Metformin improves ovarian insulin signaling alterations caused by fetal programming

Abstract

Insulin resistance is the decreased ability of insulin to mediate metabolic actions. In the ovary, insulin controls ovulation and oocyte quality. Alterations in ovarian insulin signaling pathway could compromise ovarian physiology. Here, we aimed to investigate the effects of fetal programming on ovarian insulin signaling and evaluate the effect of metformin treatment. Pregnant rats were hyperandrogenized with testosterone and female offspring born to those dams were employed; at adulthood, prenatally hyperandrogenized (PH) offspring presented two phenotypes: irregular ovulatory (PHiov) and anovulatory (PHanov). Half of each group was orally treated with metformin. Metformin treatment improved the estrous cyclicity in both PH groups. Both PH groups showed low mRNA levels ofIr,Irs1andGlut4.Irs2was decreased only in PHanov. Metformin upregulated the mRNA levels of some of the mediators studied. Protein expression of IR, IRS1/2 and GLUT4 was decreased in both PH groups. In PHiov, metformin restored the expression of all the mediators, whereas in PHanov, metformin restored only that of IR and IRS1/2. IRS1 phosphorylation was measured in tyrosine residues, which activates the pathway, and in serine residues, which impairs insulin action. PHiov presented high IRS1 phosphorylation on tyrosine and serine residues, whereas PHanov showed high serine phosphorylation and low tyrosine phosphorylation. Metformin treatment lowered serine phosphorylation only in PHanov rats. Our results suggest that PHanov rats have a defective insulin action, partially restored with metformin. PHiov rats had less severe alterations, and metformin treatment was more effective in this phenotype.

Prenatal androgen exposure affects ovarian lipid metabolism and steroid biosynthesis in rats

“…Similar to our previous findings (Abruzzese et al 2019b), lipid profile was altered at adulthood in PH animals, which showed increased levels of LDL-cholesterol (p<0.01) and TG (p<0.01) as compared with the control group. Regarding hormonal steroid profile, as previously found (Heber et al 2019), prenatal androgenization led to an increase in testosterone levels in the PHanov group (p<0.01) and a decrease in estradiol levels in both PHiov and PHanov groups (p<0.05), without alterations in progesterone levels (p>0.05). Moreover, neither of the PH…”

“…Prenatal exposure to a suboptimal intrauterine environment could lead to long term effects affecting reproductive functions. To study the impact of fetal programming of animals exposed to androgens, we reproduced a rodent model of prenatal androgen excess widely used (Wolf 2002;Ramezani Tehrani et al 2014;Abruzzese et al 2016Abruzzese et al , 2019aHeber et al 2019). Here, using this model, we addressed the question of whether ovarian lipid metabolism and specifically cholesterol metabolism are impaired in these animals when adults.…”

“…As previously reported, the control group had regular cycles (4-6 days), whereas those animals prenatally exposed to androgens displayed mostly altered estrous cycles. Vaginal smears showed that 49.5% of the PH animals showed prolonged cycles lasting 7 days or more and were classified as irregular ovulatory animals (PHiov); and that 40.5% of the animals showed no cycles at all and were classified as anovulatory animals (PHanov) (Abruzzese et al 2016;Heber et al 2019). At three months of age, the entire PHanov group remained in diestrus; for that reason, and to allow comparison among groups, all animals were euthanized on the first diestrus after 90 days of age.…”

Effects of in utero androgen excess and metformin treatment on hepatic functions

“…Serum testosterone levels, determined by radioimmunoassay (RIA) (Amalfi et al, 2012), were increased in both PH phenotypes, being higher in the PHanov group than in the PHiov and control groups (control= 67.76 ± 13.52;PHiov= 115.84 ± 34.82;PHanov= 154.34 ± 32.00;control + Metformin= 101.27 ± 17.35;PHiov= 123.73 ± 35.90;PHanov= 129.34 ± 10.65). As it has been previously reported (Heber et al, 2019), metformin treatment did not modify the testosterone levels of the PHiov or PHanov groups, but tended to diminish those of the PHanov group.…”

The effects of assisted reproduction technologies on metabolic health and disease†

“…This phenomenon of the same environmental stressor leading to different phenotypes was observed in a rat model of in utero androgen excess, where female offspring presented two distinctive phenotypes, both with alterations in reproductive and metabolic function. However, one phenotype presented more severe alterations and was less receptive to pharmacological treatment [ 112 , 113 ]. Until recently, the long-term outcomes of developmental programming were considered to be irreversible; however, there is evidence of the reversibility of the postnatal programmed phenotype.…”