INSULIN RESISTANCE AND PATHOGENESIS OF POSTMENOPAUSAL OSTEOPOROSIS.

Osteoporosis (OP) is a disease predisposing postmenopausal women to fractures, and often accompanied by insulin resistance (IR) and metabolic syndrome (MetS). Previous studies provided contradictory results concerning prevalence of MetS in postmenopausal OP. To better understand the pathogenesis of IR, we reviewed cellular and molecular aspects and systematically reviewed studies providing homeostasis model assessment (HOMA) index. Bone is an active endocrine organ maintaining its integrity by orchestrated balance between bone formation and resorption. Both osteoblasts and osteoclasts contain receptors for insulin and insulin-like growth factor-1 (IGF-1) operating in skeletal development and in the adult life. Defects in this system generate systemic IR and bone-specific IR, which in turn regulates glucose homeostasis and energy metabolism through osteocalcin. Examination of genetic syndromes of extreme IR revealed intriguing features namely high bone mineral density (BMD) or accelerated growth. Studies of moderate forms of IR in postmenopausal women reveal positive correlations between HOMA index and BMD while correlations with osteocalcin were rather negative. The relation with obesity remains complex involving regulatory factors such as leptin and adiponectin to which the contribution of potential genetic factors and in particular, the correlation with the degree of obesity or body composition should be added.

THE INVOLVEMENT OF VDR PROMOTER METHYLATION, CDX-2 VDR POLYMORPHISM AND VITAMIN D LEVELS IN MALE INFERTILITY.

INTRODUCTION: Vitamin D (VD) levels were correlated with different health conditions, including reproductive disorders in males. Vitamin D action is mediated through vitamin D receptor (VDR), which acts as a transcription factor. VDR gene promoter is embedded in a GC-rich island. The VDR gene has been shown to have several polymorphisms that affect the receptor function. AIM: To examine the relationship between Cdx-2 polymorphism (rs17883968), the methylation status of VDR's promoter and serum levels of 25-hydroxyvitamin D in male infertility. PATIENTS AND METHODS: A total of 69 infertile men and 37 age-matched controls were enrolled in this study. Vitamin D level assessments were detected using the electrochemiluminescent method. Cdx-2 VDR polymorphism identification was performed by PCR on DNA samples from blood, followed by restriction. Methylation of VDR gene promoter was assessed by qMS-PCR using bisulfite-treated DNA from fresh sperm. RESULTS: Vitamin D levels was found to be significantly decreased in infertile groups compared the controls (p=0.0279). The GG genotype was found in a higher percentage in controls and the AA genotype was higher in infertile group (p=0.0056). Infertile homozygote (GG) and heterozygote (GA) individuals had significantly higher vitamin D levels than AA homozygote. Methylation is higher in individuals with lower vitamin D levels and AA genotype is characterized by higher methylation values. CONCLUSION: The results provide new insights of Cdx-2 polymorphism is involved in vitamin D deficiency, highlighting the important role of epigenetic modification of vitamin D receptor and male infertility along with the genetic context.