Insulin exposure during in vitro bovine oocyte maturation changes blastocyst gene expression and developmental potential

Abstract

Abstract. Metabolic imbalance impairs fertility, because changes in concentrations of metabolites and hormones in the blood and follicular fluid create an unfavourable environment for early embryonic development. Insulin is a key metabolic hormone known for its effects on fertility: insulin concentrations are increased during energy balance disturbances in diabetes or metabolic syndrome. Still, insulin is frequently used at supraphysiological concentrations for embryo in vitro culture with unknown consequences for the developmental potential of the offspring. In the present study we investigated the effects of insulin exposure during in vitro bovine oocyte maturation on developmental rates, embryo quality and gene expression. Supplementation of the maturation media with insulin at 10 or 0.1 mg mL À1 decreased blastocyst rates compared with an insulin-free control (19.8 AE 1.3% and 20.4 AE 1.3% vs 23.8 AE 1.3%, respectively; P , 0.05) and led to increased cell numbers (nearly 10% more cells on Day 8 compared with control; P , 0.05). Transcriptome analysis revealed significant upregulation of genes involved in lipid metabolism, nuclear factor (erythroid-derived 2)-like 2 (NRF2) stress response and cell differentiation, validated by quantitative polymerase chain reaction. To conclude, the results of the present study demonstrate that insulin exposure during in vitro oocyte maturation has a lasting effect on the embryo until the blastocyst stage, with a potential negative effect in the form of specific gene expression perturbations.

DNA methylation pattern of bovine blastocysts associated with hyperinsulinemia in vitro

“…Elucidating the exact effects on insulin‐treated bovine embryos at the maternal versus paternal alleles at this and other imprinted loci requires further differential RNA sequencing studies scrutinizing discriminative paternal and maternal genetic variants as well as epigenomic studies, such as whole genome bisulfite sequencing. Lamin A has functions during mitosis (Gerace & Blobel, ) and the hypermethylation and upregulation of LMNA is concordant with our observations of increased proliferation in the form of a higher cell number (Laskowski et al, ; Laskowski, Sjunnesson, Humblot, Sirard et al, ) in embryos derived from hyperinsulinemic conditions during oocyte maturation.…”

“…The developmental rates of the batches used and RT‐qPCR validation of the transcriptome data have been published in Laskowski, Sjunnesson, Humblot, Sirard et al and Laskowski et al () and are available for open access. The transcriptomic and epigenetic data have been deposited in the Gene Expression Omnibus of the National Center for Biotechnology Information (Edgar, Domrachev, & Lash, ) and are accessible through GEO series accession numbers GSE62881 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE62881, Accessed 27 January 2017 [transcriptome]) and GSE97517 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE97517, Accessed 10 April 2017 [epigenetics]).…”

“…The IVP of embryos was performed according to previously described procedures (Laskowski, Sjunnesson, Humblot, Sirard et al, ). Briefly, abattoir‐derived cumulus oocyte complexes ( n = 882) were matured in groups of 30–40 in vitro for 22 hr in 500 µl serum‐free maturation medium (IVM).…”

“…Gene expression studies were performed using the EmbryoGENE platform according to standardized methods previously described in general (Robert et al, ) and specifically for this study (Laskowski, Sjunnesson, Humblot, Sirard et al, ). In brief, RNA extraction was performed with pools of ten embryos with equally distributed developmental stages and quality grades per pool.…”

“…Obesity associated metabolic changes, such as hyperinsulinemia, have been shown to alter the oocyte quality in vivo in cattle, humans, and mice (Adamiak et al, 2005;Robker, 2008;Robker et al, 2009). As negative consequences of hyperinsulinemic conditions during early development (Laskowski, Sjunnesson, Humblot, Sirard et al, 2016) and health implications for the deriving offspring cannot be excluded (Lehnen, Zechner, & Haaf, 2013;Vrachnis et al, 2012), insulin in vitro fertilization systems should be used with caution. While there is evidence for detrimental effects of obesity and hyperinsulinemia on oocyte quality and the developmental competence of ruminant and human embryos (Adamiak et al, 2005;Robker, 2008;Ashworth, Toma, & Hunter, 2009;Grazul-Bilska et al, 2012), more research is required for a better understanding of the possible pathological mechanisms at the molecular level.…”