Deleterious functional consequences of perfluoroalkyl substances accumulation into the myelin sheath

Exposure to persistent organic pollutants during the perinatal period is of particular concern because of the potential increased risk of neurological disorders in adulthood. Here we questioned whether exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) could alter myelin formation and regeneration. First, we show that PFOS, and to a lesser extent PFOA, accumulated into the myelin sheath of postnatal day 21 (p21) mice, whose mothers were exposed to either PFOA or PFOS (20 mg/L) via drinking water during late gestation and lactation, suggesting that accumulation of PFOS into the myelin could interfere with myelin formation and function. In fact, PFOS, but not PFOA, disrupted the generation of oligodendrocytes, the myelin-forming cells of the central nervous system, derived from neural stem cells localised in the subventricular zone of p21 exposed animals. Then, cerebellar slices were transiently demyelinated using lysophosphatidylcholine and remyelination was quantified in the presence of either PFOA or PFOS. Only PFOS impaired remyelination, a deleterious effect rescued by adding thyroid hormone (TH). Similarly to our observation in the mouse, we also showed that PFOS altered remyelination in Xenopus laevis using the Tg(Mbp:GFP-ntr) model of conditional demyelination and measuring, then, the number of oligodendrocytes. The functional consequences of PFOS-impaired remyelination were shown by its effects using a battery of behavioural tests. In sum, our data demonstrate that perinatal PFOS exposure disrupts oligodendrogenesis and myelin function through modulation of TH action. PFOS exposure may exacerbate genetic and environmental susceptibilities underlying myelin disorders, the most frequent being multiple sclerosis.

P3483Diet governs metabolic and electrical properties of the atrial myocardium in mice

Background

Obesity is associated with an increased risk of atrial fibrillation. This epidemiologic observation may not only be due to shared co-morbidities but also from direct impacts of metabolic disorders on myocardium Here, we examined the impact of high fat diet (HFD) induced obesity on atrial properties in mice.

Methods

Eight weeks old C57Bl/6J mice were subjected to 2 or 4 months of HFD (60% fat) or normal diet (ND, 4% fat). Rapid burst atrial pacing were delivered using a trans-esophageal probe to induced AF in anesthetized animals. Action potential (AP) were recorded in left atrial trabeculae using glass microelectrode technique. Potassium currents were recorded in isolated atrial myocytes using the whole cell or perforated patch clamp configurations. Metabolomic and lipidomic analysis were performed on whole left atria. Mitochondrial respiration was studied in situ in saponin-permeabilized atrial muscle fibres using a Clarke electrode and oxygen consumption was measured after successive addition of ADP (2 mM), malate (4 mM), palmitoyl-CoA and carnitine (pCoA-Ca) (100 μM and 2 mM), pyruvate (1 mM), glutamate (10 mM), succinate (15 mM), amytal (1 mM) and tetramethyl-paraphenylenediamine (TMPD)/ascorbate (0.5/0.5 mM).

Results

HFD mice showed a higher atrial vulnerability to AF as indicated by longer AF episodes compared to ND mice. APs were shorter in HFD versus ND mice (AP duration measured at 90% of repolarization: 47.9±2.4 msec in HFD vs 58.2±1.4 msec in ND, P<0.001 after 2 months of HFD) and more sensitive to the K ATP channel blocker, glibenclamide. In perforated but not whole cell, patch clamped atrial myocytes, the K-ATP component of the potassium current was enhanced in HFD mice (at +70 mV: 0.41±0.12 pA/pF in HFD vs 0.13±0.08 pA/pF in ND, P<0.05). Metabolomic analysis indicated an increased consumption of free fatty acid by the beta-oxidation and an accumulation of long chain fatty acid. Although the mitochondrial respiration measurements showed a trend towards a lower complex IV-driven respiration in HFD mice, no significant difference between ND and HFD was noted regarding complex I and complex II-driven respiration. However, the ability of fatty acids (pCoA-Car) to support mitochondrial respiration was higher in HFD

Conclusions

High fat diet induces a shift from carbon hydrate to a beta oxidation of the atrial myocardium metabolism together with an enhanced use of fatty acids by mitochondria. These metabolic changes could result in an enhanced activity of K-ATP channels and AP shortening that might contribute to AF vulnerability in this clinical setting.

Acknowledgement/Funding

ANR-10-IAHU-05

Serum lipidomics reveals early differential effects of gastric bypass compared with banding on phospholipids and sphingolipids independent of differences in weight loss

BACKGROUND/OBJECTIVES

Circulating phospholipids and sphingolipids are implicated in obesity-related comorbidities such as insulin resistance and cardiovascular disease. How bariatric surgery affects these important lipid markers is poorly understood. We sought to determine whether Roux-en-Y gastric bypass (RYGB), which is associated with greater metabolic improvement, differentially affects the phosphosphingolipidome compared with adjustable gastric banding (AGB).

SUBJECTS/METHODS

Fasting sera were available from 59 obese women (body mass index range 37-51 kg m^-2; n=37 RYGB and 22 AGB) before surgery, then at 1 (21 RYGB, 12 AGB) and 3 months follow-up (19 RYGB, 12 AGB). HPLC-MS/MS was used to quantify 131 lipids from nine structural classes. DXA measurements and laboratory parameters were also obtained. The associations between lipids and clinical measurements were studied with P-values adjusted for the false discovery rate (FDR).

RESULTS

Both surgical procedures rapidly induced weight loss and improved clinical profiles, with RYGB producing better improvements in fat mass, and serum total cholesterol, low-density lipoprotein-cholesterol (LDL-C) and orosomucoid (FDR <10%). Ninety-three (of 131) lipids were altered by surgery-the majority decreasing-with 29 lipids differentially affected by RYGB during the study period. The differential effect of the surgeries remained statistically significant for 20 of these lipids after adjusting for differences in weight loss between surgery types. The RYGB signature consisted of phosphatidylcholine species not exceeding 36 carbons, and ceramides and sphingomyelins containing C22 to C25 fatty acids. RYGB also led to a sustained increase in unsaturated ceramide and sphingomyelin species. The RYGB-specific lipid changes were associated with decreases in body weight, total and LDL-C, orosomucoid and increased HOMA-S (FDR <10%).

CONCLUSIONS

Concomitant with greater metabolic improvement, RYGB induced early and sustained changes in phosphatidylcholines, sphingomyelins and ceramides that were independent of greater weight loss. These data suggest that RYGB may specifically alter sphingolipid metabolism, which, in part, could explain the better metabolic outcomes of this surgical procedure.

The biological activity of high-density lipoprotein fractions and their role in the development of cardiovascular diseases

Increasing the human plasma concentration of high-density lipoproteins (HDL) may be part of strategy for control of cardiovascular diseases (CVD). HDL particles vary in their structure, metabolism, and biological activity. The review describes major HDL fractions (subpopulations) and discusses new findings on the antiatherogenic properties of HDL particles. The whole spectrum of HDL fractions, small, dense, protein-rich lipoproteins, has atheroprotective properties that are determined by the presence of specialized groups of proteins and lipids; however, this activity may be decreased in atherogenic lesion. Comprehensive structural and compositional analysis of HDL may provide key information to identify the fractions that have characteristic biological properties and lose their functionality in CVD. These fractions may be also biomarkers for the risk of CVD and hence represent pharmacological targets.

Vergelijkende erfelijke en pathogenische kenmerken van hypertrofische cardiomyopathie bij de kat en de mens

Hypertrofische cardiomyopathie (HCM) wordt gekenmerkt door een hypertrofisch, nietgedilateerd linkerventrikel. Met een prevalentie van ongeveer 0,2% bij mensen en 15% bij katten is dit één van de meest voorkomende hartafwijkingen. In het merendeel van de gevallen is de aandoening erfelijk bepaald, maar ze kan ook verworven zijn. De klinische symptomen zijn variabel. Genotypisch aangetaste individuen kunnen (ernstige) symptomen van hartfalen vertonen of zelfs abrupt sterven, maar ze kunnen ook gedurende heel het leven asymptomatisch blijven. Er zijn bij de mens reeds meer dan 1400 polymorfismen gedetecteerd in dertien genen die coderen voor sarcomeereiwitten in het hart. Een deel van deze hebben een invloed op het aangemaakte eiwit en zijn, samen met modificerende genen en omgevingsfactoren, verantwoordelijk voor de ontwikkeling van hypertrofische cardiomyopathie. Bij de kat werden tot op heden slechts drie mutaties geïdentificeerd in een gen dat codeert voor één sarcomeereiwit. Voor deze drie mutaties bestaan reeds commerciële diagnostische testen. Deze mutaties zijn slechts verantwoordelijk voor een kleine fractie van de gevallen van HCM bij de kat. Wil men preventief ingrijpen, dan is het van belang om zo veel mogelijk oorzakelijke mutaties te kennen. Er zijn veel raakpunten tussen de feliene en humane vorm van hypertrofische cardiomyopathie. Zowel de manier van overerven (autosomaal) als de klinische verschijning en de histopathologische veranderingen komen overeen tussen de verschillende species. Er is echter nog te weinig bekend over de sarcomeereiwitten en hun mutaties om informatie te extrapoleren van mens naar kat en vice versa.