The vitamin D receptor (VDR) start codon polymorphism in primary hyperparathyroidism and parathyroid VDR messenger ribonucleic acid levels

Epigenetics meets endocrinology

Although genetics determines endocrine phenotypes, it cannot fully explain the great variability and reversibility of the system in response to environmental changes. Evidence now suggests that epigenetics, i.e. heritable but reversible changes in gene function without changes in nucleotide sequence, links genetics and environment in shaping endocrine function. Epigenetic mechanisms, including DNA methylation, histone modification, and microRNA, partition the genome into active and inactive domains based on endogenous and exogenous environmental changes and developmental stages, creating phenotype plasticity that can explain interindividual and population endocrine variability. We will review the current understanding of epigenetics in endocrinology, specifically, the regulation by epigenetics of the three levels of hormone action (synthesis and release, circulating and target tissue levels, and target-organ responsiveness) and the epigenetic action of endocrine disruptors. We will also discuss the impacts of hormones on epigenetics. We propose a three-dimensional model (genetics, environment, and developmental stage) to explain the phenomena related to progressive changes in endocrine functions with age, the early origin of endocrine disorders, phenotype discordance between monozygotic twins, rapid shifts in disease patterns among populations experiencing major lifestyle changes such as immigration, and the many endocrine disruptions in contemporary life. We emphasize that the key for understanding epigenetics in endocrinology is the identification, through advanced high-throughput screening technologies, of plasticity genes or loci that respond directly to a specific environmental stimulus. Investigations to determine whether epigenetic changes induced by today's lifestyles or environmental 'exposures' can be inherited and are reversible should open doors for applying epigenetics to the prevention and treatment of endocrine disorders.

Regulatory role of promoter and 3' UTR variants of vitamin D receptor gene on cytokine response in pulmonary tuberculosis

Vitamin D receptor (VDR) gene variants are shown to regulate immune response in tuberculosis. We studied the influence of VDR promoter (Cdx-2 and A1012G), 3' untranslated region (Apa I, Bsm I, and Taq I) and start codon (Fok I) polymorphisms on 1,25(OH)(2)D(3)-modulated IL-12p40, IFN-gamma, IL-10, and IL-5 response to live Mycobacterium tuberculosis and its culture filtrate antigen (CFA) in 60 normal healthy subjects and 51 pulmonary tuberculosis patients. In peripheral blood mononuclear cell cultures with CFA and 1,25(OH)(2)D(3), IL-12p40, and IFN-gamma levels were significantly decreased (p < 0.05) and IL-10 levels were significantly increased (p < 0.05) in patients with GG genotype. The extended genotype bbaaTT (baT haplotype) was associated with decreased IL-12p40 and IFN-gamma levels and significantly increased IL-10 levels (p < 0.05). The Cdx-2 GG genotype and baT haplotype are associated with a suppressed Th1 and increased IL-10 response, which suggests that 1,25(OH)(2)D(3) probably through the VDR polymorphic variants augments the anti-inflammatory response at the site of M. tuberculosis infection.

Renal stone disease, elevated iPTH level and normocalcemia

BACKGROUND

There is a well established relationship between primary hyperparathyroidism and recurrent calcium-containing calculi. Traditionally, the diagnosis is confirmed by the presence of elevated intact parathyroid hormone (iPTH) and serum ionised calcium levels. The prevalence and role of elevated iPTH in the presence of normocalcemia in patients with renal stone disease is poorly understood. The aim of the present study was to describe the findings in patients who had renal stone disease, an elevated iPTH level and normocalcemia.

METHODS

During the last decade, 414 patients, who had normal renal function, were investigated and treated for renal calculi in the Renal Stone Clinic of the Toronto Western Hospital. Of these 414 patients, 40 (9.6%) had an elevated intact iPTH level and normal serum calcium (total and ionised) on repeated measurements. In all these patients we performed detailed clinical and laboratory investigations to determine risk factors for stone formation. Correlation analysis was done using Pearson test and the weights of factors influencing iPTH level were compared using multiple regression analysis.

RESULTS

The average duration of a history of stone disease was 12.0 +/- 10.5 years. Most of these patients had passed their stones spontaneously, 15 underwent lithotripsy, in six the stones were removed by basket catheters and one patient each had partial nephrectomy, nepholithotomy or uretero-lithotomy. Twelve had a positive family history, two had history of intestinal malabsorption and one patients had a history of immobilisation. All of these patients had elevated serum parathyroid hormone in the range of 3% to 134% (median 20.5%) above upper limit of normal (F = M); all had normal serum total and ionised calcium and normal urine excretion of calcium (except in one). Additional risk factor for stone formation included: low level of 25-hydroxyvitamin D in four patients, low output and high urine osmolality in four patients, high urine sodium in nine and high oxalate excretion in eight patients. Citrate excretion was low in seven, magnesium excretion in six patients and tubular reabsorption of phosphate in 22 patients. Urine hydroxyprolin was increased in two and decreased in four patients. Combined abnormalities were found in 14 while 17 patients did not have any abnormality apart from elevated iPTH level. Multiple regression analysis did not suggest that any of the selected predictors had a significant influence on PTH release.

CONCLUSIONS

9.6% of patients with recurrent kidney stones had normocalcemia and elevated iPTH level in the presence of normal renal function. The study did not show any distinct pattern of abnormalities that would suggest a mechanism of stone disease in these patients. Further investigations are necessary to determine the significance of elevated iPTH in normocalcemic patients with renal stone disease and establish whether we should consider neck exploration for parathyroidectomy in these patients.