Protein kinase STK25 aggravates the severity of non-alcoholic fatty pancreas disease in mice

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   Figure 1

   Morphological analysis of pancreatic islets and their cellular composition in high-fat-fed Stk25 transgenic and wild-type mice. (A) Pancreatic weight. (B–D) The mean area of islets (B), islet perimeter (C) and islet area and regional distribution (D). (E) Representative immunofluorescence images double stained with antibodies for insulin (green) and glucagon (red). Nuclei stained with DAPI are shown in blue in a merged image. Scale bars, 50 µm. Quantification of insulin- and glucagon-positive area, and the islet β/α-cell ratio. Data are mean ± s.e.m. from 5 mice/genotype. **P < 0.01. HFD, high-fat diet; TG, transgenic; WT, wild-type.
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   Figure 2

   Fasting circulating levels of insulin (A), C-peptide (B), leptin (C) and glucagon (D) in high-fat-fed Stk25 transgenic and wild-type mice at the time of termination. Data are mean ± s.e.m. from 8 to 11 mice/genotype. *P < 0.05; **P < 0.01. HFD, high-fat diet; TG, transgenic; WT, wild-type.
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   Figure 3

   Assessment of fat accumulation and mitochondrial activity in the pancreas of high-fat-fed Stk25 transgenic and wild-type mice. (A) Triacylglycerol content in pancreatic extracts. (B) Representative images stained with Oil Red O for lipids and counterstained with hematoxylin. Scale bars, 25 µm. Quantification of Oil Red O staining. (C) Free fatty acid levels in pancreatic extracts. (D) Representative images stained with MitoTracker Red; nuclei stained with DAPI (blue). Scale bars, 25 µm. Quantification of MitoTracker Red staining. For A and C, data are mean ± s.e.m. from 11 to 12 mice/genotype; for B and D, data are mean ± s.e.m. from 5–7 mice/genotype. *P < 0.05. FFA, free fatty acid; HFD, high-fat diet; ORO, Oil Red O; TAG, triacylglycerol; TG, transgenic; WT, wild-type.
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   Figure 4

   Analysis of inflammatory cell infiltration in the pancreas of high-fat-fed Stk25 transgenic and wild-type mice. (A) Representative images of non-inflamed islets in wild-type mice, and peri-insulitis and invasive insulitis in Stk25 transgenic mice. White arrowheads indicate mononuclear cell infiltration. Scale bars, 15 µm. (B) Quantification of non-inflamed islets, peri-insulitis, and insulitis. Results are shown as a dot plot where each point represents one mouse and as a pie chart. (C) The degree of insulitis as assessed using a semi-quantitative scoring system. Data are mean ± s.e.m. from 6 mice/genotype. *P < 0.05; **P < 0.01. HFD, high-fat diet; TG, transgenic; WT, wild-type.
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   Figure 5

   Assessment of fibrosis, PSC activation, and apoptosis in the pancreas of high-fat-fed Stk25 transgenic and wild-type mice. (A) Representative images stained with Picrosirius Red and counterstained with Fast Green. Quantification of Picrosirius Red staining. (B) Representative images stained with antibodies for α-SMA; nuclei stained with DAPI (blue). White arrows indicate α-SMA-positive cells within the islet. Quantification of α-SMA staining. (C) Representative images stained with TUNEL. Quantification of TUNEL-positive staining. Scale bars, 25 µm. Data are mean ± s.e.m. from 5–8 mice/genotype. *P < 0.05; **P ≤ 0.01. HFD, high-fat diet; TG, transgenic; WT, wild-type.
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   Figure 6

   In vivo glucose tolerance and glucose-stimulated insulin secretion in high-fat-fed Stk25 transgenic and wild-type mice. (A) Changes in blood glucose levels following an intraperitoneal injection of glucose. (B) Changes in plasma insulin levels during the experiment shown in (A). Data are mean ± s.e.m. from 9 to 10 mice/genotype. *P ≤ 0.05; **P < 0.01. HFD, high-fat diet; TG, transgenic; WT, wild-type.
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   Figure 7

   Schematic illustration of metabolic alterations in individual organs and at the whole-body level in Stk25 transgenic and wild-type mice fed a high-fat diet. Up- or downregulation is indicated by red arrows. The figure combines the results of this study with previously published results (Cansby et al. 2013, Amrutkar et al. 2015b, 2016a, Chursa et al. 2017).

• © 2017 The authors