OBJECTIVETo explore the mechanism and effect of maternal high-fat diet before and during pregnancy on bone growth of neonatal offspring rats.

METHODSForty female Sprague-Dawley rats were divided into high-fat diet and control groups (n=20) that were fed with 35% high-fat diet and standard chow, respectively. After 8 weeks, 8 female rats from each group were sacrificed for liver pathological examinations and the other female rats were mated with male rats and fed continuously with 35% high-fat diet and standard chow throughout gestation, respectively. The body lengths (from apex nasi to end of tail) of the offspring rats from both groups were measured within 24 hours after birth. Enzyme-linked immunosorbent assay was used to detect serum insulin-like growth factor (IFG-I) levels. Liver pathological changes were observed under a light microscope. The expression of insulin receptor substrate 1 (IRS-1) and phosphorylation IRS-1 (Phospho-IRS-1) in tibia and femur samples were detected by immunohistochemistry. The expression of mitogen-activated protein kinase (MAPK) and phosphorylation MAPK (Phospho-MAPK), phosphatidylinositol 3-kinase (PI3K) and phosphorylation PI3K (Phospho-PI3K), protein kinase B (AKT1) and phosphorylation AKT1 (Phospho-AKT1) in tibia and femur samples were detected by Western blot.

RESULTSThe offspring rats from the high-fat diet group showed a significant shorter body length compared with those from the control group (P<0.05). The level of serum IGF-I in offspring rats from the high-fat diet group decreased by 20.1% in comparison to those from the control group, but there was no significant difference between the two groups (P>0.05). Fatty degeneration was found in livers of both high-fat diet-fed maternal rats and their offspring rats under a light microscope. There were no significant differences in IRS-1 and Phospho-IRS-1 expression in chondrocytes of tibia and femur samples between the offspring rats of the two groups (P>0.05). The protein expression of MAPK in chondrocytes of tibia and femur samples of offspring rats from the high-fat diet group was higher than that from the control group (P<0.05). There were no significant differences of PI3K and AKT1/Phospho-AKT1 between the offspring rats of the two groups (P>0.05).

CONCLUSIONSA maternal high-fat diet before and during pregnancy may affect the bone growth of offspring rats in utero, which is possibly associated with the decreased IGF-I level. However, further study on the exact mechanism of IGF-I on the bone growth is needed.