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Research Question: Does advanced paternal age (APA; ≥40 years) contribute to a higher incidence of paternal origin aneuploidy in preimplantation embryos?, Design: This was a multicentre retrospective study of single-nucleotide polymorphism (SNP) microarray (Natera and Karyomapping) preimplantation genetic testing (PGT) outcomes of blastocyst-stage embryos. Whole-chromosome aneuploidy analysis was performed on 2409 embryos from 389 male patients undertaking 681 assisted reproductive technology (ART) cycles between 2012-2021. Segmental aneuploidy analysis was performed on 867 embryos from 140 men undertaking 242 ART cycles between 2016-2021. Embryos were grouped based on paternal age at sperm collection: <35, 35-39 and ≥40 years. Paternal and maternal origin aneuploidy rates were compared between groups using chi-squared and/or Fisher's exact tests., Results: There was no significant difference across groups in paternal origin whole-chromosome aneuploidy rate, overall (P=0.7561) or when segregated by type (trisomy and monosomy: P=0.2235 and 0.8156) or complexity (single versus 2, 3 or ≥4 aneuploidies: P=0.9733, 0.7517, 0.669 and 0.1481). Conversely, maternal origin whole-chromosome aneuploidy rate differed across groups (P<0.0001) in alignment with differing mean maternal age (P<0.001). Paternal origin deletions were 2.9-fold higher than maternal origin deletions (P=0.0084), independent of age stratification. No significant difference in paternal origin deletions was observed with APA ≥40 compared with the younger age groups (4.8% versus 2.5% and 2.8%, P=0.5292). Individual chromosome aneuploidy rates were too low to perform statistical comparisons., Conclusions: No significant association was found between APA and the incidence of paternal origin aneuploidy in preimplantation embryos, irrespective of type or complexity. Thus, APA may not be an indication for PGT., (Copyright © 2023 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.)

Islet amyloid is present in more than 90% of individuals with type 2 diabetes, where it contributes to β-cell apoptosis and insufficient insulin secretion. Apoptosis repressor with caspase recruitment domain (ARC) binds and inactivates components of the intrinsic and extrinsic apoptosis pathways and was recently found to be expressed in islet β-cells. Using a human islet amyloid polypeptide transgenic mouse model of islet amyloidosis, we show ARC knockdown increases amyloid-induced β-cell apoptosis and loss, while ARC overexpression decreases amyloid-induced apoptosis, thus preserving β-cells. These effects occurred in the absence of changes in islet amyloid deposition, indicating ARC acts downstream of amyloid formation. Because islet amyloid increases c-Jun N-terminal kinase (JNK) pathway activation, we investigated whether ARC affects JNK signaling in amyloid-forming islets. We found ARC knockdown enhances JNK pathway activation, whereas ARC overexpression reduces JNK, c-Jun phosphorylation, and c-Jun target gene expression ( Jun and Tnf ). Immunoprecipitation of ARC from mouse islet lysates showed ARC binds JNK, suggesting interaction between JNK and ARC decreases amyloid-induced JNK phosphorylation and downstream signaling. These data indicate that ARC overexpression diminishes amyloid-induced JNK pathway activation and apoptosis in the β-cell, a strategy that may reduce β-cell loss in type 2 diabetes., (© 2017 by the American Diabetes Association.)

Culture of isolated rodent islets is widely used in diabetes research to assess different endpoints, including outcomes requiring histochemical staining. As islet yields during isolation are limited, we determined the number of islets required to obtain reliable data by histology. We found that mean values for insulin-positive β-cell area/islet area, thioflavin S-positive amyloid area/islet area and β-cell apoptosis do not vary markedly when more than 30 islets are examined. Measurement variability declines as more islets are quantified, so that the variability of the coefficient of variation (CV) in human islet amyloid polypeptide (hIAPP) transgenic islets for β-cell area/islet area, amyloid area/islet area and β-cell apoptosis are 13.20% ± 1.52%, 10.03% ± 1.76% and 6.78% ± 1.53%, respectively (non-transgenic: 7.65% ± 1.17% β-cell area/islet area and 8.93% ± 1.56% β-cell apoptosis). Increasing the number of islets beyond 30 had marginal effects on the CV. Using 30 islets, 6 hIAPP-transgenic preparations are required to detect treatment effects of 14% for β-cell area/islet area, 30% for amyloid area/islet area and 23% for β-cell apoptosis (non-transgenic: 9% for β-cell area/islet area and 45% for β-cell apoptosis). This information will be of value in the design of studies using isolated islets to examine β cells and islet amyloid., (© The Author(s) 2015.)

Aims/hypothesis: Amyloid deposition and inflammation are characteristic of islet pathology in type 2 diabetes. The aim of this study was to determine whether islet amyloid formation is required for the development of islet inflammation in vivo., Methods: Human islet amyloid polypeptide transgenic mice and non-transgenic littermates (the latter incapable of forming islet amyloid) were fed a low-fat (10%) or high-fat (60%) diet for 12 months; high-fat feeding induces islet amyloid formation in transgenic mice. At the conclusion of the study, glycaemia, beta cell function, islet amyloid deposition, markers of islet inflammation and islet macrophage infiltration were measured., Results: Fasting plasma glucose levels did not differ by diet or genotype. Insulin release in response to i.v. glucose was significantly greater in both high vs low fat groups, and significantly lower in both transgenic compared with non-transgenic groups. Only high-fat-fed transgenic mice developed islet amyloid and showed a trend towards reduced beta cell area. Compared with islets from low-fat-fed transgenic or high-fat-fed non-transgenic mice, islets of high-fat-fed transgenic mice displayed a significant increase in the expression of genes encoding chemokines (Ccl2, Cxcl1), macrophage/dendritic cell markers (Emr1, Itgax), NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome components (Nlrp3, Pycard, Casp1) and proinflammatory cytokines (Il1b, Tnf, Il6), as well as increased F4/80 staining, consistent with increased islet inflammation and macrophage infiltration., Conclusions/interpretation: Our results indicate that islet amyloid formation is required for the induction of islet inflammation in this long-term high-fat-diet model, and thus could promote beta cell dysfunction in type 2 diabetes via islet inflammation.

The dipeptidyl peptidase-4 (DPP-4) inhibitor sitagliptin is an attractive therapy for diabetes, as it increases insulin release and may preserve β-cell mass. However, sitagliptin also increases β-cell release of human islet amyloid polypeptide (hIAPP), the peptide component of islet amyloid, which is cosecreted with insulin. Thus, sitagliptin treatment may promote islet amyloid formation and its associated β-cell toxicity. Conversely, metformin treatment decreases islet amyloid formation by decreasing β-cell secretory demand and could therefore offset sitagliptin's potential proamyloidogenic effects. Sitagliptin treatment has also been reported to be detrimental to the exocrine pancreas. We investigated whether long-term sitagliptin treatment, alone or with metformin, increased islet amyloid deposition and β-cell toxicity and induced pancreatic ductal proliferation, pancreatitis, and/or pancreatic metaplasia/neoplasia. hIAPP transgenic and nontransgenic littermates were followed for 1 yr on no treatment, sitagliptin, metformin, or the combination. Islet amyloid deposition, β-cell mass, insulin release, and measures of exocrine pancreas pathology were determined. Relative to untreated mice, sitagliptin treatment did not increase amyloid deposition, despite increasing hIAPP release, and prevented amyloid-induced β-cell loss. Metformin treatment alone or with sitagliptin decreased islet amyloid deposition to a similar extent vs untreated mice. Ductal proliferation was not altered among treatment groups, and no evidence of pancreatitis, ductal metaplasia, or neoplasia were observed. Therefore, long-term sitagliptin treatment stimulates β-cell secretion without increasing amyloid formation and protects against amyloid-induced β-cell loss. This suggests a novel effect of sitagliptin to protect the β-cell in type 2 diabetes that appears to occur without adverse effects on the exocrine pancreas.