Human Epicardial Fat Expresses Glucagon-Like Peptide 1 and 2 Receptors Genes

Abstract

Epicardial adipose tissue (EAT) is an easily measurable visceral fat of the heart with unique anatomy, functionality, and transcriptome. EAT can serve as a therapeutic target for pharmaceutical agents targeting the fat. Glucagon-like peptide-1 (GLP-1) and GLP-2 analogues are newer drugs showing beneficial cardiovascular and metabolic effects. Whether EAT expresses GLP- 1 and 2 receptors (GLP-1R and GLP-2R) is unknown. RNA-seq analysis and quantitative real-time polymerase chain reaction (qRT-PCR) were performed to evaluate the presence of GLP-1R and GLP-2R in EAT and subcutaneous fat (SAT) obtained from 8 subjects with coronary artery disease and type 2 diabetes mellitus undergoing elective cardiac surgery. Immunofluorescence was also performed on EAT and SAT samples using Mab3f52 against GLP-1R. Our RNA-sequencing (RNA-seq) analysis showed that EAT expresses both GLP-1R and GLP-2R genes. qRT-PCR analysis confirmed that GLP-1R expression was low but detected by 2 different sets of intron-spanning primers. GLP-2R expression was detected in all patients and was found to be 5-fold higher than GLP-1R. The combination of accurately spliced reads from RNA-seq and successful amplification using intron-spanning primers indicates that both GLP-1R and GLP-2R are expressed in EAT. Immunofluorescence clearly showed that GLP-1R is present and more abundant in EAT than SAT. This is the first time that human EAT is found to express both GLP-1R and GLP-2R genes. Pharmacologically targeting EAT may induce beneficial cardiovascular and metabolic effects.

• References

• 1 Iacobellis G. Local and Systemic effects of the multifaceted Epicardial Adipose Tissue Depot. Nat Rev Endocrinol 2015; 11: 363-371
• 2 McAninch EA, Fonseca TL, Poggioli R, Panos AL, Salerno TA, Deng Y, Li Y, Bianco AC, Iacobellis G. Epicardial adipose tissue has a unique transcriptome that is downregulated in severe coronary artery disease. Obesity 2015; 23: 1267-1278
• 3 Iacobellis G, di Gioia CR, Di Vito M, Petramala L, Cotesta D, De Santis V, Vitale D, Tritapepe L, Letizia C. Epicardial adipose tissue and intracoronary adrenomedullin levels in coronary artery disease. Horm Metab Res 2009; 41: 855-860
• 4 Iacobellis G. Epicardial fat: a new cardiovascular therapeutic target. Curr Opin Pharmacol 2016; 27: 13-18
• 5 Marso SP, Daniels GH, Brown-Frandsen K, Kristensen P, Mann JF, Nauck MA, Nissen SE, Pocock S, Poulter NR, Ravn LS, Steinberg WM, Stockner M, Zinman B, Bergenstal RM, Buse JB. LEADER steering committee; leader trial investigators . liraglutide and cardiovascular outcomes in type 2 diabetes. N Engl J Med 2016; 375: 311-322
• 6 Morano S, Romagnoli E, Filardi T, Nieddu L, Mandosi E, Fallarino M, Turinese I, Dagostino MP, Lenzi A, Carnevale V. Short-term effects of glucagon-like peptide 1 (GLP-1) receptor agonists on fat distribution in patients with type 2 diabetes mellitus: an ultrasonography study. Acta Diabetol 2015; 52: 727-732
• 7 Iacobellis G, Mohseni M, Bianco SD, Banga PK. Liraglutide causes large and rapid epicardial fat reduction. Obesity (Silver Spring) 2017; 25: 311-316
• 8 Vendrell J, El Bekay R, Peral B, García-Fuentes E, Megia A, Macias-Gonzalez M, Fernández Real J, Jimenez-Gomez Y, Escoté X, Pachón G, Simó R, Selva DM, Malagón MM, Tinahones FJ. Study of the potential association of adipose tissue GLP-1 receptor with obesity and insulin resistance. Endocrinology 2011; 152: 4072-4079
• 9 Amato A, Baldassano S, Mulè F. GLP2: an underestimated signal for improving glycaemic control and insulin sensitivity. J Endocrinol 2016; 229: R57-R66
• 10 Cirera S. Highly efficient method for isolation of total RNA from adipose tissue. BMC Res Notes 2013; 6: 472
• 11 Dobin A, Davis CA, Schlesinger F, Drenkow J, Zaleski C, Jha S, Batut P, Chaisson M, Gingeras TR. STAR: ultrafast universal RNA-seq aligner. Bioinformatics 2013; 29: 15-21
• 12 Gubern C, Hurtado O, Rodríguez R, Morales JR, Romera VG, Moro MA, Lizasoain I, Serena J, Mallolas J. Validation of housekeeping genes for quantitative real-time PCR in in-vivo and in-vitro models of cerebral ischaemia. BMC Mol Biol 2009; 10: 57
• 13 Pyke C, Knudsen LB. The Glucagon-Like Peptide-1 Receptor – or Not?. Endocrinology 2013; 154: 4-8
• 14 Pyke C, Heller RS, Kirk RK, Ørskov C, Reedtz-Runge S, Kaastrup P, Hvelplund A, Bardram L, Calatayud D, Knudsen LB. GLP-1 receptor localization in monkey and human tissue: novel distribution revealed with extensively validated monoclonal antibody. Endocrinology 2014; 155: 1280-1290
• 15 Iacobellis G, Zaki MC, Garcia D, Willens HJ. Epicardial fat in atrial fibrillation and heart failure. Horm Metab Res 2014; 46: 587-589
• 16 Iacobellis G, Ribaudo MC, Assael F, Vecci E, Tiberti C, Zappaterreno A, Di Mario U, Leonetti F. Echocardiographic epicardial adipose tissue is related to anthropometric and clinical parameters of metabolic syndrome: a new indicator of cardiovascular risk. J Clin Endocrinol Metab 2003; 88: 5163-5168
• 17 Grosso AF, de Oliveira SF, Higuchi Mde L, Favarato D, Dallan LA, da Luz PL. Synergistic anti-inflammatory effect: simvastatin and pioglitazone reduce inflammatory markers of plasma and epicardial adipose tissue of coronary patients with metabolic syndrome. Diabetol Metab Syndr 2014; 6: 47
• 18 Lima-Martínez MM, Paoli M, Rodney M, Balladares N, Contreras M, D’Marco L, Iacobellis G. Effect of sitagliptin on epicardial fat thickness in subjects with type 2 diabetes and obesity: a pilot study. Endocrine 2016; 51: 448-455
• 19 Elisha B, Azar M, Taleb N, Bernard S, Iacobellis G, Rabasa-Lhoret R. Body composition and epicardial fat in type 2 diabetes patients following insulin detemir versus insulin glargine initiation. Horm Metab Res 2016; 48: 42-47
• 20 Mazurek T, Zhang L, Zalewski A, Mannion JD, Diehl JT, Arafat H. Human epicardial adipose tissue is a source of inflammatory mediators. Circulation 2003; 108: 2460-2466
• 21 Yang J, Ren J, Song J, Liu F, Wu C, Wang X, Gong L, Li W, Xiao F, Yan F, Hou X, Chen L. Glucagon-like peptide 1 regulates adipogenesis in 3T3-L1 preadipocytes. Int J Mol Med 2013; 31: 1429-1435
• 22 Beiroa D, Imbernon M, Gallego R, Senra A, Herranz D, Villarroya F, Serrano M, Fernø J, Salvador J, Escalada J, Dieguez C, Lopez M, Frühbeck G, Nogueiras R. GLP-1 agonism stimulates brown adipose tissue thermogenesis and browning through hypothalamic AMPK. Diabetes 2014; 63: 3346-3358
• 23 Sacks HS, Fain JN, Holman B, Cheema P, Chary A, Parks F. Uncoupling protein-1 and related mrnas in human epicardial and other adipose tissues: epicardial fat functioning as brown fat. J Clin Endocrinol Metab 2009; 94: 3611-3615
• 24 Baldassano S, Rappa F, Amato A, Cappello F, Mulè F. GLP-2 as beneficial factor in the glucose homeostasis in mice fed a high fat diet. J Cell Physiol 2015; 230: 3029-3036