Mexican Carriers of the HNF1A p.E508K Variant Do Not Experience an Enhanced Response to Sulfonylureas

Towards the recognition of oligogenic forms of type 2 diabetes

The demarcation between monogenic and polygenic type 2 diabetes (T2D) is less distinct than previously believed. Notably, recent research has highlighted a new entity, that we suggest calling oligogenic forms of T2D, serving as a genetic link between these two forms. In this opinion article, we have reviewed scientific advances that suggest categorizing genes involved in oligogenic T2D. Research focused on polygenic T2D has faced challenges in deepening our comprehension of the pathophysiology of T2D due to the inability to directly establish causal links between a signal and the molecular mechanisms underlying the disease. However, the study of oligogenic forms of T2D has illuminated distinct causal connections between genes and disease risk, thereby indicating potential new drug targets.

Dissection of type 2 diabetes: a genetic perspective

Diabetes is a leading cause of global mortality and disability, and its economic burden is substantial. This Review focuses on type 2 diabetes, which makes up 90-95% of all diabetes cases. Type 2 diabetes involves a progressive loss of insulin secretion often alongside insulin resistance and metabolic syndrome. Although obesity and a sedentary lifestyle are considerable contributors, research over the last 25 years has shown that type 2 diabetes develops on a predisposing genetic background, with family and twin studies indicating considerable heritability (ie, 31-72%). This Review explores type 2 diabetes from a genetic perspective, highlighting insights into its pathophysiology and the implications for precision medicine. More specifically, the traditional understanding of type 2 diabetes genetics has focused on a dichotomy between monogenic and polygenic forms. However, emerging evidence suggests a continuum that includes monogenic, oligogenic, and polygenic contributions, revealing their complementary roles in type 2 diabetes pathophysiology. Recent genetic studies provide deeper insights into disease mechanisms and pave the way for precision medicine approaches that could transform type 2 diabetes management. Additionally, the effect of environmental factors on type 2 diabetes, particularly from epigenetic modifications, adds another layer of complexity to understanding and addressing this multifaceted disease.

Investigating the pathogenicity of the recessive HNF1A p.A251T variant in monogenic diabetes using iPSC-derived beta-like cells

Monogenic diabetes, formerly called Maturity-Onset Diabetes of the Young (MODY), involves single-gene mutations, typically with dominant inheritance, and has been associated with variants in 14 genes. Among these, HNF1A mutations are the most common, and their diagnosis allows the use of alternative therapies, including sulfonylureas. In an earlier study, we described a variant displaying recessive transmission, p.A251T (Misra, S et al, Diabetes Care, 2020). Initial functional studies revealed only a modest impact on protein function. We extend these earlier in vitro studies to demonstrate that beta-like cells derived from pluripotent stem cells from variant carriers show impaired differentiation into insulin-positive cells, whereas differentiation into alpha cells is significantly enhanced. Additionally, mutant cells showed impaired glucose-stimulated insulin secretion but partially preserved responsiveness to treatment with sulfonylureas. Our study provides proof of principle for the utility of using patient-derived stem cells as a platform to assess the pathogenicity of HNF1A variants, and to explore potential treatment strategies.

Diabetes subgroups and sociodemographic inequalities in Mexico: a cross-sectional analysis of nationally representative surveys from 2016 to 2022

Background

Differences in the prevalence of four diabetes subgroups have been reported in Mexico compared to other populations, but factors that may contribute to these differences are poorly understood. Here, we estimate the prevalence of diabetes subgroups in Mexico and evaluate their correlates with indicators of social disadvantage using data from national representative surveys.

Methods

We analyzed serial, cross-sectional Mexican National Health and Nutrition Surveys spanning 2016, 2018, 2020, 2021, and 2022, including 23,354 adults (>20 years). Diabetes subgroups (obesity-related [MOD], severe insulin-deficient [SIDD], severe insulin-resistant [SIRD], and age-related [MARD]) were classified using self-normalizing neural networks based on a previously validated algorithm. We used the density-independent social lag index (DISLI) as a proxy of state-level social disadvantage.

Findings

We identified 4204 adults (median age: 57, IQR: 47-66, women: 64%) living with diabetes, yielding a pooled prevalence of 16.04% [95% CI: 14.92-17.17]. When stratified by diabetes subgroup, prevalence was 6.62% (5.69-7.55) for SIDD, 5.25% (4.52-5.97) for MOD, 2.39% (1.95-2.83) for MARD, and 1.27% (1.00-1.54) for SIRD. SIDD and MOD clustered in Southern Mexico, whereas MARD and SIRD clustered in Northern Mexico and Mexico City. Each standard deviation increase in DISLI was associated with higher odds of SIDD (OR: 1.12, 95% CI: 1.06-1.12) and lower odds of MOD (OR: 0.93, 0.88-0.99). Speaking an indigenous language was associated with higher odds of SIDD (OR: 1.35, 1.16-1.57) and lower odds of MARD (OR 0.58, 0.45-0.74).

Interpretation

Diabetes prevalence in Mexico is rising in the context of regional and sociodemographic inequalities across distinct diabetes subgroups. SIDD is a subgroup of concern that may be associated with inadequate diabetes management, mainly in marginalized states.

Funding

This research was supported by Instituto Nacional de Geriatría in Mexico.

Bioinformatics pipeline for the systematic mining genomic and proteomic variation linked to rare diseases: The example of monogenic diabetes

Monogenic diabetes is characterized as a group of diseases caused by rare variants in single genes. Like for other rare diseases, multiple genes have been linked to monogenic diabetes with different measures of pathogenicity, but the information on the genes and variants is not unified among different resources, making it challenging to process them informatically. We have developed an automated pipeline for collecting and harmonizing data on genetic variants linked to monogenic diabetes. Furthermore, we have translated variant genetic sequences into protein sequences accounting for all protein isoforms and their variants. This allows researchers to consolidate information on variant genes and proteins linked to monogenic diabetes and facilitates their study using proteomics or structural biology. Our open and flexible implementation using Jupyter notebooks enables tailoring and modifying the pipeline and its application to other rare diseases.

Potassium channels in behavioral brain disorders. Molecular mechanisms and therapeutic potential: A narrative review

Potassium channels (K+-channels) selectively control the passive flow of potassium ions across biological membranes and thereby also regulate membrane excitability. Genetic variants affecting many of the human K+-channels are well known causes of Mendelian disorders within cardiology, neurology, and endocrinology. K+-channels are also primary targets of many natural toxins from poisonous organisms and drugs used within cardiology and metabolism. As genetic tools are improving and larger clinical samples are being investigated, the spectrum of clinical phenotypes implicated in K+-channels dysfunction is rapidly expanding, notably within immunology, neurosciences, and metabolism. K+-channels that previously were considered to be expressed in only a few organs and to have discrete physiological functions, have recently been found in multiple tissues and with new, unexpected functions. The pleiotropic functions and patterns of expression of K+-channels may provide additional therapeutic opportunities, along with new emerging challenges from off-target effects. Here we review the functions and therapeutic potential of K+-channels, with an emphasis on the nervous system, roles in neuropsychiatric disorders and their involvement in other organ systems and diseases.

Two case reports of maturity-onset diabetes of the young type 3 caused by the hepatocyte nuclear factor 1α gene mutation

Maturity-onset diabetes of the young type 3 (MODY3) is a specific type of diabetes mellitus with inherited impairment of the islet β cell function due to the mutation in the hepatocyte nuclear factor 1α (HNF1α) gene. It is a rare condition and easily misdiagnosed as T1DM or T2DM. In this study, the clinical features of two unrelated Chinese MODY3 probands were described and analyzed. Next-generation sequencing was performed to identify the mutated genes, and Sanger sequencing was employed to verify the location of the pathogenic variant in the related family members. It was found that proband 1 inherited a start codon mutation c.2T>C (p.Met1?) in exon 1 of the HNF1α gene from his affected mother, and proband 2 inherited a frameshift mutation c.1136_1137del (p.Pro379fs) in exon 6 of the HNF1α gene also from her affected mother. Proband 1 and proband 2 differed in islet dysfunction, complications, and treatments due to their different disease durations and levels of hemoglobin A_1c (HbA1c). The findings of this study demonstrate that early identification of MODY and diagnosis through genetic testing are critical for the treatment of the patient.

A novel splice-affecting HNF1A variant with large population impact on diabetes in Greenland

Background

The genetic disease architecture of Inuit includes a large number of common high-impact variants. Identification of such variants contributes to our understanding of the genetic aetiology of diseases and improves global equity in genomic personalised medicine. We aimed to identify and characterise novel variants in genes associated with Maturity Onset Diabetes of the Young (MODY) in the Greenlandic population.

Methods

Using combined data from Greenlandic population cohorts of 4497 individuals, including 448 whole genome sequenced individuals, we screened 14 known MODY genes for previously identified and novel variants. We functionally characterised an identified novel variant and assessed its association with diabetes prevalence and cardiometabolic traits and population impact.

Findings

We identified a novel variant in the known MODY gene HNF1A with an allele frequency of 1.9% in the Greenlandic Inuit and absent elsewhere. Functional assays indicate that it prevents normal splicing of the gene. The variant caused lower 30-min insulin (β = -232 pmol/L, β_SD = -0.695, P = 4.43 × 10^-4) and higher 30-min glucose (β = 1.20 mmol/L, β_SD = 0.441, P = 0.0271) during an oral glucose tolerance test. Furthermore, the variant was associated with type 2 diabetes (OR 4.35, P = 7.24 × 10^-6) and HbA1c (β = 0.113 HbA1c%, β_SD = 0.205, P = 7.84 × 10^-3). The variant explained 2.5% of diabetes variance in Greenland.

Interpretation

The reported variant has the largest population impact of any previously reported variant within a MODY gene. Together with the recessive TBC1D4 variant, we show that close to 1 in 5 cases of diabetes (18%) in Greenland are associated with high-impact genetic variants compared to 1-3% in large populations.

Funding

Novo Nordisk Foundation, Independent Research Fund Denmark, and Karen Elise Jensen's Foundation.

Exome Sequencing Data Analysis and a Case-Control Study in Mexican Population Reveals Lipid Trait Associations of New and Known Genetic Variants in Dyslipidemia-Associated Loci

Background: Plasma lipid levels are a major risk factor for cardiovascular diseases. Although international efforts have identified a group of loci associated with the risk of dyslipidemia, Latin American populations have been underrepresented in these studies.

Objective: To know the genetic variation occurring in lipid-related loci in the Mexican population and its association with dyslipidemia.

Methods: We searched for single-nucleotide variants in 177 lipid candidate genes using previously published exome sequencing data from 2838 Mexican individuals belonging to three different cohorts. With the extracted variants, we performed a case-control study. Logistic regression and quantitative trait analyses were implemented in PLINK software. We used an LD pruning using a 50-kb sliding window size, a 5-kb window step size and a r2 threshold of 0.1.

Results: Among the 34251 biallelic variants identified in our sample population, 33% showed low frequency. For case-control study, we selected 2521 variants based on a minor allele frequency ≥1% in all datasets. We found 19 variants in 9 genes significantly associated with at least one lipid trait, with the most significant associations found in the APOA1/C3/A4/A5-ZPR1-BUD13 gene cluster on chromosome 11. Notably, all 11 variants associated with hypertriglyceridemia were within this cluster; whereas variants associated with hypercholesterolemia were located at chromosome 2 and 19, and for low high density lipoprotein cholesterol were in chromosomes 9, 11, and 19. No significant associated variants were found for low density lipoprotein. We found several novel variants associated with different lipemic traits: rs3825041 in BUD13 with hypertriglyceridemia, rs7252453 in CILP2 with decreased risk to hypercholesterolemia and rs11076176 in CETP with increased risk to low high density lipoprotein cholesterol.

Conclusions: We identified novel variants in lipid-regulation candidate genes in the Mexican population, an underrepresented population in genomic studies, demonstrating the necessity of more genomic studies on multi-ethnic populations to gain a deeper understanding of the genetic structure of the lipemic traits.

HNF1A：From Monogenic Diabetes to Type 2 Diabetes and Gestational Diabetes Mellitus

Diabetes, a disease characterized by hyperglycemia, has a serious impact on the lives and families of patients as well as on society. Diabetes is a group of highly heterogeneous metabolic diseases that can be classified as type 1 diabetes (T1D), type 2 diabetes (T2D), gestational diabetes mellitus (GDM), or other according to the etiology. The clinical manifestations are more or less similar among the different types of diabetes, and each type is highly heterogeneous due to different pathogenic factors. Therefore, distinguishing between various types of diabetes and defining their subtypes are major challenges hindering the precise treatment of the disease. T2D is the main type of diabetes in humans as well as the most heterogeneous. Fortunately, some studies have shown that variants of certain genes involved in monogenic diabetes also increase the risk of T2D. We hope this finding will enable breakthroughs regarding the pathogenesis of T2D and facilitate personalized treatment of the disease by exploring the function of the signal genes involved. Hepatocyte nuclear factor 1 homeobox A (HNF1α) is widely expressed in pancreatic β cells, the liver, the intestines, and other organs. HNF1α is highly polymorphic, but lacks a mutation hot spot. Mutations can be found at any site of the gene. Some single nucleotide polymorphisms (SNPs) cause maturity-onset diabetes of the young type 3 (MODY3) while some others do not cause MODY3 but increase the susceptibility to T2D or GDM. The phenotypes of MODY3 caused by different SNPs also differ. MODY3 is among the most common types of MODY, which is a form of monogenic diabetes mellitus caused by a single gene mutation. Both T2D and GDM are multifactorial diseases caused by both genetic and environmental factors. Different types of diabetes mellitus have different clinical phenotypes and treatments. This review focuses on HNF1α gene polymorphisms, HNF1A-MODY3, HNF1A-associated T2D and GDM, and the related pathogenesis and treatment methods. We hope this review will provide a valuable reference for the precise and individualized treatment of diabetes caused by abnormal HNF1α by summarizing the clinical heterogeneity of blood glucose abnormalities caused by HNF1α mutation.

Familial hypertriglyceridemia: an entity with distinguishable features from other causes of hypertriglyceridemia

BACKGROUND

Familial hypertriglyceridemia (FHTG) is a partially characterized primary dyslipidemia which is frequently confused with other forms hypertriglyceridemia. The aim of this work is to search for specific features that can help physicians recognize this disease.

METHODS

This study included 84 FHTG cases, 728 subjects with common mild-to-moderate hypertriglyceridemia (CHTG) and 609 normotriglyceridemic controls. All subjects underwent genetic, clinical and biochemical assessments. A set of 53 single nucleotide polymorphisms (SNPs) previously associated with triglycerides levels, as well as 37 rare variants within the five main genes associated with hypertriglyceridemia (i.e. LPL, APOC2, APOA5, LMF1 and GPIHBP1) were analyzed. A panel of endocrine regulatory proteins associated with triglycerides homeostasis were compared between the FHTG and CHTG groups.

RESULTS

Apolipoprotein B, fibroblast growth factor 21(FGF-21), angiopoietin-like proteins 3 (ANGPTL3) and apolipoprotein A-II concentrations, were independent components of a model to detect FHTG compared with CHTG (AUC 0.948, 95%CI 0.901-0.970, 98.5% sensitivity, 92.2% specificity, P < 0.001). The polygenic set of SNPs, accounted for 1.78% of the variance in triglyceride levels in FHTG and 6.73% in CHTG.

CONCLUSIONS

The clinical and genetic differences observed between FHTG and CHTG supports the notion that FHTG is a unique entity, distinguishable from other causes of hypertriglyceridemia by the higher concentrations of insulin, FGF-21, ANGPTL3, apo A-II and lower levels of apo B. We propose the inclusion of these parameters as useful markers for differentiating FHTG from other causes of hypertriglyceridemia.

Response to multiple glucose-lowering agents in a sib-pair with a novel HNF1α (MODY3) variant

Maturity-onset diabetes of the young (MODY) is a genetically and clinically heterogeneous group of disorders characterised by early onset, lean, non-autoimmunity mediated, non-insulin-dependent diabetes often with autosomal-dominant inheritance and specific pharmaco-genetic response. We describe two siblings with HNF1A-MODY (MODY3) due to a novel germline variant p.(His126Asp) which segregates with diabetes in the family. However, contrary to anticipated therapeutic response, blood glucose in this sib-pair did not respond to sulphonylureas (both low and high dose), dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors), and glucagon-like peptide-1 receptor agonists (GLP-1RA), also known as incretin mimetics. The unexpected limited pharmaco-therapeutic response could potentially be unique to this specific variant and/or progressive pancreatic β-cell failure associated with long-standing disease duration, higher BMI and glucose-toxicity. Therefore, we report a novel-variant MODY3 sib-pair with atypical pharmaco-therapeutic response i.e. resistant to multiple anti-diabetes agents namely sulphonylurea, DPP-4 inhibitors and GLP-1RA treatment.

Hepatic Nuclear Factor 1 Alpha (HNF-1α) In Human Physiology and Molecular Medicine

The transcription factors (TFs) play a crucial role in the modulation of specific gene transcription networks. One of the hepatocyte nuclear factors (HNFs) family's member, hepatocyte nuclear factor-1α (HNF-1α) has continuously become a principal TF to control the expression of genes. It is involved in the regulation of a variety of functions in various human organs including liver, pancreas, intestine, and kidney. It regulates the expression of enzymes involved in endocrine and xenobiotic activity through various metabolite transporters located in the above organs. Its expression is also required for organ-specific cell fate determination. Despite two decades of its first identification in hepatocytes, a review of its significance was not comprehended. Here, the role of HNF-1α in the above organs at the molecular level to intimate molecular mechanisms for regulating certain gene expression whose malfunctions are attributed to the disease conditions has been specifically encouraged. Moreover, the epigenetic effects of HNF-1α have been discussed here, which could help in advanced technologies for molecular pharmacological intervention and potential clinical implications for targeted therapies. HNF-1α plays an indispensable role in several physiological mechanisms in the liver, pancreas, intestine, and kidney. Loss of its operations leads to the non-functional or abnormal functional state of each organ. Specific molecular agents or epigenetic modifying drugs that reactivate HNF-1α are the current requirements for the medications of the diseases.

How Recent Advances in Genomics Improve Precision Diagnosis and Personalized Care of Maturity-Onset Diabetes of the Young

PURPOSE OF REVIEW

Non-autoimmune monogenic diabetes (MD) in young people shows a broad spectrum of clinical presentations, which is largely explained by multiple genetic etiologies. This review discusses how the application of state-of-the-art genomics research to precision diagnosis of MD, particularly the various subtypes of maturity-onset diabetes of the young (MODY), has increasingly informed diabetes precision medicine and patient care throughout life.

RECENT FINDINGS

Due to extended genetic and clinical heterogeneity of MODY, diagnosis approaches based on next-generation sequencing have been worthwhile to better ascribe a specific subtype to each patient with young-onset diabetes. This guides the best appropriate treatment and clinical follow-up. Early etiological diagnosis of MD and individualized treatment are essential for achieving metabolic targets and avoiding long-term diabetes complications, as well as for drastically decreasing the financial and societal burden of diabetes-related healthcare. Genomic medicine-based practices help to optimize long-term clinical follow-up and patient care management.

Genetic causes and treatment of neonatal diabetes and early childhood diabetes

Diabetes mellitus and impaired fasting glucose associated with single gene mutations are less rare than previously thought and may account for more than 6% of patients attending a pediatric diabetes clinic. The number of loci involved in monogenic diabetes exceed 25, and appropriate genetic diagnosis is crucial to direct therapy, for genetic counseling and for prognosis of short- and long-term complications. Among patients with neonatal diabetes (i.e. with onset within first 6 months of life) and patients with Maturity Onset Diabetes of the Young (MODY; an autosomal dominant form of diabetes), those carrying mutations in KCNJ11, ABCC8, HNF1A and HNF4A genes usually respond to oral therapy with sulphonylurea, while those bearing GCK mutations do not necessitate any treatment. Sensor-augmented continuous subcutaneous insulin infusion has been successfully employed in neonatal diabetes, and long-lasting effectiveness of sulfonylurea in KCNJ11 mutation carriers with neonatal diabetes well documented.