Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA051

Poster Communications

Tetrahydrobiopterin (BH4) supplementation prevents the cardiorenal effects of diabetes in mice

K. Soto1, U. Novoa1, D. R. Gonzalez1

1. Ciencias Básicas Biomedicas, Universidad de Talca, Talca, Chile.

The effects of diabetes in the cardiovascular system as well as in the kidney are profound, which include hypertrophy and fibrosis (1). Diabetes also induces oxidative stress (2), at least in part due to uncoupling of nitric oxide synthase (NOS); this is a shift of NO production towards superoxide production due to reduced levels of the NOS cofactor tetrahydrobiopterin (BH4) (3). With this in mind, we tested the hypothesis that BH4 supplement may prevent the development of diabetic cardiomyopathy and nephropathy. For this purpose we induced diabetes in Balb/c mice (n= 30, male, 30-40 g) with three doses (100, 100 and 200 mg kg-1, i.p.) of streptozotocin. Then, diabetic mice were divided into two groups: one group provided with BH4 (sapropterin) in drinking water (daily doses of 20 mg kg-1day-1, during eight weeks) and the other that received only water. A third group of normoglycaemic mice that received only water were used as control. Data are means ± standard deviation, compared by ANOVA or Kruskall-Wallis test. Cardiac levels of BH4 were increased in mice treated with BH4 (8.8± 2.2 control, 9.6 ± 4.7 diabetics and 209.7 ± 99.9 pmol BH4 mg protein-1 in diabetics +BH4 , p=0.0019). Diabetes induced cardiac hypertrophy, evaluated as the ratio of heart weight /tibia length, which was prevented in the group that received BH4: (7.6 ± 1.03 g/mm control, 8.6 ± 0.63 g/mm diabetics and 7.38 ± 0.5 g/mm diabetics + BH4, p< 0.05). In addition, hypertrophy was evaluated as cardiomyocyte cross sectional area. This area was reduced in diabetic mice that received BH4 (1190±460 µm2 control, 1194±389 µm2 diabetics and 1106±375 µm2 diabetics + BH4, p= 0.0012). In addition we evaluated cardiac fibrosis that is also a hallmark of diabetic cardiomyopathy, by Masson trichrome staining (Figure, left panel). Diabetes induced cardiac interstitial fibrosis that was reduced in mice that received BH4 treatment (2.2±1.1% control, 4.12±1.6% in diabetics and 2.16±1.2% in diabetics + BH4, p< 0.05). On the other hand, we evaluated in the kidney the impact of BH4 treatment on glomerular morphology. Diabetes induced glomerular hypertrophy compared to normoglycaemic mice and was prevented by BH4 treatment (Figure, right panel): 0.79 ± 0.08 mm2 in control, 1.12±0.1 in diabetic and 0.98 ± 0.15 mm2 glomerular tuft size in diabetics + BH4, p=0.0004). In addition, diabetic mice presented increased glomerular collagen deposition, which was prevented in mice that received BH4: 1.01±0.25 in control, 2.25±0.29 in diabetics and 1.46±0.33 score units in diabetics+ BH4 (p<0.0001) Overall, these results suggest that chronic treatment with BH4 in mice ameliorates the cardiorenal effects of diabetes, probably by restoring the nitric oxide production. This offers a possible new alternative to explore a BH4-based treatment for the organ damage of diabetes.

Where applicable, experiments conform with Society ethical requirements