Summary:Purpose: To evaluate the clinical efficacy and safety of the ketogenic diet (KD) for patients with intractable childhood epilepsy and mitochondrial respiratory chain (RC) complex defects.Methods: A retrospective analysis evaluated outcomes in 14 children with intractable epilepsy and RC complex defects who were treated with the classic KD involving a 4:1 lipid to nonlipid ratio (% by weight), but without an initial fast and fluid restriction. Outcome measures included seizure frequency, electroencephalography (EEG) findings, the number of antiepileptic drugs, and adverse reactions.

Glycogen storage disease type Ia (GSD-Ia) patients deficient in glucose-6-phosphatase-alpha (G6Pase-alpha or G6PC) manifest disturbed glucose homeostasis. We examined the efficacy of liver G6Pase-alpha delivery mediated by AAV-GPE, an adeno-associated virus (AAV) serotype 8 vector expressing human G6Pase-alpha directed by the human G6PC promoter/enhancer (GPE), and compared it to AAV-CBA, that directed murine G6Pase-alpha expression using a hybrid chicken beta-actin (CBA) promoter/cytomegalovirus (CMV) enhancer. The AAV-GPE directed hepatic G6Pase-alpha expression in the infused G6pc(-/-) mice declined 12-fold from age 2 to 6 weeks but stabilized at wild-type levels from age 6 to 24 weeks. In contrast, the expression directed by AAV-CBA declined 95-fold over 24 weeks, demonstrating that the GPE is more effective in directing persistent in vivo hepatic transgene expression. We further show that the rapid decline in transgene expression directed by AAV-CBA results from an inflammatory immune response elicited by the AAV-CBA vector. The AAV-GPE-treated G6pc(-/-) mice exhibit normal levels of blood glucose, blood metabolites, hepatic glycogen, and hepatic fat. Moreover, the mice maintained normal blood glucose levels even after 6 hours of fasting. The complete normalization of hepatic G6Pase-alpha deficiency by the G6PC promoter/enhancer holds promise for the future of gene therapy in human GSD-Ia patients.

G6PC3 deficiency, characterized by neutropenia and neutrophil dysfunction, is caused by deficiencies in the endoplasmic reticulum (ER) enzyme glucose-6-phosphatase-␤ (G6Pase-␤ or G6PC3) that converts glucose-6-phosphate (G6P) into glucose, the primary energy source of neutrophils. Enhanced neutrophil ER stress and apoptosis underlie neutropenia in G6PC3 deficiency, but the exact functional role of G6Pase-␤ in neutrophils remains unknown. We hypothesized that the ER recycles G6Pase-␤-generated glucose to the cytoplasm, thus regulating the amount of available cytoplasmic glucose/ G6P in neutrophils. Accordingly, a G6Pase-␤ deficiency would impair glycolysis and hexose monophosphate shunt activities leading to reductions in lactate production, adenosine-5-triphosphate (ATP) production, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Using annexin V-depleted neutrophils, we show that glucose transporter-1 translocation is impaired in neutrophils from G6pc3 ؊/؊ mice and G6PC3-deficient patients along with impaired glucose uptake in G6pc3 ؊/؊ neutrophils. Moreover, levels of G6P, lactate, and ATP are markedly lower in murine and human G6PC3-deficient neutrophils, compared with their respective controls. In parallel, the expression of NADPH oxidase subunits and membrane translocation of p47 phox are down-regulated in murine and human G6PC3-deficient neutrophils. The results establish that in nonapoptotic neutrophils, G6Pase-␤ is essential for normal energy homeostasis. A G6Pase-␤ deficiency prevents recycling of ER glucose to the cytoplasm, leading to neutrophil dysfunction. (Blood. 2010;116(15):2783-2792) IntroductionThere are 2 enzymatically active glucose-6-phosphatases (G6Pases), the liver/kidney/intestine-restricted G6Pase-␣ (or G6PC) 1,2 and the ubiquitously expressed G6Pase-␤ (also known as G6PC3). 3,4 Both enzymes are transmembrane endoplasmic reticulum (ER) proteins, with a similar topology, that places their active site on the luminal side of the ER membrane. 5,6 Both have similar kinetic properties 2,4 and hydrolyze glucose-6-phosphate (G6P) to glucose and phosphate when coupled with the ubiquitously expressed G6P transporter (G6PT) that translocates G6P from the cytoplasm into the lumen of the ER. 7,8 The primary role of the G6Pase/G6PT complex is to provide glucose and phosphate to the ER lumen. The G6Pase-␣/G6PT complex maintains blood glucose homeostasis between meals by hydrolyzing G6P to glucose in the terminal step of gluconeogenesis and glycogenolysis. 1,2 Deficiencies in G6Pase-␣ cause glycogen storage disease type Ia (GSD-Ia) and deficiencies in G6PT result in GSD type Ib (GSD-Ib). 1,2,9 Both GSD-Ia and GSD-Ib patients manifest a phenotype of disturbed blood glucose homeostasis with GSD-Ib patients also suffering neutropenia and neutrophil dysfunction, 1,9 reflecting a role of G6PT in tissues beyond the liver and kidney.The biologic roles of G6Pase-␤ and the G6Pase-␤/G6PT complex are poorly defined. Neutrophils, which express both G6Pase-␤ and G6PT, 10 are capable ...