Bariatric surgery prevents carotid wall thickness progression

BACKGROUND

Bariatric surgery is a treatment option for patients with severe obesity and improves parameters of cardiovascular and/or metabolic disease. Carotid intima media thickness (C-IMT) is a surrogate measure of subclinical atherosclerosis. Previous studies showed short to mid-term arrest and even regression of C‑IMT progression following bariatric surgery. We aimed to investigate the long-term effect of weight loss on C‑IMT progression 10 years after bariatric surgery in comparison to a population-based control cohort.

METHODS

In total, 21 eligible patients were examined preoperatively, at 5 and 10 years after bariatric surgery. Anthropometric parameters, plasma triglycerides, total cholesterol, high-density lipoprotein cholesterol (HDL-C), insulin, and glucose were assessed at all three study visits. C‑IMT was measured via B‑mode scans of the common carotid artery. C‑IMT progression was measured in an age-matched and BMI-matched cohort selected from the population-based Bruneck study to compare with changes in C‑IMT progression after bariatric surgery.

RESULTS

C‑IMT remained stable over the 10-year observation period after bariatric surgery. The control cohort showed a significant C‑IMT progression over 10 years. The difference in C‑IMT progression over 10 years was significant (p < 0.01) between both cohorts.

CONCLUSION

Weight loss induced by bariatric surgery halts the natural progression of C‑IMT over a 10-year observation period.

Serotonin improves glucose metabolism by Serotonylation of the small GTPase Rab4 in L6 skeletal muscle cells

BACKGROUND

Serotonin (5-HT) improves insulin sensitivity and glucose metabolism, however, the underlying molecular mechanism has remained elusive. Previous studies suggest that 5-HT can activate intracellular small GTPases directly by covalent binding, a process termed serotonylation. Activated small GTPases have been associated with increased GLUT4 translocation to the cell membrane. Therefore, we investigated whether serotonylation of small GTPases may be involved in improving Insulin sensitivity and glucose metabolism.

METHODS

Using fully differentiated L6 rat skeletal muscle cells, we studied the effect of 5-HT in the absence or presence of insulin on glycogen synthesis, glucose uptake and GLUT4 translocation. To prove our L6 model we additionally performed preliminary experiments in C2C12 murine skeletal muscle cells.

RESULTS

Incubation with 5-HT led to an increase in deoxyglucose uptake in a concentration-dependent fashion. Accordingly, GLUT4 translocation to the cell membrane and glycogen content were increased. These effects of 5-HT on Glucose metabolism could be augmented by co-incubation with insulin and blunted by co incubation of 5-HT with monodansylcadaverine, an inhibitor of protein serotonylation. In accordance with this observation, incubation with 5-HT resulted in serotonylation of a protein with a molecular weight of approximately 25 kDa. We identified this protein as the small GTPase Rab4, the activity of which has been shown to be stimulated by both insulin signalling and serotonylation.

CONCLUSION

Our data suggest that 5-HT elicits its beneficial effects on Glucose metabolism through serotonylation of Rab4, which likely represents the converging point between the insulin and the 5-HT signalling cascades.

Long-term effects of weight loss after bariatric surgery on functional and structural markers of atherosclerosis

OBJECTIVE

Pronounced weight loss after bariatric surgery was demonstrated to have significant beneficial effects on surrogates of early atherosclerosis. The aim of this prospective examination was to investigate whether these improvements of endothelial function and vascular structure are persistent in the long-term.

DESIGN AND METHODS

A total of 52 obese adults were examined before and 5 years after bariatric surgery. Carotid intima media thickness (IMT), brachial flow-mediated dilation (FMD), abdominal fat distribution, and metabolic parameters were determined. Additional 18 months data were available from 27 patients.

RESULTS

After 5 years, mean weight loss ± SD of 25% ± 12 in all subjects was accompanied by known improvements in metabolism. Change in IMT was -0.02 mm ± 0.007, whereas FMD improved by +1.5% ± 0.5. In the subgroup IMT decreased by 0.04 mm ± 0.06 within the first 18 months, whereas no significant change was observed between 18 month and 5 years. FMD improved by 3.8% ± 0.6 after 18 months followed by a nonsignificant decrease of -1.4% ± 0.9.

CONCLUSIONS

These long-term results demonstrate that bariatric surgery-induced weight loss improves both functional and structural markers of early atherosclerosis providing further evidence for the beneficial effects of weight loss on obesity-associated alterations of the vasculature.

Plasminogen activator inhibitor 1 and visceral obesity during pronounced weight loss after bariatric surgery

BACKGROUND AND AIMS

Elevated plasminogen activator inhibitor 1 (PAI-1) concentrations are a hallmark of obesity and are considered to contribute to the development of cardiovascular disease. As adipose tissue constitutes a major source for PAI-1 in obesity, we investigated the individual contribution of subcutaneous and intra-abdominal fat on PAI-1 concentrations during pronounced weight loss after bariatric surgery.

METHODS AND RESULTS

Thirty-seven obese adults were examined before and 18 months after surgery. Abdominal fat distribution was determined by ultrasound, metabolic parameters and plasma PAI-1 levels by standard methods. BMI was reduced by 9.2 ± 4.9 kg/m(2), while total fat mass and visceral fat diameter (VFD) decreased by 20.7 ± 11.9 kg and 4.2 ± 2.3 cm, respectively. Concomitantly, PAI-1 levels diminished by 3.2 ± 5.6 ng/ml (all p ≤ 0.015). Change in PAI-1 levels was correlated with change in VFD (r = 0.441, p = 0.008), but not with subcutaneous fat diameter. In stepwise multiple regression analysis change in VFD was an independent predictor of change in PAI-1 concentrations. When adjusted for age and sex or total fat mass associations between PAI-1 and VFD remained significant.

CONCLUSION

We demonstrate that VFD is a major determinant for PAI-1 concentrations during pronounced weight loss after bariatric surgery. Thus, significant reduction of visceral fat mass may contribute to the reduced cardiovascular morbidity and mortality after bariatric surgery by a concomitant decrease in PAI-1 concentrations.

Effect of weight loss on serum pigment epithelium-derived factor levels

BACKGROUND

Cumulating evidence suggests that the broadly acting neurotrophic pigment epithelium-derived factor is associated with visceral adiposity, the metabolic syndrome, diabetes and exerts beneficial effects on atherosclerosis. To further elucidate the relationship between pigment epithelium-derived factor and metabolic perturbations characteristic of obesity, we examined the effect of pronounced weight loss on serum levels of pigment epithelium-derived factor.

MATERIALS AND METHODS

Thirty-six severely obese adults were examined before and 18 months after bariatric surgery. Abdominal fat distribution was determined by ultrasound, metabolic parameters by standard methods, pro-inflammatory biomarkers and serum pigment epithelium-derived factor levels by enzyme-linked immunosorbent assay.

RESULTS

Bariatric surgery resulted in a mean body mass index (BMI) reduction of 9·0 ± 5·0 kg m(-2) and concomitant improvements in glucose homoeostasis and lipid profile. Pigment epithelium-derived factor serum levels decreased from a median 11·0 μg mL(-1) (interquartile range: 3·8) to 9·2 μg mL(-1) (interquartile range: 4·5) (P < 0·0001). In univariate analysis, relative change in pigment epithelium-derived factor levels was significantly associated with change in weight, BMI, fat mass, visceral fat diameter, insulin, homoeostasis model for insulin resistance, triglyceride and leptin levels (all r > 0·370, P < 0·05). No associations were observed for C-reactive protein, interleukin-6 or tumour necrosis factor alpha. After adjustment for age, sex and smoking status, associations remained significant.

CONCLUSIONS

The beneficial effects of bariatric surgery-induced pronounced weight loss on glucose homoeostasis may partially be attributable to visceral adipose tissue reduction and concomitantly decreasing pigment epithelium-derived factor concentrations.

Effect of bariatric surgery on circulating chemerin levels

BACKGROUND

Subclinical inflammation in obesity is critical for development of several obesity-associated disorders. We set out to investigate the effect of pronounced weight loss on circulating chemerin levels, a chemoattractant protein that also influences adipose cell function by paracrine and autocrine mechanisms.

MATERIAL AND METHODS

Thirty-two obese patients undergoing bariatric surgery were tested before and on an average of 18 months after gastric banding or gastric bypass surgery.

RESULTS

Pronounced weight loss after bariatric surgery was accompanied by improvements in parameters of lipid and glucose metabolism and increased adiponectin levels. Chemoattractant chemerin significantly decreased from 175.91 +/- 24.50 to 145.53 +/- 26.44 ng mL(-1) after bariatric surgery (P < or = 0.01). Concomitantly, hs-CRP as a marker of subclinical inflammation was significantly reduced after weight reduction (P < or = 0.01).

CONCLUSIONS

We hypothesize that weight-loss induced reduction in circulating chemerin might in conjunction with other factors be associated with diminished recruitment of macrophages in adipose tissue and reduction of subclinical inflammation, which again could partly explain beneficial long-term effects of weight reduction in obese subjects.

Influence of visceral obesity and liver fat on vascular structure and function in obese subjects

Endothelial dysfunction and increased intima-media thickness (IMT) have been found in obese patients. Both regional fat distribution and liver steatosis may influence these markers of subclinical atherosclerosis. We sought to determine the interrelationships of endothelial function, carotid IMT, visceral and subcutaneous adipose tissue accumulation, and liver steatosis in severely obese subjects. In 64 severely obese patients (BMI 42.3 +/- 4.3 kg/m(2)), we determined (i) endothelial function as flow-mediated dilation (FMD) of the brachial artery, (ii) carotid IMT, (iii) visceral fat diameter, and (iv) degree of liver steatosis using ultrasound. FMD was associated inversely with visceral fat diameter and degree of steatosis (r = -0.577, P < 0.0001 and r = -0.523, P < 0.0001, respectively). Carotid IMT correlated with visceral fat mass (r = 0.343, P = 0.007) but not with liver steatosis. After adjustment for conventional cardiovascular risk factors, FMD was predicted independently by the visceral fat diameter, age, and sex (r(2) = 0.48, P < 0.0001), but not by the degree of liver steatosis or plasma adiponectin levels. In contrast, age and sex were the only predictors of IMT (r(2) = 0.33, P < 0.001). In obese patients, visceral fat diameter is a major determinant of endothelial dysfunction, independent of traditional risk factors or the degree of liver steatosis and plasma adiponectin. Measurement of visceral fat diameter by ultrasound is a novel and simple method to identify subjects with an increased risk for atherosclerosis within an obese population.

Effect of bariatric surgery on both functional and structural measures of premature atherosclerosis

AIMS

To bridge the beneficial metabolic effects of pronounced weight loss on one side and the data on morbidity and mortality on the other side, we investigated the impact of profound weight loss on structural and functional markers of early atherosclerosis.

METHODS AND RESULTS

Thirty-seven obese adults were examined before and 18 months after bariatric surgery. Carotid intima-media thickness (CIMT), brachial flow-mediated dilation (FMD), nitroglycerine-mediated dilation, and abdominal fat distribution were assessed by high-resolution ultrasound. Surgery resulted in a body mass index decrease of 9.1 +/- 4.9 kg/m(2) with concomitant improvements in glucose and lipid metabolism. Carotid intima-media thickness diminished from 0.56 +/- 0.09 to 0.53 +/- 0.08 mm (n = 37; P = 0.004). Flow-mediated dilation improved from 5.81 +/- 3.25 to 9.01 +/- 2.93% (n = 25; P < 0.001). Both CIMT and FMD were associated with intra-abdominal fat diameter.

CONCLUSION

The present results demonstrate that bariatric surgery-induced diminution of visceral fat improves both functional and structural markers of early atherosclerosis, providing a link between the weight loss-associated improvements of traditional and non-traditional risk factors and the reduced long-term morbidity and mortality after bariatric surgery.

Retinol-binding protein 4, visceral fat, and the metabolic syndrome: effects of weight loss

Retinol-binding protein 4 (RBP-4) has been reported to be associated with visceral-fat accumulation and parameters of the metabolic syndrome (MetS). In this study, we investigated the relationship between RBP-4, visceral fat, and the MetS during pronounced weight loss after bariatric surgery. Thirty-six subjects were examined before and 2 years after surgery. Abdominal-fat distribution was determined by ultrasound, metabolic parameters, and serum RBP-4 levels by standard methods. After surgery BMI decreased by 9.07 kg/m(2), visceral-fat diameter (VFD) decreased by 60.6%, and RBP-4 serum levels by 16.6%. Change of RBP-4 levels was associated with reductions of waist (r = 0.364, P = 0.037), waist-to-hip ratio (WHR) (r = 0.415, P = 0.016), and VFD (r = 0.425, P = 0.010). MetS, as defined by International Diabetes Federation (IDF), was present in 19 patients at baseline and in nine patients at follow-up. Change in RBP-4 levels was the best predictor for the diagnosis of MetS at follow-up. In the subgroup without MetS at baseline, the decrease in RBP-4 levels (-28.1% vs. -6.3%, P = 0.020) and reduction in VFD (-66.9% vs. -55.0%, P = 0.038) were significantly greater compared to the subgroup with MetS. We demonstrate a marked decrease of RBP-4 levels after bariatric surgery, which correlates with reduction in visceral-fat mass. Furthermore, the extent of changes in RBP-4 levels differs according to the severity of the MetS.

Evaluation of urinary 1-hydroxypyrene,S-phenylmercapturic acid,trans,trans-muconic acid, 3-methyladenine, 3-ethyladenine, 8-hydroxy-2′-deoxyguanosine and thioethers as biomarkers of exposure to cigarette smoke

The objective was to evaluate the utility of urinary 1-hydroxypyrene (1-OHP), S-phenylmercapturic acid (S-PMA), trans,trans-muconic acid (t,t-MA), 3-methyladenine (3-MeAd), 3-ethyladenine (3-EtAd), 8-hydroxy-2'-deoxyguanosine (8-OHdG) and thioethers as biomarkers for assessing the exposure in adult smokers who switched from smoking conventional cigarettes to candidate potential reduced exposure products (PREP) or who stopped smoking. Two electrically heated smoking systems (EHCSS) were used as prototype cigarettes that have significant reductions in a number of mainstream smoke constituents as measured by smoking machines relative to those from conventional cigarettes. Urine samples were collected from a randomized, controlled, forced-switching study in which 110 adult smokers of a conventional cigarette brand (CC1) were randomly assigned to five study groups. The groups included the CC1 smoking group, a lower-tar conventional cigarette (CC2) smoking group, EHCSS1 group, EHCSS2 group and a no smoking group that were monitored for 8 days. Biomarkers were measured at baseline and day 8. The daily excretion levels of these biomarkers were compared among the groups before and after switching, and the relationships between the daily excretion levels of these biomarkers and cigarette smoking-related exposure were investigated using Pearson product-moment correlation and multiple regression analyses. It was concluded that under controlled study conditions: (1) 1-OHP, S-PMA and t,t-MA are useful biomarkers that could differentiate exposure between smoking conventional and EHCSS cigarettes or between smoking conventional cigarettes and no smoking; between S-PMA and t,t-MA, the former appeared to be more sensitive; (2) 3-MeAd could only differentiate between smoking conventional cigarettes and no smoking; the results for 3-EtAd were not conclusive because contradictory results were observed; (3) 8-OHdG had a questionable association with smoking and therefore the utility of this biomarker for smoking-related exposure could not be established; and (4) urinary excretion of thioethers as a biomarker lacked sensitivity to demonstrate a clear dose-response relationship in conventional cigarette smokers, although it could differentiate the excretion levels between those subjects who smoked a conventional cigarette and those who stopped smoking.

A-FABP--a biomarker associated with the metabolic syndrome and/or an indicator of weight change?

OBJECTIVE

Adipocyte fatty acid-binding protein (A-FABP) is a plasma biomarker recently associated with the metabolic syndrome. The aim of these studies was to investigate changes of A-FABP during profound weight loss induced by laparoscopic adjustable gastric banding (LAGB).

METHODS AND PROCEDURES

In study one, 29 severely obese female subjects were examined before and 1 year after surgical treatment. A subgroup of 10 patients was investigated in 3-month intervals. Metabolic parameters were determined using standard methods, and A-FABP was detected using a commercially available enzyme-linked immunosorbent assay.

RESULTS

Mean weight loss after 1 year was 24.9 kg (P < 0.001), mainly due to a decrease in fat mass. Metabolic parameters improved substantially. However, serum A-FABP remained stable. In study two, a subgroup of 10 patients was examined quarterly to determine the time course of A-FABP changes. Quarterly measurements of serum A-FABP were significantly higher than baseline levels with the highest A-FABP value after the first 3 months, where patients had highest weight loss.

DISCUSSION

Our results in study one show that A-FABP serum levels are positively associated with body weight and fat mass. However, 1 year after pronounced weight loss A-FABP levels remained unchanged. In study two, time course analyses revealed maximum increase of serum A-FABP in parallel to highest weight loss, which allows to suppose that A-FABP is not only a biomarker of the metabolic syndrome in the steady state, but also a marker of weight changes in dynamic situations.

Adiponectin receptor R1 is upregulated by valproic acid but not by topiramate in human hepatoma cell line, HepG2

Valproic acid (VPA) is an effective and widely used anticonvulsant, associated with metabolic adverse effects such as weight gain, hyperinsulinemia, hyperleptinemia and hypoadiponectinemia. The aim of this study was to evaluate the influence of VPA and topiramate (TPM) on adiponectin binding receptors, adipoR1 and adipoR2, in human liver cancer cells, HepG2. AdipoR1 but not adipoR2 gene expression was upregulated by VPA treatment. TPM did neither affect adipoR1 nor adipoR2 gene expression. Given the tight association between VPA treatment, metabolic side effects and the adipocytokine-axis, upregulation of adipoR1 possibly represents a favoured and insulin-sensitizing mechanism.

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.

Spezifisches Verteilungsmuster der Knorpelelastizität und -dicke am Talus des Pferdes

Gegenstand und Ziel: In der vorliegenden Arbeit wurden erstmals Referenzwerte für die Knorpelelastizität und Knorpeldicke am Talus des Pferdes ermittelt. Die postmortal durchgeführte Untersuchung umfasste 24 Pferde verschiedenen Alters (zwei Fohlen, ein Jährling, 21 adulte Tiere). Material und Methoden: Die Knorpelelastizität wurde an 23 Messpunkten mit einer auch intra vitam einsetzbaren Indentermesssonde (Art - scan® 200) getestet. Die Bestimmung der Knorpeldicke erfolgte mit einer Messlupe an 18 Messpunkten des geschnittenen Knorpelpräparats. Ergebnisse: Die Sprunggelenke der neugeborenen Fohlen zeigten eine homogene Verteilung der Knorpelelastizität über den gesamten Rollkamm. Eine Knorpeldickemessung war aufgrund der noch nicht abgeschlossenen enchondralen Ossifikation nicht möglich. Die Tali des Jährlings wiesen bereits eine deutliche Heterogenität der Knorpelelastizität und -dickeF auf. Die adulten Tiere zeigten mit einer hohen Signifikanz (p < 0,001) einen deutlichen Trend einer nach distal abnehmenden Knorpelelastizität und einer gegenläufigen Verteilung der Knorpeldicke. An den proximalen Messpunkten wurden Werte von 0,873–1,321 Newton (N) erreicht, an den distalsten Messpunkten nur noch 0,375–0,550 N. Für die Knorpeldicke ergaben sich proximal Werte von 0,49–0,78 mm und distal von 0,68–1,08 mm. Schlussfolgerung: Die verwendete Messsonde eignet sich zur Bestimmung der Knorpelelastizität beim Pferd. Die Knorpelelastizität und -dicke am equinen Talus weisen ein lokales und altersabhängiges Verteilungs muster auf. Klinische Relevanz: Bei der Detektion von frühen pathologischen Veränderungen der Knorpelmatrix muss die lokalisations- und altersspezifische Ausprägung der Knorpelelastizität berücksichtigt werden.

Metabolic side effects of antipsychotic medication

The use of second-generation antipsychotics (SGAs) is associated with metabolic side effects including weight gain, diabetes mellitus and an atherogenic lipid profile. These adverse effects are not only the risk factors for cardiovascular disease, insulin resistance and diabetes mellitus leading to increased morbidity and mortality but may also impair the patient's adherence to treatment. SGAs in particular are associated with significant weight gain with clozapine and olanzapine carrying the highest risk, whereas newer agents, such as risperidone and aripiprazole, are considered to be less prone to cause weight gain. Consequently, a consensus development conference convened issuing recommendations on patient monitoring when treated with SGAs. The metabolic effects of antipsychotic drugs should be of concern when planning a patient's treatment strategy. Baseline screening and regular follow-up monitoring whose intervals should depend on the individual predisposition are advised. Possible therapeutical strategies for the management of drug-induced obesity include therapeutic approaches, such as life style change and pharmaceutical intervention. Drugs with a weight reducing effect become more important because of the lack of compliance with behavioural intervention. Topiramate, histamine-antagonists, dopaminergic- and serotoninergic agents have shown positive results in the management of psychotropic medication induced weight gain. However, further trials are required to support a specific therapeutical approach as well as studies to investigate the underlying mechanisms for future drug development.

Analysis of long-chain ω-3 fatty acid content in fish-oil supplements

BACKGROUND

Omega-3 polyunsaturated fatty acids (long-chain omega-3 PUFA) have proved to be beneficial in atherosclerosis, arrhythmia and hypertriglyceridemia in several studies, which has led national and international societies to recommend an intake of 1 g/d long-chain omega-3 PUFA for anti-atherosclerotic and antiarrhythmic purposes or 2-4 g/d for a lipid lowering effect. Numerous preparations are marketed for supplementing western diet, which is low in long-chain omega-3 PUFA. Since these preparations vary in their long-chain omega-3 PUFA content, we tested nine commercially available products for their fatty acid composition.

METHODS

Nine commercially available omega-3 fatty acid supplements were analyzed using capillary gas chromatography to determine their fatty acid content.

RESULTS

The nine preparations showed huge differences, up to 63.7 +/- 1.58 mol% (P = 0.002), in their longchain omega-3 fatty acid content. Most of them failed to achieve the daily recommended dose of 1 g, even when administered at the highest dosage according to the manufacturer's recommendations. Eight of the preparations contained either equal or significantly greater amounts of long-chain omega-3 PUFA than denoted by the manufacturer; one preparation did not provide any information. The highest percentage of DHA and EPA was detected in Omacor(95.80 +/- 0.63%) and Percucor (76.8 +/- 7.109%).

CONCLUSION

Administering long-chain omega-3 fatty acid preparations may result in huge differences in terms of the actual amount ingested. It is therefore advisable to use the most standardized and purified products available.

Effects of pronounced weight loss on adiponectin oligomer composition and metabolic parameters

OBJECTIVE

Adiponectin is an adipocytokine secreted into circulation in three isoforms. The aim of the study was to investigate changes of adiponectin isoforms during profound weight loss and its relation to anthropomorphometric and metabolic parameters.

RESEARCH METHODS AND PROCEDURES

Thirteen severely obese female subjects were examined before and 1 year after surgical treatment. Total adiponectin was determined by radioimmunosorbent assay, and oligomer composition was detected by nondenaturing Western blot.

RESULTS

BMI decreased substantially (p < 0.001), which was associated with an increase of total adiponectin from 12.9 +/- 5.9 to 14.3 +/- 6.1 microg/mL (p = 0.055). Medium molecular weight (MMW) adiponectin increased from 7.5 +/- 3.6 to 9.1 +/- 4.1 microg/mL (p = 0.009), whereas high (HMW) and low molecular weight adiponectin remained unchanged. Delta values of total adiponectin correlated significantly with Delta values of anthropometric parameters. Similar correlations were found for Delta values of MMW (Delta weight: r(2) = 0.4132, p = 0.0178; Delta BMI: r(2) = 0.3319, p = 0.0393; Delta fat mass: r(2) = 0.5202, p = 0.0054).

DISCUSSION

Thus, profound weight loss was associated with an increase in total adiponectin, which was mainly and consistently caused by increases in MMW adiponectin (p = 0.009). These changes result in a shift from low molecular weight to MMW and HMW adiponectin isoforms, which may be related to improvements in both anthropometric and metabolic parameters.

[Antipsychotic drug-induced changes in metabolism]

Antipsychotic medications are a mainstay in the treatment of schizophrenia and are widely used in other psychiatric conditions. New generation antipsychotic agents (NGAs) are increasingly replacing first generation antipsychotic agents (FGAs), mainly due to a decreased risk for extrapyramidal symptoms, better overall tolerability, as well as some efficacy advantages. However, some of these NGAs are associated with adverse metabolic effects such as substantial weight gain, the induction of insulin resistance and lipid disorders. Among these substances, clozapine and olanzapine induce the most significant weight gain, olanzapine mainly by increasing body fat and both of these antipsychotics have been associated with disturbances in glucose metabolism. Diabetes mellitus induced by treatment with some NGAs occurred in many cases within days to weeks after initiation of SGA therapy, in some cases hyperglycemia promptly resolved after discontinuation of the medication and several reports have documented recurrent hyperglycemia after a rechallenge with the same drug. One possible pathomechanism for hyperglycemia induced by these NGAs is the induction of insulin resistance via humoral and/or cellular pathways. Alternatively, NGA induced diabetes may occur because of weight gain or a change in body fat distribution with a shift to a predominantly visceral fat type or through a direct effect on insulin sensitive target tissues. In this article we like to review the metabolic side effects of NGA treatment, highlight recent advances in the pathogenesis of these metabolic complications and discuss potential treatments of these side effects.

Cholesteryl ester transfer protein in metabolic syndrome

OBJECTIVE

Low high-density lipoprotein cholesterol (HDL-C), hypertriglyceridemia, and small dense-low density lipoprotein (LDL) are key components of metabolic syndrome (MS). Cholesteryl ester transfer protein (CETP) mediates the transfer of triglycerides (TGs) from TG-rich lipoproteins to HDL and LDL particles in exchange for cholesteryl esters, leading to low HDL-C and small dense-LDL. The aim of this study was to investigate the role of CETP in subjects with MS.

RESEARCH METHODS AND PROCEDURES

In a cross-sectional cohort of 234 middle-aged men and 252 women randomly selected from the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) study, MS was diagnosed according to the National Cholesterol Education Program guidelines. CETP mass was determined by enzyme-linked immunosorbent assay and LDL size-by-gradient polyacrylamide gel electrophoresis.

RESULTS

Men and women with MS had lower HDL-C (45 +/- 7 vs. 58 +/- 13 and 48 +/- 10 vs. 71 +/- 14 mg/dL for men and women, respectively; p < 0.001 for all) and higher TG levels (222 +/- 71 vs. 98 +/- 54 and 167 +/- 67 vs. 90 +/- 35 mg/dL for men and women, respectively; p < 0.001 for all) than healthy subjects. LDL size was lower in subjects with MS (256 +/- 11 A vs. 267 +/- 11 A and 262 +/- 10 A vs. 273 +/- 8 A for men and women, respectively; p < 0.001 for all). CETP mass was higher in men with MS (1.87 +/- 0.78 vs. 1.40 +/- 0.65 mug/mL; p < 0.001) but not in women (1.74 +/- 0.79 vs. 1.62 +/- 0.62 mug/mL). CETP mass correlated inversely with LDL size in both men and women (r = -0.19, p < 0.01 and r = -0.13, p < 0.05 in men and women, respectively).

DISCUSSION

MS is associated with increased CETP mass in men. Increased CETP mass may be responsible for reduced HDL-C and reduced LDL particle diameter in MS.

Effect of mirtazapine treatment on body composition and metabolism

OBJECTIVE

Weight gain is a common side effect of psychotropic medications. Mirtazapine, a widely used antidepressant, induces adverse metabolic effects such as an increase in body weight. The aim of this study was to investigate the influence of mirtazapine treatment on body weight, body fat mass, glucose metabolism, lipoprotein profile, and leptin and its soluble receptor in a prospective, controlled study design.

METHOD

Seven women who met the ICD-10 diagnostic criteria for a depressive episode (ICD-10: F31-F33) were assigned to monotherapy with mirtazapine and observed for a 6-week period. Seven mentally and physically healthy female volunteers matched for age and body weight served as a control group. Data were collected from November 2002 to December 2003.

RESULTS

The mean +/- SD body weight increased from 63.6 +/- 13.1 kg to 66.6 +/- 11.9 kg during mirtazapine treatment (p = .027). Fat mass increased in study subjects from 20.9 +/- 9.6 kg to 22.1 +/- 9.3 kg (p = .018). Insulin, glucose, and the homeostasis model assessment (HOMA) index for insulin resistance and lipid parameters remained stable. Leptin concentrations increased from 23.0 +/- 17.1 ng/mL to 40.9 +/- 27.2 ng/mL (p = .018), whereas the soluble leptin receptor concentrations remained stable during mirtazapine treatment. In the control subjects, the investigated parameters remained stable. Between-group analyses of change scores revealed significant differences for body weight (p = .010), body mass index (p = .013), fat mass (p = .035), and leptin (p = .013).

CONCLUSION

The antidepressant therapy with mirtazapine was associated with a significant increase in body weight, body fat mass, and leptin concentration. In contrast to other psychotropic medications inducing weight gain, such as some second-generation antipsychotics, mirtazapine treatment did not influence the glucose homeostasis.

Olanzapine impairs glycogen synthesis and insulin signaling in L6 skeletal muscle cells

Second-generation antipsychotic agents (SGAs) are increasingly replacing first-generation antipsychotic agents due to their superior activity against the negative symptoms of schizophrenia, decreased extrapyramidal symptoms and better tolerability. However, some SGAs are associated with adverse metabolic effects as significant weight gain, lipid disorders and diabetes mellitus. The pathogenesis of SGA-induced disturbances of glucose homeostasis is unclear. In vivo studies suggest a direct influence of SGAs on peripheral insulin resistance. To this end, we analyzed whether olanzapine might alter glycogen synthesis and the insulin-signaling cascade in L6 myotubes. Glycogen content was diminished in a dose- and time-dependent manner. Within the insulin-signaling cascade IRS-1 tyrosine phosphorylation was induced several fold by insulin and was diminished by preincubation with olanzapine. IRS-1-associated PI3K activity was stimulated by insulin three-fold in L6 myotubes. Olanzapine inhibited insulin-stimulated IRS-1-associated PI3K activity in a dose-dependent manner. Protein mass of AKT, GSK-3 and GS was unaltered, whereas phosphorylation of AKT and GSK-3 was diminished, and pGS was increased. Finally, we compared olanzapine with amisulpride, an SGA clinically not associated with the induction of diabetes mellitus. Glycogen content was diminished in olanzapine-preincubated L6 cells, whereas this effect was not observed under the amisulpride conditions. We conclude that olanzapine impairs glycogen synthesis via inhibition of the classical insulin-signaling cascade and that this inhibitory effect may lead to the induction of insulin resistance in olanzapine-treated patients.

[The metabolic syndrome: effects of a pronounced weight loss induced by bariatric surgery]

The prevalence of obesity is rising worldwide dramatically, affecting up to 50 percent of the population. The epidemic of obesity leads to a marked increase in the metabolic syndrome, a cluster of cardiovascular risk factors characterized by visceral obesity, insulin resistance, low HDL-Cholesterol, hypertriglyceridemia, and a subclinical proinflammatory state. In the last years, the NCEP and the WHO highlighted and defined the key features of the metabolic syndrome to facilitate the clinical diagnosis and preventive interventions. The conservative therapy of obesity and the metabolic syndrome by life style intervention and pharmacological interventions leads only to moderate weight loss with inconstant long-term success. Intervention by bariatric surgery can serve as a model for the metabolic effects of permanent weight loss. In several studies the pronounced weight loss induced a reduction of almost all components of the metabolic syndrome, including glucose and lipid status and is followed by an improvement in the quality of life. Recent research suggested a decrease in mortality rate in addition to cost effectiveness of bariatric surgery.

Human triglyceride-rich lipoproteins impair glucose metabolism and insulin signalling in L6 skeletal muscle cells independently of non-esterified fatty acid levels

AIMS/HYPOTHESIS

Elevated fasting and postprandial plasma levels of triglyceride-rich lipoproteins (TGRLs), i.e. VLDL/remnants and chylomicrons/remnants, are a characteristic feature of insulin resistance and are considered a consequence of this state. The aim of this study was to investigate whether intact TGRL particles are capable of inducing insulin resistance.

METHODS

We studied the effect of highly purified TGRLs on glycogen synthesis, glycogen synthase activity, glucose uptake, insulin signalling and intramyocellular lipid (IMCL) content using fully differentiated L6 skeletal muscle cells.

RESULTS

Incubation with TGRLs diminished insulin-stimulated glycogen synthesis, glycogen synthase activity, glucose uptake and insulin-stimulated phosphorylation of Akt and glycogen synthase kinase 3. Insulin-stimulated tyrosine phosphorylation of IRS-1, and IRS-1- and IRS-2-associated phosphatidylinositol 3-kinase (PI3K) activity were not impaired by TGRLs, suggesting that these steps were not involved in the lipoprotein-induced effects on glucose metabolism. The overall observed effects were time- and dose-dependent and paralleled IMCL accumulation. NEFA concentration in the incubation media did not increase in the presence of TGRLs indicating that the effects observed were solely due to intact lipoprotein particles. Moreover, co-incubation of TGRLs with orlistat, a potent active-site inhibitor of various lipases, did not alter TGRL-induced effects, whereas co-incubation with receptor-associated protein (RAP), which inhibits interaction of TGRL particles with members of the LDL receptor family, reversed the TGRL-induced effects on glycogen synthesis and insulin signalling.

CONCLUSIONS/INTERPRETATION

Our data suggest that the accumulation of TGRLs in the blood stream of insulin-resistant patients may not only be a consequence of insulin resistance but could also be a cause for it.

Use of precision-cut tissue slices in organ culture to study metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) by hamster lung, liver and kidney

The pharmacokinetics of in vitro metabolism of the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK; concentration range 0.03-250 microM) and its proximal metabolite, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL; 0.04-250 microM), were determined in Syrian golden hamster liver, lung, and kidney tissue slices in organ culture under identical experimental conditions. In the lung, a target organ for NNK animal carcinogenesis, total NNK metabolism was relatively low (maximum 23%) and oxidative metabolism by alpha-hydroxylation to DNA-reactive intermediates accounted for 13-31% of metabolism. The liver, a non-target organ for NNK carcinogenesis, showed the highest capacity to metabolise NNK (total metabolism 80%), and alpha-hydroxylation accounted for 12-25% of metabolism. The kidney, another non-target organ, also showed a low capacity for NNK metabolism (maximum 32%) and alpha-hydroxylation accounted for <3% of metabolism. Detoxification of NNK by pyridyl N-oxidation was similar in lung (5-22%) and liver (5-23%), and negligible in kidney (<2%), while carbonyl reduction of NNK to NNAL was greatest in the kidney (95-100%), followed by liver (59-79%) and lung (47-81%). NNAL is devoid of biological activity in the hamster and total metabolism was about tenfold lower than that of NNK in all tissues (<13% liver; <4% lung and kidney). In the liver, alpha-hydroxylation was the predominant pathway of NNAL metabolism at almost all concentrations (31-68% of total metabolism), whereas N-oxidation prevailed in the kidney (47-68%). In the lung, a concentration dependent decrease in the relative amount of alpha-hydroxylation (23-72%) with increasing NNAL concentrations occurred at the expense of N-oxidation (25-72%). Little or no metabolism of NNAL back to NNK was evident in any tissue.

Dithiothreitol stimulates insulin receptor autophosphorylation at the juxtamembrane domain

Autophosphorylation of insulin receptors from human placental membranes prepared with iodoacetamide was more than double that of control receptors prepared without iodoacetamide. Dithiothreitol (DTT) treatment of control receptors prepared without iodoacetamide resulted in increased autophosphorylation. However, DTT was without effect on insulin receptors prepared with iodoacetamide. Phosphopeptide analysis showed that while 32P-labeling of all of the phosphopeptides was increased in insulin receptors from membranes prepared with iodoacetamide, two additional phosphopeptides were detected and identified as deriving from the juxtamembrane domain, containing tyrosine residue 960. Similar results were produced by DTT treatment of control insulin receptors. These observations suggest that a thiol(s) may be involved in insulin receptor autophosphorylation in the juxtamembrane domain.

[Possible malignant hyperthermia as reaction to an overdose of myotonolytic, antidepressive and sedative drugs (author's transl)]

A 51-year-old male patient with no history of musculo-skeletal or myopathic abnormalities, but suffering from manic-depressive psychosis, attempted suicide with an overdose of dolpersin hydrochloride (Mydocalm), dipenzepine hydrochloride (Noveril), meprobamate (Mepronox) and nitrazepam (Mogadon). He developed high fever, muscle rigidity, tachycardia, arrhythmias, hypotension and mottled cyanosis, symptoms well-known in persons with malignant hyperthermia, an autosomally inherited disease of skeletal muscle. There is also discussed the manifestation and the symptoms of an acute rhabdomyolysis. The diagnosis was confirmed by chemical pathological laboratory findings, including respiratory and metabolic acidosis, myoglobinaemia accompanied by myoglobin diuresis, and elevated creatine phosphokinase (CPK values up to 2790 U/l). Electron microscopic examination of muscle tissue revealed signs of myolysis and mitochondrial reactions with pleoconic hyperplasia. No inhalation anaesthetics or skeletal muscle relaxants, such as succinyl choline, were used in this case. Therefore, malignant hyperthermia might have been induced by a combination of drugs which were not known to induce this abnormal muscular reaction. However, the muscle relaxant effect of dolpersin hydrochloride may have acted as a possible inducer of the attack.