Development of a Novel Zebrafish Model for Type 2 Diabetes Mellitus

Abstract

Obesity is a major cause of type 2 diabetes mellitus (T2DM) in mammals. We have previously established a zebrafish model of diet-induced obesity (DIO zebrafish) by overfeeding Artemia. Here we created DIO zebrafish using a different method to induce T2DM. Zebrafish were overfed a commercially available fish food using an automated feeding system. We monitored the fasting blood glucose levels in the normal-fed group (one feed/day) and overfed group (six feeds/day) over an 8-week period. The fasting blood glucose level was significantly increased in DIO zebrafish compared with that of normal-fed zebrafish. Intraperitoneal and oral glucose tolerance tests showed impaired glucose tolerance by overfeeding. Insulin production, which was determined indirectly by measuring the EGFP signal strength in overfed Tg(−1.0ins:EGFP) sc1 zebrafish, was increased in DIO zebrafish. The anti-diabetic drugs metformin and glimepiride ameliorated hyperglycaemia in the overfed group, suggesting that this zebrafish can be used as a model of human T2DM. Finally, we conducted RNA deep sequencing and found that the gene expression profiling of liver-pancreas revealed pathways common to human T2DM. In summary, we developed a zebrafish model of T2DM that shows promise as a platform for mechanistic and therapeutic studies of diet-induced glucose intolerance and insulin resistance.

Critical Role for a Subset of Intestinal Macrophages in Shaping Gut Microbiota in Adult Zebrafish

“…Among these, 46 genes were significantly downregulated and 30 genes were significantly upregulated in irf8 mutants compared to control siblings (Figure 4B). Several transcripts related to pancreatic and intestinal functioning (glucagon a and b, ghrelin, and insulin; Eames et al, 2013; Eom et al, 2013; Ye et al, 2015; Zang et al, 2017) were found to be downregulated in irf8 mutants, but these results were not reproduced by conventional qPCR analysis on additional gut samples (Figure 4C; data not shown). Such genes, which were deemed significantly changed by RNA-seq analysis but exhibited a large variation between the control replicates, were not considered or presented in the heatmaps (Figure 4C).…”

Sweet fish: Fish models for the study of hyperglycemia and diabetes

“…The blood glucose range of zebrafish is similar to that for humans, spanning approximately 40-300 mg/dL in extreme cases with normal physiological levels around 70-80 mg/dL. 13 In addition, high glucose levels in fish stimulate insulin expression, as in humans, 14,15 and the fish glucose transporter genes Glut2 and Glut4 show significant conservation of structure, function, and glucose affinity with human orthologs. 16,17 The development and function of two key organs involved in diabetes, the pancreas and liver, is significantly conserved between mammals and zebrafish.…”

“…This model is promising especially because the symptoms can be ameliorated with antidiabetic drugs like metformin and glimepiride. 15 It is also possible to elicit hyperglycemia simply by immersing the fish in 1%-2% glucose solutions. The glucose-immersed zebrafish mimic the fluctuations in blood glucose levels of human diabetic patients and develop specific retinal lesions in a relatively short period of time.…”

“…34 This method is cheap, quick, and avoids chemical injection. In addition to simply immersing the fish in glucose or overfeeding the fish, 15 there are a few mutant and transgenic lines available that induce insulin resistance in zebrafish. [35][36][37] For example, overexpression of a forkhead box N3 (foxn3) genetic risk variant leads to elevated fasting glucose levels and causes hepatic steatosis in fish, as seen in human carriers of the risk allele.…”

“…Unlike in mice, standardized feeding regimens to induce diabetes-like conditions are somewhat limited in number, and different commercial diets lead to significantly different growth rates and body size. 15,51,52 In addition, many of the methods routinely used in mammals, such as the glucose clamp technique (considered as the gold standard for measuring insulin sensitivity), are still being adapted to work in small fish. The standard diabetes and obesity models in mouse are ob/ob and db/db, which are leptin and leptin receptor mutants, respectively.…”