Cystic fibrosis–related diabetes is caused by islet loss and inflammation
Nathaniel J. Hart, Radhika Aramandla, Gregory Poffenberger, Cody Fayolle, Ariel H. Thames, Austin Bautista, Aliya F. Spigelman, Jenny Aurielle B. Babon, Megan E. DeNicola, Prasanna K. Dadi, William S. Bush, Appakalai N. Balamurugan, Marcela Brissova, Chunhua Dai, Nripesh Prasad, Rita Bottino, David A. Jacobson, Mitchell L. Drumm, Sally C. Kent, Patrick E. MacDonald, Alvin C. Powers
Nathaniel J. Hart, Radhika Aramandla, Gregory Poffenberger, Cody Fayolle, Ariel H. Thames, Austin Bautista, Aliya F. Spigelman, Jenny Aurielle B. Babon, Megan E. DeNicola, Prasanna K. Dadi, William S. Bush, Appakalai N. Balamurugan, Marcela Brissova, Chunhua Dai, Nripesh Prasad, Rita Bottino, David A. Jacobson, Mitchell L. Drumm, Sally C. Kent, Patrick E. MacDonald, Alvin C. Powers
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Research Article Cell biology Endocrinology

Cystic fibrosis–related diabetes is caused by islet loss and inflammation

Abstract

Cystic fibrosis–related (CF-related) diabetes (CFRD) is an increasingly common and devastating comorbidity of CF, affecting approximately 35% of adults with CF. However, the underlying causes of CFRD are unclear. Here, we examined cystic fibrosis transmembrane conductance regulator (CFTR) islet expression and whether the CFTR participates in islet endocrine cell function using murine models of β cell CFTR deletion and normal and CF human pancreas and islets. Specific deletion of CFTR from murine β cells did not affect β cell function. In human islets, CFTR mRNA was minimally expressed, and CFTR protein and electrical activity were not detected. Isolated CF/CFRD islets demonstrated appropriate insulin and glucagon secretion, with few changes in key islet-regulatory transcripts. Furthermore, approximately 65% of β cell area was lost in CF donors, compounded by pancreatic remodeling and immune infiltration of the islet. These results indicate that CFRD is caused by β cell loss and intraislet inflammation in the setting of a complex pleiotropic disease and not by intrinsic islet dysfunction from CFTR mutation.

Authors

Nathaniel J. Hart, Radhika Aramandla, Gregory Poffenberger, Cody Fayolle, Ariel H. Thames, Austin Bautista, Aliya F. Spigelman, Jenny Aurielle B. Babon, Megan E. DeNicola, Prasanna K. Dadi, William S. Bush, Appakalai N. Balamurugan, Marcela Brissova, Chunhua Dai, Nripesh Prasad, Rita Bottino, David A. Jacobson, Mitchell L. Drumm, Sally C. Kent, Patrick E. MacDonald, Alvin C. Powers

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Figure 2

CFTR mRNA expression was minimal in human β cells, and CFTR protein was undetectable in human β cells.

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CFTR mRNA expression was minimal in human β cells, and CFTR protein was...
Expression of CFTR and select β cell–related transcripts from published islet cell transcriptomes: (A) 270 single human β cells from 6 healthy and 4 diabetic donors (reads per kilobase of transcript per million mapped reads [RPKM], Segerstolpe and Palasantza et al., ref. 38) and (B) sorted β cells from 7 healthy adult donors (transcript per kilobase million [TPM], Blodgett et al., refs. 39). Note: Individual expression values are not presented in A, as the log2 of the mean expression value of 270 β cells was calculated to account for the approximately 85% of β cells in this data set that do not express CFTR; individual CFTR expression values are presented in Supplemental Figure 3E. Green bar, insulin; blue bars, key islet transcription factors; pink, islet hormone secretion related genes; red, CFTR. (C) Representative immunohistochemical labeling of CFTR (red), insulin (green), and glucagon (purple) in a pancreas from 3-month-old male donor. Insets depict the islet border and interior. (D) CFTR (red) channel alone (note: CFTR ductal localization and islet absence). Scale bars: 50 μm (C and D); 10 μm (insets). (E) Representative patch clamp recording of a human β cell and a INS832/13 + wtCFTR cell (n = 5 donors, 35 β cells; Supplemental Figure 5B). (F) Insulin secretion from human islets (n = 4 donors) in medium containing 1 mM glucose (1 G), 16.7 mM glucose (16.7 G), or 16.7 G plus 100 μM forskolin (16.7 G + Fsk) and no drug (white), 1 μM VX770 (blue, ivacaftor), 5 μM VX661 (green), or 5 μM VX809 (red, lumacaftor). 1 G, n = 22–24 replicates; 16.7 G, n = 11–12 replicates; 16.7 + Fsk, n = 10–12 replicates. VX770 is a selective CFTR potentiator that increases CFTR activity at the membrane and VX661, and VX809 are CFTR channel correctors that increase membrane channel density. Data represent mean ± SEM. No statistical significance (P < 0.05) was observed in in vitro human islet insulin secretion when comparing secretory responses at 1 G, 16.7 G, and 16.7 G + Fsk in the presence of absence of CFTR modulators. One-way ANOVA was used for statistical analysis.