Background: Cardiac re-expression of fetal genes in patients with heart failure (HF) suggests the presence of low cardiac tissue thyroid hormone (TH) function. However, serum concentrations of T3 and T4 are often normal or subclinically low, necessitating an alternative serum biomarker for low cardiac TH function to guide treatment of these patients. The clinical literature suggests that serum Brain Natriuretic Peptide (BNP) levels are inversely associated with serum triiodo-L-thyronine (T3) levels. The objective of this study was to investigate BNP as a potential serum biomarker for TH function in the heart. Methods: Two animal models of thyroid hormone deficiency: (1) 8-weeks of propyl thiouracil-induced hypothyroidism (Hypo) in adult female rats were subsequently treated with oral T3 (10 µg/kg/d) for 3, 6, or 14 days; (2) HF induced by coronary artery ligation (myocardial infarction, MI) in adult female rats was treated daily with low dose oral T3 (5 µg/kg/d) for 8 or 16 wks. Results: Six days of T3 treatment of Hypo rats normalized most cardiac functional parameters. Serum levels of BNP increased 5-fold in Hypo rats, while T3 treatment normalized BNP by day 14, showing a significant inverse relationship between serum BNP and free or total T3 concentrations. Myocardial BNP mRNA was increased 2.5fold in Hypo rats and its expression was decreased to normal values by 14 days of T3 treatment. Measurements of hemodynamic function showed significant dysfunction in MI rats after 16 weeks, with serum BNP increased by 4.5-fold and serum free and total T3 decreased significantly. Treatment with T3 decreased serum BNP while increasing total T3 indicating an inverse correlation between these two biologic factors (r 2 = 0.676, p < 0.001). Myocardial BNP mRNA was increased 5-fold in MI rats which was significantly decreased by T3 over 8 to 16 week treatment periods. Conclusions: Results from the two models of TH dysfunction confirmed an inverse relationship between tissue and serum T3 and BNP, such that the reduction in serum BNP could potentially be utilized to monitor efficacy and dosing of T3 treatment. Thus, serum BNP may serve as a reliable biomarker for cardiac TH function.

Pre-clinical animal studies have shown that triiodothyronine (T3) replacement therapy improves cardiac contractile function after myocardial infarction (MI). We hypothesized that T3 treatment could prevent adverse post-infarction cardiomyocyte remodeling by maintaining transverse-tubule (TT) structures, thus improving calcium dynamics and contractility.MethodsMyocardial infarction (MI) or sham surgeries were performed on female Sprague-Dawley rats (aged 12 wks), followed by treatment with T3 (5μg/kg/d) or vehicle in drinking water for 16 wks (n = 10–11/group). After in vivo echocardiographic and hemodynamic analyses, left ventricular myocytes were isolated by collagenase digestion and simultaneous calcium and contractile transients in single cardiomyocytes were recorded using IonOptix imaging. Live cardiomyocytes were stained with AlexaFluor-488 conjugated wheat germ agglutinin (WGA-488) or di-8-ANEPPS, and multiple z-stack images per cell were captured by confocal microscopy for analysis of TT organization. RTqPCR and immunoblot approaches determined expression of TT proteins.ResultsEchocardiography and in vivo hemodynamic measurements showed significant improvements in systolic and diastolic function in T3- vs vehicle-treated MI rats. Isolated cardiomyocyte analysis showed significant dysfunction in measurements of myocyte relengthening in MI hearts, and improvements with T3 treatment: max relengthening velocity (Vmax, um/s), 2.984 ± 1.410 vs 1.593 ± 0.325, p < 0.05 and time to Vmax (sec), 0.233 ± 0.037 vs 0.314 ± 0.019, p < 0.001; MI + T3 vs MI + Veh, respectively. Time to peak contraction was shortened by T3 treatment (0.161 ± 0.021 vs 0.197 ± 0.011 s., p < 0.01; MI + T3 vs MI + Veh, respectively). Analysis of TT periodicity of WGA- or ANEPPS-stained cardiomyocytes indicated significant TT disorganization in MI myocytes and improvement with T3 treatment (transverse-oriented tubules (TE%): 9.07 ± 0.39 sham, 6.94 ± 0.67 MI + Veh and 8.99 ± 0.38 MI + T3; sham vs MI + Veh, p < 0.001; MI + Veh vs MI + T3, p < 0.01). Quantitative RT-PCR showed that reduced expression of BIN1 (Bridging integrator-1), Jph2 (junctophilin-2), RyR2 (ryanodine receptor) and Cav1.2 (L-type calcium channel) in the failing myocardium were increased by T3 and immunoblot analysis further supporting a potential T3 effect on the TT-associated proteins, BIN1 and Jph2.In conclusion, low dose T3 treatment initiated immediately after myocardial infarction attenuated adverse TT remodeling, improved calcium dynamics and contractility, thus supporting the potential therapeutic utility of T3 treatment in heart failure.

Subclinical hypothyroidism and low T3 syndrome are commonly associated with an increased risk of cardiovascular disease (CVD) and mortality. We examined effects of T3 on T-tubule (TT) structures, Ca 2+ mobilization and contractility, and clustering of dyadic proteins.Thyroid hormone (TH) deficiency was induced in adult female rats by propyl-thiouracil (PTU; 0.025%) treatment for 8 weeks. Rats were then randomized to continued PTU or triiodo-L-thyronine (T3; 10 μg/kg/d) treatment for 2 weeks (PTU + T3). After in vivo echocardiographic and hemodynamic recordings, cardiomyocytes (CM) were isolated to record Ca 2+ transients and contractility. TT organization was assessed by confocal microscopy, and STORM images were captured to measure ryanodine receptor (RyR2) cluster number and size, and L-type Ca 2+ channel (LTCC, Ca v 1.2) co-localization. Expressed genes including two integral TT proteins, junctophilin-2 (Jph-2) and bridging integrator-1 (BIN1), were analyzed in left ventricular (LV) tissues and cultured CM using qPCR and RNA sequencing. The T3 dosage used normalized serum T3, and reversed adverse effects of TH deficiency on in vivo measures of cardiac function. Recordings of isolated CM indicated that T3 increased rates of Ca 2+ release and re-uptake, resulting in increased velocities of sarcomere shortening and re-lengthening. TT periodicity was significantly decreased, with reduced transverse tubules but increased longitudinal tubules in TH-deficient CMs and LV tissue, and these structures were normalized by T3 treatment. Analysis of STORM data of PTU myocytes showed decreased RyR2 cluster numbers and RyR localizations within each cluster without significant changes in Ca v 1.2 localizations within RyR clusters. T3 treatment normalized RyR2 cluster size and number. qPCR and RNAseq analyses of LV and cultured CM showed that Jph2 expression was T3-responsive, and its increase with treatment may explain improved TT organization and RyR-LTCC coupling.

Background Aortic stenosis (AS) has been established as a precipitating factor in the development of colonic angiodysplasia, resulting in lower gastrointestinal bleeding (LGIB). While the association between AS and LGIB, termed “Heyde syndrome,” has been examined extensively, few studies assess the impact of comorbid AS on rates of LGIB in patients with colorectal cancer (CRC). Our goal is to examine this association. Methods Patients hospitalized from 2001 to 2013 diagnosed with CRC were identified via ICD-9 codes, further stratified by a diagnosis of AS. Continuous and categorical variables were analyzed by independent sample t-tests and chi-squared analyses respectively. Assessed outcomes included mortality, length of stay (LOS), hospital costs, rates of LGIB, colonic obstruction, colonic perforation, iron-deficiency anemia (IDA), and colectomy. Multivariate analysis via binary logistic regression was utilized to control confounding variables. Results Patients with CRC and AS had higher rates of mortality, lower gastrointestinal bleeding, iron deficiency anemia, and colectomy, while those without AS had higher rates of colonic obstruction. Length of stay and total hospital charges were higher in patients with AS. Discussion CRC outcomes were worse in patients with AS. This could be due to higher rates of LGIB secondary to the prevalence of angiodysplasia among AS patients. More retrospective studies are required to assess the impact of comorbid AS in patients with CRC.

Introduction Cardiac junctophilin‐2 (Jph2) plays a central role in myocardial contractility by anchoring transverse tubules (TT) to the junctional sarcoplasmic reticulum (jSR), essential for excitation‐contraction (EC) coupling and calcium signaling. Decreases in the expression levels of Jph2 have been observed in a variety of pathological conditions including hypertrophic cardiomyopathy, arrhythmias, and progression of disease in failing hearts. Studies have shown that T3 regulates SR Ca2+ ATPase (SERCa2), phospholamban (PLN), L‐type Ca2+ channels and ryanodine receptors (RyR2), that are responsible for regulating intracellular Ca2+ and maintaining normal systolic and diastolic function. We previously reported that T3 improves cardiac contractile function after induction of myocardial infarction (MI) by maintaining TT network integrity and by regulating expression of myofibrillar and Ca2+ handling proteins. We hypothesize that T3 regulates Jph2 expression and its localization within the jSR‐TT complex to maintain functional TT structures and thus normal Ca2+ transients and contractility. Methods Thyroid deficiency was induced in female Sprague Dawley rats (~220g) by ingestion of 0.025% PTU (propylthiouracil) in drinking water. Control (EU) rats had access to untreated water. After 8 weeks, a subgroup of PTU treated rats received T3 (10ug/kg/d) in PTU‐containing water for an additional 2 weeks. RNA was extracted from left ventricular (LV) tissue to measure Jph2, SERCa2, PLN, LTCC and RyR2 mRNA by RT‐qPCR. RNAseq analysis interrogated 15,000 genes. LV myocytes were isolated by collagenase digestion and cultured with and without T3 (10−7 M). Cells were harvested at 24, 48, and 72 hrs for RT‐qPCR analysis of Jph2, SERCa2, and Bridging Integrator‐1 (Bin1). Isolated myocytes from all study groups were immunolabeled with RyR2, Cav1.2 and Jph2 for nanoimaging using STORM. Results RT‐PCR analysis showed significant upregulation of Jph2 expression compared to thyroid deficiency (1.404±0.73 vs 0.322±0.17 fold change). RNAseq revealed 567 differentially expressed genes with 377 genes up‐regulated and 190 down‐regulated in T3‐treated hearts compared to TH deficient hearts. Results showed up‐regulation of Jph2 (p<0.001) and SERCa2 by >1.5‐fold (p<0.00001). Cultured EU and PTU cardiomyocytes similarly showed significantly (p<0.05) increased Jph2 expression in T3 treatment vs non‐treated cells at 48 and 72 hr time points. STORM imaging showed increased clustering of LTCC (Cav1.2) within the RyR/Cav1.2 clusters of TT‐jSR complexes in the T3‐treated vs TH deficient cardiomyocytes (0.53±0.13 vs 0.36±0.03). Conclusions T3 regulates expression of Jph2 which in turn is a critical regulator of the jSR‐TT organization in cardiomyocytes allowing for optimal calcium transients and contractile function.

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