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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.

Objective: Adipocytes secrete a series of acute phase proteins including serum amyloid A (SAA); the link with metabolic status is unknown. We studied the variations of expression of the SAA gene in adipose and liver tissues and of SAA serum levels, as well as their relationships with metabolic features during weight loss., Research Methods and Procedures: Plasmatic variations of SAA, inflammatory markers (high sensitivity C-reactive protein, interleukin-6, fibrinogen, and orosomucoid), and adipokines (adiponectin, leptin) were studied in 60 morbidly obese patients before and after gastric surgery. For 10 subjects, SAA mRNA expression was measured at baseline in subcutaneous white adipose tissue (scWAT) and visceral white adipose tissue (vWAT) and in the liver. The evolution of SAA mRNA expression was also studied after surgery in scWAT., Results: SAA serum concentration displayed a significant reduction 3 months after surgery and remained stable beyond 6 months. mRNA expression of inducible SAA isoforms (SAA 1 and 2) in scWAT was higher than in vWAT (p = 0.01) and the liver (p < 0.01) and correlated significantly with BMI, SAA, and high sensitivity C-reactive protein serum concentrations but not with metabolic markers (glucose, insulin, lipid parameters, adiponectin). SAA serum level and its variation during weight loss significantly correlated with adiposity markers (BMI and adipocyte volume, p < 0.01) and inflammatory markers but not with variations of metabolic parameters. The variations of SAA expression in scWAT after surgery correlated with changes in BMI and SAA protein serum levels (p < 0.05)., Discussion: SAA can be considered as a marker of adiposity-induced low-grade inflammation but not of the metabolic status of obese subjects.

The molecular mechanisms by which obesity increases the risk of cardiovascular diseases are poorly understood. The purpose of this study was to identify candidate biomarkers overexpressed in adipose tissue of obese subjects that could link expanded fat mass to atherosclerosis. We compared gene expression profile in subcutaneous adipose tissue (scWAT) of 28 obese and 11 lean subjects using microarray technology. This analysis identified 240 genes significantly overexpressed in scWAT of obese subjects. The genes were then ranked according to the correlation between gene expression and body mass index (BMI). In this list, the elastolytic cysteine protease cathepsin S was among the highly correlated genes. RT-PCR and Western blotting confirmed the increase in cathepsin S mRNA (P=0.006) and protein (P<0.05) in obese scWAT. The circulating concentrations of cathepsin S were also significantly higher in obese than in nonobese subjects (P<0.0001). Both cathepsin S mRNA in scWAT and circulating levels were positively correlated with BMI, body fat, and plasma triglyceride levels. In addition, we show that the proinflammatory factors, lipopolysaccharide, interleukin-1beta, and tumor necrosis factor-alpha increase cathepsin S secretion in human scWAT explants. This study identifies cathepsin S as a novel marker of adiposity. Since this enzyme has been implicated in the development of atherosclerotic lesions, we propose that cathepsin S represents a molecular link between obesity and atherosclerosis.

Adiponectin is an adipocyte-derived protein suggested to be involved in energy homeostasis and in lipid and glucose metabolism. Little is known regarding the consequence of acute changes in energy balance on adiponectin mRNA expression in human adipose tissue. Using a real-time RT-PCR assay, we investigated the effects of 2-d very low calorie diet (VLCD) and subsequent refeeding on adiponectin mRNA expression in sc adipose tissue of morbidly obese women. Basal adiponectin mRNA abundance of the obese women showed a wide distribution (2.6-14.3 mRNA/18S rRNA; coefficient of variation, 51.2%) and was significantly lower than that of lean controls (P < 0.001). In the obese group, the VLCD caused a 33% rise (P < 0.01) in the average level of mRNA, whereas refeeding caused a 32.8% fall (P < 0.05). In contrast, the change in leptin mRNA expression with either VLCD or refeeding was not statistically significant. The obese subjects who showed an acute adiponectin mRNA response to the changes in energy intake had a higher basal level of adiponectin mRNA (P = 0.02) and a borderline-significantly lower body mass index compared with the subjects who showed no or weak adiponectin mRNA response. Insulin sensitivity of the responder subgroup significantly increased by 89% (P = 0.008) after the VLCD, whereas insulin sensitivity of the nonresponder subgroup only increased by 24% (P = 1.56). This study indicates that adiponectin mRNA in sc adipose tissue can acutely respond to short-term energy changes in some obese subjects. Both the levels of adiposity and insulin sensitivity may contribute to the variation in adiponectin gene expression in response to acute energy changes.

Objectives: Adipocytokines, secreted by adipose tissue, may regulate fat metabolism, lipid and glucose homeostasis and insulin sensitivity. We analysed the relations between circulating concentrations of adiponectin, leptin, interleukin-6, tumor necrosis factor alpha and its soluble receptors sTNFR1 and R2, lipodystrophic phenotypes and metabolic alterations in patients under highly active antiretroviral therapy (HAART)., Methods: We studied 131 consecutive HIV-infected males under protease inhibitor (PI)-based HAART, with body mass index < 27 kg/m2 and C-reactive protein (CRP) < 10 mg/l. Patients were classified in four groups according to clinical examination: no lipodystrophy (NL), lipohypertrophy (LH), lipoatrophy (LA) and mixed lipodystrophy (ML). In addition to adipocytokines, we measured plasma fasting levels of triglycerides, cholesterol, cardiovascular risk markers (high-sensitivity CRP and apolipoproteins B/A1 ratio), fasted and 2 h post-glucose loading glycemia and insulinemia and calculated the quantitative insulin sensitivity check index., Results: The patients were HIV-infected and PI-treated for a mean of 8.2 and 1.6 years respectively; 74% presented lipodystrophy, 38% altered glucose tolerance and 42% hypertriglyceridemia. Insulin sensitivity correlated positively with adiponectin and negatively with leptin and interleukin-6. Adiponectin, but not leptin, negatively correlated with all metabolic parameters. Insulin resistance, metabolic defects and cardiovascular risk markers were strongly negatively correlated with the adiponectin/leptin ratio (A/L), and positively with sTNFR1. LA patients had a longer duration of infection but ML patients presented the most severe metabolic alterations, insulin resistance and A/L decrease., Conclusions: These results suggest that adiponectin and the TNFalpha system are related to lipodystrophy, insulin resistance and metabolic alterations in patients under PI-based HAART. A/L and sTNFR1 could predict insulin sensitivity and potential cardiovascular risk in these patients.