Metabolic syndrome in Africa: an emerging perspective

The high prevalence of human immunodeficiency virus infection and the emergence of HIV-related metabolic syndrome from its successful treatment in African countries are discussed. The classical factors fuelling metabolic syndrome as well as the role of urbanization are considered in this review. The future impact of ongoing conflicts and famine in large parts of Africa on the burden of metabolic syndrome in this region is given some attention. The current pattern of metabolic syndrome in Africa may be modified to an even more distinct form, far from that seen elsewhere.

Polymorphisms in perilipin gene (PLIN) are not associated with obesity and weight variation in people with high risk of type 2 diabetes

Perilipins are hormonally regulated phosphorylated proteins that coat the intracellular lipid storage droplet . They are essential for the regulation of triglyceride deposition and mobilization . The human perilipin gene (PLIN) is located to 15q26.1, near the susceptibility loci for obesity, and insulin-dependent diabetes mellitus, and hypertriglyceridemia. Therefore, it is considered as a candidate gene for these diseases . Some studies shown that lower level of perilipin protein was displayed in obese than lean subjects and polymorphisms in PLIN were associated with obesity in American and Spanish white women as well as in Korean . But some other studies showed that, this association was not significant in Chinese and French . The aim of the current study was to examine whether the associations manifested in a German population with high risk of type 2 diabetes.

Is the worldwide epidemic of obesity a communicable feature of globalization?

Globalization has a major impact on both economic and social determinants in public health. The current worldwide epidemic in obesity needs to be considered in the context of globalization as a communicable rather than non-communicable process. There is increasing evidence that global trends in lifestyle, eating behavior and cultural adaptation contribute to the rapid increase in obesity around the world. Thus, obesity may be defined as a "socially-contagious" feature of globalization. Furthermore, infectious agents are being identified that may cause obesity by central mechanisms or by modulating adipocyte function or at least by contributing to the chronic inflammatory milieu of the metabolic syndrome. Therefore, globalization may indeed form a critical platform for these pathogens to fuel the obesity epidemic. Understanding obesity in the light of globalization as a communicable disorder will allow outlining better avenues of prevention and treatment.

Heparin-induced Extracorporal LDL precipitation (H.E.L.P) in diabetic foot syndrome - preventive and regenerative potential?

Peripheral arterial disease is more aggressive in concomitant diabetes posing an increased risk for critical limb ischemia and subsequent limb loss. The majority of therapies available are not effective to prevent amputation in patients with severe disease. The current observational study reports the effect of the heparin-induced extracorporal LDL-precipitation (H.E.L.P.) as a novel therapeutic approach in patients with severe diabetic foot syndrome. Seventeen diabetic patients with septic foot lesions recruited from the diabetic outpatient clinic underwent H.E.L.P. apheresis regularly until fibrinogen levels were stabilized at 3 g/l or infection was controllable as evidenced by alleviation of necrosis. Patients were subsequently followed up for 2 to 73 months. Fibrinogen levels were reduced by 68% after H.E.L.P. treatment. No severe complications were noted. Necrosis could be confined in sixteen patients. Minor amputations were indicated in twelve patients. Three patients underwent major amputations of the lower limb and two patients received surgical reconstruction. In conclusion, H.E.L.P. apheresis may offer an alternative therapeutic option to diabetic patients with critically ischemic feet and appears to have a beneficial major/minor amputation ratio.

Current progress and future challenges in the biochemical diagnosis and treatment of pheochromocytomas and paragangliomas

Findings from five independent studies - with close to 350 patients with pheochromocytoma and more than 2,500 in whom the tumor was excluded - indicate that measurements of plasma free metanephrines provide an overall diagnostic sensitivity of 98% and specificity of 92%. The recommendation that initial testing for the tumor should always include measurements of either plasma or urinary fractionated metanephrines results from recognition of the high diagnostic sensitivity of measurements of plasma metanephrines. The few patients with pheochromocytoma in whom the test may not yield a positive result include those with very small tumors or microscopic disease and others with tumors that do not produce norepinephrine and epinephrine. Such patients are typically normotensive and do not exhibit symptoms of catecholamine excess. Additional measurements of methoxytyramine can be useful for detecting those tumors that produce only dopamine. Suboptimal diagnostic specificity and difficulties in distinguishing true- from false-positive elevations of plasma metanephrines remain challenges for diagnosis. Improvements in analytical technology (e.g., liquid chromatography with tandem mass spectrometry) and new strategies for follow-up testing provide possible solutions to these problems. The single most important remaining clinical care challenge is the development of effective cures for patients with malignant disease. Current treatments, none of which are truly satisfactory, include chemotherapy and radiopharmaceutical therapy with (131)I-labelled M-iodobenzylguanidine or radioactive somatostatin analogues. Improvements in treatment may in the future come from several fronts, but proof of efficacy ideally will require well-coordinated multicenter prospective trials in larger numbers of patients than in previous studies.

[Molecular basis of primary renal hyperuricemia : role of the human urate transporter hURAT1]

In highly industrialized countries hyperuricemia is one of the most common metabolic disorders. High uric acid blood levels may lead to the manifestation of gout owing to the precipitation of urate crystals in connective tissue, the skeletal system and kidneys. A primary reduction of renal uric acid excretion can be detected in more than 90% of all cases of hyperuricemia. Despite the identification of several uric acid transporting proteins their pathogenetic role for the induction of primary reduced renal uric acid excretion has not yet been verified. As a result of a case-control study on individuals with normal and reduced renal uric acid excretion, an association of polymorphisms in the human urate transporter 1 gene (hURAT1) with primary reduced urate excretion has been demonstrated for the first time. The hURAT1 gene is an organic anion transporter (SLC22A12), which is preferentially expressed in the apical membrane of proximal renal tubule cells. Functioning as an antiporter, hURAT1 mediates the uptake of urate from the lumen into proximal tubule cells in exchange for organic and inorganic anions. Loss-of-function mutations in the hURAT1 gene are a cause of hereditary renal hypouricemia. The precisely regulated hURAT1 is a candidate gene for hyperuricemia and an important target for the development and optimization of new diagnostic approaches and pharmacological interventions of primary reduced renal uric acid excretion.

Toll-like receptors in endocrine disease and diabetes

The body's ability to keep a steady homeostatic state is crucial to health and life. This involves providing an adequate response to a variety of challenges both physical and mental, such as microbial invasion and emotional distress. Interplay between the neuroendocrine and immune systems is essential in either case. Studies have demonstrated that toll-like receptors, or TLRs, play a regulatory role in both systems, and have been proposed as a possible link between the immune, hormonal and metabolic systems. As part of the innate immune system, these receptors control the identification by the body of microbial invaders and its immediate reaction in immune and inflammatory response. What are referred to as pattern recognition receptors are mostly expressed by cells involved in hematopoietic linkage, but an increasing number of studies have demonstrated their expression in other cell types such as neurons and endocrine cells on the hypothalamic-pituitary-adrenal (HPA) axis, thyrocytes, adipocytes and islets of Langerhans. Together with endocrine and metabolic dysregulation, immune system overreaction is often associated with infection and autoimmunity, clearly indicating TLR involvement at organ level which affects organ function. Several diseases such as autoimmune thyroid and pancreatic diseases, septic dysregulation of the HPA axis, diabetes and the metabolic syndrome have been linked to TLR activation and polymorphism. To gain insight into stress response and adaptation, we need to know more about TLRs and the specific physiological role they play in the endocrine and metabolic system and its processes.

The health status of Russian-speaking immigrants in Germany

INTRODUCTION

Germany developed today into a country of immigration, which creates an additional burden for the social security system and results in a new challenge for the healthcare. In the last 17 years more than two million "Russia Germans" have been repatriated and about two hundred thousand Jewish refugees have resettled in Germany from the former Soviet Union. Nevertheless relevant data concerning migration-related public health care are very scare.

METHODS

Search of PubMed and Journals extracts combined with the own researches, analysing the health status indices of the Russian-speaking immigrants in Germany.

RESULTS

Both repatriates of German origin and Jewish refugees demonstrated higher prevalence of impaired lipid metabolism in comparison with native population. 42 % of the 503,040 HBsAg (hepatitis B s-Antigen) carriers in Germany were migrants. The Jewish refugees demonstrated the highest rates of depression and anxiety and the highest levels of awakening cortisol. On the other side German resettlers showed lower cardiovascular as well as all-cause death rates compared to the native Germans.

CONCLUSION

The development of adequate health care programmes to address migratory aspects as well as the establishment of quality standards will realistically enhance the capability of responding rapidly to migrant health aspects and help to tackle inequalities in health.

The Metabolic Syndrome - a global challenge for prevention

In the last years we have learned a lot about the pathopysiology of a cluster of the diseases called Metabolic Syndrome but currently an exciting discussion debates the Metabolic Syndrome in a light of a mystery of medicine or a clinical paradigm with a controversary about diagnostic, treatment or preventive procedure. There is now convincing evidence that prevention is the most important and effective way to reduce the personal and socio-economic burden of the Metabolic Syndrome and its associated complications. Still, it is currently not clear how to implement preventive interventions into clinical practice but will require an integrated and transdisciplinary approach on an international level in order to efficiently reduce premature morbidity and mortality. Nevertheless, global strategies are still lacking but are needed to tackle inequalities in health between industrialized countries and the developing world. A global health strategy has to take into account political, epidemiological, environmental, infrastructural and genetic aspects. The Metabolic Syndrome is not a mystery - it is a clinical paradigm and global challenge.

Human aldehyde oxidase 1 interacts with ATP-binding cassette transporter-1 and modulates its activity in hepatocytes

AOX1, a member of the cytosolic molybdenum hydroxylase family, has been identified by us earlier as an ABCA1-interacting protein. AOX1 is well-described as xenobiotic metabolizing enzyme, which upon oxidation of acetaldehyde and retinaldehyde to acetic acid and retinoic acid generates reactive oxygen species. Here we show that knock-down of AOX1 in HepG2 by small interfering RNA significantly reduced ABCA1-dependent lipid efflux and enhanced phagocytic uptake of microspheres similar to ABCA1 deficiency, without affecting ABCA1 mRNA and protein levels. ABCA1 and AOX1 are coexpressed in human hepatocytes, kidney proximal tubular epithelial cells, Leydig, and adrenocortical cells. Expression of ABCA1 and AOX1 was investigated by immunohistochemistry in liver tissue arrays. A strong AOX1 expression was found in normal liver, and in cirrhosis. In contrast, hepatocellular carcinomas showed either a complete loss or reduced expression of AOX1. Significant correlations were found between reduced AOX1 expression and tumor stage, or metastatic or regional lymph node states. Deregulation was also observed for ABCA1 expression but to a lesser extent. Our findings show that the interaction of ABCA1 with AOX1 modulates ABCA1-linked cellular functions such as lipid efflux and phagocytosis in hepatocytes, and the reduced expression of AOX1 in malignant transformed hepatocytes supports the differentiation dependent upregulation of AOX1.

Low-density lipoproteins induce the renin-angiotensin system and their receptors in human endothelial cells

Increased levels of low-density lipoproteins are well-established risk factors of endothelial dysfunction and the metabolic syndrome. In this study, we evaluated the effect of native low-density lipoprotein (nLDL) and oxidized LDL (oxLDL) on the expression of genes of the renin-angiotensin system (angiotensin-converting enzyme, ACE; angiotensin II type 1 receptor, AT(1)) and their receptors (low-density lipoprotein receptor: LDLR; lectin-like oxLDL receptor: LOX-1; toll-like receptor 4: TLR4) in primary cultures of human umbilical vein endothelial cells. ACE and AT(1) expressions were significantly increased after stimulation with nLDL and oxLDL. OxLDL receptor LOX-1 showed a maximum induction after 7 hours. Increased LOX-1 protein expression in response to oxLDL could be blocked by a LOX-1-specific antibody. TLR4 expression was increased by nLDL and oxLDL as well. We conclude that LDL and oxLDL can activate the renin-angiotensin system and their receptors LDLR, LOX-1, and TLR4 in human endothelial cells. These data suggest a novel link between hypercholesterolemia and hypertension in patients with the metabolic syndrome.

Genetic variation of Neurogenin 3 is slightly associated with hyperproinsulinaemia and progression toward type 2 diabetes

OBJECTIVE

Transcription factor Neurogenin 3 (NGN3) is considered as a candidate gene for the development of type 2 diabetes. The aim of the current study was to investigate the relevance of NGN3 variants for the clinical spectrum of diabetes development and disease progressions.

RESEARCH DESIGN AND METHODS

A total of 552 subjects with increased risk of type 2 diabetes were investigated. They underwent a 75 g OGTT with measurements of plasma glucose, insulin and proinsulin at fasting and at 30, 60, 90 and 120 minutes after the glucose challenge, repeated after 3 years. The NGN3 SNPs, Gly167Arg and Ser199Phe were genotyped.

RESULT

Patients with type 2 diabetes carrying the variant genotype at SNP199 presented with significantly higher proinsulin levels. Proinsulin level was also associated with progression of diabetes mellitus. There was a discrete association of the Ser199Phe variant with evolution of the disease status.

CONCLUSION

A genetic variation in NGN3 gene may be among the genetic determinants involved in the pathogenesis of diabetes.

The importance and effect of dietary fiber in diabetes prevention with particular consideration of whole grain products

The state of prediabetes is characterized by an increase in insulin resistance and a decrease in pancreatic beta cell function. The prestage of type 2 diabetes mellitus can be identified by an impaired glucose tolerance and/or by an impaired fasting blood sugar. Apart from weight loss and increase in physical activity, the development of type 2 diabetes mellitus can also be prevented by dietary changes. A low-fat diet with a dietary fiber intake of more than 30g/d was shown to represent an effective preventive approach. A high-fiber diet has many positive effects on the physical health status. In addition to positive effects in the gastrointestinal tract it has an obvious potential to support weight reduction and to improve disturbances of carbohydrate and fat metabolism. At the present state of knowledge, insoluble dietary fibers as found in whole grain cereal products are considered to be especially effective in the prevention of type 2 diabetes mellitus. A high intake of fruits and vegetables as well as pulses also exerts health-promoting properties. A high-fiber diet also plays an important role in the prevention of obesity and coronary heart diseases.

Moderate weight loss reduces renin and aldosterone but does not influence basal or stimulated pituitary-adrenal axis function

Body fat mass and nutrition influence secretion of the adrenocortical hormones--aldosterone and cortisol--via several mechanisms. However, there are no data on adrenocortical function following widely prescribed mild diet-induced weight loss (10%) in obese subjects. In the present study, 25 healthy obese volunteers (BMI 32.9+/-4.3 kg/m (2)) followed a 30% calorie restricted diet over 12 weeks. Hypothalamic-pituitary-adrenal (HPA) axis function was assessed by 24-hour urine free cortisol/cortisone and a 1 mcg ACTH stimulation test with measurement of total and free cortisol and corticosteroid-binding globulin (CBG). The renin-angiotensin-aldosterone system (RAAS) was assessed by measurement of plasma aldosterone and renin under salt depleted (30 mmol/d) and loading (250 mmol/d) conditions. Volunteers' weight fell by 8.5+/-0.8 kg (8.9+/-0.7%) and seated systolic blood pressure fell by 8.7+/-2.7 mmHg and diastolic blood pressure by 7.0+/-1.4 mmHg (p<0.01). Plasma aldosterone and renin levels fell significantly with weight loss (aldosterone: 853+/-156-635+/-73 pmol/l; renin: 35.4+/-7-24+/-3 mU/l, both p<0.05). The volunteers were relatively salt insensitive (mean arterial pressure change with salt intake: 4 mmHg) and this was not affected by weight loss. Moderate weight loss had no effect on 24-hour urine free cortisol/cortisone, or on basal, or ACTH-stimulated free and total cortisol, or CBG. Hence this conventional weight loss program reduces blood pressure and activity of the RAAS via an effect on renin release. Despite various described influences of fat mass and energy restriction on HPA axis function, there were no changes in basal and stimulated HPA axis function with moderate weight loss. There may be a threshold effect of weight loss/energy restriction required to alter HPA axis function, or moderate weight loss may lead to a counterbalanced effect of stimulatory and inhibitory influences on HPA axis function.

Apoptosis in patients with dilated cardiomyopathy and diabetes: a feature of diabetic cardiomyopathy?

BACKGROUND

Dilated cardiomyopathy (DCM) has been suggested to be a consequence of a prior viral infection leading to a chronic inflammatory and immunological reaction that leads to a structural and functional deterioration of the heart. Nevertheless, the results of present studies are conflicting, regarding the natural course of heart diseases associated with detection of viral genome and inflammation. On the other hand, diabetes mellitus (DM) is the leading endocrine disorder worldwide and sufficient to induce a cardiomyopathy. It is not known whether DM contributes to the clinical picture of cardiomyopathy associated with the presence of viral genome or inflammatory cells in the myocardium. Therefore, the present study was undertaken to compare histological, immunohistochemical, biochemical, and functional data as well as the outcome of patients presenting with DCM and positive for DM with patients negative for DM to evaluate for a diabetic contribution in the course of the disease.

METHODS

A total of 216 patients were biopsied between January 1998 and April 2003. From 197 patients diagnosed as having DCM, we were able to complete data set regarding the presence of DM in 108 patients, 20 patients with and 88 patients without DM.

RESULTS

There was no significant difference regarding age, gender, body mass index, presence of viral genome and inflammatory cells in the myocardium, left ventricular function and diameter, and the degree of heart insufficiency. There was a significant difference of apoptotic cells in the myocardium of patients with DCM and DM compared to patients with DCM alone (1.7+/-1.9 vs. 0.2+/-0.4, p=0.028). During the follow-up of 16 months, left ventricular function improved in both groups significantly, but not between the groups. Death or transplantation-free survival was not significantly different.

CONCLUSION

The different findings regarding the presence of apoptotic cells suggest a contribution of pathobiological pathways in the patients with DM to the underlying heart disease.

A simplified Finnish diabetes risk score to predict type 2 diabetes risk and disease evolution in a German population

AIMS

The FINDRISC questionnaire is a screening tool to estimate the risks for type 2 diabetes as well as asymptomatic type 2 diabetes. We aimed to evaluate its performance to predict diabetes in a German population and to compare its predictive and detective ability in the same population.

METHODS

A total of 552 subjects with increased risk of type 2 diabetes were investigated. All individuals completed the FINDRISC questionnaires and underwent an oral glucose tolerance test (OGTT). All individuals were followed for 3 years and underwent an OGTT again. The performance of the opportunistic screening was assessed with the area under the receiver operating characteristics curve (AUC). An intervention program was carried out for all diabetic and IFG/IGT patients at baseline.

RESULTS

For identification, the asymptomatic type 2 DM was named Condition 1; prediction of type 2 DM risk in the follow-up survey as Condition 2; and diabetes risk predicting in a hypothetical case of survey without intervention program as Condition 3. The ROC-AUC in the three condition were AUC (FINDRISC1)=0.745, AUC (FINDRISC2)=0.789, and AUC (FINDRISC3)=0.775, respectively. A significant association between FINDRISC and evolution of disease was found, but the variation of plasma glucose during the three years follow-up was not associated with FINDRISC. People in the intervention group with an improvement of glucose tolerance had a smaller FINDRISC score than persons with an unchanged or progressive condition of disease.

CONCLUSION

FINDRISC was validated in our study as a simple tool with high performance to predict diabetes risk and less efficient to identify asymptomatic type 2 diabetes. People with lower FINDRISC score will benefit easier from preventive intervention.

[Adrenal gland tumors]

Adrenal masses are one of the most common tumors in humans. They are a very heterogenous group of diseases and include benign and malignant adrenocortical lesions, metastases, pheochromocytomas and other entities. Adrenal masses originating from steroidogenic or chromaffin cells may be silent or the source of subclinical or overt hormone excess, such as primary aldosteronism, hypercortisolism or symptomatic catecholamine excess. On the other hand, adrenal hyperplasia may be the result of excess ACTH secretion in steroid biosynthesis disorders with deficient glucocorticoid secretion, in glucocorticoid resistance, in Cushing's disease, or ectopic ACTH syndrome. Algorithms for endocrine testing, imaging studies and their combination are available for defining the tumor entity and for the characterization of the hormone excess syndromes. Recent developments in molecular biology have provided tools for testing for hereditary tumor syndromes associated with adrenal tumorigenesis and to establish strategies for further treatment and follow-up.

The satiety factor apolipoprotein A-IV modulates intestinal epithelial permeability through its interaction with alpha-catenin: implications for inflammatory bowel diseases

INTRODUCTION

Apolipoprotein A-IV (apoA-IV), an intestinally and cerebrally synthesized satiety factor and anti-atherogenic plasma apolipoprotein, was recently identified as an anti-inflammatory protein. In order to elucidate whether intestinal apoA-IV exerts similar repair function as its hepatic homologue apolipoprotein A-V (apoA-V), apoA-IV-interactive proteins were searched and in vitro functional studies were performed with apoA-IV overexpressing cells. ApoA-IV was also analyzed in the intestinal mucosa of patients with inflammatory bowel diseases (IBD), together with other genes involved in epithelial junctional integrity.

METHODS

A yeast-two-hybrid screening was used to identify apoA-IV-interactors. ApoA-IV was overexpressed in Caco-2 and HT-29 mucosal cells for colocalization and in vitro epithelial permeability studies. Mucosal biopsies from quiescent regions of colon transversum and terminal ileum were subjected to DNA-microarray analysis and pathway-related data mining.

RESULTS

Four proteins interacting with apoA-IV were identified, including apolipoprotein B-100, alpha1-antichymotrypsin, cyclin C, and the cytosolic adaptor alpha-catenin, thus linking apoA-IV to adherens junctions. Overexpression of apoA-IV was paralleled with a differentiated phenotype of intestinal epithelial cells, upregulation of junctional proteins, and decreased paracellular permeability. Colocalization between alpha-catenin and apoA-IV occurred exclusively in junctional complexes. ApoA-IV was downregulated in quiescent mucosal tissues from patients suffering from IBD. In parallel, only a distinct set of junctional genes was dysregulated in non-inflamed regions of IBD gut.

CONCLUSIONS

ApoA-IV may act as a stabilizer of adherens junctions interacting with alpha-catenin, and is likely involved in the maintenance of junctional integrity. ApoA-IV expression is significantly impaired in IBD mucosa, even in non-inflamed regions.

Pam3CSK4 and LTA-TLRs ligands associated with microdomains induce IL8 production in human adrenocortical cancer cells

Bacterially derived ligands, Pam3CSK4 and LPS, can directly impact adrenal glands steroidogenesis through microdomain-related TLR1/2 and 4, respectively, and indirectly via immune cell-derived cytokines. The bilateral immunoadrenal relationship plays an important role in the proper functioning of both systems. CXC chemokine-dependent immune cell infiltration into adrenocortical carcinomas (ACC), which correlates with poor prognosis, is a common phenomenon. Recently, IL8 was identified in ACC and NCI-H295R cells, and was found to contribute to ACC tumour growth. The aim of this study was to clarify the role of different TLR ligands in IL8 production in NCI-H295R cells. This is the first study to demonstrate the expression of several TLRs including TLR1, 3, 6, 7 and 9 in human adrenocortical cells by using the RT-PCR approach. Only stimulation with TLR1/6 together with TLR2 ligands resulted in IL8 peptide and mRNA induction in a dose and time-dependent manner. Our data suggest that gram-positive bacteria-related TLR1/2/6 ligands might contribute to adrenal gland tumorigenesis via IL8 production.

ApoA-I-binding protein (AI-BP) and its homologues hYjeF_N2 and hYjeF_N3 comprise the YjeF_N domain protein family in humans with a role in spermiogenesis and oogenesis

The screening for additional human YjeF_N domain containing proteins beside the apolipoprotein A-I interacting protein (AI-BP), identified two other genes designated hYjeF_N2-15q23 (formerly human homologue of yeast edc3) and hYjeF_N3-19p13.11 comprising the human YjeF_N family. AI-BP is ubiquitously expressed, with a predominance of these tissues where the homologues were found to be restricted including brain, mammary gland, testes and ovaries. Immunohistochemistry of human testes and ovaries showed an expression of hYjeF_N3-19p13.11 only in Leydig cells and theca cells, respectively, indicating a role in steroid hormone metabolism. Interestingly, the protein was also strongly expressed in Leydig cell tumors and in thecofibromas. The identification of hYjeF_N2-15q23 in theca cells and granulosa cells in ovaries, in human spermatids of meiotic division part II and the apical membrane of Sertoli cells in testes suggest similar functions in oogenesis and sperm maturation which is strengthened by the identification of the spermatogenesis regulator HMGA1 as a conserved transcription factor. However, in contrast to AI-BP, both homologous proteins are unable to bind apoA-I. These results relate the human YjeF_N domain containing protein family to cholesterol processing and steroid hormone metabolism in spermiogenesis and oogenesis, and AI-BP may link this function to the HDL pathway.

Glycoxidised LDL isolated from subjects with impaired glucose tolerance increases CD36 and peroxisome proliferator-activator receptor gamma gene expression in macrophages

AIMS/HYPOTHESIS

Glycoxidised LDL has been implicated in the pathogenesis of atherosclerosis, a major complication of diabetes. Since atherogenesis may occur at an early stage of diabetes, we investigated whether circulating LDL isolated from subjects with IGT (n = 20) showed an increased glycoxidation status and explored the proatherogenic effects of LDL samples on macrophages.

SUBJECTS AND METHODS

We investigated LDL modifications using GC-MS. Murine macrophages were incubated with LDL samples for 1 h, and then mRNA expression rates of the scavenger receptors CD36 and scavenger receptor class B type 1 (SCARB1, formerly known as SR-BI) and transcription factor peroxisome proliferator-activator receptor gamma (PPARgamma) were quantified by real-time RT-PCR.

RESULTS

The GC-MS experiments revealed that oxidative modifications of proline, arginine, lysine and tyrosine residues in apolipoprotein B100 were three- to fivefold higher in LDL samples from IGT subjects compared with those from NGT subjects (n = 20). Moreover, LDL glycoxidation estimated by both Nepsilon-(carboxymethyl)lysine (CML) and Nepsilon-(carboxyethyl)lysine (CEL) residues was increased more than ninefold in LDL from IGT subjects compared with samples from NGT subjects. Compared with NGT LDL, IGT LDL elicited a significantly higher CD36 (p < 0.05) and PPARG (p < 0.05) gene expression, whereas SCARB1 mRNA expression was not affected.

CONCLUSIONS/INTERPRETATION

These data suggest that IGT is associated with increased glycoxidation of circulating LDL, which might contribute to the conversion of macrophages into a proatherogenic phenotype.

Human adipocytes induce an ERK1/2 MAP kinases-mediated upregulation of steroidogenic acute regulatory protein (StAR) and an angiotensin II — sensitization in human adrenocortical cells

OBJECTIVES

Hypertension is a major complication of overweight with frequently elevated aldosterone levels in obese patients. Our previous work suggests a direct stimulation of adrenal aldosterone secretion by adipocytes. Owing to aldosterone's important role in maintaining blood pressure homeostasis, its regulation in obesity is of major importance. One objective was to determine the signaling mechanisms involved in adipocyte-induced aldosterone secretion. In addition to a direct stimulation, a sensitization toward angiotensin II (AngII) might be involved. The second objective was to determine a possible adipokines-induced sensitization of human adrenocortical cells to AngII.

DESIGN

Human subcutaneous adipocytes and adrenocortical cells, and the adrenocortical cell line NCI-H295R were used. Adrenocortical cells were screened for signal transduction protein expression and phosphorylation. Subsequently, steroidogenic acute regulatory protein (StAR), cAMP response element-binding protein (CREB), cAMP and phosphorylated extracellular regulated kinase were analyzed by Western blot, enzyme-linked immunosorbent assay, quantitative PCR, reporter gene assay and confocal microscopy to investigate their role in adipocyte-mediated aldosterone secretion.

RESULTS

AngII-mediated aldosterone secretion was largely increased by preincubating H295R cells with adipocyte secretory products. StAR mRNA and StAR protein were upregulated in a time-dependent way. This steroidogenic effect was independent of the cAMP-protein kinase A (PKA) pathway as cellular cAMP was unaltered and inhibition of PKA by H89 failed to reduce aldosterone secretion. However, CREB reporter gene activity was moderately elevated. Upregulation of StAR was accompanied by ERK1/2 MAP kinase activation and nuclear translocation of the kinases. Inhibition of MAP kinase by UO126 abolished adipokine-stimulated aldosterone secretion from primary human adrenocortical and H295R cells, and inhibited StAR gene activity. Adipokines stimulated steroidogenesis also in primary human adrenocortical cells, supporting a role in human physiology and/or pathology.

CONCLUSIONS

Adipokines induce aldosterone secretion from human adrenocortical cells and sensitization of the cells to stimulation by AngII, possibly mediated via ERK1/2-dependent upregulation of StAR activity. This stimulation of aldosterone secretion could be one link between overweight and inappropriately elevated aldosterone levels.

Corticotropin releasing hormone and its function in the skin

The skin, as the largest organ of the body, is strategically located as a barrier between the external and internal environments, being permanently exposed to noxious stressors such as bursts of radiation (solar, thermal), mechanical energy, or chemical and biological insults. Because of its functional domains and structural diversity, the skin must have a constitutive mechanism for dealing with the stressors. Activities of the skin are mostly regulated by local cutaneous factors and stressed skin can generate signals to produce rapid (neural) or slow (humoral) responses to local or systemic levels. Thus, the skin neuroendocrine system is comprised of locally produced neuroendocrine mediators that interact with corresponding specific receptors through para- or autocrine mechanisms. Furthermore, it is known for several years that the corticotropin-releasing hormone (CRH)/ pro-opiomelanocorticotropin (POMC) skin system fulfils analogous functions to the hypothalamic-pituitary-adrenal (HPA) stress axis. Additionally, skin cells produce hormones, neurotansmitters and neuropeptides, having the corresponding receptors and the skin itself is able to fulfill a multidirectional communication between endocrine, immune and central nervous systems as well as other internal organs. In summary, the skin expresses an equivalent of the prominent hypothalamic-pituitary-adrenal stress axis that may act as a cutaneous defense system, operating as a coordinator and executor of local responses to stress, in addition to its normal function: the preservation of body homeostasis.

[Prevention of diabetes mellitus: the future of German diabetology]

One of the challenges in clinical diabetology today is to develop and implement diabetes prevention management programs for clinical practice. Recent studies have convincingly demonstrated that lifestyle intervention, addressing diet and exercise as well as pharmacologic preventive strategies reduced the risk of progressing from impaired glucose tolerance to diabetes. With respect to the worldwide burden of diabetes these studies offer a compelling evidence-base for the important translation of the research findings into community-based prevention strategies and the development of a National Diabetes Prevention Program. The workgroup "diabetes prevention" from the German Diabetes Association together with the National Action Forum Diabetes and the German Diabetes Foundation developed a concept for a National Program. This comprises a 3-step-intervention: in a first step individuals at high risk to develop type 2 diabetes are identified. The second step provides an intensive group intervention to prevent diabetes and in a third step continuous intervention should facilitate motivation maintenance and evaluation. This third step is the crucial step to maintain the effect in changing lifestyle. Recently, a compendium for diabetes prevention was developed as a practical guideline explaining how to implement prevention programs. This guideline also includes the structure of a national prevention program with a prevention manager having a central role in the concept and suggestions for evaluation and quality control.

Adipocyte-derived products induce the transcription of the StAR promoter and stimulate aldosterone and cortisol secretion from adrenocortical cells through the Wnt-signaling pathway

CONTEXT

Obesity is associated with hypersecretion of cortisol and aldosterone and a high prevalence of arterial hypertension. At the cellular level, a direct effect of adipocytes on the expression of the steroidogenic acute regulatory (StAR) protein, a regulator of cortisol and aldosterone synthesis, and on aldosterone and cortisol secretion has been shown. However, the molecular mechanisms mediating this effect are not known.

OBJECTIVE

Wnt-signaling molecules are secreted by adipocytes and regulate the activity of SF-1, a key transcription factor in adrenal steroidogenesis. Therefore, we investigated whether adipocytes stimulate adrenal steroidogenesis through the activation of Wnt-signaling.

RESULTS

Using immunohistochemistry, we detected the expression of frizzled and beta-catenin in the adult human adrenal cortex. Transient transfection of a Wnt-dependent reporter-gene into adrenal NCI-H295R cells showed an induction of Wnt-mediated transcription to 308% after treatment with human fat cell-conditioned medium (FCCM). This finding was paralleled by an induction of StAR promoter activity (420%) by FCCM. The induction of StAR promoter activity by FCCM was inhibited by 49% when Wnt-signaling was blocked by the soluble Wnt-antagonist secreted Frizzled-Related-Protein-1 (sFRP-1). Overexpression of a constitutively active mutant of beta-catenin induced the transcription of the StAR promoter (440%). beta-Catenin and FCCM induced SF-1-mediated transcription at a SF-1-driven reporter gene (420 and 402%, respectively). Furthermore, the secretion of aldosterone and cortisol by NCI-H295R cells induced by FCCM was significantly inhibited by the Wnt-antagonist sFRP-1.

CONCLUSION

These data indicate that the Wnt-signaling pathway is one of the mechanisms mediating the effects of fat cells on adrenal StAR transcription and aldosterone and cortisol secretion.

Role of DHEA and growth factors in chromaffin cell proliferation

Dehydroepiandrostreone (DHEA) is a neuroactive steroid produced by the inner layer of the adrenal cortex close to the adrenomedullary cells. Chromaffin cell growth and proliferation are under the control of insulin-like growth factor II (IGF-II) and basic fibroblast growth factor (bFGF). The aim of the present study was to examine the role of DHEA on chromaffin cell proliferation induced by IGF-II and bFGF. In our model, DHEA significantly decreased IGF-II-induced proliferation by 48.7%, whereas it did not affect the proliferation induced by bFGF. These data suggest that DHEA exerts a paracrine function in the control of chromaffin cell growth.

150 years of Sigmund Freud: What would Freud have said about the obesity epidemic?

The 150th birthday of Sigmund Freud has triggered widespread interest and media coverage on his unique contribution and impact on society. Recent evidence from neuroscience and advanced imaging technology has provided support for some of his major concepts including the unconscious and the key role of early life events. In this perspective, we attempt to write on his behalf an updated version of a Freudian way of thinking focused on the current high rates of obesity and depression.

The Role of Toll-like Receptors in the Immune-Adrenal Crosstalk

Sepsis and septic shock remain major health concerns worldwide, and rapid activation of adrenal steroid release is a key event in the organism's first line of defense during this form of severe illness. Toll-like receptors (TLRs) are critical in the early immune response upon bacterial infection, and recent data from our lab demonstrate a novel link between the innate immune system and the adrenal stress response mediated by TLRs. Glucocorticoids and TLRs regulate each other in a bidirectional way. Bacterial toxins acting through TLRs directly activate adrenocortical steroid release. TLR-2 and TLR-4 are expressed in human and mice adrenals and TLR-2 deficiency is associated with an impaired glucocorticoid response. Furthermore, TLR-2 deficiency in mice is associated with marked cellular alterations in adrenocortical tissue. TLR-2-deficient mice have an impaired adrenal corticosterone release following inflammatory stress induced by bacterial cell wall compounds. This defect appears to be associated with a decrease in systemic and intraadrenal cytokine expression. In conclusion, TLRs play a crucial role in the immune-adrenal crosstalk. This close functional relationship needs to be considered in the treatment of inflammatory diseases requiring an intact adrenal stress response.

Approaching the shared biology of obesity and depression: the stress axis as the locus of gene-environment interactions

Obesity and depression are serious public health problems and also constitute cardiovascular disease risk factors. Research organizations have called for efforts to explore the interrelationship between obesity and depression. A useful starting point is the fact that in both disorders there is dysregulation of stress systems. We review molecular and clinical evidence indicating that the mediators of the stress response are a key locus for gene-environment interactions in the shared biology of depression and obesity. Scientific milestones include translational paradigms such as mice knockouts, imaging and pharmacogenomic approaches that can identify new therapeutic strategies for those burdened by these two afflictions of contemporary civilization. Perspectives for the future are promising. Our ability to dissect the underpinnings of common and complex diseases with shared substrates will be greatly enhanced by the Genes and Environment Initiative, the emerging Large Scale Studies of Genes and Environment in Common Disease, and the UK Biobank Project.