Decreased serum insulin-like growth factor-I in burn patients: Relationship with serum insulin-like growth factor binding protein-3 proteolysis and the influence of lipid composition in nutritional support
T. Abribat et al., Decreased serum insulin-like growth factor-I in burn patients: Relationship with serum insulin-like growth factor binding protein-3 proteolysis and the influence of lipid composition in nutritional support, CRIT CARE M, 28(7), 2000, pp. 2366-2372
Objectives: To test the effects of the amount and type of fat in the nutrit
ional support on serum insulin-like growth factor (IGF)-I concentrations in
burn patients and to test the hypothesis that the serum proteolytic activi
ty for insulin-like growth factor binding protein (IGFBP)-3 is a major mech
anism for the decreased serum IGF-I observed in these patients.
Design: Randomized, double-blind trial of three different nutritional suppo
rts and analysis of serum IGF-I, IGFBP-3, and serum IGFBP-3 proteolysis.
Setting: Burn center in a university hospital.
Patients: A total of 23 severely burned (>25% total body surface area burne
d) adult patients.
Interventions: Patients were randomly assigned to three types of nutritiona
l support differing in the amount of energy derived from fat and the presen
ce or absence of fish oil: Group I (control), 35% fat; Group II, 15% fat; G
roup III, 15% fat with 50% as fish oil. Nutritional support was both parent
eral and enteral and was started within 24 hrs of admission.
Measurements and Main Results: Serum IGF-I and IGFBP-3 were measured by rad
ioimmunoassay every 3 days for 28 days in 23 severely burned adults. In six
patients, IGFBP-3 was measured by ligand binding assay and the serum prote
olytic activity for rhlGFBP-3 was measured as well. Serum IGF-I concentrati
on was low in all subjects throughout the study period, but did increase wi
th time (p < .01); significantly higher values were found in Group III (p <
.05), Multivariate analysis showed that fish ail and low fat solutions wer
e significantly correlated to serum IGF-I concentrations. Serum IGFBP-3 (ra
dioimmunoassay) was higher than normal throughout the study with no differe
nce between the groups. Between days 4 and 16, IGFBP-3 was cleaved into two
fragments in all patients studied, and the molecular weights of the fragme
nts were equal to those observed in the serum of a woman late in pregnancy.
During this period of time, serum proteolytic activity for rhlGFBP-3 was >
30% in 24 of the 30 samples measured, whereas 20 of the 28 samples measured
thereafter were normal (<25%), Serum IGFBP-3 concentration from ligand bin
ding assay was correlated with serum proteolytic capacity in all subjects (
mean r(2) = 0.77; p < .01) and with serum IGF-I concentrations in five of s
ix subjects (mean P = 0.81; p < .01).
Conclusions: In burn injury, serum IGF-I concentrations are sensitive to th
e amount and type of fat in their nutritional support. The presence of fish
oil allowed for a more rapid recovery of serum IGF-I levels. The proteolys
is of IGFBP-3 may be an important cause of the decreased serum IGF-I values
and the protease(s) responsible for this seem to be similar to those obser
ved in late pregnancy.