Abstract
Aging is a universal process with progressive loss of function accompanied by decreasing fertility and increasing mortality and disability. There are several mechanisms to underlie the primary aging process and probably contribute to age-related changes in adaptive responses. These mechanisms are oxidative stress, mitochondrial theory, telomeres and cellular senescence, apoptosis and genetic mechanism. There are many physiological changes with aging process including blood pressure, temperature, fever, and composition of body fluids. Age-related changes in bioavailability may be secondary to changes in absorption or gut wall and hepatic metabolism. The stomach lining's capacity to resist damage decreases with age due to alteration of the gastric defense mechanisms and decreased mucosal blood flow. Normal aging is associated with age-related changes in motor function of the various parts of the gastrointestinal tract such as transit time and gastric emptying. The incidence of many gastrointestinal dysfunctions increases with advancing age that is associated with alterations in the structural and functional integrity of the gastrointestinal tract. The structural changes include mucosa, muscular coat and blood flow. The clinical significance of functional and structural gastric changes may all impact upon gastrointestinal adverse effects and how older people tolerate medicines. Understanding how the upper gastrointestinal tract changes with advancing age could allow interventions that lead to more appropriate prescribing for older people, potentially reduce adverse effects, increase compliance with treatment regimens, and may allow older people to take medications that they would not otherwise tolerate.
Highlights
It has been proposed that accumulation of somatic mutations of mitochondrial DNA, induced by exposure to reactive oxygen species generated within mitochondria, leads to errors in the mitochondrial DNA-encoded polypeptides and subsequent defective electron transfer activity and oxidative phosphorylation [3]
Normal aging is associated with important age-related changes in motor function of the various parts of the gastrointestinal tract and some of these important motility changes may occur, either in relation to common age-related disorders, or as a result of certain drugs commonly prescribed in the aged [6,7,8]
Paracetamol absorption kinetics has been used successfully as a model for gastric emptying of liquids as it is rapidly absorbed from the small bowel but not from the stomach
Summary
Aging is a universal process whose manifestations are familiar and unambiguous, and these manifestations can be recognized readily after minimal assessment. Changes in the regulation of the body systems increase the diversity among older people as with age, the ability of organs to control their normal homeostasis decreases, due to progressive changes in the regulatory mechanisms [1]. These mechanisms are: oxidative Stress, mitochondria, telomeres and cellular senescence and apoptosis. Increased oxidative stress has been incriminated in physiological conditions, such as aging and exercise, and in several pathological conditions, including cancer, neurodegenerative, cardiovascular diseases, diabetes, inflammatory diseases, and intoxications [2]. Age-related resistance to apoptosis involves (1) functional deficiency in p53 network, (2) increased activity in the NF-κB-IAP/JNK axis, and (3) changes in molecular chaperones, microRNAs, and epigenetic regulation [4, 5]
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