Tissue-specific sex differences in docosahexaenoic acid and Δ6-desaturase in rats fed a standard chow diet.
Docosahexaenoic acid (DHA, 22:6n-3) is higher in the blood and tissues of females relative to males, but the underlying mechanism is not clear. The present study examined the expression of enzymes involved in the biosynthesis of DHA from short-chain n-3 polyunsaturated fatty acids in male and female rats (n = 6 for each sex). Rats were maintained on an AIN-93G diet and sacrificed at 14 weeks of age after an overnight fast. Plasma, erythrocytes, liver, heart, and brain were collected for fatty acid composition analysis and the determination of enzyme and transcription factor expression by RT-PCR and immunoblotting. Females had higher DHA concentrations in the total lipids of liver, plasma, erythrocyte, and heart (53%, 75%, 36%, and 25% higher, respectively, compared with males) with no sex differences in brain DHA concentrations. The mRNA content of Δ5-desaturase, Δ6-desaturase, and elongase 2 was 1.0-, 1.4-, and 1.1-fold higher, respectively, in the livers of female rats compared with males, with no differences in the hearts or brains. The protein content of Δ6-desaturase was also higher in females. Higher hepatic mRNA of sterol-regulatory element-binding protein 1-c and estrogen receptor α in the females suggests that lipogenic and estrogen signaling mechanisms are involved. The sex difference in DHA concentration is tissue specific and is associated with higher Δ6-desaturase expression in females relative to males, which appears to be limited to the liver.
Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Alex P
AP
Kitson
Tracy L
TL
Smith
Kristin A
KA
Marks
Ken D
KD
Stark
D000818:Animals; D001921:Brain / Q000201:enzymology; D001923:Brain Chemistry; D004032:Diet; D004281:Docosahexaenoic Acids / Q000032:analysis* / Q000097:blood; D004912:Erythrocytes / Q000737:chemistry / Q000201:enzymology; D047628:Estrogen Receptor alpha / Q000235:genetics; D005260:Female; D050602:Linoleoyl-CoA Desaturase / Q000032:analysis* / Q000097:blood / Q000235:genetics*; D008099:Liver / Q000737:chemistry / Q000201:enzymology; D008297:Male; D009206:Myocardium / Q000737:chemistry / Q000201:enzymology; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D015398:Signal Transduction; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
D047628:Estrogen Receptor alpha; D012333:RNA, Messenger; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D004281:Docosahexaenoic Acids; D050602:Linoleoyl-CoA Desaturase