Unveiling the Factors Driving Plasma Water T2 as a Biomarker for Early Insulin Resistance Syndrome




Deodhar, Sneha
Mishra, Ina
Cistola, David


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Background: Approximately 86 million US adults have prediabetes, putting them at high risk for type 2 diabetes mellitus and cardiovascular disease. Prediabetes is a state of impaired glucose tolerance or moderate hyperglycemia where up to 70% of pancreatic β-cell capacity has been lost irreversibly. It is preceded by an often-undetected phase, early insulin resistance syndrome (EIRS), which consists of compensatory hyperinsulinemia, dyslipidemia, subclinical inflammation and electrolyte abnormalities. Early identification is important to preserve pancreatic function and prevent diabetes and pre-diabetes. In previous work, we showed that plasma water transverse relaxation time T2, measured using benchtop NMR relaxometry, provides a sensitive measure of EIRS in asymptomatic, normoglycemic subjects. Plasma water T2 detected EIRS in 15% of this cohort, which was undetected by fasting glucose or HbA1c. Our hypothesis is that shifts in the levels of specific acute phase proteins and lipoproteins drive plasma water T2 values lower in EIRS. Purpose: To quantify the contributions from the most abundant plasma proteins and lipoproteins to plasma water T2 by determining relaxivity values (r, slope of 1/T2 vs. concentration). Higher relaxivity means greater influence on water T2. Methods: Purified plasma protein fractions were obtain from Millipore-Sigma, Inc. and Athens, Inc., and lipoprotein fractions were prepared from human plasma using density-gradient ultracentrifugation. Two sets of serial dilutions were made for each protein and lipoprotein fraction: (1) in phosphate-buffered saline, to determine r value in buffer alone, and 2) in a mixture of human serum albumin and gamma globulin, to determine r in a background that mimics human plasma. Protein concentrations were quantified using a Pierce BCA assay, and total cholesterol and triglyceride concentrations, using kits from Wako Diagnostics. Linear regression was used to quantify and compare r values. Results: The highest relaxivity values were observed for ceruloplasmin, haptoglobin, apo-transferrin and complement C3, whereas surprisingly low values were observed for triglyceride-rich lipoproteins. Albumin, IgG and α2-macroglobulin yielded intermediate r values. Conclusions: This study unveils the factors driving plasma water T2 as a biomarker for early insulin resistance syndrome. Plasma water T2 is a promising tool for population screening and metabolic health assessment for diabetes and prediabetes prevention.