Insulinâlike growth factorâI (IGFâI) is used to screen for acromegaly in diabetic cats. In humans, most circulating IGFâI forms ternary complexes (TC) with IGFâbinding protein (IGFBPâ3) and an acidâlabile subunit. Compared to humans, the amount of TC in cats is more variable. Insulinâlike growth factorâI concentrations are reported to increase during insulin treatment, more rapidly in cats achieving remission. Thus, the objective of this study was to investigate (i) factors associated with circulating IGFâI concentrations, including IGFBPâprofiles (ii) effect of insulin treatment on IGFâI concentrations and (iii) IGFâI as prognostic marker of diabetes mellitus remission.
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Thirtyâone privately owned diabetic cats of which 24 were followed 1 year, and 13 healthy cats were enrolled in this prospective study.
Serum insulin, IGFâI, glucose, and fructosamine concentrations were measured.
IGFâbinding forms were determined by chromatography in 14 diabetic and 13 healthy cats; and IGFâI, IGFâII, IGFBPâ3, and IGFBPâ5 by mass spectrometry in 3 cats achieving remission.
Insulinâlike growth factorâI median (interquartile range) before start of insulin treatment was 300 (160â556) ng/mL.
Insulinâlike growth factorâI was positively associated with TC (Pâ<â.0001) and endogenous insulin (Pâ=â.005) and negatively associated with fructosamine (Pâ<â.0001).
Median IGFâI was higher 2â4 weeks after start of insulin treatment compared with baseline (300 versus 670 ng/mL, Pâ=â.0001) and predicted future remission (Pâ=â.046).
In cats that went into remission, the amount of TC and IGFBPâ3 increased, suggesting increase in IGFâI is dependent on TC formation.
Source: Emma M. Strage MĂ„rten Sundberg Bodil S. Holst Mikael Andersson Franko Margareta Ramström Tove Fall Moira Lewitt, Effect of insulin treatment on circulating insulinâlike growth factor I and IGFâbinding proteins in cats with diabetes mellitus. JVIM, Early View.First published: 16 August 2018 https://doi.org/10.1111/jvim.15243
Conclusions
Insulin treatment should be accounted for when interpreting IGFâI in diabetic cats. Insulinâlike growth factorâI 2â4 weeks after initiation of insulin treatment shows promise as prognostic marker for remission in diabetic cats.
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