Insulin-like growth factor-I enhances immune response in dexamethasone-treated or surgically stressed rats maintained with total parenteral nutrition.
BACKGROUND
New evidence suggests that insulin-like growth factor-I (IGF-I) is an important regulator of immune response. Our objective was to determine the effects of IGF-I on immune response during total parenteral nutrition (TPN) using two stress models.


METHODS
Male, Sprague-Dawley rats (230 to 250 g) were given TPN with or without coinfusion of recombinant human IGF-I (800 micrograms/d for 6 days) and subjected to either dexamethasone, a synthetic glucocorticoid, or surgical stress, in the form of a midline abdominal incision. In the dexamethasone model, immune response was assessed by total cellularity of the thymus and spleen, in vitro assays of lymphocyte proliferation, and interleukin 6 (IL-6) production, and concentrations of IL-6 and tumor necrosis factor alpha (TNF-alpha) in serum. In the surgical model, flow cytometry was used to identify and quantify splenic populations of T and B lymphocytes and macrophages.


RESULTS
In rats immunosuppressed by dexamethasone, IGF-I infusion increased mitogen-induced proliferation of thymocytes, but did not alter cellularity in the thymus; enhanced proliferation and IL-6 production in peripheral blood mononuclear cells following treatment with concanavalin A or lipopolysaccharide; and reduced the serum concentration of IL-6, but not TNF-alpha. In surgically stressed rats, IGF-I infusion restored the splenic populations of immature and mature B lymphocytes, which were decreased by TPN.


CONCLUSIONS
our data demonstrate that IGF-1 enhances immune response during TPN in rats.
Hinton
P S
PS
Department of Nutritional Sciences, University of Wisconsin-Madison 53706, USA.
Peterson
C A
CA
Lo
H C
HC
Yang
H
H
McCarthy
D
D
Ney
D M
DM
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D003907:Dexamethasone; D005434:Flow Cytometry; D007109:Immunity; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology; D008297:Male; D010289:Parenteral Nutrition, Total; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins; D013312:Stress, Physiological / Q000209:etiology / Q000276:immunology*; D013514:Surgical Procedures, Operative; D013601:T-Lymphocytes / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D015850:Interleukin-6; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone