Adipokine expression profile in adipocytes of different mouse models of obesity

The Adipokines in Cancer Cachexia

Cachexia is a devastating pathology induced by several kinds of diseases, including cancer. The hallmark of cancer cachexia is an extended weight loss mainly due to skeletal muscle wasting and fat storage depletion from adipose tissue. The latter exerts key functions for the health of the whole organism, also through the secretion of several adipokines. These hormones induce a plethora of effects in target tissues, ranging from metabolic to differentiating ones. Conversely, the decrease of the circulating level of several adipokines positively correlates with insulin resistance, metabolic syndrome, diabetes, and cardiovascular disease. A lot of findings suggest that cancer cachexia is associated with changed secretion of adipokines by adipose tissue. In agreement, cachectic patients show often altered circulating levels of adipokines. This review reported the findings of adipokines (leptin, adiponectin, resistin, apelin, and visfatin) in cancer cachexia, highlighting that to study in-depth the involvement of these hormones in this pathology could lead to the development of new therapeutic strategies.

Molecular cloning of feline resistin and the expression of resistin, leptin and adiponectin in the adipose tissue of normal and obese cats

Resistin, one of the adipokines that has a cycteine-rich C-terminus, is considered to relate to the development of insulin resistance in rats. However, in cats, there is little knowledge regarding resistin. In this study, we cloned the feline resistin cDNA from adipose tissue by RT-PCR. The feline resistin clone contained an entire open reading frame encoding 107 amino acids that had 72.8%, 75.4%, 50.9% and 51.8% homology with bovine, human, mouse and rat homologues, respectively. In both subcutaneous and visceral adipose tissues, the transcription levels of feline resistin mRNA were significantly higher in obese cats than normal cats, and those of feline adiponectin mRNA were significantly lower in obese cats than normal cats. However, there was no difference in the expression of feline leptin between normal and obese cats. On the other hand, in both normal and obese cats, there were no significant differences in resistin, leptin and adiponectin mRNA levels between subcutaneous and visceral adipose tissues. In cats, the altered expression of resistin and adiponectin mRNA with obesity may contribute to the pathogenesis of insulin resistance and subsequent diabetes mellitus. In addition to feline adiponectin, the feline resistin cDNA clone obtained in this study will be useful for further investigation of the pathogenesis of obesity in cats.

Reduced Slc2a4/GLUT4 expression in subcutaneous adipose tissue of monosodium glutamate obese mice is recovered after atorvastatin treatment

BACKGROUND

Decreased expression of glucose transporter protein GLUT4, encoded by the solute carrier 2A4 (Slc2a4) gene, is involved in obesity-induced insulin resistance. Local tissue inflammation, by nuclear factor-κB (NFκB)-mediated pathway, has been related to Slc2a4 repression; a mechanism that could be modulated by statins. Using a model of obesity with insulin resistance, this study investigated whether (1) inflammatory markers and Slc2a4 expression are altered; (2) atorvastatin has beneficial effects on inflammation and Slc2a4 expression; and (3) inhibitor of NFκB (IKK)/NFκB pathway is involved in subcutaneous adipose tissue (SAT).

FINDINGS

Obese mice showed insulin resistance, decreased expression of Slc2a4 mRNA (66%, P < 0.01) and GLUT4 protein (30%, P < 0.05), and increased expression of interleukin 6 (Il6) mRNA (44%, P < 0.05) in SAT. Obese mice treated with atorvastatin had enhanced in vivo insulin sensitivity, besides increased Slc2a4/GLUT4 expression and reduced Il6 expression in SAT. No alterations of tumor necrosis factor-α, interleukin 1β and adiponectin expression or IKKα/β activity in SAT of obese mice or obese mice treated with atorvastatin were observed.

CONCLUSIONS

Atorvastatin has beneficial effect upon glycemic homeostasis, which may be related to its positive impact on Il6 and Slc2a4/GLUT4 expression in SAT.

Lipopolysaccharide inhibits the expression of resistin in adipocytes

Resistin is an adipocytokine leading to insulin resistance. Endotoxin/lipopolysaccharide (LPS) has been reported to decrease the expression of resistin mRNA and protein in both lean and db/db obese mice, although the underlying mechanism remains unclear. Several models such as ex vivo culture of adipose tissues, primary rat adipocytes and 3T3-L1 adipocytes were used to further characterize the effect of LPS on the expression of resistin. LPS attenuated both the resistin mRNA and protein in a time- and dose-dependent manner. In the presence of actinomycin D, LPS failed to reduce the half-life of resistin mRNA, suggesting a transcriptional mechanism. The lipid A fraction is crucial for the inhibition of resistin expression induced by LPS. Pharmacological intervention of c-Jun N-terminal kinase (JNK) reversed the inhibitory effect of LPS. LPS down-regulated CCAAT/enhancer-binding protein α (C/EBP-α; CEBPA) and peroxisome proliferator-activated receptor γ (PPAR-γ; PPARG), while activation of C/EBP-α or PPAR-γ by either over-expressing these transcriptional factors or by rosiglitazone, an agonist of PPAR-γ, blocked the inhibitory effect of LPS on resistin. C/EBP homologous protein (CHOP-10; DDIT3) was up-regulated by LPS, while a CHOP-10 antisense oligonucleotide reversed the decrement of resistin protein induced by LPS. Taken together, these results suggest that LPS inhibits resistin expression through a unique signaling pathway involving toll-like receptor 4, JNK, CHOP-10 and C/EBP-α/PPAR-γ.

Daily regulation of hormone profiles

The highly coordinated output of the hypothalamic biological clock does not only govern the daily rhythm in sleep/wake (or feeding/fasting) behaviour but also has direct control over many aspects of hormone release. In fact, a significant proportion of our current understanding of the circadian clock has its roots in the study of the intimate connections between the hypothalamic clock and multiple endocrine axes. This chapter will focus on the anatomical connections used by the mammalian biological clock to enforce its endogenous rhythmicity on the rest of the body, using a number of different hormone systems as a representative example. Experimental studies have revealed a highly specialised organisation of the connections between the mammalian circadian clock neurons and neuroendocrine as well as pre-autonomic neurons in the hypothalamus. These complex connections ensure a logical coordination between behavioural, endocrine and metabolic functions that will help the organism adjust to the time of day most efficiently. For example, activation of the orexin system by the hypothalamic biological clock at the start of the active phase not only ensures that we wake up on time but also that our glucose metabolism and cardiovascular system are prepared for this increased activity. Nevertheless, it is very likely that the circadian clock present within the endocrine glands plays a significant role as well, for instance, by altering these glands' sensitivity to specific stimuli throughout the day. In this way the net result of the activity of the hypothalamic and peripheral clocks ensures an optimal endocrine adaptation of the metabolism of the organism to its time-structured environment.

Impaired expression of the inducible cAMP early repressor accounts for sustained adipose CREB activity in obesity

OBJECTIVE

Increase in adipose cAMP-responsive element binding protein (CREB) activity promotes adipocyte dysfunction and systemic insulin resistance in obese mice. This is achieved by increasing the expression of activating transcription factor 3 (ATF3). In this study, we investigated whether impaired expression of the inducible cAMP early repressor (ICER), a transcriptional antagonist of CREB, is responsible for the increased CREB activity in adipocytes of obese mice and humans.

RESEARCH DESIGN AND METHODS

Total RNA and nuclear proteins were prepared from visceral adipose tissue (VAT) of human nonobese or obese subjects and white adipose tissue (WAT) of C57Bl6-Rj mice that were fed with normal or high-fat diet for 16 weeks. The expression of genes was monitored by real-time PCR, Western blotting, and electromobility shift assays. RNA interference was used to silence the expression of Icer.

RESULTS

The expression of Icer/ICER was reduced in VAT and WAT of obese humans and mice, respectively. Diminution of Icer/ICER was restricted to adipocytes and was accompanied by a rise of Atf3/ATF3 and diminution of Adipoq/ADIPOQ and Glut4/GLUT4. Silencing the expression of Icer in 3T3-L1 adipocytes mimicked the results observed in human and mice cells and hampered glucose uptake, thus confirming the requirement of Icer for appropriate adipocyte function.

CONCLUSIONS

Impaired expression of ICER contributes to elevation in CREB target genes and, therefore, to the development of insulin resistance in obesity.

Congenital leptin deficiency: diagnosis and effects of leptin replacement therapy

To describe our 10-year experience in treating leptin-deficient humans. Three adults and one boy presented with childhood-onset morbid obesity, hypogonadism and family history of obesity and early death. Serum leptin was inappropriately low. A recessive C105T leptin gene mutation was identified. Metabolic and endocrine assessments were conducted, before and while on and off leptin. The adults' body mass index decreased from 51.2 ± 2.5 to 29.5 ± 2.8 kg/m(2). Serum lipids normalized, insulin resistance decreased, and one of the initially diabetic females became normoglycemic. Hypogonadotropic hypogonadism was reversed, and other changes were observed in the adrenal, sympathetic, somatotropic and thyroid functions. Leptin replacement therapy reverses endocrine and metabolic alterations associated with leptin deficiency. Some of these results may be extrapolated to other diseases.

Oral Administration of Semicarbazide Limits Weight Gain together with Inhibition of Fat Deposition and of Primary Amine Oxidase Activity in Adipose Tissue

An enzyme hitherto named semicarbazide-sensitive amine oxidase (SSAO), involved in the oxidation of primary amines, is abundantly expressed in adipocytes. Although SSAO physiological functions remain unclear, several molecules inhibiting its activity have been described to limit fat accumulation in preadipocyte cultures or to reduce body weight gain in obese rodents. Here, we studied whether oral administration of semicarbazide, a prototypical SSAO inhibitor, limits fat deposition in mice. Prolonged treatment with semicarbazide at 0.125% in drinking water limited food and water consumption, hampered weight gain, and deeply impaired fat deposition. The adiposomatic index was reduced by 31%, while body mass was reduced by 15%. Such treatment completely inhibited SSAO, but did not alter MAO activity in white adipose tissue. Consequently, the insulin-like action of the SSAO substrate benzylamine on glucose transport was abolished in adipocytes from semicarbazide-drinking mice, while their insulin sensitivity was not altered. Although semicarbazide is currently considered as a food contaminant with deleterious effects, the SSAO inhibition it induces appears as a novel concept to modulate adipose tissue development, which is promising for antiobesity drug discovery.

The purinergic P2Y1 receptor supports leptin secretion in adipose tissue

Extracellular nucleotides have been shown to trigger intracellular calcium release and influence leptin secretion in differentiated white and brown adipocytes through activation of various but not clearly identified P2 receptors. In the present study, we wished to assess whether or not the P2Y1 ADP receptor is functional in white adipocytes and whether it could affect the secretion of adipocyte-derived hormones. Stromal cells and mature adipocytes were isolated from epididymal adipose tissue from wild-type and P2Y1 knockout (KO) C57-black/six male mice. The expression of the P2Y1 receptor in adipocytes was confirmed by RT-PCR and intracellular calcium measurements with fura 2-AM. KO of P2Y1 receptors did not affect the cell size and lipid content of mature adipocytes or the differentiation of the stromal cell fraction, but the leptin production of mature adipocytes was decreased under basal and insulin-stimulated conditions. A selective P2Y1 antagonist, MRS2500, reduced leptin release in isolated adipocytes. The plasma and adipose tissue mRNA levels of leptin were also lower in P2Y1 KO mice as compared with wild-type animals. However, in mice fed a high-fat diet, the plasma leptin levels were greatly enhanced and the inhibitory effect of P2Y1 KO was not observed. These results show that the P2Y1 receptor supports leptin production in isolated white adipocytes through a transcriptional mechanism. This function of the receptor may regulate plasma leptin in lean mice but is overcome in obese animals.

Resting and exercise-induced IL-6 levels in children with Type 1 diabetes reflect hyperglycemic profiles during the previous 3 days

Poor glycemic control in Type 1 diabetes (T1DM) causes long-term cardiovascular complications, at least in part via chronic, low-grade inflammation associated with recurrent hyperglycemia. While physical activity can reduce both inflammation and cardiovascular risks, the underlying molecular mechanisms remain unclear. This is particularly important for T1DM children, for whom the prevention of long-term cardiovascular complications must include optimization of exercise-related anti-inflammatory strategies. We therefore studied the effect of prior hyperglycemia on resting and exercise-induced inflammatory status (plasma IL-6) in T1DM children. Glycemia was continuously recorded with a continuous glucose monitoring system (CGMS) system for 63 h preceding a 30-min intermittent cycling exercise protocol at approximately 80% peak rate of oxygen uptake (VO2max). Euglycemia (4.4-6.1 mM) was maintained for 90 min before, during, and 30 min after exercise. IL-6 plasma concentration (pg/ml) was measured at baseline, at end exercise, and 30 min postexercise. Subjects were then divided into quartiles based on average glycemia during the CGMS recording. IL-6 levels (pg/ml) were lowest in the quartile with lowest average 3-day glycemia and increased proportionally to greater hyperglycemic exposure; this was observed at baseline (0.86 +/- 0.10, 1.06 +/- 0.16, 1.14 +/- 0.14, 1.20 +/- 0.16), absolute IL-6 change (Delta) at end exercise (0.20 +/- 0.16, 0.32 +/- 0.10, 0.48 +/- 0.09, 0.62 +/- 0.13), and Delta at 30 min postexercise (0.49 +/- 0.13, 0.71 +/- 0.16, 0.89 +/- 0.14, 1.38 +/- 0.33). Therefore, poorly controlled glycemic profile, even in the 63 h preceding an exercise challenge, can alter inflammatory adaptation in T1DM children. Our data underscore the necessity to fully understand all molecular aspects of physical activity to provide the scientific rationale for exercise regimens that will be able to maximize health benefits for T1DM children.

Endoplasmic reticulum stress regulates adipocyte resistin expression

OBJECTIVE

Resistin is a secreted polypeptide that impairs glucose metabolism and, in rodents, is derived exclusively from adipocytes. In murine obesity, resistin circulates at elevated levels but its gene expression in adipose tissue is paradoxically reduced. The mechanism behind the downregulation of resistin mRNA is poorly understood. We investigated whether endoplasmic reticulum (ER) stress, which is characteristic of obese adipose tissue, regulates resistin expression in cultured mouse adipocytes.

RESEARCH DESIGN AND METHODS

The effects of endoplasmic stress inducers on resistin mRNA and secreted protein levels were examined in differentiated 3T3-L1 adipocytes, focusing on the expression and genomic binding of transcriptional regulators of resistin. The association between downregulated resistin mRNA and induction of ER stress was also investigated in the adipose tissue of mice fed a high-fat diet.

RESULTS

ER stress reduced resistin mRNA in 3T3-L1 adipocytes in a time- and dose-dependent manner. The effects of ER stress were transcriptional because of downregulation of CAAT/enhancer binding protein-alpha and peroxisome proliferator-activated receptor-gamma transcriptional activators and upregulation of the transcriptional repressor CAAT/enhancer binding protein homologous protein-10 (CHOP10). Resistin protein was also substantially downregulated, showing a close correspondence with mRNA levels in 3T3-L1 adipocytes as well as in the fat pads of obese mice.

CONCLUSIONS

ER stress is a potent regulator of resistin, suggesting that ER stress may underlie the local downregulation of resistin mRNA and protein in fat in murine obesity. The paradoxical increase in plasma may be because of various systemic abnormalities associated with obesity and insulin resistance.

Sepsis-induced intestinal microvascular and inflammatory responses in obese mice

Although clinical obesity is associated with increases in the morbidity and mortality of sepsis, little is known about the mechanisms that underlie the influence of obesity on sepsis. The objective of this study was to determine (a) whether obesity is associated with exaggerated inflammatory and thrombogenic responses in the intestinal microvasculature of septic mice and (b) whether these microvascular alterations are related to changes in the serum levels of cytokines that are produced by adipose tissue. Intravital microscopy was used to quantify leukocyte and platelet adhesion in intestinal postcapillary venules of lean wild-type (WT) mice, and two murine models of obesity, that is, ob/ob and db/db mice. Sepsis was induced by cecal ligation and perforation (CLP). Serum cytokine levels were measured using a cytometric bead assay, whereas adipokines were quantified using enzyme-linked immunosorbent assay. Cecal ligation and perforation elicited significant increases in the adhesion of leukocytes and platelets in venules of lean WT mice. These CLP-induced adhesive interactions were much more pronounced in the microvasculature of both ob/ob and db/db mice. Cecal ligation and perforation was associated with significant increases in serum cytokines in both WT and ob/ob mice, but such changes were not detected in db/db mice. However, db/db (but not WT or ob/ob) mice did exhibit significant increases in serum leptin and adiponectin levels after CLP. Sepsis promotes more intense inflammatory and thrombogenic responses in the gut microcirculation of obese mice than in their lean counterparts. The obesity-enhanced microvascular dysfunction in septic mice shows no consistent correlation with serum cytokines or adipokines.

Pref-1 and adipokine expression in adipose tissues of GK and Zucker rats

In view of the central role of preadipocyte factor-1, adiponectin and leptin in white adipose tissue function, the aim of the present study was to analyze the mRNA expression of these proteins and of the inflammatory markers interleukin-6 and tumor necrosis factor-alpha in visceral and subcutaneous fat pads of rats with different metabolic disorders. We demonstrated highly divergent expression of preadipocyte factor-1, upregulated expression of adiponectin, interleukin-6 and TNF-alpha mRNA in adipose tissues of the diabetic Goto Kakizaki rat compared to the obese Zucker rat. This was correlated to an increased number of large adipocytes and serum levels of adiponectin. Furthermore, in all four strains studied (as above plus Wistar Furth and Zucker Lean), significant heterogeneity was evident in adipokine expression within specific adipose tissues previously defined as belonging to the visceral or subcutaneous fat depots. These results suggest that significantly increased levels of inflammation and redistribution of adipocyte size are mechanisms contributing to the development of type 2 diabetes in the GK rat.

Nutrigenomics, beta-cell function and type 2 diabetes

INTRODUCTION

The present investigation was designed to investigate the accuracy and precision of lactate measurement obtained with contemporary biosensors (Chiron Diagnostics, Nova Biomedical) and standard enzymatic photometric procedures (Sigma Diagnostics, Abbott Laboratories, Analyticon).

MATERIALS AND METHODS

Measurements were performed in vitro before and after the stepwise addition of 1 molar sodium lactate solution to samples of fresh frozen plasma to systematically achieve lactate concentrations of up to 20 mmol/l.

RESULTS

Precision of the methods investigated varied between 1% and 7%, accuracy ranged between 2% and -33% with the variability being lowest in the Sigma photometric procedure (6%) and more than 13% in both biosensor methods.

CONCLUSION

Biosensors for lactate measurement provide adequate accuracy in mean with the limitation of highly variable results. A true lactate value of 6 mmol/l was found to be presented between 4.4 and 7.6 mmol/l or even with higher difference. Biosensors and standard enzymatic photometric procedures are only limited comparable because the differences between paired determinations presented to be several mmol. The advantage of biosensors is the complete lack of preanalytical sample preparation which appeared to be the major limitation of standard photometry methods.

Mammary tumor development from T47-D human breast cancer cells in obese ovariectomized mice with and without estradiol supplements

Obesity is a risk factor for postmenopausal breast cancer, particularly for development of estrogen-receptor (ER)-positive tumors. Additionally, obesity is implicated in breast cancer progression. However, few studies address mechanisms of action of how obesity mediates these responses. Our goal was to address how obesity and/or elevated serum leptin affects tumor formation from ER-positive T47-D cells. In Study 1 ovariectomized CD-1 nude female mice were injected with goldthioglucose (GTG) at 0.5 mg/g body weight in saline or the vehicle at 6 weeks of age. At 10 weeks of age mice were inoculated with T47-D cells and implanted with estrogen pellets. In Study 2 mice were injected with 0.3 mg/g GTG or the vehicle. At 10 weeks of age cells were inoculated and mice were implanted with estrogen or placebo pellets. Mice were followed until 30 weeks of age. Some GTG mice became obese and others were non-responders. In Study 1 no mice developed tumors. In Study 2 mice with placebo pellets developed more tumors than mice with estrogen pellets, 50% vs. 13%. GTG-obese mice with placebo pellets had a 100% tumor incidence compared to 50% and 20% for GTG-lean and controls without estrogen. Serum leptin was higher in obese compared to lean mice and adiponectin was not affected by body weight. Adiponectin:leptin ratio was significantly reduced in obese compared to lean mice. Leptin, leptin receptor and signaling protein expression were determined in mammary and tumor tissue. Leptin and STAT3 were most abundant in tumors. These findings suggest that in vivo estrogen suppressed proliferation of T47-D cells but without supplemental estrogen obesity enhanced tumor development. The exact reason for this is not presently clear.

Effect of pronounced weight loss on visceral fat, liver steatosis and adiponectin isoforms

BACKGROUND

Weight loss induced by bariatric surgery is an effective method to reverse obesity and comorbidities. The aim of this prospective weight loss study was to investigate changes of body fat distribution in relation to adiponectin and its isoforms and further to investigate the influence of both body fat distribution and adiponectin on the degree of liver steatosis.

DESIGN

Fifteen severely obese female patients (body mass index 43.1 +/- 4.1, mean age 34.5 +/- 8.6 years) were examined before and after surgical treatment. Grading of fatty liver disease and the subcutaneous and visceral fat diameters were determined by abdominal ultrasonography. Metabolic parameters were determined using standard methods; serum total adiponectin and its isoforms were detected by enzyme immuno assay (EIA).

RESULTS

Mean weight loss was 28.3 kg, which was mostly due to a loss in fat mass, accompanied by an increase in total adiponectin and the high molecular weight (HMW) adiponectin isoform. Visceral adipose tissue (VAT) diameter was highly correlated with liver steatosis, even more strongly than the parameters of liver function. In addition, liver steatosis correlated negatively with HMW adiponectin and binary logistic regression revealed that changes in fat mass, HMW adiponectin and alanine aminotransferase (ALT) were the best predictors for changes in the degree of hepatic steatosis.

CONCLUSIONS

Our results suggest that circulating HMW adiponectin is associated with both VAT and liver steatosis. In summary, the major findings were that the VAT diameter is highly correlated with liver steatosis, even stronger than the parameters of liver function and the association of HMW adiponectin with liver steatosis was better than with total adiponectin.

Enhanced muscle by myostatin propeptide increases adipose tissue adiponectin, PPAR-alpha, and PPAR-gamma expressions

Muscle tissue utilizes a large portion of metabolic energy for its growth and maintenance. Previously, we demonstrated that transgenic over-expression of myostatin propeptide in mice fed a high-fat diet enhanced muscle mass and circulating adiponectin while the wild-type mice developed obesity and insulin resistance. To understand the effects of enhanced muscle growth on adipose tissue metabolism, we analyzed adiponectin, PPAR-alpha, and PPAR-gamma mRNA expressions in several fat tissues. Results indicated muscled transgenic mice fed a high-fat diet displayed increased epididymal adiponectin mRNA expression by 12 times over wild-type littermates. These transgenic mice fed either a high or normal fat diet also displayed significantly high levels of PPAR-alpha and PPAR-gamma expressions above their wild-type littermates in epididymal fat while their expressions in mesenteric fats were not significantly different between transgenic mice and their littermates. This study demonstrates that enhanced muscle growth has positive effects on fat metabolisms through increasing adiponectin expression and its regulations.

International Day for the Evaluation of Abdominal Obesity (IDEA): a study of waist circumference, cardiovascular disease, and diabetes mellitus in 168,000 primary care patients in 63 countries

BACKGROUND

Abdominal adiposity is a growing clinical and public health problem. It is not known whether it is similarly associated with cardiovascular disease (CVD) and diabetes mellitus in different regions around the world, and thus whether measurement of waist circumference (WC) in addition to body mass index (BMI) is useful in primary care practice.

METHODS AND RESULTS

Randomly chosen primary care physicians in 63 countries recruited consecutive patients aged 18 to 80 years on 2 prespecified half days. WC and BMI were measured and the presence of CVD and diabetes mellitus recorded. Of the patients who consulted the primary care physicians, 97% agreed to participate in the present study. Overall, 24% of 69,409 men and 27% of 98,750 women were obese (BMI > or = 30 kg/m2). A further 40% and 30% of men and women, respectively, were overweight (BMI 25 to 30 kg/m2). Increased WC (> 102 for men and > 88 cm for women) was recorded in 29% and 48%, CVD in 16% and 13%, and diabetes mellitus in 13% and 11% of men and women, respectively. A statistically significant graded increase existed in the frequency of CVD and diabetes mellitus with both BMI and WC, with a stronger relationship for WC than for BMI across regions for both genders. This relationship between WC, CVD, and particularly diabetes mellitus was seen even in lean patients (BMI < 25 kg/m2).

CONCLUSIONS

Among men and women who consulted primary care physicians, BMI and particularly WC were both strongly linked to CVD and especially to diabetes mellitus. Strategies to address this global problem are required to prevent an epidemic of these major causes of morbidity and mortality.

The oral cavity of elderly patients in diabetes

Diabetes mellitus is a common and growing global health problem leading to several complications. Among these periodontal diseases are considered as the sixth complication of diabetes mellitus. This article reviews the relationship between diabetes and oral health, particularly focusing on periodontal diseases, dental caries and xerostomia. There is a bidirectional interrelationship between diabetes and periodontal diseases. Periodontitis is more prevalent and severe in patients with diabetes than in normal population. Therapy of periodontal infection contributes to a positive glycaemic control management and enables reduction of the burden of complications of diabetes mellitus. Diabetics have an increased predisposition to the manifestation of oral diseases like candidiasis which is associated with poor glycaemic control and therapeutic dentures. This predisposition also contributes to xerostomia, which may be due to increased glucose levels in oral fluids or immune dysregulation.

Metabolic syndrome and obesity in an insect

Dragonflies infected with noninvasive gregarine gut parasites (Apicomplexa: Eugregarinorida) [corrected] have reduced flight-muscle performance, an inability to metabolize lipid in their muscles, twofold-elevated hemolymph carbohydrate concentrations, and they accumulate fat in their thorax in a manner analogous to mammalian obesity. Gregarine infection is associated with inappropriate responses of hemolymph carbohydrate concentration to insulin and with chronic activation in the flight muscles of p38 MAP kinase, a signaling molecule involved in immune and stress responses. Short-term exposure to gregarine excretory/secretory products caused elevated blood carbohydrate and p38 MAPK activation in healthy individuals. These characteristics comprise a set of symptoms and processes that are known in mammals as metabolic syndrome but which have not previously been described in other animal taxa. In addition to expanding the known taxonomic breadth of metabolic disease, these results indicate that insects may be useful experimental models for studying its underlying biology and mechanisms.

Assessing a non-traditional view of adipogenesis: adipocyte dedifferentiation--mountains or molehills?

Based on our studies we propose the following hypothesis: mature, lipid-containing adipocytes possess the ability to undergo symmetrical or asymmetrical cell division, without losing lipid. While our research to discern the mechanism(s) involved in what we have termed 'dedifferentiation' of adipocytes is ongoing, we have identified several roadblocks to our work in this area. However, due to the newness of this research, we believe that none of these problems discounts the potential importance of our initial observations, or the excitement of contributing knowledge in the area. In this manuscript we address some of these problems and suggest possible solutions in an attempt to make 'molehills' out of 'mountains.'

TNFalpha up-regulates apelin expression in human and mouse adipose tissue

We have recently identified apelin as a novel adipokine up-regulated by insulin and obesity. Since obesity and insulin resistance are associated with chronically elevated levels of both insulin and TNFalpha, the present study was performed to investigate a putative regulation of apelin expression in adipocytes by TNFalpha. Herein, we report a tight correlation between apelin and TNFalpha expression in adipose tissue of lean and obese humans. Apelin regulation by TNFalpha was further studied in cultured explants of human adipose tissue. The endogenous expression of TNFalpha in adipocytes isolated from the explants was accompanied by a 6-9 h subsequent increase of apelin expression in adipocytes. This increase was reversed by inhibiting TNFalpha expression with 100 microM isobutylmethylxanthine. In different mouse models of obesity, expression of both TNFalpha and apelin was also significantly increased in adipocytes of obese mice. Furthermore, short-term exposure to an i.p. injection of TNFalpha in C57Bl6/J mice induced an increase of apelin expression in adipose tissue as well as apelin plasma levels. Finally, a direct positive effect of TNFalpha has been shown in differentiated 3T3F442A adipocytes on apelin expression and secretion. The signaling pathways of TNFalpha for the induction of apelin were dependent of PI3-kinase, c-Jun NH2-terminal kinase (JNK), and MAPK but not PKC activation. All together, these findings suggest that apelin might be a candidate to better understand potential links between obesity and associated disorders such as inflammation and insulin resistance.

The beneficial effects of high-density lipoprotein on adipocytes may relate to its anti-atherogenic properties

High-density lipoprotein (HDL) has significant anti-atherogenic properties, whereas the underlying mechanisms are complex and have not been completely elucidated. Adipocytes produce a variety of adipokines with cardiovascular effects. The dysregulated secretion of adipokines by adipocytes may contribute to the increased risk of atherosclerosis associated with obesity. Clinical evidences indicate that higher plasma HDL-C levels are associated with a favourable adipokines secretion profile, suggesting that HDL might improve the dysregulated adipokines secretion. HDL may diminish lipid accumulation in adipocytes through phosphorylation of PPARgamma and inhibition of aP2 expression, which possibly account for the favourable effects of HDL on adipokines secretion. Therefore, we hypothesize that HDL might exert several beneficial effects on adipocytes, which may relate to its anti-atherogenic properties.