title: Silk and silkworm pupa peptides suppress adipogenesis in preadipocytes and fat accumulation in rats fed a high-fat diet.
abstract: OBJECTIVE
  The objective was to confirm the anti-obesity activity of a silk peptide (SP) and a silkworm pupa peptide (SPP) in rats fed a high-fat diet (HFD) and to elucidate their action mechanism(s) in a preadipocyte culture system.
  
  
  METHODS
  In an in vitro mechanistic study, the differentiation and maturation of 3T3-L1 preadipocytes were stimulated with insulin (5 μg/mL), and effects of SP and SPP on the adipogenesis of mature adipocytes were assessed. In an in vivo anti-obesity study, male C57BL/6 mice were fed an HFD containing SP or SPP (0.3, 1.0, or 3.0%) for 8 weeks, and blood and tissue parameters of obesity were analyzed.
  
  
  RESULTS
  Hormonal stimulation of preadipocytes led to a 50-70% increase in adipogenesis. Polymerase chain reaction and Western blot analyses revealed increases in adipogenesis-specific genes (leptin and Acrp30) and proteins (peroxisome proliferator-activated receptor-γ and Acrp30). The hormone-induced adipogenesis and activated gene expression was substantially inhibited by treatment with SP and SPP (1-50 μg/mL). The HFD markedly increased body weight gain by increasing the weight of epididymal and mesenteric fat. Body and fat weights were significantly reduced by SP and SPP, in which decreases in the area of abdominal adipose tissue and the size of epididymal adipocytes were confirmed by magnetic resonance imaging and microscopic examination, respectively. Long-term HFD caused hepatic lipid accumulation and increased blood triglycerides and cholesterol, in addition to their regulatory factors Acrp30 and leptin. However, SP and SPP recovered the concentrations of Acrp30 and leptin, and attenuated steatosis.
  
  
  CONCLUSIONS
  SP and SPP inhibit the differentiation of preadipocytes and adipogenesis by modulating signal transduction pathways and improve HFD-induced obesity by reducing lipid accumulation and the size of adipocytes.
authors.affiliation: College of Veterinary Medicine and Research Institute of Veterinary Medicine, Chungbuk National University, 52 Naesudongro, Gaesin-dong, Cheongju, Chungbuk 361-763, Korea.
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Dongsun
authors.initials: D
authors.lastname: Park
authors.forename: Goeun
authors.initials: G
authors.lastname: Yang
authors.forename: Dae-Kwon
authors.initials: DK
authors.lastname: Bae
authors.forename: Yun-Hui
authors.initials: YH
authors.lastname: Yang
authors.forename: Tae Kyun
authors.initials: TK
authors.lastname: Kim
authors.forename: Dajeong
authors.initials: D
authors.lastname: Kim
authors.forename: Jangbeen
authors.initials: J
authors.lastname: Kyung
authors.forename: Sungho
authors.initials: S
authors.lastname: Yeon
authors.forename: Kyo Chul
authors.initials: KC
authors.lastname: Koo
authors.forename: Jeong-Yong
authors.initials: JY
authors.lastname: Lee
authors.forename: Seock-Yeon
authors.initials: SY
authors.lastname: Hwang
authors.forename: Seong Soo
authors.initials: SS
authors.lastname: Joo
authors.forename: Yun-Bae
authors.initials: YB
authors.lastname: Kim
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D050156:Adipogenesis / Q000187:drug effects* / Q000235:genetics; D052242:Adiponectin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D019440:Anti-Obesity Agents / Q000494:pharmacology; D001835:Body Weight / Q000187:drug effects; D012831:Bombyx / Q000737:chemistry*; D002454:Cell Differentiation / Q000187:drug effects; D059305:Diet, High-Fat; D019476:Insect Proteins / Q000494:pharmacology*; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009765:Obesity / Q000517:prevention & control; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D011679:Pupa / Q000737:chemistry; D047011:Silk / Q000737:chemistry*
chemical_list: D052242:Adiponectin; C499919:Adipoq protein, mouse; D019440:Anti-Obesity Agents; D019476:Insect Proteins; D007328:Insulin; D020738:Leptin; D047495:PPAR gamma; D010455:Peptides; D047011:Silk