Male-lineage transmission of an acquired metabolic phenotype induced by grand-paternal obesity.

OBJECTIVE: Parental obesity can induce metabolic phenotypes in offspring independent of the inherited DNA sequence. Here we asked whether such non-genetic acquired metabolic traits can be passed on to a second generation that has never been exposed to obesity, even as germ cells. METHODS: We examined the F1, F2, and F3 a/a offspring derived from F0 matings of obese prediabetic A (vy) /a sires and lean a/a dams. After F0, only lean a/a mice were used for breeding. RESULTS: We found that F1 sons of obese founder males exhibited defects in glucose and lipid metabolism, but only upon a post-weaning dietary challenge. F1 males transmitted these defects to their own male progeny (F2) in the absence of the dietary challenge, but the phenotype was largely attenuated by F3. The sperm of F1 males exhibited changes in the abundance of several small RNA species, including the recently reported diet-responsive tRNA-derived fragments. CONCLUSIONS: These data indicate that induced metabolic phenotypes may be propagated for a generation beyond any direct exposure to an inducing factor. This non-genetic inheritance likely occurs via the actions of sperm noncoding RNA.

Nutrition has a pervasive impact on cardiac microRNA expression in isogenic mice.

The complex interaction between obesity, Western-style diets, and cardiovascular disease is of increasing interest, with a growing number of children being born to obese parents with poor lifestyle choices. These offspring have themselves an increased susceptibility to obesity and subsequent cardiovascular disease in adult life, which may be 'programmed' by their intrauterine environment. Cardiac microRNAs (miRNAs) are affected by multiple disease states, and have also been shown to be capable of exerting a hormone-like control on whole body metabolism. Here we sought to determine the effect of prenatal exposure to maternal obesity and/or postnatal exposure to a Western diet on miRNA expression in the heart. Unbiased small RNA sequencing was carried out on cardiac tissue from young adult mice born to lean or obese mothers; offspring were weaned onto either a low-fat control diet or a high-fat Western-style diet. We found 8 cardiac miRNAs that were significantly altered in response to maternal obesity, but only when the offspring were challenged postnatally with the Western diet. In contrast, postnatal exposure to the diet alone induced significant changes to the expression of a much larger number of miRNAs (33 in offspring of lean and 46 in offspring of obese). Many of the affected miRNAs have previously been implicated in various cardiac pathologies. The pervasive cardiac miRNA changes induced by a Western diet suggest that an individual's lifestyle choices outweigh the impact of any programming effects by maternal obesity on miRNA-related cardiac health.

Lineage tracking of mesenchymal and endothelial progenitors in BMP-induced bone formation.

To better understand the relative contributions of mesenchymal and endothelial progenitor cells to rhBMP-2 induced bone formation, we examined the distribution of lineage-labeled cells in Tie2-Cre:Ai9 and αSMA-creERT2:Col2.3-GFP:Ai9 reporter mice. Established orthopedic models of ectopic bone formation in the hind limb and spine fusion were employed. Tie2-lineage cells were found extensively in the ectopic bone and spine fusion masses, but co-staining was only seen with tartrate-resistant acid phosphatase (TRAP) activity (osteoclasts) and CD31 immunohistochemistry (vascular endothelial cells), and not alkaline phosphatase (AP) activity (osteoblasts). To further confirm the lack of a functional contribution of Tie2-lineage cells to BMP-induced bone, we developed conditional knockout mice where Tie2-lineage cells are rendered null for key bone transcription factor osterix (Tie2-cre:Osx(fx/fx) mice). Conditional knockout mice showed no difference in BMP-induced bone formation compared to littermate controls. Pulse labeling of mesenchymal cells with Tamoxifen in mice undergoing spine fusion revealed that αSMA-lineage cells contributed to the osteoblastic lineage (Col2.3-GFP), but not to endothelial cells or osteoclast populations. These data indicate that the αSMA+ and Tie2+ progenitor lineages make distinct cellular contributions to bone formation, angiogenesis, and resorption/remodeling.

Steroid hormone (20-hydroxyecdysone) modulates the acquisition of aversive olfactory memories in pollen forager honeybees.

Here, we examine effects of the steroid hormone, 20-hydroxyecdysone (20-E), on associative olfactory learning in the honeybee, Apis mellifera. 20-E impaired the bees' ability to associate odors with punishment during aversive conditioning, but did not interfere with their ability to associate odors with a food reward (appetitive learning). The steroid had a significant impact also on the expression of amine-receptor genes in centers of the brain involved in the formation and recall of associative olfactory memories (mushroom bodies). 20-E increased expression of the dopamine receptor gene, Amdop2, and reduced the expression of the putative dopamine/ecdysone receptor gene, Amgpcr19. Interestingly, Amgpcr19 tended to be highly expressed in the brains of foragers that exhibited strong aversive learning, but expressed at lower levels in bees that performed well in appetitive learning assays. In 2-d-old bees, transcript levels of the same gene could be reduced by queen mandibular pheromone, a pheromone that blocks aversive learning in young worker bees. As ecdysteroid levels rise to a peak ∼2 d after adult emergence and then fall to low levels in foragers, we examined aversive learning also in young worker bees. Aversive learning performance in 2-d-old bees was consistently poor. The results of this study indicate that learning in honeybees can be modulated by ecdysteroids. They highlight, in addition, a potential involvement of the putative dopamine/ecdysone receptor, AmGPCR19, in hormonal regulation of associative olfactory learning in the honeybee.