EXPERIMENTAL APPROACH: We compared the ability of fully charged (QX-FL) and neutral (NU-FL) derivatives of flecainide to block individual recombinant human RyR2 channels incorporated into planar phospholipid bilayers, and their effects on the properties of Ca(2) (+) sparks in intact adult rat cardiac myocytes.
KEY RESULTS: Both QX-FL and NU-FL were partial blockers of the non-physiological cytosolic to luminal flux of cations through RyR2 channels but were significantly less effective than flecainide. None of the compounds influenced the physiologically relevant luminal to cytosol cation flux through RyR2 channels. Intracellular flecainide or QX-FL, but not NU-FL, reduced Ca(2) (+) spark frequency.
CONCLUSIONS AND IMPLICATIONS: Given its inability to block physiologically relevant cation flux through RyR2 channels, and its lack of efficacy in blocking the cytosolic-to-luminal current, the effect of QX-FL on Ca(2) (+) sparks is likely, by analogy with flecainide, to result from Na(+) channel block. Our data reveal important differences in the interaction of flecainide with sites in the cytosolic vestibules of Na(+) and RyR2 channels.
Methods: Forty-six male Sprague Dawley rats aged 3 months were randomized into six groups. The baseline control (n=6) was sacrificed at the onset of the study. The normal control (n=8) received corn oil (the vehicle of tocotrienol) orally daily and normal saline (the vehicle of buserelin) subcutaneously daily. The buserelin control (n=8) received corn oil orally daily and subcutaneous buserelin injection (75 µg/kg) daily. The calcium control (n=8) was supplemented with 1% calcium in drinking water and daily subcutaneous buserelin injection (75 µg/kg). The remaining rats were given daily oral annatto tocotrienol at 60 mg/kg (n=8) or 100 mg/kg (n=8) plus daily subcutaneous buserelin injection (75 µg/kg) (n=8). At the end of the experiment, the rats were euthanized and their blood, tibia, and femur were harvested. Structural changes of the tibial trabecular and cortical bone were examined using X-ray micro-computed tomography. Femoral bone calcium content and biomechanical strength were also evaluated.
Results: Annatto tocotrienol at 60 and 100 mg/kg significantly prevented the deterioration of trabecular bone and cortical thickness in buserelin-treated rats (P<0.05). Both doses of annatto tocotrienol also improved femoral biomechanical strength and bone calcium content in buserelin-treated rats (P<0.05). The effects of annatto tocotrienol were comparable to calcium supplementation.
Conclusion: Annatto tocotrienol supplementation is effective in preventing degeneration of the bone induced by buserelin. Therefore, it is a potential antiosteoporotic agent for men receiving androgen deprivation therapy.
METHOD: Cross-sectional study of ambulant children with epilepsy on long-term AEDs for >1 year seen in a tertiary hospital in Malaysia from 2014 to 2015. Detailed assessment of anthropometric measurements; environmental lifestyle risk factors; serum vitamin D, calcium and parathyroid hormone levels; genotyping of single nucleotide polymorphisms of genes in vitamin D and calcium metabolism; and lumbar spine BMD were obtained. Low BMD was defined as BMD Z-score ≤ -2.0 SD.
RESULTS: Eighty-seven children with mean age of 11.9 years (56 males) participated in the study. The prevalence of low lumbar BMD was 21.8% (19 patients). Multivariate logistic regression analysis identified polytherapy >2 AEDs (OR: 7.86; 95% CI 1.03-59.96), small frame size with wrist breadth of <15th centile (OR 14.73; 95% CI 2.21-98.40), and body mass index Z-score 2 AEDs, underweight or with small frame size as they are at higher risk of having low BMD.