Association of tyrosine hydroxylase 01 (TH01) microsatellite and insulin gene (INS) variable number of tandem repeat (VNTR) with type 2 diabetes and fasting insulin secretion in Mexican population.

PURPOSE: A variable number of tandem repeats (VNTR) in the insulin gene (INS) control region may be involved in type 2 diabetes (T2D). The TH01 microsatellite is near INS and may regulate it. We investigated whether the TH01 microsatellite and INS VNTR, assessed via the surrogate marker single nucleotide polymorphism rs689, are associated with T2D and serum insulin levels in a Mexican population. METHODS: We analyzed a main case-control study (n = 1986) that used univariate and multivariate logistic regression models to calculate the risk conferred by TH01 and rs689 loci for T2D development; rs689 results were replicated in other case-control (n = 1188) and cross-sectional (n = 1914) studies. RESULTS: TH01 alleles 6, 8, 9, and 9.3 and allele A of rs689 were independently associated with T2D, with differences between sex and age at diagnosis. TH01 alleles with ≥ 8 repeats conferred an increased risk for T2D in males compared with ≤ 7 repeats (odds ratio, ≥ 1.46; 95% confidence interval, 1.1-1.95). In females, larger alleles conferred a 1.5-fold higher risk for T2D when diagnosed ≥ 46 years but conferred protection when diagnosed ≤ 45 years. Similarly, rs689 allele A was associated with T2D in these groups. In males, larger TH01 alleles and the rs689 A allele were associated with a significant decrease in median fasting plasma insulin concentration with age in T2D cases; the reverse occurred in controls. CONCLUSION: Larger TH01 alleles and rs689 A allele may potentiate insulin synthesis in males without T2D, a process disabled in those with T2D.

Present and past perspectives on Clostridium difficile infection. / Perspectivas históricas y vigentes sobre la infección por Clostridium difficile.

Clostridium difficile is a Gram-positive bacillus that has become one of the main hospital-acquired human gastrointestinal infections in recent years. Its incidence is on the rise, involving more virulent strains, affecting new and previously uncontemplated groups of patients, and producing changes in clinical presentation and treatment response that influence disease outcome. Early diagnosis and disease stratification based on the severity of C.difficile infection are essential for therapeutic management and the implementation of containment measures. However, the speed at which new strains with greater pathogenicity are developing is surpassing that of the development of new drugs, making it necessary to validate other therapeutic options. The present article is a review of the epidemiologic, pathophysiologic, diagnostic, and therapeutic aspects of C.difficile infection, from its first isolation to the present date, that aims to contribute to the preparation of general physicians and specialists, so that patients with this infection receive opportune and quality medical attention.

Los polomorfismos del gen del receptor de la vitamina D (VDR) modulan la respuesta a la vitamina D de forma tejido específica / Vitamin D receptor (VDR) gene polymorphisms modulate the reponse of tissue-specific vitamin D

En los últimos años se ha discutido el posible papel de los polimorfismos en el gen del receptor de la vitamina D en diferentes enfermedades. En este trabajo se revisan diferentes estudios realizados para determinar la influencia de varios polimorfismos del receptor de la vitamina D y del colágeno tipo I sobre diferentes aspectos relacionados con el metabolismo del hueso y de la glándula paratiroides. Los estudios epidemiológicos mostraron que la combinación alélica BAt de los polimorfismos BsmI, ApaI y TaqI del receptor de la vitamina D y el genotipo ss del polimorfismo sp1 del colágeno tipo I son predictores del riesgo de fracturas osteoporóticas. Los estudios experimentales llevados a cabo en los osteoblastos en cultivo indicaron que la combinación alélica baT en el receptor de la vitamina D confiere una mayor sensibilidad del osteoblasto ante el estímulo con calcitriol. Por el contrario, en las glándulas paratiroides en cultivo fue la combinación BAt la que respondió mejor al calcitriol. La combinación alélica más favorable en el hueso no lo es en la glándula paratiroides y viceversa, lo que indicaría un efecto tejido específico del receptor de la vitamina D en la respuesta al calcitriol

In the last years, the likely role of the vitamin D receptor polymorphisms in different diseases has been discussed. In this work we review several studies performed to investigate the influence of the vitamin D receptor polymorphisms and type I collagen in different aspects of bone and parathyroid gland metabolism. On one hand, the epidemiological studies showed that BAt haplotype from BsmI, ApaI and TaqI polymorphisms in the vitamin D receptor and SS genotype in sp1 polymorphism in type I collagen gene predicted the risk for osteoporotic fractures. On the other hand, experimental studies carried out in both human primary osteoblasts and parathyroid glands showed that while baT haplotype responded better to calcitriol in osteoblasts, BAt haplotype showed the best response in parathyroid glands. The most favorable allele combination in the bone is not in the parathyroid gland and vice versa. These findings are indicative of a tissue specific effect of the vitamin D receptor in the response to calcitriol

Pathogenic mechanisms for parathyroid hyperplasia.

Parathyroid hyperplasia is the cause of parathyroid gland enlargement in kidney disease (KD). Hypocalcemia, hyperphosphatemia, and vitamin D deficiency are critical contributors to the worsening of the hyperplastic parathyroid growth induced by KD. Reproduction of the features of human KD in the 5/6 nephrectomized rat model has shown that 80% of the mitogenic signals induced by KD in parathyroid cells that are aggravated by either high phosphate (P) or low calcium (Ca) diets occurred within 5 days after the onset of KD. Enhanced parathyroid expression of the potent growth promoter transforming growth factor alpha (TGFalpha) and its receptor, the epidermal growth factor receptor (EGFR), was identified as the main cause of parathyroid hyperplasia in experimental KD. Indeed, administration of highly specific EGFR-tyrosine kinase inhibitors (TKI), which block downstream signaling from TGFalpha-activated EGFR, completely prevented high P- and low Ca-induced parathyroid hyperplasia in early KD, as well as the severe progression of high P-induced parathyroid growth in established secondary hyperparathyroidism, the latter characterized by marked TGFalpha and EGFR overexpression in the parathyroid glands. More importantly, the suppression of signals downstream from TGFalpha binding to EGFR with EGFR-TKI treatment also revealed that TGFalpha self-upregulation in the parathyroid glands is the main determinant of the severity of the hyperplastic growth, and that enhanced TGFalpha activation of EGFR mediates the reduction in parathyroid vitamin D receptor levels thereby causing resistance to both the antiproliferative and parathyroid hormone-suppressive properties of calcitriol therapy.

Genetics and molecular disorders in severe secondary hyperparathyroidism: lessons from rna and microarray studies.

Secondary hyperparathyroidism-related disorders begin in the pre-dialysis period and progressively worsen during dialysis. In a high proportion of cases, therapeutic failure in the control of PTH secretion is related to a late start in medical treatment. This may happen because recovery of the functional control of the parathyroid gland, once some irreversible molecular and genetic changes have occurred, can be only partial. These irreversible changes include promotion of cell proliferation and failure of several pathways affecting the metabolism of DNA, RNA and proteins.

A novel mutation in the calcium-sensing receptor responsible for autosomal dominant hypocalcemia in a family with two uncommon parathyroid hormone polymorphisms.

A novel missense activating mutation in the extracellular calcium-sensing receptor (CaSR) is reported in this work. It was identified in three related subjects with the phenotypic features of autosomal dominant hypocalcemia (ADH). The proband, a 27-year-old woman, diagnosed as having hypoparathyroidism at 7 years of age and a history of seizures, showed the highest penetrance of the mutation. The remaining two affected members presented asymptomatic chronic hypocalcemia despite severe hypoparathyroidism associated with high levels of serum phosphate and calcium urinary excretion. The missense mutation (Glu(604)Lys) affected an amino acid residue in the C terminus of the cysteine-rich domain of the extracellular amino-terminal domain, which seems to be required for the coupling of ligand binding to the activation of intracellular signaling pathways. This genetic change cosegregated with hypocalcemia in all the individuals where the mutation was found. As parathyroid hormone (PTH) secretion is the regulatory target of the CaSR, polymorphism analysis of the PTH gene was carried out. PTH polymorphisms were analyzed in the kindred studied. Affected members for the Glu(604)Lys CaSR mutation which also carried the uncommon PTH alleles showed higher penetrance of the mutation, with more severe autosomal dominant hypocalcemia. These results suggested that the PTH gene could act as a modifier locus of ADH, affecting the penetrance of the activating CaSR mutation described.