Role Of Annexin-A1 In The Cardiac And Renal Dysfunction Associated With Experimental Type-1 Diabetes Mellitus

Introduction. Type-1 diabetes mellitus (T1DM) is an autoimmune disease, which leads to mircovascular complications, including diabetic nephropathy and diabetic cardiomyopathy, which are secondary to excessive inflammation. Annexin A1 (ANXA1) is an endogenous anti-inflammatory peptide, which limits inflammation and is involved in the resolution of inflammation in a number of disease states.

Aims. This study investigates whether 1) endogenousANXA1plays a role in the development of the nephropathy/cardiomyopathy associated with experimental T1DM; 2) treatment with human recombinant (hr) ANXA1 attenuates nephropathy/cardiomyopathy in T1DM; and 3) late treatment with hrANXA1 halts the progression of nephropathy/cardiomyopathy in T1DM.

Methods. In C57BL/6 wild-type (WT) or ANAX1-/- mice, experimental T1DM was induced by injection of streptozotocin (45 mg/kg i.v. per day for 5 consecutive days). After 7 and 13 weeks, cardiac and renal function was measured in all animals by echocardiography and biochemical analysis of creatinine and urea (serum) and creatinine and sodium (urine). Data are expressed as mean±SEM and were analysed by one-way ANOVA followed by Tukey’s post-hoc test with P<0.05 being regarded as being significant.

Results. 1) Functional echocardiography of the left ventricle of diabetic ANXA1-/- mice at week 13 (n=6) revealed a significant decline in ejection fraction (EF; 57.9±0.9 vs. 64.2±0.8 %; P<0.05)and, hence, cardiac dysfunction when compared to age-matched diabetic WT controls(n=6). Likewise, at week 13 after STZ-induction,ANXA1-/- mice (n=6) had elevated creatinine clearance (565.2±122.0 vs. 355±48.7 µl/min; P<0.05)when compared to age-matched WT diabetic mice (n=6) indicating hyperfiltration and worsening diabetic nephropathy.2) When compared to diabetic WT-mice, treatment of diabetic WT mice with hrANXA1 (1 µg i.p. per day; n=10) from weeks 1-13attenuated the cardiac (EF; 55.0±4.9 vs. 72.4±6.4 %; P<0.05) and renal dysfunction (creatinine clearance; 533.6±68.8 vs. 211.6±10.3 µl/ml; P<0.05)caused by experimental T1DM.3) In diabetic WT mice, cardiac function progressively declined from week 7 to week 13(EF;64.7±0.5vs. 51.9±1.6 %;P<0.05).Interesting, when diabetic WT-mice were treated with hrANAX1 (1 µg i.p. daily from week 7-13; n=9), the decline in cardiac function was halted (EF;63.2±0.8 vs. 60.7±1.3 %;P>0.05). Similarly, at week 13 when mice were treated with hrANAX1 (1 µg i.p. daily from week 7-13; n=5) renal dysfunction was attenuated (creatinine clearance; 324.6±47.1 vs. 533.6±68.8µl/min; P>0.05) compared to age-matched diabetic mice.

Conclusion. In mice with experimental T1DM, ANXA1-/- mice display a more advanced disease progression, with more pronounced cardiac and renal dysfunction occurring within 13 weeks, indicating that endogenous ANXA1 limits the progression of cardiac and renal dysfunction in T1DM. In addition, treatment with hrANXA1 reduces the extent of cardiac and renal dysfunction associated with T1DM. Importantly, late treatment with hrANXA1 given after significant disease (cardiac and renal dysfunction) had already developed can halt further disease progression, showings that hrANXA1 may be useful in the treatment of the secondary complications of T1DM.

This work was funded by The British Heart Foundation grant number FS/13/58/30648.