Phospholipid transfer protein activity is determined by type 2 diabetes mellitus and metabolic syndrome, and is positively associated with serum transaminases

Background The extent to which plasma phospholipid transfer protein (PLTP) activity is affected by type 2 diabetes mellitus (DM) and metabolic syndrome (MetS) is still unknown. PLTP is synthesized in the liver, and elevated serum transaminases are considered to predict nonalcoholic fatty liver disease (NAFLD). In this study, we examined the relationship between plasma PLTP activity and liver enzymes in subjects with and without DM and MetS. Design Plasma PLTP activity, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured in 71 subjects without DM or MetS, 21 without DM but with MetS, 26 with DM but without MetS and 55 with DM and MetS (WHO and NCEP‐ATP III criteria). Results After controlling for age, sex and alcohol intake, PLTP activity was positively related to both MetS (P < 0·001) and DM (P = 0·001). Serum ALT (P = 0·006) and AST (P = 0·04) were both associated with MetS, but only ALT was associated with DM (P < 0·001). In multiple linear regression models, serum ALT and AST were positively and independently associated with PLTP activity (P < 0·01 for all), even when the presence of MetS and DM was taken into account, as well as after controlling for glycated haemoglobin (HbA_1c), insulin resistance, triglycerides, free fatty acids (FFA), C‐reactive protein (CRP), leptin and adiponectin. Conclusions Plasma PLTP activity is determined by MetS and by diabetes per se. Serum transaminases are independently associated with PLTP activity. We suggest that this lipid transfer protein may be a marker for NAFLD.     

Serum total and high molecular weight adiponectin levels are correlated with the severity of diabetic retinopathy and nephropathy

Objective Adiponectin is secreted specifically from adipocytes, and improves insulin sensitivity. Of its isoforms, the high molecular weight (HMW) complex is thought to be the most active. The aim of this study was to determine the relationship between serum total or HMW adiponectin and diabetic microangiopathy. Design, patients and measurements We analysed 198 Japanese patients with type 2 diabetes mellitus (T2DM) whose fasting serum samples were available. Serum total adiponectin and HMW adiponectin were measured using an enzyme‐linked immunosorbent assay (ELISA). Results Serum total adiponectin was found to have increased in the advanced stages of diabetic retinopathy (mean ± SE, none, 6·9 ± 0·3; simple, 8·3 ± 1·0; preproliferative, 8·4 ± 0·8; proliferative, 12 ± 1·1 mg/l; anova P = 0·0004) and nephropathy (stage I, 7·0 ± 0·3; II, 7·7 ± 0·5; III, 9·5 ± 0·9; IV, 16 ± 4·5 mg/l, P < 0·0001). Similarly, serum HMW adiponectin had increased in the advanced stages of retinopathy (3·7 ± 0·2, 4·6 ± 0·5, 4·6 ± 0·6 and 6·9 ± 0·8 mg/l, respectively, P = 0·0005) and nephropathy (3·7 ± 0·2, 4·3 ± 0·4, 5·3 ± 0·7 and 7·9 ± 2·2 mg/l, respectively, P = 0·0007). Neither serum total nor HMW adiponectin was correlated with neuropathy. The HMW/total adiponectin ratio was not correlated with microangiopathy. Multiple regression analysis revealed that serum total and HMW adiponectin were independent factors for retinopathy stage (P = 0·0055 and P = 0·0027, respectively) and nephropathy stage (P = 0·0003 and P = 0·0018, respectively), when adjusted for age, gender, body mass index (BMI) and the duration of T2DM. This correlation remained significant when serum creatinine (or estimated glomerular filtration rate) and hypertension were added as independent variables. Treatment with thiazolidinediones (TZDs) did not affect these findings. Conclusions Serum total adiponectin and HMW adiponectin were found to be positively correlated with the severity of retinopathy and nephropathy but not with neuropathy in T2DM.     

Serum retinol-binding protein 4 is not increased in obesity or obesity-associated type 2 diabetes mellitus, but is reduced after relevant reductions in body fat following gastric bypass

Objective Controversy exists regarding the elevation of serum retinol‐binding protein 4 (RBP4) in human obesity and type 2 diabetes mellitus (T2DM). In the present study, we have compared serum RBP4 in lean and obese patients with or without T2DM, and analysed the effect of weight loss on serum RBP4. Design Forty‐two Caucasian subjects were included in the study. Serum RBP4 was measured by ELISA and Western blot. In addition, serum RBP4 was measured in 21 morbidly obese patients before and after 4, 8 and 15 months of weight loss following Roux‐en‐Y gastric bypass (RYGBP). Results No significant effect of either obesity or diabetes on serum RBP4 was observed. Serum RBP4 concentrations (measured by either ELISA or Western blot) did not correlate with body mass index (BMI), body fat or any indicator of glucose metabolism or insulin resistance. Weight loss following RYGBP did not modify serum RBP4 at 15 months (P = 0·472). However, the variations in serum RBP4 were significantly associated with the reduction in body fat (r = 0·48; P = 0·026). Patients loosing over 20% of fat mass (n = 11) showed significantly different RBP4 concentrations compared to those individuals exhibiting smaller adiposity reductions (n = 10) (–11·0 ± 6·4 vs.+5·8 ± 3·6 mg/l; P = 0·036). Furthermore, RBP4 levels were significantly reduced at 4 (P = 0·006) and 8 (P = 0·015) months only in those patients loosing over 20% of fat mass. Conclusion Serum RBP4 concentrations are not increased in obese patients with or without T2DM. A decrease in RBP4 levels was only observed after surgically induced weight loss accompanied by relevant reductions in body fat. RBP4 might be considered as a dynamic marker of negative energy balance being reduced during weight loss when a negative energy balance threshold is reached. Furthermore, RBP4 variation in the first month after RYGBP may be a predictor of weight loss success.     

Glucocorticoid replacement is associated with hypertriglyceridaemia, elevated glucose and higher non-HDL cholesterol and may diminish the association of HDL cholesterol with the -629C>A CETP promoter polymorphism in GH-receiving hypopituitary patients

Objectives The effect of glucocorticoid substitution on the prevalence of metabolic syndrome components (NCEP ATP III criteria) and serum lipid levels was determined in GH‐replaced hypopituitary patients. As glucocorticoid replacement is associated with a pronounced decrease in plasma cholesteryl ester transfer protein (CETP) activity, we also tested associations of HDL cholesterol with the –629C>A CETP promoter polymorphism in subjects with and without ACTH deficiency. Design and patients In a university setting, we retrieved protocolized clinical and laboratory data from 165 adult hypopituitary patients, who had received GH for 1 year. Results After adjustment for age, sex and smoking, non‐HDL cholesterol (P = 0·05) and triglycerides (P = 0·004) were higher, but HDL cholesterol was not decreased in 117 glucocorticoid (mainly cortisone acetate in two divided doses) receiving subjects compared to 48 ACTH‐sufficient subjects. The prevalence of elevated plasma glucose and/or diabetes (P = 0·04) and hypertriglyceridaemia (P = 0·005), but not of other metabolic syndrome components, was higher in glucocorticoid‐replaced subjects. HDL cholesterol was higher in –629 A allele carriers compared to –629CC homozygotes in ACTH‐sufficient subjects (P = 0·04), but not in glucocorticoid‐treated subjects (P = 0·13). Multiple linear regression analysis demonstrated that only in ACTH‐sufficient subjects, HDL cholesterol was independently related to this CETP gene variation (P = 0·03). Conclusions In GH‐ and glucocorticoid‐replaced hypopituitary patients, serum non‐HDL cholesterol and triglycerides are higher and the prevalence of hyperglycaemia is increased, but HDL cholesterol is not decreased. Conventional glucocorticoid replacement appears to diminish the association of HDL cholesterol with a common CETP gene variation.     

Increased serum visfatin in patients with metabolic syndrome and carotid atherosclerosis

Objective Visfatin is a newly identified adipocytokine and recent studies indicated that visfatin may have potential proinflammatory effect. However, its pathophysiological role in the metabolic syndrome (MetS) is not fully understood. In this study we investigated whether serum visfatin levels is altered in patients with the MetS, and compared the levels of visfatin between patients with and without carotid plaques. Design and method A total of 139 patients with MetS and 105 controls were included. The patients were further divided into two groups: 40 with carotid plaques and 99 without carotid plaques. Serum visfatin was measured by using enzyme immunoassay method and carotid intimal‐media thickness (IMT) was measured by ultrasound in all subjects. Results Serum visfatin was elevated in both MetS patients with and without carotid plaques compared to controls (log visfatin: 1·14 ± 0·14 vs. 0·99 ± 0·17 ng/ml vs. 0·93 ± 0·23 ng/ml, P < 0·001 and P < 0·05 vs. control group, respectively), and in patients with carotid plaques more than in patients without carotid plaques (P < 0·001). Multiple stepwise regression analysis revealed that only LDL‐cholesterol correlated with visfatin, and visfatin independently correlated with max IMT in the patients with MetS. A log visfatin > 1·08 ng/ml had 70% sensitivity and 67% specificity for detecting patients with carotid plaques. Conclusions/interpretation Our results showed that serum visfatin was increased in patients with MetS, especially in those with carotid plaques. Visfatin may be an inflammatory marker of MetS.     

Concentrations of the acute phase reactants high-sensitive C-reactive protein and YKL-40 and of interleukin-6 before and after treatment in patients with acromegaly and growth hormone deficiency

Background Acromegaly is accompanied by increased cardiovascular mortality and a cluster of proatherogenic risk factors. In the general population, ischaemic heart disease (IHD) is associated with elevated levels of inflammatory markers. The acute phase reactant (APR) C‐reactive protein (CRP) has been reported to be reduced in acromegaly and increase after treatment, suggesting that excess of GH/IGF‐I could have anti‐inflammatory effects. This is in accordance with results obtained in patients with growth hormone deficiency (GHD), where increased levels of CRP have been reported. Objective To investigate the hypothesis that the GH/IGF‐I system is a suppressive regulator of inflammatory processes. Subjects and methods Twenty‐one acromegalic patients and 19 GH‐deficient patients were studied. The two APRs CRP and YKL‐40 and the proinflammatory cytokine interleukin‐6 (IL‐6) were measured before and after treatment and in healthy matched controls. Results In acromegalic patients, serum concentrations of high‐sensitive CRP (hsCRP) and YKL‐40 were reduced compared to controls (P < 0·001) and increased (P < 0·001) after treatment, together with IL‐6 (P = 0·021), to levels comparable with controls. Pretreatment serum YKL‐40 and IL‐6 showed a significant inverse correlation with IGF‐I and GH. In GH‐deficient patients, hsCRP and YKL‐40 were elevated compared to controls (P = 0·001 and P = 0·048). During treatment, levels of both APRs showed a trend towards a decrease (P = 0·087 and P = 0·060), and after treatment, levels of YKL‐40 no longer differed from that of controls. Serum IL‐6 was not different from controls and did not change during GH treatment. Conclusion The results point to the possibility of a relationship between GH disturbances and inflammatory processes.     

Resistin gene variation is associated with systemic inflammation but not plasma adipokine levels, metabolic syndrome or coronary atherosclerosis in nondiabetic Caucasians

Objective Resistin causes insulin resistance and diabetes in mice whereas in humans it is linked to inflammation and atherosclerosis. Few human genetic studies of resistin in inflammation and atherosclerosis have been performed. We hypothesized that the –420C>G putative gain‐of‐function resistin variant would be associated with inflammatory markers and atherosclerosis but not with metabolic syndrome or adipokines in humans. Design and methods We examined the association of three resistin polymorphisms, –852A>G, –420C>G and +157C>T, and related haplotypes with plasma resistin, cytokines, C‐reactive protein (CRP), adipokines, plasma lipoproteins, metabolic syndrome and coronary artery calcification (CAC) in nondiabetic Caucasians (n = 851). Results Resistin levels were higher, dose‐dependently, with the –420G allele (CC 5·9 ± 2·7 ng/ml, GC 6·5 ± 4·0 ng/ml and GG 7·2 ± 4·8 ng/ml, trend P = 0·04) after age and gender adjustment [fold higher for GC + GG vs. CC; 1·07 (1·00–1·15), P < 0·05)]. The –852A>G single nucleotide polymorphism (SNP) was associated with higher soluble tumour necrosis factor‐receptor 2 (sol‐TNFR2) levels in fully adjusted models [1·06 (95% CI 1·01–1·11), P = 0·01)]. The estimated resistin haplotype (GGT) was associated with sol‐TNFR2 (P = 0·04) and the AGT haplotype was related to CRP (P = 0·04) in the fully adjusted models. Resistin SNPs and haplotypes were not associated with body mass index (BMI), fasting glucose, insulin resistance, metabolic syndrome, adipokines or CAC scores. Conclusions Despite modest associations with plasma resistin and inflammatory biomarkers, resistin 5′ variants were not associated with metabolic parameters or coronary calcification. This suggests that resistin is an inflammatory cytokine in humans but has little influence on adiposity, metabolic syndrome or atherosclerosis.     

High plasma C-reactive protein (CRP) is related to low paraoxonase-I (PON-I) activity independently of high leptin and low adiponectin in type 2 diabetes mellitus

Objectives In type 2 diabetes mellitus, circulating C‐reactive protein (CRP) is increased, whereas the high density lipoprotein (HDL)‐associated, anti‐oxidative and anti‐inflammatory enzyme, paraoxonase‐I, is decreased. Both high CRP and low paraoxonase‐I activity may predict cardiovascular disease. It is unknown whether lower paraoxonase‐I activity contributes to higher CRP levels in diabetes. In type 2 diabetic and control subjects, we determined the relationship of CRP with paraoxonase‐I when taking account of plasma levels of pro‐ and anti‐inflammatory adipokines. Design and patients In 81 type 2 diabetic patients and 89 control subjects, plasma high‐sensitive CRP, serum paraoxonase‐I activity (arylesterase activity, assayed as the rate of hydrolysis of phenyl acetate into phenol), plasma leptin, adiponectin, resistin and lipids were determined. Results Body mass index (BMI), waist, insulin resistance, triglycerides, CRP, leptin and resistin levels were higher (P < 0·05 to P < 0·001), whereas HDL cholesterol, paraoxonase‐I activity and adiponectin levels were lower (P = 0·02 to P < 0·001) in diabetic compared to control subjects. Multiple linear regression analysis demonstrated that, after controlling for age and gender, CRP was inversely related to paraoxonase‐I activity (β = –0·15, P = 0·028) and adiponectin (β = –0·18, P = 0·009), and positively to leptin (β = 0·33, P < 0·001) and BMI (β = 0·22, P = 0·007), independently of the diabetic state (or of fasting glucose or HbA1c), insulin resistance and lipids (P > 0·20 for all). Conclusions low paraoxonase‐I activity is related to higher CRP, independently of adipokines, as well as of obesity and lipids. Low paraoxonase‐I activity in type 2 diabetes mellitus may contribute to increased cardiovascular risk via an effect on enhanced systemic low‐grade inflammation.     

Serum B-cell maturation antigen is elevated in multiple myeloma and correlates with disease status and survival

Although TNFRSF17 (also designated as B‐cell maturation antigen (BCMA)) is expressed on tumour cells in B‐cell malignancies, it has not been found in serum. The present study found that BCMA concentrations were higher in the supernatants of cultured bone marrow mononuclear cells from multiple myeloma (MM) patients than in healthy subjects. Serum BCMA levels were measured in samples from MM patients (n = 209), monoclonal gammopathy of undetermined significance (MGUS) individuals (n = 23) and age‐matched controls (n = 40). BCMA was detected in the serum of untreated MM patients (n = 50) and levels were higher than in MGUS patients (P = 0·0157) and healthy subjects (P < 0·0001). Serum BCMA levels were higher among patients with progressive disease (n = 80) compared to those with responsive disease (n = 79; P = 0·0038). Among all MM patients, overall survival was shorter among patients whose serum BCMA levels were above the median (P = 0·001). We also demonstrated that sera from mice with human MM xenografts contained human BCMA, and levels correlated with the change in tumour volume in response to melphalan or cyclophosphamide with bortezomib. These results suggest that serum BCMA levels may be a new biomarker for monitoring disease status and overall survival of MM patients.     

Inflammatory markers and visceral fat are inversely associated with maximal oxygen consumption in women with polycystic ovary syndrome (PCOS)

Background We investigated whether several different inflammatory markers including C‐reactive protein (CRP) and fibrinogen and white blood cells (WBCs) count, are associated with maximal oxygen consumption (VO_2max) in women with polycystic ovary syndrome (PCOS). Methods In PCOS women (n = 124, 24·1 ± 4·5 year‐old) VO_2max was measured during symptom‐limited cardiopulmonary exercise test. Abdominal fat distribution was determined by ultrasound. Physical activity level was assessed by a standardized questionnaire. CRP was measured by immunoassays, fibrinogen by the Clauss method, and WBCs count with a Coulter counter. Results Pearson's analysis showed a significant correlation between VO_2max and logCRP (r = –0·437, P < 0·001), fibrinogen (r = –0·479, P < 0·001), and WBCs count (r = –0·438, P < 0·001). Multivariable logistic regression model showed that age (β = –0·127, P = 0·005), AUC_INS (β = –0·335, P < 0·001), HDL‐C (β = 0·390, P < 0·001), physical activity score (β = 0·238, P = 0·002), visceral fat (β =–0·184), P = 0·023), FAI (β = –0·291, P = 0·028); CRP (β = –0·216, P = 0·011), fibrinogen (β = –0·113, P = 0·008) and WBCs count (β = –0·177, P < 0·001) were significantly associated with VO_2max. Conclusions Acute‐phase reactants, such as CRP and fibrinogen, and WBCs count were independently and inversely associated with a direct measure of cardiorespiratory fitness (VO_2max) in women with PCOS, even after adjustment for physical activity level and other potential confounding factors. These findings add to the growing body of evidence linking inflammation to cardiorespiratory fitness in PCOS women.     

Relation between plasma fibroblast growth factor-23, serum fetuin-A levels and coronary artery calcification evaluated by multislice computed tomography in patients with normal kidney function

Objective To examine the correlation of plasma fibroblast growth factor (FGF)‐23 and serum fetuin A levels with the coronary artery calcification score (CACS) in patients with normal kidney function. Background Vascular calcification is an active process that may be aggravated by hyperphosphataemia and hypercalcaemia. FGF‐23 and human fetuin‐A have been associated with calcifying arteriosclerosis in renal failure. Plasma FGF‐23 was identified as an independent factor negatively associated with peripheral vascular calcification. Fetuin‐A acts as a systemic inhibitor of ectopic calcification in dialysis patients and can be correlated to the survival of these patients. Very few data exists on the role of FGF‐23 and fetuin‐A in coronary calcification of patients without impaired kidney function. Materials and methods Sixty‐four patients, 21 females and 43 males, were subjected to 64‐slice coronary computed tomography (CT) to evaluate coronary artery calcification (CAC). Plasma intact FGF‐23 was determined by ELISA. Serum fetuin‐A concentration were evaluated nephelometrically. Results Mean plasma FGF‐23 level was 20·4 ± 9·1 pg/ml and serum fetuin‐A was 0·46 ± 0·09 g/l. There was no correlation between FGF‐23 (P = 0·777) and fetuin‐A (P = 0·767) levels and the CACS. No correlation was found between the presence of noncalcified plaques and coronary artery stenosis (CAS) ≥  50%, and FGF‐23 (P = 0·313 and P = 0·775) and fetuin‐A levels (P = 0·601 and P = 0·659). Conclusion Plasma intact FGF‐23 and serum fetuin‐A concentration do not correlate with the CACS, the grade of stenosis or presence of noncalcified plaques of the coronary arteries in patients with normal kidney function.     

Retinol-binding protein in nonobese women with polycystic ovary syndrome

Objective Although polycystic ovary syndrome (PCOS) is frequently associated with insulin resistance, cardiovascular disease and various metabolic diseases, the mechanisms linking PCOS to metabolic changes are not fully understood. Retinol‐binding protein (RBP) was recently reported as an adipocytokine that may link insulin resistance and lipid metabolism. The aim of this study was to investigate the potential role of RBP in women with PCOS. Research design and methods Fifty women with PCOS and 40 healthy women, all of whom were age‐ and weight‐matched, were studied. Blood was obtained to determine RBP levels as well as metabolic and hormonal parameters, and the homeostasis model assessment of insulin resistance (HOMA‐IR) was calculated for each subject. Results The RBP levels were higher (P < 0·01) in women with PCOS after adjusting for age, body mass index (BMI), mean blood pressure, triglyceride (TG), high density lipoprotein (HDL)‐cholesterol, low density lipoprotein (LDL)‐cholesterol, fasting glucose, fasting insulin, estimated glomerular filtration rate (GFR), LH/FSH, total testosterone and SHBG levels. PCOS status was the strongest predictor of elevated RBP levels. In both the PCOS and control groups, RBP levels were significantly correlated with HOMA‐IR (P = 0·03 in the PCOS group; P = 0·01 in controls). In addition, RBP levels were significantly correlated with total cholesterol, LDL‐cholesterol and TG levels in PCOS (P < 0·01, P < 0·01 and P = 0·01, respectively). Conclusions Higher RBP levels in the PCOS group, when compared to the non‐PCOS group, were observed, and this difference may play a role in the pathophysiology found in women with PCOS. Further studies are needed to clarify the role of RBP in these women.     

Frequency and characteristics of TBII-seronegative patients in a population with untreated Graves' hyperthyroidism: a prospective study

Objective It is claimed that second generation thyrotropin‐binding inhibitory immunoglobulin (TBII) assays have a very high sensitivity for the diagnosis of Graves’ hyperthyroidism (GH). However, studies evaluating the accuracy of TBII have been retrospective in nature and/or GH had not been diagnosed independently of TBII. The aim of the present study, therefore, was to prospectively evaluate the frequency and characteristics of TBII‐seronegative patients in a population of untreated GH diagnosed independent of serum TBII. Design Prospective multicentre observational study. Patients A total of 259 consecutive untreated patients with a first episode of GH, diagnosed independent of serum TBII. TBII levels were measured by second generation assay and correlated to thyroid function, clinical characteristics and exposure to environmental factors. Results Serum TBII was positive in 245 (94·6%) patients and negative (< 2 IU/l) in 14 (5·4%) patients. TBII‐seronegative patients had lower fT4 (median 42·5 vs. 53·9 pmol/l, P = 0·02), T3 (median 3·55 vs. 4·90 nmol/l, P < 0·01) and fT3‐index (median 4·30 vs. 6·27, P < 0·01) compared to TBII‐seropositive patients. None of the TBII‐seronegative patients had TSH‐receptor activating mutations, Graves’ orbitopathy or pretibial myxedema. Serum TBII was positively correlated to free T3 (fT3)‐index and free T4 (fT4)‐index (P < 0·01), goitre size (P < 0·01) and the prevalence of Graves’ orbitopathy (P < 0·01). There were no significant differences between TBII‐seropositive and TBII‐seronegative patients in environmental factors. Conclusion The prevalence of TBII‐seronegativity in untreated patients with GH is 5·4% using a second generation assay. TBII‐seronegative patients have biochemically less severe thyrotoxicosis and no Graves’ orbitopathy. TBII‐seronegative and TBII‐seropositive patients apparently belong to the same population of GH, albeit the severity of the autoimmune attack is less in TBII‐seronegative patients.     

Increased epicardial adipose tissue (EAT) volume in type 2 diabetes mellitus and association with metabolic syndrome and severity of coronary atherosclerosis

Objective Epicardial adipose tissue (EAT) is a part of visceral fat deposited around the heart between the pericardium and myocardium along the distribution of coronary arteries. EAT thickness is reported to be associated with coronary atherosclerosis; however, no study has measured EAT volume in patients with type 2 diabetes or investigate its association with coronary artery disease. Design A hospital‐based case control study. Patients A total of 49 patients with type 2 diabetes mellitus (T2DM) and 78 nondiabetic controls were studied. Measurements Cardiac multislice computed tomography was used to measure EAT volume, Gensini score, coronary artery calcium score and, coronary lesions. The relationships between EAT volume, markers of coronary atherosclerosis and anthropometric and biochemical parameters of metabolic syndrome (MetS) were investigated. Results EAT volume was significantly higher in patients with T2DM than in nondiabetic subjects (166·1 ± 60·6 cm³ vs. 123·4 ± 41·8 cm³, P < 0·0001). Logistic regression analysis revealed independent and significant associations between EAT and diabetic status. EAT volume was significantly associated with components of MetS (BMI, waist circumference, fasting serum glucose, total cholesterol, HDL‐cholesterol, and triglycerides levels), Gensini score, coronary lesions, coronary disease and coronary calcium scores. Univariate, multivariate and trend analyses confirmed that EAT volume was associated with MetS component clustering and the coronary atherosclerosis index. Conclusions The analytical results indicate that EAT volume is increased in T2DM patients and is associated with unfavourable components of MetS and coronary atherosclerosis. The close anatomical relationship between EAT and the coronary arteries, combined with other evidence indicating that EAT is a biologically active adipokine‐secreting tissue, suggest that EAT participates in the pathogenesis of diabetic coronary atherosclerosis.     

Significant inverse relationship between serum free T4 concentration and body mass index in euthyroid subjects: differences between smokers and nonsmokers

Objective There are conflicting data regarding the relationship between thyroid function and body mass index (BMI) in euthyroid subjects, and it is uncertain whether tobacco smoking modifies this relationship. The objective of this study was to examine the relationships between thyroid function, BMI and smoking in euthyroid subjects. Design Linear regression models were used to examine the relationships between serum free T4, serum TSH, BMI and smoking in a cross‐sectional, community‐based sample of 1853 euthyroid subjects in Busselton, Western Australia. Results There was a significant negative relationship between free T4 and BMI: after adjustment for age and sex, each 1 pmol/l increase in free T4 was associated with a decrease in BMI of 0·12 kg/m² (95% CI 0·06, 0·18; P < 0·001). The mean BMI ± SD of subjects in the highest quintile of free T4 concentration was 24·4 ± 3·5 kg/m², compared with 26·1 ± 3·8 kg/m² for the lowest quintile. The relationship between free T4 and BMI was statistically significant (adjusted for age and sex) in subjects who had never smoked (P = 0·001) and former smokers (P = 0·011), but not in current smokers (P = 0·77). There was no significant relationship between TSH and BMI: after adjustment for age and sex, each 1 mU/l increase in TSH was associated with an increase in BMI of 0·08 kg/m² (95% CI –0·16, 0·32; P = 0·53). Conclusions In euthyroid subjects, small differences in free T4 are associated with differences in BMI. This relationship is not present in current smokers. We speculate that this may be relevant to weight changes associated with smoking cessation.     

Metformin increases fasting plasma peptide tyrosine tyrosine (PYY) in women with polycystic ovarian syndrome (PCOS)

Objective The beneficial effects of metformin in patients with type 2 diabetes mellitus (T2DM) and polycystic ovarian syndrome (PCOS) are thought to be in part due to weight reduction. However, the mechanisms by which metformin causes weight loss are unclear. We sought to determine whether circulating levels of the anorectic gut hormone peptide tyrosine tyrosine (PYY) show any correlation with metformin‐induced weight loss. Design and patients We examined the acute effects of orally administrated metformin on fasting PYY levels in eight healthy normal‐weight female subjects. Subsequently, we evaluated the effects of 6 months metformin treatment on fasting PYY levels and anthropometric measurements in 20 women with PCOS. Results In normal‐weight females 10 days’ metformin treatment increased fasting PYY levels (P < 0·01). Similarly, in PCOS subjects metformin treatment increased fasting PYY concentrations (P < 0·05). In both groups a marked variation in PYY increase in response to metformin was observed. Long‐term metformin treatment was associated with improvements in weight (P < 0·05), BMI (P < 0·05), fasting glucose (P < 0·05) and menstrual frequency (P < 0·01). Interestingly, change in PYY levels were correlated with change in waist circumference (r = 0·55, P < 0·05). Conclusions Acute and chronic oral metformin administration increase fasting PYY levels and may contribute to metformin's weight loss effect. Further studies are now required to clarify whether changes in circulating PYY levels in response to metformin treatment can be used to predict which patients will subsequently lose weight long‐term and gain cycle restoration.     

Seasonal variation in serum concentrations of reproductive hormones and urinary excretion of 6-sulfatoxymelatonin in men living north and south of the Arctic Circle: a longitudinal study

Objective Seasonal variation in photoperiod or temperature may influence human reproductive biology. The present study evaluated whether seasonal changes occurred in the levels of reproductive hormones and the major melatonin metabolite, 6‐sulfatoxymelatonin (aMT6s), in populations exposed to extreme variation in photoperiod and temperature. Design Two separate cohorts of Norwegian men were recruited from the general population in either of two locations: Tromsø (69·5°N, n = 92) or Oslo (60°N, n = 112), located north and south of the Arctic Circle (66·5°N), respectively. Measurements Four blood and 12‐h overnight urine samples were obtained on separate occasions over a 12‐month period, including during the photoperiod maximum and minimum. Serum concentrations of FSH, LH, testosterone (T), oestradiol (E₂), SHBG and the urinary excretion of aMT6s were assessed. Results Statistical analysis using generalized estimating equations indicated that LH levels were lowest during early winter in both locations (both P = 0·01). In Tromsø, free T and E₂ concentrations peaked during early winter (P = 0·02 and 0·003, respectively). In Oslo, free T levels were lowest during early winter (P = 0·06) whereas E₂ levels were lowest during late summer (P < 0·001). Urinary aMT6s concentrations were lowest during early summer in Tromsø and Oslo. Concentrations peaked during early winter in Tromsø (P < 0·001) and during late winter in Oslo (P < 0·001). Conclusions LH levels exhibited similar changes in both locations, whereas the patterns of changes of the sex steroid concentrations differed, possibly indicating different underlying mechanisms. Excretion of aMT6s was lowest during early summer in both locations, indicating that the long natural photoperiod was sufficient to cause suppression of melatonin secretion. Whether these changes have any biological significance remains uncertain.     

Acute hyperinsulinaemia and hyperlipidaemia modify circulating adiponectin and its oligomers

Objective Obesity and insulin resistance are associated with low adiponectin levels, although adiponectin is exclusively expressed in white adipose tissue. The mechanism beyond that paradox is not entirely clear, although insulin itself may reduce circulating adiponectin levels. However, obesity is also associated with hyperlipidaemia and the effects of free fatty acids (FFAs) and triglycerides (TG) on circulating adiponectin levels have not yet been investigated. Materials and methods We analysed the effect of an acute and euglycaemic elevation of insulin on adiponectin oligomers in 23 healthy individuals. In a subgroup including 11 healthy men, FFAs and TG were acutely elevated by infusion of heparin/lipids over 120 min. Again the effect on circulating adiponectin and its oligomers was investigated. Adiponectin was determined by ELISA, oligomers were detected by nondenaturating Western blot. Results Acute hyperinsulinaemia resulted in a significant reduction of total adiponectin to 7·74 ± 0·98 µg/ml (P = 0·004). High molecular weight (HMW) adiponectin did not change (0·80 ± 0·12 to 0·81 ± 0·14 µg/ml; P = 0·887), whereas MMW adiponectin decreased from 4·30 ± 0·51 to 3·78 ± 0·48 µg/ml (P = 0·005) and LMW adiponectin from 3·63 ± 0·42 to 3·15 ± 0·46 µg/ml (P = 0·048). Interestingly, heparin/lipid infusion also reduced circulating adiponectin levels (P = 0·001), which was primarily the result of reduced MMW adiponectin (P = 0·004), whereas LMW and HMW were not significantly affected. Conclusions The presented data suggest that both, hyperinsulinaemia and hyperlipidaemia, may contribute to low adiponectin levels in states of obesity.