Preliminary observations of mitochondrial dysfunction in Prader-Willi syndrome

Abstract

Prader-Willi syndrome (PWS) is a complex multisystem disorder because of errors in genomic imprinting with severe hypotonia, decreased muscle mass, poor suckling, feeding problems and failure to thrive during infancy, growth and other hormone deficiency, childhood-onset hyperphagia, and subsequent obesity. Decreased energy expenditure in PWS is thought to contribute to reduced muscle mass and physical activity but may also relate to cellular metabolism and disturbances in mitochondrial function. We established fibroblast cell lines from six children and adults with PWS and six healthy controls for mitochondrial assays. We used Agilent Seahorse XF extracellular flux technology to determine real-time measurements of several metabolic parameters including cellular substrate utilization, Adenosine Triphosphate (ATP)-linked respiration, and mitochondrial capacity in living cells. Decreased mitochondrial function was observed in the PWS patients compared to the healthy controls with significant differences in basal respiration, maximal respiratory capacity, and ATP-linked respiration. These results suggest disturbed mitochondrial bioenergetics in PWS although the low number of studied subjects will require a larger subject population before a general consensus can be reached to identify if mitochondrial dysfunction is a contributing factor in PWS.

Keywords: Prader-Willi syndrome; fibroblasts; healthy controls; mitochondrial assays and dysfunction.

Figure 1.

1A Schematic diagram of Agilent Seahorse XF extra-cellular flux technology and mitochondrial function components and profiles modified from Agilent website (www.agilent.com/en/products/cell-analysis-(seahorse)/mitochondrial-respiration-xf-cell-mito-stress-test). 1B Comparison of stages of mitochondrial function and cellular respiration with time using fibroblasts from Prader-Willi syndrome and control subjects with error bars and significant differences (t test; p<0.05) noted (*) for basal respiration, ATP-linked respiration/proton leak and maximal respiratory capacity with decreased values for Prader-Willi syndrome.

Figure 2.

Comparison of mitochondrial function and cellular respiration in fibroblasts from Prader-Willi syndrome and control subjects with error bars showing individual parameters for basal respiration, proton leak, maximal respiratory capacity, spare reserve capacity, non-mitochondrial respiration and ATP-linked respiration or coupled respiration. Significant differences (t test; p<0.05) are noted (*) with decreased values in subjects with Prader- Willi syndrome for five of six parameters.

Figure 3.

Comparison of Prader-Willi syndrome genetic subtypes with p values generated using t tests indicated above the vertical bars.

Figure 4.

Comparison of mitochondrial function and cellular respiration in fibroblasts from Prader-Willi syndrome (PWS) and control subjects with error bars showing individual parameters for basal respiration, proton leak, maximal respiratory capacity, spare reserve capacity, non-mitochondrial respiration and ATP-linked respiration or coupled respiration. 4A Comparison of control and PWS subjects; 4B Comparison of age and gender matched adult subjects and 4C Comparison of age and gender matched children. Significant differences (t test; p<0.05) are noted (*) with decreased mitochondrial measures in subjects with Prader-Willi syndrome.