Age-Dependent Decrease of Mitochondrial Complex II Activity in a Familial Mouse Model for Alzheimer’s Disease

Abstract

Alzheimer’s disease (AD) is a severe neurodegenerative disorder for which the exact etiology is largely unknown. An increasingly recognized and investigated notion is the pathogenic role of mitochondrial dysfunction in AD. We assessed mitochondrial oxidative-phosphorylation (OXPHOS) enzyme activities in the APPswe/PS1ΔE9 mouse model from 4.5 to 14 months of age. We show an age-dependent decrease in mitochondrial complex-II activity starting at 9 months in APP/PS1 mice. Other enzymes of the OXPHOS do not show any alterations. Since amyloid-β (Aβ) plaques are already present from 4 months of age, mitochondrial dysfunction likely occurs downstream of Aβ pathology in this mouse model.

Keywords

Alzheimer’s disease amyloid beta-peptides electron transport complex II electron transport complex IV mice mitochondria

INTRODUCTION

Alzheimer’s disease (AD), the most common form of dementia, is characterized by cognitive decline, brain atrophy, and amyloid-β (Aβ) plaques [1]. There are several hypotheses on the etiology of AD of which the amyloid cascade hypothesis is one of the most investigated. Based on this theory, several different transgenic animal models have been created to study AD, including the double transgenic APPswe/PS1ΔE9 (APP/PS1) mouse model [2]. Animals with these mutations show amyloid deposits in the brain starting from 4 months of age [3] but cognitive impairments only from 8–10 months of age [4 –9]. However, the amyloid cascade hypothesis does not fully explain the pathobiology of AD and treatments targeting Aβ seem to be unsuccessful thus far [10, 11].

Besides the amyloid cascade hypothesis, other theories include the vascular, inflammatory, and neuroenergetic hypotheses [12 –14]. Furthermore, an increasing body of evidence points to the pathogenic significance of mitochondria in AD etiology [15, 16]. Several studies show that mitochondria are altered in AD patients and animal models for AD [16 –18]. Specifically, altered mitochondrial biogenesis, mitochondrial trafficking, oxidative stress, and lower cytochrome c oxidase (COX) activity have been reported in AD and mouse models for AD [16 –20]. Also, it has been shown in different models that Aβ can directly influence the mitochondria [21, 22] and oxidative stress can trigger Aβ production [23].

To our knowledge, thus far, five studies have investigated the mitochondria in APP/PS1 mice [24 –28]. These studies show altered mitochondrial morphology [24], function [25, 26], and expression of proteins involved in mitochondrial function [28]. However, enzyme activities of the oxidative phosphorylation (OXPHOS) system at different ages have not yet been examined. This is important as it could provide information about the possible chain of events; whether Aβ pathology and consequent cognitive decline proceed OXPHOS dysfunctions or vice versa. In the OXPHOS system, the respiratory chain enzymes produce a proton motive force in the mitochondria that drives ATP formation via the ATP synthase complex V [29].

Here, we hypothesized impaired activities of the OXPHOS enzymes in the APP/PS1 mouse model at an early age preceding the presentation of Aβ pathology in the brain. To test our hypothesis, functional biochemical assays for mitochondrial OXPHOS function of hippocampal homogenates were performed at different ages in WT and APP/PS1 mice. We report on decreased mitochondrial complex II activity in APP/PS1 mice from 9 months of age up to 14 months of age.

MATERIALS AND METHODS

Animals

Hippocampal tissue was collected from a total of 57 male APPswe/PS1ΔE9 (APP/PS1) mice and their WT littermates at different ages, namely 4.5, 6.5, 9, 12, and 14 months of age. The sample size with a minimum of n = 5 per group was determined by a power calculation based on a pilot study in aged APP/PS1 mice. Unfortunately, one 12-month-old WT animal died due to unknown reasons; therefore, this group only contained 4 animals. The 14-month-old mice contained 9 animals per genotype.

The APP/PS1 founder mice were originally obtained from John Hopkins University, Baltimore, MD, USA (D. Borchelt and J. Jankowsky, Department of Pathology) [2, 30] and a colony was started at the animal facility at the Radboud university medical center, Nijmegen, The Netherlands. This line was originally maintained on a hybrid background by backcrossing to C3HeJC57BL/6J F1 mice. For the present work, the breeder mice were backcrossed with C57BL/6JOlaHsd for 9–15 generations. Animals were socially housed with a maximum of six mice in Eurostandard type II cages (365×207×140 mm; Techniplast) with ad libitum food (sniff rm/h V1534-000, Bio Services) and water. Room temperature was kept at a constant 21°C with an artificial 12-h light-dark cycle (lights on at 7 a.m.). Biological material was collected in accordance with Dutch federal regulations for animal protection and approved under RU-DEC numbers 2012-248-001 and 2013-117. Researchers were blind to the genotypes and exact age of the animals at all times.

Tissue preparation

Naïve WT and APP/PS1 mice were sacrificed at different ages by cervical dislocation without anesthesia. The brains were rapidly removed, rinsed in PBS, and snap frozen in liquid nitrogen. At 9 months of age, the left hippocampus was freshly dissected, put in ice-cold SEF buffer (0.25 M sucrose, 2 mM EDTA in 10 mM kPi, pH 7.4), and homogenized with a Teflon pestle to determine ATP and phosphocreatine production rates. At the other ages, a crude homogenate of the left hippocampus was made with a glass-glass potter tube in SEF buffer to obtain a homogenate of approximately 5%. Following homogenization, the samples were centrifuged at 600 g for 10 min at 2°C. The supernatant was snap frozen in liquid nitrogen and stored at –80°C for following mitochondrial complex activity measurements.

Mitochondrial complex measurements

Individual complexes of the respiratory chain, succinate: Cytochrome C oxidoreductase (SCC), and citrate synthase (CS) enzyme activities in the 600 g supernatant were measured spectrophotometrically, after three freeze-thaw cycles, on a KoneLab 20XT analyzer (Thermo Scientific) following standard procedures [31]. These enzyme assays are based on previously described methods [32 –36] (see Supplementary Methods). To determine the maximal ATP and phosphocreatine production rate in 9-month-old mice, freshly prepared 600 g supernatant was used according to previously described methods [37]. As CS activity is a marker for the number of mitochondria, all measurements were normalized to CS activity [35]. Unfortunately, due to logistic difficulties in measuring mice of such different ages, we could not assess the effect of aging on mitochondrial function.

Statistics

For statistical analysis IBM SPSS 22 was used. To determine differences in enzyme complex activity at the different ages, one-tailed independent-samples t-test was used. A one-tailed test was used because from a pilot study and literature we expected the APP/PS1 animals to have a lower enzyme complex activity in comparison to WT animals. To control for multiple comparisons, the p values were tested by the Benjamini-Hochberg procedure with a critical value for false discovery of 0.10 [38]. All data were normalized to the WT at the corresponding age and presented as mean±standard error of the mean.

RESULTS

Our comprehensive analysis of individual mitochondrial complex activities of APP/PS1 mice and WT littermates at different ages revealed significantly lower mitochondrial complex II (CII) activity in APP/PS1 mice from 9 months of age compared to WT animals (Fig. 1). In comparison to the WT animals, APP/PS1 mice showed at 9 months a relative CII activity of 0.91 (t(8) = –3.78; p < 0.01), at 12 months of 0.95 (t(7) = –1.96; p < 0.05), and at 14 months an activity of 0.89 (t(16) = –2.26; p < 0.05). In animals younger than 9 months, we did not observe any difference. The other enzymatic activities (complex I, complex III, complex IV, and SCC) did not show any difference between genotypes of any ages (Fig. 2A-D). Also, we did not observe any difference in maximal ATP and phosphocreatine (CrP) production rates in 9-month-old APP/PS1 animals in comparison to their WT littermates (Fig. 2E).

Fig. 1

Effect of age and APP/PS1 genotype on mitochondrial complex II (CII) activity. From 9 months of age, the mitochondrial CII activity is lower in APP/PS1 mice compared to WT animals. The graph shows the average±SEM, with each black dot representing the result of individual animals. ^*p < 0.05, ^**p < 0.01. CII, mitochondrial complex II; CS, citrate synthase.

Fig. 2

Effect of age and APP/PS1 genotype on mitochondrial oxidative phosphorylation (OXPHOS) enzyme activities. Mitochondrial CI (A), CIII (B), COX (C), and SCC (D) activities do not show any difference between WT and APP/PS1 mice at any age. Also, maximal ATP and CrP production rates do not show any difference between genotypes at 9 months of age (E). The graphs show the average±SEM, with each individual black dot representing the result of individual animals. CI, mitochondrial complex I; CIII, complex III, COX, cytochrome c oxidase; SCC, succinate: cytochrome c oxidoreductase; CS, citrate synthase; CrP, phosphocreatine.

DISCUSSION

An increasing body of literature implicates impaired mitochondrial function in AD. It has been shown that Aβ can accumulate in the mitochondrial matrix and directly influence mitochondrial structure and function [21, 22], mitochondrial dysfunction and reactive oxygen species can trigger Aβ pathology [23, 39], and mitochondria seem necessary for the toxicity of Aβ [40]. However, how this interaction between Aβ and mitochondria influences disease initiation and progression is still largely unknown. This knowledge would be helpful to better understand AD pathobiology and development of novel treatments. Therefore, we studied mitochondrial function in APP/PS1 mice at different ages to assess the earliest presentation of mitochondrial dysfunction.

We found that APP/PS1 mice presented with decreased mitochondrial complex II activity starting at 9 months of age. No differences in the other complex activities (CI, CIII, COX, SCC) or mitochondrial ATP production were found at any age. This result is in contrast to studies that show a decreased COX activity in AD patients [41 –45], mouse models [26 , 46–50], and in vitro models [51 –54]. This is despite numerous studies showing decreased expression of multiple OXPHOS proteins, including CII, in AD patients [55 –57], mouse models of AD [28 , 59], and in vitro models [54]. One possibility for this discrepancy is the fact that only three of the aforementioned studies investigated CII activity using a functional biochemical assay [26 , 50].

To our knowledge, only one study investigated all OXPHOS enzyme activities in the APP/PS1 mouse model [26]. They show that APP/PS1 mice have an increased CI and a decreased CII, CIII, and COX activity at 9 months of age [26]. In contrast with that study, we only observed a decreased CII activity from 9 months of age. An important difference that could explain the different results is that their animals received daily gavage for 6 months [26], whereas in our study the animals were completely naïve. Gavage is stressful to the animals, and it is known that stress can directly influence mitochondrial function [60 –62]. Also, APP/PS1 mice seem to be more sensitive to stress and increase Aβ production under stress [63, 64].

While most studies show an altered mitochondrial activity in later life, some studies also reported affected mitochondria at an early stage of AD pathogenesis. For example, people with mild cognitive impairment have altered mitochondrial gene expression and functioning [42 , 65]. Also, several mouse studies show mitochondrial alterations from as early as 3 to 6 months of age [24 , 59]. However, none of these studies report on functional assays that could show an altered functioning of the OXPHOS system.

In contrast to our hypothesis, we did not find OXPHOS alterations at an early age in the APP/PS1 mouse model. It has repeatedly been shown by our group and others that Aβ pathology in the hippocampus is present from as early as 4 months of age and cognitive impairments from 8–10 months of age [3 –9]. This indicates that Aβ is influencing mitochondrial CII function. This could lead to cognitive impairments (Fig. 3), albeit other mechanisms could also be implicated in cognitive decline in AD [12 –14]. This notion is in line with the facts that: 1) Aβ accumulation in the mitochondria triggers mitochondrial impairments after 12 but not 8 months of age [50] and 2) Aβ can directly influence mitochondrial structure and function [51 , 67]. This model is however not without limitation. One has to consider that the age of onset of Aβ pathology, decline in cognitive performance, and complex II activity has not been assessed in the same individuals in this study. Therefore, individual variations could influence the sequence of events. However, our extensive experience and extensive literature data on this mouse model, the age of onset of Aβ pathology, and decline in cognitive performance combined with complex II activity data make this model highly plausible.

Fig. 3

Schematic overview showing a proposed sequence of events leading to cognitive impairments as a consequence of mitochondrial CII function. CII, mitochondrial complex II or succinate dehydrogenase.

Another study showed a decreased ATP content in the APP/PS1 mouse model [68] whereas we do not find this. However, it is not uncommon that decreased complex activity does not influence ATP production. For example, the Ndufs4 KO mouse model has a severely impaired CI activity, yet it still has normal ATP production rates [69]. Also, patients with impaired CII function do not always show a decrease in ATP production [37]. On the other hand, a slight decrease of CII could influence other processes. For example, CII is also involved in oxidizing succinate to fumarate in the TCA cycle [70]. A decreased CII activity is associated with an accumulation of succinate and decreased fumarate and malate [71, 72]. This, in turn, influences a myriad of different processes such as gene expression and epigenetics, neurodegeneration, inflammation, tumorigenesis, and pseudohypoxia [72 –77]. Furthermore, in recent years CII is more appreciated as a major source of reactive oxygen species production [75], and it is already known that oxidative stress is a major player in AD [20].

In conclusion, our observation points toward Aβ pathology triggering mitochondrial dysfunction that consequently leads to cognitive impairments in the APP/PS1 mouse model. However, one has to consider that this mouse model inherently produces Aβ, and as mentioned earlier, Aβ formation directly influences mitochondrial function. Thus, this mouse model may not perfectly model AD pathobiology in patients with sporadic AD. Therefore, our data do not exclude the possibility that in patients with sporadic AD, brain pathology may be initiated by the mitochondria triggering Aβ accumulation and initiating the vicious cycle of Aβ and mitochondrial interaction. This notion will have to be investigated in future studies by parallel assessment of Aβ and mitochondrial pathology in postmortem human brain samples of patients with sporadic AD. A limitation of our study is that we analyzed mitochondrial activity in 600 g supernatant. Some studies suggest that synaptic mitochondria are more susceptible to Aβ and non-synaptic mitochondria are only impaired from 12 months of age [78]. In our study, we may have a threshold effect because we did not differentiate between synaptic and non-synaptic mitochondria.

Footnotes

ACKNOWLEDGMENTS

We would like to thank the colleagues at the mitochondrial enzyme lab of the RCMM at the Translational Metabolic Laboratory, Radboud University Medical Center Nijmegen, for excellent technical assistance.

Authors’ disclosures available online ().

The supplementary material is available in the electronic version of this article: .

References

Mattson

(2004) Pathways towards and away from Alzheimer’s disease. Nature 430, 631–639.

Jankowsky

, Fadale

, Anderson

, Xu

, Gonzales

, Jenkins

, Copeland

, Lee

, Younkin

, Wagner

(2003) Mutant presenilins specifically elevate the levels of the 42 residue β-amyloid peptide in vivo: Evidence for augmentation of a 42-specific γ secretase. Hum Mol Genet 13, 159–170.

Garcia-Alloza

, Robbins

, Zhang-Nunes

, Purcell

, Betensky

, Raju

, Prada

, Greenberg

, Bacskai

, Frosch

(2006) Characterization of amyloid deposition in the APPswe/PS1dE9 mouse model of Alzheimer disease. Neurobiol Dis 24, 516–524.

Minkeviciene

, Ihalainen

, Malm

, Matilainen

, Keksa-Goldsteine

, Goldsteins

, Iivonen

, Leguit

, Glennon

, Koistinaho

(2008) Age-related decrease in stimulated glutamate release and vesicular glutamate transporters in APP/PS1 transgenic and wild-type mice. JNeurochem 105, 584–594.

Volianskis

, Køstner

, Mølgaard

, Hass

, Jensen

(2010) Episodic memory deficits are not related to altered glutamatergic synaptic transmission and plasticity in the CA1 hippocampus of the APPswe/PS1 AE9-deleted trans-genic mice model of β-amyloidosis. Neurobiol Aging 31, 1173–1187.

Hooijmans

, Van der Zee

, Dederen

, Brouwer

, Rei-jmer

, Van Groen

, Broersen

, Lütjohann

, Heerschap

, Kiliaan

(2009) DHA and cholesterol containing diets influence Alzheimer-like pathology, cognition and cerebral vasculature in APPswe/PS1dE9 mice. Neurobiol Dis 33, 4 482–498.

Savonenko

, Xu

, Melnikova

, Morton

, Gonzales

, Wong

, Price

, Tang

, Markowska

, Borchelt

(2005) Episodic-like memory deficits in the APPswe/PS1dE9 mouse model of Alzheimer’s disease: Relationships to β-amyloid deposition and neurotransmitter abnormalities. Neurobiol Dis 18, 602–617.

Webster

, Bachstetter

, Van Eldik

(2013) Comprehensive behavioral characterization of an APP/PS-1 double knock-in mouse model of Alzheimer’s disease. Alzheimers Res Ther 5, 28.

Puolivali

, Wang

, Heikkinen

, Heikkila

, Tapiola

, van Groen

, Tanila

(2002) Hippocampal Aβ42 levels correlate with spatial memory deficit in APP and PS1 double transgenic mice. Neurobiol Dis 9, 339–347.

10.

Pimplikar

(2009) Reassessing the amyloid cascade hypothesis of Alzheimer’s disease. Int J Biochem Cell Biol 41, 1261–1268.

11.

Rosenblum

(2014) Why Alzheimer trials fail: Removing soluble oligomeric beta amyloid is essential, inconsistent, and difficult. Neurobiol Aging 35, 969–974.

12.

Blonz

(2017) Alzheimer’s disease as the product of a progressive energy deficiency syndrome in the central nervous system: The neuroenergetic hypothesis. J Alzheimers Dis 60, 1223–1229.

13.

McGeer

, McGeer

(2013) The amyloid cascade-inflammatory hypothesis of Alzheimer disease: Implications for therapy. Acta Neuropathol 126, 479–497.

14.

de la Torre

(2004) Is Alzheimer’s disease a neurodegenerative or a vascular disorder? Data, dogma, and dialectics. Lancet Neurol 3, 184–190.

15.

Swerdlow

, Khan

(2004) A “mitochondrial cascade hypothesis” for sporadic Alzheimer’s disease. Med Hypotheses 63, 8–20.

16.

Selfridge

, Lezi

, Lu

, Swerdlow

(2013) Role of mitochondrial homeostasis and dynamics in Alzheimer’s disease. Neurobiol Dis 51, 3–12.

17.

Zhu

, Perry

, Smith

, Wang

(2013) Abnormal mitochondrial dynamics in the pathogenesis of Alzheimer’s disease. J Alzheimers Dis 33, S253–S262.

18.

Swerdlow

(2012) Mitochondria and cell bioenergetics: Increasingly recognized components and a possible etio-logic cause of Alzheimer’s disease. Antioxid Redox Signal 16, 1434–1455.

19.

Zhang

, Trushin

, Christensen

, Tripathi

, Hong

, Geroux

, Howell

, Poduslo

, Trushina

(2018) Differential effect of amyloid beta peptides on mitochondrial axonal trafficking depends on their state of aggregation and binding to the plasma membrane. Neurobiol Dis 114, 1–16.

20.

Tonnies

, Trushina

(2017) Oxidative stress, synaptic dysfunction, and Alzheimer’s disease. J Alzheimers Dis 57, 1105–1121.

21.

Chen

, Yan

(2007) Amyloid-β-induced mitochondrial dysfunction. J Alzheimers Dis 12, 177–184.

22.

Kim

, Lee

, Oh

, Kim

, Han

(2017) Relationship between β-amyloid and mitochondrial dynamics. Cell Mol Neurobiol 37, 955–968.

23.

Recuero

, Munoz

, Aldudo

, Subias

, Bullido

, Valdivieso

(2010) A free radical-generating system regulates APP metabolism/processing. FEBS Lett 584, 4611–4618.

24.

L-L

, Shen

, Wang

, Wei

L-F

, Wang

, Yang

, Wang

C-F

, Xie

Z-H

, Bi

J-Z

(2017) Mitochondrial dynamics changes with age in an APPsw/PS1dE9 mouse model of Alzheimer’s disease. Neuroreport 28, 222–228.

25.

Dixit

, Fessel

, Harrison

(2017) Mitochondrial dysfunction in the APP/PSEN1 mouse model of Alzheimer’s disease and a novel protective role for ascorbate. Free Radic Biol Med 112, 515–523.

26.

Peng

, Hou

, Yang

, Li

, Jia

, Liu

, Tang

, Shi

, Li

, Long

(2016) Hydroxytyrosol mildly improve cognitive function independent of APP processing in APP/PS1 mice. Mol Nutr Food Res 60, 2331–2342.

27.

Andersen

, Christensen

, Aldana

, Nissen

, Tanila

, Waagepetersen

(2017) Alterations in cerebral cortical glucose and glutamine metabolism precedes amyloid plaques in the APPswe/PSEN1dE9 mouse model of Alzheimer’s disease. Neurochem Res 42, 1589–1598.

28.

Pedros

, Petrov

, Allgaier

, Sureda

, Barroso

, Beas-Zarate

, Auladell

, Pallas

, Vazquez-Carrera

, Casadesu

(2014) Early alterations in energy metabolism in the hippocampus of APPswe/PS1dE9 mouse model of Alzheimer’s disease. Biochim Biophys Acta 1842, 1556–1566.

29.

Hatefi

(1985) The mitochondrial electron transport and oxidative phosphorylation system. Annu Rev Biochem 54, 1015–1069.

30.

Jankowsky

, Slunt

, Ratovitski

, Jenkins

, Copeland

, Borchelt

(2001) Co-expression of multiple transgenes in mouse CNS: A comparison of strategies. BiomolEng 17, 157–165.

31.

Rodenburg

(2011) Biochemical diagnosis of mitochondrial disorders. J Inherit Metab Dis 34, 283–292.

32.

Cooperstein

, Lazarow

(1951) A microspectrophotomet-ric method for the determination of cytochrome oxidase. J Biol Chem 189, 665–670.

33.

Janssen

, Trijbels

, Sengers

, Smeitink

, Van den Heuvel

, Wintjes

, Stoltenborg-Hogenkamp

, Rodenburg

(2007) Spectrophotometric assay for complex I of the respiratory chain in tissue samples and cultured fibroblasts. Clin Chem 53, 729–734.

34.

Mourmans

, Wendel

, Bentlage

, Trijbels

, Smeitink

, De Coo

, Gabreels

, Sengers

, Ruitenbeek

(1997) Clinical heterogeneity in respiratory chain complex III deficiency in childhood. J Neurol Sci 149, 111–117.

35.

Srere

(1969) Citrate synthase:[EC 4.1. 3.7. Citrate oxaloacetate-lyase (CoA-acetylating)]. Methods Enzymol 13, 3–11.

36.

Fischer

, Ruitenbeek

, Berden

, Trijbels

, Veerkamp

, Stadhouders

, Sengers

, Janssen

(1985) Differential investigation of the capacity of succinate oxidation in human skeletal muscle. Clin Chim Acta 153, 23–36.

37.

Janssen

, Trijbels

, Sengers

, Wintjes

, Ruitenbeek

, Smeitink

, Morava

, van Engelen

, van den Heuvel

, Rodenburg

(2006) Measurement of the energy-generating capacity of human muscle mitochondria: Diagnostic procedure and application to human pathology. Clin Chem 52, 860–871.

38.

Benjamini

, Hochberg

(1995) Controlling the false discovery rate: A practical and powerful approach to multiple testing. J R Stat Soc Series B Stat Methodol, 289–300.

39.

Leuner

, Schutt

, Kurz

, Eckert

, Schiller

, Occhip-inti

, Mai

, Jendrach

, Eckert

, Kruse

(2012) Mitochondrion-derived reactive oxygen species lead to enhanced amyloid beta formation. Antioxid Redox Signal 16, 1421–1433.

40.

Cardoso

, Santos

, Swerdlow

, Oliveira

(2001) Functional mitochondria are required for amyloid β-mediated neurotoxicity. FASEB J15, 1439–1441.

41.

Fisar

, Hroudova

, Hansikova

, Lelkova

, Wenchich

, Jirak

, Zeman

, Martasek

, Raboch

(2016) Mitochondrial respiration in the platelets of patients with Alzheimer’s disease. Curr Alzheimer Res 13, 930–941.

42.

Valla

, Schneider

, Niedzielko

, Coon

, Caselli

, Sabbagh

, Ahern

, Baxter

, Alexander

, Walker

(2006) Impaired platelet mitochondrial activity in Alzheimer’s disease and mild cognitive impairment. Mitochondrion 6, 323–330.

43.

Valla

, Berndt

, Gonzalez-Lima

(2001) Energy hypo-metabolism in posterior cingulate cortex of Alzheimer’s patients: Superficial laminar cytochrome oxidase associated with disease duration. J Neurosci 21, 4923–4930.

44.

Bosetti

, Brizzi

, Barogi

, Mancuso

, Siciliano

, Tendi

, Murri

, Rapoport

, Solaini

(2002) Cytochrome c oxidase and mitochondrial F1F0-ATPase (ATP syn-thase) activities in platelets and brain from patients with Alzheimer’s disease. Neurobiol Aging 23, 371–376.

45.

Maurer

, Zierz

, Moller

(2000) A selective defect of cytochrome c oxidase is present in brain of Alzheimer disease patients. Neurobiol Aging 21, 455–462.

46.

Hauptmann

, Scherping

, Drose

, Brandt

, Schulz

, Jendrach

, Leuner

, Eckert

, Müller

(2009) Mitochondrial dysfunction: An early event in Alzheimer pathology accumulates with age in AD transgenic mice. Neurobiol Aging 30, 1574–1586.

47.

Rhein

, Song

, Wiesner

, Ittner

, Baysang

, Meier

, Ozmen

, Bluethmann

, Drose

, Brandt

(2009) Amyloid-β and tau synergistically impair the oxidative phosphorylation system in triple transgenic Alzheimer’s disease mice. Proc Natl Acad Sci USA 106, 20057–20062.

48.

Yao

, Irwin

, Zhao

, Nilsen

, Hamilton

, Brinton

(2009) Mitochondrial bioenergetic deficit precedes Alzheimer’s pathology in female mouse model of Alzheimer’s disease. Proc Natl Acad Sci USA 106, 14670–14675.

49.

Rönnback

, Pavlov

, Mansory

, Gonze

, Marliere

, Winblad

, Graff

, Behbahani

(2016) Mitochondrial dysfunction in a transgenic mouse model expressing human amyloid precursor protein (APP) with the Arctic mutation. J Neurochem 136, 497–502.

50.

Caspersen

, Wang

, Yao

, Sosunov

, Chen

, Lustbader

, Xu

, Stern

, McKhann

, Yan

(2005) Mitochondrial Aβ: A potential focal point for neuronal metabolic dysfunction in Alzheimer’s disease. FASEB J19, 2040–2041.

51.

Casley

, Canevari

, Land

, Clark

, Sharpe

(2002) β-Amyloid inhibits integrated mitochondrial respiration and key enzyme activities. J Neurochem 80, 91–100.

52.

Anandatheerthavarada

, Biswas

, Robin

M-A

, Avad-hani

(2003) Mitochondrial targeting and a novel transmembrane arrest of Alzheimer’s amyloid precursor protein impairs mitochondrial function in neuronal cells. J Cell Biol 161,41–54.

53.

Sheehan

, Swerdlow

, Miller

, Davis

, Parks

, Parker

, Tuttle

(1997) Calcium homeostasis and reactive oxygen species production in cells transformed by mitochondria from individuals with sporadic Alzheimer’s disease. J Neurosci 17, 4612–4622.

54.

Chua

L-M

, Lim

M-L

, Wong

B-S

(2013) The Kunitz-protease inhibitor domain in amyloid precursor protein reduces cellular mitochondrial enzymes expression and function. Biochem Biophys Res Commun 437, 642–647.

55.

Liang

, Reiman

, Valla

, Dunckley

, Beach

, Grover

, Niedzielko

, Schneider

, Mastroeni

, Caselli

(2008) Alzheimer’s disease is associated with reduced expression of energy metabolism genes in posterior cingulate neurons. Proc Natl Acad Sci USA 105, 4441–4446.

56.

Lunnon

, Ibrahim

, Proitsi

, Lourdusamy

, New-house

, Sattlecker

, Furney

, Saleem

, Soininen

, Køszewska

(2012) Mitochondrial dysfunction and immune activation are detectable in early Alzheimer’s disease blood. J Alzheimers Dis 30, 685–710.

57.

Kim

, Vlkolinsky

, Cairns

, Lubec

(2000) Decreased levels of complex III core protein 1 and complex V β chain in brains from patients with Alzheimer’s disease and Down syndrome. Cell Mol Life Sci 57, 1810–1816.

58.

Fattoretti

, Balietti

, Casoli

, Giorgetti

, Di Stefano

, Bertoni-Freddari

, Lattanzio

, Sensi

(2010) Decreased numeric density of succinic dehydrogenase-positive mitochondria in CA1 pyramidal neurons of 3xTg-AD mice. Rejuvenation Res 13, 144–147.

59.

Wang

, Yin

, Ma

, Zhao

, Siedlak

, Wang

, Torres

, Fujioka

, Xu

, Perry

(2017) Inhibition of mitochondrial fragmentation protects against Alzheimer’s disease in rodent model. Hum Mol Genet 26, 4118–4131.

60.

Gong

, Chai

, Ding

J-H

, Sun

X-L

, Hu

(2011) Chronic mild stress damages mitochondrial ultrastructure and function in mouse brain. Neurosci Lett 488, 76–80.

61.

Rezin

, Cardoso

, Gonçalves

, Scaini

, Fraga

, Riegel

, Comim

, Quevedo

, Streck

(2008) Inhibition of mitochondrial respiratory chain in brain of rats subjected to an experimental model of depression. Neurochem Int 53, 395–400.

62.

Madrigal

JLM

, Olivenza

, Moro

, Lizasoain

, Lorenzo

, Rodrigo

, Leza

(2001) Glutathione depletion, lipid peroxidation and mitochondrial dysfunction are induced by chronic stress in rat brain. Neuropsychopharmacology 24, 420–429.

63.

Han

, Yu

, Geng

, Shen

, Wang

(2016) Chronic stress aggravates cognitive impairment and suppresses insulin associated signaling pathway in APP/PS1 Mice. J Alzheimers Dis 53, 1539–1552.

64.

Han

, Wang

J-H

, Geng

, Shen

, Wang

H-L

, Wang

Y-Y,

Wang

M-W

(2017) Chronic stress contributes to cognitive dysfunction and hippocampal metabolic abnormalities in APP/PS1 Mice. Cell Physiol Biochem 41, 1766–1776.

65.

Lunnon

, Keohane

, Pidsley

, Newhouse

, Riddoch-Contreras

, Thubron

, Devall

, Soininen

, Køszewska

, Mecocci

(2017) Mitochondrial genes are altered in blood early in Alzheimer’s disease. Neurobiol Aging 53, 36–47.

66.

Devi

, Prabhu

, Galati

, Avadhani

, Anan-datheerthavarada

(2006) Accumulation of amyloid precursor protein in the mitochondrial import channels of human Alzheimer’s disease brain is associated with mitochondrial dysfunction. J Neurosci 26, 9057–9068.

67.

Xie

, Guan

, Borrelli

, Xu

, Serrano-Pozo

, Bacskai

(2013) Mitochondrial alterations near amyloid plaques in an Alzheimer’s disease mouse model. J Neurosci 33,17042–17051.

68.

Zhang

, Rissman

, Feng

(2015) Characterization of ATP alternations in an Alzheimer’s disease transgenic mouse model. J Alzheimers Dis 44, 375–378.

69.

Kruse

, Watt

, Marcinek

, Kapur

, Schenkman

, Palmiter

(2008) Mice with mitochondrial complex I deficiency develop a fatal encephalomyopathy. Cell Metab 7,312–320.

70.

Cecchini

(2003) Function and structure of complex II of the respiratory chain. Annu Rev Biochem 72, 77–109.

71.

Smith

, Janknecht

, Maher III

(2007) Succinate inhibition of a-ketoglutarate-dependent enzymes in a yeast model of paraganglioma. Hum Mol Genet 16, 3136–3148.

72.

Tretter

, Patocs

, Chinopoulos

(2016) Succinate, an intermediate in metabolism, signal transduction, ROS, hypoxia, and tumorigenesis. Biochim Biophys Acta 1857, 1086–1101.

73.

Salminen

, Haapasalo

, Kauppinen

, Kaarniranta

, Soininen

, Hiltunen

(2015) Impaired mitochondrial energy metabolism in Alzheimer’s disease: Impact on pathogenesis via disturbed epigenetic regulation of chro-matin landscape. Prog Neurobiol 131, 1–20.

74.

Benit

, Letouze

, Rak

, Aubry

, Burnichon

, Favier

, Gimenez-Roqueplo

A-P

, Rustin

(2014) Unsuspected task for an old team: Succinate, fumarate and other Krebs cycle acids in metabolic remodeling. Biochim Biophys Acta 1837, 1330–1337.

75.

Bezawork-Geleta

, Rohlena

, Dong

, Pacak

, Neuzil

(2017) Mitochondrial complex II: At the crossroads. Trends Biochem Sci 42, 312–325.

76.

Rutter

, Winge

, Schiffman

(2010) Succinate dehydrogenase—assembly, regulation and role in human disease. Mitochondrion 10, 393–401.

77.

Vicha

, Taieb

, Pacak

(2014) Current views on cell metabolism in SDHx-related pheochromocytoma and para-ganglioma. Endocr Relat Cancer 21, R261–R277.

78.

, Guo

, Yan

, Sosunov

, McKhann

, Yan

(2010) Early deficits in synaptic mitochondria in an Alzheimer’s disease mouse model. Proc Natl Acad Sci U SA 107, 18670–18675.