Mitochondrial reprogramming in peripheral blood mononuclear cells of patients with glycogen storage disease type Ia

Abstract

Background: Glycogen storage disease type Ia (GSDIa) is an inborn metabolic disorder caused by the deficiency of glucose-6-phospatase-α (G6Pase-α) leading to mitochondrial dysfunction. It remains unclear whether mitochondrial dysfunction is present in patients' peripheral blood mononuclear cells (PBMC) and whether dietary treatment can play a role. The aim of this study was to investigate mitochondrial function in PBMC of GSDIa patients.

Methods: Ten GSDIa patients and 10 age-, sex- and fasting-time matched controls were enrolled. Expression of genes involved in mitochondrial function and activity of key fatty acid oxidation (FAO) and Krebs cycle proteins were assessed in PBMC. Targeted metabolomics and assessment of metabolic control markers were also performed.

Results: Adult GSDIa patients showed increased CPT1A, SDHB, TFAM, mTOR expression (p < 0.05) and increased VLCAD, CPT2 and citrate synthase activity in PBMC (p < 0.05). VLCAD activity directly correlated with WC (p < 0.01), BMI (p < 0.05), serum malonycarnitine levels (p < 0.05). CPT2 activity directly correlated with BMI (p < 0.05).

Conclusion: Mitochondrial reprogramming is detectable in PBMC of GSDIa patients. This feature may develop as an adaptation to the liver enzyme defect and may be triggered by dietary (over)treatment in the frame of G6Pase-α deficiency. PBMC can represent an adequate mean to assess (diet-induced) metabolic disturbances in GSDIa.

Keywords: Biomarker; CPT1; Diet; Fatty acid oxidation; Glycogen storage disease; Monitoring.

Fig. 1

Serum acylcarnitines (A-D) and urine organic acids (E–H) in GSDIa patients and control groups. For all metabolites mean value is shown for each group of participants. C1: controls who had blood collection after the same fasting time as their matched patients (adults: n = 6, children: n = 4). C14: miristoylcarnitine; C16: palmitoylcarnitine; C18: stearoylcarnitine * p < 0.05; ** p < 0.01; ***p < 0.001

Fig. 2

Gene expression analysis in adult GSDIa patients (n = 6) and control groups. For all genes mean value is shown for each group of participants. C1: adult controls who had blood collection after the same fasting time as their matched patient (n = 6). C2: adult controls who had blood collection after 8-h fasting (n = 6).* p < 0.05; ** p < 0.01; ***p < 0.001

Fig. 3

FAO enzymes (A) and citrate synthase (B) activity in adult GSDIa patients (n = 6) and controls. FAO enzyme activity is presented as % activity compared to the mean calculated on a pool of healthy subjects. C1: adult controls who had blood collection after the same fasting time as their matched patients (n = 6). For all proteins mean value is shown for each group of participants. * p < 0.05; ** p < 0.01; ***p < 0.001

Fig. 4

Correlation analysis in GSDIa patients. A Correlation between VLCAD activity and waist circumference (WC, black circles, ρ = 0.89, n = 7 subjects) and BMI (grey triangles, ρ = 0.77, n = 10 subjects). B Correlation between VLCAD activity and serum malonylcarnitine (C3DC, black circles, ρ = 0.67, n = 9 subjects) and ACLY mRNA levels (grey triangles, ρ = 0.66, n = 10 subjects). C Correlation between CPT2 activity and BMI (black circles, ρ = 0.64, n = 10 subjects). * p < 0.05

Fig. 5

Correlation analysis in GSDIa patients not receiving continuous nocturnal gastric drip feeding (CNGDF). A Correlation between VLCAD activity and daily carbohydrate (CH) intake (black circles, ρ = -0.79, n = 7 subjects). B Correlation between citrate synthase activity and daily carbohydrate (CH) intake (black circles, ρ = -0.89, n = 6 subjects) and daily caloric intake (grey triangles, ρ =—0.89, n = 6 subjects). * p < 0.05