Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease known by the presence of elevated blood glucose levels. Nowadays, it is perceived as a worldwide epidemic, with a very high socioeconomic impact on public health. Many are the complications caused by this chronic disorder, including a negative impact on the cardiovascular system, kidneys, eyes, muscle, blood vessels, and nervous system. Recently, there has been increasing evidence suggesting that T2DM also adversely affects the skeletal system, causing detrimental bone effects such as bone quality deterioration, loss of bone strength, increased fracture risk, and impaired bone healing. Nevertheless, the precise mechanisms by which T2DM causes detrimental effects on bone tissue are still elusive and remain poorly studied. The aim of this review was to synthesize current knowledge on the different factors influencing the impairment of bone fracture healing under T2DM conditions. Here, we discuss new approaches used in recent studies to unveil the mechanisms and fill the existing gaps in the scientific understanding of the relationship between T2DM, bone tissue, and bone fracture healing.
The microRNA-29 (miR-29) family is among the most abundantly expressed microRNA in the pancreas and liver. Here, we investigated the function of miR-29 in glucose regulation using miR-29a/b-1 (miR-29a)-deficient mice and newly generated miR-29b-2/c (miR-29c)-deficient mice. We observed multiple independent functions of the miR-29 family, which can be segregated into a hierarchical physiologic regulation of glucose handling. miR-29a, and not miR-29c, was observed to be a positive regulator of insulin secretion in vivo, with dysregulation of the exocytotic machinery sensitizing β-cells to overt diabetes after unfolded protein stress. By contrast, in the liver both miR-29a and miR-29c were important negative regulators of insulin signaling via phosphatidylinositol 3-kinase regulation. Global or hepatic insufficiency of miR-29 potently inhibited obesity and prevented the onset of diet-induced insulin resistance. These results demonstrate strong regulatory functions for the miR-29 family in obesity and diabetes, culminating in a hierarchical and dose-dependent effect on premature lethality.
Context: Inflammation during obesity is associated with higher risk of metabolic syndrome and coronary artery disease (CAD). Activation of the inflammatory toll-like receptor (TLR)/nuclear factor κB (NFκB) signaling in monocytes contributes to inflammation. Weight loss after bariatric surgery leads to significant improvement of obesity-related comorbidities. MicroRNA (miR), a class of small noncoding RNA, have been implicated as negative regulators of inflammatory processes. Objective: This study sought to identify dysregulated miR in monocytes of obese patients associated with TLR/NFκB signaling, metabolic syndrome, and CAD. Design, Setting, and Patients: This retrospective study included two independent cohorts of 21 morbidly obese and 125 high-risk obese and nonobese patients in a hospitalized care setting. Intervention: Intervention included bariatric surgery (n = 21) with a 3-month follow-up. Main Outcome Measures: miR expressions in CD14+ monocytes were determined by microarray analysis. TLR/NFκB-related miR were identified by an in silico target prediction analysis. Their expression was validated by quantitative RT-PCR. Their association with metabolic syndrome and angiographically documented CAD was assessed. Results: miR-181a, -181b, and -181d, identified as possible regulators of the TLR/NFκB signaling, were decreased in obese monocytes, and weight loss normalized their expression to levels observed in monocytes of lean persons. miR-181a but not miR-181b and miR-181d was associated with a higher number of metabolic syndrome components and with CAD even after adjustment for traditional risk factors, obesity and the metabolic syndrome. Conclusion: This study demonstrates that the TLR/NFκB-related miR-181a is down-regulated in monocytes of obese patients and suggests that it is a putative biomarker of metabolic syndrome and CAD.