Considerations for Familial Chylomicronemia Diagnosis in the Era of Next-Generation Sequencing: A Latin American Perspective

Abstract Familial chylomicronemia syndrome (FCS) is an autosomal recessive disorder, characterized by alterations in the catabolism of chylomicrons and by increased levels of plasma triglycerides. It has been shown that about 60-90% of FCS patients have biallelic mutations in the LPL gene and the remaining patients have mutations in genes encoding proteins closely related to LPL function. The objective of this manuscript is to illustrate the different clinical scenarios of FCS presentation, and to guide practitioners on the usefulness of genetic tests in each of them. To this end, several published papers about recommendations for the diagnosis of FCS are discussed briefly, in addition to the presentation of several hypothetical cases, highlighting different clinical presentations and possible associated genetic findings. These cases illustrate the multiplicity of potential aspects of family history, clinical manifestations, biochemical parameters, and patterns of genetic variants found in genomic analyses of FCS.

Eating behaviour in contrasting adiposity phenotypes: Monogenic obesity and congenital generalized lipodystrophy.

Most known types of nonsyndromic monogenic obesity are caused by rare mutations in genes of the leptin-melanocortin pathway controlling appetite and adiposity. In contrast, congenital generalized lipodystrophy represents the most extreme form of leanness in humans caused by recessive mutations in four genes involved in phospholipid/triglyceride synthesis and lipid droplet/caveolae structure. In this disease, the inability to store triglyceride in adipocytes results in hypoleptinemia and ectopic hepatic and muscle fat accumulation leading to fatty liver, hypertriglyceridemia and severe insulin resistance. As a result of hypoleptinemia, patients with lipodystrophy show alterations in eating behaviour characterized by constant increased energy intake. As it occurs in obesity caused by genetic leptin deficiency, exogenous leptin rapidly reduces hunger scores in patients with congenital generalized lipodystrophy, with additional beneficial effects on glucose homeostasis and metabolic profile normalization. The melanocortin-4 receptor agonist setmelanotide has been used in the treatment of monogenic obesities. There is only one report on the effect of setmelanotide in a patient with partial lipodystrophy resulting in mild reductions in hunger scores, with no improvements in metabolic status. The assessment of contrasting phenotypes of obesity/leanness represents an adequate strategy to understand the pathophysiology and altered eating behaviour associated with adipose tissue excessive accumulation/paucity.

Genome-wide association study identifying novel variant for fasting insulin and allelic heterogeneity in known glycemic loci in Chilean adolescents: The Santiago Longitudinal Study.

BACKGROUND: The genetic underpinnings of glycemic traits have been understudied in adolescent and Hispanic/Latino (H/L) populations in comparison to adults and populations of European ancestry. OBJECTIVE: To identify genetic factors underlying glycemic traits in an adolescent H/L population. METHODS: We conducted a genome-wide association study (GWAS) of fasting glucose (FG) and fasting insulin (FI) in H/L adolescents from the Santiago Longitudinal Study. RESULTS: We identified one novel variant positioned in the CSMD1 gene on chromosome 8 (rs77465890, effect allele frequency = 0.10) that was associated with FI (ß = -0.299, SE = 0.054, p = 2.72×10-8 ) and was only slightly attenuated after adjusting for body mass index z-scores (ß = -0.252, SE = 0.047, p = 1.03×10-7 ). We demonstrated directionally consistent, but not statistically significant results in African and Hispanic adults of the Population Architecture Using Genomics and Epidemiology Consortium. We also identified secondary signals for two FG loci after conditioning on known variants, which demonstrate allelic heterogeneity in well-known glucose loci. CONCLUSION: Our results exemplify the importance of including populations with diverse ancestral origin and adolescent participants in GWAS of glycemic traits to uncover novel risk loci and expand our understanding of disease aetiology.

Association between indicators of systemic inflammation biomarkers during puberty with breast density and onset of menarche.

BACKGROUND: Systemic inflammation may play a role in shaping breast composition, one of the strongest risk factors for breast cancer. Pubertal development presents a critical window of breast tissue susceptibility to exogenous and endogenous factors, including pro-inflammatory markers. However, little is known about the role of systemic inflammation on adolescent breast composition and pubertal development among girls. METHODS: We investigated associations between circulating levels of inflammatory markers (e.g., interleukin-6 (IL-6), tumor necrosis factor receptor 2 (TNFR2), and C-reactive protein (CRP)) at Tanner stages 2 and 4 and breast composition at Tanner stage 4 in a cohort of 397 adolescent girls in Santiago, Chile (Growth and Obesity Cohort Study, 2006-2018). Multivariable linear models were used to examine the association between breast composition and each inflammatory marker, stratifying by Tanner stage at inflammatory marker measurement. Accelerated failure time models were used to evaluate the association between inflammatory markers concentrations at each Tanner stage and time to menarche. RESULTS: In age-adjusted linear regression models, a doubling of TNFR2 at Tanner 2 was associated with a 26% (95% CI 7-48%) increase in total breast volume at Tanner 4 and a 22% (95% CI 10-32%) decrease of fibroglandular volume at Tanner 4. In multivariable models further adjusted for body fatness and other covariates, these associations were attenuated to the null. The time to menarche was 3% (95% CI 1-5%) shorter among those in the highest quartile of IL-6 at Tanner 2 relative to those in the lowest quartile in fully adjusted models. Compared to those in the lowest quartile of CRP at Tanner 4, those in the highest quartile experienced 2% (95% CI 0-3%) longer time to menarche in multivariable models. CONCLUSIONS: Systemic inflammation during puberty was not associated with breast volume or breast density at the conclusion of breast development among pubertal girls after adjusting for body fatness; however, these circulating inflammation biomarkers, specifically CRP and IL-6, may affect the timing of menarche onset.

Probing structural properties and antioxidant activity mechanisms for eleocarpanthraquinone.

In this work, we present a computational investigation on the structure and energetics of eleocarpanthraquinone, a newly isolated polyphenolic anthrone-antraquinone. Properties such as bond lengths, angles, atomic charges, bond dissociation enthalpies (BDEs), and ionization potential (IP) were determined through the use of density functional theory (DFT). The B3LYP and M06-2X exchange-correlation functionals were employed along with the 6-31+G(d,p), 6-31+ +G(d,p), and 6-311+G(d,p) basis sets for performing computations in the gas-phase, water, methanol, and ethanol. The conformation presenting all the hydroxyl groups undergoing hydrogen-bond interactions with neighboring oxygen atoms (conformation 5) was assigned as the most stable structure while its counterpart presenting no hydrogen-bond interaction was found to be 36.45 kcal/mol less stable than conformation 5 in the potential energy surface probed at the B3LYP/6-311+G(d,p) level of theory in the gas-phase, for instance. More importantly, the lowest O-H bond dissociation enthalpy was determined to be 93.80 kcal/mol at the B3LYP/6-311+G(d,p) level of theory in water against the 146.58 kcal/mol regarding the IP computed at the same approach, suggesting the hydrogen atom transfer mechanism as being preferred over the single electron transfer mechanism in regards to the antioxidant potential for the case of eleocarpanthraquinone; the same conclusion was drawn from the outcomes of all the other approaches used.

Adaptación y análisis factorial del cuestionario de conducta de alimentación del adulto (AEBQ) en idioma español / Adaptation and factorial analysis of the Spanish version of the adult eating behaviour questionnaire (AEBQ)

El Cuestionario de Conducta de Alimentación de Adultos (AEBQ, por su sigla en inglés derivada de Adult Eating Behavior Questionnaire) es una de las herramientas psicométricas más usadas para evaluar la conducta de alimentación. El objetivo de este estudio fue adaptar y analizar factorialmente la versión en idioma español del AEBQ. El cuestionario adaptado al idioma español se aplicó en un estudio piloto de 50 voluntarias universitarias entre 20 y 30 años de edad. Se utilizó la técnica de análisis factorial para reducir la dimensionalidad de los datos y evaluar preliminarmente su estructura. Se usó la estadística alfa de Cronbach para explorar la consistencia interna del cuestionario adaptado. El análisis factorial reveló una estructura de 8 factores que explican el 82,8 % de la variación de los datos, lo que es concordante con el número de dimensiones de la conducta de alimentación publicada para el AEBQ original. La consistencia interna fue alta, con valores de la estadística α de Cronbach entre 0,77 y 0,91 para las 8 dimensiones consideradas. En conclusión, la versión adaptada al idioma español del AEBQ presenta una razonable concordancia en su estructura de datos con el cuestionario publicado originalmente en inglés, así como una adecuada consistencia interna. Se deben realizar futuros estudios de mayor tamaño muestral que incluyan participantes de diferentes grupos de edad, sexo y estado nutricional(AU)

The Adult Eating Behavior Questionnaire (AEBQ) is one the most used psychometric tool to evaluate eating behavior. The objective of this study was to adapt and analyze the factorial structure of the Spanish version of the AEBQ. The adapted questionnaire was submitted to a non-probabilistic sample of 50 female university students aged 20 - 30 years old. A factorial analysis was used to preliminary assess data structure, while Cronbach's alpha statistic was used to assess internal consistency. Factor analysis revealed an8-factor structure explaining 82,8% of data variation, which is concordant with data structure of the original AEBQ. The internal consistency was high, with Cronbach's α between 0.77 and 0.91 for all eating behavior dimensions. In conclusion, this Spanish version of the AEBQ shows adequate concordance with the factor structure of the originally published AEBQ, as well as high internal consistency. Future studies will evaluate the validity of the questionnaire in different subpopulation groups according to gender, age or nutritional status(AU)

Physical and chemical profiles of nanoparticles for lymphatic targeting.

Nanoparticles (NPs) have been gaining prominence as delivery vehicles for modulating immune responses to improve treatments against cancer and autoimmune diseases, enhancing tissue regeneration capacity, and potentiating vaccination efficacy. Various engineering approaches have been extensively explored to control the NP physical and chemical properties including particle size, shape, surface charge, hydrophobicity, rigidity and surface targeting ligands to modulate immune responses. This review examines a specific set of physical and chemical characteristics of NPs that enable efficient delivery targeted to secondary lymphoid tissues, specifically the lymph nodes and immune cells. A critical analysis of the structure-property-function relationship will facilitate further efforts to engineer new NPs with unique functionalities, identify novel utilities, and improve the clinical translation of NP formulations for immunotherapy.

Platelet Serotonin Levels Are Associated with Plasma Soluble Leptin Receptor Concentrations in Normoglycemic Women.

Most peripheral serotonin (5-hydroxytryptamine (5HT)) is synthetized in the gut with platelets being its main circulating reservoir. 5HT is acting as a hormone in key organs to regulate glucose and lipid metabolism. However, the relation between platelet 5HT levels and traits related to glucose homeostasis and lipid metabolism in humans remains poorly explored. The objectives of this study were (a) to assess the association between platelet 5HT levels and plasma concentration of nonesterified fatty acids (NEFAs) and some adipokines including leptin and its soluble leptin receptor (sOb-R), (b) to assess the association between platelet 5HT levels and anthropometric traits and indexes of insulin secretion/sensitivity derived from oral glucose tolerance test (OGTT), and (c) to evaluate changes in platelet 5HT levels in response to OGTT. In a cross-sectional study, 59 normoglycemic women underwent a standard 2-hour OGTT. Plasma leptin, sOb-R, total and high molecular weight adiponectin, TNFα, and MCP1 were determined by immunoassays. Platelet 5HT levels and NEFAs were measured before and after OGTT. The free leptin index was calculated from leptin and sOb-R measurements. Insulin sensitivity indexes derived from OGTT (HOMA-S and Matsuda ISICOMP) and plasma NEFAs (Adipose-IR, Revised QUICKI) were also calculated. Our data show that among metabolic traits, platelet 5HT levels were associated with plasma sOb-R (r = 0.39, p = 0.003, corrected p = 0.018). Platelet 5HT levels were reduced in response to OGTT (779 ± 237 vs.731 ± 217 ng/109 platelets, p = 0.005). In conclusion, platelet 5HT levels are positively associated with plasma sOb-R concentrations and reduced in response to glucose intake possibly indicating a role of peripheral 5HT in leptin-mediated appetite regulation.

Inverse association between estrogen receptor-α DNA methylation and breast composition in adolescent Chilean girls.

BACKGROUND: Estrogen receptor-α (ER-α) is a transcriptional regulator, which mediates estrogen-dependent breast development, as well as breast tumorigenesis. The influence of epigenetic regulation of ER-α on adolescent breast composition has not been previously studied and could serve as a marker of pubertal health and susceptibility to breast cancer. We investigated the association between ER-α DNA methylation in leukocytes and breast composition in adolescent Chilean girls enrolled in the Growth and Obesity Cohort Study (GOCS) in Santiago, Chile. Breast composition (total breast volume (BV; cm3), fibroglandular volume (FGV; cm3), and percent fibroglandular volume (%FGV)) was measured at breast Tanner stage 4 (B4). ER-α promoter DNA methylation was assessed by pyrosequencing in blood samples collected at breast Tanner stages 2 (B2; n = 256) and B4 (n = 338). RESULTS: After adjusting for fat percentage at breast density measurement, ER-α methylation at B2, and cellular heterogeneity, we observed an inverse association between B4 average ER-α DNA methylation and BV and FGV. Geometric mean BV was 15% lower (95% CI: - 28%, - 1%) among girls in the highest quartile of B4 ER-α methylation (6.96-23.60%) relative to the lowest (0.78-3.37%). Similarly, FGV was 19% lower (95% CI: - 33%, - 2%) among girls in the highest quartile of B4 ER-α methylation relative to the lowest. The association between ER-α methylation and breast composition was not significantly modified by body fat percentage and was not influenced by pubertal timing. CONCLUSIONS: These findings suggest that the methylation profile of ER-α may modulate adolescent response to estrogen and breast composition, which may influence breast cancer risk in adulthood.

Prevención de hemorragias en el posoperatorio temprano de cirugía bariátrica: Papel de la vitamina K / Prevention of hemorrhage in the early postoperative period of bariatric surgery: Role of vitamin K

Introducción: la cirugía bariátrica es el tratamiento más eficaz para la obesidad mórbida. La hemorragia se presenta en el 0,5-5% de las pacientes. La preparación prequirúrgica con dieta líquida y el uso de antibióticos para Helicobacter pylori podría alterar el metabolismo de la vitamina K y asociarse a hemorragia. Objetivo: describir el comportamiento de la concentración de protrombina (basal = B-PT y prequirúrgica = preQ-PT) en estos pacientes. Material y métodos: se realizó un estudio de cohorte prospectivo donde se comparó la concentración de B-PT (15-180 días previos a la cirugía) y la preQ-PT (24 horas previas a la cirugía). Resultados: se incluyeron 194 pacientes, de los cuales el 72% (n = 139) fueron mujeres, de entre 19 y 69 años, con BMI (IMC) 45 (33 a 58) y pérdida de peso prequirúrgica del 7% (-2 a 17). El promedio de B-PT fue 91,9% (DE 9,529), el promedio de la preQ-PT fue 81,1% (DE 10,760); descendió un 10,8% (p < 0,001). No hubo diferencias significativas cuando se comparó el comportamiento en la preQ-PT entre los diferentes subgrupos (uso de antibióticos para Helicobacter pylori, de acuerdo con la pérdida de peso y en relación con la suplementación de vitamina K); sin embargo, siempre se detectó descenso de la preQ-PT. No hubo ninguna complicación hemorrágica (necesidad de transfusiones o reoperación); tampoco hubo muerte por hemorragias ni eventos tromboembólicos. Conclusión: realizar dosaje de protrombina 24 horas antes de la cirugía bariátrica permite detectar alteraciones iatrogénicas de la coagulación inducidas por la dieta y el uso de antibióticos.

Background: bariatric surgery is the most efficient treatment for morbid obesity. Bleeding occurs in 0.5-5% of patients. Pre-surgical preparation with liquid diet and the use of antibiotics for Helicobacter pylori could alter the metabolism of vitamin K and be associated with hemorrhage. Objective: to describe the behavior of the concentration of Prothrombin (basal = B-PT and pre-surgical = preQ-PT) in these patients. Material and methods: a prospective cohort study comparing B-PT concentration (15-180 days prior to surgery) and preQ-PT (24 h prior to surgery) was performed. Results: a total of 194 patients were included in the study, with 72% (n = 139) women aged 19-69 years, BMI 45 (33 to 58) and preoperative weight loss of 7% (-2 to 17). The media B-PT was 91.9% (SD 9.529), the media pre-PT was 81.1% (SD 10.760); declined 10.8% (p <0.001). There was no significant difference when comparing the behavior in the preQ-PT among different subgroups (use of antibiotics for Helicobacter pylori, according to weight loss and in relation to vitamin K supplementation), however, there was always a decrease of the preQ-PT. There were no bleeding complications (need for transfusions or re-intervetion), nor was there death for bleeding or thromboembolic events. Conclusion: prothrombin measurement 24 hours before bariatric surgery allows the detection of iatrogenic coagulation alterations induced by diet and the use of antibiotics.

Association of the FTO fat mass and obesity-associated gene rs9939609 polymorphism with rewarding value of food and eating behavior in Chilean children.

OBJECTIVES: The aim of this study was to assess the association between the single-nucleotide polymorphism rs9939609 in the FTO gene and homeostatic/non-homeostatic eating behavior patterns in Chilean children. METHODS: A cross-sectional study was conducted in 258 children (44% female; 8-14 y of age). Anthropometric measurements (weight, height, Z-score of height, body mass index, and waist circumference) were performed. Eating behavior was assessed using the Eating in Absence of Hunger Questionnaire; the Child Eating Behavior Questionnaire; the Three Factor Eating Questionnaire, and the Food Reinforcement Value Questionnaire. Genotype of rs9939609 was determined by a Taqman assay. Association of rs9939609 with eating behavior was assessed using non-parametric tests. RESULTS: Allelic frequencies of rs9939609 were estimated as 77% for the A allele and 23% for the T allele. We found that normal-weight girl A carriers had higher scores of Satiety Responsiveness and Slowness on the Eating subscale. Normal-weight boy A carriers showed significantly higher scores on the Negative Affect and lower scores of the Desire to Drink subscale. In overweight children, A carriers showed higher scores on the Food Responsiveness, Emotional Overeating, Enjoyment of Food, and Food Choice subscales and lower scores on the Satiety- Responsiveness and Slowness in Eating subscales. In obese children, we found higher scores on the Cognitive Restrained subscale and lower Food Choice. CONCLUSION: The rs9939609 A allele of the FTO gene is associated with eating behavior traits and may predispose to obesity.

Effect of Human Myotubes-Derived Media on Glucose-Stimulated Insulin Secretion.

Fasting to postprandial transition requires a tight adjustment of insulin secretion to its demand, so tissue (e.g., skeletal muscle) glucose supply is assured while hypo-/hyperglycemia are prevented. High muscle glucose disposal after meals is pivotal for adapting to increased glycemia and might drive insulin secretion through muscle-released factors (e.g., myokines). We hypothesized that insulin influences myokine secretion and then increases glucose-stimulated insulin secretion (GSIS). In conditioned media from human myotubes incubated with/without insulin (100 nmol/L) for 24 h, myokines were qualitatively and quantitatively characterized using an antibody-based array and ELISA-based technology, respectively. C57BL6/J mice islets and Wistar rat beta cells were incubated for 24 h with control and conditioned media from noninsulin- and insulin-treated myotubes prior to GSIS determination. Conditioned media from insulin-treated versus nontreated myotubes had higher RANTES but lower IL6, IL8, and MCP1 concentration. Qualitative analyses revealed that conditioned media from noninsulin- and insulin-treated myotubes expressed 32 and 23 out of 80 myokines, respectively. Islets incubated with conditioned media from noninsulin-treated myotubes had higher GSIS versus control islets (p < 0.05). Meanwhile, conditioned media from insulin-treated myotubes did not influence GSIS. In beta cells, GSIS was similar across conditions. In conclusion, factors being present in noninsulin-stimulated muscle cell-derived media appear to influence GSIS in mice islets.

Prolonged Activation of the Htr2b Serotonin Receptor Impairs Glucose Stimulated Insulin Secretion and Mitochondrial Function in MIN6 Cells.

AIMS: Pancreatic ß-cells synthesize and release serotonin (5 hydroxytryptamine, 5HT); however, the role of 5HT receptors on glucose stimulated insulin secretion (GSIS) and the mechanisms mediating this function is not fully understood. The aims of this study were to determine the expression profile of 5HT receptors in murine MIN6 ß-cells and to examine the effects of pharmacological activation of 5HT receptor Htr2b on GSIS and mitochondrial function. MATERIALS AND METHODS: mRNA levels of 5HT receptors in MIN6 cells were quantified by RT qPCR. GSIS was assessed in MIN6 cells in response to global serotonergic activation with 5HT and pharmacological Htr2b activation or inhibition with BW723C86 or SB204741, respectively. In response to Htr2b activation also was evaluated the mRNA and protein levels of PGC1α and PPARy by RT-qPCR and western blotting and mitochondrial function by oxygen consumption rate (OCR) and ATP cellular content. RESULTS: We found that mRNA levels of most 5HT receptors were either very low or undetectable in MIN6 cells. By contrast, Htr2b mRNA was present at moderate levels in these cells. Preincubation (6 h) of MIN6 cells with 5HT or BW723C86 reduced GSIS and the effect of 5HT was prevented by SB204741. Preincubation with BW723C86 increased PGC1α and PPARy mRNA and protein levels and decreased mitochondrial respiration and ATP content in MIN6 cells. CONCLUSIONS: Our results indicate that prolonged Htr2b activation in murine ß-cells decreases glucose-stimulated insulin secretion and mitochondrial activity by mechanisms likely dependent on enhanced PGC1α/PPARy expression.

Assessment of the Role of Metabolic Determinants on the Relationship between Insulin Sensitivity and Secretion.

BACKGROUND: Insulin secretion correlates inversely with insulin sensitivity, which may suggest the existence of a crosstalk between peripheral organs and pancreas. Such interaction might be mediated through glucose oxidation that may drive the release of circulating factors with action on insulin secretion. AIM: To evaluate the association between whole-body carbohydrate oxidation and circulating factors with insulin secretion to consecutive oral glucose loading in non-diabetic individuals. METHODS: Carbohydrate oxidation was measured after an overnight fast and for 6 hours after two 3-h apart 75-g oral glucose tolerance tests (OGTT) in 53 participants (24/29 males/females; 34±9 y; 27±4 kg/m2). Insulin secretion was estimated by deconvolution of serum C-peptide concentration, ß cell function by mathematical modelling and insulin sensitivity from an OGTT. Circulating lactate, free-fatty acids (FFA) and candidate chemokines were assessed before and after OGTT. The effect of recombinant RANTES (regulated on activation, normal T cell expressed and secreted) and IL8 (interleukin 8) on insulin secretion from isolated mice islets was also measured. RESULTS: Carbohydrate oxidation assessed over the 6-h period did not relate with insulin secretion (r = -0.11; p = 0.45) or ß cell function indexes. Circulating lactate and FFA showed no association with 6-h insulin secretion. Circulating chemokines concentration increased upon oral glucose stimulation. Insulin secretion associated with plasma IL6 (r = 0.35; p<0.05), RANTES (r = 0.30; p<0.05) and IL8 (r = 0.41; p<0.05) determined at 60 min OGTT. IL8 was independently associated with in vivo insulin secretion; however, it did not affect in vitro insulin secretion. CONCLUSION: Whole-body carbohydrate oxidation appears to have no influence on insulin secretion or putative circulating mediators. IL8 may be a potential factor influencing insulin secretion.

[Cerebrotendinous xanthomatosis: physiopathology, clinical manifestations and genetics]. / Xantomatosis cerebrotendinosa: aspectos fisiopatológicos, clínicos y genéticos.

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disease, caused by genetic deficiency of the 27-hydroxylase enzyme (encoded by CYP27A1). It plays a key role in cholesterol metabolism, especially in bile acid synthesis and in the 25-hydroxylation of vitamin D3 in the liver. Its deficiency causes reduced bile acid synthesis and tissue accumulation of cholestanol. Clinical manifestations are related to the presence of cholestanol deposits and include tendon xanthomas, premature cataracts, chronic diarrhea, progressive neurologic impairment and less frequently coronary heart disease, early onset osteoporosis and abnormalities in the optic disk and retina. An early diagnosis and treatment with quenodeoxycholic acid may prevent further complications, mainly neurological manifestations. This review summarizes cholesterol metabolism related to bile acid synthesis, physiopathology, biochemistry and treatment of cerebrotendinous xanthomatosis.

Xantomatosis cerebrotendinosa: aspectos fisiopatológicos, clínicos y genéticos / Cerebrotendinous xanthomatosis: physiopathology, clinical manifestations and genetics

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disease, caused by genetic deficiency of the 27-hydroxylase enzyme (encoded by CYP27A1). It plays a key role in cholesterol metabolism, especially in bile acid synthesis and in the 25-hydroxylation of vitamin D3 in the liver. Its deficiency causes reduced bile acid synthesis and tissue accumulation of cholestanol. Clinical manifestations are related to the presence of cholestanol deposits and include tendon xanthomas, premature cataracts, chronic diarrhea, progressive neurologic impairment and less frequently coronary heart disease, early onset osteoporosis and abnormalities in the optic disk and retina. An early diagnosis and treatment with quenodeoxycholic acid may prevent further complications, mainly neurological manifestations. This review summarizes cholesterol metabolism related to bile acid synthesis, physiopathology, biochemistry and treatment of cerebrotendinous xanthomatosis.

Divergent metabolic phenotype between two sisters with congenital generalized lipodystrophy due to double AGPAT2 homozygous mutations. a clinical, genetic and in silico study.

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder characterized by extreme reduction of white adipose tissue (WAT) mass. CGL type 1 is the most frequent form and is caused by mutations in AGPAT2. Genetic and clinical studies were performed in two affected sisters of a Chilean family. These patients have notoriously dissimilar metabolic abnormalities that correlate with differential levels of circulating leptin and soluble leptin receptor fraction. Sequencing of AGPAT2 exons and exon-intron boundaries revealed two homozygous mutations in both sisters. Missense mutation c.299G>A changes a conserved serine in the acyltransferase NHX4D motif of AGPAT2 (p.Ser100Asn). Intronic c.493-1G>C mutation destroy a conserved splicing site that likely leads to exon 4 skipping and deletion of whole AGPAT2 substrate binding domain. In silico protein modeling provided insights of the mechanisms of lack of catalytic activity owing to both mutations.

The BARD1 Cys557Ser variant and risk of familial breast cancer in a South-American population.

Since the discovery of the BRCA1 and BRCA2 genes, much work has been carried out to identify further breast cancer (BC) susceptibility genes. BARD1 (BRCA1-associated ring domain) was originally identified as a BRCA1-interacting protein but has also been described in tumor-suppressive functions independent of BRCA1. Some association studies have suggested that the BARD1 Cys557Ser variant might be associated with increased risk of BC, but others have failed to confirm this finding. To date, this variant has not been analyzed in Spanish or South-American populations. In this study, using a case-control design, we analyzed the C-terminal Cys557Ser change in 322 Chilean BC cases with no mutations in BRCA1 or BRCA2 and in 570 controls in order to evaluate its possible association with BC susceptibility. BARD1 Cys557Ser was associated with an increased BC risk (P = 0.04, OR = 3.4 [95 % CI 1.2-10.2]) among cases belonging to families with a strong family history of BC. No difference between single cases affected with age <50 years at diagnosis (n = 117) and controls was observed for carriers of Cys/Ser genotype. It is likely that this variant is not involved in BC risk in this group of women. We also analyzed a possible interaction between BARD1 557Ser/XRCC3 241Met variants considering the role of both genes in the maintenance of genome integrity. The combined genotype Cys/Ser-carrier with the XRCC3 241Met allele was associated with an increased BC risk (P = 0.02, OR = 5.01 [95 % CI 1.36-18.5]) among women belonging to families with at least three BC and/or ovarian cancer cases. Our results suggest that BARD1 557Ser and XRCC3 241Met may play roles in BC risk in women with a strong family history of BC. Nevertheless there is no evidence of an interaction between the two SNPs. These findings should be confirmed by other studies and in other populations.

Mitochondrial diabetes and deafness: possible dysfunction of strial marginal cells of the inner ear.

OBJECTIVE: Some patients with the syndrome of mitochondrial diabetes and deafness (MIDD) have a m.3243A>G mutation of the MTTL1 gene encoding transfer ribonucleic acid for the amino acid leucine (tRNALeu(UUR)). One of our MIDD patients inspired us to propose an integrated view on how a single mutation of the mitochondrial deoxyribonucleic acid (DNA) affects both the glucose metabolism and the inner ear physiology. DESIGN: (a) Study of mitochondrial DNA in a patient with MIDD. (b) REVIEW OF THE LITERATURE on the impact of the m.3243A>G mutation on glucose metabolism and on the physiology of the hearing process. SETTINGS: Outpatient diabetes and nutrition department and molecular nutrition laboratory. METHODS: (a) Polymerase chain reaction followed by restriction fragment analysis identified the m.3243A>G mutation. (b) REVIEW OF THE LITERATURE from 1994 to 2009. RESULTS: (a) Molecular study: the m.3243A>G mutation was detected with an appreciable level of heteroplasmy. (b) REVIEW OF THE LITERATURE: the strial marginal cells located near the organ of Corti fulfill two characteristics: they are rich in mitochondria, and their dysfunction may produce neurosensorial deafness by means of a reduction in the potassium ion concentration of the endolymph. CONCLUSIONS: The m.3243A>G mutation not only underlies a dysfunction of the insulin-producing beta cell of the pancreas but also results in a reduction in adenosine triphosphate production of the strial marginal cells of the inner ear, thus diminishing the energy (in the form of potassium ion gradient) needed for the outer hair cells of the organ of Corti to amplify the soundwaves, particularly at high frequencies.

Gene delivery into mesenchymal stem cells: a biomimetic approach using RGD nanoclusters based on poly(amidoamine) dendrimers.

Poly(amidoamine) dendrimers (generations 5 and 6) with amine termini were conjugated with peptides containing the arginine-glycine-aspartic acid (RGD) sequence having in view their application as gene delivery vectors. The idea behind the work was to take advantage of the cationic nature of dendrimers and of the integrin targeting capabilities of the RGD motif to improve gene delivery. Dendrimers were used as scaffolds for RGD clustering and, by controlling the number of peptides (4, 8, and 16) linked to each dendrimer, it was possible to evaluate the effect of RGD density on the gene delivery process. The new vectors were characterized in respect to their ability to neutralize and compact plasmid DNA (pDNA). The complexes formed by the vectors and pDNA were studied concerning their size, zeta potential, capacity of being internalized by cells and ability of transferring genes. Transfection efficiency was analyzed, first, by using a pDNA encoding for Enhanced Green Fluorescent Protein and Firefly Luciferase and, second, by using a pDNA encoding for Bone Morphogenetic Protein-2. Gene expression in mesenchymal stem cells was enhanced using the new vectors in comparison to native dendrimers and was shown to be dependent on the electrostatic interaction established between the dendrimer moiety and the cell surface, as well as on the RGD density of nanoclusters. The use of dendrimer scaffolds for RGD cluster formation is a new approach that can be extended beyond gene delivery applications, whenever RGD clustering is important for modulating cellular responses.