The goal of geroscience is life extension

Moderate protein intake percentage in mice for maintaining metabolic health during approach to old age

Nutritional requirements for maintaining metabolic health may vary with each life stage, such as young, middle, and old age. To investigate the appropriate ratio of nutrients, particularly proteins, for maintaining metabolic health while approaching old age, young (6-month-old) and middle-aged (16-month-old) mice were fed isocaloric diets with varying protein percentages (5%, 15%, 25%, 35%, and 45% by calorie ratio) for two months. The low-protein diet developed mild fatty liver, with middle-aged mice showing more lipids than young mice, whereas the moderate-protein diet suppressed lipid contents and lowered the levels of blood glucose and lipids. Self-organizing map (SOM) analysis revealed that plasma amino acid profiles differed depending on age and difference in protein diet and were associated with hepatic triglyceride and cholesterol levels. Results indicate that the moderate protein intake percentages (25% and 35%) are required for maintaining metabolic health in middle-aged mice, which is similar to that in young mice.

No limit to maximal lifespan in humans: how to beat a 122-year-old record

Although average human life expectancy is rising, the maximum lifespan is not increasing. Leading demographers claim that human lifespan is fixed at a natural limit around 122 years. However, there is no fixed limit in animals. In animals, anti-aging interventions (dietary restrictions, rapamycin, genetic manipulations) postpone age-related diseases and thus automatically extend maximum lifespan. In humans, anti-aging interventions have not been yet implemented. Instead, by treating individual diseases, medical interventions allow a patient to live longer (despite morbidity), expanding morbidity span. In contrast, slowly aging individuals (centenarians) enter very old age in good health, but, when diseases finally develop, they do not receive thorough medical care and die fast. Although the oldest old die from age-related diseases, death certificates often list "old age", meaning that diseases were not even diagnosed and even less treated. The concept of absolute compression of morbidity is misleading in humans (in truth, there is no other way to compress morbidity as by denying thorough medical care) and false in animals (in truth, anti-aging interventions do not condense morbidity, they postpone it). Anti-aging interventions such as rapamycin may potentially extend both healthspan and maximal lifespan in humans. Combining anti-aging medicine with cutting-edge medical care, regardless of chronological age, will extend maximal lifespan further.

Anti-aging: senolytics or gerostatics (unconventional view)

Senolytics are basically anti-cancer drugs, repurposed to kill senescent cells selectively. It is even more difficult to selectively kill senescent cells than to kill cancer cells. Based on lessons of cancer therapy, here I suggest how to exploit oncogene-addiction and to combine drugs to achieve selectivity. However, even if selective senolytic combinations will be developed, there is little evidence that a few senescent cells are responsible for organismal aging. I also discuss gerostatics, such as rapamycin and other rapalogs, pan-mTOR inhibitors, dual PI3K/mTOR inhibitors, which inhibit growth- and aging-promoting pathways. Unlike senolytics, gerostatics do not kill cells but slow down cellular geroconversion to senescence. Numerous studies demonstrated that inhibition of the mTOR pathways by any means (genetic, pharmacological and dietary) extends lifespan. Currently, only two studies demonstrated that senolytics (fisetin and a combination Dasatinib plus Quercetin) extend lifespan in mice. These senolytics slightly inhibit the mTOR pathway. Thus, life extension by these senolytics can be explained by their slight rapamycin-like (gerostatic) effects.

An essay on the nominal vs. real definitions of aging

In the current literature, the definitions of aging range from relying on certain sets of distinctive features at the molecular, organismal, populational and/or even evolutional levels/scales to declaring it a treatable disease and, moreover, to treating aging as a mental construct rather than a natural phenomenon. One reason of such a mess may be that it is common in the natural sciences to disregard philosophy of science where several categories of definitions are recognized, among which the nominal are less, and the so-called real ones are more appropriate in scientific contexts. E.g., water is, by its nominal definition, a liquid having certain observable features and, by its real definition, a specific combination (or a product of interaction) of hydrogen and oxygen atoms. Noteworthy, the real definition is senseless for people ignorant of atoms. Likewise, the nominal definition of aging as a set of observable features should be supplemented, if not replaced, with its real definition. The latter is suggested here to imply that aging is the product of chemical interactions between the rapidly turning-over free metabolites and the slowly turning-over metabolites incorporated in macromolecules involved in metabolic control. The phenomenon defined in this way emerged concomitantly with metabolic pathways controlled by enzymes coded for by information-storing macromolecules and is inevitable wherever such conditions coincide. Aging research, thus, is concerned with the elucidation of the pathways and mechanisms that link aging defined as above to its hallmarks and manifestations, including those comprised by its nominal definitions. Esoteric as it may seem, defining aging is important for deciding whether aging is what should be declared as the target of interventions aimed at increasing human life and health spans.

DNA- and telomere-damage does not limit lifespan: evidence from rapamycin

Failure of rapamycin to extend lifespan in DNA repair mutant and telomerase-knockout mice, while extending lifespan in normal mice, indicates that neither DNA damage nor telomere shortening limits normal lifespan or causes normal aging.