Acknowledgments
We would like to thank Dr. Ken Boheler for helpful discussions, Dr. Carl Pinkert for his critical review of the manuscript, and Ms. Amber Reigel for assistance with entries into the National Institute on Aging (NIA) databases. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.