Exercise-driven metabolic pathways in healthy cartilage.

OBJECTIVE: Exercise is vital for maintaining cartilage integrity in healthy joints. Here we examined the exercise-driven transcriptional regulation of genes in healthy rat articular cartilage to dissect the metabolic pathways responsible for the potential benefits of exercise. METHODS: Transcriptome-wide gene expression in the articular cartilage of healthy Sprague-Dawley female rats exercised daily (low intensity treadmill walking) for 2, 5, or 15 days was compared to that of non-exercised rats, using Affymetrix GeneChip arrays. Database for Annotation, Visualization and Integrated Discovery (DAVID) was used for Gene Ontology (GO)-term enrichment and Functional Annotation analysis of differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genome (KEGG) pathway mapper was used to identify the metabolic pathways regulated by exercise. RESULTS: Microarray analysis revealed that exercise-induced 644 DEGs in healthy articular cartilage. The DAVID bioinformatics tool demonstrated high prevalence of functional annotation clusters with greater enrichment scores and GO-terms associated with extracellular matrix (ECM) biosynthesis/remodeling and inflammation/immune response. The KEGG database revealed that exercise regulates 147 metabolic pathways representing molecular interaction networks for Metabolism, Genetic Information Processing, Environmental Information Processing, Cellular Processes, Organismal Systems, and Diseases. These pathways collectively supported the complex regulation of the beneficial effects of exercise on the cartilage. CONCLUSIONS: Overall, the findings highlight that exercise is a robust transcriptional regulator of a wide array of metabolic pathways in healthy cartilage. The major actions of exercise involve ECM biosynthesis/cartilage strengthening and attenuation of inflammatory pathways to provide prophylaxis against onset of arthritic diseases in healthy cartilage.

Follistatin-like 3 is a mediator of exercise-driven bone formation and strengthening.

Exercise is vital for maintaining bone strength and architecture. Follistatin-like 3 (FSTL3), a member of follistatin family, is a mechanosensitive protein upregulated in response to exercise and is involved in regulating musculoskeletal health. Here, we investigated the potential role of FSTL3 in exercise-driven bone remodeling. Exercise-dependent regulation of bone structure and functions was compared in mice with global Fstl3 gene deletion (Fstl3-/-) and their age-matched Fstl3+/+ littermates. Mice were exercised by low-intensity treadmill walking. The mechanical properties and mineralization were determined by µCT, three-point bending test and sequential incorporation of calcein and alizarin complexone. ELISA, Western-blot analysis and qRT-PCR were used to analyze the regulation of FSTL3 and associated molecules in the serum specimens and tissues. Daily exercise significantly increased circulating FSTL3 levels in mice, rats and humans. Compared to age-matched littermates, Fstl3-/- mice exhibited significantly lower fracture tolerance, having greater stiffness, but lower strain at fracture and yield energy. Furthermore, increased levels of circulating FSTL3 in young mice paralleled greater strain at fracture compared to the lower levels of FSTL3 in older mice. More significantly, Fstl3-/- mice exhibited loss of mechanosensitivity and irresponsiveness to exercise-dependent bone formation as compared to their Fstl3+/+ littermates. In addition, FSTL3 gene deletion resulted in loss of exercise-dependent sclerostin regulation in osteocytes and osteoblasts, as compared to Fstl3+/+ osteocytes and osteoblasts, in vivo and in vitro. The data identify FSTL3 as a critical mediator of exercise-dependent bone formation and strengthening and point to its potential role in bone health and in musculoskeletal diseases.

Use of NMR imaging in the optimization of a compression-coated regulated release system.

Nuclear magnetic resonance (NMR) imaging is routinely used to detect the protons of mobile water molecules within samples. In this investigation, this non-destructive, non-invasive technique was used to determine the cause for faster than predicted drug release from a dissolution-based regulated-release tablet. The NMR images of tablets, from two different formulations, taken at various intervals of time while immersed in static USP dissolution medium showed that the tablet with faster than predicted drug release had a porous coating. The porous coat exposed more of the core surface area to the dissolution medium than desired and this caused an increase in the rate of dissolution of the core. The data presented in this paper demonstrate the usefulness of NMR imaging in solid dosage form development.

Complications in investigations of the swelling of hydrogel matrices due to the presence of trapped gas.

In recent studies, NMR imaging has been used to investigate the swelling of hydroxypropylmethylcellulose (HPMC) tablets and to determine polymer concentration distributions in the swollen matrix. The total amount of polymer in the system was computed from these distributions and was up to 35% greater than the known weight of HPMC in the tablet. This deviation was traced to the presence of air bubbles in the swollen matrix which occupied a significant volume previously assumed to be occupied by polymer and water. When the air in the tablet was removed by vacuum, the swollen gel contained no evidence of air bubbles and the calculated total polymer weights from the HPMC distributions were equal to the amount of HPMC in the tablet.