Relationship between pulmonary function and albuminuria in type 2 diabetic patients with preserved renal function

Albuminuria is the early manifestation of the pathogenesis of diabetic nephropathy (DN). The current study was to investigate the relationship of pulmonary function with albuminuria in type 2 diabetic patients with preserved renal function to evaluate the role of pulmonary function in the early stage of DN.

A total of 326 patients with type 2 diabetes mellitus (T2DM) including 270 without albuminuria and 56 with albuminuria, and 265 non-diabetic patients were enrolled. The patients' general information, and the parameters of pulmonary function, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, total lung capacity (TLC), diffusion capacity for carbon monoxide of lung (DLCO) were compared between T2DM and control groups, as well as T2DM patients with and without albuminuria groups. All pulmonary function parameters were expressed as a percentage of those predicted (%pred). Logistic regression models were constructed to test the association of albuminuria and pulmonary function.

The values of FVC%pred, FEV1%pred, TLC%pred and DLCO%pred were lower, and the proportion of subjects with FVC%pred < 80, FEV1%pred < 80, and DLCOc%pred < 80 was higher in T2DM subjects than controls (all P < 0.05). Subgroup analysis of diabetic patients showed that the values of FVC%pred, FEV1%pred, TLC%pred, and DLCOc%pred (97.18 ± 13.45, 93.95 ± 14.51, 90.64 ± 9.97, 87.27 ± 13.13, respectively) were significantly lower in T2DM subjects with albuminuria than those without albuminuria (103.94 ± 14.12, 99.20 ± 14.25, 93.79 ± 10.36, 92.62 ± 13.45, all P < 0.05). There was a significantly negative correlation between the urine albumin-to-creatinine ratio (UACR) and DLCOc%pred (r = - 0.143, P = 0.010) in spearman linear correlation test. In logistic regression analysis, the FVC%pred (OR 0.965, 95%CI 0.944-0.988), FEV1%pred (OR 0.975, 95%CI 0.954-0.996), and DLCOc%pred (OR 0.974, 95%CI 0.951-0.998) were independently associated with albuminuria after adjustments for smoking index, duration, HbA1c, FBG, and TG.

Our results demonstrated albuminuria is associated with a restrictive pulmonary function as well as pulmonary diffusion function in T2DM with preserved renal function, which remind us to be alert of the pulmonary function decline even in the early stage of DN.