The role of circulating galectin-1 in type 2 diabetes and chronic kidney disease: evidence from cross-sectional, longitudinal and Mendelian randomisation analyses.

AIMS/HYPOTHESIS: Galectin-1 modulates inflammation and angiogenesis, and cross-sectional studies indicate that galectin-1 may be a uniting factor between obesity, type 2 diabetes and kidney function. We examined whether circulating galectin-1 can predict incidence of chronic kidney disease (CKD) and type 2 diabetes in a middle-aged population, and if Mendelian randomisation (MR) can provide evidence for causal direction of effects. METHODS: Participants (n = 4022; 58.6% women) in the Malmö Diet and Cancer Study-Cardiovascular Cohort enrolled between 1991 and 1994 (mean age 57.6 years) were examined. eGFR was calculated at baseline and after a mean follow-up of 16.6 ± 1.5 years. Diabetes status was ascertained through registry linkage (mean follow-up of 18.4 ± 6.1 years). The associations of baseline galectin-1 with incident CKD and type 2 diabetes were assessed with Cox regression, adjusting for established risk factors. In addition, a genome-wide association study on galectin-1 was performed to identify genetic instruments for two-sample MR analyses utilising the genetic associations obtained from the Chronic Kidney Disease Genetics (CKDGen) Consortium (41,395 cases and 439,303 controls) and the DIAbetes Genetics Replication And Meta-analysis (DIAGRAM) consortium (74,124 cases and 824,006 controls). One genome-wide significant locus in the galectin-1 gene region was identified (sentinel SNP rs7285699; p = 2.4 × 10-11). The association between galectin-1 and eGFR was also examined in individuals with newly diagnosed diabetes from the All New Diabetics In Scania (ANDIS) cohort. RESULTS: Galectin-1 was strongly associated with lower eGFR at baseline (p = 2.3 × 10-89) but not with incident CKD. However, galectin-1 was associated with increased risk of type 2 diabetes (per SD increase, HR 1.12; 95% CI 1.02, 1.24). Two-sample MR analyses could not ascertain a causal effect of galectin-1 on CKD (OR 0.92; 95% CI 0.82, 1.02) or type 2 diabetes (OR 1.05; 95% CI 0.98, 1.14) in a general population. However, in individuals with type 2 diabetes from ANDIS who belonged to the severe insulin-resistant diabetes subgroup and were at high risk of diabetic nephropathy, genetically elevated galectin-1 was significantly associated with higher eGFR (p = 5.7 × 10-3). CONCLUSIONS/INTERPRETATION: Galectin-1 is strongly associated with lower kidney function in cross-sectional analyses, and two-sample MR analyses suggest a causal protective effect on kidney function among individuals with type 2 diabetes at high risk of diabetic nephropathy. Future studies are needed to explore the mechanisms by which galectin-1 affects kidney function and whether it could be a useful target among individuals with type 2 diabetes for renal improvement.

Wide QRS-T angles are associated with markers of increased inflammatory activity independently of hypertension and diabetes.

BACKGROUND: Wide QRS-T angles and inflammatory activity are markers of future cardiovascular events including sudden cardiac death (SCD). The association between wide QRS-T angles and inflammatory activation is however not fully understood. METHODS: 1,094 study participants of both sexes, 50-64 years old, were included from a randomly selected population-based cohort as a part of the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot study. Serum samples were analyzed for markers of inflammation, cardiac wall stress/injury, and the metabolic syndrome. Wide QRS-T angles were defined using Frank vectorcardiography. Variables were analyzed through unsupervised principal component analysis (PCA) as well as Orthogonal Projections to Latent Structures (OPLS) modeling. In addition, a subset of study participants was analyzed in a post hoc matched group design. RESULTS: Wide QRS-T angles correlated positively with markers of inflammation, cardiac wall stress/injury, the metabolic syndrome, and male sex in both PCA and OPLS models. In the matched post hoc analysis, participants with wide QRS-T angles had significantly higher counts of white blood cells (WBC) and neutrophils in comparison with matched controls. WBC as well as the number of neutrophils, monocytes, basophils, eosinophils and levels of C-reactive protein, IL-1, IL-4, IL-6, TNF-α, and NT-pro-BNP were also significantly higher in comparison with healthy controls. CONCLUSIONS: Markers of inflammatory activation and cardiac injury/wall stress were significantly higher in the presence of wide QRS-T angles. These results corroborate an association between abnormal electrophysiological function and inflammatory activation and may have implications for the prediction of SCD.

Human cardiac fibroblasts isolated from patients with severe heart failure are immune-competent cells mediating an inflammatory response.

This study was aimed to elucidate the immunoregulatory properties of human cardiac fibroblasts cultured under pro-inflammatory and hypoxic conditions. Human heart tissue for isolating cardiac cells is generally hard to obtain, particularly from all four chambers of the same heart. Since different parts of the heart have different functions and therefore may have different immunoregulatory properties, ability to analyse cells from all chambers allows for a unique and comprehensive investigation. Cells were isolated from all four chambers of the heart from patients undergoing cardiac transplantation surgery due to severe chronic heart failure (CHF) (n = 6). Cells isolated from one donor heart, were used for comparison with the experimental group. Primary cultured human cardiac fibroblasts were treated with Lipopolysaccharide (LPS) to induce an inflammatory response. Cells were also subjected to hypoxia. To determine immunoregulatory properties of the cells, cytokine and chemokine profiles were determined using multiplex ELISA. RESULTS: On average, the fibroblasts population constituted approximately 90% of the expanded non-myocytes. Levels of cytokines and chemokines were markedly increased in human cardiac fibroblasts cultured under inflammatory conditions, with a similar response in fibroblasts from all compartments of the heart. Unexpectedly, hypoxia did not further augment cytokine and chemokine secretion. In conclusion, human cardiac fibroblasts are a robust source of pro-inflammatory mediators in the failing heart, independent of hypoxia, and might play a critical role in inflammation associated with the pathogenesis of CHF.

Targeting acid sphingomyelinase reduces cardiac ceramide accumulation in the post-ischemic heart.

Ceramide accumulation is known to accompany acute myocardial ischemia, but its role in the pathogenesis of ischemic heart disease is unclear. In this study, we aimed to determine how ceramides accumulate in the ischemic heart and to determine if cardiac function following ischemia can be improved by reducing ceramide accumulation. To investigate the association between ceramide accumulation and heart function, we analyzed myocardial left ventricle biopsies from subjects with chronic ischemia and found that ceramide levels were higher in biopsies from subjects with reduced heart function. Ceramides are produced by either de novo synthesis or hydrolysis of sphingomyelin catalyzed by acid and/or neutral sphingomyelinase. We used cultured HL-1 cardiomyocytes to investigate these pathways and showed that acid sphingomyelinase activity rather than neutral sphingomyelinase activity or de novo sphingolipid synthesis was important for hypoxia-induced ceramide accumulation. We also used mice with a partial deficiency in acid sphingomyelinase (Smpd1(+/-) mice) to investigate if limiting ceramide accumulation under ischemic conditions would have a beneficial effect on heart function and survival. Although we showed that cardiac ceramide accumulation was reduced in Smpd1(+/-) mice 24h after an induced myocardial infarction, this reduction was not accompanied by an improvement in heart function or survival. Our findings show that accumulation of cardiac ceramides in the post-ischemic heart is mediated by acid sphingomyelinase. However, targeting ceramide accumulation in the ischemic heart may not be a beneficial treatment strategy.

Oregonin reduces lipid accumulation and proinflammatory responses in primary human macrophages.

Inflammation in the vascular wall is important for the development of atherosclerosis. We have previously shown that inflammatory macrophages are more abundant in human atherosclerotic lesions than in healthy arteries. Activated macrophages produce reactive oxygen species (ROS) that promote local inflammation in atherosclerotic lesions. Here, we investigated the role of oregonin, a diarylheptanoid, on proinflammatory responses in primary human macrophages and found that oregonin decreased cellular lipid accumulation and proinflammatory cytokine secretion. We also found that oregonin decreased ROS production in macrophages. Additionally, we observed that treatment of lipopolysaccharide-exposed macrophages with oregonin significantly induced the expression of antioxidant-related genes, including Heme oxygenase-1 and NADPH dehydrogenase quinone 1. In summary, we have shown that oregonin reduces lipid accumulation, inflammation and ROS production in primary human macrophages, indicating that oregonin has anti-inflammatory bioactivities.

Production of deoxycholic acid by low-abundant microbial species is associated with impaired glucose metabolism.

Alterations in gut microbiota composition are suggested to contribute to cardiometabolic diseases, in part by producing bioactive molecules. Some of the metabolites are produced by very low abundant bacterial taxa, which largely have been neglected due to limits of detection. However, the concentration of microbially produced metabolites from these taxa can still reach high levels and have substantial impact on host physiology. To explore this concept, we focused on the generation of secondary bile acids by 7α-dehydroxylating bacteria and demonstrated that addition of a very low abundant bacteria to a community can change the metabolic output dramatically. We show that Clostridium scindens converts cholic acid into the secondary bile acid deoxycholic acid (DCA) very efficiently even though the abundance of C. scindens is low, but still detectable by digital droplet PCR. We also show that colonization of germ-free female mice with a community containing C. scindens induces DCA production and affects host metabolism. Finally, we show that DCA correlates with impaired glucose metabolism and a worsened lipid profile in individuals with type 2 diabetes, which implies that this metabolic pathway may contribute to the development of cardiometabolic disease.

Reduced expression of NLRP3 and MEFV in human ischemic heart tissue.

The innate immune system and, in particular, activation of the multi-protein complex known as the inflammasome complex are involved in ischemic injury in myocardial cells. The nucleotide-binding leucine-rich repeat-containing pyrin receptor 3 (NLRP3) inflammasome has been linked to inflammation and NLRP3 is especially important for increased inflammation in atherosclerosis, which may lead to myocardial infarction. Here we investigated how inflammasome molecules are affected in human ischemic heart tissue. Surprisingly the important member of the inflammasome complex, NLRP3, displayed markedly decreased levels in human ischemic heart tissue compared with non ischemic control heart tissue. However, subsequent gene analysis revealed mutations in NLRP3 in human ischemic heart tissues but not in non-ischemic control tissue. Gene polymorphisms in the NLRP3 inflammasome have been shown to be associated with increased IL-1ß and IL-18 production and severe inflammation. The autoinflammatory disorder familial Mediterranean fever (FMF) is associated with decreased expression of the Mediterranean fever gene (MEFV) and increased inflammation. We also observed reduced expression of MEFV in ischemic versus non-ischemic heart tissue. Further analyses showed a mutation in MEFV in human ischemic heart tissue but not in non-ischemic control tissue. Our data show that defects in the inflammasome and associated proteins may be involved in promoting ischemic heart disease.

Self-organized metabotyping of obese individuals identifies clusters responding differently to bariatric surgery.

Weight loss through bariatric surgery is efficient for treatment or prevention of obesity related diseases such as type 2 diabetes and cardiovascular disease. Long term weight loss response does, however, vary among patients undergoing surgery. Thus, it is difficult to identify predictive markers while most obese individuals have one or more comorbidities. To overcome such challenges, an in-depth multiple omics analyses including fasting peripheral plasma metabolome, fecal metagenome as well as liver, jejunum, and adipose tissue transcriptome were performed for 106 individuals undergoing bariatric surgery. Machine leaning was applied to explore the metabolic differences in individuals and evaluate if metabolism-based patients' stratification is related to their weight loss responses to bariatric surgery. Using Self-Organizing Maps (SOMs) to analyze the plasma metabolome, we identified five distinct metabotypes, which were differentially enriched for KEGG pathways related to immune functions, fatty acid metabolism, protein-signaling, and obesity pathogenesis. The gut metagenome of the most heavily medicated metabotypes, treated simultaneously for multiple cardiometabolic comorbidities, was significantly enriched in Prevotella and Lactobacillus species. This unbiased stratification into SOM-defined metabotypes identified signatures for each metabolic phenotype and we found that the different metabotypes respond differently to bariatric surgery in terms of weight loss after 12 months. An integrative framework that utilizes SOMs and omics integration was developed for stratifying a heterogeneous bariatric surgery cohort. The multiple omics datasets described in this study reveal that the metabotypes are characterized by a concrete metabolic status and different responses in weight loss and adipose tissue reduction over time. Our study thus opens a path to enable patient stratification and hereby allow for improved clinical treatments.

High expression of arachidonate 15-lipoxygenase and proinflammatory markers in human ischemic heart tissue.

A common feature of the ischemic heart and atherosclerotic plaques is the presence of hypoxia (insufficient levels of oxygen in the tissue). Hypoxia has pronounced effects on almost every aspect of cell physiology, and the nuclear transcription factor hypoxia inducible factor-1α (HIF-1α) regulates adaptive responses to low concentrations of oxygen in mammalian cells. In our recent work, we observed that hypoxia increases the proinflammatory enzyme arachidonate 15-lipoxygenase (ALOX15B) in human carotid plaques. ALOX15 has recently been shown to be present in the human myocardium, but the effect of ischemia on its expression has not been investigated. Here we test the hypothesis that ischemia of the heart leads to increased expression of ALOX15, and found an almost 2-fold increase in HIF-1α mRNA expression and a 17-fold upregulation of ALOX15 mRNA expression in the ischemic heart biopsies from patients undergoing coronary bypass surgery compared with non ischemic heart tissue. To investigate the effect of low oxygen concentration on ALOX15 we incubated human vascular muscle cells in hypoxia and showed that expression of ALOX15 increased 22-fold compared with cells incubated in normoxic conditions. We also observed increased mRNA levels of proinflammatory markers in ischemic heart tissue compared with non-ischemic controls. In summary, we demonstrate increased ALOX15 in human ischemic heart biopsies. Furthermore we demonstrate that hypoxia increases ALOX15 in human muscle cells. Our results yield important insights into the underlying association between hypoxia and inflammation in the human ischemic heart disease.

A systems biology approach to study non-alcoholic fatty liver (NAFL) in women with obesity.

Non-alcoholic fatty liver disease (NAFLD) is now the most frequent global chronic liver disease. Individuals with NAFLD exhibited an increased risk of all-cause mortality driven by extrahepatic cancers and liver and cardiovascular disease. Once the disease is established, women have a higher risk of disease progression and worse outcome. It is therefore critical to deepen the current knowledge on the pathophysiology of NAFLD in women. Here, we used a systems biology approach to investigate the contribution of different organs to this disease. We analyzed transcriptomics profiles of liver and adipose tissues, fecal metagenomes, and plasma metabolomes of 55 women with and without NAFLD. We observed differences in metabolites, expression of human genes, and gut microbial features between the groups and revealed that there is substantial crosstalk between these different omics sets. Multi-omics analysis of individuals with NAFLD may provide novel strategies to study the pathophysiology of NAFLD in humans.

Structural characterization of the microbial enzyme urocanate reductase mediating imidazole propionate production.

The human microbiome can produce metabolites that modulate insulin signaling. Type 2 diabetes patients have increased circulating concentrations of the microbially produced histidine metabolite, imidazole propionate (ImP) and administration of ImP in mice resulted in impaired glucose tolerance. Interestingly, the fecal microbiota of the patients had increased capacity to produce ImP, which is mediated by the bacterial enzyme urocanate reductase (UrdA). Here, we describe the X-ray structures of the ligand-binding domains of UrdA in four different states, representing the structural transitions along the catalytic reaction pathway of this unexplored enzyme linked to disease in humans. The structures in combination with functional data provide key insights into the mechanism of action of UrdA that open new possibilities for drug development strategies targeting type 2 diabetes.

Longitudinal plasma protein profiling of newly diagnosed type 2 diabetes.

BACKGROUND: Comprehensive proteomics profiling may offer new insights into the dysregulated metabolic milieu of type 2 diabetes, and in the future, serve as a useful tool for personalized medicine. This calls for a better understanding of circulating protein patterns at the early stage of type 2 diabetes as well as the dynamics of protein patterns during changes in metabolic status. METHODS: To elucidate the systemic alterations in early-stage diabetes and to investigate the effects on the proteome during metabolic improvement, we measured 974 circulating proteins in 52 newly diagnosed, treatment-naïve type 2 diabetes subjects at baseline and after 1 and 3 months of guideline-based diabetes treatment, while comparing their protein profiles to that of 94 subjects without diabetes. FINDINGS: Early stage type 2 diabetes was associated with distinct protein patterns, reflecting key metabolic syndrome features including insulin resistance, adiposity, hyperglycemia and liver steatosis. The protein profiles at baseline were attenuated during guideline-based diabetes treatment and several plasma proteins associated with metformin medication independently of metabolic variables, such as circulating EPCAM. INTERPRETATION: The results advance our knowledge about the biochemical manifestations of type 2 diabetes and suggest that comprehensive protein profiling may serve as a useful tool for metabolic phenotyping and for elucidating the biological effects of diabetes treatments. FUNDING: This work was supported by the Swedish Heart and Lung Foundation, the Swedish Research Council, the Erling Persson Foundation, the Knut and Alice Wallenberg Foundation, and the Swedish state under the agreement between the Swedish government and the county councils (ALF-agreement).

The Gut Microbiota in Prediabetes and Diabetes: A Population-Based Cross-Sectional Study.

The link between the gut microbiota and type 2 diabetes (T2D) warrants further investigation because of known confounding effects from antidiabetic treatment. Here, we profiled the gut microbiota in a discovery (n = 1,011) and validation (n = 484) cohort comprising Swedish subjects naive for diabetes treatment and grouped by glycemic status. We observed that overall gut microbiota composition was altered in groups with impaired glucose tolerance, combined glucose intolerance and T2D, but not in those with impaired fasting glucose. In addition, the abundance of several butyrate producers and functional potential for butyrate production were decreased both in prediabetes and T2D groups. Multivariate analyses and machine learning microbiome models indicated that insulin resistance was strongly associated with microbial variations. Therefore, our study indicates that the gut microbiota represents an important modifiable factor to consider when developing precision medicine approaches for the prevention and/or delay of T2D.

Galectin-1 is inversely associated with type 2 diabetes independently of obesity - A SCAPIS pilot study.

OBJECTIVES: Galectin-1 is a recently discovered adipokine that increases with obesity and increased energy intake in adipose tissue. Our aim was to assess whether serum galectin-1 is associated with type 2 diabetes (T2D) and other parameters of the metabolic syndrome independently of body mass index (BMI) in a cohort from the general population. METHODS: In this cross-sectional population-based cohort study from the western part of Sweden, we investigated associations between serum galectin-1, clinical characteristics and inflammatory markers in 989 women and men aged 50-65 years [part of the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot cohort]. RESULTS: We showed in linear models that serum galectin-1 was independently and: (1) inversely associated with T2D (p < 0.05) and glucose (p < 0.05); and (2) positively associated with age (p < 0.01), sex (p < 0.01), BMI (p < 0.01), insulin (p < 0.01) and C-reactive protein (p < 0.01). Furthermore, galectin-1 demonstrated univariate correlations with triglycerides (r = 0.20, p < 0.01), homeostasis model assessment for insulin resistance (r = 0.24, p < 0.01), tumor necrosis factor-α (r = 0.24, p < 0.01), interleukin-6 (IL-6; r = 0.20, p < 0.01) and HbA1c (r = 0.14, p < 0.01). CONCLUSION: In a cross-sectional study of a middle-aged population, we showed that serum galectin-1 is: (1) inversely associated with T2D independently of BMI; and (2) independently associated with other markers of the metabolic syndrome These results warrant prospective and functional studies on the role of galectin-1 in T2D.

Toll-like receptor-mediated inflammation markers are strongly induced in heart tissue in patients with cardiac disease under both ischemic and non-ischemic conditions.

BACKGROUND: A sustained low grade inflammatory state is a recognized feature of various diseases, including cardiovascular disease. This state of chronic inflammation involves activation of Toll-like receptor (TLR) signaling. However, little is known regarding the genetic profile of TLR components in cardiac tissue from patients with cardiac disease. METHODS: In this study we investigated the genetic profile of 84 TLR markers in a unique set of cardiac tissue from patients that had undergone either coronary artery bypass grafting (CABG) or aortic valve replacement (AVR). In addition, we compared the gene data from the cardiac tissue with the same gene profile in blood as well as circulating cytokines to elucidate possible targets in blood that could be used to estimate the inflammatory state of the heart in cardiac disease. RESULTS: We found a marked upregulation of TLR-induced inflammation in cardiac tissue from both patient groups compared to healthy controls. The inflammation appeared to be primarily mediated through TLR1, 3, 7, 8 and 10, resulting in a marked induction of mediators of the innate immune response. Furthermore, the gene expression data in combination with unbiased multivariate analysis suggested a difference in inflammatory response in ischemic cardiac tissue compared to non-ischemic cardiac tissue. Serum levels of IL-13 were significantly elevated in both CABG and AVR patients compared to controls, whereas other cytokines did not appear to coincide with cardiac TLR-induced inflammation. CONCLUSIONS: We propose that cardiac disease in humans may be mediated by local cardiac TLR signaling under both ischemic and non-ischemic conditions.

Hypoxic cardiac fibroblasts from failing human hearts decrease cardiomyocyte beating frequency in an ALOX15 dependent manner.

A common denominator for patients with heart failure is the correlation between elevated serum levels of proinflammatory cytokines and adverse clinical outcomes. Furthermore, lipoxygenase-induced inflammation is reportedly involved in the pathology of heart failure. Cardiac fibroblasts, which are abundant in cardiac tissue, are known to be activated by inflammation. We previously showed high expression of the lipoxygenase arachidonate 15 lipoxygenase (ALOX15), which catalyzes the conversion of arachidonic acid to 15-hydroxy eicosatetraenoic acid (15-HETE), in ischemic cardiac tissue. The exact roles of ALOX15 and 15-HETE in the pathogenesis of heart failure are however unknown. Biopsies were collected from all chambers of explanted failing human hearts from heart transplantation patients, as well as from the left ventricles from organ donors not suffering from chronic heart failure. Biopsies from the left ventricles underwent quantitative immunohistochemical analysis for ALOX15/B. Gene expression of ALOX enzymes, as well as 15-HETE levels, were examined in cardiac fibroblasts which had been cultured in either hypoxic or normoxic conditions after isolation from failing hearts. After the addition of fibroblast supernatants to human induced pluripotent stem cell-derived cardiomyocytes, intracellular calcium concentrations were measured to examine the effect of paracrine signaling on cardiomyocyte beating frequency. While ALOX15 and ALOX15B were expressed throughout failing hearts as well as in hearts from organ donors, ALOX15 was expressed at significantly higher levels in donor hearts. Hypoxia resulted in a significant increase in gene and protein expression of ALOX15 and ALOX15B in fibroblasts isolated from the different chambers of failing hearts. Finally, preconditioned medium from hypoxic fibroblasts decreased the beating frequency of human cardiomyocytes derived from induced pluripotent stem cells in an ALOX15-dependent manner. In summary, our results demonstrate that ALOX15/B signaling by hypoxic cardiac fibroblasts may play an important role in ischemic cardiomyopathy, by decreasing cardiomyocyte beating frequency.

Inflammatory activation of human cardiac fibroblasts leads to altered calcium signaling, decreased connexin 43 expression and increased glutamate secretion.

Cardiac fibroblasts, which are abundant in heart tissue, are involved not only in extracellular matrix homeostasis and repair, but also in cardiac remodeling after a myocardial infarction that, in turn, can lead to loss of cardiac function and heart failure. Ca2+ signaling is functionally important in many cell types, but the roles of fibroblast signaling and inflammation in the pathogenesis of heart disease are unclear. Here, we tested the hypothesis that inflammatory activation affects cardiac fibroblasts, both in terms of Ca2+ signaling and their capacity for intercellular communication through the gap junction channel protein connexin 43 (Cx43). We examined Ca2+ responses induced by known modulators of cardiac function such as glutamate, ATP and 5-hydroxytryptamine (5-HT) in human cardiac fibroblasts, under normal and inflammatory conditions. We showed that activation of human cardiac fibroblasts by lipopolysaccharide (LPS) for 24 h altered Ca2+ signaling, increased TLR4 and decreased Cx43 expression. In the fibroblasts, LPS treatment increased glutamate-evoked and decreased 5-HT-evoked Ca2+ signals. LPS activation also induced increased secretion of glutamate and proinflammatory cytokines from these cells. In summary, we propose that inflammatory stimuli can affect intracellular Ca2+ release, Cx43 expression, glutamate release and cytokine secretion in human cardiac fibroblasts. Inflammatory conditions may, therefore, impair intercellular network communication between fibroblasts and cardiomyocytes potentially contributing to cardiac dysfunction.

Deficiency in perilipin 5 reduces mitochondrial function and membrane depolarization in mouse hearts.

Myocardial triglycerides stored in lipid droplets are important in regulating the intracellular delivery of fatty acids for energy generation in mitochondria, for membrane biosynthesis, and as agonists for intracellular signaling. Previously, we showed that deficiency in the lipid droplet protein perilipin 5 (Plin5) markedly reduces triglyceride storage in cardiomyocytes and increases the flux of fatty acids into phospholipids. Here, we investigated whether Plin5 deficiency in cardiomyocytes alters mitochondrial function. We found that Plin5 deficiency reduced mitochondrial oxidative capacity. Furthermore, in mitochondria from Plin5-/- hearts, the fatty acyl composition of phospholipids in mitochondrial membranes was altered and mitochondrial membrane depolarization was markedly compromised. These findings suggest that mitochondria isolated from hearts deficient in Plin5, have specific functional defects.

The Arachidonate 15-Lipoxygenase Enzyme Product 15-HETE Is Present in Heart Tissue from Patients with Ischemic Heart Disease and Enhances Clot Formation.

Ischemic heart disease is a major cause of death and morbidity and the search for novel therapeutic targets is still required. We have previously shown that the enzyme arachidonate 15 lipoxygenase (ALOX15), which catalyzes the conversion of arachidonic acid to 15-hydroxy eicosatetraenoic acid (15-HETE), is highly expressed in ischemic heart tissue, but its role in the pathogenesis of ischemic heart disease is unclear. Here we showed that expression of ALOX15, but not ALOX12 or ALOX15B, was increased in ischemic versus non-ischemic human heart biopsy samples. A similar ALOX expression pattern was found in hypoxic human cardiomyocytes and cardiac endothelial cells. We also showed that levels of 15-HETE were significantly higher in ischemic versus non-ischemic human heart biopsy samples and showed a tendency to increase in serum from the patients with ischemic heart disease. Moreover, hypoxia increased the production of 15-HETE levels from human cardiomyocytes and cardiac endothelial cells. The hypoxia-induced increase in 15-HETE levels from human cardiomyocytes was inhibited by the ALOX15 inhibitor baicalein. Finally, by using intrinsic rotational thromboelastometry, we showed that human whole blood clotted faster in the presence of 15-HETE. In summary, we propose that increased ALOX15 expression in heart tissue under ischemic conditions may lead to increased production of 15-HETE, potentially contributing to thrombosis.

Perilipin 5 is protective in the ischemic heart.

BACKGROUND: Myocardial ischemia is associated with alterations in cardiac metabolism, resulting in decreased fatty acid oxidation and increased lipid accumulation. Here we investigate how myocardial lipid content and dynamics affect the function of the ischemic heart, and focus on the role of the lipid droplet protein perilipin 5 (Plin5) in the pathophysiology of myocardial ischemia. METHODS AND RESULTS: We generated Plin5(-/-) mice and found that Plin5 deficiency dramatically reduced the triglyceride content in the heart. Under normal conditions, Plin5(-/-) mice maintained a close to normal heart function by decreasing fatty acid uptake and increasing glucose uptake, thus preserving the energy balance. However, during stress or myocardial ischemia, Plin5 deficiency resulted in myocardial reduced substrate availability, severely reduced heart function and increased mortality. Importantly, analysis of a human cohort with suspected coronary artery disease showed that a common noncoding polymorphism, rs884164, decreases the cardiac expression of PLIN5 and is associated with reduced heart function following myocardial ischemia, indicating a role for Plin5 in cardiac dysfunction. CONCLUSION: Our findings indicate that Plin5 deficiency alters cardiac lipid metabolism and associates with reduced survival following myocardial ischemia, suggesting that Plin5 plays a beneficial role in the heart following ischemia.