Weight loss reduces adipose tissue cathepsin S and its circulating levels in morbidly obese women

CONTEXT: Human adipose tissue produces several adipokines, including the newly identified protein cathepsin S (CTSS), a cysteine protease involved in the pathogenesis of atherosclerosis. Obesity is characterized by high levels of CTSS in the circulation and in sc white adipose tissue (scWAT). OBJECTIVE: We investigated the effect of surgery-induced weight loss on circulating CTSS and its protein expression in scWAT. DESIGN: Fifty morbidly obese women before and 3 months after surgery and 10 healthy lean women were studied. We analyzed the relationships between circulating CTSS and clinical and biological parameters. Immunohistochemistry of the CTSS protein variations in scWAT was performed. RESULTS: Weight loss decreased by 42% (P < 0.0001) the circulating CTSS levels, which correlated with changes in body weight (P = 0.03). We observed a significant decrease in CTSS enzymatic activity by 25% after weight loss (P = 0.001). Adipose tissue CTSS content was reduced by 30% (P = 0.002) after surgery. The variations in CTSS expression in scWAT after surgery correlated with changes in circulating CTSS serum levels (P = 0.03). Most of the correlations between CTSS and clinical and biological parameters disappeared after adjustment for body mass index, emphasizing the strong link between CTSS and corpulence in humans. CONCLUSIONS: Changes in CTSS scWAT might contribute to serum variations in CTSS during weight loss. The decrease in CTSS concentrations in the circulation may contribute to vascular improvement in obese subjects after weight loss.     

TNFalpha expression of subcutaneous adipose tissue in obese and morbid obese females: relationship to adipocyte LPL activity and leptin synthesis

INTRODUCTION: Tumor necrosis factor (TNFalpha) has been invoked as an adipostat. Accordingly, the adipose tissue expression of TNFalpha has been shown to be proportional to the degree of adiposity. The regulatory role of TNFalpha in obesity may be controlled by several mechanisms. These include the inhibitory effect on LPL activity, the mediation on glucose homeostasis or the effect on leptin. To assess the role of TNFalpha in obesity we measured adipocyte TNFalpha expression in 96 females with a wide range of adiposity and with or without type 2 diabetes. We analysed the relationship between TNFalpha expression, adipocyte LPL activity, insulin resistance and leptin in this population. RESULTS: The TNFalpha and leptin expression of the adipose tissue in obese and morbid obese patients were significantly higher than in controls. Obese and morbid obese patients had slightly higher levels of LPL activity, but these differences were not significant. We observed a significant relationship between adipose TNFalpha expression and body mass index (r=0.35, P<0.001). TNFalpha expression was negatively related to LPL activity (r=-0.28, P<0.05) and positively related to leptin expression (r=0.35, P<0.001). CONCLUSION: Our results indicate that obese women, even those with morbid obesity, over-express TNFalpha in subcutaneous adipose tissue in proportion to the magnitude of the fat depot and independently of the presence of type 2 diabetes. The TNFalpha system may be a homeostatic mechanism that prevents further fat deposition by regulating LPL activity and leptin production.     

Spontaneous diurnal thyrotropin secretion is enhanced in proportion to circulating leptin in obese premenopausal women

CONTEXT: Recent evidence implicates leptin as an important modulator of thyroid axis activity. OBJECTIVE: The objective of this study was to study spontaneous 24-h TSH secretion and 24-h circulating leptin concentrations in obese and lean women. DESIGN: This was a prospective parallel study (2004). SETTING: This study was conducted at the Clinical Research Center (Leiden University Medical Center, Leiden, The Netherlands). PARTICIPANTS: Twelve healthy obese premenopausal women (body mass index, 33.2 +/- 0.9 kg/m2) and 11 lean controls (body mass index, 21.4 +/- 0.5 kg/m2) were studied in the follicular phase of their menstrual cycle. INTERVENTION(S): There were no interventions in this study. MAIN OUTCOME MEASURE(S): Spontaneous 24-h TSH concentrations (10-min time intervals) and secretion were calculated using waveform-independent deconvolution technique (pulse). Twenty-four-hour circulating leptin concentrations (20-min time intervals) were measured. RESULTS: Mean TSH concentration (obese, 1.9 +/- 0.2 vs. lean, 1.1 +/- 0.1 mU/liter; P = 0.009) and secretion rate (obese, 43.4 +/- 5.5 vs. lean, 26.1 +/- 2.2 mU/liter distribution volume.24 h; P = 0.011) were substantially enhanced in obesity, whereas the fasting free T4 (fT4) concentrations were similar (fT4 in obese, 15.4 +/- 1.5 vs. in lean, 16.4 +/- 1.5 pmol/liter; P = 0.147). TSH secretion was positively related to 24-h leptin concentrations (r2= 0.31; P = 0.007). CONCLUSIONS: TSH release is enhanced in the face of normal plasma fT4 concentrations in obese premenopausal women, and hyperleptinemia may well be involved in this neuroendocrine alteration.     

Secretion of free and protein-bound leptin from subcutaneous adipose tissue of lean and obese women

Leptin circulates as a free (FL) and a protein-bound (BL) form, with the soluble leptin receptor (LR) as an important binding compound. Here we measured these components of leptin in serum and in the incubation medium of sc adipose tissue in healthy lean (n = 10) and obese (n = 13) female subjects using recently developed specific RIA systems. In addition, immunostaining for FL, BL, and LR in adipose tissue was performed. Serum FL levels were increased in the obese subjects (P < 0.0001), whereas BL and LR concentrations in serum of lean and obese subjects were similar. Both FL and BL were secreted from human preadipocytes and increased in parallel to the differentiation of the cells. In sc fat cell explants LR antibodies predominantly stained the fat cell membrane, whereas FL and BL antibodies revealed intracytoplasmatic adipocyte staining. The release of FL, BL, and LR from adipose tissue was increased in obese compared with lean subjects (P < 0.005 for FL; P < 0.02 for BL, and P < 0.01 for LR). In summary, fat cells are capable of releasing not only FL, but also BL and LR.     

Insulin resistance is associated with a modest increase in inflammation in subcutaneous adipose tissue of moderately obese women

Aims/hypothesis  We have previously described differences in adipose cell size distribution and expression of genes related to adipocyte differentiation in subcutaneous abdominal fat obtained from insulin-sensitive (IS) and -resistant (IR) persons, matched for degree of moderate obesity. To determine whether other biological properties also differ between IR and IS obese individuals, we quantified markers of inflammatory activity in adipose tissue from overweight IR and IS individuals. Methods  Subcutaneous abdominal tissue was obtained from moderately obese women, divided into IR (n = 14) and IS (n = 19) subgroups by determining their steady-state plasma glucose (SSPG) concentrations during the insulin suppression test. Inflammatory activity was assessed by comparing expression of nine relevant genes and by immunohistochemical quantification of CD45- and CD68-containing cells. Results  SSPG concentrations were approximately threefold higher in IR than in IS individuals. Expression levels of CD68, EMR1, IL8, IL6 and MCP/CCL2 mRNAs were modestly but significantly increased (p < 0.05) in IR compared with IS participants. Results of immunohistochemical staining were consistent with gene expression data, demonstrating modest differences between IR and IS individuals. Crown-like structures, in which macrophages surround single adipocytes, were rarely seen in tissue from either subgroup. Conclusions/interpretation  A modest increase in inflammatory activity was seen in subcutaneous adipose tissue from IR compared with equally obese IS individuals. Together with previous evidence of impaired adipose cell differentiation in IR vs equally obese individuals, it appears that at least two biological processes in subcutaneous adipose tissue characterize the insulin-resistant state independent of obesity per se. Trial registration ClinicalTrials.gov NCT00285844 Funding The study was funded by grants from the National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and by the NIDDK Intramural Research Program.     

Effect of aerobic training on plasma levels and subcutaneous abdominal adipose tissue gene expression of adiponectin, leptin, interleukin 6, and tumor necrosis factor alpha in obese women

Adipocytokines secreted by adipose tissue are suggested to play a role in the development of obesity-related complications. Regular aerobic exercise has been shown to reduce the risk of metabolic complications in obese subjects. The aim of this study was to investigate the effect of aerobic training on gene expression in subcutaneous abdominal adipose tissue (SCAAT) and on plasma levels of several adipocytokines in obese women. Twenty-five obese sedentary premenopausal women (body mass index, 32.18 +/- 3.17 kg/m(2)) underwent a 12-week aerobic exercise program, with a frequency of 5 d/wk and intensity corresponding to 50% of individual maximal oxygen consumption (V(.-)(O(2)max)) consisting of 2 sessions per week of supervised aerobic exercise and 3 sessions per week of home-based exercise on a bicycle ergometer. Before and after the aerobic training, (V(.-)(O(2)max)) and body composition were measured and plasma and SCAAT biopsy samples (in a subgroup of 8 subjects) were obtained for determination of plasma and messenger RNA levels of adipocytokines (leptin, adiponectin, interleukin 6, tumor necrosis factor alpha). The aerobic training resulted in an increase of subjects' V o(2)max by 12.8% (24.6 +/- 3.9 vs 27.7 +/- 4.8 mL x min(-1) x kg(-1), P < .05). Body weight and fat mass were reduced by 5.9% (88.5 +/- 8.2 vs 83.3 +/- 7.7 kg, P < .001) and 6.4% (38.8 +/- 4.2% vs 36.3 +/- 4.6%, P < .001), respectively, and the revised QUantitative Insulin sensitivity ChecK Index (QUICKI) increased (0.43 +/- 0.06 vs 0.48 +/- 0.06, P < .05) during the aerobic training. No aerobic training-induced changes in messenger RNA levels of the investigated genes in SCAAT were observed. A decrease of plasma leptin (24.3 +/- 8.7 vs 18.1 +/- 8.3 ng/mL, P < .05) was detected, whereas plasma levels of other cytokines remained unchanged. In moderately obese females, 3 months' aerobic training did not promote changes in the adipose tissue gene expression or plasma levels of the adipocytokines (except for leptin) involved in a regulation of lipid and carbohydrate metabolism.     

Systemic inflammation is related to coronary microvascular dysfunction in obese patients without obstructive coronary disease

Background and AimsObesity, systemic inflammation and changes in the heart functions are associated with increased cardiovascular risk. This study aimed to investigate coronary microvascular dysfunction as an early marker of atherosclerosis in obese patients without any evidence of cardiovascular disease.Methods and results86 obese subjects (aged 44 ± 12 years, body mass index (BMI) 41 ± 8 kg m⁻²), without evidence of heart disease, and 48 lean controls were studied using transthoracic Doppler echocardiography for detecting coronary flow reserve (CFR). A value of CFR ≤ 2.5 was considered abnormal. We measured interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α) and adiponectin in all patients. Patients with abnormal CFR underwent coronary multislice computed tomography (MSCT) in order to exclude an epicardial stenosis. CFR in obese subjects was lower than in lean subjects (3.2 ± 0.8 vs. 3.7 ± 0.7, p = 0.02) and was abnormal in 27 (31%) obese patients and in one (2%) control (p < 0.0001). All subjects with abnormal CFR showed no coronary stenosis at MSCT. At multivariable analysis, IL-6 and TNF-α were the only determinants of CFR (p < 0.02 and p < 0.02, respectively). At multivariable logistic regression analysis, IL-6 and TNF-α were the only determinants of CFR ≤ 2.5 (p < 0.03 and p < 0.03, respectively).ConclusionsCFR is often reduced in obese subjects without clinical evidence of heart disease, suggesting a coronary microvascular impairment. This microvascular dysfunction seems to be related to a chronic inflammation mediated by adipocytokines. Our findings may explain the increased cardiovascular risk in obesity, independently of BMI.     

Increased systemic and adipose tissue inflammation differentiates obese women with T2DM from obese women with normal glucose tolerance

IntroductionObesity is strongly related to type-2 diabetes (T2DM), but there is a subset of obese individuals that remains relatively insulin sensitive and metabolically healthy. This study determined to what extent differences in metabolic health in obese women are associated with differences in adipose tissue and/or systemic inflammation.MethodsThe subject group consisted of age comparable lean (n = 12) and obese women either with T2DM (n = 28) or normal glucose tolerance (NGT; n = 26). Number of crown like structures (CLS) and adipocyte size were measured in subcutaneous and visceral adipose tissue of the obese women. Circulating cytokine and free fatty acid (FFA) levels, as well as number and activation status of peripheral leukocytes were determined.ResultsObese T2DM subjects showed higher circulating levels of IL-6, FFA and glycerol as compared to obese NGT subjects. Obese T2DM subjects had higher absolute numbers of peripheral leukocytes which were mainly due to an increase of T helper cells. Activation status of circulating cytotoxic T (CD8+CD25 +) and B (CD19+CD38 +) cells was significantly increased in obese NGT subjects as compared to lean but was not different between the two obese groups. Subcutaneous adipose tissue of obese T2DM subjects contained more CLS than adipose tissue of obese NGT subjects.ConclusionObese T2DM subjects show higher FFA levels and adipose tissue macrophage infiltration in addition to higher levels of circulating IL-6 and numbers of CD4 + T cells than obese NGT subjects. Hence, obese T2DM subjects show a higher extent of inflammation at both the systemic and adipose tissue level.     

Elevated levels of interleukin 6 are reduced in serum and subcutaneous adipose tissue of obese women after weight loss

The aim of this study was to investigate the potential role of adipose cytokines in the obesity-associated insulin resistance. To that end, we compared: 1) serum concentrations of interleukin 6 (IL-6), tumor necrosis factor alpha (TNFalpha), and leptin in eight healthy lean control females and in android obese female without (n = 14) and with (n = 7) type 2 diabetes; and 2) the levels of these cytokines both in serum and in sc adipose tissue in the 14 obese nondiabetic women before and after 3 weeks of a very low-calorie diet (VLCD). As compared with lean controls, obese nondiabetic and diabetic patients were more insulin resistant and presented increased values for leptin, IL-6, TNFalpha, and C-reactive protein. In the whole group, IL-6 values were more closely related to the parameters evaluating insulin resistance than leptin or TNFalpha values. VLCD resulted in weight loss and decreased body fat mass (approximately 3 kg). Insulin sensitivity was improved with no significant change in both serum and adipose tissue TNFalpha levels. In contrast, VLCD induced significant decreases in IL-6 and leptin levels in both adipose tissue and serum. These results suggest that, as for leptin, circulating IL-6 concentrations reflect, at least in part, adipose tissue production. The reduced production and serum concentrations after weight loss could play a role in the improved sensitivity to insulin observed in these patients.     

Epicardial adipose tissue is related to cardiac function in elderly women,but not in men

Background and aim

Epicardial adipose tissue (EAT) is easily quantifiable visceral adipose tissue that is closely associated with cardiometabolic disease including heart failure with preserved left ventricular (LV) ejection fraction. As body fat distribution and metabolism are different between men and women, we evaluated the sex difference in EAT thickness and its relationship to cardiac function.

Sexual dimorphism in circulating leptin concentrations is not accounted for by differences in adipose tissue distribution

BACKGROUND: Circulating concentrations of leptin normalized to total adipose tissue mass are significantly greater in females than in males. Rates of leptin expression (per gram of adipose tissue) are significantly greater in subcutaneous (SAT) than visceral (VAT) adipose tissue and the relative amount of fat stored as SAT vs VAT is significantly greater in pre-menopausal females than in males. Gender-related differences in the relative amounts of SAT and VAT may account for the greater circulating leptin concentration relative to fat-mass in females than males. METHODS: We examined body composition and anatomic fat distribution by dual energy X-ray-absorptiometry (DEXA) and magnetic resonance imaging (MRI), and post-absorptive circulating concentrations of leptin and insulin in 58 subjects (26 females, 32 males). Stepwise multiple linear regression analyses, treating gender as a dichotomous variable, were performed to determine inter-relationships among leptin concentrations and insulin concentrations, VAT and SAT. RESULTS: Body composition by DEXA and MRI were highly correlated (r(2)=0.97, P<0.0001). There were significant gender effects on leptin/total fat mass (males, 0.17+/-0.01 ng/ml/kg; females, 0.49+/-0.05 ng/ml/kg; P<0.0001) and relative amounts of fat in SAT and VAT depots (ratio of SAT/VAT; males, 12.3+/-1.5; females, 32.9+/-3.2; P<0.0001). Circulating leptin concentration was significantly correlated with insulin concentration (P=0.001), SAT (P<0.0001) and gender (P=0.033). Circulating concentrations of insulin were significantly correlated with VAT, but not SAT, in males and with SAT, but not VAT, in females. CONCLUSIONS: The sexual dimorphism in the relationship between leptin and adipose tissue mass cannot be explained by differences in the relative amounts of VAT and SAT. Thus, the sexual dimorphism in plasma leptin concentration appears to reflect, at least in part, effects of circulating concentrations of gonadal steroids (especially androgens) and/or primary genetic differences that are independent of amounts of VAT or SAT.     

Enzymes related to lipogenesis in the adipose tissue of obese subjects.

In a group of ten adult obese subjects, maintained for 15 days on a normal caloric intake and balanced diet, the activity of hexokinase (EC 2.7.1.1),6-phosphofructokinase (EC 2.7.1.11), and ATP citratelyase (EC 4.1.3.8) in the adipose tissue was significantly increased, both on a protein and on a fat cell number basis, compared to matched normal subjects. The activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), malate dehydrogenase (EC 1.1.1.37), and malate dehydrogenase (decarboxylating) (NADP) (EC 1.1.1.40), on the other hand, was unchanged. Since both hexokinase and 6-phosphofructokinase are rate-limiting in glycolysis, their enhanced activity would indicate the occurrence of an increased capacity to metabolize glucose and therefore to generate alpha-glycerophosphate. The elevation of ATP citrate-lyase would suggest increased lipogenesis, owing to the regulatory role that this enzyme plays in fatty acid synthesis. The normal activity of glucose-6-phosphate dehydrogenase and malate dehydrogenase (decarboxylating) (NADP), which supply NADPH for the reduction of acetyl-CoA to fatty acids, would suggest that the change in lipogenesis is of moderate degree, thereb) affecting only the most rate-limiting enzyme, ATP citrate-lyase. These data, on the whole, are consistent with the occurrence of enhanced triglyceride formation. Whether the enzyme changes observed are adaptive or genetic in nature remains to be clarified.     

Increased visceral adipose tissue is associated with increased circulating insulin and decreased sex hormone binding globulin levels in massively obese adolescent girls.

The current study was designed to examine the relationship between body fat distribution, as evaluated by anthropometry and magnetic resonance imaging (MRI), and circulating insulin, sex hormone and SHBG levels in obese adolescent girls. Twenty-nine obese adolescent girls, aged 12.6-16.9 years with a mean BMI of 30.51+/-1.86 participated in this study. All girls had breast stage B4-5 and pubic hair stage P4-5. Percent obesity and BMI as indices of being overweight were calculated; the waist-to-hip ratio (WHR) and the waist-to-thigh ratio (WTR) were calculated to obtain two anthropometric indices for the pattern of body fat distribution. The areas of visceral (VAT) and subcutaneous adipose tissue (SAT) were evaluated by MRI at the L4-L5 level. Serum concentrations of total T, DHEAS, 17beta-estradiol, progesterone and SHBG were measured. Plasma glucose and insulin concentrations were evaluated during an oral glucose tolerance test. WHR was the only anthropometric parameter that was significantly associated with the area of VAT. Insulin level showed correlation with both WHR and the area of VAT; no correlation was found between insulin levels and WTR. Both WHR and VAT were negatively correlated with serum DHEAS level and positively correlated with T level. There were strong negative correlations between serum SHBG level and the area of VAT and WHR. Inverse correlation was found between serum SHBG level and insulin. Serum 17beta-estradiol and progesterone levels showed no significant correlation with all the patterns of body fat distribution. SAT was not significantly correlated with both anthropometric parameters and any of the sex hormones evaluated. We can draw two main conclusions. Firstly, in massively obese adolescent girls, the WHR seems to be a good indicator for the accumulation of VAT, and abdominal obesity, rather than adiposity per se, appears to be related to biochemical complications. Secondly, increased upper body adiposity and, in particular, the intra-abdominal fat area are associated with increased insulin levels in massively obese adolescent girls. The associated reductions in SHBG and DHEAS levels represent an early general risk factor for the development of metabolic and cardiovascular diseases in this population, as previously described for obese adult women.