Relationship between serum 1,5-anhydroglucitol and urinary excretion of N-acetylglucosaminidase and albumin determined at onset of NIDDM with 3-year follow-up

OBJECTIVE

This prospective study was designed to elucidate the relationship between the serum level of 1,5-anhydroglucitol (1,5AG) and the urinary excretion of N-acetylglucosaminidase (NAG) and albumin in patients who were in the early stages of diabetes.

RESEARCH DESIGN AND METHODS

A total of 1,062 male nondiabetic subjects with impaired glucose tolerance were monitored for blood glucose level once every 2-3 months, and the values were evaluated. Of these 1,062 subjects, 112 showed a worsening of glycemia during the observation period to the level seen in diabetes. We began to monitor the glycemia and parameters of renal damage in the 112 patients from the onset of diabetes.

RESULTS

The urinary excretion of NAG and albumin were elevated even at the onset of diabetes. The abnormal excretion of NAG and albumin was associated with a change in serum 1,5AG and was quickly reversible when the serum 1,5AG improved. In the 3 years after the onset of diabetes, we obtained at least 18 measurements of one parameter for each patient and calculated the mean. Urinary NAG was found to be significantly correlated with the fasting plasma level of glucose (FPG; r = 0.512, P < 0.0001), the level of HbA1 (r = 0.351, P = 0.001), and the level of 1,5AG (r = -0.790, P < 0.0001). The urinary excretion of albumin was weakly but significantly correlated with levels of FPG (r = 0.383, P < 0.0001) and HbA1 (r = 0.337, P < 0.0001), but it was more strongly correlated with 1,5AG (r = -0.632, P < 0.0001). The level of 1,5AG was significantly correlated with FPG (r = -0.681, P < 0.0001) and HbA1 (r = -0.609, P < 0.0001).

CONCLUSIONS

When the renal damage is not severe, the serum level of 1,5AG appeared to be an indicator of the reversible renal damage caused by hyperglycemia, as well as of the severity of the glycemia itself.

Mechanisms of elevation of serum and urinary concentrations of soluble thrombomodulin in diabetic patients: possible application as a marker for vascular endothelial injury

Serum and urinary levels of soluble thrombomodulin (TM) were measured in 71 patients with non-insulin-dependent diabetes mellitus (NIDDM) and 132 age-matched control subjects to elucidate the mechanisms involved in increased TM levels. We compared the TM level with urinary albumin excretion (UAE), creatinine (Cr) clearance, and indices of renal tubular damage such as urinary beta2-microglobulin. Serum TM was significantly higher in diabetic patients versus control subjects (P < .001) regardless of whether the patients had diabetic nephropathy. Urinary TM levels were also higher in diabetic patients than in control subjects (P < .001). Serum TM in diabetic patients was correlated positively with serum Cr and UAE and inversely with the Cr clearance rate (P < .001, respectively). The urinary level of TM in diabetic patients was significantly correlated with 24-hour glucose excretion and the serum level of 1,5-anhydroglucitol (1,5-AG) (P < .001). However, no correlations were found between urinary TM levels and renal function in diabetic patients. There was also no correlation between serum and urinary levels of TM in the patients. These results suggest that although the serum TM level is influenced by an impairment of the renal clearance of TM, this parameter may be a useful marker for vascular endothelial injury in diabetic patients. On the other hand, since the elevated urinary level of TM in the patients paralleled their urinary excretion of glucose, urinary TM levels do not correlate with vascular endothelial injury in diabetic patients.

Decreased activity of arachidonate 12-lipoxygenase in platelets of Japanese patients with non-insulin-dependent diabetes mellitus

To study the metabolism of the platelet 12-lipoxygenase pathway in diabetes, we evaluated the correlation between the activity and amount of arachidonate 12-lipoxygenase in the platelets of patients with non-insulin-dependent-diabetes mellitus (NIDDM). There were four parts in this investigation: (1) examination of abnormalities in platelet 12-lipoxygenase in patients with NIDDM recruited from the Hospital of Juntendo University School of Medicine; (2) comparison of 12-lipoxygenase in the platelets of non-obese NIDDM patients without angiopathy versus normal subjects matched for age, sex, and body mass index (BMI); (3) evaluation of gender differences; and (4) assessment of the potential influence of glycemic control. The activity of 12-lipoxygenase was assayed by incubation of [1-14C]arachidonic acid with the platelet cytosol. The reaction mixture was extracted and separated by thin-layer chromatography, and the radioactive end products were detected. The activity of 12-lipoxygenase in the platelets of patients with NIDDM was significantly less than in normal subjects (P < .003), whereas the amount of 12-lipoxygenase protein did not differ between the two groups. Thus, the specific activity of 12-lipoxygenase in diabetic patients was significantly less than that of normal subjects (P < .001). The enzyme activity and the specific enzyme activity of 12-lipoxygenase in non-obese NIDDM patients without angiopathy were significantly lower than the values in normal subjects matched for gender, age, and BMI (P < .006 and P < .0007, respectively). No significant difference in the activity or amount of platelet 12-lipoxygenase was observed between males and females matched for age, BMI, and disease. In addition, no relationship was observed between 12-lipoxygenase activity and blood glucose levels measured at the time of specimen collection. However, slight negative correlations were noted between 12-lipoxygenase activity and 1,5-anhydroglucitol, hemoglobin A1c (HbA1c), and fructosamine (r = .369, -.354, and -.279, respectively). When recombinant 12-lipoxygenase was incubated with varying concentrations of glucose or fructose, enzyme inactivation was related to the length of incubation, and was unaffected by glucose or fructose. These observations suggest that the activity of 12-lipoxygenase in the platelets of patients with NIDDM is decreased by prolonged hyperglycemia. The mechanism involved requires further investigation.

Prior muscular contraction enhances disposal of glucose analog in the liver and muscle

To noninvasively investigate in vivo glucose disposal in muscle and liver after exercise, 19F magnetic resonance spectroscopy (19F-MRS) was applied using 3-fluoro-3-deoxy-D-glucose (3FDG) as a metabolic probe. After 30 minutes of muscle contraction of rabbit hindlimb by a 1-Hz electrical stimulation, 3FDG 250 mg/kg was injected intravenously and 19F-MRS was performed on the postcontracted hindlimb or the liver. Rabbits subjected to muscle contraction showed 1.5- and 1.7-fold higher peaks for 3FDG signal intensity in the liver and muscle than those not subjected to it. 3FDG was converted to 3-fluoro-3-deoxy-gluconic acid (3FGA) in the muscle and liver, and 3FDG oxidation was not affected by muscle contraction. During intraportal 3FDG infusion for 120 minutes at a dose of 2 mg x kg-1 x min-1 after termination of muscle contraction, the postcontracted rabbits showed a continuous increase in the signal intensity of 3FDG and a 2.1-fold higher total signal intensity of 3FDG than those not subjected to muscle contraction. In conclusion, 19F-MRS allows direct noninvasive observation of 3FDG disposal in rabbit muscle and liver. The increased intensity of 3FDG in the liver after muscle contraction suggests that exercise enhances disposal of the glucose analog in the liver, as well as in muscle, and these effects persist for at least 2 hours after exercise.

[Clinical evaluation of serum 1,5AG levels in patients with liver cirrhosis]

We measured serum 1,5 anhydroglucitol (1,5AG) levels by HPLC in 32 patients with liver cirrhosis, 32 with diabetes mellitus and 61 normal subjects. Serum 1,5AG was significantly lower in patients with diabetes mellitus and liver cirrhosis compared with that in normal subjects. Serum levels of type IV collagen were higher in patients with liver cirrhosis than in those without liver cirrhosis. A negative correlation was observed between serum 1,5AG and type IV collagen in patients with liver cirrhosis (r = -0.37, p < 0.05), but not in patients with diabetes mellitus. These data suggest that serum 1,5AG levels reflect the degree of liver cirrhosis.

A kinetic mass balance model for 1,5-anhydroglucitol: applications to monitoring of glycemic control

The polyol 1,5-anhydroglucitol (AG) present in human plasma is derived largely from ingestion and is excreted unmetabolized. Reduction of plasma [AG] has been noted in diabetics and is due to accelerated excretion of AG during hyperglycemia. Plasma [AG] has therefore been proposed as a marker for glycemic control. A precise understanding of its utility relies on a quantitative understanding of the mass balance for AG. In this study, non-steady-state data from the literature were analyzed to develop a dynamic mass balance model for AG that is based on the two-compartment model proposed by Yamanouchi et al. [T. Yamanouchi, Y. Tachibana, H. Akanuma, S. Minoda, T. Shinohara, H. Moromizato, H. Miyashita, and I. Akaoka. Am. J. Physiol. 263 (Endocrinol. Metab. 26): E268-E273, 1992]. The data are consistent with a model in which exchange between tissue and plasma pools is rapid and in which the tissue compartment mass is two to three times the mass of the plasma compartment. According to model estimates, accelerated excretion of AG due to hyperglycemia can cause marked net depletion of total AG over a time scale of days. Recovery from a depleted state is slow because the total body capacity represents >5 wk of normal intake. Accordingly, AG monitoring should be able to indicate the presence of past glucosuric hyperglycemic episodes during a period of days to weeks, as well as provide information on the extent to which high deviations from the average plasma glucose concentration are operative.

Sphingomyelinase increases 2-deoxyglucose uptake and glucose metabolism of human platelets

Recent studies have shown that the sphingomyelinase (SMase) catalyzed hydrolysis of sphingomyelin (SM) represents an important cell signalling pathway. Control of SMase activity appears to be crucial for the regulation of multiple biological events in different cell systems; in particular, SMase activity appears to be involved in the control of vascular functions and in atherogenic events. Here we report that SMase treatment of human platelets significantly increases 2-deoxyglucose uptake by decreasing K(m) value of sugar transport and increasing sugar diffusion. In addition SMase treatment enhances basal glycolytic flux of platelets as well as the stimulation of the flux induced by suboptimal concentration of thrombin. The present study demonstrates that exposure of platelets to SMase, which may take place in vivo in physiological and/or in pathological conditions, modifies biochemical parameters of resting and stimulated platelets which are essential for cell physiological role.

Effects of glycemic control on plasma 3-deoxyglucosone levels in NIDDM patients

OBJECTIVE

To clarify the effects of glycemic control on the level of 3-deoxyglucosone (3-DG), a reactive dicarbonyl compound, in plasma from diabetic patients.

RESEARCH DESIGN AND METHODS

Fasting plasma samples were collected from 15 healthy volunteers and 27 patients with NIDDM. Samples were collected from six poorly controlled patients before and after improved glycemic control for at least 2 months. Plasma 3-DG was determined by high-performance liquid chromatography (HPLC) as a 2,3-diaminonaphthalene derivative. We observed the relationship of 3-DG levels with plasma glucose or HbA1c levels and examined changes in 3-DG levels after glycemic control in the six patients.

RESULTS

Plasma 3-DG was significantly more increased in diabetic patients than in nondiabetic control subjects (31.8 +/- 11.3 vs. 12.8 +/- 5.2 ng/ml, means +/- SD, P < 0.001), but there was an approximately threefold difference in 3-DG levels among diabetic patients. 3-DG levels were well correlated with plasma glucose (r = 0.56, P < 0.005) and HbA1c levels (r = 0.74, P < 0.001) in diabetic patients. The improvement of hyperglycemia in six patients resulted in a significant decrease in 3-DG (35.2 +/- 13.2 vs. 21.3 +/- 3.4 ng/ml, P < 0.05).

CONCLUSIONS

The results indicate that the plasma glucose level is a predominant determinant of the plasma 3-DG level in diabetic patients and good glycemic control would be important to reduce this reactive metabolite.

Quantitation of 3-deoxyglucosone levels in human plasma

3-Deoxyglucosone (3DG), a reactive dicarbonyl, is an important intermediate in the formation of advanced glycation end products (AGEs). The AGEs are particularly important in diabetes since they have been correlated with the development of diabetic complications. Consequently, measurements of 3DG are likely to provide valuable insights into the role of this metabolite in the etiology of diabetic complications. While several methods of 3DG quantitation in human plasma have been previously published, a significant discrepancy (over 30-fold) exists in the reported values. Knecht et al. (Arch. Biochem. Biophys. 294, 130-137, 1992) have reported the levels of plasma 3DG in normoglycemics to be 61 nM, using a GC/MS procedure. In contrast to this, Niwa et al. (Biochem. Biophys. Res. Commun. 196, 837-843, 1993) reported 3DG levels to be 1800 nM in normoglycemics, using a totally independent GC/MS method. To resolve this disagreement and fill the need for a robust assay for this dicarbonyl, suitable for absolute quantitation, a GC/MS procedure was devised for its measurement. Plasma samples were deproteinized either by ultrafiltration or by addition of ethanol as described by Niwa et al. (Biochem. Biophys. Res. Commun. 196, 837-843, 1993). 3DG in the ultrafiltrate or the supernatant was conjugated with 2,3-diamino-naphthalene to produce a stable adduct which was then converted to a silyl ether and analyzed by GC/MS. The analyte was monitored by selected ion monitoring at an m/z of 295 and 306 and quantitated using an internal standard of [U-13C]3DG. Using this approach, 3DG levels in plasma deproteinized by ultrafiltration were found to be significantly elevated from 58.5 +/- 14 (SD) nM in normoglycemics to 98.5 +/- 34 (SD) nM in type I diabetics. When deproteinization of the plasma was carried out using ethanol, the levels of 3DG from normoglycemic plasma were similar to those reported by Niwa et al. (1710 +/- 750 (SD) nM). These results suggest that 3DG levels measured by ultrafiltration may represent the free circulating 3DG and those obtained by ethanol extraction may represent aform of 3DG bound to a macromolecule (presumbaly protein).

Imidazolone, a novel advanced glycation end product, is present at high levels in kidneys of rats with streptozotocin-induced diabetes

We produced a monoclonal antibody to imidazolones A and B, novel advanced glycation end products formed from the reaction of 3-deoxyglucosone (3-DG) with the guanidino group of arginine. Liquid chromatography/mass spectrometry demonstrated that the formation of imidazolone A by incubating 3-DG with arginine is very rapid, reaching a maximum concentration within 24 h, but the formation of imidazolone B is very slow and low in quantity even after 2 weeks. Thus, at physiological conditions the formation of imidazolone A is dominant, while that of imidazolone B is negligible. Immunochemistry demonstrated that the imidazolone content in the kidneys of streptozotocin-induced diabetic rats was significantly higher than in the control rats. Serum levels of 3-DG in the diabetic rats were also significantly higher than in control rats. 3-DG attacks the arginine residues of the tissue proteins, producing imidazolone at high levels in the kidneys affected by diabetic nephropathy.

Inhibition of glucose transport in human red blood cells by adenosine antagonists

Previous studies have suggested that adenosine antagonists can interfere with normal glucose uptake in perfused rat heart. In the present studies, fluorine-19 nuclear magnetic resonance spectroscopy was used to study the effect of the adenosine antagonist, BW-A1433U, on the equilibrium exchange of fluorinated glucose analogs in human erythrocytes. Studies of the equilibrium exchange of both 2-fluoro-2-deoxy-D-glucose and 3-fluoro-3-deoxy-D-glucose with either one-dimensional magnetization transfer or two-dimensional exchange spectroscopy were performed, and significant inhibition was observed in all cases. From concentration-dependent studies, an inhibition constant for the equilibrium exchange measured at 37 degrees C of 24 microM was determined.

Evaluation of two population-based input functions for quantitative neurological FDG PET studies

The conventional measurement of the regional cerebral metabolic rate of glucose (rCMRGlc) with fluorodeoxyglucose (FDG) and positron emission tomography (PET) requires arterial or arterialised-venous (a-v) blood sampling at frequent intervals to obtain the plasma input function (IF). We evaluated the accuracy of rCMR-Glc measurements using population-based IFs that were calibrated with two a-v blood samples. Population-based IFs were derived from: (1) the average of a-v IFs from 26 patients (Standard IF) and (2) a published model of FDG plasma concentration (Feng IF). Values for rCMRGlc calculated from the population-based IFs were compared with values obtained with IFs derived from frequent a-v blood sampling in 20 non-diabetic and six diabetic patients. Values for rCMRGlc calculated with the different IFs were highly correlated for both patient groups (r > or = 0.992) and root mean square residuals about the regression line were less than 0.24 mg/min/100 g. The Feng IF tended to underestimate high rCMRGlc. Both population-based IFs simplify the measurement of rCMRGlc with minimal loss in accuracy and require only two a-v blood samples for calibration. The reduced blood sampling requirements markedly reduce radiation exposure to the blood sampler.

Post-column enzyme reactors for chemiluminometric detection of glucose, 1,5-anhydroglucitol and 3-hydroxybutyrate in an anion-exchange chromatographic system

A liquid chromatographic system consisting of a co-immobilized 3-hydroxybutyrate dehydrogenase-NADH oxidase reactor and an immobilized pyranose oxidase reactor in series and a chemiluminometer was developed for the simultaneous determination of glucose, 1,5-anhydroglucitol and 3-hydroxybutyrate in plasma. The enzymes were immobilized on toresylated poly(vinyl alcohol) beads. Separation was achieved on a TSK gel SAX column (40 x 4 mm I.D.) with an eluent of 50 mM NaOH containing 30 mM sodium butyrate. The hydrogen peroxide produced was detected by measuring the chemiluminescence emitted on admixing with luminol and potassium hexacyanoferrate(III). The calibration curves were linear from 0.8 to 500 microM (7 ng-4 micrograms) for glucose, from 0.8 to 400 microM (7 ng-3 micrograms) for 1,5-anhydroglucitol and from 1 to 700 microM (5 ng-4 micrograms in a 50-microliter injection) for 3-hydroxybutyrate. The sample throughput was four per hour. The reactors were stable for at least ten days.

Efflux of 6-deoxy-D-glucose from Plasmodium falciparum-infected erythrocytes via two saturable carriers

Glucose transport in human erythrocytes infected with the malaria parasite, Plasmodium falciparum, has been studied using 6-deoxy-D-glucose (6DOG) as a non-metabolised glucose analogue. Inhibition studies using cytochalasin B, a powerful inhibitor of the erythrocyte glucose transporter, GLUT1, indicate that in the infected red blood cell (IRBC), glucose is transported via a saturable carrier. However, inhibition is not as complete as in the uninfected erythrocyte. The synergistic inhibition effect of 6DOG entry by niflumic acid, an inhibitor of the non-specific malaria-induced pore, in the presence of cytochalasin B suggests that some glucose may also enter the infected erythrocytes through the pore, if entry via the carrier is blocked. The time course of 6DOG efflux from infected erythrocytes in the presence of cytochalasin B did not follow simple first-order kinetics. To elucidate the kinetic mechanism of 6DOG efflux from the infected erythrocytes, the concentration dependence of efflux was determined. Eight two-compartment kinetic models were simulated, involving first-order pore diffusion and carrier-mediated saturable diffusion in two systems, one ductless and one assuming the existence of a parasitophorous duct. The only two models showing reasonable fits to the efflux data each involve two saturable carriers. It is likely that one of the saturable carriers is associated with the parasite itself. Evidence that the parasite carrier has different inhibitor sensitivities from that of GLUT1 is presented.

Effect of chronic inhibition of nitric oxide synthase on ocular blood flow and glucose metabolism in the rat

AIMS

To investigate the effects of chronic administration of nitric oxide synthase inhibition on ocular blood flow and metabolic demand in the rat and to compare these effects with changes in the cerebral and peripheral circulation.

METHODS

Male Sprague-Dawley rats were injected with the nitric oxide synthase inhibitor L-NAME (75 mg/kg i.p.), either on a single occasion only or once daily for 10 consecutive days. Controls were injected with saline. Regional blood flow and glucose metabolism were measured from tissue samples, using [14C]-iodoantipyrine and [14C]-2-deoxyglucose respectively, 1 hour after either acute L-NAME injection or 1 hour after the last injection of the chronic treatment protocol.

RESULTS

Mean arterial pressure was significantly increased (+31%) following the acute injection (indicating peripheral vasoconstriction) and this effect was enhanced (+50%) following chronic treatment. In both the ocular and cerebral circulation, blood flow was decreased following acute treatment (-48% and -43% respectively). However, while this response was totally attenuated in the cerebral circulation following chronic L-NAME treatment (-4%), the ocular circulation remained responsive (-57%). Metabolic demand in brain and eye tissue, as reflected in the accumulation of 2-deoxyglucose, was unaffected by either acute or chronic treatment with L-NAME.

CONCLUSION

Homeostatic mechanisms appear to be activated in the cerebral circulation which re-establish flow metabolism homeostasis, and the effect of L-NAME on cerebral blood flow is attenuated following repeated exposure. This process does not seem to happen in the ocular circulation and, thus, the ocular vasculature appears to behave more like those blood vessels which determine total peripheral resistance than the cerebral circulation. It remains to be seen whether the sustained decrease in blood flow in the eye is sufficient to compromise ocular function and render the eye susceptible to damage from chronic L-NAME induced oligaemia.

Change of plasma 1,5-anhydro-D-glucitol levels after the onset of diabetes in spontaneous diabetes prone BB/Wor/(/)Tky rats

Plasma 1,5-anhydro-D-glucitol (AG) is a marker of the diabetic state and also reflects the glycosuria induced by hyperglycemia but not by renal pathology. To investigate the benefits of the AG determination in order to diagnose diabetes in BB/Wor/(/)Tky rats, AG was measured in non-diabetic (n = 104) and diabetic (n = 113) BB/Wor/(/)Tky rats. AG was significantly higher in non-diabetic rats than in diabetic rats (25.2 +/- 9.3 vs 4.1 +/- 7.4 micrograms/ ml, mean +/- SD, p < 0.001). The best cut-off level for AG (8.5 micrograms/ml) was highly specific (100%) for ruling out diabetes and fairly sensitive (82.3%) to detect diabetes. Based on the AG cut-off levels, 90% of false-negative diabetic rats (18/20) were observed within 4 days after the onset of diabetes, which corresponded to 38.3% in diabetic rats (18/47) at that time. The false-negative diabetic rats and positive rats could be effectively distinguished based on the cumulative points given according to the urinary glucose after the onset of diabetes. 1 point for each cross [+] indicating glycosuria using the Testape, i.e. 2 or less points false negative and 4 or more points for diabetic rats in the first 4 days. In conclusion, there is a close inverse relation between the level of plasma AG and the amount of glycosuria detected just after the onset of overt diabetes in BB/Wor/(/)Tky rats.

Predicting long-term glycemic control of post-educational type II diabetic patients by evaluating serum 1,5-anhydroglucitol levels

1,5-Anhydroglucitol (1.5-AG) is known to closely reflect diabetic control within several days. The possibility of predicting long-term glycemic control after an educational hospitalization of type II diabetic patients was investigated by examining the relationship between changes in serum 1,5-AG levels after a short-term trial home stay following an educational program and long-term changes in glycosylated hemoglobin A1c (HbA1c) levels after discharge. After 22 patients with type II diabetes had successfully completed the educational hospitalization program, they returned as outpatients for 5 nights in a row. Changes in serum 1,5-AG levels were determined during this period. The HbA1c levels were then determined over a period of 3 months after discharge, and the relationship between changes in 1,5-AG and HbA1c levels was examined. Changes in serum 1,5-AG levels during the 5-day trial home stay and the changes in HbA1c levels during the 3 months after discharge from the hospital were found to be significantly correlated (r = 0.70, P < 0.01). A comparison of the decreased group, which exhibited a decrease in 1.5-AG levels of 5.0 mumol/l or more during the trial home stay, and the unchanged group, revealed that increases in body mass index 3 months after discharge were significantly higher in the decreased group (1.2 +/- 0.4%) than in the unchanged group (0.2 +/- 0.5%) (P < 0.05). Determination of serum 1,5-AG levels of patients with type II diabetes before and after a trial home stay following educational hospitalization was found to be useful in identifying patients at high risk of recurrence of poor glycemic control in the future.

[Screening of glucose intolerance with fasting blood samples]

Oral glucose tolerance test (OGTT) has been accepted as the standard test for screening of glucose intolerance in spite of its poor reproducibility, especially, in the impaired glucose intolerance (IGT). There have been widely assessed the diagnosis of diabetes mellitus with using glycemic control markers such as HbA1c, 1,5-AG, and FRA as an alternative method, which are not so much affected by sampling conditions. However, it has been found a wide overlap of the glycemic control marker's values between the normal and the IGT. In OGTT, subjects with lower blood glucose values 2 hours after glucose load turned out to be the normal glucose tolerance at the second examination as well. Therefore, it might be reasonable to identify people with a higher blood glucose value 2 hours after glucose load as a high risk group by the screening with fasting blood samples. We have evaluated the combination test of FBG, HbA1c and 1,5-AG for screening of the diabetes and the high risk IGT, and this combination revealed to be durable for screening. But it would be important to elucidate the natural history and the extent of the risk of the IGT, and select a proper test with a clear cut-off value for screening of impaired glucose intolerance at risk.

NMDA Receptor-dependent increase of cerebral glucose utilization after hypoxia-ischemia in the immature rat

Post-treatment with the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 reduces hypoxic-ischemic brain injury in immature animals. To elucidate possible mechanisms, cerebral glucose utilization (CMRglc) and cerebral blood flow (CBF) were measured 1-5 h after hypoxia-ischemia and administration of MK-801 in 7-day-old rats. After 100 min of unilateral hypoxia-ischemia, half of the pups were injected with MK-801. CMRglc was assessed by the [14C]deoxyglucose (2-DG) method. The brains were analyzed either by autoradiography or for energy metabolites and chromatographic separation of 2-DG-6-phosphate and 2-DG. CBF was measured by the autoradiographic [14C]iodoantipyrine method. Mean CMRglc in the cerebral cortex was increased ipsilaterally after hypoxia-ischemia to 15 +/- 3.3 mumol 100 g-1 min-1 (p < 0.01) and areas with CMRglc > 20 mumol 100 g-1 min-1 amounted to 8.0 +/- 7.7 mm2 in the ipsilateral hemisphere compared with 1.2 +/- 1.6 mm2 contralaterally (p < 0.001). Treatment with MK-801 decreased CMRglc bilaterally (p < 0.05) and reduced ipsilateral areas with increased CMRglc by 64% (p < 0.01). CBF was unaltered after hypoxia-ischemia and by MK-801 treatment. In conclusion, regional glucose hyperutilization in the parietal cortex after hypoxia-ischemia was attenuated by MK-801; this may have relevance to the neuroprotective effect of NMDA-receptor antagonists in this model.

Decreased serum 1,5-anhydroglucitol in nondiabetic subjects with a family history of NIDDM

OBJECTIVE

To investigate the effect of a family history of NIDDM on HbAlc and serum 1,5-anhydroglucitol (AG) in nondiabetic subjects.

RESEARCH DESIGN AND METHODS

A 75-g oral glucose tolerance test was performed; 258 subjects with normal glucose tolerance and 106 subjects with impaired glucose tolerance (IGT) were selected HbAlc and serum AG were compared between subjects with and without a family history of NIDDM. The relationships between age, BMI, HbAlc, serum AG, fasting and 2-h plasma glucose, and urinary glucose were also examined using principal component analysis with a varimax rotation.

RESULTS

In the normal group, only serum AG was lower in subjects with a positive family history than in those with no family history. On the other hand, in the IGT group, subjects with a positive family history were younger and had a higher 2-h plasma glucose, a higher urinary glucose, and a lower serum AG than those with no family history, whereas there was no difference in HbAlc. Principal component analysis identified three factors. The first factor, a linear combination of HbAlc and fasting plasma glucose, was labeled an average glycemic factor. The second factor, which included serum AG, 2-h plasma glucose, and urinary glucose, was labeled an oscillatory glycemic factor. The third factor, which contrasted age against BMI, was labeled an environmental factor.

CONCLUSIONS

Serum AG is related to glycosuria even among nondiabetic subjects, and its concentrations are decreased in those with a family history of NIDDM. Our results suggest that serum AG rather than HbAlc reflects early metabolic abnormalities in these subjects.

Common reabsorption system of 1,5-anhydro-D-glucitol, fructose, and mannose in rat renal tubule

1,5-Anhydro-D-glucitol (AG) is a major polyol, 99.9% of which is reabsorbed by the kidney. However, such reabsorption is inhibited by competition with glucose excreted in excess, i.e., glucosuria. Under such conditions, AG is excreted into the urine. We administered various types of sugars to rats by continuous intravenous infusion for two hours to evaluate the competition between AG and these sugars for renal reabsorption in vivo. The reabsorption of AG was significantly inhibited by competition with fructose and mannose. The excretion of AG in the 120 min after a load of 3.64 mmol of fructose was 1.99 +/- 0.33 mumol, that after 3.64 mmol of mannose loading was 2.34 +/- 0.43 mumol. These levels were comparable to the AG excretion observed after the administration of the same amount of glucose (3.87 +/- 0.61 mumol). No competition was observed with sucrose, xylose, myoinositol or galactose. The reabsorption of fructose and mannose was significantly inhibited by the presence of AG (P < 0.001) after a mixed load. Results suggest that AG is reabsorbed in the renal tubule by an AG/fructose/mannose-common transport system that is distinct from the major glucose reabsorption system. These findings may help to clarify the specific transport systems for various sugars in the renal tubule, as well as their physiological importance.