René Valéro

Hyperinsulinemia is associated with increased production rate of intestinal apolipoprotein B-48-containing lipoproteins in humans.

Objectives—Whereas postprandial hyperlipidemia is a well-described feature of insulin-resistant states and type 2 diabetes, no previous studies have examined intestinal lipoprotein production rates (PRs) in relation to hyperinsulinemia or insulin resistance in humans. Methods and Results—Apolipoprotein B-48 (apoB-48)–containing lipoprotein metabolism was examined in the steady-state fed condition with a 15-hour primed constant infusion of [D3]-l-leucine in 14 nondiabetic men with a broad range of body mass index (BMI) and insulin sensitivity. To examine the relationship between indices of insulin resistance and intestinal lipoprotein PR data were analyzed in 2 ways: by correlation and by comparing apoB-48 PRs in those whose fasting plasma insulin concentrations were above or below the median for the 14 subjects studied (60 pmol/L). ApoB-48 PR was significantly higher in hyperinsulinemic, insulin-resistant subjects (1.73±0.39 versus 0.88±0.13 mg/kg per day; P<0.05) and correlated with fasting plasma insulin concentrations (r=0.558; P=0.038), despite great heterogeneity in apoB-48 kinetic parameters, particularly among the obese subjects. There was no significant difference in clearance of apoB-48 between the 2 groups, nor was there a significant correlation between apoB-48 fractional clearance rate and fasting insulin or homeostasis model assessment-insulin resistance. Conclusions—These are the first human data to conclusively demonstrate that intestinal apoB-48–containing triglyceride-rich lipoprotein PR is increased in hyperinsulinemic, insulin-resistant humans. Intestinal lipoprotein particle overproduction is a newly described feature of insulin resistance in humans.

The Type and the Position of HNF1A Mutation Modulate Age at Diagnosis of Diabetes in Patients with Maturity-Onset Diabetes of the Young (MODY)-3

OBJECTIVE—The clinical expression of maturity-onset diabetes of the young (MODY)-3 is highly variable. This may be due to environmental and/or genetic factors, including molecular characteristics of the hepatocyte nuclear factor 1-α (HNF1A) gene mutation. RESEARCH DESIGN AND METHODS—We analyzed the mutations identified in 356 unrelated MODY3 patients, including 118 novel mutations, and searched for correlations between the genotype and age at diagnosis of diabetes. RESULTS—Missense mutations prevailed in the dimerization and DNA-binding domains (74%), while truncating mutations were predominant in the transactivation domain (62%). The majority (83%) of the mutations were located in exons 1- 6, thus affecting the three HNF1A isoforms. Age at diagnosis of diabetes was lower in patients with truncating mutations than in those with missense mutations (18 vs. 22 years, P = 0.005). Missense mutations affecting the dimerization/DNA-binding domains were associated with a lower age at diagnosis than those affecting the transactivation domain (20 vs. 30 years, P = 10−4). Patients with missense mutations affecting the three isoforms were younger at diagnosis than those with missense mutations involving one or two isoforms (P = 0.03). CONCLUSIONS—These data show that part of the variability of the clinical expression in MODY3 patients may be explained by the type and the location of HNF1A mutations. These findings should be considered in studies for the search of additional modifier genetic factors.

Both Intestinal and Hepatic Lipoprotein Production Are Stimulated by an Acute Elevation of Plasma Free Fatty Acids in Humans

Background— Hepatic lipoprotein production has been shown previously to be regulated by free fatty acid (FFA) flux to the liver, whereas intestinal lipoprotein production is stimulated mainly by ingested fat absorbed from the intestinal lumen. Emerging evidence indicates that intestinal lipoprotein production is increased in insulin resistance and type 2 diabetes mellitus, conditions that are associated with increased levels of circulating FFAs. Here we investigated whether short-term elevation of plasma FFAs stimulates intestinal apolipoprotein (apo) B-48– and hepatic apoB-100–containing triglyceride-rich lipoprotein (TRL) production in humans in the fed state. Methods and Results— TRL apoB-48 and apoB-100 metabolism were examined in 12 healthy men during a constant fed state. The studies were as follows, respectively: (1) Intralipid/heparin was infused intravenously immediately before and during the kinetics study to induce an ≈3-fold difference in plasma FFA compared with the saline study; (2) saline was infused intravenously as a control. ApoB-48– and apoB-100–containing TRL production and clearance were determined with a 12-hour primed constant infusion of [D3]l-leucine and multicompartmental kinetic modeling. TRL apoB-48 production rate was 69% higher in the Intralipid/heparin study than in the saline control (5.95±1.13 versus 3.53±0.58 mg/kg per day; P=0.027), and there was no significant difference in TRL apoB-48 clearance. TRL apoB-100 concentrations were also increased (P<0.001) and TRL apoB-100 production rate was 35% higher in the Intralipid/heparin study compared with saline (28±4 versus 21±3 mg/kg per day; P=0.020). Conclusions— This is the first study to demonstrate that intestinal TRL apoB-48 production is increased after short-term elevation of plasma FFAs in humans in the fed state, similar to the well-described stimulation of hepatic TRL apoB100–containing particles by FFAs.

Anti-PD1 Pembrolizumab Can Induce Exceptional Fulminant Type 1 Diabetes.

A 44-year-old Caucasian woman with no history of diabetes was admitted to the emergency department in 2014 for vomiting and confusion, with polyuria, polydipsia, and a very recent weight loss (15 days). Biological tests revealed severe hyperglycemia and diabetic ketoacidosis (glycemia 50.45 mmol/L, ketones 3+, pH 7.25, HCO3− 3 mEq/L), with acute renal failure (39 mL/min/1.73 m2) and elevated serum lipase. Pancreatitis was ruled out by an abdominal computed tomography scan. Intravenous insulin resulted in rapid glycemic control. Surprisingly, HbA1c was subnormal (6.85%). Furthermore, anti-GAD and anti-IA2 antibodies were negative and serum C-peptide was undetectable. All these parameters led to the unusual diagnosis of fulminant type 1 diabetes (FD). FD is a rare subtype of type 1 diabetes …

Identification of novel mutations in WFS1 and genotype-phenotype correlation in Wolfram syndrome.

Mutations in the WFS1 gene have been reported in Wolfram syndrome (WS), an autosomal recessive disorder defined by early onset of diabetes mellitus (DM) and progressive optic atrophy. Because of the low prevalence of this syndrome and the recent identification of the WFS1 gene, few data are available concerning the relationships between clinical and molecular aspects of the disease. Here, we describe 12 patients from 11 families with WS. We report on eight novel (A214fsX285, L293fsX303, P346L, I427S, V503fsX517, R558C, S605fsX711, P838L) and seven previously reported mutations. We also looked for genotype–phenotype correlation both in patients included in this study and 19 additional WS patients that were previously reported. Subsequently, we performed a systematic review and meta‐analysis of five published clinical and molecular studies of WFS1 for genotype–phenotype correlation, combined with our current French patient group for a total of 96 patients. The presence of two inactivating mutations was shown to predispose to an earlier age of onset of both DM and optic atrophy. Moreover, the clinical expression of WS was more complete and occurred earlier in patients harboring no missense mutation.

Clinical characteristics and diagnostic criteria of maturity-onset diabetes of the young (MODY) due to molecular anomalies of the HNF1A gene.

CONTEXT The diagnosis of maturity-onset diabetes of the young type 3 (MODY3), associated with HNF1A molecular abnormalities, is often missed. OBJECTIVE The objective of the study was to describe the phenotypes of a large series of MODY3 patients and to reassess parameters that may improve its diagnosis. DESIGN, SETTING, AND PATIENTS This retrospective multicenter study included 487 unrelated patients referred because of suspicion of MODY3. Genetic analysis identified 196 MODY3 and 283 non-MODY3 cases. Criteria associated with MODY3 were assessed by multivariate analysis. The capacity of the model to predict MODY3 diagnosis was assessed by the area under the receiver-operating characteristic curve and was further validated in an independent sample of 851 patients (165 MODY3 and 686 non-MODY3). RESULTS In the MODY3 patients, diabetes was revealed by clinical symptoms in 25% of the cases and was diagnosed by screening in the others. Age at diagnosis of diabetes was more than 25 yr in 40% of the MODY3 patients. There was considerable variability and overlap of all assessed parameters in MODY3 and non-MODY3 patients. The best predictive model was based on criteria available at diagnosis of diabetes, including age, body mass index, number of affected generations, presence of diabetes symptoms, and geographical origin. The area under the curve of the receiver-operating characteristic analysis was 0.81. When sensitivity was set to 90%, specificity was 49%. CONCLUSIONS Differential diagnosis between MODY3 and early-onset type 2 diabetes remains difficult. Whether the proposed model will improve the pick-up rate of MODY3 diagnosis needs to be confirmed in independent populations.

Triglyceride-Rich Lipoprotein-Associated Apolipoprotein C-III Production Is Stimulated by Plasma Free Fatty Acids in Humans

Objective—Insulin resistant states are associated with increased fatty acid flux to liver and intestine, which stimulates the production of triglyceride-rich lipoproteins (TRL). ApoC-III production and plasma and TRL concentrations are increased in insulin resistance and may contribute to the hypertriglyceridemia of these conditions. The mechanism underlying that increase is not known, but because apoC-III and VLDL production are closely linked we hypothesized that FFAs may stimulate TRL apoC-III production. Methods and Results—We used Intralipid/heparin (IH) to raise plasma FFA in 12 healthy men in the fed state, and stable isotopes to examine apoC-III metabolism. TRL apoC-III concentration was significantly higher in the IH study, and this increase was associated with higher production (PR) and fractional catabolic rate (FCR). The increase in production was greater than in FCR (90% versus 30%, respectively), accounting for the elevated concentration. Glycerol infusion had no effect on apoC-III concentration, PR, or FCR compared to saline, indicating that the effect was not attributable to glycerol released from intralipid. Conclusion—These findings confirm that TRL apoC-III production is stimulated by an acute elevation of plasma FFAs, suggesting a novel regulatory pathway that may play a role in the overproduction of TRL apoC-III in insulin resistant states.

Disorganization of thymic medulla precedes evolution towards diabetes in female NOD mice

The thymic medulla is a complex microenvironment which plays a crucial role in central tolerance induction. Using a quantitative histological analysis of non-obese diabetic (NOD) mice, we show that the medulla undergoes several structural modifications during the course of the disease in NOD mice. Indeed, the majority of 70-day-old NOD mice show a scattering of medullary epithelial cells in the cortex which is associated with a reduction in the size of the medulla in heavily disorganized thymuses. The severity of this phenotype is shown to correlate with the subsequent appearance of diabetes in older female NOD mice. This trait is mainly controlled by non-major histocompatibility complex NOD genes since C57BL/6 H-2g(7) congenic mice have a normal medulla. It persists in conditions where effector lymphocytes that lead to diabetes are inhibited in periphery. These results suggest that primary alterations of the thymic stroma might play a role in the progression towards diabetes in NOD mice.

Absence of Acute Inhibitory Effect of Insulin on Chylomicron Production in Type 2 Diabetes

Objective—Overproduction of intestinally derived apoB-48-containing triglyceride-rich lipoproteins (TRLs) (chylomicrons) has recently been described in type 2 diabetes, as is known for hepatic TRL-apoB-100 (very-low-density lipoprotein) production. Furthermore, insulin acutely inhibits both intestinal and hepatic TRL production, whereas this acute inhibitory effect on very-low-density lipoprotein production is blunted in type 2 diabetes. It is not currently known whether this acute effect on chylomicron production is similarly blunted in humans with type 2 diabetes. Methods and Results—We investigated the effect of acute hyperinsulinemia on TRL metabolism in 18 type 2 diabetic men using stable isotope methodology. Each subject underwent 1 control (saline infusion [SAL]) lipoprotein turnover study followed by a second study, under 1 of the 3 following clamp conditions: (1) hyperinsulinemic-euglycemic, (2) hyperinsulinemic-hyperglycemic, or (3) hyperinsulinemic-euglycemic plus intralipid and heparin. TRL-apoB-48 and TRL-apoB-100 production and clearance rates were not different between SAL and clamp and between the different clamp conditions, except for significantly lower TRL-apoB-100 clearance and production rates in hyperinsulinemic-euglycemic plus intralipid and heparin clamp compared with SAL. Conclusion—This is the first demonstration in individuals with type 2 diabetes that chylomicron production is resistant to the normal acute suppressive effect of insulin. This phenomenon may contribute to the highly prevalent dyslipidemia of type 2 diabetes and potentially to atherosclerosis. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00950209.

Microvascular Diabetes Complications in Wolfram Syndrome (Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy, and Deafness [DIDMOAD]): An age- and duration-matched comparison with common type 1 diabetes

OBJECTIVE—Some previous studies suggested that patients suffering from Wolfram syndrome or DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness) might be relatively preserved from diabetic retinopathy and nephropathy. However, these data were not conclusive because either observations were only anecdotic or did not match with control type 1 diabetic populations. RESEARCH DESIGN AND METHODS—A group of 26 French diabetic patients with DIDMOAD was compared with a population of 52 patients with common type 1 diabetes matched for age at diabetes diagnosis (8.62 ± 1.84 vs. 8.27 ± 1.30 years; P = NS) and diabetes duration (12.88 ± 1.58 vs. 12.87 ± 1.13 years; P = NS) to study the quality of glycemic control and the incidence of microvascular complications. RESULTS—Glycemic control was significantly better in the DIDMOAD group than in the type 1 diabetic group (A1C: 7.72 ± 0.21 vs. 8.99 ± 0.25%, respectively; P = 0.002), with significant lower daily insulin requirements (0.71 ± 0.07 vs. 0.88 ± 0.04 UI · kg−1 · day−1, respectively; P = 0.0325). The prevalence of microvascular complications in the DIDMOAD group was half that observed in the type 1 diabetic group, but the difference was not significant. CONCLUSIONS—Diabetes in DIDMOAD patients is more easily controlled despite the presence of other handicaps. This better glycemic control could explain the trend to decreased microvascular diabetes complications observed in previous studies.