Leptin-mediated reactive oxygen species production does not significantly affect primary mouse hepatocyte functions in vitro

Serum Appetite-Regulating Hormone Levels in Cystic Fibrosis Patients: Influence of the Disease Severity and the Type of Bacterial Infection-A Pilot Study

Cystic fibrosis (CF) belongs to the most common inherited diseases. The severity of the disease and chronic bacterial infections are associated with a lower body index, undernutrition, higher number of pulmonary exacerbations, more hospital admissions, and increased mortality. The aim of our study was to determine the impact of the severity of the disease and the type of bacterial infection in 38 CF patients on the serum level of appetite-regulating hormones including leptin, ghrelin, neuropeptide Y, agouti-signaling protein, proopiomelanocortin, kisspeptin, putative protein Y, and α-melanocyte-stimulating hormone. The patients were divided according to the severity of the disease according to spirometry and the type of chronic bacterial infection. We found that leptin level was significantly higher in patients with severe CF than in patients with mild disease (20.02 ± 8.09 vs. 12.38 ± 6.03 ng/mL, p = 0.028). Furthermore, leptin level was elevated in patients with chronic infection with Pseudomonas aeruginosa compared to uninfected participants (15.74 ± 7.02 vs. 9.28 ± 1.72 ng/mL, p = 0.043). The severity of the disease and the type of bacterial infection did not affect the levels of other appetite-regulating hormones. Moreover, we found a positive correlation between pro-inflammatory interleukin-6 and leptin level (p = 0.0426, R = 0.333). Taken together, our results indicate that both the severity of the disease and the type of bacterial infection are associated with elevated leptin levels in CF patients. Future CF treatment strategies should consider possible disturbances in the hormones that regulate appetite and the factors that influence their levels.

Probiotic supplementation affects IGF-1 and leptin levels in Nile tilapia hepatopancreatic tissue

ABSTRACT This work aimed to assess the effect of the probiotic strain, Lactobacillus plantarum, on the levels of leptin, IGF-1 and their receptors on the hepatopancreatic tissues of Nile tilapia (Oreochromis niloticus) and then correlate fish growth performance and gut microbiological parameters. Fish juveniles (±23g) were reared in a recirculation system with constant aeration and temperature (25°C). They were distributed into six polyethylene tanks (45L) and fed twice a day at 5% of the tank biomass with the respective diets: control (commercial diet without probiotic) and supplemented with L. plantarum inoculum (1 x 108 CFU mL-1), both in triplicate. After 30 days of feeding, L. plantarum-fed fishes showed greater weekly growth rate, final weight, and feed conversion rate, in addition to higher count of lactic-acid bacteria and lower count of pathogenic bacteria in the intestinal tract, when compared to the control group. The immunostaining intensity for IGF-1 and leptin hormones was lower after L. plantarum supplementation than in the control group, with no change in the level for receptors. This reduction could implicate important changes in fish metabolism and homeostasis.

Leptin induces NAFLD progression through infiltrated CD8+ T lymphocytes mediating pyroptotic-like cell death of hepatocytes and macrophages

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease, which causes serious health problems worldwide. Hyperleptinemia and inflammatory stress are crucial in the progression of NAFLD. However, the relationship between leptin and immune cells or hepatocytes is still unclear.

AIMS

This study aimed to clarify the regulatory mechanism of leptin-mediated disease progression through immune cells and its relationship with hepatocytes.

METHODS

An NAFLD rat model was established to verify the relationship between hyperleptinemia and CD8+ T lymphocytes and cytokines in liver tissue. CD8+ T lymphocytes isolated from blood mononuclear cells were co-cultured with macrophages or hepatocytes stimulated with leptin or treated with granzyme inhibitors to observe target cell morphology and expression of pivotal protein family members.

RESULTS

CD8+ T lymphocyte infiltration positively correlated with blood leptin, IL-18 and IL-1β levels and was related to macrophage recruitment and differentiation in a rat model of NAFLD. Leptin could induce activated caspase-1 and caspase-3 in hepatocytes and trigger hepatocyte pyroptosis.

CONCLUSIONS

Leptin may regulate the pyroptotic-like death of macrophages and hepatocytes through CD8+ T lymphocytes in NAFLD progression. The intervention of related pathways of leptin and immune cells may provide a promising strategy for treating NAFLD.

Association of Adipose Tissue and Adipokines with Development of Obesity-Induced Liver Cancer

Obesity is rapidly dispersing all around the world and is closely associated with a high risk of metabolic diseases such as insulin resistance, dyslipidemia, and nonalcoholic fatty liver disease (NAFLD), leading to carcinogenesis, especially hepatocellular carcinoma (HCC). It results from an imbalance between food intake and energy expenditure, leading to an excessive accumulation of adipose tissue (AT). Adipocytes play a substantial role in the tumor microenvironment through the secretion of several adipokines, affecting cancer progression, metastasis, and chemoresistance via diverse signaling pathways. AT is considered an endocrine organ owing to its ability to secrete adipokines, such as leptin, adiponectin, resistin, and a plethora of inflammatory cytokines, which modulate insulin sensitivity and trigger chronic low-grade inflammation in different organs. Even though the precise mechanisms are still unfolding, it is now established that the dysregulated secretion of adipokines by AT contributes to the development of obesity-related metabolic disorders. This review focuses on several obesity-associated adipokines and their impact on obesity-related metabolic diseases, subsequent metabolic complications, and progression to HCC, as well as their role as potential therapeutic targets. The field is rapidly developing, and further research is still required to fully understand the underlying mechanisms for the metabolic actions of adipokines and their role in obesity-associated HCC.

Tumor Metabolic Reprogramming by Adipokines as a Critical Driver of Obesity-Associated Cancer Progression

Adiposity is associated with an increased risk of various types of carcinoma. One of the plausible mechanisms underlying the tumor-promoting role of obesity is an aberrant secretion of adipokines, a group of hormones secreted from adipose tissue, which have exhibited both oncogenic and tumor-suppressing properties in an adipokine type- and context-dependent manner. Increasing evidence has indicated that these adipose tissue-derived hormones differentially modulate cancer cell-specific metabolism. Some adipokines, such as leptin, resistin, and visfatin, which are overproduced in obesity and widely implicated in different stages of cancer, promote cellular glucose and lipid metabolism. Conversely, adiponectin, an adipokine possessing potent anti-tumor activities, is linked to a more favorable metabolic phenotype. Adipokines may also play a pivotal role under the reciprocal regulation of metabolic rewiring of cancer cells in tumor microenvironment. Given the fact that metabolic reprogramming is one of the major hallmarks of cancer, understanding the modulatory effects of adipokines on alterations in cancer cell metabolism would provide insight into the crosstalk between obesity, adipokines, and tumorigenesis. In this review, we summarize recent insights into putative roles of adipokines as mediators of cellular metabolic rewiring in obesity-associated tumors, which plays a crucial role in determining the fate of tumor cells.

Recent insights on modulation of inflammasomes by adipokines: a critical event for the pathogenesis of obesity and metabolism-associated diseases

Aberrant production of adipokines, a group of adipocytes-derived hormones, is considered one of the most important pathological characteristics of obesity. In individuals with obesity, beneficial adipokines, such as adiponectin are downregulated, whereas leptin and other pro-inflammatory adipokines are highly upregulated. Hence, the imbalance in levels of these adipokines is thought to promote the development of obesity-linked complications. However, the mechanisms by which adipokines contribute to the pathogenesis of various diseases have not been clearly understood. Inflammasomes represent key signaling platform that triggers the inflammatory and immune responses through the processing of the interleukin family of pro-inflammatory cytokines in a caspase-1-dependent manner. Beyond their traditional function as a component of the innate immune system, inflammasomes have been recently integrated into the pathological process of multiple metabolism- and obesity-related disorders such as cardiovascular diseases, diabetes, fatty liver disease, and cancer. Interestingly, emerging evidence also highlights the role of adipokines in the modulation of inflammasomes activation, making it a promising mechanism underlying distinct biological actions of adipokines in diseases driven by inflammation and metabolic disorders. In this review, we summarize the effects of adipokines, in particular adiponectin, leptin, visfatin and apelin, on inflammasomes activation and their implications in the pathophysiology of obesity-linked complications.

Melatonin ameliorates the adverse effects of leptin on sperm

This study examined the effects of melatonin on leptin-induced changes in sperm parameters in adult rats. Five groups of Sprague-Dawley rats were treated with either leptin or leptin and melatonin or melatonin for 6 weeks. Leptin was given daily via the intraperitoneal route (60 μg kg⁻¹ body weight) and melatonin was given in drinking water (10 mg kg⁻¹ or 20 mg kg⁻¹ body weight per day). Upon completion, sperm count, sperm morphology, 8-hydroxy-2-deoxyguanosine, Comet assay, TUNEL assay, gene expression profiles of antioxidant enzymes, respiratory chain reaction enzymes, DNA damage, and apoptosis genes were estimated. Data were analyzed using ANOVA. Sperm count was significantly lower whereas the fraction of sperm with abnormal morphology, the level of 8-hydroxy-2-deoxyguanosine, and sperm DNA fragmentation were significantly higher in rats treated with leptin only. Microarray analysis revealed significant upregulation of apoptosis-inducing factor, histone acetyl transferase, respiratory chain reaction enzyme, cell necrosis and DNA repair genes, and downregulation of antioxidant enzyme genes in leptin-treated rats. Real-time polymerase chain reaction showed significant decreases in glutathione peroxidase 1 expression with increases in the expression of apoptosis-inducing factor and histone acetyl transferase in leptin-treated rats. There was no change in the gene expression of caspase-3 (CASP-3). In conclusion, the adverse effects of leptin on sperm can be prevented by concurrent melatonin administration.

An optimized method for mouse liver sinusoidal endothelial cell isolation

The objective of the present study was to develop an accurate and reproducible method for liver sinusoidal endothelial cell (LSEC) isolation in mice. Non-parenchymal cells were isolated using a modified two-step collagenase digestion combined with Optiprep density gradient centrifugation. LSEC were further purified using two prevalent methods, short-term selective adherence and CD146+ magnetic-activated cell sorting (MACS), and compared in terms of cell yield, viability and purity to our purification technique using CD11b cell depletion combined with long-term selective adherence. LSEC purification using our technique allowed to obtain 7.07±3.80 million LSEC per liver, while CD146+ MACS and short-term selective adherence yielded 2.94±1.28 and 0.99±0.66 million LSEC, respectively. Purity of the final cell preparation reached 95.10±2.58% when using our method. In contrast, CD146+ MACS and short-term selective adherence gave purities of 86.75±3.26% and 47.95±9.82%, respectively. Similarly, contamination by non-LSEC was the lowest when purification was performed using our technique, with a proportion of contaminating macrophages of only 1.87±0.77%. Further, isolated cells analysed by scanning electron microscopy presented typical LSEC fenestrations organized in sieve plates, demonstrating that the technique allowed to isolate bona fide LSEC. In conclusion, we described a reliable and reproducible technique for the isolation of high yields of pure LSEC in mice. This protocol provides an efficient method to prepare LSEC for studying their biological functions.

FXR agonist obeticholic acid reduces hepatic inflammation and fibrosis in a rat model of toxic cirrhosis

Hepatic inflammation drives hepatic stellate cells (HSC), resulting in liver fibrosis. The Farnesoid-X receptor (FXR) antagonizes inflammation through NF-κB inhibition. We investigated preventive and therapeutic effects of FXR agonist obeticholic acid (OCA) on hepatic inflammation and fibrosis in toxic cirrhotic rats. Cirrhosis was induced by thioacetamide (TAA) intoxication. OCA was given during or after intoxication with vehicle-treated rats as controls. At sacrifice, fibrosis, hemodynamic and biochemical parameters were assessed. HSC activation, cell turn-over, hepatic NF-κB activation, pro-inflammatory and pro-fibrotic cytokines were determined. The effect of OCA was further evaluated in isolated HSC, Kupffer cells, hepatocytes and liver sinusoidal endothelial cells (LSEC). OCA decreased hepatic inflammation and fibrogenesis during TAA-administration and reversed fibrosis in established cirrhosis. Portal pressure decreased through reduced intrahepatic vascular resistance. This was paralleled by decreased expression of pro-fibrotic cytokines (transforming growth-factor β, connective tissue growth factor, platelet-derived growth factor β-receptor) as well as markers of hepatic cell turn-over, by blunting effects of pro-inflammatory cytokines (e.g. monocyte chemo-attractant protein-1). In vitro, OCA inhibited both LSEC and Kupffer cell activation; while HSC remained unaffected. This related to NF-κB inhibition via up-regulated IκBα. In conclusion, OCA inhibits hepatic inflammation in toxic cirrhotic rats resulting in decreased HSC activation and fibrosis.

Modulation of Cell Death and Survival by Adipokines in the Liver

Adipokines, hormones predominantly produced from adipose tissue, have been shown to impart dynamic functions in the liver. Emerging evidence has shown that adipokines are also involved in modulating liver cell survival and/or death. Among the various adipokines, adiponectin and leptin directly regulate proliferation of hepatocytes, Kupffer cells, and hepatic stellate cells. Moreover, these adipokines control apoptosis and cell cycle of hepatic cancer cells in a complex manner. Adiponectin possesses both pro- and anti-proliferative properties, whereas leptin appears to play roles as a pro-survival hormone. Recent studies have revealed that regulation of cell death and proliferation is one of the critical factors regulating liver physiology by adipokines. In this review, we summarize the effects of adipokines on apoptosis and survival of liver cells and also demonstrate their implications in regulating various liver functions and decipher the underlying molecular mechanisms.

Methods for Isolation and Purification of Murine Liver Sinusoidal Endothelial Cells: A Systematic Review

To study the biological functions of liver sinusoidal endothelial cells (LSEC) and to identify their interplay with blood or liver cells, techniques allowing for the isolation and purification of LSEC have been developed over the last decades. The objective of the present review is to summarize and to compare the efficiency of existing methods for isolating murine LSEC. Toward this end, the MEDLINE database was searched for all original articles describing LSEC isolation from rat and mouse livers. Out of the 489 publications identified, 23 reported the main steps and outcomes of the procedure and were included in our review. Here, we report and analyse the technical details of the essential steps of the techniques used for LSEC isolation. The correlations between the prevalence of some steps and the efficiency of LSEC isolation were also identified. We found that centrifugal elutriation, selective adherence and, more recently, magnetic-activated cell sorting were used for LSEC purification. Centrifugal elutriation procured high yields of pure LSEC (for rats 30-141.9 million cells for 85-98% purities; for mice 9-9.25 million cells for >95% purities), but the use of this method remained limited due to its high technical requirements. Selective adherence showed inconsistent results in terms of cell yields and purities in rats (5-100 million cells for 73.7-95% purities). In contrast, magnetic-activated cell sorting allowed for the isolation of highly pure LSEC, but overall lower cell yields were reported (for rats 10.7 million cells with 97.6% purity; for mice 0.5-9 million cells with 90-98% purities). Notably, the controversies regarding the accuracy of several phenotypic markers for LSEC should be considered and their use for both magnetic sorting and characterization remain doubtful. It appears that more effort is needed to refine and standardize the procedure for LSEC isolation, with a focus on the identification of specific antigens. Such a procedure is required to identify the molecular mechanisms regulating the function of LSEC and to improve our understanding of their role in complex cellular processes in the liver.

P311 modulates hepatic stellate cells migration

BACKGROUND & AIMS

Liver fibrosis is induced by the accumulation of extracellular matrix, deposited mainly by activated hepatic stellate cells (HSCs). One key characteristic of stellate cell activation is the directional migration to the site of injury during the wound-healing process. P311 is a protein that has been shown to play a role in migration and we aimed to study a possible role for this protein during stellate cell migration.

METHODS

Mouse stellate cells were isolated and cultured in vitro to investigate P311 protein and gene expression during HSC activation by immunocytochemistry and RT-qPCR respectively. Expression of P311 during in vivo activation was evaluated in CCl4 and bile duct ligation-induced liver fibrosis. Production of reactive oxygen species was determined using the fluorescent probe DCFH-DA. By siRNA-mediated knockdown of P311, we investigated a possible effect on proliferation by incorporation of EdU and on migration by Boyden chamber assays.

RESULTS

P311 gene expression was increased during both in vitro and in vivo activation of HSCs. siRNA-mediated knockdown led to a decrease in reactive oxygen production and cell proliferation. Migration induced by different chemokines, such as PDGF-bb and MCP-1 was inhibited by knockdown of P311.

CONCLUSIONS

P311 is central to reactive oxygen species-mediated HSC migration induced by different chemokines.

Gene expression profiling of early hepatic stellate cell activation reveals a role for Igfbp3 in cell migration

Background

Scarring of the liver is the result of prolonged exposure to exogenous or endogenous stimuli. At the onset of fibrosis, quiescent hepatic stellate cells (HSCs) activate and transdifferentiate into matrix producing, myofibroblast-like cells.

Aim and methods

To identify key players during early HSC activation, gene expression profiling was performed on primary mouse HSCs cultured for 4, 16 and 64 hours. Since valproic acid (VPA) can partly inhibit HSC activation, we included VPA-treated cells in the profiling experiments to facilitate this search.

Results

Gene expression profiling confirmed early changes for known genes related to HSC activation such as alphasmoothmuscleactin (Acta2), lysyloxidase (Lox) and collagen, type I, alpha 1 (Col1a1). In addition we noticed that, although genes which are related to fibrosis change between 4 and 16 hours in culture, most gene expression changes occur between 16 and 64 hours. Insulin-likegrowthfactorbinding protein 3 (Igfbp3) was identified as a gene strongly affected by VPA treatment. During normal HSC activation Igfbp3 is up regulated and this can thus be prevented by VPA treatment invitro and invivo. siRNA-mediated silencing of Igfbp3 in primary mouse HSCs induced matrix metalloproteinase (Mmp) 9 mRNA expression and strongly reduced cell migration. The reduced cell migration after Igfbp3 knock-down could be overcome by tissue inhibitor of metalloproteinase (TIMP) 1 treatment.

Conclusion

Igfbp3 is a marker for culture-activated HSCs and plays a role in HSC migration. VPA treatment prevents Igfbp3 transcription during activation of HSCs invitro and invivo.

Syncoilin is an intermediate filament protein in activated hepatic stellate cells

Hepatic stellate cells (HSCs) play an important role in several (patho)physiologic conditions in the liver. In response to chronic injury, HSCs are activated and change from quiescent to myofibroblast-like cells with contractile properties. This shift in phenotype is accompanied by a change in expression of intermediate filament (IF) proteins. HSCs express a broad, but variable spectrum of IF proteins. In muscle, syncoilin was identified as an alpha-dystrobrevin binding protein with sequence homology to IF proteins. We investigated the expression of syncoilin in mouse and human HSCs. Syncoilin expression in isolated and cultured HSCs was studied by qPCR, Western blotting, and fluorescence immunocytochemistry. Syncoilin expression was also evaluated in other primary liver cell types and in in vivo-activated HSCs as well as total liver samples from fibrotic mice and cirrhotic patients. Syncoilin mRNA was present in human and mouse HSCs and was highly expressed in in vitro- and in vivo-activated HSCs. Syncoilin protein was strongly upregulated during in vitro activation of HSCs and undetectable in hepatocytes and liver sinusoidal endothelial cells. Syncoilin mRNA levels were elevated in both CCl4- and common bile duct ligation-treated mice. Syncoilin immunocytochemistry revealed filamentous staining in activated mouse HSCs that partially colocalized with α-smooth muscle actin, β-actin, desmin, and α-tubulin. We show that in the liver, syncoilin is predominantly expressed by activated HSCs and displays very low-expression levels in other liver cell types, making it a good marker of activated HSCs. During in vitro activation of mouse HSCs, syncoilin is able to form filamentous structures or at least to closely interact with existing cellular filaments.