Novel time-resolved reporter mouse reveals spatial and transcriptional heterogeneity during alpha cell differentiation.

AIMS/HYPOTHESIS: Glucagon-expressing pancreatic alpha cells have attracted much attention for their plasticity to transdifferentiate into insulin-producing beta cells; however, it remains unclear precisely when, and from where, alpha cells emerge and what regulates alpha cell fate. We therefore explored the spatial and transcriptional heterogeneity of alpha cell differentiation using a novel time-resolved reporter system. METHODS: We established the mouse model, 'Gcg-Timer', in which newly generated alpha cells can be distinguished from more-differentiated cells by their fluorescence. Fluorescence imaging and transcriptome analysis were performed with Gcg-Timer mice during the embryonic and postnatal stages. RESULTS: Fluorescence imaging and flow cytometry demonstrated that green fluorescence-dominant cells were present in Gcg-Timer mice at the embryonic and neonatal stages but not after 1 week of age, suggesting that alpha cell neogenesis occurs during embryogenesis and early neonatal stages under physiological conditions. Transcriptome analysis of Gcg-Timer embryos revealed that the mRNAs related to angiogenesis were enriched in newly generated alpha cells. Histological analysis revealed that some alpha cells arise close to the pancreatic ducts, whereas the others arise away from the ducts and adjacent to the blood vessels. Notably, when the glucagon signal was suppressed by genetic ablation or by chemicals, such as neutralising glucagon antibody, green-dominant cells emerged again in adult mice. CONCLUSIONS/INTERPRETATION: Novel time-resolved analysis with Gcg-Timer reporter mice uncovered spatiotemporal features of alpha cell neogenesis that will enhance our understanding of cellular identity and plasticity within the islets. DATA AVAILABILITY: Raw and processed RNA sequencing data for this study has been deposited in the Gene Expression Omnibus under accession number GSE229090.

Monitoring autophagic flux in vivo revealed its physiological response and significance of heterogeneity in pancreatic beta cells.

Autophagy plays an essential role in preserving cellular homeostasis in pancreatic beta cells. However, the extent of autophagic flux in pancreatic islets induced in various physiological settings remains unclear. In this study, we generate transgenic mice expressing pHluorin-LC3-mCherry reporter for monitoring systemic autophagic flux by measuring the pHluorin/mCherry ratio, validating them in the starvation and insulin-deficient model. Our findings reveal that autophagic flux in pancreatic islets enhances after starvation, and suppression of the flux after short-term refeeding needs more prolonged re-starvation in islets than in the other insulin-targeted organs. Furthermore, heterogeneity of autophagic flux in pancreatic beta cells manifests under insulin resistance, and intracellular calcium influx by glucose stimulation increases more in high- than low-autophagic flux beta cells, with differential gene expression, including lipoprotein lipase. Our pHluorin-LC3-mCherry mice enable us to reveal biological insight into heterogeneity in autophagic flux in pancreatic beta cells.

STAT3 suppression and ß-cell ablation enhance α-to-ß reprogramming mediated by Pdx1.

As diabetes results from the absolute or relative deficiency of insulin secretion from pancreatic ß cells, possible methods to efficiently generate surrogate ß cells have attracted a lot of efforts. To date, insulin-producing cells have been generated from various differentiated cell types in the pancreas, such as acinar cells and α cells, by inducing defined transcription factors, such as PDX1 and MAFA, yet it is still challenging as to how surrogate ß cells can be efficiently generated for establishing future regenerative therapies for diabetes. In this study, we demonstrated that the exogenous expression of PDX1 activated STAT3 in α cells in vitro, and STAT3-null PDX1-expressing α cells in vivo resulted in efficient induction of α-to-ß reprogramming, accompanied by the emergence of α-cell-derived insulin-producing cells with silenced glucagon expression. Whereas ß-cell ablation by alloxan administration significantly increased the number of α-cell-derived insulin-producing cells by PDX1, STAT3 suppression resulted in no further increase in ß-cell neogenesis after ß-cell ablation. Thus, STAT3 modulation and ß-cell ablation nonadditively enhance α-to-ß reprogramming induced by PDX1, which may lead to the establishment of cell therapies for curing diabetes.

Genetic ablation of p62/SQSTM1 demonstrates little effect on pancreatic ß-cell function under autophagy deficiency.

Autophagy is known to play an essential role in intracellular quality control through the degradation of damaged organelles and components. We previously demonstrated that ß-cell-specific autophagy deficient mice, which lack Atg7, exhibited impaired glucose tolerance, accompanied by the accumulation of sequestosome 1/p62 (hereafter referred to as p62). Whereas p62 has been reported to play essential roles in regulating cellular homeostasis in the liver and adipose tissue, we previously showed that ß-cell-specific p62 deficiency does not cause any apparent impairment in glucose metabolism. In the present study, we investigated the roles of p62 in ß cells under autophagy-deficient conditions, by simultaneously inactivating both Atg7 and p62 in a ß-cell specific manner. Whereas p62 accumulation was substantially reduced in the islets of Atg7 and p62 double-deficient mice, glucose tolerance and insulin secretion were comparable to Atg7 single-deficient mice. Taken together, these findings suggest that the p62 accumulation appears to have little effect on ß-cell function under conditions of autophagy inhibition.

Cumulative autophagy insufficiency in mice leads to progression of ß-cell failure.

Autophagy is known to play a pivotal role in ß-cell function. While the lifelong inhibition of autophagy through Atg7 deletion in ß cells has been demonstrated to lead to impaired glucose tolerance together with ß-cell dysfunction, the temporal association between autophagy inhibition and ß-cell dysfunction remains unclear. To address such questions, inducible ß-cell-specific Atg7-knockout (ißAtg7KO) mice were generated, and autophagy inhibition was induced for two different time durations. Whereas 2 weeks of Atg7 ablation was sufficient to induce autophagy deficiency, confirmed by the accumulation of p62, ißAtg7KO mice exhibited normal glucose tolerance. In contrast, prolonged autophagy deficiency for 6 weeks resulted in glucose intolerance together with impaired insulin secretion. Direct mRNA sequencing and pathway analysis revealed that the gene set associated with insulin secretion was downregulated only after the 6-week prolonged autophagy inhibition. Furthermore, we identified a novel gene, Sprr1a, which was expressed at more than 50-fold higher levels during both the 2-week and 6-week autophagy inhibition. These findings suggest that autophagy insufficiency cumulatively leads to ß-cell failure after a certain interval, accompanied by stepwise alterations of gene expression patterns.

Spatial and transcriptional heterogeneity of pancreatic beta cell neogenesis revealed by a time-resolved reporter system.

AIMS/HYPOTHESIS: While pancreatic beta cells have been shown to originate from endocrine progenitors in ductal regions, it remains unclear precisely where beta cells emerge from and which transcripts define newborn beta cells. We therefore investigated characteristics of newborn beta cells extracted by a time-resolved reporter system. METHODS: We established a mouse model, 'Ins1-GFP; Timer', which provides spatial information during beta cell neogenesis with high temporal resolution. Single-cell RNA-sequencing (scRNA-seq) was performed on mouse beta cells sorted by fluorescent reporter to uncover transcriptomic profiles of newborn beta cells. scRNA-seq of human embryonic stem cell (hESC)-derived beta-like cells was also performed to compare newborn beta cell features between mouse and human. RESULTS: Fluorescence imaging of Ins1-GFP; Timer mouse pancreas successfully dissected newly generated beta cells as green fluorescence-dominant cells. This reporter system revealed that, as expected, some newborn beta cells arise close to the ducts (ßduct); unexpectedly, the others arise away from the ducts and adjacent to blood vessels (ßvessel). Single-cell transcriptomic analyses demonstrated five distinct populations among newborn beta cells, confirming spatial heterogeneity of beta cell neogenesis such as high probability of glucagon-positive ßduct, musculoaponeurotic fibrosarcoma oncogene family B (MafB)-positive ßduct and musculoaponeurotic fibrosarcoma oncogene family A (MafA)-positive ßvessel cells. Comparative analysis with scRNA-seq data of mouse newborn beta cells and hESC-derived beta-like cells uncovered transcriptional similarity between mouse and human beta cell neogenesis including microsomal glutathione S-transferase 1 (MGST1)- and synaptotagmin 13 (SYT13)-highly-expressing state. CONCLUSIONS/INTERPRETATION: The combination of time-resolved histological imaging with single-cell transcriptional mapping demonstrated novel features of spatial and transcriptional heterogeneity in beta cell neogenesis, which will lead to a better understanding of beta cell differentiation for future cell therapy. DATA AVAILABILITY: Raw and processed single-cell RNA-sequencing data for this study has been deposited in the Gene Expression Omnibus under accession number GSE155742.

Rubicon in pancreatic beta cells plays a limited role in maintaining glucose homeostasis following increased insulin resistance.

Autophagy has been reported to play a crucial role in the maintenance of intracellular homeostasis, including in pancreatic beta cells. Rubicon, which interacts with the phosphoinositide 3-kinase (PI3K) complex, through autophagy-related 14 (ATG14), is among the few autophagy regulators that have been reported to inhibit autophagic flux to date and the deletion of Rubicon has been shown to increase autophagic flux. Based on previous results showing a causal relationship between autophagic dysfunction and pancreatic beta-cell impairment, we hypothesized that the deletion of Rubicon in pancreatic beta cells would improve cell integrity and confer protective effects. To test this hypothesis, we first confirmed that Rubicon knockdown (KD) promoted autophagic flux in ßTC3 pancreatic beta-cell line. Next, we generated pancreatic beta-cell-specific Rubicon knockout (ßKO) mice, by administering tamoxifen to Rubiconflox/flox:MIP-Cre-ERT mice, which showed normal glucose tolerance and insulin secretion under a normal chow diet, despite successful gene recombination. We also attempted to increase insulin resistance by feeding the mice with a high-fat diet for an additional 2 months to find little differences among the parameters evaluated for glucose metabolism. Finally, severe insulin resistance was induced with insulin receptor antagonist treatment, which resulted in comparable glucose homeostasis measurements between Rubicon ßKO and control mice. In summary, these results suggest that in pancreatic beta cells, Rubicon plays a limited role in the maintenance of systemic glucose homeostasis.

Biphasic changes in ß-cell mass around parturition are accompanied by increased serotonin production.

Pancreatic ß-cell mass is known to be considerably altered during pregnancy and after parturition in rodents and humans. While ß-cell mass increases during pregnancy and starts to return toward its original level after parturition, the cellular mechanisms by which ß-cell mass during this period is regulated remains unclear. To address this issue in mice, we quantified ß-cell mass and investigated the mechanisms underlying its regulation throughout the perinatal and postpartum period. The increased ß-cell size and proliferation during pregnancy were significantly reduced shortly after parturition, whereas there was no evidence of ß-cell reprogramming or increased apoptosis. Direct RNA sequencing of islets from pregnant and postpartum mice demonstrated dynamic changes in gene expression patterns, showing robust downregulation of cell cycle-related genes 1 day after parturition, and the reupregulation of serotonin metabolism-related genes at postpartum day 7. Serotonin synthesis was activated only in lactating females, accompanied by increased ß-cell mass. Taken together, these findings demonstrate that ß-cell mass is decreased shortly after parturition owing to reduced ß-cell size and proliferation, and is subsequently increased, in association with lactation and serotonin biosynthesis.

Conversion of pancreatic α cells into insulin-producing cells modulated by ß-cell insufficiency and supplemental insulin administration.

The emergence of bihormonal (BH) cells expressing insulin and glucagon has been reported under diabetic conditions in humans and mice. Whereas lineage tracing studies demonstrated that glucagon-producing α cells can be reprogrammed into BH cells, the underlying dynamics of the conversion process remain poorly understood. In the present study, we investigated the identities of pancreatic endocrine cells by genetic lineage tracing under diabetic conditions. When ß-cell ablation was induced by alloxan (ALX), a time-dependent increase in BH cells was subsequently observed. Lineage tracing experiments demonstrated that BH cells originate from α cells, but not from ß cells, in ALX-induced diabetic mice. Notably, supplemental insulin administration into diabetic mice resulted in a significant increase in α-cell-derived insulin-producing cells that did not express glucagon. Furthermore, lineage tracing in Ins2Akita diabetic mice demonstrated a significant induction of α-to-ß conversion. Thus, adult α cells have plasticity, which enables them to be reprogrammed into insulin-producing cells under diabetic conditions, and this can be modulated by supplemental insulin administration.

Cellular Autophagy in α Cells Plays a Role in the Maintenance of Islet Architecture.

Autophagy is known to play a pivotal role in intracellular quality control through the degradation of subcellular damaged organelles and components. Whereas autophagy is essential for maintaining ß-cell function in pancreatic islets, it remains unclear as to how the cellular autophagy affects the homeostasis and function of glucagon-secreting α cells. To investigate the role of autophagy in α cells, we generated a mutant mouse model lacking Atg7, a key molecule for autophagosome formation, specifically in α cells. Histological analysis demonstrated more glucagon-positive cells, with a multilayered structure, in the islets under Atg7 deficiency, although metabolic profiles, such as body weight, blood glucose, and plasma glucagon levels were comparable between Atg7-deficient mice and control littermates. Consistent with our previous findings that Atg7 deficiency suppressed ß-cell proliferation, cellular proliferation was suppressed in Atg7-deficient α cells. These findings suggest that α-cell autophagy plays a role in maintaining α-cell area and normal islet architecture but appears to be dispensable for metabolic homeostasis.

Establishment of a system for screening autophagic flux regulators using a modified fluorescent reporter and CRISPR/Cas9.

Autophagy is a mechanism of bulk protein degradation that plays an important role in regulating homeostasis in many organisms. Among several methods for evaluating its activity, a fluorescent reporter GFP-LC3-RFP-LC3ΔG, in which GFP-LC3 is cleaved by ATG4 following autophagic induction and degraded in lysosome, has been used for monitoring autophagic flux, which is the amount of lysosomal protein degradation. In this study, we modified this reporter by exchanging GFP for pHluorin, which is more sensitive to low pH, and RFP to mCherry, to construct pHluorin-LC3-mCherry reporter. Following starvation or mTOR inhibition, the increase of autophagic flux was detected by a decrease of the fluorescent ratio of pHluorin to mCherry; our reporter was also more sensitive to autophagy-inducing stimuli than the previous one. To establish monitoring cells for mouse genome-wide screening of regulators of autophagic flux based on CRISPR/Cas9 system, after evaluating knockout efficiency of clones of Cas9-expressing MEFs, we co-expressed our reporter and confirmed that autophagic flux was impaired in gRNA-mediated knockout of canonical autophagy genes. Finally, we performed genome-wide gRNA screening for genes inhibiting starvation-mediated autophagic flux and identified previously reported genes such as Atgs. Thus, we have successfully established a system for screening of genes regulating autophagic flux with our pHluorin-LC3-mCherry reporter in mice.

Suppression of STAT3 signaling promotes cellular reprogramming into insulin-producing cells induced by defined transcription factors.

BACKGROUND: STAT3 has been demonstrated to play a role in maintaining cellular identities in the pancreas, whereas an activating STAT3 mutation has been linked to impaired ß-cell function. METHODS: The role of STAT3 in ß-cell neogenesis, induced by the exogenous expression of Pdx1, Neurog3, and Mafa, was analyzed in vitro and in vivo. FINDINGS: The expression of phosphorylated STAT3 (pSTAT3) was induced in both Pdx1-expressing and Mafa-expressing cells, but most of the induced ß cells were negative for pSTAT3. The suppression of STAT3 signaling, together with exogenously expressed Pdx1, Neurog3, and Mafa, significantly increased the number of reprogrammed ß cells in vitro and in vivo, enhanced the formation of islet-like clusters in mice, and ameliorated hyperglycemia in diabetic mice. INTERPRETATION: These findings suggest that STAT3 inhibition promotes cellular reprogramming into ß-like cells, orchestrated by defined transcription factors, which may lead to the establishment of cell therapies for curing diabetes. FUND: JSPS, MEXT, Takeda Science Foundation, Suzuken Memorial Foundation, Astellas Foundation for Research on Metabolic Disorders, Novo Nordisk, Eli Lilly, MSD, Life Scan, Novartis, and Takeda.

Everolimus Directly Suppresses Insulin Secretion Independently of Cell Growth Inhibition.

Everolimus, an orally administered mammalian target of rapamycin inhibitor, has been widely used as an immunosuppressant and an anticancer agent. Whereas everolimus can control recurrent hypoglycemia in patients with insulinoma, possibly through tumor regression and/or the direct inhibition of insulin secretion, time-dependent changes in serum insulin levels caused by everolimus still remain unclear. Here we report a clinical case of a patient with metastatic insulinoma, in which frequent monitoring of serum insulin levels demonstrated rapid and substantial changes in insulin secretion levels, a few days after the discontinuation as well as the readministration of everolimus. To further confirm the direct effect of everolimus on ß-cell function, we performed in vitro experiments using mouse insulinoma cells (MIN6) and human induced pluripotent stem cell (hiPSC)-derived insulin-producing cells and found that everolimus significantly suppressed glucose-stimulated insulin secretion in both MIN6 cells and hiPSC-derived insulin-producing cells. Thus, both a patient with metastatic insulinoma and in vitro experiments demonstrated that everolimus directly suppresses insulin secretion, independently of its tumor regression effect.

Heterogeneity of autophagic status in pancreatic ß cells under metabolic stress.

Autophagy in ß cells has been demonstrated to play a pivotal role in cellular homeostasis and the progression of glucose intolerance. Although autophagic activity is affected by metabolic stress both in vivo and in vitro, it remains unclear as to what extent the autophagic status in each ß cell is different from its neighboring cells. To address this question, GFP-LC3 reporter mice, which can visualize the autophagic status of each ß cell as green-fluorescent puncta, were crossed with obese diabetic db/db mice. Imaging of green-fluorescent puncta in the islets of GFP-LC3 mice revealed that ß cells are a heterogeneous population, as the density of GFP-LC3 puncta in each cell was variable. Furthermore, the variability was greater in GFP-LC3; db/db mice than in non-diabetic GFP-LC3; db/+ mice. Furthermore, when GFP-LC3 mice were treated with a low dose of S961, which antagonizes insulin signaling without inducing overt hyperglycemia, the number of ß cells with a high density of GFP puncta was increased, suggesting that insulin resistance affects autophagic status independently of glucose profiles. These results suggest that pancreatic ß cells under metabolic stress are heterogeneous regarding their autophagic status, which provides insights into the cellular dynamics of each ß cell rather than the whole ß-cell population.

RELATIONSHIP BETWEEN THE EFFECTIVENESS OF INORGANIC IODINE AND THE SEVERITY OF GRAVES THYROTOXICOSIS: A RETROSPECTIVE STUDY.

OBJECTIVE: Inorganic iodine is often used to treat patients with Graves thyrotoxicosis who do not tolerate thionamides due to adverse effects. However, predictors of continued inorganic iodine efficacy have not been fully elucidated. This study aimed to investigate the factors affecting the continued efficacy of potassium iodide (KI) in patients with Graves thyrotoxicosis. METHODS: In this study, among 1,197 patients with Graves disease who were initially treated with thionamides, we retrospectively studied 24 consecutive Japanese patients whose treatment was changed to KI alone due to the adverse effects of thionamides. We divided these patients into 2 groups: patients who had maintained euthyroid function for at least 180 days (nonrecurrence group, n = 11), and patients who had not maintained euthyroid function for 180 days (recurrence group, n = 13). RESULTS: Free triiodothyronine (FT3) and free thyroxine (FT4) levels on the day of changing from thionamides to KI were statistically higher in the recurrence group than in the nonrecurrence group (FT3, 9.3 [range, 5.2-11.6] vs. 3.7 [3.3-4.8] pg/mL, P = .02 and FT4, 3.6 [1.8-4.5] vs. 1.4 [1.2-1.9] ng/dL, P = .02). FT4 levels on the day of drug change were significantly higher in the recurrence group, even after adjusting for thionamide or KI dose. In the recurrence group, the duration of KI effect was inversed correlated with FT3 and FT4 levels on the day of drug change. CONCLUSION: Continued efficacy of KI after thionamides might be inversely correlated with thyrotoxicosis severity on the day of drug change. ABBREVIATIONS: ANOVA = analysis of variance eTV = estimated thyroid volume FT3 = free triiodothyronine FT4 = free thyroxine IQR = interquartile range KI = potassium iodide MMI = thiamazole PTU = propylthiouracil RAIT = radioactive iodine therapy TRAb = TSH receptor antibody TSH = thyroid stimulating hormone.

Comparison of the therapeutic effects of prednisolone and nonsteroidal anti-inflammatory drugs in patients with subacute thyroiditis.

Subacute thyroiditis is a transient inflammatory thyroid disease of unknown etiology. The primary goal for treatment is to mitigate inflammation. The aim of this retrospective study was to compare the therapeutic effects of prednisolone and nonsteroidal anti-inflammation drugs in patients with subacute thyroiditis. In this study, 53 consecutive Japanese patients who had been diagnosed with were referred to our hospital for further management. After excluding 11 patients (9 did not need treatment, 2 did not meet the criteria for diagnosis of subacute thyroiditis), the remaining 42 patients were treated either with prednisolone (n = 25) or loxoprofen (n = 17). We compared the time periods required for resolution of clinical symptoms and signs and normalization of thyroid function between the two groups. The mean dose of prednisolone was 15.0 (range, 14-16) mg/day and that of loxoprofen was 180 mg/day. The time period to normalization of thyroid function was comparable between the prednisolone and loxoprofen groups (25, 18-36, vs 32, 21-39 days, p = 0.388). However, the time period for resolution of symptoms was shorter under prednisolone than loxoprofen (7, 7-12 days, vs 21, 14-32 days, p < 0.001). Prednisolone treatment of patients with subacute thyroiditis was superior to nonsteroidal anti-inflammation drugs with regard to resolution of symptoms.

Evanescent Hyperechoic Changes After Fine-Needle Aspiration Biopsy of the Thyroid in a Series With a Low Overall Prevalence of Complications.

OBJECTIVES: The purpose of this study was to assess the frequency of and risk factors for fine-needle aspiration biopsy (FNAB)-related complications in Japanese patients with thyroid nodules evaluated by standard FNAB techniques. METHODS: Six hundred fifty-three consecutive Japanese patients with 742 nodules who had undergone FNAB were enrolled. Nodule characteristics were evaluated, and thyroid volumes were measured. Fine-needle aspiration biopsy-related complications were identified on the basis of sonographic findings and patients' conditions after undergoing FNAB. Comparisons of patients' backgrounds and nodule characteristics were made between those with and without complications. RESULTS: The prevalence rates for FNAB-related complications, including acute transient thyroid swelling after FNAB and appearance of anechoic lesions, were 0.13% and 0.94%. In this study, we could not identify risk factors for FNAB-related complications. The sudden appearance of bright hyperechoic foci within the thyroid immediately after biopsy was reported as an FNAB-related unfamiliar appearance in 5 cases. Experimental FNA using resected porcine thyroid tissue suggested that the etiology of the hyperechoic appearance may be artificial air bubbles or reversed flow of aspirated fluid. CONCLUSIONS: Fine-needle aspiration biopsy-related complications are rare if preventive measures are performed and are not specific to Japanese patients with thyroid nodules. The sudden appearance of bright hyperechoic foci may be cause by contamination from air or fluid.

Cutoff value of thyroid uptake of (99m)Tc-pertechnetate to discriminate between Graves' disease and painless thyroiditis: a single center retrospective study.

Thyroid uptake of (99m)Tc-pertechnetate is a useful way to determine the cause of thyrotoxicosis. In daily clinical practice, (99m)Tc-pertechnetate uptake is used to discriminate between Graves' disease and painless thyroiditis when clinical information is not enough to make the distinction. However, since the optimal cutoff value of (99m)Tc-pertechnetate uptake has not yet been elucidated, our aim was to determine this value. We recruited patients with thyrotoxicosis in whom (99m)Tc-pertechnetate uptake was measured in clinical settings between 2009 and 2013. Three experienced endocrinologists (who were blinded to the value of (99m)Tc-pertechnetate uptake and initial treatment) diagnosed the cause of thyrotoxicosis based on thyrotropin, free triiodothyronine, free thyroxine, and thyrotropin receptor antibody levels, and by ultrasound findings and using images of thyroid uptake of (99m)Tc-pertechnetate without the actual values. Ninety-four patients diagnosed as having Graves' disease or painless thyroiditis were finally included. According to the diagnosis, the optimal cutoff value of (99m)Tc-pertechnetate uptake was determined by receiver operating characteristics analysis. A cutoff value of 1.0% provided optimal sensitivity and specificity of 96.6% and 97.1%, respectively. Then, its validity was confirmed in 78 patients with confirmed Graves' disease or painless thyroiditis diagnosed at another institute. Applying this cutoff value to the patients with thyrotoxicosis revealed positive and negative predictive values for Graves' disease of 100% and 88.9%, respectively. In conclusion, a cutoff value for (99m)Tc-pertechnetate uptake of 1.0% was useful to discriminate between Graves' disease and painless thyroiditis.