Longevity. The allostatic load of dietary restriction

The complex relationship between late-onset caloric restriction and synaptic plasticity in aged Wistar rats

Age-related reduction in spine density, synaptic marker expression, and synaptic efficiency are frequently reported. These changes provide the cellular and molecular basis for the cognitive decline characteristic for old age. Nevertheless, there are several approaches that have the potential to ameliorate these processes and improve cognition, caloric restriction being one of the most promising and widely studied. While lifelong caloric restriction is known for its numerous beneficial effects, including improved cognitive abilities and increased expression of proteins essential for synaptic structure and function, the effects of late-onset and/or short-term CR on synaptic plasticity have yet to be investigated. We have previously documented that the effects of CR are strongly dependent on whether CR is initiated in young or old subjects. With this in mind, we conducted a long-term study in aging Wistar rats to examine changes in the expression of several key synaptic markers under the regimen of CR started at different time points in life. We found a significant increase in the expression of both presynaptic and postsynaptic markers. However, taking into account previously reported changes in the behavior detected in these animals, we consider that this increase cannot represent beneficial effect of CR.

Mediterranean diet and inflammaging within the hormesis paradigm

A coherent set of epidemiological data shows that the Mediterranean diet has beneficial effects capable of preventing a variety of age-related diseases in which low-grade, chronic inflammation/inflammaging plays a major role, but the underpinning mechanism(s) is/are still unclear. It is suggested here that the Mediterranean diet can be conceptualized as a form of chronic hormetic stress, similar to what has been proposed regarding calorie restriction, the most thoroughly studied nutritional intervention. Data on the presence in key Mediterranean foods of a variety of compounds capable of exerting hormetic effects are summarized, and the mechanistic role of the nuclear factor erythroid 2 pathway is highlighted. Within this conceptual framework, particular attention has been devoted to the neurohormetic and neuroprotective properties of the Mediterranean diet, as well as to its ability to maintain an optimal balance between pro- and anti-inflammaging. Finally, the European Commission-funded project NU-AGE is discussed because it addresses a number of variables not commonly taken into consideration, such as age, sex, and ethnicity/genetics, that can modulate the hormetic effect of the Mediterranean diet.

Oxidative Priority, Meal Frequency, and the Energy Economy of Food and Activity: Implications for Longevity, Obesity, and Cardiometabolic Disease

In most modern societies, the relationship that many individuals have with food has fundamentally changed from previous generations. People have shifted away from viewing food as primarily sustenance, and rather now seek out foods based on pure palatability or specific nutrition. However, it is far from clear what optimal nutrition is for the general population or specific individuals. We previously described the Food Triangle as a way to organize food based on an increasing energy density paradigm, and now expand on this model to predict the impact of oxidative priority and both nutrient and fiber density in relation to caloric load. When combined with meal frequency, integrated energy expenditure, macronutrient oxidative priority, and fuel partitioning expressed by the respiratory quotient, our model also offers a novel explanation for chronic overnutrition and the cause of excess body fat accumulation. Herein, we not only review how metabolism is a dynamic process subject to many regulators that mediate the fate of ingested calories but also discuss how the Food Triangle predicts the oxidative priority of ingested foods and provides a conceptual paradigm for healthy eating supported by health and longevity research.

Modulating adult neurogenesis through dietary interventions

Three areas in the brain continuously generate new neurons throughout life: the subventricular zone lining the lateral ventricles, the dentate gyrus in the hippocampus and the median eminence in the hypothalamus. These areas harbour neural stem cells, which contribute to neural repair by generating daughter cells that then become functional neurons or glia. Impaired neurogenesis leads to detrimental consequences, such as depression, decline of cognitive abilities and obesity. Adult neurogenesis is a versatile process that can be modulated either positively or negatively by many effectors, external or endogenous. Diet can modify neurogenesis both ways, either directly by ways of food-borne molecules, or possibly by the modifications induced on gut microbiota composition. It is therefore critical to define dietary strategies optimal for the maintenance of the stem cell pools.

Genetics and pharmacology of longevity: the road to therapeutics for healthy aging

Aging can be defined as the progressive decline in tissue and organismal function and the ability to respond to stress that occurs in association with homeostatic failure and the accumulation of molecular damage. Aging is the biggest risk factor for human disease and results in a wide range of aging pathologies. Although we do not completely understand the underlying molecular basis that drives the aging process, we have gained exceptional insights into the plasticity of life span and healthspan from the use of model organisms such as the worm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. Single-gene mutations in key cellular pathways that regulate environmental sensing, and the response to stress, have been identified that prolong life span across evolution from yeast to mammals. These genetic manipulations also correlate with a delay in the onset of tissue and organismal dysfunction. While the molecular genetics of aging will remain a prosperous and attractive area of research in biogerontology, we are moving towards an era defined by the search for therapeutic drugs that promote healthy aging. Translational biogerontology will require incorporation of both therapeutic and pharmacological concepts. The use of model organisms will remain central to the quest for drug discovery, but as we uncover molecular processes regulated by repurposed drugs and polypharmacy, studies of pharmacodynamics and pharmacokinetics, drug-drug interactions, drug toxicity, and therapeutic index will slowly become more prevalent in aging research. As we move from genetics to pharmacology and therapeutics, studies will not only require demonstration of life span extension and an underlying molecular mechanism, but also the translational relevance for human health and disease prevention.

A reason for intermittent fasting to suppress the awakening of dormant breast tumors

For their growth, dormant tumors, which lack angiogenesis may critically depend on gradients of nutrients and oxygen from the nearest blood vessel. Because for oxygen depletion the distance from the nearest blood vessel to depletion will generally be shorter than for glucose depletion, such tumors will contain anoxic living tumor cells. These cells are dangerous, because they are capable of inducing angiogenesis, which will "wake up" the tumor. Anoxic cells are dependent on anaerobic glucose breakdown for ATP generation. The local extracellular glucose concentration gradient is determined by the blood glucose concentration and by consumption by cells closer to the nearest blood vessel. The blood glucose concentration can be lowered by 20-40% during fasting. We calculated that glucose supply to the potentially hazardous anoxic cells can thereby be reduced significantly, resulting in cell death specifically of the anoxic tumor cells. We hypothesize that intermittent fasting will help to reduce the incidence of tumor relapse via reducing the number of anoxic tumor cells and tumor awakening.

Dissection of the hormetic curve: analysis of components and mechanisms

The relationship between the dose of an effector and the biological response frequently is not described by a linear function and, moreover, in some cases the dose-response relationship may change from positive/adverse to adverse/positive with increasing dose. This complicated relationship is called "hormesis". This paper provides a short analysis of the concept along with a description of used approaches to characterize hormetic relationships. The whole hormetic curve can be divided into three zones: I - a lag-zone where no changes are observed with increasing dose; II - a zone where beneficial/adverse effects are observed, and III - a zone where the effects are opposite to those seen in zone II. Some approaches are proposed to analyze the molecular components involved in the development of the hormetic character of dose-response relationships with the use of specific genetic lines or inhibitors of regulatory pathways. The discussion is then extended to suggest a new parameter (half-width of the hormetic curve at zone II) for quantitative characterization of the hormetic curve. The problems limiting progress in the development of the hormesis concept such as low reproducibility and predictability may be solved, at least partly, by deciphering the molecular mechanisms underlying the hormetic dose-effect relationship.

Caloric restriction and aging stem cells: the stick and the carrot?

Adult tissue stem cells have the ability to adjust to environmental changes and affect also the proliferation of neighboring cells, with important consequences on tissue maintenance and regeneration. Stem cell renewal and proliferation is strongly regulated during aging of the organism. Caloric restriction is the most powerful anti-aging strategy conserved throughout evolution in the animal kingdom. Recent studies relate the properties of caloric restriction to its ability in reprogramming stem-like cell states and in prolonging the capacity of stem cells to self-renew, proliferate, differentiate, and replace cells in several adult tissues. However this general paradigm presents with exceptions. The scope of this review is to highlight how caloric restriction impacts on diverse stem cell compartments and, by doing so, might differentially delay aging in the tissues of lower and higher organisms.

The yeast forkhead transcription factors fkh1 and fkh2 regulate lifespan and stress response together with the anaphase-promoting complex

Forkhead box O (FOXO) transcription factors have a conserved function in regulating metazoan lifespan. A key function in this process involves the regulation of the cell cycle and stress responses including free radical scavenging. We employed yeast chronological and replicative lifespan assays, as well as oxidative stress assays, to explore the potential evolutionary conservation of function between the FOXOs and the yeast forkhead box transcription factors FKH1 and FKH2. We report that the deletion of both FKH genes impedes normal lifespan and stress resistance, particularly in stationary phase cells, which are non-responsive to caloric restriction. Conversely, increased expression of the FKHs leads to extended lifespan and improved stress response. Here we show the Anaphase-Promoting Complex (APC) genetically interacts with the Fkh pathway, likely working in a linear pathway under normal conditions, as fkh1Δ fkh2Δ post-mitotic survival is epistatic to that observed in apc5(CA) mutants. However, under stress conditions, post-mitotic survival is dramatically impaired in apc5(CA) fkh1Δ fkh2Δ, while increased expression of either FKH rescues APC mutant growth defects. This study establishes the FKHs role as evolutionarily conserved regulators of lifespan in yeast and identifies the APC as a novel component of this mechanism under certain conditions, likely through combined regulation of stress response, genomic stability, and cell cycle regulation.