Vascular measures
PAT
At each of the study visits at baseline, 4-weeks, 8-weeks and washout, heart rate and blood pressure were measured in a seated position, after 10 min of rest, with an automated blood pressure monitor. Two measurements were performed 10 min apart, with the average recorded. At the study visits at baseline, 8-weeks and washout, endothelial function was assessed by peripheral arterial tonometry (PAT) with the Endo-PAT2000 device (Itamar Medical Inc, Framingham, MA). This assessment was performed after overnight fasting (with glargine held that night). On the morning of the testing, meal insulin and exenatide were not administered because of the intention to assess the primary outcome of the trial (beta-cell function) on oral glucose tolerance test (OGTT) in the absence of these medications [The COVID-19 pandemic prevented completion of the Endo-PAT portion of the protocol in the full study population of 102 participants, first by preventing some in-person visits and later because of unavailability of the PAT finger probes. Accordingly, Endo-PAT assessment was completed in 73 participants, yielding the study population for the current analysis.