Hepatic triglyceride (HTG) accumulation from peripheral dietary sources and from endogenous de novo lipogenesis (DNL) was quantified in adult Sprague-Dawley rats by combining in vivo localized 1 H MRS measurement of total hepatic lipid with a novel ex vivo 2 H NMR analysis of HTG 2 H enrichment from 2 H-enriched body water. The methodology for DNL determination needs further validation against standard methodologies. To examine the effect of a high-fat diet on HTG concentrations and sources, animals (n ¼ 5) were given high-fat chow for 35 days. HTG accumulation, measured by in vivo 1 H MRS, increased significantly after 1 week (3.85 W 0.60% vs 2.13 W 0.34% for animals fed on a standard chow diet, P < 0.05) and was maintained until week 5 (3.30 W 0.60% vs 1.12 W 0.30%, P < 0.05). Animals fed on a high-fat diet were glucose intolerant (13.3 W 1.3 vs 9.4 W 0.8 mM in animals fed on a standard chow diet, for 60 min glycemia after glucose challenge, P < 0.05). In control animals, DNL accounted for 10.9 W 1.0% of HTG, whereas in animals given the high-fat diet, the DNL contribution was significantly reduced to 1.0 W 0.2% (P < 0.01 relative to controls). In a separate study to determine the response of HTG to weaning from a high-fat diet, animals with raised HTG (3.33 W 0.51%) after 7days of a high-fat diet reverted to basal HTG concentrations (0.76 W 0.06%) after an additional 7 days of weaning on a standard chow diet. These studies show that, in healthy rats, HTG concentrations are acutely influenced by dietary lipid concentrations. Although the DNL contribution to HTG content is suppressed by a high-fat diet in adult Sprague-Dawley rats, this effect is insufficient to prevent overall increases in HTG concentrations.

The contributions of hepatic glycogenolysis to fasting glucose production and direct pathway to hepatic glycogen synthesis were quantified in eight type 1 diabetic patients and nine healthy control subjects by ingestion of 2 H 2 O and acetaminophen before breakfast followed by analysis of urinary water and acetaminophen glucuronide. After overnight fasting, enrichment of glucuronide position 5 relative to body water (G5/body water) was significantly higher in type 1 diabetic patients compared with control subjects, indicating a reduced contribution of glycogenolysis to glucose production (38 ؎ 3 vs. 46 ؎ 2%). Following breakfast, G5/body water was significantly higher in type 1 diabetic patients, indicating a smaller direct pathway contribution to glycogen synthesis (47 ؎ 2 vs. 59 ؎ 2%). Glucuronide hydrogen 2 enrichment (G2) was equivalent to body water during fasting (G2/body water 0.94 ؎ 0.03 and 1.02 ؎ 0.06 for control and type 1 diabetic subjects, respectively) but was significantly lower after breakfast (G2/body water 0.78 ؎ 0.03 and 0.82 ؎ 0.05 for control and type 1 diabetic subjects, respectively). The reduced postprandial G2 levels reflect incomplete glucose-6-phosphate-fructose-6-phosphate exchange or glycogen synthesis from dietary galactose. Unlike current measurements of human hepatic glycogen metabolism, the 2 H 2 O/acetaminophen assay does not require specialized on-site clinical equipment or personnel. Diabetes

A multinuclear ( 1 H, 13 C, 17 O, 51 V) 1D and 2D NMR study of the complexation of L-lactic acid with vanadium(V) and hydrogen peroxide shows that four peroxo complexes are formed in aqueous solution in the pH range 1−7. Two isomeric 2:2:1 (metal:ligand:peroxo) complexes, together with a 2:2:2 species, are found over the entire pH range. At pH [a]

Quantification of 2 H and 13 C enrichment distributions in human urinary glucuronide following ingestion of 2 H 2 O and 13 C gluconeogenic tracers was achieved by NMR spectroscopy of the 1,2-O-isopropylidene-a-D-glucofuranurono-6,3-lactone and 5-O-acetyl-1,2-O-isopropylidene-a-D-glucofuranurono-6,3-lactone derivatives. The derivatization process is simple and can be applied to any glucuronide species. The derivatives are highly soluble in acetonitrile and generate well-resolved and narrow 2 H and 13 C NMR signals.The 1,2-O-isopropylidene-a-D-glucofuranurono-6,3-lactone derivative provided resolution of the six glucuronide 13 C signals and numerous 13 C isotopomer populations through one-and two-bond 13 C-13 C-coupling, while the 5-O-acetyl-1,2-Oisopropylidene-a-D-glucofuranurono-6,3-lactone derivative provided complete resolution of the 2 H NMR signals for the five glucuronide hydrogens. The isopropylidene methyl signals were also resolved and provided an internal 2 H enrichment standard following the acetonation of glucuronolactone with deuterated acetone.

No abstract