Identifying the links between obesity, insulin resistance and beta-cell function: potential role of adipocyte-derived cytokines in the pathogenesis of type 2 diabetes

Haemostatic and cytokine changes in gestational diabetes mellitus

BACKGROUND

Limited data indicate the existence of a hypercoagulable state and the possible involvement of pro-inflammatory cytokines in the pathogenesis of gestational diabetes mellitus (GDM).

AIM

To characterise the coagulation inhibitor and cytokine profiles in women with GDM.

METHODS

Two groups of women in the third trimester of pregnancy were studied: GDM (n = 150) and controls: women with normal pregnancy (n = 100); GDM in their first post-delivery day (n = 52). LABORATORY ASSAYS: Plasma fibrinogen, antithrombin (AT), protein C, total and free protein S, interleukins-2, 6 and 8 (IL-2, 6, 8).

RESULTS

During pregnancy, the only significant alterations noted were higher levels of body mass index, fibrinogen and total protein S in women with GDM when compared to normal pregnancy. In the post-delivery group, there was further elevation in the levels of plasma fibrinogen and significant drop in the level of total protein S, protein C and AT. Significant elevation of IL-2 and IL-6 levels was recorded only in post-delivery group.

CONCLUSION

In GDM, the only indicator of a tendency towards hypercoagulability is the higher fibrinogen levels as compared to normal pregnancy. This feature along with the higher body mass index and presumed associated insulin resistance suggests that GDM may be a mild form of the metabolic syndrome. The lack of significant change in the levels of pro-inflammatory cytokines do not support the existence of an inflammatory state in GDM.

Hormones and cytokines in childhood obesity

OBJECTIVE

Obesity is a growing worldwide health problem affecting both adults and children. Effective prevention and treatment modalities can be achieved by understanding the pathogenesis of obesity better. This review addresses some of the issues related to the hormones and cytokines taking part in the pathogenesis of obesity, energy balance and inflammation.

DESIGN

We reviewed current literature on this broad subject especially concentrating on the functions of the hormones and cytokines taking part in the pathogenesis of the childhood obesity. Using the key words obesity, children, hormones, cytokines publications and cross references were evaluated from PubMed database between 1957 and 2009.

RESULTS

In children, leptin and ghrelin are two hormones which have major influence on energy balance. Leptin is responsible from long term regulation of energy balance and ghrelin functions as an appetite stimulatory signal. In contrast to ghrelin, obestatin acts as an anorexigenic hormone by suppressing food intake. Adipokines secreted from adipose tissue are the key regulators of inflammation in obesity. Increased TNF-alpha and IL-6 levels but decreased levels of adiponectin and IL-10 are associated with increased inflammation, tissue injury and complications of obesity.

CONCLUSIONS

Development, pathogenesis and complications of childhood obesity consist of complex mechanisms including numerous cytokines and hormones. New treatment modalities depend on understanding these complex mechanisms.

A novel fluorescence imaging approach for comparative measurements of pancreatic islet function in vitro

Pancreatic islet dysfunction is a key element in the development of type 2 diabetes. Determining possible early warning signs of dysfunction is thus important to determining the underlying causes of diabetes. We describe an improved fluorescent imaging approach to detect potential islet dysfunction. Using Cell Tracker Red (CTR, a mildly thiol-reactive fluorescent probe) to positively label particular islets, we measured intracellular free calcium with fura-2 AM in both CTR-labeled and unlabeled sets of pancreatic islets simultaneously in vitro. This approach enhances sensitivity by controlling for differences in background fluorescence, temperature, and perifusion dynamics. We confirmed that 200 nM CTR produced no spectral overlap with fura-2 and no significant physiological effects in selective tests of islet function. To demonstrate the utility of dual-labeling, we compared untreated islets with islets pretreated with low-dose pro-inflammatory cytokines (IL-6 + IL-1B) to induce mild dysfunction. We alternated CTR-labeling between control and test islets and identified consistent reductions in the amplitude and trajectory of glucose-stimulated calcium responses (GSCa) among cytokine-treated islets that were independent of labeling. Observations were verified using a MATLAB program specifically designed to identify key features in the GSCa. Our findings thus demonstrate the utility of CTR-labeling in identifying islet dysfunction and propose that this technique can be adapted for other cells and tissues.

Obesity, inflammatory markers, and endometrial cancer risk: a prospective case-control study

Obesity, a major risk factor for endometrial cancer, is a low-grade inflammatory state characterized by elevated concentrations of cytokines and acute phase reactants. The current study had two aims: first to investigate the associations of C-reactive protein (CRP), interleukin 6 (IL6), and IL1 receptor antagonist (IL1Ra) with endometrial cancer risk and second to examine to which extent these markers can influence the association between obesity and endometrial cancer. We conducted a case-control study, nested within the European Prospective Investigation into Cancer and Nutrition, which comprised 305 incident cases of endometrial cancer and 574 matched controls. CRP, IL6, and IL1Ra were measured in prospectively collected blood specimens by immunoassays. Data were analyzed using conditional logistic regression. All statistical tests were two-sided, and P values <0.05 were considered statistically significant. We observed a significant increase in risk of endometrial cancer with elevated levels of CRP (odds ratio (OR) for top versus bottom quartile: 1.58, 95% confidence interval (CI): 1.03-2.41, P(trend)=0.02), IL6 (OR for top versus bottom quartile: 1.66, 95% CI: 1.08-2.54, P(trend)=0.008), and IL1Ra (OR for top versus bottom quartile: 1.82, 95% CI: 1.22-2.73, P(trend)=0.004). After adjustment for body mass index (BMI), the estimates were strongly reduced and became non-significant. The association between BMI and endometrial cancer was also substantially attenuated (∼10-20%) after adjustment for inflammatory markers, even when the effects of C-peptide or estrone had already been taken into account. We provided epidemiological evidence that chronic inflammation might mediate the association between obesity and endometrial cancer and that endometrial carcinogenesis could be promoted by an inflammatory milieu.

Systemic inflammation and the metabolic syndrome among middle-aged community volunteers

The metabolic syndrome is conceptualized as a clustering of risk factors--including insulin resistance, dyslipidemia, central adiposity, and elevated blood pressure (BP)--that increase the risk for cardiovascular disease and type 2 diabetes mellitus. Recent evidence suggests that markers of systemic inflammation may be included in the definition of the syndrome and play some role in its pathogenesis. In this study, we use a statistical modeling technique, confirmatory factor analysis, to evaluate relationships of systemic inflammation, as measured by plasma concentrations of C-reactive protein and interleukin-6, with the component factors of the metabolic syndrome (insulin resistance, dyslipidemia, central adiposity, and elevated BP) and to examine whether inflammation is a potential common pathway linking established components to the full syndrome. Subjects were 645 community volunteers aged 30 to 54 years (48% male, 82% European American, 18% African American). Consistent with existing literature, structural equation modeling adjusting for age, sex, and race confirmed a higher-order common factor underlying the covariation of insulin resistance, dyslipidemia, adiposity, and BP. Inflammation was positively associated with this common factor, accounting for 54% of its variance and partially mediating statistical aggregation of the component factors comprising the metabolic syndrome. These results were particularly strong for adiposity, raising the possibility that inflammatory processes stimulated by intraabdominal adipose tissue contribute to the development of the metabolic syndrome. The inclusion of inflammatory markers in the clinical definition of metabolic syndrome seems warranted and may improve prognostic assessment of risk of type 2 diabetes mellitus and cardiovascular disease.

Manifestations of chronic hepatitis C virus infection beyond the liver

In addition to its effects in the liver, chronic hepatitis C virus (HCV) infection can have serious consequences for other organ systems. Extrahepatic manifestations include mixed cryoglobulinemia (MC) vasculitis, lymphoproliferative disorders, renal disease, insulin resistance, type 2 diabetes, sicca syndrome, rheumatoid arthritis-like polyarthritis, and autoantibody production; reductions in quality of life involve fatigue, depression, and cognitive impairment. MC vasculitis, certain types of lymphoma, insulin resistance, and cognitive function appear to respond to anti-HCV therapy. However, treatments for HCV and other biopsychosocial factors can reduce quality of life and complicate management. HCV treatment has a high overall cost that increases when extrahepatic manifestations are considered. HCV appears to have a role in the pathogenesis of MC vasculitis, certain types of lymphoma, and insulin resistance. Clinicians who treat patients with HCV infections should be aware of potential extrahepatic manifestations and how these can impact and alter management of their patients.

Puerarin enhances adipocyte differentiation, adiponectin expression, and antioxidant response in 3T3-L1 cells

Puerarin, a major isoflavone glycoside from Kudzu root (Pueraria lobata), has been reported to exert antihyperglycemic and antioxidant effects and thus have pharmacological actions in the treatment of diabetes and cardiovascular diseases. We investigated the effects of puerarin on the changes of key gene expression associated with adipocyte differentiation and insulin sensitivity and link to cellular antioxidant response pathways. Puerarin treatment significantly enhanced differentiation of 3T3-L1 preadipocytes accompanying increased lipid accumulation and glucose-6-phosphate dehydrogenase (G6PDH) activity. At a molecular level, puerarin upregulated mRNA expression of peroxisome proliferator-activated receptor γ (PPARγ) and its target genes, an adipocyte-specific fatty acid binding protein (aP2) and GLUT4. Puerarin also caused a significant increase in mRNA level of adiponectin, an important insulin-sensitizing adipocytokine that is downregulated in insulin-resistant and diabetic states. In addition, treatment with puerarin was found to upregulate mRNA levels of G6PDH, glutathione reductase, and catalase, all of which are important for endogenous antioxidant responses. These data suggest that the hypoglycemic effects of puerarin can be attributed to the upregulation of PPARγ and its downstream target genes, GLUT4 and adiponectin expression, leading to increased glucose utilization. Puerarin may also be effective in preventing the rise of oxidative stress during adipocyte differentiation by increasing endogenous antioxidant responses.

Effect of PAR2 in regulating TNF-α and NAD(P)H oxidase in coronary arterioles in type 2 diabetic mice

Protease-activated receptor-2 (PAR2) is expressed in endothelial cells and mediates endothelium-dependent vasodilation. We hypothesized that PAR2 regulates tumor necrosis factor-alpha (TNF-α)-induced coronary arteriolar dysfunction in type 2 diabetic (db/db) mice. To test this, coronary arterioles from WT control, db/db, db/db mice treated with PAR2 antagonist FSLLRY-NH₂ (db/db+FSLLRY-NH₂) and db/db mice null for TNF (db(TNF-)/db(TNF-)) were isolated and pressurized (60 cmH₂O) without flow. Although vasodilation to the endothelium-independent vasodilator sodium nitroprusside (SNP) was not different among WT, db/db, db/db+FSLLRY-NH₂ and db(TNF-)/db(TNF-), endothelium-dependent acetylcholine (ACh)- and flow-mediated vasodilation were impaired in db/db mice but were enhanced in db(TNF-)/db(TNF-) mice and db/db mice treated with PAR2 antagonist. NOS inhibitor N (G)-nitro-L-arginine-methyl ester (L-NAME) significantly reduced ACh-induced dilation in WT, db(TNF-)/db(TNF-) and db/db+FSLLRY-NH₂, but did not alter the vasodilation in db/db mice. In contrast, cyclooxygenase (COX) inhibitor indomethacin (Indo) did not alter ACh-induced vasodilation in these four groups of mice. PAR2-activating peptide (PAR2-AP, 2-Furoyl-LIGRLO-am)-induced dilation was higher in db/db mice than that in WT, db(TNF-)/db(TNF-) and db/db mice treated with PAR2 antagonist. These effects were abolished by denudation, or in the presence of L-NAME or Indo. Protein expressions of TNF-α, PAR2, gp91(phox) and p47(phox) in the heart and isolated coronary arterioles were higher in db/db mice compared to WT mice. Administration of PAR2 antagonist to db/db mice reduced protein expression of TNF-α, gp91(phox) and PAR2. Protein expression of gp91(phox) and p47(phox) was lower in db(TNF-)/db(TNF-) compared to db/db mice. These results indicate that PAR2 plays a pivotal role in endothelial dysfunction in type 2 diabetes by up-regulating the expression/production of TNF-α and activating NAD(P)H oxidase subunit p47(phox).

Functional interactions between pancreatic beta cells and (pre)adipocytes

Type 2 diabetes is causally related to obesity and characterized by dysfunctional pancreatic beta cells. It is so far unclear whether direct interactions exist between adipocytes and beta cells and possibly raise any pathogenic relevance. In this study, we examined whether 9-day co-cultured 3T3-F442A (pre)adipocytes and primary rat pancreatic beta cells exert an influence on each other's function. In the presence of beta cells, 3T3-F442A cells became lipid-storing cells expressing markers of differentiated adipocytes and releasing adiponectin. This effect was attributed to the medium insulin levels (around 0.1 μM) and was associated with an elevated glucose consumption by the 3T3-F442A cells. The subsequent decrease in medium glucose concentration reduced the rate of insulin release by beta cells cultured at 10 mM glucose, and thus suppressed their degranulation during culture. These changes in beta cell function did not occur at 20 mM glucose and were reversible upon removal of the 3T3-F422A cells. They could not be reproduced by 3T3-F422A-conditioned medium containing varying adiponectin concentrations. These data indicate that insulin secreted by beta cells is sufficient to induce differentiation of preadipocytes without addition of exogenous adipogenic factors. Over 9 days culture, (pre)adipocytes did not directly and irreversibly affect beta cell functions.

Evidence that low-grade systemic inflammation can induce islet dysfunction as measured by impaired calcium handling

In obesity and the early stages of type 2 diabetes (T2D), proinflammatory cytokines are mildly elevated in the systemic circulation. This low-grade systemic inflammation exposes pancreatic islets to these circulating cytokines at much lower levels than seen within the islet during insulitis. These low-dose effects have not been well described. We examined mouse islets treated overnight with a low-dose cytokine combination commonly associated with inflammation (TNF-alpha, IL-1 beta, and IFN-gamma). We then examined islet function primarily using intracellular calcium ([Ca(2+)](i)), a key component of insulin secretion and cytokine signaling. Cytokine-treated islets demonstrated several features that suggested dysfunction including excess [Ca(2+)](i) in low physiological glucose (3mM), reduced responses to glucose stimulation, and disrupted [Ca(2+)](i) oscillations. Interestingly, islets taken from young db/db mice showed similar disruptions in [Ca(2+)](i) dynamics as cytokine-treated islets. Additional studies of control islets showed that the cytokine-induced elevation in basal [Ca(2+)](i) was due to both greater calcium influx through L-type-calcium-channels and reduced endoplasmic reticulum (ER) calcium storage. Many of these cytokine-induced disruptions could be reproduced by SERCA blockade. Our data suggest that chronic low-grade inflammation produces circulating cytokine levels that are sufficient to induce beta-cell dysfunction and may play a contributing role in beta-cell failure in early T2D.

A high cholesterol diet elevates hippocampal cytokine expression in an age and estrogen-dependent manner in female rats

BACKGROUND

While the effects of a proatherogenic diet have been widely studied in the context of systemic inflammation, much less is known about its effects on central or brain inflammation and its modulation with age. In this study, we examined the effect of a high cholesterol/choline diet in adult and older acyclic females to assess its impact on systemic and central inflammatory markers. Moreover, since the loss of ovarian hormones at menopause may predispose women to increased production of pro-inflammatory cytokines, we also tested the impact of estrogen replacement to adult and older females in diet-induced inflammation.

METHODS

Ovariectomized adult female rats and older (reproductive senescent) female rats were replaced with estrogen or a control pellet and maintained thereafter on a diet containing either 4% cholesterol/1% choline or control chow for 10 weeks. Interleukin 1beta (IL-1beta) expression in the liver was used as a marker of systemic inflammation, while a panel of cytokine/chemokines were used to examine the effects of diet on the hippocampus.

RESULTS

IL-1beta expression was elevated in the liver of adult and reproductive senescent females fed with the high cholesterol diet, although this was restricted to groups that were ovariectomized and not replaced with estrogen. Estrogen-treated animals of both ages did not have elevated IL-1beta levels when fed the high cholesterol diet. Diet-induced changes in cytokine/chemokine expression in the hippocampus however were critically age dependent and restricted to the reproductive senescent females. In this group, the high cholesterol diet led to an increase in interleukin (IL)-4, IL-6, IL-12p70, IL-13, RANTES (Regulated on Activation, Normal T Expressed and Secreted) and VEGF (vascular endothelial growth factor). Moreover, estrogen treatment to reproductive senescent females suppressed diet-induced expression of specific cytokines (RANTES, VEGF, IL-6) and attenuated the expression of others (IL-4, IL-12p70, and IL-13).

CONCLUSIONS

These data indicate that a proatherogenic diet presents a significant risk for central inflammation in older females that are deprived of estrogen treatment.

Sudden Progression from Impaired Glucose Tolerance to Type 2 Diabetes after Discontinuation of Administration of Anti-Tumor Necrosis Factor-Alpha Antibody Infliximab

We present the case of a 45-year-old man with psoriasis and psoriatic arthritis and concomitant impaired fasting glucose (IFG) and impaired glucose tolerance (IGT). In this patient, refractory to DMARD's, infliximab was started to control the arthritis. After achieving clinical remission of the disease, infliximab was discontinued and a 75 g- oral glucose tolerance test (OGTT) was performed. After the test, we observed a conversion from IFG/IGT glucose tolerance status to type 2 diabetes. No diet, lifestyle or therapy modifications were made during the observation period. Autoimmune diabetes was ruled out by serum antibodies determination and body weight remained constant, sustaining a protective role of infliximab in the worsening of glucose tolerance.

Obesity and gastrointestinal cancer

BACKGROUND

There is emerging evidence of a strong association between obesity and gastrointestinal cancer. This review summarizes the evidence from an epidemiological and pathophysiological perspective.

METHODS

Relevant medical literature was identified from searches of PubMed and references cited in appropriate articles were identified. Selection of articles was based on peer review, journal and relevance.

RESULTS

Numerous epidemiological studies consistently identified an increased risk of developing oesophageal adenocarcinoma and colorectal carcinoma in the obese. The association between obesity and other gastrointestinal malignancies was less robust. Sex seems important with respect to cancer risk. Adipose tissue, particularly viscerally located fat, is metabolically active and exerts systemic endocrine effects. Putative pathophysiological mechanisms linking obesity and carcinogenesis include the insulin-like growth factor axis, adipocytokines and sex steroids.

CONCLUSION

A better understanding of the mechanisms that link obesity and cancer may uncover targets for intervention. Tackling obesity may result in a reduction in the incidence in addition to mortality of certain cancers in future.

Association between polymorphisms in human tumor necrosis factor-alpha (--308) and -beta (252) genes and development of gestational diabetes mellitus

OBJECTIVE

The aim of this study is to investigate if an association exists between single nucleotide polymorphism (SNP) in the tumor necrosis factor-alpha (TNF-alpha) and TNF-beta genes.

METHODS

The DNA was extracted and SNP in the human TNF-alpha and TNF-beta genes at positions -308 (G/A) and 252 (A/G), respectively, was analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Plasma levels of TNF-alpha in different stages of pregnancy were quantified using enzyme linked immunosorbent assay (ELISA).

RESULTS

There was no significant difference in genotype and allele frequency of SNP at position -308 (G/A) in the promoter region of the human TNF-alpha gene as well as the SNP at position 252 (A/G) in the human TNF-beta gene between the GDM and control subjects. Using the logistic regression model, it was found that the SNP in the TNF-alpha as well as TNF-beta were not associated with development of GDM. In addition, the TNF-alpha levels in the plasma of GDM and control mothers were not significantly different.

CONCLUSIONS

In the population studied, the SNP in position -308 (G/A) of the human TNF-alpha or in position 252 (A/G) of the human TNF-beta gene is not an independent risk factor or a predictor for GDM.

Altered metabolism and lipodystrophy in the early B-cell factor 1-deficient mouse

We previously reported that mice deficient for the transcription factor early B-cell factor (Ebf1) exhibit markedly increased numbers of osteoblasts, bone formation rate, and serum osteocalcin, but the bone marrow of Ebf1(-/-) mice is also striking in its increased marrow adiposity. The purpose of this work was to analyze the metabolic phenotype that accompanies the altered bone morphology of Ebf1(-/-) mice. Whereas marrow adiposity was increased, deposition of white adipose tissue in other regions of the body was severely reduced (sc 40-50%, abdominally 80-85%). Brown adipose exhibited decreased lipid deposition. Subcutaneous and perigonadal white adipose tissue showed a decrease in mRNA transcripts for peroxisomal proliferator-activated receptor-gamma2 and CCAAT/enhancer-binding protein-beta in Ebf1(-/-) tissue compared with wild type. Circulating levels of leptin were decreased in Ebf1(-/-) animals compared with their littermate controls (down 65-95%), whereas adiponectin remained comparable after 2 wk of age. Serum analysis also found the Ebf1(-/-) animals were hypoglycemic and hypotriglyceridemic. After ip injection of insulin, the serum glucose levels in Ebf1(-/-) mice took longer to recover, and after a glucose challenge the Ebf1(-/-) animals reached serum glucose levels almost twice that of their wild-type counterparts. Measurement of circulating pancreatic hormones revealed normal or reduced insulin levels in the Ebf1(-/-) mice, whereas glucagon was significantly increased (up 1.7- to 8.5-fold). Metabolically the Ebf1(-/-) mice had increased O(2) consumption, CO(2) production, food and water intake, and activity. Markers for gluconeogenesis, however, were decreased in the Ebf1(-/-) mice compared with controls. In conclusion, the Ebf1-deficient animals exhibit defects in adipose tissue deposition with increased marrow adiposity and impaired glucose mobilization.

Benefits of moderate weight loss in patients with type 2 diabetes

Weight loss is a primary goal of therapy in overweight patients with type 2 diabetes. This review examines whether positive patient outcomes are observed even after relatively small amounts of weight loss, that is, weight loss being more easily attainable in practice. Clinical studies demonstrate that therapeutic benefit rises with increasing weight loss, but that losses as low as 0.45-4 kg (1-9 lb) have positive effects on metabolic control, cardiovascular risk factors and mortality rates. Even the intention to lose weight, without significant success, can improve outcomes in patients with diabetes, presumably because of the healthy behaviours associated with the attempt. The current data support a continued focus on weight loss, including moderate weight loss, as a key component of good care for overweight patients with type 2 diabetes.

Epidemiological evidence for the links between sleep, circadian rhythms and metabolism

Epidemiological data reveal parallel trends of decreasing sleep duration and increases in metabolic disorders such as obesity, diabetes and hypertension. There is growing evidence that these trends are mechanistically related. The seasonal expression of the thrifty genotype provides a conceptual framework to connect circadian and circannual rhythms, sleep and metabolism. Experimental studies have shown sleep deprivation to decrease leptin, increase ghrelin, increase appetite, compromise insulin sensitivity and raise blood pressure. Habitually short sleep durations could lead to insulin resistance by increasing sympathetic nervous system activity, raising evening cortisol levels and decreasing cerebral glucose utilization that over time could compromise beta-cell function and lead to diabetes. Prolonged short sleep durations could lead to hypertension through raised 24-h blood pressure and increased salt retention resulting in structural adaptations and the entrainment of the cardiovascular system to operate at an elevated pressure equilibrium. Cross-sectional and longitudinal epidemiological studies have shown associations between short sleep duration and obesity, diabetes and hypertension. If metabolic changes resulting from sleep restriction function to increase body weight, insulin resistance and blood pressure then interventions designed to increase the amount and improve the quality of sleep could serve as treatments and as primary preventative measures for metabolic disorders.

Association of hematological parameters with insulin resistance and beta-cell dysfunction in nondiabetic subjects

OBJECTIVE

Previous studies reported independent associations of hematological parameters with risk of incident type 2 diabetes, although limited data are available on associations of these parameters with insulin resistance (IR) and (especially) pancreatic beta-cell dysfunction in large epidemiological studies. Our objective was to evaluate the associations of hematological parameters, including hematocrit (HCT), hemoglobin (Hgb), red blood cell count (RBC), and white blood cell count with IR and beta-cell dysfunction in a cohort of nondiabetic subjects at high metabolic risk.

METHODS

Nondiabetic subjects (n = 712) were recruited in Toronto and London, Ontario, Canada, between 2004 and 2006, based on the presence of one or more risk factors for type 2 diabetes mellitus including obesity, hypertension, a family history of diabetes, and/or a history of gestational diabetes. Fasting blood samples were collected and oral glucose tolerance tests administered, with additional samples for glucose and insulin drawn at 30 and 120 min. Measures of IR included the homeostasis model assessment (HOMA-IR) and Matsuda's insulin sensitivity index, whereas measures of beta-cell dysfunction included the insulinogenic index divided by HOMA-IR as well as the insulin secretion-sensitivity index-2. Associations of hematological parameters with IR and beta-cell dysfunction were assessed using multiple linear regression and analysis of covariance with adjustments for age, gender, ethnicity, smoking, cardiovascular disease, systolic and diastolic blood pressure, and waist circumference.

RESULTS

HOMA-IR increased across quartiles of HCT, Hgb, RBC, and white blood cell count after adjustment for age, gender, ethnicity, and smoking (all P (trend) <0.0001). Similarly, there was a strong stepwise decrease in the Matsuda's insulin sensitivity index across increasing quartiles of these hematological measures (all P (trend) <0.0001). The associations remained significant after further adjustment for previous cardiovascular disease, blood pressure, and waist circumference (all P (trend) <0.0001). Similarly, there was a strong pattern of decreasing beta-cell function across increasing quartiles of all hematological patterns (all P (trend) <0.0001). The findings for HCT, Hgb, and RBC were attenuated slightly after full multivariate adjustment, although the trend across quartiles remained highly significant.

CONCLUSION

These findings suggest that standard, clinically relevant hematological variables may be related to the underlying pathophysiological changes associated with type 2 diabetes mellitus.

Felodipine downregulates serum interleukin-18 levels in rats with fructose-induced metabolic syndrome

OBJECTIVE

Human studies suggest that calcium-channel blockers have cardiovascular protection besides reducing blood pressure, and interleukin-18 (IL-18) levels which are elevated in obese population are associated with metabolic syndrome (MetS). The purpose of this research was to study the change of serum IL-18 levels and the effect of felodipine on it in high-fructose diet-fed rats.

METHODS

In this research, 30 Wistar male rats were randomized into 3 groups. A control group (no.=12) was fed with normal feeds, and high-fructose diet was given to a fructose group and a flodioine group (no.=9 in each group). All animals were fed for a period of 32 weeks, during which body weight and systolic blood pressure (BP) were measured once every 4 weeks. Felodipine (5 mg/kg/d) was then administered by gavage daily for 6 weeks to the felodipine group. Before and after treatment with felodipine, fasting plasma lipid, blood glucose, plasma insulin, and serum IL-18 were detected.

RESULTS

Body weight, systolic BP, triglycerides, fasting insulin, and the R-value of homeostasis model (HOMA-R) were significantly increased in high-fructose rats (p<0.01). Serum IL-18 levels were elevated and had significant positive correlation with HOMA-R in rats with fructose-induced MetS (p<0.01). We also found that felodipine may decrease HOMA-R and serum IL-18 levels besides reducing blood pressure (p<0.05, p<0.01).

CONCLUSION

IL-18 plays an important role in the development of MetS, while felodipine exerts an anti-inflammatory effect on rats with fructose-induced MetS by downregulating serum IL-18 levels.

Exercise training decreases proinflammatory profile in Zucker diabetic (type 2) fatty rats

OBJECTIVE

In the present study we evaluated the effect of exercise on the plasma levels of proinflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), and the anti-inflammatory molecule uric acid in the Zucker diabetic fatty (ZDF) rats that are more prone to develop type 2 diabetes mellitus.

METHODS

Sixteen obese ZDF (Gmi fa/fa) rats (8 wk old, 228.40 +/- 4.05 g) were randomly assigned to one of two groups (n = 8 each): an exercise-trained group and a sedentary one. In addition, 16 lean ZDF (Gmi +/+) rats (8 wk old, 199.00 +/- 3.50 g) were subjected to identical sedentary and exercise conditioning (n = 8 each). Initially, rats swam 15 min/d (5 d/wk) in a 36 degrees C bath. The exercise protocol was gradually increased by 15 min/d until a swimming period of 1 h/d (1 wk) was attained. Thereafter, rats swam 1 h/d, 3 d/wk, for an additional period of 11 wk. Rats were sacrificed 48 h after the last training period and the blood and pancreas were collected. Circulating levels of glucose, glycosylated hemoglobin, total cholesterol, triglycerides, insulin, uric acid, IL-6, and TNF-alpha were assessed. The concentrations of proinflammatory cytokines in the pancreas were also evaluated.

RESULTS

In the diabetic ZDF (fa/fa) rats, exercise decreased hyperuricemia (-37.3%) and IL-6 and TNF-alpha levels (-16.9% and -12.7% respectively) and maintained the weight of the pancreas at near normal. Immunohistochemistry revealed a marked decrease in the expression of TNF-alpha and IL-6 in the pancreatic islet cells of ZDF (fa/fa) rats.

CONCLUSION

These results indicate that aerobic exercise is anti-inflammatory in nature.

Novel aspects of adipocyte-induced skeletal muscle insulin resistance

Insulin resistance in skeletal muscle is an early event in the development of diabetes with obesity being one of the major contributing factors. Conditioned medium (CM) from differentiated human adipocytes impairs insulin signalling in human skeletal muscle cells. Recent data on adipocyte-induced insulin resistance in skeletal muscle cells describes underlying mechanisms of this process. Skeletal muscle insulin resistance involves multiple pathways and irreversible changes in the expression level of critical proteins. Furthermore, the reversibility of insulin resistance could be demonstrated. Several strategies to combat insulin resistance have been developed. One recent approach to treat obesity and the metabolic syndrome is the use of endocannabinoid receptor antagonists such as rimonabant. These compounds might also reduce insulin resistance in type 2 diabetes with effects on adipose tissue and liver and possibly skeletal muscle.

Felodipine reduces cardiac expression of IL-18 and perivascular fibrosis in fructose-fed rats

Metabolic syndrome is associated with accelerated macrovascular and microvascular coronary disease, cardiomyopathy, and elevated inflammatory status. To determine whether metabolic syndrome-associated elevation of the inflammatory cytokine interleukin-18 (IL-18) in serum and cardiac tissue, and its potential sequelae could be attenuated pharmacologically, we studied fructose-fed rats. The fructose-fed rats exhibited increases in systolic blood pressure (SBP), body weight, heart weight, left ventricular weight, and blood insulin. Serum IL-18 levels in these rats were also elevated significantly. These changes were significantly different compared to those in control rats. Perivascular fibrosis around coronary arterioles was evident in the fructose-fed rats, accompanied by a paralleled increase in IL-18 by immunohistochemical analysis and real time polymerase chain reaction. Felodipine attenuated the increased levels in serum IL-18 and cardiac IL-18 mRNA as well as coronary perivascular fibrosis. Thus, augmented IL-18 in serum and cardiac tissue in metabolic syndrome may contribute to the coronary perivascular fibrosis; felodipine administration can attenuate the inflammatory and fibrosis process.

Nutrition, metabolic factors and cancer risk

Excess body weight (adiposity) and physical inactivity are increasingly being recognized as major nutritional risk factors for cancer, and especially for many of those cancer types that have increased incidence rates in affluent, industrialized parts of the world. In this review, an overview is presented of some key biological mechanisms that may provide important metabolic links between nutrition, physical activity and cancer, including insulin resistance and reduced glucose tolerance, increased activation of the growth hormone/IGF-I axis, alterations in sex-steroid synthesis and/or bioavailability, and low-grade chronic inflammation through the effects of adipokines and cytokines.

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.

Inflammation and its relationship to insulin resistance, type 2 diabetes mellitus, and endothelial dysfunction

In the past decade, clinical, laboratory, and epidemiological research have coalesced to give rise to a new paradigm for understanding type 2 diabetes mellitus (DM). In this review, we present data that DM has an inflammatory etiology and that inflammation plays a role in diabetic complications, especially cardiovascular disease. This new paradigm offers insight into the relationship between DM and obesity. It also suggests possible new avenues of treatment.

Metabolic syndrome and incidence of type 2 diabetes in patients with manifest vascular disease

Risk reduction in patients with clinically manifest vascular disease focuses on preventing new vascular events and not on prevention of type 2 diabetes. However, given the common pathophysiological pathways involved in the development of atherosclerosis and type 2 diabetes, it is probable that people with atherosclerotic vascular disease have an elevated risk of type 2 diabetes. The present prospective cohort study investigated the incidence of type 2 diabetes and the effect of the presence of metabolic syndrome on the incidence of type 2 diabetes in 4,022 patients with clinically manifest atherosclerosis, included in the study from September 1996 to June 2006. Patients who died (n=456), who were lost to follow-up (n=84) and those with diabetes at baseline (n=558) were excluded, leaving 2,924 patients for analysis. The incidence of diabetes was assessed by questionnaire (self-reported diabetes). During 13,726 person-years of follow-up (median follow-up 4.3 years, range 2.4-7.0 years), there were 152 type 2 diabetes cases (5.2%), corresponding to an incidence rate of 11.1 (95% CI 9.4-13.0) per 1,000 person-years. Patients with metabolic syndrome were at increased risk of incident type 2 diabetes compared to those without metabolic syndrome, with an adjusted hazard ratio of 5.7 (95% CI 3.7-8.9) for Revised National Cholesterol Education Program, 6.0 (4.1-9.0) for National Cholesterol Education Program and 4.0 (2.7-6.1) for International Diabetes Federation definitions of metabolic syndrome. Of all metabolic syndrome components, abdominal obesity was most strongly associated with incident type 2 diabetes (94% higher risk of type 2 diabetes for 1 standard deviation (11.3 cm) increase in waist circumference). In conclusion, patients with manifest atherosclerosis are at high risk of developing type 2 diabetes. Metabolic syndrome identifies those at the highest risk and is an easy to use clinical tool. Abdominal obesity is a strong individual predictor of type 2 diabetes. Patients with manifest atherosclerosis and metabolic syndrome may derive particular benefit from lifestyle interventions focusing on weight reduction.

Eicosanoids and renal damage in cardiometabolic syndrome

BACKGROUND

Obesity, hypertension and Type 2 diabetes are major contributing factors to the increase in the number of patients that have chronic kidney disease. The clustering of visceral obesity and cardiovascular risk factors has been designated metabolic syndrome or cardiometabolic syndrome. Cardiometabolic syndrome is associated with a complex systemic inflammatory state that has been implicated in medically important complications, including endothelial dysfunction. Inflammation, endothelial dysfunction and insulin resistance are interrelated and have reciprocal relationships that link cardiovascular and metabolic diseases. Ultimately, cardiometabolic syndrome increases the risk for cardiovascular events and end-organ damage. Although the number of patients with cardiometabolic syndrome is escalating, therapeutic approaches have not been developed that provide protection to the kidney.

OBJECTIVE

The objective of this review is to provide an overview of the contribution of eicosanoids to renal damage in cardiometabolic syndrome.

RESULTS/CONCLUSION

Eicosanoids are altered in cardiometabolic syndrome and contribute to the progression of renal injury. The antihypertensive and anti-inflammatory actions of epoxides and soluble epoxide hydrolase inhibitors make these attractive eicosanoid therapeutic targets for chronic kidney disease in patients with cardiometabolic syndrome.

Sleep duration as a risk factor for diabetes incidence in a large U.S. sample

STUDY OBJECTIVES

To explore the relationship between sleep duration and diabetes incidence over an 8- to 10-year follow-up period in data from the First National Health and Nutrition Examination Survey (NHANES I). We hypothesized that prolonged short sleep duration is associated with diabetes and that obesity and hypertension act as partial mediators of this relationship. The increased load on the pancreas from insulin resistance induced by chronically short sleep durations can, over time, compromise beta-cell function and lead to type 2 diabetes. No plausible mechanism has been identified by which long sleep duration could lead to diabetes.

DESIGN

Multivariate longitudinal analyses of the NHANES I using logistic regression models.

SETTING

Probability sample (n=8992) of the noninstitutionalized population of the United States between 1982 and 1992.

PARTICIPANTS

Subjects between the ages of 32 and 86 years.

MEASUREMENTS AND RESULTS

Between 1982 and 1992, 4.8% of the sample (n=430) were determined by physician diagnosis, hospital record, or cause of death to be incident cases of diabetes. Subjects with sleep durations of 5 or fewer hours (odds ratio = 1.47, 95% confidence interval 1.03-2.09) and subjects with sleep durations of 9 or more hours (odds ratio = 1.52, 95% confidence interval 1.06-2.18) were significantly more likely to have incident diabetes over the follow-up period after controlling for covariates.

CONCLUSIONS

Short sleep duration could be a significant risk factor for diabetes. The association between long sleep duration and diabetes incidence is more likely to be due to some unmeasured confounder such as poor sleep quality.

Progress in hepatogenous insulin-resistance

Chronic liver disease and insulin resistance are in close correlation and promote each other, which has been studied a lot in its field. In this article, we review the new progress in viral hepatitis, hepatic cirrhosis, hepatoma related to insulin resistance.

Reduced incidence of new-onset posttransplantation diabetes mellitus during the last decade

BACKGROUND

A previous study (1995-1996) of 173 nondiabetic renal transplant recipients (historical cohort; HC) revealed a 20% incidence of new-onset posttransplantation diabetes mellitus (PTDM) and 32% with impaired glucose tolerance (IGT) or impaired fasting glucose (IFG). We examined whether glucose tolerance has improved after recent changes in our immunosuppressive protocol and a switch from deferred to preemptive cytomegalovirus (CMV) therapy.

METHODS

A total of 321 consecutive, nondiabetic patients (new cohort; NC) were examined 10 weeks after kidney transplantation with an oral glucose tolerance test (n=301) between January 2004 and December 2005.

RESULTS

Although recipients in the NC were on average 3 years older [mean (SD): 50.3 (14.6) vs. 47.4 (16.0), P=0.038] and had a higher mean body mass index [24.5 (3.6) vs. 23.5 (3.8) kg/m(2), P=0.003], a significantly lower incidence of both PTDM (13%) and IGT/IFG (18%) was observed in the NC (P<0.001) as compared to the HC. The patients in the NC received a significantly lower mean daily oral prednisolone dose [13.2 (4.7) vs. 15.3 (6.6) mg/day, P<0.001], and had lower frequencies of rejections (36% vs. 57%, P<0.001) and CMV infection (54% vs. 63%, P=0.071). Patients in the NC had significantly lower odds of developing PTDM, even after adjustment for age, prednisolone dose, HLA-B27 status and CMV infection (odds ratio: 0.42, 95% CI: 0.23-0.77, P=0.005).

CONCLUSIONS

The odds of developing PTDM are more than halved over the last decade. Possible explanations are changes in immunosuppressive therapy, fewer rejections, and lower doses of steroids.

The importance of beta-cell management in type 2 diabetes

Despite intervention with effective oral glucose-lowering agents, most patients with type 2 diabetes will experience a gradual loss of glycaemic control. Irrespective of underlying levels of insulin resistance, the progressive failure and loss of beta-cells are ultimately responsible for the onset of frank type 2 diabetes. The mechanisms responsible for loss of beta-cell function are likely to be multifactorial, but may involve toxicity because of elevated glucose and/or lipid levels, increased secretory demand because of insulin resistance, amyloid deposition and altered levels of cytokines. Preservation of beta-cell function is now gaining recognition as a critical target in the management of type 2 diabetes. For patients with frank type 2 diabetes, preservation of beta-cell function has the potential to reduce or stabilise the progression of type 2 diabetes and to decrease the need for additional oral glucose-lowering agents and/or insulin therapy. There is a growing body of animal/preclinical evidence for improved and preserved beta-cell function with current glucose-lowering agents, such as the thiazolidinediones, metformin and the glucagon-like peptide-1 analogue, exenatide. Clinical studies incorporating indirect measures of beta-cell function also support a protective effect with some agents. A number of novel therapies that are currently under investigation may also offer beta-cell structural and functional protection, including dipeptidyl peptidase IV inhibitors and cannabinoid receptor type 1 blockers. Emerging evidence from interventional trials suggests that both intensive lifestyle changes and pharmacotherapy can delay or possibly prevent the onset of type 2 diabetes in high-risk individuals. For patients newly diagnosed with type 2 diabetes, early and aggressive intervention strategies that combine maximal glucose-lowering efficacy alongside potential beta-cell preserving properties may provide an opportunity to delay or prevent progression of the disease.

Severity of metabolic syndrome unfavorably influences oxidative stress and fatty acid metabolism in men

Metabolic syndrome (MS) is defined by the clustering of several components (MSC), which include abdominal fat accumulation, impaired glucose homeostasis, hypertriglyceridemia, lowered high-density lipoprotein cholesterol, increased blood pressure, and hyperuricemia. Metabolic syndrome is also accompanied by increased oxidative stress and inflammation as well as by altered composition of esterified fatty acids (FA). Therefore, we have investigated 210 men (categorized into six groups with increasing number of MSC) to find trends in the extent of oxidative stress, FA pattern and frequency of pathological alleles of the selected candidate genes for lipid metabolism. Increasing number of MSC was connected with the raised serum glucose and insulin, increased concentrations of conjugated dienes in low-density lipoprotein (all p < 0.0001), and high frequency of e2 and e4 alleles of the apolipoprotein E gene (p < 0.005). However, the last significance was lost after the adjustment for age. The incidence of 54Thr allele for intestinal isoform of the fatty acid-binding protein (FABP-2) gene was comparable in all groups. The most important findings were the raised content of saturated FA and the increased activities of Delta9 and Delta6 desaturases (all p < 0.0001), and the decreased content of polyunsaturated FA n-6 family and the decreased activity of Delta5 desaturase (both p < 0.001) in connection with increasing number of MSC. In conclusion, the severity of MS is connected with the progression of oxidative stress and the unfavorable changes in the FA composition. These changes are independent of the studied gene polymorphisms.

TNF-alpha inhibition reduces renal injury in DOCA-salt hypertensive rats

Studies suggest that the inflammatory cytokine TNF-alpha plays a role in the prognosis of end-stage renal diseases. We previously showed that TNF-alpha inhibition slowed the progression of hypertension and renal damage in angiotensin II salt-sensitive hypertension. Thus, we hypothesize that TNF-alpha contributes to renal inflammation in a model of mineralocorticoid-induced hypertension. Four groups of rats (n = 5 or 6) were studied for 3 wk with the following treatments: 1) placebo, 2) placebo + TNF-alpha inhibitor etanercept (1.25 mg.kg(-1).day(-1) sc), 3) deoxycorticosterone acetate + 0.9% NaCl to drink (DOCA-salt), or 4) DOCA-salt + etanercept. Mean arterial blood pressure (MAP) measured by telemetry increased in DOCA-salt rats compared with baseline (177 +/- 4 vs. 107 +/- 3 mmHg; P < 0.05), and TNF-alpha inhibition had no effect in the elevation of MAP in these rats (177 +/- 8 mmHg). Urinary protein excretion significantly increased in DOCA-salt rats compared with placebo (703 +/- 76 vs. 198 +/- 5 mg/day); etanercept lowered the proteinuria (514 +/- 64 mg/day; P < 0.05 vs. DOCA-salt alone). Urinary albumin excretion followed a similar pattern in each group. Urinary monocyte chemoattractant protein (MCP)-1 and endothelin (ET)-1 excretion were also increased in DOCA-salt rats compared with placebo (MCP-1: 939 +/- 104 vs. 43 +/- 7 ng/day, ET-1: 3.30 +/- 0.29 vs. 1.07 +/- 0.03 fmol/day; both P < 0.05); TNF-alpha inhibition significantly decreased both MCP-1 and ET-1 excretion (409 +/- 138 ng/day and 2.42 +/- 0.22 fmol/day, respectively; both P < 0.05 vs. DOCA-salt alone). Renal cortical NF-kappaB activity also increased in DOCA-salt hypertensive rats, and etanercept treatment significantly reduced this effect. These data support the hypothesis that TNF-alpha contributes to the increase in renal inflammation in DOCA-salt rats.

Development of diabetes in obese, insulin-resistant mice: essential role of dietary carbohydrate in beta cell destruction

AIMS/HYPOTHESIS

The role of dietary carbohydrate in the pathogenesis of type 2 diabetes is still a subject of controversial debate. Here we analysed the effects of diets with and without carbohydrate on obesity, insulin resistance and development of beta cell failure in the obese, diabetes-prone New Zealand Obese (NZO) mouse.

MATERIALS AND METHODS

NZO mice were kept on a standard diet (4% [w/w] fat, 51% carbohydrate, 19% protein), a high-fat diet (15, 47 and 17%, respectively) and a carbohydrate-free diet in which carbohydrate was exchanged for fat (68 and 20%, respectively). Body composition and blood glucose were measured over a period of 22 weeks. Glucose tolerance tests and euglycaemic-hyperinsulinaemic clamps were performed to analyse insulin sensitivity. Islet morphology was assessed by immunohistochemistry.

RESULTS

Mice on carbohydrate-containing standard or high-fat diets developed severe diabetes (blood glucose >16.6 mmol/l, glucosuria) due to selective destruction of pancreatic beta cells associated with severe loss of immunoreactivity of insulin, glucose transporter 2 (GLUT2) and musculoaponeurotic fibrosarcoma oncogene homologue A (MafA). In contrast, mice on the carbohydrate-free diet remained normoglycaemic and exhibited hyperplastic islets in spite of a morbid obesity associated with severe insulin resistance and a massive accumulation of macrophages in adipose tissue.

CONCLUSIONS/INTERPRETATION

These data indicate that the combination of obesity, insulin resistance and the inflammatory response of adipose tissue are insufficient to cause beta cell destruction in the absence of dietary carbohydrate.

Adipocytokines and the regulation of lipid metabolism in growth hormone transgenic and calorie-restricted mice

Chronic elevation of GH induces resistance to insulin and hyperinsulinemia in both humans and animals, whereas calorie restriction (CR) improves peripheral insulin sensitivity in many species. To investigate the mechanisms that lead to insulin resistance in animals with high levels of GH as well as the mechanisms that might improve insulin sensitivity, we fed GH-overexpressing transgenic mice ad libitum or subjected them to 30% CR. We then assayed the plasma adipocytokines levels related to insulin sensitivity, plasma lipid levels, and tissue triglycerides accumulation and examined adipocyte morphology. Furthermore, we evaluated mRNA expression and protein levels of enzymes or regulators involved in regulating hepatic lipid metabolism. Our results suggest that decreased plasma adiponectin, increased plasma resistin and cholesterol, and elevated levels of TNF-alpha and IL-6 in adipocytes may all contribute to the insulin resistance observed in GH-Tg mice. Increased accumulation of triglycerides and impaired adipocytes differentiation in GH-transgenic mice provide plausible mechanisms for the alterations of adipocytokines. Hepatic and muscle insulin resistance in these mice is probably related to excessive accumulation of fatty acids and their metabolites. An increase in plasma adiponectin and decrease in plasma IL-6, triglycerides, and cholesterol levels in response to CR may improve insulin sensitivity.

Phospholipid scramblases: An overview

Phospholipid scramblases are a group of homologous proteins that are conserved in all eukaryotic organisms. They are believed to be involved in destroying plasma membrane phospholipid asymmetry at critical cellular events like cell activation, injury and apoptosis. However, a detailed mechanism of phospholipid scrambling still awaits a proper understanding. The most studied member of this family, phospholipid scramblase 1 (PLSCR1) (a 37kDa protein), is involved in rapid Ca2+ dependent transbilayer redistribution of plasma membrane phospholipids. Recently the function of PLSCR1 as a phospholipids translocator has been challenged and evidences suggest that PLSCR1 acts as signaling molecule. It has been shown to be involved in protein phosphorylation and as a potential activator of genes in response to interferon and other cytokines. Interferon induced rapid biosynthesis of PLSCR1 targets some of the protein into the nucleus, where it binds to the promoter region of inositol 1,4,5-triphosphate (IP3) receptor type 1 (IP3R1) gene and induces its expression. Palmitoylation of PLSCR1 acts as a switch, controlling its localization either to the PM or inside the nucleus. In the present review, we discuss the current understanding of PLSCR1 in relation to its trafficking, localization and signaling functions.

Beta-cell preservation with thiazolidinediones

Progressive beta-cell dysfunction and beta-cell failure are fundamental pathogenic features of type 2 diabetes. Ultimately, the development and continued progression of diabetes is a consequence of the failure of the beta-cell to overcome insulin resistance. Strategies that aim to prevent diabetes must, therefore, ultimately aim to stabilize the progressive decline of the beta-cell. Clinical study evidence from several sources now suggests that thiazolidinediones (TZDs) have profound effects on the beta-cell, such as improving insulin secretory capacity, preserving beta-cell mass and islet structure and protecting beta-cells from oxidative stress, as well as improving measures of beta-cell function, such as insulinogenic index and homeostasis model assessment of beta-cell function (HOMA-%B). Furthermore, intervention studies suggest that TZDs have the potential to delay, stabilize and possibly even prevent the onset on diabetes in high-risk individuals, and these effects appear to accompany improvements in beta-cell function. Here, we review the evidence, from in vitro studies to large intervention trials, for the effects of TZDs on beta-cell function and the consequences for glucose-lowering therapy.

Association between inadequate sleep and insulin resistance in obese children

OBJECTIVE

To analyze the relationships between sleep duration, obstructive sleep apnea syndrome (OSAS), and markers of insulin resistance in obese children.

STUDY DESIGN

Forty obese children were evaluated for sleep-related complaints. Each child underwent a polysomnogram, an oral glucose tolerance test (OGTT), and fasting lipid panel tests. Indices of insulin resistance (HOMA-IR and WBISI) and insulin secretion (IGI) were calculated based on the results of the OGTT. Markers of insulin resistance were compared among groups categorized according to polysomnogram results.

RESULTS

Subjects with shorter sleep duration had higher fasting insulin, peak insulin, and HOMA-IR levels and lower WBISI levels, findings suggestive of insulin resistance. In contrast, differences in body mass index z scores were not observed. Subjects with OSAS (32 of 40 children) had higher triglyceride levels and HOMA-IR values than those without OSAS, but did not differ in sleep duration. Multiple linear regression analysis revealed that HOMA-IR was significantly correlated with age, sleep duration, and percentage of rapid-eye-movement sleep.

CONCLUSIONS

Insulin resistance in obese children is associated with short sleep duration and OSAS.

New insights into the pathophysiology of gestational diabetes mellitus: possible role of human leukocyte antigen-G

Diabetes can develop in up to 10% of pregnant women who have not previously had the condition. This condition which usually begins in the second half of the pregnancy is called gestational diabetes mellitus (GDM). In most cases, all diabetic symptoms disappear following delivery. However, women with GDM have an increased risk of developing type 2 diabetes mellitus (DM) later in life, especially if they were overweight before the pregnancy. The cause of GDM is unknown. Although hormones present in the pregnancy, especially human placental lactogen, are thought to be responsible for the development of this condition, many questions remain to be answered. It is still not known why GDM develops in a subgroup of pregnant women. It may be possible that events leading to the development of GDM are triggered by an antigenic load which is the fetus itself. Human leukocyte antigen-G (HLA-G) expression that functions to protect the fetus from immune attack by down-regulating cytotoxic T cell responses to fetal trophoblast antigens is postulated to protect the islet cells of the pancreatic tissue also. HLA-G and nuclear factor-kappaB (NF-kappaB) interaction is suggested to be central in the events leading to GDM development. An analogy between the development of DM in some transplant patients and GDM development in a proportion of pregnancies is postulated, so that an antigenic load triggers the diabetogenic process. Further support of this hypothesis with new studies may lead to the possibility that recombinant HLA-G can be used for the prevention of diabetes in high risk patients.

Effects of rosiglitazone and metformin on inflammatory markers and adipokines: decrease in interleukin-18 is an independent factor for the improvement of homeostasis model assessment-beta in type 2 diabetes mellitus

OBJECTIVE

We examined the individual pharmacological effects of the addition of rosiglitazone and metformin to glimepiride on inflammatory markers and adipokines in patients with type 2 diabetes mellitus. We analysed the relationships between these variables, the measurements of insulin sensitivity and beta-cell function in patients treated with rosiglitazone plus glimepiride.

DESIGN AND PATIENTS

One hundred twenty (120) patients with type 2 diabetes mellitus were randomized and treated with glimepiride plus rosiglitazone or glimepiride plus metformin for 12 weeks. The plasma concentrations of the inflammatory markers and adipokines were measured at baseline and after 12 weeks.

MEASUREMENTS

Markers of insulin sensitivity and beta-cell function were determined by the quantitative insulin sensitivity check index (QUICKI) and the homeostasis model assessment of beta-cell function (HOMA-beta), respectively. Plasma concentrations of adiponectin were measured by radioimmunoassay. Plasma concentrations of resistin, tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-18 (IL-18) were measured using ELISA.

RESULTS

Improvements in fasting insulin level, QUICKI and HOMA-beta were noted in the rosiglitazone-treated group. Only the QUICKI value improved in the metformin-treated group. Adiponectin concentrations significantly increased in the rosiglitazone-treated group after 12 weeks. Significant decreases in resistin, C-reactive protein, TNF-alpha, IL-6 and IL-18 were seen in the rosiglitazone-treated patients but not in the metformin-treated patients. The independent risk factor for the HOMA-beta change according to stepwise multivariate regression analysis was a change in IL-18.

CONCLUSIONS

Rosiglitazone, but not metformin, improved the plasma concentrations of inflammatory markers and adipokines in patients with type 2 diabetes mellitus. A decrease in IL-18 is an independent factor for the improvement of HOMA-beta in type 2 diabetes mellitus.

Increased glycation of hemoglobin and plasma proteins in normotensive, non-diabetic obese Indian subjects: putative role of lipid peroxides

BACKGROUND

Glycation and lipid peroxidation are spontaneous reactions believed to contribute to the pathogenesis of many clinical disorders. The purpose of the present study was to evaluate the levels of lipid peroxides and glycated proteins in normotensive, non-diabetic obese Indian subjects and to assess possible associations between them.

METHODS

A total of 28 obese male subjects and 20 non-obese subjects were included in the present study. Whole blood glycated hemoglobin, plasma lipid peroxides and fructosamine levels were estimated in both groups.

RESULTS

Lipid peroxides, glycated hemoglobin and fructosamine levels were significantly higher in obese subjects in comparison with non-obese subjects. We also found a significant association between malondialdehyde and body mass index (r=0.424, p=0.025). Partial correlation analysis revealed that malondialdehyde was significantly correlated with glycated hemoglobin (r=0.590, p=0.01) and fructosamine (r=0.442, p=0.021) after controlling for glucose.

CONCLUSIONS

Increased glycation of proteins was found in normotensive, non-diabetic obese Indian subjects. These data also support the premise that lipid peroxides per se play a role in the glycation of hemoglobin and plasma proteins.

The relationship between the metabolic syndrome and energy-utilization deficit in the pathogenesis of obesity-induced osteoarthritis

We propose that the pathogenesis of obesity-induced osteoarthritis may be explained by the metabolic changes in the striated muscle induced by the interaction of insulin resistance and systemic inflammation in obese individuals with metabolic syndrome being osteoarthritis the latest consequence by the physiological changes seen in the metabolic syndrome. Increased levels of TH1 cytokines are produced by activated macrophages in the presence of an acute or chronic infectious disease and suppress the sensitivity of insulin receptors on the membrane of muscle cell and adipocytes. Both cells are activated by inflammatory cytokines and contribute to enhance acute inflammation and to maintain a state of chronic, low-grade inflammation in apparently healthy obese individuals. The increased number of macrophage in the adipose tissue of obese individuals acts as an amplifier of inflammation. Patients with osteoarthritis and metabolic syndrome frequently are complaining about hotness and recurrent edema of feet and hands. It is probable that hyperinsulinemia in the presence of insulin resistance and inflammation, induce vasodilation through the TNF mediated-iNOS overexpression. Patients with metabolic syndrome express clinically the consequence of a poor uptake, storage and energy expenditure by the muscle and any other insulin dependent tissue and the consequence of high insulin plasma levels are vasodilation and increased protein synthesis. The fatigue and muscle weakness induced by insulin resistance and inflammation in obese patients with metabolic syndrome increase the frequency and the intensity of traumatic events of peripheral or axial joints that result in stretch and breaking of tenoperiosteal junction and abrasive damage of cartilage and therefore in these patients with metabolic syndrome and pro-inflammatory state the reparative process of cartilage and periarticular tissues would be severely modified by the growth factor activity in presence of high levels of insulin.

The metabolic syndrome: metabolic changes with vascular consequences

Despite criticism regarding its clinical relevance, the concept of the metabolic syndrome improves our understanding of both the pathophysiology of insulin resistance and its associated metabolic changes and vascular consequences. Free fatty acids (FFA) and tumour necrosis factor-alpha (TNF-alpha) play prominent roles in the development of insulin resistance by impairing the intracellular insulin signalling transduction pathway. Obesity is an independent risk factor for cardiovascular disease and strongly related to insulin resistance. In case of obesity, FFAs and TNF-alpha are produced in abundance by adipocytes, whereas the production of adiponectin, an anti-inflammatory adipokine, is reduced. This imbalanced production of pro- and anti-inflammatory adipokines, as observed in adipocyte dysfunction, is thought to be the driving force behind insulin resistance. The role of several recently discovered adipokines such as resistin, visfatin and retinol-binding protein (RBP)-4 in the pathogenesis of insulin resistance is increasingly understood. Insulin resistance induces several metabolic changes, including hyperglycaemia, dyslipidaemia and hypertension, all leading to increased cardiovascular risk. In addition, the dysfunctional adipocyte, reflected largely by low adiponectin levels and a high TNF-alpha concentration, directly influences the vascular endothelium, causing endothelial dysfunction and atherosclerosis. Adipocyte dysfunction could therefore be regarded as the common antecedent of both insulin resistance and atherosclerosis and functions as the link between obesity and cardiovascular disease. Targeting the dysfunctional adipocyte may reduce the risk for both cardiovascular disease and the development of type 2 diabetes. Although lifestyle intervention remains the cornerstone of therapy in improving insulin sensitivity and its associated metabolic changes, medical treatment might prove to be important as well.

Role of adipokines in the obesity-inflammation relationship: the effect of fat removal

During the past 10 years, there has been a dramatic increase in the prevalence of obesity in the United States and other developed nations. Recent studies indicate that adipose tissue is an endocrine organ producing numerous proteins, collectively referred to as adipokines, with broad biological activity, that play an important autocrine role in obesity-associated complications. Adipose tissue in general and visceral fat in particular are thought to be key regulators of inflammation. Inflammation is heavily involved in the onset and development of atherothrombotic disease. Moreover, chronic inflammation may also represent a triggering factor in the origin of the metabolic syndrome and type 2 diabetes mellitus. According to a hypothesis, stimuli such as overnutrition, physical inactivity, and aging would result in cytokine hypersecretion and eventually lead to insulin resistance and diabetes in genetically or metabolically predisposed individuals. This article discusses the current understanding of important adipokines thought to be involved in the metabolic and cardiovascular risk associated with obesity. Available evidence linking fat removal by liposuction to modification of cardiovascular risk and vascular inflammatory markers in the obese patient is also presented. Most studies have shown that liposuction produces beneficial effects on insulin resistance and vascular inflammation in the obese patient, reducing its cardiovascular risk. Besides having a significant role in body contouring of the obese patient at the end of the lengthy process of bariatric surgery and massive weight loss, plastic surgery should be incorporated into a multifaceted program of lifestyle changes that allows the obese patient to obtain weight loss and, more importantly, to maintain the reduced weight in the long term.

Modulation of adipokines and cytokines in gestational diabetes and macrosomia

CONTEXT/OBJECTIVE

Not much is known about the implication of adipokines and different cytokines in gestational diabetes mellitus (GDM) and macrosomia. The purpose of this study was to assess the profile of these hormones and cytokines in macrosomic babies, born to gestational diabetic women.

DESIGN/SUBJECTS

A total of 59 women (age, 19-42 yr) suffering from GDM with their macrosomic babies (4.35 +/- 0.06 kg) and 60 healthy age-matched pregnant women and their newborns (3.22 +/- 0.08 kg) were selected.

METHODS

Serum adipokines (adiponectin and leptin) were quantified using an obesity-related multiple ELISA microarray kit. The concentrations of serum cytokines were determined by ELISA.

RESULTS

Serum adiponectin levels were decreased, whereas the concentrations of leptin, inflammatory cytokines, such as IL-6 and TNF-alpha, were significantly increased in gestational diabetic mothers compared with control women. The levels of these adipocytokines were diminished in macrosomic babies in comparison with their age-matched control newborns. Serum concentrations of T helper type 1 (Th1) cytokines (IL-2 and interferon-gamma) were decreased, whereas IL-10 levels were significantly enhanced in gestational diabetic mothers compared with control women. Macrosomic children exhibited high levels of Th1 cytokines and low levels of IL-10 compared with control infants. Serum IL-4 levels were not altered between gestational diabetic mothers and control mothers or the macrosomic babies and newborn control babies.

CONCLUSIONS

GDM is linked to the down-regulation of adiponectin along with Th1 cytokines and up-regulation of leptin and inflammatory cytokines. Macrosomia was associated with the up-regulation of Th1 cytokines and the down-regulation of the obesity-related agents (IL-6 and TNF-alpha, leptin, and adiponectin).

Proinflammatory cytokines, insulin resistance, and insulin secretion in chronic hepatitis C patients: A case-control study

OBJECTIVE

The purpose of this study was to explore the initial pathogenic mechanisms of diabetes associated with hepatitis C virus (HCV) infection.

RESEARCH DESIGN AND METHODS

Insulin resistance, proinflammatory cytokines, and beta-cell function were evaluated in a case-control study. A total of 28 consecutive nondiabetic patients with chronic hepatitis C were included in the study (anti-HCV+). Fourteen patients with chronic hepatitis other than HCV infection served as the control group (anti-HCV-). Both groups were closely matched by the main clinical variables associated with insulin resistance and the degree of liver fibrosis. In addition, there were no differences between groups regarding hepatic insulin extraction measured by calculating the ratio between C-peptide and insulin. Serum levels of proinflammatory cytokines (tumor necrosis factor [TNF]-alpha, soluble TNF receptor [sTNFR] 1, soluble TNFR2, and interleukin-6) were measured by enzyme-linked immunosorbent assay. Insulin resistance (homeostasis model assessment [HOMA] of insulin resistance [HOMA-IR]) and insulin secretion at baseline (HOMA-beta) and after various stimulus (oral glucose tolerance test, standard food intake, and intravenous glucagon) were determined by previously validated mathematic indexes.

RESULTS

HOMA-IR was higher in anti-HCV+ than in anti-HCV- patients (4.35 +/- 2.27 vs. 2.58 +/- 1.74; P = 0.01). All the proinflammatory cytokines analyzed were significantly higher in anti-HCV+ patients than in anti-HCV- patients. In addition, sTNFR1 and sTNFR2 were directly correlated to HOMA-IR. HOMA-beta as well as insulin and C-peptide responses after the intravenous glucagon test were significantly higher in anti-HCV+ patients than in anti-HC- patients.

CONCLUSIONS

Insulin resistance mediated by proinflammatory cytokines, but not a deficit in insulin secretion, could be the primary pathogenic mechanism involved in the development of diabetes associated with HCV infection.