GC-MS-Based metabolomics discovers a shared serum metabolic characteristic among three types of epileptic seizures.

OBJECTIVE: Understanding the overall and common metabolic changes of seizures can provide novel clues for their control and prevention. Here, we aim to investigate the global metabolic feature of serum for three types of seizures. METHODS: We recruited 27 patients who had experienced a seizure within 48h (including 11 who had a generalized seizure, nine who had a generalized seizure secondary to partial seizure and seven who had a partial seizure) and 23 healthy controls. We analyzed the global metabolic changes of serum after seizures using gas chromatography-mass spectrometry-based metabolomics. Based on differential metabolites, the metabolic pathways and their potential to diagnose seizures were analyzed, and metabolic differences among three types of seizures were compared. RESULTS: The metabolic profiles of serum were distinctive between the seizure group and the controls but were not different among the three types of seizures. Compared to the controls, patients with seizures had higher levels of lactate, butanoic acid, proline and glutamate and lower levels of palmitic acid, linoleic acid, elaidic acid, trans-13-octadecenoic acid, stearic acid, citrate, cysteine, glutamine, asparagine, and glyceraldehyde in the serum. Furthermore, these differential metabolites had common change trends among the three types of seizures. Related pathophysiological processes reflected by these metabolites are energy deficit, inflammation, nervous excitation and neurotoxicity. Importantly, transamination inhibition is suspected to occur in seizures. Lactate, glyceraldehyde and trans-13-octadecenoic acid in serum jointly enabled a precision of 92.9% for diagnosing seizures. CONCLUSIONS: There is a common metabolic feature in three types of seizures. Lactate, glyceraldehyde and trans-13-octadecenoic acid levels jointly enable high-precision seizure diagnosis.

The Association between Glyceraldehyde-Derived Advanced Glycation End-Products and Colorectal Cancer Risk.

BACKGROUND: A large proportion of colorectal cancers are thought to be associated with unhealthy dietary and lifestyle exposures, particularly energy excess, obesity, hyperinsulinemia, and hyperglycemia. It has been suggested that these processes stimulate the production of toxic reactive carbonyls from sugars such as glyceraldehyde. Glyceraldehyde contributes to the production of a group of compounds known as glyceraldehyde-derived advanced glycation end-products (glycer-AGEs), which may promote colorectal cancer through their proinflammatory and pro-oxidative properties. The objective of this study nested within a prospective cohort was to explore the association of circulating glycer-AGEs with risk of colorectal cancer. METHODS: A total of 1,055 colorectal cancer cases (colon n = 659; rectal n = 396) were matchced (1:1) to control subjects. Circulating glycer-AGEs were measured by a competitive ELISA. Multivariable conditional logistic regression models were used to calculate ORs and 95% confidence intervals (95% CI), adjusting for potential confounding factors, including smoking, alcohol, physical activity, body mass index, and diabetes status. RESULTS: Elevated glycer-AGEs levels were not associated with colorectal cancer risk (highest vs. lowest quartile, 1.10; 95% CI, 0.82-1.49). Subgroup analyses showed possible divergence by anatomical subsites (OR for colon cancer, 0.83; 95% CI, 0.57-1.22; OR for rectal cancer, 1.90; 95% CI, 1.14-3.19; Pheterogeneity = 0.14). CONCLUSIONS: In this prospective study, circulating glycer-AGEs were not associated with risk of colon cancer, but showed a positive association with the risk of rectal cancer. IMPACT: Further research is needed to clarify the role of toxic products of carbohydrate metabolism and energy excess in colorectal cancer development.

Detection and determination of glyceraldehyde-derived pyridinium-type advanced glycation end product in streptozotocin-induced diabetic rats.

GLAP, glyceraldehyde-derived pyridinium-type advanced glycation end product (AGE), formed by glyceraldehyde-related glycation, was identified in the plasma protein and the tail tendon collagen of streptozotocin (STZ)-induced diabetic rats. It was detected in the plasma protein and the collagen in diabetic rats by LC-MS and LC-MS/MS analysis, but was not detected in normal rats. In addition, GLAP was formed from glyceraldehyde-3-phosphate (GA3P) with lysine as well as glyceraldehyde (GLA) with lysine in vitro. Accordingly, it is suggested that an increase in the GLAP level reflects an increase in the GLA level and the GA3P level. GLAP might be a biomarker for reduced activity of the glyceraldehyde-related enzymes in the metabolic diseases such as diabetic complications.

AGE down-regulation of monocyte RAGE expression and its association with diabetic complications in type 1 diabetes.

Advanced glycation end product (AGE) engagement of a cell surface receptor for AGE (RAGE) has been implicated in the development of diabetic complications. In this study, we determined the RAGE mRNA levels in monocytes from type 1 diabetic patients and analyzed their relationship with diabetic vascular complications. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that the monocyte expression of RAGE mRNA was significantly lower in patients with retinopathy than in those without retinopathy and was also significantly down-regulated in patients with nephropathy in comparison with those without nephropathy. Experiments with monocyte-enriched cultures revealed that RAGE mRNA and protein levels were down-regulated by the exposure to glyceraldehyde-derived AGE-the recently identified high-affinity RAGE ligand. Accordingly, we then assayed for the serum levels of glyceraldehyde-derived AGE as well as those of carboxymethyllysine (CML)-the known RAGE ligand and related them to the monocyte levels of RAGE mRNA. This screen revealed a negative correlation between the two parameters. The results thus suggest that the decrease in monocyte RAGE expression can be at least partly accounted for by the ligand engagement and may be a factor contributing to the development of diabetic vascular complications.

Hyperglycemia-induced activation of human erythrocyte aldose reductase and alterations in kinetic properties.

Incubation of human erythrocytes with varying concentrations of glucose resulted in a several-fold increase in aldose reductase (alditol:NADP+ 1-oxidoreductase, EC 1.1.1.21) activity as determined by the rate of NADPH oxidation and the rate of sorbitol formation. As compared to aldose reductase from human erythrocytes not incubated with glucose (native enzyme), aldose reductase from 30 mM glucose-incubated erythrocytes (activated enzyme) exhibited altered kinetic and inhibition properties. Native enzyme showed biphasic kinetics with substrates (glucose and glyceraldehyde), was strongly inhibited by 15 microM ADP, 1,3-diphosphoglycerate, 2,3-diphosphoglycerate and 3-phosphoglycerate, and aldose reductase inhibitors such as sorbinil and alrestatin. The activated enzyme, on the other hand, exhibited monophasic kinetics, low Km for substrates, was not inhibited by the phosphorylated intermediates, and was less susceptible to inhibition by aldose reductase inhibitors. In erythrocytes of the diabetic subjects, we have found an excellent correlation between aldose reductase activity and plasma glucose levels and have observed that whenever the blood glucose level was higher than 15 mM, all of the erythrocyte aldose reductase was present in the activated form and exhibited properties similar to those observed with aldose reductase obtained from 30 mM glucose-incubated erythrocytes.

The effect of glyceraldehyde on red cells. Haemoglobin status, oxidative metabolism and glycolysis.

Glyceraldehyde induces changes in the flux of glucose oxidised through the hexose monophosphate pathway, the concentrations of intermediates in the Embden-Meyerhoff pathway, the oxidative status of haemoglobin and levels of reduced and oxidised pyridine nucleotides and glutathione in red cells. Glyceraldehyde autoxidises in the cellular incubations, consuming oxygen and producing glyoxalase I- and II-reactive materials. Major fates of glyceraldehyde in red cells appear to be: (i) adduct formation with reduced glutathione and cellular protein; (ii) autoxidation and reaction with oxyhaemoglobin and pyridine nucleotides, and (iii) phosphorylation of D-glyceraldehyde and entry into the glycolytic pathway as glyceraldehyde 3-phosphate. The production of glycerol from glyceraldehyde by red cell L-hexonate dehydrogenase appears not to be a major reaction of glyceraldehyde in red cells. These results indicate that high concentrations of glyceraldehyde (1-50 mM) may induce oxidative stress in red cells by virtue of the spontaneous autoxidation of glyceraldehyde, forming hydrogen peroxide and alpha-ketoaldehydes (glyoxalase substrates). The implications of glyceraldehyde-induced oxidative stress for the in vitro anti-sickling effect of DL-glyceraldehyde and for the polyol pathway metabolism of glyceraldehyde are discussed.

The reversibility of the ketoamine linkages of aldoses with proteins.

The reaction of glyceraldehyde (aldotriose) with hemoglobin A is analogous to the nonenzymic glycosylation of the protein with glucose in that the initial reversible Schiff base adduct (aldimine) of aldotriose undergoes Amadori rearrangement as does that of aldohexose to form the more stable ketoamine adduct. The modification of the alpha-amino group on Val-1(beta) of hemoglobin A as a ketoamine (2-oxo-3-hydroxypropyl group) apparently lowers the pKa of the alpha-amino group of the protein, since this derivative of hemoglobin elutes earlier on carboxymethylcellulose columns than the derivatives containing 2-oxo-3-hydroxypropyl groups on the epsilon-amino groups, and unmodified hemoglobin A. Similar chromatographic behavior has been reported for hemoglobin A1c which contains glucose at its Val-1(beta) as the ketoamine adduct. This suggests the similarity in the chemical consequences of having the ketoamine adduct of an aldose at Val-1(beta) of hemoglobin A under physiological conditions. The formation of the 2-oxo-3-hydroxypropyl groups on Val-1(beta) is nearly irreversible as has been suggested for similar adducts of glucose. On the other hand, the 2-oxo-3-hydroxypropyl groups on the epsilon-amino groups appear to be labile. The buffer conditions considerably influence the reversibility of the ketoamine adducts of aldotriose on the epsilon-amino groups; the reversibility is significantly higher in Tris buffers as compared with that in phosphate buffers. It is suggested that under physiological conditions the ketoamine adducts of aldotriose on the epsilon-amino groups exist in equilibrium with the aldimine, the equilibrium being favored toward the ketoamine. The enhanced release of the 2-oxo-3-hydroxypropyl groups in Tris buffers is probably a reflection of the trans-Schiff base reaction of aldimine with Tris. In support of this hypothesis, sodium cyanoborohydride, a reagent selective for the reduction of the aldimine linkages, inhibited the labilizing influence of Tris. A similar reversibility appears to be true of the ketoamine adducts of aldohexoses at the epsilon-amino groups of hemoglobin A, and ribonuclease A as well. This information on the reversibility of the ketoamine adducts of glucose on the epsilon-amino groups of proteins should be useful in understanding the details of the mechanism of nonenzymic glycosylation. It is also expected to influence the interpretation of the measurements of nonenzymically glucosylated hemoglobin A in diabetic patients.

Inhibition of human serum alpha-amylase activity.

Amylase activity was measured in normal sera and serum of patients with acute pancreatitis and mumps. A significant decrease of enzyme activity in patients with acute pancreatitis was observed after incubation with specific antibody against hog pancreas amylase. A minimal effect of the antibody on normal serum and on that from mumps patients was noted. A comparable effect was observed in the presence of glyceraldehyde used as an amylase differentiating factor.

Cow red blood cells. III. Postnatal adaptation of energy metabolism in the calf red blood cells.

1. The change in energy metabolism of red blood cells from the newborn calf to adult cow was examined utilizing a number of metabolic substrates including glyceraldehyde, dihydroxyacetone, ribose, glucose, adenosine and inosine. 2. All of these substrates are utilizes by the newborn calf cells to a varying degree. With glyceraldehyde, dihydroxyacetone or glucose as a substrate, lactate is formed at a rate of 2-3 mumol/ml cells per h. As in other species, ribose utilization depends on substrate concentration, with an optimum of 3 mM ribose yielding lactate 1-1.5 mumol/ml cells per h in the calf cells. 3. In sharp contrast, adult cow red blood cells lost the bulk of the postnatal metabolic substrate affinities except for glyceraldehyde and glucose which are consumed at less than half of the rate at birth. 4. While the transition of the metabolic properties from the newborn to the adult state takes place within 2 to 3 months after birth, the red blood cells produced shortly after birth have already assumed the metabolic machinery characteristic to the adult cells. 5. Even though adenosine in itself is a poor substrate in producing lactate, a net synthesis of ATP from adenosine can take place in both calf and cow cells provided that an alternate carbon source such as glyceraldehyde, dihydroxyacetone or glucose is given. 6. Of the test substrates, glucose is the only substrate for the adult cow cells exhibiting a greater than 50% increase in utilization by exogenously added adenine. By contrast, the calf cell is affected to a much lesser extent. The possible in vivo regulatory metabolic role of certain purine and pyrimidine compounds unique to the adult stage of this species is discussed.

Thermodynamics of red cell glycolysis.

1. Changes of Gibbs energy, enthalpy and entropy in red cells during steady-state glycolysis were discussed. 2. The heat production of red cells at various metabolic conditions was measured on a flow microcalorimeter with simultaneous analyses of lactate and other metabolites. The results were discussed in relation to enthalpy changes of the different metabolic steps in the glycolytic pathway.