Transgenic overexpression of insulin-like growth factor I prevents streptozotocin-induced cardiac contractile dysfunction and beta-adrenergic response in ventricular myocytes.

Abstract

Diabetic cardiomyopathy is characterized by cardiac dysfunction and altered level/function of insulin-like growth factor I (IGF-I). Both endogenous and exogenous IGF-I have been shown to effectively alleviate diabetes-induced cardiac dysfunction and oxidative stress. This study was designed to examine the effect of cardiac overexpression of IGF-I on streptozotocin (STZ)-induced cardiac contractile dysfunction in mouse myocytes. Both IGF-I heterozygous transgenic mice and their wild-type FVB littermates were made diabetic with a single injection of STZ (200 mg/kg, i.p.) and maintained for 2 weeks. The following mechanical indices were evaluated in ventricular myocytes: peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR90) and maximal velocity of shortening/relengthening (+/- dL/dt). Intracellular Ca2+ was evaluated as resting and peak intracellular Ca2+ levels, Ca2+-induced Ca2+ release and intracellular Ca2+ decay rate (tau). STZ led to hyperglycemia in FVB and IGF-I mice. STZ treatment prolonged TPS and TR90, reduced Ca2+-induced Ca2+ release, increased resting intracellular Ca2+ levels and slowed tau associated with normal PS and +/- dL/dt. All of which, except the elevated resting intracellular Ca2+, were prevented by the IGF-I transgene. In addition, myocytes from STZ-treated FVB mice displayed an attenuated contractile response to the beta-adrenergic agonist isoproterenol, which was restored by the IGF-I transgene. Contractile response to the alpha-adrenergic agonist phenylephrine and angiotensin II was not affected by either STZ treatment or IGF-I. These results validate the beneficial role of IGF-I in diabetic cardiomyopathy, possibly due to an improved beta-adrenergic response.

• Authors: F L Norby, N S Aberle 2nd, J Kajstura, P Anversa, J Ren
• Journal: The Journal of endocrinology (J Endocrinol) Vol. 180 Issue 1 Pg. 175-82 (Jan 2004) ISSN: 0022-0795 [Print] England
• PMID: 14709156 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Adrenergic alpha-Agonists
• Adrenergic beta-Agonists
• Angiotensin II
• Phenylephrine
• Insulin-Like Growth Factor I
• Isoproterenol
• Calcium

Topics

• Adrenergic alpha-Agonists (pharmacology)
• Adrenergic beta-Agonists (pharmacology)
• Angiotensin II (pharmacology)
• Animals
• Body Weight
• Calcium (metabolism)
• Cells, Cultured
• Diabetes Mellitus, Experimental (metabolism, physiopathology)
• Gene Expression
• Heart Ventricles
• Insulin-Like Growth Factor I (genetics)
• Isoproterenol (pharmacology)
• Male
• Mice
• Mice, Inbred Strains
• Mice, Transgenic
• Models, Animal
• Myocardial Contraction (drug effects)
• Myocardium (pathology)
• Myocytes, Cardiac (metabolism)
• Organ Size
• Phenylephrine (pharmacology)