Diet-induced obesity in zebrafish shares common pathophysiological pathways with mammalian obesity

<p>Abstract</p> <p>Background</p> <p>Obesity is a multifactorial disorder influenced by genetic and environmental factors. Animal models of obesity are required to help us understand the signaling pathways underlying this condition. Zebrafish possess many structural and functional similarities with humans and have been used to model various human diseases, including a genetic model of obesity. The purpose of this study was to establish a zebrafish model of diet-induced obesity (DIO).</p> <p>Results</p> <p>Zebrafish were assigned into two dietary groups. One group of zebrafish was overfed with <it>Artemia </it>(60 mg dry weight/day/fish), a living prey consisting of a relatively high amount of fat. The other group of zebrafish was fed with <it>Artemia </it>sufficient to meet their energy requirements (5 mg dry weight/day/fish). Zebrafish were fed under these dietary protocols for 8 weeks. The zebrafish overfed with <it>Artemia </it>exhibited increased body mass index, which was calculated by dividing the body weight by the square of the body length, hypertriglyceridemia and hepatosteatosis, unlike the control zebrafish. Calorie restriction for 2 weeks was applied to zebrafish after the 8-week overfeeding period. The increased body weight and plasma triglyceride level were improved by calorie restriction. We also performed comparative transcriptome analysis of visceral adipose tissue from DIO zebrafish, DIO rats, DIO mice and obese humans. This analysis revealed that obese zebrafish and mammals share common pathophysiological pathways related to the coagulation cascade and lipid metabolism. Furthermore, several regulators were identified in zebrafish and mammals, including APOH, IL-6 and IL-1β in the coagulation cascade, and SREBF1, PPARα/γ, NR1H3 and LEP in lipid metabolism.</p> <p>Conclusion</p> <p>We established a zebrafish model of DIO that shared common pathophysiological pathways with mammalian obesity. The DIO zebrafish can be used to identify putative pharmacological targets and to test novel drugs for the treatment of human obesity.</p

Pancreatectomy in patients with LC

Background : Several reports have shown a high mortality rate in patients with liver cirrhosis (LC) who undergo pancreaticoduodenectomy, however, there are few reports on its long-term prognosis. Methods : Twelve patients with LC who had undergone pancreatic resection were enrolled. To compare clinicopathological variables, 159 non-LC patients who had undergone resection for pancreatic cancer were enrolled. Results : Pancreaticoduodenectomy (PD) was performed in 5 LC patients and distal pancreatectomy (DP) was performed in 7 LC patients. Patients in the LC group had more co-morbidities, lower platelet counts and higher Fib4 index than the non-LC group. The postoperative complication rate was higher in the LC group (83.3% vs 47.8%). While the postoperative hospital stay and 30-day mortality rate were not different, the 90-day mortality rate was higher in the LC group (25.0% vs 2.5% ; p < 0.01). Comparison by operative procedure showed no significant differences of postoperative outcomes in DP cases. However, in PD cases, postoperative complications were more frequent (100% vs 42.3%) and 90-day mortality was higher (40.0% vs 2.9% ; p < 0.01) in the LC group. Conclusions : PD resulted in higher postoperative morbidity and mortality rates in patients with LC compared with non-LC patients. DP could be tolerated in the LC patients

In vivo imaging of zebrafish retinal cells using fluorescent coumarin derivatives

<p>Abstract</p> <p>Background</p> <p>The zebrafish visual system is a good research model because the zebrafish retina is very similar to that of humans in terms of the morphologies and functions. Studies of the retina have been facilitated by improvements in imaging techniques. <it>In vitro </it>techniques such as immunohistochemistry and <it>in vivo </it>imaging using transgenic zebrafish have been proven useful for visualizing specific subtypes of retinal cells. In contrast, <it>in vivo </it>imaging using organic fluorescent molecules such as fluorescent sphingolipids allows non-invasive staining and visualization of retinal cells <it>en masse</it>. However, these fluorescent molecules also localize to the interstitial fluid and stain whole larvae.</p> <p>Results</p> <p>We screened fluorescent coumarin derivatives that might preferentially stain neuronal cells including retinal cells. We identified four coumarin derivatives that could be used for <it>in vivo </it>imaging of zebrafish retinal cells. The retinas of living zebrafish could be stained by simply immersing larvae in water containing 1 μg/ml of a coumarin derivative for 30 min. By using confocal laser scanning microscopy, the lamination of the zebrafish retina was clearly visualized. Using these coumarin derivatives, we were able to assess the development of the zebrafish retina and the morphological abnormalities induced by genetic or chemical interventions. The coumarin derivatives were also suitable for counter-staining of transgenic zebrafish expressing fluorescent proteins in specific subtypes of retinal cells.</p> <p>Conclusions</p> <p>The coumarin derivatives identified in this study can stain zebrafish retinal cells in a relatively short time and at low concentrations, making them suitable for <it>in vivo </it>imaging of the zebrafish retina. Therefore, they will be useful tools in genetic and chemical screenings using zebrafish to identify genes and chemicals that may have crucial functions in the retina.</p

A high-throughput fluorescence-based assay system for appetite-regulating gene and drug screening.

The increasing number of people suffering from metabolic syndrome and obesity is becoming a serious problem not only in developed countries, but also in developing countries. However, there are few agents currently approved for the treatment of obesity. Those that are available are mainly appetite suppressants and gastrointestinal fat blockers. We have developed a simple and rapid method for the measurement of the feeding volume of Danio rerio (zebrafish). This assay can be used to screen appetite suppressants and enhancers. In this study, zebrafish were fed viable paramecia that were fluorescently-labeled, and feeding volume was measured using a 96-well microplate reader. Gene expression analysis of brain-derived neurotrophic factor (bdnf), knockdown of appetite-regulating genes (neuropeptide Y, preproinsulin, melanocortin 4 receptor, agouti related protein, and cannabinoid receptor 1), and the administration of clinical appetite suppressants (fluoxetine, sibutramine, mazindol, phentermine, and rimonabant) revealed the similarity among mechanisms regulating appetite in zebrafish and mammals. In combination with behavioral analysis, we were able to evaluate adverse effects on locomotor activities from gene knockdown and chemical treatments. In conclusion, we have developed an assay that uses zebrafish, which can be applied to high-throughput screening and target gene discovery for appetite suppressants and enhancers

Gene expression and the effect of knocking down genes associated with appetite regulation.

<p>(A) Analysis by qPCR of brain-derived neurotrophic factor mRNA (<i>bdnf</i>) during paramecia feeding, <i>n</i> = 5, *<i>P</i><0.05. (B and C) Western blots showing embryonic injection of neuropeptide Y (<i>npy</i>) MO (B) and preproinsulin a (<i>insa</i>) MO. (D) Embryonic injection of <i>npy</i> MO and <i>npy</i> mRNA. Orexigenic gene knockdown decreased feeding volume. (E) <i>insa</i> MO and <i>insa</i> mRNA, orexigenic gene knockdown increased feeding volume at 7 dpf. <i>n</i> = 15, *<i>P</i><0.05. All values are mean ± SEM. (F and G) Knockdown of <i>npy</i> (F) and <i>insa</i> (G) affected locomotor activities at 5 dpf. <i>n</i> = 16, *<i>P</i><0.05. All values are mean ± SEM. (H) Detection of gene knockdown for splicing MOs in 2% (w/v) agarose gels stained with ethidium bromide.</p

Effect of appetite suppressants on feeding volume.

<p>Effects of appetite-regulating drugs that are used clinically in humans affected zebrafish larvae. (A) Fluoxetine, (B) Sibutramine, (C) Mazindol, (D) Phentermine, and (E) Rimonabant treatment decreased feeding volume in young zebrafish (7 dpf). All values are mean ± SEM, <i>n</i> = 16, *<i>P</i><0.05, **<i>P</i><0.01.</p

Green tea extract suppresses adiposity and affects the expression of lipid metabolism genes in diet-induced obese zebrafish

<p>Abstract</p> <p>Background</p> <p>Visceral fat accumulation is one of the most important predictors of mortality in obese populations. Administration of green tea extract (GTE) can reduce body fat and reduce the risk of obesity-related diseases in mammals. In this study, we investigated the effects and mechanisms of GTE on adiposity in diet-induced obese (DIO) zebrafish.</p> <p>Methods</p> <p>Zebrafish at 3.5 to 4.5 months post-fertilization were allocated to four groups: non-DIO, DIO, DIO + 0.0025%GTE, and DIO + 0.0050%GTE. The non-DIO group was fed freshly hatched <it>Artemia</it> once daily (5 mg cysts/fish daily) for 40 days. Zebrafish in the three DIO groups were fed freshly hatched <it>Artemia</it> three times daily (60 mg cysts/fish daily). Zebrafish in the DIO + 0.0025%GTE and DIO + 0.0050%GTE groups were exposed to GTE after the start of feeding three times daily for 40 days.</p> <p>Results</p> <p>Three-dimensional microcomputed tomography analysis showed that GTE exposure significantly decreased the volume of visceral but not subcutaneous fat tissue in DIO zebrafish. GTE exposure increased hepatic expression of the lipid catabolism genes <it>ACOX1</it> (<it>acyl-coenzyme A oxidase 1, palmitoyl</it>), <it>ACADM</it> (<it>acyl-coenzyme A dehydrogenase, c-4 to c-12 straight chain)</it>, and <it>PPARA</it> (<it>peroxisome proliferator-activated receptor alpha</it>). GTE exposure also significantly decreased the visceral fat expression of <it>SOCS3</it> (<it>suppressor of cytokine signaling 3b</it>) which inhibits leptin signaling.</p> <p>Conclusions</p> <p>The present results are consistent with those seen in mammals treated with GTE, supporting the validity of studying the effects of GTE in DIO zebrafish. Our results suggest that GTE exerts beneficial effects on adiposity, possibly by altering the expression of lipid catabolism genes and <it>SOCS3</it>.</p