In vitro anti-influenza activity of a protein-enriched fraction from larvae of the housefly (Musca domestica)

Polysaccharides extracted from larvae of Lucilia sericata ameliorated ulcerative colitis by regulating the intestinal barrier and gut microbiota

Pest management technology has been a promising bioconversion method for waste resource utilization. Unlike many pests that consume waste, the larvae of Lucilia sericata, also known as maggots, have many outstanding advantages as following: with their strong adaption to environment and not easily infected and exhibiting a medicinal nutritional value. Herein, the potential efficacies of maggot polysaccharides (MP), as well as their underlying mechanisms, were explored in Dextran sulfate sodium (DSS)-induced colitis mice and TNF-α-elicited Caco-2 cells. We extracted two bioactive polysaccharides from maggots, MP-80 and MP-L, whose molecular weights were 4.25 × 103 and 2.28 × 103 g/mol, respectively. MP-80 and MP-L contained nine sugar residues: 1,4-α-Arap, 1,3-β-Galp, 1,4,6-β-Galp, 1,6-α-Glcp, 1-α-Glcp, 1,4-β-Glcp, 1-β-Xylp, 1,2-α-Manp, and 1-β-Manp. We demonstrated that MP-80 and MP-L significantly ameliorated DSS-induced symptoms and histopathological damage. Immuno-analysis revealed that compared with MP-L, MP-80 could better restore intestinal barrier and reduced inflammation by suppressing NLRP3/NF-κB pathways, which might be attributed to its enriched galactose fraction. Moreover, 16S rRNA sequencing revealed that MP-80 and MP-L both improved the dysbiosis and diversity of gut microbiota and acted on multiple microbial functions. Our study sheds new light on the possibility of using maggot polysaccharides as an alternative therapy for colitis.

Enhanced Antioxidant and Cytotoxic Potentials of Lipopolysaccharides-Injected Musca domestica Larvae

The usage of insects as a sustainable and functional natural products resource is a new promise in complementary and alternative medicine. The present study aimed to investigate the ability of Musca domestica (housefly) larval hemolymph (insect blood) to display the enhanced in vitro antioxidant and cytotoxic effects. The oxidative stress (OS) was elicited by inducing lipopolysaccharides (LPS) treatment as an exogenous stressor. Determination of superoxide dismutase 1 (SOD1), glutathione (GSH), malondialdehyde (MDA) and total antioxidant capacity (TAC), and mRNA and protein expressions of SOD1, was investigated as confirmatory markers of oxidative stress induction. Cytotoxicity on cancerous MCF-7 and normal Vero cells were also evaluated using an MTT assay at 24 h post-injection. The injection of LPS induced a significant (p < 0.05) increase in SOD, GSH and TAC, whereas, the MDA was diminished. Hemolymph was collected from normal and treated larvae after 6, 12 and 24 h. The M. domestica superoxide dismutase (MdSOD1) transcripts were significantly (p < 0.05) upregulated 6 and 12 h post-treatment, while a significant downregulation was observed after 24 h. Western blot analysis showed that MdSOD1 was expressed in the hemolymph of the treated larvae with an increase of 1.2 folds at 6 and 12 h and 1.6 folds at 24 h relative to the control group. LPS-treated larval hemolymphs exhibited significant cytotoxicity with respect to the untreated ones against MCF-7 while Vero cells showed no cytotoxicity for both hemolymphs. The DPPH free radical scavenging activity was examined and a significant antioxidant potential potency was observed at 6 h (50% maximal inhibitory concentration (IC50): 63.3 ± 3.51 µg/mL) when compared to the control M. domestica larval hemolymph (IC50: 611.7 ± 10.41 µg/mL). Taken together, M. domestica larval hemolymph exhibited enhanced antioxidant and consequently increased cytotoxic capacities under stressed conditions.

Dietary Supplementation with Housefly (Musca domestica) Maggot Meal in Growing Beagles: Hematology, Serum Biochemistry, Immune Responses and Oxidative Damage

The present study was carried out to evaluate the hematology, serum biochemistry, immune responses and oxidative damage of growing beagles fed a diet supplemented with housefly (Musca domestica) maggot meal (MM). Weanling beagles (initial body weight 2.69 ± 0.17 kg) were fed a control diet (0% MM) or experimental diet (5% MM) for 42 days. The results indicated that the diet supplemented with 5% MM had no significant effects on the hematology and serum biochemistry of growing beagles (P>0.05). Meanwhile, neither the serum concentrations of lysozyme and C-reactive protein nor the serum antibody responses to canine distemper virus and canine parvovirus were influenced by dietary MM supplementation (P>0.05). However, dogs in the experimental group had lower serum levels of malondialdehyde and protein carbonyl than those in the control group (P<0.05). These findings demonstrated that MM could be used as an alternative protein source in growing beagles without any adverse effects on hematology, serum biochemistry and immune responses. Furthermore, dietary MM could alleviate oxidative damage in growing beagles.

The effect of fly maggot in pig feeding diets on growth performance and gut microbial balance in Ningxiang pigs

Fly maggot meal has been regarded as one of the substitutes of fish meal and soybean meal in pig feed. However, its effects on pig growth performance and faecal micro-organism remain unclear. The purpose of this study was to investigate the effect of dietary fly maggot meal on fattening performance, plasma indices related to gut hormones, immunity and faecal microbial communities composition of finishing pigs. A total of 40 Ningxiang fattening pigs were randomly allocated to two dietary treatments and pigs in each group were arranged by control group (CK) diet or 8% maggot meal group (MMG) diet for 45 days respectively. Growth performance, indices of gut hormones and immunity in plasma were evaluated. Microbiota composition in faeces was determined using 16S rDNA Amplicon Sequencing. The results showed that dietary MMG did not affect gut hormones and immune proteins in the trial compared with CK group (p > .05). However, dietary MMG significantly increased average daily gain (ADG). The population of the Firmicutes in MMG treatment was increased, while the percentage of the Bacteroidetes was decreased (p < .05). In particular, the number of Clostridiales related to hydrolyzed sugar and protein were increased (p < .05). It can inhibit the growth of harmful intestinal bacteria, promote the proliferation of beneficial bacteria and effectively improve the ability of digestion and absorption of nutrients. In conclusion, a diet containing 8% MMG changed the proportion of intestinal micro-organisms in finishing pigs, especially the higher richness of Firmicutes, and promoted the fattening ability of pigs to a certain extent. These changes should benefit finishing pig production during fattening period.

A Novel Natural Influenza A H1N1 Virus Neuraminidase Inhibitory Peptide Derived from Cod Skin Hydrolysates and Its Antiviral Mechanism

In this paper, a novel natural influenza A H1N1 virus neuraminidase (NA) inhibitory peptide derived from cod skin hydrolysates was purified and its antiviral mechanism was explored. From the hydrolysates, novel efficient NA-inhibitory peptides were purified by a sequential approach utilizing an ultrafiltration membrane (5000 Da), sephadex G-15 gel column and reverse-phase high-performance liquid chromatography (RP-HPLC). The amino acid sequence of the pure peptide was determined by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) was PGEKGPSGEAGTAGPPGTPGPQGL, with a molecular weight of 2163 Da. The analysis of the Lineweacer–Burk model indicated that the peptide was a competitive NA inhibitor with Ki of 0.29 mM and could directly bind free enzymes. In addition, docking studies suggested that hydrogen binding might be the driving force for the binding affinity of PGEKGPSGEAGTAGPPGTPGPQGL to NA. The cytopathic effect reduction assay showed that the peptide PGEKGPSGEAGTAGPPGTPGPQGL protected Madin–Darby canine kidney (MDCK) cells from viral infection and reduced the viral production in a dose-dependent manner. The EC₅₀ value was 471 ± 12 μg/mL against H1N1. Time-course analysis showed that PGEKGPSGEAGTAGPPGTPGPQGL inhibited influenza virus in the early stage of the infectious cycle. The virus titers assay indicated that the NA-inhibitory peptide PGEKGPSGEAGTAGPPGTPGPQGL could directly affect the virus toxicity and adsorption by host cells, further proving that the peptide had an anti-viral effect with multiple target sites. The activity of NA-inhibitory peptide was almost inactivated during the simulated in vitro gastrointestinal digestion, suggesting that oral administration is not recommended. The peptide PGEKGPSGEAGTAGPPGTPGPQGL acts as a neuraminidase blocker to inhibit influenza A virus in MDCK cells. Thus, the peptide PGEKGPSGEAGTAGPPGTPGPQGL has potential utility in the treatment of the influenza virus infection.

Toxicological characteristics of edible insects in China: A historical review

Edible insects are ideal food sources, which contain important nutrients and health-promoting compounds. With a rapid development of industrial insect farming, insect-derived food is a novel and emerging food industry. Edible insects have been traditionally consumed in various communities, while continuously gaining relevance in today's society; however, they currently remain underutilized. Although there are a large number of literature on edible insects, these literature primarily focus on the nutritional value edible insects. The toxicity assessment data of edible insects remain incomprehensive, especially for the new national standard that is currently in effect; and many data and conclusions are not accurately specified/reported. Therefore, we performed a literature review and summarized the data on the toxicological assessment of edible insects in China. The review first describes the research progress on safety toxicological assessment, and then offers references regarding the development of 34 edible insect species in China. These data can be a platform for the development of future toxicological assessment strategies, which can be carried out by a multidisciplinary team, possibly consisting of food engineers, agronomists, farmers, and so on, to improve the acceptability of edible insects.

Synthesis and Functional Characterization of MAF-1A Peptide Derived From the Larvae of Housefly, Musca domestica (Diptera: Muscidae)

The Musca domestica antifungal peptide-1A (MAF-1A peptide) from housefly larvae was synthesized by solid-phase synthesis technique, and antiviral, antioxidant, and antifungal properties were evaluated in this study. Present results indicated that it could significantly inhibit the infection of influenza virus H₁N₁, Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), and Bombyx mori nuclear polyhydrosis virus (BmNPV), which displayed excellent virucidal activities. Antioxidant results demonstrated that the MAF-1A peptide had effective scavenging activity for hydroxyl and superoxide radicals, which were similar to that of ascorbic acid. Besides, antifungal results showed that it can also significantly inhibit the growth of four fungi, and the half inhibitory concentrations (IC₅₀) values were ∼59.3, 84.2, 144.9, and 48.5 μg/ml, respectively, highlighting an important role of MAF-1A peptide in the defense of M domestica against pathogenic microorganisms. These results revealed that the MAF-1A peptide from housefly larvae has great potential as a natural ingredient for the exploitation of antiviral and antifungal therapeutic agents, avoiding abuse of chemical agents and environmental pollution.

Housefly maggot-treated composting as sustainable option for pig manure management

In traditional composting, large amounts of bulking agents must be added to reduce the moisture of pig manure, which increases the cost of composting and dilutes the N, P and K content in organic fertilizers. In this study, maggot treatment was used in composting instead of bulking agents. In experiment of selecting an optimal inoculum level for composting, the treatment of 0.5% maggot inoculum resulted in the maximum yield of late instar maggots, 11.6% (maggots weight/manure weight). The manure residue became noticeably granular by day 6 and its moisture content was below 60%, which was suitable for further composting without bulking agents. Moreover, in composting experiment with a natural compost without maggot inoculum and maggot-treated compost at 0.5% inoculum level, there were no significant differences in nutrient content between the two organic fertilizers from the two treatments (paired Student's t15=1.0032, P=0.3317). Therefore, maggot culturing did not affect the characteristics of the organic fertilizer. The content of TNPK (total nitrogen+total phosphorus+total potassium) in organic fertilizer from maggot treatment was 10.72% (dry weight), which was far more than that of organic fertilizer made by conventional composting with bulking agents (about 8.0%). Dried maggots as feed meet the national standard (GB/T19164-2003) for commercial fish meal in China, which contained 55.32 ± 1.09% protein; 1.34 ± 0.02% methionine; 4.15 ± 0.10% lysine. This study highlights housefly maggot-treated composting can be considered sustainable alternatives for pig manure management to achieve high-quality organic fertilizer and maggots as feed without bulking agents.

Antihepatitis B virus activity of a protein-enriched fraction from housefly (Musca domestica) in a stable HBV-producing cell line

Hepatitis B virus (HBV) infection remains a major public health problem. Although several vaccines and therapeutic strategies are currently being implemented to combat HBV virus, effective antiviral therapy against HBV infection has not been fully developed. Alternative strategies and new drugs to combat this disease are urged. Insects and insect derivatives are a large and unexploited source of potentially useful compounds for modern medicine. In the present study, we investigated the first anti-HBV activity of a protein-enriched fraction (PE) from the larvae of the housefly (Musca domestica) in a stable HBV-producing cell line. HBsAg and HBeAg in the culture medium were measured by enzyme-linked immunosorbent assay. HBV-DNA was quantified by fluorescent quantification PCR. HBV core protein was assayed by immunofluorescent staining. Results indicate PE treatment inhibited both HBsAg, HBeAg secretion, and HBV-DNA replication. Furthermore, PE could also suppress HBV core protein expression. PE could be a potential candidate for the development of a novel and effective drug for the treatment of HBV infection.