Lap Ho

PGC-1α Expression Decreases in the Alzheimer Disease Brain as a Function of Dementia

OBJECTIVESnTo explore mechanisms through which altered peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha) expression may influence Alzheimer disease (AD) amyloid neuropathology and to test the hypothesis that promotion of PGC-1alpha expression in neurons might be developed as a novel therapeutic strategy in AD.nnnDESIGNnCase-control. Patients Human postmortem brain (hippocampal formation) samples from AD cases and age-matched non-AD cases.nnnRESULTSnUsing genome-wide complementary DNA microarray analysis, we found that PGC-1alpha messenger RNA expression was significantly decreased as a function of progression of clinical dementia in the AD brain. Following confirmatory real-time polymerase chain reaction assay, we continued to explore the role of PGC-1alpha in clinical dementia and found that PGC-1alpha protein content was negatively associated with both AD-type neuritic plaque pathology and beta-amyloid (Abeta)(X-42) contents. Moreover, we found that the predicted elevation of amyloidogenic Abeta(1-42) and Abeta(1-40) peptide accumulation in embryonic cortico-hippocampal neurons derived from Tg2576 AD mice under hyperglycemic conditions (glucose level, 182-273 mg/dL) coincided with a dose-dependent attenuation in PGC-1alpha expression. Most importantly, we found that the reconstitution of exogenous PGC-1alpha expression in Tg2576 neurons attenuated the hyperglycemic-mediated beta-amyloidogenesis through mechanisms involving the promotion of the nonamyloidogenic alpha-secretase processing of amyloid precursor protein through the attenuation of the forkheadlike transcription factor 1 (FoxO3a) expression.nnnCONCLUSIONnTherapeutic preservation of neuronal PGC-1alpha expression promotes the nonamyloidogenic processing of amyloid precursor protein precluding the generation of amyloidogenic Abeta peptides.

Bioavailability of Gallic Acid and Catechins from Grape Seed Polyphenol Extract is Improved by Repeated Dosing in Rats: Implications for Treatment in Alzheimer's Disease

The present study explored the bioavailability and brain deposition of a grape seed polyphenolic extract (GSPE) previously found to attenuate cognitive deterioration in a mouse model of Alzheimers disease (AD). Plasma pharmacokinetic response of major GSPE phenolic components was measured following intragastric gavage of 50, 100, and 150 mg GSPE per kg body weight. Liquid chromatography-mass spectrometry (LC-MS) analysis identified gallic acid (GA), catechin (C), and epicatechin (EC) in plasma of rats gavaged acutely with GSPE. Additionally, 4-methylgallic acid (4-OMeGA), 3-methylcatechin (3-OMeC), and 3-methylepicatechin (3-OMeEC) were identified as circulating metabolites of GSPE phenolic constituents. Cmax for individual GSPE constituents and their metabolites increased in a dose-dependent fashion (with increasing GSPE oral dose). Repeated daily exposure to GSPE was found to significantly increase bioavailability (defined as plasma AUC0-8h) of GA, C, and EC by 198, 253, and 282% relative to animals receiving only a single acute GSPE dose. EC and C were not detectable in brain tissues of rats receiving a single GSPE dose but reached levels of 290.7 +/-45.9 and 576.7 +/- 227.7 pg/g in brain tissues from rats administered GSPE for 10 days. This study suggests that brain deposition of GA, C, and EC is affected by repeated dosing of GSPE.

Nucleotide sequence of a cDNA for the dihydrolipoamide acetyltransferase component of human pyruvate dehydrogenase complex

Deoxynucleotide sequencing of a cDNA for the dihydrolipoamide acetyltransferase (PDC‐E2) component of human pyruvate dehydrogenase complex (PDC) revealed an open reading frame of 1848 base pairs corresponding to a leader sequence of 54 amino acids and a mature protein of 561 amino acids (59 551 Da). Both an amino‐terminal lipoyl‐bearing domain and a carboxy‐terminal catalytic domain are present in the deduced amino acid sequence. The lipoyl‐bearing domain contains two repeating units of 127 amino acids, each harboring one lipoic acid‐binding lysine. Thus, mammalian PDC‐E2 differs as to the number of lipoic acid‐binding sites from other dihydrolipoamide acyltransferases in both prokaryotic and eukaryotic organisms.

Regulation of Forkhead Transcription Factor FoxO3a Contributes to Calorie Restriction‐induced Prevention of Alzheimer's Disease‐type Amyloid Neuropathology and Spatial Memory Deterioration

Forkhead transcription factor FoxO3a, also known as DAF‐16 in Caenorhabditis elegans, is a key regulator of the insulin receptor (IR)/insulin‐like growth factor‐I signaling pathway mediated extension of life span in worms and yeast. In this study, we report that calorie restriction (CR)‐mediated activation of the IR signaling pathway leads to hyperphosphorylation of FoxO3a transcription factor and, consequently, its exclusion from the nucleus. This inactivation of FoxO3a activity is correlated with attenuation of Alzheimers disease (AD)‐type amyloid neuropathology and with preservation of spatial reference memory in the Tg2576 mouse model of AD. Further, in vitro studies reveal that exogenous expression of viral, triple‐mutant, constitutively active FoxO3a resulting in increased nuclear FoxO3a activity in primary neuron cultures derived from Tg2576 mouse embryos, causally promotes AD amyloid‐β peptide (Aβ) levels by inhibiting nonamyloidogenic α‐secretase activity, indicating the existence of an inverse correlation between FoxO3a activity and cerebral Aβ amyloidosis. Moreover, we report for the first time that the exclusion of the FoxO3a transcription factor from the nucleus in combination with inhibition of nuclear FoxO3a activity by SIRT1‐mediated deacetylation in response to CR is a mechanism resulting in the repression of Rho‐associated protein kinase‐1 gene expression, thereby activating nonamyloidogenic α‐secretase processing of the amyloid precursor protein and lowering Aβ generation. This study provides a novel metabolic pathway for prevention and/or treatment of AD.

Systemic deficiency of the first component of the pyruvate dehydrogenase complex.

ABSTRACT: An infant with lactic acidosis and developmental delay had neuropathological changes consistent with Leighs necrotizing encephalomyelopathy. Total pyruvate dehydrogenase complex (PDC) activity was low relative to controls in lymphocytes (0.2 versus 1.9 ± 0.6 SD nmol/min/mg protein) and cultured skin fibroblasts (0.9 versus 2.7 ± 1.0). Liver, muscle, heart, and kidney mitochondria oxidized several substrates normally, but did not oxidize pyruvate. PDC activity was absent in these mitochondria (0.1 versus 9.8 ± 4.2 in liver and 0.7 versus 75 ± 26 in muscle) and was very low in all tissue homogenates. Activity of the first component was low in liver mitochondria, whereas activities of the second and third components were normal. Western blot analysis of tissue proteins showed normal amounts of second and third component of PDC but undetectable to trace amounts of both a and B subunits of the first component of PDC in liver, brain, kidney, heart, and skin fibroblasts. Thus, profound systemic deficiency of PDC was due to lack of both subunit proteins of the first component of PDC.

A deficiency of both subunits of pyruvate dehydrogenase which is not expressed in fibroblasts

ABSTRACT: Pyruvate dehydrogenase complex (PDC) deficiency usually has been detected by decreased activity in cultured skin fibroblasts. We investigated two brothers in whom PDC activity was less than 10% of controls in lymphocytes but normal in skin fibroblasts. They both had abnormal neuromuscular development and lactic acidosis which was aggravated by ingestion of carbohydrate. One brother died at age 3 yr and tissues were obtained at autopsy soon after death. The brain was swollen with diffuse acute hemorrhages but without the lesions characteristic of Leighs disease. PDC activity was virtually un-detectable in mitochondria or homogenates of liver, skeletal muscle, and heart, but was about 30% of controls in kidney. The activity of the first component E1 was not detectable in mitochondria from liver, whereas the activities of the second and third components were normal; the activities of all components were normal in fibroblasts. Western immunoblot analysis showed absent to trace amounts of both the E1α and E1β subunits in liver, skeletal muscle, and heart, with normal amounts of the second and third components. About one-fourth of control amounts of E1α and E1β were present in kidney and normal levels were present in fibroblasts. PDC activity in lymphocytes from the mother was 35% of controls; she had normal PDC activity in her fibroblasts. PDC activity was normal in lymphocytes from the brothers sister, father, and maternal grandparents and great-grandmother. The mode of inheritance was not established. In conclusion, PDC deficiency may not be detected in skin fibroblasts in some cases; the mechanism of variable tissue expression of E1 remains to be delineated

Survey of Polyphenol Constituents in Grapes and Grape-Derived Products

A rapid and comprehensive qualitative method has been developed to characterize the different classes of polyphenols, such as anthocyanins, flavonols, phenolic acids, and flavanols/proanthocyanidins, in grape products. The detection was achieved by two runs with the same LC gradient in different MS ionization modes and mobile phase modifiers (positive ionization mode and 0.4% trifluoroacetic acid for anthocyanins and flavonols; negative ionization mode and 0.1% formic acid for phenolic acids and flavanols). From an analysis of the MS and UV data and in comparison with the authenticated standards, a total of 53 compounds were identified, including 33 anthocyanins, 12 flavonols, 4 phenolic acids, and 4 flavanols/proanthocyanidins. With the method developed, a survey was then conducted to qualitatively assess the composition of polyphenols among 29 different grape products including original grape, grape juice, grape wine, and grape-derived dietary supplements, and their chemical profiles were systematically compared. This method provided a comprehensive qualitative insight into the composition of polyphenols in grape-derived products.

nELAV Proteins Alteration in Alzheimer's Disease Brain: A Novel Putative Target for Amyloid-β Reverberating on AβPP Processing

Neuronal ELAV (nELAV) proteins are RNA-binding proteins which play a physiological role in controlling gene expression in memory formation, and their alteration may contribute to cognitive impairment associated with neurodegenerative pathologies such as Alzheimers disease (AD). Indeed, we found that the content of nELAV proteins is significantly decreased along with clinical dementia progression in the hippocampi of AD brains, where it inversely correlates with the amount of amyloid-beta (Abeta). To check the direct influence of Abeta on nELAV, we performed in vitro experiments using human SH-SY5Y cells, finding that Abeta(1-42) specifically determines nELAV proteins reduction. Since ADAM10 mRNA has the predicted sequences targeted by nELAV, we investigated whether Abeta, through nELAV proteins, could originate a vicious circle affecting amyloid-beta protein precursor (AbetaPP) processing. Immunoprecipitation experiments showed that indeed nELAV proteins bind to ADAM10 mRNA and that this binding is disrupted by Abeta(1-42) exposure, resulting in a decreased ADAM10 protein expression. ADAM10 protein diminution was also found in AD hippocampi. These data show for the first time the involvement of nELAV in AD pathology and suggest that their alteration may affect genes implicated in AbetaPP processing.

Dietary supplementation with decaffeinated green coffee improves diet-induced insulin resistance and brain energy metabolism in mice

Abstract Objectives There is accumulating evidence that coffee consumption may reduce risk for type 2 diabetes, a known risk factor for Alzheimers and other neurological diseases. Coffee consumption is also associated with reduced risk for Alzheimers disease and non-Alzheimers dementias. However, preventive and therapeutic development of coffee is complicated by the cardiovascular side effects of caffeine intake. As coffee is also a rich source of chlorogenic acids and many bioactive compounds other than caffeine, we hypothesized that decaffeinated coffee drinks may exert beneficial effects on the brain. Methods We have investigated whether dietary supplementation with a standardized decaffeinated green coffee preparation, Svetol®, might modulate diet-induced insulin resistance and brain energy metabolism dysfunction in a high-fat diet mouse model. Results As expected, dietary supplementation with Svetol® significantly attenuated the development of high-fat diet-induced deficits in glucose-tolerance response. We have also found that Svetol® treatment improved brain mitochondrial energy metabolism as determined by oxygen consumption rate. Consistent with this evidence, follow-up gene expression profiling with Agilent whole-genome microarray revealed that the decaffeinated coffee treatment modulated a number of genes in the brain that are implicated in cellular energy metabolism. Discussion Our evidence is the first demonstration that dietary supplementation with a decaffeinated green coffee preparation may beneficially influence the brain, in particular promoting brain energy metabolic processes.

Genetic defects in human pyruvate dehydrogenase.

The nature of PDC deficiency has been characterized at the levels of total and component catalytic activities as well as at the levels of component proteins and specific mRNAs. Defects in 14 cases were shown to involve the E1 component, and there was one case each of an apparent E2 and E3 deficiency. Defects involving the E1 component exhibit heterogeneous expression of E1 proteins and mRNAs, indicating that different types of mutations cause E1 deficiency. E1 deficiencies can occur either in the presence or absence of E1 proteins, representing catalytic mutations or mutations affecting the expression of E1 proteins, respectively. In every case where the content of E1 proteins is reduced, both the E1 alpha and the E1 beta peptides are simultaneously affected. This is likely to be due to rapid degradation of any E1 peptide that is not complexed into the alpha 2 beta 2 conformation. Among subjects with reduced levels of both E1 peptides, some had normal amounts of specific E1 alpha and E1 beta mRNAs. In these subjects, the primary mutations affect either translational or post-translational processes leading to the formation of mature E1 proteins in the mitochondria. In contrast, two cases of simultaneous reduction of both E1 alpha and E1 beta proteins had decreases in the amounts of E1 alpha mRNA only. Mutations in these cases may impair the transcription, nuclear processing, or stability of E1 alpha mRNA. E1 deficiency may manifest in a variable manner. Further characterization of this phenomenon might provide insight into the discrepancy between the clinical severity of the defect and the residual level of PDC catalytic activity. Available information indicates that the E1 alpha gene is located on the X chromosome, but sex distribution of E1 alpha defects suggests that the mode of inheritance may not follow a simple X-linked pattern. The availability of specific PDC antibodies and cDNA clones, as well as the application of molecular biological techniques, should facilitate the characterization of the molecular basis of various PDC deficiencies. This information should provide better understanding of the function of PDC, pathophysiology of PDC deficiency, and mechanisms of inheritance and expression of these genes.