The dipeptidyl peptidase-4 inhibitor, linagliptin, improves cognitive impairment in streptozotocin-induced diabetic mice by inhibiting oxidative stress and microglial activation

Upregulation of NADPH-oxidase, inducible nitric oxide synthase and apoptosis in the hippocampus following impaired insulin signaling in the rats: Development of sporadic Alzheimer's disease

NADPH-oxidase (NOX) is a multi-subunit enzyme complex. The upregulation of NOX causes massive production of superoxide (O2¯), which avidly reacts with nitric oxide (NO) and increases cellular reactive oxygen/nitrogen species (ROS/RNS). Increased ROS/RNS plays pivotal role in the sporadic Alzheimer's disease (sAD) development and brain damage following impaired insulin signaling. Hence, this study aimed to examine early-time course of changes in NOX and NOS expression, and apoptotic proteins in the rats hippocampi following insulin signaling impairment [induced by STZ injection; intraperitoneal (IP) or in cerebral ventricles (ICV)]. Early effects (1, 3, or 6 weeks) on the NOX activity, translocation of NOX subunits from cytosol to the membrane, NO-synthases [neuronal-, inducible- and endothelial-NOS; nNOS, iNOS and eNOS], The Rac-1 protein expression, levels of NO and O2¯, cytochrome c release, caspase-3 and 9 activations (cleavage) were studied. STZ injection (in both models) increased NOX activity, O2¯ production, and enhanced cytosolic subunits translocation into membrane. The iNOS but not nNOS and eNOS expression and NO levels were increased in STZ treated rats. Finally, STZ injection increased cytochrome c release, caspase-3 and 9 activations in a manner that was significantly associated with levels of O2¯ and NO in the hippocampus. ICV-STZ administration resulted in significant profound changes over the IP route. In conclusion, impairment in insulin function induces early changes in ROS/RNS contents through NOX and iNOS upregulation and neuronal apoptosis in the hippocampus. Our results could mechanistically explain the role of impaired insulin function in the development of sAD.

DPP-4 inhibition by linagliptin ameliorates age-related mild cognitive impairment by regulating microglia polarization in mice

Extensive preclinical evidence demonstrates a causative link between insulin signaling dysfunction and the pathogenesis of Alzheimer's disease (AD), and diabetic drugs may represent a promising approach to fighting AD. However, it remains to be determined which antidiabetic drugs are more effective in preventing cognitive impairment. Thus, the present study investigated the effect of dipeptidyl peptidase-4 (DPP-4) inhibitor linagliptin on cognitive impairment in middle-aged mice by comparing it with the effect of metformin. We found that DPP-4 activity increased in the hippocampus of middle-aged mice, and DPP-4 was mainly expressed by microglia rather than astrocytes and oligodendrocytes. DPP-4 directly regulated M1/M2 microglia polarization following LPS or IL-4 stimulation, while DPP-4 inhibitor, linagliptin, suppressed M1-polarized activation and induced M2-polarized activation. Both linagliptin and metformin enhanced cognitive ability, increased hippocampal synaptic plasticity and neurogenesis, and decreased age-related oxidative stress and inflammation by regulating microglia polarization in the hippocampus of middle-aged mice. The combination of linagliptin and metformin showed a maximum protective effect compared to the individual drugs alone. Loss of macrophage inflammatory protein-1α (MIP-1α), a DPP-4 substrate, abrogated the cognitive protection and anti-inflammation effects of linagliptin. Therefore, the current investigation exhibits a potential utility for DPP-4 inhibition in attenuating microglia-mediated inflammation and preventing mild cognitive impairment (MCI) in middle-aged mice, and the effect was partly mediated by MIP-1α.

Imeglimin Exhibits Novel Anti-Inflammatory Effects on High-Glucose-Stimulated Mouse Microglia through ULK1-Mediated Suppression of the TXNIP-NLRP3 Axis

Type 2 diabetes mellitus (T2DM) is an epidemiological risk factor for dementia and has been implicated in multifactorial pathologies, including neuroinflammation. In the present study, we aimed to elucidate the potential anti-inflammatory effects of imeglimin, a novel antidiabetic agent, on high-glucose (HG)-stimulated microglia. Mouse microglial BV2 cells were stimulated with HG in the presence or absence of imeglimin. We examined the effects of imeglimin on the levels of proinflammatory cytokines, intracellular reactive oxygen species (ROS), mitochondrial integrity, and components related to the inflammasome or autophagy pathways in these cells. Our results showed that imeglimin suppressed the HG-induced production of interleukin-1beta (IL-1β) by reducing the intracellular ROS levels, ameliorating mitochondrial dysfunction, and inhibiting the activation of the thioredoxin-interacting protein (TXNIP)-NOD-like receptor family pyrin domain containing 3 (NLRP3) axis. Moreover, the inhibitory effects of imeglimin on the TXNIP-NLRP3 axis depended on the imeglimin-induced activation of ULK1, which also exhibited novel anti-inflammatory effects without autophagy induction. These findings suggest that imeglimin exerted novel suppressive effects on HG-stimulated microglia through the ULK1-TXNIP-NLRP3 axis, and may, thereby, contribute to the development of innovative strategies to prevent T2DM-associated cognitive impairment.

Insights into early pathogenesis of sporadic Alzheimer's disease: role of oxidative stress and loss of synaptic proteins

Oxidative stress, induced by impaired insulin signaling in the brain contributes to cognitive loss in sporadic Alzheimer's disease (sAD). This study evaluated early hippocampal oxidative stress, pre- and post-synaptic proteins in intraperitoneal (IP) and intracerebroventricular (ICV) streptozotocin (STZ) models of impaired insulin signaling. Adult male Wistar rats were injected with STZ, IP, or ICV, and sacrificed 1-, 3-, or 6-weeks post injection. Rat's cognitive behavior was assessed using Morris water maze (MWM) tests at weeks 3 and 6. Hippocampal synaptosomal fractions were examined for oxidative stress markers and presynaptic [synapsin I, synaptophysin, growth-associated protein-43 (GAP-43), synaptosomal-associated protein-25 (SNAP-25)] and postsynaptic [drebrin, synapse-associated protein-97 (SAP-97), postsynaptic density protein-95 (PSD-95)] proteins. IP-STZ and ICV-STZ treatment impaired rat's cognition, decreased the levels of reduced glutathione (GSH) and increased the levels of thiobarbituric acid reactive species (TBARS) in a time dependent manner. In addition, it reduced the expression of pre- and post-synaptic proteins in the hippocampus. The decline in cognition is significantly correlated with the reduction in synaptic proteins in the hippocampus. In conclusion, impaired insulin signaling in the brain is deleterious in causing early synaptosomal oxidative damage and synaptic loss that exacerbates with time and correlates with cognitive impairments. Our data implicates oxidative stress and synaptic protein loss as an early feature of sAD and provides insights into early biochemical and behavioral changes during disease progression.

Dipeptidyl peptidase-4 inhibitors alleviate cognitive dysfunction in type 2 diabetes mellitus

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) are commonly at high risk for developing cognitive dysfunction. Antidiabetic agents might be repurposed for targeting cognitive dysfunction in addition to modulation on glucose homeostasis. This study aimed to evaluate the impact of dipeptidyl peptidase-4 inhibitors (DPP-4i) on cognitive function in T2DM.

METHODS

PubMed, Embase, Cochrane Library and Web of Science were systematically searched from inception to September 30, 2023. Weighted mean differences were calculated using the Mantel-Haenszel (M-H) fixed or random effects model based on the degree of heterogeneity among studies. Heterogeneity was evaluated using a Chi-squared test and quantified with Higgins I2. Sensitivity analysis was performed with the leave-one-out method, and publication bias was evaluated according to Begg's and Egger's tests.

RESULTS

Six clinical trials involving 5,178 participants were included in the pooled analysis. Administration of DPP-4i generally correlated with an increase of Mini-Mental State Examination (MMSE) scores (1.09, 95% CI: 0.22 to 1.96). DPP-4i alleviated cognitive impairment in the copying skill subdomain of MMSE (0.26, 95% CI: 0.12 to 0.40). Treatment with DPP-4i also resulted in an increase of Instrumental Activities of Daily Living (IADL) scores (0.82, 95% CI: 0.30 to 1.34). However, DPP-4i produced no significant effects on Barthel Activities of Daily Living (BADL) scores (0.37, 95% CI: -1.26 to 1.99) or other test scores.

CONCLUSIONS

DPP-4i treatment favourably improved cognitive function in patients with T2DM. Further trials with larger samples should be performed to confirm these estimates and investigate the association of different DPP-4i with cognitive function among diabetic patients.

TRIAL REGISTRATION IN PROSPERO

CRD42023430873.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

Crosstalk between Alzheimer's disease and diabetes: a focus on anti-diabetic drugs

Alzheimer's disease (AD) and Type 2 diabetes mellitus (T2DM) are two of the most common age-related diseases. There is accumulating evidence of an overlap in the pathophysiological mechanisms of these two diseases. Studies have demonstrated insulin pathway alternation may interact with amyloid-β protein deposition and tau protein phosphorylation, two essential factors in AD. So attention to the use of anti-diabetic drugs in AD treatment has increased in recent years. In vitro, in vivo, and clinical studies have evaluated possible neuroprotective effects of anti-diabetic different medicines in AD, with some promising results. Here we review the evidence on the therapeutic potential of insulin, metformin, Glucagon-like peptide-1 receptor agonist (GLP1R), thiazolidinediones (TZDs), Dipeptidyl Peptidase IV (DPP IV) Inhibitors, Sulfonylureas, Sodium-glucose Cotransporter-2 (SGLT2) Inhibitors, Alpha-glucosidase inhibitors, and Amylin analog against AD. Given that many questions remain unanswered, further studies are required to confirm the positive effects of anti-diabetic drugs in AD treatment. So to date, no particular anti-diabetic drugs can be recommended to treat AD.

Neuroprotective Impact of Linagliptin against Cadmium-Induced Cognitive Impairment and Neuropathological Aberrations: Targeting SIRT1/Nrf2 Axis, Apoptosis, and Autophagy

Cadmium is an environmental contaminant associated with marked neurotoxicity and cognitive impairment. Linagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has demonstrated promising neuroprotection against cerebral ischemia and diabetic dementia. However, there has been no study of its effect on cadmium-induced cognitive deficits. In the present work, linagliptin's prospective neuroprotective effects against cadmium-evoked cognitive decline were examined in vivo in rats. The molecular pathways related to oxidative stress, apoptosis, and autophagy were investigated. Histology, immunohistochemistry, ELISA, and biochemical assays were performed on brain hippocampi after receiving linagliptin (5 mg/kg/day). The current findings revealed that cadmium-induced learning and memory impairment were improved by linagliptin as seen in the Morris water maze, Y-maze, and novel object recognition test. Moreover, linagliptin lowered hippocampal neurodegeneration as seen in histopathology. At the molecular level, linagliptin curtailed hippocampal DPP-4 and augmented GLP-1 levels, triggering dampening of the hippocampal neurotoxic signals Aβ42 and p-tau in rats. Meanwhile, it enhanced hippocampal acetylcholine and GABA and diminished the glutamate spike. The behavioral recovery was associated with dampening of the hippocampal pro-oxidant response alongside SIRT1/Nrf2/HO-1 axis stimulation. Meanwhile, linagliptin counteracted hippocampal apoptosis markers and inhibited the pro-apoptotic kinase GSK-3β. In tandem, linagliptin activated hippocampal autophagy by lowering SQSTM-1/p62 accumulation, upregulating Beclin 1, and stimulating AMPK/mTOR pathway. In conclusion, linagliptin's antioxidant, antiapoptotic, and pro-autophagic properties advocated its promising neuroprotective impact. Thus, linagliptin may serve as a management approach against cadmium-induced cognitive deficits.

Impaired Insulin Signaling Alters Mediators of Hippocampal Synaptic Dynamics/Plasticity: A Possible Mechanism of Hyperglycemia-Induced Cognitive Impairment

Alzheimer's disease (AD) is a neurological condition that affects the elderly and is characterized by progressive and irreversible neurodegeneration in the cerebral cortex [...].

Early-life metabolic dysfunction impairs cognition and mitochondrial function in mice

The impact of overnutrition early in life is not restricted to the onset of cardiovascular and metabolic diseases, but also affects critical brain functions related to cognition. This study aimed to evaluate the relationship between peripheral metabolic and bioenergetic changes induced by a two-hit protocol and their impact on cognitive function in juvenile mice. Three-week-old male C57BL/6 mice received a high-fat diet (HFD) or control diet for 7 weeks, associated with 2 low doses of streptozotocin (STZ) or vehicle. Despite the absence of obesity, HFD+STZ impaired glucose metabolism and induced a trend towards cholesterol increase. The two-hit protocol impaired recognition and spatial memories in juvenile mice, without inducing a depressive-like behavior. HFD+STZ mice presented increased immunoreactivity for GFAP and a trend towards a decrease in NeuN in the hippocampus. The treatment caused a bioenergetic impairment in the hippocampus, characterized by a decrease in both O₂ consumption related to ATP production and in the maximum respiratory capacity. The thermogenic capacity of brown adipose tissue was impaired by the two-hit protocol, here verified through the absence of a decrease in O₂ consumption after uncoupled protein-1 inhibition and an increase in the reserve respiratory capacity. Impaired mitochondrial function was also observed in the liver of HFD+STZ juvenile mice, but not in their heart. These results indicate that exposure to HFD+STZ early in life has a detrimental impact on the bioenergetic and mitochondrial function of tissues with metabolic and thermogenic activities, which is likely related to hippocampal metabolic changes and cognitive impairment.

Effects of diabetes on microglial physiology: a systematic review of in vitro, preclinical and clinical studies

Diabetes mellitus is a heterogeneous chronic metabolic disorder characterized by the presence of hyperglycemia, commonly preceded by a prediabetic state. The excess of blood glucose can damage multiple organs, including the brain. In fact, cognitive decline and dementia are increasingly being recognized as important comorbidities of diabetes. Despite the largely consistent link between diabetes and dementia, the underlying causes of neurodegeneration in diabetic patients remain to be elucidated. A common factor for almost all neurological disorders is neuroinflammation, a complex inflammatory process in the central nervous system for the most part orchestrated by microglial cells, the main representatives of the immune system in the brain. In this context, our research question aimed to understand how diabetes affects brain and/or retinal microglia physiology. We conducted a systematic search in PubMed and Web of Science to identify research items addressing the effects of diabetes on microglial phenotypic modulation, including critical neuroinflammatory mediators and their pathways. The literature search yielded 1327 records, including 18 patents. Based on the title and abstracts, 830 papers were screened from which 250 primary research papers met the eligibility criteria (original research articles with patients or with a strict diabetes model without comorbidities, that included direct data about microglia in the brain or retina), and 17 additional research papers were included through forward and backward citations, resulting in a total of 267 primary research articles included in the scoping systematic review. We reviewed all primary publications investigating the effects of diabetes and/or its main pathophysiological traits on microglia, including in vitro studies, preclinical models of diabetes and clinical studies on diabetic patients. Although a strict classification of microglia remains elusive given their capacity to adapt to the environment and their morphological, ultrastructural and molecular dynamism, diabetes modulates microglial phenotypic states, triggering specific responses that include upregulation of activity markers (such as Iba1, CD11b, CD68, MHC-II and F4/80), morphological shift to amoeboid shape, secretion of a wide variety of cytokines and chemokines, metabolic reprogramming and generalized increase of oxidative stress. Pathways commonly activated by diabetes-related conditions include NF-κB, NLRP3 inflammasome, fractalkine/CX3CR1, MAPKs, AGEs/RAGE and Akt/mTOR. Altogether, the detailed portrait of complex interactions between diabetes and microglia physiology presented here can be regarded as an important starting point for future research focused on the microglia-metabolism interface.

Plasma sDPP4 (Soluble Dipeptidyl Peptidase-4) and Cognitive Impairment After Noncardioembolic Acute Ischemic Stroke

BACKGROUND

DPP4 (dipeptidyl peptidase-4) inhibitors have been proven to promote neuronal regeneration, reverse the development of cognitive deficits. However, the association of circulating soluble form (sDPP4 [soluble DPP4]) with poststroke cognitive impairment (PSCI) is unclear. We aimed to investigate the association between plasma sDPP4 levels and PSCI in patients with ischemic stroke.

METHODS

A total of 600 noncardioembolic stroke patients were included based on a preplanned ancillary study from the CATIS (China Antihypertensive Trial in Acute Ischemic Stroke). We used the Montreal Cognitive Assessment to evaluate cognitive function at 3 months follow-up after ischemic stroke. Binary logistic regression analyses were performed to investigate the association of plasma sDPP4 levels with subsequent PSCI. We further calculated integrated discrimination improvement and category-free net reclassification improvement to investigate the incremental prognostic effect of plasma sDPP4 beyond the basic model with conventional risk factors.

RESULTS

Plasma sDPP4 was inversely associated with PSCI after ischemic stroke, and the adjusted odds ratio (95% CI) for the highest versus lowest quartile of sDPP4 was 0.49 (0.29-0.81; P for trend=0.011). Each 1-SD increase of logarithm-transformed plasma sDPP4 concentration was associated with 17% (odds ratio, 0.83 [95% CI, 0.70-0.99]) lower risk of PSCI. Adding plasma sDPP4 to the basic model notably improved risk reclassification for PSCI, as shown by a category-free net reclassification improvement of 19.10% (95% CI, 2.52%-35.68%; P=0.03) and integrated discrimination improvement of 0.79% (95% CI, 0.13%-1.46%; P=0.02).

CONCLUSIONS

Higher plasma sDPP4 levels were associated with decreased risk of cognitive impairment after noncardioembolic ischemic stroke.

Repositioning Linagliptin for the Mitigation of Cadmium-Induced Testicular Dysfunction in Rats: Targeting HMGB1/TLR4/NLRP3 Axis and Autophagy

Cadmium, a ubiquitous environmental toxicant, disrupts testicular function and fertility. The dipeptidyl peptidase-4 inhibitor linagliptin has shown pronounced anti-inflammatory and anti-apoptotic features; however, its effects against cadmium-evoked testicular impairment have not been examined. Herein, the present study investigated targeting inflammation, apoptosis, and autophagy by linagliptin for potential modulation of cadmium-induced testicular dysfunction in rats. After 60 days of cadmium chloride administration (5 mg/kg/day, by gavage), testes, epididymis, and blood were collected for analysis. The present findings revealed that linagliptin improved the histopathological lesions, including spermatogenesis impairment and germ cell loss. Moreover, it improved sperm count/motility and serum testosterone. The favorable effects of linagliptin were mediated by curbing testicular inflammation seen by dampening of HMGB1/TLR4 pathway and associated lowering of nuclear NF-κBp65. In tandem, linagliptin suppressed the activation of NLRP3 inflammasome/caspase 1 axis with consequent lowering of the pro-inflammatory IL-1β and IL-18. Jointly, linagliptin attenuated testicular apoptotic responses seen by Bax downregulation, Bcl-2 upregulation, and suppressed caspase 3 activity. With respect to autophagy, linagliptin enhanced the testicular autophagy flux seen by lowered accumulation of p62 SQSTM1 alongside upregulation of Beclin 1. The observed autophagy stimulation was associated with elevated AMPK (Ser487) phosphorylation and lowered mTOR (Ser2448) phosphorylation, indicating AMPK/mTOR pathway activation. In conclusion, inhibition of testicular HMGB1/TLR4/NLRP3 pro-inflammatory axis and apoptosis alongside stimulation of autophagy were implicated in the favorable actions of linagliptin against cadmium-triggered testicular impairment.

Diabetes and cognitive decline

Epidemiologic studies have documented an association between diabetes and increased risk of cognitive decline in the elderly. Based on animal model studies, several mechanisms have been proposed to explain such an association, including central insulin signaling, neurodegeneration, brain amyloidosis, and neuroinflammation. Nevertheless, the exact mechanisms in humans remain poorly defined. It is reasonable, however, that many pathways may be involved in these patients leading to cognitive impairment. A major aim of clinicians is identifying early onset of neurologic signs and symptoms in elderly diabetics to improve quality of life of those with cognitive impairment and reduce costs associated with long-term complications. Several biomarkers have been proposed to identify diabetics at higher risk of developing dementia and diagnose early stage dementia. Although biomarkers of brain amyloidosis, neurodegeneration and synaptic plasticity are commonly used to diagnose dementia, especially Alzheimer disease, their role in diabetes remains unclear. The aim of this review is to explore the molecular mechanisms linking diabetes with cognitive decline and present the most important findings on the clinical use of biomarkers for diagnosing and predicting early cognitive decline in diabetics.

Linagliptin ameliorates pulmonary fibrosis in systemic sclerosis mouse model via inhibition of endothelial-to-mesenchymal transition

Systemic sclerosis (SSc) is a connective tissue disease that often causes pulmonary fibrosis. Dipeptidyl peptidase 4 (DPP4) inhibitor has shown anti-fibrotic properties in various fibrotic diseases. However, only two studies have reported its anti-fibrosis effects in pulmonary fibrosis, and the mechanism is not completely clear. In the present study, we further investigated the protective effects of linagliptin, a highly specific DPP4 inhibitor, on pulmonary fibrosis in SSc mouse model and the potential mechanisms. The results showed that linagliptin ameliorated pulmonary fibrosis in SSc mouse model, as evidenced by improved pathological changes of lung and body weight loss induced by BLM. Linagliptin also reduced BLM-induced oxidative stress, inflammation in lung in vivo. We revealed that linagliptin attenuated BLM-induced endothelial-to-mesenchymal transition (EndMT) in vitro and in vivo. BLM-induced enhanced migration ability of endothelial cells was also alleviated by linagliptin. Moreover, we confirmed that the Akt/mammalian target of rapamycin pathway was involved in BLM-induced EndMT in vivo, which was suppressed by linagliptin. In summary, we further confirmed the therapeutic effects of linagliptin on pulmonary fibrosis in SSc mouse model, which is based on its inhibitory effects on EndMT, oxidative stress, and inflammation.

Sodium-Glucose Cotransporter 2 (SGLT2) Inhibitors vs. Dipeptidyl Peptidase-4 (DPP4) Inhibitors for New-Onset Dementia: A Propensity Score-Matched Population-Based Study With Competing Risk Analysis

Introduction: The effects of sodium-glucose cotransporter 2 inhibitors (SGLT2I) and dipeptidyl peptidase-4 inhibitors (DPP4I) on new-onset cognitive dysfunction in type 2 diabetes mellitus remain unknown. This study aimed to evaluate the effects of the two novel antidiabetic agents on cognitive dysfunction by comparing the rates of dementia between SGLT2I and DPP4I users.

Methods: This was a population-based cohort study of type 2 diabetes mellitus patients treated with SGLT2I and DPP4I between January 1, 2015 and December 31, 2019 in Hong Kong. Exclusion criteria were <1-month exposure or exposure to both medication classes, or prior diagnosis of dementia or major neurological/psychiatric diseases. Primary outcomes were new-onset dementia, Alzheimer's, and Parkinson's. Secondary outcomes were all-cause, cardiovascular, and cerebrovascular mortality.

Results: A total of 13,276 SGLT2I and 36,544 DPP4I users (total n = 51,460; median age: 66.3 years old [interquartile range (IQR): 58–76], 55.65% men) were studied (follow-up: 472 [120–792] days). After 1:2 matching (SGLT2I: n = 13,283; DPP4I: n = 26,545), SGLT2I users had lower incidences of dementia (0.19 vs. 0.78%, p < 0.0001), Alzheimer's (0.01 vs. 0.1%, p = 0.0047), Parkinson's disease (0.02 vs. 0.14%, p = 0.0006), all-cause (5.48 vs. 12.69%, p < 0.0001), cerebrovascular (0.88 vs. 3.88%, p < 0.0001), and cardiovascular mortality (0.49 vs. 3.75%, p < 0.0001). Cox regression showed that SGLT2I use was associated with lower risks of dementia (hazard ratio [HR]: 0.41, 95% confidence interval [CI]: [0.27–0.61], P < 0.0001), Parkinson's (HR:0.28, 95% CI: [0.09–0.91], P = 0.0349), all-cause (HR:0.84, 95% CI: [0.77–0.91], P < 0.0001), cardiovascular (HR:0.64, 95% CI: [0.49–0.85], P = 0.0017), and cerebrovascular (HR:0.36, 95% CI: [0.3–0.43], P < 0.0001) mortality.

Conclusions: The use of SGLT2I is associated with lower risks of dementia, Parkinson's disease, and cerebrovascular mortality compared with DPP4I use after 1:2 ratio propensity score matching.

Development of 20 cm sample bore size dynamic nuclear polarization (DNP)-MRI at 16 mT and redox metabolic imaging of acute hepatitis rat model

Tissue redox metabolism is involved in various diseases, and an understanding of the spatio-temporal dynamics of tissue redox metabolism could be useful for diagnosis of progression and treatment. In in vivo dynamic nuclear polarization (DNP)-MRI, electron paramagnetic resonance (EPR) irradiation at the resonance frequency of nitroxyl radicals administered as a redox probe for induction of DNP, increases the intensity of MRI signals. For electron spin, it is necessary to apply a resonant frequency 658 times higher than that required for nuclear spin because of the higher magnetic moment of unpaired electrons. Previous studies using a disease model of small animals and in vivo DNP-MRI have revealed that an abnormal redox status is involved in many diseases, and that it could be used to visualize the dynamics of alterations in redox metabolism. To use the current methods in clinical practice, the development of a prototype DNP-MRI system for preclinical examinations of large animals is indispensable for clarifying the problems peculiar to the increase in size of the DNP-MRI device. Therefore, we developed a in vivo DNP-MRI system with a sample bore size of 20 cm and a 16-mT magnetic field using a U-shaped permanent magnet. Because the NMR frequency is very low, we adopted a digital radiofrequency transmission/reception system with excellent filter and dynamic range characteristics and equipped with a digital eddy current compensation system to suppress large eddy currents. The pulse sequence was based on the fast spin-echo sequence, which was improved for low frequency and large-eddy current equipment. The in vivo DNP-MRI system developed was used to non-invasively image the redox reaction of a carbamoyl-PROXYL probe in the livers of large rats weighing 800 g. Furthermore, DNP-MRI analysis was able to capture significant changes in redox metabolism in hepatitis-model rats.

Trelagliptin Mitigates Macrophage Infiltration by Preventing the Breakdown of the Blood-Brain Barrier in the Brain of Middle Cerebral Artery Occlusion Mice

Stroke is a significant cardiovascular disease that influences the health of human beings all over the world, especially the elderly population. It is reported that the blood-brain barrier (BBB) can be easily destroyed by stroke, which is one of the main factors responsible for macrophage infiltration and central nervous inflammation. Here, we report the protective effects of Trelagliptin against BBB injury and macrophage infiltration. Our results indicate that the infraction volume, the neurological score, and macrophage infiltration staining with CD68 were increased in middle cerebral artery occlusion (MCAO) mice but significantly reversed by treatment with Trelagliptin. Additionally, Trelagliptin reduced the permeability of the BBB by increasing the expression of the tight junction zonula occludens protein-1 (ZO-1) in the cerebral cortex. In an in vitro hypoxia model of endothelial cells, the increased migration of macrophages, enlarged permeability of endothelial monolayer, downregulation of ZO-1, and elevated expression level of CXCL1 by hypoxic conditions were all reversed by treatment with Trelagliptin in a dose-dependent manner. Our results demonstrate that Trelagliptin might mitigate macrophage infiltration by preventing the breakdown of the blood-brain barrier in the brains of MCAO mice.

Targeting AGE-RAGE signaling pathway by Saxagliptin prevents myocardial injury in isoproterenol challenged diabetic rats

The role of Saxagliptin in diabetes-associated cardiovascular complications is controversial. This study aimed to investigate whether Saxagliptin could prevent Isoproterenol-induced myocardial changes in diabetic rats and to identify the possible mechanism as well. The high-fat diet/low-dose Streptozotocin-induced type 2 diabetic rats were divided into 3 groups: the control group (0.25% CMC for 28 days), the Isoproterenol group (85 mg/kg Isoproterenol for the last 2 days plus 0.25% CMC for 28 days), and the treatment group (10 mg/kg Saxagliptin for 28 days plus 85 mg/kg Isoproterenol for the last 2 days). Hemodynamic measurements were performed, and samples were examined for RAGE and NF-κB expressions, histopathological and ultrastructural changes, AGEs level, myocardial injury markers, oxidative stress, and apoptosis. Saxagliptin significantly recovered cardiac function (p < .001), reverted myocardial injury and oxidative stress levels back to the control value (p < .05 to p < .001). Saxagliptin alleviates Isoproterenol-induced myocardial injury in diabetic rats by suppressing AGE-RAGE pathway.

Effects of the linagliptin, dipeptidyl peptidase-4 inhibitor, on bone fragility induced by type 2 diabetes mellitus in obese mice

Recently, it has been suggested that glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1), which play important roles in the homeostasis of glucose metabolism, could be involved in the regulation of bone metabolism. Inhibitors of dipeptidyl peptidase 4 (DPP-4), an enzyme that degrades GIP and GLP-1, are widely used clinically as a therapeutic agent for diabetes. However, the effects of DPP-4 inhibitors on bone metabolism remain unclear. In this study, we investigated the effects of linagliptin, a DPP-4 inhibitor, on bone fragility induced by type 2 diabetes mellitus (T2DM). Non-diabetic mice were used as controls, and T2DM mice were administered linagliptin orally on a daily basis for 12 weeks. In T2DM mice, decreased bone mineral density was observed in the lower limb bones along with low serum osteocalcin levels and high serum tartrate-resistant acid phosphatase-5b (TRAP) levels. In contrast, the decreased serum osteocalcin levels and increased serum TRAP levels observed in T2DM mice were significantly suppressed after the administration of linagliptin 30 mg/kg. Bone histomorphometric analysis revealed a reduced osteoid volume and osteoblast surface with an increase in the eroded surface and number of osteoclasts in T2DM mice. This decreased bone formation and increased bone resorption observed in the T2DM mice were suppressed and trabecular bone volume increased following the administration of 30 mg/kg linagliptin. Collectively, these findings suggest that linagliptin may improve the microstructure of trabecular bone by inhibiting both a decrease in bone formation and an increase in bone resorption induced by T2DM.