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Text sizeFramingham, MA - A low serum level of insulinlike growth factor-1 (IGF-1), often found in older people, is an important risk factor for congestive heart failure (CHF), according to new data from the Framingham Heart Study, published in the October 21, 2003 issue of Annals of Internal Medicine.1
"A high serum IGF-1 level was associated with a diminished hazard of heart failure in a continuous fashion without evidence of a threshold," the report states.
IGF-1, which decreases with age, is known to have antiapoptotic effects and to play a positive role in ventricular remodeling. In CHF patients, IGF-1 levels were found to be low. In addition, gender, nutrition, body fat, hormonal influences, presence of catabolic illnesses, and genetic factors can influence IGF-1 levels, lead investigator Dr Ramachandran Vasan (Framingham Heart Study) explained to heartwire.Old age, female sex, and poor nutrition are associated with lower IGF-1 levels.
The present study is the first to prospectively study a possible association between IGF-I and the risk of developing CHF. Vasan and colleagues studied 717 elderly Framingham Heart Study participants without MI or CHF at baseline.
During a mean follow-up of 5.2 years, 56 of them (7.8%) developed CHF. The researchers observed that the risk for CHF was "noticeably higher" in participants with serum IGF-1 levels below 140 g/L. Moreover, after adjustment for known CHF risk factors and other covariables, those with levels of 140 g/L or above had a 51% lower hazard of CHF compared with individuals with lower levels. In contrast, serum levels below 75 g/L were associated with a more than 2.5 fold increase in CHF risk.
IGF-I: "A double-edged sword"
Experimental and clinical data have suggested cardioprotective actions of IGF-1, even in those without CHF or MI. However, growth hormone infusions in patients with dilated cardiomyopathy have rendered "disappointing results," which may have been related to the selection of an inappropriate agent, the authors suggest. They point to several mechanisms that could explain the association between serum IGF-1 levels and CHF risk, among them the growth factor's vasodilatory action, its positive effects on myocyte survival by inhibiting apoptotic and activating survival pathways, and its ability to promote myofibrillar hypertrophy. However, Vasan and colleagues also refer to the downside of high IGF-levels, which could, due to their antiapoptotic properties, increase the risk for common cancers. The next challenge, thus, will be to pinpoint IGF-1 levels that are cardioprotective but do not increase cancer hazards. "A potential approach to increase IGF-1 levels that may merit further exploration is through exercise," the authors conclude.
"IGF is a double-edged sword," Vasan told heartwire. "Analyses relating IGF levels to several outcomescancer and CHFwould seem to be important before any conclusions are drawn about therapeutic benefits from IGF."
