Conditions with moderate pathology, but not chronic or severe settings. Given the current enthusiasm and anticipation regarding therapeutic development of miR-34a and miR-34 family-targeted antimiRs, and the differences in cardiac protection in acute versus chronic settings, it is important to assess the therapeutic potential of inhibiting miR34a in more sustained pathological settings. This is also important because a challenge facing miRNA-based therapies is the vast number of predicted targets which could result in off-target Tubeimoside-I effects. Since the miR-34 family has approximately 31�C55% more targets in humans than miR-34a alone, interventions that modulate the entire miRNA family have greater theoretical potential to generate off-target effects. Thus, if manipulation of a single miRNA can provide adequate cardiac protection, this approach may be an advisable alternative means of obtaining a therapeutic effect with lower risk of off-target complications. In the current study, we assessed the therapeutic potential of inhibiting miR-34a in a mouse model with pre-existing pathological hypertrophy and systolic dysfunction due to pressure overload induced by TAC. We report here, that administration of a locked nucleic acid –Tulathromycin B antimiR-34a in a model of pressure overloadinduced hypertrophic cardiomyopathy with moderate systolic dysfunction was able to prevent further deterioration in cardiac function over an eight week period. In contrast, this approach was unable to attenuate pathological remodeling in a model of pressure overload with severe systolic dysfunction, whereby systolic function continued to decline eight weeks after treatment. In a previous study, we reported that inhibition of the miR-34 family attenuated LV remodeling and atrial enlargement in mouse models with established cardiac dysfunction due to MI or pressure overload. Interestingly, inhibition of miR-34a alone provided no significant benefit in the MI setting, but was not explored in the pressure overload model. Given that inhibition of miR-34a is being considered as a possible therapy for cardiovascular disease, we set out to determine whether miR-34a inhibition could provide benefit in a mouse model of pressure overloadinduced pathological hypertrophy. A potential advantage of inhibiting miR-34a alone, as opposed to the entire family, is related to fewer possible off-target effects. The major finding of the present study is that inhibition of miR34a provided some protection in the TAC moderate model, but not in the TAC severe model. LNA-antimiR-34a treated TAC moderate mice did not develop lung congestion, atrial enlargement was attenuated, and importantly, there was no further deterioration in cardiac function at 12 weeks post TAC compared to pretreatment values at four weeks post TAC. In contrast, systolic function continued to fall in TAC moderate LNA-control mice. HW/TL increased by approximately 49% in TAC moderate LNA-control mice, and only 30% in TAC moderate LNA-antimiR-34a mice. Despite attenuation of adverse cardiac remodeling, treatment with LNA-antimiR-34a was not 
associated with a more favorable cardiac molecular signature or less fibrosis. The only parameter which showed a tendency to be attenuated in antimiR-34a treated mice was b-MHC expression. Treatment with LNA-antimiR-34a was associated with a trend for increased Sirt1 expression. Sirt1 protects the heart against ageing and stress, thus increased Sirt1 mRNA may contribute to the modest cardiac protection observed in TAC moderate mice.