Novel Interactomes of Cardiac Noncoding RNA Transcriptome under Altered Thyroid Hormonal States
Authors: Chakraborty Sankalpa , Rajagopalan Viswanathan , Lin Richard 
Published: May 2023

Background: Noncoding RNAs are emerging as key players in cardiovascular diseases. Both Hypothyroidism (HypoTH; low thyroid hormones [THs]) and hyperthyroidism (HyperTH; high THs) can be deleterious to the heart. We recently showed the involvement of long noncoding RNAs (lncRNAs) in HypoTH under caloric restriction. However, a comprehensive view of the cardiac transcriptome and its interactions under altered TH states is lacking. We hypothesized that cardiac noncoding interaction networks are significantly altered in the cardiac-TH regulatory axis. Methods: In this randomized, blinded study (2.5 mon), adult C57 mixed-sex mice (n=8-10/group; 5 females, 3-5 males) were divided into Control, HypoTH (low iodine diet with oral methimazole), HyperTH (1 microgram [ug]/gram Thyroxine, T4; intraperitoneal) and HypoTH+T3 (similar to HypoTH with oral 12 ug/kilogram/day Triiodothyronine, T3). Morphometrics, ultrasound, immunosorbent assay, Quantitative real-time PCR (qPCR) and whole transcriptome sequencing were performed. Statistical analyses were done by Tukey’s analysis of variance (with post hoc), Benjamini & Hochberg and others using Prism, R, etc. RNA quality was validated by Nanodrop, gel electrophoresis and Bioanalyzer. Results: In mixed-sex mice, HypoTH showed significant cardiac atrophy (whole heart, LV and right ventricle), low serum total T3 and T4 levels (p<0.001), low heart rate, (p<0.01) diminished systolic LV posterior (p<0.05) and septal wall thicknesses (p<0.01) and fractional shortening (-34%; p<0.01) compared to controls. T3 therapy showed feedback inhibition of T4 (p<0.001) and restored all other parameters including LV systolic diameter (p<0.05). Among others, HyperTH had cardiac hypertrophy and increased T3 and T4 (p<0.05) compared to controls (p<0.001). Similar significant results were obtained in males and females. qPCR of shorter-term treatment showed significantly altered lncRNAs in inflammatory and immune pathways. Whole transcriptome sequencing showed numerous differentially expressed, significantly altered and enriched ( GO and KEGG) targets across the groups among all RNA species studied (p-adjusted; padj<0.05). These include novel and known lncRNAs, microRNAs (miRNAs) and messenger (m) RNAs that change in opposite directions in low vs high TH groups. These also include 11 novel circular RNAs (circRNAs; CIRI2) decreased with HyperTH (padj<0.05). We also uncovered novel co-expression and interactions of miRNA-mRNA, miRNA-lncRNA, mRNA-lncRNA, circRNA-miRNA and miRNA-lncRNA-mRNA (including TH receptor alpha; miRanda, Cytoscape) and also splicing and base editing events (padj<0.05). Conclusions: This is the first cross-disciplinary study reporting a comprehensive cardiac transcriptome-wide interactome network of circRNA, lncRNA, miRNA and mRNA in a TH-responsive manner. This offers significant translational potential to develop diadiagnostic and therapeutic targets for cardiac-endocrine co-morbid conditions. NYITCOM at A-State, ABI This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.