Nonenzymatic function of DPP4 promotes diabetes-associated cognitive dysfunction through IGF-2R/PKA/SP1/ERp29/IP3R2 pathway-mediated impairment of Treg function and M1 microglia polarization.

BACKGROUND: Impairment of regulatory T (Treg) cells function is implicated in the pathogenesis of immune imbalance-mediated cognitive impairment. A complete understanding of whether and how this imbalance affect cognitive function in type 2 diabetes is lacking, and the driver affecting this imbalance remains unknown. METHODS: We examined the impact of enzymatic and non-enzymatic function of DPP4 on Treg cell impairment, microglia polarization and diabetes-associated cognitive defects and identified its underlying mechanism in type 2 diabetic patients with cognitive impairment and in db/db mice. RESULTS: We report that DPP4 binds to IGF2-R on Treg cell surface and activates PKA/SP1 signaling, which upregulate ERp29 expression and promote its binding to IP3R2, thereby inhibiting IP3R2 degradation and promoting mitochondria-associated ER membrane formation and mitochondria calcium overload in Tregs. This, in turn, impairs Tregs function and polarizes microglia toward a pro-inflammatory phenotype in the hippocampus and finally leads to neuroinflammation and cognitive impairment in type 2 diabetes. Importantly, inhibiting DPP4 enzymatic activity in type 2 diabetic patients or mutating DPP4 enzymatic active site in db/db mice did not reverse these changes. However, IGF-2R knockdown or blockade ameliorated these effects both in vivo and in vitro. CONCLUSION: These findings highlight the nonenzymatic role of DPP4 in impairing Tregs function, which may facilitate the design of novel immunotherapies for diabetes-associated cognitive impairment.

Nonenzymatic function of DPP4 in diabetes-associated mitochondrial dysfunction and cognitive impairment.

Dipeptidyl peptidase-4 (DPP4) has been proven to exert its functions by both enzymatic and nonenzymatic pathways. The nonenzymatic function of DPP4 in diabetes-associated cognitive impairment remains unexplored. We determined DPP4 protein concentrations or its enzymatic activity in type 2 diabetic patients and db/db mice and tested the impact of the non-enzymatic function of DPP4 on mitochondrial dysfunction and cognitive impairment both in vivo and in vitro. The results show that increased DPP4 activity was an independent risk factor for incident mild cognitive impairment (MCI) in type 2 diabetic patients. In addition, DPP4 was highly expressed in the hippocampus of db/db mice and contributed to mitochondria dysfunction and cognitive impairment. Mechanistically, DPP4 might bind to PAR2 in the hippocampus and trigger GSK-3ß activation, which downregulates peroxisome proliferator-activated receptor gamma coactivator 1 alpha expression and leads to mitochondria dysfunction, thereby promoting cognitive impairment in diabetes. Our findings indicate that the nonenzymatic function of DPP4 might promote mitochondrial dysfunction and cognitive impairment in diabetes.

[The protective mechanism study of fengshiqing recipe against bone destruction in CIA rats].

OBJECTIVE: To explore the protective mechanism of Fengshiqing Recipe (FR) against bone destruction in collagen-induced arthritis (CIA) rats. METHODS: Rats were divided into four groups in the experiment,i.e., the blank control group, the model group, the MTX group (MTX, 1 mg/1 000 g), and the FR group (24 g crude FR/kg). The CIA model was prepared except the blank control group. Medication was started in the MTX group and the FR group from the 14th day after modeling to the 56th day. The toe volume was measured on every Tuesday and Friday. Expression levels of serum IL-17, RANKL, MIP-1alpha were detected after 3-and 6-week intervention. The bone scintigraphy with nuclide (SPECT), bone mineral density (BMD), and the pathological section were observed to assess the intervention of drugs of heat clearing blood activating actions in the bone destruction of CIA rats. RESULTS: From the 10th day of modeling, the volume of both toes started to swell and reached the peak at about 21 days. It was obviously shrunk at about 30 days. Of them, the swelling degree was milder in the MTX group and the FR group than in the model group. Compared with the model group at the same phase, the levels of IL-17 and RANKL decreased in the MTX group after 3 weeks of intervention (P < 0.01, P < 0.05). The IL-17 level decreased in the FR group after three weeks of intervention (P < 0.05). The RANKL level decreased in the MTX group and the FR group after 6 weeks of intervention (P < 0.01, P < 0.05). Compared with the model group and the MTX group, the overall BMD and ankle BMD increased in the FR group after 6 weeks of intervention (P < 0.01, P < 0.05). The ankle ROI/mandible and the toe ROI/mandible were elevated in the FR group after 3 weeks of intervention (P < 0.05). Pathological results suggested that the joint lacunae was significantly widened, the hyperplasia of the synovial tissue was so severe, and the bone tissue was destroyed in the model group. Compared with the model group, the aforesaid conditions were significantly improved in the MTX group and the FR group. The cartilage structure was complete. CONCLUSION: QR could inhibit decreased BMD, prevent bone destruction, which might be achieved by down-regulating expression levels of IL-17, RANKL, and MIP-1alpha through the osteo immunological Th/RANKL system,inhibiting maturation and differentiation of osteoclasts, thereby, inhibiting bone destruction.

[99mTc-Pingyangmycin imaging in the diagnosis of primary lung cancer].

OBJECTIVE: To evaluate the clinical value of (99m)Tc-Pingyangmycin (PYM) imaging for the diagnosis of primary lung cancer. METHODS: Radionuclide (99m)Tc-Pingyangmycin (PYM) imaging was performed in 56 patients with pulmonary lesions. RESULTS: The uptake ratio and retention index (RI) were different in malignant and benign lesions. With the delayed ratio regarded as the threshold for lung cancer, the overall accuracy, sensitivity and specificity of (99m)Tc-PYM in the diagnosis of lung cancer were 82.1%, 82.7% and 80%, respectively. If RI was regarded as the threshold, the overall accuracy, sensitivity and specificity were 94.6%, 93% and 100%, respectively. There was no significant difference among different histological types of the lung carcinoma. CONCLUSION: (99m)Tc-PYM, as a good imaging agent, is useful in differentiating malignant lung lesions from benign ones.