Expression of apelin‑13 and its negative correlation with TGF‑β1 in patients with diabetic kidney disease.

Diabetic kidney disease (DKD) is a severe microvascular complication of diabetes, one key feature of which includes renal fibrosis. As apelin is an adipokine closely related to diabetes, the present study aimed to evaluate apelin-13 expression levels and the relationship between apelin-13 and disease indicators in patients with diabetic kidney disease (DKD). The present case-control study enrolled 70 patients with diabetes, including 31 with diabetic kidney disease (DKD group), 39 without DKD (non-DKD group) and 30 healthy controls. The levels of serum apelin-13 and TGF-β1, the key driver of renal fibrosis, were determined by ELISA. Additionally, age, mean disease duration, weight, blood pressure, fasting blood glucose, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein, cholesterol, urea nitrogen, blood creatinine and 24-hour urinary total protein (24-h UTP) were recorded. The results demonstrated that apelin-13 and TGF-β1 expression levels, age, blood pressure, fasting blood glucose, cholesterol and blood urea nitrogen levels were significantly higher in patients with diabetes compared with the healthy controls (P<0.05). Moreover, apelin-13 and TGF-β1 expression levels, mean disease duration, systolic pressure, blood creatinine, blood urea nitrogen and 24-h UTP were significantly higher in the DKD group compared with the non-DKD group (P<0.05). The estimated glomerular filtration rate (eGFR) was significantly reduced in the DKD group compared with the non-DKD group (P<0.05). Correlation analysis demonstrated a negative correlation between apelin-13 and eGFR expression and a positive correlation between apelin-13 expression and 24-h UTP in both the DKD and non-DKD groups (P<0.05). A negative correlation was also demonstrated between apelin-13 and TGF-β1 expression levels in the DKD group and non-DKD groups (both P<0.05). In conclusion, apelin-13 and TGF-β1 expression levels were significantly higher in the DKD group compared with those in the non-DKD group. Additionally, apelin-13 expression was negatively correlated with TGF-β1 expression in the DKD and non-DKD groups. Therefore, apelin-13 could potentially be used in the future as an indicator of renal fibrosis or destruction in patients with DKD. The present trial was retrospectively registered in the Chinese Clinical Trial Registry (trial registration no. ChiCTR2200060945) on 14.06.2022.