{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nAlthough the query mentions MIR4303, the provided abstracts do not contain any reference to this microRNA. Instead, they focus on elucidating the functions of multiple stearoyl‐CoA desaturase (SCD) isoforms in lipid metabolism and cardiac physiology. Recent work has identified a novel heart‐specific SCD isoform—SCD4—which is distinct from the previously described SCD1, SCD2, and SCD3 enzymes. In leptin-deficient ob/ob mice, SCD4 mRNA levels are markedly elevated, and its expression is modulated by leptin administration, LXRα agonists, and specific dietary inputs, underscoring unique regulatory mechanisms that differentiate it from other SCD isoforms."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nFunctional studies further reveal that the various SCD isoforms display distinct substrate specificities. In particular, SCD1, SCD2, and SCD4 catalyze the desaturation of both stearoyl‐CoA (C18:0) and palmitoyl‐CoA (C16:0) fatty acids, whereas SCD3 exhibits specificity for palmitoyl-CoA only. These findings highlight the specialized roles these enzymes play in fatty acid metabolism."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn addition to their roles in fatty acid desaturation, SCD isoforms contribute significantly to cardiac repair mechanisms following myocardial infarction. Evidence demonstrates that SCD activity—encompassing the actions of the predominant SCD1 isoform and the heart-specific SCD4—is critical for stimulating angiogenesis in the hypoxic myocardium. This occurs through the regulation of proangiogenic factors and cytokines, as well as by modulating key metabolic signaling pathways such as those governed by AMPK, AKT, and PGC1α, thereby meeting the energy demands of the recovering heart."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Makoto Miyazaki, Mark J Jacobson, Weng Chi Man, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Identification and characterization of murine SCD4, a novel heart-specific stearoyl-CoA desaturase isoform regulated by leptin and dietary factors."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Biol Chem (2003)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1074/jbc.M304724200"}], "href": "https://doi.org/10.1074/jbc.M304724200"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "12815040"}], "href": "https://pubmed.ncbi.nlm.nih.gov/12815040"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Makoto Miyazaki, Sean M Bruggink, James M Ntambi "}, {"type": "b", "children": [{"type": "t", "text": "Identification of mouse palmitoyl-coenzyme A Delta9-desaturase."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Lipid Res (2006)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1194/jlr.C500025-JLR200"}], "href": "https://doi.org/10.1194/jlr.C500025-JLR200"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "16443825"}], "href": "https://pubmed.ncbi.nlm.nih.gov/16443825"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Ana-Maria Gan, Zuzanna Tracz-Gaszewska, Aleksandra Ellert-Miklaszewska, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Stearoyl-CoA Desaturase Regulates Angiogenesis and Energy Metabolism in Ischemic Cardiomyocytes."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Int J Mol Sci (2022)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.3390/ijms231810459"}], "href": "https://doi.org/10.3390/ijms231810459"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "36142371"}], "href": "https://pubmed.ncbi.nlm.nih.gov/36142371"}]}]}]}