Leptin blocks the inhibitory effect of vitamin D on adipogenesis and cell proliferation in 3T3-L1 adipocytes.

Recently, we demonstrated high serum leptin and 25(OH)D (calcidiol) in obese animals, with high C/EBPß and PPARγ expression in adipose tissue. Since the role of vitamin D in adipogenesis remains controversial and hyperleptinemia is found in obesity, we asked if leptin could interfere in vitamin D action on adipocytes. Here, we studied the direct effect of these two hormones upon 3T3L1 preadipocytes incubated with or without 1,25(OH)2D (100 nM, 24 h) and with leptin (10-7 M, 4 h later). RT-PCR (VDR and Cyp27b1/1α-hydroxylase), western blotting (VDR, Cyp27b1/1α-hydroxylase, ObR-b, C/EBPß, PPARγ and Bax content), a cell proliferation assay and an Annexin V-FITC binding assay were performed. Incubation with 1,25(OH)2D decreased Cyp27b1/1α-hydroxylase and VDR. Co-incubation of 1,25(OH)2D and leptin did not change Cyp27b1/1α-hydroxylase and had no additive effect upon the decreased VDR mRNA. Incubation with 1,25(OH)2D decreased C/EBPß and PPARγ. In the cell proliferation assay, 1,25(OH)2D decreased the number of 3T3L1 cells. No changes in OBR-b or apoptotic parameters (Bax and annexin-V) were observed. The 1,25(OH)2D decreased pro-adipogenic factors and proliferation of adipocytes. However, since it inhibits the conversion of 25(OH)D to 1,25(OH)2D and VDR mRNA long-term, it could decrease the vitamin D response in adipocytes, leading to greater adipogenesis. The co-incubation of both hormones, simulating what occurs in obesity, even neutralizing the effect on Cyp27b1/1α-hydroxylase, did not change the vitamin D sensitivity but decreased SOCS-3 and pSTAT-3. Thus, an excess of vitamin D and hyperleptinemia could decrease vitamin D sensitivity in adipocytes, contributing to increased adipogenesis.

Light cigarette smoke-induced emphysema and NFkappaB activation in mouse lung.

Light cigarette (LC) exposure is supposed to be less hazardous with a decreased incidence of cancer and tobacco-associated diseases. C57BL/6 mouse groups were subjected to smoke from 3, 6 or 12 LC for 60 days and compared with mice exposed to ambient air (EAA) in order to study lung injury by morphometrical and biochemical methods. Bronchoalveolar lavage (BAL) analysis and histology and stereology were performed. Tissue from the right lung was used for measuring thiobarbituric acid reactive substances (TBARS) and Western blot analysis. One way anova was performed followed by the Student-Newman Keuls post-test (P < 0.05). The cellular content of BAL was 95% alveolar macrophages in all groups except in mice exposed to 3 LC, where 23% neutrophils were observed. Emphysema was not observed in three and 6 LC, but it was found in 12 LC parallel to increased volume density (Vv) of airspaces from 61.0 +/- 0.6 (EAA) to 80.9 +/- 1.0 (12 LC) and decreased Vv of elastic fibres from 17.8 +/- 0.9 (EAA) to 11.8 +/- 0.6 (12 LC). All exposed groups to LC showed low TBARS levels compared with mice EAA. Lung tissue from animals exposed to 12 LC showed decreased tissue inhibitor of metalloprotease-2 and increased matrix metalloprotease-12 detection, which suggests an imbalance in extracellular matrix (ECM). Increased tumour necrosis factor-alpha and nuclear factor-kappaB detection were observed in exposed groups to LC when compared with mice EAA. The data suggest that LC is so dangerous to lungs as full-flavour cigarettes inducing ECM imbalance and emphysema.