Solid-phase extraction treatment is required for measurement of active glucagon-like peptide-1 by enzyme-linked immunosorbent assay kit affected by heterophilic antibodies.

AIMS/INTRODUCTION: It is reported that interfering substances in the blood might influence the value for measurement of active glucagon-like peptide-1 (GLP-1) in human plasma. Solid phase extraction (SPE) pretreatment is recommended to reduce their influence, but it requires a lot of cost and time. However, there is little investigation about causative inhibitory substances and about methods that can replace solid phase extraction. In the present study, we aimed to seek the candidate of the substances that might interfere with an active GLP-1 enzyme-linked immunosorbent assay (ELISA). MATERIALS AND METHODS: Two kinds of active GLP-1 ELISA kits using different antibodies, plural extraction carriers and elution solutions were used to evaluate the SPE method. Active GLP-1 concentration was compared with or without SPE, and with or without a heterophilic blocking tube. RESULTS: Active GLP-1 values were often higher without SPE compared with those with SPE pretreatment. This difference was eliminated by pretreatment with a heterophilic blocking tube or ELISA kits that did not use a mouse monoclonal antibody, and was independent of SPE. CONCLUSIONS: Substances absorbed to a heterophilic blocking tube carrier might interfere with an active GLP-1 immunoassay. Solid-phase extraction treatment is required for measurement of active GLP-1 by an ELISA kit affected by heterophilic antibodies.

Correlation of Glypican-4 Level with Basal Active Glucagon-Like Peptide 1 Level in Patients with Type 2 Diabetes Mellitus.

BACKGROUND: Previous studies have reported that glypican-4 (GPC4) regulates insulin signaling by interacting with insulin receptor and through adipocyte differentiation. However, GPC4 has not been studied with regard to its effects on clinical factors in patients with type 2 diabetes mellitus (T2DM). We aimed to identify factors associated with GPC4 level in T2DM. METHODS: Between January 2010 and December 2013, we selected 152 subjects with T2DM and collected serum and plasma into tubes pretreated with aprotinin and dipeptidyl peptidase-4 inhibitor to preserve active gastric inhibitory polypeptide (GIP) and glucagon-like peptide 1 (GLP-1). GPC4, active GLP-1, active GIP, and other factors were measured in these plasma samples. We performed a linear regression analysis to identify factors associated with GPC4 level. RESULTS: The subjects had a mean age of 58.1 years, were mildly obese (mean body mass index [BMI], 26.1 kg/m²), had T2DM of long-duration (mean, 101.3 months), glycated hemoglobin 7.5%, low insulin secretion, and low insulin resistance (mean homeostatic model assessment of insulin resistance [HOMA-IR], 1.2). Their mean GPC4 was 2.0±0.2 ng/mL. In multivariate analysis, GPC4 was independently associated with age (ß=0.224, P=0.009), and levels of active GLP-1 (ß=0.171, P=0.049) and aspartate aminotransferase (AST; ß=-0.176, P=0.043) after being adjusted for other clinical factors. CONCLUSION: GPC4 was independently associated with age, active GLP-1, and AST in T2DM patients, but was not associated with HOMA-IR and BMI, which are well known factors related to GPC4. Further study is needed to identify the mechanisms of the association between GPC4 and basal active GLP-1 levels.

Correlation of Glypican-4 Level with Basal Active Glucagon-Like Peptide 1 Level in Patients with Type 2 Diabetes Mellitus

BACKGROUND: Previous studies have reported that glypican-4 (GPC4) regulates insulin signaling by interacting with insulin receptor and through adipocyte differentiation. However, GPC4 has not been studied with regard to its effects on clinical factors in patients with type 2 diabetes mellitus (T2DM). We aimed to identify factors associated with GPC4 level in T2DM. METHODS: Between January 2010 and December 2013, we selected 152 subjects with T2DM and collected serum and plasma into tubes pretreated with aprotinin and dipeptidyl peptidase-4 inhibitor to preserve active gastric inhibitory polypeptide (GIP) and glucagon-like peptide 1 (GLP-1). GPC4, active GLP-1, active GIP, and other factors were measured in these plasma samples. We performed a linear regression analysis to identify factors associated with GPC4 level. RESULTS: The subjects had a mean age of 58.1 years, were mildly obese (mean body mass index [BMI], 26.1 kg/m2), had T2DM of long-duration (mean, 101.3 months), glycated hemoglobin 7.5%, low insulin secretion, and low insulin resistance (mean homeostatic model assessment of insulin resistance [HOMA-IR], 1.2). Their mean GPC4 was 2.0±0.2 ng/mL. In multivariate analysis, GPC4 was independently associated with age (β=0.224, P=0.009), and levels of active GLP-1 (β=0.171, P=0.049) and aspartate aminotransferase (AST; β=–0.176, P=0.043) after being adjusted for other clinical factors. CONCLUSION: GPC4 was independently associated with age, active GLP-1, and AST in T2DM patients, but was not associated with HOMA-IR and BMI, which are well known factors related to GPC4. Further study is needed to identify the mechanisms of the association between GPC4 and basal active GLP-1 levels.