Human RFX6 regulates endoderm patterning at the primitive gut tube stage

Transcriptional factor RFX6 is known to be a causal gene of Mitchell-Riley syndrome (MRS), an autosomal recessive neonatal diabetes associated with pancreatic hypoplasia and intestinal atresia/malformation. The morphological defects are limited to posterior foregut and mid-hindgut endodermal lineages and do not occur in the anterior foregut lineage; the mechanism remains to be fully elucidated. In this study, we generated RFX6+/eGFP heterozygous knockin and RFX6eGFP/eGFP homozygous knockin/knockout human-induced pluripotent stem cell (hiPSC) lines and performed in vitro endoderm differentiation to clarify the role of RFX6 in early endoderm development. RFX6 expression was found to surge at the primitive gut tube (PGT) stage in comparison with that in the undifferentiated or definitive endoderm stage. At the PGT stage, the expression of PDX1 and CDX2, posterior foregut and mid-hindgut master regulators, respectively, was decreased by the RFX6 deficit. PDX1+ and CDX2+ cells were mostly green fluorescent protein (GFP)+ in RFX6+/eGFP hiPSCs, but their cell number was markedly decreased in RFX6eGFP/eGFP hiPSCs. The expression of SOX2, an anterior foregut marker, was not affected by the RFX6 deficit. In addition, we found a putative RFX6-binding X-box motif using cap analysis of gene expression-seq and the motif-containing sequences in the enhancer regions of PDX1 and CDX2 bound to RFX6 in vitro. Thus, RFX6 regulates the ParaHox genes PDX1 and CDX2 but does not affect SOX2 in early endodermal differentiation, suggesting that defects in early stage endoderm patterning account for the morphological pathology of MRS.

Elucidation of HHEX in pancreatic endoderm differentiation using a human iPSC differentiation model

For pluripotent stem cell (PSC)-based regenerative therapy against diabetes, the differentiation efficiency to pancreatic lineage cells needs to be improved based on the mechanistic understanding of pancreatic differentiation. Here, we aimed to elucidate the molecular mechanisms underlying pancreatic endoderm differentiation by searching for factors that regulate a crucial pancreatic endoderm marker gene, NKX6.1. Unbiasedly screening an siRNA knockdown library, we identified a candidate transcription factor, HHEX. HHEX knockdown suppressed the expression of another pancreatic endoderm marker gene, PTF1A, as well as NKX6.1, independently of PDX1, a known regulator of NKX6.1 expression. In contrast, the overexpression of HHEX upregulated the expressions of NKX6.1 and PTF1A. RNA-seq analysis showed decreased expressions of several genes related to pancreatic development, such as NKX6.1, PTF1A, ONECUT1 and ONECUT3, in HHEX knockdown pancreatic endoderm. These results suggest that HHEX plays a key role in pancreatic endoderm differentiation.

Stabilization of kidney function and reduction in heart failure events with sodium-glucose co-transporter 2 inhibitors: A meta-analysis and meta-regression analysis

AIMS

Sodium-glucose co-transporter 2 (SGLT2) inhibitors reduce the risk of heart failure (HF) events regardless of diabetes status. However, factors associated with their efficacy in HF reduction remain unknown. This study aims to identify clinically relevant markers for the efficacy of SGLT2 inhibitors in HF risk reduction.

MATERIALS AND METHODS

We searched PubMed/MEDLINE and EMBASE for randomized placebo-controlled trials of SGLT2 inhibitors reporting a composite of HF hospitalization or cardiovascular death in participants with or without type 2 diabetes published until 28 February 2023. Random-effects meta-analysis and mixed-effects meta-regression were conducted to evaluate the association between the outcomes and clinical variables, including changes in glycated haemoglobin, body weight, systolic blood pressure, haematocrit and overall/chronic estimated glomerular filtration rate (eGFR) slope.

RESULTS

Thirteen trials with 90 413 participants were included. SGLT2 inhibitors reduced the hazard ratio of the composite of HF hospitalization or cardiovascular death (hazard ratio 0.77; 95% confidence interval, 0.74-0.81; p < .0001). In meta-regression analysis, chronic eGFR slope (eGFR change after the initial dip) was significantly associated with the composite outcome (p = .017), and each 1 ml/min/1.73 m² /year improvement in chronic eGFR slope led to a 14% reduction in the composite outcome. By contrast, changes in the other parameters showed no significant associations.

CONCLUSIONS

Improvement in chronic eGFR slope, which reflects the stabilization of kidney function, is significantly associated with the efficacy of the SGLT2 inhibitor in HF, highlighting the cardiorenal axis role in the beneficial effects on HF. The chronic eGFR slope can be a surrogate marker of the effects of SGLT2 inhibitors on HF reduction.

Efficacy of antihyperglycemic therapies on cardiovascular and heart failure outcomes: an updated meta-analysis and meta-regression analysis of 35 randomized cardiovascular outcome trials

BACKGROUND

Effects of antihyperglycemic therapies on cardiovascular and heart failure (HF) risks have varied widely across cardiovascular outcome trials (CVOTs), and underlying factors remain incompletely understood. We aimed to determine the relationships of glycated hemoglobin (HbA1c) or bodyweight changes with these outcomes in all CVOTs of antihyperglycemic therapies.

METHODS

We searched PubMed and EMBASE up to 25 January 2023 for all randomized controlled CVOTs of antihyperglycemic therapies reporting both major adverse cardiovascular events (MACE) and HF outcomes in patients with type 2 diabetes or prediabetes. We performed meta-regression analyses following random-effects meta-analyses to evaluate the effects of HbA1c or bodyweight reductions on each outcome.

RESULTS

Thirty-five trials comprising 256,524 patients were included. Overall, antihyperglycemic therapies reduced MACE by 9% [risk ratio (RR): 0.91; 95% confidence interval (CI) 0.88-0.94; P < 0.001; I2 = 36.5%]. In meta-regression, every 1% greater reduction in HbA1c was associated with a 14% reduction in the RR of MACE (95% CI 4-24; P = 0.010), whereas bodyweight change was not associated with the RR of MACE. The magnitude of the reduction in MACE risk associated with HbA1c reduction was greater in trials with a higher baseline prevalence of atherosclerotic cardiovascular disease. On the other hand, antihyperglycemic therapies showed no overall significant effect on HF (RR: 0.95; 95% CI 0.87-1.04; P = 0.28; I2 = 75.9%). In a subgroup analysis based on intervention type, sodium-glucose cotransporter-2 inhibitors (SGLT2i) conferred the greatest HF risk reduction (RR: 0.68; 95% CI 0.62-0.75; P < 0.001; I2 = 0.0%). In meta-regression, every 1 kg bodyweight reduction, but not HbA1c reduction, was found to reduce the RR of HF by 7% (95% CI 4-10; P < 0.001); however, significant residual heterogeneity (P < 0.001) was observed, and SGLT2i reduced HF more than could be explained by HbA1c or bodyweight reductions.

CONCLUSIONS

Antihyperglycemic therapies reduce MACE in an HbA1c-dependent manner. These findings indicate that HbA1c can be a useful marker of MACE risk reduction across a wide range of antihyperglycemic therapies, including drugs with pleiotropic effects. In contrast, HF is reduced not in an HbA1c-dependent but in a bodyweight-dependent manner. Notably, SGLT2i have shown class-specific benefits for HF beyond HbA1c or bodyweight reductions.

Exploratory study on glycemic control improvement for patients with diabetes mellitus by appropriate re-education on insulin self-injection technique during COVID-19 pandemic

AIMS

To conduct a study on glycemic control improvement by appropriate re-education on the self-injection technique (SIT) in patients with diabetes mellitus undergoing insulin therapy.

METHODS

Patients who received appropriate SIT and were treated with insulin for more than a year were re-educated. For the observation period of six months, the subjects' SIT was checked, and hemoglobin A1c (HbA1c) levels were measured at each visit. HbA1c levels, insulin doses, and behavioral changes in SIT were investigated at baseline and at the end of the observation period.

RESULTS

In the per-protocol set population, the HbA1c level decreased by 0.2 % (2.0 mmol/mol) on average, showing a significant difference (p = 0.009). No significant difference was observed in the proportion of subjects with decreased HbA1c levels, changes in total daily insulin doses, or blood glucose levels. Four of the six SIT items covered by re-education were improved.

CONCLUSIONS

Providing re-education on insulin SIT was considered effective in reducing HbA1c levels and improving adherence to proper SIT.

Big insulin-like growth factor 2-producing multiple solitary fibrous tumors treated with debulking surgery: A case report

BACKGROUND

Non-islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic syndrome caused by a tumor-producing high molecular weight form of insulin-like growth factor 2 (IGF2) known as big IGF2. The only curative treatment for this condition is surgical resection of the responsible tumors. However, this may not be feasible in cases with multiple metastases at diagnosis of NICTH, and no standard treatment strategy for multiple tumors has been established. The effects of pharmacological therapies including somatostatin analogs are often inefficient and remain difficult to predict.

CASE DESCRIPTION

A 68-year-old man was admitted to our hospital due to impaired consciousness and severe hypoglycemia. His medical history included diagnosis of a left temporal solitary fibrous tumor (SFT) at the age of 48 years, after which local recurrent and metastatic tumors were repeatedly resected. Four years before admission, multiple intraabdominal and subcutaneous tumors were detected and, being asymptomatic, were managed conservatively. Laboratory exam on admission demonstrated hypoglycemia accompanied with low serum insulin and IGF1 levels. Computed tomography (CT) scan revealed multiple intraabdominal and subcutaneous tumors increasing in size. Serum big IGF2 was detected on immunoblot analysis, and he was diagnosed as NICTH. In addition, tumor uptake was observed on ⁶⁸Ga-labelled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe¹-Tyr³-octreotide positron emission tomography/CT (DOTATOC-PET/CT). Since larger tumor is more suspicious about responsible producibility of big IGF2, we planned to resect large ones preferentially and reduce the amounts of residual tumors. Debulking surgery was performed by removing eleven intraabdominal tumors; the hypoglycemia was then completely corrected. Histological analyses revealed the resected tumors to be metastases of SFT having somatostatin receptor 2 expression. In immunoblot analysis, the resected tumors were found to be positive for big IGF2; serum big IGF2 was undetectable after surgery.

CONCLUSION

We present a case of NICTH with multiple metastatic SFTs. We strategically performed debulking surgery, which led to remission of hypoglycemia. This result demonstrates a pioneering practical solution for NICTH cases with multiple tumors. In addition, in cases of SFTs presenting with NICTH, positivity of DOTATOC-PET/CT as well as single-dose administration of octreotide may be predictive of the efficacy of somatostatin-based therapy.

A unique profile of insulin antibody titer in islet-transplanted patients

Insulin antibodies (IAs) can cause glycemic variability. Islet transplantation (ITx) is a treatment for insulin‐deficient diabetes that aims to establish on‐target glycemic control in the absence of hypoglycemia. To date, there has not been a detailed case study of the association between ITx and IA levels. In this study, we identified a unique profile of IA titers, which differed from glutamic acid decarboxylase antibody titers, in four ITx patients. IA levels decreased with intensified immunosuppressive therapy, whereas glutamic acid decarboxylase antibodies increased transiently after ITx. These data suggest the possibility that IAs, unlike other islet autoantibodies, were eliminated due to immunosuppression after transplantation therapy. The disappearance of IAs, as well as the restoration of regulated insulin secretion after ITx, might have a positive effect on glycemic control in recipients with diabetes. Furthermore, this unique feature is suggestive of immunological pathogenesis and has implications for the treatment of IA‐causing disease conditions.

Plant sterol hyperabsorption caused by uncontrolled diabetes in a patient with a heterozygous ABCG5 variant

Plant sterol intake is widely recommended in patients with cardiovascular risk factors based on the inhibitory effect on intestinal cholesterol absorption. Although plant sterols, once absorbed, can promote atherosclerosis, their intake is believed to be safe because of poor absorption, except in rare hyperabsorbers with homozygous ABCG5/8 mutations. We report a case of new-onset type 1 diabetes accompanied by hypercholesterolemia. At the initial presentation with diabetic ketoacidosis, the patient showed marked hypercholesterolemia. Whole-exome sequencing revealed a heterozygous pathogenic variant in ABCG5 (p.R419H). The initial serum plant sterol levels were markedly high (sitosterol, 32.5 μg/mL; campesterol, 66.0 μg/mL) close to the range observed in patients with homozygous ABCG5/8 mutations, which were largely reduced by insulin treatment without ezetimibe. The addition of ezetimibe normalized plant sterol levels. These findings provide the first evidence that uncontrolled diabetes plays a causal role in the pathogenesis of phytosterolemia.

Exploring a Suitable Marker of Glycemic Response to Dulaglutide in Patients with Type 2 Diabetes: A Retrospective Study

INTRODUCTION

Previous studies suggested that β-cell function markers such as fasting and postprandial serum C-peptide and C-peptide increment (FCPR, PCPR, and ΔCPR, respectively) may be useful in estimating glycemic response to glucagon-like peptide-1 receptor agonists. However, it remains elusive whether baseline glycemic control confounds these markers. Here we aimed to identify the least confounded β-cell function markers and investigate whether these markers could predict glycemic response to dulaglutide.

METHODS

We evaluated FCPR, PCPR, and ΔCPR levels in patients with type 2 diabetes who initiated dulaglutide treatment after a standardized meal tolerance test (MTT). We first investigated the confounding effects of baseline HbA1c on β-cell function markers using Pearson's correlation test. Then, we evaluated the association between each β-cell function marker and glycemic response (HbA1c change 0-6 months) to dulaglutide using generalized linear model and logistic regression analysis with adjustment for baseline HbA1c.

RESULTS

In 141 patients, baseline HbA1c was significantly inversely correlated with PCPR and ΔCPR (P < 0.01 for both) but not with FCPR (r = 0.02; P = 0.853), suggesting that FCPR was the marker least confounded by baseline glycemic control. Of all patients, 59 continued dulaglutide for at least 6 months without initiating any additional glucose-lowering medications. Mean ± SE HbA1c change 0-6 months was - 1.16 ± 0.17% (P < 0.001 vs. baseline). The β-cell function markers were significantly associated with HbA1c change 0-6 months in the generalized linear model. FCPR was also a significant predictor for achieving a reduction in HbA1c of at least 1% (P = 0.044) with an area under the receiver operating characteristic curve of 0.83 (sensitivity = 0.81 and specificity = 0.79).

CONCLUSION

Fasting and meal-induced C-peptide levels are associated with glycemic response to dulaglutide, among which FCPR is least confounded by baseline glycemic control, suggesting its utility as a marker for glycemic response to dulaglutide.

Sporadic Pseudohypoparathyroidism Type 1B in Monozygotic Twins: Insights Into the Pathogenesis of Methylation Defects

CONTEXT

Sporadic pseudohypoparathyroidism type 1B (sporPHP1B) is an imprinting disease without a defined genetic cause, characterized by broad methylation changes in differentially methylated regions (DMRs) of the GNAS gene.

OBJECTIVE

This work aims to provide insights into the causative event leading to the GNAS methylation defects through comprehensive molecular genetic analyses of a pair of female monozygotic twins concordant for sporPHP1B who were conceived naturally, that is, without assisted reproductive techniques.

METHODS

Using the leukocyte genome of the twins and family members, we performed targeted bisulfite sequencing, methylation-sensitive restriction enzyme (MSRE)-quantitative polymerase chain reaction (qPCR), whole-genome sequencing (WGS), high-density single-nucleotide polymorphism (SNP) array, and Sanger sequencing.

RESULTS

Methylation analyses by targeted bisulfite sequencing and MSRE-qPCR revealed almost complete losses of methylation at the GNAS AS, XL, and A/B DMRs and a gain of methylation at the NESP55 DMR in the twins, but not in other family members. Except for the GNAS locus, we did not find apparent methylation defects at other imprinted genome loci of the twins. WGS, SNP array, and Sanger sequencing did not detect the previously described genetic defects associated with familial PHP1B. Sanger sequencing also ruled out any novel genetic alterations in the entire NESP55/AS region. However, the analysis of 28 consecutive SNPs could not exclude the possibility of paternal heterodisomy in a span of 22 kb comprising exon NESP55 and AS exon 5.

CONCLUSION

Our comprehensive analysis of a pair of monozygotic twins with sporPHP1B ruled out all previously described genetic causes. Twin concordance indicates that the causative event was an imprinting error earlier than the timing of monozygotic twinning.

First Japanese Family With PDX1-MODY (MODY4): A Novel PDX1 Frameshift Mutation, Clinical Characteristics, and Implications

CONTEXT

The PDX1 gene encodes pancreatic and duodenal homeobox, a critical transcription factor for pancreatic β-cell differentiation and maintenance of mature β-cells. Heterozygous loss-of-function mutations cause PDX1-MODY (MODY4).

CASE DESCRIPTION

Our patient is an 18-year-old lean man who developed diabetes at 16 years of age. Given his early-onset age and leanness, we performed genetic testing. Targeted next-generation sequencing and subsequent Sanger sequencing detected a novel heterozygous frameshift mutation (NM_00209.4:c.218delT. NP_000200.1: p.Leu73Profs*50) in the PDX1 transactivation domain that resulted in loss-of-function and was validated by an in vitro functional study. The proband and his 56-year-old father, who had the same mutation, both showed markedly reduced insulin and gastric inhibitory polypeptide (GIP) secretion compared with the dizygotic twin sister, who was negative for the mutation and had normal glucose tolerance. The proband responded well to sitagliptin, suggesting its utility as a treatment option. Notably, the proband and his father showed intriguing phenotypic differences: the proband had been lean for his entire life but developed early-onset diabetes requiring an antihyperglycemic agent. In contrast, his father was overweight, developed diabetes much later in life, and did not require medication, suggesting the oligogenic nature of PDX1-MODY. A review of all reported cases of PDX1-MODY also showed heterogeneous phenotypes regarding onset age, obesity, and treatment, even in the presence of the same mutation.

CONCLUSIONS

We identified the first Japanese family with PDX1-MODY. The similarities and differences found among the cases highlight the wide phenotypic spectrum of PDX1-MODY.

Sporadic Pseudohypoparathyroidism 1B in Monozygotic Twins: Insights Into the Pathogenesis of Methylation Defects

Background: Pseudohypoparathyroidism (PHP) 1B is an imprinting disorder characterized by renal resistance to parathyroid hormone (PTH) without Albright Hereditary Osteodystrophy (AHO). PHP1B is associated with methylation defects at the GNAS differentially methylated regions (DMRs). In sporadic cases with PHP1B, the mechanistic basis of methylation defects remains to be solved, except in rare cases with uniparental disomy of chromosome 20. In addition, to date, monozygotic twin cases with sporadic PHP1B have not been reported.

Clinical Case: The patients were 26-year-old Japanese female monozygotic twins. They had been born to nonconsanguineous parents after an uneventful pregnancy. Both twins had common biochemical features, including hypocalcemia, hyperphosphatemia, elevated PTH levels, and impaired urinary excretion of phosphorus and cAMP in response to teriparatide. They showed no signs of AHO. The serum calcium levels of their parents and brother were within the normal range, and family history was unremarkable. Based on these findings, the twins were diagnosed with PHP1B. Targeted bisulfite sequencing of the GNAS DMRs in all family members revealed almost complete gain-of-methylation at the NESP55 DMR, and loss-of-methylation at the AS, XL, and A/B DMRs in the twins, but not in other family members. Except for the GNAS locus, we did not find clear methylation defects in other imprinted genome loci in the twins. Methylation defects at the GNAS locus were further confirmed by methylation-sensitive restriction enzyme-qPCR. Whole-genome sequencing of the twins showed no pathogenic variants in the GNAS exons encoding the Gs alpha subunit. No large deletions or insertions were found at the STX16 locus or in the region from AS exon 5 to XL. Based on the SNP genotyping results, large paternal isodisomies in the GNAS DMRs were unlikely. Collectively, these results suggested that the twins had concordant methylation defects that are seen in the sporadic form of PHP1b. We speculate that an early developmental event before the twin splitting is responsible for the abnormal methylation of the GNAS DMRs.

Conclusion: We report, for the first time, monozygotic twins with sporadic PHP1B who were phenotypically and epigenetically concordant. Our comprehensive molecular genetic analyses have thus far ruled out the previously described genetic defects underlying PHP1B. The current findings provide new insights into the mechanistic basis of the GNAS methylation defects in sporadic PHP1B.

"Switched" metabolic acidosis in mitochondrial diabetes mellitus

A patient with mitochondrial diabetes mellitus developed diabetic ketoacidosis. During insulin treatment, although diabetic ketoacidosis improved, lactic acidosis unexpectedly worsened. This clinical course, named “switched metabolic acidosis,” could reflect the unique pathophysiology of the mitochondrial disorder.