Angiotensin (1-7) exaggerates albuminuria and nephrin gene expression but does not modulate renal function-specific microRNAs expressions in kidneys of db/db mice.

AIM: This study investigated the effects of angiotensin (1-7) on diabetes-induced renal injury and renal miRNA levels in obese type 2 diabetic db/db mice.

METHODS

Treatment with angiotensin (1-7) (500 μg/kg; i.p.) was started when the mice were 12 weeks old and given daily for four weeks. Renal function was assessed by measuring creatinine clearance and albumin excretion rate. The effect of diabetes and/or angiotensin (1-7) treatment on renal miR-29a-3p, miR-29a-5p, miR-155-5p, and miR-30 mRNA expression was studied using real-time PCR. Nephrin and podocin mRNA and protein expressions were studied using real-time PCR and Western blotting.

RESULTS

At 16 weeks, diabetes caused a significant increase in albumin excretion rate, which was further increased with angiotensin (1-7) treatment. Diabetes and/or angiotensin (1-7) did not affect creatinine clearance. Real-time PCR showed no significant changes in expressions of miR-29a-3p, miR-29a-5p, miR-155-5p, or miR-30 in untreated or angiotensin (1-7)-treated control or db/db mice. There was no change in podocin mRNA or protein expression; however, nephrin mRNA expression was increased in angiotensin (1-7)-treated db/db mice. Nephrin protein expression was increased in kidney homogenates of db/db mice but was unaltered in renal membrane fractions. Treatment with angiotensin (1-7) did not affect nephrin or podocin protein expressions in homogenates or membrane fractions.

CONCLUSIONS

The marked albuminuria observed at 16 weeks in db/db mice was independent of the expression of the studied miRNAs or nephrin and podocin expression. Angiotensin (1-7) was not protective as it further exacerbated albuminuria despite having no impact on nephrin and podocin renal protein expression.