Objective The impact of increased fructose consumption on carbohydrate metabolism is a topic of current interest, but determination of serum level has been hindered due to low concentration and interference from serum glucose. We are reporting a method for the quantification of glucose and fructose in clinical samples using gas chromatography/mass spectrometry (GC/MS). The accuracy and precision of GC/MS and an enzymatic assay were compared. Design and methods Mass spectrometry fragmentation patterns of methyloxime peracetate derivatized aldose and ketose were determined. Unique fragments for glucose and fructose were used for quantitative analysis using isotope labeled recovery standards. Results Methyloxime peracetate derivatives of glucose and fructose showed characteristic loss of acetate (M-60) or ketene (M-42) under chemical ionization (CI). Under electron impact (EI) ionization, a unique C1-C2 fragment of glucose was formed, while a C1-C3 fragment was formed from keto-hexoses. These unique fragments were used in the quantitative assay of glucose and fructose in clinical samples. In clinical samples, the GC/MS assay has a lower limit of detection than that of the enzymatic assay. In plasma samples from patients evaluated for diabetes the average serum glucose and fructose were 6.19±2.72 mM and 46± 25.22 μM. Fructose concentrations in many of these samples were below the limit of detection of the enzymatic method. Conclusion Derivatization of aldose and ketose monosaccharides to their respective O-methyloxime acetates for GC/MS analysis is a facile method for determination of serum/plasma glucose and fructose samples.

ObjectiveEnhanced fatty acid desaturation by stearoyl-CoA desaturase enzyme-1 (SCD1) is associated with obesity. This study determined desaturation in cord plasma of newborns of mothers with and without gestational diabetes (GDM).Study designNewborns of mothers with GDM (n=21) and without (Control, n=22) were recruited. Cord plasma fatty acid desaturation indices (palmitoleic/palmitic, oleic/stearic ratios) were compared, and correlated with anthropometrics and biochemical measures. A subset of VLDL desaturation indices were determined to approximate liver SCD1 activity.ResultsThe total oleic/stearic index was higher in GDM, despite adjustment for cord glucose concentrations. Among GDM and Controls, the oleic/stearic index correlated with cord glucose concentrations (rs=0.36, p=0.02). Both palmitoleic/palmitic and oleic/stearic indices correlated with waist circumference (r=0.47, p=0.001; r=0.37, p=0.01). The VLDL oleic/stearic index was higher in GDM.ConclusionThe elevated total oleic/stearic index suggests increased lipogenesis in GDM newborns. Factors in addition to glucose supply may influence fetal SCD1 activity.