The effects of insulin on 3 beta-hydroxysteroid dehydrogenase expression in human luteinized granulosa cells.
OBJECTIVE
We determined the relative effects of insulin and FSH on progesterone accumulation as well as activity, protein content, and mRNA expression of 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in human luteinized granulosa cells.


METHODS
Luteinized granulosa cells obtained from women undergoing in vitro fertilization were plated and grown to near confluence and treated with FSH, insulin, or a combination of insulin and FSH. Progesterone production as well as enzyme activity, protein content, and mRNA expression for 3 beta HSD were evaluated.


RESULTS
Progesterone production was not affected by insulin alone but increased threefold in the presence of FSH (50 ng/microL) alone. The presence of FSH plus insulin (100 nmol/L) caused a significant increase in progesterone accumulation greater than that of FSH alone. The already high basal levels of 3 beta HSD activity were unaffected by insulin alone but increased 1.7-fold in the presence of FSH. The combination of FSH (50 ng/mL) and insulin (100 nmol/L) increased activity 1.3-fold over FSH alone (P < .02). Insulin (greater than 100 nmol/L) alone increased 3 beta HSD protein content as measured by Western analysis 1.8-2-fold over basal levels, whereas FSH alone increased protein content 2.8-fold, and was further augmented by the addition of insulin in a dose-related fashion up to 3.5-fold over basal levels. Insulin increased 3 beta HSD mRNA twofold over basal levels; FSH alone increased mRNA expression of 3 beta HSD 3.2-fold. In the presence of insulin plus FSH, 3 beta HSD mRNA expression increased 7.6-fold over basal levels. For comparison, insulin also stimulated cytochrome P450 aromatase activity, P450 aromatase protein, and mRNA but to a greater degree than that seen for 3 beta HSD.


CONCLUSIONS
Insulin is a regulator of both 3 beta HSD and aromatase expression in human granulosa cells. Elevated insulin levels could therefore affect steroid production in human granulosa cells and presumably alter the menstrual cycle and fertility.
McGee
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Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center at Dallas 75235, USA.
Sawetawan
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C
Bird
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Rainey
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WE
Carr
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BR
D015096:3-Hydroxysteroid Dehydrogenases / Q000096:biosynthesis*; D001141:Aromatase / Q000096:biosynthesis; D002478:Cells, Cultured; D003338:Corpus Luteum / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D011374:Progesterone / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects*
D007328:Insulin; D012333:RNA, Messenger; D011374:Progesterone; D005640:Follicle Stimulating Hormone; D015096:3-Hydroxysteroid Dehydrogenases; D001141:Aromatase