Effects of the Rate of Impaired Insulin Secretion on Bone Mineral Density in Type 1 Diabetes

Background: Type 1 Diabetes mellitus (T1DM) is a well-known condition associated with low bone mineral density (BMD) and bone fracture, in which one of the risk factor is impaired endogenous insulin secretion. However, the association between the rate of impaired insulin secretory capacity in T1DM and BMD remains to be elucidated. Objective: To clarify the effect of the rate of impaired insulin secretion on BMD in T1DM. Patients and Methods: This a retrospective single-center cross-sectional study, in which consecutive one-hundred seventy Japanese patients with T1DM at Kobe University Hospital were registered. According to the diagnostic criteria of The Japan Diabetes Society, patients were stratified into three subtypes; acute-onset (AO) (n =51, male 25%, 39 ± 15 years), slowly-progressive (SP) (n =37, male 37%, 57 ± 14 years), and fulminant (F) (n =12, male 33%, 51 ± 15 years) mainly by insulin secretory capacity at onset of T1DM. Lumbar spine (LS) and femoral neck (FN) BMD Z-score between three groups were evaluated. Results: The LS BMD is lower in AO than SP (p =0.03), while no differences were observed compared to F (SP/AO/F; 0.38 ± 1.08/-0.25 ± 0.96/-0.35 ± 1.01). The FN BMD also tended to be lower in AO than in SP (p =0.08) and in F (p =1.00) (SP/AO/F;0.03 ± 1.01/-0.44 ± 0.96/-0.35 ± 0.70). To identify the factors associated with decreased BMD, the multivariate regression analysis was performed using AO and SP. The LS BMD was associated with the pathogenic group (p =0.01). Since a negative correlation was seen between durations and CPR both in AO and SP group (p <0.01, p <0.01), we divided these subjects into following 5 groups; 1 to 4, 5 to 9, 10 to 14, 15 to 19, and more than 20 years. In these groups, the CPR was lower in AO than in SP in 1 to 4 years (p <0.01). Intriguingly, LS BMD was started to decline in 5 to 9 years (p =0.03) and was still continued in 10 to 14 years (p =0.01). In FN, BMD was started to decline in 10 to 14 years (p =0.01), suggesting the BMD decline followed by impaired insulin secretion. However, the difference of both BMD and CPR between AO and SP groups were not seen in more than 15 years group, indicating this tangent BMD difference is link to the difference of insulin secretion. Conclusions: This study firstly showed that pathogenic subtypes of T1DM differently affected on BMD. A detailed examination of each disease period showed that BMD continued to decrease as impaired insulin secretion.

Silencing of lncRNA PVT1 ameliorates streptozotocin-induced pancreatic β cell injury and enhances insulin secretory capacity via regulating miR-181a-5p

Diabetes mellitus (DM) is a kind of metabolic disorder characterized by long-term hyperglycemia. Accumulating evidence shows that long noncoding RNAs (lncRNAs) play significant roles in the occurrence and development of DM. This study intended to investigate the role of lncRNA plasmacytoma variant translocation 1 (PVT1) in rat insulinoma (INS-1) cells damaged by streptozotocin (STZ) and to identify the potential mechanisms. Firstly, PVT1 expression in INS-1 cells was assessed using RT-qPCR after STZ stimulation. After PVT1-knockdown, cell apoptosis, the contents of oxidative stress-related markers and the changes of insulin secretion were detected. Results indicated that PVT1 was remarkably upregulated after STZ stimulation. PVT1-knockdown inhibited STZ-induced oxidative stress and apoptosis of INS-1 cells. Moreover, the insulin secretory capacity was notably elevated following PVT1 silencing. Subsequently, a luciferase reporter assay verified that miR-181a-5p was directly targeted by PVT1. The rescue assays revealed that miR-181a-5p inhibitor dramatically abrogated the effects of PVT1 silencing on oxidative stress, apoptosis and insulin secretion. Taken together, these findings demonstrated that PVT1-knockdown could ameliorate STZ-induced oxidative stress and apoptosis and elevate insulin secretory capacity in pancreatic β cell via regulating miR-181a-5p, suggesting a promising biomarker in DM diagnosis and treatment.