Circulating Surfactant Protein A (SP-A), a marker of lung injury, is associated with insulin resistance

Abstract

Objectives: Impaired lung function and inflammation have both attracted growing interest as a potentially novel risk factor for glucose intolerance, insulin resistance, and type 2 diabetes. We hypothesised that circulating levels of surfactant protein A (SP-A), that reflects interstitial lung injury, could be associated with altered glucose tolerance and insulin resistance.

Research designs and methods: Circulating SP-A concentration and metabolic variables (including insulin sensitivity by minimal model method, n=89) were measured in 164 non-smoking men.

Results: Circulating SP-A concentration was significantly higher among patients with glucose intolerance and type 2 diabetes than in subjects with normal glucose tolerance even after adjustment for BMI and age and ex-smoking/never smoking status.

Results: The most significant differences were found in overweight and obese subjects with altered glucose tolerance (AGT, n=59) who showed significantly increased serum SP-A concentrations (by a mean of 24%) compared with obese subjects with normal glucose tolerance (n%58) (Log SP-A 1.54 ± 0.13 vs. 1.44 ± 0.13, p<0.0001). Insulin sensitivity (p=0.003) contributed independently to 22% of SP-A variance among all subjects. In AGT subjects, insulin sensitivity (p%0.01) and fasting triglycerides (p=0.02) contributed to 37% of SP-A variance. Controlling for serum creatinine or C-reactive protein in these models did not change significantly the results.

Conclusions: The lung-derived SP-A protein was associated with altered glucose tolerance and insulin resistance.