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.

Taleb S, Cancello R, Poitou C, et al. Weight loss reduces adipose tissue cathepsin S and its circulating levels in morbidly obese women. J Clin Endocrinol Metab. 2006;91(3):1042-7.

OBJECTIVE: Lysosomal proteinases have been implicated in a number of pathologies associated with extracellular matrix breakdown. Therefore, we investigated the possibility that the lysosomal proteinase cathepsin S may be involved in atherosclerotic plaque destabilization. METHODS AND RESULTS: Atherosclerotic plaques in the brachiocephalic arteries of fat-fed apolipoprotein E/cathepsin S double knockout mice had 73% fewer acute plaque ruptures (P=0.026) and were 46% smaller (P=0.025) than those in age-, strain-, and sex-matched apolipoprotein E single knockout controls. When the incidence of acute plaque rupture was normalized for plaque size, the reduction in the double knockouts was 72% (P=0.039). The number of buried fibrous layers, indicative of an unstable plaque phenotype, was reduced by 67% in the double knockouts (P=0.008). The cysteine proteinase inhibitor, egg white cystatin, was biotinylated and used as an active-site-directed probe for cathepsins. Biotinylated cystatin selectively detected cathepsin S in extracts of human carotid atherosclerotic plaque. Active cathepsin S was detectable in extracts of human atherosclerotic plaque but not in nondiseased carotid arteries. Active cathepsins were especially prominent in macrophages in the shoulder regions of plaques, areas considered to be vulnerable to rupture. Cathepsin S protein colocalized with regions of elastin degradation in human coronary plaques.
CONCLUSIONS: These data provide direct evidence that an endogenous proteinase, cathepsin S, plays an important role in atherosclerotic plaque destabilization and rupture.

Rodgers KJ, Watkins DJ, Miller AL, et al. Destabilizing role of cathepsin S in murine atherosclerotic plaques. Arterioscler Thromb Vasc Biol. 2006;26(4):851-6.

Various adipocyte-secreted factors have been described which profoundly affect insulin sensitivity and might potentially link obesity, insulin resistance and cardiovascular disease. Among those, adiponectin, visfatin and omentin appear as insulin-sensitising adipocytokines, whereas TNF-alpha, IL-6 and resistin induce insulin resistance. Moreover, leptin is a fat-derived key regulator of appetite and energy expenditure. Due to their profound effect on whole-body glucose and energy metabolism, adipocytokines have attracted interest as potential new therapeutics for diabetes mellitus and obesity. The current knowledge on function, regulation and therapeutic potential of various adipocytokines, as well as their clinical implications, are discussed in this review.

Kralisch S, Klein J, Bluher M, Paschke R, Stumvoll M, Fasshauer M. Therapeutic perspectives of adipocytokines. Expert Opin Pharmacother. 2005;6(6):863-72.