Insulin signaling in human visceral and subcutaneous adipose tissue in vivo.
In this study, we evaluated the activation of various insulin signaling molecules in human fat in vivo and compared signaling reactions in visceral and subcutaneous fat depots. Paired abdominal omental and subcutaneous fat biopsies were obtained from nonobese subjects with normal insulin sensitivity under basal conditions and 6 and 30 min following administration of intravenous insulin. Insulin receptor phosphorylation was more intense and rapid and insulin receptor protein content was greater in omental than in subcutaneous adipose tissue (P < 0.05). Insulin-induced phosphorylation of Akt also occurred to a greater extent and earlier in omental than in subcutaneous fat (P < 0.05) in the absence of significant changes in Akt protein content. Accordingly, phosphorylation of the Akt substrate glycogen synthase kinase-3 was more responsive to insulin stimulation in omental fat. Protein content of extracellular signal-regulated kinase (ERK)-1/2 was threefold higher in omental than in subcutaneous fat (P < 0.05), and ERK phosphorylation showed an early 6-min peak in omental fat, in contrast with a more gradual increase observed in subcutaneous fat. In conclusion, the adipocyte insulin signaling system of omental fat shows greater and earlier responses to insulin than that of subcutaneous fat. These findings may contribute to explain the biological diversity of the two fat depots.
Department of Emergency and Organ Transplantation, Section of Internal Medicine, Endocrinology and Metabolic Diseases, University of Bari, Piazza Giulio Cesare, 11, I-70124 Bari, Italy.
Luigi
L
Laviola
Sebastio
S
Perrini
Angelo
A
Cignarelli
Annalisa
A
Natalicchio
Anna
A
Leonardini
Francesca
F
De Stefano
Marilena
M
Cuscito
Michele
M
De Fazio
Vincenzo
V
Memeo
Vincenzo
V
Neri
Mauro
M
Cignarelli
Riccardo
R
Giorgino
Francesco
F
Giorgino
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000502:physiology; D000273:Adipose Tissue / Q000166:cytology / Q000502:physiology*; D000818:Animals; D001706:Biopsy; D001786:Blood Glucose / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007328:Insulin / Q000502:physiology*; D008297:Male; D051379:Mice; D008875:Middle Aged; D009852:Omentum; D011972:Receptor, Insulin / Q000378:metabolism; D012016:Reference Values; D015398:Signal Transduction; D012867:Skin; D014781:Viscera
D001786:Blood Glucose; D007328:Insulin; D011972:Receptor, Insulin