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Insulin Signaling Pathway in Regulation of Pancreatic β-cell dynamics in Zebrafish
Antinea Jones, Mingyu Li, Wenbiao Chen
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine Nashville, TN 37232
Pancreatic β-cells play a crucial role in glucose homeostasis,
secreting insulin to lower blood glucose levels. When insulin
signaling activity is impaired due to obesity or genetic
predisposition, more insulin is required to maintain glucose
homeostasis. The increased insulin demand initially elicits a
compensatory increase of β-cell mass and function but,
eventually causes β-cell dysfunction, resulting in type 2
diabetes mellitus (T2DM). T2DM is currently a growing
pandemic that has doubled globally in the past three decades.
Here we examine the role of the insulin signaling pathway in
regulation of β-cell number dynamics in zebrafish.
Specifically, we determine whether zebrafish mutants for
insulin receptor a (insra) and insulin receptor b (insrb) have
abnormal β-cell numbers. Because of the genetic and
chemical tractability, these mutant zebrafish may provide a
platform for identification of drugs and drug targets for the
treatment of insulin resistance and T2DM.
Chen L, Magliano DJ, Zimmet PZ. The worldwide
epidemiology of type 2 diabetes mellitus-present and future
perspectives. Nat Rev Endocrinol 8: 228-236, 2012.
Li M, Maddison LA, Page-McCaw P, Chen W. Overnutrition
induces β-cell differentiation through prolonged activation of
β-cells in zebrafish larvae. Am J Physiol Endocrinol Metab
306: E799-E807,2014
.
Maddison LA, Chen W. Nutrient excess stimulates β-cell
neogenesis in zebrafish. Diabetes 61: 2517-2524, 2012
.
Schlegel A, Gut P. Metabolic insights from zebrafish
genetics, physiology, and chemical biology. Cell Mol Life Sci
72: 2249-2260, 2015.
Sin Oh Y. Mechanistic insights into pancreatic beta-cell mass
regulation by glucose and free fatty acids. Anat and Cell Biol
48: 16-24, 2015.
This research was supported by the Vanderbilt Summer
Science Academy and The Chen lab. I would like to thank
the Chen lab for their support and assistance. The research
was funded through Dr. James Patton by the
5R25HL118679-03 grant.
.
Abstract Goals
Conclusions
References
Methods
To determine whether the loss of one co-ortholog insulin receptor (insra and
insrb) alters β-cell number in normal and metabolically stressed conditions.
Zebrafish larvae and β-Cell Composition
Results
5 dpf
A. Magnified zebrafish 5 days post fertilization (dpf)
of a fluorescent islet B. Magnified zebrafish islet of
β-cells when unfed C. Magnified zebrafish islet of
β-cells when fed with 5% egg yolk
Unfed Fed
A
B C
The experiments were conducted in the incross progeny of insra or insrb
heterozygotes carrying Tg(ins:H2BmCherry). The zebrafish were cultured in
5% egg yolk for 8 hours or nutrient-free medium for 8 hours at 6-day post
fertilization (dpf). mCherry-expressing larvae were euthanized and fixed with
4% paraformaldehyde. The genotype of the fixed larvae was determined using
genomic DNA from the posterior half and the number of β-cells was
determined by fluorescent microscopy.
Acknowledgements
1. Under normal condition, there was a significant
(*pvalue <0.6 for insra samples; *p value <0.05 **p
value <0.01 for insrb samples) reduction of β-cell
number in mutants homozygous for either insra or insrb.
2. The data was preliminary and needs to be repeated since
there was no increase of β-cell number under metabolic
stress condition in wild-type animals.
Figure 1. β-cell number in the three genotype groups of insra
under normal and metabolic stress conditions. The bars are
mean and error bars are standard error (*p value<0.6).
Figure 2. β-cell number in the three genotype groups of insrb
under normal and metabolic stress conditions. The bars are
mean and error bars are standard error (*p value<0.05, **p
value <0.01)
Results
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Wildtype Heterozygous Homozygous
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Figure 1.
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Figure 2.