Adiponectin Receptor-1 C-Terminal Fragment (CTF) in Plasma: Putative Biomarker for Diabetes

Abstract

Introduction Polypeptide fragments from cell surface receptors when found in plasma may be indicators of receptor regulation in disease conditions. It is known that subjects with diabetes have significantly lower plasma concentrations of adiponectin, a hormone released by adipose tissue, compared with nondiabetic controls. This hormone interacts with cell surface receptors in muscle (AdipoR1) and liver (AdipoR2). Methods We analyzed the relative distribution of specific fragments of AdipoR1 in healthy and diabetic individuals using an immunoaffinity mass spectrometry approach. We used antibodies raised against AdipoR1 immobilized on pre-activated protein chip surfaces to determine the molecular weights of bound polypeptide fragments using immunomass spectrometry (immuno-MS). Results Initially, immuno-MS analyses using a polyclonal antibody revealed two peaks (m/z 3,902 and 7,812) in plasma from normal, healthy individuals (n=5) that were not present in the plasma of diabetics (n=5). To confirm the detection of these fragments, a monoclonal antibody was developed against the last 25 amino acids of the AdipoR1 C-terminal fragment (CTF). Using the immuno-MS method, the monoclonal antibody detected the AdipoR1 CTF (m/z 3475) in all healthy controls (n=10), but did not detect these fragments in the diabetic patients (n=10). Discussion These preliminary observations suggest that the plasma levels of this receptor fragment may serve as an indicator of diabetic condition.

Role of Soluble Adiponectin Receptor 2 in Non-Alcoholic Fatty Liver Disease in Children

“…With respect to NAFLD diagnosis and adipocyte activity anomaly, researchers have tried to develop new methods. For instance, C-terminal fragments of adiponectin receptors in diabetic patients were measured by plasma mass spectrometry and were found to be useful in the diagnosis of diabetic patients [11].…”

“…Adiponectin stops glucose production when it interferes with adiponectin receptor 2 in the liver and adiponectin receptor 1 in the muscle and causes glycolysis and fatty acid oxidation. C-terminal fragments of adiponectin receptors are soluble and can be detected in the plasma [11].…”

Utilization of electronic health records for the assessment of adiponectin receptor autoantibodies during the progression of cardio-metabolic comorbidities

“…Available plasma specimens (n=1783) were measured for IgG-CTF using a previously described sandwich ELISA based on a monoclonal antibody specific for AdipoR1 CTF (ATCC 444–1D12.1H7) and a human IgG-specific antibody conjugated to ALP [ 14 ] ( Table 3 ). Plasma (~0.5 mL) was thawed to room temperature, and 10 μL was diluted with 480 μL of stabilization buffer (PBS supplemented with 1% BSA, 0.1 M citrate and 0.01 M EDTA, pH 6.4).…”

“…Diagnostic accuracy can be improved by the detection of autoantibodies, as shown for autoantibodies against cytokines that predict autoimmune disease and tissue injury caused by autoreactive antibodies and T cells [ 12 , 13 ]. Autoantibodies can be quantified using anti-antigen antibodies, as shown for the adiponectin receptor C-terminal fragment (AdipoR1 CTF 344–375 ) antigen, which circulates freely in the plasma of healthy individuals but not in some diabetes patients (P>0.001) [ 14 ]. Proteomic analysis of autoantigens is complex and difficult to translate due to the low transient concentrations (<5 ng/mL) and the need to use both stable isotope standards and monoclonal antibodies for capture [ 15 – 17 ].…”

Role of adiponectin and its receptor in prediction of reproductive outcome of metformin treatment in patients with polycystic ovarian syndrome

“…Adiponectin and AdipoR1 levels were measured by ELISA kits. The soluble C‐terminal fragment of AdipoR1 in blood was used to represent tissue receptor expression to minimize invasive procedures . The levels of total testosterone (T), luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) were assessed with specific ELISA kits.…”