Disulfide Bonds of Thyroid Peroxidase Are Critical Elements for Subcellular Localization, Proteasome-Dependent Degradation, and Enzyme Activity.

Background: Congenital hypothyroidism (CH) is caused by mutations in cysteine residues, including Cys655 and Cys825 that form disulfide bonds in thyroid peroxidase (TPO). It is highly likely that these disulfide bonds could play an important role in TPO activity. However, to date, no study has comprehensively analyzed cysteine mutations that form disulfide bonds in TPO. In this study, we induced mutations in cysteine residues involved in disulfide bonds formation and analyzed their effect on subcellular localization, degradation, and enzyme activities to evaluate the importance of disulfide bonds in TPO activity. Methods: Vector plasmid TPO mutants, C655F and C825R, known to occur in CH, were transfected into HEK293 cells. TPO activity and protein expression levels were measured by the Amplex red assay and Western blotting. The same procedure was performed in the presence of MG132 proteasome inhibitor. Subcellular localization was determined using immunocytochemistry and flow cytometry. The locations of all disulfide bonds within TPO were predicted using in silico analysis. All TPO mutations associated with disulfide bonds were induced. TPO activity and protein expression levels were also measured in all TPO mutants associated with disulfide bonds using the Amplex red assay and Western blotting. Results: C655F and C825R showed significantly decreased activity and protein expression compared with the wild type (WT) (p < 0.05). In the presence of the MG132 proteasome inhibitor, the protein expression level of TPO increased to a level comparable with that of the WT without increases in its activity. The degree of subcellular distribution of TPO to the cell surface in the mutants was lower compared with the WT TPO. Twenty-four cysteine residues were involved in the formation of 12 disulfide bonds in TPO. All TPO mutants harboring an amino acid substitution in each cysteine showed significantly reduced TPO activity and protein expression levels. Furthermore, the differences in TPO activity depended on the position of the disulfide bond. Conclusions: All 12 disulfide bonds play an important role in the activity of TPO. Furthermore, the mutations lead to misfolding, degradation, and membrane insertion.

Clinical characteristics and human leukocyte antigens in patients with immune checkpoint inhibitor-induced type 1 diabetes and pituitary dysfunction: a single center prospective study.

PURPOSE: Immune checkpoint inhibitor (ICI) induced type 1 diabetes (T1D) and pituitary dysfunction are life-threatening adverse events, yet there is little clinical data available. We aimed to investigate the clinical characteristics of patients with these adverse events and report their human leukocyte antigen (HLA) profile to determine its relevance. METHODS: This is a single-center prospective study. We enrolled patients with cancers who were administered ICI and diagnosed as ICI induced T1D (ICI-T1D) and pituitary dysfunction (ICI-PD). Clinical data and extracted DNA from blood samples were collected. HLA typing was performed using next-generation sequencing. We compared our results with those previously reported in healthy controls and investigated the correlation between HLA and the occurrence of ICI-T1D and ICI-PD. RESULTS: We identified 914 patients treated with ICI in our facility from 1st September, 2017 to 30th June, 2022. Six of these patients developed T1D and 15 developed pituitary dysfunction. The duration from the initiation of ICI treatment to the onset of T1D or pituitary dysfunction averaged 492 ± 196 days and 191 ± 169 days. Among the six patients with T1D, two were positive for anti-GAD antibody. The frequencies of HLA-DR11, -Cw10, -B61, -DRB1*11:01, and -C*03:04 were significantly higher in patients with ICI-T1D than in controls. The frequencies of HLA-DR15 and -DRB*15:02 were significantly higher in patients with ICI-PD than in controls. CONCLUSION: This study revealed the clinical characteristics of ICI-T1D and ICI-PD and the association between specific HLAs and these adverse events.

Nephroprotective Effects of Dapagliflozin in Patients with Type 2 Diabetes.

Objective This study analyzed changes in the estimated glomerular filtration rate calculated using cystatin C (eGFRcys) and sodium excretion in the urine after administering dapagliflozin as an add-on therapy to conventional treatment for diabetes. Methods This was a single-center, single-group, prospective interventional study. Dapagliflozin was administered to improve the plasma glucose control in 30 subjects with type 2 diabetes mellitus (age 53±8 years old; 66.6% men). Blood and urine tests were performed before and 6 and 12 months after dapagliflozin administration. The daily sodium excretion was estimated with the Kawasaki formula using second-morning urine samples. Results The eGFRcys did not markedly differ before and 6 months after the dapagliflozin administration but was significantly increased after 12 months (p<0.001), and the estimated daily sodium excretion was also significantly increased (p<0.001 at 6 months and p=0.002 at 12 months). The systolic and diastolic blood pressures tended to decrease after administration. The HbA1c level after the administration of dapagliflozin tended to be lower in the T3 group, showing the smallest increase in changes in the estimated daily sodium excretion from baseline to 6 months (28.2-107.5 mEq/day), than in the combined groups of T1 (219.5-110.1 mEq/day) and T2 (101.4-28.9 mEq/day). In contrast, the eGFRcys was significantly higher in the combined groups of T1 and T2 than that in the T3 group at both 6 and 12 months (p=0.031 and p=0.007, respectively). Conclusions Add-on therapy with dapagliflozin increased the urinary sodium excretion and decreased the blood pressure even in the early phase of this therapy. Our results suggest that dapagliflozin add-on therapy may exert nephroprotective effects in subjects with type 2 diabetes mellitus.

New-onset atypical fulminant type 1 diabetes after COVID-19 vaccination: A case report.

Adverse reactions, including the onset of diabetes, after coronavirus disease 2019 (COVID-19) vaccination have been reported. Herein, we report a case of a man who developed anti-glutamic acid decarboxylase (GAD) antibody-positive fulminant type 1 diabetes 15 weeks after COVID-19 vaccination, atypical of the previously reported anti-GAD antibody-negative cases.

A Case Series of Ketoacidosis After Coronavirus Disease 2019 Vaccination in Patients With Type 1 Diabetes.

Introduction: We report a case series of severe ketoacidosis after COVID-19 vaccination in a type 1 diabetes patients treated with insulin and an SGLT-2 inhibitor. Case Report: We present two cases of type 1 diabetes mellitus. One patient was treated with insulin therapy and an SGLT-2 inhibitor, and the other patient was treated with insulin therapy alone. Both patients became ill after coronavirus disease-2019 vaccination, making it difficult to continue their diet or insulin injections. On admission, they developed severe diabetic ketoacidosis. This is the first report of ketoacidosis after coronavirus disease-2019 vaccination. Conclusion: The vaccine should be carefully administered to type 1 diabetes patients receiving intensive insulin therapy and a sodium-glucose transporter due to the high risk ketoacidosis. It is important to instruct patients to drink sufficient fluids and to continue insulin injections when they become sick.

Hypercalcemia associated with dysgerminoma and elevation of calcitriol: A case report and review of the literature.

We report on the case of a patient with dysgerminoma, a rare germ cell tumor, which showed hypercalcemia with an elevation of 1α,25-dihydroxycholecalciferol (calcitriol). A 27-year-old nulliparous woman presented with hypercalcemia during the examination of a right ovarian tumor with an elevation of calcitriol, lactate dehydrogenase, and alkaline phosphatase. Fractional excretion of calcium was elevated, and intact parathyroid hormone was suppressed. After undergoing right salpingo-oophorectomy, the patient's serum calcium and calcitriol returned to the normal range within a week. A literature search was conducted on the topic by reviewing databases for dysgerminoma showing hypercalcemia. We identified 14 patients from the literature and performed a pooled analysis, including the results of our case. However, most cases lack data that can help investigate the potential association between parathyroid hormone, parathyroid hormone-related protein, calcitriol, and phosphorus in hypercalcemia. Thus, more case reports that include additional information are required to fully elucidate the mechanism of hypercalcemia associated with dysgerminoma.

A Novel Homozygous Mutation of Thyroid Peroxidase Gene Abolishes a Disulfide Bond Leading to Congenital Hypothyroidism.

Congenital hypothyroidism (CH) is the most prevalent congenital endocrine disorder and causes mental retardation. A male Japanese patient with first cousin marriage parents was diagnosed as CH at 10 months. He was born before introduction of mass screening for CH. With continuous thyroid hormone replacement therapy, normal thyroid hormone status was maintained until adulthood. Genetic screening of next-generation sequencing was performed at the age of 52 years, and we identified a new homozygous thyroid peroxidase (TPO) gene mutation (GRCh38.p13, chromosome 2 at position 1493997, c.1964 G>T, p.Cys655Phe). TPO is an important enzyme to produce thyroid hormone. As demonstrated by a homology analysis of TPO proteins among different species, cysteine 655 residue is highly conserved, suggesting an important role in maintaining TPO function and structure. An in silico study with three-dimensional structure of the novel mutation was performed and suggested that the mutation abolished disulfide bond between cysteines at positions 598 and 655. An in vitro functional analysis using HEK293 cells revealed that TPO activity of the mutant was significantly impaired compared with that of the wild type. Furthermore, study of immunohistochemistry showed that localization of TPO in cells did not differ between the wild type and the mutant. In conclusion, this single disulfide bond loss mutation of a new TPO homozygous mutation, p.Cys655Phe, reduced TPO activity and caused congenital hypothyroidism without affecting subcellular localization of TPO proteins.