title: Pre-diabetes alters testicular PGC1-α/SIRT3 axis modulating mitochondrial bioenergetics and oxidative stress.
abstract: Pre-diabetes, a risk factor for type 2 diabetes development, leads to metabolic changes at testicular level. Peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α) and Sirtuin 3 (Sirt3) are pivotal in mitochondrial function. We hypothesized that pre-diabetes disrupts testicular PGC-1α/Sirt3 axis, compromising testicular mitochondrial function. Using a high-energy-diet induced pre-diabetic rat model, we evaluated testicular levels of PGC-1α and its downstream targets, nuclear respiratory factors 1 (NRF-1) and 2 (NRF-2), mitochondrial transcription factor A (TFAM) and Sirt3. We also assessed mitochondrial DNA (mtDNA) content, mitochondrial function, energy levels and oxidative stress parameters. Protein levels were quantified by Western Blot, mtDNA content was determined by qPCR. Mitochondrial complex activity and oxidative stress parameters were spectrophotometrically evaluated. Adenine nucleotide levels, adenosine and its metabolites (inosine and hypoxanthine) were determined by reverse-phase HPLC. Pre-diabetic rats showed increased blood glucose levels and impaired glucose tolerance. Both testicular PGC-1α and Sirt3 levels were decreased. NRF-1, NRF-2 and TFAM were not altered. Testicular mtDNA content was decreased. Mitochondrial complex I activity was increased, whereas mitochondrial complex III activity was decreased. Adenylate energy charge was decreased in pre-diabetic rats, as were ATP and ADP levels. Conversely, AMP levels were increased, evidencing a decreased ATP/AMP ratio. Concerning to oxidative stress pre-diabetes decreased testicular antioxidant capacity and increased lipid and protein oxidation. In sum, pre-diabetes compromises testicular mitochondrial function by repressing PGC-1α/Sirt3 axis and mtDNA copy number, declining respiratory capacity and increasing oxidative stress. This study gives new insights into overall testicular bioenergetics at this prodromal stage of disease.
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6201-506 Covilhã, Portugal; CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Rato
authors.affiliation: CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal; Institute for Interdisciplinary Research (IIIUC), University of Coimbra, 3030-789 Coimbra, Portugal.
authors.forename: Ana I
authors.initials: AI
authors.lastname: Duarte
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6201-506 Covilhã, Portugal.
authors.forename: Gonçalo D
authors.initials: GD
authors.lastname: Tomás
authors.affiliation: CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal; Life Sciences Department, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal.
authors.forename: Maria S
authors.initials: MS
authors.lastname: Santos
authors.affiliation: CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal; Laboratory of Physiology, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal.
authors.forename: Paula I
authors.initials: PI
authors.lastname: Moreira
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6201-506 Covilhã, Portugal.
authors.forename: Sílvia
authors.initials: S
authors.lastname: Socorro
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6201-506 Covilhã, Portugal.
authors.forename: José E
authors.initials: JE
authors.lastname: Cavaco
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6201-506 Covilhã, Portugal.
authors.forename: Marco G
authors.initials: MG
authors.lastname: Alves
authors.affiliation: CICS-UBI-Health Sciences Research Centre, University of Beira Interior, 6201-506 Covilhã, Portugal. Electronic address: pfobox@gmail.com.
authors.forename: Pedro F
authors.initials: PF
authors.lastname: Oliveira
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D042967:Electron Transport Complex I / Q000378:metabolism; D014450:Electron Transport Complex III / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D051268:GA-Binding Protein Transcription Factor / Q000378:metabolism; D007328:Insulin / Q000097:blood; D008297:Male; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D051266:Nuclear Respiratory Factor 1 / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology*; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D016133:Polymerase Chain Reaction; D011236:Prediabetic State / Q000097:blood / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D056566:Sirtuin 3 / Q000378:metabolism*; D013737:Testis / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D004272:DNA, Mitochondrial; D051268:GA-Binding Protein Transcription Factor; D007328:Insulin; D051266:Nuclear Respiratory Factor 1; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; C501429:Ppargc1a protein, rat; C489030:Tfam protein, rat; D014157:Transcription Factors; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D056566:Sirtuin 3; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III
keywords: High-energy diet; Mitochondria; PGC-1α/Sirt3 axis; Pre-diabetes; Testicular bioenergetics