Doubling the referral rate of monogenic diabetes through a nationwide information campaign--update on glucokinase gene mutations in a Polish cohort

Identification of Variants Responsible for Monogenic Forms of Diabetes in Brazil

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.

Whole‑exome sequencing in Russian children with non‑type 1 diabetes mellitus reveals a wide spectrum of genetic variants in MODY‑related and unrelated genes

The present study reports on the frequency and the spectrum of genetic variants causative of monogenic diabetes in Russian children with non-type 1 diabetes mellitus. The present study included 60 unrelated Russian children with non-type 1 diabetes mellitus diagnosed before the age of 18 years. Genetic variants were screened using whole-exome sequencing (WES) in a panel of 35 genes causative of maturity onset diabetes of the young (MODY) and transient or permanent neonatal diabetes. Verification of the WES results was performed using PCR-direct sequencing. A total of 38 genetic variants were identified in 33 out of 60 patients (55%). The majority of patients (27/33, 81.8%) had variants in MODY-related genes: GCK (n=19), HNF1A (n=2), PAX4 (n=1), ABCC8 (n=1), KCNJ11 (n=1), GCK+HNF1A (n=1), GCK+BLK (n=1) and GCK+BLK+WFS1 (n=1). A total of 6 patients (6/33, 18.2%) had variants in MODY-unrelated genes: GATA6 (n=1), WFS1 (n=3), EIF2AK3 (n=1) and SLC19A2 (n=1). A total of 15 out of 38 variants were novel, including GCK, HNF1A, BLK, WFS1, EIF2AK3 and SLC19A2. To summarize, the present study demonstrates a high frequency and a wide spectrum of genetic variants causative of monogenic diabetes in Russian children with non-type 1 diabetes mellitus. The spectrum includes previously known and novel variants in MODY-related and unrelated genes, with multiple variants in a number of patients. The prevalence of GCK variants indicates that diagnostics of monogenic diabetes in Russian children may begin with testing for MODY2. However, the remaining variants are present at low frequencies in 9 different genes, altogether amounting to ~50% of the cases and highlighting the efficiency of using WES in non-GCK-MODY cases.

Monogenic diabetes prevalence among Polish children-Summary of 11 years-long nationwide genetic screening program

BACKGROUND

Estimated monogenic diabetes (MD) prevalence increases as screening programs proceeds.

OBJECTIVE

To estimate prevalence of MD among Polish children.

SUBJECTS

Patients and their family members suspected of suffering from MD (defined as causative mutation in one of the Maturity Onset Diabetes of the Young or permanent neonatal diabetes mellitus genes) were recruited between January 2005 and December 2015.

METHODS

Nationwide prevalence was estimated based on data from 6 administrative provinces (out of 16 in Poland) with high referral rates of patients (>10 per 100 000 children).

RESULTS

During the analysis, probands from 322 of 788 screened families tested positive yielding a total of 409 children and 299 family members with MD. An average of 70 probands/year were referred. Screening success rate reached 40% over the study period. We estimated the prevalence of MD in 2015 to 7.52/100 000 children (1 in 13 000). The most frequent MODY in this group was GCK- MODY (6.88/100 000). The prevalence estimates increased nearly 2-fold since our report in 2011 (4.4/100 000). However, the figure reached a plateau because of screening saturation in 2014 what was also proven by lowering of the median age of diagnosis lowered in time (R = -0.73, P = .0172) along with shortening of the delay between clinical and genetic diagnosis (R = -0.65, P = .0417).

CONCLUSIONS

The screening for childhood MD in Poland reached a plateau phase after 10 years showing a stable prevalence estimate. The true frequency of MD in the overall population may be higher given later onset of reportedly more frequent types of MD than GCK -MODY.

GCK gene mutations are a common cause of childhood-onset MODY (maturity-onset diabetes of the young) in Turkey

OBJECTIVE

Inactivating heterozygous mutations in the GCK gene are a common cause of MODY and result in mild fasting hyperglycaemia, which does not require treatment. We aimed to identify the frequency, clinical and molecular features of GCK mutations in a Turkish paediatric cohort.

DESIGN AND PATIENTS

Fifty-four unrelated probands were selected based on the following criteria: age of diagnosis ≤17 years, family history of diabetes in at least two generations, anti-GAD/ICA negative, BMI<95.p and follow-up with diet, oral antidiabetic drug or low-dose insulin treatment (≤0·5U/kg/d). A MODY probability score (www.diabetesgenes.org) was calculated and 21 patients with a score ≥75%, HbA1c levels ≤7·5% (58·5 mmol/mol) and fasting blood glucose (FBG) levels 99-145 mg/dl (5·5-8·0 mmol/l) were selected for Sanger sequencing of the GCK gene. Targeted next-generation sequencing for all known monogenic diabetes genes was undertaken for any patient without a GCK gene mutation.

RESULTS

GCK gene mutations (pathogenic or likely pathogenic variants) and a novel intronic variant of uncertain significance (c.208 + 3A>T) were identified in 13/54 probands (24%). Twelve of these patients had a MODY probability score ≥75%. FBG level and 2-h glucose level in OGTT were 123 ± 14 mg/dl (6·8 ± 0·7 mmol/l) (107-157 mg/dl) and 181 ± 30 mg/dl (10·1 ± 1·6 mmol/l) (136-247 mg/dl), respectively. Average of glucose increment in OGTT was 58 ± 27 mg/dl (3·2 ± 1·5 mmol/l) (19-120 mg/dl), and mean HbA1c level was 6·5 ± 0·5% (47·5 ± 5·5 mmol/mol) (5·9-7·6%). Five novel missense mutations were identified (p.F123S, p.L58P, p.G246A, p.F419C, and p.S151C). Two patients treated with low-dose insulin before the molecular analysis were able to stop treatment.

CONCLUSIONS

Approximately 1 in 4 MODY cases in this Turkish paediatric cohort have a GCK mutation. Selection of patients for GCK gene analysis using the MODY probability score was an effective way of identifying most (11/12) patients with a GCK mutation.

Differential regulation of serum microRNA expression by HNF1β and HNF1α transcription factors

AIMS/HYPOTHESIS

We aimed to identify microRNAs (miRNAs) under transcriptional control of the HNF1β transcription factor, and investigate whether its effect manifests in serum.

METHODS

The Polish cohort (N = 60) consisted of 11 patients with HNF1B-MODY, 17 with HNF1A-MODY, 13 with GCK-MODY, an HbA1c-matched type 1 diabetic group (n = 9) and ten healthy controls. Replication was performed in 61 clinically-matched British patients mirroring the groups in the Polish cohort. The Polish cohort underwent miRNA serum level profiling with quantitative real-time PCR (qPCR) arrays to identify differentially expressed miRNAs. Validation was performed using qPCR. To determine whether serum content reflects alterations at a cellular level, we quantified miRNA levels in a human hepatocyte cell line (HepG2) with small interfering RNA knockdowns of HNF1α or HNF1β.

RESULTS

Significant differences (adjusted p < 0.05) were noted for 11 miRNAs. Five of them differed between HNF1A-MODY and HNF1B-MODY, and, amongst those, four (miR-24, miR-27b, miR-223 and miR-199a) showed HNF1B-MODY-specific expression levels in the replication group. In all four cases the miRNA expression level was lower in HNF1B-MODY than in all other tested groups. Areas under the receiver operating characteristic curves ranged from 0.79 to 0.86, with sensitivity and specificity reaching 91.7% (miR-24) and 82.1% (miR-199a), respectively. The cellular expression pattern of miRNA was consistent with serum levels, as all were significantly higher in HNF1α- than in HNF1β-deficient HepG2 cells.

CONCLUSIONS/INTERPRETATION

We have shown that expression of specific miRNAs depends on HNF1β function. The impact of HNF1β deficiency was evidenced at serum level, making HNF1β-dependent miRNAs potentially applicable in the diagnosis of HNF1B-MODY.

Undiagnosed MODY: Time for Action

Maturity-onset diabetes of the young (MODY) is a monogenic form of diabetes that accounts for at least 1 % of all cases of diabetes mellitus. MODY classically presents as non-insulin-requiring diabetes in lean individuals typically younger than 25 with evidence of autosomal dominant inheritance, but these criteria do not capture all cases and can also overlap with other diabetes types. Genetic diagnosis of MODY is important for selecting the right treatment, yet ~95 % of MODY cases in the USA are misdiagnosed. MODY prevalence and characteristics have been well-studied in some populations, such as the UK and Norway, while other ethnicities, like African and Latino, need much more study. Emerging next-generation sequencing methods are making more widespread study and clinical diagnosis increasingly feasible; at the same time, they are detecting other mutations in the same genes of unknown clinical significance. This review will cover the current epidemiological studies of MODY and barriers and opportunities for moving toward a goal of access to an appropriate diagnosis for all affected individuals.

Less but better: cardioprotective lipid profile of patients with GCK-MODY despite lower HDL cholesterol level

Patients with diabetes caused by single-gene mutations generally exhibit an altered course of diabetes. Those with mutations of the glucokinase gene (GCK-MODY) show good metabolic control and low risk of cardiovascular complications despite paradoxically lowered high-density lipoprotein (HDL) cholesterol levels. In order to investigate the matter, we analyzed the composition of low-density lipoprotein (LDL) and HDL subpopulations in such individuals. The LipoPrint(©) system (Quantimetrix, USA) based on non-denaturing, linear polyacrylamide gel electrophoresis was used to separate and measure LDL and HDL subclasses in fresh-frozen serum samples from patients with mutations of glucokinase or HNF1A, type 1 diabetes (T1DM) and healthy controls. Fresh serum samples from a total of 37 monogenic diabetes patients (21 from GCK-MODY and 16 from HNF1A-MODY), 22 T1DM patients and 15 healthy individuals were measured in this study. Concentrations of the small, highly atherogenic LDL subpopulation were similar among the compared groups. Large HDL percentage was significantly higher in GCK-MODY than in control (p = 0.0003), T1DM (p = 0.0006) and HNF1A-MODY groups (p = 0.0246). Patients with GCK-MODY were characterized by significantly lower intermediate HDL levels than controls (p = 0.0003) and T1DM (p = 0.0005). Small, potentially atherogenic HDL content differed significantly with the GCK-MODY group showing concentrations of that subfraction from control (p = 0.0096), T1DM (p = 0.0193) and HNF1A-MODY (p = 0.0057) groups. Within-group heterogeneity suggested the existence of potential gene-gene or gene-environment interactions. GCK-MODY is characterized by a strongly protective profile of HDL cholesterol subpopulations. A degree of heterogeneity within the groups suggests the existence of interactions with other genetic or clinical factors.

Prevalence of monogenic diabetes amongst Polish children after a nationwide genetic screening campaign

AIMS/HYPOTHESIS

The aim of this study was to study dynamic changes in the prevalence of different types of diabetes in paediatric populations in Poland, with a specific focus on monogenic diabetes (MD).

METHODS

Using epidemiologic data (PolPeDiab Collaboration) and nationwide genetic test results (TEAM Programme), we compared the prevalence of type 1, type 2 and cystic fibrosis-related diabetes (CFRD) and MD. Genetically confirmed MD included MODY, neonatal diabetes and Wolfram and Alström syndromes. The study covered all children aged 0-18 years treated for diabetes between 2005 and 2011 in three regions, inhabited by 23.7% (1,989,988) of Polish children, with a low prevalence of childhood obesity (<5%).

RESULTS

The prevalence of type 1 diabetes showed a continuous increase, from 96 to 138/100,000 children. The prevalence of type 2 diabetes and CFRD also increased, from 0.3 to 1.01/100,000 children and from 0.1 to 0.95/100,000 children, respectively. The prevalence of MD was stable at between 4.2 and 4.6/100,000 children, accounting for 3.1-4.2% of children with diabetes, with glucokinase (GCK)-MODY being the most frequent type, amounting to 83% of patients with MD. The percentage of positive test results decreased with the number of referrals, suggesting that children with the highest probability of MD were referred initially, followed by those with a less clear-cut phenotype. The prevalence of neonatal diabetes equalled 1 in 300,000 children.

CONCLUSIONS/INTERPRETATION

The prevalence of MD in a paediatric population with a low prevalence of obesity remains stable and is nearly fivefold higher than that of type 2 diabetes and CFRD, justifying a need for increased access to genetic diagnostic procedures in diabetic children.