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PubMed2004

Fructosamine 3-kinase-related protein and deglycation in human erythrocytes.

Fructosamine 3-kinase (FN3K), an enzyme initially identified in erythrocytes, catalyses the phosphorylation of fructosamines on their third carbon, leading to their destabilization and their removal from protein. We show that human erythrocytes also contain FN3K-related protein (FN3K-RP), an enzyme that phosphorylates psicosamines and ribulosamines, but not fructosamines, on the third carbon of their sugar moiety. Protein-bound psicosamine 3-phosphates and ribulosamine 3-phosphates are unstable, decomposing at pH 7.1 and 37 degrees C with half-lives of 8.8 h and 25 min respectively, as compared with 7 h for fructosamine 3-phosphates. NMR analysis indicated that 1-deoxy-1-morpholinopsicose (DMP, a substrate for FN3K and FN3K-RP), like 1-deoxy-1-morpholinofructose (DMF, a substrate of FN3K), penetrated erythrocytes and was converted into the corresponding 3-phospho-derivative. Incubation of erythrocytes with 50 mM allose, 200 mM glucose or 10 mM ribose for 24 h resulted in the accumulation of glycated haemoglobin, and this accumulation was approx. 1.9-2.6-fold higher if DMP, a competitive inhibitor of both FN3K and FN3K-RP, was present in the incubation medium. Incubation with 50 mM allose or 200 mM glucose also caused the accumulation of ketoamine 3-phosphates, which was inhibited by DMP. By contrast, DMF, a specific inhibitor of FN3K, only affected the glucose-dependent accumulation of glycated haemoglobin and ketoamine 3-phosphates. These data indicate that FN3K-RP can phosphorylate intracellular, protein-bound psicosamines and ribulosamines, thus leading to deglycation.

Amines↗

PubMed2000

Identification, cloning, and heterologous expression of a mammalian fructosamine-3-kinase.

Fructosamines are thought to play an important role in the development of diabetic complications. Little is known about reactions that could metabolize these compounds in mammalian tissues, except for recent indications that they can be converted to fructosamine 3-phosphates. The purpose of the present work was to identify and characterize the enzyme responsible for this conversion. Erythrocyte extracts were found to catalyze the ATP-dependent phosphorylation of 1-deoxy-1-morpholinofructose (DMF), a synthetic fructosamine. The enzyme responsible for this conversion was purified approximately 2,500-fold by chromatography on Blue Sepharose, Q Sepharose, and Sephacryl S-200 and shown to copurify with a 35,000-M(r) protein. Partial sequences of tryptic peptides were derived from the protein by nanoelectrospray-ionization mass spectrometry, which allowed for the identification of the corresponding human and mouse cDNAs. Both cDNAs encode proteins of 309 amino acids, showing 89% identity with each other and homologous to proteins of unknown function predicted from the sequences of several bacterial genomes. Both proteins were expressed in Escherichia coli and purified. They were shown to catalyze the phosphorylation of DMF, fructoselysine, fructoseglycine, and fructose in order of decreasing affinity. They also phosphorylated glycated lysozyme, though not unmodified lysozyme. Nuclear magnetic resonance analysis of phosphorylated DMF and phosphorylated fructoseglycine showed that the phosphate was bound to the third carbon of the 1-deoxyfructose moiety. The physiological function of fructosamine-3-kinase may be to initiate a process leading to the deglycation of fructoselysine and of glycated proteins.

Adenosine Triphosphate↗

PubMed1995

Determination of a reference range for fructosamine in feline serum samples.

Fructosamine, the product of a non-enzymatic reaction between glucose and serum proteins, is a component of serum which reflects long-term deviations from normal glucose and protein homeostasis. Thirty-one healthy, intact, domestic short-haired cats, living under uniform feeding and environmental conditions, were sampled to calculate a reference range for feline serum fructosamine. The results were obtained using a nitroblue tetrazolium colorimetric method. The analytical assay was evaluated by calculation of within-run and between-day variation, detection limit, and accuracy. Serum fructosamine concentrations were approximately normally distributed and the calculated reference range was 146-271 mumol/L (mean 209 mumol/L, standard deviation 31.6 mumol/L). There were no significant differences between male and female cats, or between cats older and younger than 12 months. Previously conducted studies give higher reference ranges, possibly because of differences in the test procedure and homogeneity of the test population.

Animals↗

PubMed1988

Comparison of fructosamine and glycated haemoglobin in children with type 1 (insulin-dependent) diabetes mellitus.

In six children (age: mean 8.4 years, range 2.2-12.6 years) with newly diagnosed Type 1 (insulin-dependent) diabetes mellitus, plasma fructosamine and glycated haemoglobin (HbA1) were compared in respect to their disappearance during the first month after diagnosis during well controlled glycaemia. The disappearance of the surplus plasma fructosamine and HbA1 was calculated applying exponential equations. The estimated half-lives of fructosamine (mean 57.2 days, range 40.7-77 days) and HbA1 (mean 59.7 days, range 43.3-82 days) were not significantly different, a finding which is left unexplained.

Child↗

PubMed1990

Maternal serum fructosamine and maternofetal glucose and insulin homeostasis in normal pregnancy.

Well-defined normal values are necessary to identify pregnancies complicated by gestational diabetes (GD) and thus further reduce perinatal morbidity and mortality from this condition. The present study defined the range for the oral glucose tolerance test (oGTT) in 2578 pregnancies. After exclusion of abnormal results 822 randomized patients were used to define normal values for fructosamine, HbA1c, insulin, glucose and C-peptide in the maternal serum; insulin, glucose and fructosamine in the amniotic fluid; and insulin, glucose, C-peptide and fructosamine in the cord blood.

Adult↗

PubMed1987

Hemoglobin A1 and serum fructosamine levels in hyperthyroidism.

The severity, prevalence and pathogenesis of abnormalities of carbohydrate metabolism in hyperthyroidism are incompletely defined. The extent of glycosylation of proteins provides an objective, retrospective index of glycemic control. We have measured the percent hemoglobin A1, random plasma glucose level and serum concentrations of fructosamine, total protein and albumin in hyperthyroid and euthyroid subjects attending a hospital-based thyroid clinic. A significant (p = 0.002) increase in the mean value for hemoglobin A1 and a significant (p = 0.0003) decrease in the mean values for fructosamine were found in the hyperthyroid group. The lower mean fructosamine value in the hyperthyroid group was attributed to a concomitant decline in the mean albumin concentration (p = 0.001). The mean value for glucose tended to be higher in the hyperthyroid group, but the difference did not reach significance at the 0.05 level (p = 0.09). The finding of a higher mean hemoglobin A1 concentration in hyperthyroid patients compared to euthyroid subjects is new evidence for a persistent abnormality in glycemic regulation in most thyrotoxic patients.

Adult↗

PubMed1991

Serum fructosamine is not a useful screening test for gestational diabetes.

Serum fructosamine was measured in 569 samples of pregnant women without gestational diabetes. We defined abnormal fructosamine as mean + 2SD, and analysed its potential value to detect patients with gestational diabetes diagnosed with current screening criteria. We found serum fructosamine to be an insensitive parameter: Measured at the time of a positive 50 g glucose screening, SF would have detected 4/48 gestational diabetes.

Blood Glucose↗

PubMed1989

Clinical usefulness of estimation of serum fructosamine concentration as screening test for gestational diabetes.

Serum fructosamine levels and fructosamine/protein ratios were measured in 100 pregnant women who underwent glucose tolerance tests because of clinical risk. Compared with normal pregnant women, the 13 study participants with gestational diabetes had higher fructosamine/protein levels (39 +/- 3.9 mumol/gm versus 37 +/- 3.2 mumol/gm, p less than 0.05), fasting serum glucose levels (107 +/- 13.7 mg/dl versus 82 +/- 8.6 mg/dl, p less than 0.001), and area under curve of glucose tolerance test (36 +/- 5 gm x min x dl-1 versus 22 +/- 3.6 gm x min x dl-1, p less than 0.001). The serum fructosamine levels were not significantly different between the two groups of participants (2.3 +/- 0.26 mmol/L versus 2.2 +/- 0.17 mmol/L); 10 of the 13 women with diabetes had a fructosamine/protein ratio within 2 SD of the mean of the groups of normal pregnant women. Spontaneous caloric intakes (r = 0.72, p less than 0.005) and the hospital mean daily capillary glucose levels during diabetic diet (r = 0.72, p less than 0.005) correlated better with the fructosamine/protein ratio than with fasting serum glucose levels (r = 0.58, p less than 0.05) and area under curve (r = 0.57, p less than 0.05). Consequently, serum fructosamine and fructosamine/protein ratio levels should be considered insensitive as a screening test in pregnant patients with clinical risk of gestational diabetes.

Adult↗

PubMed1988

Evaluation of Roche fructosamine test: use for diabetic patient monitoring.

A fructosamine assay using commercially available reagents on an IL Multistat III centrifugal analyser was evaluated. Within- and between-batch precision were less than 4% (CV). Results were similar using serum or oxalated plasma, but were 5% lower than those using sodium heparinate. We compared serum fructosamine and Hb A1c results in insulin-dependent and non-insulin-dependent diabetics: serum fructosamine correlated with Hb A1c (r = 0.80) and gave at least as good a separation of patients from normal controls as did Hb A1c.

Adult↗

PubMed2001

Effect of 'antidiabetis' herbal preparation on serum glucose and fructosamine in NOD mice.

The antihyperglycemic effect of the Antidiabetis herbal preparation ((Myrtilli folium (Vaccinium myrtillus L.), Taraxaci radix (Taraxacum officinale Web.), Cichorii radix (Cichorium intybus L.), Juniperi fructus (Juniperus communis L.), Centaurii herba (Centaurium umbellatum Gilib.), Phaseoli pericarpium (Phaseolus vulgaris), Millefollii herba (Achillea millefolium L.), Morii folium (Morus nigra L.), Valeriane radix (Valleriana officinalis L.), Urticae herba et radix (Urtica dioica L.)), patent No. P-9801091 Zagreb, Croatia was investigated. Two extracts were prepared: ethanol extract (extract 1), and ethanol extract from which ethanol was evaporated on a rotatory evaporator at a temperature of 45 degrees C (extract 2). Extract 1 and extract 2 were administered (in experiment 1) to alloxan-induced non-obese diabetic (NOD) mice in the same dose of 20 mg/kg. Blood glucose was determined before, and 10, 30, 60 and 120 min after the preparation administration. Extract 1 and extract 2 decreased the level of blood glucose by 10 and 20%, respectively, of the initial value (at 0 min, mean = 22.6 +/- 8.3 mmol/l). Serum levels of glucose and fructosamine were determined in NOD mice, NOD mice administered extract 2 in a dose of 20 mg/kg of extract 2, and NOD mice administered acarbose in a dose of 25 mg/100 g chow, in order to verify the hypoglycemic action of extract 2 (in experiment 2). Extract 2 and acarbose were admixed to the chow. The duration of treatment was 7 days. Significantly lower glucose (P < 0.05) and fructosamine (P < 0.001) levels were recorded in extract 2 treated NOD mice as compared with NOD mice. Study results showed extract 2 to significantly decrease the level of glucose and fructosamine in alloxan induced NOD mice. Our future studies will be focused on the search of active principles of the extracts.

Acarbose↗

PubMed2000

Effect of acute hyperglycaemia on the serum fructosamine and blood glycated haemoglobin concentrations in canine samples.

The effect was studied of an acute and non-persistent hyperglycaemia on the serum fructosamine and blood glycated haemoglobin concentrations in canine samples. Five dogs were given glucose solution intravenously and blood samples were taken from each dog before and at 5, 15, 30, 60 and 120 min and 24 h after the infusion. There was an intense hyperglycaemia 5 min after the injection was given, but no statistically significant differences in the serum fructosamine and glycated haemoglobin were observed. It was concluded that an acute and transient hyperglycaemia does not cause significant changes in the glycated haemoglobin and fructosamine concentrations in healthy dogs.

Acute Disease↗

PubMed1987

[Determination of the metabolic condition in diabetics with renal insufficiency by means of the fructosamine test].

We determined HBA1 (microcolumn method) and glycosylated albumin (fructosamine) in 23 healthy subjects, 35 patients with renal insufficiency without diabetes and 14 patients with diabetes mellitus and renal insufficiency. All patients with renal insufficiency required dialysis. All diabetics were of type I and had been compensated on insulin. The HBA1 in the nondiabetic patients with renal insufficiency (9.4 +/- 1.4%) was significantly raised compared to that in the control group with healthy metabolism (7.3 +/- 0.6%). Irrespective of the quality of compensation, the diabetic patients had HBA1 values of more than 11% of average. On the other hand, the concentrations of glycosylated albumin in healthy nondiabetic patients and in diabetic patients with renal insufficiency did not differ (1.3 +/- 0.5 as compared to 1.1 +/- 0.4 mmol/l) and were all in the normal range. Well-adjusted diabetics with renal insufficiency had a fructosamine concentration of 1.9 +/- 0.7 mmol/l (theoretical value for a good compensation 2.0 to 2.8). We conclude that determination of HBA1 in pronounced renal insufficiency does not provide reliable values because carbamylated hemoglobin is also registered and determination of fructosamine (which only indicates the metabolic situation in the last three weeks, however) is to be preferred in this situation.

Diabetes Mellitus, Type 1↗

PubMed1995

Novel degradation pathway of glycated amino acids into free fructosamine by a Pseudomonas sp. soil strain extract.

A Pseudomonas sp. soil strain, selected for its ability to grow on epsilon-(1-deoxyfructosyl) aminocaproic acid, was induced to express a membrane-bound enzymatic activity which oxidatively degrades Amadori products into free fructosamine. Apparent Km values for fructosyl aminocaproate, epsilon-fructosyl lysine, fructosyl glycine, and ribated lysine were 0.21 mM, 2.73 mM, 3.52 mM, and 1.57 mM, respectively. The enzyme was also active against alpha-fructosyl lysine and borohydride-reduced Amadori product, weakly active with ribated and glycated polylysine, and inactive with reducing sugars, amino acids, and glycated proteins. The enzymatic activity was highest at pH 6.5 and 25 degrees C in 0.1 M sodium phosphate, while over 80% of the activity was lost above 65 degrees C. Complete inhibition was observed by HgCl2, NaN3, and NaCN suggesting a role for SH groups and copper in the enzymatic activity. The reaction products were characterized by 1H NMR, 13C NMR, and GC/MS and found to correspond to 1-deoxy-1-aminofructose, i.e. free "fructosamine," and adipic acid. Confirmation of the free fructosamine structure was based on the complete spectroscopic identity of the borohydride reduction product with commercially available glucamine (1-amino-1-deoxyglucitol). The new enzyme is provisorily classified as fructosyl N-alkyl amino acid oxidase (EC 1.5.3) (fructosyl-amino acid:oxygen oxidoreductase) and may thus belong to a novel class of "Amadoriases" which deglycate Amadori products oxidatively. In contrast, however, the new enzyme acts on the alkylamine bond rather than the ketoamine bond of the Amadori product.

Amino Acids↗

PubMed2001

Glucose and lactate in vitreous humor compared with the determination of fructosamine for the postmortem diagnosis of diabetes mellitus.

Diabetes mellitus is a chronic metabolic illness responsible for a great number of deaths. In postmortem diagnosis, because of the difficulty involved in interpreting blood glucose levels and relatively nonspecific pathologic features, biochemical markers in vitreous humor are useful. The aim of this study was to compare the results obtained for the combined determination of lactate and glucose with fructosamine levels recorded in the vitreous humor of two diagnostic groups (one diabetic and the other nondiabetic). The authors intended to ascertain the capacity of different markers measured in vitreous humor to diagnose diabetes mellitus. Fifty-one cadavers (mean age, 58.7 years; standard deviation, 17.09) were studied. The mean postmortem interval was 16.4 hours (standard deviation, 9.05). Cases were assigned to two diagnostic groups according to whether they were previously diagnosed as either diabetic or nondiabetic. Statistically significant differences for glucose, fructosamine, and the sum values of glucose and lactate were found between the two diagnostic groups. The highest levels were obtained in the group of cases with a previous diagnosis of diabetes mellitus. After the comparison of receiver operating characteristic curves, the sum values of glucose and lactate in vitreous humor is a better predictor of antemortem diabetes mellitus than the fructosamine.

Adult↗

PubMed1990

Fructosamine compared with a glucose load as a screening test for gestational diabetes.

Five hundred seven women were screened for gestational diabetes between 20-36 weeks' gestation. All received a 100-g glucose (polycose) load at 28 weeks with measurement of plasma glucose 1 hour later. Fructosamine levels were measured at 4-week intervals from 20-36 weeks. At 36 weeks, a full 100-g 3-hour glucose tolerance test was performed on all subjects. Eighteen women were diagnosed as having gestational diabetes. The glucose load had a sensitivity of 81% in detection of gestational diabetes, compared with 50% for fructosamine at 36 weeks. Fructosamine is not useful as a screening test for gestational diabetes as currently defined.

Diabetes Mellitus↗

PubMed1988

Plasma fructosamine in non-diabetic pregnancy.

Plasma fructosamine and its relation to plasma total protein and albumin was examined in 40 non-diabetic pregnant women. Plasma fructosamine did not correlate with haemoglobin A1 or plasma albumin. The mean intra-individual ranges were plasma fructosamine 0.53 mmol/l (SD 0.17); haemoglobin A1 1.42% (SD 0.42); plasma fructosamine/g albumin 0.024 mmol (SD 0.005) and plasma fructosamine/g total protein 0.008 mmol (SD 0.003). A high degree of individuality for these variables was also observed.

Adolescent↗

PubMed1995

Pancreatic insulin-secreting carcinoma in a dog: fructosamine for determining persistent hypoglycaemia.

A five-year-old intact male rottweiler was presented with a history of episodic weakness and mild-generalised seizures. A tentative diagnosis of an insulin-secreting tumour in the pancreas was made based on fasting hypoglycaemia with concomitant hyperinsulinaemia and a subnormal fructosamine value. The diagnosis was confirmed by exploratory coeliotomy, intravenous infusion of methylene blue, histopathology and immuno-histochemical analysis of suspected neoplastic tissue. Fructosamine assays are traditionally used for monitoring the metabolic status of diabetics where a single elevated measurement reflects persistent hyperglycaemia. This report suggests that a single low measurement of fructosamine may indicate persistent hypoglycaemia and may be helpful, in conjunction with an insulin measurement, in the diagnosis of insulin-secreting tumours.

Animals↗

PubMed1985

The estimation of serum fructosamine: an alternative measurement to glycated haemoglobin.

A method is presented for the estimation of fructosamine using a Cobas Bio centrifugal analyser. The effect of three different preparations of human serum albumin used for construction of calibration curves of 1-deoxy-1-morpholinofructose is described. The selection of serum albumin and the concentration used in the standard solutions is critical since the dose-response curve is affected differently and will therefore influence the estimated values. Normal ranges were obtained for non-diabetic subjects with normal protein status and for a group of females with reduced albumin levels due to pregnancy or oestrogen therapy. There was no significant difference between fructosamine levels in these populations. Fructosamine was also estimated in 250 patients attending a diabetic out-patient department and this correlated well with haemoglobin A1 estimated simultaneously. The method is rapid, technically simple and inexpensive and may prove to be a useful and reliable alternative to HbA1 estimation.

Adolescent↗