Genotoxic evaluation of the biocomponents of the cricket, Gryllus bimaculatus, using three mutagenicity tests

Road to The Red Carpet of Edible Crickets through Integration into the Human Food Chain with Biofunctions and Sustainability: A Review

The Food and Agriculture Organization of the United Nations (FAO) estimates that more than 500 million people, especially in Asia and Africa, are suffering from malnutrition. Recently, livestock farming has increased to supply high-quality protein, with consequent impact on the global environment. Alternative food sources with high nutritive values that can substitute livestock demands are urgently required. Recently, edible crickets have been promoted by the FAO to ameliorate the food crisis. In this review, the distribution, nutritive values, health-promoting properties (antioxidant, anti-inflammatory, anti-diabetic and anti-obesity), safety, allergenicity as well as the potential hazards and risks for human consumption are summarized. Cricket farming may help to realize the United Nations sustainable development goal No. 2 Zero Hunger. The sustainability of cricket farming is also discussed in comparison with other livestock. The findings imply that edible crickets are safe for daily intake as a healthy alternative diet due to their high protein content and health-promoting properties. Appropriate use of edible crickets in the food and nutraceutical industries represents a global business potential. However, people who are allergic to shellfish should pay attention on cricket allergy. Thus, the objective of this review was to present in-depth and up-to-date information on edible crickets to advocate and enhance public perception of cricket-based food.

Insights into the genomic evolution of insects from cricket genomes

Most of our knowledge of insect genomes comes from Holometabolous species, which undergo complete metamorphosis and have genomes typically under 2 Gb with little signs of DNA methylation. In contrast, Hemimetabolous insects undergo the presumed ancestral process of incomplete metamorphosis, and have larger genomes with high levels of DNA methylation. Hemimetabolous species from the Orthopteran order (grasshoppers and crickets) have some of the largest known insect genomes. What drives the evolution of these unusual insect genome sizes, remains unknown. Here we report the sequencing, assembly and annotation of the 1.66-Gb genome of the Mediterranean field cricket Gryllus bimaculatus, and the annotation of the 1.60-Gb genome of the Hawaiian cricket Laupala kohalensis. We compare these two cricket genomes with those of 14 additional insects and find evidence that hemimetabolous genomes expanded due to transposable element activity. Based on the ratio of observed to expected CpG sites, we find higher conservation and stronger purifying selection of methylated genes than non-methylated genes. Finally, our analysis suggests an expansion of the pickpocket class V gene family in crickets, which we speculate might play a role in the evolution of cricket courtship, including their characteristic chirping.

Ylla, Extavour et al. use genomic data from crickets to investigate the evolution of large genome sizes and DNA methylation events in insects. Their findings indicate that transposable element activity drove genome expansion in hemimetabolous insects, such as crickets and grasshoppers, and that DNA methylation is predominant in conserved genes.

Protaetia brevitarsis seulensis Derived Protein Isolate with Enhanced Osteomodulatory and Antioxidative Property

The osteogenic differentiation of stem cells is profoundly affected by their microenvironmental conditions. The differentiation behavior of stem cells can be tuned by changing the niche environments. The proteins or peptides that are derived by living organisms facilitate the osteogenic differentiation of stem cells. Here, we have evaluated the osteoinductive and antioxidative potential of the Protaetia brevitarsis seulensis insect-derived protein for human bone marrow-derived mesenchymal stem cells (hBMSCs). The amino acid contents in the isolated protein were determined by an amino acid analyzer. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to analyze the extract’s functional groups and surface morphology. The extracted protein exhibited 51.08% β-sheet conformation. No adverse effects were observed in extract-treated cells, indicating their biocompatibility. The protein isolate showed an excellent antioxidative property. Besides this, an enhancement in the hBMSCs’ mineralization has been observed in the presence of treated protein isolates. Notably, osteogenic marker genes and proteins were effectively expressed in the treated cells. These results indicated that the P. brevitarsis-derived protein isolate can be used as a potential antioxidative biomaterial for bone tissue engineering applications.

Toxicity assessment of Gryllus bimaculatus (a type of cricket) glycosaminoglycan

We performed general toxicity studies of Gryllus bimaculatus (two-spotted cricket) glycosaminoglycan (GbG), including a single, 4-week repeated oral dose toxicity test in ICR mice, and short-term genotoxicity tests. The mutagenic potential of the purified GbG was non-genotoxic when it was evaluated using short-term genotoxicity tests, namely Ames, chromosome aberration (CA), and micronuclei (MN) tests. In Salmonella typhimurium and Escherichia coli assays, GbG did not produce any mutagenic response in the absence or presence of S9 mix with five bacterial strains (TA98, TA100, TA1535, TA1537, and WP2uvrA). Chromosome aberration test showed that GbG had no significant effect on Chinese hamster ovary (CHO) cells. In mouse micronuclei tests after twice oral treatments per day for two days, no significant alteration in the occurrence of micronucleated polychromatic erythrocytes was observed in ICR male mice intraperitoneally administered with GbG at doses of 15.63, 31.25, or 62.50 mg/kg. These results indicate that GbG has no mutagenic potential in these in vitro and in vivo systems. After GbG was orally administered at doses of 20, 40, 80, and 160 mg/kg for a single oral dose toxicity study and at 0, 40, 80, and 160 mg/kg bw/day for 4-week oral dose toxicity study, there were no observed clinical signs or deaths related to treatment in any group tested. Therefore, the approximate lethal oral dose of GbG was considered to be higher than 160 mg/kg in mice. Throughout the administration period, no significant changes in diet consumption, ophthalmologic findings, organ weight, clinical pathology (hematology, clinical chemistry, coagulation, and urinalysis), or gross pathology were detected. Microscopic examination did not identify any treatment-related histopathologic changes in organs of GbG-treated mice in the high dose group. These results indicate that the no-observed adverse effect level (NOAEL) of GbG is higher than 160 mg/kg bw/day in mice.

Glucose-lowering effect of Gryllus bimaculatus powder on streptozotocin-induced diabetes through the AKT/mTOR pathway

This study was carried out to elucidate the antidiabetic effects of Gryllus bimaculatus powder using a streptozotocin (STZ)-induced rat model of type I diabetes. Administration of the insect powder significantly rescued representative diabetes markers (i.e., insulin and C-peptide) in STZ-treated rats. Improved glucose tolerance test (GTT) and insulin tolerance test (ITT) results were also observed, indicating that Gryllus bimaculatus powder exerts antidiabetic effects. Gryllus bimaculatus powder administration rescued STZ-induced alterations in both islet morphology and insulin staining patterns. The extract increased antiapoptotic Bcl2 expression and decreased proapoptotic Bax and active caspase 3 expressions. In addition, the Gryllus bimaculatus powder supplementation enhanced AKT/mTOR pathway, a key marker of the state of anabolic metabolism, and its downstream effector, mTOR. Collectively, our results suggest that Gryllus bimaculatus contributes to the maintenance of pancreatic β-cell function and morphology against a diabetic state through the regulations against apoptosis and anabolic metabolism.

(±)-Kituramides A and B, pairs of enantiomeric dopamine dimers from the two-spotted cricket Gryllus bimaculatus

Two-spotted cricket Gryllus bimaculatus is one of many cricket species, and it is widely used as a food source for insectivorous animals. Moreover, this species is one of the edible insects approved by the Korea Food and Drug Administration (KFDA). (±)-Kituramides A (1) and B (2), which are pairs of novel enantiomeric dopamine dimers possessing a formamide group, were isolated from the two-spotted cricket, together with four other known biosynthetically related compounds (3-6). The chemical structures of 1 and 2 were elucidated using a combination of 1D and 2D NMR spectroscopic experiments and HR-ESIMS data. Compounds 1 and 2 were identified as racemic mixtures; the enantiomers (+)-1/2 and (-)-1/2 were successfully separated by utilizing a chiral HPLC column. The absolute configurations of (±)-1 and (±)-2 were unambiguously delineated by the application of quantum chemical ECD calculations. Further, these insect-derived substances were evaluated to understand their effects on cytokine expression in adipocytes. Treatment with (-)-1, (+)-2, and (-)-2 during adipocyte differentiation significantly promoted the expression of Leptin and IL-6, which resembles the actions of dopamine.

Mutagenic properties of linuron and chlorbromuron evaluated by means of cytogenetic biomarkers in mammalian cell lines

Agricultural practices are usually supported by several chemical substances, such as herbicides. Linuron and chlorbromuron are phenylurea herbicides largely used to protect crops from weeds, blocking photosynthesis by inhibition of the photosystem II complex. The former, also commercially known as lorox or afalon, is selectively used to protect bean and French bean plants, fennels, and celeriacs; the second, commercially known as maloran, is selectively used for carrots, peas, potatoes, soy sprouts, and sunflowers. Considering the widespread use of herbicides and, more generally, pesticides, it is important to clarify their involvement on human health, one of them concerning the possible direct or indirect effect on the genome of exposed populations. Here, we show that these herbicides are endowed by mutagenic properties, as demonstrated by an increased number of chromosomal aberrations (CAs) in two exposed Chinese hamster cell lines derived from ovary and epithelial liver, respectively. This was also confirmed by sister chromatid exchange (SCE) and micronucleus (MN) assays. Our present and previously obtained data clearly indicate that phenylurea herbicides must be used with great caution, especially for agricultural workers who use large amounts of herbicides during their work, and particular attention should be given to residues of these herbicides and their involvement in environmental pollution.

Gene expression profiling and inhibition of adipose tissue accumulation of G. bimaculatus extract in rats on high fat diet

Background

Molecular genetic mechanisms underlying the anti-inflammatory effects of ethanol extract (GB) from G. bimaculatus, a type of cricket, are not fully elucidated. G. bimaculatus was reported to be rich in unsaturated fatty acid and to decrease the omega-6/omega-3 fatty acid ratio when fed to chickens. GB may reduce the amount of fat or increase the unsaturated fatty acid ratio.

Methods

Male Wistar rats fed a high-fat diet (HFD) were orally administered with 5 groups: phosphate buffered saline (PBS, control), GB (100 mg/kg or 200 mg/kg), Pravastatin or Isaria sinclairii (IS) extract, which is reported to have fat-reducing effects, for either 1 or 2 months. GB’s sero-biochemial, hematological and anti-oxidizing hepato-cellular biomarker levels were evaluated to dertermine their antilipidemic, anti-inflammatory, and anti-coagulant effect in rats after 1 or 2 month GB treatments on HFD (fat 60 %) Wistar rat. The abdominal and epididymidal fat weight were measured and the composition of fatty acid was analyzed by GC/MS. Microarray analyses were performed with a rat 28 K cDNA clone set array to identify the gene-expression profiles for the GB exposed high fat dieted Wistar rat.

Results

The weight and fatty acid composition of abdominal fat and epididymidal fat, total cholesterol, LDL-cholesterol, and triglyceride in GB treated rats were at lower levels than those of the control group. The anti-oxidant hepato-cellular biomarker levels, protein carbonyl content and malondialdehyde concentration in GB treated rats were significantly decreased. Compared to the control, the GB treated rat group (treated at a dose of 100 and 200 mg/kg), had 190 up-regulated genes including Gpm6a (glycoprotein m6a), Tmem14a (transmembrane protein 14A) and Fasin (fatty acid synthase), with down-regulated 235 genes including Cc121b (chemokine ligand 21b), Glycan1 (glycosylation dependent cell adhesion moleule, Serpinb1a (serine proteinase inhibitor) and Tcrb (T-cell receptor beta chain).

Conclusion

The data suggest Fasin-related fatty acid synthesis and adipose differentiation related protein (Adfp), which is related to obesity, were upregulated by GB treatment, indicating their potential therapeutic markers for anti-atheriosclerosis or inflammation.

Anti-aging Effect and Gene Expression Profiling of Aged Rats Treated with G. bimaculatus Extract

Extract from Gryllus bimaculatus crickets inhibits oxidation at the DNA level, with reduced production of 8-hydroxy-2'-deoxyguanosine (8-OHdG). Microarray analyses were performed with a rat 28K cDNA clone set array to identify the gene expression profiles of aged (10 months old) Wistar Kyoto rats treated for one month with 100 mg/kg G. bimaculatus ethanol extract to assess the effects. The extract produced a meaningful anti-edema effect, evident by the inhibition of creatinine phosphokinase activity. The weights of abdominal and ovarian adipose tissues were reduced and the proportion of unsaturated fatty acids in adipose tissues was increased in an extract dose-dependent manner. Compared with untreated control rats, rats treated with the extract displayed the upregulation of 1053 genes including Fas (tumor necrosis factor receptor superfamily, member 6), Amigo3 (adhesion molecule with an immunoglobulin-like domain), Reticulon 4, 3-hydroxy-3-methylglutaryl-coenzyme (Hmgcr; a reductase), related anti-fatigue (enzyme metabolism), and Rtn antioxidant, and the downregulation of 73 genes including Ugt2b (UDP glycosyltransferase 2 family), Early growth response 1, and Glycoprotein m6a. Data suggest that G. bimaculatus extract may have value in lessening the effects of aging, resulting in a differential gene expression pattern indicative of a marked stress response and lower expression of metabolic and biosynthetic genes.

Anti-inflammatory effect of glycosaminoglycan derived from Gryllus bimaculatus (a type of cricket, insect) on adjuvant-treated chronic arthritis rat model

Anti-inflammatory effects of glycosaminoglycan (GAG) derived from cricket (Gryllus bimaculatus, Gb) were investigated in a complete Freund's adjuvant (CFA)-treated chronic arthritic rat model. This GAG produced a significant anti-edema effect as evidenced by inhibition of C-reactive protein (CRP) and rheumatoid factor, and interfered with atherogenesis by reducing proinflammatory cytokine levels of (1) vascular endothelial growth factor (VEGF) production in human umbilical vein endothelial cells (HUVEC), (2) interleukin-6, (3) prostaglandin E2-stimulated lipopolysaccharide in RAW 264.7 cells, and (4) tumor necrosis factor (TNF)-α production in normal splenocytes, in a dose-dependent manner. This GAG was also found to induce nitric oxide (NO) production in HUVEC cells and elevated endothelial nitric oxide synthase (eNOS) activity levels. Histological findings demonstrated the fifth lumbar vertebrae (LV) dorsal root ganglion, which was linked to the paw treated with Gb GAG, was repaired against CFA-induced cartilage destruction. Further, combined indomethacin (5 mg/kg)-Gb GAG (10 mg/kg) inhibited more effectively CFA-induced paw edema at 3 h and 2 or 3 d after treatment to levels comparable to only the anti-inflammatory drug indomethacin. Ultraviolet (UV)-irritated skin inflammation also downregulated nuclear factor κB (NFκB) activity in transfected HaCaT cells. Data suggest that the anti-inflammatory effects of GAG obtained from cricket (Gb) may be useful for treatment of inflammatory diseases including chronic arthritis.

Thirteen-Week Oral Dose Toxicity Study of G. bimaculatus in Sprague-Dawley Rats

Gryllus bimaculatus (Gb) was orally administered at doses of 0, 0.04, 0.2, 1 and 5 g/kg bw/day for 13 consecutive weeks. There were no observed clinical signs or deaths related to treatment in all the groups tested. Therefore, the approximate lethal oral dose of G. bimaculatus was considered to be higher than 5 g/kg in rats. Throughout the administration period, no significant changes in diet consumption, ophthalmologic findings, organ weight, clinical pathology (hematology, clinical chemistry, coagulation, and urinalysis) or gross pathology were detected. Minor changes were found in hematological parameters for the 5 g/kg Gb-treated group (triglyceride reduction of 35.8%), but all changes were within normal physiological ranges. Microscopic examination did not identify any treatment-related histopathologic changes in the organs of Gb-treated rats in the high dose group. From these results, one can conclude that the no-observed adverse effect level (NOAEL) of G. bimaculatus is higher than 5 g/kg bw/day in rats.