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Since its discovery in 1994, leptin has been considered as an adipokine with pleiotropic effects. In this review, we summarize the actual information about the impact of this hormone on cartilage metabolism and pathology. Leptin signalling depends on the interaction with leptin receptor LEPR, being the long isoform of the receptor (LEPRb) the one with more efficient intracellular signalling. Chondrocytes express the long isoform of the leptin receptor and in these cells, leptin signalling, alone or in combination with other molecules, induces the expression of pro-inflammatory molecules and cartilage degenerative enzymes. Leptin has been shown to increase the proliferation and activation of immune cells, increasing the severity of immune degenerative cartilage diseases. Leptin expression in serum and synovial fluid are related to degenerative diseases such as osteoarthritis (OA), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Inhibition of leptin signalling showed to have protective effects in these diseases showing the key role of leptin in cartilage degeneration.

Bionanocomposites of poly(3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV) with cellulose nanocrystals (CNC) were processed by extrusion. Differential scanning calorimetry (DSC) showed that with increasing the amount of CNC the overall crystallization time was reduced. Wide angle X -ray scattering (WAXS) showed diffraction peaks of orthorhombic a-type crystalline structure and confirmed the nucleating agent effect of CNC particles in the PHBV matrix. Small angle X-ray scattering (SAXS) showed that the reducing rate of long spacing was slower in the filled sample than in PHBV. Microscopy images (Scanning Electron Microscopy, SEM, and Transmission Electron Microscopy, TEM) revealed well-dispersed morphology in low loading of the filler while slight agglomerations appeared at higher filler concentration. Statistical analysis was done by applying a one-way ANOVA (a 5 0.05) to evaluate the effect of filler on mechanical properties of PHBV. Water vapor, oxygen and carbon dioxide transmission rate showed that the incorporation of CNC nanocrystals led to an improvement in the barrier properties of the bionanocomposites due to higher crystallinity and more tortuosity in their morphologies. POLYM. COMPOS., 00:000-000, 2017.

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