Response to Qian and Colvin : zinc-mediated regulation of the cardiac ryanodine receptor occurs via multiple binding sites

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Reduced plasma magnesium levels in type-1 diabetes associate with prothrombotic changes in fibrin clotting and fibrinolysis

This research was funded by the British Heart Foundation, grant numbers PG/15/9/31270 and FS/15/42/3155. The study sponsor was not involved in the design of the study; the collection, analysis, and interpretation of data.Individuals with type-1 diabetes mellitus (T1DM) have a higher risk of thrombosis and low plasma magnesium concentrations. As magnesium is a known regulator of fibrin network formation, we investigated potential associations between fibrin clot properties and plasma magnesium concentrations in 45 individuals with T1DM and 47 age- and sex-matched controls without diabetes. Fibrin clot characteristics were assessed using a validated turbidimetric assay and associations with plasma magnesium concentration were examined. Plasma concentrations of fibrinogen, plasminogen activator inhibitor-1 (PAI-1), and lipids were measured and fibrin fiber diameters assessed using scanning electron microscopy. Fibrin clot maximum absorbance was unchanged in subjects with T1DM compared with controls, while lysis time was prolonged (p = 0.0273). No differences in fibrin fiber diameters or in lipid profile were observed between T1DM and controls. PAI-1 concentration was lower in the T1DM group compared with the controls (p = 0.0232) and positively correlated with lysis time (p = 0.0023). Plasma magnesium concentration was lower in the T1DM group compared with controls (p < 0.0001). Magnesium concentration negatively correlated with clot maximum absorbance (p = 0.0215) and lysis time (p = 0.0464). A turbidimetric fibrin clot lysis assay performed in a purified system that included PAI-1 and 0 to 3.2 mM Mg2+ showed a shortening of lysis time with increasing Mg2+ concentrations (p = 0.0004). Our findings reveal that plasma magnesium concentration is associated with changes in fibrin clot and lysis parameters.Publisher PDFPublisher PDFPeer reviewe

Lipidomic profiling of plasma free fatty acids in type-1 diabetes highlights specific changes in lipid metabolism

This research was funded by the British Heart Foundation [grant numbers PG/15/9/31270, FS/15/42/3155].Type-1 diabetes mellitus (T1DM) is associated with metabolic changes leading to alterations in glucose and lipid handling. While T1DM- associated effects on many major plasma lipids have been characterised, such effects on plasma free fatty acids (FFA) have not been fully examined. Using gas chromatography-mass spectrometry, we measured the plasma concentrations of FFA species in individuals with T1DM (n=44) and age/sex-matched healthy controls (n=44). Relationships between FFA species and various parameters were evaluated. Plasma concentrations of myristate (14:0), palmitoleate (16:1), palmitate (16:0), linoleate (18:2), oleate (18:1c9), cis-vaccenate (18:1c11), eicosapentaenoate (20:5), arachidonate (20:4) and docosahexanoate (22:6) were reduced in the T1DM group (p<0.0001 for all, except p=0.0020 for eicosapentaenoate and p=0.0068 for arachidonate); α-linolenate (18:3) and dihomo-γ- linolenate (20:3) concentrations were unchanged. Saturated/unsaturated FFA ratio, n-3/n-6 ratio, de novo lipogenesis index (palmitate (main lipogenesis product)/linoleate (only found in diet)) and elongase index (oleate/palmitoleate) were increased in the T1DM group (p=0.0166, p=0.0089, p<0.0001 and p=0.0008 respectively). The stearoyl-CoA desaturase 1 (SCD1) index 1 (palmitoleate/palmitate) and index 2 (oleate/stearate) were reduced in T1DM (p<0.0001 for all). The delta-(5)- desaturase (D5D) index (arachidonate/dihomo-γ-linolenate) was unchanged. Age and sex had no effect on plasma FFA concentrations in T1DM, while SCD1 index 1 was positively correlated (p=0.098) and elongase index negatively correlated with age (p=0.0363). HbA1c was negatively correlated with all plasma FFAs concentrations measured except α- linolenate and dihomo-γ-linolenate. Correlations were observed between plasma FFAs and cholesterol and HDL, but not LDL or diabetes duration. Collectively, these results aid our understanding of T1DM and its effects on lipid metabolism.Publisher PDFPeer reviewe

Dysregulated Zn2+ homeostasis impairs cardiac type-2 ryanodine receptor and mitsugumin 23 functions, leading to sarcoplasmic reticulum Ca2+ leakage

SJP is supported by a Royal Society of Edinburgh Biomedical Fellowship. Benedict Reilly-O’Donnell is supported by a University of St Andrews 600th Anniversary Scholarship. This work was supported by the British Heart Foundation (grant no: FS/14/69/31001 to SJP) and the Japan Society for the Promotion of Science (Core-to-Core Program awarded to HT).Aberrant Zn2+ homeostasis is associated with dysregulated intracellular Ca2+ release, resulting in chronic heart failure. In the failing heart a small population of cardiac ryanodine receptors (RyR2) displays sub-conductance-state gating leading to Ca2+ leakage from sarcoplasmic reticulum (SR) stores, which impairs cardiac contractility. Previous evidence suggests contribution of RyR2-independent Ca2+ leakage through an uncharacterized mechanism. We sought to examine the role of Zn2+ in shaping intracellular Ca2+ release in cardiac muscle. Cardiac SR vesicles prepared from sheep or mouse ventricular tissue were incorporated into phospholipid bilayers under voltage-clamp conditions, and the direct action of Zn2+ on RyR2 channel function was examined. Under diastolic conditions, the addition of pathophysiological concentrations of Zn2+ (≥2 nm) caused dysregulated RyR2-channel openings. Our data also revealed that RyR2 channels are not the only SR Ca2+-permeable channels regulated by Zn2+. Elevating the cytosolic Zn2+ concentration to 1 nm increased the activity of the transmembrane protein mitsugumin 23 (MG23). The current amplitude of the MG23 full-open state was consistent with that previously reported for RyR2 sub-conductance gating, suggesting that in heart failure in which Zn2+ levels are elevated, RyR2 channels do not gate in a sub-conductance state, but rather MG23-gating becomes more apparent. We also show that in H9C2 cells exposed to ischemic conditions, intracellular Zn2+ levels are elevated, coinciding with increased MG23 expression. In conclusion, these data suggest that dysregulated Zn2+ homeostasis alters the function of both RyR2 and MG23 and that both ion channels play a key role in diastolic SR Ca2+ leakage.Publisher PDFPeer reviewe

Microlaser-based contractility sensing in single cardiomyocytes and whole hearts

Microscopic whispering gallery mode lasers detect minute changes in cellular refractive index inside individual cardiac cells and in live zebrafish. We show that these signals encode cardiac contractility that can be used for intravital sensing.Postprin

17ß-Estradiol protects against the effects of a high fat diet on cardiac glucose, lipid and nitric oxide metabolism in rats

This work is supported by the grant No.173033 (to E.R.I.) from the Ministry of Education, Science and Technological Development, Republic of Serbia.The aim of this study was to investigate the in vivo effects of estradiol (E2) on myocardial metabolism and inducible nitric oxide synthase (iNOS) expression/activity in obese rats. Male Wistar rats were fed with a normal or a high fat (HF) diet (42% fat) for 10 weeks. Half of the HF fed rats were treated with a single dose of E2 while the other half were placebo-treated. 24h after treatment animals were sacrificed. E2 reduced cardiac free fatty acid (FFA) (p<0.05), L-arginine (p<0.01), iNOS mRNA (p<0.01), and protein (p<0.05) levels and translocation of the FFA transporter (CD36) (p<0.01) to the plasma membrane (PM) in HF fed rats. In contrast, Akt phosphorylation at Thr308 (p<0.05) and translocation of the glucose transporter GLUT4 (p<0.05) to the PM increased after E2 tretment in HF rats. Our results indicate that E2 acts via PI3K/Akt signaling pathway to partially protect myocardial metabolism by attenuating the detrimental effects of increased iNOS expression/activity in HF fed rats.PostprintPeer reviewe

Changes in cardiac Na+/K+-ATPase expression and activity in female rats fed a high fat diet

This work is supported by the Grant Nos. 173033 and III41028 from the Ministry of Science, Republic of Serbia.The aim of this study was to investigate whether the presence of endogenous estradiol alters the effects of a high-fat (HF) diet on activity/expression of the cardiac Na+/K+-ATPase, via PI3K/IRS and RhoA/ROCK signalling cascades in female rats. For this study, female Wistar rats (8 weeks old, 150–200 g) were fed a standard diet or a HF diet (balanced diet for laboratory rats enriched with 42% fat) for 10 weeks. The results show that rats fed a HF diet exhibited a decrease in phosphorylation of the α1 subunit of Na+/K+-ATPase by 30% (p < 0.05), expression of total α1 subunit of Na+/K+-ATPase by 31% (p < 0.05), and association of IRS1 with p85 subunit of PI3K by 42% (p < 0.05), while the levels of cardiac RhoA and ROCK2 were significantly increased by 84% (p < 0.01) and 62% (p < 0.05), respectively. Our results suggest that a HF diet alters cardiac Na+/K+-ATPase expression via molecular mechanisms involving RhoA/ROCK and IRS-1/PI3K signalling in female rats.PostprintPeer reviewe

Young people’s awareness of the timing and placement of gambling advertising on traditional and social media platforms: a study of 11–16-year-olds in Australia

Background Research has demonstrated that the promotion of gambling, particularly within sport, may have a significant impact on positively shaping young people’s attitudes towards gambling. While some governments have implemented restrictions to limit young people’s exposure to gambling advertising, few studies have investigated where young people recall seeing gambling advertising, and whether they perceive that advertising restrictions have gone far enough in reducing exposure to these promotions. Method Mixed methods, interviewer-assisted surveys were conducted with n = 111 young people aged 11–16 years, who were self-reported fans of basketball in Victoria, Australia. Interviews were conducted at basketball stadiums between May and July 2018. The study assessed media viewing patterns; recall and awareness of the timing, placement, and content of gambling advertising; the impact of gambling advertising restrictions; and attitudes towards sporting organisations’ roles in the promotion of gambling. Results The majority of young people recalled seeing gambling advertising on television (n = 101, 91.0%), with most recalling advertising within sporting matches or games (n = 79, 71.2%). Most young people recalled seeing gambling advertising in the early evening before 8:30 pm (n = 75, 67.6%). Just over half of young people described seeing gambling advertisements on social media (n = 61, 55.0%), and over a third (n = 40, 36.0%) recalled gambling advertising on YouTube, predominantly before watching sporting or gaming videos. The majority stated that they continued to watch sport after 8:30 pm (n = 93, 83.7%), which is when restrictions on advertising in live sport in Australia end. The majority (n = 88, 79.3%) stated that there were too many gambling advertisements in sport. Three quarters believed that sporting codes should do more to prevent young people from being exposed to advertising for gambling in sport (n = 84, 75.7%). Conclusions There is now a clear body evidence that current regulatory systems for gambling advertising are ineffective, with further restrictions urgently needed across a range of media channels to prevent exposure to promotions that may encourage young people’s interest and involvement in gambling