SummaryObesity (OB) and type 2 diabetes (T2D) are among the most prevalent metabolic diseases. They currently affect a substantial part of the world population and are characterized by several systemic co‐morbidities, including cardiovascular diseases, stroke, cancer, liver steatosis, and musculoskeletal disorders, by increasing the risk of developing osteoarthritis and intervertebral disc degeneration (IVDD). IVDD is a chronic, progressive process whose main features are disc dehydration, loss of disc height, and changes of load distribution across the spine, resulting in disc structure disruption and leading to low back pain onset. Given the high prevalence of these metabolic disorders and their association with IVDD, several studies have been conducted in order to investigate the causative role of biological and biomechanical characteristics proper to these conditions in the development of IVDD. This review aims to analyse the role of OB and T2D on IVDD, in order to clarify the pathophysiological drivers of the degenerative process and to delineate possible targets to which appropriate treatments may be addressed in the near future.

Increased circulating sclerostin and accumulation of advanced glycation end‐products (AGEs) are two potential mechanisms underlying low bone turnover and increased fracture risk in type 2 diabetes (T2D). Whether the expression of the sclerostin‐encoding SOST gene is altered in T2D, and whether it is associated with AGEs accumulation or regulation of other bone formation‐related genes is unknown. We hypothesized that AGEs accumulate and SOST gene expression is upregulated in bones from subjects with T2D, leading to downregulation of bone forming genes (RUNX2 and osteocalcin) and impaired bone microarchitecture and strength. We obtained bone tissue from femoral heads of 19 T2D postmenopausal women (mean glycated hemoglobin [HbA1c] 6.5%) and 73 age‐ and BMI‐comparable nondiabetic women undergoing hip replacement surgery. Despite similar bone mineral density (BMD) and biomechanical properties, we found a significantly higher SOST (p = .006) and a parallel lower RUNX2 (p = .025) expression in T2D compared with non‐diabetic subjects. Osteocalcin gene expression did not differ between T2D and non‐diabetic subjects, as well as circulating osteocalcin and sclerostin levels. We found a 1.5‐fold increase in total bone AGEs content in T2D compared with non‐diabetic women (364.8 ± 78.2 versus 209.9 ± 34.4 μg quinine/g collagen, respectively; p < .001). AGEs bone content correlated with worse bone microarchitecture, including lower volumetric BMD (r = −0.633; p = .02), BV/TV (r = −0.59; p = .033) and increased trabecular separation/spacing (r = 0.624; p = .023). In conclusion, our data show that even in patients with good glycemic control, T2D affects the expression of genes controlling bone formation (SOST and RUNX2). We also found that accumulation of AGEs is associated with impaired bone microarchitecture. We provide novel insights that may help understand the mechanisms underlying bone fragility in T2D. © 2020 American Society for Bone and Mineral Research (ASBMR).

Physical exercise favors weight loss and ameliorates articular pain and function in patients suffering from osteoarthritis. Irisin, a myokine released upon muscle contraction, has demonstrated to yield anabolic effects on different cell types. This study aimed to investigate the effect of irisin on human osteoarthritic chondrocytes (hOAC) in vitro. Our hypothesis was that irisin would improve hOAC metabolism and proliferation. Cells were cultured in growing media and then exposed to either phosphate-buffered saline (control group) or human recombinant irisin (experimental group). Cell proliferation, glycosaminoglycan content, type II/X collagen gene expression and protein quantification as well as p38/extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK), protein kinase B (Akt), c-Jun N-terminal kinase (JNK), and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) involvement were evaluated. Furthermore, gene expression of interleukin (IL)-1 and -6, matrix metalloproteinase (MMP)-1 and -13, inducible nitric oxide synthase (iNOS), and tissue inhibitor of matrix metalloproteinases (TIMP)-1 and -3 were investigated following irisin exposure. Irisin increased hOAC cell content and both type II collagen gene expression and protein levels, while decreased type X collagen gene expression and protein levels. Moreover, irisin decreased IL-1, IL-6, MMP-1, MMP-13 and iNOS gene expression, while increased TIMP-1 and TIMP-3 levels. These effects seemed to be mediated by inhibition of p38, Akt, JNK and NFκB signaling pathways. The present study suggested that irisin may stimulate hOAC proliferation and anabolism inhibiting catabolism through p38, Akt, JNK, and NFκB inactivation in vitro, demonstrating the existence of a cross-talk between muscle and cartilage.

One of the main goals of diabetic therapy is to achieve the best metabolic control to prevent the development and progression of potential complications. A multidisciplinary approach characterized by the combination of diet, physical activity (PA) and drug therapy with oral and injectable (non-insulin) pharmacological agents, is desirable to optimize metabolic control. The aim of this review is to explain the contribution of PA and its beneficial effects on patients affected by type 1 (T1D) and type 2 diabetes (T2D). We provide an overview of evidence on the effects of PA for the main two types of diabetes mellitus (DM) to identify the right level of PA to be recommended. We discuss the physiological and clinical role of PA in people with DM. It can be concluded that the objective of antidiabetic therapy should be the achievement and optimization of metabolic control through a multidisciplinary approach involving non-pharmacological therapy such as diet and PA, which has a crucial role.

Summary Over the last decades, osteoarthritis (OA) and type 2 diabetes (T2D) prevalence increased due to the global ageing population and the pandemic obesity. They currently affect a substantial part of the Western world population and are characterized by enhancing the risk of disability and reduction of quality of life. OA is a multifactorial condition whose development derives from the interaction between individual and environmental factors: The best known primarily include age, female gender, genetic determinants, articular biomechanics, and obesity (OB). Given the high prevalence of OA and T2D and their association with OB and inflammation, several studies have been conducted to investigate the causative role of biological characteristics proper to T2D on the development of OA. This review aims to analyse the relationship between of OA and T2D, in order to explain the pathophysiological drivers of the degenerative process and to delineate possible targets to which appropriate treatments may be addressed in the near future.