The Science of Healthy Aging: Genes, Milieu, and Chance

Biogerontology: research status, challenges and opportunities

Biogerontology is the study of the biological basis of ageing and age-related diseases. The phenomenon and the process of ageing are well understood in evolutionary and biological terms; and a conceptual framework has been established within which general principles of ageing and longevity can be formulated. The phenotype of ageing in terms of progressive loss of physical function and fitness is best seen during the period of survival after the evolution-determined essential lifespan (ELS) of a species. However, the ageing phenotype is highly heterogenous and individualistic at all levels from the whole body to the molecular one. Most significantly, the process and the progression of ageing are not determined by any specific gerontogenes. Ageing is the result of imperfect maintenance and repair systems that allow a progressive shrinkage of the homeodynamic space of an individual. The challenge is to develop and apply wholistic approaches to the complex trait of ageing for maintaining and/or improving health. One such approach is that of mild stress-induced physiological hormesis by physical, mental and nutritional hormetins. Biogerontological research offers numerous opportunities for developing evidence-based novel biomedical technologies for maintaining and improving health, for preventing the onset of age-related diseases, and for extending the health-span.

Healthy ageing, but what is health?

Ageing occurs in spite of complex pathways of maintenance and repair. There is no "enemy within", which has the specific evolution-selected function to cause ageing and death. This understanding of ageing should transform our approach towards interventions from therapeutic "anti-ageing" to maintaining health. But what is health? Ideally, health is a state of complete physical and mental independence in activities of daily living. But in pragmatic terms, health is a state of adequate physical and mental independence in activities of daily living. In order to identify a set of measurable, evidence-based and demonstratable parameters of health, robustness and resilience at various levels, the concept of homeodynamic space can be a useful one. Age-related health problems for which there are no clear-cut causative agents, except the complex process of ageing, may be better tackled by focusing on health mechanisms and their maintenance, rather than disease management and treatment. Continuing the disease-oriented research approaches are economically, socially and psychologically unsustainable as compared with health-oriented and preventive strategies, such as hormesis. Supporting health-oriented research is the urgency of our time.

Detoxification and antioxidative therapy for levodopa-induced neurodegeneration in Parkinson's disease

Levodopa is the most efficacious drug treatment option for Parkinson's disease. However, in particular, high levodopa dosing may contribute to disease progression. Chronic levodopa metabolism reduces the methylation capacity and the antioxidant defense. Thus, this levodopa-induced free radical production complements the disease process, which considerably depends on free radical-induced, apoptotic neuronal cell death. Accordingly, clinical long-term studies with in the laboratory neuroprotective compounds failed in clinical investigations, as these studies were performed in levodopa-naive patients with Parkinson's disease over a relative short interval. Therefore, the likelihood for a positive outcome was rather low, since trials only focused on the disease process in levodopa-naive patients. However, studies on antioxidant therapeutic strategies were positive in levodopa-treated Parkinson's disease patients. To counteract these metabolic long-term levodopa-associated effects, chronic levodopa therapy should be combined with supplemental application of free radical scavengers and methyl group donating vitamins.

Establishing cellular stress response profiles as biomarkers of homeodynamics, health and hormesis

Aging is the progressive shrinkage of the homeodynamic space. A crucial component of the homeodynamic space is the stress response (SR), by virtue of which a living system senses disturbance and initiates a series of events for maintenance, repair, adaptation, remodeling and survival. Here we discuss the main intracellular SR pathways in human cells, and argue for the need to define and establish the immediate and delayed stress response profiles (SRP) during aging. Such SRP are required to be established at several age-points, which can be the molecular biomarkers of homeodynamic space and the health status of cells and organisms. SRP can also be useful for testing potential protectors and stimulators of homeodynamics, and can be a standard for monitoring the efficacy of potential pro-survival, health-promoting and aging-modulating conditions, food components and other compounds. An effective strategy, which makes use of SRP for achieving healthy aging and extending the healthspan, is that of strengthening the homeodynamics through repeated mild stress-induced hormesis by physical, biological and nutritional hormetins. Furthermore, SRP can also be the basis for defining health as a state of having adequate physical and mental independence of activities of daily living, by identifying a set of measurable parameters at the most fundamental level of biological organization.

Testing the hormetic nature of homeopathic interventions through stress response pathways

The scientific foundations of hormesis are now well established and include various biochemical and molecular criteria for testing the hormetic nature of chemicals and other modulators. In order to claim homeopathy as being hormetic, it is essential that, in addition to the hormetic biphasic dose response, homeopathic remedies should fulfill one or more molecular criteria. Since stress response pathways, such as heat shock response, antioxidative response, autophagic response and unfolded protein response, are integral components of the physiological hormesis, it is important that homeopathic drugs be tested for these pathways if these are to be considered as hormetins and to cause hormesis.

Hyperbaric oxygen treatment induces antioxidant gene expression

Although the underlying molecular causes of aging are not entirely clear, hormetic agents like exercise, heat, and calorie restriction may generate a mild pro-oxidant stress that induces cell protective responses to promote healthy aging. As an individual ages, many cellular and physiological processes decline, including wound healing and reparative angiogenesis. This is particularly critical in patients with chronic non-healing wounds who tend to be older. We are interested in the potential beneficial effects of hyperbaric oxygen as a mild hormetic stress on human microvascular endothelial cells. We analyzed global gene expression changes in human endothelial cells following a hyperbaric exposure comparable to a clinical treatment. Our analysis revealed an upregulation of antioxidant, cytoprotective, and immediate early genes. This increase coincided with an increased resistance to a lethal oxidative stress. Our data indicate that hyperbaric oxygen can induce protection against oxidative insults in endothelial cells and may provide an easily administered hormetic treatment to help promote healthy aging.

Hormesis can and does work in humans

If we accept the validity of the general concept of physiological hormesis as being the phenomenon of achieving health beneficial effects by exposure to mild stress, then hormesis is being applied already and successfully to humans. The evidence for this is the well-demonstrated health benefits of regular and moderate exercise. Mild stress-induced activation of one or more intracellular pathways of stress response are central to this. Experimental studies performed on human cells in culture exposed to mild heat shock and other stresses provide biochemical and molecular evidence in support of the application of hormesis to human systems. Although several issues remain to be resolved by more research with respect to the extent and duration of hormetic exposure, making use of the cellular stress response pathways can facilitate discovering novel hormetins for human applications.

Anti-aging medicine: pitfalls and hopes

Since the beginnings of time humans have searched for a fountain of youth. This has led to many extravagant claims which have been highly profitable for their proponents. This area has become known as anti-aging medicine and has deservedly been frowned upon by the medical establishment. On the other hand, in the last decades dramatic advances in our understanding of the aging process have come from studies in worms, flies and mice. This article reviews some of these advances and places the extravagant claims of anti-aging medicine in perspective. We conclude that a balanced diet of moderate proportions and exercise remain today the only proven fountain of youth.

Progress & prospects: gene therapy in aging

Studies performed on various experimental model systems indicate that genetic interventions can increase longevity, even if in a highly protected laboratory condition. Generally, such interventions required partial or complete switching off of the gene and inhibiting the activity of its gene products, which normally have other well-defined roles in metabolic processes. Overexpression of some genes, such as stress response and antioxidant genes, in some model systems also extends their longevity. Such genetic interventions may not be easily applicable to humans without knowing their effects on human growth, development, maturation, reproduction and other characteristics. Studies on the association of single nucleotide polymorphisms and multiple polymorphisms (haplotype) in genes with human longevity have identified several genes whose frequencies increase or decrease with age. Whether genetic redesigning can be achieved in the wake of numerous and complex epigenetic factors that effectively determine the life course and the life span of an individual still appears to be a 'mission impossible'.

Increased molecular damage and heterogeneity as the basis of aging

Aging at the molecular level is characterized by the progressive accumulation of molecular damage. The sources of damage act randomly through environmental and metabolically generated free radicals, through spontaneous errors in biochemical reactions, and through nutritional components. However, damage to a macromolecule may depend on its structure, localization and interactions with other macromolecules. Damage to the maintenance and repair pathways comprising homeodynamic machinery leads to age-related failure of homeodynamics, increased molecular heterogeneity, altered cellular functioning, reduced stress tolerance, diseases and ultimate death. Novel approaches for testing and developing effective means of intervention, prevention and modulation of aging involve means to minimize the occurrence and accumulation of molecular damage. Mild stress-induced hormesis by physical, biological and nutritional methods, including hormetins, represents a promising strategy for achieving healthy aging and for preventing age-related diseases.