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Proteinuria is an important hallmark of diabetic nephropathy models, however it takes a long time for the proteinuria and is not stable. Therefore, low-dose lipopolysaccharide (LPS) was investigated in this work to induce rapid and stable proteinuria in hyperglycemic rats and the underlying mechanism was studied. Hyperglycemia rats was induced by high-fat feeding combined with intraperitoneal injection of streptozotocin (STZ). After 21 days, the model rats received a subinjury dose of 0.8 mg / kg LPS intraperitoneally (i.p.). We detected related biochemical indexes at different time periods after LPS injection and examined the expression of glomerular podocyte-associated proteins. Simultaneously, we measured expression of inflammatory factors, apoptotic proteins and albumin (ALB) in the renal cortex and renal medulla, respectively. PAS (Periodic Acid Schiff) staining was used to observe renal pathology. After LPS injection, urinary microalbumin (umALB) increased significantly and lasted longer. The expression of Nephrin, Podocin and necroptosis factor kappa B (NF-κB) in rennal cortex and Interleukin 18 (IL-18), Caspase-1, NF-κB and ALB in the renal medulla was significantly changed. Pathologically, the glomerular basement membrane was observed to be significantly thickened, the renal tubules were dilated, and the epithelial cells fell off in a circle. LPS promoted the continuous increase in urinary microalbumin in hyperglycemic rats, which was related to the damage to the glomerular basement membrane and renal tubular epithelial cells and to the inflammatory reaction in the kidney involved in NF-κB signaling, and this pathological damage can help to establish a stable model of diabetic nephropathy with increased proteinuria.</div

Changes of liver function (AST and ALT) and kidney function (BUN and CRE) on day 9 and day 12 after the intraperitoneal injection of LPS.

(A)—(D) Changes of liver function and kidney function on the 9th day. (E)—(H) Changes of liver function and kidney function on the 12th day. The data were shown as mean ± S.E.M with 5~9 rats in each group. # and ##, compared with normal groups, P P P P < 0.01. NS: no significance.</p

Protein expression of inflammatory cytokines in rat renal medulla after the intraperitoneal injection of LPS.

The data were shown as mean ± S.E.M., # and ##, compared with normal groups, P P P < 0.01.</p

Changes of blood glucose on the 6^th and 10^th day after the intraperitoneal injection of LPS.

(A) Changes of blood glucose on day 6. (B) Changes of blood glucose on day 10. The data were shown as mean ± S.E.M with 5~9 rats in each group. ## compared with the normal group, P < 0.01. NS: no significance.</p

Changes of urinary total protein (uCSF) and urinary microalbumin (umALB) in hyperglycemia rats before and after the intraperitoneal injection of LPS.

(A)—(C) Changes of uCSF before and after LPS injection. (D)—(F) Changes of umALB before and after LPS injection. The data were shown as mean ± S.E.M from 3~14 rats in each group. # and ## compared with the normal groups, P P P P < 0.01. $ compared with normal groups, P = 0.057. NS: no significance.</p

The expression of Caspase3 and ALB in the both renal cortex and medulla after the intraperitoneal injection of LPS.

(A)—(C) Protein expression of Caspase3 and ALB in the renal cortex. (D)—(F) Protein expression of Caspase3 and ALB in the renal medulla. (G) mRNA expression of ALB in renal medulla. The data were shown as mean ± S.E.M., # and ##, compared with the normal group, P P P < 0.01. NS: no significance.</p

Morphological images of renal cortex and renal medulla cells in each group (400×amplification).

Morphological images of renal cortex and renal medulla cells in each group (400×amplification).</p

Protein and mRNA expression of Nephrin and Podocin in renal cortex after the intraperitoneal injection of LPS.

(A)–(B) mRNA expression of Nephrin and Podocin. (C)–(D) Protein expression of Nephrin and Podocin. The data were shown as mean ± S.E.M., # and ##, compared with normal groups, P P P < 0.05. NS: no significance.</p

Protein expression of inflammatory cytokines in rat renal cortex after the intraperitoneal injection of LPS.

The data were shown as mean ± S.E.M., ##, compared with normal groups, P P P < 0.01. NS: no significance.</p