Developmental programming: differential effects of prenatal testosterone excess on insulin target tissues

Abstract

Polycystic ovarian syndrome (PCOS) is the leading cause of infertility in reproductive-aged women with the majority manifesting insulin resistance. To delineate the causes of insulin resistance in women with PCOS, we determined changes in the mRNA expression of insulin receptor (IR) isoforms and members of its signaling pathway in tissues of adult control (n = 7) and prenatal testosterone (T)-treated (n = 6) sheep (100 mg/kg twice a week from d 30-90 of gestation), the reproductive/metabolic characteristics of which are similar to women with PCOS. Findings revealed that prenatal T excess reduced (P < 0.05) expression of IR-B isoform (only isoform detected), insulin receptor substrate-2 (IRS-2), protein kinase B (AKt), peroxisome proliferator-activated receptor-γ (PPARγ), hormone-sensitive lipase (HSL), and mammalian target of rapamycin (mTOR) but increased expression of rapamycin-insensitive companion of mTOR (rictor), and eukaryotic initiation factor 4E (eIF4E) in the liver. Prenatal T excess increased (P < 0.05) the IR-A to IR-B isoform ratio and expression of IRS-1, glycogen synthase kinase-3α and -β (GSK-3α and -β), and rictor while reducing ERK1 in muscle. In the adipose tissue, prenatal T excess increased the expression of IRS-2, phosphatidylinositol 3-kinase (PI3K), PPARγ, and mTOR mRNAs. These findings provide evidence that prenatal T excess modulates in a tissue-specific manner the expression levels of several genes involved in mediating insulin action. These changes are consistent with the hypothesis that prenatal T excess disrupts the insulin sensitivity of peripheral tissues, with liver and muscle being insulin resistant and adipose tissue insulin sensitive.

Figure 1

Mean ± sem of IR, IRS-1 and -2, PI3K, AKt, Glut-2 and -4, and GSK-3α and -3β mRNA expression in the liver, skeletal muscle, and adipose tissue. Asterisks indicate significant treatment differences. *, P < 0.05; **, P < 0.01. C, Control (n = 7); T, prenatal T-treated (n = 6).

Figure 2

RT-PCR analysis for detection and determination of the relative abundance of IR-A and IR-B isoforms in the liver (panel A), muscle (panel B), and fat tissue (panel C). The amplified products of RT-PCR were analyzed on 3% agarose gel and visualized under UV light. The ratio of IR-A to IR-B was determined by scanning densitometry (panel D). C, Control (n = 7); T, prenatal T-treated (n = 6). All samples were run in triplicate.

Figure 3

Mean ± sem of mTOR, rictor, eIF4E, ERK1, PPARγ, HSL, G6Pase, and PEPCK mRNA expression in the liver, skeletal muscle, and adipose tissue. Asterisks indicate significant treatment differences. *, P < 0.05; **, P < 0.01; ***, P < 0.001. C, Control (n = 7); T, prenatal T-treated (n = 6).

Figure 4

Composite changes in gene expression of members of the insulin signaling pathway in the liver, skeletal muscle, and adipose tissue in response to prenatal T excess: IR, IRS-1 and -2, PI3K, AKt, Glut-2 and -4, GSK-3α and -3β), mTOR, rictor, eIF4E, ERK1, PPARγ, HSL, G6Pase), and PEPCK.