Dietary conjugated linoleic acids alter serum IGF-I and IGF binding protein concentrations and reduce bone formation in rats fed (n-6) or (n-3) fatty acids.
A study was designed to examine the effects of dietary conjugated linoleic acid (CLA) on serum concentrations of insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBP) and the relationship of these factors to bone metabolism. Weanling male rats were fed AIN-93G diet containing 70 g/kg of added fat for 42 days. Treatments included 0 g/kg or 10 g/kg of CLA and soybean oil (SBO) or menhaden oil + safflower oil (MSO) following a 2 x 2 factorial design. Serum IGFBP was influenced by dietary polyunsaturated fatty acid (PUFA) type ((n-6) and (n-3)) and CLA (p = 0.01 for 38-43 kDa bands corresponding to IGFBP-3). CLA increased IGFBP level in rats fed SBO (p = 0.05) but reduced it in those fed MSO (p = 0.01). Rats fed MSO had the highest serum IGFBP-3 level. Both (n-3) fatty acids and CLA lowered ex vivo prostaglandin E2 production in bone organ culture. In tibia, rats given CLA had reduced mineral apposition rate (3.69 vs. 2.79 microm/day) and bone formation rate (BFR) (0.96 vs. 0.65 microm3/microm2/day); however, the BFR tended to be higher with MSO. Dietary lipid treatments did not affect serum intact osteocalcin or bone mineral content. These results showed that dietary PUFA type and CLA modulate local factors that regulate bone metabolism.
Department of Food Science, Lipid Chemistry and Molecular Biology Laboratory, Purdue University, West Lafayette, Indiana 47907, USA.
Y
Y
Li
M F
MF
Seifert
D M
DM
Ney
M
M
Grahn
A L
AL
Grant
K G
KG
Allen
B A
BA
Watkins
D000818:Animals; D015519:Bone Density / Q000187:drug effects; D046508:Culture Techniques; D005227:Fatty Acids / Q000097:blood; D015525:Fatty Acids, Omega-3 / Q000494:pharmacology*; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D005526:Food, Formulated; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008041:Linoleic Acids / Q000494:pharmacology*; D008297:Male; D010012:Osteogenesis / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D005227:Fatty Acids; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D018969:Insulin-Like Growth Factor Binding Proteins; D008041:Linoleic Acids; D007334:Insulin-Like Growth Factor I