Adiposity, Dysmetabolic Traits, and Earlier Onset of Female Puberty in Adolescent Offspring of Women With Gestational Diabetes Mellitus: A Clinical Study Within the Danish National Birth Cohort

OBJECTIVE Offspring of pregnancies affected by gestational diabetes mellitus (GDM) are at increased risk of the development of type 2 diabetes. However, the extent to which these dysmetabolic traits may be due to offspring and/or maternal adiposity is unknown. We examined body composition and associated cardiometabolic traits in 561 9- to 16-year-old offspring of mothers with GDM and 597 control offspring. RESEARCH DESIGN AND METHODS We measured anthropometric characteristics; puberty status; blood pressure; and fasting glucose, insulin, C-peptide, and lipid levels; and conducted a DEXA scan in a subset of the cohort. Differences in the outcomes between offspring of mothers with GDM and control subjects were examined using linear and logistic regression models. RESULTS After adjustment for age and sex, offspring of mothers with GDM displayed higher weight, BMI, waist-to-hip ratio (WHR), systolic blood pressure, and resting heart rate and lower height. Offspring of mothers with GDM had higher total and abdominal fat percentages and lower muscle mass percentages, but these differences disappeared after correction for offspring BMI. The offspring of mothers with GDM displayed higher fasting plasma glucose, insulin, C-peptide, HOMA-insulin resistance (IR), and plasma triglyceride levels, whereas fasting plasma HDL cholesterol levels were decreased. Female offspring of mothers with GDM had an earlier onset of puberty than control offspring. Offspring of mothers with GDM had significantly higher BMI, WHR, fasting glucose, and HOMA-IR levels after adjustment for maternal prepregnancy BMI, and glucose and HOMA-IR remained elevated in the offspring of mothers with GDM after correction for both maternal and offspring BMIs. CONCLUSIONS In summary, adolescent offspring of women with GDM show increased adiposity, an adverse cardiometabolic profile, and earlier onset of puberty among girls. Increased fasting glucose and HOMA-IR levels among the offspring of mothers with GDM may be explained by the programming effects of hyperglycemia in pregnancy. </jats:sec

Emerging role of the calcium-activated, small conductance, SK3 K ⁺ channel in distal tubule function: Regulation by TRPV4

The Ca2+-activated, maxi-K (BK) K+ channel, with low Ca2+-binding affinity, is expressed in the distal tubule of the nephron and contributes to flow-dependent K+ secretion. In the present study we demonstrate that the Ca2+-activated, SK3 (KCa2.3) K + channel, with high Ca2+-binding affinity, is also expressed in the mouse kidney (RT-PCR, immunoblots). Immunohistochemical evaluations using tubule specific markers demonstrate significant expression of SK3 in the distal tubule and the entire collecting duct system, including the connecting tubule (CNT) and cortical collecting duct (CCD). In CNT and CCD, main sites for K+ secretion, the highest levels of expression were along the apical (luminal) cell membranes, including for both principal cells (PCs) and intercalated cells (ICs), posturing the channel for Ca2+- dependent K+ secretion. Fluorescent assessment of cell membrane potential in native, split-opened CCD, demonstrated that selective activation of the Ca2+-permeable TRPV4 channel, thereby inducing Ca2+ influx and elevating intracellular Ca2+ levels, activated both the SK3 channel and the BK channel leading to hyperpolarization of the cell membrane. The hyperpolarization response was decreased to a similar extent by either inhibition of SK3 channel with the selective SK antagonist, apamin, or by inhibition of the BK channel with the selective antagonist, iberiotoxin (IbTX). Addition of both inhibitors produced a further depolarization, indicating cooperative effects of the two channels on Vm. It is concluded that SK3 is functionally expressed in the distal nephron and collecting ducts where induction of TRPV4-mediated Ca2+ influx, leading to elevated intracellular Ca2+ levels, activates this high Ca2+- affinity K+ channel. Further, with sites of expression localized to the apical cell membrane, especially in the CNT and CCD, SK3 is poised to be a key pathway for Ca2+-dependent regulation of membrane potential and K+ secretion. © 2014 Berrout et al

Leukocyte telomere length is associated with elevated plasma glucose and HbA1c in young healthy men independent of birth weight.

Telomeres are protein-bound regions of repetitive nucleotide sequences (TTAGGG) at the end of human chromosomes, and their length is a marker of cellular aging. Intrauterine growth restriction is associated with shorter blood cell telomeres at birth and individuals with type 2 diabetes have shorter telomeres. Individuals with a low birth weight (LBW) have an increased risk of metabolic disease and type 2 diabetes. Therefore, we aimed to investigate the relationship between birth weight and telomere length and the association between birth weight, telomere length and cardiometabolic phenotype in adulthood. Young, healthy men with LBW (n = 55) and normal birth weight (NBW) (n = 65) were examined including blood pressure, blood samples and body composition. Leukocyte telomere length was determined using a high-throughput qPCR method. The LBW men were more insulin resistant as determined by the HOMA-IR index. There was no difference in telomere length between LBW and NBW subjects. When adjusting for birth weight and cohort effect, significant negative associations between telomere length and fasting glucose (P = 0.003) and HbA1c (P = 0.0008) were found. In conclusion, no significant difference in telomere length was found between LBW and NBW men. The telomere length was negatively associated with glucose concentrations and HbA1c levels within the normal non-diabetic range independent of birth weight

TRPM2-mediated rise in mitochondrial Zn2+ promotes palmitate-induced mitochondrial fission and pancreatic β-cell death in rodents

Rise in plasma free fatty acids (FFAs) represents a major risk factor for obesity-induced type 2 diabetes. Saturated FFAs cause a progressive decline in insulin secretion by promoting pancreatic β-cell death through increased production of reactive oxygen species (ROS). Recent studies have demonstrated that palmitate (a C16-FFA)-induced rise in ROS causes β-cell death by triggering mitochondrial fragmentation, but the underlying mechanisms are unclear. Using the INS1-832/13 β-cell line, here we demonstrate that palmitate generates the ROS required for mitochondrial fission by activating NOX (NADPH oxidase)-2. More importantly, we show that chemical inhibition, RNAi-mediated silencing and knockout of ROS-sensitive TRPM (transient receptor potential melastatin)-2 channels prevent palmitate-induced mitochondrial fission. Although TRPM2 activation affects the intracellular dynamics of Ca2+ and Zn2+, chelation of Zn2+ alone was sufficient to prevent mitochondrial fission. Consistent with the role of Zn2+, palmitate caused a rise in mitochondrial Zn2+, leading to Zn2+-dependent mitochondrial recruitment of Drp-1 (a protein that catalyses mitochondrial fission) and loss of mitochondrial membrane potential. In agreement with the previous reports, Ca2+ caused Drp-1 recruitment, but it failed to induce mitochondrial fission in the absence of Zn2+. These results indicate a novel role for Zn2+ in mitochondrial dynamics. Inhibition or knockout of TRPM2 channels in mouse islets and RNAi-mediated silencing of TRPM2 expression in human islets prevented FFA/cytokine-induced β-cell death, findings that are consistent with the role of abnormal mitochondrial fission in cell death. To conclude, our results reveal a novel, potentially druggable signalling pathway for FFA-induced β-cell death. The cascade involves NOX-2-dependent production of ROS, activation of TRPM2 channels, rise in mitochondrial Zn2+, Drp-1 recruitment and abnormal mitochondrial fission

Antiarrhythmic and electrophysiologic effects of flecainide on acutely induced atrial fibrillation in healthy horses

BACKGROUND: Only few pharmacologic compounds have been validated for treatment of atrial fibrillation (AF) in horses. Studies investigating the utility and safety of flecainide to treat AF in horses have produced conflicting results, and the antiarrhythmic mechanisms of flecainide are not fully understood. OBJECTIVES: To study the potential of flecainide to terminate acutely induced AF of short duration (≥15 minutes), to examine flecainide‐induced changes in AF duration and AF vulnerability, and to investigate the in vivo effects of flecainide on right atrial effective refractory period, AF cycle length, and ventricular depolarization and repolarization. ANIMALS: Nine Standardbred horses. Eight received flecainide, 3 were used as time‐matched controls, 2 of which also received flecainide. METHODS: Prospective study. The antiarrhythmic and electrophysiologic effects of flecainide were based on 5 parameters: ability to terminate acute pacing‐induced AF (≥15 minutes), and drug‐induced changes in atrial effective refractory period, AF duration, AF vulnerability, and ventricular depolarization and repolarization times. Parameters were assessed at baseline and after flecainide by programmed electrical stimulation methods. RESULTS: Flecainide terminated all acutely induced AF episodes (n = 7); (AF duration, 21 ± 5 minutes) and significantly decreased the AF duration, but neither altered atrial effective refractory period nor AF vulnerability significantly. Ventricular repolarization time was prolonged between 8 and 20 minutes after initiation of flecainide infusion, but no ventricular arrhythmias were detected. CONCLUSIONS AND CLINICAL IMPORTANCE: Flecainide had clear antiarrhythmic properties in terminating acute pacing‐induced AF, but showed no protective properties against immediate reinduction of AF. Flecainide caused temporary prolongation in the ventricular repolarization, which may be a proarrhythmic effect

Increased Risk of Type 2 Diabetes in Elderly Twins

Udgivelsesdato: JuneObjective: Genetic susceptibility, low birth weight (LBW) and ageing are key etiological factors in the development of type 2 diabetes (T2D). LBW is common among twins. It is unknown whether twin status per se is associated with risk of T2D, and valid concordance rates of T2D in twins on a life-time perspective are lacking. Research design and methods: Clinical study of a population-based cohort of same-sex elderly monozygotic (MZ) and dizygotic (DZ) twins (n=297) and singleton controls (C) (n=71) including measures of anthropometry and glucose tolerance. In addition, T2D incidence cases in twins (n=626) and singletons (n=553) were identified through the National Diabetes Register. Results: Twins were more abdominal obese, insulin resistant and glucose intolerant as evidenced by a higher HbA1c (%) (mean (SD)) (MZ: 6.0 (1.0), DZ: 5.8 (0.7), C: 5.6 (0.3), p=0.004) and 120-min post OGTT plasma glucose levels (mmol/l) (MZ: 8.6 (4.6), DZ: 8.4 (3.9), C: 6.8 (2.4), p=0.003) compared to singletons. Importantly, twins had a higher prevalence of T2D (MZ: 17.5% (95% CI; 14.4-20.6), DZ: 15.7% (13.1-18.3), C: 5.6% (3.0-8.2), p=0.03) together with a 60% higher incidence rate of T2D compared to singletons. Cumulative concordance rates of T2D to the age of 84 years were similar among elderly MZ (0.76 (0.68-0.84)) and DZ (0.71 (0.63-0.78)) twins. Conclusion: Twin status per se is associated with abdominal obesity, insulin resistance and increased prevalence of T2D in elderly twins. The data supports a quantitatively significant impact of the fetal environment as opposed to genetics on risk of T2D

NKX6.1 induced pluripotent stem cell reporter lines for isolation and analysis of functionally relevant neuronal and pancreas populations

Recent studies have reported significant advances in the differentiation of human pluripotent stem cells to clinically relevant cell types such as the insulin producing beta-like cells and motor neurons. However, many of the current differentiation protocols lead to heterogeneous cell cultures containing cell types other than the targeted cell fate. Genetically modified human pluripotent stem cells reporting the expression of specific genes are of great value for differentiation protocol optimization and for the purification of relevant cell populations from heterogeneous cell cultures. Here we present the generation of human induced pluripotent stem cell (iPSC) lines with a GFP reporter inserted in the endogenous NKX6.1 locus. Characterization of the reporter lines demonstrated faithful GFP labelling of NKX6.1 expression during pancreas and motor neuron differentiation. Cell sorting and gene expression profiling by RNA sequencing revealed that NKX6.1-positive cells from pancreatic differentiations closely resemble human beta cells. Furthermore, functional characterization of the isolated cells demonstrated that glucose-stimulated insulin secretion is mainly confined to the NKX6.1-positive cells. We expect that the NKX6.1-GFP iPSC lines and the results presented here will contribute to the further refinement of differentiation protocols and characterization of hPSC-derived beta cells and motor neurons for disease modelling and cell replacement therapies