Insulin resistance associated with obesity has been suggested to contribute to an increased risk and poor prognosis for breast cancer. In this study, a HER2/Neu transgenic mouse model of breast cancer was used to assess how obesity-induced insulin resistance and hyperinsulinemia can influence the development and progression of breast cancer. We investigated the effect of a high-fat diet and found a tumor-promoting effect in the absence of overt insulin resistance. In contrast, a high-fat combined with fructose diet induced significant hyperinsulinemia but no tumor promoting or growth effect was observed. Treatment with the anti-diabetic, insulin-lowering agent metformin led to a delay in tumor onset in mice on control diet, but this effect was abrogated by the high-fat fructose diet. These data indicate that the effects and potential interactions of insulin, nutrition and drugs on breast cancer development and progression are complex and require further study.

Insulin resistance associated with obesity has been suggested to contribute to an increased risk and poor prognosis for breast cancer. In this study, a HER2/Neu transgenic mouse model of breast cancer was used to assess how obesity-induced insulin resistance and hyperinsulinemia can influence the development and progression of breast cancer. We investigated the effect of a high-fat diet and found a tumor-promoting effect in the absence of overt insulin resistance. In contrast, a high-fat combined with fructose diet induced significant hyperinsulinemia but no tumor promoting or growth effect was observed. Treatment with the anti-diabetic, insulin-lowering agent metformin led to a delay in tumor onset in mice on control diet, but this effect was abrogated by the high-fat fructose diet. These data indicate that the effects and potential interactions of insulin, nutrition and drugs on breast cancer development and progression are complex and require further study.

Abstract Previous observations have indicated that reproductive endocrine disorders are common among patients with epilepsy. Valproate (VPA) treatment is associated with hyperandrogenism, polycystic ovaries, and obesity in women. Carbamazepine (CBZ) may also induce endocrine disorders, while the hormonal effects of oxcarbazepine (OXC) are poorly known. The aim of this study was to elucidate the effects of antiepileptic drugs on reproductive hormones, linear growth and pubertal maturation in patients with epilepsy. Altogether 223 patients taking VPA, CBZ, or OXC monotherapy for epilepsy and 103 healthy age- and sex-matched volunteers participated in the study. Seventy-eight girls and 90 men with epilepsy participated in the cross-sectional parts of the study. Thirty-nine adult patients with newly diagnosed epilepsy participated in a 3-month longitudinal study and VPA was replaced with lamotrigine (LTG) in 16 women with VPA-related endocrine disorders in a 1-year longitudinal study. The girls were between 8-18 years, the women 17-41 years and the men 17-51 years of age. None of the antiepileptic drugs studied significantly influenced linear growth or pubertal development in girls with epilepsy, but hyperandrogenemia, increased number of ovarian follicles, and weight gain were observed in prepubertal, pubertal and postpubertal girls taking VPA for epilepsy. Increased serum testosterone levels were observed in half of the women after the first 3 months of VPA medication, and high serum concentrations of androgens were common (prevalence 57 %, p < 0.001) in men taking long-term VPA treatment. The women with VPA-related hyperandrogenism and polycystic ovaries were also found to present other features of insulin resistance (i.e. hyperinsulinemia, centripetal obesity, and an unfavorable serum lipid profile). Reproductive endocrine disorders associated with VPA treatment in women began to normalize after VPA was replaced by LTG. CBZ reduced the bioactivity of androgens, whereas OXC did not have similar effects. Serum concentrations of sex hormone-binding globulin (SHBG) were increased and dehydroepiandrosterone sulfate decreased already during the first months of CBZ treatment. Serum hormone levels were normal in patients with low OXC doses (< 900 mg/d), but serum concentrations of testosterone, gonadotropins and SHBG were high in men with a daily OXC dose ≥ 900 mg. The adverse reproductive endocrine effects of antiepileptic drugs should be considered at the beginning of and during antiepileptic medication.

Abstract Type 2 diabetes causes impairment of peripheral nervous system (PNS) function, which can result in symptoms such as pain and numbness. Disturbances in glucose metabolism inflict negative alterations on PNS function even before diabetes occurs. Forty non-diabetic overweight (BMI 25–30) or obese (BMI > 30) working-age adults without polyneuropathy were enrolled in this study. PNS function was measured at baseline and after 3 years by peroneal motor nerve and radial, sural, and medial plantar sensory nerve conduction studies (NCS). At baseline, serum insulin and glucose levels (fasting, 30 min, and 120 min) were measured with a 2-hour oral glucose tolerance test (OGTT), and fasting serum cholesterol and triglyceride levels were measured. Maximal oxygen uptake (VO2max) was measured with an incremental bicycle ergometer test. Physical activity at the age of 15, 30, and current age was defined by a questionnaire. Current physical activity was also measured with a pedometer. At 3-year follow-up, serum insulin and glucose values were measured with a 2-hour OGTT, and serum fasting cholesterol and triglyceride values were measured. At baseline, a serum insulin level at 120 min was positively and statistically significantly associated with peroneus nerve F-wave minimum and maximum latency time, sural nerve latency and nerve conduction velocity (NCV), and medial plantar NCV. VO2max was positively associated with amplitudes of the distal and proximal peroneus nerve and medial plantar nerve. Physical activity at the age of 30 was positively and significantly associated with peroneus NCV, F-wave maximum latency, medial plantar latency, and NCV. At the 3-year follow-up study, all sensory nerve amplitudes decreased significantly, and a 120-min insulin change was positively associated with changes in peroneus NCV, F-wave average latency, sural NCV, and medial plantar NCV. Serum 120-min insulin values were positively associated with NCVs. Physical activity and fitness were positively associated with PNS function. The significant decrease in all sensory nerve amplitudes during follow-up demonstrates that negative alterations may already occur in overweight and obese adults without diabetes. Overweight and obese adults should be encouraged to have an active lifestyle, as even a small increase in physical activity might have a positive effect on PNS function. / Tiivistelmä Tyypin 2 diabetes aiheuttaa ääreishermoston toiminnan heikentymistä, mikä voi oireilla raajoissa kipuna ja tunnottomuutena. Sokeritasapainon häiriintyminen vaikuttaa haitallisesti ääreishermoston toimintaan jo ennen varsinaisen diabeteksen puhkeamista. Tutkimusaineistona olivat 40 ylipainoista (BMI 25-30) tai lihavaa (BMI>30) työikäistä henkilöä, jotka eivät sairastaneet tyypin 2 diabetesta tai polyneuropatiaa. Heille tehtiin seurannan alussa ja lopussa motorisen peroneushermon sekä sensoristen radius-, suralis- ja mediaalisen plantaarihermon hermoratatutkimus. Seurannan alussa heiltä määritettiin seerumin insuliini- ja glukoosiarvot (paasto, 30 min ja 120 min) kahden tunnin sokerirasituskokeella sekä seerumin paastokolesteroli- ja paastotriglyseridiarvot. Maksimaalinen hapenottokyky (VO2max) mitattiin polkupyöräergometrillä. Fyysinen aktiivisuus 15- ja 30-vuotiaana sekä tutkimushetkellä selvitettiin kyselyllä. Nykyinen aktiivisuus mitattiin myös kiihtyvyysanturiin perustuvalla askelmittarilla. Kolmen vuoden seurannassa 29 tutkittavalta määritettiin seerumin insuliini- ja glukoosiarvot kahden tunnin sokerirasituskokeella sekä seerumin paastokolesteroli- ja paastotriglyseridiarvot. Alkutilanteessa 120 minuutin insuliiniarvo oli positiivisesti ja tilastollisesti merkitsevästi yhteydessä peroneushermon F-aallon minimi- ja maksimilatenssiaikaan, suralishermon latenssiaikaan ja johtumisnopeuteen sekä mediaalisen plantaarihermon johtumisnopeuteen. VO2max oli positiivisesti yhteydessä peroneushermon distaalisen ja proksimaalisen vasteen voimakkuuteen (amplitudi) sekä mediaalisen plantaarihermon vasteen voimakkuuteen. Fyysinen aktiivisuus 30 vuoden iässä oli positiivisesti ja merkitsevästi yhteydessä peroneushermon johtumisnopeuteen, F-aallon maksimilatenssiaikaan, mediaalisen plantaarihermon latenssiaikaan sekä johtumisnopeuteen. Seurantatutkimuksessa kaikkien sensoristen hermojen vasteet pienenivät merkitsevästi ja seerumin 120 min insuliiniarvon muutos oli positiivisesti yhteydessä peroneushermon johtumisnopeuden, F-aallon keskiarvolatenssiajan, suralishermon johtumisnopeuden sekä mediaalisen plantaarihermon johtumisnopeuden muutokseen. Seerumin 120 min insuliiniarvot olivat positiivisesti yhteydessä ääreishermojen johtumisnopeuksiin. Fyysinen aktiivisuus ja kunto olivat positiivisesti yhteydessä ääreishermoston toimintaan. Negatiiviset muutokset sensoristen hermojen vasteissa seurantatutkimuksessa osoittavat, että negatiivisia muutoksia ääreishermoston toimintaan voi tapahtua ylipainoisilla henkilöillä jo ilman diabetesta. Ylipainoisia tulee kannustaa liikkumaan, sillä vähäiselläkin liikunnan lisäyksellä voi olla positiivinen vaikutus myös ääreishermoston toimintaan.

Pancreatic beta-cells regulate blood glucose by secreting insulin in response to nutrients. The development of Type 2 Diabetes (T2D) is characterized by elevated insulin secretion in the fasted state and a failure to adequately respond to nutrient influx, particularly glucose. Current dogma states that insulin resistance is the initiating event in the development of T2D, with compensation by beta-cells necessary to maintain glucose homeostasis. An alternative model, which will be a central theme throughout this thesis, is that hypersecretion of insulin is the initiating and sustaining event in the development of T2D. The underlying cause of insulin hypersecretion is unclear. Determining this is important in order to test this alternative model as a viable target for prevention and treatment of T2D. Because of the association between obesity and hyperinsulinemia, we hypothesized that exposure of the β-cell to high levels of nutrients stimulates insulin hypersecretion. We found that chronic incubation of β-cells in high glucose and/or oleate, which mimics nutrient conditions in obesity, lowered the half-maximal response for glucose to stimulate insulin secretion. The degree of the left-shift correlated with lipid stores. We determined that heightened sensitivity of granule exocytosis to Ca2+ was driving this left-shift. Thus glucose, while not necessarily abnormal in obesity, may cause hypersecretion of insulin due to altered sensitivity of the β-cell to this secretagogue. Iron stores are increased in obesity and are predictive of T2D development. We found that iron acutely stimulated both basal and glucose-stimulated insulin secretion (GSIS) in a reactive oxygen species dependent manner. Interestingly, iron did not increase insulin secretion via Ca2+ influx. Thus, both iron and glucose/oleate induce insulin hypersecretion via an aspect of the triggering pathway that is not Ca2+, the putative triggering signal. Previous work in our laboratory documented that exogenous mono-oleoyl-glycerol, an endogenous lipid signaling molecule and food additive, increases basal insulin secretion. We found that inhibition of monoacylglycerol lipase, which increases cellular monacylglycerol species, reduced GSIS, possibly via a reduction in long-chain CoA. Collectively, our works supports the hypothesis that chronic exposure to high nutrient levels drives insulin hypersecretion in obesity. / 2018-06-15T00:00:00Z

Prevalence of diabetes, especially type 2 diabetes mellitus (T2DM) is increasing worldwide. Millions of people are already affected by T2DM and estimates predict over half a billion people will likely be suffering from the disease by 2030. T2DM is associated with an increased risk of developing cardiovascular disease. Cardiovascular dysfunction is the leading cause of mortality among type 2 diabetics. Treatment for T2DM has changed over time. Though it was once known as insulin independent, a large portion of type 2 diabetics are now treated with insulin injections. However, type 2 diabetics treated with insulin are more likely to suffer from heart complications. Due to this, we sought to determine the specific effect of insulin and insulin-induced ceramide accrual on heart mitochondrial bioenergetics. To do so we used both in vitro and in vivo models. H9c2 cardiomyocytes and adult male mice were treated with insulin with or without the ceramide biosynthesis inhibitor myriocin. Mitochondrial bioenergetics were determined in permeabilized cardiomyocytes and myocardium. In this study we demonstrate that insulin induced ceramide accrual in both isolated cardiomyocytes and whole murine myocardium. We further found that insulin treatment is sufficient to disrupt mitochondrial respiration in both models. Inhibition of the ceramide accrual rescued mitochondrial respiration, indicating that ceramide is necessary for the insulin-induced alterations in heart mitochondrial respiration. These results suggest that insulin has a role in the development of heart complications associated with T2DM due to cardiomyocyte mitochondrial disruption. They also implicate ceramide as a possible mediator in the development of insulin-related heart disorders.

Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Biological and Medical Sciences Student: Monika Dobrovodová Supervisor of master thesis: PharmDr. Miroslav Kovařík, Ph.D. Advisor of master thesis: prof. MUDr. Karel Martiník, DrSc. Title of master thesis: Relation among BMI, hyperinsulinemia and selected biochemical indicators This thesis is focussed on specification of relations among BMI, insulinemia, age of the patients, C-peptid blood levels and glycemia and also searching relations among selected parameters of lipid spectrum in group of selected patients. Measuring of body height and weight and investigation of fasting glycemia, insulinemia, total cholesterolemia, blood levels of HDL and LDL and also C-peptid were done at 3472 patients. Afterwards few basic indexes of insulin resistance and sensitivity were counted. In this group was proven, that fasting insulinemia and C-peptid levels are increasing in according to increasing BMI. Also fasting glycemia is increasing modestly. Insulin resistance and sensitivity indexes used in this theses depends on BMI. Although statistically significant differences between age groups were proven according to insulin resistance and sensitivity indexes, we can't see clearly increasing or decreasing tendency in according to...

Obesity, a major risk factor in the development of Type 2 Diabetes (T2D), is commonly associated with insulin resistance and hyperinsulinemia. The long accepted view has been that insulin resistance drives hyperinsulinemia; however, there are multiple lines of evidence that hyperinsulinemia can precede and drive insulin resistance. The signals and mechanisms by which chronic excess nutrients promote pancreatic β-cell dysfunction remain poorly understood. This prompted us to define the signaling events that contribute to basal insulin hypersecretion induced by excess glucose. Of particular interest is signaling through mechanistic target of rapamycin complex 1 (mTORC1), a nutrient sensitive kinase complex whose hyperactivation has been shown to promote hyperinsulinemia. Clonal ß-cells (INS-1 cells) with and without mTORC1 inhibition were pre-exposed to physiological (5mM) or excess (11mM) glucose for 4 to 24 hrs. Basal insulin secretion, respiration and metabolites were measured. Pre-exposure to excess glucose resulted in sustained mTORC1 hyperactivation, basal insulin secretion, higher basal respiration and increased maximal respiratory capacity, due to accelerated mitochondrial pyruvate metabolism. Inhibition of mTORC1 reduced basal insulin secretion, basal respiration and maximal respiratory capacity. Moreover, cells challenged with excess glucose had increased levels of glycolysis and TCA cycle intermediates. Our results suggest that hyperactivation of mTORC1 induced by excess glucose results in increased energy demand and in the generation of metabolic factors that can lead to basal insulin hypersecretion. Therefore, targeting mitochondrial pyruvate metabolism and /or mTORC1 signaling could potentially lead to specific therapies to control hyperinsulinemia and diabetes progression.

Cancer is a leading cause of mortality in the United States. Despite much research on specific carcinogens, the cause of many cancers remains unclear. The identification of novel causative agents offers the potential for cancer prevention. Diseases such as obesity and diabetes mellitus, characterized by hyperinsulinemia, are associated with increased risk of endometrial, colorectal, and breast carcinomas. There is increasing evidence that insulin is a growth factor for tumor formation. The mechanisms underlying insulin-mediated neoplasia may include enhanced DNA synthesis with resultant tumor cell growth, inhibition of apoptosis, and altered sex hormone milieu. The reduced insulin levels seen with physical activity, weight loss, and a high fiber diet may account for decreased cancer risk. The role of newer drugs that restore sensitivity to insulin, thereby reducing hyperinsulinemia, is an exciting potential area of cancer prevention. In this review, we discuss the potential role of insulin as a tumor growth factor.

It is estimated by the World Health Organization (WHO) that 422 million people had diabetes worldwide in 2014, including 30.3 million people in the US. The cost of treating the disease is has tripled from 2003-2013 due to the increased number of patients. One of the genes strongly associated with type 2 diabetes (T2D) is the transcription factor 7 like 2 (TCF7L2). A single nucleotide polymorphism (SNP) of the TCF7L2 results in increased expression of long chain acyl-CoA synthetase 5 (ACSL5) while deletion of this part of the TCF7L2 gene reduces ACSL5 mRNA level. The regulation of ACSL5 gene expression by the high risk TCF7L2 allele highlights the importance of investigating the role of ACSL5 in T2D. ACSL5 is one of a family of enzymes that activates FA to its CoA ester and is required for FA metabolism within cells. Mice lacking this protein have reduced fat mass and are more insulin sensitive. Chronic exposure of clonal pancreatic ß-cells to excess nutrients has been shown to result in increased intrinsic lipid droplets, reduced insulin content, a left-shift in glucose dose-dependent insulin secretion curve characterized by basal insulin hypersecretion (IH) and blunted glucose stimulated insulin secretion (GSIS). We tested the hypothesis that the use of a putative ACSL5 inhibitor (Adipo C) can reduce accumulated lipid droplets, rescue insulin content and reverse the left-shift in glucose dose-dependent insulin secretion curve. INS-1 (823/13) cells were cultured in either 4 mM or 11 mM glucose media representing physiological and excess nutrients environment. Adipo C (10-25 µM) was added to cells to both acutely (2 hrs) and chronically (72 hrs) inhibit ACSL5 activity. Thin layer chromatography with C11 Bodipy fatty acid (BFA) was used to detect acute fatty acid incorporation into neutral lipids. Nile red was used to visualize intrinsic lipid droplets inside cells. Intracellular Ca2+ activity was detected using fura 2. Insulin assay was measured by HTRF. Acute fatty acid incorporation and lipid accumulation were reduced in cells exposed to Adipo C. An Adipo C concentration dependent right shift of glucose dose-dependent insulin release and increased insulin content were observed. 11 mM glucose cells cultured in 25 µM Adipo C showed decreased intracellular Ca2+ activity at 3 mM glucose and increased Ca2+ activity at 12 mM glucose, which are characteristic of cells cultured in 4 mM glucose having reduced lipid stores. These results all indicate possible protective effects on -cells exposed to excess nutrients. Islets of T2D patients who have a physiologically elevated blood glucose level are exposed to a similar excess nutrient environment. Therefore, the results illustrated here warrant further research on Adipo C compound to explore its therapeutic potential on T2D.