Alterations of insulin sensitivity by the implantation of 3T3-L1 cells in nude mice. A role for TNF-alpha?
OBJECTIVE
Visceral adipocytes have different functions than those from the subcutaneous fat area. These differences could contribute to the pathological significance of excessive visceral fat accumulation for accompanying insulin resistance and hyperinsulinaemia. This study addresses this hypothesis and describes a unique method to clarify whether the functional differences between visceral and subcutaneous adipocytes depend on their anatomical location.


METHODS
3T3-L1 cells or TNF-alpha overexpressing CHO cells were implanted into subcutaneous fat area or mesenteric area as visceral fat area in athymic mice of BALB/C strain. Then, serum insulin, glucose, TNF-alpha, and several markers of lipid metabolism were measured in the fasting condition. OGTT was also analysed.


RESULTS
During the course of glucose loading, the mice which had 3T3-L1 cells implanted into mesenteric area but not into subcutaneous fat area showed remarkably increased serum insulin and TMF-alpha concentrations, compared to the control mice. Moreover, serum insulin concentrations of the mice, implanted with TNF-alpha overexpressing cells into subcutaneous fat area, were apparently higher than that of control mice.


CONCLUSIONS
This method of implanting adipose cells into subcutaneous or visceral fat area showed high TNF-alpha concentration and insulin resistance by the adipose cells in visceral area of nude mice. Furthermore, we found that the functional significance of visceral fat accumulation for TNF-alpha-induced insulin resistance is partly caused by the interaction of adipocytes with surrounding conditions in mesenteric area.
Shibasaki
M
M
Department of Clinical Cell Biology, Graduate School of Medicine, Chiba University, Chiba, Japan.
Takahashi
K
K
Itou
T
T
Miyazawa
S
S
Ito
M
M
Kobayashi
J
J
Bujo
H
H
Saito
Y
Y
D016475:3T3 Cells; D017667:Adipocytes / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D001786:Blood Glucose / Q000378:metabolism*; D001835:Body Weight; D016466:CHO Cells; D017690:Cell Transplantation; D006224:Cricetinae; D017931:DNA Primers; D005215:Fasting; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood / Q000502:physiology*; D008055:Lipids / Q000097:blood*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
D001786:Blood Glucose; D017931:DNA Primers; D007328:Insulin; D008055:Lipids; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha