CAN CALORIE RESTRICTION DELAYS THE CELLULAR METABOLISM LEADS TO SENESCENCE? 1Upasana; 2Parveen Shaista; 3Chakravarty Archana 1Research Scholar in Department of Home Science (Food and Nutrition), 2Research Scholar in Department of Home Science (Food and Nutrition), 3 Professor in Department of Home Science (Food and Nutrition), BHU, Varanasi INTRODUCTION Ageing results in a progressive decline in multiple organ systems, thus affecting reproductive, metabolic, physical and cognitive function and eventually, survival. Human ageing is due to interactions between genetic and epigenetic factors but in addition to the genetic background, successful or unsuccessful ageing is also determined by environmental factors associated with social structure, culture and lifestyle. A longer and healthier lifespan in successful ageing process may be upgraded by creating resistance against cellular stress. Nutrition is believed to be a chief contributor or to the gene regulation in ageing process by impacting epigenetic pathways and mitochondrial function. A complex array of Calorie restriction, epigenetic factor and mitochondrial function plays an important role in modulating lifespan. CR elicits coordinated and adaptive stress responses at the cellular and whole-organism level by modulating epigenetic mechanisms (e.g., DNA methylation, posttranslational histone modifications), signaling pathways that regulate cell growth and ageing (e.g., TOR, AMPK, p53, and FOXO), and cell-to-cell signaling molecules (e.g., adiponectin).Mitochondrial activity is also triggered by calorie restriction (CR), a dietary regimen that is known to extend lifespan in organism, exerts its salutary effects by slowing carbohydrate use, respiration and the rate of damage produced by reactive oxygen species (ROS). Nutrient sensing pathways also considered as contributing factors in ageing process because several nutrients can activate different pathways directly or indirectly. Here, this review paper is an attempt to understand the role of CR and its effect on mitochondrial function and epigenetic modulation during ageing, which will offer exciting new opportunities to explore the role of CR influencing the biology of ageing. . MITOCHONDRIA, ROS PRODUCTION AND AGEING EPIGENETIC FACTORS METABOLIC PATHWAYS OF CELLULAR METABOLISM Adiponectin secretion DNA methylation 1 1 Insulin/ IGF-1 pathway Histone modification 2 2 3 Mammalian target of rapamycin (mTOR) pathway miRNA modification 3 4 Sirtuins pathway EPIGENETIC MODIFICATIONS BY CALORIE RESTRICTION THROUGH DIETARY FACTORS DURING AGEING EFFECT OF CALORIE RESTRICTION ON METABOLIC PATHWAYS MONITORED BY p53 HISTONE MODIFICATION DNA METHYLATIONS miRNA CONCLUSION Calorie restriction (CR) can serves an ameliorate role in delaying the process of ageing by modulating epigenetic factors that include DNA methylation, histone modification and mi RNA. miRNA regulates three major conserved pathways which include insulin/IGF-1, mTOR and Sirtuins , and are monitored by p53.CR decreased the activity of insulin / IGF-1 signalling pathway that can improves longevity in humans. mTOR and Sirtuins can be manipulated by CR which enhance the cellular stress resistance and is a known defence mechanism against ageing process. CR also plays an extensive role in delaying ageing by altering the mechanism of mitochondria which is the energy currency of the cell. CR reduces ROS formation, which increases during ageing and thus increases life span. Therefore, CR changes the gene expression via epigenetic factor which is a major molecular mechanism that potentially improves cell function and health, leading to delay ageing processes and thus extending longevity.