Hamizah Shahirah Hamezah

Volumetric changes in the aging rat brain and its impact on cognitive and locomotor functions

ABSTRACT Impairments in cognitive and locomotor functions usually occur with advanced age, as do changes in brain volume. This study was conducted to assess changes in brain volume, cognitive and locomotor functions, and oxidative stress levels in middle‐ to late‐aged rats. Forty‐four male Sprague‐Dawley rats were divided into four groups: 14, 18, 23, and 27 months of age. 1H magnetic resonance imaging (MRI) was performed using a 7.0‐Tesla MR scanner system. The volumes of the lateral ventricles, medial prefrontal cortex (mPFC), hippocampus, striatum, cerebellum, and whole brain were measured. Open field, object recognition, and Morris water maze tests were conducted to assess cognitive and locomotor functions. Blood was taken for measurements of malondialdehyde (MDA), protein carbonyl content, and antioxidant enzyme activity. The lateral ventricle volumes were larger, whereas the mPFC, hippocampus, and striatum volumes were smaller in 27‐month‐old rats than in 14‐month‐old rats. In behavioral tasks, the 27‐month‐old rats showed less exploratory activity and poorer spatial learning and memory than did the 14‐month‐old rats. Biochemical measurements likewise showed increased MDA and lower glutathione peroxidase (GPx) activity in the 27‐month‐old rats. In conclusion, age‐related increases in oxidative stress, impairment in cognitive and locomotor functions, and changes in brain volume were observed, with the most marked impairments observed in later age. HighlightsBrain volume altered with age in specific regions such as the hippocampus.Locomotor activity, spatial and learning memory impaired in the late‐aged rats.Oxidative stress and antioxidant enzyme activity changed with age.

Tocotrienol-Rich Fraction Modulates Amyloid Pathology and Improves Cognitive Function in AβPP/PS1 Mice

Alzheimer’s disease (AD) is the most common cause of dementia. The cardinal neuropathological characteristic of AD is the accumulation of amyloid-β (Aβ) into extracellular plaques that ultimately disrupt neuronal function and lead to neurodegeneration. One possible therapeutic strategy therefore is to prevent Aβ aggregation. Previous studies have suggested that vitamin E analogs slow AD progression in humans. In the present study, we investigated the effects of the tocotrienol-rich fraction (TRF), a mixture of vitamin E analogs from palm oil, on amyloid pathology in vitro and in vivo. TRF treatment dose-dependently inhibited the formation of Aβ fibrils and Aβ oligomers in vitro. Moreover, daily TRF supplementation to AβPPswe/PS1dE9 double transgenic mice for 10 months attenuated Aβ immunoreactive depositions and thioflavin-S-positive fibrillar type plaques in the brain, and eventually improved cognitive function in the novel object recognition test compared with control AβPPswe/PS1dE9 mice. The present result indicates that TRF reduced amyloid pathology and improved cognitive functions, and suggests that TRF is a potential therapeutic agent for AD.

Age-related changes in the metabolic profiles of rat hippocampus, medial prefrontal cortex and striatum

We have recently shown that age-dependent regional brain atrophy and lateral ventricle expansion may be linked with impaired cognitive and locomotor functions. However, metabolic profile transformation in different brain regions during aging is unknown. This study examined metabolic changes in the hippocampus, medial prefrontal cortex (mPFC) and striatum of middle- and late-aged Sprague-Dawley rats using ultrahigh performance liquid chromatography coupled with high-resolution accurate mass-orbitrap tandem mass spectrometry. Thirty-eight potential metabolites were altered in hippocampus, 29 in mPFC, and 14 in striatum. These alterations indicated that regional metabolic mechanisms in lated-aged rats are related to multiple pathways including glutathione, sphingolipid, tyrosine, and purine metabolism. Thus, our findings might be useful for understanding the complexity of metabolic mechanisms in aging and provide insight for aging and health span.

Tocotrienol-Rich Fraction of Palm Oil Improves Behavioral Impairments and Regulates Metabolic Pathways in AβPP/PS1 Mice

We have recently shown that the tocotrienol-rich fraction (TRF) of palm oil, a mixture of vitamin E analogs, improves amyloid pathology in vitro and in vivo. However, precise mechanisms remain unknown. In this study, we examined the effects of long-term (10 months) TRF treatment on behavioral impairments and brain metabolites in (15 months old) AβPP/PS1 double transgenic (Tg) Alzheimer’s disease (AD) mice. The open field test, Morris water maze, and novel object recognition tasks revealed improved exploratory activity, spatial learning, and recognition memory, respectively, in TRF-treated Tg mice. Brain metabolite profiling of wild-type and Tg mice treated with and without TRF was performed using ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution accurate mass (HRAM)-orbitrap tandem mass spectrometry (MS/MS). Metabolic pathway analysis found perturbed metabolic pathways that linked to AD. TRF treatment partly ameliorated metabolic perturbations in Tg mouse hippocampus. The mechanism of this pre-emptive activity may occur via modulation of metabolic pathways dependent on Aβ interaction or independent of Aβ interaction.

Proteome profiling in the hippocampus, medial prefrontal cortex, and striatum of aging rat

Abstract Decrease in multiple functions occurs in the brain with aging, all of which can contribute to age‐related cognitive and locomotor impairments. Brain atrophy specifically in hippocampus, medial prefrontal cortex (mPFC), and striatum, can contribute to this age‐associated decline in function. Our recent metabolomics analysis showed age‐related changes in these brain regions. To further understand the aging processes, analysis using a proteomics approach was carried out. This study was conducted to identify proteome profiles in the hippocampus, mPFC, and striatum of 14‐, 18‐, 23‐, and 27‐month‐old rats. Proteomics analysis using ultrahigh performance liquid chromatography coupled with Q Exactive HF Orbitrap mass spectrometry identified 1074 proteins in the hippocampus, 871 proteins in the mPFC, and 241 proteins in the striatum. Of these proteins, 97 in the hippocampus, 25 in mPFC, and 5 in striatum were differentially expressed with age. The altered proteins were classified into three ontologies (cellular component, molecular function, and biological process) containing 44, 38, and 35 functional groups in the hippocampus, mPFC, and striatum, respectively. Most of these altered proteins participate in oxidative phosphorylation (e.g. cytochrome c oxidase and ATP synthase), glutathione metabolism (e.g. peroxiredoxins), or calcium signaling pathway (e.g. protein S100B and calmodulin). The most prominent changes were observed in the oldest animals. These results suggest that alterations in oxidative phosphorylation, glutathione metabolism, and calcium signaling pathway are involved in cognitive and locomotor impairments in aging. HighlightsLC‐MS/MS analysis identified potential proteins associated with brain aging.Proteins altered with age in hippocampus, medial prefrontal cortex, and striatumAltered proteins involved in various pathways

Behavioral Assessment and Blood Oxidative Status of Aging Sprague Dawley Rats through a Longitudinal Analysis

BACKGROUND Cognitive frailty emerges as one of the threats to healthy aging. It is in continuum with advancing of age with uncertain indicator between pathological and physiological changes. Alterations in pathways associated with the aging process have been observed including oxidative stress, lipid metabolism, and inflammation. However, the exact mechanisms leading to cognitive decline are still unclear. OBJECTIVE This study was sought to assess the level of cognitive functions and linked with blood oxidative status during normal aging in rats. METHODS A longitudinal study using male Sprague Dawley rats was performed starting from the age of 14 months old to 27 months old. Cognitive functions tests such as open field, Morris water maze and object recognition were determined at the age of 14, 18, 23, and 27 months old and were compared with group 3 months old. Blood was collected from the orbital venous sinus and oxidative status was determined by measuring the level of DNA damage, lipid peroxidation, protein oxidation and antioxidant enzymes activity. RESULTS Aged rats showed declining exploratory behavior and increased in the level of anxiety as compared to the young rats. The level of DNA damage increased with increasing age. Interestingly, our study found that both levels of malondialdehyde and plasma carbonyl content decreased with age. In addition, the level of superoxide dismutase activity was significantly decreased with age whereas catalase activity was significantly increased from 18 months of age. However, no significant difference was found in glutathione peroxidase activity among all age groups. CONCLUSION The progressions of cognitive impairment in normal aging rats are linked to the increment in the level of DNA damage.

BRAIN IMAGING, BEHAVIORAL EVALUATIONS, BIOCHEMICAL ANALYSIS, AND PROTEOMES PROFILING IN AGED RATS

pathways among biological groups by summarizing all pairwise GSEA results. Hierarchical clustering was applied to identify significant interactions between emerged pathways. Results: PCA revealed that rats undergoing perimenopause exhibit substantially higher variances in overall hippocampal gene expression relative to other groups, supporting the perimenopausal brain being in an unstable transition state. While PCA and DEG analyses of hippocampal RNA suggest significant difference among age-matched pre-/peri-/menopause brains, the difference in the hypothalamus was minor, suggesting hippocampus but not hypothalamus as a major brain site affected by endocrine aging. GSEA further revealed alterations in bioenergetic-, inflammatory-, and cell proliferation pathways during the transition featured by declining bioenergetic genes and low-grade activation of immune pathways. Moreover, nuclear(nDNA) or mitochondrial DNA (mtDNA)-encoded bioenergetic genes are differentially regulated by chronologicaland endocrine aging: mtDNA genes correlated closely with chronological aging while nDNA-encoded counterparts were largely endocrine dependent. Lastly, the strong correlation between bioenergetic pathway with genes involved in AD and other neurodegenerative disorders linked bioenergetic deficits to neurodegeneration and elevated AD vulnerability. Conclusions: Our findings suggest that hippocampal gene expression during perimenopause is a transition state characterized by perturbations to primarily bioenergeticand inflammatory pathways, which could contribute to increased AD risk in women. This study provides novel mechanistic insights into the impact of perimenopausal transition on brain function, which could have implications for identifying phenotypes of AD risk for earliest detection in aging females.

Effects of Aging and Tocotrienol-Rich Fraction Supplementation on Brain Arginine Metabolism in Rats

Accumulating evidence suggests that altered arginine metabolism is involved in the aging and neurodegenerative processes. This study sought to determine the effects of age and vitamin E supplementation in the form of tocotrienol-rich fraction (TRF) on brain arginine metabolism. Male Wistar rats at ages of 3 and 21 months were supplemented with TRF orally for 3 months prior to the dissection of tissue from five brain regions. The tissue concentrations of L-arginine and its nine downstream metabolites were quantified using high-performance liquid chromatography and liquid chromatography tandem mass spectrometry. We found age-related alterations in L-arginine metabolites in the chemical- and region-specific manners. Moreover, TRF supplementation reversed age-associated changes in arginine metabolites in the entorhinal cortex and cerebellum. Multiple regression analysis revealed a number of significant neurochemical-behavioral correlations, indicating the beneficial effects of TRF supplementation on memory and motor function.

Curcumin against amyloid pathology in mental health and brain composition

Abstract Recent evidence suggests that amyloid pathology occurs 10–20 years before the clinical onset of Alzheimer’s disease (AD). Accordingly, modulating abnormal amyloid-β (Aβ) aggregation is now considered as a potential therapeutic target in AD. Curcumin, a low molecular weight polyphenol derived from the well-known spice turmeric, has various pharmacological properties, including antitumor, antioxidative, antiinflammatory, and antiamyloid effects. Curcumin binds both Aβ fibrils and oligomers and inhibits Aβ aggregation as well as Aβ-related oxidative stress and inflammation. The keto–enol tautomerism of curcumin is involved in its binding to Aβ aggregates. The enol form, but not the keto form, of curcumin can bind to Aβ aggregates. When curcumin was administered to transgenic mouse models of AD, it effectively suppressed amyloid pathology in the mouse brain. However, the results of early clinical trials of curcumin for AD have been negative, probably due to its low bioavailability. Several approaches have been proposed to improve the bioavailability of curcumin.