Characterization of regulatory elements on the promoter region of human ATP-citrate lyase

ATP-citrate lyase (ACL), an enzyme catalyzing the first step in biosynthesis of fatty acids, is induced during the lipogenesis and cholesterologenesis. We demonstrate that the region -213 to -128 of human ACL promoter is responsible for conferring glucose-mediated transcription. This region in the ACL promoter contains Sp1 binding sites determined by DNase I foot-printing assay. Gel retardation assay using oligonucleotides from -179 to -141 and -140 to -110 showed two specific DNA-protein complexes postulated to be formed by transcription factor Sp1. Competition gel shift and supershift assays have confirmed that these DNA-protein complexes were the result of induced Sp1 as well as another Sp1-related proteins. Western blot analysis also demonstrated that transcription factor Sp1 was slightly increased in the nuclear proteins extracted from Alexander cells following supplementation of glucose. In addition, expression of 110 kDa protein reacting with antibody against Sp3 was dramatically increased by glucose supplementation, while isoforms of Sp3, about 80 kDa in size was decreased in its amounts. Our results suggest that changes in the expression of Sp1 family proteins play an important role in activation of the ACL promoter by glucose.

Effect of FSH and insulin on lipogenesis in cultures of Sertoli cells from immature rats

Follicle-stimulating hormone (FSH) and insulin regulate glycide metabolism in Sertoli cells, thus stimulating lactate production. These stimulatory effects of FSH and insulin do not require protein synthesis, suggesting a modulation of enzyme activity and/or regulation of glucose transport. The present investigation was performed to characterize the hormonal control of lipid metabolism in Sertoli cells. The data indicate that FSH and insulin have a regulatory effect on lipid metabolism in Sertoli cells. After 8 h of preincubation with insulin (5 mug/ml), the activity of the enzyme ATP-citrate lyase in sultured Sertoli cells was increased from 0.19 to 0.34 nmol NAD+ formed mug protein(-1) min(-1). FSH (100 ng/ml) had no effect on this enzyme. Glycerol phosphate dehydrogenase activity was not affected by any of the hormones tested. When Sertoli cells from 19-day old rats were incubated with [1,2-14C] acetate for 90 or 360 min, the [14C] label was present predominantly in triglyceride and phospholipid fractions with minor amounts in other lipids. In Sertoli cells pretreated for 16 h with insulin and FSH, an increase in acetate incorporation into lipids was observed. Most of the label was in esterified lipids and this percentage increased with the time of treatment; this increase was remarkable in triglycerides of control cells (18.8 percent to 30.6 percent). Since Sertoli cell triglycerides participate in the control of spermatogenesis, the present data suggest that the hormonal control of lipid metabolism in Sertoli cells is important not only for maintaining the energy of the cell itself, but also for the control of the spermatogenesis process.

Relationship between fatty acid synthesis, transport and total lipid content during human fetal lung development.

Levels of fatty acid binding proteins (FABPs), lipids as well as activities of fatty acid synthesizing enzymes such as fatty acid synthase and ATP-citrate lyase increase with gestation showing maximum at term in human fetal lung. However, the activity of ATP-citrate lyase showed the same trend up to 30 weeks of gestation before declining slightly at term. These results indicate the importance of supply and/or synthesis of fatty acids when lung surfactant synthesis begins; thereby showing a correlation between the FABPs, lipid pattern and the activities of fatty acid synthesizing enzymes during prenatal lung development.