Long-term effects of calorie or protein restriction on serum IGF-1 and IGFBP-3 concentration in humans.
Reduced function mutations in the insulin/IGF-I signaling pathway increase maximal lifespan and health span in many species. Calorie restriction (CR) decreases serum IGF-1 concentration by ~40%, protects against cancer and slows aging in rodents. However, the long-term effects of CR with adequate nutrition on circulating IGF-1 levels in humans are unknown. Here we report data from two long-term CR studies (1 and 6 years) showing that severe CR without malnutrition did not change IGF-1 and IGF-1 : IGFBP-3 ratio levels in humans. In contrast, total and free IGF-1 concentrations were significantly lower in moderately protein-restricted individuals. Reducing protein intake from an average of 1.67 g kg(-1) of body weight per day to 0.95 g kg(-1) of body weight per day for 3 weeks in six volunteers practicing CR resulted in a reduction in serum IGF-1 from 194 ng mL(-1) to 152 ng mL(-1). These findings demonstrate that, unlike in rodents, long-term severe CR does not reduce serum IGF-1 concentration and IGF-1 : IGFBP-3 ratio in humans. In addition, our data provide evidence that protein intake is a key determinant of circulating IGF-1 levels in humans, and suggest that reduced protein intake may become an important component of anticancer and anti-aging dietary interventions.
Fontana
Luigi
L
Division of Geriatrics & Nutritional Sciences, Washington University School of Medicine, St Louis, MO 63110, USA. lfontana@dom.wustl.edu
Weiss
Edward P
EP
Villareal
Dennis T
DT
Klein
Samuel
S
Holloszy
John O
JO
D000375:Aging / Q000097:blood*; D031204:Caloric Restriction / Q000009:adverse effects; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake / Q000502:physiology; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D011488:Protein Deficiency / Q000097:blood* / Q000150:complications; D013997:Time Factors
D004044:Dietary Proteins; C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I