Laura L. Dugan’s research while affiliated with Vanderbilt University and other places

Objective Medium-chain fatty acids (MCFAs) can rapidly cross the blood-brain barrier and provide an alternative energy source for the brain. This study aims to determine 1) whether plasma caprylic acid (C8:0) is associated with risk of incident mild cognitive impairment (MCI) among baseline cognitively normal (CN) participants, and incident Alzheimer’s Disease (AD) among baseline MCI participants; and 2) whether these associations differ by sex, comorbidity of cardiometabolic diseases, apolipoprotein E (APOE) ε4 alleles, and ADAS-Cog 13.Methods Within the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort, plasma C8:0 was measured at baseline in 618 AD-free participants aged 55 to 91. Logistic regression models were used to estimate odds ratios (ORs) and 95% CIs with incident MCI and AD as dependent variables, separately.ResultsThe inverse association between circulating C8:0 and risk of incident MCI was of borderline significance. The inverse association between circulating levels of C8:0 and risk of incident MCI was significant among CN participants with ≥1 cardiometabolic diseases [OR (95% CI): 0.75 (0.58–0.98) (P=0.03)], those with one copy of APOE ε4 alleles [OR (95% CI): 0.43 (0.21–0.89) (P=0.02)], female [OR (95% CI): 0.60 (0.38–0.94) (P=0.02)], and ADAS-Cog 13 above the median [OR (95%CI): 0.69 (0.50–0.97)(P=0.03)] after adjusting for all covariates.Conclusion The inverse associations were present only among subgroups of CN participants, including female individuals, those with one or more cardiometabolic diseases, or one APOE ε4 allele, or higher ADAS-Cog 13 scores. If confirmed, this finding will facilitate precision prevention of MCI, in turn, AD among CN older adults.

Background & aims Ketogenic medium-chain-fatty acids (MCFAs) with profound health benefits are commonly found in dairy products, palm kernel oil and coconut oil. We hypothesize that magnesium (Mg) supplementation leads to enhanced gut microbial production of MCFAs and, in turn, increased circulating MCFAs levels. Methods We tested this hypothesis in the Personalized Prevention of Colorectal Cancer Trial (PPCCT) (NCT01105169), a double-blind 2 × 2 factorial randomized controlled trial enrolling 240 participants. Six 24-hour dietary recalls were performed for all participants at the baseline and during the intervention period. Based on the baseline 24-hour dietary recalls, the Mg treatment used a personalized dose of Mg supplementation that would reduce the calcium (Ca): Mg intake ratio to around 2.3. We measured plasma MCFAs, sugars, ketone bodies and tricarboxylic acid cycle (TCA cycle) metabolites using the Metabolon's global Precision Metabolomics™ LC-MS platform. Whole-genome shotgun metagenomics (WGS) sequencing was performed to assess microbiota in stool samples, rectal swabs, and rectal biopsies. Results Personalized Mg treatment (mean dose 216.5 mg/day with a range from 77.25 mg/day to 389.55 mg/day) significantly increased the plasma levels of C7:0, C8:0, and combined C7:0 and C8:0 by 18.45%, 25.28%, and 24.20%, respectively, compared to 14.15%, 10.12%, and 12.62% decreases in the placebo arm. The effects remain significant after adjusting for age, sex, race and baseline level (P=0.0126, P=0.0162, and P=0.0031, respectively) and FDR correction at 0.05 (q=0.0324 for both C7:0 and C8:0). Mg treatment significantly reduced the plasma level of sucrose compared to the placebo arm (P=0.0036 for multivariable-adjusted and P=0.0216 for additional FDR correction model) whereas alterations in daily intakes of sucrose, fructose, glucose, maltose and C8:0 from baseline to the end of trial did not differ between two arms. Mediation analysis showed that combined C7:0 and C8:0 partially mediated the effects of Mg treatment on total and individual ketone bodies (P for indirect effect =0.0045, 0.0043, 0.03, respectively). The changes in plasma levels of C7:0 and C8:0 were significantly and positively correlated with the alterations in stool microbiome α diversity (r=0.51, p=0.0023 and r=0.34, p=0.0497, respectively) as well as in stool abundance for the signatures of MCFAs-related microbiota with acyl-ACP thioesterase gene producing C7:0 (r=0.46, p=0.0067) and C8:0 (r=0.49, p=0.003), respectively, following Mg treatment. Conclusions Optimizing Ca:Mg intake ratios to around 2.3 through 12-week personalized Mg supplementation leads to increased circulating levels of MCFAs (i.e. C7:0 and C8:0), which is attributed to enhanced production from gut microbial fermentation and, maybe, sucrose consumption.

N-methyl- D -aspartate (NMDA) receptors are critical for higher-order nervous system function, but in previously published protocols to convert human induced pluripotent stem cells (iPSCs) to mature neurons, functional NMDA receptors (NMDARs) are often either not reported or take an extended time to develop. Here, we describe a protocol to convert human iPSC-derived neural progenitor cells (NPCs) to mature neurons in only 37 days. We demonstrate that the mature neurons express functional NMDARs exhibiting ligand-activated calcium flux, and we document the presence of NMDAR-mediated electrically evoked postsynaptic current. In addition to being more rapid than previous procedures, our protocol is straightforward, does not produce organoids which are difficult to image, and does not involve co-culture with rodent astrocytes. This could enhance our ability to study primate/human-specific aspects of NMDAR function and signaling in health and disease.

Human serum albumin (HSA) is the frontline antioxidant protein in blood with established anti-inflammatory and anticoagulation functions. Here we report that COVID-19-induced oxidative stress inflicts structural damages to HSA and is linked with mortality outcome in critically ill patients. We recruited 39 patients who were followed up for a median of 12.5 days (1-35 days), among them 23 had died. Analyzing blood samples from patients and healthy individuals (n=11), we provide evidence that neutrophils are major sources of oxidative stress in blood and that hydrogen peroxide is highly accumulated in plasmas of non-survivors. We then analyzed electron paramagnetic resonance (EPR) spectra of spin labelled fatty acids (SLFA) bound with HSA in whole blood of control, survivor, and non-survivor subjects (n=10-11). Non-survivor' HSA showed dramatically reduced protein packing order parameter, faster SLFA correlational rotational time, and smaller S/W ratio (strong-binding/weak-binding sites within HSA), all reflecting remarkably fluid protein microenvironments. Following loading/unloading of 16-DSA we show that transport function of HSA maybe impaired in severe patients. Stratified at the means, Kaplan–Meier survival analysis indicated that lower values of S/W ratio and accumulated H 2 O 2 in plasma significantly predicted in-hospital mortality (S/W≤0.15, 81.8% (18/22) vs. S/W>0.15, 18.2% (4/22), p =0.023; plasma [H 2 O 2 ]>8.6 mM, 65.2% (15/23) vs. 34.8% (8/23), p =0.043). When we combined these two parameters as the ratio ((S/W)/[H 2 O 2 ]) to derive a risk score, the resultant risk score lower than the mean (< 0.019) predicted mortality with high fidelity (95.5% (21/22) vs. 4.5% (1/22), logrank c ² = 12.1, p =4.9x10 ⁻⁴ ). The derived parameters may provide a surrogate marker to assess new candidates for COVID-19 treatments targeting HSA replacements and/or oxidative stress.

Parvalbumin-expressing interneurons (PV-INs) are highly vulnerable to stressors and have been implicated in many neuro-psychiatric diseases such as schizophrenia, Alzheimer’s disease, autism spectrum disorder, and bipolar disorder. We examined the literature about the current knowledge of the physiological properties of PV-INs and gathered results from diverse research areas to provide insight into their vulnerability to stressors. Among the factors that confer heightened vulnerability are the substantial energy requirements, a strong excitatory drive, and a unique developmental trajectory. Understanding these stressors and elaborating on their impact on PV-IN health is a step toward developing therapies to protect these neurons in various disease states and to retain critical brain functions.

Humans and orcas are among the very rare species that have a prolonged post‐reproductive lifespan (PRLS), during which the aging process continues. Reactive oxygen species (ROS) derived from mitochondria and from the NADPH oxidase (NOX) enzymes of innate immune cells are known to contribute to aging, with the former thought to be dominant. CD33‐related‐Siglecs are immune receptors that recognize self‐associated‐molecular‐patterns and modulate NOX‐derived‐ROS. We herewith demonstrate a strong correlation of lifespan with CD33rSIGLEC gene number in 26 species, independent of body weight or phylogeny. The correlation is stronger when considering total CD33rSIGLEC gene number rather than those encoding inhibitory and activating subsets, suggesting that lifetime balancing of ROS is important. Combining independent lines of evidence including the short half‐life and spontaneous activation of neutrophils, we calculate that even without inter‐current inflammation, a major source of lifetime ROS exposure may actually be neutrophil NOX‐derived. However, genomes of human supercentenarians (>110 years) do not harbor a significantly higher number of functional CD33rSIGLEC genes. Instead, lifespan correlation with CD33rSIGLEC gene number was markedly strengthened by excluding the post‐reproductive lifespan of humans and orcas (R² = 0.83; P < .0001). Thus, CD33rSIGLEC modulation of ROS likely contributes to maximum reproductive lifespan, but other unknown mechanisms could be important to PRLS.

Background: Asphyxia is the most common cause of brain damage in newborns. Substantial evidence indicates that leukocyte recruitment in the cerebral vasculature during asphyxia contributes to this damage. We tested the hypothesis that superoxide radical (O2⋅_) promotes an acute post-asphyxial inflammatory response and blood-brain barrier (BBB) breakdown. We investigated the effects of removing O2⋅_ by superoxide dismutase (SOD) or C3, the cell-permeable SOD mimetic, in protecting against asphyxia-related leukocyte recruitment. We also tested the hypothesis that xanthine oxidase activity is one source of this radical. Methods: Anesthetized piglets were tracheostomized, ventilated, and equipped with closed cranial windows for the assessment of post-asphyxial rhodamine 6G-labeled leukocyte-endothelial adherence and microvascular permeability to sodium fluorescein in cortical venules. Asphyxia was induced by discontinuing ventilation. SOD and C3 were administered by cortical superfusion. The xanthine oxidase inhibitor oxypurinol was administered intravenously. Results: Leukocyte-venular adherence significantly increased during the initial 2 h of post-asphyxial reperfusion. BBB permeability was also elevated relative to non-asphyxial controls. Inhibition of O2⋅_ production by oxypurinol, or elimination of O2⋅_ by SOD or C3, significantly reduced rhodamine 6G-labeled leukocyte-endothelial adherence and improved BBB integrity, as measured by sodium fluorescein leak from cerebral microvessels. Conclusion: Using three different strategies to either prevent formation or enhance elimination of O2⋅_ during the post-asphyxial period, we saw both reduced leukocyte adherence and preserved BBB function with treatment. These findings suggest that agents which lower O2⋅_ in brain may be attractive new therapeutic interventions for the protection of the neonatal brain following asphyxia.

Background: Fullerene-based compounds are being developed for an extensive range of biomedical applications, and may provide a completely new class of biologically useful reagents. In support of our continuing investigation and characterization of one such compound, e,e,e-fullerene(60)-63-tris malonic acid (1) we optimized the conditions for obtaining mass spectra. Methods: Both positive and negative ion mass spectra are obtained using electrospray ionization (ESI). However, the spectra are dramatically different in the different ionization modes. We studied the effect of solvent media, acid content as well as the concentration of the compound (1) on mass fragmentation pattern both in positive and negative mode. We also analyzed the ion current as function of capillary voltage for selected ion. Results: The best mass spectra were obtained when 1 was sprayed from a solution containing a weak organic acid added to aqueous methanol (1:1) in positive mode. Fragment ions formed by the direct loss of carboxyl groups from the doubly-charged dimer occur for the loss of one, two and six carboxyl groups. Of these, the loss of one carboxyl is the most abundant. The dominant mechanism for the formation of singly-charged fragment ions arises from splitting of the doubly-charged dimers into singly-charged monomers with subsequent carboxyl losses. Conclusion: In positive ion mode, the spectra are simple with minimal fragmentation and the molecular ion region increases linearly with analyte concentration over the range studied. In negative ion mode, the spectra are more complex with the formation of dimer and fragment ions and the molecular ion region increases in a non-linear way with concentration. Further, in negative ion mode, fragment ions are affected by nearly every instrumental parameter controlling the ionization process.

Background and objectives: Fullerene-based compounds are a novel class of molecules being developed for a variety of biomedical applications, with nearly 1000 publications in this area in the last 4 years alone. One such compound, the e,e,e-methanofullerene(60)-63-tris malonic acid (designated C3), is a potent catalytic superoxide dismutase mimetic which has shown neuroprotective efficacy in a number of animal models of neurologic disease, including Parkinsonian Macaca fascicularis monkeys. The aim of this study was to characterize its toxicity and pharmacokinetics in mice and monkeys. Methods: To assess pharmacokinetics in mice, we synthesized and administered14C-C3to mice using various routes of delivery, including orally. To assess potential toxicity in primates, serial blood studies and electrocardiograms (ECGs) were obtained from monkeys treated with C3(3 or 7 mg/kg/day) for 2 months. Results and conclusions: The plasma half-life of C3 was 8.2 ± 0.2 h, and there was wide tissue distribution, including uptake into brain. The compound was cleared by both hepatic and renal excretion. C3was quite stable, with minimal metabolism of the compound even after 7 days of treatment. The LD50in mice was 80 mg/kg for a single intraperitoneal injection, and was > 30 mg/kg/day for sustained administration; therapeutic doses are 1-5 mg/kg/day. For primates, no evidence of renal, hepatic, electrolyte, or hematologic abnormalities were noted, and serial ECGs demonstrated no alteration in cardiac electrical activity. Thus, doses of C3that have therapeutic efficacy appear to be well tolerated after 2 years (mice) or 2 months (non-human primates) of treatment.