O accumulate over time. At present it is unclear how such continual exposure compares to bolus treatment, as employed here. However it has been reported that methylglyoxal has a plasma lifetime of seconds – minutes (the rate constant for initial reaction of methylglyoxal with N-acetylarginine is reported as 8.561023 M21 s21 in [33], yielding a half-life, t1/2, of approximately 80 s) and apoA-I has a lifetime of 24 h (or greater at sites where it may be retained) and therefore the total flux of methylglyoxal to which this protein will be exposed is likely to be orders of magnitude greater than the plasma steady-state level described above. CML levels detected in this study with 3 mM glycolaldehyde (approximately 16 nmoles/mg apoA-I, 7 mg CML/mg), lie within the range reported by others for HDL of people with diabetes and renal deficiency [22], also suggesting that the damage induced by these bolus concentrations may be pathologically relevant. Overall, these data indicate that apoA-I glycation, using relatively modest excesses of glucose and reactive aldehydes can inhibit phospholipid association, but not macrophage cholesterol efflux. Modulation of these processes requires significant protein modification, and may arise from conformational or amino acid side-chain modifications within the lipid-binding regions of apoAI. These changes are more extensive than those detected on apoAI from people with complication-free Type 1 diabetes, but poor glycaemic control, and severe disease, may result in a greater extent of protein modification such that this impairment of efflux could be of relevance. Glycation inhibitors can attenuate such apoA-I modification and prevent impaired efflux, suggesting that such compounds may benefit people with diabetes with impaired reverse cholesterol transport.AcknowledgmentsThe authors thank Connie Karshimkus and Andrzej Januszewski for subject evaluation and venesection, Michelle Fryirs, Shilpi Yadav, Yeliz Cakan and Liming Hou for the apoA-I and drHDL preparations, Dr. David Pattison for advice on the kinetic analyses and Pat Pisansarakit for cell culture.Author ContributionsConceived and designed the experiments: BEB KAR MJD. Performed the experiments: BEB EN JZ. Analyzed the data: BEB EN JZ. Contributed reagents/materials/analysis tools: AJJ KAR. 23148522 Wrote the paper: BEB AJJ KAR MJD.
Alzheimer’s Disease (AD), the most prevalent form of dementia in the elderly, is characterized by cognitive decline and by the occurrence of brain senile plaques and neurofibrillary tangles (NFT), as well as by synaptic and neuronal loss [1?]. Synaptic dysfunction and loss is the earliest histological neuronal pathology in AD [4?] and is also apparent in mild cognitive impaired (MCI) individuals prior to their conversion to clinical AD [8]. Furthermore, synaptic Title Loaded From File degeneration evolves in a distinct spatio-temporal pattern [9] which, like NFT, radiates from the entorhinal cortex to the hippocampus and subsequently to the rest of the brain [10]. Although AD is not a single neurotransmitter disease, it is associated with distinct and specific neuronal and synaptic impairments. Accordingly, the cholinergic and glutamatergic systems are particularly susceptible to AD [11,12], whereas the GABAergic system is more resilient and relatively spared [13,14]. The mechanisms Title Loaded From File underlying synaptic degeneration in AD and its neuronal specificity are not fully understood. Genetic and epidemiological studies revealed allelic segregation of the apolipopro.O accumulate over time. At present it is unclear how such continual exposure compares to bolus treatment, as employed here. However it has been reported that methylglyoxal has a plasma lifetime of seconds – minutes (the rate constant for initial reaction of methylglyoxal with N-acetylarginine is reported as 8.561023 M21 s21 in [33], yielding a half-life, t1/2, of approximately 80 s) and apoA-I has a lifetime of 24 h (or greater at sites where it may be retained) and therefore the total flux of methylglyoxal to which this protein will be exposed is likely to be orders of magnitude greater than the plasma steady-state level described above. CML levels detected in this study with 3 mM glycolaldehyde (approximately 16 nmoles/mg apoA-I, 7 mg CML/mg), lie within the range reported by others for HDL of people with diabetes and renal deficiency [22], also suggesting that the damage induced by these bolus concentrations may be pathologically relevant. Overall, these data indicate that apoA-I glycation, using relatively modest excesses of glucose and reactive aldehydes can inhibit phospholipid association, but not macrophage cholesterol efflux. Modulation of these processes requires significant protein modification, and may arise from conformational or amino acid side-chain modifications within the lipid-binding regions of apoAI. These changes are more extensive than those detected on apoAI from people with complication-free Type 1 diabetes, but poor glycaemic control, and severe disease, may result in a greater extent of protein modification such that this impairment of efflux could be of relevance. Glycation inhibitors can attenuate such apoA-I modification and prevent impaired efflux, suggesting that such compounds may benefit people with diabetes with impaired reverse cholesterol transport.AcknowledgmentsThe authors thank Connie Karshimkus and Andrzej Januszewski for subject evaluation and venesection, Michelle Fryirs, Shilpi Yadav, Yeliz Cakan and Liming Hou for the apoA-I and drHDL preparations, Dr. David Pattison for advice on the kinetic analyses and Pat Pisansarakit for cell culture.Author ContributionsConceived and designed the experiments: BEB KAR MJD. Performed the experiments: BEB EN JZ. Analyzed the data: BEB EN JZ. Contributed reagents/materials/analysis tools: AJJ KAR. 23148522 Wrote the paper: BEB AJJ KAR MJD.
Alzheimer’s Disease (AD), the most prevalent form of dementia in the elderly, is characterized by cognitive decline and by the occurrence of brain senile plaques and neurofibrillary tangles (NFT), as well as by synaptic and neuronal loss [1?]. Synaptic dysfunction and loss is the earliest histological neuronal pathology in AD [4?] and is also apparent in mild cognitive impaired (MCI) individuals prior to their conversion to clinical AD [8]. Furthermore, synaptic degeneration evolves in a distinct spatio-temporal pattern [9] which, like NFT, radiates from the entorhinal cortex to the hippocampus and subsequently to the rest of the brain [10]. Although AD is not a single neurotransmitter disease, it is associated with distinct and specific neuronal and synaptic impairments. Accordingly, the cholinergic and glutamatergic systems are particularly susceptible to AD [11,12], whereas the GABAergic system is more resilient and relatively spared [13,14]. The mechanisms underlying synaptic degeneration in AD and its neuronal specificity are not fully understood. Genetic and epidemiological studies revealed allelic segregation of the apolipopro.
