Improvement of Insulin Resistance and Early Atherosclerosis in Patients after Gastric Banding

Hexokinase-linked glycolytic overload and unscheduled glycolysis in hyperglycemia-induced pathogenesis of insulin resistance, beta-cell glucotoxicity, and diabetic vascular complications

Hyperglycemia is a risk factor for the development of insulin resistance, beta-cell glucotoxicity, and vascular complications of diabetes. We propose the hypothesis, hexokinase-linked glycolytic overload and unscheduled glycolysis, in explanation. Hexokinases (HKs) catalyze the first step of glucose metabolism. Increased flux of glucose metabolism through glycolysis gated by HKs, when occurring without concomitant increased activity of glycolytic enzymes-unscheduled glycolysis-produces increased levels of glycolytic intermediates with overspill into effector pathways of cell dysfunction and pathogenesis. HK1 is saturated with glucose in euglycemia and, where it is the major HK, provides for basal glycolytic flux without glycolytic overload. HK2 has similar saturation characteristics, except that, in persistent hyperglycemia, it is stabilized to proteolysis by high intracellular glucose concentration, increasing HK activity and initiating glycolytic overload and unscheduled glycolysis. This drives the development of vascular complications of diabetes. Similar HK2-linked unscheduled glycolysis in skeletal muscle and adipose tissue in impaired fasting glucose drives the development of peripheral insulin resistance. Glucokinase (GCK or HK4)-linked glycolytic overload and unscheduled glycolysis occurs in persistent hyperglycemia in hepatocytes and beta-cells, contributing to hepatic insulin resistance and beta-cell glucotoxicity, leading to the development of type 2 diabetes. Downstream effector pathways of HK-linked unscheduled glycolysis are mitochondrial dysfunction and increased reactive oxygen species (ROS) formation; activation of hexosamine, protein kinase c, and dicarbonyl stress pathways; and increased Mlx/Mondo A signaling. Mitochondrial dysfunction and increased ROS was proposed as the initiator of metabolic dysfunction in hyperglycemia, but it is rather one of the multiple downstream effector pathways. Correction of HK2 dysregulation is proposed as a novel therapeutic target. Pharmacotherapy addressing it corrected insulin resistance in overweight and obese subjects in clinical trial. Overall, the damaging effects of hyperglycemia are a consequence of HK-gated increased flux of glucose metabolism without increased glycolytic enzyme activities to accommodate it.

Emerging Glycation-Based Therapeutics-Glyoxalase 1 Inducers and Glyoxalase 1 Inhibitors

The abnormal accumulation of methylglyoxal (MG) leading to increased glycation of protein and DNA has emerged as an important metabolic stress, dicarbonyl stress, linked to aging, and disease. Increased MG glycation produces inactivation and misfolding of proteins, cell dysfunction, activation of the unfolded protein response, and related low-grade inflammation. Glycation of DNA and the spliceosome contribute to an antiproliferative and apoptotic response of high, cytotoxic levels of MG. Glyoxalase 1 (Glo1) of the glyoxalase system has a major role in the metabolism of MG. Small molecule inducers of Glo1, Glo1 inducers, have been developed to alleviate dicarbonyl stress as a prospective treatment for the prevention and early-stage reversal of type 2 diabetes and prevention of vascular complications of diabetes. The first clinical trial with the Glo1 inducer, trans-resveratrol and hesperetin combination (tRES-HESP)-a randomized, double-blind, placebo-controlled crossover phase 2A study for correction of insulin resistance in overweight and obese subjects, was completed successfully. tRES-HESP corrected insulin resistance, improved dysglycemia, and low-grade inflammation. Cell permeable Glo1 inhibitor prodrugs have been developed to induce severe dicarbonyl stress as a prospective treatment for cancer-particularly for high Glo1 expressing-related multidrug-resistant tumors. The prototype Glo1 inhibitor is prodrug S-p-bromobenzylglutathione cyclopentyl diester (BBGD). It has antitumor activity in vitro and in tumor-bearing mice in vivo. In the National Cancer Institute human tumor cell line screen, BBGD was most active against the glioblastoma SNB-19 cell line. Recently, potent antitumor activity was found in glioblastoma multiforme tumor-bearing mice. High Glo1 expression is a negative survival factor in chemotherapy of breast cancer where adjunct therapy with a Glo1 inhibitor may improve treatment outcomes. BBGD has not yet been evaluated clinically. Glycation by MG now appears to be a pathogenic process that may be pharmacologically manipulated for therapeutic outcomes of potentially important clinical impact.

Dicarbonyl stress, protein glycation and the unfolded protein response

The reactive dicarbonyl metabolite, methylglyoxal (MG), is increased in obesity and diabetes and is implicated in the development of insulin resistance, type 2 diabetes mellitus and vascular complications of diabetes. Dicarbonyl stress is the metabolic state of abnormal high MG concentration. MG is an arginine-directed glycating agent and precursor of the major advanced glycation endproduct, arginine-derived hydroimidazolone MG-H1. MG-H1 is often formed on protein surfaces and an uncharged hydrophobic residue, inducing protein structural distortion and misfolding. Recent studies indicate that dicarbonyl stress in human endothelial cells and fibroblasts in vitro induced a proteomic response consistent with activation of the unfolded protein response (UPR). The response included: increased abundance of heat shock proteins and ubiquitin ligases catalysing the removal of proteins with unshielded surface hydrophobic patches and formation of polyubiquitinated chains to encapsulate misfolded proteins; and increased low grade inflammation. Activation of the UPR is implicated in insulin resistance. An effective strategy to counter increased MG is inducing increased expression of glyoxalase-1 (Glo1). An optimized inducer of Glo1 expression, trans-resveratrol and hesperetin combination, normalized increased MG concentration, corrected insulin resistance and decreased low grade inflammation in overweight and obese subjects. We propose that dicarbonyl stress, through increased formation of MG-glycated proteins, may be an important physiological stimulus of the UPR and Glo1 inducers may provide a route to effective suppression and therapy. With further investigation and validation, this may provide key new insight into physiological activators of the UPR and association with dicarbonyl stress.

Effect of Surgically Induced Weight Loss on Biomarkers of Endothelial Dysfunction: a Systematic Review and Meta-Analysis

BACKGROUND

This meta-analysis was performed to assess the effects of bariatric surgery (BS) on the selected markers of endothelial dysfunction, including monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin.

METHODS

PubMed, Scopus, and Google scholar were systematically searched to identify related studies published from inception to November 2019 to find eligible studies.

RESULTS

A total of 29 different studies were included. BS reduced the concentrations of MCP-1 (weighted mean difference (WMD) = - 58.91; 95%CI (confidence interval), - 77.10 to - 40.72; P = ˂ 0.001), ICAM-1 (WMD = - 36.58; 95%CI, - 49.65 to - 23.52; P = ˂ 0.001), and E-selectin (WMD = - 11.22; 95%CI, - 14.43 to - 8.01; P < 0.001), but had no significant effect on VCAM-1.

CONCLUSION

Bariatric surgery reduces circulating concentration of MCP-1, ICAM-1, and E-selectin, but not VCAM-1.

Glyoxalase 1 Modulation in Obesity and Diabetes

Significance: Obesity and type 2 diabetes mellitus are increasing globally. There is also increasing associated complications, such as non-alcoholic fatty liver disease (NAFLD) and vascular complications of diabetes. There is currently no licensed treatment for NAFLD and no recent treatments for diabetic complications. New approaches are required, particularly those addressing mechanism-based risk factors for health decline and disease progression. Recent Advances: Dicarbonyl stress is the abnormal accumulation of reactive dicarbonyl metabolites such as methylglyoxal (MG) leading to cell and tissue dysfunction. It is a potential driver of obesity, diabetes, and related complications that are unaddressed by current treatments. Increased formation of MG is linked to increased glyceroneogenesis and hyperglycemia in obesity and diabetes and also down-regulation of glyoxalase 1 (Glo1)-which provides the main enzymatic detoxification of MG. Glo1 functional genomics studies suggest that increasing Glo1 expression and activity alleviates dicarbonyl stress; slows development of obesity, related insulin resistance; and prevents development of diabetic nephropathy and other microvascular complications of diabetes. A new therapeutic approach constitutes small-molecule inducers of Glo1 expression-Glo1 inducers-exploiting a regulatory antioxidant response element in the GLO1 gene. A prototype Glo1 inducer, trans-resveratrol (tRES)-hesperetin (HESP) combination, in corrected insulin resistance, improved glycemic control and vascular inflammation in healthy overweight and obese subjects in clinical trial. Critical Issues: tRES and HESP synergize pharmacologically, and HESP likely overcomes the low bioavailability of tRES by inhibition of intestinal glucuronosyltransferases. Future Directions: Glo1 inducers may now be evaluated in Phase 2 clinical trials for treatment of NAFLD and vascular complications of diabetes.

Methylglyoxal-induced dicarbonyl stress in aging and disease: first steps towards glyoxalase 1-based treatments

Dicarbonyl stress is the abnormal accumulation of dicarbonyl metabolites leading to increased protein and DNA modification contributing to cell and tissue dysfunction in aging and disease. It is produced by increased formation and/or decreased metabolism of dicarbonyl metabolites. MG (methylglyoxal) is a dicarbonyl metabolite of relatively high flux of formation and precursor of the most quantitatively and functionally important spontaneous modifications of protein and DNA clinically. Major MG-derived adducts are arginine-derived hydroimidazolones of protein and deoxyguanosine-derived imidazopurinones of DNA. These are formed non-oxidatively. The glyoxalase system provides an efficient and essential basal and stress-response-inducible enzymatic defence against dicarbonyl stress by the reduced glutathione-dependent metabolism of methylglyoxal by glyoxalase 1. The GLO1 gene encoding glyoxalase 1 has low prevalence duplication and high prevalence amplification in some tumours. Dicarbonyl stress contributes to aging, disease and activity of cytotoxic chemotherapeutic agents. It is found at a low, moderate and severe level in obesity, diabetes and renal failure respectively, where it contributes to the development of metabolic and vascular complications. Increased glyoxalase 1 expression confers multidrug resistance to cancer chemotherapy and has relatively high prevalence in liver, lung and breast cancers. Studies of dicarbonyl stress are providing improved understanding of aging and disease and the basis for rational design of novel pharmaceuticals: glyoxalase 1 inducers for obesity, diabetes and cardiovascular disease and glyoxalase 1 inhibitors for multidrug-resistant tumours. The first clinical trial of a glyoxalase 1 inducer in overweight and obese subjects showed improved glycaemic control, insulin resistance and vascular function.

Improved Glycemic Control and Vascular Function in Overweight and Obese Subjects by Glyoxalase 1 Inducer Formulation

Risk of insulin resistance, impaired glycemic control, and cardiovascular disease is excessive in overweight and obese populations. We hypothesized that increasing expression of glyoxalase 1 (Glo1)-an enzyme that catalyzes the metabolism of reactive metabolite and glycating agent methylglyoxal-may improve metabolic and vascular health. Dietary bioactive compounds were screened for Glo1 inducer activity in a functional reporter assay, hits were confirmed in cell culture, and an optimized Glo1 inducer formulation was evaluated in a randomized, placebo-controlled crossover clinical trial in 29 overweight and obese subjects. We found trans-resveratrol (tRES) and hesperetin (HESP), at concentrations achieved clinically, synergized to increase Glo1 expression. In highly overweight subjects (BMI >27.5 kg/m(2)), tRES-HESP coformulation increased expression and activity of Glo1 (27%, P < 0.05) and decreased plasma methylglyoxal (-37%, P < 0.05) and total body methylglyoxal-protein glycation (-14%, P < 0.01). It decreased fasting and postprandial plasma glucose (-5%, P < 0.01, and -8%, P < 0.03, respectively), increased oral glucose insulin sensitivity index (42 mL ⋅ min(-1) ⋅ m(-2), P < 0.02), and improved arterial dilatation Δbrachial artery flow-mediated dilatation/Δdilation response to glyceryl nitrate (95% CI 0.13-2.11). In all subjects, it decreased vascular inflammation marker soluble intercellular adhesion molecule-1 (-10%, P < 0.01). In previous clinical evaluations, tRES and HESP individually were ineffective. tRES-HESP coformulation could be a suitable treatment for improved metabolic and vascular health in overweight and obese populations.

The Role of Physical Activity Participation in Weight Loss Outcomes Following Weight Loss Surgery

Weight loss surgery (WLS) is an effective intervention for the reduction of body mass and the resolution of obesity-related comorbidities. Excess weight loss following WLS has been reported in the range of 40% to 78% depending on the surgery type and the follow-up time period. Initial weight loss outcomes and weight loss maintenance have been shown to depend on several factors, including the type of surgical procedure, preexisting comorbidities, and compliance with postoperative medical, nutritional, and behavioral recommendations. One factor that has received limited attention in the scientific literature is the role of physical activity in initial weight loss and maintenance following WLS. Physical activity participation of sufficient frequency, intensity, and duration during both the pre- and postoperative time periods has the potential to reduce surgical complications, enhance weight loss outcomes, and improve physical fitness and overall health following WLS. In addition, physical activity has the potential to improve the quality of postoperative weight loss by enhancing fat mass loss while preserving fat-free mass, thereby minimizing the impact of massive weight loss on metabolic rate. In light of these potential benefits, appropriate interventions should be employed to promote physical activity participation of appropriate frequency, intensity, and duration both before and after WLS.

Improvement in insulin resistance and reduction in plasma inflammatory adipokines after weight loss in obese dogs

Obesity is now a major disease of dogs, predisposing to numerous disorders including diabetes mellitus. Adipocytes are active endocrine cells, and human obesity is characterized by derangements in inflammatory adipokine production. However, it is unclear as to whether similar changes occur in dogs. The purpose of the current study was to assess insulin sensitivity and inflammatory adipokine profiles in dogs with naturally occurring obesity and to investigate the effect of subsequent weight loss. Twenty-six overweight dogs were studied, representing a range of breeds and both sexes. All dogs underwent a weight loss program involving diet and exercise. Body fat mass was measured by dual-energy x-ray absorptiometry; plasma concentrations of insulin, glucose, and a panel of inflammatory adipokines (including acute-phase proteins, cytokines, and chemokines) were also analyzed. Body fat mass before weight loss was positively correlated with both plasma insulin concentrations (Kendall tau=0.30, P=0.044) and insulin:glucose ratio (Kendall tau=0.36, P=0.022), and both decreased after weight loss (P=0.0037 and 0.0063, respectively). Weight loss also led to notable decreases in plasma tumor necrosis factor-alpha (TNF-alpha), haptoglobin, and C-reactive protein concentrations (P<0.05 for all), suggesting improvement of a subclinical inflammatory state associated with obesity. This study has demonstrated that in obese dogs, insulin resistance correlates with degree of adiposity, and weight loss improves insulin sensitivity. Concurrent decreases in TNF-alpha and adipose tissue mass suggest that in dogs, as in humans, this adipokine may be implicated in the insulin resistance of obesity.

Non-conventional markers of atherosclerosis before and after gastric banding surgery

AIMS

Obesity and type 2 diabetes are associated with increased cardiovascular risk and elevation of traditional and non-traditional risk markers. As bariatric surgery reduces overweight and improves metabolic derangement, we examined a cluster of established and emerging cardiovascular risk factors, such as soluble CD40 ligand (sCD40L) and lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), which might improve prediction of future cardiovascular events because of their more direct involvement in plaque destabilization.

METHODS AND RESULTS

Obese patients [n = 32, body mass index (BMI) 46.1 +/- 5.9 kg/m(2)] underwent clinical examinations and blood sampling for measurement of glucose and lipid parameters as well as non-traditional cardiovascular risk markers, i.e. high-sensitivity C-reactive protein, plasminogen activator inhibitor-1 (PAI-1), soluble cellular adhesion molecules (CAM), MMP-2, MMP-9, CD40L, and Lp-PLA(2) before and after 1 year following laparoscopic adjustable gastric banding (LAGB), respectively. In patients undergoing LAGB, blood pressure (P < 0.0001) and blood glucose (P = 0.02) were significantly lowered by approximately 16% as well as triglyceride levels by approximately 29% (P = 0.002). In addition to a decrease of the inflammatory and pro-thrombotic marker PAI-1 (P = 0.001), CAMs, and MMP-9 (P = 0.004) were reduced, whereas no change was observed for plasma levels of MMP-2, sCD40L, and Lp-PLA(2) after LAGB, respectively. Individual changes in (ICAM-1) intercellular adhesion molecule-1 (DeltaICAM-1) were related to changes in insulin (Deltafasting insulin) before and after LAGB (r = 0.36 and r = 0.38; both P = 0.04). E-selectin correlated positively with changes in BMI (r = 0.38; P = 0.04 and r = 0.36; P = 0.05), while Lp-PLA(2) concentration was negatively correlated with BMI (r =-0.41; P = 0.02) after 1 year. Changes were comparable in both overweight diabetic and non-diabetic subjects.

CONCLUSION

LAGB not only induced weight loss but also an improvement in the subclinical pro-inflammatory state. However, concentrations of most of the non-traditional risk factors for plaque instability, i.e. MMP-9, sCD40L, and Lp-PLA(2) remained unchanged.

Obesity and inflammation: the effects of weight loss

Following the discovery of TNF-α and leptin as secretory products of adipocytes in the early 1990s, subsequent obesity research focused on the new functional role of adipose tissue, as an active endocrine organ. Many more inflammatory peptides have been linked to adiposity, which ultimately characterised obesity as a state of low-grade systemic inflammation, or ‘metaflammation’ which may link obesity to its co-morbidities. The aim of the present review is to examine the effects of weight loss on inflammation in overweight and obese, but otherwise healthy, populations. Studies were broadly classified into four types (diet, physical activity, diet and physical activity combined, and surgical interventions) and discussed according to the method used to induce weight loss. All studies measured at least one obesity-related inflammatory marker (ORIM). The overall finding from the present review is that weight loss does improve inflammation in terms of both the inflammatory (C-reactive protein, TNF-α, IL-6 and leptin) and anti-inflammatory (adiponectin) ORIM. Within this, the greatest improvements in ORIM are observed in studies achieving a weight loss of at least 10 %. However, a number of methodological issues have been identified as potential limitations within the literature including the sex and age of subjects, sample size, study duration and the assessment of body composition. In conclusion, although a period of weight loss per se is capable of reversing the unfavourable inflammatory profile evident in the obese state, further studies are required to determine the time needed, in which a reduced weight is maintained, in order to benefit from improved inflammatory status long term.

In morbid obesity, metabolic abnormalities and adhesion molecules correlate with visceral fat, not with subcutaneous fat: effect of weight loss through surgery

BACKGROUND

Decrease of both visceral fat (surgery, physical exercise) and subcutaneous fat (liposuction) is accompanied by improvement of insulin sensitivity.

METHODS

In this study, metabolic variables (glucose, insulin, high-density lipoprotein-cholesterol, triglycerides, aspartate aminotransferase, alanine aminotransferase, uric acid, ferritin) and adhesion molecules (ICAM-1, entothelin-1, E-selectin) were determined in 126 morbidly obese subjects before and 1 year after bariatric restrictive surgery (laparoscopic gastric banding) and correlated with anthropometric measures, i.e., body mass index (BMI) and waist circumference (waist), and with echographic measures of thickness of visceral (usVT) and subcutaneous (usST) abdominal fat.

RESULTS

Under basal conditions and after 1 year, metabolic variables correlated with BMI and waist (r from 0.157 to 0.507, p from 0.0182 to 0.0001) and with usVT (r from 0.211 to 0.512, p from 0.05 to 0.0001); insulin also correlated with usST, and adhesion molecules only correlated with BMI and usVT (r from 0.341 to 0.502, p from 0.0066 to 0.0001). Changes of metabolic variables correlated with changes of BMI and waist (r from 0.163 to 0.356, p from 0.0328 to 0.0001) and with usVT changes (r from 0.211 to 0.361, p from 0.0339 to 0.0002); changes of adhesion molecules only correlated with BMI and usVT changes (r from 0.227 to 0.361, p from 0.0444 to 0.0108). Changes of metabolic variables and of adhesion molecules virtually never correlated with changes of usST.

CONCLUSION

These data indicate that in morbid obesity, most metabolic abnormalities are associated with visceral fat and that their improvements after weight loss are associated with decrease of visceral fat.

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

BACKGROUND

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

The effect of loss of excess weight on the metabolic risk factors after bariatric surgery in morbidly and super-obese patients

BACKGROUND

Changes in metabolic risk factors such as dyslipidemia and hyperinsulinemia as well as levels of sex hormones and leptin were studied in morbidly obese (MO) and super-obese (SO) patients during excess weight loss (EWL), separately in males and females.

METHODS

In this prospective clinical intervention study, 431 patients were included (361 females and 70 males). There were 217 patients with MO (BMI 40-49.9 kg/m2) and 214 patients with SO (BMI > or =50 kg/m2). All patients underwent restrictive bariatric operations. Metabolic parameters (lipids, insulin, leptin, hepatic transaminases, uric acid, and sex hormones) were measured before obesity surgery and at defined postoperative points of EWL (25%, 50%, 75% and 100%).

RESULTS

Successful weight reduction of 25% EWL was achieved by 94% of patients at 2 months. With this moderate EWL, most of the patients already improved their risk profile considerably, including normalization of insulin levels. Additional EWL led to a further amelioration of risk profile in all patients, including normalization of triglyceride levels. Male MO and SO patients had a worse metabolic situation preoperatively and a greater benefit after weight loss. Even though SO patients did not lose as much excess weight as MO patients, they did profit comparably.

CONCLUSION

Bariatric surgery is a valuable tool not only to reduce excess weight in severely obese patients but also to improve the metabolic risk profile within a short time-frame. This benefit is most pronounced in high-risk males.

Release in vitro of adipsin, vascular cell adhesion molecule 1, angiotensin 1-converting enzyme, and soluble tumor necrosis factor receptor 2 by human omental adipose tissue as well as by the nonfat cells and adipocytes

The relative release in vitro of adipsin, vascular cell adhesion molecule (VCAM) 1, angiotensin 1-converting enzyme (ACE), and soluble tumor necrosis factor alpha receptor 2 (sTNFR2) by explants of human omental and subcutaneous adipose tissue as well as the nonfat cell fractions and adipocytes from morbidly obese gastric bypass women was compared with that by tissue from obese abdominoplasty patients. Release of VCAM-1 and ACE by omental adipose tissue explants was 220% and 80% greater, respectively, over 48 hours of incubation than that by subcutaneous adipose tissue explants. However, this difference was not seen when release by adipocytes derived from omental fat was compared with that by adipocytes from subcutaneous fat. The release of adipsin and sTNFR2 by omental adipose tissue explants did not differ from that by subcutaneous tissue adipose tissue. The release of adipsin by tissue explants over 48 hours was 100-fold greater than that of VCAM-1, ACE, or sTNFR2. Most of the release of all 4 adipokines was due to the nonfat cells because adipsin release by adipocytes was only 13% of that by the nonfat cells derived from the same amount of adipose tissue, whereas ACE release by adipocytes was 7% and release of VCAM-1 as well as sTNFR2 by adipocytes was 4% or less of that by nonfat cells. The total release in vitro of ACE and sTNFR2, but not that of adipsin or VCAM-1, was enhanced in adipose tissue explants from morbidly obese women as compared with those by explants derived from obese women. We conclude that although human adipose tissue explants release appreciable amounts of adipsin and far smaller amounts of VCAM-1, ACE, and sTNFR2 in vitro, more than 87% of the release is due to the nonfat cells present in adipose tissue. Furthermore, the enhanced release of VCAM-1 and ACE seen in omental adipose tissue explants as compared with explants of subcutaneous adipose tissue is due to release by nonfat cells.

Plasma adhesion and inflammation markers: asymmetrical dimethyl-L-arginine and secretory phospholipase A2 concentrations before and after laparoscopic gastric banding in morbidly obese patients

BACKGROUND

The aim of this study was to examine the relationship between subclinical inflammation and weight loss by laparoscopic adjustable gastric banding (LAGB).

METHODS

Plasma concentrations of intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), sensitive C-Reactive Protein (sCRP), asymmetrical dimethyl-L-arginine (ADMA), Secretory Phospholipase A2 (sPLA2), and metabolic markers, such as homeostatic model assessment insulin resistance (HOMA-IR) and body mass index (BMI) were determined in morbidly obese patients (n=18, BMI 48.6 +/- 1.7 kg/m2) at baseline and 1 month after operations. Baseline levels in patients were also compared with age-matched controls (n=20, BMI 21.3 +/- 1.8 kg/m2). Plasma ICAM-1, VCAM, sCRP and ADMA, and sPLA2 concentrations were determined by enzyme-linked immunoassay methods and colorimetric method, respectively.

RESULTS

Plasma sCRP, ICAM-1, ADMA and sPLA2 concentrations and HOMA-IR were significantly higher in morbidly obese patients than in controls (for each, P<0.01). Plasma VCAM-1 concentration was not changed in obese patients. HOMA-IR was significantly correlated with ICAM-1, ADMA and sPLA2 in the obese group at baseline (for each, P<0.01). There was a significant correlation between plasma sCRP and plasma glucose, VCAM-1, ICAM-1, ADMA and sPLA2 concentrations (for each, P<0.01). 1 month after LAGB, mean body weight loss was 13.2 +/- 6.3 kg, and plasma sCRP and ADMA concentrations and HOMA-IR and BMI were significantly decreased (for each, P<0.01). However, these levels cannot be decreased to the levels of the controls.

CONCLUSION

Obesity and insulin resistance appear to be associated with low-grade inflammation and endothelial dysfunction. Insulin resistance and endothelial dysfunction were improved by weight loss after LAGB.

Relation of fasting plasma peptide YY to glucose metabolism and cardiovascular risk factors after restrictive bariatric surgery

INTRODUCTION

Surgically induced weight loss results in reduction of comorbidities in severely obese humans. Reversal of abnormal secretion of appetite-regulating gut hormones such as peptide YY (PYY) could be contributing to the improvement of cardiovascular risk factors.

METHODS

Severely obese patients (n = 42, BMI = 45.7 +/- 5.3 kg/m(2)) underwent clinical examination and blood sampling for measurement of PYY, plasma lipids, oral glucose tolerance testing and assessment of insulin secretion (HOMA-%B) and action (HOMA-R, QUICKI) before and during 12 months following gastric banding. Comparisons were made at each time point of the study as well as across the total study period.

RESULTS

Weight loss after bariatric surgery resulted in improvement of insulin resistance by 54% (p < 0.03) and plasma triglycerides by 26% (p < 0.01) without changes in fasting PYY (16.2 +/- 8.7 pmol/l at baseline, 15.1 +/- 6.3 pmol/l at 12 months). Fasting PYY correlated negatively with plasma total cholesterol at baseline (p = 0.02) but was not associated with body weight, body mass or abdominal diameter. Individual changes in PYY (DeltaPYY) related to changes in insulin (Deltafasting insulin) at 12 months (r = -0.582, p = 0.02) and HOMA-B at 6 months (r = -0.677, p = 0.006) and 12 months (r = -0.660, p = 0.007). Diabetic status had no impact on these correlations.

DISCUSSION

PYY correlates with a major cardiovascular risk factor and surrogate parameters of insulin secretion but not to weight loss or body mass in severe obesity.

The link between abdominal obesity, metabolic syndrome and cardiovascular disease

AIM

The prevalence of metabolic syndrome has increased dramatically in recent years, and the cluster of metabolic abnormalities it encompasses results in increased cardiovascular morbidity and mortality. The role of abdominal (visceral) obesity and the underlying molecular and cellular mechanisms central to this association have been the subject of intensive research in recent times. The aim of this review is to correlate data in this area, highlighting the central role of excess visceral fat and its secreted adipokines, and to review existing and emerging therapies.

DATA SYNTHESIS

Data were generated from a search of the PubMed database using the terms 'abdominal obesity', 'metabolic syndrome', 'insulin resistance', 'adipokines', 'interleukin-6 (IL-6)', 'adiponectin', 'tumour necrosis factor-alpha (TNF-alpha)' and 'cardiovascular disease'.

CONCLUSION

Metabolic syndrome is associated with a pro-inflammatory state, and the role of visceral obesity is thought to be central to this. Visceral obesity leads to alteration of the normal physiological balance of adipokines, insulin resistance, endothelial dysfunction and a pro-atherogenic state. In association with this, the presence of conventional cardiovascular risk factors such as hypertension, dyslipidaemia and smoking results in a significantly elevated cardiovascular and metabolic (cardiometabolic) risk. Better understanding of the molecular mechanisms central to this association has led to the development of potential therapeutic agents.

Insulin sensitivity during oral glucose tolerance test and its relations to parameters of glucose metabolism and endothelial function in type 2 diabetic subjects under metformin and thiazolidinedione

AIM

This study was designed to assess the usefulness of a model-based index of insulin sensitivity during an oral glucose tolerance test (OGTT) in the identification of possible changes in this metabolic parameter produced by pharmacological agents known to be potent insulin sensitizers, that is metformin (M) and thiazolidinedione (T). The association of these agents with several other factors related to glucose metabolism was also investigated, as well as the relation of insulin sensitivity and secretion with markers of endothelial function such as different adhesion molecules (cAMs), that is vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and E-Selectin.

METHODS

Twenty type 2 diabetic patients treated with diet only underwent a 3-h OGTT for measurement of plasma glucose, insulin, proinsulin, C-peptide and cAMs before and after administration of randomly given M (n = 9; 1700 mg/day) or T (n = 11; 600 mg/day). After 16 weeks of treatment, a second OGTT was performed. Insulin sensitivity was calculated with homeostasis model assessment and with oral glucose insulin sensitivity (OGIS), which quantifies dynamic glucose clearance per unit change of insulin. Insulin secretion was assessed by modelling technique. Differences in these parameters before and after treatment, as well as possible relationships with cAMs, were assessed.

RESULTS

Basal and stimulated plasma glucose decreased after therapy in both the groups by approximately 20%. Basal insulin resistance also decreased. Insulin sensitivity in dynamic conditions (OGIS: ml/min/m(2)) increased with M (289.3 +/- 18.8 vs. 234.7 +/- 18.1, p < 0.02) and tended to improve with T (323.5 +/- 18.1 vs. 286.8 +/- 22.1, p = 0.09). Total insulin secretion over the OGTT [TIS: nmol/l(3 h)] tended to decrease with M (17.1 +/- 2.5 vs. 27.3 +/- 0.3, p = 0.08) but not with T (23.6 +/- 3.5 vs. 22.5 +/- 2.7). Plasma concentrations of E-Selectin decreased in T (38.0 +/- 2.3 vs. 51.2 +/- 6.1 ng/ml, p < 0.05). No correlation was found between insulin sensitivity and cAMs.

CONCLUSIONS

Model-based indices of insulin sensitivity and secretion during an OGTT can be able to detect changes observed in patients under treatment with pharmacological agents such as M or T. Both the drugs improved glucose control similarly. Decreased plasma E-Selectin concentrations were seen in patients on T therapy only.

Soluble CD40L in patients with morbid obesity: significant reduction after bariatric surgery

BACKGROUND

Morbid obesity is associated with increased cardiovascular morbidity and mortality. Recent studies suggest that soluble CD40 Ligand (sCD40L) may play a pathogenetic role in atherothrombotic complications in cardiovascular disease as well as in inflammation and thrombosis. As morbid obesity is closely associated with chronic inflammation and insulin resistance (IR), it was of interest to study sCD40L in patients with morbid obesity before and after massive weight loss induced by bariatric surgery.

PATIENTS AND METHODS

A total of 34 patients (mean age 40 +/- 12 years) with morbid obesity were studied before and 27.2 months after bariatric surgery. High sensitivity assays were used to measure concentrations of fasting sCD40L, monocyte-chemoattractant-protein-1 (MCP-1) and high-sensitive C-reactive protein (hsCRP). To investigate the associations of concentration changes of the parameters studied, differences between pre- and post-operative data were assessed and tested by univariate and multivariate linear regression analysis.

RESULTS

After a mean weight loss of 33.1 +/- 18.4 kg, circulating sCD40L decreased significantly from (3.7 +/- 1.5) ng mL(-1) to (2.2 +/- 0.7) ng mL(-1), (P < 0.001). The decline in sCD40L after weight loss correlated significantly with the decrease in fasting insulin, 2-h insulin, HOMA insulin resistance (HOMA-IR), triglycerides, and the inflammatory biomarkers MCP-1 and hsCRP.

CONCLUSIONS

We have shown a marked decrease in circulating sCD40L in association with an improvement of both insulin resistance and chronic inflammation in morbidly obese patients after bariatric surgery. As high sCD40L was shown to predict cardiovascular death and myocardial infarction in several prospective studies, the observed marked lowering of sCD40L might be of clinical relevance in morbidly obese patients.

Cellular adhesion molecules and their relationship with measures of obesity and metabolic syndrome in a multiethnic population

BACKGROUND

The relationships between adhesion molecules and measures of obesity and metabolic syndrome in different ethnic populations are unclear.

OBJECTIVE

Our aim was to study the association between body mass index (BMI), waist-hip ratio (WHR) and the parameters of the metabolic syndrome with four different adhesion molecules, adjusting for potential confounders, in men and women from different ethnic origins.

METHODS

Soluble plasma adhesion molecules (sP-selectin, sE-selectin, intracellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) were measured in 261 white (120 women), 188 African origin (99 women) and 215 South Asian (99 women) individuals living in South London. All were free from coronary heart disease (CHD), stroke and other cardiovascular disease (CVD), diabetes, drug therapy for hypertension or high lipids, hormone replacement therapy or oral contraceptive pill.

RESULTS

sE-selectin levels were positively and significantly associated with both BMI (P < 0.001) and WHR (P < 0.001). There were no major interactions with either sex or ethnicity. The strength of the association between sE-selectin and WHR was not affected by multiple adjustment for age, sex, ethnicity smoking, blood pressure, serum lipids and insulin (P < 0.001), whereas the association with BMI was attenuated by multiple adjustments (P = 0.037). An approximate 2% higher sE-selectin levels would be associated with a 1 unit higher BMI and a 0.01 unit greater WHR.

CONCLUSIONS

The relationships between adhesion molecules and conventional measures of obesity are adhesion molecule specific and are strongest between sE-selectin and WHR.

Effect of pronounced weight loss on the nontraditional cardiovascular risk marker matrix metalloproteinase-9 in middle-aged morbidly obese women

OBJECTIVE

Obesity is associated with increased morbidity and mortality from atherosclerotic disease. Nontraditional cardiovascular risk factors such as C-reactive protein (CRP) and interleukin-6 (IL-6) are elevated in obese subjects and weight loss is associated with an attenuation of these risk factors. Matrix metalloproteinase-9 (MMP-9) has been linked to plaque rupture, and is, thus, a candidate marker of future myocardial events. The aim of this study was to determine the influence of weight loss on MMP-9 plasma concentrations.

METHODS AND RESULTS

CRP, IL-6 and MMP-9 were analyzed from samples of 45 morbidly obese, middle-aged women before gastric banding and 1 y postsurgical treatment in this prospective study. The body mass index (BMI) of subjects decreased from 42.5+/-4.9 to 32.3+/-5.3 kg/m(2) 1 y after gastric banding. In parallel, both MMP-9 and CRP were reduced by 23 and 41%, respectively. A positive relationship was found between BMI and MMP-9 (r=0.312, P<0.05), and between CRP and IL-6 (r=0.508, P<0.05), whereas no correlation was found between CRP and MMP-9.

CONCLUSIONS

We conclude that weight loss is associated with a pronounced decrease in the nontraditional cardiovascular risk markers MMP-9 and CRP, which could indicate future beneficial effects of weight loss on the cardiovascular risk in weight loosing subjects.

Effective treatments for insulin resistance: trim the fat and douse the fire

Currently, only limited treatments are available for insulin resistance, a major cause of type 2 diabetes (T2D) and the metabolic syndrome. Combined innovative pharmaceutical and non-pharmaceutical strategies are needed. Obesity, a major cause of insulin resistance in T2D, can be treated relatively safely with modern bariatric surgery. Exercise training to increase VO(2max) is an important non-pharmaceutical approach to decrease insulin resistance. The thiazolidinediones are useful in treating insulin resistance, but newer agents with broader specificity might be more efficacious without deleterious side effects. Recently oxidative stress has been implicated in insulin resistance. One antioxidant that is safe and appears effective is alpha-lipoic acid. Thus, combinations of surgery, exercise training, insulin sensitizers and antioxidants will probably constitute future insulin resistance management.