Rol de la osteocalcina más allá del hueso / Role of osteocalcin beyond bone

Los hallazgos osteológicos se intensi!caron en los últimos años. Se demostró que el esqueleto se comporta, además de sus funciones clásicas, como un órgano de secreción endocrina que sintetiza al menos dos hormonas: el factor de crecimiento de !broblastos 23 (FGF-23) y la osteocalcina (Ocn). La Ocn es un péptido pequeño que contiene 3 residuos de ácido glutámico. Estos residuos se carboxilan postraduccionalmente, quedando retenida en la matriz ósea. La forma decarboxilada en el primer residuo de ácido glutámico (GluOcn) fue reportada por poseer efectos biológicos; la resorción ósea es el mecanismo clave para su bioactivación. La presente revisión se centra en los conocimientos actuales sobre la función hormonal de la Ocn. A la fecha se reporta que la Ocn regularía el metabolismo energético aumentando la proliferación de células ` pancreáticas, y la secreción de insulina y de adiponectina. Sobre el músculo esquelético actuaría favoreciendo la absorción y el catabolismo de nutrientes. La función reproductiva masculina estaría regulada mediante el estímulo a las células de Leydig para sintetizar testosterona; en el desarrollo cerebral y la cognición, la Ocn aumentaría la síntesis de neurotransmisores monoaminados y disminuiría el neurotransmisor inhibidor GABA. Si bien son indispensables mayores evidencias para dilucidar los mecanismos reguladores por medio de los cuales actuaría la Ocn, los resultados enumerados en los distintos estudios experimentales establecen la importancia de este novedoso integrante molecular. Dilucidar su rol dentro de estos procesos interrelacionados en seres humanos abriría la posibilidad de utilizar a la Ocn en el tratamiento de enfermedades endocrino-metabólicas. (AU)

Osteological !ndings have intensi!ed in recent years. The skeleton behaves as an endocrine secretion organ that synthesizes at least two hormones: osteocalcin (Ocn) and !broblast growth factor 23 (FGF-23). Ocn is a small peptide that contains 3 glutamic acid residues. After translation, these residues are carboxylated to make possible its retention into the bone matrix. Decarboxylation on the !rst glutamic acid residue (GluOcn) has been reported to have biological effects. Bone resorption is the key mechanism for its bioactivation. This review focuses on current knowledge on Ocn hormonal function. It has been reported that Ocn regulates energy metabolism by increasing the proliferation of pancreatic ` cells, and the secretion of insulin and adiponectin. On the skeletal muscle, it may act by favoring the absorption and catabolism of nutrients. Male reproductive function might be regulated by stimulating Leydig cells to synthesize testosterone. Regarding brain development and cognition, Ocn would increase monoamine neurotransmitters synthesis and decrease inhibitory neurotransmitter GABA. Although more evidence is needed to elucidate the regulatory mechanisms of Ocn, different experimental studies establish the importance of this novel molecular mediator. Clarifying its role within interrelated processes in humans, might open the possibility of using Ocn in different treatments of endocrine-metabolic diseases. (AU)

Pancreatic ß-cell function is inhibited by miR-3666 in type 2 diabetes mellitus by targeting adiponectin

Type 2 diabetes mellitus (T2D) is a common endocrine and metabolic disorder, and poses threats to human health worldwide. Recently, microRNAs (miRNAs) have been suggested to play important roles in the pathophysiology of T2D. In this study, we explored the role of miR-3666 in T2D. miR-3666 was significantly down-regulated in the serum of T2D patients when compared to that of healthy volunteers, and miR-3666 expression level was negatively correlated with blood glucose levels of T2D patients. Overexpression of miR-3666 inhibited cell proliferation, reduced insulin secretion, and promoted cell apoptosis of pancreatic β-cell line (INS-1 cells). On the other hand, knockdown of miR-3666 had the opposite effects in INS-1 cells. The bio-informatics analysis using TargetScan revealed that adiponectin (ADIPOQ) was a downstream target of miR-3666, and the interaction between miR-3666 and ADIPOQ was validated by luciferase reporter assay. In addition, miR-3666 negatively regulated the mRNA and protein expression of ADIPOQ. Overexpression of ADIPOQ promoted insulin secretion after glucose stimulation, promoted cell proliferation, inhibited cell apoptosis, and partially abolished the effects of miR-3666 overexpression on insulin secretion, cell proliferation, and cell apoptosis of INS-1 cells. In conclusion, our results revealed that miR-3666 inhibited pancreatic cell proliferation, reduced insulin sensitivity, and promoted apoptosis by targeting ADIPOQ.

Relación entre los niveles séricos de proteína C reactiva y α1-antitripsina y la resistencia a la insulina en mujeres con obesidad / Relationship between serum levels of C-reactive protein and α1-antitrypsin and insulin resistance in obese women

El tejido adiposo produce citocinas implicadas en la resistencia a la insulina (RI) tales como IL-6, IL-8, TNF-α y moléculas proinflamatorias como la proteína C reactiva (PCR). La α1-antitripsina es una proteína plasmática sensible a la inflamación. El objetivo de este estudio fue determinar la correlación existente entre los niveles séricos de PCR ultrasensible (PCRus) y de α1-antitripsina con los índices de RI en mujeres venezolanas obesas. La población del estudio estuvo conformada por 15 mujeres normopeso (IMC 21,8 ± 1,9 kg/m²) y 15 mujeres con obesidad (IMC 35,3 ± 5,3 kg/m²). Se realizó a los grupos la prueba de tolerancia oral a la glucosa (carga de 75g, 2h) y se calcularon los siguientes índices: Modelo de Determinación de la Homeostasis de la resistencia a la insulina (HOMA-IR), Modelo de Determinación de la Homeostasis de la función de la célula-β (HOMA-β), Índice Matsuda e Índice Insulinogénico. Se determinó la relación entre los niveles séricos de PCRus y α1-antitripsina y estos índices. Las mujeres con obesidad presentaron mayores niveles de PCRus (p = 0,001) en comparación con las mujeres normopeso. Los niveles séricos de PCRus se correlacionaron positivamente con HOMA-IR (r= 0,73, p=0,0021), HOMA-β (r= 0,53, p=0,031) y negativamente con el Índice Matsuda (r= -0,60, p=0,017), en las mujeres con obesidad. No se observó ninguna correlación entre los niveles séricos de α1-antitripsina y los índices de RI en el grupo obeso ni en el grupo normopeso. Se encontró una relación entre los niveles séricos de PCRus y la RI, sugiriendo un rol de la inflamación subclínica en la RI.

Adipose tissue produces cytokines involved in insulin resistance (IR) such as IL-6, IL-8, TNF-α and proinflammatory molecules such as C reactive protein (CRP). α1-antitrypsin is an inflammation-sensitive plasma protein. The objective of this study is to determine the correlation between serum CRP high-sensitivity (CRPhs) and α1-antitrypsin levels with IR indices in obese Venezuelan women. The study population consisted of 15 normal weight women (BMI 21.8 ± 1.9 kg/m²) and 15 obese women (BMI 35.3 ± 5.3 kg/m²). Obese and lean women underwent a 2 h-75g oral glucose tolerance test and the following indices were calculated: homeostatic model assessment of insulin resistance (HOMA-IR), homeostatic model assessment of β cell function (HOMA-β), Matsuda Index and Insulinogenic Index. The relationship between serum CRPhs and α1-antitrypsin levels and these indices were determined. Obese women had higher CRPhs levels (p = 0.001) compared with normal weight women. In obese women, serum CRPhs levels were positively correlated with HOMA-IR (r=0.73, p=0.0021), HOMA-β (r=0.53, p=0.031) and negatively correlated with the Matsuda Index (r= -0.60, p=0.017). No correlation between serum levels of α1-antitrypsin and IR indices in the obese group and the lean group was observed. There was a relation between serum CRPhs levels and insulin resistance, suggesting a role of subclinical inflammation in IR.

Caracterización morfológica, génica y protéica en la diferenciación de células madre embrionarias de ratón a células pancreáticas tempranas / Morphological, genetic and protein characterization in the differentiation of embryonic stem cells to early pancreatic cells

Debido al auge de la medicina regenerativa, las Células Madre (SC) representan una fuente de reemplazo celular para cualquier tejido, decidiendo emprender este trabajo de investigación con el objetivo de diferenciar células madre embrionarias de ratón (mESC) a células pancreáticas tempranas, realizando su caracterización génica y morfológica. Primeramente se cultivaron y arrestaron en su ciclo celular fibroblastos embrionarios de ratón (MEF) con mitomicina, posteriormente se expandieron las mESC y se sometieron a un protocolo de diferenciación de 21 días hacía células pancreáticas tempranas, evaluándose durante la diferenciación su morfología y expresión relativa de los genes sox-17, pdx-1, ins-1 e ins-2, determinando además la producción de las proteínas insulina y glucagón mediante inmunocitoquímica y citometría de flujo. Se obtuvieron cuerpos embrionarios (EBs) a partir de mESC, con características morfológicas diferentes de acuerdo a su diferenciación, los cuales expresaron genes de la línea germinal endodérmica (sox-17 y pdx-1) a los días 0, 11 y 17 de diferenciación, gen inductor del desarrollo embrionario pancreático (pdx-1) al día 11 de diferenciación y, genes de expresión pancreática (ins-1 e ins-2) a los días 17 y 21 de diferenciación. Finalmente se detectó la producción de proteínas insulina y glucagón en los EBs al día 21 de diferenciación. Se logró diferenciar mESC. El análisis morfológico evidenció cúmulos celulares tridimensionales correspondientes a EBs. Con el análisis de los patrones de expresión génica, se distinguieron inicialmente células con características genéticas de endodermo y posteriormente a partir del día 17 células pancreáticas tempranas, las cuales al día 21 de diferenciación expresaron las proteínas insulina y glucagón...

Due to the boom in regenerative medicine, Stem Cells (SC) represent a source of cell replacement to any tissue, we decided to undertake this research with the objective of differentiating mouse embryonic stem cells (mESC) to early pancreatic cells, developing their genetic and morphological characterization. Initially Mouse embryonic fibroblasts (MEF) were grown and arrested in their cell cycle with mitomycin, subsequently mouse embryonic SC (mESC) were expanded and subjected in to a pancreatic cell differentiation protocol of 21 days. During differentiation, morphology and the relative expression of sox-17, pdx-1, Ins-1 and Ins-2 genes were assessed, also the production of insulin and glucagon proteins was determinated by fluorescence microscopy and flow cytometry. Embryoid bodies (EBs) were obtained from mESC, with different morphological characteristics according to their differentiation, which expressed endodermal germ line genes (sox-17 y pdx-1) at days 0, 11 and 17 of differentiation, an inductor gene of embryonic pancreas development (pdx-1) was detected at day 11 of differentiation. Pancreas genes (ins-1 e ins-2) were expressed at day 17 and 21 of differentiation. Finally the production of insulin and glucagon proteins was detected on the EBS at day 21 of differentiation. In conclusion, the mESC differentiation was achieved. The morphological analysis evidenced three-dimensional cell clusters corresponding to EBs. Analysis of the gene expression patterns in the differentiation process, cells initially showed genetic characteristics of endoderm and thereafter from day 17 of differentiation characteristics of early pancreatic cells which by day 21 of differentiation expressed insulin and glucagon proteins...

Taurine ameliorates hyperglycemia and dyslipidemia by reducing insulin resistance and leptin level in Otsuka Long-Evans Tokushima fatty (OLETF) rats with long-term diabetes

This study aimed to determine whether taurine supplementation improves metabolic disturbances and diabetic complications in an animal model for type 2 diabetes. We investigated whether taurine has therapeutic effects on glucose metabolism, lipid metabolism, and diabetic complications in Otsuka Long-Evans Tokushima fatty (OLETF) rats with long-term duration of diabetes. Fourteen 50-week-old OLETF rats with chronic diabetes were fed a diet supplemented with taurine (2%) or a non-supplemented control diet for 12 weeks. Taurine reduced blood glucose levels over 12 weeks, and improved OGTT outcomes at 6 weeks after taurine supplementation, in OLETF rats. Taurine significantly reduced insulin resistance but did not improve beta-cell function or islet mass. After 12 weeks, taurine significantly decreased serum levels of lipids such as triglyceride, cholesterol, high density lipoprotein cholesterol, and low density lipoprotein cholesterol. Taurine significantly reduced serum leptin, but not adiponectin levels. However, taurine had no therapeutic effect on damaged tissues. Taurine ameliorated hyperglycemia and dyslipidemia, at least in part, by improving insulin sensitivity and leptin modulation in OLETF rats with long-term diabetes. Additional study is needed to investigate whether taurine has the same beneficial effects in human diabetic patients.

Demographic and metabolic characteristics of individuals with progressive glucose tolerance

We evaluated changes in glucose tolerance of 17 progressors and 62 non-progressors for 9 years to improve our understanding of the pathogenesis of type 2 diabetes mellitus. Changes in anthropometric measurements and responses to an oral glucose tolerance test (OGTT) were analyzed. We identified 14 pairs of individuals, one from each group, who were initially normal glucose tolerant and were matched for gender, age, weight, and girth. We compared initial plasma glucose and insulin curves (from OGTT), insulin secretion (first and second phases) and insulin sensitivity indices (from hyperglycemic clamp assay) for both groups. In the normal glucose tolerant phase, progressors presented: 1) a higher OGTT blood glucose response with hyperglycemia in the second hour and a similar insulin response vs non-progressors; 2) a reduced first-phase insulin secretion (2.0 ± 0.3 vs 2.3 ± 0.3 pmol/L; P < 0.02) with a similar insulin sensitivity index and a lower disposition index (3.9 ± 0.2 vs 4.1 ± 0.2 µmol·kg-1·min-1 ; P < 0.05) vs non-progressors. After 9 years, both groups presented similar increases in weight and fasting blood glucose levels and progressors had an increased glycemic response at 120 min (P < 0.05) and reduced early insulin response to OGTT (progressors, 1st: 2.10 ± 0.34 vs 2nd: 1.87 ± 0.25 pmol/mmol; non-progressors, 1st: 2.15 ± 0.28 vs 2nd: 2.03 ± 0.39 pmol/mmol; P < 0.05). Theses data suggest that β-cell dysfunction might be a risk factor for type 2 diabetes mellitus.

Potencial role of stem cell therapy in type 1 diabetes mellitus: [review]

Type 1 diabetes mellitus is the result of the autoimmune response against pancreatic beta-cell(s). At the time of clinical diagnosis near 70 percent of beta-cell mass is been destroyed as a consequence of the auto-destruction that begins months or even years before the clinical diagnosis. Although marked reduction of chronic complications was seen after development and progression of insulin therapy over the years for type 1 diabetic population, associated risks of chronic end-organ damage and hypoglycemia still remain. Besides tight glucose control, beta-cell mass preservation and/or increase are known to be other important targets in management of type 1 diabetes as long as it reduces chronic microvascular complications in the eyes, kidneys and nerves. Moreover, the larger the beta-cell mass, the lower the incidence of hypoglycemic events. In this article, we discuss some insights about beta-cell regeneration, the importance of regulation of the autoimmune process and what is being employed in human type 1 diabetes in regard to stem cell repertoire to promote regeneration and/or preservation of beta-cell mass.

O diabetes melito tipo 1 (DM1) é o resultado de uma resposta auto-imune contra as células-beta pancreáticas. Por ocasião do diagnóstico clínico do DM1, aproximadamente 70 por cento da massa de células-beta foram destruídas como conseqüência de uma autodestruição que se iniciou há anos ou meses antes dos primeiros sinais da doença. Embora a redução acentuada das complicações crônicas na população com DM1 foi observada após o desenvolvimento e evolução da insulinoterapia, os riscos associados às lesões dos órgãos-alvo e hipoglicemia persistem. Além do controle intensivo da glicemia, a preservação e/ou o aumento da massa de células-beta são reconhecidos como alvos importantes no tratamento do DM1. Isto vem associado à redução das complicações crônicas microvasculares na retina, rins e nervos e a menor incidência de eventos hipoglicêmicos. Neste artigo, discutimos alguns aspectos da regeneração das células-beta pancreáticas, a importância da regulação do processo auto-imune e o que está sendo empregado no DM1 humano com relação ao repertório das células-tronco nesse sentido.

Análise crítica do uso dos índices do Homeostasis Model Assessment (HOMA) na avaliação da resistência à insulina e capacidade funcional das células-beta pancreáticas: [revisão] / Critical analysis on the use of the homeostasis hodel assessment (HOMA) indexes in the evaluation of the insulin resistance and the pancreatic beta cells functional capacity: [review]

A disfunção das células-beta e a resistência insulínica são anormalidades metabólicas inter-relacionadas na etiologia do diabetes tipo 2. Em diversos países, tem sido observado o aumento da prevalência de obesidade e diabetes em associação com a presença da resistência insulínica. Nesse contexto, é útil a mensuração da resistência insulínica e da capacidade funcional das células-beta nos indivíduos. Os índices Homeostasis Model Assessment (HOMA) têm sido amplamente utilizados, representando uma das alternativas para avaliação desses parâmetros, principalmente por figurarem um método rápido, de fácil aplicação e de menor custo. Esta revisão discute sobre a origem e a evolução dos índices HOMA, bem como as particularidades do método, abordando aspectos relacionados à sua validação e aos pontos de corte existentes para sua interpretação.

Beta-cell dysfunction and insulin resistance are interrelated metabolic abnormalities in the aetiology of Type 2 Diabetes. In several countries, increases in the prevalence of obesity and diabetes have been observed in association with the presence of insulin resistance. In this context, measurement of insulin resistance and beta-cell function is useful. The HOMA indexes (Homeostasis Model Assessment) have been widely used, representing an alternative for the evaluation of these parameters, particularly as a fast, easy and cheap method. This review discusses the origin and evolution of the HOMA index, as well as details of the method, analyzing features related to its validation and the cutoff limits for its interpretation.

Avaliação morfológica e dos mecanismos de mobilização de Ca2+ pela glicose e acetilcolina em células pancreáticas humanas / Morphologic evaluation and Ca2+ mobilization by glicose and acetylcholine in human pancreatic cells

OBJETIVOS: Avaliar a morfologia das organelas e do citoesqueleto em células pancreáticas humanas cultivadas e a mobilização de Ca2+ em resposta à glicose e ACh por medidas fluorimétricas. MATERIAL E MÉTODOS: As células foram semeadas em lamínulas, fixadas e marcadas com uma combinação de fluoróforos: o núcleo foi corado com DAPI e as mitocôndrias, com Mytotracker Red. Foram utilizados faloidina e anticorpos secundários conjugados com Alexa Fluor verde e vermelho fluorescentes (488 e 594) para identificar proteína actina F e receptor muscarínico tipo M3, respectivamente. Para estudar a mobilização de Ca2+, as células foram incubadas com fura-2/AM. RESULTADOS: As células pancreáticas humanas apresentaram morfologia preservada com grande quantidade de mitocôndrias. Na região de maior densidade celular, evidenciou-se as pseudo-ilhotas e os receptores muscarínicos M3. Por meio da elevação da [Ca2+]c, devido à ação da glicose e ACh, mostrou-se preservação da capacidade responsiva a esses estímulos e foi dependente de concentração desses agonistas. A glicose promoveu uma resposta sustentada e a ACh induziu uma resposta bifásica. CONCLUSÃO: As células pancreáticas humanas cultivadas conservaram sua morfologia. A mobilização de Ca2+ em resposta à glicose e a ACh confirma a sua funcionalidade. Os receptores muscarínicos M3 estão presentes nessas células.

AIMS: The proposal of this study was to analyze morphology of the organelles and cytoskeleton in human pancreatic cells cultured and the mobilization of the cytosolic calcium ([Ca2+]c) in response to glucose and ACh by fluorimetry method. MATERIAL AND METHODS: The cells were plated on glass coverslips, fixed and stained with a combination of fluorophores: the nuclei were stained with DAPI and mitochondria with Mytotracker Red. It was used phalloidin and the secondary antibodies Alexa Fluor conjugated green and red-fluorescent (488 and 594) to identify the protein cell actin F and type M3 muscarinic receptor respectively. The cells also were loaded with fura-2/AM to study Ca2+ mobilization. RESULTS: The human pancreatic cells show characteristics morphologically preserved with great amount of mitochondria. In region major cell density was evidenced pseudo-islets and type M3 muscarinic receptors. Through increase of [Ca2+]c due to action of glucose and ACh were shown that the cellsÆ capacity to respond to these stimuli were conserved. The elevation of the [Ca2+]c depended on concentration by glucose-induced promoting sustained phase and ACh-induced a biphasic response. CONCLUSION: The morphologic characteristics of human pancreatic cells cultured were preserved. The Ca2+ mobilization in response to glucose and ACh confirmed its functionality. The expression of the M3 muscarinic receptors in human pancreatic cell cultured was demonstrated.

Distribución de las concentraciones de glucosa e indulina basal, HOMA IR Y MOMA ßcell en niños y adolescentes de la ciudad de Maracaibo, Venezuela / Distribution of fasting glucose, insulin, homeostasis model assessment (HOMA) insulin resistance (IR) and HOMA ß cell in children and adolescents from Maracaibo, Venezuela

Background: The raising prevalence of obesity among children increases the risk of insulin resistance and its adverse metabolic consequences. Aim: To determine the distributions of fasting serum glucose, insulin, HOMA IR and HOMA ß cell in a representative sample of children and adolescents from Maracaibo-Venezuela. Subjects and Methods: Fasting insulin and glucose were measured in 418 children and adolescents (191 boys and 227 girls) of 7, 9, 11, 13, 15 years of age. HOMA IR and HOMA ß cell were calculated. Results: Insulin levels were lower in 7 and 9 year-old girls and 7 year-old boys compared with 11, 13 and 15 year-old girls and boys. Fasting glucose concentrations were similar in boys and girls. HOMA IR was lower in 7 year-old girls compared to 11, 13 and 15 years-old girls, whereas boys in every age showed similar values. HOMA ß cell was higher in 11 and 13 year-old girls. Conclusions: Our findings provide useful values to assess insulin resistance and ß-cell functioning in children and adolescents.

Insulin resistance and beta cell function in chronically transfused patients of thalassemia major.

OBJECTIVE: To assess the glycometabolic function in chronically transfused patients of beta- thalassemia major in terms of glucose tolerance, insulin secretion, insulin resistance index, and beta cell function index and to determine their relationship with clinical and biochemical profile. METHODS: 30 homozygous thalassemia major children (aged 8-15 years) receiving regular blood transfusion and 10 age and sex matched normal children attending a tertiary level hospital were subjected to glucose tolerance test, estimation of fasting plasma insulin level, insulin resistance index and beta cell function index. Liver enzymes, liver size and indicators of iron overload (serum ferritin, total units of blood transfused, splenic size) were recorded. RESULTS: There was no diabetes mellitus or impaired glucose tolerance test in either the cases or the controls. Fasting plasma insulin levels were significantly higher in cases than controls (P = 0.004), and correlated well with indicators of iron overload like total units of blood transfused (r = 0.41, P = 0.03), serum ferritin (r = 0.38, P = 0.038) and splenic size (r = 0.43, P = 0.03). Insulin resistance was higher in cases compared to controls (P = 0.01). It correlated well with age (r = 0.56, P = 0.006), fasting blood glucose (r = 0.8, P = 0.003), fasting plasma insulin (r = 0.95, P = 0.00001), total units of blood transfused (r = 0.52, P = 0.005), serum ferritin (r = 0.4, P = 0.02) and splenomegaly (r = 0.51, P = 0.004). Insulin resistance was higher in patients not on chelation therapy compared with those on chelation therapy (P = 0.003). The beta cell function index was higher in cases compared to the controls, but not of statistic significance (P = 0.077). It did not correlate well with total amount of blood transfused (r = -0.32, P = 0.08), serum ferritin (r = -0.138, P = 0.46), spleen size (r = 0.16, P = 0.36), or chelation therapy (P = 0.98). CONCLUSION: Diabetes mellitus or impaired glucose was not seen in chronically transfused patients of thalassemia major (between 8 and 15 years of age), in our study. Insulin resistance, compensated by hyperinsulinemia, sets in early even before the onset of frank diabetes mellitus and correlated well with age, chelation therapy and indicators of iron overload like total units of blood transfused, splenomegaly and serum ferritin.

Properties of voltage-gated Ca2+ currents measured from mouse pancreatic â-cells in situ

We used the single-microelectrode voltage-clamp technique to record ionic currents from pancreatic â-cells within intact mouse islets of Langerhans at 37C, the typical preparation for studies of glucose-induced "bursting" electrical activity. Cells were impaled with intracellular microelectrodes, and voltage pulses were applied in the presence of tetraethylammonium. Under these conditions, a voltage-dependent Ca2+ current (I Cav), containing L-type and non-L-type components, was observed. The current measured in situ was larger than that measured in single cells with whole-cell patch clamping, particularly at membrane potentials corresponding to the action potentials of â-cell electrical activity. The temperature dependence of I Cav was not sufficient to account for the difference in size of the currents recorded with the two methods. During prolonged pulses, the voltage-dependent Ca2+ current measured in situ displayed both rapid and slow components of inactivation. The rapid component was Ca2+-dependent and was inhibited by the membrane-permeable Ca2+ chelator, BAPTA-AM. The effect of BAPTA-AM on â-cell electrical activity then demonstrated that Ca2+-dependent inactivation of I Cav contributes to action potential repolarization and to control of burst frequency. Our results demonstrate the utility of voltage clamping â-cells in situ for determining the roles of ion channels in electrical activity and insulin secretion.

The Relation between Birth Weight and Insulin Resistance in Korean Adolescents

Low birth weight is associated with insulin resistance and type 2 diabetes in adults. The fetal programming hypothesis has shown that insulin resistance and its associated metabolic disturbances result from a poor gestational environment, for which low birth weight is a surrogate. An at-home questionnaire survey was performed on 660 middle school students (12-15 years) in Seoul, Korea, and 152 cases were randomly selected based on their birth weight. Subjects were divided into three groups according to birth weight. We recorded their birth weight and measured their current anthropometric data, blood pressure, lipid profile, HOMA-IR, and HOMA-beta, and compared these parameters among the groups. The relation of birth weight to physiological characteristics in adolescence was examined. Systolic blood pressure, lipid profiles, and fasting plasma glucose, HOMA-beta were not significantly different among the groups, but diastolic blood pressure was lower in the third tertile. Insulin, C-peptide, and HOMA-IR were higher in the lower birth weight tertile. After adjustment for confounding factors, birth weight was inversely related to diastolic blood pressure, insulin, C-peptide, and HOMA-IR. We conclude that low birth weight may predict the risk of the insulin resistance and its progression over age, and that adequate gestational nutrition is therefore necessary to prevent low birth weight.

The influence of the Pro12Ala mutation of PPARgamma2 receptor gene on beta-cells restoration and insulin resistance in type 2 diabetes with hypertension / 华中科技大学学报（医学）（英德文版）

The aim of this investigation was to determine whether a PPARgamma2 Pro12Ala polymorphism was associated with insulin resistance, beta-cell function and hypertension in Chinese populations. 289 unrelated Chinese subjects first diagnosed Type 2 diabetes (HbAC1 < 6.0) were investigated, including 132 hypertensive diabetic (HTD) subjects, 157 normotensive diabetic (NTD) subjects. Blood pressure and anthropometric measurements were collected from all participants, as well as several venous blood samples during oral glucose tolerance test (OGTT). Biochemical measurements (high-density lipoprotein (HDL) and low-density lipoprotein-cholesterol (LDL), triglycerides) and PPARgamma2 Pro12Ala genotype were also determined. And insulin resistance and beta-cells function was assessed by HOMA-IR and HOMA-beta respectively. The frequency of subjects bearing the Pro12Ala was lower in the hypertension group (3.03%) than in the non-hypertension group (5.7%) (P < 0.05) after adjusted for age, BMI and gender. Hypertensive diabetic Pro12Ala subjects had lower fasting plasma glucose level (P = 0.0127), and better glucose tolerance 60 min after oral glucose (P = 0.0361). Moreover, plasma insulin concentrations at 60 min was lower than those without A variant (P = 0.0275), and both hypertensive Ala/Pro in HOMA-beta (P = 0.0455) and AUC for insulin (P = 0.0473) were higher, and HOMA-IR was lower (P = 0.0375) as compared with hypertensive Pro/Pro subjects. No association was observed between Pro12Ala genotype and BMI, total cholesterol, HDL- cholesterol or triglycerides in either group. Our findings suggested that the Ala 12 allele of the PPARgamma2 gene may improve insulin resistance and ameliorate beta-cell function reserves in T2DM with hypertension, and protect patients from hypertension in T2DM. As an important thrifty gene, environment factors may exerts an effect of PPAR gamma2 on glucose homeostasis and insulin resistance.