Elevated IGFBP3 levels in diabetic tears: a negative regulator of IGF-1 signaling in the corneal epithelium

Ocul Surf. 2012 Apr;10(2):100-7. doi: 10.1016/j.jtos.2012.01.004. Epub 2012 Jan 12.


To determine the ratio of IGFBP3:IGF-1 in normal and diabetic human tears, and in telomerase-immortalized human corneal epithelial cells (hTCEpi) cultured under elevated glucose conditions and to correlate these changes with total and phosphorylated levels of IGF-1R. Tear samples were collected noninvasively from diabetic subjects and non-diabetic controls; corneal sensitivity was assessed using a Cochet-Bonnet Aesthesiometer. Conditioned media were collected following culture of hTCEpi cells in normal (5 mM) and elevated (25 mM) glucose conditions; mannitol was used as an osmotic control. IGFBP3, IGF-1, and phosphorylated IGF-1R levels were assessed by ELISA. IGFBP3 and IGF-1R mRNA were assessed by real-time polymerase chain reaction (PCR). Total and phosphorylated IGF-1R expression in whole cell lysates was assessed by western blot. There was a 2.8-fold increase in IGFBP3 in diabetic tears compared to non-diabetic controls (P=0.006); IGF-1 levels were not significantly altered. No difference in corneal sensitivity was detected between groups. The concentration of IGFBP3 in tears was independent of IGF-1. Consistent with human tear measurements in vivo, IGFBP3 secretion was increased 2.2 fold (P<0.001) following culture of hTCEpi cells under elevated glucose conditions in vitro. Treatment with glucose and the mannitol control reduced IGFBP3 mRNA (P<0.001). Total IGF-1R levels were unchanged. The increase in the IGFBP3:IGF-1 ratio detected in diabetic tears compared to normal controls blocked phosphorylation of the IGF-1R by IGF-1 (P<0.001) when tested in vitro. Taken together, these in vivo and confirmatory in vitro findings suggest that the observed increase in IGFBP3 found in human tears may attenuate IGF-1R signaling in the diabetic cornea. A long-term increase in IGFBP3 may contribute to epithelial compromise and the pathogenesis of ocular surface complications reported in diabetes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Blotting, Western
  • Cells, Cultured
  • Corneal Diseases / metabolism
  • Diabetes Mellitus, Type 1 / metabolism*
  • Diabetes Mellitus, Type 2 / metabolism*
  • Enzyme-Linked Immunosorbent Assay
  • Epithelium, Corneal / metabolism*
  • Female
  • Humans
  • Insulin-Like Growth Factor Binding Protein 3 / genetics
  • Insulin-Like Growth Factor Binding Protein 3 / metabolism*
  • Insulin-Like Growth Factor I / metabolism*
  • Male
  • Middle Aged
  • Real-Time Polymerase Chain Reaction
  • Receptor, IGF Type 1 / genetics
  • Tears / metabolism*


  • IGFBP3 protein, human
  • Insulin-Like Growth Factor Binding Protein 3
  • Insulin-Like Growth Factor I
  • Receptor, IGF Type 1