Proteomic Insight Reveals Elevated Levels of Albumin in Circulating Immune Complexes in Diabetic Plasma.

A Hyperglycemic condition in diabetes promotes formation of advanced glycation end products, which are known to elicit immune response and form complexes with immunoglobulins called circulating immune complexes. To investigate the involvement of advanced glycation end product (AGE)-modified proteins in the elicitation of an immune response, circulating immune complexes were isolated and proteins associated were identified and characterized. Label-free-based mass spectrometric analysis of circulating immune complexes in clinical plasma of prediabetic, newly diagnosed diabetes, and diabetic microalbuminurea revealed elevated levels of serum albumin in the circulating immune complexes, which were also observed to be AGE modified. Further, to examine the role of glycation, circulating immune complexeswere analyzed in the streptozotocin-induced diabetic mice treated with or without aminoguanidine, a prototype glycation inhibitor. Mass spectrometric analysis of circulating immune complexes showed elevated levels of serum albumin in plasma from diabetic mice over that of control animals. Aminoguanidine-treated diabetic mice displayed decreased AGE modification of plasma albumin, accompanied by a reduced level of albumin in the circulating immune complexes. In addition, elevated levels of proinflammatory cytokines such as IL-1b, IL-2, and TNF-alpha were observed in diabetes, which were reduced with aminoguanidine treatment, suggesting the involvement of glycation in the immune response.

Development of Diagnostic Fragment Ion Library for Glycated Peptides of Human Serum Albumin: Targeted Quantification in Prediabetic, Diabetic, and Microalbuminuria Plasma by Parallel Reaction Monitoring, SWATH, and MSE.

Human serum albumin is one of the most abundant plasma proteins that readily undergoes glycation, thus glycated albumin has been suggested as an additional marker for monitoring glycemic status. Hitherto, only Amadori-modified peptides of albumin were quantified. In this study, we report the construction of fragment ion library for Amadori-modified lysine (AML), N(ε)-(carboxymethyl)lysine (CML)-, and N(ε)-(carboxyethyl)lysine (CEL)-modified peptides of the corresponding synthetically modified albumin using high resolution accurate mass spectrometry (HR/AM). The glycated peptides were manually inspected and validated for their modification. Further, the fragment ion library was used for quantification of glycated peptides of albumin in the context of diabetes. Targeted Sequential Window Acquisition of all THeoretical Mass Spectra (SWATH) analysis in pooled plasma samples of control, prediabetes, diabetes, and microalbuminuria, has led to identification and quantification of 13 glycated peptides comprised of four AML, seven CML, and two CEL modifications, representing nine lysine sites of albumin. Five lysine sites namely K549, K438, K490, K88, and K375, were observed to be highly sensitive for glycation modification as their respective m/z showed maximum fold change and had both AML and CML modifications. Thus, peptides involving these lysine sites could be potential novel markers to assess the degree of glycation in diabetes.

Association of neutrophil-lymphocyte ratio with glucose intolerance: an indicator of systemic inflammation in patients with type 2 diabetes.

BACKGROUND: The neutrophil-lymphocyte ratio (NLR) has been demonstrated to be a better risk factor than total white blood cell count in the prediction of adverse outcomes in various medical conditions. This study analyzed the association of NLR with different grades of glucose tolerance and insulin resistance in Asian Indians. SUBJECTS AND METHODS: Study subjects were recruited from Phase 3 of the Chennai Urban Rural Epidemiology Study (CURES). For this cross-sectional analysis, subjects with normal glucose tolerance (NGT) (n=237), impaired glucose tolerance (IGT) (n=63), and type 2 diabetes mellitus (DM) (n=286) were selected. The hemogram was done in all subjects using a five-part hematology analyzer (model SF-3000; Sysmex, Kobe, Japan). The NLR was calculated as the ratio between counts for neutrophils and total lymphocytes. Fasting insulin was measured by enzyme-linked immunosorbent assay, and insulin resistance was calculated using the homeostasis model assessment (HOMA-IR). RESULTS: Subjects with DM showed a significantly higher NLR (2.2 ± 1.12) compared with IGT subjects (1.82 ± 0.63), who in turn had a higher ratio than NGT subjects (1.5 ± 0.41) (P<0.01). Pearson correlation analysis showed a significant positive correlation of NLR with glycated hemoglobin (r=0.411), fasting plasma glucose (r=0.378), and HOMA-IR (r=0.233) (P<0.001). Regression analysis showed a linear increase in NLR with increasing severity of glucose intolerance even after adjusting for age, waist circumference, blood pressure, triglycerides, and smoking. CONCLUSIONS: This is the first report on the correlation of NLR with different grades of glucose intolerance and insulin resistance. NLR can be used as an adjuvant prognostic marker for macro- and microvascular complications in patients with glucose intolerance.

Noninvasive type 2 diabetes screening: clinical evaluation of SCOUT DS in an Asian Indian cohort.

OBJECTIVE: This study evaluated the noninvasive, point-of-care diabetes screening device, Scout DS (VeraLight Inc., Albuquerque, NM) (SCOUT), in a native Asian Indian cohort. RESEARCH DESIGN AND METHODS: SCOUT is a tabletop, skin fluorescence spectrometer that reports a risk score following a 3-4-min noninvasive measurement of a subject's left volar forearm. SCOUT, fasting plasma glucose (FPG), and hemoglobin A(1c) (A1C) were compared for detection of abnormal glucose tolerance (AGT) in a cohort of 256 subjects without previous diagnosis of diabetes or impaired glucose tolerance in Chennai, India. After an overnight fast, a 75-g, 2-h oral glucose tolerance test was administered, and AGT was defined as a plasma glucose value ≥ 140 mg/dL (7.8 mmol/dL). Sensitivity, false-positive rate (FPR), and receiver-operating characteristics area under the curve for AGT detection were computed for SCOUT, FPG, and A1C. Intra-day reproducibility of SCOUT was assessed. RESULTS: SCOUT, FPG, and A1C (at respective thresholds of 50, 110 mg/dL, and 5.7%) exhibited sensitivities of 87%, 32%, and 86%, respectively, and FPR of 52%, 3%, and 58%, respectively. For the 177 subjects receiving a valid SCOUT Diabetes Score on both measurement attempts, the coefficient of variation was 5.8%, and the Pearson correlation was 0.91. A SCOUT score could be obtained on 91% of subjects after two attempts. CONCLUSIONS: The performance of SCOUT is similar to that of A1C, whereas FPG had a much lower sensitivity. SCOUT is an effective tool for AGT screening in Asian Indians.