Mouse
parathyroid hormone-related peptide (
PTHrP) is a
peptide hormone consisting of 139
amino acids. It is target of proteolysis resulting in circulation of N- and C-terminal
peptides. C-terminal
PTHrP peptides act in a
PTH/PTHrP receptor-independent way with a minimal
peptide sequence required to exert these effects covering
amino acids 107-111 also known as
osteostatin. Although effects of
osteostatin on
cardiac hypertrophy have been described in vitro, the in vivo relevance of these findings remained to be defined. The study was performed in two experimental series. In the first series, mice were randomly distributed into placebo or treatment group (each n=7) and
osteostatin was administered via osmotic minipumps. In the second series, mice underwent a banding of the thoracic aorta to induce pressure overload and were again randomly distributed into placebo or treatment group (n=9 each). After 14 days, mice were anaesthetized and cardiac function, ECG, and
cardiac hypertrophy were determined.
Osteostatin increased the expression of
ANF and reduced P-wave duration with little effects on cardiac performance in mice without pressure overload. In TAC banded mice, however,
osteostatin significantly reduced TAC-induced loss of
body weight, induced
right ventricular hypertrophy, and reduced P-wave duration again. In
osteostatin treated mice with pressure overload, the
protein kinase C-dependent phosphorylation of
connexin 43 was preserved. In summary,
osteostatin attenuated pressure-overload-dependent loss of
body weight without affecting
left ventricular hypertrophy or left ventricular function but preserved atrial conduction.
Osteostatin exerts moderate cardioprotective effects in mice under hemodynamic stress.