The Biochemical Landscapes Of Longevity: Interplay Between Mitochhondrial Dysfunction, Nutrient Sensing Pathways, And Metabolic Strategies To Halt Aging

Aging is characterized by a progressive decline in physiological integrity, leading to impaired cellular function and increased vulnerability to metabolic, neurodegenerative, and cardiovascular diseases. In the field of medical biochemistry, aging is no longer viewed as a passive, entropic process but rather as a highly regulated biological phenomenon governed by interconnected molecular pathways. This academic review aims to analyze the intricate biochemical interplay between mitochondrial dysfunction and nutrient-sensing networks during cellular senescence, while critically evaluating the efficacy of current metabolic interventions designed to preserve healthspan and extend human longevity. A systematic literature search was conducted across the PubMed, Web of Science, and Google Scholar databases for peer-reviewed studies, clinical cohort analyses, and systematic reviews published up to October 2026. Search strings combined core biochemical keywords including "human longevity", "mitochondrial dysfunction", "nutrient-sensing pathways", "Sirtuins", "mTORC1", and "NAD+ boosters". Prioritization was given to multi-omics studies, clinical trials, and geroscience frameworks validated in human plasma, serum, or non-human primate models. Studies tracking macrovascular pathologies without clear aging biomarker endpoints were excluded. The biochemical hallmarks of aging are centered around a state of cellular energy crisis and dysregulated nutrient signaling. Mitochondria, the main hubs of Adenosine Triphosphate (ATP) generation via oxidative phosphorylation (OXPHOS), experience a marked functional decline with age. This is driven by the accumulation of mitochondrial DNA (mtDNA) mutations, loss of membrane potential, and a failure in selective macroautophagy (mitophagy). The resulting mitochondrial collapse drastically increases the production of Reactive Oxygen Species (ROS), triggering cellular stress responses and the chronic, sterile inflammation known as "inflammaging." Simultaneously, nutrient-sensing networks undergo pathological shifts. The continuous, hyperactivation of the Mechanistic Target of Rapamycin Complex 1 (mTORC1)-driven by nutrient-rich diets-suppresses cytoprotective autophagy and accelerates cellular senescence. Conversely, critical energy sensors such as Adenosine Monophosphate-Activated Protein Kinase (AMPK) and the nicotinamide adenine dinucleotide (NAD+)-dependent Sirtuins (SIRT1-7) exhibit severe systemic depletion. The age-dependent drop in the NAD+/NADH ratio impairs the activation of the rate-limiting salvage enzyme Nicotinamide Phosphoribosyltransferase (NAMPT), paralyzing nuclear-mitochondrial communication. To counteract these transformations, advanced metabolic interventions show great therapeutic potential. Administering exogenous NAD+ precursors, such as Nicotinamide Mononucleotide (NMN) or Nicotinamide Riboside (NR), successfully restores the NAD+ pool, re-activating SIRT1 and SIRT6 to improve insulin sensitivity and mitigate epigenetic biological aging. Furthermore, lifestyle interventions—including dietary amino acid restriction and intermittent fasting—activate the stress-response transcription factor ATF4, downregulate mTORC1, and promote mitochondrial biogenesis via PGC-1alpha. Human longevity is dynamically dictated by the functional synchronization of mitochondrial health and nutrient-sensing pathways. Transitioning clinical focus toward multi-analyte biochemical profiling—quantifying plasma NAD+ availability, sirtuin enzyme kinetics, and circulating epigenetic methylation markers—provides a non-invasive strategy to measure biological age and design precise geroscience interventions capable of halting metabolic degeneration.