title: 4-Hydroxyisoleucine ameliorates an insulin resistant-like state in 3T3-L1 adipocytes by regulating TACE/TIMP3 expression.
abstract: BACKGROUND
  Obesity-associated insulin resistance (IR) is highly correlated with soluble tumor necrosis factor-α (sTNF-α), which is released from transmembranous TNF-α by TNF-α converting enzyme (TACE). In vivo, TACE activity is suppressed by tissue inhibitor of metalloproteinase 3 (TIMP3). Agents that can interact with TACE/TIMP3 to improve obesity-related IR would be highly valuable. In the current study, we assessed whether (2S,3R,4S)-4-hydroxyisoleucine (4-HIL) could modulate TACE/TIMP3 and ameliorate an obesity-induced IR-like state in 3T3-L1 adipocytes.
  
  
  METHODS
  3T3-L1 adipocytes were incubated in the presence of 25 mM glucose and 0.6 nM insulin to induce an IR-like state, and were then treated with different concentrations of 4-HIL or 10 µM pioglitazone (positive control). The glucose uptake rate was determined using the 2-deoxy-[(3)H]-D-glucose method, and the levels of sTNF-α in the cell supernatant were determined using ELISA. The protein expression of TACE, TIMP3, and insulin signaling-related molecules was measured using western blotting.
  
  
  RESULTS
  Exposure to high glucose and insulin for 18 hours increased the levels of sTNF-α in the cell supernatant. The phosphorylation of insulin receptor substrate-1 (IRS-1) Ser(307) and Akt Ser(473) was increased, whereas the protein expression of IRS-1, Akt, and glucose transporter-4 was decreased. The insulin-induced glucose uptake was reduced by 67% in 3T3-L1 adipocytes, which indicated the presence of an IR-like state. The above indexes, which demonstrated the successful induction of an IR-like state, were reversed by 4-HIL in a dose-dependent manner by downregulating and upregulating the protein expression of TACE and TIMP3 proteins, respectively.
  
  
  CONCLUSIONS
  4-HIL improved an obesity-associated IR-like state in 3T3-L1 adipocytes by targeting TACE/TIMP3 and the insulin signaling pathway.
authors.affiliation: Department of Endocrinology, Union Hospital, Wuhan, Hubei, People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.affiliation: Department of Endocrinology, Union Hospital, Wuhan, Hubei, People's Republic of China ; Chengdu First People's Hospital, Sichuan, People's Republic of China.
authors.forename: Wen
authors.initials: W
authors.lastname: Du
authors.affiliation: Department of Endocrinology, Union Hospital, Wuhan, Hubei, People's Republic of China.
authors.forename: Mohammad Ishraq
authors.initials: MI
authors.lastname: Zafar
authors.affiliation: Department of Medicine, Tongji Hospital, Wuhan, Hubei, People's Republic of China.
authors.forename: Raja Adeel
authors.initials: RA
authors.lastname: Shafqat
authors.affiliation: Department of Endocrinology, Union Hospital, Wuhan, Hubei, People's Republic of China.
authors.forename: Liumeng
authors.initials: L
authors.lastname: Jian
authors.affiliation: Department of Endocrinology, Union Hospital, Wuhan, Hubei, People's Republic of China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Cai
authors.affiliation: Department of Integrated Traditional Chinese and Western Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People's Republic of China.
authors.forename: Furong
authors.initials: F
authors.lastname: Lu
mesh_terms: D041721:3T3-L1 Cells; D051722:ADAM Proteins / Q000378:metabolism*; D000072198:ADAM17 Protein; D017667:Adipocytes / Q000187:drug effects* / Q000201:enzymology; D000818:Animals; D003847:Deoxyglucose / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D007532:Isoleucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051379:Mice; D000077205:Pioglitazone; D015398:Signal Transduction / Q000187:drug effects; D045162:Thiazolidinediones / Q000494:pharmacology; D013997:Time Factors; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism*; D000097792:Tissue Inhibitor of Metalloproteinase-4
chemical_list: D051722:ADAM Proteins; D000072198:ADAM17 Protein; D003847:Deoxyglucose; D007328:Insulin; D007532:Isoleucine; D000077205:Pioglitazone; D045162:Thiazolidinediones; D019714:Tissue Inhibitor of Metalloproteinases; D000097792:Tissue Inhibitor of Metalloproteinase-4; C104672:4-hydroxyisoleucine; C000606463:Adam17 protein, mouse
keywords: 4-hydroxyisoleucine; Fenugreek seed; TACE; TIMP3; glucose uptake; insulin signaling; obesity-related insulin resistance; soluble TNF-α