Sandra Feijóo-Bandín

Des-Acyl Ghrelin Has Specific Binding Sites and Different Metabolic Effects from Ghrelin in Cardiomyocytes

The current study aimed to compare the effects of the peptide hormone ghrelin and des-G, its unacylated isoform, on glucose and fatty acid uptake and to identify des-G-specific binding sites in cardiomyocytes. In the murine HL-1 adult cardiomyocyte line, ghrelin and des-G had opposing metabolic effects: des-G increased medium-chain fatty acid uptake (BODIPY fluorescence intensity), whereas neither ghrelin alone nor in combination with des-G did so. Ghrelin inhibited the increase in glucose uptake normally induced by insulin (rate of 2-[(3)H]deoxy-d-glucose incorporation), but des-G did not; des-G was also able to partially reverse the inhibitory effect of ghrelin. In HL-1 cells and primary cultures of neonatal rat cardiomyocytes, des-G but not ghrelin increased insulin-induced translocation of glucose transporter-4 from nuclear to cytoplasmic compartments (immunohistochemistry and quantitative confocal analysis). AKT was phosphorylated by insulin but not affected by ghrelin or des-G, whereas neither AMP-activated protein kinase nor phosphatase and tensin homolog deleted from chromosome 10 was phosphorylated by any treatments. HL-1 and primary-cultured mouse and rat cardiomyocytes each possessed two independent specific binding sites for des-G not recognized by ghrelin (radioreceptor assays). Neither ghrelin nor des-G affected viability (dimethylthiazol diphenyltetrazolium bromide assays), whereas both isoforms were equally protective against apoptosis. Therefore, in cardiomyocytes, des-G binds to specific receptors and has effects on glucose and medium-chain fatty acid uptake that are distinct from those of ghrelin. Real-time PCR indicated that expression levels of ghrelin O-acyltransferase RNA were comparable between HL-1 cells, human myocardial tissue, and human and murine stomach tissue, indicating the possibility of des-G conversion to ghrelin within our model.

Nesfatin-1 in human and murine cardiomyocytes: synthesis, secretion, and mobilization of GLUT-4.

Nesfatin-1, a satiety-inducing peptide identified in hypothalamic regions that regulate energy balance, is an integral regulator of energy homeostasis and a putative glucose-dependent insulin coadjuvant. We investigated its production by human cardiomyocytes and its effects on glucose uptake, in the main cardiac glucose transporter GLUT-4 and in intracellular signaling. Quantitative RT-PCR, Western blots, confocal immunofluorescence microscopy, and ELISA of human and murine cardiomyocytes and/or cardiac tissue showed that cardiomyocytes can synthesize and secrete nesfatin-1. Confocal microscopy of cultured cardiomyocytes after GLUT-4 labeling showed that nesfatin-1 mobilizes this glucose transporter to cell peripherals. The rate of 2-deoxy-D-[(3)H]glucose incorporation demonstrated that nesfatin-1 induces glucose uptake by HL-1 cells and cultured cardiomyocytes. Nesfatin-1 induced dose- and time-dependent increases in the phosphorylation of ERK1/2, AKT, and AS160. In murine and human cardiac tissue, nesfatin-1 levels varied with diet and coronary health. In conclusion, human and murine cardiomyocytes can synthesize and secrete nesfatin-1, which is able to induce glucose uptake and the mobilization of the glucose transporter GLUT-4 in these cells. Nesfatin-1 cardiac levels are regulated by diet and coronary health.

Increased expression of fatty-acid and calcium metabolism genes in failing human heart.

Background Heart failure (HF) involves alterations in metabolism, but little is known about cardiomyopathy-(CM)-specific or diabetes-independent alterations in gene expression of proteins involved in fatty-acid (FA) uptake and oxidation or in calcium-(Ca2+)-handling in the human heart. Methods RT-qPCR was used to quantify mRNA expression and immunoblotting to confirm protein expression in left-ventricular myocardium from patients with HF (n = 36) without diabetes mellitus of ischaemic (ICM, n = 16) or dilated (DCM, n = 20) cardiomyopathy aetiology, and non-diseased donors (CTL, n = 6). Results Significant increases in mRNA of genes regulating FA uptake (CD36) and intracellular transport (Heart-FA-Binding Protein (HFABP)) were observed in HF patients vs CTL. Significance was maintained in DCM and confirmed at protein level, but not in ICM. mRNA was higher in DCM than ICM for peroxisome-proliferator-activated-receptor-alpha (PPARA), PPAR-gamma coactivator-1-alpha (PGC1A) and CD36, and confirmed at the protein level for PPARA and CD36. Transcript and protein expression of Ca2+-handling genes (Two-Pore-Channel 1 (TPCN1), Two-Pore-Channel 2 (TPCN2), and Inositol 1,4,5-triphosphate Receptor type-1 (IP3R1)) increased in HF patients relative to CTL. Increases remained significant for TPCN2 in all groups but for TPCN1 only in DCM. There were correlations between FA metabolism and Ca2+-handling genes expression. In ICM there were six correlations, all distinct from those found in CTL. In DCM there were also six (all also different from those found in CTL): three were common to and three distinct from ICM. Conclusion DCM-specific increases were found in expression of several genes that regulate FA metabolism, which might help in the design of aetiology-specific metabolic therapies in HF. Ca2+-handling genes TPCN1 and TPCN2 also showed increased expression in HF, while HF- and CM-specific positive correlations were found among several FA and Ca2+-handling genes.

Endolysosomal two‐pore channels regulate autophagy in cardiomyocytes

Two‐pore channels (TPCs) were identified as a novel family of endolysosome‐targeted calcium release channels gated by nicotinic acid adenine dinucleotide phosphate, as also as intracellular Na+ channels able to control endolysosomal fusion, a key process in autophagic flux. Autophagy, an evolutionarily ancient response to cellular stress, has been implicated in the pathogenesis of a wide range of cardiovascular pathologies, including heart failure. We report direct evidence indicating that TPCs are involved in regulating autophagy in cardiomyocytes, and that TPC knockout mice show alterations in the cardiac lysosomal system. TPC downregulation implies a decrease in the viability of cardiomyocytes under starvation conditions. In cardiac tissues from both humans and rats, TPC transcripts and protein levels were higher in females than in males, and correlated negatively with markers of autophagy. We conclude that the endolysosomal channels TPC1 and TPC2 are essential for appropriate basal and induced autophagic flux in cardiomyocytes, and also that they are differentially expressed in male and female hearts.

The Adipokine Chemerin Induces Apoptosis in Cardiomyocytes

Background: The adipokine chemerin has been associated with cardiovascular disease. We investigated the effects of chemerin on viability and intracellular signalling in murine cardiomyocytes, and the effects of insulin and TNF-α on cardiomyocyte chemerin production. Methods: Hoechst dye vital staining and cell cycle analysis were used to analyse the viability of murine cardiac cells in culture. Western blot was used to explore the phosphorylation of AKT and caspase-9 activity in neonatal rat cardiomyocytes and HL-1 cells. Finally, RT-qPCR, ELISA and western blot were performed to examine chemerin and CMKLR1 expression after insulin and TNF-α treatment in cardiac cells. Results: Chemerin treatment increased apoptosis, reduced phosphorylation of AKT at Thr308 and increased caspase-9 activity in murine cardiomyocytes. Insulin treatment lowered chemerin and CMKLR1 mRNA and protein levels, and the amount of chemerin in the cell media, while TNF-α treatment increased chemerin mRNA and protein levels but decreased expression of the CMKLR1 gene. Conclusion: Chemerin induces apoptosis, reduces AKT phosphorylation and increases the cleavage of caspase-9 in murine cardiomyocytes. The expression of chemerin is regulated by important metabolic (insulin) and inflammatory (TNF-α) mediators at cardiac level. Our results suggest that chemerin could play a role in the physiopathology of cardiac diseases.

20 years of leptin: Role of leptin in cardiomyocyte physiology and physiopathology.

Since the discovery of leptin in 1994 by Zhang et al., there have been a number of reports showing its implication in the development of a wide range of cardiovascular diseases. However, there exists some controversy about how leptin can induce or preserve cardiovascular function, as different authors have found contradictory results about leptin beneficial or detrimental effects in leptin deficient/resistant murine models and in wild type tissue and cardiomyocytes. Here, we will focus on the main discoveries about the leptin functions at cardiac level within the last two decades, focusing on its role in cardiac metabolism, remodeling and contractile function.

24 h nesfatin-1 treatment promotes apoptosis in cardiomyocytes.

The appetite-regulating neuropeptide nesfatin-1 can influence cardiovascular function: in vivo analyses have shown that in rats it regulates blood pressure [1] and heart rate [2], and is cardioprotective against lesions from ischemia/reperfusion (I/ R) [3]. It has been suggested that it may also regulate cell viability, but the evidence is contradictory [4–6]. We previously found that a short nesfatin-1 treatment regulates cardiomyocyte metabolism without affecting cell viability [7]. We have now investigated the effect of longer (24 h) nesfatin1 treatment on the survival of culturedmurine cardiomyocytes.

Two-pore channels (TPCs): Novel voltage-gated ion channels with pleiotropic functions.

ABSTRACT Two-pore channels (TPC1-3) comprise a subfamily of the eukaryotic voltage-gated ion channels (VGICs) superfamily that are mainly expressed in acidic stores in plants and animals. TPCS are widespread across the animal kingdom, with primates, mice and rats lacking TPC3, and mainly act as Ca+ and Na+ channels, although it was also suggested that they could be permeable to other ions. Nowadays, TPCs have been related to the development of different diseases, including Parkinson´s disease, obesity or myocardial ischemia. Due to this, their study has raised the interest of the scientific community to try to understand their mechanism of action in order to be able to develop an efficient drug that could regulate TPCs activity. In this review, we will provide an updated view regarding TPCs structure, function and activation, as well as their role in different pathophysiological processes.

Aliskiren affects fatty-acid uptake and lipid-related genes in rodent and human cardiomyocytes.

PURPOSE We investigated whether the direct renin inhibitor aliskiren can affect metabolism in cardiomyocytes from rat, mouse and human sources. METHODS AND RESULTS At 10-50 μmol/L, aliskiren significantly increased medium-chain-fatty-acid uptake in primary-cultured neonatal-rat and HL-1 adult-mouse-derived cardiomyocytes (BODIPY-induced fluorescence intensity). The fatty-acid transporter CD-36 was correspondingly translocated to, but the glucose transporter Glut-4 away from, the sarcoplasmic reticulum/plasma membrane, in primary-cultured neonatal-rat (CD-36, Glut-4) and adult-human (CD-36) cardiomyocytes (confocal immunocytochemistry). Immunoblotting showed that aliskiren induced phosphorylation of ERK1/2 in cardiomyocytes from all three sources; responses were dose- and time-dependent, unaffected by renin treatment, and did not cause alterations in expression of (P)R or Igf2/M6P receptors. Microarray analysis of the complete genome of aliskiren-treated neonatal-rat cardiomyocytes, with RT-qPCR and immunoblot confirmation assays in rat and human primary cardiomyocytes, showed that aliskiren up-regulated mRNA and increased protein expression of several enzymes important in lipid and glucose metabolism and in cholesterol biosynthesis. Cardiomyocyte cell-cycle and viability were unaffected by aliskiren. CONCLUSIONS Aliskiren can induce changes in fatty-acid and glucose uptake and expression of key enzymes of lipid and cholesterol metabolism, which are not associated with increased expression of (P)R or Igf2/M6P receptors, in cultured cardiomyocytes.

Relaxin-2 in Cardiometabolic Diseases: Mechanisms of Action and Future Perspectives

Despite the great effort of the medical community during the last decades, cardiovascular diseases remain the leading cause of death worldwide, increasing their prevalence every year mainly due to our new way of life. In the last years, the study of new hormones implicated in the regulation of energy metabolism and inflammation has raised a great interest among the scientific community regarding their implications in the development of cardiometabolic diseases. In this review, we will summarize the main actions of relaxin, a pleiotropic hormone that was previously suggested to improve acute heart failure and that participates in both metabolism and inflammation regulation at cardiovascular level, and will discuss its potential as future therapeutic target to prevent/reduce cardiovascular diseases.