The Group VIA Phospholipase A 2 (iPLA 2 ␤) is the first recognized cytosolic Ca 2؉ -independent PLA 2 and has been proposed to participate in arachidonic acid (20:4) incorporation into glycerophosphocholine lipids, cell proliferation, exocytosis, apoptosis, and other processes. To study iPLA 2 ␤ functions, we disrupted its gene by homologous recombination to generate mice that do not express iPLA 2 ␤. Heterozygous iPLA 2 ␤ ؉/؊ breeding pairs yield a Mendelian 1:2:1 ratio of iPLA 2 ␤ ؉/؉ , iPLA 2 ␤ ؉/؊ , and iPLA 2 ␤ ؊/؊ pups and a 1:1 male:female gender distribution of iPLA 2 ␤ ؊/؊ pups. Several tissues of wild-type mice express iPLA 2 ␤ mRNA, immunoreactive protein, and activity, and testes express the highest levels. Testes or other tissues of iPLA 2 ␤ ؊/؊ mice express no iPLA 2 ␤ mRNA or protein, but iPLA 2 ␤ ؊/؊ testes are not deficient in 20:4-containing glycerophosphocholine lipids, indicating that iPLA 2 ␤ does not play an obligatory role in formation of such lipids in that tissue. Spermatozoa from iPLA 2 ␤ ؊/؊ mice have reduced motility and impaired ability to fertilize mouse oocytes in vitro and in vivo, and inhibiting iPLA 2 ␤ with a bromoenol lactone suicide substrate reduces motility of wild-type spermatozoa in a time-and concentration-dependent manner. Mating iPLA 2 ␤ ؊/؊ male mice with iPLA 2 ␤ ؉/؉ , iPLA 2 ␤ ؉/؊ , or iPLA 2 ␤ ؊/؊ female mice yields only about 7% of the number of pups produced by mating pairs with an iPLA 2 ␤ ؉/؉ or iPLA 2 ␤ ؉/؊ male, but iPLA 2 ␤ ؊/؊ female mice have nearly normal fertility. These findings indicate that iPLA 2 ␤ plays an important functional role in spermatozoa, suggest a target for developing male contraceptive drugs, and complement reports that disruption of the Group IVA PLA 2 (cPLA 2 ␣) gene impairs female reproductive ability.

Women with polycystic ovarian syndrome are at increased risk of miscarriage. Although evidence exists that metformin reduces this risk, the mechanism is unknown. This study tests the hypothesis that AMP kinase (AMPK) activation with metformin directly improves insulin signaling within the blastocyst, leading to improved pregnancy outcomes. Murine embryos were exposed to 200 nmol/l IGF-I, similar to the concentrations that can occur during polycystic ovary syndrome (PCOS). Resulting blastocysts were compared with embryos cocultured with excess IGF-I plus metformin and embryos cultured in control medium for the following: AMPK phosphorylation, insulin-stimulated glucose uptake, and apoptosis. Study and control blastocysts were also transferred into control animals. On embryonic day (E) 14.5, resulting fetuses were examined for size and rates of fetal implantation and resorption. Compared with control blastocysts, blastocysts exposed to high concentrations of IGF-I showed a decrease in AMPK activation and insulin-stimulated glucose uptake and an increase in the number of apoptotic nuclei. Blastocysts cocultured in metformin and excess IGF-I performed as well as controls in all studies. 5-Aminoimidazole-4-carboxamide 1-␤-D-ribofuranoside, another AMPK activator, also prevented the effects of excess IGF-I on blastocysts. Implantation rates and fetal size at day 14.5 were significantly lower among IGF-I-exposed embryos transferred into control mothers compared with control embryos transferred into control mothers. Both of these parameters were reversed by coincubation with metformin and IGF-I before transfer. Activation of embryonic AMPK may be the mechanism responsible for the improved pregnancy outcomes seen in PCOS patients taking metformin. Diabetes 56:2228-2234, 2007 W omen with polycystic ovary syndrome (PCOS) experience oligomenorrhea/anovulation, clinical or biochemical hyperandrogenism, and polycystic ovaries (1). The clinical presentation is variable, but many women with PCOS also exhibit obesity, hyperinsulinemia with insulin resistance, and infertility with recurrent pregnancy loss (2-4). The etiology of this recurrent pregnancy loss remains unclear. Both high concentrations of androgens and gonadotropins have been suggested, but only small, correlative clinical investigations have been conducted (5,6). Bioactive levels of the insulin-like growth factor, IGF-I, are also increased in PCOS patients because of an insulininduced decrease in the production of IGF binding protein-1 (IGFBP-1) (7,8).The preimplantation blastocyst stage embryo is an insulin-sensitive tissue (9,10). Prior studies have shown that the murine blastocyst responds to insulin or IGF-I by increasing glucose uptake and that this event occurs via the IGF-I receptor. IGF-I receptor signaling induces translocation of GLUT8 to the plasma membrane of the trophectoderm cells of the embryo (11). Expression of GLUT8 and translocation to the plasma membrane are critical for embryo survival (12,13). On exposure to high concentration of IGF-I or insul...

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