What is the clinical evidence from this study?

Population: Cardiac function. Intervention: TnIDD22,23 mutation (constitutive TnI PKA phosphorylation) vs. Nontransgenic controls. Primary outcome: Peak frequency response (inotropy and relaxation) (2-fold greater, p=<0.005).

What question did this study set out to answer?

To determine the specific in vivo role of cardiac troponin I phosphorylation by protein kinase A in modulating rate- and afterload-dependent cardiac function.

January 20, 2004Circulation Research

Frequency- and Afterload-Dependent Cardiac Modulation In Vivo by Troponin I With Constitutively Active Protein Kinase A Phosphorylation Sites

Q: What are the key findings of this study?

Transgenic mice with constitutive TnI PKA phosphorylation displayed marked augmentation of frequency-dependent inotropy and relaxation, with a peak frequency response 2-fold greater than controls (P<0.005).

Q: What question did this study set out to answer?

To determine the specific in vivo role of cardiac troponin I phosphorylation by protein kinase A in modulating rate- and afterload-dependent cardiac function.

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Key result

Transgenic mice with constitutive TnI PKA phosphorylation displayed marked augmentation of frequency-dependent inotropy and relaxation, with a peak frequency response 2-fold greater than controls (P<0.005).

Why the study?

Does constitutive PKA phosphorylation of troponin I improve frequency- and afterload-dependent cardiac modulation in vivo in mice?

Key Points

To determine the specific in vivo role of cardiac troponin I phosphorylation by protein kinase A in modulating rate- and afterload-dependent cardiac function.
Generated transgenic mice overexpressing cardiac troponin I with serine-to-aspartic acid mutations (TnIDD22,23) to mimic constitutive protein kinase A phosphorylation.
Assessed in vivo hemodynamics across varying pacing frequencies and afterload elevations, with and without isoproterenol challenge.
Evaluated isolated isometric trabeculae in vitro to assess contractility and relaxation in the absence of muscle shortening.
TnIDD22,23 mice displayed mildly enhanced baseline function and a peak frequency-dependent inotropic and lusitropic response 2-fold greater than control mice (P<0.005).
Increasing afterload prolonged relaxation significantly more in control mice compared to TnIDD22,23 mice (P<0.02), an effect abolished by isoproterenol treatment.
Isolated isometric trabeculae showed similar basal, frequency-stimulated, and isoproterenol-stimulated performance between strains, indicating an essential role for muscle shortening in vivo.

Structured PICO

Does constitutive PKA phosphorylation of troponin I improve frequency- and afterload-dependent cardiac modulation in vivo in mice?

Population

Transgenic mice overexpressing cardiac troponin I with mutated serine residues to mimic constitutive PKA phosphorylation (TnIDD22,23) and nontransgenic control mice

Intervention

Transgenic mutation mimicking constitutive PKA phosphorylation of troponin I (TnIDD22,23)

Comparator

Nontransgenic control mice

Outcome

Cardiac systolic and diastolic function, frequency-dependent inotropy and relaxation, and afterload sensitivity of relaxationsurrogate

Main Result

Effect estimate: 2-fold greater

p-value: p=<0.005

Constitutive PKA phosphorylation of cardiac troponin I enhances rate-dependent systolic and diastolic function and reduces afterload sensitivity of relaxation in vivo, providing mechanistic insights relevant to heart failure.

Discussion

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Implication

Does not alter clinical practice; extends mechanistic insights on troponin I phosphorylation in preclinical frequency-dependent contractility.

Cite This Study

Takimoto et al. (2004) studied Cardiac function. TnIDD22,23 mutation (constitutive TnI PKA phosphorylation) vs. Nontransgenic controls was evaluated on Peak frequency response (inotropy and relaxation) (2-fold greater, p=<0.005). Transgenic mice with constitutive TnI PKA phosphorylation displayed marked augmentation of frequency-dependent inotropy and relaxation, with a peak frequency response 2-fold greater than controls (P<0.005).

synapsesocial.com/papers/6a1596ac79ff98d0de4eda1d https://doi.org/10.1161/01.res.0000117307.57798.f5

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Implication

Does not alter clinical practice; extends mechanistic insights on troponin I phosphorylation in preclinical frequency-dependent contractility.

Frequency- and Afterload-Dependent Cardiac Modulation In Vivo by Troponin I With Constitutively Active Protein Kinase A Phosphorylation Sites

Key Points

Structured PICO

Main Result

Discussion

Implication

Cite This Study

Frequency- and Afterload-Dependent Cardiac Modulation In Vivo by Troponin I With Constitutively Active Protein Kinase A Phosphorylation Sites

Key Points

Structured PICO

Main Result

Discussion

Implication

Cite This Study

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