Ageing: the many-headed monster

Adaptation, aging, and genomic information

Aging is not simply an accumulation of damage or inappropriate higher-order signaling, though it does secondarily involve both of these subsidiary mechanisms. Rather, aging occurs because of the extensive absence of adaptive genomic information required for survival to, and function at, later adult ages, due to the declining forces of natural selection during adult life. This absence of information then secondarily leads to misallocations and damage at every level of biological organization. But the primary problem is a failure of adaptation at later ages. Contemporary proposals concerning means by which human aging can be ended or cured which are based on simple signaling or damage theories will thus reliably fail. Strategies based on reverse-engineering age-extended adaptation using experimental evolution and genomics offer the prospect of systematically greater success.

Rosa damascena decreased mortality in adult Drosophila

The effects of a rose-flower extract, Rosa damascena, on the mortality rate of Drosophila melanogaster was evaluated in this study. R. damascena is a potent antioxidant that has many therapeutic uses in addition to its perfuming effects. Supplementing Drosophila with this rose extract resulted in a statistically significant decrease in mortality rate in male and female flies. Moreover, the observed anti-aging effects were not associated with common confounds of anti-aging properties, such as a decrease in fecundity or metabolic rate.

Rhodiola: a promising anti-aging Chinese herb

Using the fruit fly, Drosophila melanogaster, we investigated the effects of Rhodiola on life-span. Rhodiola is a plant root used in traditional Chinese medicine that may increase an organism's resistance to stress. It has been proposed that Rhodiola can extend longevity and improve health span by alleviating oxidative stress. Rhodiola supplied every other day at 30 mg/mL significantly increased the lifespan of Drosophila melanogaster. When comparing the distribution of deaths between Rhodiola-supplemented and control flies, Rhodiola-fed flies exhibited decelerated aging. Although the observed extension in lifespan was associated with statistically insignificant reductions in fecundity, correcting for a possible dietary restriction effect still did not eliminate the difference between supplemented and control flies, nor does the effect of Rhodiola depend on dietary manipulation, strongly suggesting that Rhodiola is not a mere dietary restriction mimetic. Although this study does not reveal the causal mechanism behind the effect of Rhodiola, it does suggest that the supplement is worthy of continued investigation, unlike the other Chinese herbals, Lu Duo Wei (LDW), Bu Zhong Yi Qi Tang (BZYQT), San Zhi Pian (SZP, Three Imperial Mushrooms), Hong Jing Tian (Rhodiola) that were evaluated in this study.

The new biology: beyond the Modern Synthesis

BACKGROUND

The last third of the 20th Century featured an accumulation of research findings that severely challenged the assumptions of the "Modern Synthesis" which provided the foundations for most biological research during that century. The foundations of that "Modernist" biology had thus largely crumbled by the start of the 21st Century. This in turn raises the question of foundations for biology in the 21st Century.

CONCLUSION

Like the physical sciences in the first half of the 20th Century, biology at the start of the 21st Century is achieving a substantive maturity of theory, experimental tools, and fundamental findings thanks to relatively secure foundations in genomics. Genomics has also forced biologists to connect evolutionary and molecular biology, because these formerly Balkanized disciplines have been brought together as actors on the genomic stage. Biologists are now addressing the evolution of genetic systems using more than the concepts of population biology alone, and the problems of cell biology using more than the tools of biochemistry and molecular biology alone. It is becoming increasingly clear that solutions to such basic problems as aging, sex, development, and genome size potentially involve elements of biological science at every level of organization, from molecule to population. The new biology knits together genomics, bioinformatics, evolutionary genetics, and other such general-purpose tools to supply novel explanations for the paradoxes that undermined Modernist biology.

Pioglitazone: an anti-diabetic compound with anti-aging properties

Insulin and Insulin-Growth-Factor-like (IGF) signaling pathways are well known longevity pathways in nematodes, insects and mammals. To our knowledge, there are no systematic pharmacological studies evaluating the anti-aging properties of medications that target this pathway in Drosophila. Although there are no published data implicating an anti-aging role for these compounds in Drosophila, we hypothesized that their promising pharmacological profile might decrease mortality. However, the decrease in mortality could be due to a number of potential artifacts and confounds such as fecundity depression, decrease in metabolic rate, or CNS depression. Therefore, the mere finding that a compound decreases mortality does not qualify it as an anti-aging compound. In this study, we evaluated the anti-aging properties of four compounds that might target the insulin signaling pathway in Drosophila. Once it was established that the compound decreased mortality, we proceeded to evaluate possible confounding factors that could have contributed to the mortality reduction. We show that only piolglitazone displayed anti-aging properties. At present, we do not have a mechanistic explanation for this pharmacological disparity.

Rules for the use of model organisms in anti-aging pharmacology

The use of animal models for initially screening anti-aging drugs is a promising approach for drug discovery. However, there a number of potential artifacts, confounds and errors that can arise in such research programs. The following rules are intended to minimize such problems: (1) since aging occupies an increasing proportion of human adulthood, data that conflate aging and late life should not be extrapolated to human aging; (2) the response to candidate medications should show a normal dose-response pattern, although not necessarily a linear response; (3) medicated animal models should not be hypometabolic; (4) medicated animal models should not show pronounced reductions in fertility; (5) medicated animal models should not exhibit general nervous system depression; (6) the effect of the medication should not be highly sensitive to the culture environment; (7) the effect of the medication should not be highly dependent on the genetic ancestry of the stock employed, leaving aside inbreeding, which should be avoided because humans are not generally inbred. While these rules do not guarantee successful extrapolation of successful drug results from the animal model to humans in a clinical setting, the failure to adhere to these rules should raise doubts about such extrapolation.

Age-specific changes in epistatic effects on mortality rate in Drosophila melanogaster

Models for the evolution of senescence assume that genes with age-specific effects act independently of one another. Although recent empirical data show that longevity is influenced in part by interactions between genes, there are currently few data on whether epistasis influences age-specific components of mortality. To gauge if and how interactions affect age-specific traits, we incorporated the Drosophila visible marker mutations ebony, forked, and purple into seven wild-caught strains of D. melanogaster to examine gene x genetic background interactions. We found significant natural genetic variation for longevity and baseline mortality rates. Gene x genetic background interactions were prevalent not only for longevity but also for baseline mortality rates and age-specific mortality rates. We conclude that gene x genetic background epistasis is prevalent for aging-related traits and could play a significant role in the evolution of aging. These results suggest that future genetic models for the evolution of aging should incorporate the effects of epistasis.

Breakdown in correlations during laboratory evolution. II. Selection on stress resistance in Drosophila populations

We trace the evolutionary correlation between stress resistance and longevity in populations of Drosophila melanogaster selected for stress resistance over many generations. Females selected for desiccation resistance and both females and males selected for increasing starvation resistance initially show concurrent increases in longevity, but then begin to decrease in longevity, even as stress resistance continues to increase. We demonstrate that the correlation between two fitness traits can change and that this change is due to sustained selection rather than a genotype-by-environment interaction or inbreeding depression. The breakdown in evolutionary correlation we report underscores the difficulty of extrapolating the results from short-term selection experiments to predictions of long-term evolution.