Circulating tricarboxylic acid cycle metabolite levels in citrin-deficient children with metabolic adaptation, with and without sodium pyruvate treatment

Citrin deficiency causes adult-onset type II citrullinemia (CTLN-2), which later manifests as severe liver steatosis and life-threatening encephalopathy. Long-standing energy deficit of the liver and brain may predispose ones to CTLN-2. Here, we compared the energy-driving tricarboxylic acid (TCA) cycle and fatty acid β-oxidation cycle between 22 citrin-deficient children (age, 3–13 years) with normal liver functions and 37 healthy controls (age, 5–13 years). TCA cycle analysis showed that basal plasma citrate and α-ketoglutarate levels were significantly higher in the affected than the control group (p < 0.01). Conversely, basal plasma fumarate and malate levels were significantly lower than those for the control (p < 0.001). The plasma level of 3-OH-butyrate derived from fatty acid β-oxidation was significantly higher in the affected group (p < 0.01). Ten patients underwent sodium pyruvate therapy. However, this therapy did not correct or attenuate such deviations in both cycles. Sodium pyruvate therapy significantly increased fasting insulin secretion (p < 0.01); the fasting sugar level remained unchanged. Our results suggest that citrin-deficient children show considerable deviations of TCA cycle metabolite profiles that are resistant to sodium pyruvate treatment. Thus, long-standing and considerable TCA cycle dysfunction might be a pivotal metabolic background of CTLN-2 development.