Enrichment of hepatic glycogen and plasma glucose from H218 O informs gluconeogenic and indirect pathway fluxes in naturally feeding mice.

Deuterated water (2 H2 O) is a widely used tracer of carbohydrate biosynthesis in both preclinical and clinical settings, but the significant kinetic isotope effects (KIE) of 2 H can distort metabolic information and mediate toxicity. 18 O-water (H2 18 O) has no significant KIE and is incorporated into specific carbohydrate oxygens via well-defined mechanisms, but to date it has not been evaluated in any animal model. Mice were given H2 18 O during overnight feeding and 18 O-enrichments of liver glycogen, triglyceride glycerol (TG), and blood glucose were quantified by 13 C NMR and mass spectrometry (MS). Enrichment of oxygens 5 and 6 relative to body water informed indirect pathway contributions from the Krebs cycle and triose phosphate sources. Compared with mice fed normal chow (NC), mice whose NC was supplemented with a fructose/glucose mix (i.e., a high sugar [HS] diet) had significantly higher indirect pathway contributions from triose phosphate sources, consistent with fructose glycogenesis. Blood glucose and liver TG 18 O-enrichments were quantified by MS. Blood glucose 18 O-enrichment was significantly higher for HS versus NC mice and was consistent with gluconeogenic fructose metabolism. TG 18 O-enrichment was extensive for both NC and HS mice, indicating a high turnover of liver triglyceride, independent of diet. Thus H2 18 O informs hepatic carbohydrate biosynthesis in similar detail to 2 H2 O but without KIE-associated risks.

Increased Intake of Both Caffeine and Non-Caffeine Coffee Components Is Associated with Reduced NAFLD Severity in Subjects with Type 2 Diabetes.

Coffee may protect against non-alcoholic fatty liver disease (NAFLD), but the roles of the caffeine and non-caffeine components are unclear. Coffee intake by 156 overweight subjects (87% with Type-2-Diabetes, T2D) was assessed via a questionnaire, with 98 subjects (all T2D) also providing a 24 h urine sample for quantification of coffee metabolites by LC-MS/MS. NAFLD was characterized by the fatty liver index (FLI) and by Fibroscan® assessment of fibrosis. No associations were found between self-reported coffee intake and NAFLD parameters; however, total urine caffeine metabolites, defined as Σcaffeine (caffeine + paraxanthine + theophylline), and adjusted for fat-free body mass, were significantly higher for subjects with no liver fibrosis than for those with fibrosis. Total non-caffeine metabolites, defined as Σncm (trigonelline + caffeic acid + p-coumaric acid), showed a significant negative association with the FLI. Multiple regression analyses for overweight/obese T2D subjects (n = 89) showed that both Σcaffeine and Σncm were negatively associated with the FLI, after adjusting for age, sex, HbA1c, ethanol intake and glomerular filtration rate. The theophylline fraction of Σcaffeine was significantly increased with both fibrosis and the FLI, possibly reflecting elevated CYP2E1 activity-a hallmark of NAFLD worsening. Thus, for overweight/obese T2D patients, higher intake of both caffeine and non-caffeine coffee components is associated with less severe NAFLD. Caffeine metabolites represent novel markers of NAFLD progression.

Acute increase of the glutamate-glutamine cycling in discrete brain areas after administration of a single dose of amphetamine.

The glutamate-glutamine cycle between neurons and glia is tightly related to excitatory glutamatergic and inhibitory GABAergic regulation in brain. The role of this neuron-astrocyte cross-talk on the neurotoxicity induced by amphetamines is not understood. Also, the impact of neurotoxic doses of amphetamines on the balance between glutamatergic and GABAergic circuits is largely unknown. The aim of this work was to assess the acute effect of a neurotoxic regimen of amphetamine (AMPH) on glutamine (GLN, an astrocytic marker) levels and on glutamine/glutamate (an index for glutamate-glutamine cycle) and GABA/glutamate ratios in rat brain. Sprague-Dawley rats were sacrificed 4 and 24 h after a single-dose regimen of AMPH (30 mg/kg, i.p.), and the caudate-putamen (CPu), frontal cortex (FC), and hippocampus (Hp) were dissected for analysis of glutamate (GLU), gamma-aminobutyric acid (GABA), and GLN. The total content of these amino acids was measured using a microbore HPLC electrochemical detector. Although AMPH did not change GLU levels, it increased both GLN content and GLN/GLU ratio (160-469%) at 4 h, but not at 24 h, in all regions after injection. Striatal GABA levels and GABA/GLU ratio were increased (46 and 100%, respectively) at 24 h. In hippocampus the GABA/GLU increase (60%) occurred as early as 4 h after treatment. To the contrary, AMPH exerted no effect in GABA/GLU balance in frontal cortex. These data strongly suggest that this neurotoxic AMPH regimen provoked an early increase in the glutamate-glutamine cycle between neurons and glia. This increase may ultimately lead to an upregulation of the inhibitory system as a compensatory response.