Silkworm ( Bombyx mori ) powder supplementation alleviates alcoholic fatty liver disease in rats

Recent advances of silk fibroin materials: From molecular modification and matrix enhancement to possible encapsulation-related functional food applications

Silk fibroin materials are emergingly explored for food applications due to their inherent properties including safe oral consumption, biocompatibility, gelatinization, antioxidant performance, and mechanical properties. However, silk fibroin possesses drawbacks like brittleness owing to its inherent specific composition and structure, which limit their applications in this field. This review discusses current progress about molecular modification methods on silk fibroin such as extraction, blending, self-assembly, enzymatic catalysis, etc., to address these limitations and improve their physical/chemical properties. It also summarizes matrix enhancement strategies including freeze drying, spray drying, electrospinning/electrospraying, microfluidic spinning/wheel spinning, desolvation and supercritical fluid, to generate nano-, submicron-, micron-, or bulk-scale materials. It finally highlights the food applications of silk fibroin materials, including nutraceutical improvement, emulsions, enzyme immobilization and 3D/4D printing. This review also provides insights on potential opportunities (like safe modification, toxicity risk evaluation, and digestion conditions) and possibilities (like digital additive manufacturing) in functional food industry.

Fermented Protaetia brevitarsis Larvae Ameliorates Chronic Ethanol-Induced Hepatotoxicity in Mice via AMPK and TLR-4/TGF-β1 Pathways

This study evaluated the hepatoprotective effect of fermented Protaetia brevitarsis larvae (FPB) in ethanol-induced liver injury mice. As a result of amino acids in FPB, 18 types of amino acids including essential amino acids were identified. In the results of in vitro tests, FPB increased alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities. In addition, FPB treatment increased cell viability on ethanol- and H2O2-induced HepG2 cells. FPB ameliorated serum biomarkers related to hepatoxicity including glutamic oxaloacetic transaminase, glutamine pyruvic transaminase, total bilirubin, and lactate dehydrogenase and lipid metabolism including triglyceride, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol. Also, FPB controlled ethanol metabolism enzymes by regulating the protein expression levels of ADH, ALDH, and cytochrome P450 2E1 in liver tissue. FPB protected hepatic oxidative stress by improving malondialdehyde content, reduced glutathione, and superoxide dismutase levels. In addition, FPB reversed mitochondrial dysfunction by regulating reactive oxygen species production, mitochondrial membrane potential, and ATP levels. FPB protected ethanol-induced apoptosis, fatty liver, and hepatic inflammation through p-AMP-activated protein kinase and TLR-4/NF-κB signaling pathways. Furthermore, FPB prevented hepatic fibrosis by decreasing TGF-β1/Smad pathway. In summary, these results suggest that FPB might be a potential prophylactic agent for the treatment of alcoholic liver disease via preventing liver injury such as fatty liver, hepatic inflammation due to chronic ethanol-induced oxidative stress.

Anti-Obesity Effects of the Larval Powder of Steamed and Lyophilized Mature Silkworms in a Newly Designed Adult Mouse Model

Recently, "mature" silkworms (MS) of Bombix mori have been considered a potential nutraceutical, with a number of health benefits reported for steamed and lyophilized MS powder (SMSP). However, no obesity-related effects have been reported for SMSP. In the present study, anti-obesity effects of SMSP were investigated in adult mice in vivo, aged 12 weeks at the onset of SMSP treatment, fed a normal diet (ND) and a high-fat diet (HFD), respectively, for 12 weeks. SMSP significantly suppressed body weight gain, intra-abdominal adipose tissue, and food efficiency in both ND-fed and HFD-fed adult mice. In addition, SMSP significantly decreased food intake and liver weight in HFD-fed mice, indicating that SMSP suppressed appetite and simultaneously reduced the conversion of feed into body weight in HFD-fed mice. SMSP also significantly lowered the serum levels of glucose, triglyceride, total cholesterol, low-density lipoprotein cholesterol, asparagine transaminase, alanine transaminase, and alkaline phosphatase. However, SMSP had no significant effect on the weights of the kidney, spleen, or thymus or the serum levels of blood urea nitrogen and creatinine. Taken together, the above results suggest that SMSP has potent anti-obesity effects and is safe for long-term use as a potential therapeutic and/or nutraceutical in both obese patients and non-obese individuals.

Use of a Silkworm (Bombyx mori) Larvae By-Product for the Treatment of Atopic Dermatitis: Inhibition of NF-κB Nuclear Translocation and MAPK Signaling

Atopic dermatitis (AD) is a long-lasting inflammatory skin disease that contributes to the global health burden and impacts 10–20% of the world’s population. In this study, we determined the anti-AD effect of a by-product of silkworm (Bombyx mori) larval powder, strain Yeonnokjam (SLPY), as a sustainable, natural source for the development of therapeutic agents for AD. HaCaT cells were used to assess the in vitro anti-inflammatory activity of SLPY, and a 1-chloro-2,4-dinitrobenzene (DNCB)-induced mouse model was used to study the in vivo anti-AD effects. SLPY treatment downregulated the expression of the inflammatory cytokines TNF-α, IL1β, IL-8, and Cox-2 in stimulated HaCaT cells. Similarly, the topical application of SLPY in DNCB-treated mice downregulated the expression of inflammatory cytokines and proteins while ameliorating the clinical features of AD. Further, SLPY treatment inhibited the nuclear translocation of NF-κb p65, thereby supporting the efficacy of SLPY in the treatment of AD.

An Alkaline Protease-Digestion of Silkworm Powder Enhances Its Effects Over Healthspan, Autophagy, and Mitochondria Function in a Rotenone-Induced Drosophila Model

Background

Recent studies have reported that steamed and freeze-dried mature silkworms, also known as HongJam, have various health-promoting effects.

Objective

The goal of this study was to elucidate changes in the various health-promoting effects of HongJam, after its digestion with a food-grade protease.

Materials and Methods

We examined whether healthspan-promotion and rotenone-induced loss of motor-control prevention effects were enhanced in Drosophila fed with food-grade alkaline protease-digested HongJam compared to those fed with non-digested HongJam. The differences in mitochondrial functions, chemical susceptibilities, and activations of signal transduction pathways between Drosophila supplemented with various feed were examined to elucidate the molecular and biochemical basis of healthspan-promotion and locomotor-improvement effects of protease-digested HongJam.

Results

We first found that the healthspan-promotion effect of HongJam digested with a food-grade protease was different depending on the silkworm variety used for its production. Digestion with food-grade protease into White-Jade HongJam (WJ) as prepared from the White-Jade silkworm variety that spins white cocoons did not enhance its functionality. However, compared to Golden-Silk HongJam (GS), a food-grade protease-digested Golden-Silk HongJam (GSD) produced from the Golden-Silk silkworm variety that spins yellow cocoons, it further promoted the healthspan in a Drosophila model. By conducting a series of studies to reveal the molecular and biochemical basis for healthspan-promoting effects, we found that GS and GSD similarly enhanced mitochondrial activity, but GSD activated autophagy signaling more than GS. In addition, GSD feed (GSDf)-, GSD supernatant feed (GSDsupf)-, and GSD precipitate feed (GSDprecf)-reared Drosophila were also found to have increased resistance to an autophagy inhibitor compared to that of normal feed- or GS feed-reared Drosophila. Furthermore, we found that the rotenone-induced loss of motor control prevention effect was superior for GSDsup compared to GS, GSD, or GSDprec. This result may have occurred because GSDsup has more phenolic compounds and antioxidant activities than other samples.

Conclusion

GSDsup contained more digested small peptides and free phytochemicals than other samples due to the digestion of proteins with a food-grade protease. Thus, GSDsup leads to further healthspan-promoting and locomotor-improvement effects than GS, GSD, or GSDprec.

Synergistic Neuroprotective Effects of Mature Silkworm and Angelica gigas Against Scopolamine-Induced Mild Cognitive Impairment in Mice and H2O2-Induced Cell Death in HT22 Mouse Hippocampal Neuronal Cells

We previously reported that mature Bombyx mori silkworm (SW) ameliorated scopolamine (Sco)-induced amnesia, and Angelica gigas (AG) prevented cognitive impairment. SW is known for its gastroprotective effects such as improving liver function and alleviating the effects of Parkinson's disease. AG is known for its neuroprotective effects and for lowering the effects of low-density lipoprotein cholesterol. However, the neuroprotective effect of combined SW and AG (SWA-1) treatment and the underlying molecular mechanism by which SWA-1 regulates neurodegenerative diseases remains unclear. We evaluated the neuroprotective effect of SWA-1 against Sco-induced mild cognitive impairment in mice and H₂O₂-induced cell death in HT22 mouse hippocampal neuronal cells and elucidated the underlying molecular mechanism. Morris water maze and Y-maze tests were performed to examine the learning and memory abilities of mice. The underlying molecular mechanism was investigated by using western blotting. We demonstrated that SWA-1 significantly protects against H₂O₂-induced cell death in HT22 mouse hippocampal neuronal cells. SWA-1 also significantly reversed Sco-induced spatial learning and memory impairment. Specifically, SWA-1 upregulates the protein levels of phosphorylated extracellular signal-related kinase (Erk1/2) and phosphorylated p38 MAP kinase (p38). SWA-1 remarkably decreased the apoptotic index Bax/Bcl2 expression in the hippocampus of Sco-treated mice. Our results suggest that SWA-1 may be administered as alternative therapy for cognitive impairment and neurodegenerative diseases and should be studied further in human trials.

Effect of Bombyx mori on the Liver Protection of Non-Alcoholic Fatty Liver Disease Based on In Vitro and In Vivo Models

Edible insects, Bombyx mori (silkworm; SW), which feed on mulberry leaves, have been consumed by humans for a long time as supplements or traditional medication. Non-alcoholic fatty liver disease (NAFLD) is a liver metabolic disorder that affects many people worldwide. We examined the hepatoprotective effects of SW using in vitro and high-fat and high-fructose (HFHF) diet-induced obese in vivo model mice by real-time PCR, immunoblot analysis, and fecal microbiota analysis. SW significantly reduced lipid accumulation and expression of the lipogenic genes in HepG2 cells and the livers of HFHF-induced mice. SW caused significant reductions in triglycerides, and total cholesterol in serum and upregulation of fatty acid oxidation markers compared to the HFHF group. Besides, SW significantly induced phosphorylation of AMPK and ACC in both models, suggesting roles in AMPK activation and the ACC signaling pathway. Furthermore, the gut microbiota analysis demonstrated that SW treatment reduced Firmicutes to Bacteroidetes ratios and the relative abundance of the Lachnospiraceae family compared to HFHF-induced obese mice. These results provide a novel therapeutic agent of hepatoprotective effects of SW for non-alcoholic hepatic steatosis that targets hepatic AMPK and ACC-mediated lipid metabolism.

Metformin and Probiotics Interplay in Amelioration of Ethanol-Induced Oxidative Stress and Inflammatory Response in an In Vitro and In Vivo Model of Hepatic Injury

Alcohol-induced liver injury implicates inflammation and oxidative stress as important mediators. Despite rigorous research, there is still no Food and Drug Administration (FDA) approved therapies for any stage of alcoholic liver disease (ALD). Interestingly, metformin (Met) and several probiotic strains possess the potential of inhibiting alcoholic liver injury. Therefore, we investigated the effectiveness of combination therapy using a mixture of eight strains of lactic acid-producing bacteria, commercialized as Visbiome® (V) and Met in preventing the ethanol-induced hepatic injury using in vitro and in vivo models. Human HepG2 cells and male Wistar rats were exposed to ethanol and simultaneously treated with probiotic V or Met alone as well as in combination. Endoplasmic reticulum (ER) stress markers, inflammatory markers, lipid metabolism, reactive oxygen species (ROS) production, and oxidative stress were evaluated, using qRT-PCR, Oil red O staining, fluorimetry, and HPLC. In vitro, probiotic V and Met in combination prevented ethanol-induced cellular injury, ER stress, oxidative stress, and regulated lipid metabolism as well as inflammatory response in HepG2 cells. Probiotic V and Met also promoted macrophage polarization towards the M2 phenotype in ethanol-exposed RAW 264.7 macrophage cells. In vivo, combined administration of probiotic V and Met ameliorated the histopathological changes, inflammatory response, hepatic markers (liver enzymes), and lipid metabolism induced by ethanol. It also improved the antioxidant markers (HO-1 and Nrf-2), as seen by their protein levels in both HepG2 cells as well as liver tissue using ELISA. Hence, probiotic V may act, in addition to the Met, as an effective preventive treatment against ethanol-induced hepatic injury.

Hepatoprotective Effects of Steamed and Freeze-Dried Mature Silkworm Larval Powder against Ethanol-Induced Fatty Liver Disease in Rats

Silkworm, Bombyx mori, contains high amounts of beneficial nutrients, including amino acids, proteins, essential minerals, and omega-3 fatty acids. We have previously reported a technique for producing steamed and freeze-dried mature silkworm larval powder (SMSP), which makes it easier to digest mature silkworm. In this study, we investigated the preventive effects of SMSP on alcoholic fatty liver disease and elucidated its mechanism of action. Male Sprague-Dawley rats treated with SMSP (50 mg/kg) or normal diet (AIN-76A) were administered 25% ethanol (3 g/kg body weight) by oral gavage for 4 weeks. SMSP administration for 4 weeks significantly decreased hepatic fat accumulation in ethanol-treated rats by modulating lipogenesis and fatty acid oxidation-related molecules such as sirtuin 1, AMP-activated protein kinase, and acetyl-CoA carboxylase 1. Moreover, SMSP administration significantly diminished the levels of triglyceride in liver tissues by as much as 35%, as well as lowering the serum levels of triglyceride, gamma glutamyl transpeptidase, alanine transaminase, and aspartate aminotransferase in ethanol-treated rats. SMSP supplementation also decreased the pro-inflammatory tumor necrosis factor-alpha and interleukin 1 beta levels and cytochrome P450 2E1 generating oxidative stress. These results suggest that SMSP administration may be possible for the prevention of alcoholic liver disease.

Administration of Steamed and Freeze-Dried Mature Silkworm Larval Powder Prevents Hepatic Fibrosis and Hepatocellular Carcinogenesis by Blocking TGF-β/STAT3 Signaling Cascades in Rats

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related deaths worldwide and the majority of HCC patients occur with a background of hepatic fibrosis and cirrhosis. We have previously reported the hepatoprotective effects of steamed and freeze-dried mature silkworm larval powder (SMSP) in a chronic ethanol-treated rat model. Here, we assessed the anti-fibrotic and anti-carcinogenic effects of SMSP on diethylnitrosamine (DEN)-treated rats. Wistar rats were intraperitoneally injected with DEN once a week for 12 or 16 weeks with or without SMSP administration (0.1 and 1 g/kg). SMSP administration significantly attenuated tumor foci formation and proliferation in the livers of the rats treated with DEN for 16 weeks. SMSP administration also inhibited hepatic fibrosis by decreasing the levels of collagen fiber and the expression of pro-collagen I and alpha-smooth muscle actin (α-SMA). Moreover, SMSP supplementation improved the major parameters of fibrosis such as transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), tumor necrosis factor-alpha (TNF-α), plasminogen activator inhibitor-1 (PAI-1), and collagen type I (Col1A1) in the livers from the rats treated with DEN for 16 weeks. As s possible mechanisms, we investigated the effects of SMSP on the TGF-β and signal transducer and activator of transcription 3 (STAT3)-mediated signaling cascades, which are known to promote hepatic fibrosis. We found that SMSP treatment inhibited the activation of TGF-β and the phosphorylation of STAT3 pathway in DEN-treated rats. Moreover, SMSP administration suppressed the expressions of the target genes of TGF-β and STAT3 induced by DEN treatment. Our findings provide experimental evidences that SMSP administration has inhibitory effects of hepatic fibrosis and HCC induced by DEN in vivo and could be a promising strategy for the prevention or treatment of hepatic fibrosis and hepatocellular carcinogenesis.

Protective Effects of Fucoxanthin against Alcoholic Liver Injury by Activation of Nrf2-Mediated Antioxidant Defense and Inhibition of TLR4-Mediated Inflammation

Fucoxanthin (Fx) is a natural extract from marine seaweed that has strong antioxidant activity and a variety of other bioactive effects. This study elucidated the protective mechanism of Fx on alcoholic liver injury. Administration of Fx was associated with lower pathological effects in liver tissue and lower serum marker concentrations for liver damage induced by alcohol. Fx also alleviated oxidative stress, and lowered the level of oxides and inflammation in liver tissue. Results indicate that Fx attenuated alcohol-induced oxidative lesions and inflammatory responses by activating the nuclear factor erythrocyte-2-related factor 2 (Nrf2)-mediated signaling pathway and down-regulating the expression of the toll-like receptor 4 (TLR4)-mediated nuclear factor-kappa B (NF-κB) signaling pathway, respectively. Our findings suggest that Fx can be developed as a potential nutraceutical for preventing alcohol-induced liver injury in the future.

Shanxi Aged Vinegar Protects against Alcohol-Induced Liver Injury via Activating Nrf2-Mediated Antioxidant and Inhibiting TLR4-Induced Inflammatory Response

Shanxi aged vinegar (SAV) is a typical fermented and antioxidant food, which has various health-promoting effects. This work aimed to explore the effects of SAV on alcohol-induced liver injury. A mice model of alcoholic liver injury was established to illuminate its potential mechanisms. All mice pretreated with SAV and then received an ethanol solution (50% w/v, 4.8 g/kg b.w.). The results showed that SAV ameliorated alcohol-induced histological changes and elevation of liver enzymes. SAV attenuated alcohol-induced oxidative stress by declining levels of hepatic oxidants, and restoring depletion of antioxidant enzyme activities in mice livers. Moreover, SAV alleviated alcohol-induced oxidative damage by activating nuclear factor erythroid-2-related factor 2 (Nrf2)-mediated signal pathway. In addition, SAV prevented alcohol-induced inflammation by suppressing lipopolysaccharide (LPS) level and activities of pro-inflammatory enzymes, and regulating inflammatory cytokines. SAV inhibited alcohol-induced inflammation through down-regulating the expression of Toll-like receptor 4 (TLR4)-mediated inflammatory response. The findings provide crucial evidence for elucidating the hepatoprotective mechanisms of SAV and encourage the future application of SAV as a functional food for liver protection.