Role of miRNAs and alternative mRNA 3'-end cleavage and polyadenylation of their mRNA targets in cardiomyocyte hypertrophy.

miRNAs play critical roles in heart disease. In addition to differential miRNA expression, miRNA-mediated control is also affected by variable miRNA processing or alternative 3'-end cleavage and polyadenylation (APA) of their mRNA targets. To what extent these phenomena play a role in the heart remains unclear. We sought to explore miRNA processing and mRNA APA in cardiomyocytes, and whether these change during cardiac hypertrophy. Thoracic aortic constriction (TAC) was performed to induce hypertrophy in C57BL/6J mice. RNA extracted from cardiomyocytes of sham-treated, pre-hypertrophic (2 days post-TAC), and hypertrophic (7 days post-TAC) mice was subjected to small RNA- and poly(A)-test sequencing (PAT-Seq). Differential expression analysis matched expectations; nevertheless we identified ~400 mRNAs and hundreds of noncoding RNA loci as altered with hypertrophy for the first time. Although multiple processing variants were observed for many miRNAs, there was little change in their relative proportions during hypertrophy. PAT-Seq mapped ~48,000 mRNA 3'-ends, identifying novel 3' untranslated regions (3'UTRs) for over 7000 genes. Importantly, hypertrophy was associated with marked changes in APA with a net shift from distal to more proximal mRNA 3'-ends, which is predicted to decrease overall miRNA repression strength. We independently validated several examples of 3'UTR proportion change and showed that alternative 3'UTRs associate with differences in mRNA translation. Our work suggests that APA contributes to altered gene expression with the development of cardiomyocyte hypertrophy and provides a rich resource for a systems-level understanding of miRNA-mediated regulation in physiological and pathological states of the heart.

Effects of acetate on left ventricular function in hemodialysis patients.

Two approaches were chosen to assess the controversially debated influence of acetate on the heart in dialysis patients: (1) To separate acetate effects from influences of dialysis, acetate was infused in 12 chronic dialysis patients with normal systolic function on a dialysis-free day, and left ventricular (LV) function was assessed by LV pressure/volume loops. Hyperacetatemia (3-5 mmol/l) resulted in a decrease in LV preload (LV end-diastolic pressure decreased from 16 +/- 3 to 10 +/- 4 mm Hg, p < 0.01) but had no influence on LV contractility. (2) In 8 dialysis patients without cardiac disease, isovolemic acetate or bicarbonate dialysis was performed. During both procedures, there were comparable changes in serum electrolytes as well as in echocardiographic parameters. LV contractility measured by velocity of circumferential fiber shortening increased during acetate and bicarbonate dialysis (1.47 +/- 0.22 to 1.77 +/- 0.29, p < 0.01; 1.47 +/- 0.21 to 1.70 +/- 0.22 circ/s, p < 0.01). It is concluded that mild hyperacetatemia does not influence LV contractility and that dialysis-induced changes in serum electrolytes are responsible for the increase in LV contractility during dialysis. However, the pronounced acetate effect on LV preload implies considerable therapeutic implications.

[Assessment of the effect of piracetam (Nootrop) on hydrogen clearance in the inner ear]. / Prüfung der Wirkung von Piracetam (Nootrop) auf die Wasserstoff-Clearance am Innenohr.

The animal experiment described in this report was conducted to study the effect of piracetam on the blood flow of the inner ear. Blood flow was measured indirectly by means of hydrogen clearance using the polarographic microanalysis technique. A group of twelve crossbred male and female guinea pigs were given 400 mg/kg body weight piracetam (2 ml/kg body weight of commercial solution for injection) by intravenous injection, and hydrogen clearance was measured before and after administering the study drug at the round window in the scala media at the base of the cochlea. Twelve animals in an control group were given an equal volume of physiological saline instead of the study drug. The H2 clearance measurements were taken before and after intravenous injection of saline. The operation and clearance measurements were performed under injection anaesthesia with 2.5 mg. diazepam and 25 mg. pentobarbital sodium, each per kg body weight. The guinea pigs were premedicated with atropine (0.5 mg./kg. body weight i.p.) and, after tracheotomy, were relaxed with pancuronium bromide (1 mg./kg. body weight i.v.) and respirated with a pneumatic respiration pump and the parameters blood pressure, pH and blood gases (pO2, pCO2) were continuously recorded. The results show that intravenous injection of piracetam in the above mentioned dose accelerates hydrogen clearance processes at the base of the cochlea from 8.68 +/- 3.48 to 5.37 +/- 2.05 minutes half-life. This effect is statistically significant (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)