Objective       To investigate the expression of mannose-binding lectin (MBL1) in the serum and renal tissue and preventive effects of leflunomide (LEF) in diabetic nephropathy rats.      Methods       Fifty-six SD male rats (8 weeks old

weighing 180 to 220 g) were randomly divided in

to control group (group N

n=16) and diabetes model group (n=40). Diabetic rat model was induced by intra-peritoneal injection of streptozotocin. The diabetic rats were randomly divided into group of diabetic mellitus (group DM) and leflunomide treatment group (group LEF). Group LEF were treated with leflunomide (5 mg/kg every day) through intra-gastric infusing

and group DM and group N were treated with equal volume of normal saline. The rats were sacrificed in 4 and 8 weeks after establishment of diabetic nephropathy model

and then 24 hours urine protein

blood glucose

serum creatinine

and blood urea nitrogen were detected. PSA staining was used to observe the pathological changes in the renal tissues. Serum level of MBL1 was detected by ELISA

and its expression in the renal tissue was detected by immunohistochemical assay

RT-PCR and Western blotting.       Results      Compared with control group

the blood glucose

renal mass index

serum creatinine

blood urea nitrogen and 24 hours urine protein were significantly increased in DM group and LEF group (

P

0.01). The renal mass index

serum creatinine

blood urea nitrogen

serum MBL1 (4 weeks: 1.117±0.067 vs 1.249±0.054 μg/L; 8 weeks: 1.222±0.074 vs 1.470±0.132 μg/L) and 24 hours urine protein was significantly lower in the group LEF than group DM (

P

0.05 for blood urea nitrogen

P

0.01 for other indexes). MBL1 was mildly expressed in normal control group renal tissue

significantly enhanced in group DM

and was significantly decreased in group LEF than in group DM at the 2 time points (

P

0.01). Correlation analysis showed that the change of serum and renal MBL1 expression was positively correlated with renal mass index

serum creatinine

blood urea nitrogen

24 hours urine protein

mean glomerular area and mean glomerular volume.       Conclusion      MBL1 participates in the incidence and development of diabetic nephropathy. Leflunomide attenuates inflammatory response and ameliorates renal injury through reducing expression of MB

L in serum and renal  tissue.