Current Aging Science (v.1, #3)
Metabolic Effects of Resveratrol in Mammals - a Link Between Improved Insulin Action and Aging by Sara Frojdo, Christine Durand, Luciano Pirola (145-151).
Resveratrol, a polyphenol found in several vegetal sources, has been shown to possess lifespan-promoting properties in yeast and metazoans, including small mammals. While in yeast and low metazoans resveratrol acts mainly by activating the histone deacetylase Sir2, in mammals it appears to target - besides the Sir2 homolog SIRT1 - several crucial pathways for the control of metabolism, including the AMPK and the insulin-IGF1 receptors axis. The action of resveratrol on these pathways has been linked to its capability to i) prolong lifespan following chronic administration to mice and ii) protect from the development of diet-induced obesity and obesity-dependent metabolic disorders. Here we summarise the current understanding on how resveratrol displays its remarkable properties by acting on the control of insulin secretion and by modulation of insulin action in pheripheral insulin-responsive tissues. Since resveratrol has the potential for pharmacological exploitation to prevent the establishment of insulin-resistance and thus postpone - or even prevent - the onset of type 2 diabetes, toxicologic and pharmacodynamics studies in humans have been initiated. These studies show that resveratrol is non-toxic and easily absorbed by humans. As a drawback, its bioavailability is very limited due to the fast metabolic alterations to which it is subjected in the plasma. Therefore, we also review here the efforts that have been made - in the drug discovery field - to identify new molecules endowed with resveratrol-like pharmacological properties but with better bioavailability, which could prove to possess therapeutic potential.
Melatonin Causes Gene Expression in Aged Animals to Respond to Inflammatory Stimuli in a Manner Differing from that of Young Animals by Edward Sharman, Kaizhi Sharman, Stephen Bondy (152-158).
Groups of younger and aged mice were fed either minimal basal diet or the same diet containing 40 ppm melatonin. After 9.3 weeks half of each of these 4 groups of animals received either an intraperitoneal injection of lipopolysaccharide (LPS) or of saline. Three hours after this treatment, all animals were killed and mRNA from brains extracted. Quantitative PCR was performed on 13 selected mRNA species reflecting various aspects of the inflammatory pathway, the melatonin receptor, and a key glycolytic enzyme. An overall trend observed was that the effect of melatonin in modulating LPS-provoked immune responses differed markedly in old and young animals. Melatonin tended to enhance the reaction of younger animals to LPS but suppressed the inflammatory response of older mice. This difference with aging suggests that key immune processes are markedly altered by aging. It is likely that the ability of the immune system to mount a defense is impaired in older animals.
Is the Yeast a Relevant Model for Aging of Multicellular Organisms? An Insight from the Total Lifespan of Saccharomyces cerevisiae by Renata Zadrag, Grzegorz Bartosz, Tomasz Bilinski (159-165).
The applicability of the free radical theory of aging to the yeast S. cerevisiae is a matter of debate. In order to get an insight into this question, we studied the reproductive potential (the number of buds produced), reproductive lifespan (the time during which a yeast cell is able to divide), postreproductive lifespan (duration of life of yeast cells which ceased to divide) and total lifespan (sum of reproductive lifespan and postreproductive lifespan) of three isogenic pairs of yeast strains. Each pair contained a parent strain and a disruptant of gene(s) coding for important antioxidant enzyme( s) (CuZn-superoxide dismutase, all five peroxiredoxins or glutaredoxin 5). Although the reproductive potential was decreased in all antioxidant enzyme-deficient mutants, the differences in the reproductive lifespan between the parent strains and the mutants were less pronounced while postreproductive lifespan and total lifespan were not diminished in the mutants. These results suggest that either the free-radical theory of aging is not applicable to S. cerevisiae or that this yeast is not a proper model organism for the study of aging of higher organisms. In our opinion the latter possibility is more apparent and the increase in cell volume (unavoidable for a cell propagating by budding) rather than accumulation of oxidative damage may be the main reason for the cessation of budding (and perhaps postreproductive death) in S. cerevisiae.
Possible Links of Age Related Hypertension and Evolution Imposed Features of Heart and Aorta by Sven Kurbel (166-168).
The left ventricle thickness is a limiting factor of optimal heart size and strength. Due to disappearance of all the features compromising left ventricular compliance, mammalian heart has decreased vascular density and coronary vessel diameter and it requires sufficient diastolic aortic pressure for the left ventricle perfusion. Atrial muscle and the right ventricle are perfused during the entire heart cycle. The systolic pressure in the left ventricle forces blood vessels in the muscle wall to collapse, particularly in the subendocardial muscle layer. This makes the most active part of the heart prone to hypoxia. Optimal perfusion of the left ventricle wall requires sufficient aortic pressure during diastole, making individuals with higher diastolic pressures advantageous, in situations requiring combination of increased heart rate and output. Described mechanisms might have contributed to the hereditary quality of age-related hypertension in humans.
Nanoparticulated Quercetin in Combating Age Related Cerebral Oxidative Injury by Sanchari Das, Ardhendu Mandal, Aparajita Ghosh, Subhamay Panda, Nirmalendu Das, Sibani Sarkar (169-174).
Reactive oxygen species e.g. O .-, H O and .OH generated by the induction of oxidative stress exert a potential threat on the activity of endogenous antioxidant enzymes and substantially influence the aging process and agedependant neuropathology. Chemical antioxidant is almost ineffective in protecting neuronal cells from oxidative damage as Blood Brain Barrier exists in between blood and brain interstitial fluid that restricts undegradable influx from the circulation into cerebral region. Quercetin (QC), a flavonoidal antioxidant is known as a potent antioxidant for its polyphenolic configuration. Formulation of QC in polylactide nanocapsule has been done and the efficacy of this vesicular flavonoid has been tested against cerebral ischemia induced oxidative damage in young and old rat brains. Antioxidant potential of QC loaded in nanocapsule (QC 7.2 mmol/kg b.wt., size 50 nm) was investigated by an in vivo model of cerebral ischemia and reperfusion on Sprague Dawley young (2 months, b.wt. 160-180 g) and aged (20 months, b.wt. 415 440 g) rats. Diene level, the index of lipid peroxidation and GSSG/GSH ratio were found to be higher in normal aged, compared to normal young rat brain. Endogenous antioxidants activities were lower in aged rat brain compared to young. Further reduction of these antioxidants were observed in aged rat brain by the induction of cerebral ischemia - reperfusion. Nanocapsule encapsulated QC treatment resulted a significant protection to endogenous antioxidant enzymes against ischemia induced oxidative damage in neuronal cells of young and old rats.
Thyroid Hormone Levels in the Prefrontal Cortex of Post-Mortem Brains of Alzheimer's Disease Patients by Jennifer Davis, Anna Podolanczuk, John Donahue, Edward Stopa, James Hennessey, Lu-Guong Luo, Yow-Pin Lim, Robert Stern (175-181).
Converging evidence suggests a possible link between thyroid state and Alzheimer's disease (AD), including a higher probability of dementia in individuals with higher TSH levels and a two-fold risk of AD in patients with hypothyroidism. Thyroid hormones modulate factors associated with AD, including amyloid precursor protein expression in the brain, suggesting a possible role for thyroid hormone in AD pathology. The present study is the first to directly evaluate brain thyroid hormone levels in AD. Triiodothyronine (T ) and thyroxine (T ) levels were measured with radioimmunoassay (RIA) in post-mortem samples of prefrontal cortex of patients with pathologically confirmed AD, including Braak stage I-II (n=8), Braak stage V-VI (n=8), and controls without any primary neurological disease (n=8). T levels did not differ between groups. T levels were significantly lower in Braak stage V-VI brains relative to controls, but there was no statistically significant difference between T levels in Braak stage I-II versus controls. Results suggest that the conversion of T to T may be affected in advanced AD, perhaps due to alterations in deiodinase activity. Reduced conversion of T to T3 in AD may be associated with both AD pathology and the clinical presentation of dementia.
Human Skeletal Muscle Aging and the Oxidative System: Cellular Events by Paola Rossi, Barbara Marzani, Silvana Giardina, Massimo Negro, Fulvio Marzatico (182-191).
As we age, the aerobic and functional capacities of our major physiological systems progressively decline. In the case of the neuromuscular system, reductions in strength and mobility cause a deterioration in motor performance and in turn a greater tendency to fall (with increased risk of fractures), impaired mobility, disability and loss of independence in the elderly. Given the increase in our life expectancy and the consequent growth in the elderly population, these conditions will have an increasing impact on modern healthcare systems, and their prevention and attenuation needs to be addressed. Several intervention strategies have been used to improve motor performance among the aging. At the cellular level, aging is caused by a progressive decline in mitochondrial function that results in the accumulation of reactive oxygen species (ROS) generated by the addition of a single electron to the oxygen molecule As the level of oxidative stress in skeletal muscle increases with age, the production of some antioxidant enzymes increases adaptively to compensate in part. The aging process is characterized by an imbalance between an increase in the production of reactive oxygen species in the organism and the antioxidant defences as a whole. The goal of this review is to examine the results of existing studies on oxidative stress in aging human skeletal muscles, taking into account different physiological factors (sex, fiber composition, muscle type and function).
Interleukin-4-Induced Oxidative Stress Via Microglial NADPH Oxidase Contributes to the Death of Hippocampal Neurons In Vivo by Keun Park, Hyung Baik, Byung Jin (192-201).
We investigated the effects of interleukin-4 (IL-4), a well-known anti-inflammatory cytokine, on thrombintreated rat hippocampi in vivo. Intrahippocampal injection of thrombin resulted in a significant loss of hippocampal CA1 neurons, as determined by Nissl staining and NeuN immunohistochemistry. Thrombin-induced neurotoxicity was accompanied by substantial microglial activation, as demonstrated by OX-42 immunohistochemistry. In parallel, Western blot analysis and hydroethidine histochemistry revealed activation of NADPH oxidase (as demonstrated by increased translocation of the cytosolic proteins p67 and p47 ), generation of reactive oxygen species (ROS), and oxidative damage in the hippocampal CA1 area, where degeneration of hippocampal neurons was evident. Interestingly, immunohistochemical and biochemical analysis demonstrated that intrahippocampal injection of thrombin increased immunoreactivity and levels of IL-4 as early as 8 h post-treatment, reaching a peak at 7 days that was maintained for up to 14 days. Moreover, double-label immunohistochemistry detected IL-4 immunoreactivity solely in activated microglia. In experiments to explore the involvement of IL-4 in neurotoxicity, IL-4-neutralizing antibodies significantly increased the survival of CA1 hippocampal neurons at 7 days post-thrombin treatment. Consistent with these results, IL-4 neutralization inhibited activation of NADPH oxidase, ROS production and oxidative damage. Thus, the present study is the first to demonstrate that IL-4 generates microglial NADPH oxidase-derived oxidative stress and leads to the degeneration of hippocampal neurons in vivo, as occurs in Alzheimer's disease.
Prematurely Aged Children: Molecular Alterations Leading to Hutchinson-Gilford Progeria and Werner Syndromes by Lourdes Dominguez-Gerpe, David Araujo-Vilar (202-212).
Ageing is thought to be a polygenic and stochastic process in which multiple mechanisms operate at the same time. At the level of the individual organism ageing is associated with a progressive deterioration of health and quality of life, sharing common features such as: alopecia and grey hair, loss of audition, macular degeneration, neurodegeneration, cardiovascular diseases, osteoporosis, cataract formation, type-2 diabetes, lipodystrophies; a generally increased susceptibility to infection, autoimmune disorders and diseases such as cancer; and an impaired ability to cope with stress. Recent studies of mechanisms involved in the ageing process are contributing to the identification of genes involved in longevity. Monogenic heritable disorders causing premature ageing, and animal models have contributed to the understanding of some of the characteristic organism-level features associated with human ageing. Werner syndrome and Hutchinson- Gilford progeria syndrome are the best characterized human disorders. Werner syndrome patients have a median life expectancy of 47 years with clinical conditions from the second decade of life. Hutchinson-Gilford progeria syndrome patients die at a median age of 11-13 years with clinical conditions appearing soon after birth. In both syndromes, alterations in specific genes have been identified, with mutations in the WRN and LMNA genes respectively being the most closely associated with each syndrome. Results from molecular studies strongly suggest an increase in DNA damage and cell senescence as the underlying mechanism of pathological premature ageing in these two human syndromes. The same general mechanism has also been observed in human cells undergoing the normal ageing process. In the present article the molecular mechanisms currently proposed for explaining these two syndromes, which may also partly explain the normal ageing process, are reviewed.