Impaired islet function and normal exocrine enzyme secretion occur with low inter-regional variation in type 1 diabetes

Abstract

Histopathological heterogeneity in the human pancreas is well documented; however, functional evidence at the tissue level is scarce. Herein, we investigate in situ glucose-stimulated islet and carbachol-stimulated acinar cell secretion across the pancreas head (PH), body (PB), and tail (PT) regions in donors without diabetes (ND; n = 15), positive for one islet autoantibody (1AAb+; n = 7), and with type 1 diabetes (T1D; <14 months duration, n = 5). Insulin, glucagon, pancreatic amylase, lipase, and trypsinogen secretion along with 3D tissue morphometrical features are comparable across regions in ND. In T1D, insulin secretion and beta-cell volume are significantly reduced within all regions, while glucagon and enzymes are unaltered. Beta-cell volume is lower despite normal insulin secretion in 1AAb+, resulting in increased volume-adjusted insulin secretion versus ND. Islet and acinar cell secretion in 1AAb+ are consistent across the PH, PB, and PT. This study supports low inter-regional variation in pancreas slice function and, potentially, increased metabolic demand in 1AAb+.

Keywords: 3D morphometry; CP: Immunology; CP: Metabolism; exocrine pancreas enzymes; function; glucagon; human; insulin; pancreas regions; pancreas tissue slices; secretion; type 1 diabetes.

Figure 1.. Similar islet and acinar cell secretion across the PH, PB, and PT in ND human pancreas

(A and E) Insulin (A) and glucagon (E) secretion traces from PH (teal), PB (purple), and PT (gray) slices shown as stimulation index (fold of baseline: 1G for insulin, 5.5G for glucagon). (B–D) Quantification of insulin responses to 5.5G (B), 11.1G (C), and KCl (D). (F–I) Quantification of glucagon responses to 1G (F), 11.1G (G), 1G (H), and KCl (I). (J–O) 3D morphometry of perifused slices showing slice volume (J), islet density (K), endocrine (L), insulin (M), and glucagon (N) volumes and the contribution of insulin and glucagon to total endocrine volume (O). (P–R) Baseline pancreatic amylase (P), lipase (Q), and trypsinogen (R) release expressed as a percentage of total enzyme content. (S–U) Carbachol-stimulated amylase (S), lipase (T), and trypsinogen (U) secretion expressed as stimulation index (fold of baseline). n = 15 ND donors (A–I), 7 ND donors (J–O), with 4 slices/region/donor, and 14 ND donors (P–U) with 5 slices/region/donor. Dots represent individual donors with means shown in black. Data are represented as mean ± SEM with repeated measures (RM) one-way ANOVA of log-transformed data.

Figure 2.. Reduced insulin, but not glucagon secretion in all pancreas regions in recent-onset T1D

(A–C) Insulin secretion from slices of PH (A), PB (B), and PT (C) from ND, 1AAb+, and T1D shown as absolute amounts (mU/min). (D–F) Insulin secretion traces from slices of PH (D), PB (E), and PT (F) from ND, 1AAb+, and T1D donors shown as stimulation index (fold of 1G baseline). (G–I) Quantification of insulin responses to 5.5G (G), 11.1G (H), and KCl (I) stimulation. (J–L) Glucagon secretion from slices of PH (J), PB (K), and PT (L) from ND, 1AAb+, and T1D shown as absolute amounts (pg/min). (M–O) Glucagon secretion traces from slices of PH (M), PB (N), and PT (O) from ND, 1AAb+, and T1D donors shown as stimulation index (fold of 5.5G baseline). (P–S) Quantification of glucagon responses to 1G (P), 11.1G (Q), 1G (R), and KCl (S). n = 15 ND, 7 1AAb+, and 5 T1D donors with 4 slices/region/donor. Dots represent individual donors shown with mean ± SEM and RM two-way ANOVA of log-transformed data. *p < 0.05, **p < 0.01, ***p < 0.001, and ****p < 0.0001. See also Figures S2 and S3.

Figure 3.. Preserved acinar cell function at T1D onset

(A–C) Baseline pancreatic amylase (A), lipase (B), and trypsinogen (C) release in ND, 1AAb+, and T1D slices from PH, PB, and PT expressed as a percentage of total enzyme content. (D–F) Carbachol-stimulated amylase (D), lipase (E), and trypsinogen (F) secretion in ND, 1AAb+, and T1D slices from PH, PB, and PT expressed as a percentage of total enzyme content. (G–I) Carbachol-stimulated amylase (G), lipase (H), and trypsinogen (I) secretion in ND, 1AAb+, and T1D slices from PH, PB, and PT expressed as stimulation index (fold of baseline). n = 14 ND, 7 1AAb+, and 5 T1D donors with 5 slices/region/donor. Dots represent individual donors shown with mean ± SEM and RM two-way ANOVA. *p < 0.05.

Figure 4.. Decreased endocrine and beta-cell mass across the pancreas at T1D onset

(A–H) 3D morphometry of perifused slices showing whole-slice (A), endocrine (B), insulin (C), and glucagon (D) volumes, islet density (E), and the contributions of insulin and glucagon to total endocrine volume across disease groups in PH (F), PB (G), and PT (H). (I–K) Insulin secretion traces from slices of PH (I), PB (J), and PT (K) from ND, 1AAb+, and T1D shown as secreted insulin normalized to respective beta-cell volume. (L–O) Quantification of insulin responses to 1G (L), 5.5G (M), 11.1G (N), and KCl (O). (P–R) Glucagon secretion traces from slices of PH (P), PB (Q), and PT (R) from ND, 1AAb+, and T1D shown as secreted glucagon normalized to respective alpha-cell volume. (S–V) Quantification of glucagon responses to 5.5G (S), 1G (T), 11.1G (U), and 1G (V). n = 7 ND, 5 1AAb+, and 5 T1D donors with 4 slices/region/donor. Dots represent individual donors with mean ± SEM and RM two-way ANOVA of log-transformed data. *p < 0.05 and **p < 0.01. See also Figure S4.