Leptin Is an Important Endocrine Player That Directly Activates Gonadotropic Cells in Teleost Fish, Chub Mackerel

Leptin, secreted by adipocytes, directly influences the onset of puberty in mammals. Our previous study showed that leptin stimulation could promote the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from pituitary cells in primary culture and ovarian development in chub mackerel. This study aimed to elucidate the detailed mechanism of leptin-induced effects on gonadotropin hormone-producing cells. We produced recombinant leptin using silkworm pupae and investigated the effects of leptin on FSH and LH secretion and gene expression in the primary culture of pituitary cells from chub mackerel. The presence or absence of co-expression of lepr mRNA, FSH and LH b-subunit mRNA in gonadotropic cells was examined by double-labeled in situ hybridization. The addition of leptin significantly increased the secretion and gene expression of FSH and LH from male and female pituitary cells in primary culture. In contrast, gonadotropin-releasing hormone 1 affected neither FSH secretion in cells from females nor fshb and lhb expression in cells from males and females. The expression of lepr was observed in FSH- and LH-producing cells of both males and females. The results indicate that leptin directly regulates gonadotropin synthesis and secretion and plays an important role in the induction of puberty in teleost fish.

Energy consumption, physical properties, protein structure and digestibility of edible insects dried using three methods

This study evaluated the effects of three drying techniques, tray drying, roasting and microwave vacuum drying, on the physical properties, secondary structures, in vitro protein digestibility and X-ray tomographic structure of crickets (Acheta domesticus) and mulberry silkworm pupae (Bombyx mori L.). The protein contents of dried crickets and silkworm pupae were 49-54% and 51-53% (dry basis), respectively. Roasting produced a significantly higher browning index than the other two methods for crickets and silkworm pupae. The microwave vacuum-dried crickets exhibited the lowest hardness, with hardness values of approximately half those of the tray-dried and roasted crickets. Tray-drying and microwave vacuum drying silkworm pupae produced similar hardness values, which were lower than that of roasted silkworm pupae. The energy consumption of the tray dryer was the lowest, followed by the roaster and microwave vacuum dryer. No significant changes in the secondary protein structure of dried silkworm pupae were observed. A significant decrease in α-helix and β-turn and increase in β-sheet was observed in roasted crickets. Cricket and silkworm pupae powders produced from all drying techniques could be easily digested (90-95% digestibility). This work presents valuable knowledge for understanding the effects of different drying techniques on the properties of dried edible insects, aiming to support the production of alternative and sustainable protein sources for the growing population to improve food security.

Biology of Attagenus fasciatus Thunberg (Coleoptera: Dermestidae) on four different diets of animal origin

Biology of dermestid beetle, Attagenus fasciatus was studied on four different diets of animal origin included dried silkworm pupae and moths of Bombyx mori, feathers of white leghorn and on an equal mixture of fur of goat and sheep under laboratory conditions, to know the dietary effect on the developmental process. The mean incubation period was 12-16 days. There were 10-12 larval instars. The life-cycle on four different diets of animal origin varied. On dried silkworm pupae, total larval period ranged from 243 to 298 days and total life-cycle 267-326 days; on dried silk moths, total larval period was 251-307 and total life-cycle 272-330 days; on feathers of white leghorn, total larval period was 264-329 and total life-cycle was 288-355 days, and on an equal mixture of fur of goat and sheep, total larval period was 273-317 and total life-cycle was 297-343 days.

Highly-Expressed Aspartic Protease from Aspergillus Fumigatus-Mediated Enzymolysis of Silkworm (Bombyx Mori) Pupae Protein

Aspartic protease emerges as an optimistic hydrolytic agent to obtain several protein hydrolysates. An aspartic protease gene from Aspergillus fumigatus Af293 was successfully expressed in Pichia pastoris (GS115) and its hydrolytic potentials on silkworm (Bombyx mori) pupae protein were determined. It was optimum at pH 4.0 and 50 °C and stable over pH range 4.0-5.0 and temperatures 45-55 °C with a specific activity of 8408.9 ± 305.6 U/mg. SDS-PAGE analysis revealed the molecular weight of the recombinant protease to be 45 kDa. The half-life (t1/2) of the recombinant protease at 40, 50, 60, and 70 °C was 30, 25, 35, and 20 min, respectively. The protease showed enhanced activity in the presence of Cu2+, Pb2+ and SDS. Its substrate specificity studies were revealed in the order of cleaving ability to Bovine Serum Albumin (BSA) > Silkworm pupae powder (SPP) > Casein > Casein sodium salt (CSS). Upon hydrolysis of silkworm pupae protein, it showed enhanced and plausible hydrolytic potentials, increasing the degree of hydrolysis to 50 ± 6.1% at 6 h, increased solubility by 80%, and improved functional properties. The stable characteristics and hydrolytic performance of the recombinant aspartic protease qualify it for industrial application, especially within the food and related industries.

Protein hydrolysates from silkworm (Bombyx mori) pupae protein treated with a novel neutral protease

Edible insects, regarded as a potential contributor to food security are currently given wide consideration due to their rich protein and other micronutrients contents. In this study, protease-assisted hydrolysis proposes an economically effective approach to hydrolyse proteins from silkworm (Bombyx mori) pupae to improve its functional properties. The proteolytic activity of a novel neutral protease (265.14 U/ml) with appreciable thermal activities, was identified using 16S rDNA as Stenotrophomonas maltophilia JW20 (SmNP20). The neutral protease with an apparent molecular weight of 28 kDa emerged active at pH 7 and maintained stability in pH range 6.0-8.0. The optimum temperature was 60 °C and stable at 55-60 °C, maintaining over 80% of its initial activity, with a half-life of 78.75, 89, 66.8 and 44 min at 50, 60, 70 and 80 °C. It was purified to 9.98-fold with a specific activity of 455.06 U/mg and 63.73% yield. The Km and Vmax values were 0.70 mg/ml and 9.48 μmol/min/mg, respectively. Enzymolysis with neutral protease enhanced the degree of hydrolysis (97.46±4.87%), increased water solubility over 50%, and a significant protein solubility of 63.44±0.65%. The Km and Vmax of the protein yield were 0.24 mg/ml and 165.63 μmol/min/mg respectively. A total of 17 amino acids have been detected in the hydrolysates obtained from the silkworm pupae protein. In comparison with neutrase and flavorzyme®, the enzyme possesses an elevated hydrolytic and catalytic efficiency. Emulsion activity and foam capacity ranged from 8-48 m2/g and 6-25% respectively. Hence, this study confirms the unique and efficient characteristics of an insect-enzyme correlation that is practically significant with potential improvement in nutritional composition and functional quality of insect proteins.