Age-related changes in energy metabolism in peripheral mononuclear blood cells (PBMCs) and the brains of cognitively healthy seniors.

Mitochondrial dysfunction is a hallmark of cellular senescence and many age-related neurodegenerative diseases. We therefore investigated the relationship between mitochondrial function in peripheral blood cells and cerebral energy metabolites in young and older sex-matched, physically and mentally healthy volunteers. Cross-sectional observational study involving 65 young (26.0 ± 0.49 years) and 65 older (71.7 ± 0.71 years) women and men recruited. Cognitive health was evaluated using established psychometric methods (MMSE, CERAD). Blood samples were collected and analyzed, and fresh peripheral blood mononuclear cells (PBMCs) were isolated. Mitochondrial respiratory complex activity was measured using a Clarke electrode. Adenosine triphosphate (ATP) and citrate synthase activity (CS) were determined by bioluminescence and photometrically. N-aspartyl-aspartate (tNAA), ATP, creatine (Cr), and phosphocreatine (PCr) were quantified in brains using 1H- and 31P-magnetic resonance spectroscopic imaging (MRSI). Levels of insulin-like growth factor 1 (IGF-1) were determined using a radio-immune assay (RIA). Complex IV activity (CIV) (- 15%) and ATP levels (- 11%) were reduced in PBMCs isolated from older participants. Serum levels of IGF-1 were significantly reduced (- 34%) in older participants. Genes involved in mitochondrial activity, antioxidant mechanisms, and autophagy were unaffected by age. tNAA levels were reduced (- 5%), Cr (+ 11%), and PCr (+ 14%) levels were increased, and ATP levels were unchanged in the brains of older participants. Markers of energy metabolism in blood cells did not significantly correlate with energy metabolites in the brain. Age-related bioenergetic changes were detected in peripheral blood cells and the brains of healthy older people. However, mitochondrial function in peripheral blood cells does not reflect energy related metabolites in the brain. While ATP levels in PBMCs may be be a valid marker for age-related mitochondrial dysfunction in humans, cerebral ATP remained constant.

Age-Dependent Alterations of Cognition, Mitochondrial Function, and Beta-Amyloid Deposition in a Murine Model of Alzheimer's Disease-A Longitudinal Study.

Aging is the main risk factor for sporadic Alzheimer's disease (AD), which is characterized by the cerebral deposition of ß-amyloid peptides (Aß) and cognitive decline. Mitochondrial dysfunction is also characteristic of the disease and represents a hallmark of both, aging and neurodegeneration. We longitudinally followed Aß levels, cognition, and mitochondrial function in the same cohort of Thy1-APP751SL mice representing a murine model of AD. In the course of time, changes were most prominent at an age of 13 months including the latency time in the passive avoidance test, the activity of complexes I and IV of the mitochondrial respiration chain, and expression of genes related to mitochondrial biogenesis and synaptic plasticity including Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α), CAMP responsive element binding protein 1 (CREB1), and Synaptophysin 1 (SYP1). These changes occurred in parallel with massively increasing cerebral Aß levels. Other parameters were changed in younger mice including the alteration rate in the Y-maze test and the nesting score when Aß levels were not changed yet. The results are consistent in the cohort described. However, previous, non-longitudinal studies reported divergent time points for the occurrence of the parameters studied. These findings are discussed in light of the current results.

Effects of different standard and special diets on cognition and brain mitochondrial function in mice.

Objectives: Human nutrition plays an important role in prevention or at least slowing down the progression of age- and diet-related diseases. Thereby, mitochondrial dysfunction represents one common underlying mechanism, which is being investigated in mouse models. However, the influence of the selected diets in preclinical studies on cognition and mitochondrial function has not yet been reported cohesively.Methods: Therefore, we present the results of three different studies that addressed this question. First, we investigated the influence of two standard control chow diets and a special diet low in antioxidants over 6 months in aged NMRI mice. Additionally, a 70% high-fat (HF) chow diet as well as a western-style diet (WSD) rich in lard and fructose were examined in C57/BL6 mice. Cognitive performance, mitochondrial function and bioenergetics in the brain were investigated. Moreover, cerebral expression of genes involved in biogenesis and antioxidant defence (citrate synthase, complex I, complex IV, SOD2, Cat1, GPx-1) were quantified.Results: The results show that a modified, low antioxidant diet increased ATP levels in the brain of aged mice, while cognitive functions remained largely unaffected. A HF diet also showed significant effects on ATP levels and gene expression levels of relevant antioxidant markers, while the WSD had marginal effects on mitochondrial function and bioenergetics in the brain.Discussion: Our results indicate that standard- and special diets have an impact on cognition and mitochondrial function in the brain. Thus, appropriate caution is warranted when selecting a suitable diet for preclinical studies in mice.

Fucose as a Cleavage Product of 2'Fucosyllactose Does Not Cross the Blood-Brain Barrier in Mice.

SCOPE: To further examine the role of the human milk oligosaccharide 2'fucosyllactose (2´FL) and fucose (Fuc) in cognition. Using 13 C-labeled 2'FL,thestudy previously showed in mice that 13 C-enrichment of the brain is not caused by 13 C1 -2´FL itself, but rather by microbial metabolites. Here, the study applies 13 C1 -Fuc in the same mouse model to investigate its uptake into the brain. METHODS AND RESULTS: Mice received 13 C1 -Fuc via oral gavage (2 mmol 13 C1 -Fuc/kg-1 body weight) or intravenously (0.4 mmol/kg-1 body weight). 13 C-enrichment is measured in organs, including various brain regions, biological fluids and excrements. By EA-IRMS, the study observes an early rise of 13 C-enrichment in plasma, 30 min after oral dosing. However, 13 C-enrichment in the brain does not occur until 3-5 h post-dosing, when the 13 C-Fuc bolus has already reached the lower gut. Therefore, the researcher assume that 13 C-Fuc is absorbed in the upper small intestine but cannot cross the blood-brain barrier which is also observed after intravenous application of 13 C1 -Fuc. CONCLUSIONS: Late 13 C-enrichment in the rodent brain may be derived from 13 C1 -Fuc metabolites derived from bacterial fermentation. The precise role that Fuc or 2´FL metabolites might play in gut-brain communication needs to be investigated in further studies.

Cerebral Mitochondrial Function and Cognitive Performance during Aging: A Longitudinal Study in NMRI Mice.

Brain aging is one of the major risk factors for the development of several neurodegenerative diseases. Therefore, mitochondrial dysfunction plays an important role in processes of both, brain aging and neurodegeneration. Aged mice including NMRI mice are established model organisms to study physiological and molecular mechanisms of brain aging. However, longitudinal data evaluated in one cohort are rare but are important to understand the aging process of the brain throughout life, especially since pathological changes early in life might pave the way to neurodegeneration in advanced age. To assess the longitudinal course of brain aging, we used a cohort of female NMRI mice and measured brain mitochondrial function, cognitive performance, and molecular markers every 6 months until mice reached the age of 24 months. Furthermore, we measured citrate synthase activity and respiration of isolated brain mitochondria. Mice at the age of three months served as young controls. At six months of age, mitochondria-related genes (complex IV, creb-1, ß-AMPK, and Tfam) were significantly elevated. Brain ATP levels were significantly reduced at an age of 18 months while mitochondria respiration was already reduced in middle-aged mice which is in accordance with the monitored impairments in cognitive tests. mRNA expression of genes involved in mitochondrial biogenesis (cAMP response element-binding protein 1 (creb-1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α), nuclear respiratory factor-1 (Nrf-1), mitochondrial transcription factor A (Tfam), growth-associated protein 43 (GAP43), and synaptophysin 1 (SYP1)) and the antioxidative defense system (catalase (Cat) and superoxide dismutase 2 (SOD2)) was measured and showed significantly decreased expression patterns in the brain starting at an age of 18 months. BDNF expression reached, a maximum after 6 months. On the basis of longitudinal data, our results demonstrate a close connection between the age-related decline of cognitive performance, energy metabolism, and mitochondrial biogenesis during the physiological brain aging process.

Purified oleocanthal and ligstroside protect against mitochondrial dysfunction in models of early Alzheimer's disease and brain ageing.

As components of the Mediterranean diet (MedDiet) olive polyphenols may play a crucial role for the prevention of Alzheimer's disease (AD). Since mitochondrial dysfunction is involved in both, brain ageing and early AD, effects of 10 different purified phenolic secoiridoids (hydroxytyrosol, tyrosol, oleacein, oleuroside, oleuroside aglycon, oleuropein, oleocanthal, ligstroside, ligstroside aglycone and ligustaloside B) and two metabolites (the plant metabolite elenolic acid and the mammalian metabolite homovanillic acid) were tested in very low doses on mitochondrial function in SH-SY5Y-APP695 cells - a cellular model of early AD. All tested secoiridoids significantly increased basal adenosine triphosphate (ATP) levels in SY5Y-APP695 cells. Oleacein, oleuroside, oleocanthal and ligstroside showed the highest effect on ATP levels and were additionally tested on mitochondrial respiration. Only oleocanthal and ligstroside were able to enhance the capacity of respiratory chain complexes. To investigate their underlying molecular mechanisms, the expression of genes associated with mitochondrial biogenesis, respiration and antioxidative capacity (PGC-1α, SIRT1, CREB1, NRF1, TFAM, complex I, IV and V, GPx1, SOD2, CAT) were determined using qRT-PCR. Exclusively ligstroside increased mRNA expression of SIRT1, CREB1, complex I, and GPx1. Furthermore, oleocanthal but not ligstroside decreased Aß 1-40 levels in SH-SY5Y-APP695 cells. To investigate the in vivo effects of purified secoiridoids, the two most promising compounds (oleocanthal and ligstroside) were tested in a mouse model of ageing. Female NMRI mice, aged 12 months, received a diet supplemented with 50 mg/kg oleocanthal or ligstroside for 6 months (equivalent to 6.25 mg/kg b.w.). Young (3 months) and aged (18 months) mice served as controls. Ligstroside fed mice showed improved spatial working memory. Furthermore, ligstroside restored brain ATP levels in aged mice and led to a significant life extension compared to aged control animals. Our findings indicate that purified ligstroside has outstanding performance on mitochondrial bioenergetics in models of early AD and brain ageing by mechanisms that may not interfere with Aß production. Additionally, ligstroside expanded the lifespan in aged mice and enhanced cognitive function.

Metabolic Fate and Distribution of 2´-Fucosyllactose: Direct Influence on Gut Microbial Activity but not on Brain.

SCOPE: 2´-Fucosyllactose (2´FL) is an abundant oligosaccharide in human milk. It is hypothesized that its brain enrichment is associated with improved learning. Accumulation of 2´FL in organs, biological fluids, and feces is assessed in wild-type and germ-free mice. METHODS AND RESULTS: 13 C-labelled 2´FL is applied to NMRI wild-type mice intravenously (0.2 g kg-1 ) or orally (1 g kg-1 ), while controls receive saline. Biological samples are collected (0.5-15 h) and 13 C-enrichment is measured by elemental analysis isotope ratio mass spectrometry (EA-IRMS). After oral application, 2´FL is primarily eliminated in the feces. 13 C-enrichment in organs including the brain follows the same pattern as in plasma with a maximum peak after 5 h. However, 13 C-enrichment is only detected when the 13 C-2´FL bolus reaches the colon. In contrast, in germ-free mice, the 13 C-bolus remains in the intestinal content and is expelled via the feces. Furthermore, intravenously applied 13 C-2´FL is eliminated via urine; no 13 C-enrichment of organs is observed, suggesting that intact 2´FL is not retained. CONCLUSIONS: 13 C-enrichment in brain and other organs after oral application of 13 C-2´FL in wild-type mice indicates cleaved fucose or other gut microbial 2´FL metabolites may be incorporated, as opposed to intact 2´FL.

Effects of Long-Term Treatment with a Blend of Highly Purified Olive Secoiridoids on Cognition and Brain ATP Levels in Aged NMRI Mice.

Aging represents a major risk factor for developing neurodegenerative diseases such as Alzheimer's disease (AD). As components of the Mediterranean diet, olive polyphenols may play a crucial role in the prevention of AD. Since mitochondrial dysfunction acts as a final pathway in both brain aging and AD, respectively, the effects of a mixture of highly purified olive secoiridoids were tested on cognition and ATP levels in a commonly used mouse model for brain aging. Over 6 months, female NMRI mice (12 months of age) were fed with a blend containing highly purified olive secoiridoids (POS) including oleuropein, hydroxytyrosol and oleurosid standardized for 50 mg oleuropein/kg diet (equivalent to 13.75 mg POS/kg b.w.) or the study diet without POS as control. Mice aged 3 months served as young controls. Behavioral tests showed deficits in cognition in aged mice. Levels of ATP and mRNA levels of NADH-reductase, cytochrome-c-oxidase, and citrate synthase were significantly reduced in the brains of aged mice indicating mitochondrial dysfunction. Moreover, gene expression of Sirt1, CREB, Gap43, and GPx-1 was significantly reduced in the brain tissue of aged mice. POS-fed mice showed improved spatial working memory. Furthermore, POS restored brain ATP levels in aged mice which were significantly increased. Our results show that a diet rich in purified olive polyphenols has positive long-term effects on cognition and energy metabolism in the brain of aged mice.

MH84 improves mitochondrial dysfunction in a mouse model of early Alzheimer's disease.

BACKGROUND: Current approved drugs for Alzheimer's disease (AD) only attenuate symptoms, but do not cure the disease. The pirinixic acid derivate MH84 has been characterized as a dual gamma-secretase/proliferator activated receptor gamma (PPARγ) modulator in vitro. Pharmacokinetic studies in mice showed that MH84 is bioavailable after oral administration and reaches the brain. We recently demonstrated that MH84 improved mitochondrial dysfunction in a cellular model of AD. In the present study, we extended the pharmacological characterization of MH84 to 3-month-old Thy-1 AßPPSL mice (harboring the Swedish and London mutation in human amyloid precursor protein (APP)) which are characterized by enhanced AßPP processing and cerebral mitochondrial dysfunction, representing a mouse model of early AD. METHODS: Three-month-old Thy-1 AßPPSL mice received 12 mg/kg b.w. MH84 by oral gavage once a day for 21 days. Mitochondrial respiration was analyzed in isolated brain mitochondria, and mitochondrial membrane potential and ATP levels were determined in dissociated brain cells. Citrate synthase (CS) activity was determined in brain tissues and MitoTracker Green fluorescence was measured in HEK293-AßPPwt and HEK293-AßPPsw cells. Soluble Aß1-40 and Aß1-42 levels were determined using ELISA. Western blot analysis and qRT-PCR were used to measure protein and mRNA levels, respectively. RESULTS: MH84 reduced cerebral levels of the ß-secretase-related C99 peptide and of Aß40 levels. Mitochondrial dysfunction was ameliorated by restoring complex IV (cytochrome-c oxidase) respiration, mitochondrial membrane potential, and levels of ATP. Induction of PPARγ coactivator-1α (PGC-1α) mRNA and protein expression was identified as a possible mode of action that leads to increased mitochondrial mass as indicated by enhanced CS activity, OXPHOS levels, and MitoTracker Green fluorescence. CONCLUSIONS: MH84 modulates ß-secretase processing of APP and improves mitochondrial dysfunction by a PGC-1α-dependent mechanism. Thus, MH84 seems to be a new promising therapeutic agent with approved in-vivo activity for the treatment of AD.

A diet rich in omega-3 fatty acids enhances expression of soluble epoxide hydrolase in murine brain.

Several studies suggest that intake of omega-3 polyunsaturated fatty acids (n3-PUFA) beneficially influences cognitive function. However, effects on the adult brain are not clear. Little is known about the impact of dietary intervention on the fatty acid profile in adult brain, the modulation in the expression of enzymes involved in fatty acid biosynthesis and metabolism as well as changes in resulting oxylipins. These questions were addressed in the present study in two independent n3-PUFA feeding experiments in mice. Supplementation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA, 1% each in the diet) for 30days to adult NMRI and C57BL/6 mice led to a distinct shift in the brain PUFA pattern. While n3-PUFAs EPA, n3 docosapentaenoic acid and DHA were elevated, many n6-PUFAs were significantly decreased (except, e.g. C20:3 n6 which was increased). This shift in PUFAs was accompanied by immense differences in concentrations of oxidative metabolites derived from enzymatic conversion of PUFAs, esp. arachidonic acid whose products were uniformly decreased, and a modulation in the activity and expression pattern of delta-5 and delta-6 desaturases. In both mouse strains a remarkable increase in the soluble epoxide hydrolase (sEH) activity (decreased epoxy-FA concentrations and epoxy-FA to dihydroxy-FA-ratios) as well as sEH expression was observed. Taking the high biological activity of epoxy-FA, e.g. on blood flow and nociceptive signaling into account, this finding might be of relevance for the effects of n3-PUFAs in neurodegenerative diseases. On any account, our study suggests a new distinct regulation of brain PUFA and oxylipin pattern by supplementation of n3-PUFAs to adult rodents.