Mitochondrial Metabolism in a Large-Animal Model of Huntington Disease: The Hunt for Biomarkers in the Spermatozoa of Presymptomatic Minipigs

Abstract

Background: Huntington disease (HD) is a fatal neurodegenerative disorder involving reduced muscle coordination, mental and behavioral changes, and testicular degeneration. In order to further clarify the decreased fertility and penetration ability of the spermatozoa of transgenic HD minipig boars (TgHD), we applied a set of mitochondrial metabolism (MM) parameter measurements to this promising biological material, which can be collected noninvasively in longitudinal studies. Objective: We aimed to optimize methods for MM measurements in spermatozoa and to establish possible biomarkers of HD in TgHD spermatozoa expressing the N-terminal part of mutated human huntingtin. Methods: Semen samples from 12 TgHD and wild-type animals, aged 12-65 months, were obtained repeatedly during the study. Respiration was measured by polarography, MM was assessed by the detection of oxidation of radiolabeled substrates (mitochondrial energy-generating system; MEGS), and the content of the oxidative phosphorylation system subunits was detected by Western blot. Three possibly interfering factors were statistically analyzed: the effect of HD, generation and aging. Results: We found 5 MM parameters which were significantly diminished in TgHD spermatozoa and propose 3 specific MEGS incubations and complex I-dependent respiration as potential biomarkers of HD in TgHD spermatozoa. Conclusions: Our results suggest a link between the gain of toxic function of mutated huntingtin in TgHD spermatozoa and the observed MM and/or glycolytic impairment. We determined 4 biomarkers useful for HD phenotyping and experimental therapy monitoring studies in TgHD minipigs.

A transgenic minipig model of Huntington's disease shows early signs of behavioral and molecular pathologies

“…The neurological phenotype in the TgHD model emerges subsequent to the reduced sperm count and motility ( Macakova et al, 2016 ) in concordance with significantly diminished mitochondrial parameters ( Krizova et al, 2017 ) and muscle ultrastructural alterations (M.R. and H.H., unpublished).…”

Large Animal Models of Huntington’s Disease: What We Have Learned and Where We Need to Go Next

“…The HD phenotype in this model progresses gradually with age compared to age-matched WT minipigs. A severe reproductive phenotype precedes the gradual neurodegeneration, and is detected around the age of 13 months [ 44 ] with low count, reduced motility, low mitochondrial energy-generating system and respiratory parameters in TgHD (N548) boars’ spermatozoa [ 47 ] and decreased phosphodiesterase (PDE) concentration (24 months) in testicular parenchyma [ 48 ]. The neurodegenerative phenotype starts gradually with reduction of DARPP-32, an integrator of neurotransmission, at 16 months in the neostriatum [ 43 ] and remains downregulated until at least the age of 70 months [ 45 ].…”

Transgenic minipig model of Huntington's disease exhibiting gradually progressing neurodegeneration

“…Pigs from subsequent generations express human mHTT in all tissues, with the highest levels being detected in the brain and testes (Macakova et al, 2016;Vidinská et al, 2018). Previously, sperm and testicular degeneration, impairments of mitochondrial metabolism and glycolysis, a reduction of DARPP32 (dopamine-regulated neuronal phosphoprotein) and the presence of other markers of neurological phenotype progression were demonstrated (Askeland et al, 2018;Krizova et al, 2017;Macakova et al, 2016;Vidinská et al, 2018). The TgHD minipig model was proven to be useful in preclinical testing of human HTT-lowering gene therapy, showing widespread vector distribution and considerable HTT lowering (Evers et al, 2018).…”