Abnormal Calcium Research Articles

Calcium and Magnesium Levels in Subclinical and Overt Hypothyroidism: A Cross-sectional Study

Introduction: Hypothyroidism, one of the most common thyroid gland disorders, can cause electrolyte disturbances in the body. Hypothyroidism can alter mineral metabolism by changing the levels of serum calcium and magnesium. Therefore, it is essential to study any abnormalities in calcium and magnesium metabolism in patients with hypothyroidism. Aim: The aim of this study was to assess the levels of calcium and magnesium in patients with hypothyroidism and to study the correlation between Thyroid Stimulating Hormone (TSH), fT3, and fT4 with calcium and magnesium in subclinical and Overt Hypothyroidism (OH). Materials and Methods: This cross-sectional study was held from August 2019 to January 2020 in the Department of Biochemistry, BS Medical College, Bankura. A total of 150 subjects were included in the study, distributed equally among three groups: euthyroidism, subclinical hypothyroidism, and OH. Serum TSH, fT3, fT4, calcium, and magnesium levels were determined in the laboratory, and the data obtained were statistically analysed using ANOVA test and Pearson’s correlation test. Results: Out of a total of 150 subjects, 61 were female, among whom 23 had subclinical hypothyroidism and 21 had OH. There were significant differences in the mean levels of TSH, fT3, fT4, calcium, and magnesium between the SCH, OH, and euthyroid groups. The study showed that the mean serum calcium level was significantly lower in SCH and OH compared to euthyroids, while the level of serum magnesium was significantly increased in SCH and OH compared to euthyroid. There was a statistically significant negative correlation between TSH and serum calcium in both OH and SCH, while a statistically significant positive correlation was observed between TSH and serum magnesium levels in both groups. Conclusion: The present study revealed that serum magnesium levels were high while serum calcium levels were low in both subclinical hypothyroidism and OH when compared to euthyroid subjects. Additionally, calcium levels negatively correlated with TSH, while magnesium levels positively correlated with TSH levels.

Calcinosis cutis in a patient with severe COVID-19 infection

Background: Atypical presentation of calcinosis cutis in the context of COVID-19 infection complicated by acute renal failure has not been described in literature. We report a case of severe COVID-19 infection and its associated uncommon skin manifestation. It is a rare condition and its association with different diseases has been established in the past. However, to the authors’ knowledge, calcinosis cutis has not yet been described in relation to COVID-19 infection complicated by acute renal failure. Case Presentation: Here we describe a case of a 55-year-old gentleman admitted to the intensive care unit with severe COVID-19 infection whose hospital stay was complicated by acute renal failure and development of hypocalcemia which was treated with oral and intravenous calcium. Subsequently, he developed an atypical fleshy lesion on his left ankle during his in-patient stay which was histologically proven calcinosis cutis. It was successfully treated with topical medications. Conclusion: This case highlights the importance of considering a wide differential of skin lesions including calcinosis cutis in patients who are critically unwell with COVID-19 or any other severe infections and develop isolated skin lesions in the setting of impaired renal functions and abnormal calcium phosphate metabolism with calcium administration.

FAHR's Disease and MCA Aneurysm Bleeding Case Report

Fahr's disease is named after the German neurologist Karl Theodor Fahr, who first reported it in 1930. This is a rare neurological condition characterized by abnormal idiopathic calcification of the basal ganglia and is usually inherited in autosomal dominant manner.

Metabolic Maturation Exaggerates Abnormal Calcium Handling in a Lamp2 Knockout Human Pluripotent Stem Cell-Derived Cardiomyocyte Model of Danon Disease.

Danon disease (DD) is caused by mutations of the gene encoding lysosomal-associated membrane protein type 2 (LAMP2), which lead to impaired autophagy, glycogen accumulation, and cardiac hypertrophy. However, it is not well understood why a large portion of DD patients develop arrhythmia and sudden cardiac death. In the current study, we generated LAMP2 knockout (KO) human iPSC-derived cardiomyocytes (CM), which mimic the LAMP2 dysfunction in DD heart. Morphologic analysis demonstrated the sarcomere disarrangement in LAMP2 KO CMs. In functional studies, LAMP2 KO CMs showed near-normal calcium handling at base level. However, treatment of pro-maturation medium (MM) exaggerated the disease phenotype in the KO cells as they exhibited impaired calcium recycling and increased irregular beating events, which recapitulates the pro-arrhythmia phenotypes of DD patients. Further mechanistic study confirmed that MM treatment significantly enhanced the autophagic stress in the LAMP2 KO CMs, which was accompanied by an increase of both cellular and mitochondrial reactive oxygen species (ROS) levels. Excess ROS accumulation in LAMP2 KO CMs resulted in the over-activation of calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) and arrhythmogenesis, which was partially rescued by the treatment of ROS scavenger. In summary, our study has revealed ROS induced CaMKIIδ overactivation as a key mechanism that promotes cardiac arrhythmia in DD patients.

Protection of dystrophic muscle cells using Idebenone correlates with the interplay between calcium, oxidative stress and inflammation.

There is strong cross-talk between abnormal intracellular calcium concentration, high levels of reactive oxygen species (ROS) and an exacerbated inflammatory process in the dystrophic muscles of mdx mice, the experimental model of Duchenne muscular dystrophy (DMD). In this study, we investigated effects of Idebenone, a potent anti-oxidant, on oxidative stress markers, the anti-oxidant defence system, intracellular calcium concentrations and the inflammatory process in primary dystrophic muscle cells from mdx mice. Dystrophic muscle cells were treated with Idebenone (0.05 μM) for 24 h. The untreated mdx muscle cells were used as controls. The MTT assay showed that Idebenone did not have a cytotoxic effect on the dystrophic muscle cells. The Idebenone treatment was able to reduce the levels of oxidative stress markers, such as H2 O2 and 4-HNE, as well as decreasing intracellular calcium influx in the dystrophic muscle cells. Regarding Idebenone effects on the anti-oxidant defence system, an up-regulation of catalase levels, glutathione reductase (GR), glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity was observed in the dystrophic muscle cells. In addition, the Idebenone treatment was also associated with reduction in inflammatory molecules, such as nuclear factor kappa-B (NF-κB) and tumour necrosis factor (TNF) in mdx muscle cells. These outcomes supported the use of Idebenone as a protective agent against oxidative stress and related signalling mechanisms involved in dystrophinopathies, such as DMD.

Mechanism of Hypoxia-Mediated Smooth Muscle Cell Proliferation Leading to Vascular Remodeling.

Vascular remodeling refers to changes in the size, contraction, distribution, and flow rate of blood vessels and even changes in vascular function. Vascular remodeling can cause cardiovascular and cerebrovascular diseases. It can also lead to other systemic diseases, such as pulmonary hypertension, pulmonary atherosclerosis, chronic obstructive pulmonary disease, stroke, and ascites of broilers. Hypoxia is one of the main causes of vascular remodeling. Prolonged hypoxia or intermittent hypoxia can lead to loss of lung ventilation, causing respiratory depression, irregular respiratory rhythms, and central respiratory failure. Animals that are unable to adapt to the highland environment are also prone to sustained constriction of the small pulmonary arteries, increased resistance to pulmonary circulation, and impaired blood circulation, leading to pulmonary hypertension and right heart failure if they live in a highland environment for long periods of time. However, limited studies have been found on the relationship between hypoxia and vascular remodeling. Therefore, this review will explore the relationship between hypoxia and vascular remodeling from the aspects of endoplasmic reticulum stress, mitochondrial dysfunction, abnormal calcium channel, disordered cellular metabolism, abnormal expression of miRNA, and other factors. This will help to understand the detailed mechanism of hypoxia-mediated smooth muscle cell proliferation and vascular remodeling for the better treatment and management of diseases due to vascular remodeling.

Baseline electrolyte disorders predict disease severity and mortality in patients with COVID-19

Distinguishing critical laboratory biomarkers for disease severity at the time of hospital presentation is important for early identification of patients who are most likely to have poor outcomes and effective use of health resources. This study aimed to evaluate whether electrolyte imbalances on hospital admission predict severe disease and mortality in patients with coronavirus disease 2019 (COVID-19). We retrospectively collected data on the blood electrolyte concentrations of 286 COVID-19 patients at admission. The correlations between electrolyte imbalances, inflammation, and thrombosis markers in COVID-19 patients were also evaluated. We assessed the predictive performance of baseline blood electrolyte concentrations for severe disease and death using receiver operating characteristic curve analysis and multivariate logistic regression methods. Abnormalities in serum sodium, calcium, and potassium levels at admission were found at 20.6%, 14%, and 4.2%, respectively in this study. In the receiver operating characteristic curve analyses, hypocalcemia and hyponatremia effectively predicted disease progression to hospitalization (area under the curve 0.82, P < .001 and 0.81, P < .001, respectively) and 30-day mortality (area under the curve 0.85, P < .001 and 0.91, P < .001, respectively). In the multivariate logistic regression analysis, baseline hypocalcemia was identified as an independent risk factor associated with the risk of hospitalization (β = 2.019, P = .01; odds ratio: 7.53). Baseline hypocalcemia and hyponatremia effectively predicted disease progression toward hospitalization and 30-day mortality in patients with COVID-19. Clinicians should closely follow up or reevaluate COVID-19 patients with baseline electrolyte disorders.

Lithium induced hypercalcemia: an expert opinion and management algorithm

BackgroundLithium is the gold standard prophylactic treatment for bipolar disorder. Most clinical practice guidelines recommend regular calcium assessments as part of monitoring lithium treatment, but easy-to-implement specific management strategies in the event of abnormal calcium levels are lacking.MethodsBased on a narrative review of the effects of lithium on calcium and parathyroid hormone (PTH) homeostasis and its clinical implications, experts developed a step-by-step algorithm to guide the initial management of emergent hypercalcemia during lithium treatment.ResultsIn the event of albumin-corrected plasma calcium levels above the upper limit, PTH and calcium levels should be measured after two weeks. Measurement of PTH and calcium levels should preferably be repeated after one month in case of normal or high PTH level, and after one week in case of low PTH level, independently of calcium levels. Calcium levels above 2.8 mmol/l may require a more acute approach. If PTH and calcium levels are normalized, repeated measurements are suggested after six months. In case of persistent PTH and calcium abnormalities, referral to an endocrinologist is suggested since further examination may be needed.ConclusionsStandardized consensus driven management may diminish the potential risk of clinicians avoiding the use of lithium because of uncertainties about managing side-effects and consequently hindering some patients from receiving an optimal treatment.

Diagnosis and treatment of osteoporosis in patients with chronic kidney disease : Joint guidelines of the Austrian Society for Bone and Mineral Research (ÖGKM), the Austrian Society of Physical and Rehabilitation Medicine (ÖGPMR) and the Austrian Society of Nephrology (ÖGN)

Chronic kidney disease (CKD): abnormalities of kidney structure or function, present for over 3months. Staging of CKD is based on GFR and albuminuria (not graded). Osteoporosis: compromised bone strength (low bone mass, disturbance of microarchitecture) predisposing to fracture. By definition, osteoporosis is diagnosed if the bone mineral density T‑score is ≤ -2.5. Furthermore, osteoporosis is diagnosed if alow-trauma (inadequate trauma) fracture occurs, irrespective of the measured T‑score (not graded). The prevalence of osteoporosis, osteoporotic fractures and CKD is increasing worldwide (not graded). PATHOPHYSIOLOGY, DIAGNOSIS AND TREATMENT OF CHRONIC KIDNEY DISEASE-MINERAL AND BONE DISORDER (CKD-MBD): Definition of CKD-MBD: asystemic disorder of mineral and bone metabolism due to CKD manifested by either one or acombination of the following: abnormalities of calcium, phosphorus, PTH, or vitaminDmetabolism; renal osteodystrophy; vascular calcification (not graded). Increased, normal or decreased bone turnover can be found in renal osteodystrophy (not graded). Depending on CKD stage, routine monitoring of calcium, phosphorus, alkaline phosphatase, PTH and 25-OH-vitaminD is recommended (2C). Recommendations for treatment of CKD-MBD: Avoid hypercalcemia (1C). In cases of hyperphosphatemia, lower phosphorus towards normal range (2C). Keep PTH within or slightly above normal range (2D). VitaminDdeficiency should be avoided and treated when diagnosed (1C). Densitometry (using dual X‑ray absorptiometry, DXA): low T‑score correlates with increased fracture risk across all stages of CKD (not graded). Adecrease of the T‑score by 1unit approximately doubles the risk for osteoporotic fracture (not graded). AT-score ≥ -2.5 does not exclude osteoporosis (not graded). Bone mineral density of the lumbar spine measured by DXA can be increased and therefore should not be used for the diagnosis or monitoring of osteoporosis in the presence of aortic calcification, osteophytes or vertebral fracture (not graded). FRAX can be used to aid fracture risk estimation in all stages of CKD (1C). Bone turnover markers can be measured in individual cases to monitor treatment (2D). Bone biopsy may be considered in individual cases, especially in patients with CKD G5 (eGFR < 15 ml/min/1.73 m2) or CKD 5D (dialysis). Hypocalcemia should be treated and serum calcium normalized before initiating osteoporosis therapy (1C). CKD G1-G2 (eGFR ≥ 60 ml/min/1.73 m2): treat osteoporosis as recommended for the general population (1A). CKD G3-G5D (eGFR < 60 ml/min/1.73 m2 to dialysis): treat CKD-MBD first before initiating osteoporosis treatment (2C). CKD G3 (eGFR 30-59 ml/min/1.73 m2) with PTH within normal limits and osteoporotic fracture and/or high fracture risk according to FRAX: treat osteoporosis as recommended for the general population (2B). CKD G4-5 (eGFR < 30 ml/min/1.73 m2) with osteoporotic fracture (secondary prevention): Individualized treatment of osteoporosis is recommended (2C). CKD G4-5 (eGFR < 30 ml/min/1.73 m2) and high fracture risk (e.g. FRAX score > 20% for amajor osteoporotic fracture or > 5% for hip fracture) but without prevalent osteoporotic fracture (primary prevention): treatment of osteoporosis may be considered and initiated individually (2D). CKD G4-5D (eGFR < 30 ml/min/1.73 m2 to dialysis): Calcium should be measured 1-2weeks after initiation of antiresorptive therapy (1C). Resistance training prioritizing major muscle groups thrice weekly (1B). Aerobic exercise training for 40 min four times per week (1B). Coordination and balance exercises thrice weekly (1B). Flexibility exercise 3-7times per week (1B).

Thyroid function analysis and other biochemical parameters in patients with moderate and severe COVID-19

Background and objective: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of coronavirus disease-19 (COVID-19). The effects of COVID-19 on the thyroid axis remain uncertain. This study aimed to determine the occurrence of thyroid dysfunction, as previously demonstrated for SARS-CoV-1 infection, and to analyze electrolytes (sodium, potassium, and chloride) to determine the severity of the disease. Methods: Blood samples were taken from patients who were admitted to Erbil hospitals from July to October 2021. Infection was detected by polymerase chain reaction (PCR). The 306 cases were labeled as moderate or severe. The samples were assessed for doing C-reactive protein (CRP), as a marker of systemic inflammation, thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4), and (sodium, potassium, and chloride) electrolytes. Results: Patients comprised of 157 (51.3%) males and 149 (48.7%) females. The result revealed that 274 (89.5%), 278 (90.8%), 292 (95.4%) of patients had normal TSH, T3, T4 level respectively, 22 (7.2%), 23 (7.5%), 9 (2.9%) of patients had low TSH, T3, T4 level respectively, and 10 (3.3%), 5 (1.6%), 5 (1.6%), had high TSH, T3, T4 level respectively. There was no significant difference between moderate and severe cases in alterations of TSH, T3, T4 level. There was a significant difference between moderate and severe cases in sodium, potassium, and chloride electrolyte abnormality. Conclusion: The occurrence of thyroid dysfunction in moderate and severe cases. The severity of the COVID-19 infection is associated with abnormalities in sodium, calcium, and chloride electrolytes.

Comparison of calcium and phosphorus homeostasis between hemodialysis and peritoneal dialysis in patients with end-stage renal disease

Introduction: Chronic kidney disease (CKD) and subsequent end-stage renal disease (ESRD) are public health problems worldwide, and their prevalence is increasing worldwide. Abnormalities in calcium and phosphorus are common problems that need to be considered alongside other important factors when choosing a dialysis method. Hence, the present study aimed to assess and compare the calcium and phosphorus homeostasis in ESRD patients on hemodialysis and peritoneal dialysis (PD). Methods: In this descriptive cross-sectional study, 150 patients with ESRD on hemodialysis and 150 patients with ESRD on PD in the dialysis department of Imam Reza hospital of Tabriz University were selected randomly. The serum levels of calcium, phosphorus, and intact parathyroid hormone (iPTH) before the initiation of dialysis and one year afterward were considered for comparison. Results: In the hemodialysis group, 33.1% of patients were female and 66.9% were male but in the PD group, sex distribution was 47% males and 53% females. Following one year of dialysis, mean calcium (Ca), phosphorus (P), and iPTH levels were significantly higher in the hemodialysis group compared to PD patients (P&lt;0.05). Also, the mean Ca×P product was significantly higher in patients undergoing PD (P=0.05). Conclusion: Our findings suggested that calcium, phosphorus and iPTH levels increase with prolonged hemodialysis rather than PD, and the rate of Ca×P in patients is significantly higher in PD patients after one year.

Analysis of influencing factors of serum total protein and serum calcium content in plasma donors.

The adverse effects of plasma donation on the body has lowered the odds of donation. The aim of this study was to investigate the prevalence of abnormal serum calcium and total serum protein related to plasma donation, identify the influencing factors, and come up with suggestions to make plasma donation safer. Donors from 10 plasmapheresis centers in five provinces of China participated in this study. Serum samples were collected before donation. Serum calcium was measured by arsenazo III colorimetry, and the biuret method was used for total serum protein assay. An automatic biochemical analyzer was used to conduct serum calcium and total serum protein tests. The mean serum calcium was 2.3±0.15 mmol/L and total serum protein was 67.75±6.02 g/L. The proportions of plasma donors whose serum calcium and total serum protein were lower than normal were 20.55% (815/3,966) and 27.99% (1,111/3,969), respectively. There were significant differences in mean serum calcium and total serum protein of plasma donors with different plasma donation frequencies, gender, age, regions, and body mass index (BMI), (all p<0.05). Logistic regression analysis revealed that donation frequencies, age, BMI and regions were significantly associated with a higher risk of low serum calcium level, and donation frequencies, gender, age and regions were significant determinants factors of odds of abnormal total serum protein. Donation frequencies, gender, age, regions, and BMI showed different effects on serum calcium and total serum protein. More attention should be paid to the age, donation frequency and region of plasma donors to reduce the probability of low serum calcium and low total serum protein.

Neuronal calcium dysregulation in mice at an early stage of tauopathy and its alleviation by a tau antibody

AbstractBackgroundTau immunotherapies are promising approaches to treat Alzheimer’s disease and other tauopathies. How tau antibodies restore neuronal function remains unknown. Neuronal activity can be monitored by two‐photon calcium imaging in awake and behaving animals. Using this method, we observed altered neuronal calcium activity in the motor cortex of 12‐month‐old JNPL3 tauopathy mice during quiet wakefulness or forced running (Wu Q et al, Neurobiol. Dis. 2021). We also demonstrated that a mouse monoclonal antibody, targeting phosphorylated tau‐Ser396/Ser404, significantly restored the abnormal calcium activity and decreased pathological tau levels in these mice. Analysis of possible neuronal functional deficits and tau antibody efficacy in younger tauopathy mice warrants further investigation.MethodsSomatic calcium activity in the motor cortex of 6‐month‐old JNPL3 mice were assessed by two‐photon microscopy when animals were either resting or running on a treadmill. At this age, JNPL3 mice are in their early stage of tauopathy. The frequency, amplitude and total activity of calcium transients were analyzed and compared between wild‐type and JNPL3 mice. After the first imaging session, two doses (100 µg each) of a tau antibody were administered intravenously to JNPL3 mice four days apart. The somatic calcium activity was assessed again in these animals four days later, and compared to their neuronal calcium activity profile before tau antibody treatment.ResultsWe found abnormal cortical calcium activity in resting and running JNPL3 mice at 6 months of age. Brain levels of pathological tau correlated with the degree of calcium dysfunction. Acute treatment with a tau antibody attenuated these changes, whereas littermate JNPL3 mice treated with control IgG showed no improvements.ConclusionThese findings revealed neuronal calcium dysregulation in JNPL3 mice at an early stage of tauopathy that was partially corrected by an acute tau antibody treatment, analogous to our prior findings at a later stage of tauopathy. Together, these results indicate that neuronal dysfunction correlates with tau pathology at various stages of tauopathy, which can be consistently alleviated by a tau antibody treatment. This type of functional evaluation in vivo is a valuable way to study tau pathogenesis, and assess therapeutic efficacy at different stages of tauopathy.

Abnormal mitochondrial calcium content in angiotensin-induced hypertrophy is ameliorated by cannabidiol mimicking PPAR-g activation

Abnormal mitochondrial calcium content in angiotensin-induced hypertrophy is ameliorated by cannabidiol mimicking PPAR-g activation

Mitochondrial transport along RGC axons: Strategies to restore energy homeostasis and visual function

AbstractDeficits in mitochondria anterograde axonal transport is a common feature of neurodegenerative diseases including glaucoma. Whether aberrant expression of components in the transport machinery impinge directly on metabolic stress, neuronal death, and circuit dysfunction, is currently unknown. We used multiphoton microscope live imaging to monitor mitochondrial transport along the axons of retinal ganglion cells (RGC), the neurons that die in glaucoma. We found that high intraocular pressure, the most important risk factor to develop the disease, impairs anterograde movement of mitochondria along RGC axons leading to mitochondria depletion and energy decline. Molecular profiling of motor and adaptor proteins revealed loss of Disrupted in schizophrenia (Disc1) expression in glaucomatous RGC. Adeno‐associated virus (AAV)‐based Disc1 gene delivery rescued anterograde transport and replenished mitochondria in proximal and distal axonal segments. Delivery of a genetically encoded ATP sensor combined with longitudinal live imaging revealed that Disc1 supplementation increased ATP production in stressed neurons. Strikingly, Disc1 gene therapy promoted neuronal survival, reversed abnormal RGC calcium dynamics, and restored light‐evoked retinal responses and visual behaviour. Our study provides proof‐of‐principle that enhancing mitochondrial anterograde transport is an effective strategy to alleviate metabolic stress and glaucomatous neurodegeneration.

Abstract 11976: Functional Characterization of Calcium Handling Kinetics in Patient-Derived Ipsc-Cm Models of Pkp2-Mediated Arrhythmogenic Right Ventricular Cardiomyopathy

Introduction: Pathogenic variants in PKP2 -encoded plakophilin 2 cause arrhythmogenic right ventricular cardiomyopathy (ARVC). Electrocardiographically, PKP2 -mediated ARVC may mimic RYR2 -mediated catecholaminergic polymorphic ventricular tachycardia (CPVT). We compare the underlying mechanism of arrhythmia in ARVC and CPVT using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Methods: iPSC-CMs were generated from 2 ARVC patients with different PKP2 variants [E149X (PKP2-1) and c.2146-1G&gt;C (PKP2-2)], 1 patient with a CPVT variant [RyR2-R176Q (CPVT1)], and a wild-type (WT) control. Fluo-4 AM calcium dye was used to assess calcium kinetics in iPSC-CMs before and during treatment with 100 nM isoproterenol (ISO) at 8-10 min. Results: Compared to WT, PKP2 and RYR2 iPSC-CMs had a greater amplitude before (WT: 0.331±0.031, PKP2-1: 1.048±0.074, PKP2-2: 1.076±0.095, CPVT1: 0.966±0.061; P&lt;0.0001) and during ISO (WT: 0.277±0.022, PKP2-1: 0.971±0.069, PKP2-2: 0.622±0.041, CPVT1: 0.756±0.051; P&lt;0.0001). The Ca 2+ transient duration (CTD100) was longer in PKP2 and RYR2 iPSC-CMs compared to WT before (WT: 1.01±0.05 s, PKP2-1: 1.84±0.01 s, PKP2-2: 1.76±0.02 s, CPVT1: 1.81±0.02 s; P&lt;0.0001) and during ISO (WT: 1.38±0.05 s, PKP2-1: 1.65±0.03 s, PKP2-2: 1.71±0.03 s, CPVT1: 1.61±0.05 s; P&lt;0.001). Before (WT: 259±13 ms, PKP2-1: 538±23 ms, PKP2-2: 493±28 ms, CPVT1: 586±24 ms; P&lt;0.0001) and during ISO (WT: 311±19 ms, PKP2-1: 406±21 ms, P=0.0172, PKP2-2: 487±28 ms, P&lt;0.0001, CPVT1: 453±21 ms, P=0.0001), peak to 50% decay time was slower in PKP2 and RYR2 iPSC-CMs compared with WT. Upstroke time was longer in PKP2 and RYR2 iPSC-CMs compared to WT before (WT: 205±5 ms, PKP2-1: 539±13 ms, PKP2-2: 429±19 ms, CPVT1: 455±12 ms; P&lt;0.0001) and during ISO (WT: 213±7 ms, PKP2-1: 375±16 ms, PKP2-2: 416±20 ms, CPVT1: 389±10 ms; P&lt;0.0001). Conclusion: Here, iPSC-CMs, derived from patients with either PKP2 -mediated ARVC or RYR2 -mediated CPVT, display similar abnormal calcium handling properties such as greater amplitude, longer CTD100, and slower peak to 50% decay time and upstroke time compared to WT iPSC-CMs before and during ISO treatment. This may explain why patients with PKP2 -mediated ARVC often mimic the treadmill stress test seen in patients with CPVT1.

Abstract 15591: Acute Dantrolene Treatment Reverses Arrhythmogenic Substrate and Reduces Triggers Induced by Ryanodine Receptor 2 Hyperactivity in Human Hearts

Introduction: Ryanodine receptor 2 (RyR2) hyperactivity is commonly observed in structural heart diseases that are a result of ischemia or heart failure. It results in abnormal calcium handling and calcium leak that can trigger arrhythmias. Dantrolene, a RyR inhibitor, is used to prevent calcium leak from RyR1 in skeletal muscles. Hypothesis: Suppressing RyR2 hyperactivity with acute dantrolene treatment can reduce arrhythmia burden in human hearts. Methods: Human donor hearts that were not used in transplantation were obtained and 1 cm 3 cubes were isolated from the left ventricle. Slices at 400 μm thickness were generated from these cubes, pinned and perfused with Tyrode’s solution in a recording tissue chamber. Pseudo-ECGs were recorded with ECG electrodes and the slices were optically mapped to measure conduction velocity (CV), action potential duration (APD) and calcium transient duration (CaTD). After an initial 30 min equilibration period, baseline optical recordings were obtained. Slices were then treated with 1) Isoproterenol (Iso, 250 nM) to stimulate β-adrenergic receptors, 2) Caffeine (200 μM) for RyR2 receptor activation and 3) Dantrolene (10 μM), sequentially. Dual optical recordings, Vm and Ca, were obtained after each treatment. Results: Substrate: Iso reduced APD (425±36 vs 394±43, p=0.03), as expected, and addition of Caffeine restored APD to baseline. More importantly, addition of Dantrolene prolonged APD even further (460±90, p=0.04). CaTD was also similarly reduced by Iso (445±48 vs 387±25, p=0.04) and restored to baseline by Caffeine+Iso. No significant changes in CV were measured under any condition. Trigger: In slices where PVCs were inducible, Caffeine+Iso increased occurrence of PVCs (20 vs 53 PVCs/min) while addition of Dantrolene reduced PVC incidence (18 PVCs/min). Conclusions: Dantrolene treatment, acutely reversed proarrhythmogenic substrate and reduced triggers and could therefore be a suitable approach for anti-arrhythmic therapy in patients with structural heart disease. Additionally, human LV slice preparation is useful in antiarrhythmic drug studies.

ODP104 Isolated familial hypoparathyroidism with Tbx1 mutation in Korea

Abstract Background Non-surgical hypoparathyroidism due to lack of PTH secretion or action is uncommon disorder characterized by hypocalcemia and hyperphosphatemia. Familial hypoparathyroidism is classified into syndromic hypoparathyroidism, including DiGeorge syndrome and isolated familial hypoparathyroidism. Deletion of Tbx1 is the cause of DiGeorge syndrome characterized by hypoparathyroidism, immunodeficiency, and congenital heart disease. Most cases of isolated familial hypoparathyroidism are caused by GCM2, SOX3, CASR, Gα11, and PTH. Isolated familial hypoparathyroidism also can be caused by mutations in TBX1 genes(1). In this study, we also identified a splice-altering mutation in TBX1 (c.1009+1G. C), leading to skipping of exon 8 in an idiopathic hypoparathyroidism patient in Korea. Case A 35-year-old woman was referred to our hospital in March 2016 for hypocalcemia. It had been detected after recurrent abortion and seizure during exercise. Her second older brother was diagnosed as idiopathic hypoparathyroidism with no abnormalities in the TUPLE1 FISH test and chromosome test eight years ago. Initial laboratory studies showed low corrected calcium (7.4 mg/dL, normal range: 8.5-10.5), hyperphosphatemia (4.7 mg/dL, normal range: 2.5-4.1), inappropriately normal parathyroid hormone (18.4 pg/mL, normal range: 15-65), corresponded to hypoparathyroidism. A brain computed tomography showed bilateral globus pallidi calcification. She had no history of renal stones or cataracts. She did not show congenital anomaly including cleft palate, facial dysmorphism, conotruncal heart defects, and immunodeficiency, and neither did her brother. Molecular diagnoses were analyzed by whole-exome sequencing, identifying the heterozygous TBX1 mutation (c.1009+2T/A). She was treated with conventional therapy such as calcium and calcitriol. The patient gave birth 18 months after referring to our hospital, and the child did not show any abnormalities in calcium or phosphorus. During a follow-up of 6 years, the patient had no additional symptoms related to hypocalcemia with the lower normal range of calcium and normal phosphorous. Conclusion We identified a rare heterozygous TBX1 mutation in a patient with isolated familial hypoparathyroidism in Korea.

Manganese-Enhanced Magnetic Resonance Imaging in Takotsubo Syndrome.

Takotsubo syndrome is an acute cardiac emergency characterized by transient left ventricular systolic dysfunction typically following a stressful event. Despite its rapidly rising incidence, its pathophysiology remains poorly understood. Takotsubo syndrome may pass unrecognized, especially if timely diagnostic imaging is not performed. Defective myocardial calcium homeostasis is a central cause of contractile dysfunction and has not been explored in takotsubo syndrome. We aimed to investigate myocardial calcium handling using manganese-enhanced magnetic resonance imaging during the acute and recovery phases of takotsubo syndrome. Twenty patients with takotsubo syndrome (63±12 years of age; 90% female) and 20 volunteers matched on age, sex, and cardiovascular risk factors (59±11 years of age; 70% female) were recruited from the Edinburgh Heart Centre between March 2020 and October 2021. Patients underwent gadolinium and manganese-enhanced magnetic resonance imaging during index hospitalization with repeat manganese-enhanced magnetic resonance imaging performed after at least 3 months. Compared with matched control volunteers, patients had a reduced left ventricular ejection fraction (51±11 versus 67±8%; P<0.001), increased left ventricular mass (86±11 versus 57±14 g/m2; P<0.001), and, in affected myocardial segments, elevated native T1 (1358±49 versus 1211±28 ms; P<0.001) and T2 (60±7 versus 38±3 ms; P<0.0001) values at their index presentation. During manganese-enhanced imaging, kinetic modeling demonstrated a substantial reduction in myocardial manganese uptake (5.1±0.5 versus 8.2±1.1 mL/[100 g of tissue ·min], respectively; P<0.0001), consistent with markedly abnormal myocardial calcium handling. After recovery, left ejection fraction, left ventricular mass, and T2 values were comparable with those of matched control volunteers. Despite this, native and postmanganese T1 and myocardial manganese uptake remained abnormal compared with matched control volunteers (6.6±0.5 versus 8.2±1.1 mL/[100 g of tissue ·min]; P<0.0001). In patients with takotsubo syndrome, there is a profound perturbation of myocardial manganese uptake, which is most marked in the acute phase but persists for at least 3 months despite apparent restoration of normal left ventricular ejection fraction and resolution of myocardial edema, suggesting abnormal myocardial calcium handling may be implicated in the pathophysiology of takotsubo syndrome. Manganese-enhanced magnetic resonance imaging has major potential to assist in the diagnosis, characterization, and risk stratification of patients with takotsubo syndrome. URL: https://www. gov; Unique identifier: NCT04623788.

OR29-5 Phase 3 PaTHway Trial: Participants Treated With TransCon PTH Achieved Independence From Conventional Therapy While Maintaining Normal Serum Calcium

Abstract Background Adults with chronic hypoparathyroidism managed with conventional therapy (calcitriol, alfacalcidol, and oral calcium) generally report a reduced quality of life (QoL) and remain at risk for long-term complications from abnormal calcium and phosphate metabolism. The PaTHway trial assessed the efficacy and safety of TransCon PTH at Week 26. Methods PaTHway was a double-blind, placebo-controlled 26-week trial with 3: 1 randomization to TransCon PTH 18 mcg/d or placebo, co-administered with conventional therapy. The composite primary efficacy endpoint was the proportion of participants at Week 26 who achieved: serum calcium levels in the normal range (8.3–10.6 mg/dL), independence from conventional therapy defined as requiring no active vitamin D and ≤600 mg/day of calcium supplementation, and no increase in prescribed study drug over 4 weeks prior to Week 26. Key secondary endpoints included Hypoparathyroidism Patient Experience Scale (HPES) domain scores and 36-Item Short Form Survey (SF-36) subscale scores. Results 82 participants were dosed (78% female, mean age 49 years). 79 completed treatment through Week 26. 79% (48/61) of participants randomized to TransCon PTH met the composite primary efficacy endpoint, compared to 5% (1/21) in the placebo group (p &amp;lt;0.0001). 93% (57/61) participants treated with TransCon PTH achieved independence from conventional therapy. At baseline, mean serum calcium was 8.8 and 8.7 mg/dL for TransCon PTH and placebo respectively; 8.9 mg/dL and 8.2 mg/dL at Week 26, respectively. For TransCon PTH, mean urine calcium decreased significantly from 390 mg/24-hour at baseline to 220 mg/24-hour (normal range &amp;lt;250 mg/24-hour) at Week 26 compared to 329 mg/24-hour at baseline to 292 mg/24-hour at Week 26 for placebo. TransCon PTH therapy demonstrated a significant improvement in HPES-Symptom domain scores − Physical (p = 0.0038) and Cognitive (p = 0.0055), HPES-Impact domain scores − Physical Functioning (p = 0.0046) and Daily Life (p = 0.0061), and SF-36 Physical Functioning subscale score (p = 0.0347) compared to placebo. Overall, TransCon PTH was well-tolerated. The majority of adverse events (AE) were mild or moderate in severity. The most commonly reported study drug-related AEs were injection site reactions, hypercalcemia, and headaches. No study drug-related AEs led to withdrawal from the study. Conclusions In the PaTHway phase 3 trial, 79% of participants on TransCon PTH therapy (versus 5% on placebo) were able to achieve independence from conventional therapy while maintaining normocalcemia at Week 26. Uniquely, TransCon PTH therapy decreased and normalized 24-hour urine calcium excretion and significantly improved QoL (symptom burden and impact) from baseline compared to placebo. These data suggest the potential for TransCon PTH to improve clinical outcomes and QoL compared to current conventional therapy. Presentation: Tuesday, June 14, 2022 10:45 a.m. - 11:00 a.m.