Glucose-6-phosphate transporter (G6PT) and microsomal glucose-6-phosphatase-α (G6Pase-α) perform the terminal step in glycogenolysis and gluconeogenesis. Deficiency of these
proteins leads to
glycogen storage diseases. Partial inhibition of G6Pase in rats results in increased hepatic
triglyceride content and de novo lipogenesis leading to hepatic steatosis. Hepatic steatosis represents hepatic manifestation of the
metabolic syndrome. We investigated molecular mechanisms that may explain the relationship between
fatty liver and G6Pase-α in humans in detail. A total of 27 patients (11 men, 16 women) underwent liver biopsy. Histological diagnosis identified nonfatty liver in seven patients and
nonalcoholic fatty liver in 20 patients. We quantified G6Pase-α and G6PT
mRNA expression by real-time PCR. Anthropometric measurements and analysis of plasma
lipids and liver
enzymes were performed. Patients with
fatty liver showed no significant differences in age, HOMA(IR) (homeostasis model assessment of
insulin resistance), BMI, liver
enzymes or waist-to-hip ratio compared to those with nonfatty liver, but total plasma
cholesterol levels and liver fat content were higher in patients with
fatty liver (P < 0.05). G6Pase-α and G6PT
mRNA expressions were significantly downregulated in fatty compared to histologically normal liver (P < 0.05). G6Pase-α and G6PT
mRNA expressions correlated positively (R(2) = 0.406 P < 0.05). Both expressions did not correlate with age, BMI,
aspartate transaminase,
alanine transaminase,
alkaline phosphatase, γ-glutamyl
transferase,
triglycerides or
glucose levels. Our data suggest that expression of hepatic G6Pase-α and G6PT are closely interlinked. Downregulation of G6Pase-α in
fatty liver might be associated with hepatic fat accumulation and pathogenesis of hepatic steatosis.