Next-generation sequencing identifies monogenic diabetes in 16% of patients with late adolescence/adult-onset diabetes selected on a clinical basis: a cross-sectional analysis.

BACKGROUND: Monogenic diabetes (MgD) accounts for 1-2% of all diabetes cases. In adults, MgD is difficult to distinguish from common diabetes causes. We assessed the diagnosis rate and genetic spectrum of MgD using next-generation sequencing in patients with late adolescence/adult-onset diabetes referred for a clinical suspicion of MgD. METHODS: This cross-sectional study was performed in 1564 probands recruited in 116 Endocrinology departments. Inclusion criteria were the absence of diabetes autoantibodies, and at least two of the three following criteria: an age ≤ 40 years and a body mass index (BMI) < 30 kg/m2 at diagnosis in the proband or in at least two relatives with diabetes, and a family history of diabetes in ≥ 2 generations. Seven genes (GCK, HNF1A, HNF4A, HNF1B, ABCC8, KCNJ11, and INS) were analyzed. Variant pathogenicity was assessed using current guidelines. RESULTS: Pathogenic variants were identified in 254 patients (16.2%) and in 23.2% of EuroCaucasian patients. Using more stringent selection criteria (family history of diabetes in ≥ 3 generations, age at diabetes ≤ 40 years and BMI < 30 kg/m2 in the proband, EuroCaucasian origin) increased the diagnosis rate to 43%, but with 70% of the identified cases being missed. GCK (44%), HNF1A (33%), and HNF4A (10%) accounted for the majority of the cases. HNF1B (6%), ABCC8/KCNJ11 (4.4%), and INS (2.8%) variants accounted for 13% of the cases. As compared to non-monogenic cases, a younger age, a lower BMI and the absence of diabetes symptoms at diagnosis, a EuroCaucasian origin, and a family history of diabetes in ≥ 3 generations were associated with MgD, but with wide phenotype overlaps between the two groups. In the total population, two clusters were identified, that mainly differed by the severity of diabetes at onset. MgDs were more prevalent in the milder phenotypic cluster. The phenotypes of the 59 patients (3.8%) with variants of uncertain significance were different from that of patients with pathogenic variants, but not from that of non-monogenic patients. CONCLUSION: Variants of HNF1B and the K-ATP channel genes were more frequently involved in MgD than previously reported. Phenotype overlapping makes the diagnosis of MgD difficult in adolescents/adults and underlies the benefit of NGS in clinically selected patients.

Identification of AgRP cells in the murine hindbrain that drive feeding.

OBJECTIVE: The central melanocortin system is essential for the regulation of food intake and body weight. Agouti-related protein (AgRP) is the sole orexigenic component of the central melanocortin system and is conserved across mammalian species. AgRP is currently known to be expressed exclusively in the mediobasal hypothalamus, and hypothalamic AgRP-expressing neurons are essential for feeding. Here we characterized a previously unknown population of AgRP cells in the mouse hindbrain. METHODS: Expression of AgRP in the hindbrain was investigated using gene expression analysis, single-cell RNA sequencing, immunofluorescent analysis and multiple transgenic mice with reporter expressions. Activation of AgRP neurons was achieved by Designer Receptors Exclusively Activated by Designer Drugs (DREADD) and by transcranial focal photo-stimulation using a step-function opsin with ultra-high light sensitivity (SOUL). RESULTS: AgRP expressing cells were present in the area postrema (AP) and the adjacent subpostrema area (SubP) and commissural nucleus of the solitary tract (cNTS) of the mouse hindbrain (termed AgRPHind herein). AgRPHind cells consisted of locally projecting neurons as well as tanycyte-like cells. Food deprivation stimulated hindbrain Agrp expression as well as neuronal activity of subsets of AgRPHind cells. In adult mice that lacked hypothalamic AgRP neurons, chemogenetic activation of AgRP neurons resulted in hyperphagia and weight gain. In addition, transcranial focal photo-stimulation of hindbrain AgRP cells increased food intake in adult mice with or without hypothalamic AgRP neurons. CONCLUSIONS: Our study indicates that the central melanocortin system in the hindbrain possesses an orexigenic component, and that AgRPHind neurons stimulate feeding independently of hypothalamic AgRP neurons.

A neuronal circuit driven by GLP-1 in the olfactory bulb regulates insulin secretion.

Glucagon-like peptide 1 (GLP-1) stimulates insulin secretion and holds significant pharmacological potential. Nevertheless, the regulation of energy homeostasis by centrally-produced GLP-1 remains partially understood. Preproglucagon cells, known to release GLP-1, are found in the olfactory bulb (OB). We show that activating GLP-1 receptors (GLP-1R) in the OB stimulates insulin secretion in response to oral glucose in lean and diet-induced obese male mice. This is associated with reduced noradrenaline content in the pancreas and blocked by an α2-adrenergic receptor agonist, implicating functional involvement of the sympathetic nervous system (SNS). Inhibiting GABAA receptors in the paraventricular nucleus of the hypothalamus (PVN), the control centre of the SNS, abolishes the enhancing effect on insulin secretion induced by OB GLP-1R. Therefore, OB GLP-1-dependent regulation of insulin secretion relies on a relay within the PVN. This study provides evidence that OB GLP-1 signalling engages a top-down neural mechanism to control insulin secretion via the SNS.

MRAP2 regulates energy homeostasis by promoting primary cilia localization of MC4R.

The G protein-coupled receptor melanocortin-4 receptor (MC4R) and its associated protein melanocortin receptor-associated protein 2 (MRAP2) are essential for the regulation of food intake and body weight in humans. MC4R localizes and functions at the neuronal primary cilium, a microtubule-based organelle that senses and relays extracellular signals. Here, we demonstrate that MRAP2 is critical for the weight-regulating function of MC4R neurons and the ciliary localization of MC4R. More generally, our study also reveals that GPCR localization to primary cilia can require specific accessory proteins that may not be present in heterologous cell culture systems. Our findings further demonstrate that targeting of MC4R to neuronal primary cilia is essential for the control of long-term energy homeostasis and suggest that genetic disruption of MC4R ciliary localization may frequently underlie inherited forms of obesity.

Clinical diagnosis, outcomes and treatment of thiamine deficiency in a tertiary hospital.

BACKGROUND: Acute thiamine deficiency can occur in patients with or without history of alcohol abuse and can lead to life-threatening complications. Clinical diagnosis is challenging, often resulting in delayed recognition and treatment. Patients may present with heterogenous symptoms, more diverse than the historical neurological description. Cerebral MRI can contribute to the diagnosis in patients with neurological signs but it is not always feasible in emergency settings. Prompt parenteral supplementation is required to obtain the improvement of symptoms and avoid chronic complications. AIMS: To describe the clinical presentation of reported cases of thiamine deficiency, assess prescription and results of cerebral imaging, review treatments that had been prescribed in accordance or not with available guidelines, and study the short-term outcome of these patients. METHODS: This is a monocentric retrospective analysis of all reported cases of thiamine deficiency in a French tertiary hospital between January 1st 2008 and December 31st 2018. RESULTS: Fifty-six cases were identified during the study period. Forty-five (80%) patients had a history of alcohol abuse. Most patients were diagnosed based on neurological symptoms but non-specific and digestive symptoms were frequent. Thirty-four percent of patients fulfilled clinical criteria for malnutrition. A brain MRI was performed in 54% of patients and was abnormal in 63% of these cases. Eighty-five percent of patients were treated by parenteral thiamine administration and the supplementation was continued orally in 55% of them. The majority of patients initially received 1000 mg daily of IV thiamine but the dose and duration of thiamine supplementation were variable. At the time of discharge, partial or complete improvement of symptoms was noted in 59% of patients. CONCLUSION: This study highlights the clinical and radiological heterogeneity of thiamine deficiency. These observations should encourage starting thiamine supplementation early in patients with risk factors or suggestive symptoms even in non-alcoholic patients, and underline the importance of early nutritional support.

Behaviour of plasma citrulline after bariatric surgery in the BARIASPERM cohort.

BACKGROUND: Plasma citrulline is currently used in clinical practice as a marker of small bowel functional mass. Behaviour of plasma citrulline after bariatric surgery and its link with post-operative outcome are still poorly understood. OBJECTIVE: Primary objective was to compare plasma citrulline 12 months after two types of bariatric surgery with pre-operative concentrations. Secondary objectives were to search for correlation between plasma citrulline variation and body weight and fat mass loss. DESIGN: This is an ancillary study of the BARIASPERM study. Forty-six adult men (mean age 38.9 ± 7.9 years) who underwent gastric bypass (GB, n = 20) or sleeve gastrectomy (SG, n = 26) were included in this prospective study. Plasma citrulline was measured at baseline, 6 months and 12 months after surgery, as well as total body weight and fat mass measured by dual x-ray absorptiometry (DEXA). RESULTS: Plasma citrulline increased significantly 12 months after surgery, both after gastric bypass and sleeve gastrectomy (respectively 30.2% [18.3-42.2] and 17.8% [5.8-29.7]). The increase was significantly higher after GB than after SG (p = 0.02) while total body weight and fat mass loss were not significantly different between GB and SG. The increase in plasma citrulline levels tended to be positively correlated with both weight and fat mass loss however the association did not reach statistical significance (p = 0.07 and p = 0.06 respectively). CONCLUSION: These results confirm the increase in plasma citrulline after GB published in two previous small studies. Citrulline also significantly increased after SG, and in spite of similar weight loss obtained with both surgery types, citrulline increase was higher after GB than SG. This suggests different modifications of intestinal functional mass after these two different techniques.

Joint Destruction Is Associated With All Types of Cardiovascular Events in French Rheumatoid Patients: A Real-Life Study With Very Long Follow-Up.

Objective: Rheumatoid arthritis (RA) leads not only to joint destruction but also to systemic manifestations, with an increased incidence of cardiovascular events (CVE). Many studies have shown a link between RA severity and CV risk, but the duration of follow-up remains often insufficient to allow a conclusion. The CVE definition was generally reduced to myocardial infarction and stroke, and few studies were conducted in non-Anglo-Saxon countries with low CV incidence. This study aimed to assess the relationship between joint destruction and the occurrence of different types of CVE in a large cohort of French RA patients with a long-term follow-up. Methods: This historical cohort study included 571 RA patients followed between 1992 and 2012 in Lyon, France. The primary endpoint was the first occurrence of a CVE. Logistic regressions were used to identify factors associated with CVE occurrence. Cox proportional hazard models were performed as a separate analysis to take advantage of the long-term follow-up. Results: During a mean follow-up of 16.1 years, 30.3% of patients experienced a CVE, mostly acute arterial events. Joint destruction was associated with an increased risk of CVE [odds ratio = 3.72; 95% confidence interval (CI), 1.09-15.35; p = 0.047] among non-smoker RA patients. A survival analysis revealed that joint destruction was associated with a shorter time to onset of the first CVE only among non-smokers (hazard ratio = 3.44; 95% CI, 1.07-11.04; p = 0.038). Conclusion: Joint destruction is associated with CVE occurrence in RA patients from a population with a lower incidence of CV disease. This study suggests that RA patients, especially those with destruction, merit the institution of precise guidelines to manage this CV risk, and trials are required to evaluate them.

Synergistic Interaction Between High Bioactive IL-17A and Joint Destruction for the Occurrence of Cardiovascular Events in Rheumatoid Arthritis.

Rheumatoid arthritis (RA) remains a cause of morbidity and mortality in many patients while new treatments have changed the face of the disease. Despite the emergence of these new drugs, cardiovascular (CV) diseases remain more frequent in RA patients compared with the general population. However, predictive biomarkers of RA severity and precise guidelines to manage the CV risk in these patients are still lacking. Pro-inflammatory cytokines contribute both to RA and CV pathogenesis. Focusing on IL-17A, high levels of bioactive IL-17A were associated with destruction in RA but also during myocardial infarction. The study aimed to assess the relationship between bioactive IL-17A, destruction and the occurrence of CV events (CVE) in RA patients with a very long follow-up. Thirty-six RA patients were followed between 1970 and 2012 in Lyon, France. They were tested for bioactive IL-17A and clinical and biological characteristics were recorded at baseline. Then, the occurrence of CVE was registered during the follow-up. To study the bioactive fraction of IL-17A, the bioassay used the ability of human umbilical vein endothelial cells to produce IL-8 in presence of RA plasma samples with or without an anti-IL-17A antibody. Bioactive IL-17A level at baseline was higher in RA patients who later experienced a CVE compared to those without (0.77 vs 0.21 ng/ml, p-value = 0.0095, Mann-Whitney test) and synergized with joint destruction (p-value = 0.020, Kruskal-Wallis test). Through its effects on vessels and thrombosis, high levels of bioactive IL-17A could represent a long-term marker of CV risk.