Regulation of Free Fatty Acid by Sitagliptin Monotherapy in DRUG-NAÏVE Subjects with Type 2 Diabetes

Abstract

The aim of this study was to investigate the effects of sitagliptin on the regulation of free fatty acid (FFA) and other metabolic parameters in drug-naïve subjects with type 2 diabetes mellitus (T2DM). This was a prospective, nonrandomized, observational study. Drug-naïve subjects with T2DM received 25 to 50 mg/day sitagliptin monotherapy (n = 64). At 3 months, FFA and other metabolic parameters were compared with those at baseline. FFA was measured by colorimetry with enzymatic reactions. As a comparator, 12.5 to 25 mg/day alogliptin monotherapy was given to drug-naïve subjects with T2DM (n = 55). Significant reductions in FFA (-13.2%, P<0.01) levels were observed with sitagliptin but not alogliptin. Both drugs showed similar glycemic efficacies. Significant correlations were observed between the changes (Δ) of FFA and Δglycated hemoglobin A1c (HbA1c), Dtotal cholesterol (TC), Δnon-high-density lipoprotein cholesterol (HDL-C), or Δlow-density lipoprotein cholesterol (LDL-C), and significant negative correlations were seen between ΔFFA and Δhomeostasis model assessment-B (HOMA-B), ΔC-peptide immunoreactivity (CPR)-index or Δbody mass index (BMI) in the sitagliptin group. The subjects in the sitagliptin group were further divided into 2 subgroups (n = 32 each) according to the changes of FFA (group B [above the median] ΔFFA = 23.1 %, P<.0005; group A [below the median] ΔFFA = -37.3 %, P<.00001). At baseline, FFA levels were significantly higher in group A versus group B ( P<.001). Higher degrees of reductions of FBG (-14.6% vs. -9.3%, P<0.05) or HbA1c (-20.6% vs. -16.9%, P<.05), and increases of HOMA-B (52.7% vs. 38.3%, P<.03) or CPR-index (37.5% vs. 18.8%, P<.02) were observed in group A versus group B. Significant reductions of TC (-5.8%, P<.002), non-HDL-C (-7.8%, P<.001) or LDL-C (-6.3%, P<.02), and significant increases of C-peptide (11.3%, P<.05) were seen only in group A. Sitagliptin could downregulate high FFA levels. Subjects with reductions of FFA levels had better glycemic efficacies and higher degrees of enhancement of beta-cell function than others. Reductions of atherogenic cholesterols were seen in these populations. CPR = C-peptide immunoreactivity; DPP-4 = dipeptidyl peptidase 4; FBG = fasting blood glucose; FFA = free fatty acid; HbA1c = glycated hemoglobin A1c; HDL-C = high-density lipoprotein cholesterol; HOMA-R = homeostasis model assessment-R; HOMA-B = homeostasis model assessment-B; non-HDL-C = non-HDL-cholesterol; LDL-C = low-density lipoprotein cholesterol; TC = total cholesterol; T2DM = type 2 diabetes; TG = triglyceride; UA = uric acid.