Aynun N. Begum

Curcumin Structure-Function, Bioavailability, and Efficacy in Models of Neuroinflammation and Alzheimer's Disease

Curcumin can reduce inflammation and neurodegeneration, but its chemical instability and metabolism raise concerns, including whether the more stable metabolite tetrahydrocurcumin (TC) may mediate efficacy. We examined the antioxidant, anti-inflammatory, or anti-amyloidogenic effects of dietary curcumin and TC, either administered chronically to aged Tg2576 APPsw mice or acutely to lipopolysaccharide (LPS)-injected wild-type mice. Despite dramatically higher drug plasma levels after TC compared with curcumin gavage, resulting brain levels of parent compounds were similar, correlating with reduction in LPS-stimulated inducible nitric-oxide synthase, nitrotyrosine, F2 isoprostanes, and carbonyls. In both the acute (LPS) and chronic inflammation (Tg2576), TC and curcumin similarly reduced interleukin-1β. Despite these similarities, only curcumin was effective in reducing amyloid plaque burden, insoluble β-amyloid peptide (Aβ), and carbonyls. TC had no impact on plaques or insoluble Aβ, but both reduced Tris-buffered saline-soluble Aβ and phospho-c-Jun NH2-terminal kinase (JNK). Curcumin but not TC prevented Aβ aggregation. The TC metabolite was detected in brain and plasma from mice chronically fed the parent compound. These data indicate that the dienone bridge present in curcumin, but not in TC, is necessary to reduce plaque deposition and protein oxidation in an Alzheimers model. Nevertheless, TC did reduce neuroinflammation and soluble Aβ, effects that may be attributable to limiting JNK-mediated transcription. Because of its favorable safety profile and the involvement of misfolded proteins, oxidative damage, and inflammation in multiple chronic degenerative diseases, these data relating curcumin dosing to the blood and tissue levels required for efficacy should help translation efforts from multiple successful preclinical models.

Prevention of Alzheimer's disease: Omega-3 fatty acid and phenolic anti-oxidant interventions

Alzheimers disease (AD) and cardiovascular disease (CVD) are syndromes of aging that share analogous lesions and risk factors, involving lipoproteins, oxidative damage and inflammation. Unlike in CVD, in AD, sensitive biomarkers are unknown, and high-risk groups are understudied. To identify potential prevention strategies in AD, we have focused on pre-clinical models (transgenic and amyloid infusion models), testing dietary/lifestyle factors strongly implicated in reducing risk in epidemiological studies. Initially, we reported the impact of non-steroidal anti-inflammatory drugs (NSAIDs), notably ibuprofen, which reduced amyloid accumulation, but suppressed few inflammatory markers and without reducing oxidative damage. Safety concerns with chronic NSAIDs led to a screen of alternative NSAIDs and identification of the phenolic anti-inflammatory/anti-oxidant compound curcumin, the yellow pigment in turmeric that we found targeted multiple AD pathogenic cascades. The dietary omega-3 fatty acid, docosahexaenoic acid (DHA), also limited amyloid, oxidative damage and synaptic and cognitive deficits in a transgenic mouse model. Both DHA and curcumin have favorable safety profiles, epidemiology and efficacy, and may exert general anti-aging benefits (anti-cancer and cardioprotective.).

Oral curcumin for Alzheimer's disease: tolerability and efficacy in a 24-week randomized, double blind, placebo-controlled study

IntroductionCurcumin is a polyphenolic compound derived from the plant Curcuma Long Lin that has been demonstrated to have antioxidant and anti-inflammatory effects as well as effects on reducing beta-amyloid aggregation. It reduces pathology in transgenic models of Alzheimers disease (AD) and is a promising candidate for treating human AD. The purpose of the current study is to generate tolerability and preliminary clinical and biomarker efficacy data on curcumin in persons with AD.MethodsWe performed a 24-week randomized, double blind, placebo-controlled study of Curcumin C3 Complex® with an open-label extension to 48 weeks. Thirty-six persons with mild-to-moderate AD were randomized to receive placebo, 2 grams/day, or 4 grams/day of oral curcumin for 24 weeks. For weeks 24 through 48, subjects that were receiving curcumin continued with the same dose, while subjects previously receiving placebo were randomized in a 1:1 ratio to 2 grams/day or 4 grams/day. The primary outcome measures were incidence of adverse events, changes in clinical laboratory tests and the Alzheimers Disease Assessment Scale - Cognitive Subscale (ADAS-Cog) at 24 weeks in those completing the study. Secondary outcome measures included the Neuropsychiatric Inventory (NPI), the Alzheimers Disease Cooperative Study - Activities of Daily Living (ADCS-ADL) scale, levels of Aβ1-40 and Aβ1-42 in plasma and levels of Aβ1-42, t-tau, p-tau181 and F2-isoprostanes in cerebrospinal fluid. Plasma levels of curcumin and its metabolites up to four hours after drug administration were also measured.ResultsMean age of completers (n = 30) was 73.5 years and mean Mini-Mental Status Examination (MMSE) score was 22.5. One subject withdrew in the placebo (8%, worsened memory) and 5/24 subjects withdrew in the curcumin group (21%, 3 due to gastrointestinal symptoms). Curcumin C3 Complex® was associated with lowered hematocrit and increased glucose levels that were clinically insignificant. There were no differences between treatment groups in clinical or biomarker efficacy measures. The levels of native curcumin measured in plasma were low (7.32 ng/mL).ConclusionsCurcumin was generally well-tolerated although three subjects on curcumin withdrew due to gastrointestinal symptoms. We were unable to demonstrate clinical or biochemical evidence of efficacy of Curcumin C3 Complex® in AD in this 24-week placebo-controlled trial although preliminary data suggest limited bioavailability of this compound.Trial registrationClinicalTrials.gov Identifier: NCT00099710.

NSAID and Antioxidant Prevention of Alzheimer's Disease: Lessons from In Vitro and Animal Models

Abstract: Both oxidative damage and inflammation are elevated in brains of Alzheimers disease (AD) patients, but their pathogenic significance remains unclear. The reduced AD risk associated with high intake of both nonsteroidal anti‐inflammatory drugs (NSAIDs) and antioxidants suggests causal roles, but clinical trials in AD patients have yielded only limited or negative results. To test the potential efficacy and mechanisms of candidate approaches, we have explored conventional and unconventional NSAIDs, antioxidants, and combined NSAID/antioxidants in cell culture and animal models for AD (including aging APPsw transgenic mice and soluble Aβ rodent infusion models). The conventional NSAID ibuprofen has the strongest epidemiological support. At sustainable doses designed to mimic protective consumption in the epidemiology, ibuprofen reduces amyloid accumulation but suppresses a surprisingly limited subset of inflammatory markers in APPsw transgenic mice. Both Ab production (APP, β‐ and γ‐secretases) and post‐production pathways (those affecting Aβ aggregation or clearance: e.g., IL‐1 or α1ACT) are potentially involved in ibuprofen and other NSAID anti‐AD activities. The post‐production pathways are predictably shared with other seemingly protective NSAIDs, including naproxen that do not lower Aβ42 in vitro. Using clinically feasible dosing, brain levels of NSAIDs appear too low to implicate a number of pharmacological dose targets that have been demonstrated in vitro. Ibuprofen did not suppress microglial markers related to phagocytosis. The putative anti‐inflammatory omega‐3 fatty acid DHA had a profound impact on pathogenesis but did not lower inflammation, while vitamin E was surprisingly ineffective in reducing oxidative damage or amyloid in the aged APPsw mouse. In contrast, the unconventional NSAID/antioxidant curcumin was effective, lowering oxidative damage, cognitive deficits, synaptic marker loss, and amyloid deposition. Curcumin proved to be immunomodulatory, simultaneously inhibiting cytokine and microglial activation indices related to neurotoxicity, but increasing an index of phagocytosis. Curcumin directly targeted Aβ and was also effective in other models, warranting further preclinical and clinical exploration.

GSK3 inhibitors show benefits in an Alzheimer's disease (AD) model of neurodegeneration but adverse effects in control animals

The dysregulation of glycogen synthase kinase-3 (GSK3) has been implicated in Alzheimer disease (AD) pathogenesis and in Abeta-induced neurotoxicity, leading us to investigate it as a therapeutic target in an intracerebroventricular Abeta infusion model. Infusion of a specific GSK3 inhibitor SB216763 (SB) reduced a downstream target, phospho-glycogen synthase 39%, and increased glycogen levels 44%, suggesting effective inhibition of enzyme activity. Compared to vehicle, Abeta increased GSK3 activity, and was associated with elevations in levels of ptau, caspase-3, the tau kinase phospho-c-jun N-terminal kinase (pJNK), neuronal DNA fragmentation, and gliosis. Co-infusion of SB corrected all responses to Abeta infusion except the induction of gliosis and behavioral deficits in the Morris water maze. Nevertheless, SB alone was associated with induction of neurodegenerative markers and behavioral deficits. These data support a role for GSK3 hyperactivation in AD pathogenesis, but emphasize the importance of developing inhibitors that do not suppress constitutive activity.

Use of Copper and Insulin-Resistance to Accelerate Cognitive Deficits and Synaptic Protein Loss in a Rat Aβ-Infusion Alzheimer’s Disease Model

The rat amyloid-beta (Abeta) intracerebroventricular infusion can model aspects of Alzheimers disease (AD) and has predicted efficacy of therapies such as ibuprofen and curcumin in transgenic mouse models. High density lipoprotein (HDL), a normal plasma carrier of Abeta, is used to attenuate Abeta aggregation within the pump, causing Abeta-dependent toxicity and cognitive deficits within 3 months. Our goal was to identify factors that might accelerate onset of Abeta-dependent deficits to improve efficiency and cost-effectiveness of model. We focused on: 1) optimizing HDL-Abeta preparation for maximal toxicity; 2) evaluating the role of copper, a factor typically in water that can impact oligomer stability; and 3) determining impact of insulin resistance (type II diabetes), a risk factor for AD. In vitro studies were performed to determine doses of copper and methods of Abeta-HDL preparation that maximized toxicity. These preparations when infused resulted in earlier onset of cognitive deficits within 6 weeks post-infusion. Induction of insulin resistance did not exacerbate Abeta-dependent cognitive deficits, but did exacerbate synaptic protein loss. In summary, the newly described in vivo infusion model may be useful cost-effective method for screening for new therapeutic drugs for AD.

ULTRASENSITIVE AND ACCURATE ALZHEIMER’S DISEASE DIAGNOSTICS: FROM BENCH TO BEDSIDE

Dementia, Institute Born-Bunge, Antwerp, Belgium; Neurodegenerative Brain Diseases Group, Center for Molecular Neurology, VIB, Antwerp, Belgium; Reference Center for Biological Markers of Dementia, Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium; Institute Born-Bunge, Wilrijk, Belgium; Neurodegenerative Brain Diseases Group, VIB-UAntwerp Center for Molecular Neurology, Antwerp, Belgium; Laboratory of Neurobiology, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium; Institute Born-Bunge, University of Antwerp, Antwerp, Belgium; VU University Medical Center, Amsterdam, Netherlands; Reference Center for Biological Markers of Dementia, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium. Contact e-mail: e.willemse@vumc.nl