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[Klotho gene attenuates the progression of hypertension and heart damage in spontaneous hypertensive rats].

OBJECTIVE
To assess the effect of Klotho gene transduction on the progression of hypertension and heart damage in spontaneous hypertensive rats (SHRs).


METHODS
An adeno-associated virus (AAV) carrying full-length mouse Klotho cDNA (rAAV.mKL) was constructed for in vivo expression of Klotho. Three different groups of male SHRs and a control group of sex and age-matched Sprague Dawley (SD) rats (5 rats per group) were used. The experimental groups of SHRs received an IV injection of phosphate buffered saline (PBS), rAAV.mKL and rAAV.EGFP, respectively. The control group only received equal-volume of PBS. The whole study has spanned 12 weeks. Plasma levels of insulin-like growth factor-1 (IGF-1) and insulin were measured with ELISA. The weight of whole heart was measured to calculate the heart weight index (HWI). EGFP expression of heart frozen sections was observed by fluorescence microscopy. Expression of mRNA and protein of Klotho, IGF-1, IGF-1 receptor (IGF-1R) and p-Akt were determined with RT-PCR, immunohistochemical analysis, and Western blotting. Hypertrophic myocardial cell and collagen fiber were observed by histological examination following Haematoxylin-Eosin and Masson staining.


RESULTS
Transduction of rAAV.mKL can significantly prevent the increase of blood pressure in SHRs. Compared with the control group, the levels of Klotho mRNA and protein have both increased, and the plasma levels of IGF-1, insulin and glucose were elevated, whereas the expression of phosphor-Akt (also called Protein Kinase B, PKB) was decreased in the rAAV.mKL group. Furthermore, a decrease of hypertrophic myocardial cells and collagen fibers was noticed in the rAAV.mKL group compared with the control group.


CONCLUSION
The Klotho gene can attenuate the progression of hypertension and abolishes myocardial hypertrophy and myocardial fibrosis. The protective effect observed in the rAAV.mKL group of SHRs may be attributed to increased Klotho protein and suppression of insulin and IGF-1 signaling pathways through inhibition of Akt phosphorylation.