Bay Area Aging: A summary of important themes in aging

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Bryan Bishop

Dec 17, 2010, 10:05:31 AM12/17/10
to,,, Bryan Bishop
A summary of important themes in aging (Melanie Swan)

Some of us know Melanie via DIYgenomics, CureTogether, or others from her more transhumanist work.. here's something recent on gerontology and aging.

Melanie Swan, MBA, is an Affiliate Scholar of the IEET – The Institute for Ethics and Emerging Technologies. Ms. Swan is a science generalist, hedge fund manager, and founder of citizen science organization DIYgenomics. She serves as a researcher and advisor to foundations, government agencies, corporations, and startups, and is active in the community promoting science and technology. Her life mission is to impact millions of people by facilitating the widespread deployment of beneficial high-impact science and technology.

Melanie recently summarized some important themes in aging research that were discussed at the second Bay Area Aging Meeting:

Processes work in younger organisms but not in older organisms

A common theme in aging is that processes function well in the first half of an organism’s life, then break-down in the second half, particularly the last 20% of the lifespan. In one example, visualizations and animations were created from the 3D tissue-sectioning of the intestine of young (4 days old) and old (20 days old) C. elegans. In the younger worms, nuclei and cells were homogenous and regularly spaced over the course of the intestine running down the length of the worm. In older worms, nuclei disappeared (an initial 30 sometimes ultimately dropped to 10), and the intestine became twisted and alternately shrunken and convoluted due to DNA accumulation and bacterial build-up.

Metabolism and oxidation critically influence aging processes

Two interesting talks concerned UCP2 (mitochondrial uncoupling protein 2) an enzyme which reduces the rate of ATP synthesis and regulates bioenergy balance. UCP2 and UCP3 have an important but not yet fully understood role in regulating ROS (reactive oxygen species) and overall metabolic function, possibly by allowing protons to enter the mitochondria without oxidative phosphorylation. The mechanism was explored in results that worm lifespan was extended by inserting zebrafish UCP2 genes (not natively present in the worm).

Immune system becomes compromised in older organisms

Two talks addressed the issue of immune system compromise. One team created a predictive analysis that could be used to assess an individual’s immune profile and potential response to vaccines by evaluating demographics, chronic infection status, gene expression data, cytokine levels, and cell subset function. Other work looked into the specific mechanisms that may degrade immune systems in older organisms. SIRT1 (an enzyme related to cell regulation) levels decline with age. This leads to the instable acetylation of transcription factor FoxP3 (a gene involved in immune system response), which suppresses the immune system by reducing regulatory T cell (Treg) differentiation to respond to pathogens.

Systems-level understanding of aging processes

Many aging processes are systemic in nature with complex branching pathways and unclear causality. Research was presented regarding two areas: P53 is a critical tumor suppressor protein controlling many processes related to aging and cell maintenance: cell division, apoptosis, and senescence, and is estimated to be mutated in 50% of cancers. Research suggested that more clues for understanding the multifactorial p53 pathway could come from SnoN, which may be an alternative mechanism for activating p53 as part of cellular stress response. Neurodegenerative pathologies such as Alzheimer’s disease remain unsolved problems in aging. For example, it is not known if the amyloid beta plaques that arise are causal, or a protection mechanism in response to other causal agents. Some research looked at where amyloid beta is produced in cells, finding that after the amyloid precursor protein (APP) leaves the endosome, both the Golgi and a related recycling complex may be related in the generation of amyloid beta.

Lack of conservation progressing up the model organism chain

Aging and other biological processes become more complicated with progression up the chain of model organisms. What works in yeast and worms may not work in mice, and what works in mice and rats may not work in humans. Some interesting research looked at ribosomal proteins, whose deletion is known to extend lifespan in model organisms. The key points were first that there was fairly little (perhaps less than 20%) overlap in lifespan-extending ribosomal protein deletions conserved between yeast and worms. Second, an examination of some of the shared deletions in mice (especially RPL19, 22, and 29) found some conservation (e.g.; RPL29), and also underlined the systemic-nature of biology, finding that other homologous genes (e.g.; RPL22L) may compensate for the deletion, and thereby not extend lifespan.

Trade-offs is a key dynamic of aging processes

The idea of trade-offs is another common theme in aging; the trade-offs between processes, resource consumption, and selection. Exemplar of this was research showing that the deletion of a single gene involved in lipid synthesis, DGAT1, is beneficial and promotes longevity in mice when calories are abundant, but is also crucial for survival in calorie restricted situations. This supports the use of directed methylation to turn genes on and off in different situations. More details were presented in a second area of trade-offs: reproduction-lifespan. It is known that reproduction is costly and organisms without reproductive mechanisms may have extended lifespans. Research examined the specific pathways, finding that Wnt and steroid hormone signaling in germline and somatic reproductive tissues influenced worm longevity, particularly through non-canonical (e.g.; not the usual) pathways by involving signaling components MOM-2/Wnt and WRM-1/beta-catenin.

My conclusion: I have to say that I understand the Systems-level biology of aging differently. Basically, it’s integrating the existing knowledge in all the aspects of aging into a single system, computational, visual or some other kind of system. Therefore, I would certainly add the necessity of creating such an integrated system to this list of goals / problems.

In general, it is clear that more research is needed in each of the listed areas, as well as the set of established biomarkers in order to translate the findings from model animals to humans. The problem of biomarkers brings us back to the systems biology of aging. 

- Bryan
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