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. 2018 Sep 18;293(47):18086–18098. doi: 10.1074/jbc.RA118.005403

Figure 6.

Figure 6.

The effect of C1ql3 on exendin-4 incretin signaling stimulated insulin secretion. Mouse islets were isolated and incubated overnight in the supplemented RPMI 1640 culture media at 8 mm glucose. Next day, the insulin secretion experiment was performed in the presence of C1ql3 or control CM as described under “Experimental procedures” in response to different insulin secretagogues. A, insulin secretion experiments were performed in mouse islets treated with 10 nm exendin-4 (a stable analog of GLP-1) in response to 3 and 11 mm glucose, in the presence of C1ql3 or control CM. B, the effect of C1ql3 and IgG isotype control antibody at 0.1 and 5 ng/ml concentrations was determined in mouse islets treated with 10 nm exendin-4 at 11 mm glucose in the presence of C1ql3 CM. The following two control treatments were used in this experiment to show the specificity of C1ql3 and control IgG in this experiment: the effect of C1ql3 IgG in the presence of 10 nm exendin-4 (at 11 mm glucose) along with control CM and isotype control IgG in the presence of 10 nm exendin-4 (at 11 mm glucose) along with C1ql3 CM. The effect of C1ql3 and control CM on insulin secretion was determined in the presence of 3 mm 8Br-cAMP at 11 mm glucose (membrane permeable cAMP) in mouse (C) and human (D) islets. E, the effect of diluting C1ql3 CM five times in the culture media on insulin secretion. F, the effect of mouse C1ql3 recombinant protein compared with the control GST protein (28 kDa, molecular mass similar to C1ql3) on insulin secretion in mouse islets in response to 3 mm 8Br-cAMP at 11 mm glucose. Also, the effect of anti-C1ql3 and IgG isotype control antibodies was determined on insulin secretion from islets treated with C1ql3 recombinant protein in the presence of 3 mm 8Br-cAMP at 11 mm glucose. G, dose-dependent effect of the human C1ql3 recombinant protein compared with the GST protein in mouse islets in response to 3 mm 8Br-cAMP at 11 mm glucose. Also, the effect of anti-C1ql3 and isotype control antibodies was determined on insulin secretion from islets treated with C1ql3 recombinant protein in the presence of 3 mm 8Br-cAMP at 11 mm glucose. The insulin secreted in response to treatments was normalized to the total insulin and is reported as a percent of total insulin (secreted plus cellular). Values are mean ± S.E. of n ≥ 3. The asterisk (*) indicates that the p value is significantly lower (p ≤ 0.05) for the insulin secreted in the presence of C1ql3 compared with control treated islets. The hash mark (#) indicates that the p value (p ≤ 0.05) is significantly lower for the insulin secreted from cells treated with C1ql3 antibody and C1ql3 versus C1ql3 alone.