Abstract
Excessive adipose accretion causes health issues in humans and decreases feed efficiency in poultry. Although vitamin A has been known to be involved in adipogenesis, effects of all-trans retinoic acid (atRA), as a metabolite of vitamin A, on embryonic adipose development have not been studied yet. Avian embryos are developing in confined egg environments, which can be directly modified to study effects of nutrients on embryonic adipogenesis. With the use of quail embryos, different concentrations of atRA (0 M to 10 μM) were injected in ovo at embryonic day (E) 9, and adipose tissues were sampled at E14. Percentages of fat pad weights in embryo weights were significantly increased in the group injected with 300 nM of atRA. Also, among three injection time points, E5, E7, or E9, E7 showed the most significant increase in weight and percentage of inguinal fat at E14. Injection of atRA at E7 increased fat cell size in E14 embryos with up-regulation of pro-adipogenic marker genes (Pparγ and Fabp4) and down-regulation of a preadipocyte marker gene (Dlk1) in adipose tissues. These data demonstrate that atRA promotes hypertrophic fat accretion in quail embryos, implying important roles of atRA in embryonic development of adipose tissues.
Highlights
Excessive fat accretion causes obesity and associated diseases in humans
As described in our previous study (Chen et al, 2014), to visualize fat pads, quail embryo was removed from the egg, and feathers were removed by using forceps during washing with phosphatebuffered saline (PBS) three times
The current study showed that adipose tissues in quail embryos were not found at E8 but initially appeared around the neck at E9 (Figure 1)
Summary
Excessive fat accretion causes obesity and associated diseases in humans. Excessive fat is undesirable due to economic concerns of animal producers on low feed efficiency associated with fat accretion and health issues of consumers on high fat contents in meat. Discovery and understanding of roles of genetic and nutritional factors in fat regulation will lead to improving health and efficiency of animal production. Chicken embryos at E10–E12 have preadipocytes and multilocular immature fat cells (Chen et al, 2014). These cells are further developed toward more numbers of unilocular fat cells at E14 (Chen et al, 2014). This study showed how rapidly adipocytes are developed during embryonic development
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