Background: The mechanisms which cause age-dependent remodeling of connective tissue are still not fully understood. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) constitute an important proteolytic pathway affecting physiological matrix remodeling. Objective: The way in which changes in the extracellular matrix metabolism during the ageing process influence the level of circulating MMP-3 and MMP-10, as well as their tissue inhibitors TIMP-1 and TIMP-2, in a healthy population was investigated in this study. Methods: Blood samples were taken from 81 healthy individuals aged 6–62 years and measured for MMP-3, MMP-10, TIMP-1 and TIMP-2 levels using enzyme-linked immunosorbent assays. Polyacrylamide gel electrophoresis followed by Western immunoblotting allowed for the detection of pro- and active forms of both MMPs. Results: Serum MMP-3 and TIMP-1 values were positively correlated with age (r = 0.44, p = 0.00001 and r = 0.28, p = 0.012, respectively). A contrary tendency was found for MMP-10 and TIMP-2 serum levels. A strong age-related decrease in MMP-10 (–0.53; p = 0.000) and TIMP-2 (–0.52; p = 0.000) was noticed in our study. Gender was a significant factor modifying MMP/TIMP potential, except for the MMP-10 level. Conclusions: The data presented indicate that changes in MMP/TIMP balance occur in physiological ageing. Moreover, these findings highlight the necessity of utilizing age- and sex-matched values for analysis of MMPs and TIMPs in the pathological conditions.

The aim of the present study is to quantitatively assess the expression of selected regulatory molecules, such as leptin, leptin receptor, and adiponectin in the blood of obese patients with type 2 diabetes both before treatment and after six months of pharmacological therapy with the long-lasting insulin analogue, insulin detemir. A significant decrease in the analysed regulatory molecules, i.e., leptin receptor and adiponectin, was found in blood plasma of the patients with untreated type 2 diabetes. These changes were accompanied by an increase in plasma leptin concentrations. Insulin treatment resulted in the normalization of plasma leptin receptor and adiponectin concentrations. The circulating leptin level did not change following anti-diabetic therapy with insulin detemir. Gender was a significant factor modifying the circulating level of all the analysed regulatory active compounds. Bioinformatic analysis was performed using Matlab with the Signal Processing Toolbox. The conducted discriminant analysis revealed that the leptin receptor, Δw(19), and adiponectin, Δw(21), were the parameters undergoing the most significant quantitative changes during the six-month therapy with insulin detemir. The conducted examinations indicated the contribution of adipocytokines—the biologically-active mediators of systemic metabolism, such as leptin and adiponectin in the pathomechanism of disorders being the basis for obesity which leads to development of insulin resistance, which, in turn, results in the occurrence of type 2 diabetes.

This study was undertaken to reveal how the physiological ageing process influences plasma glycosaminoglycans (GAGs) content and composition. GAGs isolated from plasma samples obtained from 105 healthy subjects were quantified using a hexuronic acid assay and subjected to electrophoretic fractionation. We found that total GAGs decreased gradually with advancing age. The electrophoretic analysis allowed identifying chondroitin sulfates, dermatan sulfates and heparan sulfates and heparin in plasma of healthy individuals. Chondroitin sulfates, predominant plasma GAGs, showed declining values with age and displayed higher structural diversity in subjects from the first five decades of life compared to older subjects. An age-related increase in plasma dermatan sulfates content during the first four decades of life followed by a decrease in a later period of life was apparent. Structural heterogeneity of these glycans was found in subjects until 10 years of age. Heparan sulfates and heparin plasma levels were inversely correlated with age until 25 years of age, without age-dependent changes thereafter. These macromolecules displayed higher heterogeneity of structure in subjects over 50 years of age than in younger subjects. The obtained results indicate that age should be taken into account in all studies investigating blood GAGs alterations during pathological conditions.

The authors studied the role of increased oxidative stress in the development of oxidative protein damage and extracellular matrix (ECM) components in ageing. The age- and gender-associated disturbances in connective tissue metabolism were evaluated by the plasma chondroitin sulphated glycosaminoglycans (CS-GAG) and non-sulphated GAG-hyaluronan (HA) measurements. Plasma concentration of advanced oxidation protein products (AOPP) was analysed in order to assess oxidative protein damage and evaluate the possible deleterious role of oxidative phenomenon on tissue proteoglycans' metabolism during the physiological ageing process. Sulphated and non-sulphated GAGs as well as AOPP were quantified in plasma samples from 177 healthy volunteers. A linear age-related decline of plasma CS-GAG level was found in this study (r=-0.46; p<0.05). In contrast, HA concentrations rise gradually with age (r=0.44; p<0.05) in plasma samples. For both ECM components, the observed differences were not gender-specific. A strong age-dependent relationship has been shown in regard to AOPP. AOPP levels significantly increased with age (r=0.63; p<0.05), equally strongly in both men (r=0.69; p<0.05) and women (r=0.57; p<0.05) during physiological ageing. A significant correlation was found between the concentrations of AOPP and both CS-GAG (r=-0.31; p<0.05) and HA (r=0.33; p<0.05). Proceeding with age changes in the ECM are reflected by CS-GAG and HA plasma levels. Strong correlations between AOPP and ECM components indicate that oxidative stress targets protein and non-protein components of the connective tissue matrix during human ageing.