Reduced lipofuscin accumulation in senescent rat brain by long-term acetyl-L-carnitine treatment

Reversal of biochemical and behavioral parameters of brain aging by melatonin and acetyl L-carnitine

The potential utility of dietary supplementation in order to prevent some of the oxidative and inflammatory changes occurring in the brain with age, has been studied. The cerebral cortex of 27-month-old male B6C3F1 mice had elevated levels of nitric oxide synthase 1 (EC 1.14.13.39) (nNOS) and peptide nitrotyrosine relative to cortices of younger (4-month-old) animals. After 25-month-old mice received basal diet together with 300 mg/l acetyl L-carnitine in the drinking water for 8 weeks, these levels were fully restored to those found in younger animals. A partial restoration was found when old animals received basal diet supplemented with 200 ppm melatonin in the diet. Levels of mRNA (messenger RNA) for nNOS were unchanged following these treatments implying translational regulation of nNOS activity. Behavioral indices indicative of exploratory behavior were also depressed in aged animals. Dietary supplementation with melatonin or acetyl L-carnitine partially reversed these changes. These findings suggest that dietary supplementation cannot merely arrest but indeed reverse some age-related increases in markers of oxidative and inflammatory events occurring with the cortex.

Acetyl-L-carnitine enhances Na(+), K(+)-ATPase glutathione-S-transferase and multiple unit activity and reduces lipid peroxidation and lipofuscin concentration in aged rat brain regions

This study investigated the effects of chronically administered acetyl-L-carnitine (ALC) on sodium potassium adenosine triphosphatase (Na(+), K(+)-ATPase), glutathione-S-transferase (GST), glutathione peroxidase (GPx), multiple unit activity (MUA) and lipid peroxidation (LP) and lipofuscin (LF) concentration in brain regions: cerebral cortex, hippocampus, striatum and thalamus, of 24-month-old rats. The activity of Na(+), K(+)-ATPase and GST was enhanced; that of GPx was unaffected. The MUA was increased while the levels of LP and LF were decreased. These novel data provide new additional evidence concerning the antiaging attributes of ALC.

Analysis of the mechanisms underlying the age-related impairment in long-term potentiation in the rat

The process of ageing is common to all organisms but despite its universality, understanding of the cellular and molecular changes which accompany ageing is poor. With the increase in the ageing population, the need for systematic study of the process becomes a priority but the development of a systematic approach to the problem requires the development of a testable theory of ageing. While several theories of ageing have been proposed /336/, between which there is at least some overlap, no generally-accepted theory has been identified. In relation to the brain, four interrelated theories of ageing have received significant attention; these are (1) the membrane hypothesis, (2) the free radical hypothesis, (3) the calcium hypothesis and (4) the glucocorticoid theory. The overlap between these hypotheses is such that a causal relationship between them is very likely with age-related changes in membrane composition triggered by changes in free radical production, while changes in membrane composition are likely to account for changes in membrane function including age-related changes in calcium homeostasis. The glucocorticoid theory could equally well be termed the stress hypothesis of ageing, which in the hippocampus at least, might trigger age-related changes in free radical production. This review is not intended to be a balanced appraisal of each theory but emphasizes aspects of the membrane hypothesis of ageing and discusses some relevant aspects of the other hypotheses. Attention is focussed on analysis of the biochemical changes which might underlie age-related changes in hippocampal function, particularly maintenance of long-term potentiation (LTP), and these changes are discussed in the context of the four hypotheses of ageing.

Age-related changes in brain microanatomy: sensitivity to treatment with the dihydropyridine calcium channel blocker darodipine (PY 108-068)

The influence of aging and of treatment with the dihydropyridine Ca2+ antagonist darodipine (PY 108-068) on the age-related microanatomical changes of rat brain were studied in male Wistar rats treated from the 18th to the 24th month of age with an oral dose of 5 mg/kg/day of darodipine. Twelve-month-old untreated rats were used as an adult reference group. A decreased number of nerve cells and of alkaline phosphatase-positive capillaries and an increased lipofuscin deposition were observed in the frontal and occipital cortex, in the hippocampus, and in the cerebellar cortex of rats of 24 months in comparison with 12-month-old animals. The number of nerve cells was higher in the occipital cortex and in the hippocampus, but not in the frontal cortex and in the cerebellar cortex, of darodipine-treated rats in comparison with age-matched untreated animals. Lipofuscin deposition is reduced in all the brain areas investigated. The density of alkaline phosphatase-reactive capillaries is also increased in the frontal and occipital cortex and in the hippocampus of aged rats treated with darodipine. The above results suggest that treatment with darodipine is able to counter some microanatomical changes occurring in the brain of aged rats and involving not only microvascular parameters. The occipital (visual) cortex and the hippocampus were the cerebral areas more sensitive to treatment with darodipine. The possible relevance of these findings is discussed.

Oxidative damage and mitochondrial decay in aging

We argue for the critical role of oxidative damage in causing the mitochondrial dysfunction of aging. Oxidants generated by mitochondria appear to be the major source of the oxidative lesions that accumulate with age. Several mitochondrial functions decline with age. The contributing factors include the intrinsic rate of proton leakage across the inner mitochondrial membrane (a correlate of oxidant formation), decreased membrane fluidity, and decreased levels and function of cardiolipin, which supports the function of many of the proteins of the inner mitochondrial membrane. Acetyl-L-carnitine, a high-energy mitochondrial substrate, appears to reverse many age-associated deficits in cellular function, in part by increasing cellular ATP production. Such evidence supports the suggestion that age-associated accumulation of mitochondrial deficits due to oxidative damage is likely to be a major contributor to cellular, tissue, and organismal aging.

Modulation of melatonin secretion by acetyl-L-carnitine in adult and old rats

Modification of melatonin synthesis and release by acetyl-L-carnitine (ALC) was studied in adult (2 month old) and old (24-month-old) male Sprague Dawley rats. When ALC was injected at 1500 into adult rats at doses of 10, 30, or 90 mg/kg, there was a remarkable increase in their pineal and serum melatonin 1 hr later. However, using the same experimental protocol acute ALC administration in old rats did not modify pineal and serum melatonin levels. ALC administered in the same dose range induced a significant increase in pineal and serum melatonin in adult rats treated at 0100 h following exposure of 30 min to bright, white light to suppress endogenous melatonin. In the same conditions, in old rats, only the higher dose (90 mg/kg) caused any noteworthy increase in melatonin pineal content while lower doses were uneffective both on serum and pineal melatonin levels. It is known that ALC affects fatty acid transport in the cells, modulates CoA, modifies neuronal transmission and reduces lipofuscin accumulation which is related to lipid peroxidation. The action of ALC on melatonin synthesis could be the result of a modulation of the neuronal transmission related to circadian pineal endocrine activity. Moreover, since both ALC and melatonin exert remarkable scavenger activity, it is possible to suppose that ALC effects in reversing certain aging processing may be due to its ability to promote melatonin production.

Microanatomical changes in the frontal cortex of aged rats: effect of L-deprenyl treatment

The present study was designed to assess whether treatment with L-deprenyl has any effect on the age-related microanatomical changes in the rat frontal cortex. Male Sprague-Dawley rats of 19 months of age were treated until the 24th month with an oral daily dose of 1.25 mg/kg or of 5 mg/kg of L-deprenyl. Eleven-month-old untreated rats were used as an adult reference group. The density of nerve cell profiles and of glial fibrillary acidic protein-(GFAP) immunoreactive astroglial profiles, lipofuscin accumulation within the cytoplasm of pyramidal neurons, and MAO-B reactivity were assessed. A decreased density of nerve cell profiles and an increased density of astroglial profiles as well as augmented lipofuscin deposition and MAO-B reactivity were observed in the frontal cortex of rats of 24 months in comparison with 12-month-old animals. In the frontal cortex of rats treated with 5 mg/kg/day L-deprenyl, which is a dose inhibiting MAO-B activity, the density of nerve cell and GFAP-immunoreactive astrocyte profiles is increased and decreased respectively in comparison with age-matched untreated subjects. Lipofuscin deposition is reduced. The lower dose of L-deprenyl (1.25 mg/kg/day) which did not affect MAO-B activity, decreased lipofuscin deposition but was without effect on the density of nerve cell or GFAP-immunoreactive astrocyte profiles. The above findings suggest that treatment with L-deprenyl is able to counter some microanatomical changes occurring in the frontal cortex of aged rats. Some of these effects are probably not related to the inhibitory MAO-B activity of the compound.

A cluster analysis study of acetyl-L-carnitine effect on NMDA receptors in aging

Aging is associated with a reduction in the maximum density of n-methyl-d-aspartate (NMDA)-sensitive glutamate binding sites in the hippocampus of Fischer 344 rats. This study was designed to investigate the effect of acetyl-l-carnitine (ALCAR) on NMDA receptors in the old rat (24 months) after chronic or single-dose treatments. The number of NMDA receptors was significantly decreased in the old rat hippocampus by 19.5% compared with the young rat. A six-month treatment with ALCAR in the old rat attenuated the loss of NMDA binding sites in the hippocampus. A single-dose treatment with ALCAR in the old rat increased the Bmax value by 35%, while no change was observed in the young group. We conclude that ALCAR can exert two actions: a trophic/neuro-preserving one when chronically administered during aging, and a stimulatory one when given at a single dose in the aged rat.

Effects of chronic chlorpromazine or lithium administration on ageing-related lipopigment in rat Purkinje neurones

Ageing-related accumulation of neuronal lipopigment is considered to be debris from processes of renewal of cellular constituents, but can also reflect cell damage and certain diseases. Chlorpromazine (an example of a class of drug chronically administered in psychiatric practice) has been reported to reduce neuronal lipopigment accumulation, and the present study investigated the effects of 28 weeks of chlorpromazine administration on lipopigment in rat Purkinje neurones. The effects of 26 weeks of lithium administration (also chronically administered in psychiatric practice) were also studied. Lipopigment was identified by fluorescence microscopy and the area enclosed by an outline of each discrete region of lipopigment was measured. While lithium administration was not associated with significant changes in lipopigment variables, chlorpromazine administration was associated with a significant (p=0.001) reduction in the number of discrete lipopigment regions and with significant (p=0.001) differences in the numbers of discrete lipopigment regions in various size categories. The findings are similar to those associated with the administration of acetyl-L-carnitine (which has been reported to reduce some morphological and behavioural associations of brain ageing) and are compatible with a reduction in the rate of lipopigment formation. This could reflect an adverse effect of chlorpromazine administration (i.e. reduced functional activity of neurones) or a beneficial effect (i.e. a reduction in ageing-related changes).

The morphology of lipopigment in rat Purkinje neurons after chronic acetyl-L-carnitine administration: a reduction in aging-related changes

The aging-related accumulation of neuronal lipopigment is considered to be cellular debris from processes of renewal of cellular constituents, but it can also reflect cell damage and certain diseases. Acetyl-L-carnitine (AC) has been reported to reduce some morphological and behavioral associations of brain aging and the present study investigated the effects of 37 weeks of AC administration on lipopigment in rat Purkinje neurons. Lipopigment was identified by fluorescence microscopy and the area enclosed by an outline of each discrete region of lipopigment was measured. Acetyl-L-carnitine was associated with a significant (p = 0.05) reduction in the number of discrete lipopigment regions and there was a significant (p = 0.001) association of AC administration with numbers of lipopigment regions in various size categories. As AC administration was associated with a reduction in some of the aging-related morphological changes in lipopigment, this compound is a candidate for evaluation as a long-term prophylactic agent for the adverse effects of cerebral aging.

Active avoidance learning in old rats chronically treated with levocarnitine acetyl

The aging laboratory animal is recognized as a suitable experimental model for the investigation on drugs potentially able to retard the age-dependent decline in cognitive functions. There is robust evidence that levocarnitine acetyl (ALCAR), the acetyl derivative of carnitine, when administered chronically, prevents some age-related deficits of the central nervous system, mainly at the hippocampal level. On the basis of this evidence and because learning of active avoidance was demonstrated to become impaired with age, we decided to investigate the effect of ALCAR in rats. For statistical evaluation of results, the Cluster Analysis technique was chosen. This procedure pointed out the great heterogeneity of the old population and allowed the classification of the animals into homogeneous groups according to their response pattern. The effect of ALCAR was evident in the higher number of treated old animals yielding escape responses, indicating that ALCAR can preserve, at least partially, learning and memory from the natural decay occurring with age.

Acetyl-L-carnitine influences the fluidity of brain microsomes and of liposomes made of rat brain microsomal lipid extracts

The fluorescence anisotropy (r) of diphenylhexatriene (DPH) was measured in different preparations (bovine spinal cord phosphatidylserine liposomes, rat brain microsomes, liposomes made with rat brain microsomal lipid having different phospholipid:cholesterol ratios) at temperatures ranging from 10 degrees to 55 degrees C. Phosphatidylserine liposomes exhibited an exponential relationship of r versus temperature, whereas the relationship shown by microsomes and liposomes prepared with microsomal lipid extracts was a linear one. The removal of protein and high phospholipid:cholesterol ratios decreased the slope of the lines (fluidity increased), although the intercept was unaffected. This means that differences were better appreciated at high temperatures and were well evident at 37 degrees C. Acetyl-L-carnitine decreased r in rat brain microsomes and in liposomes made with microsomal lipids with different phospholipid:cholesterol ratios. The fluidifying effect of acetyl-L-carnitine was mild but statistically significant and could explain, at least in part, the data reported in the literature of acetyl-L-carnitine acting on some parameters affected by ageing. Besides, acetyl-L-carnitine seemed to oppose the changes of viscosity due to lipid peroxidation, which has been reported to increase in ageing and dementia. L-carnitine shares the properties of its acetyl ester, but only in part.

Age-dependent deficits in radial maze performance in the rat: effect of chronic treatment with acetyl-L-carnitine

1. An eight-arm radial maze was the experimental model used to investigate spatial learning in rats of different ages and in old rats treated with Acetyl-L-Carnitine. 2. Extramaze visual cues were minimized in order to study the rat's ability to perform using a strategy. 3. The experimental findings indicated a deterioration of the old rat's ability to learn and solve the radial maze. 4. Long-term treatment (8 months) with Acetyl-L-Carnitine was found to antagonize such a deterioration.