Zebrafish respond efficiently and rapidly to streptozotocin (STZ) injection induced diabetes, and hypercholesterolemia caused by high cholesterol diet (HCD)—associated with a high risk of DFUs) Cho et al.
[60] injected 30 μL 5 mM citrate buffer containing 0.3% STZ into the subcutaneous tissue adjacent to the abdomen for eight consecutive days utilizing a 26-needle micro-syringe. Prior to that, they were given a 4% cholesterol high cholesterol diet (HCD) for 4 weeks, consisting of normal diet (ND) alone group, ND+STZ group, HCD alone group. and HCD+STZ group. Finally, patients were treated with Heberprot-P75
®, Easyef
® (two commercial epidermal growth factor (EGF) products, intraperitoneal injection of 10 μL, 50 μg/mL) and PBS on day 3, 5 and 7, respectively. As a result of treatment with PBS in the ND+STZ and HCD+STZ groups, adult fish showed serious delays in healing, as well as multiple cracks which is the typical damage pattern induced by STZ injection in diabetic zebrafish on their caudal fins. However, no cracks appeared in the HCD alone group
[61]. Heberprot-P75
® showed caudal fin regeneration activity 2.1 times higher than Easyef
® (ND+STZ group) and 1.7 and 1.5 times higher than the Easyef
® group and PBS group (HCD+STZ group) under the same injection and amputation regimen, with more distinct and clean regeneration modes
[61]. Intine et al. injected 0.35 mg/g of STZ intraperitoneally for 1, 3, and 5 days and maintained the injection weekly with the tank temperature maintained at 22–24 °C, as well as amputating the caudal fin in a straight line using a sterile size 10 scalpel, proximal to the first lepidotrichia branching point to obtain an adult zebrafish wound model of type I diabetes bearing an average blood glucose of more than 300 mg/dL, impaired caudal fin regeneration, accumulation of AGEs, and epigenetic changes including genome-wide demethylation. At 21 days to stop the injection of STZ, and restore normal blood insulin and glucose control through pancreas regeneration, and obtain the metabolic memory (MM) fish, whose limb regeneration was still the same as the state of acute diabetes damage, even at 30, 60, 90 days, and this affects the genetic to daughter cells
[62], as well as bnormal DNA methylation was also retained, but AGEs did not accumulate and ROS induced stress signals did not increase. In conclusion, restoring physiologically normal glycemic control may not save altered target tissue from diabetes-induced changes
[63].
4.2. Caudal Fin Model of Type II Diabetes in Adult Zebrafish Induced by Alloxan and Glucose Combined with Aqueous Solution Exposure
Aquaporin (AQP) and GLUT1, both present in the gill and skin epithelium, are thought to be responsible for the production of HG zebrafish following the application of alloxan and glucose in water. Wibowo et al. combined 0.4% Alloxan and glucose (E-Merck) % solution, and placed adult zebrafish aged from 3 to 6 months in 100 mL Alloxan solution for 1 h a day for 5 days, and then transferred 2L 2% glucose solution for 24 h for 6 days, as well as amputating using a lancet (Aesculap Scalpel Handle No. 3 and Aesculap Scalpel Blade No. 10 of B BRAUN) at the first or the second segment below the level of the first ray bifurcation. The expressions of
shha,
igf2a,
bmp2b, and
col1a2 were down-regulated in the experimental group, which may be related to the glucose metabolism inducing the generation of superoxide or ROS, the inhibition of GAPDH, the accumulation of methyl glyoxal, and the disruption of hypoxia inducible factor-1α transcription factor stability, leading to the transcriptional inhibition of some of the above target genes. The percentage of caudal fin regeneration and the expression of
shha,
igf2a,
bmp2b, and
col1a2 were increased after treatment with 15 ppm propolis ethanol extract
[64].
4.3. Caudal Fin Regeneration Model of Zebrafish Juvenile Type II Diabetes Induced by Single Immersion or Injection of Glucose
With zebrafish, each process can be studied separately, which allows us to observe wound healing more directly. Morris et al. studied the wound model of hyperglycemic transgenic
Tg (mfap4:turquoise)xt27 induced by immersion (5% glucose) and injection (15 nmol). Macrophages of transgenic
Tg (mfap4:turquoise)xt27 juveniles were labeled with turquoise fluorescent protein, neutrophils of
Tg (lyzC:DsRed)nz50 juveniles were labeled with DsRed fluorescent protein, and reduced neutrophils were found in the juveniles injected with glucose. That is, innate immune cell development is affected.
Tg (itga2b:gfp)LA2 juvenile tail fin transection was observed to stop bleeding, while injection and immersion showed reduced platelet accumulation. At the same time, the accumulation of fibrin was reduced by using
Tg (fabp10a:fgb-gfp)mi4001, which expresses fluorescently tagged fibrinogen and allows visualization of clots. Finally, the infusion of glucose at 0 day post fertilization (dpf) and the feeding of a HFD at 5 dpf found a significant acceleration of lipid accumulation after only one day of feeding, providing a more rapid model for studying lipid accumulation
[65].
4.4. Skin Wound Model of Adult Zebrafish Type I Diabetes Induced by STZ Injection
The full-layer wound healing mechanism of zebrafish is very similar to that of humans. On the one hand, in the embryonic and larval stages, the skin of zebrafish is already composed of the outer layer of peritrind, the middle layer of epidermis, and the basal layer attached to the basal membrane. In the process of metamorphosis on the 25th day after fertilization, multiple layers of epidermis are formed. At the same time, fibroblasts penetrate the dermis and take over collagen produced by basal keratinocytes to form locally thickened dermal papilla and scale, which is very similar to human skin structure. On the other hand, skin healing of zebrafish involves activation of signal transduction pathways downstream of hydrogen peroxide, including epidermal growth factor EGF, forkhead box-1, and IkappaB kinase-alpha. EGF regulates TGF-β through ERK1/2 and EGFR signal transduction. Damaged cells bind to EGFR to trigger cascades (such as TGF-β/integrin and ROCK/JNK pathways) to induce DNA synthesis and cell proliferation at the wound site.