Running exercise increases tumor necrosis factor-alpha secreting from mesenteric fat in insulin-resistant rats.
Tumor necrosis factor-alpha (TNF-alpha) is an important mediator of insulin resistance in obese subjects, through its overexpression in fat tissue. However, how exercise can modify the expression of TNF-alpha is controversial. We examined TNF-alpha in adipose tissue using an animal model of insulin resistance that was produced by feeding rats a diet high in sucrose. The rats were allocated to one of three groups: those receiving a starch-based diet (control group): those fed a high-sucrose diet (sucrose-fed group): and those fed a high-sucrose diet and given wheel exercise (exercised group). The animals were allowed to eat and drink ad lib for 4 or 12 weeks (4 wk: control n=7, sucrose-fed n=7, exercised n=10; 12 wk: control n=5, sucrose-fed n=5, exercised n=9). The voluntary wheel exercise was initiated with the feeding of the high-sucrose diet. The rats in the exercise groups ran 15 +/- 3 km/week. We showed that 12-week voluntary running exercise significantly (P<0.05) increased both TNF-alpha protein (5-fold) and mRNA (1.4 fold) in the mesenteric fat of insulin-resistant rats compared to non-exercised sucrose-fed mice. Accordingly, in exercised group, plasma glucose (124 +/- 9 mEq/L vs 141 +/- 11 mEq/L). and free fatty acid (0.98 +/- 0.07 mEq/L vs 1.4 +/- 0.05 mEq/L) concentrating in portal vein blood were reduced compared to sucrose-fed group. The amounts of fatty tissue both in mesenteric and subcutaneous tissues were significantly (P<0.05) decreased through running exercise. We consider that up-regulation of TNF-alpha in mesenteric fat may be a compensatory mechanism for the reduction of fatty acid in adipose tissues and this change could control metabolic homeostasis during exercise to modulate a hyperinsulinemic state.
Nara
M
M
Department of Laboratory Medicine, Gunma University School of Medicine, Maebashi, Japan.
Kanda
T
T
Tsukui
S
S
Inukai
T
T
Shimomura
Y
Y
Inoue
S
S
Kobayashi
I
I
D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D019422:Dietary Sucrose / Q000378:metabolism; D002149:Energy Intake; D005947:Glucose / Q000378:metabolism; D007333:Insulin Resistance; D008297:Male; D008643:Mesentery / Q000378:metabolism; D051379:Mice; D005082:Physical Exertion / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D001786:Blood Glucose; D019422:Dietary Sucrose; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D005947:Glucose