Paternal Diet-Induced Obesity Retards Early Mouse Embryo Development, Mitochondrial Activity and Pregnancy Health

Abstract

Worldwide, 48% of adult males are overweight or obese. An association between infertility and excessive body weight is now accepted, although focus remains primarily on females. It has been shown that parental obesity results in compromised embryo development, disproportionate changes in embryo metabolism and reduced blastocyst cell number. The aim of this study was to determine whether paternal obesity has negative effects on the resultant embryo. Specifically, using in vitro fertilisation (IVF), we wanted to isolate the functional effects of obesity on sperm by examining the subsequent embryo both pre- and post-implantation. Epididymal sperm was collected from age matched normal and obese C57BL/6 mice and cryopreserved for subsequent IVF with oocytes collected from Swiss females (normal diet/weight). Obesity was induced in male mice by feeding a high fat diet of 22% fat for 10 weeks. Resultant embryos were cultured individually and development monitored using time-lapse microscopy. Paternal obesity resulted in a significant delay in preimplantation embryo development as early as syngamy (P<0.05). Metabolic parameters were measured across key developmental stages, demonstrating significant reduction in mitochondrial membrane potential (P<0.01). Blastocysts were stained to determine trophectoderm (TE) and inner cell mass (ICM) cell numbers, revealing significant differences in the ratio of cell allocation to TE and ICM lineages (P<0.01). Functional studies examining blastocyst attachment, growth and implantation demonstrated that blastocysts derived from sperm of obese males displayed significantly reduced outgrowth on fibronectin in vitro (P<0.05) and retarded fetal development in vivo following embryo transfer (P<0.05). Taken together, these data clearly demonstrate that paternal obesity has significant negative effects on the embryo at a variety of key early developmental stages, resulting in delayed development, reduced placental size and smaller offspring.

Homage to the ‘H’ in developmental origins of health and disease

“…62 While fathers cannot provide direct nourishment to the young after birth, additional attention should be paid to whether a healthy diet of the father, and the mother, before conception can lead to long-term beneficial offspring consequences. It is increasingly becoming apparent that sub-optimal paternal diets, those high in fat or protein restricted, can result in negative offspring sequelae, [14][15][16][17][18][19][20][21][146][147][148][149] but the impacts of a healthy diet have been largely ignored. In conclusion, much work remains on identifying various steps that both parents can adapt to ensure the lifelong health of their offspring and potentially even triumph over negative influences that the conceptus or neonate may encounter.…”

“…4,[6][7][8][9][10][11][12][13] It is also increasingly becoming apparent that the environmental state of both the mother and father can underpin later diseases in offspring, even those who appear healthy at birth. [14][15][16][17][18][19][20][21][22][23][24][25][26] Such intrinsic and extrinsic factors in animal models and humans include exposure to endocrine disrupting chemicals, such as bisphenol A, phthalates, heavy metals, stress, obesity, high fat/ high caloric diets, metabolic status and starvation conditions to provide a few examples. It is also clear that in general, males may be at greater risk for later disorders, including those of the cardiovascular and neurological systems, than females.…”

Paternal obesity in a rodent model affects placental gene expression in a sex-specific manner

“…Following the 10-week feeding period, male mice were killed and cauda epididymal sperm was collected and cryopreserved for IVF as described previously (Binder et al 2012a). Control diet-fed 4-6-week-old Swiss female mice were superovulated with i.p.…”

“…Embryos were generated in vitro from the cryopreserved sperm of normal and obese males and fresh oocytes due to decreased fecundity with high-fat feeding (Binder et al 2012a). Following a 4 h fertilisation period, pronucleate oocytes were cultured to the blastocyst stage in sequential G1/G2 media supplemented with 5 mg/ml human serum albumin under paraffin oil (Vitrolife, Goteborg, Sweden; Gardner & Lane 2004.…”

“…Fetuses from obese fathers are significantly smaller, have decreased crown-rump length and retarded limb morphology, as well as significantly smaller placentas (Binder et al 2012a, McPherson et al 2013. Embryos derived from obese fathers also have an increased propensity for zygote arrest, delayed preimplantation development, disproportionate changes in both pre-and post-compaction metabolism, mitochondrial dysfunction, reduced blastocyst formation, decreased cell number and aberrant cell lineage allocation to the trophectoderm (TE) or inner cell mass (ICM) , Binder et al 2012a. Furthermore, paternal obesity increases the likelihood of metabolic syndrome, namely obesity, in offspring (Danielzik et al 2002, Li et al 2009).…”