Research led by Wardah Shahzadi

Writers: Shahzadi Fatima, Aamna Asim, Fatima Shamim

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Introduction:

Why do we age, and can we slow it down? These questions have captivated humanity for centuries, sparking myths of eternal youth and modern quests for scientific breakthroughs. From the microscopic dance of our cells to the intricate interplay of genes, hormones, and immunity, the aging process is a complex symphony of biological mechanisms. But aging is more than wrinkles and gray hair—it’s a journey shaped by cellular decay, genetic codes, and the body's ever-evolving defense systems. Yet, as science peels back the layers of this enigma, astonishing possibilities emerge: Can we unlock the secrets to living not just longer but healthier? In this exploration, we’ll delve into the hidden workings of aging and discover how cutting-edge research is paving the way toward longevity and vibrant living. The science of aging isn’t just about time—it’s about rewriting the rules of life itself.

Biological Mechanisms of Aging:

Aging can be defined as the time-dependent general decline of physiological functions of an organism, which is associated with a progressively increasing risk of morbidity and mortality.

Stochastic damage inflicted to biological macro-molecules is the driving force for the aging process. The damage is derived from small reactive molecules, most prominently reactive oxygen intermediates (ROI), that arise during normal cellular metabolism and are associated with important if not essential cellular functions. The major classes of macro-molecules at risk are proteins, lipids and DNA, but damage to DNA (both nuclear and mitochondrial) may entail particularly severe consequences, since in contrast to most other macro-molecules there is little if any turnover of DNA to dilute the damage. In addition, since all genetic information of the cells resides in DNA and most genes are present at a low copy numbers, any errors in the coding function of DNA can' amplify' to the level of proteins and their respective functions Cellular dysfunction resulting from macro-molecular damage can be detected as a variety of expressions, such as genomic instability, inappropriate cell differentiation events or cell death. While for post-mitotic cell types replacement of the dead cell by another cell of the same lineage is not possible, mitotic cell types may initially replace dead cells via cell proliferation. But exhaustion of the self-renewal capacity of the respective lineage, by either replication-associated or damage associated telomere shortening, will ultimately also lead to loss of  cell mass and functional impairment of tissues, the latter being a typical feature of ageing of tissues and organs. It has been demonstrated in various experimental systems that the rate ageing of can be retarded by lowering the production of endogenous ROI or by improving cellular anti-oxidative defenses.

The Role of Genetics of Longevity:

The definition of longevity is based on the maximum duration of life of human beings. Longevity depends on the possibility of survival after the end of the reproductive period and the genes that lead to longevity are “survival genes” rather than “Longevity genes”.

Several studies of formal genetics strongly suggest the role of genes in achieving longevity. The comparison between the survival of the siblings of centenarians and that of their brothers-in-law, who likely shared the same lifestyle for most of their lives, showed that “the survival advantage” of siblings of long-lived subjects was not fully shared from their brothers-in-law. This suggested that beyond the family environment, there are genetic factors that influence survival and, consequently, longevity. This was not true comparing the survival of sisters with that of sisters-in-law. Interestingly, in this study, the survival curve of the sisters of long-lived subjects did not differ from the one of sisters-in-law, suggesting that the genetic component explains longevity in men more than in women . This allowed us to estimate that about 25% of the variation in human longevity can be due to genetic factors and indicated that this component is higher at older ages and is more important in males than in females.

 For the first eight decades of life, a correct lifestyle is a stronger determinant of health and life span than genetics. Genetics then appears to play a progressively important role in keeping individuals healthy and living as they age into their eighties and beyond. For centenarians, it reaches up to 33% for women and 48% for men. However, in general, the effect sizes are not large, suggesting that many genes of small effect play a role, as indeed in all multi-factorial traits however, it needs to be considered that there is a dynamic interplay between genetic and environmental variations in the development of individual differences in health and hence, longevity.

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Impact of Hormones on Aging:

Hormones play a significant role in the aging process, influencing everything from physical appearance to mental health, metabolism, and the function of various organs. As we age, hormonal levels naturally fluctuate and decline, which can contribute to many of the signs associated with aging.

1.   Oestrogen and progesterone: Their levels drop significantly during menopause. This reduction can lead to various physical and emotional changes, including mood swings, decreased bone density, and increased risk of heart disease.

2.   Growth hormone: produced by the pituitary gland, is vital for growth, tissue repair, and maintaining muscle and bone mass. Its production declined significantly after the age of 30.

3.   Thyroid Gland: it’s function tends to slow with age, and hypothyroidism is more common in older adults, especially women.

4.   Cortisol: produced by the adrenal glands, is released in response to stress. Chronic stress can lead to elevated levels of cortisol over time, which may impact the aging process. It can also suppress the immune system, making older adults more susceptible to infections and illnesses.

5.   Insulin: As people age, they may become more insulin resistant, leading to higher blood sugar levels, a risk factor for type 2 diabetes.

6.   DHEA: it plays a role in maintaining energy levels and mood. Its decline is linked to feeling of fatigue, depression, decreased well-being.

7.   Leptin: which regulates hunger and energy balance, tends to increase with age

8.   Gherlin: which stimulus appetite increases.

Hormones are critical regulators of the aging process. Their decline contributes to many of the changes seen in aging including physical, cognitive, emotional symptoms hormonal fluctuations and imbalances may accelerate aging or make it more noticeable that the impact varies widely between individuals. Understanding the role of hormones and aging can help guide interventions and lifestyle choices that may mitigate some of the negative effects of hormonal changes as we age.

Cellular Senescence and It’s Role in Aging:

Cellular senescence is a state in which a cell stops dividing and enters a permanent growth arrest, but remains metabolically active. 

Senescence can be induced by several factors including:

1.   DNA damage

2.   Telomere shortening

3.   Oncogene activation

4.   Mitochondrial dysfunction

5.   Unresolved cellular stress.

Cellular senescence is a critical biological process that plays a key role in aging and age-related diseases. It refers to the irreversible cessation of cell division and growth, typically triggered by various forms of stress or damage. While senescence is a protective mechanism in the short term, helping to prevent damage cells from proliferating, it's accumulation over time contributes to the aging process and development of age-related disorders.

While cellular senescence can prevent damaged cells from becoming cancerous, the accumulation of senescent cells over time has several detrimental effects that accelerate the aging process. This includes inflammation and tissue dysfunction, tissue repair and regeneration, loss of homeostasis, stem cell exhaustion, etc. The accumulation of senescent cells has been linked to many chronic and age-related diseases including cardiovascular disease, neuro-degenerative diseases, osteoporosis and arthritis and cancer.

One of the most exciting areas of aging research is senolytics, a class of drugs or interventions aimed at selectively eliminating senescent cells. The idea is that by removing senescent cells, it may be possible to delay aging and improve health span, the period of lifespan spent in good health.

Cellular senescence is a double edged sword in the context of aging. On one hand it acts as a protective mechanism by preventing the proliferation of damaged or cancerous cells. On the other hand, the accumulation of senescent cells over time leads to inflammation, tissue dysfunction and a variety of age-related diseases. Targeting senescent cells either by eliminating them or modulating their effects holds promise as a strategy for expanding lifespan and improving health span however, much research is still needed to fully understand the complex role of senescence and aging to develop safe and effective treatments.

The Role of Immune System in Aging:

The function of the immune system declines during aging, compromising its response against pathogens, a phenomenon termed as “immuno-senescence.” The aging immune system loses the ability to protect against infections and cancer and fails to support appropriate wound healing.  Vaccine responses are typically impaired in older individuals.

The immune system is the body's defense against foreign or dangerous invaders. Such invaders include:

1.   Microorganisms (commonly called germs, such as bacteria, viruses, and fungi)

2.   Parasites (such as worms)

3.   Cancer cells

4.   Transplanted organs and tissues

Newborns have some antibodies, which crossed the placenta from the mother during pregnancy. These antibodies protect them against infections until their own immune system fully develops. Breastfed newborns also receive antibodies from the mother in breast milk. but as people age, the immune system becomes less effective in the following ways:

1.   The immune system becomes less able to distinguish self from non-self (that is, to identify foreign antigens). As a result, autoimmune disorders become more common.

2.   Macrophages (which ingest bacteria and other foreign cells) destroy bacteria, cancer cells, and other antigens more slowly. This slowdown may be one reason that cancer is more common among older people.

3.   T cells (which remember antigens they have previously encountered) respond less quickly to the antigens.

4.   There are fewer white blood cells capable of responding to new antigens. Thus, when older people encounter a new antigen, the body is less able to remember and defend against it. They have smaller amounts of complement proteins and do not produce as many of these proteins as younger people do in response to bacterial infections.

5.   Although the amount of antibody produced in response to an antigen remains about the same overall, the antibodies become less able to attach to the antigen. This change may partly explain why pneumonia, influenza, infective endocarditis, and tetanus are more common among older people and result in death more often. These changes may also somewhat explain why vaccines are less effective in older people and thus why it is important for them to get booster shots (which are available for some vaccines).

Aging-Related Diseases and Their Prevention:

Common conditions in older age include sensory changes (like hearing loss, visual acuity, and vestibular function), cataracts and refractive errors, muscle strength and fat changes, back and neck pain and osteoarthritis, chronic obstructive pulmonary disease, cardiovascular disease, cancer,  diabetes, depression and dementia just to name a few. As people age, they are more likely to experience several conditions at the same time.

Older age is also characterized by the emergence of several complex health states commonly called geriatric syndromes. They are often the consequence of multiple underlying factors such as:

1.   Frailty

2.   Urinary incontinence

3.   Falls

4.   Delirium

5.   Pressure Ulcers.

Although some of the variations in older people’s health are genetic, most is due to people’s physical and social environments – including their homes, neighbourhood, and communities, as well as their personal characteristics – such as their sex, ethnicity, or socioeconomic status. The environments that people live in as children – or even as developing fetuses – combined with their personal characteristics, have long-term effects on how they age. Physical and social environments can affect health directly or through barriers or incentives that affect opportunities, decisions and health behaviour. Maintaining healthy behaviours throughout life, particularly eating a balanced diet, engaging in regular physical activity and refraining from tobacco use, all contribute to reducing the risk of non-communicable diseases, improving physical and mental capacity and delaying care dependency.

Preventing age-related diseases involves adopting a comprehensive approach to health that encompasses diet, physical activity, mental stimulation, and regular health management. A balanced diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats is crucial for overall wellness, while limiting processed foods, sugar, and unhealthy fats helps prevent conditions like diabetes and cardiovascular disease. Regular physical activity, such as at least 150 minutes of moderate-intensity exercise weekly, combined with strength training, supports muscle health and helps maintain a healthy weight. Including activities that improve flexibility and balance, like yoga or tai chi, can further enhance mobility and prevent falls.

Mental health is equally important, so staying mentally active through puzzles, reading, or learning new skills, and maintaining social connections can protect cognitive function. Quality sleep of 7-9 hours a night is vital for the body's repair processes and brain health, while effective stress management through mindfulness, meditation, or hobbies promotes emotional balance. Regular health screenings and vaccinations play a significant role in early detection and prevention of age-related diseases. Avoiding harmful habits like smoking and excessive alcohol consumption and minimizing exposure to pollutants can reduce the risk of chronic conditions. Bone health should be supported by adequate calcium and vitamin D intake and weight-bearing exercises. Finally, fostering a positive outlook on life can contribute to both mental and physical resilience, leading to healthier aging overall.

 Conclusion:

The science of ageing and longevity reveals a complex interplay of biological mechanisms, genetic influences, and lifestyle factors that shape the course of our lives. While the inevitability of ageing cannot be denied, advancements in research are empowering us to better understand its processes and mitigate its effects. From unlocking the secrets of cellular senescence to leveraging genetics for tailored interventions, science is bringing us closer to not just extending life but enhancing its quality. The role of hormones, the immune system, and preventive care underscores the importance of a holistic approach to healthy ageing.

As we stand at the crossroads of innovation and discovery, the future holds immense promise. With continued exploration, the dream of thriving well into old age may transform from aspiration to reality. The journey toward longevity is no longer merely about adding years to life—it’s about adding life to years, empowering us to live with vitality, purpose, and resilience.

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