Effect of Vitamin D on Serum Fibroblast Growth Factor-23 and Cardiac Tissue Hydroxyproline Levels in Experimentally Induced Insulin Resistance Associated with Left Ventricular Hypertrophy in Rats

Abstract
Background: Insulin resistance cardiomyopathy refers to functional and structural changes at the level of myocar-dium; independent of hypertension, coronary artery disease, or any other known cardiac diseases, leading to HF, with LVH as the main structural hall mark for it. Several factors have been documented in its pathogenesis; in obese insulin resistant FGF-23 a bone derived hormone can be involved .The role of vitamin D, has gained much attention over the last years as a potential therapeutic agent for prevention of insulin resistance and its protective role against ventricular hypertrophy.
Aim of Study: Was to evaluate the potential effect of vitamin D as a protective factor against the development of LVH in experimentally induced insulin resistance in rats using the level of FGF-23 as a predictor and cardiac tissue hydrox-yproline as a biomarker for cardiac affection.
Material and Methods: This study was conducted on 60 male albino rats divided randomly into four equal groups as follow group I (normal control group), group II (vitamin D treated control group), group III (high sucrose subjected group) and group IV (vitamin D co-treated high sucrose subjected group). In order to induce insulin resistance and cardiomyopathy both third and fourth groups were allowed to get free access to 35% sucrose as their drinking water for 16 weeks, during induction of insulin resistance cardiomyop-athy by sucrose in the fourth group rats were co-treated by giving vitamin D orally in a dose (1000IU/kg) dissolved in 1ml olive oil, given every other day by gavage for 12 weeks. At the end of the experiment blood samples were collected by cardiac puncture after ether anesthesia, chest and abdomen were opened and the heart was extracted. All groups were subjected to estimation of: Serum measurement of fasting glucose level using colorimetric assay and fasting insulin level by rat insulin ELISA kit to asses insulin resistance using (HOMA-IR index). Also, serum FGF-23 by rat FGF-23 ELISA kit as well as left ventricular tissue hydroxyproline content using colorimetric assay. Histopathological examination of the left ventricle specimens was done.
Results: There were statistically significant differences between group III compared to other groups (I, II, IV), regarding fasting serum glucose, serum insulin, HOMA-IR, serum FGF-23 hydroxyproline content of the left ventricle. These parameters were significantly increased in high sucrose subjected group compared to other groups. Also, histopatho-logical study confirmed the biochemical findings.
Conclusion: Vitamin D helped to ameliorate metabolic derangement in IR and the associated left ventricular hyper-trophy directly and through modifying FGF-23 levels.