PRMT1 Deficiency in Mouse Juvenile Heart Induces Dilated Cardiomyopathy and Reveals Cryptic Alternative Splicing Products

Protein arginine methyltransferase 1 (PRMT1) catalyzes the asymmetric dimethylation of arginine residues in proteins and methylation of various RNA-binding proteins and is associated with alternative splicing in vitro. Although PRMT1 has essential in vivo roles in embryonic development, CNS development, and skeletal muscle regeneration, the functional importance of PRMT1 in the heart remains to be elucidated. Here, we report that juvenile cardiomyocyte-specific PRMT1-deficient mice develop severe dilated cardiomyopathy and exhibit aberrant cardiac alternative splicing. Furthermore, we identified previously undefined cardiac alternative splicing isoforms of four genes (Asb2, Fbxo40, Nrap, and Eif4a2) in PRMT1-cKO mice and revealed that eIF4A2 protein isoforms translated from alternatively spliced mRNA were differentially ubiquitinated and degraded by the ubiquitin-proteasome system. These findings highlight the essential roles of PRMT1 in cardiac homeostasis and alternative splicing regulation

PRMT1 Deficiency in Mouse Juvenile Heart Induces Dilated Cardiomyopathy and Reveals Cryptic Alternative Splicing Products

Summary: Protein arginine methyltransferase 1 (PRMT1) catalyzes the asymmetric dimethylation of arginine residues in proteins and methylation of various RNA-binding proteins and is associated with alternative splicing in vitro. Although PRMT1 has essential in vivo roles in embryonic development, CNS development, and skeletal muscle regeneration, the functional importance of PRMT1 in the heart remains to be elucidated. Here, we report that juvenile cardiomyocyte-specific PRMT1-deficient mice develop severe dilated cardiomyopathy and exhibit aberrant cardiac alternative splicing. Furthermore, we identified previously undefined cardiac alternative splicing isoforms of four genes (Asb2, Fbxo40, Nrap, and Eif4a2) in PRMT1-cKO mice and revealed that eIF4A2 protein isoforms translated from alternatively spliced mRNA were differentially ubiquitinated and degraded by the ubiquitin-proteasome system. These findings highlight the essential roles of PRMT1 in cardiac homeostasis and alternative splicing regulation. : Genetics; Molecular Biology; Cell Biology; Developmental Biology Subject Areas: Genetics, Molecular Biology, Cell Biology, Developmental Biolog

Effects of supplementation with essential amino acids on intrahepatic lipid concentrations during fructose overfeeding in humans.

BACKGROUND: A high dietary protein intake has been shown to blunt the deposition of intrahepatic lipids in high-fat- and high-carbohydrate-fed rodents and humans. OBJECTIVE: The aim of this study was to evaluate the effect of essential amino acid supplementation on the increase in hepatic fat content induced by a high-fructose diet in healthy subjects. DESIGN: Nine healthy male volunteers were studied on 3 occasions in a randomized, crossover design after 6 d of dietary intervention. Dietary conditions consisted of a weight-maintenance balanced diet (control) or the same balanced diet supplemented with 3 g fructose · kg(-1) · d(-1) and 6.77 g of a mixture of 5 essential amino acids 3 times/d (leucine, isoleucine, valine, lysine, and threonine) (HFrAA) or with 3 g fructose · kg(-1) · d(-1) and a maltodextrin placebo 3 times/d (HFr); there was a washout period of 4 to 10 wk between each condition. For each condition, the intrahepatocellular lipid (IHCL) concentration, VLDL-triglyceride concentration, and VLDL-[(13)C]palmitate production were measured after oral loading with [(13)C]fructose. RESULTS: HFr increased the IHCL content (1.27 ± 0.31 compared with 2.74 ± 0.55 vol %; P < 0.05) and VLDL-triglyceride (0.55 ± 0.06 compared with 1.40 ± 0.15 mmol/L; P < 0.05). HFr also enhanced VLDL-[(13)C]palmitate production. HFrAA significantly decreased IHCL compared with HFr (to 2.30 ± 0.43 vol%; P < 0.05) but did not change VLDL-triglyceride concentrations or VLDL-[(13)C]palmitate production. CONCLUSIONS: Supplementation with essential amino acids blunts the fructose-induced increase in IHCL but not hypertriglyceridemia. This is not because of inhibition of VLDL-[(13)C]palmitate production. This trial was registered at www.clinicaltrials.gov as NCT01119989

Ketogenic essential amino acids modulate lipid synthetic pathways and hepatic steatosis in mice

Background Although dietary ketogenic essential amino acid (KAA) content modifies accumulation of hepatic lipids, the molecular interactions between KAAs and lipid metabolism are yet to be fully elucidated. Methodology/Principal Findings We designed a diet with a high ratio (E/N) of essential amino acids (EAAs) to non-EAAs by partially replacing dietary protein with 5 major free KAAs (Leu, Ile, Val, Lys and Thr) without altering carbohydrate and fat content. This high-KAA diet was assessed for its preventive effects on diet-induced hepatic steatosis and whole-animal insulin resistance. C57B6 mice were fed with a high-fat diet, and hyperinsulinemic ob/ob mice were fed with a high-fat or high-sucrose diet. The high-KAA diet improved hepatic steatosis with decreased de novo lipogensis (DNL) fluxes as well as reduced expressions of lipogenic genes. In C57B6 mice, the high-KAA diet lowered postprandial insulin secretion and improved glucose tolerance, in association with restored expression of muscle insulin signaling proteins repressed by the high-fat diet. Lipotoxic metabolites and their synthetic fluxes were also evaluated with reference to insulin resistance. The high-KAA diet lowered muscle and liver ceramides, both by reducing dietary lipid incorporation into muscular ceramides and preventing incorporation of DNL-derived fatty acids into hepatic ceramides. Conclusion Our results indicate that dietary KAA intake improves hepatic steatosis and insulin resistance by modulating lipid synthetic pathways.National Institutes of Health (U.S) (Bioengineering Research Partnership Grant DK58533)National Institutes of Health (U.S) (NIH Metabolomics Roadmap Initiative DK070291)National Institutes of Health (U.S) (DK072856