (-/-) mice. This was in part related to elevated serum triacylglycerol levels and a reduced ability to clear triacylglycerol upon a challenge. Additional phenotypic changes, such as increased body weight and reduced glucose clearance, independent of the Ldlr (-/-) background, confirmed increased adiposity associated with a more pronounced insulin resistance. A hallmark of elevated resistin was the disproportionate increase in circulating leptin levels. These mice thus recapitulated both the proposed negative cardiovascular correlation and the insulin resistance. A unifying mechanism for this complex phenotype was a resistin-mediated central leptin resistance, which we demonstrate directly both in vivo and in organotypic brain slices. In line with reduced sympathetic nervous system outflow, we found decreased brown adipose tissue (BAT) activity. The resulting elevated triacylglycerol levels provide a likely explanation for accelerated atherosclerosis.

CONCLUSIONS/INTERPRETATION

Resistin overexpression leads to a complex metabolic phenotype driven by resistin-mediated central leptin resistance and reduced BAT activity. Hypothalamic leptin resistance thus provides a unifying mechanism for both resistin-mediated insulin resistance and enhanced atherosclerosis.

Role of resistin in insulin resistance and obesity

Resistin is an adipose-derived hormone postulated to link adiposity to insulin resistance. Rodent animal experiments and in vitro experimental studies showed that resistin can induce insulin resistance, glucose and lipid metabolism disorders, and be closely related to metabolic syndrome. However, the specific mechanisms of action of resistin in humans are not clear. There is still controversy over the relationship between resistin and obesity. This review aims to elucidate the role of resistin in insulin resistance and discuss the relationship between resistin and obesity.

Adipokines, metabolic syndrome and rheumatic diseases

The metabolic syndrome (MetS) is a cluster of cardiometabolic disorders that result from the increasing prevalence of obesity. The major components of MetS include insulin resistance, central obesity, dyslipidemia, and hypertension. MetS identifies the central obesity with increased risk for cardiovascular diseases (CVDs) and type-2 diabetes mellitus (T2DM). Patients with rheumatic diseases, such as rheumatoid arthritis, osteoarthritis, systemic lupus erythematosus, and ankylosing spondylitis, have increased prevalence of CVDs. Moreover, CVD risk is increased when obesity is present in these patients. However, traditional cardiovascular risk factors do not completely explain the enhanced cardiovascular risk in this population. Thus, MetS and the altered secretion patterns of proinflammatory adipokines present in obesity could be the link between CVDs and rheumatic diseases. Furthermore, adipokines have been linked to the pathogenesis of MetS and its comorbidities through their effects on vascular function and inflammation. In the present paper, we review recent evidence of the role played by adipokines in the modulation of MetS in the general population, and in patients with rheumatic diseases.

Type 2 diabetes, PUFAs, and vitamin D: their relation to inflammation

Chronic diseases have become one of the most important public health problems, due to their high costs for treatment and prevention. Until now, researchers have considered that the etiology of Type 2 diabetes mellitus (T2DM) is multifactorial. Recently, the study of the innate immune system has offered an explanation model of the pathogenesis of T2DM. On the other hand, there is evidence about the beneficial effect of polyunsaturated fatty acids (PUFA) n-3 and n-6 in patients with chronic inflammatory diseases including diabetes. Furthermore, high vitamin D plasmatic concentrations have been associated with the best performance of pancreatic β cells and the improving of this disease. In conclusion, certain fatty acids in the adequate proportion as well as 25-hydroxivitamin D can modulate the inflammatory response in diabetic people, modifying the evolution of this disease.