Sericin as treatment of obesity: morphophysiological effects in obese mice fed with high-fat diet / Sericina como tratamento da obesidade: efeitos morfofisiológicos de camundongos obesos por dieta hiperlipídica

ABSTRACT Objective To investigate the effects of sericin extracted from silkworm Bombyx mori cocoon on morphophysiological parameters in mice with obesity induced by high-fat diet. Methods Male C57Bl6 mice aged 9 weeks were allocated to one of two groups - Control and Obese, and fed a standard or high-fat diet for 10 weeks, respectively. Mice were then further subdivided into four groups with seven mice each, as follows: Control, Control-Sericin, Obese, and Obese-Sericin. The standard or high fat diet was given for 4 more weeks; sericin (1,000mg/kg body weight) was given orally to mice in the Control-Sericin and Obese-Sericin Groups during this period. Weight gain, food intake, fecal weight, fecal lipid content, gut motility and glucose tolerance were monitored. At the end of experimental period, plasma was collected for biochemical analysis. Samples of white adipose tissue, liver and jejunum were collected and processed for light microscopy analysis; liver fragments were used for lipid content determination. Results Obese mice experienced significantly greater weight gain and fat accumulation and had higher total cholesterol and glucose levels compared to controls. Retroperitoneal and periepididymal adipocyte hypertrophy, development of hepatic steatosis, increased cholesterol and triglyceride levels and morphometric changes in the jejunal wall were observed. Conclusion Physiological changes induced by obesity were not fully reverted by sericin; however, sericin treatment restored jejunal morphometry and increased lipid excretion in feces in obese mice, suggesting potential anti-obesity effects.

RESUMO Objetivo Investigar os efeitos da sericina extraída de casulos de Bombyx mori na morfofisiologia de camundongos com obesidade induzida por dieta hiperlipídica. Métodos Camundongos machos C57Bl6, com 9 semanas de idade, foram distribuídos em Grupos Controle e Obeso, que receberam ração padrão para roedores ou dieta hiperlipídica por 10 semanas, respectivamente. Posteriormente, os animais foram redistribuídos em quatro grupos, com sete animais cada: Controle, Controle-Sericina, Obeso e Obeso-Sericina. Os animais permaneceram recebendo ração padrão ou hiperlipídica por 4 semanas, período no qual a sericina foi administrada oralmente na dose de 1.000mg/kg de massa corporal aos Grupos Controle-Sericina e Obeso-Sericina. Parâmetros fisiológicos, como ganho de peso, consumo alimentar, peso das fezes em análise de lipídios fecais, motilidade intestinal e tolerância à glicose foram monitorados. Ao término do experimento, o plasma foi coletado para dosagens bioquímicas e fragmentos de tecido adiposo branco; fígado e jejuno foram processados para análises histológicas, e amostras hepáticas foram usadas para determinação lipídica. Resultados Camundongos obesos apresentaram ganho de peso e acúmulo de gordura significativamente maior que os controles, aumento do colesterol total e glicemia. Houve hipertrofia dos adipócitos retroperitoneais e periepididimais, instalação de esteatose e aumento do colesterol e triglicerídeos hepáticos, bem como alteração morfométrica da parede jejunal. Conclusão O tratamento com sericina não reverteu todas as alterações fisiológicas promovidas pela obesidade, mas restaurou a morfometria jejunal e aumentou a quantidade de lipídios eliminados nas fezes dos camundongos obesos, apresentando-se como potencial tratamento para a obesidade.

Sericin and swimming on histomorphometric parameters of denervated plantar muscle in Wistar rats / Sericina e natação sobre parâmetros histomorfométricos de músculo plantar desnervado de ratos Wistar

Abstract Objective To analyze the combined effects of the silk protein sericin and swimming exercise on histomorphometry of the plantar muscle in Wistar rats. Methods Forty adult rats were randomly allocated into 5 groups comprising 8 animals each, as follows: Control, Injury, Sericin, Swim, and Swim plus Sericin. Three days after crushing of the sciatic nerve the rats in the Swim and Swim plus Sericin Groups were submitted to swimming exercise for 21 days. Rats were then euthanized and the plantar muscle harvested and processed. Results Cross-sectional area, peripheral nuclei and muscle fiber counts, nucleus/fiber ratio and smallest muscle fiber width did not differ significantly between groups. Morphological analysis revealed hypertrophic fibers in the Swim Group and evident muscle damage in the Swim plus Sericin and Injury Groups. The percentage of intramuscular collagen was apparently maintained in the Swim Group compared to remaining groups. Conclusion Combined treatment with sericin and swimming exercise did not improve muscle properties. However, physical exercise alone was effective in maintaining intramuscular connective tissue and preventing progression of deleterious effects of peripheral nerve injury.

RESUMO Objetivo Analisar o efeito da proteína sericina associada ao exercício físico de natação na histomorfometria do músculo plantar de ratos Wistar. Métodos Foram utilizados 40 ratos adultos divididos aleatoriamente em 5 grupos, com 8 animais cada: Controle, Lesão, Sericina, Natação, Natação e Sericina. Três dias após a compressão do nervo isquiático, os Grupos Natação e Exercício e Sericina foram submetidos ao exercício físico de natação durante 21 dias. Após, os animais foram sacrificados, e o músculo plantar foi processado. Resultados Não houve diferença da área da secção transversa entre os grupos, quantidade de núcleos periféricos, quantidade de fibra, relação núcleo/fibra e diâmetro menor. A análise morfológica revelou que no Grupo Natação ocorreu hipertrofia das fibras, assim como nos Grupos Exercício e Sericina e Lesão, o dano muscular foi evidente. O percentual de conjuntivo intramuscular parece ter sido mantido no Grupo Exercício em relação aos demais grupos. Conclusão A associação da proteína sericina e exercício físico de natação não foi eficiente na melhora das propriedades musculares, embora a aplicação do exercício físico tenha sido eficiente na manutenção do conjuntivo intramuscular, e no não agravamento dos efeitos deletérios consequentes da lesão nervosa periférica.

Effect of urea-extracted sericin on melanogenesis: potential applications in post-inflammatory hyperpigmentation

BACKGROUND: Hyperpigmentation disorders such as post-inflammatory hyperpigmentation are major concerns not only in light-skinned people but also in Asian populations with darker skin. The anti-tyrosinase and immunomodulatory effects of sericin have been known for decades. However, the therapeutic effects of sericin on hyperpigmentation disorders have not been well documented. METHODS: In this study, we used an in vitro model to study the anti-tyrosinase, tolerogenic, and anti-melanogenic effects of sericin on Staphylococcus aureus peptidoglycan (PEG)-stimulated melanocytes, dendritic cells (DCs), and artificial skin (MelanoDerm™). Enzyme-linked immunosorbent assay, conventional and immunolabeled electron microscopy, and histopathological studies were performed. RESULTS: The results revealed that urea-extracted sericin has strong anti-tyrosinase properties as shown by a reduction of tyrosinase activity in melanin pigments both 48 h and 10 days after allergic induction with PEG. Anti-inflammatory cytokines including interleukin (IL)-4, IL-10, and transforming growth factor-p were upregulated upon sericin treatment (10, 20, and 50 µg/mL), whereas production of allergic chemokines, CCL8 and CCL18, by DCs was diminished 48 h after allergic induction with PEG. Moreover, sericin lowered the expression of micropthalmia-associated transcription factor (MITF), a marker of melanogenesis regulation, in melanocytes and keratinocytes, which contributed to the reduction of melanin size and the magnitude of melanin deposition. However, sericin had no effect on melanin transport between melanocytes and keratinocytes, as demonstrated by a high retention of cytoskeletal components. CONCLUSION: In summary, sericin suppresses melanogenesis by inhibition of tyrosinase activity, reduction of inflammation and allergy, and modulation of MITF function.

Effects of silk sericin on the proliferation and apoptosis of colon cancer cells

Sericin is a silk protein woven from silkworm cocoons (Bombyx mori). In animal model, sericin has been reported to have anti-tumoral action against colon cancer. The mechanisms underlying the activity of sericin against cancer cells are not fully understood. The present study investigated the effects of sericin on human colorectal cancer SW480 cells compared to normal colonic mucosal FHC cells. Since the size of the sericin protein may be important for its activity, two ranges of molecular weight were tested. Sericin was found to decrease SW480 and FHC cell viability. The small sericin had higher anti-proliferative effects than that of the large sericin in both cell types. Increased apoptosis of SW480 cells is associated with increased caspase-3 activity and decreased Bcl-2 expression. The anti-proliferative effect of sericin was accompanied by cell cycle arrest at the S phase. Thus, sericin reduced SW480 cell viability by inducing cell apoptosis via caspase-3 activation and down-regulation of Bcl-2 expression. The present study provides scientific data that support the protective effect of silk sericin against cancer cells of the colon and suggests that this protein may have significant health benefits and could potentially be developed as a dietary supplement for colon cancer prevention.