Ghrelin deletion and conditional ghrelin cell ablation increase pancreatic islet size in mice
Deepali Gupta, … , John N. Campbell, Jeffrey M. Zigman
Deepali Gupta, … , John N. Campbell, Jeffrey M. Zigman
Published December 15, 2023
Citation Information: J Clin Invest. 2023;133(24):e169349. https://doi.org/10.1172/JCI169349.
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Research Article Endocrinology Metabolism

Ghrelin deletion and conditional ghrelin cell ablation increase pancreatic islet size in mice

Abstract

Ghrelin exerts key effects on islet hormone secretion to regulate blood glucose levels. Here, we sought to determine whether ghrelin’s effects on islets extend to the alteration of islet size and β cell mass. We demonstrate that reducing ghrelin — by ghrelin gene knockout (GKO), conditional ghrelin cell ablation, or high-fat diet (HFD) feeding — was associated with increased mean islet size (up to 62%), percentage of large islets (up to 854%), and β cell cross-sectional area (up to 51%). In GKO mice, these effects were more apparent in 10- to 12-week-old mice than in 4-week-old mice. Higher β cell numbers from decreased β cell apoptosis drove the increase in β cell cross-sectional area. Conditional ghrelin cell ablation in adult mice increased the β cell number per islet by 40% within 4 weeks. A negative correlation between islet size and plasma ghrelin in HFD-fed plus chow-fed WT mice, together with even larger islet sizes in HFD-fed GKO mice than in HFD-fed WT mice, suggests that reduced ghrelin was not solely responsible for diet-induced obesity–associated islet enlargement. Single-cell transcriptomics revealed changes in gene expression in several GKO islet cell types, including upregulation of Manf, Dnajc3, and Gnas expression in β cells, which supports decreased β cell apoptosis and/or increased β cell proliferation. These effects of ghrelin reduction on islet morphology might prove useful when designing new therapies for diabetes.

Authors

Deepali Gupta, Avi W. Burstein, Dana C. Schwalbe, Kripa Shankar, Salil Varshney, Omprakash Singh, Subhojit Paul, Sean B. Ogden, Sherri Osborne-Lawrence, Nathan P. Metzger, Corine P. Richard, John N. Campbell, Jeffrey M. Zigman

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Figure 4

Inducible ghrelin cell ablation increases islet size in adult mice.

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Inducible ghrelin cell ablation increases islet size in adult mice. (A) ...
(A) Representative images of stomach sections stained for ghrelin IR (in red) and with DAPI (nuclear staining, in blue) from mice with intact ghrelin cells or ablated ghrelin cells. (B) Plasma ghrelin and (C) blood glucose levels after a 24-hour fast. (D) Representative islet images from intact and ablated groups. (E) Islet cross-sectional area. (F) Percentage of islets in each islet cross-sectional area range, in which each range except the last represents a 5 μm2 × 103 interval. (G) Ferret’s diameter of islets. (H) Circularity of islets. (I) β Cell cross-sectional area per islet. (J) Relative β cell cross-sectional area. (K) β Cell mass. (L) Number of β cells per islet. (M) β Cell size. (N) Representative images of islets stained for cleaved caspase-3 IR (in red), insulin IR (in green), and DAPI (nuclear staining, in blue) from mice with intact ghrelin cells or ablated ghrelin cells. (O) Percentage of cleaved caspase-3+ β cells per total β cells. (P) α Cell cross-sectional area per islet. (Q) δ Cell cross-sectional area per islet. (R) Total number of islets per total pancreas area (within 4 pancreas sections per mouse). (S) Pancreas plus spleen weight per BW. (T) Blood glucose and (U) plasma insulin levels at various time points after glucose administration. Scale bars: 100 μm (A) and 50 μm (D and N). n = 3 mice (A and Q), n = 14–16 mice (B and C), n = 7–8 mice (E–M, P, R, and S), n = 5 mice (N and O), and n = 7–10 mice (T and U). Data were analyzed by unpaired, 2-tailed Student’s t test (B, C, E, G–M, and O–S) and 2-way repeated-measures ANOVA followed by Bonferroni’s multiple-comparison test (F, T, and U). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001; actual P values of 0.05 or greater and of less than 0.1 are indicated.