Introduction Aging is a complex biological process and the single greatest risk factor for many chronic diseases [1]. Unlike early-life development, aging was once thought to be immutable, but discoveries over the past decades have revealed that lifespan and healthspan (the period of healthy life) are surprisingly plastic. Classic experiments demonstrated that lifespan has a genetic basis: for example, fruit flies selectively bred for late reproduction lived nearly twice as long as normal, confirming that genetic factors can heritably influence longevity [1]. Similarly, studies in simple animals found that single gene mutations can dramatically extend lifespan – an early landmark was the discovery that a mutation in the age-1 gene of roundworms (C. elegans) increases their lifespan by ~60% [1]. Environmental and metabolic factors also play critical roles: the first evidence that aging could be decelerated came in 1939, when researchers found that severe caloric restriction in rodents extends life and delays age-related diseases [1]. Together, these findings set the stage for modern biogerontology – a science which now seeks to understand aging’s mechanisms and develop interventions to promote healthy aging and longevity in humans. In this article, we review key themes in aging and longevity, focusing on genetic pathways, metabolic and dietary influences, environmental and lifestyle factors, insights from model organisms, cardiovascular aging, and emerging therapeutic approaches. Genetic Factors in Aging and Longevity Heritability of Lifespan Biologists have long observed that different species (and even strains or families within a species) have characteristic lifespans, implying a genetic basis to aging. Early evolutionary theories (e.g. Medawar’s and Williams’ hypotheses) proposed that aging results from genes that have beneficial effects early in life but deleterious effects in later life – a concept known as antagonistic pleiotropy [2]. Experimental support for a genetic influence on longevity came from breeding studies: for instance, selecting fruit flies for longer reproductive periods produced offspring that lived significantly longer than unselected flies, and these lifespan differences were heritable [1]. Such results confirmed that genes can modulate lifespan in a measurable way. Longevity Pathways Discovered in Model Organisms Pioneering genetic screens in short-lived animals revealed specific genes and molecular pathways that regulate aging. In the nematode C.elegans, Cynthia Kenyon’s group famously showed that a single-gene mutation (daf-2, affecting an insulin/IGF-1 hormone receptor) could double the worm’s lifespan [2]. This effect required another gene, daf-16, which encodes a FOXO-family transcription factor that turns on stress-resistance and maintenance genes [2]. The DAF-2/DAF-16 pathway in worms was the first clear example that an evolutionarily conserved endocrine signaling network (insulin/IGFsignaling) controls aging. Subsequent work in fruit flies and mice confirmed that reducing insulin/IGF signaling can extend lifespan in those organisms as well [2]. Another key pathway is the mTOR pathway: mutations that inhibit mTOR(a protein kinase that senses nutrient abundance) were found to mimic the effects of dietary restriction and extend lifespan in yeast, worms, and flies [1]. Notably, combining mutations in both the insulin/IGFpathway and the mTORpathway produced an almost five-fold lifespan increase in worms, illustrating that these longevity pathways can have additive effects [1]. Genes controlling cellular stress resistance and macromolecular quality control have also emerged as longevity determinants. For example, boosting the expression of antioxidant enzymes (like superoxide dismutase or catalase) in fruit flies extends their lifespan [2], consistent with the theory that enhanced defense against molecular damage slows aging. More broadly, many genetic alterations that promote longevity in model organisms converge on a few conserved processes – nutrient sensing, growth factor signaling, stress response, DNA repair, and proteostasis– suggesting that evolution has “reused” the same aging mechanisms in many species. Longevity Genes in Humans Do similar genetic factors influence human longevity? While experiments can’t be done in humans, studies of centenarians (people who live to 100+) and long- lived families indicate that genetics does play a role in exceptional longevity. One prominent example is the gene FOXO3(the human version of the worm daf-16): certain variants of FOXO3are significantly overrepresented in long- lived individuals across multiple ethnic populations [2]. FOXO3 is involved in insulin signaling and stress resistance, and its link to human longevity aligns with the importance of those pathways seen in animals. Other gene variants associated with longevity affect similar pathways, such as growth hormone/ IGF-1 signaling, lipid metabolism, and inflammation regulation [2][3]. It’s important to note that human longevity is polygenic (influenced by many genes of small effect) and strongly modulated by environment. Nevertheless, the identification of longevity-associated genes in humans reinforces the idea that genetic modulators of aging discovered in animals are relevant to our own species [2]. For instance, variants that keep IGF-1 levels lower or preserve telomere length have been linked to longer life [2][3], echoing findings in lab organisms. In summary, genetic factors set the potential limits of lifespan by governing fundamental aging processes – and intriguingly, many of these factors are evolutionarily conserved, pointing to core aging mechanisms shared across life. Metabolic and Dietary Influences on Longevity Metabolic regulation is a central pillar of aging biology. Organisms have evolved nutrient-sensing pathways to toggle between growth/reproduction versus maintenance/repair mode depending on food availability. Those same pathways – insulin/IGF, mTOR, AMPK, sirtuins, and others – have a profound impact on aging rate. Caloric Restriction and Nutrient Sensing The most robust environmental intervention to extend lifespan in laboratory animals is caloric restriction (CR), typically a 20–40% reduction in calorie intake without malnutrition. CR has been shown to lengthen lifespan in organisms ranging from yeast to mice and even in primate studies [1]. Mechanistically, CR induces a metabolic shift from growth to preservation: under low calories, cells reduce insulin/IGFsignaling and mTOR activity, and activate stress-responsive factors like AMP-activated proteinkinase(AMPK)and sirtuins[1]. This triggers enhanced autophagy (cellular cleaning of damaged components), improved DNA repair, and other anti-aging processes. Indeed, genetic evidence supports the link between metabolism and longevity: drastically suppressing the insulin/IGFand mTOR pathways can extend lifespan synergistically (as noted in worms with both pathways mutated) [1]. Conversely, excessive nutrient intake and high blood sugar accelerate aging. Experimental models show that high-glucose diets shorten the lifespan of worms and flies by causing cellular damage and metabolic dysfunction [3]. In mammals, chronically elevated insulinand IGF-1 (as seen in overnutrition or diabetes) are associated with accelerated aging and increased incidence of age-related diseases like cardiovascular disease and cancer [3]. Thus, caloric intake and nutrient quality have direct impacts on molecular aging pathways. Insulin and Glucose Metabolism Aging is often accompanied by insulin resistance (where tissues respond poorly to insulin) and other metabolic disorders. These not only predispose to diseases (like type 2 diabetes and atherosclerosis) but also seem to feed into aging processes themselves [3]. For example, insulin resistance leads to high blood sugar (hyperglycemia), which triggers harmful biochemical pathways (such as advanced glycation and oxidative stress) that damage cells and tissues over time [3]. Supporting this connection, centenarians – who aged successfully – tend to have remarkably youthful metabolic profiles. Studies of healthy 100-year-olds find that they often maintain high insulin sensitivity and lower levels of IGF-1 compared to typical elderly adults [2]. In effect, their carbohydrate metabolism more closely resembles that of much younger individuals, which may protect them from the degenerative effects of aging [2]. This observation mirrors what is seen in animal models: genetic or dietary interventions that improve insulin sensitivity (like CR or fasting) slow aging, whereas inducing diabetic metabolic states accelerates aging. On a cellular level, insulin/IGFsignaling status influences the FOXOand mTORpathways, tipping the balance between cell growth and stress resistance [2]. Figure 1. Glucose Metabolism and Longevity Abnormal glucose metabolism, defined as hyperglycemia, hyperinsulinemia, and insulin resistance, contributes to accelerated cardiovascular aging but also to short life span through several pathophysiological mechanisms, such as inhibition of antiaging proteins. Moreover, disrupted regulation of molecules related to longevity (such as mammalian target of rapamycin and sirtuins) have been related to abnormal glucose metabolism, thus demonstrating a bidirectional relationship between longevity and abnormal glucose metabolism [3]. Other Metabolic Factors Beyond insulin and calories, many aspects of metabolism factor into longevity. Lipid metabolism, for instance, changes with age – “good” HDL cholesterol often declines and pro-atherogenic factors rise. Long-lived populations tend to have healthier lipid profiles (lower LDL, higher HDL) and genetic studies have probed variants in lipid-related genes in centenarians [2][3]. Another major factor is oxidative metabolism and mitochondrial function. Mitochondria produce energy but also generate reactive oxygen species (ROS) as a byproduct. The “free radical theory of aging” postulates that accumulated oxidative damage to cells drives aging [3]. There is evidence that increased oxidative stress correlates with aging and age-related diseases, including heart disease [3]. For example, very long-lived individuals exhibit lower markers of oxidative damage and more robust antioxidant defenses [3]. However, the
