THE MOLECULAR BASIS OF DIABETIC CARDIOMYOPATH

Diabetes mellitus (DM) is a major and worsening global health problem. Type 2 diabetes mellitus (T2DM) accounts for more than 90% of DM and the global epidemic of obesity largely explains the dramatic increase in the incidence and prevalence of T2DM over the past 20 years. Cardiovascular complications are the major cause of morbidity and mortality in diabetic patients. The electrocardiogram (ECG) of diabetic and obese patients is frequently disturbed. The aim of this project was to characterize and clarify the molecular basis of electro-mechanical dysfunction in the hearts of type 2 diabetic and type 2 diabetic/obese rats. Experiments were performed in Zucker diabetic fatty (ZDF), Zucker fatty (ZF), and Zucker lean (ZL) rats. In vivo, biotelemetry experiments were performed to establish how the ECG was altered by diabetes and diabesity. Experiments were also carried out in isolated hearts to investigate further how diabetes and diabesity affect the electrical conduction system of the heart. Cell imaging was employed to assess ventricular myocyte shortening. Fluorescence photometry and whole-cell patch-clamp techniques were used to assess the effects of diabetes and diabesity on ion channel currents. Molecular biology and electron microscopy techniques were employed to assess proteins and structures associated with cardiac muscle contraction. Heart rate (HR) was reduced by aging and by diabesity in the absence of changes in physical activity and body temperature. Reductions in heart rate variability linked with altered sympathovagal drive may partly underlie disturbed HR in the ZDF rat even in the absence of autonomic nervous system control in the isolated perfused heart. The amplitude of shortening is generally well preserved in ZDF myocytes. There was evidence of altered time course of the Ca2+ transient and shortening in ventricular myocytes from ZDF rats. Molecular and structural defects in the ZF and ZDF rat hearts were observed. The results suggest that sarcoplasmic reticulum (SR) Ca2+ handling as well as energy utilization are compromised in ZDF and ZF myocytes. Myocyte contraction and relaxation may also be affected in the ZDF and ZF rats due to protein and ventricular structural defects. Isoprenaline was less effective at generating an increase in the AMP of shortening in ZDF and ZF compared to ZL myocytes and defects in Ca2+ signaling, and in particular, SR Ca2+ transport might partly underlie these abnormalities

The Effects of Thujone on the Function of Nicotinic Acetylcholine Receptors

Thujone is a natural compound found in plants such as “wormwood” and “sage” and it’s also found in the alcoholic drink “Absinthe”. Thujone has been suggested as a neurotoxic compound and reported to modulate GABAA receptors. In this study, we investigated the pharmacology of Thujone on nicotinic receptors expressed in Xenopus oocytes using the two electrode voltage clamp method. Thujone (100μM) caused an 80% inhibition of Acetylcholine (ACh) induced currents in human α7-nAChRs expressed in frog oocytes while only 30% inhibition currents in α4β2 expressed oocytes and no effect on α3β4, α3β2 and α4β4 nAChRs. The mechanisms of Thujone effect on the α7-nAChR were further investigated and found to be independent of membrane potential and did not compete with ACh. Furthermore, Thujone did not affect the activity of endogenous Ca2+ dependent Cl- channels. In conclusion, Thujone inhibits human nAChRs with different potencie