Prevalence and phenotypic features of diabetes due to recessive, non-syndromic WFS1 mutations

Objective: Recessive WFS1 mutations are known to cause Wolfram syndrome, a very rare systemic disorder. However, they were also found in non-syndromic diabetes in Han Chinese misdiagnosed with type 1 diabetes, a molecular cause that appears to be considerably more common than the fully expressed syndrome. We aimed to better define the incidence and clinical features of non-syndromic diabetes due to recessive WFS1 mutation. Design: We analyzed the genotype and phenotype of 320 consecutive incident Chinese pediatric diabetic patients diagnosed from 2016 to 2019 to search for non-syndromic diabetic cases due to recessive WFS1 mutation. Methods: A cohort of 105 pancreatic autoantibody-negative patients were recruited for exome sequencing. All patients tested positive for pathogenic diallelic WFS1 mutations were examined for phenotypic features (fundoscopy, audiogram, urine density). Results: We found three cases of non-syndromic diabetes due to recessive WFS1 mutations (incidence = 0.94% (95CI 0.25%-2.7%)). All three cases only had mild diabetes when diagnosed. All patients had well conserved fasting C-peptide when diagnosed but one of them progressed to T1D-like insulin deficiency. In addition, we found a fourth case with previously undetected features of Wolfram syndrome. Conclusions: Non-syndromic diabetes due to WFS1 mutation may be common among Chinese pediatric patients with diabetes. It is important to differentiate it from other MODY subtypes with similar phenotype by molecular diagnosis because of different prognosis and, potentially, therapy.

Distinct Molecular Signatures of Clinical Clusters in People with Type 2 Diabetes: an IMI-RHAPSODY Study

Type 2 diabetes is a multifactorial disease with multiple underlying aetiologies. To address this heterogeneity a previous study clustered people with diabetes into five diabetes subtypes. The aim of the current study is to investigate the aetiology of these clusters by comparing their molecular signatures. In three independent cohorts, in total 15,940 individuals were clustered based on five clinical characteristics. In a subset, genetic- (N=12828), metabolomic- (N=2945), lipidomic- (N=2593) and proteomic (N=1170) data were obtained in plasma. In each datatype each cluster was compared with the other four clusters as the reference. The insulin resistant cluster showed the most distinct molecular signature, with higher BCAAs, DAG and TAG levels and aberrant protein levels in plasma enriched for proteins in the intracellular PI3K/Akt pathway. The obese cluster showed higher cytokines. A subset of the mild diabetes cluster with high HDL showed the most beneficial molecular profile with opposite effects to those seen in the insulin resistant cluster. This study showed that clustering people with type 2 diabetes can identify underlying molecular mechanisms related to pancreatic islets, liver, and adipose tissue metabolism. This provides novel biological insights into the diverse aetiological processes that would not be evident when type 2 diabetes is viewed as a homogeneous disease

Distinct Molecular Signatures of Clinical Clusters in People with Type 2 Diabetes: an IMI-RHAPSODY Study

Type 2 diabetes is a multifactorial disease with multiple underlying aetiologies. To address this heterogeneity a previous study clustered people with diabetes into five diabetes subtypes. The aim of the current study is to investigate the aetiology of these clusters by comparing their molecular signatures. In three independent cohorts, in total 15,940 individuals were clustered based on five clinical characteristics. In a subset, genetic- (N=12828), metabolomic- (N=2945), lipidomic- (N=2593) and proteomic (N=1170) data were obtained in plasma. In each datatype each cluster was compared with the other four clusters as the reference. The insulin resistant cluster showed the most distinct molecular signature, with higher BCAAs, DAG and TAG levels and aberrant protein levels in plasma enriched for proteins in the intracellular PI3K/Akt pathway. The obese cluster showed higher cytokines. A subset of the mild diabetes cluster with high HDL showed the most beneficial molecular profile with opposite effects to those seen in the insulin resistant cluster. This study showed that clustering people with type 2 diabetes can identify underlying molecular mechanisms related to pancreatic islets, liver, and adipose tissue metabolism. This provides novel biological insights into the diverse aetiological processes that would not be evident when type 2 diabetes is viewed as a homogeneous disease

Replication and cross-validation of type 2 diabetes subtypes based on clinical variables: an IMI-RHAPSODY study

Aims/hypothesis Five clusters based on clinical characteristics have been suggested as diabetes subtypes: one autoimmune and four subtypes of type 2 diabetes. In the current study we replicate and cross-validate these type 2 diabetes clusters in three large cohorts using variables readily measured in the clinic. Methods In three independent cohorts, in total 15,940 individuals were clustered based on age, BMI, HbA1c, random or fasting C-peptide, and HDL-cholesterol. Clusters were cross-validated against the original clusters based on HOMA measures. In addition, between cohorts, clusters were cross-validated by re-assigning people based on each cohort’s cluster centres. Finally, we compared the time to insulin requirement for each cluster. Results Five distinct type 2 diabetes clusters were identified and mapped back to the original four All New Diabetics in Scania (ANDIS) clusters. Using C-peptide and HDL-cholesterol instead of HOMA2-B and HOMA2-IR, three of the clusters mapped with high sensitivity (80.6–90.7%) to the previously identified severe insulin-deficient diabetes (SIDD), severe insulin-resistant diabetes (SIRD) and mild obesity-related diabetes (MOD) clusters. The previously described ANDIS mild age-related diabetes (MARD) cluster could be mapped to the two milder groups in our study: one characterised by high HDL-cholesterol (mild diabetes with high HDL-cholesterol [MDH] cluster), and the other not having any extreme characteristic (mild diabetes [MD]). When these two milder groups were combined, they mapped well to the previously labelled MARD cluster (sensitivity 79.1%). In the cross-validation between cohorts, particularly the SIDD and MDH clusters cross-validated well, with sensitivities ranging from 73.3% to 97.1%. SIRD and MD showed a lower sensitivity, ranging from 36.1% to 92.3%, where individuals shifted from SIRD to MD and vice versa. People belonging to the SIDD cluster showed the fastest progression towards insulin requirement, while the MDH cluster showed the slowest progression. Conclusions/interpretation Clusters based on C-peptide instead of HOMA2 measures resemble those based on HOMA2 measures, especially for SIDD, SIRD and MOD. By adding HDL-cholesterol, the MARD cluster based upon HOMA2 measures resulted in the current clustering into two clusters, with one cluster having high HDL levels. Cross-validation between cohorts showed generally a good resemblance between cohorts. Together, our results show that the clustering based on clinical variables readily measured in the clinic (age, HbA1c, HDL-cholesterol, BMI and C-peptide) results in informative clusters that are representative of the original ANDIS clusters and stable across cohorts. Adding HDL-cholesterol to the clustering resulted in the identification of a cluster with very slow glycaemic deterioration. Graphical abstract

SERCA2a stimulation by istaroxime improves intracellular Ca2+ handling and diastolic dysfunction in a model of diabetic cardiomyopathy

Aims Diabetic cardiomyopathy is a multifactorial disease characterized by an early onset of diastolic dysfunction (DD) that precedes the development of systolic impairment. Mechanisms that can restore cardiac relaxation improving intracellular Ca2+ dynamics represent a promising therapeutic approach for cardiovascular diseases associated to DD. Istaroxime has the dual properties to accelerate Ca2+ uptake into sarcoplasmic reticulum (SR) through the SR Ca2+ pump (SERCA2a) stimulation and to inhibit Na+/K+ ATPase (NKA). This project aims to characterize istaroxime effects at a concentration (100 nmol/L) marginally affecting NKA, in order to highlight its effects dependent on the stimulation of SERCA2a in an animal model of mild diabetes. Methods and results Streptozotocin (STZ) treated diabetic rats were studied at 9 weeks after STZ injection in comparison to controls (CTR). Istaroxime effects were evaluated in vivo and in left ventricular (LV) preparations. STZ animals showed (i) marked DD not associated to cardiac fibrosis, (ii) LV mass reduction associated to reduced LV cell dimension and T-tubules loss, (iii) reduced LV SERCA2 protein level and activity and (iv) slower SR Ca2+ uptake rate, (v) LV action potential (AP) prolongation and increased short-term variability (STV) of AP duration, (vi) increased diastolic Ca2+, and (vii) unaltered SR Ca2+ content and stability in intact cells. Acute istaroxime infusion (0.11 mg/kg/min for 15 min) reduced DD in STZ rats. Accordingly, in STZ myocytes istaroxime (100 nmol/L) stimulated SERCA2a activity and blunted STZ-induced abnormalities in LV Ca2+ dynamics. In CTR myocytes, istaroxime increased diastolic Ca2+ level due to NKA blockade albeit minimal, while its effects on SERCA2a were almost absent. Conclusions SERCA2a stimulation by istaroxime improved STZ-induced DD and intracellular Ca2+ handling anomalies. Thus, SERCA2a stimulation can be considered a promising therapeutic approach for DD treatment.

Altering the inhibitory kinetics and molecular conformation of maltase by Tangzhiqing (TZQ), a natural α-glucosidase inhibitor

Background Tangzhiqing (TZQ), as a potential α-glycosidase inhibitor, possesses postprandial hypoglycaemic effects on maltose in humans. The aim of this study was to investigate the mechanisms by which TZQ attenuates postprandial glucose by interrupting the activity of maltase, including inhibitory kinetics and circular dichroism studies. Methods In this study, we determined the inhibitory effect of TZQ on maltase by kinetic analysis to determine the IC50 value and enzyme velocity studies and line weaver-burk plot generation to determine inhibition type. Acarbose was chosen as a standard control drug. After the interaction with TZQ and maltase, secondary structure analysis was conducted with a circular dichroism method. Results TZQ showed notable inhibition activity on maltase in a reversible and competitive manner with an IC50 value of 1.67 ± 0.09 μg/ml, which was weaker than that of acarbose (IC50 = 0.29 ± 0.01 μg/ml). The circular dichroism spectrum demonstrated that the binding of TZQ to maltase changed the conformation of maltase and varied with the concentration of TZQ in terms of the disappearance of β-sheets and an increase in the α-helix content of the enzyme, similar to acarbose. Conclusions This work provides useful information for the inhibitory effect of TZQ on maltase. TZQ has the potential to be an α-glycosidase inhibitor for the prevention and treatment of prediabetes or mild diabetes mellitus.

Considering Insulin Secretory Capacity as Measured by a Fasting C-Peptide/Glucose Ratio in Selecting Glucose-Lowering Medications

Type 2 diabetes mellitus is a heterogeneous disease. Recently introduced new subclassifications promise more efficacious, tailored treatments which could complement current guidelines. In the differentiation of the new diabetes subphenotypes, assessment of insulin secretion is one of the essential components. Based on a large number of insulin secretion measurements, we propose fasting C-peptide/glucose ratio (CGR) as an adequate and practicable estimate of insulin secretion. CGR discriminates insulin deficiency from insulin hypersecretion. We suggest using insulin secretion, determined from CGR, as an essential input for therapeutic decisions at the beginning or modification of diabetes treatment. Furthermore, we propose 3 practical steps to guide decisions in the subtype-specific therapy of diabetes mellitus. The first step consists of detecting insulin deficiency indicated by a low CGR with the need for immediate insulin therapy. The second step is related to high CGR and aims at lowering cardiovascular risk associated with diabetes. The third step is the consideration of a de-escalation of glucose-lowering therapy in individuals with mild diabetes subphenotypes.

Insulin Secretory Granules Release Exosomal miR-503 to Promote Insulin Resistance and β-Cell Senescence

Chronic inflammation promotes pancreatic β-cell decompensation to insulin resistance due to local accumulation of supraphysiologic IL-1β levels. However, the underlying molecular mechanism(s) remains elusive. We show that miR-503, exclusively induced in islets from type 2 diabetic humans and rodents, is specifically upregulated by IL-1β in β cells. β-cell–specific miR-503 transgenic (miR-503TG) mice display expression-dependent mild diabetes, severe diabetes, and premature death due to inflammation-induced multiple organ failure. By contrast, deletion of the miR-503 cluster protects mice from high-fat-diet–induced insulin resistance. Single-cell RNA sequencing indicates infiltration of immune cells and senescent β cells in miR-503TG islets. Exosomes containing miR-503 localize in insulin granules of senescent β cells. Autocrine miR-503 activates MAPKs to inhibit β-cell function and replication. Telecrine miR-503 targets Insr/Igf1r to dampen insulin signals in liver and adipose tissues. A metaflammation-related and inflammaging-related miR-503 expression may therefore induce type 2 diabetes via insulin resistance and β-cell dysfunction.