Obesity and comorbid pathologies such as type 2 diabetes and sub-fertility are becoming increasingly prevalent worldwide.  Although the paternal genomic contribution to the next generation is clear, less is known about how epigenetic alterations might impact offspring health.  We have previously documented that a paternal high fat diet (HFD) increased adiposity without overt diabetes and transmitted diminished reproductive viability through two subsequent generations.

Here we recapitulated a HFD fed founder C57Bl6 male mouse phenotype of paternal obesity, hyperlipidaemia and hyperletinaemia without alterations to glucose/insulin homeostasis (blood glucose/insulin concentrations and glucose/insulin tolerance).  Control diet/HFD fed founder mice (CD/HFD-F₀; n=10 each) were mated to normal weight CD females.

HFD-F₀ sired first generation (F₁) animals exhibited muted responses to glucose and insulin, acutest in F₁ females.  At 8 weeks old F₁ females were already glucose intolerant (CD-F₀ 267±33; HFD-F₀ 295±16; P<0.05) with reduced insulin sensitivity by 16 weeks (CD-F₀ 158±28; HFD-F₀ 90±18; P<0.05) that persisted throughout life (8-39 weeks), concomitant with increased adiposity (+65.6%; P<0.0001).  Although F₁ males also displayed glucose intolerance at 8 weeks old (CD-F₀ 378±59; HFD-F₀ 476±87; P<0.05), reduced insulin sensitivity presented later at 26 weeks (CD-F₀ 220±29; HFD-F₀ 129±33; P<0.05) without increased adiposity.

Strikingly, metabolic derangements were further transmitted to the second generation (F₂), albeit with incomplete penetrance.  3/4 F₂ animal groups from a HFD-F₀ lineage (except of F₂ males from F₁ males) exhibited muted insulin sensitivity, with glucose intolerance and increased adiposity (+24.1%; P<0.05) limited to F₂ males from F₁ females.  Milder metabolic disturbances observed in grand-paternal HFD lineage F₂ offspring imply that F₃ metabolic health might not be compromised.

Founder male obesity reduced global DNA methylation in testes (-27.0%; P<0.01) and spermatids (-24.9%; P<0.0001), and altered microRNA content in testes and sperm.  This study associates paternal obesity with epigenetic alterations to testis and sperm, which might partly explain intergenerational transmission of impaired metabolism and obesity observed through two generations.