Comparison of efficacy between dipeptidyl peptidase-4 inhibitor and sodium-glucose cotransporter 2 inhibitor on metabolic risk factors in Japanese patients with type 2 diabetes mellitus: Results from the CANTABILE study

AIMS

The aim of this study was to compare the effectiveness of teneligliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, and canagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, at reducing a composite outcome of three metabolic risk factors (obesity, hypertension, and dyslipidemia) in Japanese patients with type 2 diabetes mellitus (T2DM) and metabolic risks.

METHODS

In this prospective, multicenter, open-label, randomized, parallel-group comparison study, 162 patients with T2DM and one or more metabolic risk factors were randomized into a teneligliptin or canagliflozin group and treated for 24 weeks. The primary endpoint was the composite percentage of subjects who experienced an improvement in at least one metabolic risk after 24 weeks of treatment.

RESULTS

The primary endpoint was achieved significantly by more patients in the canagliflozin group than in the teneligliptin group (62.2% vs. 31.3%, p = 0.0004). A ≥ 3% body weight loss was also achieved by significantly more participants in the canagliflozin group than in the teneligliptin group (55.9% vs. 10.5%, p < 0.0001).

CONCLUSIONS

This study showed canagliflozin to be more effective at reducing metabolic risks than teneligliptin. In Japanese patients with T2DM and metabolic risk factors, SGLT2 inhibitors may be superior to DPP-4 inhibitors at controlling multiple metabolic risk.

Renal transplantation between siblings with unrecognized Fabry disease

Fabry disease is an X-linked lysosomal storage disease caused by deficiency of the lysosomal hydrolase, α-galactosidase A (α-Gal A). We report a case of a renal transplant recipient with unrecognized Fabry disease who received the allograft from a sibling donor with unrecognized Fabry disease. The recipient began to show a gradual increase of the serum creatinine with mild proteinuria at 3 years after transplantation. Histopathologic examination revealed finely vacuolated podocytes, demonstrated by ultrastructural examination to contain osmophilic myelin bodies. Furthermore, the recipient showed reduced circulating levels of α-Gal A and elevated urinary levels of globotriaosylceramide. These findings indicated that both the recipient and the donor suffered from Fabry disease of the renal variant phenotype. Enzyme replacement therapy (ERT) was initiated in the recipient, which resulted in a slight decrease of serum creatinine. Although mild proteinuria persisted, initiation of ERT in the recipient led to improvement of the renal function.

Effect of Rolipram, a Phosphodiesterase IV Inhibitor, on Allergic Footpad Swelling using Various Adjuvants in Mice

We studied the effect of rolipram, a phosphodiesterase (PDE) IV inhibitor, on allergic footpad swelling in mice. For this study, varying adjuvants including complete Freund's adjuvant (CFA), incomplete Freund's adjuvant (IFA) and Imject Alum (Alum) were used because the extent of antigen-specifically induced T helper type 1 (Th1) and Th2 responses had been shown to depend on adjuvants used. To induce allergic footpad swelling, we immunized mice with ovalbumin (OVA) emulsified in either CFA or IFA, dissolved in Alum or in phosphate-buffered saline (PBS) as a control (day 0), followed by subcutaneous injection of the antigen into footpads on day 21. Rolipram was given orally to the animals daily from days 0-20. Results showed that treatment with rolipram was followed by an increase in early swelling at 0.5 h and a decrease in late swelling at 6 and 24 h in the CFA group. In the IFA group, rolipram significantly enhanced swelling at, but not after, 30 min. In the Alum and the PBS groups, the PDE inhibitor failed to affect the OVA-specific footpad reaction at all times examined. Treatment of the CFA and IFA groups with rolipram significantly inhibited the production of the Th1 antibody anti-OVA immunoglobulin G2a (IgG2a), and the drug enhanced Th2 cell-dependent anti-OVA IgE production. In both groups, rolipram also enhanced the secretion of Th2 cytokines including interleukin-4 (IL-4) and IL-10. These findings suggest that rolipram may facilitate early allergic footpad swelling mediated by Th2 immune responses, while the late phase of swelling associated with Th1 responses may be attenuated by the PDE IV inhibitor.

Reactivation of antigen-induced arthritis in mice by oral administration of lipopolysaccharide

We examined whether oral administration of lipopolysaccharide (LPS) from Escherichia coli reactivated antigen-induced arthritis (AIA) in mice that is one of models of human rheumatoid arthritis. To induce AIA, mice were immunized by subcutaneous injection of ovalbumin (OVA) emulsified with complete Freund's adjuvant into the base of the tail (day 0) followed by intraarticular injection of OVA on day 21. To investigate the ability of LPS to reactivate AIA, varying doses of LPS were p.o. administered 48 h after the challenge injection. The results showed that administration of LPS was followed by reactivation of AIA in a dose-related fashion. The reactivation of AIA by LPS was associated with increases in interferon-gamma, interleukin-1beta and tumour necrosis factor-alpha. Polymyxin B sulfate given immediately before administration of LPS suppressed the reactivation of AIA. These findings suggest that LPS from intestinal bacteria may play a role in the reactivation of joint inflammation in which immune responses to pathogenic antigens are involved.

Effects of diesel exhaust particle extracts on Th1 and Th2 immune responses in mice

The present study was undertaken to investigate the effects of extracts of diesel exhaust particles (DEP) on Th1 and Th2 immune responses. In order to separate compounds from DEP different in hydrophobicity, a single DEP sample was consecutively extracted with hexane (HEX-DEP), benzene (BEN-DEP), dichloromethane (DIC-DEP), methanol (MET-DEP), and 1M ammonia (AMM-DEP). The last unextracted residue (UNE-DEP) was also used to test its effect on immune responses. To immunize mice, hen egg lysozyme (HEL) was injected i.p. (day 0). Varying doses of DEP, each DEP extract, and UNE-DEP were intranasally administered every 2 days from days 0 to 18. Anti-HEL IgG2a antibodies in sera and IFN-&#x03B3; secreted from spleen cells were measured as an indicator of Th1 immune responses, while anti-HEL IgG1 antibodies and IL-4 as that of Th2 responses. The results showed that treatment with DEP and DIC-DEP increased both Th1 and Th2 responses to HEL. UNE-DEP facilitated Th1 but not Th2 responses, while MET- and AMM-DEP administration was followed by enhancement of Th2 but not Th1 responses. Neither HEX- nor BEN-DEP modulated Th1 as well as Th2 responses. These results suggest that DEP contain various compounds different in hydrophobicity which may affect both Th1 and Th2, Th1 but not Th2, and Th2 but not Th1 immune responses.

Cryoglobulinemic glomerulonephritis in thymic stromal lymphopoietin transgenic mice

Mixed cryoglobulins are complexes of immunoglobulins that reversibly precipitate in the cold and lead to a systemic disease in humans. Renal involvement usually manifests as a membranoproliferative glomerulonephritis with marked monocyte infiltration and, at times, intracapillary thrombi. Thymic stromal lymphopoietin (TSLP) is a recently cloned cytokine that supports differentiation and long-term growth of B cells. Here we report that TSLP overexpression in mice results in the development of mixed cryoglobulins, with renal involvement closely resembling cryoglobulinemic glomerulonephritis as it occurs in humans. One hundred twenty-three mice were sacrificed at monthly intervals, with at least five TSLP transgenic mice and five controls in each group. Blood, kidneys, spleen, liver, lung, and ear were collected and studied by routine microscopy, immunofluorescence, immunohistochemistry, and electron microscopy. TSLP transgenic animals developed polyclonal mixed cryoglobulinemia (type III) and a systemic inflammatory disease involving the kidney, spleen, liver, lung, and ears. Renal involvement was of a membranoproliferative type demonstrating thickened capillary walls with cellular interposition and double contours of the basement membrane, expansion of the mesangium because of increased matrix and accumulation of immune-deposits, subendothelial immune-deposits, focal occlusion of capillary loops, and monocyte/macrophage influx. In contrast to the severe glomerular lesions, the tubulointerstitium was not involved in the disease process. The renal lesions and the disease course were more severe in females when compared to males. We describe a mouse strain in which a B-cell-promoting cytokine leads to formation of large amounts of mixed cryoglobulins and a systemic inflammatory injury that resembles important aspects of human cryoglobulinemia. This is the first reproducible mouse model of renal involvement in mixed cryoglobulinemia, which enables detailed studies of a membranoproliferative pattern of glomerular injury.

Up-regulation of extracellular matrix proteoglycans and collagen type I in human crescentic glomerulonephritis

BACKGROUND

The pathogenesis of crescentic glomerulonephritis (CGN) involves cellular migration and proliferation in the urinary space, frequently followed by fibrous organization. Extracellular matrix proteoglycans (PGs) may regulate these events via effects on cellular migration, interactions with growth factors, including transforming growth factor-beta (TGF-beta), and control of collagen fibrillogenesis. The expression of PG in human CGN is unknown.

METHODS

Renal tissues from 18 patients with CGN were examined immunohistochemically for versican, decorin, biglycan and collagen type I, and were compared with morphologically normal tissues from six tumor nephrectomies. Synthesis of decorin, biglycan, and procollagen type I mRNAs was evaluated by in situ hybridization.

RESULTS

Versican was strongly expressed in cellular crescents and periglomerular areas, whereas decorin and biglycan accumulated in collagen type I-enriched regions, including fibrocellular and fibrous crescents, and interstitial fibrosis. PG and collagen type I accumulation colocalized with myofibroblasts in crescents, periglomerular areas, and interstitium.

CONCLUSIONS

The temporal and spatial patterns of expression demonstrated in this study provide evidence to support pathogenic roles for PG in the evolution of CGN. Based on known biological properties of this molecule, versican may facilitate migration of cells in developing crescents. Decorin and biglycan may contribute to progression of CGN, perhaps via interactions with collagen type I in the remodeled extracellular matrix.

Anti-estrogenic activity of diesel exhaust particles

Estrogenic and anti-estrogenic activities of diesel exhaust particles (DEP) were evaluated using yeast cells expressing the human estrogen receptor and the responsive element regulating the expression of the receptor gene for beta-galactosidase (Routledge and Sumpter, 1996). It was found that a suspension of whole DEP suspension is not estrogenic but that this preparation possesses the ability to reduce the estrogen-dependent reporter activity. DEP were serially extracted with hexane, benzene, dichloromethane, methanol, and 1 M ammonia, and the estrogenic and anti-estrogenic activities of these preparations were determined. None of the extracts of DEP were estrogenic, but the extracts of benzene, dichloromethane and methanol possessed anti-estrogenic activity, and the activity of estrogen in the presence of hexane extract was slightly decreased. These results indicated that DEP contain heterologous compounds having anti-estrogenic activity. It is thought that those compounds in DEP can modulate the activity of estrogen, leading to the distruption of balance between estrogen and androgen. In this paper, the environmental effects of DEP in relation to the endocrine disrupting effect of organic compounds in DEP are discussed.

Identification of pentosidine as a native structure for advanced glycation end products in beta-2-microglobulin-containing amyloid fibrils in patients with dialysis-related amyloidosis

beta-2-Microglobulin (beta-2m) is a major constituent of amyloid fibrils in patients with dialysis-related amyloidosis (DRA). Recently, we found that the pigmented and fluorescent adducts formed nonenzymatically between sugar and protein, known as advanced glycation end products (AGEs), were present in beta-2m-containing amyloid fibrils, suggesting the possible involvement of AGE-modified beta-2m in bone and joint destruction in DRA. As an extension of our search for the native structure of AGEs in beta-2m of patients with DRA, the present study focused on pentosidine, a fluorescent cross-linked glycoxidation product. Determination by both HPLC assay and competitive ELISA demonstrated a significant amount of pentosidine in amyloid-fibril beta-2m from long-term hemodialysis patients with DRA, and the acidic isoform of beta-2m in the serum and urine of hemodialysis patients. A further immunohistochemical study revealed the positive immunostaining for pentosidine and immunoreactive AGEs and beta-2m in macrophage-infiltrated amyloid deposits of long-term hemodialysis patients with DRA. These findings implicate a potential link of glycoxidation products in long-lived beta-2m-containing amyloid fibrils to the pathogenesis of DRA.

Formation and stability of pyrrole adducts in the reaction of levuglandin E2 with proteins

Levuglandin (LG) E2 is rapidly sequestered by covalent binding with proteins. The reaction of LGE2 with a protein in neutral aqueous solution exhibits two phases. A metastable adduct rapidly accumulates initially. In the second phase, a protein-bound pyrrole is generated. Pyrrole formation and stability were monitored with an immunoassay using antibodies that were raised against a stable isostere. That LG-derived pyrroles are the major products (> 76%) of the LGE2-protein reaction is suggested by the level of antibody binding found for LG-protein adducts compared with that found for a pyrrole derived from LGE2 and 6-amino-1-hexanol. Because the initial metastable LG-protein adduct is a reactive electrophile, it can be trapped with amines, such as glycine, to give stable ternary adducts that do not cross-react with the antibodies. Although highly alkylated pyrroles are chemically sensitive compounds, the protein-bound LG-derived pyrrole appears to be stable in aqueous solution at pH 7.4. Thus, it shows no decrease in immunoreactivity over several weeks. This discovery leads to the expectation that such pyrroles will accumulate in vivo, especially in proteins that do not turn over rapidly. Thus, the LG-derived protein-bound pyrrole may be a useful marker of oxidative lipid damage, and an immunoassay for this post-translational protein modification can be exploited as a mild, sensitive method for detecting and quantifying the generation of LGs in chronic inflammatory states.

Isolation, purification, and characterization of an Amadori product binding protein from a Pseudomonas sp. soil strain

Sugars react nonenzymatically with protein amino groups to form a ketoamine adduct (Amadori product), which leads to the formation of advanced glycation end-products. These compounds are involved in the development of tissue modifications such as cross-linking and fluorescence in diabetes and aging. Searching for an enzyme to reverse protein glycation, we isolated a Pseudomonas sp. soil strain growing selectively on the Amadori product epsilon-fructosyl-aminocaproate. An Amadori product binding protein (ABP) was purified from the bacterial extract by single-step affinity chromatography on glycated lysine-Sepharose. The protein, a monomer of 45 kDa, did not bind to unglycated or NaBH4-reduced glycated lysine-Sepharose suggesting specificity for the Amadori compound. The concentration-dependent binding of glycated aminocaproate showed saturation with Kd = 1.49 microM and Bmax = 17.63 nmol/mg of protein corresponding to 0.8 mol/mol of protein. The binding of epsilon-1-[14C]fructosyl-aminocaproate to the protein was inhibited by other glucose-derived Amadori products, but not by free sugars, unglycated amines, or ribated lysine. The sequence of the first 16 NH2-terminal amino acids and a GenBank search revealed that ABP is a novel protein. Its synthesis was inducible by growth of the organism in Amadori product. Immunoblotting studies showed that ABP is not found in cell extracts from other prokaryotes, yeast, or liver homogenate and does not bind Amadori products in glycated proteins. ABP has no enzymatic activity toward glycated substrates and may thus have transport or permease function for glycated amino acids.

ELISA of pentosidine, an advanced glycation end product, in biological specimens

Pentosidine is a fluorescent protein cross-link and glycoxidation marker for the advanced glycation reaction in diabetes, aging, and uremia. We raised polyclonal antibodies in New Zealand White rabbits against this hapten coupled to keyhole limpet hemocyanin. The antibodies detected by ELISA reacted strongly with free pentosidine but not with pentosidine-like compounds. The working range of the competitive ELISA for standard pentosidine was 0.1-100 pmol. Pentosidine was detectable in bovine serum albumin incubated with ribose as a function of incubation time. Immunoblotting studies showed that pentosidine specifically stained in oligomers of lysozyme incubated with ribose. Digestion with protease (Pronase E, 20 g/kg) as well as acid hydrolysis enhanced the immunoreactivity of samples, the pentosidine values in digested human plasma correlating with those measured by HPLC (r = 0.98). Pentosidine in diabetic and uremic plasma digested with Pronase E was significantly higher than normal (P &lt; 0.01; mean +/- SD): 1620 +/- 1940 and 2630 +/- 1320 [corrected] nmol/L, respectively, vs 151 +/- 55 nmol/L (normal). Amounts of pentosidine in hydrolyzed skin collagen increased with age and were increased in diabetes and uremia. This ELISA provides a new tool for assessing the role of the advanced Maillard reaction in aging and age-related diseases.

ELISA of pentosidine, an advanced glycation end product, in biological specimens

Pentosidine is a fluorescent protein cross-link and glycoxidation marker for the advanced glycation reaction in diabetes, aging, and uremia. We raised polyclonal antibodies in New Zealand White rabbits against this hapten coupled to keyhole limpet hemocyanin. The antibodies detected by ELISA reacted strongly with free pentosidine but not with pentosidine-like compounds. The working range of the competitive ELISA for standard pentosidine was 0.1-100 pmol. Pentosidine was detectable in bovine serum albumin incubated with ribose as a function of incubation time. Immunoblotting studies showed that pentosidine specifically stained in oligomers of lysozyme incubated with ribose. Digestion with protease (Pronase E, 20 g/kg) as well as acid hydrolysis enhanced the immunoreactivity of samples, the pentosidine values in digested human plasma correlating with those measured by HPLC (r = 0.98). Pentosidine in diabetic and uremic plasma digested with Pronase E was significantly higher than normal (P < 0.01; mean +/- SD): 1620 +/- 1940 and 2630 +/- 1320 [corrected] nmol/L, respectively, vs 151 +/- 55 nmol/L (normal). Amounts of pentosidine in hydrolyzed skin collagen increased with age and were increased in diabetes and uremia. This ELISA provides a new tool for assessing the role of the advanced Maillard reaction in aging and age-related diseases.

Advanced Maillard reaction end products are associated with Alzheimer disease pathology

During aging long-lived proteins accumulate specific post-translational modifications. One family of modifications, termed Maillard reaction products, are initiated by the condensation between amino groups of proteins and reducing sugars. Protein modification by the Maillard reaction is associated with crosslink formation, decreased protein solubility, and increased protease resistance. Here, we present evidence that the characteristic pathological structures associated with Alzheimer disease contain modifications typical of advanced Maillard reaction end products. Specifically, antibodies against two Maillard end products, pyrraline and pentosidine, immunocytochemically label neurofibrillary tangles and senile plaques in brain tissue from patients with Alzheimer disease. In contrast, little or no staining is observed in apparently healthy neurons of the same brain. The Maillard-reaction-related modifications described herein could account for the biochemical and insolubility properties of the lesions of Alzheimer disease through the formation of protein crosslinks.

Characterization of antibodies to advanced glycosylation end products on protein

Antibodies directed against advanced glycosylation end products (AGEs) formed during a Maillard reaction have been generated and characterized. Since protein-bound AGEs recognized by the antibodies were labile to acid hydrolysis, the antibodies were further characterized by using the AGE-alpha-acetyl-L-lysine methyl ester (AGE-ALME) with a brown and fluorescent property as well as the AGE-proteins. The antibodies reacted with fluorescent compounds, rather than brown pigment compounds, in the AGE-ALME. The fluorescent compounds in the AGE-ALME were separated into four fluorescent compounds by reversed-phase thin layer chromatography (TLC). Of the fluorescent compounds tested, compound 3 (Rf = 0.63), as designated on a TLC plate, showed the highest affinity for the antibodies. In addition, the antibody recognition to the cross-linked oligomers with fluorescence in the AGE-protein was investigated by using bovine pancreatic ribonuclease A (RNase), which is known as a model protein for studying AGE-induced cross-linking. Fluorescence in the AGE-RNase existed in both of the oligomers and the monomer. The cross-linked oligomers exhibited higher affinity to the antibodies than did the monomer, which has a similar degree of fluorescent intensity. These results indicate that our antibodies against cross-linked protein-bound AGEs may serve as a useful tool to elucidate pathophysiological roles of advanced Maillard reaction in diabetic complications and aging processes.

Radioimmunoassay for the determination of glycated haemoglobin

A competitive radioimmunoassay for the quantitative determination of glycated haemoglobin was developed. The antiserum, obtained by immunizing guinea pigs with reduced glycated human albumin, was capable of identifying and quantitating the glucitollysine residues of glycated Hb after reduction with sodium borohydride. To simplify the sample preparation we introduced trichloroacetic acid precipitation to remove unreacted sodium borohydride instead of using dialysis or gel filtration. Using this procedure, our radioimmunoassay became relatively simple and provided satisfactory within- and between-run (1.3-2.8% and 1.9-5.4% coefficient of variation, respectively). The radioimmunoassay method was compared to the measurement of HbAlc by high performance liquid chromatography which is the most widely used method for quantitating glycated Hb. For this purpose glycated Hb was measured in normal glucose tolerance, impaired glucose tolerance, and diabetes mellitus groups based on WHO criteria. Both assays were able to discriminate between the normal and diabetic groups. In addition, while the determination of glycated Hb by the radioimmunoassay method was able to clearly discriminate between the normal and impaired glucose tolerance groups, the determination of HbAlc by the high performance liquid chromatography method failed to discriminate between these two groups. Moreover, 15 of the 20 impaired glucose tolerance patients exceeded the upper normal range (mean normal values + 2 SD) in radioimmunoassay. But all 20 patients with impaired glucose tolerance were within the upper normal range in HbAlc values. These results demonstrate that the measurement of glycated Hb by radioimmunoassay is more sensitive than the measurement of HbAlc by high performance liquid chromatography since it can discriminate between the normal and impaired glucose tolerance groups.

[Successful CYVADIC combination chemotherapy of metastatic pulmonary lesions involving a mediastinal leiomyosarcoma--a case report]

Discussed is a 34-year-old man who hospitalized for manifesting the superior vena cava syndrome. Chest radiograph and chest CT scan revealed a gross tumor shadow in the superior mediastinum and a tiny shadow in the right lung. Superior vena cavography showed intimal stenosis, irregularities, and stiffness of the superior vena cava. Thus, radiotherapy applied to primary lesion of the mediastinum was provided to relieve his complaints. One year later, predominant metastatic pulmonary lesions and skin lesions developed. Light and electron microscopic findings of a biopsied specimen of the skin lesion were consistent with leiomyosarcoma. CYVADIC combination chemotherapy reduced the pulmonary metastatic lesions dramatically. The literature of mediastinal leiomyosarcoma is reviewed and the origin of this tumor is discussed.

Production and characterization of antibodies to advanced glycation products on proteins

Antibodies directed against advanced glycation products formed during Maillard reaction have been generated and characterized. These antibodies reacted specifically with advanced glycation products in common among proteins incubated with glucose, but not early-stage compounds such as a Schiff base adduct and Amadori rearrangement products. Incubation of bovine serum albumin with glucose caused a time-related increase in immunoreactivity and a concomitant increase in fluorescence intensity. These antibodies may serve as a useful tool to elucidate pathophysiological roles of advanced Maillard reaction in diabetic complications and aging processes.

[Radioimmunoassay of nonenzymatically glucosylated albumin]

A radioimmunoassay (RIA), to quantitate nonenzymatically glucosylated albumin (GA), was established. Antiserum A was obtained by immunizing guinea pigs with reduced glucosylated guinea pig albumin (RedGlc-GPA), and antiserum B was obtained by immunizing with reduced glucosylated human albumin (RedGlc-HA) and absorbing the antibody against human native albumin. For antiserum A; RedGlc-GPA and NaBH4-reduced guinea pig serum, in which epsilon-N-1-(1-deoxy glucitol) lysine (GL) was present, were effective competitors. But NaBH4-reduced human serum, NaBH4-reduced human hemoglobin, and RedGlc-HA, in which GL were also present, were not so effective competitors. For antiserum B; RedGlc-HA, and RedGlc-GPA, in which GL were present, and GL were equally effective competitors. Thus it seemed that for antiserum A, the antigenic region was not only GL, and for antiserum B, the antigenic region was GL almost specifically. So we used antiserum B for this RIA, and GA in NaBH4-reduced human albumin was quantitated by measuring its ability to compete for antibody binding, compared with that of GL as a standard. Reproducibility of GA-values with this RIA was a enough to use for clinical purpose. With this RIA method, the following results were obtained: 1) These GA values were correlated with GA values, measured by boronate-affinity chromatographic method. 2) Average of GA values in 44 diabetics was significantly higher than that of 24 normal subjects. 3) These GA values were also correlated with HbA1, HbA1c, and fasting blood sugar (FBS). 4) These GA values were more closely correlated with FBS, 2 weeks before, than with FBS, at the same time, and with FBS, 4 weeks before. 5) After insulin treatment to untreated diabetics, these GA values were more rapidly decreased than HbA1c. These result indicated that GA values quantitated in this RIA was available for monitoring blood sugar level for shorter period than that represented by HbA1c.

Quantitative enzyme-linked immunosorbent assay (ELISA) for non-enzymatically glycated serum protein

A competitive ELISA for quantitative determination of glucitollysine, the reduced hexose alcohol form of glucose conjugated to the epsilon amino group of lysine was developed. We applied it to measure non-enzymatically glycated serum proteins. The antiserum obtained by immunizing guinea pigs with reductively glycated human albumin was capable of identifying and quantitating glucitollysine residues of serum proteins in normal and diabetic subjects after reduction of the proteins with sodium borohydride. The ELISA assay developed here had satisfactory reproducibility as judged by the intra-assay precision of 2.3-7.6% and the interassay precision of 6.7-9.8%. Results from this assay procedure correlated well with those from the radioimmunoassay and the boronate affinity chromatography procedure. The data suggested that diabetic serum proteins contained at least three times as much immunochemically detectable glucitollysine residues as normal serum proteins after reduction of the proteins with sodium borohydride. This method allows to quantitate glucitollysine residues on any of the proteins that have been implicated in the pathological sequelae of diabetes.

Antibodies to nonenzymatically glucosylated albumin in the human serum

The existence of antibodies to nonenzymatically glucosylated albumin was investigated in nondiabetic and diabetic subjects. The sera from both the nondiabetic and the diabetic subjects were shown to contain the proteins which bound to reductively glucosylated albumin. An enzyme-linked immunosorbent assay demonstrated that the antibodies specific for reductively glucosylated albumin existed in the sera containing the binding proteins. For binding the antibodies glucitollysine as the glucose adduct in reductively glucosylated albumin was an effective competitor. The hexose alcohol epimers glucitol and mannitol were also effective competitors compatible with glucitollysine. Our results suggest that the antibodies to reductively glucosylated albumin are widely present not only in the diabetic subjects but also in the nondiabetic subjects and cross-react with the hexose alcohol.