MODULATING EFFECTS OF IGF I AND LEPTIN LEVELS ON BONE MINERAL CONTENT

SUAREZ C; FERREIRA MONTEIRO A; RODRIGUEZ P; ZENI SN; FRIEDMAN S

San Francisco, USA

Congreso; Experimental Biology 2006; 2006

Knowledge the strong relationship between body lipid size and serum leptin levels due to its appetite regulation and the insulin like growth factor (IGF) I involved as a signal of calories, body lipid composition and proteins viability, it is important to begin to answer questions concerning bone formation throughout leptin and IGF I receptors. The aim of this study was to evaluate the strong association among leptin and IGF I levels during active growth. The experimental rat model consisted of individuals under 50% of energy restriction diets with or without calcium restriction. Forty two weanling Wistar rats were randomly assigned one of the three diets providing a carbohydrate to fat calorie ratio of 1:1 (reference group) (a) or 3:1 calorie ratio with either 0.6% or 0.3% of calcium content (b and c, respectivately).  At day= 35, animals were sacrificed. Body weights (BW=g) and lengths (BL=cm) were measured and body composition (percentage of body fat by chemical method AOAC) and bone mineral content (BMC) (by DEXA Lunar DPX) were determined. In five of them serum IGF I and leptin levels were measured (ELISA ng/ml). Results are presented as mean + SD and p<0.05 was considered statistically significant.   Diet Body length % body fat IGF I Leptin BMC/BW % 1:1 0,6 % Ca 15.9 ±  0.7 10.0 ±  1.7 706.08  ±  243.09 1.30 ±  0.86 0.34 ±   0.05 3:1 0,6 % Ca 15.5 ±  0.7 7.9  ±  1.5 ** 592.88 ±  132.23 0.70 ±   0.45 0.27  ±  0.03 * 3: 1 0,3 % Ca 15.3 ± 0.6 ** 6.1  ± 1.2 ** 564.1 ±  297.19 0.87 ±  0.74 0.15  ±  0.01** ANOVA, Dunnett test   *P<0.05;  **P<0.01. Diets in which fat were restricted (b and c), affected the percentage of body fat, and bone mineral content. Body length remained unchanged in adequate calcium diets while there was a tendency towards serum IGF I and serum leptin levels more diminished in a and b, than a. Therefore serum IGF I and leptin appear to account for an accurate bone tissue development. Awarded by UBACyT O 004.