Transcript Resetting the Genetic Clock: Telomeres and Telomerase Promoters

Resetting the Genetic Clock:
Telomeres and Telomerase Promoters
Dr. Al Sears
“The discovery of the function of
telomeres and telomerase is the
single MOST important discovery
in the field of anti-aging
medicine”
• The relationship between telomeres and aging.
• The effect of shortened telomeres on age-related health
conditions.
• Implications for anti-aging clinicians, including:
•
Avoidance of factors that accelerate the loss of telomeres
•
Currently available therapies that have been shown to slow
the loss of the telomere.
•
Telomerase activators as anti-aging therapy.
Telomeres and Aging
What Causes Aging?
Leonard Hayflick:
 Cell division is a finite biological function and is inexorably tied
to the aging process
 “Hayflick Number” describes the number of times a cell can
divide
 Hayflick was the first to suggest the relationship between cell
division and mortality, but the mechanism was not initially
understood
End Replication Problem
• DNA polymerase can only synthesize DNA in the 5′ to 3′ direction,
resulting in discontinuous replication of the lagging strand.
• Consequently, DNA synthesis does not extend to the very end of the
lagging strand.
• In the absence of a protective mechanism, the end replication
problem means vital genetic material (from the end of the lagging
strand) would be lost during each cell division.
• Telomeres solve the end replication problem by protecting
the cell from the loss of critical, coding base pairs.
What are Telomeres?
• First described in 1975 by Elizabeth Blackburn, who
recently earned a Nobel Prize for her discovery.
• Telomeres are found at the end of all eukaryotic
chromosomes
• The telomeres protect the chromosome from the
replication-related loss of vital genetic information
Telomeres
Telomere Length as Marker for Aging
• There is an age-dependent attrition of telomere length, with losses
ranging from between 30 and 150 nucleotide pairs per replication,
depending on cell type.
• Cell division/telomere shortening continues until a critical telomere
length is reached, at which point the cell is forced into senescence
and can no longer replicate.
• Cellular senescence prevents replication of incomplete or damaged
DNA.
Harley CB, Futcher AB, Greider CW (1990) Telomeres shorten during ageing of human fibroblasts. Nature 345:458–460
Vaziri H, Schachter F, Uchida I, Wei L, Zhu X, Effros R, Cohen D, Harley CB (1993) Loss of telomeric DNA during aging of normal
and trisomy 21 human lymphocytes. Am J Hum Genet 52:661–667
Telomeres Tell Cells How Old They Are
Telomeric mediation of gene expression may
explain the relationship between telomere length
and aging
DNA has Four Structural Levels
• Primary: the sequence of nucleotide bases
• Secondary: the interaction between base pairs as it
forms the double-helix
• Tertiary: the structure of DNA in 3-dimensional space,
as it wraps around histones. This structural level is
partially mediated by steric effects
• Quaternary: the higher-level organization of DNA in
chromatin
Telomeres May Affect All Four
Structural Levels
• Primary and Secondary Structure
 Telomeres protect the integrity of the base pairs and
preserve basic genetic information
• Tertiary and Quaternary Structure
 As telomeres shorten they may exert different
steric/electronic effects, resulting in changes in the
shape of DNA. These changes may, in turn, affect
the genes exposed and available for transcription
Telomeres and Age-Related Health
Conditions
Numerous studies have reported
significant relationships between short
telomeres and a variety of age-related
health conditions.
Telomere Length & All-Cause Mortality
• Telomere length was assessed in 143 normal,
unrelated men and women >60 years of age
• Individuals with the shortest telomeres had
significantly decreased survival rates:
 3.18-fold higher mortality rate from heart disease
 8.54-fold higher mortality rate from infectious disease
Cawthon RM, Smith KR, O'Brien E, Sivatchenko A, Kerber RA. Association between telomere length in blood and
mortality in people aged 60 years or older. Lancet. 2003 Feb 1;361(9355):393-5.
Relationship Between Telomere Length and
Age-Related Conditions
0.6
0.5
*
T/S ratio
0.4
*
*
*
* = p< .05
w/disease
0.3
w/o disease
0.2
0.1
0
Hypertension
Metabolic
Syndrome
Diabetes
MMSE Score <25
Atzmon G, Cho M, Cawthon RM, Budagov T, et al. Evolution in health and medicine Sackler colloquium: Genetic variation
in human telomerase is associated with telomere length in Ashkenazi centenarians. Proc Natl Acad Sci U S A. 2010 Jan
26;107 Suppl 1:1710-7.
Telomere Length & Dementia –
Nurses’ Health Study
▫ 62 women, > 70 years of age
▫ telomere length below the median:
 12-times greater risk of being
diagnosed with dementia
 9.6-times greater risk of being
diagnosed with mild cognitive
impairment.
Relative telomere/single gene ratio
▫ Controlled for: age, education,
smoking history, cardiovascular
disease, hypertension, cholesterol
levels, and diabetes
0.6
0.55
0.5
0.45
0.4
Healthy
Controls
MCI
Dementia
Grodstein F, van Oijen M, Irizarry MC, Rosas HD, Hyman BT, Growdon JH, De Vivo I. Shorter telomeres may
mark early risk of dementia: preliminary analysis of 62 participants from the nurses' health study. PLoS One.
2008 Feb 13;3(2):e1590.
Telomere Length & Cardiovascular Disease
3.52
• 674 Caucasian males
• Found that decreased T/S
ratio was significantly
associated with risk of MI
3.48
loge-transformed T/S ratios
• Measured mean telomere
repeat copy number to single
gene copy number (T/S ratio)
3.5
3.46
3.44
3.42
MI
No MI
3.4
3.38
3.36
3.34
Zee RY, Michaud SE, Germer S, Ridker PM. Association of shorter mean telomere length with risk of incident myocardial
infarction: a prospective, nested case-control approach. Clin Chim Acta. 2009 May;403(1-2):139-41.
Implications for Anti-Aging Clinicians
Telomere Length - a Crucial Health
Indicator
Telomere length is both:
 A marker for both cellular and organismic aging
 A predictor of age-related disease
Maintenance and Manipulation of
Telomere Length
• Factors that accelerate telomere shortening
• Factors that slow telomere shortening
• Telomerase activators
Accelerating Telomere Shortening -Homocysteine
Multiple studies have shown that elevated
homocysteine levels are associated with short
telomeres.
In one study, elevated homocysteine tripled the
rate of shortening.
Bull CF, O'Callaghan NJ, Mayrhofer G, Fenech MF. Telomere length in lymphocytes of older South
Australian men may be inversely associated with plasma homocysteine. Rejuvenation Res. 2009
Oct;12(5):341-9.
Richards JB, Valdes AM, Gardner JP, Kato BS, et al. Homocysteine levels and leukocyte telomere length.
Atherosclerosis. 2008 Oct;200(2):271-7.
Accelerating Telomere Shortening - Stress
1.6
• Chronic stress has been shown
to accelerate telomere
shortening.
• The degree of telomere
shortening correlated to a
minimum of a full decade of
again
1.2
Average T/S Ratio
• After adjusting for age and
various health/behavioral
factors, women with the highest
stress levels had the shortest
telomeres.
1.4
1
0.8
0.6
0.4
0.2
0
High Stress
Low Stress
Epel ES, Blackburn EH, Lin J, Dhabhar FS, Adler NE, Morrow JD, Cawthon RM. Accelerated telomere shortening
in response to life stress. Proc Natl Acad Sci U S A. 2004 Dec 7;101(49):17312-5.
Slowing Telomere Shortening – Vitamin C
• Vitamin levels were assessed
in 586 women aged 35-74
800
• Analysis controlled for age,
overall health, BMI, smoking,
stress level, cardiovascular
disease, and diabetes.
600
Mean Telomere Length (BP)
• Women in the 4th quartile of
vitamin C intake had
significantly longer telomeres
relative to women in the 1st
quartile.
700
500
400
300
200
100
0
1st Quartile
4th Quartile
Xu Q, Parks CG, DeRoo LA, Cawthon RM, Sandler DP, Chen H. Multivitamin use and telomere length in women. Am J
Clin Nutr. 2009 Jun;89(6):1857-63.
Slowing Telomere Shortening – Omega-3
P<.001 for linear trend across quartiles
Farzaneh-Far R, Lin J, Epel ES, Harris WS, Blackburn EH, Whooley MA. Association of marine
omega-3 fatty acid levels with telomeric aging in patients with coronary heart disease. JAMA. 2010
Jan 20;303(3):250-7.
Telomerase Activators
Telomerase
• Telomerase is the enzyme responsible for rebuilding telomeres by adding nucleotide repeats
(TTAGGG).
• Telomerase activity is observed in fetal tissue,
adult germ cells, and tumor cells.
• Activity is nearly undetectable in somatic cells.
Activation of telomerase has been
shown to reverse aging in cells, tissues
and whole organisms
Telomerase Can “Immortalize” Cells
• Study published in the journal Science:
▫ Human retinal pigment epithelial cells and foreskin fibroblasts, were
transfected with vectors encoding the human telomerase catalytic
subunit (hTERT).
▫ Control cells showed telomere shortening, as well as normal levels of βgalactosidase, a marker of cellular senescence.
▫ Telomerase+ transfected cells exhibited longer telomeres, and reduced
levels of β-galactosidase.
▫ By the time the study was published, the telomerase+ cells had exceeded
their expected lifespan by 20+ replications.
Bodnar AG, Ouellette M, Frolkis M, Holt SE, et al. Extension of life-span by introduction of
telomerase into normal human cells. Science. 1998 Jan 16;279(5349):349-52.
Telomerase Can Restore Youthful Phenotypes
in Live Tissue
• Normal human dermal fibroblasts were transfected with hTERT and
then grafted onto mouse skin.
• Mice grafted with telomerase-negative control cells exhibited
phenotypic signs of senescence (increased fragility, reduced levels of
collagen I and III, and subepidermal blistering).
• Mice grafted with telomerase+ cells exhibited a youthful phenotype,
despite the same number of replications.
Funk WD, Wang CK, Shelton DN, Harley CB, Pagon GD, Hoeffler WK. Telomerase expression restores
dermal integrity to in vitro-aged fibroblasts in a reconstituted skin model. Exp Cell Res. 2000 Aug
1;258(2):270-8.
Telomerase Can Restore Youthful
Phenotypes in a Whole Organism
A 2010 study in the journal Nature showed that telomerase activation
in mice dramatically reversed the effects of aging.
A restoration of youthful phenotypes was seen in in:




Testes
Spleen
Liver
Intestines.
Additional effects of telomerase activation included:
 Restoration of fertility
 Reversal of cerebral atrophy
 Reactivation of neural progenitor cells
Jaskelioff M, Muller FL, Paik JH, Thomas E, et al. Telomerase reactivation reverses tissue
degeneration in aged telomerase-deficient mice. Nature. 2010 Nov 28
Telomerase Activity Predicts Longevity
• Multi-generational study of Ashkenazi Jews with
exceptional longevity
▫ Parent group (n = 86; average age of 97 years)
▫ Offspring group (n = 175)
▫ Control group (n = 93)
• Found that the population exhibited abnormally high
telomerase activity, mediated by a mutation of hTERT –
a catalytic subunit of telomerase.
• Results link longevity with telomerase activity
Atzmon G, Cho M, Cawthon RM, Budagov T, et al. Evolution in health and medicine Sackler colloquium: Genetic variation
in human telomerase is associated with telomere length in Ashkenazi centenarians. Proc Natl Acad Sci U S A. 2010 Jan
26;107 Suppl 1:1710-7.
Telomerase Activators
Telomerase Activation
TA-65®
 A naturally-occurring, highly-purified single molecule derived
from the Chinese herb Astragalus
 Activates the hTERT gene
 In-vitro: Moderately activated telomerase in human
keratinocytes, fibroblasts, and immune cells
 In vivo: Administered as part of the PattonProtocol-1, with
participants given 10-50 mg of TA-65 per day for 12-months
Harley CB, Liu W, Blasco M, Vera E, Andrews WH, Briggs LA, Raffaele JM. A natural product telomerase activator as part of a
health maintenance program. Rejuvenation Res. 2011 Feb;14(1):45-56.
PattonProtocol-1:Results
Following 1-year on protocol, researchers
observed a significant decrease in the percent of
critically-short telomeres.
PattonProtocol-1:Results
Percent Change from Baseline Following 1-Year on PattonProtocol-1
10
P=0.028
5
0
P=0.033
P=0.017
%CD8+/28+
-5
-10
-15
-20
%CD8CD28% NK Cells
Harley CB, Liu W, Blasco M, Vera E, Andrews WH, Briggs LA, Raffaele JM. A natural product telomerase activator as part of a
health maintenance program. Rejuvenation Res. 2011 Feb;14(1):45-56.
Additional Telomerase Activators are in
Development
• Sierra Sciences
 Screened 254, 593 compounds
 Identified 858 telomerase inducers
 Most potent compound is at 15.89% of goal
http://www.sierrasci.com/
What Can you do Today?
Exercise Increases Telomerase Activity
Murine model
 Voluntary running for 3 weeks
 Exercise induced:
▫ A 2.9-fold increase in aortic telomerase activity and a
▫ A 3.3-fold increase in telomerase activity in circulating mononuclear cells
in the spleen
Human model
 Compared to controls, professional athletes exhibited a:
▫ 2.5-fold increase in telomerase activity in young athletes
▫ 1.8-fold increase in telomerase activity in middle-aged athletes
Werner C, Fürster T, Widmann T, Pöss J, et al. Physical exercise prevents cellular senescence in circulating leukocytes and
in the vessel wall. Circulation. 2009 Dec 15;120(24):2438-47.
What other natural telomerase activity
promoters do you want to include?