The association between ultra-processed food (UPF) and risk of cardiometabolic disorders is an ongoing concern. Different food processing-based classification systems have originated discrepancies in the conclusions among studies. To test whether the association between UPF consumption and cardiometabolic markers changes with the classification system, we used baseline data from 5636 participants (48.5% female and 51.5% male, mean age 65.1 ± 4.9) of the PREDIMED-Plus (“PREvention with MEDiterranean DIet”) trial. Subjects presented with overweight or obesity and met at least three metabolic syndrome (MetS) criteria. Food consumption was classified using a 143-item food frequency questionnaire according to four food processing-based classifications: NOVA, International Agency for Research on Cancer (IARC), International Food Information Council (IFIC) and University of North Carolina (UNC). Mean changes in nutritional and cardiometabolic markers were assessed according to quintiles of UPF consumption for each system. The association between UPF consumption and cardiometabolic markers was assessed using linear regression analysis. The concordance of the different classifications was assessed with intra-class correlation coefficients (ICC3, overall = 0.51). The highest UPF consumption was obtained with the IARC classification (45.9%) and the lowest with NOVA (7.9%). Subjects with high UPF consumption showed a poor dietary profile. We detected a direct association between UPF consumption and BMI (p = 0.001) when using the NOVA system, and with systolic (p = 0.018) and diastolic (p = 0.042) blood pressure when using the UNC system. Food classification methodologies markedly influenced the association between UPF consumption and cardiometabolic risk markers.

Evidence suggests that the stress hormones glucocorticoids (GCs) can cause cognitive deficits and neurodegeneration. Previous studies have found GCs facilitate physiological synapse weakening, termed long-term depression (LTD), though the precise mechanisms underlying this are poorly understood. Here we show that GCs activate glycogen synthase kinase-3 (GSK-3), a kinase crucial to synapse weakening signals. Critically, this ultimately leads to phosphorylation of the microtubule associated protein tau, specifically at the serine 396 residue, and this is a causal factor in the GC-mediated impairment of synaptic function. These findings reveal the link between GCs and synapse weakening signals, and the potential for stress-induced priming of neurodegeneration. This could have important implications for our understanding of how stress can lead to neurodegenerative disease.

Aggregation of amyloid beta and loss of cholinergic innervation in the brain are predominant components of Alzheimer’s disease pathology, and likely underlie cognitive impairment. Acetylcholinesterase inhibitors are one of the few treatment options for Alzheimer’s disease, where levels of available acetylcholine are enhanced to counteract the cholinergic loss. However, these inhibitors show limited clinical efficacy. One potential explanation for this is a concomitant dysregulation of cholinergic receptors themselves as a consequence of the amyloid beta pathology. We tested this hypothesis by examining levels of M1 muscarinic acetylcholine receptors in the temporal cortex from 7 Alzheimer’s disease and 7 non-disease age-matched control brain tissue samples (Control: 85 ± 2.63 years old, Moderate Alzheimer’s disease: 84 ± 2.32 years old, p value = 0.721; 8 female and 6 male patients). The samples were categorized into two groups: ‘Control’ (Consortium to Establish a Registry for Alzheimer’s Disease diagnosis of ‘No Alzheimer’s disease’, and Braak staging pathology of I-II) and ‘Moderate Alzheimer’s disease’ (Consortium to Establish a Registry for Alzheimer’s Disease diagnosis of ‘possible/probable Alzheimer’s disease’, and Braak staging pathology of IV). We find that in comparison to age-matched controls, there is loss of M1 muscarinic acetylcholine receptors in Moderate Alzheimer’s disease tissue (control: 2.17 ± 0.27 arbitrary units, n = 7, Mod-AD: 0.83 ± 0.16 arbitrary units, n = 7, two-tailed t-test, t = 4.248, p = 0.00113). Using a functional rat cortical brain slice model, we find that postsynaptic muscarinic acetylcholine receptor function is dysregulated by aberrant amyloid beta-mediated activation of metabotropic glutamate receptor 5. Crucially, blocking metabotropic glutamate receptor 5 restores muscarinic acetylcholine receptor function and object recognition memory in 5XFAD transgenic mice. This indicates that the amyloid beta-mediated activation of metabotropic glutamate receptor 5 negatively regulates muscarinic acetylcholine receptor and illustrates the importance of muscarinic acetylcholine receptors as a potential disease-modifying target in the moderate pathological stages of Alzheimer’s disease.