Investigation of relationship of the mitochondrial DNA 16189 T>C polymorphism with metabolic syndrome and its associated clinical parameters in Turkish patients.

OBJECTIVE: Mitochondrial DNA (mtDNA) polymorphisms have been implicated in the pathophysiology of human diseases. Among them, a T>C nucleotide transition on the 16189 nucleotide position of mtDNA has been studied in several metabolic diseases including diabetes and obesity. In this study we aimed to investigate the association of this polymorphism among Turkish metabolic syndrome patients. DESIGN: A total of 220 cases (70 MetS patients and 150 healthy control subjects) were evaluated for their mtDNA 16189 variant by PCR-RFLP technique. In addition, clinical and biochemical variables, such as cholesterol levels, body fat percentage, insulin resistance and presence of type II diabetes, were also evaluated. RESULTS: Overall frequency of polymorphic C allele was determined as 0.19 without a significant association with type II diabetes and metabolic syndrome. This may be partly due to ethnical differences of populations studied and may also be related to other genetic and environmental factors. Moreover, there were no significant associations with biochemical variables among metabolic syndrome patients, except LDL and suppressed cortisol (sup-cortisol) levels. Low levels of LDL and sup-cortisol were significantly associated with the mtDNA 16189 variant, though the biochemical mechanism underlying this effect is not clear. CONCLUSIONS: This is the first study involving a Turkish population on the mtDNA 16189 T>C polymorphism. Further studies with larger cohorts will be needed to elucidate its relation with metabolic syndrome as well as lipid metabolism.

Mitochondrial DNA common deletion is not associated with thyroid, breast and colorectal tumors in Turkish patients.

Recently, efforts have been focused on mitochondrial DNA changes and their relation to human cancers. Among them, a 4977 bp deletion of mitochondrial DNA, named "common deletion", has been investigated in several types of tumors, with inconsistent results. In this study, we investigated the presence of the common deletion in tissues from 25 breast, 25 colorectal and 50 thyroid tumors and in the adjacent healthy tissues from Turkish patients. Samples from healthy volunteers were also evaluated for comparison. Two PCR-based methods were used for the detection of the common deletion. First, two pairs of primers were used to amplify wild-type and deleted mtDNA. Then, a highly sensitive nested-PCR was performed, to determine low amounts of deleted genomes. By the first method, wild-type mtDNAs were observed in all samples, but a deletion was observed in only six thyroid samples, by using the nested-PCR method. In conclusion, the mitochondrial common deletion was very rare in our study group and did not appear to be not related with cancer.

Mitochondrial DNA common deletion is not associated with thyroid, breast and colorectal tumors in Turkish patients

Recently, efforts have been focused on mitochondrial DNA changes and their relation to human cancers. Among them, a 4977 bp deletion of mitochondrial DNA, named "common deletion", has been investigated in several types of tumors, with inconsistent results. In this study, we investigated the presence of the common deletion in tissues from 25 breast, 25 colorectal and 50 thyroid tumors and in the adjacent healthy tissues from Turkish patients. Samples from healthy volunteers were also evaluated for comparison. Two PCR-based methods were used for the detection of the common deletion. First, two pairs of primers were used to amplify wild-type and deleted mtDNA. Then, a highly sensitive nested-PCR was performed, to determine low amounts of deleted genomes. By the first method, wild-type mtDNAs were observed in all samples, but a deletion was observed in only six thyroid samples, by using the nested-PCR method. In conclusion, the mitochondrial common deletion was very rare in our study group and did not appear to be not related with cancer.

The effect of subclinical hypothyroidism on platelet parameters.

BACKGROUND: Hypothyroidism has a broad clinical spectrum. Today, physicians frequently encounter patients with very mild thyroid dysfunction instead of overt hypothyroidism. These patients have normal serum levels of thyroxine and triiodothyronine and only mildly elevated serum thyrotropin levels. Such patients are often identified through routine screening or in the course of an evaluation of common nonspecific symptoms. On the other hand, coronary heart disease is the leading cause of death in developed countries. There are studies, which suggest platelets play a role in the pathogenesis of atherosclerosis and coronary heart disease. AIM: The aim of this study is to compare the platelet count and other platelet parameters in subclinical hypothyroidic and euthyroidic healthy control group and to investigate whether these parameters have a predictive significance in patients with subclinical hypothyroidism. MATERIALS AND METHODS: Forty-seven patients with subclinical hypothyroidism and 30 euthyroidic healthy control group were enrolled into the study. RESULTS: Patients with subclinical hypothyroidism had higher mean platelet volume (MPV) and platelet distribution width (PDW) values than control group, which were statistically significant (p<0.001 and p<0.001), respectively. CONCLUSION: Our results indicate that MPV and PDW play an important predictive role in subclinical hypothyroidism.

Analysis of DAX1 (NR0B1) and steroidogenic factor-1 (NR5A1) in children and adults with primary adrenal failure: ten years' experience.

CONTEXT: Primary adrenal failure is a life-threatening condition that can be caused by a range of etiologies, including autoimmune, metabolic, and developmental disorders. The nuclear receptors DAX1 (NR0B1) and steroidogenic factor-1 (SF1/Ad4BP, NR5A1) play an important role in adrenal development and function, and mutations in these transcription factors have been found in patients with adrenal hypoplasia. OBJECTIVE: Our objective was to investigate the prevalence of DAX1 and SF1 mutations in children and adults with primary adrenal failure of unknown etiology (i.e. not caused by congenital adrenal hyperplasia, adrenoleukodystrophy, or autoimmune disease). PATIENTS: One hundred seventeen patients were included. Eighty-eight individuals presented in infancy or childhood with adrenal hypoplasia or primary adrenal failure of unknown etiology (n = 64 46,XY phenotypic males; n = 17 46,XY gonadal dysgenesis/impaired androgenization; n = 7 46,XX females). Twenty-nine individuals presented in adulthood with Addison's disease of unknown etiology. METHODS: Mutational analysis of DAX1 (NR0B1) (including exon 2alpha/1A) and SF1 (NR5A1) was done by direct sequencing. RESULTS: DAX1 mutations were found in 58% (37 of 64) of 46,XY phenotypic boys referred with adrenal hypoplasia and in all boys (eight of eight) with hypogonadotropic hypogonadism and a family history suggestive of adrenal failure in males. SF1 mutations causing adrenal failure were found in only two patients with 46,XY gonadal dysgenesis. No DAX1 or SF1 mutations were identified in the adult-onset group. CONCLUSIONS: DAX1 mutations are a relatively frequent cause of adrenal failure in this group of boys. SF1 mutations causing adrenal failure in humans are rare and are more likely to be associated with significant underandrogenization and gonadal dysfunction in 46,XY individuals.

Battle of the sexes: new insights into genetic pathways of gonadal development.

Sex determination is governed by a series of genetic switches that influence cell fate and differentiation during critical periods of gonadal development. Remarkably, the primordial fetal gonad is bipotential. Therefore, gonadal development provides an excellent opportunity to identify genes involved in differential organogenesis. The identification of the testis-determining gene, SRY (Sex-reversed on the Y), was a pivotal first step towards unraveling this genetic pathway. It is now clear that numerous other genes, in addition to SRY, are necessary for normal testis development. For example, human mutations in a variety of genes (SOX9, WT1, SF1) impair testis development. Murine models provide evidence for additional genes (Lhx9, Emx2, M33, Dmrt, Fgf9). This lecture will highlight insights gleaned from human mutations in the nuclear receptors, SF1 (Steroidogenic Factor1) (NR5A1) and DAX1 (Dosage-sensitive sex reversal, Adrenal hypoplasia congenita, X chromosome) (NR0B1). These studies reveal the exquisite sensitivity of SF1-dependent developmental pathways to gene dosage and function in humans.

SF1 in the development of the adrenal gland and gonads.

SF1 (steroidogenic factor-1; NR5A1) is an orphan nuclear receptor that is expressed in the adrenal gland, gonads, spleen, ventromedial hypothalamus and pituitary gonadotroph cells. Combined approaches of targeted mutagenesis in mice and examination of the effects of naturally occurring mutations in humans have clarified the role of SF1 in steroidogenesis and development. Targeted disruption of SF1 (FTZF1) in mice prevents gonadal and adrenal development and causes male-to-female sex reversal. A heterozygous loss-of-function human SF1 mutation (G35E) was described in a patient with adrenal failure and complete 46,XY sex reversal, indicating that haploinsufficiency of this transcription factor is sufficient to cause a severe clinical phenotype. In an infant with a similar clinical phenotype, a homozygous SF1 mutation (R92Q) was identified. In functional assays, this mutant SF1 protein exhibited partial loss of DNA binding and transcriptional activity when compared with the more severe G35E P-box mutant. These patients reveal the exquisite sensitivity of SF1-dependent developmental pathways to gene dosage and function in humans.

A novel single base deletion at codon 434 (1301delT) of the DAX1 gene associated with prepubertal testis enlargement.

We have identified a novel DAX1 frameshift mutation (1301delT) at codon 434 in a patient with primary adrenal insufficiency. This 11-day-old boy was admitted to the hospital with hyponatremia, hyperkalemia, and suspected congenital adrenal abnormality. He exhibited severe hypoglycemia, pallor of the skin, buccal and genital hyperpigmentation, hypotension (90/45 mm Hg), anemia, and diarrhea. Although basal gonadotropins were low, and responded minimally to exogenous GnRH, the size of his testes began to increase at age 4 and reached 4.5 mL at the age of 9 years and 8 months. Testosterone levels were prepubertal. These findings further emphasize the variable clinical presentation in children with DAX1 gene mutations and indicate the value of genetic testing in boys with primary adrenal insufficiency.

An alternate translation initiation site circumvents an amino-terminal DAX1 nonsense mutation leading to a mild form of X-linked adrenal hypoplasia congenita.

Mutations in DAX1 [dosage-sensitive sex reversal-adrenal hypoplasia congenita (AHC) critical region on the X chromosome gene 1; NR0B1] cause X-linked AHC, a disease characterized by primary adrenal failure in infancy or childhood and reproductive abnormalities later in life. Most of these patients have nonsense or frameshift mutations that cause premature truncation of the DAX1 protein, thereby eliminating its transcriptional silencing activity. We evaluated a patient with an unusual form of AHC manifest as late-onset adrenal insufficiency and gonadal failure. DNA sequence analysis revealed a novel amino-terminal DAX1 nonsense mutation (Q37X), predicted to cause a severe truncation of the protein. Using a combination of in vitro translation assays and studies of DAX1 expression and function in transfected cells, we demonstrate that, in contrast to more distal mutations leading to a nonfunctional protein, this mutation is associated with a milder phenotype due to the expression of a partially functional, amino-truncated DAX1 protein generated from an alternate in-frame translation start site (methionine, codon 83). The production of this amino-truncated isoform appears to rescue the classical AHC phenotype, thereby delaying the onset of clinically significant adrenal dysfunction until early adulthood. Thus, this case demonstrates a relatively rare phenomenon by which the clinical severity of an inherited human disease is reduced after alternate translation from a site downstream of a premature stop codon.

The role of SF1 in adrenal and reproductive function: insight from naturally occurring mutations in humans.

Steroidogenic factor 1 is a monomeric orphan nuclear receptor and one of several hundreds of transcription factors encoded in the human genome. It regulates the transcription of many genes involved in gonadal development, sexual differentiation, steroidogenesis and reproduction. Recently, mutations in the gene encoding SF1 have been identified in several patients with primary adrenal failure and 46,XY sex-reversal. Interpreting the consequences of these mutations provides further understanding of transcription factor haploinsufficiency in human genetic disease as well as the exquisite sensitivity of humans to gene-dosage effects during adrenal and gonadal development.

Gonadal determination and adrenal development are regulated by the orphan nuclear receptor steroidogenic factor-1, in a dose-dependent manner.

The orphan nuclear receptor steroidogenic factor-1 (SF-1, NR5A1) regulates the transcription of multiple genes involved in steroidogenesis, reproduction, and male sexual differentiation. A heterozygous loss-of-function SF-1 mutation (G35E) has been described in a patient with adrenal failure and complete 46XY sex-reversal, indicating that haploinsufficiency of this factor is sufficient to cause a severe clinical phenotype. This mutation in the P-box region of the DNA-binding domain markedly impairs SF-1 binding to most response elements. In an infant with a similar clinical phenotype, we identified an SF-1 mutation (R92Q) in a highly conserved residue of the A-box, a region that functions as a secondary DNA-binding domain. Strikingly, the affected infant was homozygous for the R92Q mutation, but three relatives (parents, sister) were phenotypically normal despite being heterozygous for the mutation. In functional assays, the R92Q mutant exhibited partial loss of DNA binding and transcriptional activity when compared with the G35E P-box change, consistent with its phenotypic expression only when transmitted as a homozygous trait. Taken together, these two naturally-occurring SF-1 mutations reveal the relative functional importance of the P-box and A-box regions for monomeric binding by nuclear receptors. In addition, these patients reveal the exquisite sensitivity of SF-1-dependent developmental pathways to gene dosage and function in humans.

Hypogonadotropic hypogonadism as a presenting feature of late-onset X-linked adrenal hypoplasia congenita.

Mutations in the orphan nuclear receptor DAX-1 cause X-linked adrenal hypoplasia congenita. Affected boys usually present with primary adrenal failure in early infancy or childhood. Impaired sexual development because of hypogonadotropic hypogonadism becomes apparent at the time of puberty. We report adult-onset adrenal hypoplasia congenita in a patient who presented with hypogonadism at 28 yr of age. Although he had no clinical evidence of adrenal dysfunction, compensated primary adrenal failure was diagnosed by biochemical testing. Semen analysis showed azoospermia, and he did not achieve fertility after 8 months of treatment with gonadotropins. A novel Y380D DAX-1 missense mutation, which causes partial loss of function in transient gene expression assays, was found in this patient. This case demonstrates that partial loss-of-function mutations in DAX1 can present with hypogonadotropic hypogonadism and covert adrenal failure in adulthood. Further, an important role for DAX-1 in spermatogenesis in humans is confirmed, supporting findings in the Dax1 (Ahch) knockout mouse.