MCB 135K Discussion

Monday, January 29, 2007

GSI: Ryan Klimczak

Information

• GSI: Ryan Klimczak

• E-Mail: RRK135@gmail.com

• Review sessions will be held prior to each exam – Time and locations TBA

Discussion Material

1. Course Introduction

2. Demography

3. Comparative Aging

4. Delaying the Degenerative Diseases of Aging

5. Theories of Aging

Course Introduction

• Age Related Terminology– Aging– Geriatrics– Gerontology– Senescence– Biomarkers– Life-Span– Average Life Span– Life Expectancy– Active Life Expectancy– Longevity– Maximum Life Span

1. Increased length of lifespan & increased number of the elderly in the human population

2. Increased proportion of persons aged 65+ in the population as compared to those aged 14-19

3. This change in the human population is acknowledged by the industries and professions

4. Need to better educate the population in healthy habits

5. Need to support research in biomedicine

6. Points 4 and 5 must take into consideration the entire life cycle as our health today depends on our health yesterday and will influence our health tomorrow

Divisions of the Lifespan

Prenatal LifeOvum: Fertilization

- end 1st week

Embryo: 2nd-8th week

Fetus: 3rd-10 lunar month

Neonatal Period

Newborn: end of 2nd week

Infancy: 3rd week-1st year

Childhood: 2-15 years

Adolescence: 6 yrs after puberty

Postnatal Life Adulthood

Prime & transition (20-65 yrs)

Old age & senescence (65

yrs+)

Life expectancy and infant mortality throughout human history

Life expectancy Infant mortality rate

at birth (years) (per 1000 live births)

Prehistoric 20-35 200-300

Sweden, 1750s 37 210

India, 1880s 25 230

U. S., 1900 48 133

France, 1950 66 52

Japan, 1996 80 4

Questions

• Lecture 1 - The Journey of Life What is the primary reason that life span has doubled since

~1900?

What was the average life span in prehistoric times, ~1900, now?

When does the process of aging begin?

Why doesn’t the degree of pathophysiology correlate directly with age?

What is the reason for the increase in average life span from ~1880 - 1960? From 1960 - present?

Demography

• Statistical study of human populations:– Size and density distribution

• Vital Statistics:– epidemiology: Births, deaths, diseases

Life expectancy at birth by sex, France 1806-1997

Proportion of population aged 0-14 versus 65+(In Italy)

Centenarians

• Generally good health– Escapers– Late onset of disease– Early disease that was

overcome

• SSC (Semi-Super)– 105+

• SC (Super)– 110+

• Possible role of IGF-1 Receptor

• Oldest Female– 122 years– Jeanne Calment

• Oldest Male – 115 years– Christian Mortensen

Questions

• Lecture 2 - Demography of Aging What is epidemiology?

How long was the longest recorded human life span, male and female?

What are some probable causes that favor longevity in women?

What does the concordance between centenarians and the increased likelihood of prolonged lifespan in their offspring suggest?

What physiological characteristics are generally observed in individuals who live past the age of 100?

Comparative and Differential Aging

• Aging amongst different animal species

• Aging differences between people of the same species

• Chronological vs. Physiological Age

Figure 3.2: Comparison of the relationship of brain weight to

life span in vertebrates

Figure 3.1: Comparative Maximum Life Spans

**Detailed discussion of figure in the legend, pg. 26

Table 3-1 Physiologic Correlates with Longevity

INDEX STUDIED CORRELATION

Body weight Direct

Brain/ body weight Direct

Basal metabolic rate Inverse

Stress Inverse

Reproductive function/Fe cundity Inverse

Length of growth period DirectEvolution Uncertain

Among invertebrates, the most used models have been the fly (Drosophila melanogaster) and the nematode (C. elegans)

Suppression of the receptor for insulin/IGF hormone will produce a mutant nematode that will live 6x longer than corresponding controls and be more resistant to all stress.

C. Elegans 2 week lifespanhermaphrodite19,000 genes959 cells

Examples of ways in which environment influences the genome (cont.)

Kenyon et al. Science, 2003

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Figure 3.3: The

heterogeneity of the elderly

population as illustrated by scores in

a hypothetical

test.

Transcriptional Profile of Aging Related Genes in the Human Brain

Rodwell et al. 2004

Recent approaches challenge the inevitability of

function pathology by grouping the aging processes into three categories:

1. Aging with disease and disability2. Usual aging, with absence of overt

pathology but presence of some declines in function

3. Successful or healthy aging, with no pathology and little or no functional loss

Assessment of Physiological Age in Humans

Physiological age depends onPhysiologic competence: good to optimal function of all body systems

&Health status: absence of disease

Physiological age may or may not coincide with chronological age

Laboratory Values in Old Age:

1. Most values unchanged (e.g. hepatic, coagulation, electrolytes, renal, thyroid, blood count, etc.)

2. Some values decreased (e.g. HDL in women)

3. Some values increased (e.g. LDL in men, glucose)

**See Table 3.2**

Question•Comparative and Differential Aging

How well does chronological age correlate with physiological age? In young versus old individuals?

What parameters do you use to define "healthy" aging?

What sorts of behavior favor a long life span?

What are the mechanisms or traits associated with "successful" aging?

What is aging vs. usual aging vs. successful aging?

Discuss the idea that women have more disability than men.

Delaying the Degenerative Diseases of Aging•Oxidative DNA damage as a function of aging

•Mitochondrial decay and aging

•ALCAR and Lipoic Acid, potential supplements to extend lifespan/enhance quality of life

•Nutrient deficiency and aging

Estimated oxidative DNA adducts per rat liver cell

0

Old (26-mo)

Young (4-mo)

70,000

60,000

50,000

40,000

30,000

20,000

10,00024,000

67,000

Young

Old

Mitochondria in hippocampal neurons

Electron Microscopy Images

Cardiolipin Levels in 3 and 24 Month Old Rat Hepatocytes

Ca

rdio

lipin

(µ

g p

er 1

06 C

ells

) 30

20

10

0Young Old

10

**

Cardiolipin (diphosphatidyl glycerol) is an important component of the mitochondrial membrane, typically present in metabolically active cells of the heart and skeletal muscle. It has also been observed in certain bacterial membranes. It serves as an insulator and stabilizes the activity of protein complexes important to the electron transport chain.

R123 Fluorescence in old and young rat hepatocytes

Fluorescence/cell

No

rma

l ce

ll n

umbe

r0.03

Young

1000100100.00

0.01

0.02

Old

11

Rhodamine 123 -

A popular green fluorescent mitochondrial dye that stains mitochondria in living cells in a membrane potential-dependent fashion. Widely used in flow cytometry studies involving mitochondrial membrane potential.

Mitochondria from old rats compared to those from young rats:

1) Lower Cardiolipin

2) Lower Membrane Potential

3) Lower Oxygen Utilization

4) Increased Oxidant Leakage

L-Carnitine/Acetyl-L-Carnitine (ALCAR)

• Mediates the ratio of acetyl-CoA/CoA• Decreases with age in plasma and in brain• Improves cognitive function in rats

• Transports long-chain fatty acids into mitochondria• Removes short- and medium-chain fatty acids that accumulate

WIKIPEDIA DEFINITION:

Carnitine transports long-chain acyl groups from fatty acids into the mitochondrial matrix so they can be oxidized for energy. Fatty acids must be activated before binding to the carnitine molecule to form acyl-carnitine. The free fatty acid in the cytosol is attached with a thioester bond to coenzyme A (CoA). This reaction is catalyzed by the enzyme fatty acyl-CoA synthetase and driven to completion by inorganic pyrophosphatase.

The acyl group on CoA can now be transferred to carnitine and the resulting acyl-carnitine transported into the mitochondrial matrix. This occurs via a series of similar steps:-Acyl-CoA is conjugated to carnitine by carnitine acyltransferase (palmitoyltransferase) I located on the outer mitochondrial membrane-Acyl-carnitine is shuttled inside by a translocase-Acyl-carnitine is converted to acyl-CoA by carnitine acyltransferase (palmitoyltransferase) II located on the inner mitochondrial membrane. The liberated carnitine returns to the cytosol.

R--Lipoic Acid (LA) in mitochondria

• LA reduced to dihydrolipoic acid, a potent antioxidant, & chelator of Fe & Cu• Coenzyme of pyruvate and -ketoglutarate dehydrogenases, involved in the citric

acid cycle• Involved with carbohydrate utilization for ATP production, shown to increase the

cellular uptake of glucose in vitro by recruiting a glucose transporter to the cellular membrane

15

Effects of ALCAR and LA supplements•ALCAR increases Cardiolipin levels, increases mitochondrial membrane potential

•ALCAR/LA reduce the amount of mitochondrial DNA adduct levels in old rats

-increases ambulatory activity of old rats

-enhances immune function

-improves spatial memory/ mental acuity

•Clinical trials in humans suggest LA can improve neuropathic symptoms and deficits in diabetic patients

MicronutrientDeficiency

HemeDeficit

Complex IV

Deficit

Oxidative Stress

DNA Damag

e

Early Senescen

ce

Pyridoxine [+] ++ ++

Zinc + # #

Riboflavin

Iron + + [+] [+]

Copper [+] [+] [+]

Biotin + + + + +

Lipoic Acid [+]Pantothenate [+] [+]

Micronutrient deficiency and heme synthesis in human cell culture

+ = Atamna/Ames, ++Askree /Ames, #Ho/Ames [+] Literature

Calcium Deficiency Vitamin B12

Fenech: chromosome breaks Fenech: Chromosome breaks

Lipkin: colon cancer mice

Folate Deficiency Selenium

MacGregor/Ames/Fenech: chromosome Rao: DNA damage

breaks mice/humans Combs/Trumbo: Cancer humans

Willett: epi colon cancer humans

Vitamin D Deficiency Omega-3 FA

Garland: epi colorectal cancer humans Denkins: Cancer

Magnesium Deficiency Niacin

Bell: chromosome breaks humans Kirkland/Depeint: DNA damage

Larsson: epi colorectal cancer humans

Zinc Deficiency Choline

Fong: esophageal cancer humans/rodents da Costa: DNA damage in humans

Potassium Deficiency Chang: Cardiovascular Disease

Questions

•Discuss the correlation between DNA Oxidative Damage and aging.

•How may ALCAR or LA mediate their potential effects?

•What are the effects of aging on mitochondria and mitochondrial function?

•List some nutrient deficiencies and describe their potential contribution

to accelerated aging.

Theories of Aging

MolecularCodon restriction

Somatic mutation

Error catastrophe

Gene regulation.

Dysdifferentiation

Classification and brief description of main theories of aging

CellularWear-and-tear

Free radical accumulation

Apoptosis

SystemRate-of-living

Neuroendocrine

Immunologic

Evolutionary

Disposable Soma

Antagonistic Pleiotropy

Mutation Accumulation

Evolutionary Theories of Aging

Disposable Soma - Somatic cells are maintained only to ensure

continued reproductive success, following reproduction

the soma is disposable. (life span theory)

Antagonistic Pleiotropy - Genes that are beneficial at younger

ages are deleterious at older ages.(Pleiotropism = The control by a single gene of several distinct

and seemingly unrelated phenotypic effects)

Mutation Accumulation - Mutations that affect health at older

ages are not selected against (no strong evidence).

0

20

40

60

80

100

120

0 4 812 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96

100

Evolution in the Laboratory

young flies selected

Normal

% Surviving

Age in Days

- Early adult fecundity increased *antagonistic pleiotropy

Offspring of “young” flies are selected

- Reproductive period extended- Stress resistant, -super flies- Early adult fecundity reduced *antagonistic pleiotropy

Offspring of “old” flies are selected

Molecular Theories of AgingCodon restriction

Fidelity and/or accuracy of mRNA message translation is impaired with aging due to cell inability to decode the triple codons (bases) in mRNA molecules

Somatic mutation

Type of stochastic* theory of aging that assumes that an accumulation of environmental insults eventually reaches a level incompatible with life, primarily because of genetic damage.

Error catastropheErrors in information transfer due to alterations in RNA polymerase and

tRNA synthetase may increase with age resulting in increased production of abnormal proteins

Gene regulationAging is caused by changes in the expression of genes regulating both

development and aging

DysdifferentiationGradual accumulation of random molecular damage impairs regulation of

gene expression

* Involving Random Chance

Cellular Theories of Aging

Wear-and-tearIntrinsic and extrinsic factors influence life

span

Free radical accumulationOxidative metabolism produces free radicals which

are highly reactive and thus damages DNA and/or proteins and thus degrades the system structure and function.

ApoptosisProcess of systematically dismantling key cellular

components as the outcome of a programmed intracellular cascade of genetically determined steps.

System Theories of Aging

Rate-of-living

An old theory that assumes that there is a certain number of calories or heart beats allotted to an individuals and the faster these are used the shorter the life.

Neuroendocrine

Alterations in either the number or the sensitivity of various neuroendocrine receptors gives rise to homeostatic or homeodynamcis changes that results in senescence.

Immunologic

Immune system reduces its defenses against antigens and thus results in an increasing incidence of infections and autoimmune diseases.

Free Radical Theory of AgingThe free-radical theory of aging (FRTA) is that organisms age because protein, lipid and nucleic acids (DNA, RNA) accumulate free radical damage with the passage of time. Free radical attack on protein, lipid and nucleic acids leads to a reduction in their respective function, thereby decreasing cell function, then organ function, and finally, organismal function.

Any element that has an unpaired electron in its outermost shell is considered to possess a "free radical”. In biochemistry, the free radicals of interest are often referred to as reactive oxygen species (ROS) because the most biologically significant free radicals are oxygen-centered. But not all free radicals are ROS and not all ROS are free radicals.

Questions:Describe the genetic changes that may underlie the short lived and

long-lived phenotypes in the evolutionary fly studies.

What is a real world example that demonstrates the disposable soma theory?

How can the lifespan extending effects of caloric restriction be explained by the various theories of aging?