Theories of Biological Aging

• Aging is linked to the progressive decline of cells and their regenerative ability, eventually causing organism death.

Chronological Age vs. Biological Age

• Chronological age refers to the time elapsed since an individual's birth
• It is the simplest aging measure
• Chronological Age does not precisely reflect a person's health or functional capacity.
• Biological age relates to the body's actual condition at a cellular and molecular level
• It can be gauged through various biomarkers

Biological Aging Theories

• Scientific proposals seek to explain why organisms age
• Free radicals
• Telomeres and wear
• Genetic errors
• Mitochondria

Free Radical Theory

• Proposed by Harman in 1956
• Aging results from cumulative damage caused by free radicals released during respiration
• Not all studies are conclusive.

Telomere Theory

• Telomeres are DNA regions protecting chromosome ends
• Telomeres shorten with cell division
• Telomere shortening is associated with cell aging and tissue/system deterioration.

Genetic Error Theory

• Also known as mutation theory, involves alterations in DNA sequence that can change the genetic code
• These changes disrupt protein synthesis
• Changes results in health issues like cancer.

Mitochondrial Theory

• Accumulation of radicals damages macromolecules
• Cumulative damage leads to age-related changes.

Cellular Cycle

• It is a series of events or stages in a cell during the duration of its growth and division
• A typical human cell requires approximately 24 hours to divide
• Mammalian cells have a faster division

Apoptosis

• Is carried out through mitochondrial permeabilization and caspase activation
• It involves the removal of unnecessary or damaged cells from multicellular organisms
• Apoptosis minimizes damage to neighboring cells.
• Apoptosis eliminates old and damaged cells for replacement with younger, healthier cells
• It occurs more frequently when there is constant stress and hunger
• The process involves breaking down and reusing components for more efficient new cells

Molecular Aging

• It refers to changes happening in molecules composing cells like DNA, proteins, and lipids
• Example: DNA damage from radiation exposure.
• Cellular aging (changes in cells themselves)
• Occurrences like increased apoptosis

Epigenetics

• It refers to the set of external factors modifying DNA activity without alternating its sequence
• Classified as:
  • Mutations and somatic alterations in DNA
  • Epigenetic changes
  • Histone modification
  • DNA damage
• Proteins are molecular machines required for the functioning of cells

Cross-linkage Theory

• Molecular bonds between proteins or nucleic acid strands form
• Links increases with age due to free radicals from normal metabolic processes.

Error Catastrophe Theory

• Proposed by Orgel(21), aging causes synthesis errors produce abnormal proteins,

Cellular Repair Mechanisms

• Lesion reversal: Direct repair.
• Indirect repair systems.
• Double-strand break (DSB) repair.

Direct Repair Mechanisms

• Three direct repair mechanisms exist: photoreactivation, alkyltransferase, and oxidative demethylation
• UV radiation can induce chemical changes in DNA bases
• Photolyase uses light energy to reverse pyrimidine dimers, breaking covalent bonds.
• Alkyltransferase removes alkyl adducts from DNA bases.

Oxidative Demethylation

• Removes cytotoxic methylations in DNA
• It often presents mutagenic action and is caused by harmful, endogenously-produced compounds

Indirect Repair Mechanisms

• Base Excision Repair (BER) corrects oxidative damage and depurination.
• Nucleotide Excision Repair (NER) repairs UV radiation and mutagen damage
• NER involves 4 proteins in prokaryotes (UvrA, UvrB, UvrC, UvrD) and over 30 in mammals.

Mismatch Repair

• It removes mismatched bases from spontaneous damage and replication errors.

Double-Strand Break Repair

• This involves homologous recombination (HR) and non-homologous end-joining (NHEJ).
• HR detects/repairs damage from agents in the G2 cell cycle phase.
• NHEJ joins non-homologous ends without needing a homologous sequence.

Autophagy

• It is a process where cells break down/destroy abnormal/damaged proteins and substances in its cytoplasm
• Autophagy releases amino acids, glucose, proteins, fatty acids and iron for metabolism
• Lack of autophagy causes damaged molecules to accumulate.

Aging

• Gradual process starting in adulthood and continuous through life
• Characterized by accumulated cellular and molecular damage leading to physical and mental decline
• Environmental, lifestyle factors and genetics influence aging.
• Radiation and air pollution are examples of environmental factors.
• Diet, exercise and sleep are lifestyle factors.

Radiation

• Especially ultraviolet (UV) is a leading cause of skin aging
• Prolonged sun exposure damages DNA
• Sun exposure causes free radical production and decreased collagen leading to wrinkles, spots and elasticity loss.

Air Pollution

• It contains harmful particles like heavy metals/free radicals
• Harmful particles affect skin and internal organs
• Contamination generates oxidative stress, promotes chronic inflammation, and accelerates cellular deterioration.
• Chronic stress raises cortisol levels
• Elevated cortisol damages neurons inhibits immune responses and encourages systemic inflammation.

Diet

• Negative impact of high saturated fat, refined sugar, and processed food diets
• Such diets accelerate aging by increasing inflammation and free radicals.
• It is recommended to eat fresh food and avoid alcohol.
• Positive impact of diets rich in fruits, vegetables, healthy fats (omega-3s), and antioxidants
• Such diets protect cells from oxidative damage and promote tissue regeneration.

Exercise

• Moderate exercise stimulates circulation, improves cardiovascular health, and reduces inflammation.
• Sedentary lifestyles increase chronic disease risk and muscle/bone loss.
• Recommendation: Exercise weekly for at least 150 minutes (walking, swimming, yoga).

Sleep

• Inadequate sleep affects cellular repair and may accelerate aging
• Recommendation: Get 7-9 hours of quality sleep nightly.

Genetic Factors

• FOXO3 gene is linked to oxidative stress resistance and longevity
• Sirtuins regulate DNA repair, inflammation, and cell metabolism.
• Individuals whose parents had long lifespans are more likely to age slower with good health
• Genetic predispositions include Alzheimer’s, cardiovascular ailments, and tumors have heredity components.

Cellular Death

• Cellular death keeps bodies healthy and functioning.
• Problems arise, when not performed correctly.

Types of cellular death

• Apoptosis
• Autophagy
• Necrosis

Apoptosis

• Is a continuous process of eliminating damages/old cells in the body
• Its what help keep the human body young and healthy

Autophagy

• Part of what makes up what our body does with stress and hunger
• Our body will reuse some of the cells to create new efficient cells

Necroptosis

• A type of cellular death
• Characterized by cellular inflammation, activation of series of molecular signaling
• Signals will lead to cellular breakdown

Sensory systems

• Changes in vision, smell, and taste.
• Cataracts may develop due to aging or injuries, tissue changes the eye lense
• Presbycusis: hearing loss caused by aging changes in auditory structures

Disease

• It comes as people get older and more vulnerable
• Enters aging diseases
• Arthritis affects more then half are population (sixty years or older) due to Cartilage joint degeneration
• Mechanisms of Replication and DNA repair increase as you age, causing mutations and metastasis
• Vascular System changes as you age, can cause blood pressure to increase
• Alzheimer's degenerate and can cause the inability to function important things
• Osteoporosis Decreases bone mass, causes bones to turn brittle
• Higher chance for older adult to develop diabetes type 2 due to combined of a poor lifestyle

Lymphoid organs aging

• Causes significant aging in the human system.
• The thymus decreases production in the body
• Leads to consequences.

The Spleen aging impact

• Reduce Lymphoid tissue
• Filtering Capacity will decrease
• Will not produce antibodies
• Causes higher change of sickness's and pneumonia.
• Will reduce effectiveness of vaccines.
• The T cells will have shorts telomeres

Inflammation

• Is our body reactions homeostasis
• In respond to different situations (foreign and native)
• As you get older your more prone to inflammation
• Leading to long term illnesses

Things you can do to prevent

• Exercise
• Healthy Foods
• Less stress
• Rest

Your immune

• Uses everything to defend itself from pathogens
• As you age your T cells have increase of of T cells that don't age

Factors aging the immune

• Inadequate diet
• Genes
• Hormonal influence
• Influence of oxidation

Oxudation

• Is a process from generating the amount of free radicals
• The amount of radicals damage cells (protein, lipids, and DNA)
• And will need a antioxidants.

Antioxidants

• Is what keeps our cells safe to allow us to slow the aging process
• Free radicals is produce in the body during metabolism that is also due to contamination
• Imbalance between oxidants affects aging and cell health.
• Stress will produce more hormones that can cause that radicals to produces

Oxidative Damages.

• Can damage proteins, lipids and other cells.
• oxidative damage can trigger inflammatory which creates radicals
• Endogenous and Exogenous
• The sun an heat that hits or skin.