Fig. 1.

Fatty acid-stimulated insulin secretion (FASIS) in perifused isolated murine pancreatic islets – A,B,D–K) Instantaneous yields of insulin secretion are plotted vs. time. They represent the accumulated amount of insulin over each previous 2 min (5 min after 25 min). Hence, “ng/μgDNA” can be easily transferred into rates of insulin secretion in units of 0.5 ng min⁻¹·μgDNA⁻¹ up to 22 min and 0.2 ng min⁻¹ ·μgDNA⁻¹ after 25 min of perifusion (data after recalculation, see Fig. S2A). 100 PIs of backcrossed wt mice (black, open, gray, or black/cyan semi-filled symbols) and iPLA₂γKO mice (green, dark-green, green/yellow or green/orange semi-filled symbols) were initially perifused with the KRH medium containing 5.5 mM glucose. Arrows indicate the moment from which 2.55 nM free palmitic acid (PA) or other FAs were included (all in 30 μM, i.e. 0.2 % BSA: total PA and linoleic acid were 50 μM; stearic 65 μM, oleic 70 μM, lauric 90 μM, hexanoic 180 μM, and ω-bromopalmitic 50 μM). For perifusion without FAs, see gray trace (“wt no FA” in B). Representative perifusions are shown (otherwise, N = 3–7 for each type). After 50 min (60 min in A), 30 mM KCl was added (arrows). Panel C shows the accumulated amount of insulin secreted at 0–12 min (derived from areas under curve, AUCs), while data are plotted as the PA dose-response at constant BSA (30 μM). AUCs relative to PA are summarized in Figs. S2E and F (2–16 min for the 1st phase, 18–50 min for the 2nd phase). For other AUCs and AUCs of iPLA₂γKO PIs see Fig. 2A and B below and Fig. 2 legend.

Additional agents were also supplied over the entire time course of perifusion when indicated, such as 1 μM GW1100 (black/cyan or dark green/white semi-filled symbols; perifused 10 min before FAs) (A,E); 2.5 μM etomoxir (red/dark red) (G–I); and 2.5 μM r-BEL (yellow) or 2.5 μM s-BEL (orange) (J,K). The latter assessed stereospecific FASIS inhibition by r-BEL, as also expressed by AUCs (L,M).

N–P): Respiration and ATP levels in pancreatic islets – N) The respiration of PIs (N = 5; n = 3–15) was assayed on a SeahorseXF analyzer (exemplified in Fig. S4) and ratios of rates obtained without (V₃) and with oligomycin (V₄) are plotted for standard FASIS (“PA”) under conditions of Fig. 1A with the indicated agents and also without PA, but with indicated glucose (“Glc”) concentrations. O,P) ATP levels 60 min after the addition of PA, or PA plus denoted agents, are shown with and without indicated agents (N = 3; n = 3–7). In N–P), Etomoxir (red, violet) was 2.5 μM; SkQ1 10 nM (cyan; “SkQ”) (O) or as indicated (cyan) (Q). In panels C,L–P, ANOVA is indicated: **p < 0.05; ***p < 0.001; and Student's T-test between two groups: ##p < 0.05.