A multi-omics census reveals miRNA miR-let-7 as instigator of paternal mitochondrial dysfunction and in epigenetic heredity of intergenerational metabolic decline [PeWA]

We describe that diet-induced obesity and weight loss development in male mice causes reversible abnormalities in glucose and lipid metabolism, serum metabolomes, and adipose tissue and liver gene expression and causes specific, but reversible, reductions in activity of genes controlling mitochondrial energy dissipation in white adipose tissue. When mating obese mice with isogenic lean females, we observed highly concordant reductions in mitochondrial gene expression and translation in offspring that resemble those observed in obese fathers. When mapping small RNA responses across somatic and gametic cell types and between generations, we saw that obesity and weight loss reversible affected miRNA abundance, and observed several miR-let7 isoforms induced in obese adipose tissues of the paternal (F0) and offspring (F1) generation, as well as in sperm of F0 mice. Mechanistically, when overexpressing miR-let-7 in primary adipocytes, we found it to silence DICER1, a key rheostat required for adipose tissue adaptation in obesity as evidenced by functional deficiency in mitochondrial functioon following DICER1 loss. Upon ectopic delivery of miR-let7d/e levels into fertilized oocytes by microinjection, we elicited glucose intolerance and impairments in adipose mitochondrial gene expression in mice sired from miRNA-injected embryos, thus phenocopying key aspects of paternal obesity itself. When performing single-cell RNA-Seq in embryos, we found that miR-let7d/e delivery impaired mitochondrial gene expression, suggesting altered energy metabolism following sperm-mediated changes in zygotic miRNA pools. When studying miRNA alterations in human gametes, we found that lifestyle-induced weight loss downregulated MIR-LET7D/E in semen from human subjects, suggesting similar roles for human miR-let7d/e in gametic epigenomes and embryogenesis.