Olanzapine-induced accumulation of adipose tissue is associated with an inflammatory state.

Second-generation antipsychotics are widely used in the treatment of all forms of psychoses, but they often produce undesirable side effects, among which are weight gain and other elements of metabolic syndrome. The mechanisms of these adverse effects are not known. The liver and adipose tissue are the principal candidate organs implicated in the development of antipsychotic-induced metabolic adverse effects. The present study investigated in the rat the effects on liver and white adipose tissue of a chronic treatment (46 days) with olanzapine 2 mg/kg or haloperidol 1 mg/kg, as compared with a control solution. In the liver, the expression of key genes involved in glucose transport and lipid metabolism and of regulatory transcription factors, as well as the TNFalpha gene, was not altered in response to either antipsychotic. Similarly, key genes involved in glucose transport and lipid metabolism were not changed in adipose tissue. However, the white adipose tissue was inflammatory in olanzapine-treated rats, with extensive macrophage infiltration and a significant increase in TNFalpha expression. In the plasma, TNFalpha and IL-1beta concentrations were slightly elevated. Chronic olanzapine treatment therefore produces a low-grade inflammatory state, likely initiated in the adipose tissue. Such an inflammatory state is known to be associated with an increased risk of insulin-resistance and cardiovascular diseases. This antipsychotic-induced inflammatory syndrome may participate in the inflammatory syndrome often observed in patients with schizophrenia. The strong and rather selective effect of olanzapine on TNFalpha expression may open new therapeutic opportunities for the prevention of olanzapine-induced metabolic abnormalities.

Cathepsins and cystatin C in atherosclerosis and obesity.

Given the increasing prevalence of human obesity worldwide, there is an urgent need for a better understanding of the molecular mechanisms linking obesity to metabolic and cardiovascular diseases. Our knowledge is nevertheless limited regarding molecules linking adipose tissue to downstream complications. The importance of cathepsins was brought to light in this context. Through a large scale transcriptomic analysis, our group recently identified the gene encoding cathepsin S as one of the most deregulated gene in the adipose tissue of obese subjects and positively correlated with body mass index. Other members of the cathepsin family are expressed in the adipose tissue, including cathepsin K and cathepsin L. Given their implication in atherogenesis, these proteases could participate into the well established deleterious relationship between enlarged adipose tissue and increased cardiovascular risk. Here, we review the clinical and experimental evidence relevant to the role of cathepsins K, L and S and their most abundant endogenous inhibitor, cystatin C, in atherosclerosis and in obesity.

Cathepsins in human obesity: changes in energy balance predominantly affect cathepsin s in adipose tissue and in circulation.

CONTEXT: Recent studies in humans and mice suggest the implication of the cysteine proteases cathepsins S, L, and K in vascular and metabolic complications of obesity. OBJECTIVE: Our objective was to identify clinically relevant forms of cathepsin in human obesity. DESIGN AND SETTING: We conducted a prospective study on two independent cohorts. PARTICIPANTS AND INTERVENTIONS: The first cohort includes 45 obese women eligible for gastric surgery (age, 39 +/- 1.6 yr; body mass index, 47 +/- 0.99 kg/m(2)) and 17 nonobese women (age, 38 +/- 1.8 yr; body mass index, 21 +/- 0.44 kg/m(2)). The second cohort comprises 29 obese women (age, 57 +/- 0.8 yr; body mass index, 34 +/- 0.69 kg/m(2)) undergoing 6 months of medically supervised caloric restriction. MAIN OUTCOMES: Cathepsin S, L, and K mRNA levels were determined in surgical adipose tissue biopsies. The proteins were measured in conditioned medium of adipose tissue explants and in circulation. RESULTS: Obese subjects had a 2-fold increase in cathepsin S mRNA in adipose tissue as compared with normal-weight subjects and an increased rate (1.5-fold) of cathepsin S release in adipose tissue explants. Cathepsin S circulating concentrations were increased with obesity (+30%) and reduced after weight reduction (P < 0.05 for both). By contrast, cathepsin L was unaffected in adipose tissue and serum; cathepsin K was undetectable in circulation and unchanged in adipose tissue. CONCLUSION: In humans, cathepsin S is more influenced than cathepsins L and K by changes in energy balance in adipose tissue and circulation. This opens new avenues to explore whether selective inhibition of this protease could reduce cardiovascular risk and ameliorate metabolic status in obese subjects.

Secretory type II phospholipase A2 is produced and secreted by epicardial adipose tissue and overexpressed in patients with coronary artery disease.

CONTEXT: Epicardial adipose tissue (EAT) is a visceral adipose tissue in close contact with coronary vessels, the excess of which is associated with coronary artery disease (CAD). OBJECTIVE: Our goal was to identify candidate molecule(s) characterizing EAT that could intervene in the pathogenesis of CAD. DESIGN: An approach combining microarrays and bioinformatic sequence analysis tools for predicting secreted proteins (TargetP) was applied to paired biopsies of sc adipose tissue (SAT) and EAT, obtained from patients with or without CAD (NCAD). RESULTS were validated in three independent groups of subjects by quantitative RT-PCR, Western blot, immunohistochemistry, and explant secretion. RESULTS: Secretory type II phospholipase A2 (sPLA2-IIA) ranked as the highest gene coding for potentially secreted proteins with the highest overexpression in EAT in both CAD and NCAD. Quantitative RT-PCR confirmed its increased expression in EAT (P < 0.01) as well as EAT from CAD as compared with NCAD (49.3 +/- 13 vs. 17.4 +/- 9.7 P < 0.01). sPLA2-IIA protein levels were higher in EAT than SAT (P < 0.001). EAT explants also showed significantly higher sPLA2-IIA secretion levels than SAT ones (4.37 +/- 2.7 vs. 0.67 +/- 0.28 ng/ml to 1 per gram tissue per 24 h, P < 0.03). sPLA2-IIA labeling was seen in the stroma vascular fraction between adipocytes and in connective capsules in EAT, with no immunostaining of the adipocytes. SAT was weakly labeled following the same process. CONCLUSION: We have shown for the first time an increased expression of sPLA2-IIA in EAT in patients with CAD. sPLA2-IIA is a phospholipase, which has been shown to be an independent risk factor for CAD. These findings suggest that EAT has a potentially pathophysiological role in CAD.

Potential contribution of adipose tissue to elevated serum cystatin C in human obesity.

Cystatin C, an endogenous inhibitor of cathepsin proteases has emerged as a biomarker of cardiovascular risk and reduced renal function. Epidemiological studies indicate that serum cystatin C increased in human obesity. Here, we evaluated the contribution of adipose tissue to this elevation, based on our previous observation that cystatin C is produced by in vitro differentiated human adipocytes. We measured serum cystatin C in 237 nonobese (age: 51 +/- 0.8 years; BMI: 22.8 +/- 0.11 kg/m(2)) and 248 obese subjects (age: 50 +/- 0.8 years; BMI: 34.7 +/- 0.29 kg/m(2)). Creatinine-based estimated glomerular filtration rate (eGFR) was calculated to account for renal status. Cystatin C gene expression and secretion were determined on surgical adipose tissue biopsies in a distinct group of subjects. Serum cystatin C is elevated in obese subjects of both genders, independently of reduced eGFR. Cystatin C mRNA is expressed in subcutaneous and omental adipose tissue, at twice higher levels in nonadipose than in adipose cells. Gene expression and cystatin C release by adipose tissue explants increase two- to threefold in obesity. These data confirm elevation of serum cystatin C in human obesity and strongly argue for a contribution of increased production of cystatin C by enlarged adipose tissue. Because cystatin C has the potential to affect adipose tissue and vascular homeostasis through local and/or systemic inhibition of cathepsins, this study adds a new factor to the list of adipose tissue secreted bioactive molecules implicated in obesity and obesity-linked complications.

Gamma-synuclein is an adipocyte-neuron gene coordinately expressed with leptin and increased in human obesity.

Recently, we characterized tumor suppressor candidate 5 (Tusc5) as an adipocyte-neuron PPARgamma target gene. Our objective herein was to identify additional genes that display distinctly high expression in fat and neurons, because such a pattern could signal previously uncharacterized functional pathways shared in these disparate tissues. gamma-Synuclein, a marker of peripheral and select central nervous system neurons, was strongly expressed in white adipose tissue (WAT) and peripheral nervous system ganglia using bioinformatics and quantitative PCR approaches. Gamma-synuclein expression was determined during adipogenesis and in subcutaneous (SC) and visceral adipose tissue (VAT) from obese and nonobese humans. Gamma-synuclein mRNA increased from trace levels in preadipocytes to high levels in mature 3T3-L1 adipocytes and decreased approximately 50% following treatment with the PPARgamma agonist GW1929 (P < 0.01). Because gamma-synuclein limits growth arrest and is implicated in cancer progression in nonadipocytes, we suspected that expression would be increased in situations where WAT plasticity/adipocyte turnover are engaged. Consistent with this postulate, human WAT gamma-synuclein mRNA levels consistently increased in obesity and were higher in SC than in VAT; i.e. they increased approximately 1.7-fold in obese Pima Indian adipocytes (P = 0.003) and approximately 2-fold in SC and VAT of other obese cohorts relative to nonobese subjects. Expression correlated with leptin transcript levels in human SC and VAT (r = 0.887; P < 0.0001; n = 44). Gamma-synuclein protein was observed in rodent and human WAT but not in negative control liver. These results are consistent with the hypothesis that gamma-synuclein plays an important role in adipocyte physiology.

Treatment for 2 mo with n 3 polyunsaturated fatty acids reduces adiposity and some atherogenic factors but does not improve insulin sensitivity in women with type 2 diabetes: a randomized controlled study.

BACKGROUND: Information is lacking on the potential effect of n-3 polyunsaturated fatty acids (PUFAs) on the adipose tissue of patients with type 2 diabetes. OBJECTIVE: We evaluated whether n-3 PUFAs have additional effects on adiposity, insulin sensitivity, adipose tissue function (production of adipokines and inflammatory and atherogenic factors), and gene expression in type 2 diabetes. DESIGN: Twenty-seven women with type 2 diabetes without hypertriglyceridemia were randomly allocated in a double-blind parallel design to 2 mo of 3 g/d of either fish oil (1.8 g n-3 PUFAs) or placebo (paraffin oil). RESULTS: Although body weight and energy intake measured by use of a food diary were unchanged, total fat mass (P < 0.019) and subcutaneous adipocyte diameter (P < 0.0018) were lower in the fish oil group than in the placebo group. Insulin sensitivity was not significantly different between the 2 groups (measured by homeostasis model assessment in all patients and by euglycemic-hyperinsulinemic clamp in a subgroup of 5 patients per group). By contrast, atherogenic risk factors, including plasma triacylglycerol (P < 0.03), the ratio of triacylglycerol to HDL cholesterol (atherogenic index, P < 0.03), and plasma plasminogen activator inhibitor-1 (P < 0.01), were lower in the fish oil group than in the placebo group. In addition, a subset of inflammation-related genes was reduced in subcutaneous adipose tissue after the fish oil, but not the placebo, treatment. CONCLUSIONS: A moderate dose of n-3 PUFAs for 2 mo reduced adiposity and atherogenic markers without deterioration of insulin sensitivity in subjects with type 2 diabetes. Some adipose tissue inflammation-related genes were also reduced. These beneficial effects could be linked to morphologic and inflammatory changes in adipose tissue. This trial was registered at clinicaltrials.gov as NCT0037.

Insulin and leptin induce Glut4 plasma membrane translocation and glucose uptake in a human neuronal cell line by a phosphatidylinositol 3-kinase- dependent mechanism.

The insulin-sensitive glucose transporter Glut4 is expressed in brain areas that regulate energy homeostasis and body adiposity. In contrast with peripheral tissues, however, the impact of insulin on Glut4 plasma membrane (PM) translocation in neurons is not known. In this study, we examined the role of two anorexic hormones (leptin and insulin) on Glut4 translocation in a human neuronal cell line that express endogenous insulin and leptin receptors. We show that insulin and leptin both induce Glut4 translocation to the PM of neuronal cells and activate glucose uptake. Wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase, totally abolished insulin- and leptin-dependent Glut4 translocation and stimulation of glucose uptake. Thus, Glut4 translocation is a phosphatidylinositol 3-kinase-dependent mechanism in neuronal cells. Next, we investigated the impact of chronic insulin and leptin treatments on Glut4 expression and translocation. Chronic exposure of neuronal cells to insulin or leptin down-regulates Glut4 proteins and mRNA levels and abolishes the acute stimulation of glucose uptake in response to acute insulin or leptin. In addition, chronic treatment with either insulin or leptin impaired Glut4 translocation. A cross-desensitization between insulin and leptin was apparent, where exposure to insulin affects leptin-dependent Glut4 translocation and vice versa. This cross-desensitization could be attributed to the increase in suppressor of cytokine signaling-3 expression, which was demonstrated in response to each hormone. These results provide evidence to suggest that Glut4 translocation to neuronal PM is regulated by both insulin and leptin signaling pathways. These pathways might contribute to an in vivo glucoregulatory reflex involving a neuronal network and to the anorectic effect of insulin and leptin.