Abstract
There is a growing need for early biomarkers for Type 2 diabetes (T2D). Fatty-Acid-Hydroxy-Fatty-Acids (FAHFAs) are bioactive lipids with >580 regioisomers in human tissues. FAHFAs such as Palmitic Acid Hydroxy Stearic Acids (PAHSAs) are anti-diabetic and anti-inflammatory. PAHSA concentrations in human serum and adipose tissue strongly correlate with insulin-sensitivity. Since PAHSAs and palmitic acid hydroxy oleic acids (PAHOAs) are among the most abundant FAHFAs in human serum, we investigated whether they predict worsening glucose tolerance in first-degree relatives of people with T2D. All participants had normal glucose tolerance (NGT) at baseline; 27 remained NGT (NGT-NGT) and 21 developed impaired glucose tolerance (NGT-IGT). In NGT-NGT, total PAHSA and PAHSA regioisomer concentrations were unchanged from baseline to follow up, while in NGT-IGT participants, most PAHSA regioisomers decreased. The initial total PAHSAs, 5-PAHSA, and 9-PAHSA, and changes in these correlated inversely with worsening glucose tolerance. Low total PAHSA concentrations at baseline and the decrease in total PAHSAs, 5-PAHSAs and 9-PAHSAs over time predicted IGT independent of initial BMI or %body fat, change in BMI or %body fat, initial fasting glucose, fasting insulin or triglyceride/HDL ratio. In contrast, baseline and follow up total PAHOA and PAHOA regioisomer levels were higher in NGT-IGT than NGT-NGT and some PAHOA regioisomers increased during follow up in NGT-IGT. Higher initial total PAHOAs predicted IGT independent of the same clinical variables. Thus, lower serum PAHSAs and higher PAHOAs predict worsening glucose tolerance/IGT independent of BMI, %body fat or change in these parameters even in lean, relatively young people.