Possible involvement of 15-deoxy-Δ(12,14) -prostaglandin J2 in the development of leptin resistance.

Obesity is a worldwide health problem that urgently needs to be solved. Leptin is an anti-obesity hormone that activates satiety signals to the brain. Evidence to suggest that leptin resistance is involved in the development of obesity is increasing; however, the molecular mechanisms involved remain unclear. We herein demonstrated that 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) was involved in the development of leptin resistance. A treatment with 15d-PGJ2 inhibited the leptin-induced activation of signal transducer and activator of transcription 3 (STAT3) in neuronal cells (SH-SY5Y-Ob-Rb cells). Furthermore, the intracerebroventricular administration of 15d-PGJ2 reversed the inhibitory effects of leptin on food intake in rats. The peroxisome proliferator-activated receptor gamma (PPAR-γ) antagonist, GW9662, slightly reversed the inhibitory effects of 15d-PGJ2 on the leptin-induced activation of STAT3 in neuronal cells. The PPAR-γ agonist, rosiglitazone, also inhibited leptin-induced STAT3 phosphorylation. Therefore, the inhibitory effects of 15d-PGJ2 may be mediated through PPAR-γ. On the other hand, 15d-PGJ2 -induced leptin resistance may not be mediated by endoplasmic reticulum stress or suppressor of cytokine signaling 3. The results of the present study suggest that 15d-PGJ2 is a novel factor for the development of leptin resistance in obesity. Leptin resistance, an insensitivity to the actions of leptin, is involved in the development of obesity. Here, we found 15-deoxy-Δ(12,14) -prostaglandin J2 (15d-PGJ2 ) may be involved in the development of leptin resistance. The present results suggest that the 15d-PGJ2 may be a novel factor for the development of leptin resistance in obesity. 15d-PGJ2 , 15-Deoxy-Δ(12,14) -prostaglandin J2; STAT3, signal tranducer and activator of transcription 3.

Endoplasmic reticulum stress induces leptin resistance.

Leptin is an important circulating signal for inhibiting food intake and body weight gain. In recent years, "leptin resistance" has been considered to be one of the main causes of obesity. However, the detailed mechanisms of leptin resistance are poorly understood. Increasing evidence has suggested that stress signals, which impair endoplasmic reticulum (ER) function, lead to an accumulation of unfolded proteins, which results in ER stress. In the present study, we hypothesized that ER stress is involved in leptin resistance. Tunicamycin, thapsigargin, or brefeldin A was used to induce ER stress. The activation status of leptin signals was measured by Western blotting analysis using a phospho-(Tyr705) signal transducer and activator of transcription 3 (STAT3) antibody. We observed that ER stress markedly inhibited leptin-induced STAT3 phosphorylation. In contrast, ER stress did not affect leptin-induced c-Jun NH(2)-terminal kinase activation. These results suggest that ER stress induces leptin resistance. ER stress-induced leptin resistance was mediated through protein tyrosine phosphatase 1B but not through suppressors of cytokine signaling 3. It is noteworthy that a chemical chaperone, which could improve the protein-folding capacity, reversed ER stress-induced leptin resistance. Moreover, homocysteine, which induces ER stress, caused leptin resistance both in vitro and in vivo. Together, these findings suggest that the pathological mechanism of leptin resistance is derived from ER stress.

Severity and predictive factors of adverse events in pemetrexed-containing chemotherapy for non-small cell lung cancer.

Pemetrexed is a key anticancer agent for treatment of advanced non-small cell lung cancer (NSCLC). Pemetrexed is generally well tolerated, but individual-patient differences exist in severity of adverse events. Our study aimed to characterize the adverse events of pemetrexed that result in discontinuation of chemotherapy and to identify risk factors associated with those adverse events. We retrospectively studied the incidence of adverse events in 257 patients with NSCLC who received pemetrexed (P) with or without bevacizumab (B) and/or carboplatin (C): P, PB, CP, or CPB. Patients whose chemotherapy was discontinued were divided into two groups according to adverse events and disease progression. Grade 2/3 nausea, fatigue with P and PB, and rash with CP and CPB occurred more frequent in the adverse events group than in the disease progression group. Multivariate analysis indicated that grade 2/3 nausea [odds ratio (OR) 9.94; 95% confidence interval (CI) 1.46-67.37; p = 0.01] and fatigue (OR 10.62; CI 1.60-70.20; p = 0.01) with P or PB, and rash (OR 6.12; CI 1.34-27.88; p = 0.01) with CP or CPB, were independent risk factors for discontinuation of chemotherapy. Administration of dexamethasone at doses less than 4 mg after the day of pemetrexed administration was associated with nausea following P or PB (OR 11.08; 95% CI 1.02-119.95; p = 0.04). Grade 2/3 nausea and fatigue with P or PB, and rash with CP or CPB, were associated with discontinuation of chemotherapy.

Fluvoxamine attenuated endoplasmic reticulum stress-induced leptin resistance.

Increasing evidence indicates that endoplasmic reticulum stress (ER stress) is involved in the development of metabolic syndrome. However, pharmacological treatments targeting ER stress are not well understood. In the present study, we found that fluvoxamine, a selective serotonin reuptake inhibitor used for depression, can attenuate ER stress-induced "leptin resistance," i.e., insensitivity to the anti-obesity hormone leptin. Treatment with tunicamycin, an ER stress-inducing reagent, caused cell death which was significantly inhibited by fluvoxamine. Leptin activates JAK2-STAT3 signaling. ER stress caused an impairment of leptin-induced STAT3 phosphorylation which was reversed by fluvoxamine. Fluvoxamine would be a novel leptin-sensitizing drug, which targets ER stress.