Basic Scientific Research
Fertilized vs. Unfertilized Egg Yolk
Chicken egg yolk is a rich source of nutrients providing high quality proteins, vitamins, minerals, carotenoids and antioxidants. Chicken egg yolk, recovered from whole egg within 24 hours post-lay has been utilized as a starting material in the preparation of a dietary supplement that has been demonstrated to lead to gains in muscle mass in a human clinical study. Further, an oil derived from chicken egg yolk has been utilized as a topical agent to treat third degree burn injury. The molecular changes that take place in fertilized, chicken egg yolk during the first 24 hours post-lay are not well understood. By studying how the protein composition of egg yolk varies with fertility status, one can utilize this knowledge to develop egg yolk-based products that have been optimized for specific applications. In this study, a direct quantitative comparison was made between the proteome of fertilized chicken egg yolk and the proteome of unfertilized chicken egg yolk, both maintained at 20 °C and analyzed within 24 hours post-lay. Egg yolk proteins from each fertility state were digested with trypsin, labeled with distinct chemical labels (tandem mass tag reagents) and then combined in a 1 : 1 ratio. A TMT-labeled tryptic digest derived from chicken egg yolk proteins (fertilized and unfertilized) was separated using high-pH/low-pH reverse-phase chromatography and analyzed using mass spectrometry. 225 protein identifications were made from this TMT-labeled tryptic digest based on a minimum of 2 unique peptides observed per protein. 9 proteins increased in abundance in fertilized egg yolk relative to unfertilized egg yolk and 9 proteins decreased in abundance in fertilized egg yolk relative to unfertilized egg yolk. Some proteins that increased in abundance in fertilized egg yolk play an important role in angiogenesis (pleiotrophin, histidine rich glycoprotein) and defense against pathogens (mannose-binding lectin, β-defensin 11, serum amyloid P-component, ovostatin). Based on this study, fertilized chicken egg yolk may be more useful as a starting material relative to unfertilized chicken egg yolk for the purpose of enriching or isolating proteins with pro-angiogenic and anti-microbial properties.
Impact of Fertilized Egg Yolk on Myoblast Proliferation
Muscle disorders like sarcopenia are characterized by compromised skeletal muscle mass and function. This is caused by the failure of satellite cells or myoblasts to fuse together to form myofibers, or decreases in their number and function. Therefore, any analysis of interventions for muscle wasting should observe their effects at the cellular level. There are a number of commercially available nutritional products that claim to increase muscle mass and health. One potential supplement is fertilized chicken egg yolk; it is rich in vitamins, minerals, fats, amino acids, and proteins which can provide a sustained supply of nutrition to the myoblasts. As reversing the effects of sarcopenia involve muscle tissue growth, and tissue growth is a prime component of regenerative/tissue engineering, one could evaluate the effectiveness of nutritional supplements using regenerative/tissue engineering tools. In the present study, we evaluated the effect of different concentrations of fertilized chicken egg yolk extract on the viability, morphology, and myogenic gene expression of C2C12 myoblasts, common tools in regenerative/tissue engineering and regenerative medicine. Egg yolk (fertilized and unfertilized) extract in media enhanced the proliferation and differentiation of myoblasts in a dose-ependent manner as observed by increased cell viability, number of nuclei, number of myofibers, and mRNA expression of muscle-specific genes such as MyoD and myogenin. There was no significant difference in cellular metabolism/proliferation between myoblasts exposed to fertilized and unfertilized egg yolk, but there were differences in cellular morphology and cell fusion between the two groups at specific concentrations.