Adipose tissue, insulin action and vascular disease: inflammatory signals

Measures of body composition and risk of heart failure in the elderly: the Rotterdam study

OBJECTIVES

The incidence of heart failure increases with aging. Aim of the present study was to determine whether measures body composition predict incident heart failure in older adults.

SETTING

Prospective community-based cohort study. 5, 868 men and women aged 55 years and older participating the Rotterdam study. Measures of body mass index and waist circumference were obtained at baseline. Information on incident heart failure was obtained during follow-up. Cox regression analyses were performed to investigate the possible association between measure of body composition and incident heart failure.

RESULTS

During a mean follow up of 10.9 (SD ±4.4) years, 765 participants had heart failure. After adjustment for age and gender, 1-standard deviation of body mass index, waist circumference and the waist-hip ratio predicted heart failure (HR 1.25; 95% CI 1.17-1.34; HR 1.26; 95% CI 1.18-1.36; and HR 1.17; 95% CI 1.08-1.27), respectively. In age-stratified analyses, 1-standard deviation of body mass index (1.17; 95% CI 1.06- 1.29) and waist circumference (1.16; 95% CI 1.05- 1.29) were still associated with the risk of heart failure in the oldest participants, whereas the waist-hip ratio was not (1.06; 95% CI 0.945-1.18).

CONCLUSION

Although estimates decrease with age, measures of overall and central adiposity predict incident heart failure among community dwelling older adults.

Secreted proteins from adipose tissue and skeletal muscle - adipokines, myokines and adipose/muscle cross-talk

White adipose tissue and skeletal muscle are the largest organs in the body and both are composed of distinct cell types. The signature cell of adipose tissue is the adipocyte while myocytes are the defining cell of skeletal muscle. White adipocytes are major secretory cells and this is increasingly apparent also for myocytes. Both cells secrete a range of bioactive proteins, generally termed adipokines in the case of adipocytes and myokines for muscle cells. There has, however, been some confusion over nomenclature and we suggest that the name myokine is restricted to a protein that is secreted from myocytes, while the term adipokine should be used to describe all proteins secreted from any type of adipocyte (white, brown or brite). These definitions specifically exclude proteins secreted from other cells within adipose tissue and muscle, including macrophages. There is some commonality between the myokines and adipokines in that both groups include inflammation-related proteins - for example, IL-6, Il-8 and MCP-1. Adipokines and myokines appear to be involved in local autocrine/paracrine interactions within adipose tissue and muscle, respectively. They are also involved in an endocrine cross-talk with other tissues, including between adipose tissue and skeletal muscle, and this may be bi-directional. For example, IL-6, secreted from myocytes may stimulate lipolysis in adipose tissue, while adipocyte-derived IL-6 may induce insulin resistance in muscle.

Left ventricle relative wall thickness and plasma leptin levels: baseline relationships and effects of 4 months of walking training in healthy overweight postmenopausal women

OBJECTIVE

Whether leptin has positive or negative influences on cardiac structure and function in healthy sedentary overweight postmenopausal women is unknown. We investigated the role of leptin in cardiac health and whether aerobic fitness enhancement influences any relationships revealed between leptin and echocardiographic measurements.

METHODS

Thirty-nine sedentary postmenopausal women were enrolled after an initial screening. The women underwent blood sampling for hormone levels, anthropometric and echocardiographic measurements, dietary habits investigation, and fitness testing, both before and after 4 months of walking training.

RESULTS

After the intervention, the women who had an adherence to training of 75% or higher showed significantly reduced percentage fat mass (P = 0.006) and plasma leptin levels (P < 0.001), whereas their maximum oxygen consumption increased significantly (P < 0.001). The women showed a significant reduction in left ventricle relative wall thickness (P = 0.039) and significant increases in both left ventricular end-diastolic diameter (P = 0.040) and left ventricular mass index (P = 0.043). At baseline, a negative correlation was seen between plasma leptin levels and left ventricle relative wall thickness (r = -0.553; P = 0.009). Further negative correlations were seen for the changes in left ventricle relative wall thickness with leptin levels (r = -0.456; P = 0.038) and with tricipital skinfold (r = -0.436; P = 0.05).

CONCLUSIONS

In healthy overweight sedentary postmenopausal women with low fitness level, high plasma leptin levels seem to have a protective role against left ventricle relative wall thickness hypertrophy and to participate in its remodeling after 4 months of aerobic training.

Obesity, metabolic syndrome and esophageal adenocarcinoma: epidemiology, etiology and new targets

BACKGROUND

Rates of distal and junctional adenocarcinomas are increasing in Western countries.

METHODS

Systematic review of epidemiological evidence linking obesity to esophageal adenocarcinoma (EA) was performed for studies published from 2005 to 2010. The current understanding of obesity's role in the etiology and potential dysplastic progression of Barrett's esophagus (BE) to EA is reviewed.

RESULTS

Accumulating epidemiological studies provide evidence of obesity's role as a driving force behind the increasing rates of EA. The simplest construct is that obesity promotes reflux, causing chronic inflammation and BE, predisposing to adenocarcinoma. However, as obesity is positively associated with the prevalence of many cancers, other mechanisms are important. A link may exist between fat distribution patterns and the risk of BE and EA. Altered metabolic profiles in the metabolic syndrome (MetS) may be a key factor in cell cycle/genetic abnormalities that mark the progression of BE towards cancer. Research highlighting a unique role of MetS in the length of BE, and its association with systemic inflammation and insulin resistance is discussed, as well as adipokine receptor expression in both BE and esophageal epithelium, and how MetS and the systemic response impacts on key regulators of inflammation and tumorigenesis. CONCLUSIONS/IMPACT: Obesity is positively associated with EA. The systemic inflammatory state consequent on the altered metabolism of obese patients, and the associated impact of adipocytokines and pro-coagulant factors released by adipocytes in central fat, may underlie obesity's relationship to this cancer. Novel therapeutic agents that may antagonize adipo-cytokines and potentially offer a promising role in cancer therapy are discussed.

Circulating inflammatory and endothelial markers and risk of hypertension in white and black postmenopausal women

BACKGROUND

Systemic inflammation and endothelial activation are implicated in the development of hypertension. However, epidemiologic studies have yet to compare multiple corresponding biomarkers in relation to risk of hypertension, particularly in multiethnic populations.

METHODS

We identified 800 individuals with incident hypertension and 800 matched controls, each group with equal numbers of white and black women, in a nested case-control study within the Women's Health Initiative Observational Study. We measured markers of inflammation [high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-6, IL-1β, tumor necrosis factor receptor 2 (TNF-r2)] and endothelial activation [soluble intercellular adhesion molecule-1 (sICAM-1)] in baseline blood samples.

RESULTS

Before adjustment for measures of adiposity, higher hsCRP and IL-6 concentrations were associated with increased risk of hypertension in both white and black women, higher TNF-r2 was associated with increased risk of hypertension in black women only, and IL-1β and sICAM-1 were not associated with risk of hypertension. All the positive associations were attenuated after adjustment for body mass index. The resulting multivariable-adjusted relative risks (95% CI) of hypertension comparing the highest vs lowest quartile were 1.52 (0.94-2.48) and 1.23 (0.76-1.97) for hsCRP and IL-6 in white women and 1.30 (0.81-2.07), 1.58 (0.96-2.59), and 1.49 (0.94-2.36) for hsCRP, IL-6, and TNF-r2 in black women. The results after adjustment for waist circumference were similar.

CONCLUSIONS

After adjustment for measures of adiposity, there was no significant association of hsCRP, IL-6, IL-1β, TNF-r2, or sICAM-1 with incident hypertension in either white or black women. The interrelationships between inflammation and adiposity in development of hypertension need further investigation.

Circulating levels of interleukin-18 in patients with non-alcoholic fatty liver disease

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with obesity and diabetes mellitus. IL-18 is associated with obesity and metabolic syndrome. Our aim was to investigate the relationship of IL-18 with adiponectin and liver histology in subjects with NAFLD who had no additional disorder such as morbid obesity, diabetes mellitus and hypertension.

METHODS

Plasma levels of IL-18 and adiponectin were measured by ELISA in 96 male subjects with NAFLD [n = 65 for non-alcoholic steatohepatitis (NASH) and n = 31 for simple steatosis (SS)].

RESULTS

IL-18 levels were not different between the two groups (p = 0.89). There was no significant association of IL-18 with adiponectin, insulin resistance and histopathological findings. Adiponectin was lower in the NASH group compared to the SS group (p = 0.02) and it was found to be negatively correlated with hepatic steatosis and fibrosis (r = -0.442, p < 0.001 and r = -0.292, p = 0.02, respectively).

CONCLUSIONS

This study indicates that circulating IL-18 levels are not altered in male subjects with NAFLD. These results suggest that in the absence of metabolic risk factors, IL-18 per se may not be involved in the pathogenesis of NASH and SS.

Relationship between vaspin gene expression and abdominal fat distribution of Korean women

Visceral adipose tissue-derived serpin (vaspin) is a novel adipokine that is thought to have insulin-sensitizing effects. We investigated vaspin mRNA expression in abdominal adipose tissue and examined how gene expression related to abdominal fat distribution and metabolic parameters in Korean women. We measured anthropometric variables, metabolic parameters, serum vaspin concentration, and vaspin mRNA expression in abdominal adipose tissue obtained from women who underwent abdominal gynecological surgery and were aged 18-67 years (n = 85). Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) area were measured in 40 subjects using computed tomography (CT). Vaspin expression was analyzed by real-time quantitative RT-PCR according to abdominal fat distribution. Vaspin mRNA expression was greater in adipocytes than in stroma/vascular cells. In the total subjects, vaspin expression was significantly higher in SAT than in VAT. Vaspin expression in SAT in subcutaneous fat type (VSR ≤ 0.3) was significantly higher than in visceral fat type (VSR > 0.3), although vaspin expression in VAT was similar between subcutaneous and visceral fat type. There was a significant negative correlation between vaspin expression in SAT and VAT area (r = -0.55, p = 0.001). Serum vaspin concentration was significantly correlated with fasting insulin (r = 0.30, p = 0.02), HOMA-IR (r = 0.29, p = 0.02), and the ratio of vaspin expression in VAT to vaspin expression in SAT (r = 0.41, p = 0.04). Vaspin expression in abdominal adipose tissue was adipocyte-specific and vaspin expression in SAT decreased as VAT area increased.

Effects of weight reduction on serum vaspin concentrations in obese subjects: modification by insulin resistance

Visceral adipose tissue-derived serpin (vaspin) has been regarded as a novel adipokine with potential insulin sensitizing properties. We investigated the changes of serum vaspin concentration in response to weight reduction, and the associations between changes in serum vaspin concentrations and changes of anthropometric and metabolic variables in obese subjects after weight reduction. We performed a longitudinal clinical intervention study on 63 obese persons enrolled in a 12-week weight reduction program that included lifestyle modification and adjuvant treatment with the antiobesity agent orlistat. Anthropometric variables, lipid profiles, fasting glucose, fasting insulin, and serum vaspin concentrations were measured. Statistical analyses were performed according to the homeostasis model assessment of insulin resistance (HOMA(IR)). Serum vaspin concentrations decreased significantly in responders (≥2% reduction in baseline weight), but not in nonresponders (<2% reduction in baseline weight). Changes in serum vaspin concentrations were significantly correlated with body weight, BMI, waist circumference, and hip circumference in the higher, but not in the lower, HOMA(IR) group. In multivariate linear regression analysis, change in serum vaspin concentrations in the higher, but not in the lower, HOMA(IR) group was positively correlated with change in BMI and negatively correlated with initial HOMA(IR) level. The associations between changes in serum vaspin concentrations and changes in anthropometric and metabolic parameters differed according to insulin resistance status in obese subjects. These relationships were more prominent in the higher HOMA(IR) group. Insulin resistance may influence the correlations between changes in serum vaspin concentration and related metabolic variables.

The Nε-(carboxymethyl)lysine-RAGE axis: putative implications for the pathogenesis of obesity-related complications

Obesity is an important contributor to the burden of insulin resistance, Type 2 diabetes and cardiovascular disease. An important mechanism by which excess adiposity causes obesity-associated complications is the dysregulated production and secretion of biologically active molecules derived from adipocytes. These adipokines affect the vascular wall and contribute to the development of insulin resistance and Type 2 diabetes. However, factors that cause an increased production of pro-inflammatory adipokines, while decreasing anti-inflammatory adipokines, have not been fully clarified. Owing to local conditions in adipose tissue, that is, increased fatty acids, hypoxia and oxidative stress, we speculate that an increased formation of the major advanced lipoxidation end product, N^ε-(carboxymethyl)lysine (CML), may play a role. CML-adducts in proteins are major ligands for the receptor for advanced glycation end products (RAGE). The consequence of RAGE activation by CML is the activation of important signaling inflammatory pathways. The putative role of CML-modified proteins in obesity is addressed in this article. The identification of this pathway may provide an important strategy for novel therapeutic approaches against obesity-associated complications.

The relationship between inflammation, obesity and risk for hypertension in the Multi-Ethnic Study of Atherosclerosis (MESA)

It has been suggested that inflammation is important in the aetiology of hypertension and that this may be most relevant among obese persons. To study this, we examined the independent relationships between obesity, inflammation-related proteins (interleukin-6 (IL-6), C-reactive protein (CRP) and fibrinogen) and risk for hypertension in the Multi-Ethnic Study of Atherosclerosis (MESA). Hypertension status, defined as a blood pressure ≥140/90 mm Hg or a history of hypertension and use of blood pressure medications, was determined at baseline and two subsequent exams over 5 years. Among 3543 non-hypertensives at baseline, 714 individuals developed incident hypertension by Exam 3. Cox proportional hazard models were used to determine the relationship between baseline levels of IL-6, CRP and fibrinogen and future risk of hypertension. One s.d. difference in baseline concentration of IL-6, CRP or fibrinogen was associated with 20-40% greater risk of incident hypertension. This risk was attenuated after accounting for other hypertension risk factors (hazard ratio (HR) IL-6: 1.13 (95% CI: 1.04-1.23); CRP: 1.11 (95% CI: 1.02-1.21); fibrinogen 1.0 (95% CI: 0.92-1.08)). Conversely, obesity was an independent risk factor for hypertension risk, minimally impacted by other covariates, including IL-6 and CRP (HR 1.72 (95% CI: 1.36-2.16)). IL-6 and CRP did not modify the relationship between obesity and hypertension, though an adjusted twofold greater risk was observed for obese individuals with a CRP >3 mg l⁻¹ compared with CRP <1 mg l⁻¹. The relationship between inflammation-related proteins and hypertension risk was predominantly explained by other hypertension risk factors. Obesity, independent of inflammation, remained a potent risk factor for future hypertension.

Relationship between severe obesity and gut inflammation in children: what's next?

BACKGROUND

Preliminary evidence suggests an association between obesity and gut inflammation.

AIMS

To evaluate the frequency of glucose abnormalities and their correlation with systemic and intestinal inflammation in severely obese children.

PATIENTS AND METHODS

Thirty-four children (25 males; median age 10.8 ± 3.4 yrs) with severe obesity (BMI >95%) were screened for diabetes with oral glucose tolerance test (OGTT), systemic inflammation with C-reactive protein (CRP) and gut inflammation with rectal nitric oxide (NO) and faecal calprotectin.

RESULTS

BMI ranged from 23 to 44 kg/m2, and BMI z-score between 2.08 e 4.93 (median 2.69 ± 0.53). Glucose abnormalities were documented in 71% of patients: type 2 diabetes in 29%, impaired fasting glucose (IFG) in 58%, and impaired glucose tolerance (IGT) in 37.5%. Thirty-one patients (91%) were hyperinsulinemic. CRP was increased in 73.5% with a correlation between BMI z-score and CRP (p 0.03). Faecal calprotectin was increased in 47% patients (mean 77 ± 68), and in 50% of children with abnormal glucose metabolism (mean 76 ± 68 μg/g), with a correlation with increasing BMI z-score. NO was pathological in 88%, and in 87.5% of glucose impairment (mean 6.8 ± 5 μM).

CONCLUSIONS

In this study, the prevalence of glucose abnormalities in obese children is higher than in other series; furthermore, a correlation is present between markers of systemic and intestinal inflammation and glucose abnormalities.

Association between serum vaspin concentrations and visceral adipose tissue in Korean subjects

Adipokines modulate multiple signaling pathways of insulin resistance via endocrine, paracrine, or autocrine mechanisms. Visceral adipose tissue (VAT)-derived serpin (vaspin) is a novel adipokine with potential insulin-sensitizing effects. We investigated the association between serum vaspin concentrations and abdominal adiposity. We recruited subjects (N = 150) aged 20 to 69 years who visited our hospital for regular health examinations. Abdominal VAT and subcutaneous adipose tissue areas were assessed by computed tomography. We measured serum vaspin concentrations by enzyme-linked immunosorbent assay. Statistical analysis was performed after stratification, using a homeostasis model for insulin resistance (HOMA-IR). Serum vaspin concentrations correlated positively with age (r = 0.196) when data from all subjects were analyzed. In the higher-HOMA-IR group, serum vaspin levels correlated more prominently with age (r = .344) and VAT area (r = .327) although these associations were not found in the lower-HOMA-IR group. In multivariate linear regression analysis, the VAT area was independently correlated with serum vaspin concentrations in the higher-HOMA-IR group. The association between serum vaspin concentrations and VAT differs according to insulin resistance. Insulin resistance might influence the correlation between serum vaspin concentration and VAT in human subjects.

The association between BMI and plasma cytokine levels in patients with acute lung injury

BACKGROUND

Obesity is associated with poor outcomes in many diseases, although recent data suggest that acute lung injury (ALI) is an exception. This is particularly interesting because obesity is marked by increased levels of proinflammatory mediators associated with increased morbidity and mortality in ALI. We hypothesized that cytokine response might be attenuated in patients who are obese and critically ill or that obesity might modify the relationship between plasma cytokines and clinical outcomes in ALI.

METHODS

We analyzed plasma biomarker levels (interleukin [IL]-6, IL-8, tumor necrosis factor-alpha receptor 1, surfactant protein D [SP-D], soluble intracellular adhesion molecule, von Willebrand factor (vWF), protein C, and plasminogen activator inhibitor-1) collected at baseline and day 3 in 1,409 participants in prior National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Network (ARDSNet) trials. BMI was calculated for each patient, and associations with cytokine levels and ventilator-free days (VFDs), organ failure-free days (OFDs), and mortality were investigated in regression models adjusting for confounders.

RESULTS

In adjusted analyses, plasma IL-6 (P = .052), IL-8 (P = .001), and SP-D (P < .001) were inversely related to BMI, whereas vWF (P = .001) and WBC count (P = .042) increased proportionally with BMI. BMI was not associated with increased morbidity or mortality and did not modify the association between baseline biomarker levels and mortality, VFDs, or OFDs.

CONCLUSIONS

Patients who are obese and have ALI have lower levels of several proinflammatory cytokines, suggesting that the inflammatory response may be altered in patients with ALI and a high BMI. Lower SP-D but higher vWF suggests decreased epithelial and increased endothelial injury in the lung of patients who are obese. Mechanisms by which obesity may modulate innate immunity in critical illness are unclear, and future studies should elucidate such mechanisms.

Identifying molecular effects of diet through systems biology: influence of herring diet on sterol metabolism and protein turnover in mice

Background

Changes in lifestyle have resulted in an epidemic development of obesity-related diseases that challenge the healthcare systems worldwide. To develop strategies to tackle this problem the focus is on diet to prevent the development of obesity-associated diseases such as cardiovascular disease (CVD). This will require methods for linking nutrient intake with specific metabolic processes in different tissues.

Methodology/Principal Finding

Low-density lipoprotein receptor-deficient (Ldlr −/−) mice were fed a high fat/high sugar diet to mimic a westernized diet, being a major reason for development of obesity and atherosclerosis. The diets were supplemented with either beef or herring, and matched in macronutrient contents. Body composition, plasma lipids and aortic lesion areas were measured. Transcriptomes of metabolically important tissues, e.g. liver, muscle and adipose tissue were analyzed by an integrated approach with metabolic networks to directly map the metabolic effects of diet in these different tissues. Our analysis revealed a reduction in sterol metabolism and protein turnover at the transcriptional level in herring-fed mice.

Conclusion

This study shows that an integrated analysis of transcriptome data using metabolic networks resulted in the identification of signature pathways. This could not have been achieved using standard clustering methods. In particular, this systems biology analysis could enrich the information content of biomedical or nutritional data where subtle changes in several tissues together affects body metabolism or disease progression. This could be applied to improve diets for subjects exposed to health risks associated with obesity.

Maternal obesity and fetal metabolic programming: a fertile epigenetic soil

The incidence of obesity and overweight has reached epidemic levels in the United States and developed countries worldwide. Even more alarming is the increasing prevalence of metabolic diseases in younger children and adolescents. Infants born to obese, overweight, and diabetic mothers (even when normal weight) have increased adiposity and are at increased risk of later metabolic disease. In addition to maternal glucose, hyperlipidemia and inflammation may contribute to the childhood obesity epidemic through fetal metabolic programming, the mechanisms of which are not well understood. Pregravid obesity, when combined with normal changes in maternal metabolism, may magnify increases in inflammation and blood lipids, which can have profound effects on the developing embryo and the fetus in utero. Fetal exposure to excess blood lipids, particularly saturated fatty acids, can activate proinflammatory pathways, which could impact substrate metabolism and mitochondrial function, as well as stem cell fate, all of which affect organ development and the response to the postnatal environment. Fetal and neonatal life are characterized by tremendous plasticity and the ability to respond to environmental factors (nutrients, oxygen, hormones) by altering gene expression levels via epigenetic modifications. Given that lipids act as both transcriptional activators and signaling molecules, excess fetal lipid exposure may regulate genes involved in lipid sensing and metabolism through epigenetic mechanisms. Epigenetic regulation of gene expression is characterized by covalent modifications to DNA and chromatin that alter gene expression independent of gene sequence. Epigenetic modifications can be maintained through positive and negative feedback loops, thereby creating stable changes in the expression of metabolic genes and their main transcriptional regulators. The purpose of this article is to review current literature on maternal-fetal lipid metabolism and maternal obesity outcomes and to suggest some potential mechanisms for fetal metabolic programming in key organ systems that regulate postnatal energy balance, with an emphasis on epigenetics and the intrauterine environment.

Adipokine expression and secretion by canine adipocytes: stimulation of inflammatory adipokine production by LPS and TNFalpha

Adiposity and obesity are increasing in dogs. We have examined here the endocrine function of canine adipose tissue and the regulation of production of inflammation-related adipokines by dog adipocytes. Adiponectin, leptin, IL-6, MCP-1 and TNFalpha genes were expressed in the main adipose depots of dogs, but there were no major depot differences in mRNA levels. Each adipokine was expressed in canine adipocytes differentiated in culture and secreted into the medium (leptin undetected). IL-6, MCP-1 and TNFalpha were also expressed and secreted by preadipocytes; adiponectin and leptin were only expressed after adipocyte differentiation. The inflammatory mediators LPS and TNFalpha had major stimulatory effects on the expression and secretion of IL-6, MCP-1 and TNFalpha; there was a >5,000-fold increase in IL-6 mRNA level with LPS. IL-6 release into the medium was increased >50-fold over 24 h with LPS and TNFalpha, while MCP-1 release was increased 23- and 40-fold by TNFalpha and LPS, respectively. However, there was no effect, or small reductions, in adiponectin and leptin mRNA levels with the inflammatory mediators. Dexamethasone-stimulated leptin gene expression, had no effect on adiponectin expression, but decreased the expression and secretion of IL-6 and MCP-1. The PPARgamma agonist rosiglitazone stimulated both adiponectin and leptin expression and inhibited the expression of IL-6, MCP-1 and TNFalpha; MCP-1 secretion was reduced. These results demonstrate that canine adipocytes express and secrete key adipokines and show that adipocytes of this species are highly responsive to inflammatory mediators with the induction of major increases in the production of inflammation-related adipokines.

Bean amylase inhibitor and other carbohydrate absorption blockers: effects on diabesity and general health

Many believe that excessive intake of refined carbohydrates (CHO) plays a major role in the development of obesity/overweight, type 2 diabetes mellitus and insulin resistance, a collection of events commonly referred to as "diabesity," and have sought natural means to overcome these linked perturbations. As a first approach, planned diets with low portions of refined CHO have become popular. However, these diets do not satisfy everyone; and many are concerned over replacing CHO with more fats. As a second option, addition of soluble fiber to the diet can slow absorption of refined CHO, i.e., lower the glycemic index of foods and overcome or at least ameliorate many of the adverse reactions resulting from increased refined CHO ingestion. Unfortunately, the general public does not favor diets high in fiber content, and various fibers can lead to gastrointestinal problems such as gas and diarrhea. A third choice to favorably influence CHO absorption is to use natural dietary supplements that block or slow CHO absorption in the gastrointestinal tract via inhibiting enzymes necessary for CHO absorption -amylase and alpha-glucosidases. Although a number of natural supplements with anti-amylase activity have been recognized, the most studied and favored one is white kidney bean extract. Animal and human studies clearly show that this agent works in vivo and has clinical utility. This paper reviews many aspects of diabesity and the use of "carb blockers" to prevent and ameliorate the situation. In many respects, carb blockers mimic the beneficial effects of fibers.

Fibrinogen kinetics and protein turnover in obese non-diabetic males: effects of insulin

BACKGROUND

Although hyperfibrinogenemia and insulin resistance are common in obesity and diabetes mellitus, the impact of obesity per se on fibrinogen turnover and the insulin effects on fibrinogen and protein kinetics is unknown.

METHODS

We measured fibrinogen and albumin fractional (FSR) and absolute (ASR) synthesis rates, as well as protein turnover, in non-diabetic, obese and in control male subjects both before and following an euglycemic, euaminoacidemic, hyperinsulinemic clamp, using L-[(2)H(3)]-Leucine isotope infusion.

RESULTS

In the obese, basal fibrinogen concentrations was approximately 25% greater (p < 0.035), and fibrinogen pool approximately 45% greater (p < 0.005), than in controls. Both FSR and ASR of fibrinogen were similar to control values. With hyperinsulinemia, although fibrinogen FSR and ASR were not significantly modified with respect to baseline in either group, fibrinogen ASR resulted to be approximately 50% greater in the obese than in controls (p < 0.015). Hyperinsulinemia equally stimulated albumin synthesis and suppressed leucine appearance from endogenous proteolysis in both groups. Amino acid clearance was also similar. In the obese, the insulin-mediated glucose disposal was approximately 50% lower (p < 0.03) than in controls, and it was inversely correlated with fibrinogen ASR during the clamp in both groups (r = - 0.58).

CONCLUSIONS

In obese, non-diabetic males, post absorptive fibrinogen production is normal. Whole-body amino acid disposal, basal and insulin-responsive protein degradation, and albumin synthesis are also normal. However, the greater fibrinogen ASR in the obese with hyperinsulinemia, and the inverse relationship between insulin sensitivity and clamp fibrinogen production, suggest a role for hyperinsulinemia and/or insulin resistance on fibrinogen production in obesity.

Elevated plasma levels of TNF-alpha and interleukin-6 in patients with diastolic dysfunction and glucose metabolism disorders

Background

Diabetes mellitus (DM) has reached epidemic proportions and is an important risk factor for heart failure (HF). Left ventricular diastolic dysfunction (LVDD) is recognized as the earliest manifestation of DM-induced LV dysfunction, but its pathophysiology remains incompletely understood. We sought to evaluate the relationship between proinflammatory cytokine levels (TNF-alpha, IL-6) and tissue Doppler derived indices of LVDD in patients with stable coronary artery disease.

Methods

We enrolled 41 consecutive patients (mean age 65+/-10 years) submitted for coronary angiography. Echocardiographic assessment was performed in all patients. Pulsed tissue Doppler imaging was performed at the mitral annulus and was characterized by the diastolic early relaxation velocity Em. Conventional transmitral flow was measured with pw-doppler. Early (E) transmitral flow velocity was measured. LVDD was defined as E/Em ratio ≥ 15, E/Em 8-14 was classified as borderline. Plasma levels of TNF-alpha and IL-6 were determined in all patients. A standardized oral glucose tolerance test was performed in subjects without diabetes.

Results

Patients with E/Em ratio ≥ 15, classified as LVDD and those with E/Em ratio 8-14 (classified as borderline) had significantly higher IL-6 (P = 0,001), TNF-alpha (P < 0,001) and NT-pro- BNP (P = 0,001) plasma levels compared to those with normal diastolic function. TNF-alpha and IL-6 levels remains significantly elevated after adjustment for sex, age, left ventricular ejection function, body mass index, coronary heart disease, smoking, hypertension and diabetes mellitus with linear regression analysis. Furthermore, in subjects LVDD or borderline LV diastolic function, 75% had diabetes or IGT, respectively. When subjects without diabetes were excluded, both IL-6 (P = 0,006) and TNF-alpha (P = 0,002) remained significantly elevated in subjects with E/Em ratio ≥ 15.

Conclusion

This study reveals that increased plasma levels of IL-6 and TNF-alpha were associated with LVDD. These findings suggest a link between low-grade inflammation and the presence of LVDD. An active proinflammatory process may be of importance in the pathogenesis of diastolic dysfunction.

Obesidade e adipocinas inflamatórias: implicações práticas para a prescrição de exercício

A obesidade é uma doença complexa de etiologia multifacetada, com sua própria fisiopatologia, comorbidades e capacidades desabilitantes. Aceitar a obesidade como uma doença é fundamental para o seu tratamento. Atualmente, o tecido adiposo é um dos principais focos das pesquisas em obesidade, devido a uma revolução no entendimento da função biológica desse tecido desde a última década. Já está muito claro que o tecido adiposo branco secreta múltiplos peptídeos bioativos, denominados adipocinas (proteínas sintetizadas e secretadas pelo tecido adiposo). Dessa forma, o objetivo deste trabalho de revisão foi investigar a relação entre obesidade e adipocinas inflamatórias, buscando discutir o papel do exercício físico no tratamento dessa patologia. Os resultados demonstram que uma das mais importantes descobertas das pesquisas recentes em obesidade é o conceito de que ela é caracterizada por uma inflamação crônica. Dentre todas as adipocinas, sem dúvida, a IL-6, o TNF-α, a leptina (pró-inflamatórias) e a adiponectina (anti-inflamatória) vêm recebendo atenção especial da literatura especializada. O aumento da concentração dessas adipocinas promove grande impacto em diversas funções corporais que estão fortemente correlacionadas com doenças cardiovasculares. Uma vez que a obesidade é considerada uma doença inflamatória e o exercício físico modula de forma direta tais processos, é essencial que tenhamos como um dos objetivos principais de nossos programas de exercícios físicos a melhora da resposta inflamatória de obesos.

Circulating IL-18 and the risk of type 2 diabetes in women

AIMS/HYPOTHESIS

The pathophysiology of type 2 diabetes involves pro-inflammatory pathways. We tested the hypothesis that IL-18 predicts future diabetes cases.

METHODS

We used a nested case-control design based in the Nurses' Health Study. Baseline blood samples were collected between 1989 and 1990. Questionnaires to assess body weight, lifestyle (physical activity, diet, smoking) and diabetes diagnosis were sent out and assessed biennially (follow-up until 2002). Cases (n = 1,012) were defined as women developing type 2 diabetes at least 1 year after blood sampling. Control women (n = 1,081) were matched to cases by age, date of blood draw, fasting status and race. We calculated the RR (95% CI) of type 2 diabetes in quintiles of IL-18 using conditional logistic regression with the first quintile as referent; adjustments included matching factors, diabetes risk factors, BMI, adipokine levels (adiponectin, resistin) and inflammatory proteins (C-reactive protein, tumour necrosis factor receptor 2 (TNFalpha-R2) and IL-6).

RESULTS

Higher IL-18 levels were associated with increased risk of developing diabetes, even after adjustment for matching factors and multiple diabetes risk factors: being in the highest quintile of IL-18 was associated with a RR of 1.75 (1.41-2.18) for diabetes relative to the first quintile (p < 0.0001 for trend). Significant trends in association were still observed after adjustment for BMI (RR 1.44 [1.15-1.80], p < 0.0001 for trend) and adiponectin levels (RR 1.28 [1.02-1.60], p = 0.006 for trend). Further adjustment for inflammatory markers in a sub-sample did not significantly change the results.

CONCLUSIONS/INTERPRETATION

Elevated IL-18 levels are associated with higher risk of diabetes. This association is independent of usual risk factors, including BMI and adipokine levels.

Is the use of resveratrol in the treatment and prevention of obesity premature?

Obesity is a multi-faceted disease, predisposing sufferers to numerous co-morbidities such as epithelial dysfunction and insulin resistance which ultimately result in CVD. Visceral adipose tissue in particular is associated with inflammation due to the release of pro-inflammatory cytokines by adipocytes. Inflammation seems to be rather central in causing damage to endothelial cells as well as exerting negative effects on glucose metabolism, ultimately leading to insulin resistance. Resveratrol is a naturally occurring phenolic substance which has been found to display anti-inflammatory, vasoprotective and insulin-sensitising effects, among others. The popularity of resveratrol use is escalating in the treatment of various ailments including obesity in adults. The use of the substance in childhood obesity is, however, a worrying factor, as no studies have as yet been performed on adolescent animals and there is evidence of kidney toxicity of resveratrol and its metabolites at intake levels below those currently approved as safe. Another cause for concern is the uncertainty surrounding long-term, low-dose administration of the substance in humans. The supplement should thus not be recommended for use in the prevention and treatment of obesity until conclusive research is established on the safety of long-term usage of resveratrol in both children and adults.

Cellular hypoxia and adipose tissue dysfunction in obesity

Expansion of adipose tissue mass, the distinctive feature of obesity, is associated with low-grade inflammation. White adipose tissue secretes a diverse range of adipokines, a number of which are inflammatory mediators (such as TNFalpha, IL-1beta, IL-6, monocyte chemoattractant protein 1). The production of inflammatory adipokines is increased with obesity and these adipokines have been implicated in the development of insulin resistance and the metabolic syndrome. However, the basis for the link between increased adiposity and inflammation is unclear. It has been proposed previously that hypoxia may occur in areas within adipose tissue in obesity as a result of adipocyte hypertrophy compromising effective O2 supply from the vasculature, thereby instigating an inflammatory response through recruitment of the transcription factor, hypoxic inducible factor-1. Studies in animal models (mutant mice, diet-induced obesity) and cell-culture systems (mouse and human adipocytes) have provided strong support for a role for hypoxia in modulating the production of several inflammation-related adipokines, including increased IL-6, leptin and macrophage migratory inhibition factor production together with reduced adiponectin synthesis. Increased glucose transport into adipocytes is also observed with low O2 tension, largely as a result of the up-regulation of GLUT-1 expression, indicating changes in cellular glucose metabolism. Hypoxia also induces inflammatory responses in macrophages and inhibits the differentiation of preadipocytes (while inducing the expression of leptin). Collectively, there is strong evidence to suggest that cellular hypoxia may be a key factor in adipocyte physiology and the underlying cause of adipose tissue dysfunction contributing to the adverse metabolic milieu associated with obesity.

Maternal obesity, inflammation, and fetal skeletal muscle development

Maternal obesity coupled with Western-style high-energy diets represents a special problem that can result in poor fetal development, leading to harmful, persistent effects on offspring, including predisposition to obesity and type 2 diabetes. Mechanisms linking maternal obesity to the increased incidence of obesity and other metabolic diseases in offspring remain poorly defined. Because skeletal muscle is the principal site for glucose and fatty acid utilization and composes 40%-50% of total body mass, changes in the properties of offspring skeletal muscle and its mass resulting from maternal obesity may be responsible for the increase in type 2 diabetes and obesity. Fetal stage is crucial for skeletal muscle development because there is no net increase in the muscle fiber number after birth. Fetal skeletal muscle development involves myogenesis, adipogenesis, and fibrogenesis, which are all derived from mesenchymal stem cells (MSCs). Shifting commitment of MSCs from myogenesis to adipogenesis and fibrogenesis will result in increased intramuscular fat and connective tissue, as well as reduced numbers of muscle fiber and/or diameter, all of which have lasting negative effects on offspring muscle function and properties. Maternal obesity leads to low-grade inflammation, which changes the commitment of MSCs in fetal muscle through several possible mechanisms: 1) inflammation downregulates wingless and int (WNT) signaling, which attenuates myogenesis; 2) inflammation inhibits AMP-activated protein kinase, which promotes adipogenesis; and 3) inflammation may induce epigenetic modification through polycomb group proteins. More studies are needed to further explore the underlying mechanisms associated with maternal obesity, inflammation, and the commitment of MSCs.

IL-33, a recently identified interleukin-1 gene family member, is expressed in human adipocytes

Inflammation occurs in adipose tissue in obesity. We have examined whether IL-33, a recently identified IL-1 gene family member, and its associated receptors are expressed in human adipocytes. IL-33, IL-1RL1 and IL-1RAP gene expression was observed in human visceral white fat, in preadipocytes and in adipocytes (SGBS cells). Treatment with TNFalpha for 24h induced a 6-fold increase in IL-33 mRNA level in preadipocytes and adipocytes. Time-course studies with adipocytes showed that the increase in IL-33 mRNA with TNFalpha was maximal (>55-fold) at 12h. This response was markedly different to IL-1beta (peak mRNA increase at 2h; 5.4-fold) and 1L-18 (peak mRNA increase at 6h; >1500-fold). Exposure of adipocytes to hypoxia (1% O(2), 24h) did not alter IL-33 mRNA level; in preadipocytes, however, there was a 3-fold increase. Human adipocytes and preadipocytes express IL-33, but the various IL-1 family members exhibit major differences in responsiveness to TNFalpha.

Adipose tissue-mediated inflammation: the missing link between obesity and cardiovascular disease?

Until relatively recently, the role of adipose tissue in the development of obesity and its consequences was considered to be a passive one. Mounting evidence highlights the role of adipose tissue in the development of a systemic inflammatory state that contributes to obesity-associated vasculopathy and cardiovascular risk. It is now clear that, in addition to storing calories as triglycerides, adipocytes secrete a large variety of cytokines, chemokines and hormone-like factors, such as leptin, resistin, and acute-phase proteins. In addition, insulin resistance, both in nondiabetic and diabetic subjects, is frequently associated with obesity, particularly with an excess of intraabdominal fat. This production of pro-atherogenic substances is of particular interest since an increase in the plasma levels of these mediators may provide a novel mechanistic link between obesity and its vascular complications.

Internet-delivered lifestyle physical activity intervention: limited inflammation and antioxidant capacity efficacy in overweight adults

Overweight and physical inactivity are associated with elevated reactive oxygen species and chronic low-grade inflammation. Exercise training studies have measured changes in systemic inflammatory and oxidative/antioxidative biomarkers but predominantly at moderate-high intensities. Few low-intensity, lifestyle-based physical activity (PA) studies have been conducted. The purpose of this study was to determine whether improvements in lifestyle-oriented PA resulting from a 16-wk Internet-delivered PA program [Active Living Every Day-Internet (ALED-I)] elicit cardioprotective improvements in measures of inflammation, oxidation, or antioxidant enzyme capacity. Forty-one men and women (age 23-62 yr) were randomized to either the ALED-I intervention [n = 19; age = 40.4 +/- 1.9 yr; body mass index (BMI) = 31.4 +/- 1.1 kg/m(2)] or a delayed intent-to-treat control condition (n = 22; age = 46.6 +/- 1.3 yr; BMI = 31.0 +/- 0.7 kg/m(2)). TNF-alpha, C-reactive protein, myeloperoxidase, superoxide dismutase, catalase, total antioxidative capacity, change in PA, and other cardiometabolic disease risk factors were measured at baseline and postintervention. The ALED-I group increased PA and decreased central adiposity without changes in the control group. There was no change in the control group for any inflammation, oxidation, or antioxidant biomarkers. TNF-alpha decreased (P = 0.01) in the intervention group but was not statistically different from the control group. In conclusion, modest improvements in daily low-intensity ambulatory PA as a result of an Internet-delivered lifestyle PA intervention may be cardioprotective in sedentary and overweight adults through reductions in central adiposity and inflammation. However, the absence of favorable changes in other inflammation, oxidation, and antioxidant biomarkers highlights the need for further attention to the dose response of lifestyle-structured PA promotion strategies for health maintenance/improvement.

Intermittent high glucose stimulate MCP-l, IL-18, and PAI-1, but inhibit adiponectin expression and secretion in adipocytes dependent of ROS

Elevated circulating concentrations of interleukin-18 (IL-18), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1) and decrease of adiponectin are associated with obesity-related diseases. The mechanism that mediates the aberrant production of the adipokines remains poorly understood. The aim of this study was to investigate the effect of intermittent high glucose on the expression of IL-18, MCP-1, and PAI-1 and adiponectin in 3T3-L1 adipocytes. 3T3-L1 adipocytes were incubated for 24 h in media containing different glucose concentrations: 5 mmol/l, 20 mmol/l and a daily alternating 5 or 20 mmol/l glucose, with or without the addition of1.0 mmol/l N-acetylcysteine (NAC). The expression and secretion of IL-18, MCP-1, PAI-1, and adiponectin were determined by real-time RT-PCR and ELISA, respectively.The production of reactive oxygen species (ROS) and 8-hydroxydeoxyguanosine(8-OHdG) were measured. Stable high glucose significantly increased expression and secretion of IL-18, MCP-1, and PAI-1, and reduced adiponectin expression and secretion compared to normal glucose conditions.These effects were significantly greater under intermittent high glucose conditions compared to stable high glucose. The level of ROS and 8-OHdG were significantly elevated under both intermittent and stable high glucose conditions, the effect being greater under intermittent high glucose. The intermittent glucose was more effective in triggering the generation of ROS than stable high glucose. The adding of the NAC, aspecific pharmacological inhibitor of ROS, normalized the expression of these adipokines and the levels of ROS and 8-OHdG under both stable and intermittent glucose conditions.Intermittent high glucose induces a greater aberrant production of key adipokines than stable high glucose, and this effect seems to be related to over-production of ROS.

Parameters of inflammation in morbid obesity: lack of effect of moderate weight loss

BACKGROUND

Obesity has been associated with a chronic activation of the acute-phase response. The aims of our study were to investigate whether levels of inflammatory cytokines are higher in obese patients, to evaluate their relationship with metabolic syndrome, and to analyze the effect of moderate weight loss upon their levels.

METHODS

Sixty-seven severe or morbid obese patients were compared with 67 controls. Patients were submitted to a 4-week very low calorie diet followed by a low calorie diet for 2 months. Exclusion criteria were organic disease, ischemic heart disease or stroke, diabetes mellitus, hyperlipidemia, and hypertension. An evaluation was performed before and after the diet, in which fibrinogen, blood count, high-sensitive C-reactive protein (CRP), interleukin 6 (IL-6), and tumoral necrosis factor alpha (TNF-alpha) were measured. The Student t test was employed to compare differences between the groups and Pearson correlation coefficients were calculated.

RESULTS

Obese patients showed higher levels of CRP (P < 0.001), IL-6 (P < 0.001), TNF-alpha (P < 0.001), leukocyte (P = 0.001), and neutrophil count (P < 0.001) than controls. In obese patients, inflammatory parameters were significantly correlated with anthropometric parameters and did not differ between obese subjects with or without metabolic syndrome. Moderate weight loss (excess weight loss 19.6%) was achieved through dieting, but no change was observed in any inflammatory parameter.

CONCLUSIONS

Obesity is associated to a chronic inflammatory state that seems to be due to an increased secretion of cytokines, and this state is not related to the presence of metabolic syndrome. Moderate weight loss does not ameliorate this inflammatory state in the short term.

Insulin stimulates interleukin-6 expression and release in LS14 human adipocytes through multiple signaling pathways

IL-6 is an important cytokine that regulates both immune and metabolic functions. Within adipose tissue, preadipocytes produce significant amounts of IL-6, but little is known about the factors or mechanisms that regulate IL-6 production in these cells. Using LS14, a newly developed human adipocyte cell line, our objective was to determine the mechanisms by which insulin stimulates IL-6 production and release in preadipocytes. Insulin increased IL-6 gene expression and secretion in a time- and dose-dependent manner. Insulin decreased cyclic AMP (cAMP) but increased cyclic GMP (cGMP) levels, and IL-6 expression/release was stimulated by a cGMP analog. The stimulatory effect of insulin and cGMP was abrogated by a specific inhibitor of protein kinase G (cyclic GMP-dependent protein kinase). Both insulin and cGMP rapidly induced phosphorylation of cAMP response element binding protein. Insulin also activated the MAPK signaling pathway, and its blockade prevented the insulin-stimulated increases in IL-6 cell content and release, but not IL-6 gene expression. Although inhibition of the proteosome increased IL-6 cell content and release, proteosome activity was unaffected by insulin. These data suggest that the stimulatory effects of insulin on IL-6 release involve several interrelated components: transcription, intracellular releasable pool, and secretion, which are differentially regulated and, thus, determine the size of the releasable pool of IL-6. Insulin-induced IL-6 gene expression is mediated by cGMP/cyclic GMP-dependent protein kinase/cAMP response element binding protein, whereas MAPK is involved in the insulin-stimulated IL-6 synthesis/release.

Hypoxia and the endocrine and signalling role of white adipose tissue

White adipose tissue is a major endocrine and signalling organ. It secretes multiple protein hormones and factors, termed adipokines (such as adiponectin, leptin, IL-6, MCP-1, TNFalpha) which engage in extensive cross-talk within adipose tissue and with other tissues. Many adipokines are linked to inflammation and immunity and these include cytokines, chemokines and acute phase proteins. In obesity, adipose tissue exhibits a major inflammatory response with increased production of inflammation-related adipokines. It has been proposed that hypoxia may underlie the inflammatory response in adipose tissue and evidence that the tissue is hypoxic in obesity has been obtained in animal models. Cell culture studies have demonstrated that the expression and secretion of key adipokines, including leptin, IL-6 and VEGF, are stimulated by hypoxia, while adiponectin (with an anti-inflammatory action) production falls. Hypoxia also stimulates glucose transport by adipocytes and may have a pervasive effect on cell function within adipose tissue.

Increased tumor necrosis factor-alpha concentrations with interleukin-4 concentrations in exacerbations of schizophrenia

Several studies have indicated that cytokines may be involved in the pathophysiology of schizophrenia. Previous studies, however, have yielded contradictory results; in this study we assess the plasma levels of both T-helper-1 (Th1) and T-helper-2 (Th2) cytokines in patients with acute exacerbations of schizophrenia. Plasma concentrations of interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha) and soluble receptor of interleukin-6 (sIL-6R) were measured with high sensitivity, enzyme-linked immunosorbent assays (ELISA) in patients with acute exacerbations of schizophrenia as compared with healthy controls. Patients with an acute exacerbation of schizophrenia had significantly increased production of TNF-alpha and significantly reduced production of IL-4 as compared with healthy subjects. No significant difference was observed in IL-6, sIL-6R, IL-8 and IL-10. Acute exacerbations of schizophrenia are associated with increased TNF-alpha concentrations (Th1) with concomitantly reduced concentrations of IL-4 (Th2) and a resulting increased TNF-alpha/IL-4 ratio.

The genetic variation of the tenomodulin gene (TNMD) is associated with serum levels of systemic immune mediators--the Finnish Diabetes Prevention Study

PURPOSE

We have reported that the genetic variation of the tenomodulin gene (TNMD) is associated with the risk of type 2 diabetes (T2DM), central obesity, and impaired glucose metabolism and the TNMD mRNA levels correlate with serum and mRNA levels of inflammatory markers. Our objective was to investigate the genetic associations of the single nucleotide polymorphisms of the TNMD gene with the serum levels of systemic immune mediators.

METHODS

Seven single nucleotide polymorphisms were genotyped from 507 participants of the Finnish Diabetes Prevention Study. All subjects had body mass index >25 and impaired glucose tolerance.

RESULTS

The sequence variation of tenomodulin was consistently associated with the serum concentrations of acute phase reactants, macrophage migration inhibitory factor, and CCR5 receptor ligands. The genotype effects were modified by status of glucose metabolism and central obesity. Markers associated with increased risk of T2DM in our previous study were associated with serum concentrations of acute phase proteins in men so that the subjects possessing the genotypes associated with increased risk of T2DM had higher serum concentrations of acute phase reactants.

CONCLUSIONS

These results indicate that the genetic variation of TNMD is associated with low-grade inflammation. The putative link between TNMD and T2DM could be mediated through the effects on systemic immune mediators.

The role of adiposity as a determinant of an inflammatory milieu

With the growing prevalence of obesity, scientific interest in the biology of adipose tissue has been extended to the secretory products of adipocytes, since they have been shown increasingly to affect several aspects of the pathogenesis of obesity-related diseases. Until relatively recently, the role of adipose tissue itself in the development of obesity and its consequences was considered to be a passive one. It is now clear that, in addition to storing energy in the form of triglycerides, adipocytes also secrete a large variety of proteins, including cytokines, chemokines and hormone-like factors. This production of proatherogenic chemokines by adipose tissue is of particular interest, since their local secretion, for example by perivascular adipose depots, may provide a novel mechanistic link between obesity and associated vascular complications.

Inflammation, insulin resistance, and diabetes--Mendelian randomization using CRP haplotypes points upstream

BACKGROUND

Raised C-reactive protein (CRP) is a risk factor for type 2 diabetes. According to the Mendelian randomization method, the association is likely to be causal if genetic variants that affect CRP level are associated with markers of diabetes development and diabetes. Our objective was to examine the nature of the association between CRP phenotype and diabetes development using CRP haplotypes as instrumental variables.

METHODS AND FINDINGS

We genotyped three tagging SNPs (CRP + 2302G > A; CRP + 1444T > C; CRP + 4899T > G) in the CRP gene and measured serum CRP in 5,274 men and women at mean ages 49 and 61 y (Whitehall II Study). Homeostasis model assessment-insulin resistance (HOMA-IR) and hemoglobin A1c (HbA1c) were measured at age 61 y. Diabetes was ascertained by glucose tolerance test and self-report. Common major haplotypes were strongly associated with serum CRP levels, but unrelated to obesity, blood pressure, and socioeconomic position, which may confound the association between CRP and diabetes risk. Serum CRP was associated with these potential confounding factors. After adjustment for age and sex, baseline serum CRP was associated with incident diabetes (hazard ratio = 1.39 [95% confidence interval 1.29-1.51], HOMA-IR, and HbA1c, but the associations were considerably attenuated on adjustment for potential confounding factors. In contrast, CRP haplotypes were not associated with HOMA-IR or HbA1c (p = 0.52-0.92). The associations of CRP with HOMA-IR and HbA1c were all null when examined using instrumental variables analysis, with genetic variants as the instrument for serum CRP. Instrumental variables estimates differed from the directly observed associations (p = 0.007-0.11). Pooled analysis of CRP haplotypes and diabetes in Whitehall II and Northwick Park Heart Study II produced null findings (p = 0.25-0.88). Analyses based on the Wellcome Trust Case Control Consortium (1,923 diabetes cases, 2,932 controls) using three SNPs in tight linkage disequilibrium with our tagging SNPs also demonstrated null associations.

CONCLUSIONS

Observed associations between serum CRP and insulin resistance, glycemia, and diabetes are likely to be noncausal. Inflammation may play a causal role via upstream effectors rather than the downstream marker CRP.

Hypoxia in adipose tissue: a basis for the dysregulation of tissue function in obesity?

White adipose tissue is a key endocrine and secretory organ, releasing multiple adipokines, many of which are linked to inflammation and immunity. During the expansion of adipose tissue mass in obesity there is a major inflammatory response in the tissue with increased expression and release of inflammation-related adipokines, including IL-6, leptin, monocyte chemoattractant protein-1 and TNF-α, together with decreased adiponectin production. We proposed in 2004 (Trayhurn & Wood, Br J Nutr92, 347–355) that inflammation in adipose tissue in obesity is a response to hypoxia in enlarged adipocytes distant from the vasculature. Hypoxia has now been directly demonstrated in adipose tissue of several obese mouse models (ob/ob, KKAy, diet-induced) and molecular studies indicate that the level of the hypoxia-inducible transcription factor, hypoxia-inducible factor-1α, is increased, as is expression of the hypoxia-sensitive marker gene, GLUT1. Cell- culture studies on murine and human adipocytes show that hypoxia (induced by low O2 or chemically) leads to stimulation of the expression and secretion of a number of inflammation-related adipokines, including angiopoietin-like protein 4, IL-6, leptin, macrophage migration inhibitory factor and vascular endothelial growth factor. Hypoxia also stimulates the inflammatory response of macrophages and inhibits adipocyte differentiation from preadipocytes. GLUT1 gene expression, protein level and glucose transport by human adipocytes are markedly increased by hypoxia, indicating that low O2 tension stimulates glucose utilisation. It is suggested that hypoxia has a pervasive effect on adipocyte metabolism and on overall adipose tissue function, underpinning the inflammatory response in the tissue in obesity and the subsequent development of obesity-associated diseases, particularly type 2 diabetes and the metabolic syndrome.

Overweight and obesity in postpartum Hispanic women

Overweight and obesity vary in prevalence among particular groups, and are especially problematic for childbearing Hispanic women. The complex interaction between physical changes associated with pregnancy, role changes accompanying birth, and family and cultural values related to childbearing are superimposed upon the underlying mechanisms that create or perpetuate obesity. In this article we review biological and behavioral research on obesity in postpartum Hispanic women to identify critical components for intervention studies focused on weight management. Recommendations are offered for health care providers and researchers.

Beta-cell failure in type 2 diabetes mellitus

Diabetes mellitus has been defined as a "group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both" and encompasses a wide range of heterogeneous conditions. Common type 2 diabetes mellitus (T2DM) results from a combination of genetic and acquired factors. However, lifestyle factors, particularly overeating and physical inactivity, are the major clinical determinants of T2DM. Insulin resistance is a common feature of T2DM, but it is unlikely to cause T2DM unless progressive loss of beta-cell function develops. Significant reduction in beta-cell function is already present at the time of T2DM diagnosis, and it continuously declines irrespective of treatment. As such, the progressive loss of beta-cell function dictates the rate of worsened glycemic control. Development of progressive deterioration accelerates via gluco- and lipotoxicity, loss of beta-cell function, and shrinkage of beta-cell mass. Understanding the causes for beta-cell failure is therefore of capital importance to develop new and more effective therapeutic strategies.

The importance of treating cardiometabolic risk factors in patients with type 2 diabetes

Cardiometabolic risk factors are the combined vascular and metabolic components of risk that may lead to a cardiovascular event. There are numerous such factors. Underlying the concept of cardiometabolic risk is an association with excess visceral fat, leading to the dysregulation of the adipokines, the signalling proteins derived from adipose tissue. Changes in the levels of the adipokines - tumour necrosis factor-alpha, cholesteryl ester transfer protein and adiponectin, for example - can lead to alterations in insulin sensitivity and high-density lipoprotein cholesterol metabolism. At present, specific cardiometabolic risk factors are commonly managed on an individual basis. We are now moving from the era of single risk factor intervention, however, to multiple risk factor intervention in people at high cardiovascular risk, with the additional possibility of using new drug classes to target the underlying cardiometabolic problems more effectively.

Endothelial dysfunction and microvascular complications in type 1 diabetes mellitus

We examined whether alterations in vascular endothelial function and early structural changes in atherosclerosis are associated with microvascular complications in patients with type 1 diabetes mellitus (DM). Flow-mediated dilation (FMD) of the brachial artery and carotid intima-media thickness (IMT) measurement were performed in 70 young adults (aged 19 to 35 yr), 48 with type 1 DM, and 22 normal controls. Patients with diabetes had a lower peak FMD response (7.8+/-3.9 vs. 11.1+/-1.9%, p<0.001) and increased IMT (0.51+/-0.10 vs. 0.42+/-0.07 mm, p<0.001) compared with controls. Twenty (41.7%) of the patients had microvascular complications including neuropathy, nephropathy, or retinopathy. In these complicated diabetic patients, we found a lower FMD response (6.1+/-2.5 vs. 9.9+/-3.5%, p=0.001) compared with diabetics without microvascular complications. The presence of microvascular complications was also associated with older age and longer duration of the disease. However, no differences were observed in IMT, body size, blood pressure, HbA1c, C-reactive protein, low-density lipoprotein or high-density lipoprotein cholesterol levels between complicated and non-complicated patients. Endothelial dysfunction and early structural atherosclerotic changes are common manifestations in type 1 DM, and endothelial dysfunction is thought to be an early event in the atherosclerotic process and important in the pathogenesis of microvascular complications.

PCR arrays identify metallothionein-3 as a highly hypoxia-inducible gene in human adipocytes

Hypoxia-signalling pathway PCR arrays were used to examine the integrated response of human adipocytes to low O₂ tension. Incubation of adipocytes in 1% O₂ for 24 h resulted in no change in the expression of 63 of the 84 genes on the arrays, a reduction in expression of 9 genes (including uncoupling protein 2) and increased expression of 12 genes. Substantial increases (>10-fold) in leptin, angiopoietin-like protein 4, VEGF and GLUT-1 mRNA levels were observed. The expression of one gene, metallothionein-3 (MT-3), was dramatically (>600-fold) and rapidly (by 60 min) increased by hypoxia. MT-3 gene expression was also substantially induced by hypoxia mimetics (CoCl₂, desferrioxamine, dimethyloxalylglycine), indicating transcriptional regulation through HIF-1. Hypoxia additionally induced MT-3 expression in preadipocytes, and MT-3 mRNA was detected in human (obese) subcutaneous and omental adipose tissue. MT-3 is a highly hypoxia-inducible gene in human adipocytes; the protein may protect adipocytes from hypoxic damage.