The purpose of the study was to determine the roles of interleukin-6 (IL6) in fat and bone communication. Male wild-type (WT) mice and IL6 knockout (IL6^−/−) mice were fed with either regular diet (RD) or high-fat diet (HFD) for 12 weeks. Bone mass and bone microstructure were evaluated by micro-computed tomography. Gene expression related to lipid and bone metabolisms was assayed with real-time quantitative polymerase chain reaction. Bone marrow cells from both genotypes were induced to differentiate into osteoblasts or osteoclasts, and treated with palmitic acid (PA). HFD increased the body weight and fat pad weight, and impaired lipid metabolism in both WT and IL6^−/− mice. The dysregulation of lipid metabolism was more serious in IL6^−/− mice. Trabecular bone volume fraction, trabecular bone number and trabecular bone thickness were significantly downregulated in WT mice after HFD than those in the RD (P < 0.05). However, these bone microstructural parameters were increased by 53%, 34% and 40%, respectively, in IL6^−/− mice than those in WT mice on the HFD (P < 0.05). IL6^−/− osteoblasts displayed higher alkaline phosphatase (ALP) activity and higher mRNA levels of Runx2 and Colla1 than those in WT osteoblasts both in the control and PA treatment group (P < 0.05). IL6^−/− mice showed significantly lower mRNA levels of PPARγ and leptin and higher mRNA levels of adiponectin in comparison with WT mice on HFD. In conclusion, these findings suggested that IL6 gene deficiency antagonized HFD-induced bone loss. IL6 might bridge lipid and bone metabolisms and could be a new potential therapeutic target for lipid metabolism disturbance-related bone loss.

Resistin is an adipocytokine leading to insulin resistance. Endotoxin/lipopolysaccharide (LPS) has been reported to decrease the expression of resistin mRNA and protein in both lean and db/db obese mice, although the underlying mechanism remains unclear. Several models such as ex vivo culture of adipose tissues, primary rat adipocytes and 3T3-L1 adipocytes were used to further characterize the effect of LPS on the expression of resistin. LPS attenuated both the resistin mRNA and protein in a time- and dose-dependent manner. In the presence of actinomycin D, LPS failed to reduce the half-life of resistin mRNA, suggesting a transcriptional mechanism. The lipid A fraction is crucial for the inhibition of resistin expression induced by LPS. Pharmacological intervention of c-Jun N-terminal kinase (JNK) reversed the inhibitory effect of LPS. LPS down-regulated CCAAT/enhancer-binding protein α (C/EBP-α; CEBPA) and peroxisome proliferator-activated receptor γ (PPAR-γ; PPARG), while activation of C/EBP-α or PPAR-γ by either over-expressing these transcriptional factors or by rosiglitazone, an agonist of PPAR-γ, blocked the inhibitory effect of LPS on resistin. C/EBP homologous protein (CHOP-10; DDIT3) was up-regulated by LPS, while a CHOP-10 antisense oligonucleotide reversed the decrement of resistin protein induced by LPS. Taken together, these results suggest that LPS inhibits resistin expression through a unique signaling pathway involving toll-like receptor 4, JNK, CHOP-10 and C/EBP-α/PPAR-γ.

We examined the effects of tumor necrosis factor-α (TNFα) and interleukin-6 (IL6) gene knockout in preserving the bone loss induced by ovariectomy (OVX) and the mechanisms involved in bone metabolism. Twenty female wild-type (WT), TNFα-knockout (TNFα^−/−) or IL6-knockout (IL6^−/−) mice aged 12 weeks were sham-operated (SHAM) or subjected to OVX and killed after 4 weeks. Bone mass and skeletal microarchitecture were determined using micro-CT. Bone marrow stromal cells (BMSCs) from all three groups (WT, TNFα^−/− and IL6^−/−) were induced to differentiate into osteoblasts or osteoclasts and treated with 17-β-estradiol. Bone metabolism was assessed by histological analysis, serum analyses and qRT-PCR. OVX successfully induced a high turnover in all mice, but a repair effect was observed in TNFα^−/− and IL6^−/− mice. The ratio of femoral trabecular bone volume to tissue volume, trabecular number and trabecular thickness were significantly decreased in WT mice subjected to OVX, but increased in TNFα^−/− mice (1.62, 1.34, 0.27-fold respectively; P < 0.01) and IL6^−/− mice (1.34, 0.80, 0.22-fold respectively; P < 0.01). Furthermore, we observed a 29.6% increase in the trabecular number in TNFα^−/− mice when compared to the IL6^−/− mice. Both, TNFα^−/− and IL6^−/− BMSCs exhibited decreased numbers of TRAP-positive cells and an increase in ALP-positive cells, with or without E2 treatment (P < 0.05). While the knockout of TNFα or IL6 significantly upregulated mRNA expressions of osteoblast-related genes (Runx2 and Col1a1) and downregulated osteoclast-related mRNA for TRAP, MMP9 and CTSK in vivo and in vitro, TNFα knockout appeared to have roles beyond IL6 knockout in upregulating Col1a1 mRNA expression and downregulating mRNA expressions of WNT-related genes (DKK1 and Sost) and TNF-related activation-induced genes (TRAF6). TNFα seemed to be more potentially invasive in inhibiting bone formation and enhancing TRAF6-mediated osteoclastogenesis than IL6, implying that the regulatory mechanisms of TNFα and IL6 in bone metabolism may be different.

Telmisartan provides renal benefit at all stages of the renal continuum in patients with type 2 diabetes mellitus. This research is to investigate the effect of telmisartan on kidney function in diabetic rats and to identify the underlying molecular mechanisms. Diabetic rats were divided into vehicle group, low dosage (TeL) group, and high dosage of telmisartan (TeH) group. We performed Illumina RatRef-12 Expression BeadChip gene array experiments. We found 3-months of treatment with telmisartan significantly decreased 24-h urinary albumin, serum creatinine, blood urea nitrogen, and increased creatinine clearance rate. Kidney hypertrophy and glomerular mesangial matrix expansion were ameliorated. The glomeruli from the TeH group had 1541 genes with significantly changed expression (554 increased, 987 decreased). DAVID (Database for annotation, visualization and Integrated discovery) analyses showed that the most enriched term was ‘mitochondrion’ (Gene Ontology (GO:0005739)) in all 67 GO functional categories. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses indicated that all differentially expressed genes included seven KEGG pathways. Of those pathways, four are closely related to the oxidative phosphorylation pathway. Quantitative real-time PCR verified that the H+ transporting mitochondrial F1 complex, beta subunit (Atp5b), cytochrome c oxidase subunit VIc (Cox6c), and NADH dehydrogenase (ubiquinone) Fe-S protein 3 (Ndufs3) were significantly downregulated both in TeL and TeH groups, while nephrosis 1 homolog (Nphs1) and nephrosis 2 homolog (Nphs2) were significantly upregulated. The increased expression of malonaldehyde and NDUFS3 in the glomeruli of diabetic rats was attenuated by telmisartan. The other significantly changed pathway we found was the peroxisome proliferator-activated receptor (PPAR) signaling pathway. Our data suggest that telmisartan can improve kidney function in diabetic rats. The mechanism may be involved in mitochondrion oxidative phosphorylation, the PPAR-γ pathway, and the slit diaphragm.

Neuromedin B (NMB), a mammalian bombesin-related peptide, has numerous physiological functions, including regulating hormone secretions, cell growth, and reproduction, by binding to its receptor (NMBR). In this study, we investigated the effects of NMB on testosterone secretion, steroidogenesis, cell proliferation, and apoptosis in cultured primary porcine Leydig cells. NMBR was mainly expressed in the Leydig cells of porcine testes, and a specific dose of NMB significantly promoted the secretion of testosterone in the primary Leydig cells; moreover, NMB increased the expression of mRNA and/or proteins of NMBR and steroidogenic mediators (steroidogenic acute regulatory (STAR), CYP11A1, and HSD3B1) in the Leydig cells. In addition, specific doses of NMB promoted the proliferation of Leydig cells and increased the expression of proliferating cell nuclear antigen and Cyclin B1 proteins, while suppressing Leydig cell apoptosis and decreasing BAX and Caspase-3 protein expression. These results suggest that the NMB/NMBR system might play an important role in regulating boar reproductive function by modulating steroidogenesis and/or cell growth in porcine Leydig cells.