Cellular Bioenergetics and AMPK and TORC1 Signalling in Blood Lymphoblasts Are Biomarkers of Clinical Status in FMR1 Premutation Carriers

Danuta Z Loesch; Bruce E Kemp; Minh Q Bui; Paul R Fisher; Claire Y Allan; Oana Sanislav; Kevin R W Ngoei; Anna Atkinson; Flora Tassone; Sarah J Annesley; Elsdon Storey

doi:10.3389/fpsyt.2021.747268

Cellular Bioenergetics and AMPK and TORC1 Signalling in Blood Lymphoblasts Are Biomarkers of Clinical Status in FMR1 Premutation Carriers

Front Psychiatry. 2021 Nov 22:12:747268. doi: 10.3389/fpsyt.2021.747268. eCollection 2021.

Authors

Danuta Z Loesch¹, Bruce E Kemp^{2

3}, Minh Q Bui⁴, Paul R Fisher⁵, Claire Y Allan⁵, Oana Sanislav⁵, Kevin R W Ngoei³, Anna Atkinson¹, Flora Tassone^{6

7}, Sarah J Annesley⁵, Elsdon Storey⁸

Affiliations

¹ School of Psychology and Public Health, La Trobe University, Bundoora, VA, Australia.
² Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, VA, Australia.
³ St. Vincent's Institute of Medical Research and Department of Medicine, University of Melbourne, Fitzroy, VA, Australia.
⁴ Centre for Molecular, Environmental, Genetic and Analytic, Epidemiology, University of Melbourne, Parkville, VA, Australia.
⁵ Department of Physiology Anatomy and Microbiology, La Trobe University, Bundoora, VA, Australia.
⁶ Department of Biochemistry and Molecular Medicine, School of Medicine, University of California, Davis, Sacramento, CA, United States.
⁷ Department of Biochemistry and Molecular Medicine M.I.N.D. Institute, University of California Davis Medical Center, Davis, Sacramento, CA, United States.
⁸ Department of Medicine (Neuroscience), Monash University, Alfred Hospital Campus, Melbourne, VIC, Australia.

Abstract

Fragile X Associated Tremor/Ataxia Syndrome (FXTAS) is a neurodegenerative disorder affecting carriers of premutation alleles (PM) of the X-linked FMR1 gene, which contain CGG repeat expansions of 55-200 range in a non-coding region. This late-onset disorder is characterised by the presence of tremor/ataxia and cognitive decline, associated with the white matter lesions throughout the brain, especially involving the middle cerebellar peduncles. Nearly half of older male and ~ 20% of female PM carriers develop FXTAS. While there is evidence for mitochondrial dysfunction in neural and some peripheral tissues from FXTAS patients (though less obvious in the non-FXTAS PM carriers), the results from peripheral blood mononuclear cells (PBMC) are still controversial. Motor, cognitive, and neuropsychiatric impairments were correlated with measures of mitochondrial and non-mitochondrial respiratory activity, AMPK, and TORC1 cellular stress-sensing protein kinases, and CGG repeat size, in a sample of adult FXTAS male and female carriers. Moreover, the levels of these cellular measures, all derived from Epstein- Barr virus (EBV)- transformed and easily accessible blood lymphoblasts, were compared between the FXTAS (N = 23) and non-FXTAS (n = 30) subgroups, and with baseline data from 33 healthy non-carriers. A significant hyperactivity of cellular bioenergetics components as compared with the baseline data, more marked in the non-FXTAS PMs, was negatively correlated with repeat numbers at the lower end of the CGG-PM distribution. Significant associations of these components with motor impairment measures, including tremor-ataxia and parkinsonism, and neuropsychiatric changes, were prevalent in the FXTAS subgroup. Moreover, a striking elevation of AMPK activity, and a decrease in TORC1 levels, especially in the non-FXTAS carriers, were related to the size of CGG expansion. The bioenergetics changes in blood lymphoblasts are biomarkers of the clinical status of FMR1 carriers. The relationship between these changes and neurological involvement in the affected carriers suggests that brain bioenergetic alterations are reflected in this peripheral tissue. A possible neuroprotective role of stress sensing kinase, AMPK, in PM carriers, should be addressed in future longitudinal studies. A decreased level of TORC1-the mechanistic target of the rapamycin complex, suggests a possible future approach to therapy in FXTAS.

Keywords: AMPK; FMR1 premutation; Fragile X-associated tremor/ataxia syndrome (FXTAS); SCL-90 scale; TORC1; cognitive measures; lymphoblasts' bioenergetics measures; motor scores.