Population pharmacokinetics of metformin in late pregnancy

The pharmacokinetic disposition of metformin in late pregnancy was studied together with the level of fetal exposure at birth. Blood samples were obtained in the third trimester of pregnancy from women with gestational diabetes or type 2 diabetes, 5 had a previous diagnosis of polycystic ovary syndrome. A cord blood sample also was obtained at the delivery of some of these women, and also at delivery of others who had been taking metformin during pregnancy but from whom no blood had been taken. Plasma metformin concentrations were assayed by a new, validated, reverse-phase HPLC method, A 2-compartment, extravascular maternal model with transplacental partitioning of drug to a fetal compartment was fitted to the data. Nonlinear mixed-effects modeling was performed in'NONMEM using FOCE with INTERACTION. Variability was estimated using logarithmic interindividual and additive residual variance models; the covariance between clearance and volume was modeled simultaneously. Mean (range) metformin concentrations in cord plasma and in maternal plasma were 0.81 (range, 0.1-2.6) mg/L and 1.2 (range, 0. 1-2.9) mg/L, respectively. Typical population values (interindividual variability, CV%) for allometrically scaled maternal clearance and volume of distribution were 28 L/h/70 kg (17.1%) and 190 L/70 ka (46.3%), giving a derived population-wide half-life of 5.1 hours. The placental partition coefficient for metformin was 1.07 (36.3%). Neither maternal age nor weight significantly influenced the pharmacokinetics. The variability (SD) of observed concentrations about model-predicted concentrations was 0.32 mg/L. The pharmacokinetics were similar to those in nonpregnant patients and, therefore, no dosage adjustment is warranted. Metformin readily crosses the placenta, exposing the fetus to concentrations approaching those in the maternal circulation. The sequelae to such exposure, ea, effects on neonatal obesity and insulin resistance, remain unknown.

The subcellular fractionation properties and function of insulin receptor substrate-1 (IRS-1) are independent of cytoskeletal integrity

Efficient insulin action requires spatial and temporal coordination of signaling cascades. The prototypical insulin receptor substrate, IRS-1 plays a central role in insulin signaling. By subcellular fractionation IRS-1 is enriched in a particulate fraction, termed the high speed pellet (HSP), and its redistribution from this fraction is associated with signal attenuation and insulin resistance. Anecdotal evidence suggests the cytoskeleton may underpin the localization of IRS-1 to the HSP. In the present study we have taken a systematic approach to examine whether the cytoskeleton contributes to the subcellular fractionation properties and function of IRS-1. By standard microscopy or immunoprecipitation we were unable to detect evidence to support a specific interaction between IRS-1 and the major cytoskeletal components actin (microfilaments), vimentin (intermediate filaments), and tubulin (microtubules) in 3T3-L1 adipocytes or in CHO.IR.IRS-1 cells. Pharmacological disruption of microfilaments and microtubules, individually or in combination, was without effect on the subcellular distribution of IRS-1 or insulin-stimulated tyrosine phosphorylation in either cell type. Phosphorylation of Akt was modestly reduced (20-35%) in 3T3-L1 adipocytes but not in CHO.IR.IRS-1 cells. In cells lacking intermediate filaments (Vim(-/-)) IRS-1 expression, distribution and insulin-stimulated phosphorylation appeared normal. Even after depolymerisation of microfilaments and microtubules, insulin-stimulated phosphorylation of IRS-1 and Akt were maintained in Vim-/- cells. Taken together these data indicate that the characteristic subcellular fractionation properties and function of IRS-1 are unlikely to be mediated by cytoskeletal networks and that proximal insulin signaling does not require an intact cytoskeleton. (c) 2006 Elsevier Ltd. All rights reserved.

Muscle glycogen inharmoniously regulates glycogen synthase activity, glucose uptake, and proximal insulin signaling

Muscle glycogen inharmoniously regulates glycogen synthase activity, glucose uptake, and proximal insulin signaling. Am J Physiol Endocrinol Metab 290: E154-E162, 2006. First published August 23, 2005; doi:10.1152/ajpendo. 00330.2005.-Insulin-stimulated glucose uptake and incorporation of glucose into skeletal muscle glycogen contribute to physiological regulation of blood glucose concentration. In the present study, glucose handling and insulin signaling in isolated rat muscles with low glycogen (LG, 24-h fasting) and high glycogen (HG, refed for 24 h) content were compared with muscles with normal glycogen (NG, rats kept on their normal diet). In LG, basal and insulin-stimulated glycogen synthesis and glycogen synthase activation were higher and glycogen synthase phosphorylation (Ser645, Ser649, Ser653, Ser657) lower than in NG. GLUT4 expression, insulin-stimulated glucose uptake, and PKB phosphorylation were higher in LG than in NG, whereas insulin receptor tyrosyl phosphorylation, insulin receptor substrate-1-associated phosphatidylinositol 3-kinase activity, and GSK-3 phosphorylation were unchanged. Muscles with HG showed lower insulin-stimulated glycogen synthesis and glycogen synthase activation than NG despite similar dephosphorylation. Insulin signaling, glucose uptake, and GLUT4 expression were similar in HG and NG. This discordant regulation of glucose uptake and glycogen synthesis in HG resulted in higher insulin-stimulated glucose 6-phosphate concentration, higher glycolytic flux, and intracellular accumulation of nonphosphorylated 2-deoxyglucose. In conclusion, elevated glycogen synthase activation, glucose uptake, and GLUT4 expression enhance glycogen resynthesis in muscles with low glycogen. High glycogen concentration per se does not impair proximal insulin signaling or glucose uptake. Insulin resistance is observed at the level of glycogen synthase, and the reduced glycogen synthesis leads to increased levels of glucose 6-phosphate, glycolytic flux, and accumulation of nonphosphorylated 2-deoxyglucose.

Investigation of potential intervention targets to improve insulin action: a therapeutic approach

Impaired insulin action (insulin resistance) is a key factor in the pathogenesis of diabetes mellitus. To investigate therapeutic targets against insulin resistance, this thesis explores the mechanism of action of pharmacological agents and exogenous peptides known or suspected to modify insulin action. These included leptin, a hormone primarily involved in the regulation of body weight; sibutramine, an antiobesity agent; plant-derived compounds (pinitol and chamaemeloside) and agents known to affect insulin sensitivity, e.g. metformin, tolbutamide, thiazolidinediones, vanadyl sulphate and thioctic acid. Models used for investigation included the L6 skeletal muscle cell line and isolated skeletal muscles. In vivo studies were undertaken to investigate glycaemia, insulinaemia, satiety and body weight in streptozotocin-induced diabetic mice and obese (ob/ob) mice. Leptin acutely altered insulin action in skeletal muscle cells via the short form of the leptin receptor. This direct action of leptin was mediated via a pathway involving PI 3-kinase but not Jak2. The active metabolites of sibutramine had antidiabetic properties in vivo and directly improved insulin sensitivity in vitro. This effect appeared to be conducted via a non-PI 3-kinase-mediated increase in protein synthesis with facilitated glucose transport, and was independent of the serotonin and noradrenaline reuptake inhibition produced by sibutramine. Pinitol (a methyl inositol) had an insulin mimetic effect and was an effective glucose-lowering agent in insulinopenic states, acting directly on skeletal muscle. Conversely chamaemeloside appeared to improve glucose tolerance without directly altering glucose transport. Metformin directly increased basal glucose uptake independently of PI 3-kinase, possibly via an increase in the intrinsic activity of glucose transporters. Neither tolbutamide nor thiazolidinediones directly altered insulin sensitivity in L6 skeletal muscle cells: however vanadyl sulphate and thioctic acid increased glucose transport but appeared to exert toxic effects at therapeutic concentrations. Examination of glucose transport in skeletal muscle in this thesis has identified various components of post-receptor insulin signalling pathways which may be targeted to ameliorate insulin resistance. Type 2 Diabetes Mellitus Obesity L6 Skeletal Muscle Cells Glucose Transport Insulin Signalling 2

Diabetes : insulin plus metformin for T2DM-are there benefits?

During the natural history of type 2 diabetes mellitus (T2DM), the effects of insulin resistance are compounded by progressive deterioration of the insulin-secreting pancreatic ß cells. Escalating hyperglycaemia during disease progression may, initially, be stemmed by lifestyle interventions.

Treatment with metformin

Metformin is an anti-hyperglycaemic agent widely used in the treatment of type 2 diabetes. It counters insulin resistance through insulin-dependent and -independent effects on cellular nutrient and energy metabolism, improving glycaemic control without weight gain and without increasing the risk of hypoglycaemia. Metformin can also benefit several risk factors for vascular disease independently of glycaemic control. In subjects with metabolic syndrome, metformin improves prognosis. It decreases progression of impaired glucose tolerance to type 2 diabetes, assists weight reduction especially in conjunction with lifestyle management and exerts other potentially favourable cardiovascular effects. For example, metformin can modestly improve the lipid profile in some dyslipidaemic individuals, reduce pro-inflammatory cytokines and monocyte adhesion molecules and decrease advanced glycation end products. Metformin can also improve parameters of endothelial function in the macro- and micro-vasculature, indicating lower athero-thrombotic risk, but it does not appear to reduce blood pressure. In normoglycaemic individuals with risk factors for diabetes and in women with polycystic ovary syndrome there is evidence that metformin can defer or prevent the development of diabetes. Thus, metformin offers beneficial effects to delay the onset and reverse or reduce the progression of many of the metabolic features and cardiovascular risk factors associated with metabolic syndrome.

Defective peroxisomal proliferators activated receptor gamma activity due to dominant-negative mutation synergizes with hypertension to accelerate cardiac fibrosis in mice

Aims: Humans with inactivating mutations in peroxisomal proliferators activated receptor gamma (PPAR?) typically develop a complex metabolic syndrome characterized by insulin resistance, diabetes, lipodystrophy, hypertension, and dyslipidaemia which is likely to increase their cardiovascular risk. Despite evidence that the activation of PPAR? may prevent cardiac fibrosis and hypertrophy, recent evidence has suggested that pharmacological activation of PPAR? causes increased cardiovascular mortality. In this study, we investigated the effects of defective PPAR? function on the development of cardiac fibrosis and hypertrophy in a murine model carrying a human dominant-negative mutation in PPAR?. Methods and results: Mice with a dominant-negative point mutation in PPAR? (P465L) and their wild-type (WT) littermates were treated with either subcutaneous angiotensin II (AngII) infusion or saline for 2 weeks. Heterozygous P465L and WT mice developed a similar increase in systolic blood pressure, but the mutant mice developed significantly more severe cardiac fibrosis to AngII that correlated with increased expression of profibrotic genes. Both groups similarly increased the heart weight to body weight ratio compared with saline-treated controls. There were no differences in fibrosis between saline-treated WT and P465L mice. Conclusion: These results show synergistic pathogenic effects between the presence of defective PPAR? and AngII-induced hypertension and suggest that patients with PPAR? mutation and hypertension may need more aggressive therapeutic measures to reduce the risk of accelerated cardiac fibrosis. © The Author 2009.

Resistin down-regulates insulin receptor expression, and modulates cell viability in rodent pancreatic beta-cells

The adipokine resistin is known to induce insulin resistance in rodent tissues. Increases in adipose tissue mass are known to have a negative effect on pancreatic beta-cell function, although the mechanisms are poorly understood. This study investigated the effects of resistin on insulin secretion, insulin receptor expression and cell viability in pancreatic beta-cells. BTC-6 or BRIN-BD11 cells were treated for 24h with resistin, and insulin receptor expression, insulin secretion and cell viability were measured. Incubation with 40ng/ml resistin caused significant decreases in insulin receptor mRNA and protein expression, but did not affect insulin secretion. At low concentrations, resistin caused significant increases in cell viability. These data implicate resistin as a factor that may regulate beta-cell function/viability, and suggests a potential mechanism by which increased adiposity causes beta-cell dysfunction.

The interaction between metabolic disease and ageing

Two of the greatest crises that civilisation faces in the 21st century are the predicted rapid increases in the ageing population and levels of metabolic disorders such as obesity and type 2 diabetes. A growing amount of evidence now supports the notion that energy balance is a key determinant not only in metabolism but also in the process of cellular ageing. Much of genetic evidence for a metabolic activity-driven ageing process has come from model organisms such as worms and flies where inactivation of the insulin receptor signalling cascade prolongs lifespan. At its most simplistic, this poses a conundrum for ageing in humans – can reduced insulin receptor signalling really promote lifespan and does this relate to insulin resistance seen in ageing? In higher animals, caloric restriction studies have confirmed a longer lifespan when daily calorie intake is reduced to 60% of normal energy requirement. This suggests that for humans, it is energy excess which is a likely driver of metabolic ageing. Interventions that interfere with the metabolic fate of nutrients offer a potentially important target for delaying biological ageing.

Beyond BMI: The “Metabolically healthy obese” phenotype & its association with clinical/subclinical cardiovascular disease and all-cause mortality -- a systematic review

Background A subgroup has emerged within the obese that do not display the typical metabolic disorders associated with obesity and are hypothesized to have lower risk of complications. The purpose of this review was to analyze the literature which has examined the burden of cardiovascular disease (CVD) and all-cause mortality in the metabolically healthy obese (MHO) population. Methods Pubmed, Cochrane Library, and Web of Science were searched from their inception until December 2012. Studies were included which clearly defined the MHO group (using either insulin sensitivity and/or components of metabolic syndrome AND obesity) and its association with either all cause mortality, CVD mortality, incident CVD, and/or subclinical CVD. Results A total of 20 studies were identified; 15 cohort and 5 cross-sectional. Eight studies used the NCEP Adult Treatment Panel III definition of metabolic syndrome to define “metabolically healthy”, while another nine used insulin resistance. Seven studies assessed all-cause mortality, seven assessed CVD mortality, and nine assessed incident CVD. MHO was found to be significantly associated with all-cause mortality in two studies (30%), CVD mortality in one study (14%), and incident CVD in three studies (33%). Of the six studies which examined subclinical disease, four (67%) showed significantly higher mean common carotid artery intima media thickness (CCA-IMT), coronary artery calcium (CAC), or other subclinical CVD markers in the MHO as compared to their MHNW counterparts. Conclusions MHO is an important, emerging phenotype with a CVD risk between healthy, normal weight and unhealthy, obese individuals. Successful work towards a universally accepted definition of MHO would improve (and simplify) future studies and aid inter-study comparisons. Usefulness of a definition inclusive of insulin sensitivity and stricter criteria for metabolic syndrome components as well as the potential addition of markers of fatty liver and inflammation should be explored. Clinicians should be hesitant to reassure patients that the metabolically benign phenotype is safe, as increased risk cardiovascular disease and death have been shown.

Parâmetros bioquímicos e níveis de IgE total e específicas para aeroalérgenos em mulheres obesas com síndrome dos ovários policísticos

Introduction: Polycystic ovary syndrome (PCOS) whose classic features (menstrual irregularity of oligo/ amenorrhea type, chronic anovulation, infertility and hyperandrogenism clinical and/ or biochemical), is associated with aspects of metabolic syndrome (MS), as obesity and insulin resistance. The level of obesity determines different levels of inflammation, increasing cytokines participants of metabolic and endocrine functions, beyond modulate the immune response. Metabolic changes, added to the imbalance of sex hormones underlying irregular menstruation observed in (PCOS) can trigger allergic processes and elevation of total and specific IgE antibodies indicate that a sensitization process was started. Objective: To evaluate the influence of PCOS on biochemical parameters and levels of total and specific IgE to aeroallergens in obese women. Methods: After approval by the Committee of Ethics in Research, were recruited 80 volunteers with BMI ≥ 30 kg/m2 and age between 18 and 45 years. Among these, 40 with PCOS according to the Rotterdam criteria and 40 women without PCOS (control group). All participants were analysed with regard to anthropometric, clinical, gynecological parameters, interviewed using a questionnaire, and underwent blood sampling for realization of laboratory tests of clinical biochemistry: Total cholesterol, LDL-cholesterol, HDL- cholesterol, Triglycerides, Fasting glucose, Urea, Creatinine, Aspartate aminotransferase (AST), Alanine aminotransferase (ALT) and immunological: total and specific IgE to Dermatophagoides pteronyssinus, Blomia tropicalis, Dermatophagoides farinae and Dermatophagoides microceras.Statistical analysis was performed using SPSS 15.0 software through the chi-square tests, Fisher, Student t test and binary logistic regression, with significance level (p <0.05). Results: It was observed in the group of obese women with PCOS that 29 (72.5%) had menstrual cycle variable and 27 (67.5%) had difficulty getting pregnant. According to waist-hip ratio, higher average was also observed in obese PCOS (0.87). Blood level of HDL (36.9 mg/dL) and ALT (29.3 U/L) were above normal levels in obese women with PCOS, with statistically significant relationship. In the analysis of total and specific IgE to D. pteronyssinus high results were also prevalent in obese PCOS, with blood level (365,22 IU/mL) and (6.83 kU/L), respectively, also statistically significant. Conclusions: Observed predominance of cases with high levels of total IgE in the group of obese women with PCOS, 28 (70%) of the participants, whose mean blood concentration of the group was 365.22 IU/mL. In the analysis of Specific IgE between the groups, the allergen Dermatophagoides pteronyssinus showed greater dispersion and average the results of sensitization in the group of obese PCOS, whose mean blood concentration was 6.83 kU/l. Keywords: Obesity, Allergens and Polycystic Ovary Syndrome

A influência da perda de peso no perfil inflamatório de mulheres com síndrome dos ovários policísticos

The polycystic ovary syndrome (PCOS) is considered the most common endocrine disorder in reproductive age women, with a prevalence ranging from 15 to 20%. In addition to hormonal and reproductive changes, it is common in PCOS the presence of risk factors for developing cardiovascular disease (CVD) and diabetes mellitus, insulin resistance (IR), visceral obesity, chronic low-grade inflammation and dyslipidemia. Due to the high frequency of obesity associated with PCOS, weight loss is considered as the first-line treatment for the syndrome by improving metabolic and normalizes serum androgens, restoring reproductive function of these patients. Objectives: To evaluate the inflammatory markers and IR in women with PCOS and healthy ovulatory with different nutritional status and how these parameters are displayed after weight loss through caloric restriction in with Down syndrome. Methods: Tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and C-reactive protein (CRP) were assessed in serum samples from 40 women of childbearing age. The volunteers were divided into four groups: Group I (not eutrophic with PCOS, n = 12); Group II (not eutrophic without PCOS, n = 10), Group III (eutrophic with PCOS, n = 08) and Group IV (eutrophic without PCOS, n = 10). The categorization of groups was performed by body mass index (BMI), according to the World Health Organization (WHO) does not eutrophic, overweight and obesity (BMI> 25 kg / m²) and normal weight (BMI <24.9 kg / m²). IR was determined by HOMA-IR index. In the second phase of the study a controlled dietary intervention was performed and inflammatory parameters were evaluated in 21 overweight and obese women with PCOS, before and after weight loss. All patients received a low-calorie diet with reduction of 500 kcal / day of regular consumption with standard concentrations of macronutrients. Results: Phase 1: PCOS patients showed increased levels of CRP (p <0.01) and HOMAIR (p <0.01). When divided by BMI, both not eutrophic group with PCOS (I) as eutrophic with PCOS (III) showed increased levels of CRP (I = 2.35 ± 0,55mg / L and 2.63 ± III = 0,65mg / L; p <0.01) and HOMA-IR (I = 2.16 ± 2.54 and III = 1.07 ± 0.55; p <0.01). There were no differences in TNF-α and IL-6 between groups. Step 2: After the weight loss of 5% of the initial weight was reduced in all of the components of serum assessed inflammatory profile, PCR (154.75 ± 19:33) vs (78.06 ± 8.9) TNF α (10.89 ± 5.09) vs (6:39 ± 1:41) and IL6 (154.75 ± 19:33) vs (78.06 ± 08.09) (p <0:00) in association with improvement some hormonal parameters evaluated. Conclusion: PCOS contributed to the development of chronic inflammation and changes in glucose metabolism by increasing CRP, insulin and HOMA-IR, independent of nutritional status. The weight loss, caloric restriction has improved the inflammatory condition and hormonal status of the evaluated patients.

Avaliação da genotoxicidade em mulheres com síndrome dos ovários policísticos: impacto da dieta

Introduction: Polycystic Ovary Syndrome (PCOS), present in 6-12% of women of reproductive age, the criterion of Rotterdam, is characterized by hyperandrogenism, insulin resistance (IR) and its inflammatory state, exacerbated by obesity and factors associated with the increase in damage DNA. Weight loss, combined with healthy eating, acts restoring the reproductive and metabolic functions in the SOP, though its influence in reducing DNA damage in PCOS are unknown. Aim: To investigate whether there are differences between DNA damage markers and factors of cardiometabolic risk in women with PCOS and control, and evaluate the effectiveness of nutritional intervention in DNA damage markers and cardiometabolic risk markers in overweight and obese women with PCOS. Methods: the study was conducted in two studies and the participants were aged between 18 and 35 years. In the first study, a prospective case-control, were included 27 women diagnosed with PCOS and 20 controls. In the second study, clinical trial of nutritional intervention with 12-week calorie-restricted diet 500Kcal / day. The genotoxicity, DNA damage (intensity tail, tail moment and tail length) was evaluated by the comet assay. Anthropometric data, dietary intake, hormonal, biochemical and inflammatory were evaluated in different studies. Results: there was no significant difference between the DNA damage marker tail intensity (p = 0.18), tail moment (p = 0.76) and tail length (p = 0.109) in PCOS when compared to the control group. Data after nutritional intervention in PCOS women with overweight and obesity showed a decrease in DNA damage markers: tail intensity (24.35 ± 5.86 - pre-diet vs. 17.15 ± 5.04 -Post-diet) and tail moment (20.47 ± 7.85 - pre-diet vs. 14.13 ± 6.29 -post-diet) (p <0.001). Reduction of weight (3.5%) and decreased cardiometabolic markers IR and hyperandrogenism. Conclusion: women with PCOS have a worse cardiometabolic risk profile compared to control however similar genotoxicity identified by DNA damage. Nutritional intervention reduced the genotoxicity of overweight and obese women with PCOS, and reduce the factors of cardiometabolic risk.

Factors of Inflammation in Haitian Americans and African Americans with and without Type 2 Diabetes

Chronic low-grade inflammation has been implicated in the processes leading to the development of type 2 diabetes (T2D) and its progression. Non-Hispanic Blacks bear a disproportionate burden of T2D and are highly susceptible to inflammation. This cross-sectional study assessed and compared the serum levels of established adipocytokines; interleukin-6 (IL-6), C-reactive protein (CRP), leptin, and novel adipocytokines; chemerin and omentin in Haitian and African Americans with and without T2D. The relationships of these adipocytokines with metabolic syndrome (MetS), anthropometric and HOMA2 measures by ethnicity and diabetes status were also assessed. Serum levels of IL-6, CRP, leptin, chemerin and omentin were determined by the ELISA method. HOMA2 measures were calculated for insulin sensitivity (HOMA2-IS) and insulin resistance (HOMA2-IR). Analyses of available data for 230 Haitian Americans and 241 African Americans (240 with and 231 without T2D) for the first study showed that Haitian Americans with and without MetS had lower levels of IL-6 and CRP compared to African Americans with and without MetS (P Ethnic-specific diabetes intervention and treatment programs must be designed to target Haitian Americans and African Americans as separate unique groups, in order to reduce the burden of T2D among the non-Hispanic Black community. Further research is needed to gain better understanding of the role of inflammation and T2D in this population.