Existence of ATP sensitive potassium currents on human periodontal ligament cells

The surprising complexity of KATP channel biology and of genetic diseases

The ATP-sensitive K+ channel (KATP) is formed by the association of four inwardly rectifying K+ channel (Kir6.x) pore subunits with four sulphonylurea receptor (SUR) regulatory subunits. Kir6.x or SUR mutations result in KATP channelopathies, which reflect the physiological roles of these channels, including but not limited to insulin secretion, cardiac protection, and blood flow regulation. In this issue of the JCI, McClenaghan et al. explored one of the channelopathies, namely Cantu syndrome (CS), which is a result of one kind of KATP channel mutation. Using a knockin mouse model, the authors demonstrated that gain-of-function KATP mutations in vascular smooth muscle resulted in cardiac remodeling. Moreover, they were able to reverse the cardiovascular phenotypes by administering the KATP channel blocker glibenclamide. These results exemplify how genetic mutations can have an impact on developmental trajectories, and provide a therapeutic approach to mitigate cardiac hypertrophy in cases of CS.

Tripartite motif 31 alleviates IL-1ß secretion via promoting the ubiquitination of pyrin domain domains-containing protein 3 in human periodontal ligament fibroblasts

Apical periodontitis (AP) is an inflammatory disease caused by bacteria infection and is regarded as a common disease in the world. In the progression of AP, the function of nucleotide-binding oligomerization, leucine-rich repeat and pyrin domain domains-containing protein 3 (NLRP3) inflammasome has been revealed. Although tripartite motif 31 (TRIM31) has been suggested to regulate many chronic inflammations by mediating NLRP3 inflammasome, such mechanism in AP remains unclear. In this study, co-treatment of human periodontal ligament fibroblasts (HPDLFs) with lipopolysaccharides (LPS) and adenosine triphosphate (ATP) were conducted to establish AP cell model. ELISA assay was used to measure the concentration of secretive interleukin 1 beta (IL-1β). In addition, the expression levels of NLRP3 after TRIM31 up- or down-regulation were detected by real-time PCR and western blot. Immunoprecipitation was used to explore the interaction between TRIM31 and NLRP3. We found that co-treatment with LPS and ATP increased the secretion of IL-1β and expression of NLRP3 in HPDLFs, while TRIM31 overexpression could reverse these effects caused by LPS and ATP. Furthermore, the interaction between TRIM31 and NLRP3 was observed, and TRIM31 was found to promote the ubiquitination of NLRP3. TRIM31 may alleviate IL-1ß secretion caused by LPS and ATP via promoting the ubiquitination of NLRP3 and may exert an influence on the development of AP.

Diabetes pharmacotherapy and effects on the musculoskeletal system

Persons with type 1 or type 2 diabetes have a significantly higher fracture risk than age-matched persons without diabetes, attributed to disease-specific deficits in the microarchitecture and material properties of bone tissue. Therefore, independent effects of diabetes drugs on skeletal integrity are vitally important. Studies of incretin-based therapies have shown divergent effects of different agents on fracture risk, including detrimental, beneficial, and neutral effects. The sulfonylurea class of drugs, owing to its hypoglycemic potential, is thought to amplify the risk of fall-related fractures, particularly in the elderly. Other agents such as the biguanides may, in fact, be osteo-anabolic. In contrast, despite similarly expected anabolic properties of insulin, data suggests that insulin pharmacotherapy itself, particularly in type 2 diabetes, may be a risk factor for fracture, negatively associated with determinants of bone quality and bone strength. Finally, sodium-dependent glucose co-transporter 2 inhibitors have been associated with an increased risk of atypical fractures in select populations, and possibly with an increase in lower extremity amputation with specific SGLT2I drugs. The role of skeletal muscle, as a potential mediator and determinant of bone quality, is also a relevant area of exploration. Currently, data regarding the impact of glucose lowering medications on diabetes-related muscle atrophy is more limited, although preclinical studies suggest that various hypoglycemic agents may have either aggravating (sulfonylureas, glinides) or repairing (thiazolidinediones, biguanides, incretins) effects on skeletal muscle atrophy, thereby influencing bone quality. Hence, the therapeutic efficacy of each hypoglycemic agent must also be evaluated in light of its impact, alone or in combination, on musculoskeletal health, when determining an individualized treatment approach. Moreover, the effect of newer medications (potentially seeking expanded clinical indication into the pediatric age range) on the growing skeleton is largely unknown. Herein, we review the available literature regarding effects of diabetes pharmacotherapy, by drug class and/or by clinical indication, on the musculoskeletal health of persons with diabetes.