Different physiological roles of insulin receptors in mediating nutrient metabolism in zebrafish.

Insulin, the most potent anabolic hormone, is critical for somatic growth and metabolism in vertebrates. Type 2 diabetes, which is the primary cause of hyperglycemia, results from an inability of insulin to signal glycolysis and gluconeogenesis. Our previous study showed that double knockout of insulin receptor a ( insra) and b ( insrb) caused ß-cell hyperplasia and lethality from 5 to 16 days postfertilization (dpf) (Yang BY, Zhai G, Gong YL, Su JZ, Han D, Yin Z, Xie SQ. Sci Bull (Beijing) 62: 486-492, 2017). In this study, we characterized the physiological roles of Insra and Insrb, in somatic growth and fueling metabolism, respectively. A high-carbohydrate diet was provided for insulin receptor knockout zebrafish from 60 to 120 dpf to investigate phenotype inducement and amplification. We observed hyperglycemia in both insra-/- fish and insrb-/- fish. Impaired growth hormone signaling, increased visceral adiposity, and fatty liver were detected in insrb-/- fish, which are phenotypes similar to the lipodystrophy observed in mammals. More importantly, significantly diminished protein levels of P-PPARα, P-STAT5, and IGF-1 were also observed in insrb-/- fish. In insra-/- fish, we observed increased protein content and decreased lipid content of the whole body. Taken together, although Insra and Insrb show overlapping roles in mediating glucose metabolism through the insulin-signaling pathway, Insrb is more prone to promoting lipid catabolism and protein synthesis through activation of the growth hormone-signaling pathway, whereas Insra primarily acts to promote lipid synthesis via glucose utilization.

Effects of photoperiod on growth, lipid metabolism and oxidative stress of juvenile gibel carp (Carassius auratus).

A 58-day cultivation experiment was carried out to investigate the effects of photoperiods on growth, lipid metabolism and oxidative stress of juvenile gibel carp. Juveniles (5.41 ±â€¯0.01 g) were cultured under seven light photoperiods (0 h of light (L):24 h of darkness (D), 4L:20D (12:00-16:00 light), 8L:16D (10:00-18:00 light), 12L:12D (8:00-20:00 light), 16L:8D (6:00-22:00 light), 20L:4D (4:00-24:00 light) and 24L:0D) in an indoor recirculating aquaculture system. The light intensity was 1.02 µmol·m-2·s-1 (at the tank bottom in a 0.5-m water depth). The fish were fed to satiety three times daily (8:30, 14:30 and 18:30). At the end of the experiment, final body weight, specific growth rate, feed efficiency and feed intake were significantly higher in 16L:8D, 20L:4D and 24L:0D groups than those in other groups (P < 0.05). Long-day photoperiods (16L:8D, 20L:4D and 24L:0D) simultaneously promoted lipogenesis, lipolysis and fatty acid oxidation. The increases in lipid retention efficiency, whole body lipid concentration and liver lipid content (P < 0.05) indicated that lipogenesis exceeded fatty acid oxidation. Liver oxidative stress was induced in juvenile gibel carp by short day lengths. The hepatic total antioxidant capacity, superoxide dismutase, glutathione peroxidase and the contents of metabolite glutathione were the highest in the short-day-length groups (0L:24D, 4L:20D and 8L:16D) (P < 0.05). Based on the growth performance and health status in the long-term cultivation experiment, the optimal photoperiods were 16L:8D, 20L:4D and 24L:0D in juvenile gibel carp.

Different roles suggested by sex-biased expression and pheromone binding affinity among three pheromone binding proteins in the pink rice borer, Sesamia inferens (Walker) (Lepidoptera: Noctuidae).

Pheromone binding proteins (PBPs) are thought to bind and transport hydrophobic sex pheromone molecules across the aqueous sensillar lymph to specific pheromone receptors on the dendritic membrane of olfactory neurons. A maximum of 3 PBP genes have been consistently identified in noctuid species, and each of them shares high identity with its counterparts in other species within the family. The functionality differences of the 3 proteins are poorly understood. In the present study, 3 PBP cDNAs (SinfPBP1, 2, 3) were identified from the pink rice borer, Sesamia inferens, for the first time. The quantitative real-time PCR indicated that the 3 PBPs displayed similar temporal but very different sex related expression profiles. Expression of SinfPBP1 and SinfPBP2 were highly and moderately male biased, respectively, while SinfPBP3 was slightly female biased, as SinfPBPs were expressed at very different levels (PBP1>PBP2≫PBP3) in male antennae, but at similar levels in female antennae. Furthermore, the 3 SinfPBPs displayed different ligand binding profiles in fluorescence competitive binding assays. SinfPBP1 exhibited high and similar binding affinities to all 3 sex pheromone components (Ki=0.72-1.60 µM), while SinfPBP2 showed selective binding to the alcohol and aldehyde components (Ki=0.78-1.71 µM), and SinfPBP3 showed no obvious binding to the 3 sex pheromone components. The results suggest that SinfPBP1 plays a major role in the reception of female sex pheromones in S. inferens, while SinfPBP3 plays a least role (if any) and SinfPBP2 functions as a recognizer of alcohol and aldehyde components.

Differential expression patterns in chemosensory and non-chemosensory tissues of putative chemosensory genes identified by transcriptome analysis of insect pest the purple stem borer Sesamia inferens (Walker).

BACKGROUND: A large number of insect chemosensory genes from different gene subfamilies have been identified and annotated, but their functional diversity and complexity are largely unknown. A systemic examination of expression patterns in chemosensory organs could provide important information. METHODOLOGY/PRINCIPAL FINDINGS: We identified 92 putative chemosensory genes by analysing the transcriptome of the antennae and female sex pheromone gland of the purple stem borer Sesamia inferens, among them 87 are novel in this species, including 24 transcripts encoding for odorant binding proteins (OBPs), 24 for chemosensory proteins (CSPs), 2 for sensory neuron membrane proteins (SNMPs), 39 for odorant receptors (ORs) and 3 for ionotropic receptors (IRs). The transcriptome analyses were validated and quantified with a detailed global expression profiling by Reverse Transcription-PCR for all 92 transcripts and by Quantitative Real Time RT-PCR for selected 16 ones. Among the chemosensory gene subfamilies, CSP transcripts are most widely and evenly expressed in different tissues and stages, OBP transcripts showed a clear antenna bias and most of OR transcripts are only detected in adult antennae. Our results also revealed that some OR transcripts, such as the transcripts of SNMP2 and 2 IRs were expressed in non-chemosensory tissues, and some CSP transcripts were antenna-biased expression. Furthermore, no chemosensory transcript is specific to female sex pheromone gland and very few are found in the heads. CONCLUSION: Our study revealed that there are a large number of chemosensory genes expressed in S. inferens, and some of them displayed unusual expression profile in non-chemosensory tissues. The identification of a large set of putative chemosensory genes of each subfamily from a single insect species, together with their different expression profiles provide further information in understanding the functions of these chemosensory genes in S. inferens as well as other insects.

Antibacterial and antiviral roles of a fish ß-defensin expressed both in pituitary and testis.

Defensins are a group of cationic peptides that exhibit broad-spectrum antimicrobial activity. In this study, we cloned and characterized a ß-defensin from pituitary cDNA library of a protogynous hermaphroditic orange-spotted grouper (Epinephelus coioides). Interestingly, the ß-defensin was shown to be dominantly expressed in pituitary and testis by RT-PCR and Western blot analysis, and its transcript level is significantly upregulated in reproduction organs from intersexual gonad to testis during the natural and artificial sex reversal. Promoter sequence and the responsible activity region analyses revealed the pituitary-specific POU1F1a transcription binding site and testis-specific SRY responsible site, and demonstrated that the pituitary-specific POU1F1a transcription binding site that locates between -180 and -208 bp is the major responsible region of grouper ß-defensin promoter activity. Immunofluorescence localization observed its pituicyte expression in pituitary and spermatogonic cell expression in testis. Moreover, both in vitro antibacterial activity assay of the recombinant ß-defensin and in vivo embryo microinjection of the ß-defensin mRNA were shown to be effective in killing gram-negative bacteria. And, its antiviral role was also demonstrated in EPC cells transfected with the ß-defensin construct. Additionally, the antibacterial activity was sensitive to concentrations of Na(+), K(+), Ca(2+) and Mg(2+). The above intriguing findings strongly suggest that the fish ß-defensin might play significant roles in both innate immunity defense and reproduction endocrine regulation.

Antimicrobial activity-specific to Gram-negative bacteria and immune modulation-mediated NF-kappaB and Sp1 of a medaka beta-defensin.

Defensins are a group of cationic antimicrobial peptides which play an important role in the innate immune system by exerting their antimicrobial activity against pathogens. In this study, we cloned a novel beta-defensin cDNA from medaka (Oryzias latipes) by rapid amplification of cDNA ends (RACE) technique. The full-length cDNA consists of 480 bp, and the open reading frame (ORF) of 189 bp encodes a polypeptide of 63 amino acids (aa) with a predicted molecular weight of 7.44 kDa. Its genomic organization was analyzed, and Southern blot detection confirmed that only one copy of beta-defensin exists in the medaka HNI strain. RT-PCR, Western blot and immunohistochemistry detections showed that the beta-defensin transcript and protein could be detected in eyes, liver, kidney, blood, spleen and gill, and obviously prevalent expression was found in eyes. Antimicrobial activity of the medaka beta-defensin was evaluated, and the antibacterial activity-specific to Gram-negative bacteria was revealed. Furthermore, the lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, was demonstrated to be able to induce about 13-fold up-regulation of the beta-defensin within first 12h. In addition, promoter and promoter mutagenesis analysis were performed in the medaka beta-defensin. A proximal 100 base pair (bp) sequence (+26 to -73) and the next 1700 bp sequence (-73 to -1755) were demonstrated to be responsible for the basal promoter activity and for the transcription regulation. Three nuclear factor kappa B (NF-kappaB) cis-elements and a Sp1 cis-element were revealed by mutagenesis analysis to exist in the 5' flanking sequence, and they were confirmed to be responsible for the up-regulation of medaka beta-defensin stimulated by LPS. And, the Sp1 cis-element was further revealed to be related to the basal promoter activity, and transcriptional factor II D (TFIID) was found to be in charge of the gene transcription initiation. All the obtained data suggested that the novel medaka beta-defensin should have antimicrobial activity-specific to Gram-negative bacteria, and the antibacterial immune function should be modulated by NF-kappaB and Sp1.