Felicia Hanzu

Histone Demethylase LSD1 Regulates Adipogenesis

Epigenetic mechanisms, in particular the enzymatic modification of histones, are a crucial element of cell differentiation, a regulated process that allows a precursor cell basically to turn into a different cell type while maintaining the same genetic equipment. We have previously described that the promoters of adipogenic genes display significant levels of dimethylation at the Lys4 of histone H3 (H3K4) in preadipocytes, where these genes are still silenced, thus maintaining the chromatin of the precursor cell in a receptive state. Here, we show that the expression of several histone demethylases and methyltransferases increases during adipogenesis, suggesting an important role for these proteins in this process. Knockdown of the H3K4/K9 demethylase LSD1 results in markedly decreased differentiation of 3T3-L1 preadipocytes. This outcome is associated with decreased H3K4 dimethylation and increased H3K9 dimethylation at the promoter of transcription factor cebpa, whose expression must be induced >200-fold upon stimulation of differentiation. Thus, our data suggest that LSD1 acts to maintain a permissive state of the chromatin in this promoter by opposing the action of a H3K9 methyltransferase. Knockdown of H3K9 methyltransferase SETDB1 produced the opposite results, by decreasing H3K9 dimethylation and increasing H3K4 dimethylation levels at the cebpa promoter and favoring differentiation. These findings indicate that the histone methylation status of adipogenic genes as well as the expression and function of the proteins involved in its maintenance play a crucial role in adipogenesis.

FTO gene associates to metabolic syndrome in women with polycystic ovary syndrome

The FTO (Fat mass and obesity associated) locus has recently been associated with obesity and type 2 diabetes (T2D) in humans. To understand the role of the FTO gene in polycystic ovary syndrome (PCOS) we genotyped single nucleotide polymorphism (SNP) rs1421085 (C/T) in women with PCOS (n=207) and controls (n=100) from a Central European population. The homozygous C/C genotype showed increased prevalence in PCOS patients either obese or with metabolic syndrome (MetS) compared to lean PCOS patients or controls (27.6%, 38.9%, 22.3%, and 16.3%, respectively). In logistic regression, this genotype strongly associated with MetS (P<0.0001, OR 3.2, 95% CI 1.8-5.7) and impaired fasting glucose (IFG) with P<0.0007, OR 7.7, 95% CI 2.1-28.6, independently of BMI or age, and to AUC(gluc) during OGTT (P<0.0001, alpha=0.99), indicating an influential role of the FTO gene in the glucose intolerance component of MetS.

Role of IGFBP-3 in the Regulation of β-Cell Mass during Obesity: Adipose Tissue/β-Cell Cross Talk

In obesity an increase in β-cell mass occurs to cope with the rise in insulin demand. This β-cell plasticity is essential to avoid the onset of hyperglycemia, although the molecular mechanisms that regulate this process remain unclear. This study analyzed the role of adipose tissue in the control of β-cell replication. Using a diet-induced model of obesity, we obtained conditioned media from three different white adipose tissue depots. Only in the adipose tissue depot surrounding the pancreas did the diet induce changes that led to an increase in INS1E cells and the islet replication rate. To identify the factors responsible for this proliferative effect, adipose tissue gene expression analysis was conducted by microarrays and quantitative RT-PCR. Of all the differentially expressed proteins, only the secreted ones were studied. IGF binding protein 3 (Igfbp3) was identified as the candidate for this effect. Furthermore, in the conditioned media, although the blockage of IGFBP3 led to an increase in the proliferation rate, the blockage of IGF-I receptor decreased it. Taken together, these data show that obesity induces specific changes in the expression profile of the adipose tissue depot surrounding the pancreas, leading to a decrease in IGFBP3 secretion. This decrease acts in a paracrine manner, stimulating the β-cell proliferation rate, probably through an IGF-I-dependent mechanism. This cross talk between the visceral-pancreatic adipose tissue and β-cells is a novel mechanism that participates in the control of β-cell plasticity.

Differential Methylation of TCF7L2 Promoter in Peripheral Blood DNA in Newly Diagnosed, Drug-Naïve Patients with Type 2 Diabetes

TCF7L2 is the susceptibility gene for Type 2 diabetes (T2D) with the largest effect on disease risk that has been discovered to date. However, the mechanisms by which TCF7L2 contributes to the disease remain largely elusive. In addition, epigenetic mechanisms, such as changes in DNA methylation patterns, might have a role in the pathophysiology of T2D. This study aimed to investigate the differences in terms of DNA methylation profile of TCF7L2 promoter gene between type 2 diabetic patients and age- and Body Mass Index (BMI)- matched controls. We included 93 type 2 diabetic patients that were recently diagnosed for T2D and exclusively on diet (without any pharmacological treatment). DNA was extracted from whole blood and DNA methylation was assessed using the Sequenom EpiTYPER system. Type 2 diabetic patients were more insulin resistant than their matched controls (mean HOMA IR 2.6 vs 1.8 in controls, P<0.001) and had a poorer beta-cell function (mean HOMA B 75.7 vs. 113.6 in controls, P<0.001). Results showed that 59% of the CpGs analyzed in TCF7L2 promoter had significant differences between type 2 diabetic patients and matched controls. In addition, fasting glucose, HOMA-B, HOMA-IR, total cholesterol and LDL-cholesterol correlated with methylation in specific CpG sites of TCF7L2 promoter. After adjustment by age, BMI, gender, physical inactivity, waist circumference, smoking status and diabetes status uniquely fasting glucose, total cholesterol and LDL-cholesterol remained significant. Taken together, newly diagnosed, drug-naïve type 2 diabetic patients display specific epigenetic changes at the TCF7L2 promoter as compared to age- and BMI-matched controls. Methylation in TCF7L2 promoter is further correlated with fasting glucose in peripheral blood DNA, which sheds new light on the role of epigenetic regulation of TCF7L2 in T2D.

Cirugía endoscópica endonasal en tumores de hipófisis. Resultados en una serie de 121 casos operados en un mismo centro y por un mismo neurocirujano

INTRODUCTION Pituitary adenomas account for approximately 15% of intracranial benign tumors. The neurosurgical results achieved since the endoscopic endonasal transsphenoidal (EET) approach was introduced in our center in 2005 are reported here. PATIENTS AND METHODS A retrospective analysis of 121 patients with sellar lesions (58% females, age 55.7 ± 16 years, range 18-82) who underwent EET surgery from February 2005 to January 2012 and were followed up for a mean time of 4.58 years (range 1.08-8.58). RESULTS Six Rathke cleft cysts (3 intra-suprasellar, 1 intrasellar, 2 suprasellar); 114 pituitary adenomas (16 microadenomas, 98 macroadenomas), and 1 case of normal MRI were included. Baseline findings included hormonal changes in 59 patients (48,7%) and visual field changes in 38 patients (31%); in 7 patients (5.8%), clinical presentation was pituitary apoplexy. Complete resection was achieved in 77 patients (63.6%), subtotal resection in 29 (23.9%), and partial resection in 15 (12.3%). In patients with Grade 3 and 4 cavernous sinus invasion, resection was subtotal in 30% (12/39) and complete in 46% (18/39). Hormonal remission was achieved in 16 patients with Cushing disease (84%), 18 patients with prolactinoma (78.2%), and 18 patients with acromegaly (85,7%). There were 12 cases (9%) of cerebrospinal fluid leak, 4 cases of diabetes insipidus, and 3 cases with transient SIADH/hyponatremia. Seven patients developed panhypopituitarism. Postoperative mortality rate was 2.4%. One hundred and three patients (85.3%) were discharged from the hospital less than 48 hours after surgery. CONCLUSION Our results are similar to those reported by renowned pituitary units. Results achieved using an endoscopic approach in pituitary neurosurgery are better than those of microneurosurgery for cavernous sinus invasion.

Effect of cross-sex hormone treatment on cardiovascular risk factors in transsexual individuals. Experience in a specialized unit in Catalonia

BACKGROUND AND AIMS Since the onset of cross hormone therapy (CHT) in transsexual individuals, there has been concern about possible chronic side effects. Our objective was to assess baseline differences in lipid profile in individuals with gender identity disorder in relation to prior CHT, and changes in the lipid profile and other cardiovascular (CV) risk factors after 24 months of treatment. METHODS Retrospective longitudinal study including all individuals assisted for the first time in the Gender Identity Unit of Catalonia from 2006 to 2010. Socio-demographical, anthropometric and laboratory data were collected. RESULTS We evaluated 247 transsexuals, 150 male to female (MtF: 60.7%) and 97 female to male (FtM; 39.3%). At baseline, FtM transsexuals were younger and had started prior CHT less often than MtF (13.4% vs. 64.7%; p<0.001). During follow up, in MtF weight and BMI increased significantly, as well as systolic and diastolic blood pressure, though these latter remained within normal range. No significant differences in lipid profile were observed. FtM transsexuals also presented an increase in weight and BMI, without differences in blood pressure. A general worsening in lipid profile was observed in this group, with increased total cholesterol (166.0 ± 35.1 vs. 175.6 ± 38.2mg/dL; p=0.001), triglycerides (70.6 ± 30.7 vs. 102.3 ± 68.5 mg/dL; p<0.001) and LDL cholesterol (103.8 ± 28.7 vs. 112.8 ± 30.3 mg/dL; p=.013) and decreased HDL cholesterol (52.2 ± 12.2 vs. 45.4 ± 13.8 mg/dL; p=0.001), even though final levels were all within normal range. CONCLUSION There is no detectable increase in CV risk factors in MtF transsexuals who were treated with currently prescribed estrogenic compounds, while a slight worsening in lipid profile takes place in the FtM group, though within normal limits.

Expression of TMEM16A and SLC4A4 in human pancreatic islets.

Background/aims: Stimulation of insulin release by D-glucose is accompanied by Cl- and HCO3- efflux from pancreatic islet cells. The efflux of these anions may involve volume-regulated anion channels, including possibly TMEM16A, and the Na+-HCO3--cotransporter SLC4A4. The present study was designed to explore the expression of both TMEM16A and SLC4A4 in human pancreatic islets. Methods: Pancreases were obtained from human cadaveric donors. Immunodetection of TMEM16A and SLC4A4 was performed by immunohistochemistry on sections of fixed pancreas, while real-time PCR for the study of corresponding gene expression was performed on RNA extracted from both total pancreatic pieces and isolated pancreatic islets. Results: RT-PCR yielded lower levels of SLC4A4 in isolated islets than in the total pancreas, whilst a mirror image prevailed for TMEM16A mRNA. Immunohistochemistry of human pancreas, however, indicated comparable immunostaining of SLC4A4 in insulin-producing cells and exocrine pancreatic cells, whilst that of TMEM16A appeared less pronounced in insulin-producing cells than in exocrine cells. Conclusion: The present findings support the view that, in humans like in rodent, the regulation of anion fluxes in insulin-producing cells may involve both SLC4A4 and TMEM16A.

Association of insulin receptor genetic variants with polycystic ovary syndrome in a population of women from Central Europe

To assess the role of the insulin receptor gene in polycystic ovary syndrome (PCOS) we performed a case-control study in a female population (n=226) from Central Europe by examining the genetic associations of single nucleotide polymorphisms (rs8107575, rs2245648, rs2245649, rs2963, rs2245655, and rs2962) and inferred haplotypes around exon 9 of this gene. The ancestral T allele of single nucleotide polymorphism rs2963 or the corresponding haplotype (GGTC-C) showed association with PCOS with odds ratio 2.99, 95% confidence interval 1.4-6.3, independent of obesity but related to the presence of Acanthosis nigricans and insulin resistance, metabolic syndrome, or hyperandrogeny, thus providing a frame for future fine mapping of the susceptibility loci in PCOS.

Urinary cysteinyl progestogens: Occurrence and origin.

The presence of two cysteinyl progestogens, 16-cysteinyl-progesterone (16-Cys-Prog) and 16-cysteinyl-pregnenolone (16-Cys-Preg), in human urine is described for the first time. Their occurrence was unequivocally confirmed by comparison with synthesized material by using mass spectrometric detectors. Several experiments were performed in order to clarify their origin. The adrenal origin of both 16-Cys-Prog and 16-Cys-Preg can be inferred from the increase in their concentrations after ACTH stimulatory test, together with their circadian variation similar to the one observed for cortisol. Moreover, the notable increase in excretions of 16-Cys-Prog during the luteal phase of the menstrual cycle points towards an ovarian production for this progestogen. However, the analysis of samples during the course of two pregnancies revealed that, in spite of the large amounts of progesterone produced during gestation, the human placenta lacks the capacity to make 16-Cys-Prog. The adrenal and ovarian origin has been further indicated by the absence of both metabolites in samples collected from a subject with bilateral adrenalectomy and hypogonadotrophyic hypogonadism. Regarding liver action, in vitro studies with hepatocytes and progesterone indicate that, although the liver is able to metabolize progesterone to 6-dehydroprogesterone, it has not the enzymatic machinery for the generation of 16-dehydroprogesterone. Taken together, these results open the possibility for a noninvasive test for the simultaneous evaluation of progesterone biosynthesis in different organs.

Gastric Inhibitory Polypeptide Receptor Methylation in Newly Diagnosed, Drug-Naïve Patients with Type 2 Diabetes: A Case-Control Study

GIP action in type 2 diabetic (T2D) patients is altered. We hypothesized that methylation changes could be present in GIP receptor of T2D patients. This study aimed to assess the differences in DNA methylation profile of GIPR promoter between T2D patients and age- and Body Mass Index (BMI)-matched controls. We included 93 T2D patients (cases) that were uniquely on diet (without any anti-diabetic pharmacological treatment). We matched one control (with oral glucose tolerance test negative, non diabetic), by age and BMI, for every case. Cytokines and hormones were determined by ELISA. DNA was extracted from whole blood and DNA methylation was assessed using the Sequenom EpiTYPER system. Our results showed that T2D patients were more insulin resistant and had a poorer β cell function than their controls. Fasting adiponectin was lower in T2D patients as compared to controls (7.0±3.8 µgr/mL vs. 10.0±4.2 µgr/mL). Levels of IL 12 in serum were almost double in T2D patients (52.8±58.3 pg/mL vs. 29.7±37.4 pg/mL). We found that GIPR promoter was hypomethylated in T2D patients as compared to controls. In addition, HOMA-IR and fasting glucose correlated negatively with mean methylation of GIPR promoter, especially in T2D patients. This case-control study confirms that newly diagnosed, drug-naïve T2D patients are more insulin resistant and have worse β cell function than age- and BMI-matched controls, which is partly related to changes in the insulin-sensitizing metabolites (adiponectin), in the proinflammatory profile (IL12) and we suggest in the methylation pattern of GIPR. Our study provides novel findings on GIPR promoter methylation profile which may improve our ability to understand type 2 diabetes pathogenesis.