The Clinical Significance of Glycoprotein Phospholipase D Levels in Distinguishing Early Stage Latent Autoimmune Diabetes in Adults and Type 2 Diabetes

Exercise mimetics: a novel strategy to combat neuroinflammation and Alzheimer's disease

Neuroinflammation is a pathological hallmark of Alzheimer's disease (AD), characterized by the stimulation of resident immune cells of the brain and the penetration of peripheral immune cells. These inflammatory processes facilitate the deposition of amyloid-beta (Aβ) plaques and the abnormal hyperphosphorylation of tau protein. Managing neuroinflammation to restore immune homeostasis and decrease neuronal damage is a therapeutic approach for AD. One way to achieve this is through exercise, which can improve brain function and protect against neuroinflammation, oxidative stress, and synaptic dysfunction in AD models. The neuroprotective impact of exercise is regulated by various molecular factors that can be activated in the same way as exercise by the administration of their mimetics. Recent evidence has proven some exercise mimetics effective in alleviating neuroinflammation and AD, and, additionally, they are a helpful alternative option for patients who are unable to perform regular physical exercise to manage neurodegenerative disorders. This review focuses on the current state of knowledge on exercise mimetics, including their efficacy, regulatory mechanisms, progress, challenges, limitations, and future guidance for their application in AD therapy.

Mechanisms underlying HIV-associated cognitive impairment and emerging therapies for its management

People living with HIV are affected by the chronic consequences of neurocognitive impairment (NCI) despite antiretroviral therapies that suppress viral replication, improve health and extend life. Furthermore, viral suppression does not eliminate the virus, and remaining infected cells may continue to produce viral proteins that trigger neurodegeneration. Comorbidities such as diabetes mellitus are likely to contribute substantially to CNS injury in people living with HIV, and some components of antiretroviral therapy exert undesirable side effects on the nervous system. No treatment for HIV-associated NCI has been approved by the European Medicines Agency or the US Food and Drug Administration. Historically, roadblocks to developing effective treatments have included a limited understanding of the pathophysiology of HIV-associated NCI and heterogeneity in its clinical manifestations. This heterogeneity might reflect multiple underlying causes that differ among individuals, rather than a single unifying neuropathogenesis. Despite these complexities, accelerating discoveries in HIV neuropathogenesis are yielding potentially druggable targets, including excessive immune activation, metabolic alterations culminating in mitochondrial dysfunction, dysregulation of metal ion homeostasis and lysosomal function, and microbiome alterations. In addition to drug treatments, we also highlight the importance of non-pharmacological interventions. By revisiting mechanisms implicated in NCI and potential interventions addressing these mechanisms, we hope to supply reasons for optimism in people living with HIV affected by NCI and their care providers.

Modulation of GPC-4 and GPLD1 serum levels by improving glycemic indices in type 2 diabetes: Resistance training and hawthorn extract intervention

Aims

This study was designed to investigate the effects of resistance training (RT) and hawthorn extract (Ha) on Glypican-4 (GPC-4) and Insulin-regulated glycosylphosphatidylinositol-specific phospholipase D (GPLD1) serum levels in T2DM and to examine the relationship of these variables with glycemic indexes.

Method

40 male Wistar rats were divided into five equal groups: Healthy Control (H-C), Diabetes Control (D-C), Diabetes Resistance training (D-RT), Diabetes Hawthorn (D-Ha), and Diabetes Resistance training Hawthorn (D-RT-Ha). T2DM was induced with a 4-week high-fat diet (HFD) and one dose of STZ intraperitoneal injection (35 mg/kg). 1-week after the injection, RT (with a range of 50%-100%1RM/3 day/week) and gavage of Ha extract (100 mg/kg/day) was performed for 12 weeks.

Results

The glycemic indices improvement (reducing blood glucose and increasing serum insulin level) caused by RT and/or Ha increased GPC-4 and decreased GPLD1 in the T2DM rats, but these positive changes were more effective in the combination of RT + Ha. A strong correlation was also observed between GPC-4 and GPLD1 with blood glucose and insulin.

Conclusion

The increase in serum GPC-4 levels was probably due to the direct effect of RT + Ha, and the improvement of glycemic indexes after RT and Ha. The double effect of RT + Ha can be a regulatory mechanism for GPC-4 and its related factors in controlling T2DM complications.

Cap-independent translation of GPLD1 enhances markers of brain health in long-lived mutant and drug-treated mice

Glycosylphosphatidylinositol-specific phospholipase D1 (GPLD1) hydrolyzes inositol phosphate linkages in proteins anchored to the cell membrane. Mice overexpressing GPLD1 show enhanced neurogenesis and cognition. Snell dwarf (DW) and growth hormone receptor knockout (GKO) mice show delays in age-dependent cognitive decline. We hypothesized that augmented GPLD1 might contribute to retained cognitive function in these mice. We report that DW and GKO show higher GPLD1 levels in the liver and plasma. These mice also have elevated levels of hippocampal brain-derived neurotrophic factor (BDNF) and of doublecortin (DCX), suggesting a mechanism for maintenance of cognitive function at older ages. GPLD1 was not increased in the hippocampus of DW or GKO mice, suggesting that plasma GPLD1 increases elevated these brain proteins. Alteration of the liver and plasma GPLD1 was unaltered in mice with liver-specific GHR deletion, suggesting that the GH effect was not intrinsic to the liver. GPLD1 was also induced by caloric restriction and by each of four drugs that extend lifespan. The proteome of DW and GKO mice is molded by selective translation of mRNAs, involving cap-independent translation (CIT) of mRNAs marked by N⁶ methyladenosine. Because GPLD1 protein increases were independent of the mRNA level, we tested the idea that GPLD1 might be regulated by CIT. 4EGI-1, which enhances CIT, increased GPLD1 protein without changes in GPLD1 mRNA in cultured fibroblasts and mice. Furthermore, transgenic overexpression of YTHDF1, which promotes CIT by reading m6A signals, also led to increased GPLD1 protein, showing that elevation of GPLD1 reflects selective mRNA translation.

DIA-Based Proteomic Analysis of Plasma Protein Profiles in Patients with Severe Acute Pancreatitis

Acute pancreatitis (AP) is a pancreatic inflammatory disease that varies greatly in course and severity. To further the understanding of the pathology of AP, we carried out data-independent acquisition-based proteomic analyses using proteins extracted from the plasma of patients with severe acute pancreatitis (SAP) (experimental group) and healthy volunteers (control group). Compared to the control group, there were 35 differentially expressed proteins (DEPs) in the plasma of patients with SAP. Of those, the expression levels for 6 proteins were significantly increased, and 29 proteins were significantly decreased. Moreover, six candidate biomarkers—VWF, ORM2, CD5L, CAT, IGLV3-10, and LTF—were matched as candidate biomarkers of the disease severity of AP. The area under the receiver operating characteristic of 0.903 (95% CI: 0.839, 0.967) indicated that this combination of these six candidate biomarkers had a good prediction accuracy for predicting the severity of AP. Our study provides specific DEPs that may be useful in the diagnosis and prognosis of SAP, which suggests new theoretical bases for the occurrence and development of SAP and offers potential novel treatment strategies for SAP.

Characterization of lncRNA Profiles of Plasma-Derived Exosomes From Type 1 Diabetes Mellitus

BACKGROUNDS

Exosomes contain several types of transcripts, including long non-coding RNAs (lncRNAs), and have been shown to exert important effects in human diseases. However, the roles of exosomal lncRNAs in type 1 diabetes mellitus (T1DM) have not been well investigated. In the present study, we characterized the plasma-derived exosomal lncRNAs expression profiles of T1DM and predict their potential function in the pathogenesis of T1DM.

MATERIAL AND METHODS

Exosomal lncRNA expression profiles were detected by Illumina Hiseq platform (T1DM subjects N=10; age-, sex- matched Control subjects N=10). Six exosomal lncRNAs were selected to validate their expression level by using quantitative real-time PCR (qRT-PCR) (T1DM subjects N=30; age-, sex- matched Control subjects N=30). Bioinformatics analysis approaches were carried out to explore the potential biological function of differentially expressed lncRNAs.

RESULTS

A total of 162 differentially expressed exosomal lncRNAs were identified in T1DM patients compared with control subjects, among which 77 up-regulated and 85 down-regulated. The expression level of the selected six lncRNAs didn't show significant difference in the following qRT-PCR analysis. Gene Ontology analysis enriched terms such as activation of phospholipase D activity, neuronal cell body membrane, and calcium sensitive guanylate cyclase activator activity for cis-acting genes of lncRNAs, and metal ion binding for trans-acting genes. The most enriched Kyoto Encyclopedia of Genes and Genomes pathways for the lncRNAs were associated with oxidative phosphorylation and Parkinson's disease for cis-acting genes, and pathways in cancer as well as focal adhesion for trans-acting genes.

CONCLUSIONS

This study characterized the lncRNA profiles of plasma-derived exosomes from T1DM for the first time and these results highlighted the potential role of exosomal lncRNAs in T1DM pathogenesis. A better understanding of exosomal lncRNA profiling will provide novel insights into its molecular mechanisms.

Plasma exosomal proteomic studies of corneal epithelial injury in diabetic and non-diabetic group

OBJECTIVE

Diabetic Keratopathy (DK) is one of the significant complications of type II diabetes (T2DM) with pathogenesis not yet clarified. Since hyperglycemia is able to change the protein components contained in plasma exosomes, liquid chromatography-tandem mass spectrometry (LC-MS/MS) is considered as feasible to analyze the expression of plasma exosomal proteins in patients with T2DM and non-diabetic patients respectively, find critical biological markers, and explore the mechanism of DK as well as potential therapeutic targets.

METHOD

Blood and clinical information of corneal epithelial injury in a diabetic group (the study group) and a non-diabetic group (the control group), who were patients admitted to the Department of Ophthalmology, Yangpu Hospital, Tongji University School of Medicine from July 2020 to November 2020, were collected. The qEV size exclusion method was adopted to separate exosomes from plasma. The exosomes were then identified through transmission electron microscopy (TEM), nanoparticle tracking analyzer (NTA), and Western blot. The plasma exosomes of the study group and the control group were quantitatively analyzed by proteomics. A bioinformatics method is utilized to screen differential proteins and the expression of the differential proteins was verified by Western blot.

RESULT

TEM indicated that the exosomes had a double-concave disc-like appearance, with a size of about 100 nm, and Western blot expressed as CD63 and TSG101. The plasma exosomes of the study group and the control group were analyzed by quantitative proteomics with a total number of 952 proteins detected of which 245 proteins existed in the ExoCarta exosomal protein database. Through adoption of P-value to screen credible differential proteins, the heat map displayed 28 differential proteins, 7 upregulated proteins, and 21 downregulated proteins; the volcano map displayed 7 upregulated proteins and 22 downregulated proteins; the PPI interaction map displayed 12 upregulated proteins and 18 downregulated proteins. Through GO enrichment analysis, it was identified that the differential protein participated in the main biological processes and was involved in regulating the cell's stimulation response to insulin, the insulin receptor signaling pathway, and the activity of glycosylphosphatidylinositol phospholipase D as well as anti-oxidation. The enriched cell components include main components such as exosomes, blood particles, and cytoplasm. KEGG enrichment analysis indicated that the target protein FLOT2 was mainly concentrated in insulin-related signaling pathways. Western blot indicated that the expression of FLOT2 in the study group was lower compared with the control group while the expression of Exo70 was higher.

CONCLUSION

Proteomic analysis of the study group and the control group displayed a variety of proteins in plasma exosomes. The downregulated protein FLOT2 in the study group was closely related to the occurrence, development, and complication of DK in T2DM patients. The expression status of plasma FLOT2 protein in T2DM patients is expected to be a biomarker for diagnosing and monitoring of DK.

Emerging Diabetic Novel Biomarkers of the 21st Century

Diabetes is a growing epidemic with estimated prevalence of infected to reach ~592 million by the year 2035. An effective way to approach is to detect the disease at a very early stage to reduce the complications and improve lifestyle management. Although several traditional biomarkers including glucated hemoglobin, glucated albumin, fructosamine, and 1,5-anhydroglucitol have helped in ease of diagnosis, there is lack of sensitivity and specificity and are inaccurate in certain clinical settings. Thus, search for new and effective biomarkers is a continuous process with an aim of accurate and timely diagnosis. Several novel biomarkers have surged in the present century that are helpful in timely detection of the disease condition. Although it is accepted that a single biomarker will have its inherent limitations, combining several markers will help to identify individuals at high risk of developing prediabetes and eventually its progression to frank diabetes. This review describes the novel biomarkers of the 21st century, both in type 1 and type 2 diabetes mellitus, and their present potential for assessing risk stratification due to insulin resistance that will pave the way for improved clinical outcome.

Interaction of Full-Length Glycosylphosphatidylinositol-Anchored Proteins with Serum Proteins and Their Translocation to Cells In Vitro Depend on the (Pre-)Diabetic State in Rats and Humans

Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs), which are anchored at the surface of mammalian cultured and tissue cells through a carboxy-terminal GPI glycolipid, are susceptible to release into incubation medium and (rat and human) blood, respectively, in response to metabolic stress and ageing. Those GPI-APs with the complete GPI still attached form micelle-like complexes together with (lyso)phospholipids and cholesterol and are prone to degradation by serum GPI-specific phospholipase D (GPLD1), as well as translocation to the surface of acceptor cells in vitro. In this study, the interaction of GPI-APs with GPLD1 or other serum proteins derived from metabolically deranged rat and humans and their translocation were measured by microfluidic chip- and surface acoustic wave-based sensing of micelle-like complexes reconstituted with model GPI-APs. The effect of GPI-AP translocation on the integrity of the acceptor cell surface was studied as lactate dehydrogenase release. For both rats and humans, the dependence of serum GPLD1 activity on the hyperglycemic/hyperinsulinemic state was found to be primarily based on upregulation of the interaction of GPLD1 with micelle-like GPI-AP complexes, rather than on its amount. In addition to GPLD1, other serum proteins were found to interact with the GPI phosphoinositolglycan of full-length GPI-APs. Upon incubation of rat adipocytes with full-length GPI-APs, their translocation from the micelle-like complexes (and also with lower efficacy from reconstituted high-density lipoproteins and liposomes) to acceptor cells was observed, accompanied by upregulation of their lysis. Both GPI-AP translocation and adipocyte lysis became reduced in the presence of serum proteins, including (inhibited) GPLD1. The reduction was higher with serum from hyperglycemic/hyperinsulinemic rats and diabetic humans compared to healthy ones. These findings suggest that the deleterious effects of full-length GPI-APs following spontaneous release into the circulation of metabolically deranged rats and humans are counterbalanced by upregulated interaction of their GPI anchor with GPLD1 and other serum proteins. Thereby, translocation of GPI-APs to blood and tissue cells and their lysis are prevented. The identification of GPI-APs and serum proteins interacting within micelle-like complexes may facilitate the prediction and stratification of diseases that are associated with impaired cell-surface anchorage of GPI-APs, such as obesity and diabetes.

The Biomedical Uses of Inositols: A Nutraceutical Approach to Metabolic Dysfunction in Aging and Neurodegenerative Diseases

Inositols are sugar-like compounds that are widely distributed in nature and are a part of membrane molecules, participating as second messengers in several cell-signaling processes. Isolation and characterization of inositol phosphoglycans containing myo- or d-chiro-inositol have been milestones for understanding the physiological regulation of insulin signaling. Other functions of inositols have been derived from the existence of multiple stereoisomers, which may confer antioxidant properties. In the brain, fluctuation of inositols in extracellular and intracellular compartments regulates neuronal and glial activity. Myo-inositol imbalance is observed in psychiatric diseases and its use shows efficacy for treatment of depression, anxiety, and compulsive disorders. Epi- and scyllo-inositol isomers are capable of stabilizing non-toxic forms of β-amyloid proteins, which are characteristic of Alzheimer’s disease and cognitive dementia in Down’s syndrome, both associated with brain insulin resistance. However, uncertainties of the intrinsic mechanisms of inositols regarding their biology are still unsolved. This work presents a critical review of inositol actions on insulin signaling, oxidative stress, and endothelial dysfunction, and its potential for either preventing or delaying cognitive impairment in aging and neurodegenerative diseases. The biomedical uses of inositols may represent a paradigm in the industrial approach perspective, which has generated growing interest for two decades, accompanied by clinical trials for Alzheimer’s disease.

Upregulated phospholipase D activity toward glycosylphosphatidylinositol-anchored proteins in micelle-like serum complexes in metabolically deranged rats and humans

Glycosylphosphatidylinositol-anchored proteins (GPI-AP) with the complete glycolipid anchor attached have previously been shown to be released from the outer plasma membrane leaflet of rat adipocytes in positive correlation to cell size and blood glucose/insulin levels of the donor rats. Furthermore, they are present in rat and human serum, however, at amounts that are lower in insulin-resistant/obese rats compared with normal ones. These findings prompted further evaluation of the potential of full-length GPI-AP for the prediction and stratification of metabolically deranged states. A comparison of the signatures of horizontal surface acoustic waves that were generated by full-length GPI-AP in the course of their specific capture by and subsequent dissociation from a chip-based sensor between those from rat serum and those reconstituted into lipidic structures strongly argues for expression of full-length GPI-AP in serum in micelle-like complexes in concert with phospholipids, lysophospholipids, and cholesterol. Both the reconstituted and the rat serum complexes were highly sensitive toward mechanical forces, such as vibration. Furthermore, full-length GPI-AP reconstituted into micelle-like complexes represented efficient substrates for cleavage by serum glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD). These findings raised the possibility that the upregulated release of full-length GPI-AP into micelle-like serum complexes from metabolically deranged cells is compensated by elevated GPI-PLD activity. In fact, serum GPI-PLD activity toward full-length GPI-AP in micelle-like complexes, but not in detergent micelles, was positively correlated to early states of insulin resistance and obesity in genetic and diet-induced rat models as well as to the body weight in humans. Moreover, the differences in the degradation of GPI-AP in micelle-like complexes were found to rely in part on the interaction of serum GPI-PLD with an activating serum factor. These data suggest that serum GPI-PLD activity measured with GPI-AP in micelle-like complexes is indicative of enhanced release of full-length GPI-AP from relevant tissues into the circulation as a consequence of early metabolic derangement in rats and humans.

Structure-function relationships of HDL in diabetes and coronary heart disease

High-density lipoproteins (HDL) contain hundreds of lipid species and proteins and exert many potentially vasoprotective and antidiabetogenic activities on cells. To resolve structure-function-disease relationships of HDL, we characterized HDL of 51 healthy subjects and 98 patients with diabetes (T2DM), coronary heart disease (CHD), or both for protein and lipid composition, as well as functionality in 5 cell types. The integration of 40 clinical characteristics, 34 nuclear magnetic resonance (NMR) features, 182 proteins, 227 lipid species, and 12 functional read-outs by high-dimensional statistical modeling revealed, first, that CHD and T2DM are associated with different changes of HDL in size distribution, protein and lipid composition, and function. Second, different cellular functions of HDL are weakly correlated with each other and determined by different structural components. Cholesterol efflux capacity (CEC) was no proxy of other functions. Third, 3 potentially novel determinants of HDL function were identified and validated by the use of artificially reconstituted HDL, namely the sphingadienine-based sphingomyelin SM 42:3 and glycosylphosphatidylinositol-phospholipase D1 for the ability of HDL to inhibit starvation-induced apoptosis of human aortic endothelial cells and apolipoprotein F for the ability of HDL to promote maximal respiration of brown adipocytes.

Endurance exercise training restores diabetes-induced alteration in circulating Glycosylphosphatidylinositol-specific phospholipase D levels in rats

BACKGROUND

Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is responsible for cleaving membrane-associated glycosylphosphatidylinositol (GPI) molecules, which is affected by diabetes. We aimed to examine the effect of 14 weeks treadmill running on serum GPLD1 levels and its association with glycemic indexes and serum glypican-4 (GPC-4), a novel GPI-anchored adipokine, in streptozotocin-nicotinamide-induced diabetic rats.

METHODS

Thirty-six male Wister rats were randomly divided into three groups of twelve animals each, involving sedentary control (SC), sedentary diabetic (SD), and trained diabetic (TD) groups. The diabetes was induced through intraperitoneal injection of 120 mg/kg nicotinamide 15 min prior to intraperitoneal injection of 65 mg/kg streptozotocin in SD and TD groups. The TD group was exercised on a treadmill for 60 min/days, 5 days/wk at 26 m/min, and zero grade for 14 weeks. Following the experiment period, blood samples were taken from all animals and analyzed for experimental indexes via sandwich ELISA.

RESULTS

Exercise training caused a significant decrease in the elevated blood glucose levels and a significant increase in the lowered blood insulin levels in TD rats (both p < 0.001). Glucose tolerance of TD rats significantly improved following experimental protocol, as indicated by OGTT (p < 0.001). Experimental diabetes significantly increased serum GPLD1 levels (p < 0.001), while exercise training significantly decreased its levels (p < 0.001). Serum GPLD1 levels correlated directly with glycemic indexes involving FBS, 2hOGTT, and AUC of glucose (r = 0.80, r = 0.79, r = 0.79, respectively, all p < 0.001) and inversely with serum insulin levels (r = - 0.83, p < 0.001). There were no significant differences in serum GPC-4 levels among groups, and no association with GPLD1 alteration.

CONCLUSIONS

Sedentary diabetic rats have higher circulating GPLD1 compared to controls, which can be reversed by exercise training and is associated with modifying in glycemic and insulin profile.