Search

Genome-wide association studies have identified several hundred loci associated with type 2 diabetes mellitus (T2DM). Additionally, pathogenic variants in several genes are known to cause monogenic diabetes that overlaps clinically with T2DM. Whole-exome sequencing of related individuals with T2DM is a powerful approach to identify novel high-penetrance disease variants in coding regions of the genome. We performed whole-exome sequencing on four related individuals with T2DM - including one individual diagnosed at the age of 33 years. The individuals were negative for mutations in monogenic diabetes genes, had a strong family history of T2DM, and presented with several characteristics of metabolic syndrome. A missense variant (p.N2291D) in the type 2 ryanodine receptor (RyR2) gene was one of eight rare coding variants shared by all individuals. The variant was absent in large population databases and affects a highly conserved amino acid located in a mutational hotspot for pathogenic variants in Catecholaminergic polymorphic ventricular tachycardia (CPVT). Electrocardiogram data did not reveal any cardiac abnormalities except a lower-than-normal resting heart rate (< 60 bpm) in two individuals - a phenotype observed in CPVT individuals with RyR2 mutations. RyR2-mediated Ca2+ release contributes to glucose-mediated insulin secretion and pathogenic RyR2 mutations cause glucose intolerance in humans and mice. Analysis of glucose tolerance testing data revealed that missense mutations in a CPVT mutation hotspot region - overlapping the p.N2291D variant - are associated with complete penetrance for glucose intolerance. In conclusion, we have identified an atypical missense variant in the RyR2 gene that co-segregates with diabetes in the absence of overt CPVT. [ABSTRACT FROM AUTHOR]

Genome-wide association studies have identified several hundred loci associated with type 2 diabetes mellitus (T2DM). Additionally, pathogenic variants in several genes are known to cause monogenic diabetes that overlaps clinically with T2DM. Whole-exome sequencing of related individuals with T2DM is a powerful approach to identify novel high-penetrance disease variants in coding regions of the genome. We performed whole-exome sequencing on four related individuals with T2DM – including one individual diagnosed at the age of 33 years. The individuals were negative for mutations in monogenic diabetes genes, had a strong family history of T2DM, and presented with several characteristics of metabolic syndrome. A missense variant (p.N2291D) in the type 2 ryanodine receptor (RyR2) gene was one of eight rare coding variants shared by all individuals. The variant was absent in large population databases and affects a highly conserved amino acid located in a mutational hotspot for pathogenic variants in Catecholaminergic polymorphic ventricular tachycardia (CPVT). Electrocardiogram data did not reveal any cardiac abnormalities except a lower-than-normal resting heart rate (< 60 bpm) in two individuals – a phenotype observed in CPVT individuals with RyR2 mutations. RyR2-mediated Ca2+ release contributes to glucose-mediated insulin secretion and pathogenic RyR2 mutations cause glucose intolerance in humans and mice. Analysis of glucose tolerance testing data revealed that missense mutations in a CPVT mutation hotspot region – overlapping the p.N2291D variant – are associated with complete penetrance for glucose intolerance. In conclusion, we have identified an atypical missense variant in the RyR2 gene that co-segregates with diabetes in the absence of overt CPVT.

Cellular senescence is a response to a wide variety of stressors, including DNA damage, oncogene activation and physiologic aging, and pathologically accelerated senescence contributes to human disease, including diabetes mellitus. Indeed, recent work in this field has demonstrated a role for pancreatic β-cell senescence in the pathogenesis of Type 1 Diabetes, Type 2 Diabetes and monogenic diabetes. Small molecule or genetic targeting of senescent β-cells has shown promise as a novel therapeutic approach for preventing and treating diabetes. Despite these advances, major questions remain around the molecular mechanisms driving senescence in the β-cell, identification of molecular markers that distinguish senescent from nonsenescent β-cell subpopulations, and translation of proof-of-concept therapies into novel treatments for diabetes in humans. Here, we summarize the current state of the field of β-cell senescence, highlighting insights from mouse models as well as studies on human islets and β-cells. We identifymarkers that have been used to detect β-cell senescence to unify future research efforts in this field. We discuss emerging concepts of the natural history of senescence in β-cells, heterogeneity of senescent β-cells subpopulations, role of sex differences in senescent responses, and the consequences of senescence on integrated islet function and microenvironment. As a young and developing field, there remain many open research questions which need to be addressed to move senescence-targeted approaches towards clinical investigation. [ABSTRACT FROM AUTHOR]

Aims: Wolfram Syndrome Spectrum Disorder (WFS1-SD), in its "classic" form, is a rare autosomal recessive disease with poor prognosis and wide phenotypic spectrum. Insulin dependent diabetes mellitus (DM), optic atrophy (OA) diabetes insipidus (DI) and sensorineural deafness (D) are the main features of WFS1-SD. Gonadal dysfunction (GD) has been described mainly in adults with variable prevalence and referred to as a minor clinical feature. This is the first case series investigating gonadal function in a small cohort of paediatric patients affected by WFS1-SD. Methods: Gonadal function was investigated in eight patients (3 male and 5 female) between 3 and 16 years of age. Seven patients have been diagnosed with classic WFS1-SD and one with non-classic WFS1-SD. Gonadotropin and sex hormone levels were monitored, as well as markers of gonadal reserve (inhibin-B and anti-Mullerian hormone). Pubertal progression was assessed according to Tanner staging. Results: Primary hypogonadism was diagnosed in 50% of patients (n=4), more specifically 67% (n=2) of males and 40% of females (n=2). Pubertal delay was observed in one female patient. These data confirm that gonadal dysfunction may be a frequent and underdiagnosed clinical feature in WFS1-SD. Conclusions: GD may represent a frequent and earlier than previously described feature in WFS1-SD with repercussions on morbidity and quality of life. Consequently, we suggest that GD should be included amongst clinical diagnostic criteria for WFS1-SD, as has already been proposed for urinary dysfunction. Considering the heterogeneous and elusive presentation of WFS1-SD, this clinical feature may assist in an earlier diagnosis and timely follow-up and care of treatable associated diseases (i.e. insulin and sex hormone replacement) in these young patients. [ABSTRACT FROM AUTHOR]

Aims: Monogenic diabetes accounts for 1-2% of diabetes cases yet is often misdiagnosed as type 2 diabetes. The aim of this study was to examine in Māori and Pacific adults clinically diagnosed with type 2 diabetes within 40 years of age, (a) the prevalence of monogenic diabetes in this population (b) the prevalence of beta-cell autoantibodies and (c) the pre-test probability of monogenic diabetes. Methods: Targeted sequencing data of 38 known monogenic diabetes genes was analyzed in 199 Māori and Pacific peoples with BMI of 37.9 ± 8.6 kg/m² who had been diagnosed with type 2 diabetes between 3 and 40 years of age. A triplescreen combined autoantibody assay was used to test for GAD, IA-2, and ZnT8. MODY probability calculator score was generated in those with sufficient clinical information (55/199). Results: No genetic variants curated as likely pathogenic or pathogenic were found. One individual (1/199) tested positive for GAD/IA-2/ZnT8 antibodies. The pre-test probability of monogenic diabetes was calculated in 55 individuals with 17/55 (31%) scoring above the 20% threshold considered for diagnostic testing referral. Discussion: Our findings suggest that monogenic diabetes is rare in Māori and Pacific people with clinical age, and the MODY probability calculator likely overestimates the likelihood of a monogenic cause for diabetes in this population. [ABSTRACT FROM AUTHOR]

Neonatal diabetes mellitus (NDM) is a rare genetic disease characterized by severe hyperglycemia requiring insulin therapy with onsetmostly within the first 6 months and rarely between 6-12 months of age. The disease can be classified into transient (TNDM) or permanent neonatal diabetes mellitus (PNDM), or it can be a component of a syndrome. The most frequent genetic causes are abnormalities of the 6q24 chromosomal region and mutations of the ABCC8 or KCNJ11 genes coding for the pancreatic beta cell's potassium channel (KATP). After the acute phase, patients with ABCC8 or KCNJ11 mutations treated with insulin therapy can switch to hypoglycemic sulfonylureas (SU). These drugs close the KATP channel binding the SUR1 subunit of the potassium channel and restoring insulin secretion after a meal. The timing of this switch can be different and could affect long-term complications. We describe the different management and clinical outcome over the time of two male patients with NDM due to KCNJ11 pathogenetic variants. In both cases, continuous subcutaneous insulin infusion pumps (CSII) were used to switch therapy from insulin to SU, but at different times after the onset. The two patients kept adequate metabolic control after the introduction of glibenclamide; during the treatment, insulin secretion was evaluated with c-peptide, fructosamine, and glycated hemoglobin (HbA1c), which were within the normal range. In neonates or infants with diabetes mellitus, genetic testing is an indispensable diagnostic tool and KCNJ11 variants should be considered. A trial of oral glibenclamide must be considered, switching from insulin, the first line of NDM treatment. This therapy can improve neurological and neuropsychological outcomes, in particular in the case of earlier treatment initiation. A new modified protocol with glibenclamide administered several times daily according to continuous glucose monitoring profile indications, was used. Patients treated with glibenclamide maintain good metabolic control and prevent hypoglycemia, neurological damage, and apoptosis of beta cells during long-term administration. [ABSTRACT FROM AUTHOR]

AimsWolfram Syndrome Spectrum Disorder (WFS1-SD), in its “classic” form, is a rare autosomal recessive disease with poor prognosis and wide phenotypic spectrum. Insulin dependent diabetes mellitus (DM), optic atrophy (OA) diabetes insipidus (DI) and sensorineural deafness (D) are the main features of WFS1-SD. Gonadal dysfunction (GD) has been described mainly in adults with variable prevalence and referred to as a minor clinical feature. This is the first case series investigating gonadal function in a small cohort of paediatric patients affected by WFS1-SD.MethodsGonadal function was investigated in eight patients (3 male and 5 female) between 3 and 16 years of age. Seven patients have been diagnosed with classic WFS1-SD and one with non-classic WFS1-SD. Gonadotropin and sex hormone levels were monitored, as well as markers of gonadal reserve (inhibin-B and anti-Mullerian hormone). Pubertal progression was assessed according to Tanner staging.ResultsPrimary hypogonadism was diagnosed in 50% of patients (n=4), more specifically 67% (n=2) of males and 40% of females (n=2). Pubertal delay was observed in one female patient. These data confirm that gonadal dysfunction may be a frequent and underdiagnosed clinical feature in WFS1-SD.ConclusionsGD may represent a frequent and earlier than previously described feature in WFS1-SD with repercussions on morbidity and quality of life. Consequently, we suggest that GD should be included amongst clinical diagnostic criteria for WFS1-SD, as has already been proposed for urinary dysfunction. Considering the heterogeneous and elusive presentation of WFS1-SD, this clinical feature may assist in an earlier diagnosis and timely follow-up and care of treatable associated diseases (i.e. insulin and sex hormone replacement) in these young patients.

AimsMonogenic diabetes accounts for 1-2% of diabetes cases yet is often misdiagnosed as type 2 diabetes. The aim of this study was to examine in Māori and Pacific adults clinically diagnosed with type 2 diabetes within 40 years of age, (a) the prevalence of monogenic diabetes in this population (b) the prevalence of beta-cell autoantibodies and (c) the pre-test probability of monogenic diabetes.MethodsTargeted sequencing data of 38 known monogenic diabetes genes was analyzed in 199 Māori and Pacific peoples with BMI of 37.9 ± 8.6 kg/m2 who had been diagnosed with type 2 diabetes between 3 and 40 years of age. A triple-screen combined autoantibody assay was used to test for GAD, IA-2, and ZnT8. MODY probability calculator score was generated in those with sufficient clinical information (55/199).ResultsNo genetic variants curated as likely pathogenic or pathogenic were found. One individual (1/199) tested positive for GAD/IA-2/ZnT8 antibodies. The pre-test probability of monogenic diabetes was calculated in 55 individuals with 17/55 (31%) scoring above the 20% threshold considered for diagnostic testing referral.DiscussionOur findings suggest that monogenic diabetes is rare in Māori and Pacific people with clinical age, and the MODY probability calculator likely overestimates the likelihood of a monogenic cause for diabetes in this population.

Neonatal diabetes mellitus (NDM) is a rare genetic disease characterized by severe hyperglycemia requiring insulin therapy with onset mostly within the first 6 months and rarely between 6-12 months of age. The disease can be classified into transient (TNDM) or permanent neonatal diabetes mellitus (PNDM), or it can be a component of a syndrome. The most frequent genetic causes are abnormalities of the 6q24 chromosomal region and mutations of the ABCC8 or KCNJ11 genes coding for the pancreatic beta cell’s potassium channel (KATP). After the acute phase, patients with ABCC8 or KCNJ11 mutations treated with insulin therapy can switch to hypoglycemic sulfonylureas (SU). These drugs close the KATP channel binding the SUR1 subunit of the potassium channel and restoring insulin secretion after a meal. The timing of this switch can be different and could affect long-term complications. We describe the different management and clinical outcome over the time of two male patients with NDM due to KCNJ11 pathogenetic variants. In both cases, continuous subcutaneous insulin infusion pumps (CSII) were used to switch therapy from insulin to SU, but at different times after the onset. The two patients kept adequate metabolic control after the introduction of glibenclamide; during the treatment, insulin secretion was evaluated with c-peptide, fructosamine, and glycated hemoglobin (HbA1c), which were within the normal range. In neonates or infants with diabetes mellitus, genetic testing is an indispensable diagnostic tool and KCNJ11 variants should be considered. A trial of oral glibenclamide must be considered, switching from insulin, the first line of NDM treatment. This therapy can improve neurological and neuropsychological outcomes, in particular in the case of earlier treatment initiation. A new modified protocol with glibenclamide administered several times daily according to continuous glucose monitoring profile indications, was used. Patients treated with glibenclamide maintain good metabolic control and prevent hypoglycemia, neurological damage, and apoptosis of beta cells during long‐term administration.

Aims: To evaluate (a) the diagnostic yield of genetic testing for monogenic diabetes when using single gene and gene panel-based testing approaches in the New Zealand (NZ) population, (b) whether the MODY (Maturity Onset Diabetes of the Young) pre-test probability calculator can be used to guide referrals for testing in NZ, c) the number of referrals for testing for Maori/Pacific ethnicities compared to NZ European, and (d) the volume of proband vs cascade tests being requested. Methods: A retrospective audit of 495 referrals, from NZ, for testing of monogenic diabetes genes was performed. Referrals sent to LabPlus Auckland) laboratory for single gene testing or small multi-gene panel testing, or to the Exeter Genomics Laboratory, UK, for a large gene panel, received from January 2014 -- December 2021 were included. Detection rates of single gene, small multi-gene and large gene panels (neonatal and non-neonatal), and cascade testing were analysed. Pre-test probability was calculated using the Exeter MODY probability calculator and ethnicity data was also collected. Results: The diagnostic detection rate varied across genes, from32% inGCK, to 2% in HNF4A, with single gene or small gene panel testing averaging a 12% detection rate. Detection rate by type of panel was 9% for small gene panel, 23% for nonneonatal monogenic diabetes large gene panel and 40% for neonatal monogenic diabetes large gene panel. 45% (67/147) of patients aged 1-35 years at diabetes diagnosis scored <20% on MODY pre-test probability, of whom 3 had class 4/5 variants in HNF1A, HNF4A or HNF1B. Ethnicity data of those selected for genetic testing correlated with population diabetes prevalence for Māori (15% vs 16%), but Pacific People appeared under-represented (8% vs 14%). Only 1 in 6 probands generated a cascade test. Conclusions: A new monogenic diabetes testing algorithm for NZ is proposed, which directs clinicians to choose a large gene panel in patients without syndromic features who score a pre-test MODY probability of above 20%. [ABSTRACT FROM AUTHOR]

AimsTo evaluate (a) the diagnostic yield of genetic testing for monogenic diabetes when using single gene and gene panel-based testing approaches in the New Zealand (NZ) population, (b) whether the MODY (Maturity Onset Diabetes of the Young) pre-test probability calculator can be used to guide referrals for testing in NZ, (c) the number of referrals for testing for Māori/Pacific ethnicities compared to NZ European, and (d) the volume of proband vs cascade tests being requested.MethodsA retrospective audit of 495 referrals, from NZ, for testing of monogenic diabetes genes was performed. Referrals sent to LabPlus (Auckland) laboratory for single gene testing or small multi-gene panel testing, or to the Exeter Genomics Laboratory, UK, for a large gene panel, received from January 2014 – December 2021 were included. Detection rates of single gene, small multi-gene and large gene panels (neonatal and non-neonatal), and cascade testing were analysed. Pre-test probability was calculated using the Exeter MODY probability calculator and ethnicity data was also collected.ResultsThe diagnostic detection rate varied across genes, from 32% in GCK, to 2% in HNF4A, with single gene or small gene panel testing averaging a 12% detection rate. Detection rate by type of panel was 9% for small gene panel, 23% for non-neonatal monogenic diabetes large gene panel and 40% for neonatal monogenic diabetes large gene panel. 45% (67/147) of patients aged 1-35 years at diabetes diagnosis scored

Monogenic diabetes is a rare form of diabetes, accounting for approximately 1% to 6% of pediatric diabetes patients. Some types of monogenic diabetes can be misdiagnosed as type 1 diabetes in children or adolescents because of similar clinical features. Identification of the correct etiology of diabetes is crucial for clinical, therapeutic, and prognostic issues. Our main objective was to determine the prevalence of monogenic diabetes in patients with diabetes mellitus, diagnosed in childhood or in adolescence, and negative autoimmunity. We retrospectively analyzed clinical data of 275 patients diagnosed with insulin-dependent diabetes at age <18yr in the last 10 years. 8.4% of subjects has negative autoimmunity. Their DNA was sequenced by NGS custom panel composed by 45 candidate genes involved in glucose metabolism disorder. Two novel heterozygous pathogenic or likely pathogenic variants (10,5% of autoantibody negative subjects) were detected: the frameshift variant c.617_618insA in NEUROD1 exon 2 and the missense change c.116T>C in INS exon 2. Our study corroborates previous results of other reports in literature. NGS assays are useful methods for a correct diagnosis of monogenic diabetes, even of rarest forms, highlighting mechanisms of pediatric diabetes pathogenesis. [ABSTRACT FROM AUTHOR]

Monogenic forms of diabetes mellitus may affect a significant number of patients of this disease, and it is an important molecular cause to be investigated. However, studies of the genetic causes of monogenic diabetes, especially in populations with mixed ethnic backgrounds, such as the one in Brazil, are scarce. The aim of this study was to screen several genes associated with monogenic diabetes in fifty-seven Brazilian patients with recurrence of the disease in their families and thirty-four relatives. Inclusion criteria were: Age of onset ≤ 40 years old, BMI < 30 kg/m², at least two affected generations and negative anti-GAD and anti-IA2 antibodies. MODY genes HNF4A , GCK , HNF1A , HNF1B , NEUROD1 , KLF11 , PAX4 , INS , KCNJ11 , and MT-TL1 were sequenced by Sanger sequencing. We identified a total of 20 patients with variants, 13 GCK-MODY, four HNF1A-MODY, and one variant in each of the following genes, HNF4A , HNF1B and MT-TL1. Segregation analysis was performed in 13 families. Four variants were novel, two in GCK (p.(Met115Val) [c.343A>G] and p.(Asp365GlufsTer95) [c.1094_1095insGCGA]) and two in HNF1A (p.(Tyr163Ter) [c.489C>G] and p.(Val380CysfsTer39) [c.1136_1137insC]). Here we highlight the importance of screening for monogenic diabetes in admixed populations. [ABSTRACT FROM AUTHOR]

Monogenic diabetes is a rare form of diabetes, accounting for approximately 1% to 6% of pediatric diabetes patients. Some types of monogenic diabetes can be misdiagnosed as type 1 diabetes in children or adolescents because of similar clinical features. Identification of the correct etiology of diabetes is crucial for clinical, therapeutic, and prognostic issues. Our main objective was to determine the prevalence of monogenic diabetes in patients with diabetes mellitus, diagnosed in childhood or in adolescence, and negative autoimmunity. We retrospectively analyzed clinical data of 275 patients diagnosed with insulin-dependent diabetes at age C in INS exon 2. Our study corroborates previous results of other reports in literature. NGS assays are useful methods for a correct diagnosis of monogenic diabetes, even of rarest forms, highlighting mechanisms of pediatric diabetes pathogenesis.

Monogenic forms of diabetes mellitus may affect a significant number of patients of this disease, and it is an important molecular cause to be investigated. However, studies of the genetic causes of monogenic diabetes, especially in populations with mixed ethnic backgrounds, such as the one in Brazil, are scarce. The aim of this study was to screen several genes associated with monogenic diabetes in fifty-seven Brazilian patients with recurrence of the disease in their families and thirty-four relatives. Inclusion criteria were: Age of onset ≤ 40 years old, BMI < 30 kg/m², at least two affected generations and negative anti-GAD and anti-IA2 antibodies. MODY genes HNF4A, GCK, HNF1A, HNF1B, NEUROD1, KLF11, PAX4, INS, KCNJ11, and MT-TL1 were sequenced by Sanger sequencing. We identified a total of 20 patients with variants, 13 GCK-MODY, four HNF1A-MODY, and one variant in each of the following genes, HNF4A, HNF1B and MT-TL1. Segregation analysis was performed in 13 families. Four variants were novel, two in GCK (p.(Met115Val) [c.343A>G] and p.(Asp365GlufsTer95) [c.1094_1095insGCGA]) and two in HNF1A (p.(Tyr163Ter) [c.489C>G] and p.(Val380CysfsTer39) [c.1136_1137insC]). Here we highlight the importance of screening for monogenic diabetes in admixed populations.

Toxic misfolding of proinsulin variants in β-cells defines a monogenic diabetes syndrome, designated mutant INS-gene induced diabetes of the young (MIDY). In our first study (previous article in this issue), we described a one-disulfide peptide model of a proinsulin folding intermediate and its use to study such variants. The mutations (LeuB15→Pro, LeuA16→Pro, and PheB24→Ser) probe residues conserved among vertebrate insulins. In this companion study, we describe 1H and 1H-13C NMR studies of the peptides; key NMR resonance assignments were verified by synthetic 13C-labeling. Parent spectra retain nativelike features in the neighborhood of the single disulfide bridge (cystine B19-A20), including secondary NMR chemical shifts and nonlocal nuclear Overhauser effects. This partial fold engages wild-type side chains LeuB15, LeuA16 and PheB24 at the nexus of nativelike α-helices α1 and α3 (as defined in native proinsulin) and flanking β-strand (residues B24-B26). The variant peptides exhibit successive structural perturbations in order: parent (most organized) > SerB24 >> ProA16 > ProB15 (least organized). The same order pertains to (a) overall α-helix content as probed by circular dichroism, (b) synthetic yields of corresponding three-disulfide insulin analogs, and (c) ER stress induced in cell culture by corresponding mutant proinsulins. These findings suggest that this and related peptide models will provide a general platform for classification of MIDY mutations based on molecular mechanisms by which nascent disulfide pairing is impaired. We propose that the syndrome's variable phenotypic spectrum—onsets ranging from the neonatal period to later in childhood or adolescence—reflects structural features of respective folding intermediates. [ABSTRACT FROM AUTHOR]

The mutant proinsulin syndrome is a monogenic cause of diabetes mellitus due to toxic misfolding of insulin's biosynthetic precursor. Also designated mutant INS-gene induced diabetes of the young (MIDY), this syndrome defines molecular determinants of foldability in the endoplasmic reticulum (ER) of β-cells. Here, we describe a peptide model of a key proinsulin folding intermediate and variants containing representative clinical mutations; the latter perturb invariant core sites in native proinsulin (LeuB15→Pro, LeuA16→Pro, and PheB24→Ser). The studies exploited a 49-residue single-chain synthetic precursor (designated DesDi), previously shown to optimize in vitro efficiency of disulfide pairing. Parent and variant peptides contain a single disulfide bridge (cystine B19-A20) to provide a model of proinsulin's first oxidative folding intermediate. The peptides were characterized by circular dichroism and redox stability in relation to effects of the mutations on (a) in vitro foldability of the corresponding insulin analogs and (b) ER stress induced in cell culture on expression of the corresponding variant proinsulins. Striking correlations were observed between peptide biophysical properties, degree of ER stress and age of diabetes onset (neonatal or adolescent). Our findings suggest that age of onset reflects the extent to which nascent structure is destabilized in proinsulin's putative folding nucleus. We envisage that such peptide models will enable high-resolution structural studies of key folding determinants and in turn permit molecular dissection of phenotype-genotype relationships in this monogenic diabetes syndrome. Our companion study (next article in this issue) employs two-dimensional heteronuclear NMR spectroscopy to define site-specific perturbations in the variant peptides. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to analyze the clinical characteristics and the pattern of long-term changes of fasting plasma C-peptide in patients with mitochondrial diabetes (MD), and to provide guidance for the diagnosis and treatment of MD. Methods: We retrieved MD patients with long-term follow-up at Peking Union Medical College Hospital from January 2005 to July 2021 through the medical record retrieval system and retrospectively analyzed their clinical data, biochemical parameters, fasting plasma C-peptide, glycosylated hemoglobin and treatment regimens. Non-parametric receiver operating characteristic (ROC) curves were used to assess the relationship between exercise test-related plasma lactate levels and suffering from MD. Results: A total of 12 MD patients were included, with clinical characteristics of early-onset, normal or low body weight, hearing loss, maternal inheritance, and negative islet-related autoantibodies. In addition, patients with MD exhibited significantly higher mean plasma lactate levels immediately after exercise compared to patients with type 1 diabetes mellitus (T1DM) (8.39 ± 2.75 vs. 3.53 ± 1.47 mmol/L, p=0.003) and delayed recovery time after exercise (6.02 ± 2.65 vs. 2.17 ± 1.27 mmol/L, p=0.011). The optimal cut-off points identified were 5.5 and 3.4 mmol/L for plasma lactate levels immediately after and 30 minutes after exercise, respectively. The fasting plasma C-peptide levels decreased as a negative exponential function with disease progression (Y= 1.343*e-0.07776X, R2 = 0.4154). Treatment regimens in MD patients were varied, with no metformin users and a weak correlation between insulin dosage and body weight. Conclusions: The increased level of plasma lactate during exercise or its delayed recovery after exercise would contribute to the diagnosis of MD. Changes of fasting plasma C-peptide in MD patients over the course of the disease indicated a rapid decline in the early stages, followed by a gradual slowing rate of decline. [ABSTRACT FROM AUTHOR]

Toxic misfolding of proinsulin variants in β-cells defines a monogenic diabetes syndrome, designated mutant INS-gene induced diabetes of the young (MIDY). In our first study (previous article in this issue), we described a one-disulfide peptide model of a proinsulin folding intermediate and its use to study such variants. The mutations (LeuB15→Pro, LeuA16→Pro, and PheB24→Ser) probe residues conserved among vertebrate insulins. In this companion study, we describe 1H and 1H-13C NMR studies of the peptides; key NMR resonance assignments were verified by synthetic 13C-labeling. Parent spectra retain nativelike features in the neighborhood of the single disulfide bridge (cystine B19-A20), including secondary NMR chemical shifts and nonlocal nuclear Overhauser effects. This partial fold engages wild-type side chains LeuB15, LeuA16 and PheB24 at the nexus of nativelike α-helices α1 and α3 (as defined in native proinsulin) and flanking β-strand (residues B24-B26). The variant peptides exhibit successive structural perturbations in order: parent (most organized) > SerB24 >> ProA16 > ProB15 (least organized). The same order pertains to (a) overall α-helix content as probed by circular dichroism, (b) synthetic yields of corresponding three-disulfide insulin analogs, and (c) ER stress induced in cell culture by corresponding mutant proinsulins. These findings suggest that this and related peptide models will provide a general platform for classification of MIDY mutations based on molecular mechanisms by which nascent disulfide pairing is impaired. We propose that the syndrome’s variable phenotypic spectrum—onsets ranging from the neonatal period to later in childhood or adolescence—reflects structural features of respective folding intermediates.

The mutant proinsulin syndrome is a monogenic cause of diabetes mellitus due to toxic misfolding of insulin’s biosynthetic precursor. Also designated mutant INS-gene induced diabetes of the young (MIDY), this syndrome defines molecular determinants of foldability in the endoplasmic reticulum (ER) of β-cells. Here, we describe a peptide model of a key proinsulin folding intermediate and variants containing representative clinical mutations; the latter perturb invariant core sites in native proinsulin (LeuB15→Pro, LeuA16→Pro, and PheB24→Ser). The studies exploited a 49-residue single-chain synthetic precursor (designated DesDi), previously shown to optimize in vitro efficiency of disulfide pairing. Parent and variant peptides contain a single disulfide bridge (cystine B19-A20) to provide a model of proinsulin’s first oxidative folding intermediate. The peptides were characterized by circular dichroism and redox stability in relation to effects of the mutations on (a) in vitro foldability of the corresponding insulin analogs and (b) ER stress induced in cell culture on expression of the corresponding variant proinsulins. Striking correlations were observed between peptide biophysical properties, degree of ER stress and age of diabetes onset (neonatal or adolescent). Our findings suggest that age of onset reflects the extent to which nascent structure is destabilized in proinsulin’s putative folding nucleus. We envisage that such peptide models will enable high-resolution structural studies of key folding determinants and in turn permit molecular dissection of phenotype-genotype relationships in this monogenic diabetes syndrome. Our companion study (next article in this issue) employs two-dimensional heteronuclear NMR spectroscopy to define site-specific perturbations in the variant peptides.

ObjectiveThe aim of this study was to analyze the clinical characteristics and the pattern of long-term changes of fasting plasma C-peptide in patients with mitochondrial diabetes (MD), and to provide guidance for the diagnosis and treatment of MD.MethodsWe retrieved MD patients with long-term follow-up at Peking Union Medical College Hospital from January 2005 to July 2021 through the medical record retrieval system and retrospectively analyzed their clinical data, biochemical parameters, fasting plasma C-peptide, glycosylated hemoglobin and treatment regimens. Non-parametric receiver operating characteristic (ROC) curves were used to assess the relationship between exercise test-related plasma lactate levels and suffering from MD.ResultsA total of 12 MD patients were included, with clinical characteristics of early-onset, normal or low body weight, hearing loss, maternal inheritance, and negative islet-related autoantibodies. In addition, patients with MD exhibited significantly higher mean plasma lactate levels immediately after exercise compared to patients with type 1 diabetes mellitus (T1DM) (8.39 ± 2.75 vs. 3.53 ± 1.47 mmol/L, p=0.003) and delayed recovery time after exercise (6.02 ± 2.65 vs. 2.17 ± 1.27 mmol/L, p=0.011). The optimal cut-off points identified were 5.5 and 3.4 mmol/L for plasma lactate levels immediately after and 30 minutes after exercise, respectively. The fasting plasma C-peptide levels decreased as a negative exponential function with disease progression (Y= 1.343*e-0.07776X, R2 = 0.4154). Treatment regimens in MD patients were varied, with no metformin users and a weak correlation between insulin dosage and body weight.ConclusionsThe increased level of plasma lactate during exercise or its delayed recovery after exercise would contribute to the diagnosis of MD. Changes of fasting plasma C-peptide in MD patients over the course of the disease indicated a rapid decline in the early stages, followed by a gradual slowing rate of decline.

IntroductionDNAJC3, abundant in the pancreatic cells, attenuates endoplasmic reticulum stress. Homozygous DNAJC3 mutations have been reported to cause non-immune juvenile-onset diabetes, neurodegeneration, hearing loss, short stature, and hypothyroidism.Case DescriptionWe report a case of homozygous DNAJC3 mutation in two siblings of a consanguineous family. A 3-year-old boy presented with short stature and a thyroid nodule. Laboratory findings confirmed hypothyroidism. Subsequently, levothyroxine was administered. Growth hormone (GH) stimulation test results were within the normal limits. His stature was exceedingly short (80.5 cm) (−3.79 SDS). The patient developed sensorineural hearing loss at age 6 years; his intellectual functioning was impaired. Recombinant Human Growth Hormine (rhGH) treatment was postponed until the age of 6.9 years due to a strong family history of diabetes. At age 9 years, he developed an ataxic gait. Brain magnetic resonance imaging (MRI) revealed neurodegeneration. The patient developed diabetes at the age of 11 years—5 years after the initiation of rhGH treatment. Tests for markers of autoimmune diabetes were negative. Lifestyle modification was introduced, but insulin therapy was eventually required. Whole-exome-sequencing (WES) revealed a homozygous DNAJC3 mutation, which explained his clinical presentation. MRI revealed a small, atrophic pancreas. At the age of 17, his final adult height was 143 cm (−4.7 SDS). His elder brother, who had the same mutation, had a similar history, except that he had milder ataxia and normal brain MRI finding at the age of 28 years.ConclusionWe propose that DNAJC3 mutation can be considered as a cause of maturity onset diabetes of the young. Patients with DNAJC3 mutations may possess a small atrophic pancreas.

ObjectiveTo determine the pathogenic gene and explore the clinical characteristics of maturity-onset diabetes of the young type 2 (MODY2) pedigree caused by a mutation in the glucokinase (GCK) gene.MethodsUsing whole-exome sequencing (WES), the pathogenic gene was detected in the proband—a 20-year-old young man who was accidentally found with hyperglycemia, no ketosis tendency, and a family history of diabetes. The family members of the proband were examined. In addition, relevant clinical data were obtained and genomic DNA from peripheral blood was obtained. Pathologic variants of the candidate were verified by Sanger sequencing technology, and cosegregation tests were conducted among other family members and non-related healthy controls. After adjusting the treatment plan based on the results of genetic testing, changes in biochemical parameters, such as blood glucose levels and HAblc levels were determined.ResultsIn the GCK gene (NM_000162) in exon 9, a heterozygous missense mutation c.1160C > T (p.Ala387Val) was found in the proband, his father, uncle, and grandmother. Thus mutation, which was found to co-segregate with diabetes, was the first discovery of such a mutation in the Asian population. After stopping hypoglycemic drug treatment, good glycemic control was achieved with diet and exercise therapy.ConclusionGCK gene mutation c.1160C > T (p.Ala387Val) is the pathogenic gene in the GCK-MODY pedigree. Formulating an optimized and personalized treatment strategy can reduce unnecessary excessive medical treatment and adverse drug reactions, and maintain a good HbA1c compliance rate

β-cell ER stress plays an important role in β-cell dysfunction and death during the pathogenesis of diabetes. Proinsulin misfolding is regarded as one of the primary initiating factors of ER stress and unfolded protein response (UPR) activation in β-cells. Here, we found that the ER stress sensor inositol-requiring enzyme 1α (IRE1α) was activated in the Akita mice, a mouse model of mutant insulin gene-induced diabetes of youth (MIDY), a monogenic diabetes. Normalization of IRE1α RNase hyperactivity by pharmacological inhibitors significantly ameliorated the hyperglycemic conditions and increased serum insulin levels in Akita mice. These benefits were accompanied by a concomitant protection of functional β-cell mass, as shown by the suppression of β-cell apoptosis, increase in mature insulin production and reduction of proinsulin level. At the molecular level, we observed that the expression of genes associated with β-cell identity and function was significantly up-regulated and ER stress and its associated inflammation and oxidative stress were suppressed in islets from Akita mice treated with IRE1α RNase inhibitors. This study provides the evidence of the in vivo efficacy of IRE1α RNase inhibitors in Akita mice, pointing to the possibility of targeting IRE1α RNase as a therapeutic direction for the treatment of diabetes. [ABSTRACT FROM AUTHOR]

Introduction: DNAJC3, abundant in the pancreatic cells, attenuates endoplasmic reticulum stress. Homozygous DNAJC3 mutations have been reported to cause non-immune juvenile-onset diabetes, neurodegeneration, hearing loss, short stature, and hypothyroidism. Case Description: We report a case of homozygous DNAJC3 mutation in two siblings of a consanguineous family. A 3-year-old boy presented with short stature and a thyroid nodule. Laboratory findings confirmed hypothyroidism. Subsequently, levothyroxine was administered. Growth hormone (GH) stimulation test results were within the normal limits. His stature was exceedingly short (80.5 cm) (−3.79 SDS). The patient developed sensorineural hearing loss at age 6 years; his intellectual functioning was impaired. Recombinant Human Growth Hormine (rhGH) treatment was postponed until the age of 6.9 years due to a strong family history of diabetes. At age 9 years, he developed an ataxic gait. Brain magnetic resonance imaging (MRI) revealed neurodegeneration. The patient developed diabetes at the age of 11 years—5 years after the initiation of rhGH treatment. Tests for markers of autoimmune diabetes were negative. Lifestyle modification was introduced, but insulin therapy was eventually required. Whole-exome-sequencing (WES) revealed a homozygous DNAJC3 mutation, which explained his clinical presentation. MRI revealed a small, atrophic pancreas. At the age of 17, his final adult height was 143 cm (−4.7 SDS). His elder brother, who had the same mutation, had a similar history, except that he had milder ataxia and normal brain MRI finding at the age of 28 years. Conclusion: We propose that DNAJC3 mutation can be considered as a cause of maturity onset diabetes of the young. Patients with DNAJC3 mutations may possess a small atrophic pancreas. [ABSTRACT FROM AUTHOR]

Objective: To determine the pathogenic gene and explore the clinical characteristics of maturity-onset diabetes of the young type 2 (MODY2) pedigree caused by a mutation in the glucokinase (GCK) gene. Methods: Using whole-exome sequencing (WES), the pathogenic gene was detected in the proband—a 20-year-old young man who was accidentally found with hyperglycemia, no ketosis tendency, and a family history of diabetes. The family members of the proband were examined. In addition, relevant clinical data were obtained and genomic DNA from peripheral blood was obtained. Pathologic variants of the candidate were verified by Sanger sequencing technology, and cosegregation tests were conducted among other family members and non-related healthy controls. After adjusting the treatment plan based on the results of genetic testing, changes in biochemical parameters, such as blood glucose levels and HAblc levels were determined. Results: In the GCK gene (NM_000162) in exon 9, a heterozygous missense mutation c.1160C > T (p.Ala387Val) was found in the proband, his father, uncle, and grandmother. Thus mutation, which was found to co-segregate with diabetes, was the first discovery of such a mutation in the Asian population. After stopping hypoglycemic drug treatment, good glycemic control was achieved with diet and exercise therapy. Conclusion: GCK gene mutation c.1160C > T (p.Ala387Val) is the pathogenic gene in the GCK-MODY pedigree. Formulating an optimized and personalized treatment strategy can reduce unnecessary excessive medical treatment and adverse drug reactions, and maintain a good HbA1c compliance rate [ABSTRACT FROM AUTHOR]