Adipose tissue-specific deletion of 12/15-lipoxygenase protects mice from the consequences of a high-fat diet

Transgenic mice overexpressing human ALOX15 under the control of the aP2 promoter are partly protected in the complete Freund's adjuvant-induced paw inflammation model

BACKGROUND, OBJECTIVES AND DESIGN

Arachidonic acid 15-lipoxygenase (ALOX15) has been implicated in the pathogenesis of inflammatory diseases but since pro- and anti-inflammatory roles have been suggested, the precise function of this enzyme is still a matter of discussion. To contribute to this discussion, we created transgenic mice, which express human ALOX15 under the control of the activating protein 2 promoter (aP2-ALOX15 mice) and compared the sensitivity of these gain-of-function animals in two independent mouse inflammation models with Alox15-deficient mice (loss-of-function animals) and wildtype control animals.

MATERIALS AND METHODS

Transgenic aP2-ALOX15 mice were tested in comparison with Alox15 knockout mice (Alox15-/-) and corresponding wildtype control animals (C57BL/6J) in the complete Freund's adjuvant induced hind-paw edema model and in the dextran sulfate sodium induced colitis (DSS-colitis) model. In the paw edema model, the degree of paw swelling and the sensitivity of the inflamed hind-paw for mechanic (von Frey test) and thermal (Hargreaves test) stimulation were quantified as clinical readout parameters. In the dextran sodium sulfate induced colitis model the loss of body weight, the colon lengths and the disease activity index were determined.

RESULTS

In the hind-paw edema model, systemic inactivation of the endogenous Alox15 gene intensified the inflammatory symptoms, whereas overexpression of human ALOX15 reduced the degree of hind-paw inflammation. These data suggest anti-inflammatory roles for endogenous and transgenic ALOX15 in this particular inflammation model. As mechanistic reason for the protective effect downregulation of the pro-inflammatory ALOX5 pathways was suggested. However, in the dextran sodium sulfate colitis model, in which systemic inactivation of the Alox15 gene protected female mice from DSS-induced colitis, transgenic overexpression of human ALOX15 did hardly impact the intensity of the inflammatory symptoms.

CONCLUSION

The biological role of ALOX15 in the pathogenesis of inflammation is variable and depends on the kind of the animal inflammation model.

Functional Characterization of Transgenic Mice Overexpressing Human 15-Lipoxygenase-1 (ALOX15) under the Control of the aP2 Promoter

Arachidonic acid lipoxygenases (ALOX) have been implicated in the pathogenesis of inflammatory, hyperproliferative, neurodegenerative, and metabolic diseases, but the physiological function of ALOX15 still remains a matter of discussion. To contribute to this discussion, we created transgenic mice (aP2-ALOX15 mice) expressing human ALOX15 under the control of the aP2 (adipocyte fatty acid binding protein 2) promoter, which directs expression of the transgene to mesenchymal cells. Fluorescence in situ hybridization and whole-genome sequencing indicated transgene insertion into the E1-2 region of chromosome 2. The transgene was highly expressed in adipocytes, bone marrow cells, and peritoneal macrophages, and ex vivo activity assays proved the catalytic activity of the transgenic enzyme. LC-MS/MS-based plasma oxylipidome analyses of the aP2-ALOX15 mice suggested in vivo activity of the transgenic enzyme. The aP2-ALOX15 mice were viable, could reproduce normally, and did not show major phenotypic alterations when compared with wildtype control animals. However, they exhibited gender-specific differences with wildtype controls when their body-weight kinetics were evaluated during adolescence and early adulthood. The aP2-ALOX15 mice characterized here can now be used for gain-of-function studies evaluating the biological role of ALOX15 in adipose tissue and hematopoietic cells.

Amelioration of obesity-induced white adipose tissue inflammation by Bacillus coagulans T4 in a high-fat diet-induced obese murine model

AIM

Fresh evidence suggests that B. coagulans can be regarded as a promising therapeutic alternative for metabolic disorders. However, the possible effects of this probiotic on obesity-induced adipose tissue inflammation are unknown.

METHODS

C57BL/6j male mice were assigned to a normal-chow diet (NCD) or a high-fat diet (HFD) for 10 weeks. After this period, HFD-fed mice were randomly divided into two groups; HFD control group and HFD plus B. coagulans T4 (IBRC-N10791) for another 8 weeks. B. coagulans T4 was administrated daily by oral intragastric gavage (1 × 10⁹ colony-forming units).

KEY FINDINGS

Here, we found that B. coagulans successfully mitigated obesity and related metabolic disorder, as indicated by reduced body weight gain, decreased adiposity, and improved glucose tolerance. B. coagulans T4 administration also inhibited HFD-induced macrophage accumulation in white adipose tissue and switched M1 to M2 macrophages. In parallel, B. coagulans T4 treatment attenuated HFD-induced alteration in mRNA expression of pro/anti-inflammatory cytokines and Tlr4 in white adipose tissue. Moreover, B. coagulans T4 supplementation reduced the Firmicutes/Bacteriodetes ratio and increased the number of Lactobacillus and Faecalibacterium compared to the HFD group. Additionally, a significant increase in propionate and acetate levels in the HFD group was seen following B. coagulans T4 administration.

SIGNIFICANCE

Taken together, the present study provides evidence that B. coagulans T4 supplementation exerts anti-obesity effects in part through attenuating inflammation in adipose tissue. The present study will have significant implications for obesity management.

Proinflammatory signaling in islet β cells propagates invasion of pathogenic immune cells in autoimmune diabetes

Type 1 diabetes is a disorder of immune tolerance that leads to death of insulin-producing islet β cells. We hypothesize that inflammatory signaling within β cells promotes progression of autoimmunity within the islet microenvironment. To test this hypothesis, we deleted the proinflammatory gene encoding 12/15-lipoxygenase (Alox15) in β cells of non-obese diabetic mice at a pre-diabetic time point when islet inflammation is a feature. Deletion of Alox15 leads to preservation of β cell mass, reduces populations of infiltrating T cells, and protects against spontaneous autoimmune diabetes in both sexes. Mice lacking Alox15 in β cells exhibit an increase in a population of β cells expressing the gene encoding the protein programmed death ligand 1 (PD-L1), which engages receptors on immune cells to suppress autoimmunity. Delivery of a monoclonal antibody against PD-L1 recovers the diabetes phenotype in knockout animals. Our results support the contention that inflammatory signaling in β cells promotes autoimmunity during type 1 diabetes progression.

Branched-Chain Fatty Acids Alter the Expression of Genes Responsible for Lipid Synthesis and Inflammation in Human Adipose Cells

Recently, we have demonstrated a decreased level of iso-branched-chain fatty acids (iso-BCFAs) in patients with excessive weight. However, it is still unclear whether BCFAs may influence lipid metabolism and inflammation in lipogenic tissues. To verify this, human visceral adipocytes were cultured with three different concentrations of selected iso-BCFA (14-methylpentadecanoic acid) and anteiso-BCFA (12-methyltetradecanoic acid), and then the expression of genes associated with lipid metabolism (FASN-fatty acid synthase; SREBP1-sterol regulatory element-binding protein 1; SCD1-stearoyl-CoA desaturase; ELOVL4-fatty acid elongase 4; ELOVL6-fatty acid elongase 6; FADS2-fatty acid desaturase 2; FADS1-fatty acid desaturase 1) and inflammation (COX-2-cyclooxygenase 2; ALOX-15-lipoxygenase 15; IL-6-interleukin 6) were determined. This study demonstrates for the first time that incubation with iso-BCFA decreases the expression of adipocyte genes that are associated with lipid metabolism (except FASN) and inflammation. These findings suggest that changes in the iso-BCFA profile in obese patients may contribute to adipose inflammation and dyslipidemia. Further studies should evaluate whether iso-BCFA supplementation in obese patients would be beneficial.

Metabolite G-Protein Coupled Receptors in Cardio-Metabolic Diseases

G protein-coupled receptors (GPCRs) have originally been described as a family of receptors activated by hormones, neurotransmitters, and other mediators. However, in recent years GPCRs have shown to bind endogenous metabolites, which serve functions other than as signaling mediators. These receptors respond to fatty acids, mono- and disaccharides, amino acids, or various intermediates and products of metabolism, including ketone bodies, lactate, succinate, or bile acids. Given that many of these metabolic processes are dysregulated under pathological conditions, including diabetes, dyslipidemia, and obesity, receptors of endogenous metabolites have also been recognized as potential drug targets to prevent and/or treat metabolic and cardiovascular diseases. This review describes G protein-coupled receptors activated by endogenous metabolites and summarizes their physiological, pathophysiological, and potential pharmacological roles.

Novel role of xanthine oxidase-dependent H2O2 production in 12/15-lipoxygenase-mediated de novo lipogenesis, triglyceride biosynthesis and weight gain

12/15-lipoxygenase (12/15-LOX) plays an essential role in oxidative conversion of polyunsaturated fatty acids into various bioactive lipid molecules. Although 12/15-LOX's role in the pathophysiology of various human diseases has been well studied, its role in weight gain is controversial and poorly clarified. Here, we demonstrated the role of 12/15-LOX in high-fat diet (HFD)-induced weight gain in a mouse model. We found that 12/15-LOX mediates HFD-induced de novo lipogenesis (DNL), triglyceride (TG) biosynthesis and the transport of TGs from the liver to adipose tissue leading to white adipose tissue (WAT) expansion and weight gain via xanthine oxidase (XO)-dependent production of H₂O₂. 12/15-LOX deficiency leads to cullin2-mediated ubiquitination and degradation of XO, thereby suppressing H₂O₂ production, DNL and TG biosynthesis resulting in reduced WAT expansion and weight gain. These findings infer that manipulation of 12/15-LOX metabolism may manifest a potential therapeutic target for weight gain and obesity.

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12/15-LOX-12(S)-HETE axis via activation of CREB-Egr1 enhances TG biosynthesis.

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12/15-LOX-12(S)-HETE axis via activation of SREBP1c triggers DNL.

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H₂O₂ mediates 12/15-LOX-12(S)-HETE axis-induced DNL and TG biosynthesis.

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12/15-LOX via TG biosynthesis leads to WAT expansion and body weight gain.

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Downstream to 12/15-LOX, H₂O₂-mediates WAT expansion and body weight gain.

12-Lipoxygenase governs the innate immune pathogenesis of islet inflammation and autoimmune diabetes

Macrophages and related myeloid cells are innate immune cells that participate in the early islet inflammation of type 1 diabetes (T1D). The enzyme 12-lipoxygenase (12-LOX) catalyzes the formation of proinflammatory eicosanoids, but its role and mechanisms in myeloid cells in the pathogenesis of islet inflammation have not been elucidated. Leveraging a model of islet inflammation in zebrafish, we show here that macrophages contribute significantly to the loss of β cells and the subsequent development of hyperglycemia. The depletion or inhibition of 12-LOX in this model resulted in reduced macrophage infiltration into islets and the preservation of β cell mass. In NOD mice, the deletion of the gene encoding 12-LOX in the myeloid lineage resulted in reduced insulitis with reductions in proinflammatory macrophages, a suppressed T cell response, preserved β cell mass, and almost complete protection from the development of T1D. 12-LOX depletion caused a defect in myeloid cell migration, a function required for immune surveillance and tissue injury responses. This effect on migration resulted from the loss of the chemokine receptor CXCR3. Transgenic expression of the gene encoding CXCR3 rescued the migratory defect in zebrafish 12-LOX morphants. Taken together, our results reveal a formative role for innate immune cells in the early pathogenesis of T1D and identify 12-LOX as an enzyme required to promote their prodiabetogenic phenotype in the context of autoimmunity.

The Emerging Role of COX-2, 15-LOX and PPARγ in Metabolic Diseases and Cancer: An Introduction to Novel Multi-target Directed Ligands (MTDLs)

Emerging evidence supports an intertwining framework for the involvement of different inflammatory pathways in a common pathological background for a number of disorders. Of importance are pathways involving arachidonic acid metabolism by cyclooxygenase-2 (COX-2) and 15-lipoxygenase (15-LOX). Both enzyme activities and their products are implicated in a range of pathophysiological processes encompassing metabolic impairment leading to adipose inflammation and the subsequent vascular and neurological disorders, in addition to various pro- and antitumorigenic effects. A further layer of complexity is encountered by the disparate, and often reciprocal, modulatory effect COX-2 and 15-LOX activities and metabolites exert on each other or on other cellular targets, the most prominent of which is peroxisome proliferator-activated receptor gamma (PPARγ). Thus, effective therapeutic intervention with such multifaceted disorders requires the simultaneous modulation of more than one target. Here, we describe the role of COX-2, 15-LOX, and PPARγ in cancer and complications of metabolic disorders, highlight the value of designing multi-target directed ligands (MTDLs) modifying their activity, and summarizing the available literature regarding the rationale and feasibility of design and synthesis of these ligands together with their known biological effects. We speculate on the potential impact of MTDLs in these disorders as well as emphasize the need for structured future effort to translate these early results facilitating the adoption of these, and similar, molecules in clinical research.

Regulation of Tissue Inflammation by 12-Lipoxygenases

Lipoxygenases (LOXs) are lipid metabolizing enzymes that catalyze the di-oxygenation of polyunsaturated fatty acids to generate active eicosanoid products. 12-lipoxygenases (12-LOXs) primarily oxygenate the 12th carbon of its substrates. Many studies have demonstrated that 12-LOXs and their eicosanoid metabolite 12-hydroxyeicosatetraenoate (12-HETE), have significant pathological implications in inflammatory diseases. Increased level of 12-LOX activity promotes stress (both oxidative and endoplasmic reticulum)-mediated inflammation, leading to damage in these tissues. 12-LOXs are also associated with enhanced cellular migration of immune cells-a characteristic of several metabolic and autoimmune disorders. Genetic depletion or pharmacological inhibition of the enzyme in animal models of various diseases has shown to be protective against disease development and/or progression in animal models in the setting of diabetes, pulmonary, cardiovascular, and metabolic disease, suggesting a translational potential of targeting the enzyme for the treatment of several disorders. In this article, we review the role of 12-LOXs in the pathogenesis of several diseases in which chronic inflammation plays an underlying role.

High-fat diet activates liver iPLA2γ generating eicosanoids that mediate metabolic stress

High-fat (HF) diet-induced obesity precipitates multiple metabolic disorders including insulin resistance, glucose intolerance, oxidative stress, and inflammation, resulting in the initiation of cell death programs. Previously, we demonstrated murine germline knockout of calcium-independent phospholipase A2γ (iPLA2γ) prevented HF diet-induced weight gain, attenuated insulin resistance, and decreased mitochondrial permeability transition pore (mPTP) opening leading to alterations in bioenergetics. To gain insight into the specific roles of hepatic iPLA2γ in mitochondrial function and cell death under metabolic stress, we generated a hepatocyte-specific iPLA2γ-knockout (HEPiPLA2γKO). Using this model, we compared the effects of an HF diet on wild-type versus HEPiPLA2γKO mice in eicosanoid production and mitochondrial bioenergetics. HEPiPLA2γKO mice exhibited higher glucose clearance rates than WT controls. Importantly, HF-diet induced the accumulation of 12-hydroxyeicosatetraenoic acid (12-HETE) in WT liver which was decreased in HEPiPLA2γKO. Furthermore, HF-feeding markedly increased Ca2+ sensitivity and resistance to ADP-mediated inhibition of mPTP opening in WT mice. In contrast, ablation of iPLA2γ prevented the HF-induced hypersensitivity of mPTP opening to calcium and maintained ADP-mediated resistance to mPTP opening. Respirometry revealed that ADP-stimulated mitochondrial respiration was significantly reduced by exogenous 12-HETE. Finally, HEPiPLA2γKO hepatocytes were resistant to calcium ionophore-induced lipoxygenase-mediated lactate dehydrogenase release. Collectively, these results demonstrate that an HF diet increases iPLA2γ-mediated hepatic 12-HETE production leading to mitochondrial dysfunction and hepatic cell death.

12(S)-HETE mediates diabetes-induced endothelial dysfunction by activating intracellular endothelial cell TRPV1

Patients with diabetes develop endothelial dysfunction shortly after diabetes onset that progresses to vascular disease underlying the majority of diabetes-associated comorbidities. Increased lipid peroxidation, mitochondrial calcium overload, and mitochondrial dysfunction are characteristics of dysfunctional endothelial cells in diabetic patients. We here identified that targeting the lipid peroxidation product 12(S)-hydroxyeicosatetraenoic acid-induced [12(S)-HETE-induced] activation of the intracellularly located cation channel transient receptor potential vanilloid 1 (TRPV1) in endothelial cells is a means to causally control early-stage vascular disease in type I diabetic mice. Mice with an inducible, endothelium-specific 12/15-lipoxygenase (12/15Lo) knockout were protected similarly to TRPV1-knockout mice from type 1 diabetes-induced endothelial dysfunction and impaired vascular regeneration following arterial injury. Both 12(S)-HETE in concentrations found in diabetic patients and TRPV1 agonists triggered mitochondrial calcium influx and mitochondrial dysfunction in endothelial cells, and 12(S)-HETE effects were absent in endothelial cells from TRPV1-knockout mice. As a therapeutic consequence, we found that a peptide targeting 12(S)-HETE-induced TRPV1 interaction at the TRPV1 TRP box ameliorated diabetes-induced endothelial dysfunction and augmented vascular regeneration in diabetic mice. Our findings suggest that pharmacological targeting of increased endothelial lipid peroxidation can attenuate diabetes-induced comorbidities related to vascular disease.

A 12-lipoxygenase-Gpr31 signaling axis is required for pancreatic organogenesis in the zebrafish

12-Lipoxygenase (12-LOX) is a key enzyme in arachidonic acid metabolism, and alongside its major product, 12-HETE, plays a key role in promoting inflammatory signaling during diabetes pathogenesis. Although 12-LOX is a proposed therapeutic target to protect pancreatic islets in the setting of diabetes, little is known about the consequences of blocking its enzymatic activity during embryonic development. Here, we have leveraged the strengths of the zebrafish-genetic manipulation and pharmacologic inhibition-to interrogate the role of 12-LOX in pancreatic development. Lipidomics analysis during zebrafish development demonstrated that 12-LOX-generated metabolites of arachidonic acid increase sharply during organogenesis stages, and that this increase is blocked by morpholino-directed depletion of 12-LOX. Furthermore, we found that either depletion or inhibition of 12-LOX impairs both exocrine pancreas growth and unexpectedly, the generation of insulin-producing β cells. We demonstrate that morpholino-mediated knockdown of GPR31, a purported G-protein-coupled receptor for 12-HETE, largely phenocopies both the depletion and the inhibition of 12-LOX. Moreover, we show that loss of GPR31 impairs pancreatic bud fusion and pancreatic duct morphogenesis. Together, these data provide new insight into the requirement of 12-LOX in pancreatic organogenesis and islet formation, and additionally provide evidence that its effects are mediated via a signaling axis that includes the 12-HETE receptor GPR31.

Transcriptomic responses of hypothalamus to acute exercise in type 2 diabetic Goto-Kakizaki rats

The hypothalamus has an integral role in energy homeostasis regulation, and its dysfunctions lead to the development of type 2 diabetes (T2D). Physical activity positively affects the prevention and treatment of T2D. However, there is not much information on the adaptive mechanisms of the hypothalamus. In this study, RNA sequencing was used to determine how acute exercise affects hypothalamic transcriptome from both type 2 diabetic Goto-Kakizaki (GK) and control Wistar rats with or without a single session of running (15 m/min for 60 min). Through pairwise comparisons, we identified 957 differentially expressed genes (DEGs), of which 726, 197, and 98 genes were found between GK and Wistar, exercised GK and GK, and exercised Wistar and Wistar, respectively. The results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment revealed that lipid metabolism-related terms and pathways were enriched in GK and exercised GK rats, and nervous system related terms and pathways were enriched in exercised GK and Wistar rats. Furthermore, 45 DEGs were associated with T2D and related phenotypes according to the annotations in the Rat Genome Database. Among these 45 DEGs, several genes (Plin2, Cd36, Lpl, Wfs1, Cck) related to lipid metabolism or the nervous system are associated with the exercise-induced benefits in the hypothalamus of GK rats. Our findings might assist in identifying potential therapeutic targets for T2D prevention and treatment.

Role of the 12-lipoxygenase pathway in diabetes pathogenesis and complications

12-lipoxygenase (12-LOX) is one of several enzyme isoforms responsible for the metabolism of arachidonic acid and other poly-unsaturated fatty acids to both pro- and anti-inflammatory lipid mediators. Mounting evidence has shown that 12-LOX plays a critical role in the modulation of inflammation at multiple checkpoints during diabetes development. Due to this, interventions to limit pro-inflammatory 12-LOX metabolites either by isoform-specific 12-LOX inhibition, or by providing specific fatty acid substrates via dietary intervention, has the potential to significantly and positively impact health outcomes of patients living with both type 1 and type 2 diabetes. To date, the development of truly specific and efficacious inhibitors has been hampered by homology of LOX family members; however, improvements in high throughput screening have improved the inhibitor landscape. Here, we describe the function and role of human 12-LOX, and mouse 12-LOX and 12/15-LOX, in the development of diabetes and diabetes-related complications, and describe promise in the development of strategies to limit pro-inflammatory metabolites, primarily via new small molecule 12-LOX inhibitors.

Hepatocyte ALOXE3 is induced during adaptive fasting and enhances insulin sensitivity by activating hepatic PPARγ

The hepatic glucose fasting response is gaining traction as a therapeutic pathway to enhance hepatic and whole-host metabolism. However, the mechanisms underlying these metabolic effects remain unclear. Here, we demonstrate the epidermal-type lipoxygenase, eLOX3 (encoded by its gene, Aloxe3), is a potentially novel effector of the therapeutic fasting response. We show that Aloxe3 is activated during fasting, glucose withdrawal, or trehalose/trehalose analogue treatment. Hepatocyte-specific Aloxe3 expression reduced weight gain and hepatic steatosis in diet-induced and genetically obese (db/db) mouse models. Aloxe3 expression, moreover, enhanced basal thermogenesis and abrogated insulin resistance in db/db diabetic mice. Targeted metabolomics demonstrated accumulation of the PPARγ ligand 12-KETE in hepatocytes overexpressing Aloxe3. Strikingly, PPARγ inhibition reversed hepatic Aloxe3–mediated insulin sensitization, suppression of hepatocellular ATP production and oxygen consumption, and gene induction of PPARγ coactivator-1α (PGC1α) expression. Moreover, hepatocyte-specific PPARγ deletion reversed the therapeutic effect of hepatic Aloxe3 expression on diet-induced insulin intolerance. Aloxe3 is, therefore, a potentially novel effector of the hepatocellular fasting response that leverages both PPARγ-mediated and pleiotropic effects to augment hepatic and whole-host metabolism, and it is, thus, a promising target to ameliorate metabolic disease.

The lipoxygenase ALOXE3 is an effector of the hepatic fasting response that improves insulin sensitivity by activating hepatic PPARγ.

Activation of the 12/15 lipoxygenase pathway accompanies metabolic decline in db/db pre-diabetic mice

The 12-lipoxygenase (12LO) pathway is a promising target to reduce islet dysfunction, adipose tissue (AT) inflammation and insulin resistance. Optimal pre-clinical models for the investigation of selective12LO inhibitors in this context have not yet been identified. The objective of this study was to characterize the time course of 12LO isoform expression and metabolite production in pancreatic islets and AT of C57BLKS/J-db/db obese diabetic mouse in a pre-diabetic state in order to establish a suitable therapeutic window for intervention with selective lipoxygenase inhibitors. Mice have 2 major 12LO isoforms -the leukocyte type (12/15LO) and the platelet type (p12LO) and both are expressed in islets and AT. We found a sharp increase in protein expression of 12/15LO in the pancreatic islets of 10-week old db-/- mice compared to 8- week old counterparts. Immunohistochemistry showed that the increase in islet 12/15LO parallels a decline in islet number. Analysis of 12- and 15-hydroperoxytetraeicosanoid acids (HETE)s showed a 2-3 fold increase especially in 12(S)-HETE that mirrored the increase in 12/15LO expression in islets. Analysis of AT and stromal vascular fraction (SVF) showed a significant increase of platelet 12LO gene expression along with 12- and 15- HETEs. The data demonstrate that the db/db mouse is a suitable model for investigation of 12/15LO inhibitors in the development of inflammatory mediated type 2 diabetes, with a narrow window of therapeutic intervention prior to 8 weeks of age.

Molecular mechanisms of nonalcoholic fatty liver disease: Potential role for 12-lipoxygenase

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of pathologies associated with fat accumulation in the liver. NAFLD is the most common cause of liver disease in the United States, affecting up to a third of the general population. It is commonly associated with features of metabolic syndrome, particularly insulin resistance. NAFLD shares the basic pathogenic mechanisms with obesity and insulin resistance, such as mitochondrial, oxidative and endoplasmic reticulum stress. Lipoxygenases catalyze the conversion of poly-unsaturated fatty acids in the plasma membrane-mainly arachidonic acid and linoleic acid-to produce oxidized pro-inflammatory lipid intermediates. 12-Lipoxygenase (12-LOX) has been studied extensively in setting of inflammation and insulin resistance. As insulin resistance is closely associated with development of NAFLD, the role of 12-LOX in pathogenesis of NAFLD has received increasing attention in recent years. In this review we discuss the role of 12-LOX in NAFLD pathogenesis and its potential role in emerging new therapeutics.

12-Lipoxygenase Inhibitor Improves Functions of Cytokine-Treated Human Islets and Type 2 Diabetic Islets

CONTEXT

The 12-lipoxygenase (12-LO) pathway produces proinflammatory metabolites, and its activation is implicated in islet inflammation associated with type 1 and type 2 diabetes (T2D).

OBJECTIVES

We aimed to test the efficacy of ML355, a highly selective, small molecule inhibitor of 12-LO, for the preservation of islet function.

DESIGN

Human islets from nondiabetic donors were incubated with a mixture of tumor necrosis factor α , interluekin-1β, and interferon-γ to model islet inflammation. Cytokine-treated islets and human islets from T2D donors were incubated in the presence and absence of ML355.

SETTING

In vitro study.

PARTICIPANTS

Human islets from organ donors aged >20 years of both sexes and any race were used. T2D status was defined from either medical history or most recent hemoglobin A1c value >6.5%.

INTERVENTION

Glucose stimulation.

MAIN OUTCOME MEASURES

Static and dynamic insulin secretion and oxygen consumption rate (OCR).

RESULTS

ML355 prevented the reduction of insulin secretion and OCR in cytokine-treated human islets and improved both parameters in human islets from T2D donors.

CONCLUSIONS

ML355 was efficacious in improving human islet function after cytokine treatment and in T2D islets in vitro. The study suggests that the blockade of the 12-LO pathway may serve as a target for both form of diabetes and provides the basis for further study of this small molecule inhibitor in vivo.

Enzymatic lipid oxidation by eosinophils propagates coagulation, hemostasis, and thrombotic disease

Blood coagulation is essential for physiological hemostasis but simultaneously contributes to thrombotic disease. However, molecular and cellular events controlling initiation and propagation of coagulation are still incompletely understood. In this study, we demonstrate an unexpected role of eosinophils during plasmatic coagulation, hemostasis, and thrombosis. Using a large-scale epidemiological approach, we identified eosinophil cationic protein as an independent and predictive risk factor for thrombotic events in humans. Concurrent experiments showed that eosinophils contributed to intravascular thrombosis by exhibiting a strong endogenous thrombin-generation capacity that relied on the enzymatic generation and active provision of a procoagulant phospholipid surface enriched in 12/15-lipoxygenase-derived hydroxyeicosatetraenoic acid-phosphatidylethanolamines. Our findings reveal a previously unrecognized role of eosinophils and enzymatic lipid oxidation as regulatory elements that facilitate both hemostasis and thrombosis in response to vascular injury, thus identifying promising new targets for the treatment of thrombotic disease.

12-Lipoxygenase Inhibition on Microalbuminuria in Type-1 and Type-2 Diabetes Is Associated with Changes of Glomerular Angiotensin II Type 1 Receptor Related to Insulin Resistance

(1) BACKGROUND: 12-lipoxygenase (12-LO) is involved in the development of diabetic nephropathy (DN). In the present study, we investigated whether 12-LO inhibition may ameliorate type-2 DN (T2DN) by interfering with insulin resistance (IR); (2) METHODS: Rat glomerular mesangial cells, glomeruli and skeletal muscles were isolated and used in this study. Kidney histological changes were confirmed by periodic-acid Schiff staining; mRNA expression was detected by competitive reverse transcription polymerase chain reaction; and the protein level was determined by Western blot and the enzyme-linked immunosorbent assay, respectively; (3) RESULTS: The inhibition of 12-LO attenuated microalbuminuria (MAU) increases in type-2 diabetic rats, but not in type-1 diabetic rats. Infusion of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) significantly increased the expression of angiotensin II (Ang II) and Ang II type 1 receptor (AT1R), but decreased the expression of AT1R-associated protein (ATRAP) in rat glomeruli, compared to the control. An in vitro study revealed that both 12(S)-HETE and insulin upregulated AT1R expression in rat mesangial cells. In the presence of p38 mitogen-activated protein kinase (MAPK) inhibitor, SB202190, the 12(S)-HETE-induced ATRAP reduction was significantly abolished. Interestingly, 12-LO inhibition did not influence AT1R expression in type-1 diabetic rats, but significantly abolished the increased AT1R and Ang II expression in glomeruli of type-2 diabetic rats. Furthermore, the inhibition of 12-LO significantly corrected impaired insulin sensitivity and fast serum insulin level, as well as the p-AMP-activated protein kinase (AMPK) reduction in skeletal muscle of type-2 diabetic rats; (4) CONCLUSION: The inhibition of 12-LO potentially ameliorated MAU by preventing IR through the downregulation of glomerular AT1R expression in T2DN.

Lipids and immunoinflammatory pathways of beta cell destruction

Islet inflammation contributes to beta cell demise in both type 1 and type 2 diabetes. 12-Lipoxygenase (12-LO, gene expressed as ALOX12 in humans and 12-Lo in rodents in this manuscript) produces proinflammatory metabolites such as 12(S)-hydroxyeicosatetraenoic acids through dioxygenation of polyunsaturated fatty acids. 12-LO was first implicated in diabetes when the increase in 12-Lo expression and 12(S)-hydroxyeicosatetraenoic acid was noted in rodent models of diabetes. Subsequently, germline 12-Lo (-/-) was shown to prevent the development of hyperglycemia in mouse models of type 1 diabetes and in high-fat fed mice. More recently, beta cell-specific 12-Lo (-/-) was shown to protect mice against hyperglycaemia after streptozotocin and a high-fat diet. In humans, 12-LO expression is increased in pancreatic islets of autoantibody-positive, type 1 diabetic and type 2 diabetic organ donors. Interestingly, the high expression of ALOX12 is associated with the alteration in first-phase glucose-stimulated insulin secretion in human type 2 diabetic islets. To further clarify the role of islet 12-LO in diabetes and to validate 12-LO as a therapeutic target of diabetes, we have studied selective pharmacological inhibitors for 12-LO. The compounds we have identified show promise: they protect beta cell lines and human islets from apoptosis and preserve insulin secretion when challenged by proinflammatory cytokine mixture. Currently studies are underway to test the compounds in mouse models of diabetes. This review summarises a presentation given at the 'Islet inflammation in type 2 diabetes' symposium at the 2015 annual meeting of the EASD. It is accompanied two other mini-reviews on topics from this symposium (by Simone Baltrusch, DOI: 10.1007/s00125-016-3891-x and Marc Donath, DOI: 10.1007/s00125-016-3873-z ) and a commentary by the Session Chair, Piero Marchetti (DOI: 10.1007/s00125-016-3875-x ).

Structural and functional biology of arachidonic acid 15-lipoxygenase-1 (ALOX15)

Lipoxygenases (LOX) form a family of lipid peroxidizing enzymes, which have been implicated in a number of physiological processes and in the pathogenesis of inflammatory, hyperproliferative and neurodegenerative diseases. They occur in two of the three domains of terrestrial life (bacteria, eucarya) and the human genome involves six functional LOX genes, which encode for six different LOX isoforms. One of these isoforms is ALOX15, which has first been described in rabbits in 1974 as enzyme capable of oxidizing membrane phospholipids during the maturational breakdown of mitochondria in immature red blood cells. During the following decades ALOX15 has extensively been characterized and its biological functions have been studied in a number of cellular in vitro systems as well as in various whole animal disease models. This review is aimed at summarizing the current knowledge on the protein-chemical, molecular biological and enzymatic properties of ALOX15 in various species (human, mouse, rabbit, rat) as well as its implication in cellular physiology and in the pathogenesis of various diseases.

Adipogenic role of alternatively activated macrophages in β-adrenergic remodeling of white adipose tissue

De novo brown adipogenesis involves the proliferation and differentiation of progenitors, yet the mechanisms that guide these events in vivo are poorly understood. We previously demonstrated that treatment with a β3-adrenergic receptor (ADRB3) agonist triggers brown/beige adipogenesis in gonadal white adipose tissue following adipocyte death and clearance by tissue macrophages. The close physical relationship between adipocyte progenitors and tissue macrophages suggested that the macrophages that clear dying adipocytes might generate proadipogenic factors. Flow cytometric analysis of macrophages from mice treated with CL 316,243 identified a subpopulation that contained elevated lipid and expressed CD44. Lipidomic analysis of fluorescence-activated cell sorting-isolated macrophages demonstrated that CD44+ macrophages contained four- to five-fold higher levels of the endogenous peroxisome-proliferator activated receptor gamma (PPARγ) ligands 9-hydroxyoctadecadienoic acid (HODE), and 13-HODE compared with CD44- macrophages. Gene expression profiling and immunohistochemistry demonstrated that ADRB3 agonist treatment upregulated expression of ALOX15, the lipoxygenase responsible for generating 9-HODE and 13-HODE. Using an in vitro model of adipocyte efferocytosis, we found that IL-4-primed tissue macrophages accumulated lipid from dying fat cells and upregulated expression of Alox15. Furthermore, treatment of differentiating adipocytes with 9-HODE and 13-HODE potentiated brown/beige adipogenesis. Collectively, these data indicate that noninflammatory removal of adipocyte remnants and coordinated generation of PPARγ ligands by M2 macrophages provides localized adipogenic signals to support de novo brown/beige adipogenesis.

Adipocyte iron regulates leptin and food intake

Dietary iron supplementation is associated with increased appetite. Here, we investigated the effect of iron on the hormone leptin, which regulates food intake and energy homeostasis. Serum ferritin was negatively associated with serum leptin in a cohort of patients with metabolic syndrome. Moreover, the same inverse correlation was observed in mice fed a high-iron diet. Adipocyte-specific loss of the iron exporter ferroportin resulted in iron loading and decreased leptin, while decreased levels of hepcidin in a murine hereditary hemochromatosis (HH) model increased adipocyte ferroportin expression, decreased adipocyte iron, and increased leptin. Treatment of 3T3-L1 adipocytes with iron decreased leptin mRNA in a dose-dependent manner. We found that iron negatively regulates leptin transcription via cAMP-responsive element binding protein activation (CREB activation) and identified 2 potential CREB-binding sites in the mouse leptin promoter region. Mutation of both sites completely blocked the effect of iron on promoter activity. ChIP analysis revealed that binding of phosphorylated CREB is enriched at these two sites in iron-treated 3T3-L1 adipocytes compared with untreated cells. Consistent with the changes in leptin, dietary iron content was also directly related to food intake, independently of weight. These findings indicate that levels of dietary iron play an important role in regulation of appetite and metabolism through CREB-dependent modulation of leptin expression.

Minireview: 12-Lipoxygenase and Islet β-Cell Dysfunction in Diabetes

The insulin producing islet β-cells have increasingly gained attention for their role in the pathogeneses of virtually all forms of diabetes. Dysfunction, de-differentiation, and/or death of β-cells are pivotal features in the transition from normoglycemia to hyperglycemia in both animal models of metabolic disease and humans. In both type 1 and type 2 diabetes, inflammation appears to be a central cause of β-cell derangements, and molecular pathways that modulate inflammation or the inflammatory response are felt to be prime targets of future diabetes therapy. The lipoxygenases (LOs) represent a class of enzymes that oxygenate cellular polyunsaturated fatty acids to produce inflammatory lipid intermediates that directly and indirectly affect cellular function and survival. The enzyme 12-LO is expressed in all metabolically active tissues, including pancreatic islets, and has received increasing attention for its role in promoting cellular inflammation in the setting of diabetes. Genetic deletion models of 12-LO in mice reveal striking protection from metabolic disease and its complications and an emerging body of literature has implicated its role in human disease. This review focuses on the evidence supporting the proinflammatory role of 12-LO as it relates to islet β-cells, and the potential for 12-LO inhibition as a future avenue for the prevention and treatment of metabolic disease.

Selective inhibition of 12-lipoxygenase protects islets and beta cells from inflammatory cytokine-mediated beta cell dysfunction

AIMS/HYPOTHESIS

Islet inflammation leads to loss of functional pancreatic beta cell mass. Increasing evidence suggests that activation of 12-lipoxygenase leads to inflammatory beta cell loss. This study evaluates new specific small-molecule inhibitors of 12-lipoxygenase for protecting rodent and human beta cells from inflammatory damage.

METHODS

Mouse beta cell lines and mouse and human islets were treated with inflammatory cytokines IL-1β, TNFα and IFNγ in the absence or presence of novel selective 12-lipoxygenase inhibitors. Glucose-stimulated insulin secretion (GSIS), gene expression, cell survival and 12-S-hydroxyeicosatetraenoic acid (12-S-HETE) levels were evaluated using established methods. Pharmacokinetic analysis was performed with the lead inhibitor in CD1 mice.

RESULTS

Inflammatory cytokines led to the loss of human beta cell function, elevated cell death, increased inflammatory gene expression and upregulation of 12-lipoxygenase expression and activity (measured by 12-S-HETE generation). Two 12-lipoxygenase inhibitors, Compounds 5 and 9, produced a concentration-dependent reduction of stimulated 12-S-HETE levels. GSIS was preserved in the presence of the 12-lipoxygenase inhibitors. 12-Lipoxygenase inhibition preserved survival of primary mouse and human islets. When administered orally, Compound 5 reduced plasma 12-S-HETE in CD1 mice. Compounds 5 and 9 preserved the function and survival of human donor islets exposed to inflammatory cytokines.

CONCLUSIONS/INTERPRETATION

Selective inhibition of 12-lipoxygenase activity confers protection to beta cells during exposure to inflammatory cytokines. These concept validation studies identify 12-lipoxygenase as a promising target in the prevention of loss of functional beta cells in diabetes.

Targeting 12-lipoxygenase as a novel strategy to combat the effects of inflammation on beta cells in diabetes

Inflammation is a pathological feature of the pancreatic islet in type 1 and 2 diabetes, contributing to islet endocrine cell failure and the onset of hyperglycaemia in both diseases. Indeed, numerous immune targets have recently been found to be altered in type 2 diabetes, but few have yet to be translated to the clinic. Taylor-Fishwick and colleagues aimed to change this by performing proof-of-concept studies investigating the efficacy of small molecule inhibitors of 12-lipoxygenase in rodent and human beta cells exposed to proinflammatory cytokines. The results of these studies, published in this issue of Diabetologia (DOI: 10.1007/s00125-014-3452-0), build on a wealth of preclinical data that have implicated 12-lipoxygenase in rodent models of type 1 and 2 diabetes. While there remain some unanswered mechanistic questions regarding how cytokines regulate 12-lipoxygenase activation and the downstream consequences of activation, it is hoped that future studies with newly identified selective inhibitors may overcome the in vitro limitations of this study and allow for the eventual clinical translation of these highly interesting findings.

Utilizing past and present mouse systems to engineer more relevant pancreatic cancer models

The study of pancreatic cancer has prompted the development of numerous mouse models that aim to recapitulate the phenotypic and mechanistic features of this deadly malignancy. This review accomplishes two tasks. First, it provides an overview of the models that have been used as representations of both the neoplastic and carcinoma phenotypes. Second, it presents new modeling schemes that ultimately will serve to more faithfully capture the temporal and spatial progression of the human disease, providing platforms for improved understanding of the role of non-epithelial compartments in disease etiology as well as evaluating therapeutic approaches.

Fat, epigenome and pancreatic diseases. Interplay and common pathways from a toxic and obesogenic environment

The worldwide obesity epidemic is paralleled by a rise in the incidence of pancreatic disorders ranging from "fatty" pancreas to pancreatitis and cancer. Body fat accumulation and pancreatic dysfunctions have common pathways, mainly acting through insulin resistance and low-grade inflammation, frequently mediated by the epigenome. These mechanisms are affected by lifestyle and by the toxic effects of fat and pollutants. An early origin is common, starting in pediatric age or during the fetal life in response to nutritional factors, endocrine disruptor chemicals (EDCs) or parental exposure to toxics. A "fatty pancreas" is frequent in obese and is able to induce pancreatic damage. The fat is a target of EDCs and of the cytotoxic/mutagenic effects of heavy metals, and is the site of bioaccumulation of lipophilic and persistent pollutants related with insulin resistance and able to promote pancreatic cancer. Increased Body Mass Index (BMI) can act as independent risk factor for a more severe course of acute pancreatitis and obesity is also a well-known risk factor for pancreatic cancer, that is related with BMI, insulin resistance, and duration of exposure to the toxic effects of fat and/or of environmental pollutants. All these mechanisms involve gene-environment interactions through epigenetic factors, and might be manipulated by primary prevention measures. Further studies are needed, pointing to better assess the interplays of modifiable factors on both obesity and pancreatic diseases, and to verify the efficacy of primary prevention strategies involving lifestyle and environmental exposure to toxics.

Adipose tissue 12/15 lipoxygenase pathway in human obesity and diabetes

CONTEXT

Visceral adipose tissue (VAT) is a key contributor to chronic inflammation in obesity. The 12/15-lipoxygenase pathway (ALOX) is present in adipose tissue (AT) and leads to inflammatory cascades that are causal for the onset of insulin resistance in rodent models of obesity.

OBJECTIVE

The pathophysiology of the ALOX 12/15 pathway in human AT is unknown. We characterized the ALOX pathway in different AT depots in obese humans with or without type 2 diabetes (T2D).

DESIGN

This study includes a cross-sectional cohort of 46 morbidly obese (body mass index >39 kg/m(2)) nondiabetic (n = 25) and T2D (n = 21) subjects.

SETTING

This study was conducted at Eastern Virginia Medical School (Norfolk, Virginia) in collaboration with Sentara Metabolic and Weight Loss Surgery Center (Sentara Medical Group, Norfolk, Virginia).

PATIENTS

Twenty-five obese (body mass index 44.8 ± 4.4 kg/m(2)) nondiabetic (hemoglobin A1c 5.83% ± 0.27%) and 21 obese (43.4 ± 4.1 kg/m(2)) and T2D (hemoglobin A1c 7.66% ± 1.22%) subjects were included in the study. The subjects were age matched and both groups had a bias toward female gender.

MAIN OUTCOMES AND MEASURES

Expression of ALOX isoforms along with fatty acid substrates and downstream lipid metabolites were measured. Correlations with depot-specific inflammatory markers were also established.

RESULTS

ALOX 12 expression and its metabolite 12(S)-hydroxyeicosatetraenoic acid were significantly increased in the VAT of T2D subjects. ALOX 15A was exclusively expressed in VAT in both groups. ALOX 12 expression positively correlated with expression of inflammatory genes IL-6, IL-12a, CXCL10, and lipocalin-2.

CONCLUSIONS

ALOX 12 may have a critical role in regulation of inflammation in VAT in obesity and T2D. Selective ALOX 12 inhibitors may constitute a new approach to limit AT inflammation in human obesity.

12-lipoxygenase promotes obesity-induced oxidative stress in pancreatic islets

High-fat diets lead to obesity, inflammation, and dysglycemia. 12-Lipoxygenase (12-LO) is activated by high-fat diets and catalyzes the oxygenation of cellular arachidonic acid to form proinflammatory intermediates. We hypothesized that 12-LO in the pancreatic islet is sufficient to cause dysglycemia in the setting of high-fat feeding. To test this, we generated pancreas-specific 12-LO knockout mice and studied their metabolic and molecular adaptations to high-fat diets. Whereas knockout mice and control littermates displayed identical weight gain, body fat distribution, and macrophage infiltration into fat, knockout mice exhibited greater adaptive islet hyperplasia, improved insulin secretion, and complete protection from dysglycemia. At the molecular level, 12-LO deletion resulted in increases in islet antioxidant enzymes Sod1 and Gpx1 in response to high-fat feeding. The absence or inhibition of 12-LO led to increases in nuclear Nrf2, a transcription factor responsible for activation of genes encoding antioxidant enzymes. Our data reveal a novel pathway in which islet 12-LO suppresses antioxidant enzymes and prevents the adaptive islet responses in the setting of high-fat diets.

Metabolic signatures of cultured human adipocytes from metabolically healthy versus unhealthy obese individuals

Background and Aims

Among obese subjects, metabolically healthy and unhealthy obesity (MHO/MUHO) can be differentiated: the latter is characterized by whole-body insulin resistance, hepatic steatosis, and subclinical inflammation. Aim of this study was, to identify adipocyte-specific metabolic signatures and functional biomarkers for MHO versus MUHO.

Methods

10 insulin-resistant (IR) vs. 10 insulin-sensitive (IS) non-diabetic morbidly obese (BMI >40 kg/m²) Caucasians were matched for gender, age, BMI, and percentage of body fat. From subcutaneous fat biopsies, primary preadipocytes were isolated and differentiated to adipocytes in vitro. About 280 metabolites were investigated by a targeted metabolomic approach intracellularly, extracellularly, and in plasma.

Results/Interpretation

Among others, aspartate was reduced intracellularly to one third (p = 0.0039) in IR adipocytes, pointing to a relative depletion of citric acid cycle metabolites or reduced aspartate uptake in MUHO. Other amino acids, already known to correlate with diabetes and/or obesity, were identified to differ between MUHO's and MHO's adipocytes, namely glutamine, histidine, and spermidine. Most species of phosphatidylcholines (PCs) were lower in MUHO's extracellular milieu, though simultaneously elevated intracellularly, e.g., PC aa C32∶3, pointing to increased PC synthesis and/or reduced PC release. Furthermore, altered arachidonic acid (AA) metabolism was found: 15(S)-HETE (15-hydroxy-eicosatetraenoic acid; 0 vs. 120pM; p = 0.0014), AA (1.5-fold; p = 0.0055) and docosahexaenoic acid (DHA, C22∶6; 2-fold; p = 0.0033) were higher in MUHO. This emphasizes a direct contribution of adipocytes to local adipose tissue inflammation. Elevated DHA, as an inhibitor of prostaglandin synthesis, might be a hint for counter-regulatory mechanisms in MUHO.

Conclusion/Interpretation

We identified adipocyte-inherent metabolic alterations discriminating between MHO and MUHO.

Ultrastructural changes of airway in murine models of allergy and diet-induced metabolic syndrome

Studying ultrastructural changes could reveal novel pathophysiology of obese-asthmatic condition as existing concepts in asthma pathogenesis are based on the histological changes of the diseased airway. While asthma is defined in functional terms, the potential of electron microscopy (EM) in providing cellular and subcellular detail is underutilized. With this view, we have performed transmission EM in the lungs from allergic mice that show key features of asthma and high-fat- or high-fructose-fed mice that mimicked metabolic syndrome to illustrate the ultrastructural changes. The primary focus was epithelial injury and metaplasia, which are cardinal features of asthma and initiate airway remodeling. EM findings of the allergically inflamed mouse lungs correlate with known features of human asthma such as increased mitochondria in airway smooth muscle, platelet activation and subepithelial myofibroblasts. Interestingly, we found a clear and unambiguous evidence to suggest that ciliated cells can become goblet cells using immunoelectron microscopy. Additionally, we show for the first time the stressed mitochondria in the bronchial epithelia of high-fat- or high-fructose-fed mice even without allergen exposure. These results may stimulate interest in using EM in understanding novel pathological mechanisms for different subtypes of asthma including obese asthma.

Interaction between cytokines and inflammatory cells in islet dysfunction, insulin resistance and vascular disease

Inflammation is an established pathogenic player in insulin resistance, islet demise and atherosclerosis. The complex interactions between cytokines, immune cells and affected tissues result in sustained inflammation in diabetes and atherosclerosis. 12- and 15-lipoxygenase (LO), such as 12/15-LO, produces a variety of metabolites through peroxidation of fatty acids and potentially contributes to the complex molecular crosstalk at the site of inflammation. 12- and 15-LO pathways are frequently activated in tissues affected by diabetes and atherosclerosis including adipose tissue (AT), islets and the vasculature. Moreover, mice with whole body and tissue-specific knockout of 12/15-LO are protected against insulin resistance, hyperglycaemia and atherosclerosis supporting functional contribution of 12- and 15-LO pathways in diabetes and atherosclerosis. Recently, it has emerged that there is a temporal regulation of the particular isoforms of 12- and 15-LO in human AT and islets during the development of type 1 and type 2 diabetes and obesity. Analyses of tissues affected by diabetes and atherosclerosis also implied the roles of interleukin (IL)-12 and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-1 (NOX-1) in islets and IL-17A in atherosclerosis. Future studies should aim to test the efficacy of inhibitions of these mediators for treatment of diabetes and atherosclerosis.

Transgenic increase in N-3/n-6 Fatty Acid ratio reduces maternal obesity-associated inflammation and limits adverse developmental programming in mice

Maternal and pediatric obesity has risen dramatically over recent years, and is a known predictor of adverse long-term metabolic outcomes in offspring. However, which particular aspects of obese pregnancy promote such outcomes is less clear. While maternal obesity increases both maternal and placental inflammation, it is still unknown whether this is a dominant mechanism in fetal metabolic programming. In this study, we utilized the Fat-1 transgenic mouse to test whether increasing the maternal n-3/n-6 tissue fatty acid ratio could reduce the consequences of maternal obesity-associated inflammation and thereby mitigate downstream developmental programming. Eight-week-old WT or hemizygous Fat-1 C57BL/6J female mice were placed on a high-fat diet (HFD) or control diet (CD) for 8 weeks prior to mating with WT chow-fed males. Only WT offspring from Fat-1 mothers were analyzed. WT-HFD mothers demonstrated increased markers of infiltrating adipose tissue macrophages (P<0.02), and a striking increase in 12 serum pro-inflammatory cytokines (P<0.05), while Fat1-HFD mothers remained similar to WT-CD mothers, despite equal weight gain. E18.5 Fetuses from WT-HFD mothers had larger placentas (P<0.02), as well as increased placenta and fetal liver TG deposition (P<0.01 and P<0.02, respectively) and increased placental LPL TG-hydrolase activity (P<0.02), which correlated with degree of maternal insulin resistance (r = 0.59, P<0.02). The placentas and fetal livers from Fat1-HFD mothers were protected from this excess placental growth and fetal-placental lipid deposition. Importantly, maternal protection from excess inflammation corresponded with improved metabolic outcomes in adult WT offspring. While the offspring from WT-HFD mothers weaned onto CD demonstrated increased weight gain (P<0.05), body and liver fat (P<0.05 and P<0.001, respectively), and whole body insulin resistance (P<0.05), these were prevented in WT offspring from Fat1-HFD mothers. Our results suggest that reducing excess maternal inflammation may be a promising target for preventing adverse fetal metabolic outcomes in pregnancies complicated by maternal obesity.

Mitochondrial dysfunction in metabolic syndrome and asthma

Though severe or refractory asthma merely affects less than 10% of asthma population, it consumes significant health resources and contributes significant morbidity and mortality. Severe asthma does not fell in the routine definition of asthma and requires alternative treatment strategies. It has been observed that asthma severity increases with higher body mass index. The obese-asthmatics, in general, have the features of metabolic syndrome and are progressively causing a significant burden for both developed and developing countries thanks to the westernization of the world. As most of the features of metabolic syndrome seem to be originated from central obesity, the underlying mechanisms for metabolic syndrome could help us to understand the pathobiology of obese-asthma condition. While mitochondrial dysfunction is the common factor for most of the risk factors of metabolic syndrome, such as central obesity, dyslipidemia, hypertension, insulin resistance, and type 2 diabetes, the involvement of mitochondria in obese-asthma pathogenesis seems to be important as mitochondrial dysfunction has recently been shown to be involved in airway epithelial injury and asthma pathogenesis. This review discusses current understanding of the overlapping features between metabolic syndrome and asthma in relation to mitochondrial structural and functional alterations with an aim to uncover mechanisms for obese-asthma.