Welcome to the second installation of Hourglass, a blog carnival devoted to the biology of aging. The entries are representatives of the excellent (and growing) community of bloggers who are writing about biogerontology, lifespan extension technologies, and aging in general. The inaugural issue of the carnival went up last month.

One of the underappreciated mysteries of aging is how it is coordinated throughout the body. As an animal gets older, its whole body ages; individual organ systems don’t suddenly become decrepit all on their own. Consistent with this, genetic studies of aging have been very successful at finding mutants that either accelerate or delay aging at a system-wide level, but far less successful at identifying mutants with dysregulated coordination of the aging process (imagine, e.g., a mouse with a youthful body and extremely old ears). How does this work? It sounds like a job for a circulating factor that is present throughout the body — and indeed, such factors do indeed seem to play an important role in the determination of lifespan and the temporal coordination of aging throughout the body. At Fight Aging!, Reason reports on multiple aspects of the roles played by the endocrine system in governing aging — and discusses a potential relationship between the mechanisms of life extension by growth hormone deficiency and methionine restriction.

Although the tissues and organs of the body age all age at comparable rates, there is nonetheless considerable heterogeneity at the cellular level. Old and damaged cells enter a permanent growth arrest known as senescence, which is both good (because they can’t initiate tumors) and bad (because persistent senescent cells behave in a ridiculously antisocial manner, secreting growth factors and proteases that both encourage nearby tumors to metastasize and degrade tissue function). Fortunately, senescent cells make up a very small proportion of the overall population, even in very aged tissues — so one could imagine removing them from the body without harm (and, indeed, to great benefit, because removal of these cells would also eliminate senescence-derived secreted factors). Needless to say, the extermination of senescent cells is an active subject of research. At his new site Anti-Ageing Research, Dominick Burton discusses ways in which specifically targeted cancer therapies might be adapted to attack senescent cells instead.

Continuing the theme of connecting cancer and aging, Ward Plunet at BrainHealthHacks asks a timely and important question: Can our track record in cancer research give us a hint of what we can expect in longevity research? In other words, is past performance in research and treatment of a major health issue in any way indicative of how we’re likely to do in addressing the grandmother of all health issues? Like many of Ward’s post, this piece is particularly well-researched and data-rich, so remember to show up with an appetite for information.

We can certainly learn a great deal from our past experiences of large-scale research, but there’s also good deal to be learned from reflection on a more individual scale. At the delightfully named Existence is Wonderful, Anne C. shares a parable about taking care of her friend Nigel the Fish and what that led her to realize about longevity: specifically, that environment is critical, and that the combination of extrinsic factors that one might collectively term “nurture” can make all the difference between a short unhappy life and a long fulfilled one. In her words: “We don’t necessarily know what hard limits are on longevity until we optimize care. I saw a dramatic turnaround in my fish when I learned how to properly configure the tank setup, and I hope to see the day when human medicine makes a similar leap in effectiveness.”

Strongly related to environmental surroundings are lifestyle choices, including the sort of exercise we choose to do. The benefits of physical exercise of all sorts are already well-documented, but it’s becoming increasingly clear that mental exercise will be an essential part of the brain maintenance that must accompany a successful aging process. At SharpBrains, Alvaro Fernandez discusses the Top Ten Brain Training Future Trends, including the idea that creative uses of cognitive training metrics might someday be used to allow early detection of neurodegenerative diseases such as Alzheimer’s.

That’s a wrap for this installation. Hourglass III will be hosted on September 9th by Alvaro at SharpBrains, and Hourglass IV on October 14th by Anne at Existence is Wonderful. We’ll set up a standalone email address and archive page for the carnival at some point — but for now, if you have submissions (or want to volunteer to host the carnival), please email me and I will forward them to the current host.