Monounsaturated fatty acids prevent the aversive effects of obesity on locomotion, brain activity, and sleep behavior

Acute treatment of bilateral rTMS combined with antidepressants on the plasma fatty acids for major depressive episodes

Bilateral repetitive transcranial magnetic stimulation (B-rTMS) has been largely used in the treatment of major depressive disorder (MDD). Nonetheless, information on the acute treatment by B-rTMS combined with antidepressants (ADs) on the plasma fatty acids in MDD is limited. The present study focused on depressive symptoms; Plasma was obtained from 27 adult patients with MDD at baselinephase (MDD), after 2 weeks of treatment (MDD-2w), and 27 healthy controls (HC). Meanwhile, we evaluated the composition of short-chain fatty acids (SCFAs) and medium-and long-chain fatty acids (MLCFAs) in the plasma. Consequently, the levels of Isobutyric acid, Caproic acid, and Propionic acid were low both in the MDD and MDD-2w groups and negatively correlated with the scores of HAMD and HAMA. Besides, minimal changes were observed between the MDD and HC groups, whereas significant MLCFA levels were high in the MDD-2w group. Moreover, we developed combined panels that could effectively differentiate MDD from HCs (AUC=0.99), MDD-2w from HC (AUC=0.983), and MDD from MDD-2w (AUC=0.852). These findings may provide a reference for the use of B-rTMS combined with ADs against the acute phase of depressive episodes and shed light on the relationship between plasma FAs and MDD.

Causality Investigation between Gut Microbiome and Sleep-Related Traits: A Bidirectional Two-Sample Mendelian Randomization Study

Recent research has highlighted associations between sleep and microbial taxa and pathways. However, the causal effect of these associations remains unknown. To investigate this, we performed a bidirectional two-sample Mendelian randomization (MR) analysis using summary statistics of genome-wide association studies (GWAS) from 412 gut microbiome traits (N = 7738) and GWAS studies from seven sleep-associated traits (N = 345,552 to 386,577). We employed multiple MR methods to assess causality, with Inverse Variance Weighted (IVW) as the primary method, alongside a Bonferroni correction ((p < 2.4 × 10-4) to determine significant causal associations. We further applied Cochran's Q statistical analysis, MR-Egger intercept, and Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) for heterogeneity and pleiotropy assessment. IVW estimates revealed 79 potential causal effects of microbial taxa and pathways on sleep-related traits and 45 inverse causal relationships, with over half related to pathways, emphasizing their significance. The results revealed two significant causal associations: genetically determined relative abundance of pentose phosphate decreased sleep duration (p = 9.00 × 10-5), and genetically determined increase in fatty acid level increased the ease of getting up in the morning (p = 8.06 × 10-5). Sensitivity analyses, including heterogeneity and pleiotropy tests, as well as a leave-one-out analysis of single nucleotide polymorphisms, confirmed the robustness of these relationships. This study explores the potential causal relationships between sleep and microbial taxa and pathways, offering novel insights into their complex interplay.

Effect of Peanut Butter Intake on Sleep Health in Firefighters: A Randomized Controlled Trial

Sleep is often impaired in firefighters due to the psychologically and physiologically intense nature of their work and working shift schedules. Peanut butter is affordable and a substantial source of monounsaturated fatty acids, which may aid sleep health. Thus, this study sought to determine if a daily serving of peanut butter consumed before bedtime for seven weeks altered sleep quality and quantity among full-time firefighters. Forty firefighters (peanut butter group = 20; control group = 20) participated in this eight-week randomized controlled trial. All participants completed a subjective questionnaire on mood, focus, and alertness twice daily and wore an Actigraph wristwatch to measure sleep variables, including latency, efficiency, time in bed, time asleep, wake after sleep onset, number of awakenings, and time spent awake. After a baseline week, the peanut butter group consumed two tablespoons of peanut butter two hours prior to bedtime for seven weeks. Compared to the control group, the peanut butter group did not demonstrate significant changes (p > 0.05) in sleep measures or subjective feelings of mood, focus, or alertness after consuming peanut butter for seven weeks. Therefore, peanut butter as a source of peanuts did not alter sleep quality or quantity in this group of firefighters.

Dietary palmitic acid to oleic acid ratio modulates energy metabolism and biological rhythms in young healthy Japanese males

The present study investigated the potential role of the composition of dietary fatty acids in the regulation of biological rhythms, such as the sleep architecture, core body temperature and leukocyte clock gene expression, in subjects fed meals rich in palmitic acid (PA) or oleic acid (OA). Eleven males participated in two sessions of indirect calorimetry in a whole-room metabolic chamber. In each session, subjects consumed three meals rich in PA (44·3 % of total fat as PA and 42·3 % as OA) or OA (11·7 % of total fat as PA and 59·3 % as OA) in the metabolic chamber. The ratio of PA to OA in plasma was significantly lower and fat oxidation was significantly higher during 24 h of indirect calorimetry in the session with meals rich in OA than in that with meals rich in PA. The duration of slow wave sleep (SWS) was shorter, the latency of SWS was longer and the nadir of core body temperature after bedtime was later in the session with meals rich in PA than in that with meals rich in OA. The peak in CRY1 gene expression was earlier and its amplitude was higher in the session with meals rich in PA than in that with meals rich in OA. In healthy young males, meals rich in PA decreased fat oxidation and disrupted biological rhythms, particularly the sleep architecture and core body temperature during sleep, more than meals rich in OA.

High-Fat Diets in Animal Models of Alzheimer's Disease: How Can Eating Too Much Fat Increase Alzheimer's Disease Risk?

High dietary intake of saturated fatty acids is a suspected risk factor for neurodegenerative diseases, including Alzheimer's disease (AD). To decipher the causal link behind these associations, high-fat diets (HFD) have been repeatedly investigated in animal models. Preclinical studies allow full control over dietary composition, avoiding ethical concerns in clinical trials. The goal of the present article is to provide a narrative review of reports on HFD in animal models of AD. Eligibility criteria included mouse models of AD fed a HFD defined as > 35% of fat/weight and western diets containing > 1% cholesterol or > 15% sugar. MEDLINE and Embase databases were searched from 1946 to August 2022, and 32 preclinical studies were included in the review. HFD-induced obesity and metabolic disturbances such as insulin resistance and glucose intolerance have been replicated in most studies, but with methodological variability. Most studies have found an aggravating effect of HFD on brain Aβ pathology, whereas tau pathology has been much less studied, and results are more equivocal. While most reports show HFD-induced impairment on cognitive behavior, confounding factors may blur their interpretation. In summary, despite conflicting results, exposing rodents to diets highly enriched in saturated fat induces not only metabolic defects, but also cognitive impairment often accompanied by aggravated neuropathological markers, most notably Aβ burden. Although there are important variations between methods, particularly the lack of diet characterization, these studies collectively suggest that excessive intake of saturated fat should be avoided in order to lower the incidence of AD.

rTMS ameliorates depressive-like behaviors and regulates the gut microbiome and medium- and long-chain fatty acids in mice exposed to chronic unpredictable mild stress

INTRODUCTION

Repetitive transcranial magnetic stimulation (rTMS) is a clinically useful therapy for depression. However, the effects of rTMS on the metabolism of fatty acids (FAs) and the composition of gut microbiota in depression are not well established.

METHODS

Mice received rTMS (15 Hz, 1.26 T) for seven consecutive days after exposure to chronic unpredictable mild stress (CUMS). The subsequent depressive-like behaviors, the composition of gut microbiota of stool samples, as well as medium- and long-chain fatty acids (MLCFAs) in the plasma, prefrontal cortex (PFC), and hippocampus (HPC) were evaluated.

RESULTS

CUMS induced remarkable changes in gut microbiotas and fatty acids, specifically in community diversity of gut microbiotas and PUFAs in the brain. 15 Hz rTMS treatment alleviates depressive-like behaviors and partially normalized CUMS induced alterations of microbiotas and MLCFAs, especially the abundance of Cyanobacteria, Actinobacteriota, and levels of polyunsaturated fatty acids (PUFAs) in the hippocampus and PFC.

CONCLUSION

These findings revealed that the modulation of gut microbiotas and PUFAs metabolism might partly contribute to the antidepressant effect of rTMS.

Alteration of brain function and systemic inflammatory tone in older adults by decreasing the dietary palmitic acid intake

Prior studies in younger adults showed that reducing the normally high intake of the saturated fatty acid, palmitic acid (PA), in the North American diet by replacing it with the monounsaturated fatty acid, oleic acid (OA), decreased blood concentrations and secretion by peripheral blood mononuclear cells (PBMCs) of interleukin (IL)-1β and IL-6 and changed brain activation in regions of the working memory network. We examined the effects of these fatty acid manipulations in the diet of older adults. Ten subjects, aged 65-75 years, participated in a randomized, cross-over trial comparing 1-week high PA versus low PA/high OA diets. We evaluated functional magnetic resonance imaging (fMRI) using an N-back test of working memory and a resting state scan, cytokine secretion by lipopolysaccharide (LPS)-stimulated PBMCs, and plasma cytokine concentrations. During the low PA compared to the high PA diet, we observed increased activation for the 2-back minus 0-back conditions in the right dorsolateral prefrontal cortex (Broadman Area (BA) 9; p < 0.005), but the effect of diet on working memory performance was not significant (p = 0.09). We observed increased connectivity between anterior regions of the salience network during the low PA/high OA diet (p < 0.001). The concentrations of IL-1β (p = 0.026), IL-8 (p = 0.013), and IL-6 (p = 0.009) in conditioned media from LPS-stimulated PBMCs were lower during the low PA/high OA diet. This study suggests that lowering the dietary intake of PA down-regulated pro-inflammatory cytokine secretion and altered working memory, task-based activation and resting state functional connectivity in older adults.

A Preliminary Comparison of Plasma Tryptophan Metabolites and Medium- and Long-Chain Fatty Acids in Adult Patients with Major Depressive Disorder and Schizophrenia

Background and Objectives: Disturbance of tryptophan (Trp) and fatty acid (FA) metabolism plays a role in the pathogenesis of psychiatric disorders. However, quantitative analysis and comparison of plasma Trp metabolites and medium- and long-chain fatty acids (MCFAs and LCFAs) in adult patients with major depressive disorder (MDD) and schizophrenia (SCH) are limited. Materials and Methods: Clinical symptoms were assessed and the level of Trp metabolites and MCFAs and LCFAs for plasma samples from patients with MDD (n = 24) or SCH (n = 22) and healthy controls (HC, n = 23) were obtained and analyzed. Results: We observed changes in Trp metabolites and MCFAs and LCFAs with MDD and SCH and found that Trp and its metabolites, such as N-formyl-kynurenine (NKY), 5-hydroxyindole-3-acetic acid (5-HIAA), and indole, as well as omega-3 polyunsaturated fatty acids (N3) and the ratio of N3 to omega-6 polyunsaturated fatty acids (N3: N6), decreased in both MDD and SCH patients. Meanwhile, levels of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) decreased in SCH patients, and there was a significant difference in the composition of MCFAs and LCFAs between MDD and SCH patients. Moreover, the top 10 differential molecules could distinguish the two groups of diseases from HC and each other with high reliability. Conclusions: This study provides a further understanding of dysfunctional Trp and FA metabolism in adult patients with SCH or MDD and might develop combinatorial classifiers to distinguish between these disorders.

Can Following Paleolithic and Mediterranean Diets Reduce the Risk of Stress, Anxiety, and Depression: A Cross-Sectional Study on Iranian Women

Background

Psychiatric disorders have been a challenge for public health and will bring economic problems to individuals and healthcare systems in the future. One of the important factors that could affect these disorders is diet.

Objective

In the current study with a cross-sectional design, we investigated the association of Paleolithic and Mediterranean diets with psychological disorders in a sample of adult women.

Methods

Participants were 435 adult women between 20 and 50 years old that refer to healthcare centers in the south of Tehran, Iran. The diet scores were created by the response to a valid and reliable semiquantitative food frequency questionnaire (FFQ), and the psychological profile was determined by response to the Depression, Anxiety, and Stress Scale (DASS-21). The multivariable-adjusted logistic regression was applied to compute the odds ratio (OR) and 95% confidence interval (CI).

Results

After adjusted for potential confounders, it is evident that participants in the highest Paleolithic diet tertile had lower odds of depression (OR = 0.21; 95% CI: 0.12, 0.37: P < 0.001), anxiety (OR = 0.27; 95% CI: 0.16, 0.45: P < 0.001), and stress (OR = 0.19; 95% CI: 0.11, 0.32; P < 0.001) in comparison to the lowest tertile. Furthermore, those in the third tertile of the Mediterranean diet score were at lower risk of depression (OR = 0.20; 95% CI: 0.11, 0.36; P < 0.001), anxiety (OR = 0.22; 95% CI: 0.13, 0.38; P < 0.001), and stress (OR = 0.23; 95% CI: 0.13, 0.39; P < 0.001) compared with those in the first tertile.

Conclusion

The result of the current study suggests that greater adherence to Paleolithic and Mediterranean dietary patterns may be related with a decreased risk of psychological disorders such as depression, anxiety, and stress.

Fish oil supplementation alters emotion-generated corticolimbic functional connectivity in depressed adolescents at high-risk for bipolar I disorder: A 12-week placebo-controlled fMRI trial

OBJECTIVE

To evaluate the effects of fish oil (FO), a source of the omega-3 polyunsaturated fatty acids (n-3 PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on emotion-generated corticolimbic functional connectivity in depressed youth at high risk for developing bipolar I disorder.

METHODS

Thirty-nine antidepressant-free youth with a current depressive disorder diagnosis and a biological parent with bipolar I disorder were randomized to 12-week double-blind treatment with FO or placebo. At baseline and endpoint, fMRI (4 Tesla) scans were obtained while performing a continuous performance task with emotional and neutral distractors (CPT-END). Seed-to-voxel functional connectivity analyses were performed using bilateral orbitofrontal cortex (OFC) and amygdala (AMY) seeds. Measures of depression, mania, global symptom severity, and erythrocyte fatty acids were obtained.

RESULTS

Erythrocyte EPA+DHA composition increased significantly in the FO group (+47%, p ≤ 0.0001) but not in the placebo group (-10%, p = 0.11). Significant group by time interactions were found for functional connectivity between the left OFC and the left superior temporal gyrus (STG) and between the right AMY and right inferior temporal gyrus (ITG). OFC-STG connectivity increased in the FO group (p = 0.0001) and decreased in the placebo group (p = 0.0019), and AMY-ITG connectivity decreased in the FO group (p = 0.0014) and increased in the placebo group (p < 0.0001). In the FO group, but not placebo group, the decrease in AMY-ITG functional connectivity correlated with decreases in Childhood Depression Rating Scale-Revised and Clinical Global Impression-Severity Scale scores.

CONCLUSIONS

In depressed high-risk youth FO supplementation alters emotion-generated corticolimbic functional connectivity which correlates with changes in symptom severity ratings.

The menace of obesity to depression and anxiety prevalence

The incidence of depression and anxiety is amplified by obesity. Mounting evidence reveals that the psychiatric consequences of obesity stem from poor diet, inactivity, and visceral adipose accumulation. Resulting metabolic and vascular dysfunction, including inflammation, insulin and leptin resistance, and hypertension, have emerged as key risks to depression and anxiety development. Recent research advancements are exposing the important contribution of these different corollaries of obesity and their impact on neuroimmune status and the neural circuits controlling mood and emotional states. Along these lines, this review connects the clinical manifestations of depression and anxiety in obesity to our current understanding of the origins and biology of immunometabolic threats to central nervous system function and behavior.

Prolonged saturated, but not monounsaturated, high-fat feeding provokes anxiodepressive-like behaviors in female mice despite similar metabolic consequences

Obesity significantly increases the risk for anxiety and depression. Our group has recently demonstrated a role for nucleus accumbens (NAc) pro-inflammatory nuclear factor kappa-B (NFkB) signaling in the development of anxiodepressive-like behaviors by diet-induced obesity in male mice. The NAc is a brain region involved in goal-oriented behavior and mood regulation whose functions are critical to hedonic feeding and motivation. While the incidence of depression and anxiety disorders is significantly higher in women than in men, the use of female animal models in psychiatric research remains limited. We set out to investigate the impact of chronic intake of saturated and monounsaturated high-fat diets (HFD) on energy metabolism and on anxiety- and despair-like behaviors in female mice and to ascertain the contribution of NAc NFkB-mediated inflammation herein.

Adult C57Bl6N female mice were fed either a saturated HFD, an isocaloric monounsaturated HFD or a control low-fat diet for 24 weeks, after which metabolic profiling and behavioral testing for anxiodepressive-like behaviors were conducted. Plasma was collected at time of sacrifice for quantification of leptin, inflammatory markers as well as 17 β-estradiol levels and brains were harvested to analyze NAc expression of pro-inflammatory genes and estrogen-signaling molecules. In another group of female mice placed on the saturated HFD or the control diet for 24 weeks, we performed adenoviral-mediated invalidation of the NFkB signaling pathway in the NAc prior to behavioral testing.

While both HFDs provoked obesity and metabolic impairments, only the saturated HFD triggered anxiodepressive-like behaviors and caused marked elevations in plasma estrogen. This saturated HFD-specific behavioral phenotype could not be explained by NAc inflammation alone and was unaffected by NAc invalidation of the NFkB signaling pathway. Instead, we found changes in the expression of estrogen signaling markers. Such results diverge from the inflammatory mechanisms underlying diet- and obesity-induced metabolic dysfunction and anxiodepressive-like behavior onset in male mice and call attention to the role of estrogen signaling in diet-related anxiodepressive-like phenotypes in female mice.

Healthy Lifestyle and Cognition: Interaction between Diet and Physical Activity

PURPOSE OF REVIEW

This review discusses current research on the impact of specific dietary patterns and exercise, both individually and combined, on cognitive function in older adults.

RECENT FINDINGS

Observational evidence generally supports a relationship between diet adherence and positive cognitive outcomes related to memory, executive function, and risk for cognitive impairment; however, randomized controlled trials (RCTs) are limited. Exercise research is more extensive, showing improvements in cognitive performance after exercise interventions regardless of baseline cognitive status and noting lower incidences of cognitive impairment in people who engage in regular physical activity. Evidence supports adherence to specific dietary patterns and a combination of aerobic and resistance exercise as an effective approach to mitigate age-associated cognitive decline. Further research on older adults at various stages of cognitive decline, as well as longer-term RCTs, will help determine the best clinical markers of early cognitive dysfunction, and the effectiveness of early lifestyle intervention on cognitive function.

The effects of lutein and zeaxanthin on resting state functional connectivity in older Caucasian adults: a randomized controlled trial

The carotenoids lutein (L) and zeaxanthin (Z) accumulate in retinal regions of the eye and have long been shown to benefit visual health. A growing literature suggests cognitive benefits as well, particularly in older adults. The present randomized controlled trial sought to investigate the effects of L and Z on brain function using resting state functional magnetic resonance imaging (fMRI). It was hypothesized that L and Z supplementation would (1) improve intra-network integrity of default mode network (DMN) and (2) reduce inter-network connectivity between DMN and other resting state networks. 48 community-dwelling older adults (mean age = 72 years) were randomly assigned to receive a daily L (10 mg) and Z (2 mg) supplement or a placebo for 1 year. Resting state fMRI data were acquired at baseline and post-intervention. A dictionary learning and sparse coding computational framework, based on machine learning principles, was used to investigate intervention-related changes in functional connectivity. DMN integrity was evaluated by calculating spatial overlap rate with a well-established DMN template provided in the neuroscience literature. Inter-network connectivity was evaluated via time series correlations between DMN and nine other resting state networks. Contrary to expectation, results indicated that L and Z significantly increased rather than decreased inter-network connectivity (Cohen's d = 0.89). A significant intra-network effect on DMN integrity was not observed. Rather than restoring what has been described in the available literature as a "youth-like" pattern of intrinsic brain activity, L and Z may facilitate the aging brain's capacity for compensation by enhancing integration between networks that tend to be functionally segregated earlier in the lifespan.

Lack of Gαi2 proteins in adipocytes attenuates diet-induced obesity

OBJECTIVES

Typically, obesity results from an inappropriate balance between energy uptake from nutrient consumption and burning of calories, which leads to a pathological increase in fat mass. Obesity is a major cause of insulin resistance and diabetes. Inhibitory G proteins (Gαi) form a subfamily that is involved in the regulation of adipose tissue function. Among the three Gαi members, i.e. Gαi1, Gαi2, Gαi3, the Gαi2, protein is predominantly expressed in adipose tissue. However, the functions of the Gαi2 isoform in adipose tissue and its impact on the development of obesity are poorly understood.

METHODS

By using AdipoqCreERT2 mice, we generated adipocyte-specific Gnai2-deficient mice to study Gαi2 function, specifically in white and brown adipocytes. These mice were fed either a control diet (CD) or a high fat diet (HFD). Mice were examined for obesity development, insulin resistance and glucose intolerance. We examined adipocyte morphology and the development of inflammation in the white adipose tissue. Finally, intracellular cAMP levels as an indicator of Gαi signaling and glycerol release as an indicator of lipolysis rates were measured to verify the impact of Gαi2 on the signaling pathway in brown and white adipocytes.

RESULTS

An adipocyte-specific deficiency of Gαi2 significantly reduced diet-induced obesity, leading to decreased fat masses, smaller adipocytes and decreased inflammation in the white adipose tissue relative to littermate controls. Concurrently, oxygen consumption of brown adipocytes and in vivo measured energy expenditure were significantly enhanced. In addition, glucose tolerance and insulin sensitivity of HFD-fed adipocyte-specific Gnai2-deficient mice were improved compared to the respective controls. In the absence of Gαi2, adrenergic stimulation of intracellular adipocyte cAMP levels was increased, which correlated with increased lipolysis and energy expenditure.

CONCLUSION

We conclude that adipocyte Gαi2 is a major regulator of adipocyte lipid content in diet-induced obesity by inhibiting adipocyte lipolysis in a cAMP-dependent manner resulting in increased energy expenditure.

Diet and Mental Health: Review of the Recent Updates on Molecular Mechanisms

Over the last decades, there has been a substantial increase in the prevalence of mental health disorders, including an increased prevalence of depression, anxiety, cognitive, and sleep disorders. Diet and its bioactive components have been recognized among the modifiable risk factors, possibly influencing their pathogenesis. This review aimed to summarize molecular mechanisms underlying the putative beneficial effects toward brain health of different dietary factors, such as micro- and macronutrient intake and habits, such as feeding time and circadian rhythm. The role of hormonal homeostasis in the context of glucose metabolism and adiponectin regulation and its impact on systemic and neuro-inflammation has also been considered and deepened. In addition, the effect of individual bioactive molecules exerting antioxidant activities and acting as anti-inflammatory agents, such as omega-3 fatty acids and polyphenols, considered beneficial for the central nervous system via modulation of adult neurogenesis, synaptic and neuronal plasticity, and microglia activation has been summarized. An overview of the regulation of the gut–brain axis and its effect on the modulation of systemic inflammation and oxidative stress has been provided. Finally, the impact of bioactive molecules on inflammation and oxidative stress and its association with brain health has been summarized.

Dietary total antioxidant capacity and its association with sleep, stress, anxiety, and depression score: A cross-sectional study among diabetic women

BACKGROUND

Diabetes as a common chronic disease leads to several serious disabilities and complications. Patients with type 2 diabetes are involved with psychological and sleep disorders which diet can be effective in the management of these problems. The present study aimed to investigate the association of Dietary Total Antioxidant Capacity (DTAC) and sleep, stress, anxiety, and depression among diabetic women.

METHODS

This cross-sectional study conducted on 265 women with type 2 diabetes. A validated food frequency questionnaire was filled to evaluate dietary intakes. We calculated DTAC based on amounts of antioxidant in each dietary item using the ferric reducing ability of plasma (FRAP) and oxygen radical absorbance capacity (ORAC) databases. Pittsburgh Sleep Quality Index was used to assess sleep quality. Moreover, 21 items Depression, Anxiety, and Stress Scale was used to assess mental disorders.

RESULTS

Subjects in the highest tertile of FRAP and ORAC score compared to those in the lowest tertile of these scores had 94% and 87% lower risk of poor sleep, respectively. The odds of depression were negatively related to the highest tertile of FRAP and ORAC score (OR: 0.21, 95%CI: 0.09-0.50 and OR: 0.21, 95%CI: 0.10-0.48, respectively). Participants with the highest tertile of FRAP compared to those within the lowest tertile of FRAP score had a 59% lower risk of anxiety. The odds of stress were negatively related to the highest tertile of FRAP and ORAC score (OR: 0.10, 95%CI: 0.04-0.23 and OR: 0.13, 95%CI: 0.06-0.29, respectively).

CONCLUSION

There is a significant association between DTAC, sleep status and psychological disorders. However, prospective studies in both genders should be conducted to confirm the actual relationship.

High-fat diet protects the blood-brain barrier in an Alzheimer's disease mouse model

Type 2 diabetes (T2D) is associated with increased risk of Alzheimer's disease (AD). There is evidence for impaired blood-brain barrier (BBB) in both diseases, but its role in the interplay between them is not clear. Here, we investigated the effects of high-fat diet (HFD), a model for T2D, on the Tg2576 mouse model of AD, in regard to BBB function. We showed that HFD mice had higher weight, more insulin resistance, and higher serum HDL cholesterol levels, primarily in Tg2576 mice, which also had higher brain lipids content. In terms of behavior, Tg2576 HFD mice were less active and more anxious, but had better learning in the Morris Water Maze compared to Tg2576 on regular diet. HFD had no effect on the level of amyloid beta 1-42 in the cortex of Tg2576 mice, but increased the transcription level of insulin receptor in the hippocampus. Tg2576 mice on regular diet demonstrated more BBB disruption at 8 and 12 months accompanied by larger lateral ventricles volume in contrast to Tg2576 HFD mice, whose BBB leakage and ventricular volume were similar to wild-type (WT) mice. Our results suggest that in AD, HFD may promote better cognitive function through improvements of BBB function and of brain atrophy but not of amyloid beta levels. Lipid metabolism in the CNS and peripheral tissues and brain insulin signaling may underlie this protection.

Estimates of genomic heritability and genome-wide association study for fatty acids profile in Santa Inês sheep

BACKGROUND

Despite the health concerns and nutritional importance of fatty acids, there is a relative paucity of studies in the literature that report genetic or genomic parameters, especially in the case of sheep populations. To investigate the genetic architecture of fatty acid composition of sheep, we conducted genome-wide association studies (GWAS) and estimated genomic heritabilities for fatty acid profile in Longissimus dorsi muscle of 216 male sheep.

RESULTS

Genomic heritability estimates for fatty acid content ranged from 0.25 to 0.46, indicating that substantial genetic variation exists for the evaluated traits. Therefore, it is possible to alter fatty acid profiles through selection. Twenty-seven genomic regions of 10 adjacent SNPs associated with fatty acids composition were identified on chromosomes 1, 2, 3, 5, 8, 12, 14, 15, 16, 17, and 18, each explaining ≥0.30% of the additive genetic variance. Twenty-three genes supporting the understanding of genetic mechanisms of fat composition in sheep were identified in these regions, such as DGAT2, TRHDE, TPH2, ME1, C6, C7, UBE3D, PARP14, and MRPS30.

CONCLUSIONS

Estimates of genomic heritabilities and elucidating important genomic regions can contribute to a better understanding of the genetic control of fatty acid deposition and improve the selection strategies to enhance meat quality and health attributes.

Nucleus accumbens inflammation mediates anxiodepressive behavior and compulsive sucrose seeking elicited by saturated dietary fat

OBJECTIVE

The incidence of depression is significantly compounded by obesity. Obesity arising from excessive intake of high-fat food provokes anxiodepressive behavior and elicits molecular adaptations in the nucleus accumbens (NAc), a region well-implicated in the hedonic deficits associated with depression and in the control of food-motivated behavior. To determine the etiology of diet-induced depression, we studied the impact of different dietary lipids on anxiodepressive behavior and metabolic and immune outcomes and the contribution of NAc immune activity.

METHODS

Adult C57Bl/6 mice were subjected to isocaloric high-fat/high-sucrose diets (HFD), enriched in either saturated or monounsaturated fat, or a control low-fat diet (LFD). Metabolic responses, anxiodepressive behavior, and plasma and NAc inflammatory markers were assessed after 12 weeks. In separate experiments, an adenoviral construct inhibiting IKKβ, an upstream component of the nuclear factor kappa-b (NFkB) pathway, was a priori injected into the NAc.

RESULTS

Both HFDs resulted in obesity and hyperleptinemia; however, the saturated HFD uniquely triggered anxiety-like behavior, behavioral despair, hyperinsulinemia, glucose intolerance, peripheral inflammation, and multiple pro-inflammatory signs in the NAc, including reactive gliosis, increased expression of cytokines, antigen-presenting markers and NFкB transcriptional activity. Selective NAc IKKβ inhibition reversed the upregulated expression of inflammatory markers, prevented anxiodepressive behavior and blunted compulsive sucrose-seeking in mice fed the saturated HFD.

CONCLUSIONS

Metabolic inflammation and NFкB-mediated neuroinflammatory responses in the NAc contribute to the expression of anxiodepressive behavior and heightened food cravings caused by a diet high in saturated fat and sugar.

The Relationship between Fatty Acids and Different Depression-Related Brain Regions, and Their Potential Role as Biomarkers of Response to Antidepressants

Depression is a complex disorder influenced by a variety of biological and environmental factors. Due to significant heterogeneity, there are remarkable differences in how patients respond to treatment. A primary objective of psychiatric research is to identify biological markers that could be used to better predict and enhance responses to antidepressant treatments. Diet impacts various aspects of health, including depression. The fatty acid composition of the Western diet, which has a high ratio of n-6:n-3 polyunsaturated fatty acids, is associated with increased incidence of depression. The brain is rich in lipids, and dietary fatty acids act within specific brain regions to regulate processes that impact emotional behavior. This manuscript reviews existing evidence demonstrating brain region-specific fatty acid profiles, and posits that specific fatty acids may serve as predictive biomarkers of response to antidepressants. Furthermore, increasing blood levels of certain fats, such as n-3s, via dietary intervention may serve as an adjunct to improve the efficacy of antidepressants. Notably, most of the existing research regarding fats and depression-related brain regions has focused on n-3s, as compared to n-6s, monounsaturated, and saturated fats. This review article will help guide future work investigating the relationships between fatty acids, brain regions, and antidepressant efficacy.

Dietary saturated fat and monounsaturated fat have reversible effects on brain function and the secretion of pro-inflammatory cytokines in young women

BACKGROUND

Previous literature suggests that a higher ratio of palmitic acid (PA)/oleic acid (OA) in the diet induces inflammation, which may result in deficient brain insulin signaling, and, secondarily, impaired physical activity, sleep efficiency, and cognitive functioning.

OBJECTIVE

We hypothesized that lowering the typical dietary PA/OA would affect the activation of relevant brain networks during a working memory task and would also lower secretion of pro-inflammatory cytokines.

DESIGN

In 12 female subjects participating in a randomized, cross-over trial comparing 3-week high PA diet (HPA) and low PA and a high OA diet (HOA), we evaluated functional magnetic resonance imaging (fMRI) using an N-back test of working memory, cytokine secretion by lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC), and plasma cytokine concentrations.

RESULTS

Brain activation during the HPA diet compared to the HOA diet was increased in regions of the basal ganglia including the caudate and putamen (p<0.005). In addition, compared to the HOA diet, during the HPA diet, the plasma concentrations of IL-6 (p=0.04) and IL-1β (p=0.05) were higher, and there was a higher secretion of IL-18 (p=0.015) and a trend for higher IL-1β secretion (p=0.066) from LPS-stimulated PBMCs.

CONCLUSIONS

The HPA diet resulted in increased brain activation in the basal ganglia compared to the HOA diet as well as increased secretion of pro-inflammatory cytokines. These data provide evidence that short-term (2week) diet interventions impact brain network activation during a working memory task and that these effects are reversible since the order of the study diets was randomized. These data are consistent with the hypothesis that lowering the dietary PA content via substitution with OA also could affect cognition.

Sustained Treatment with Insulin Detemir in Mice Alters Brain Activity and Locomotion

Aims

Recent studies have identified unique brain effects of insulin detemir (Levemir^®). Due to its pharmacologic properties, insulin detemir may reach higher concentrations in the brain than regular insulin. This might explain the observed increased brain stimulation after acute insulin detemir application but it remained unclear whether chronic insulin detemir treatment causes alterations in brain activity as a consequence of overstimulation.

Methods

In mice, we examined insulin detemir’s prolonged brain exposure by continuous subcutaneous (s.c.) application using either micro-osmotic pumps or daily s.c. injections and performed continuous radiotelemetric electrocorticography and locomotion recordings.

Results

Acute intracerebroventricular injection of insulin detemir activated cortical and locomotor activity significantly more than regular insulin in equimolar doses (0.94 and 5.63 mU in total), suggesting an enhanced acute impact on brain networks. However, given continuously s.c., insulin detemir significantly reduced cortical activity (theta: 21.3±6.1% vs. 73.0±8.1%, P<0.001) and failed to maintain locomotion, while regular insulin resulted in an increase of both parameters.

Conclusions

The data suggest that permanently-increased insulin detemir levels in the brain convert its hyperstimulatory effects and finally mediate impairments in brain activity and locomotion. This observation might be considered when human studies with insulin detemir are designed to target the brain in order to optimize treatment regimens.

The anterior medial temporal lobes: Their role in food intake and body weight regulation

The anterior medial temporal lobes are one of the most studied parts of the brain. Classically, their two main structures - the amygdalae and the hippocampi - have been linked to key cognitive and affective functions, related in particular to learning and memory. Based on abundant evidence, we will argue for an alternative but complementary point of view: they may also play a major role in food intake and body weight regulation. First, an overview is given of early clinical evidence in this line of thought. Subsequently, empirical evidence is presented on how food intake, including in the extreme case of obesity, may relate to amygdalian and hippocampal functioning. The focus is on the amygdala's role in processing the relevance of food stimuli, cue-induced feeding, and stress-induced eating and on the hippocampus' involvement in the use of interoceptive signals of hunger and satiety, as well as memory and inhibitory processes related to food intake. Additionally, an elaboration takes place on possible reciprocal links between food intake, body weight, and amygdala and hippocampus functioning. Finally, issues that seemed particularly critical for future research in the field are discussed.

Deleterious effects of lard-enriched diet on tissues fatty acids composition and hypothalamic insulin actions

Altered tissue fatty acid (FA) composition may affect mechanisms involved in the control of energy homeostasis, including central insulin actions. In rats fed either standard chow or a lard-enriched chow (high in saturated/low in polyunsaturated FA, HS-LP) for eight weeks, we examined the FA composition of blood, hypothalamus, liver, and retroperitoneal, epididymal and mesenteric adipose tissues. Insulin-induced hypophagia and hypothalamic signaling were evaluated after intracerebroventricular insulin injection. HS-LP feeding increased saturated FA content in adipose tissues and serum while it decreased polyunsaturated FA content of adipose tissues, serum, and liver. Hypothalamic C20:5n-3 and C20:3n-6 contents increased while monounsaturated FA content decreased. HS-LP rats showed hyperglycemia, impaired insulin-induced hypophagia and hypothalamic insulin signaling. The results showed that, upon HS-LP feeding, peripheral tissues underwent potentially deleterious alterations in their FA composition, whist the hypothalamus was relatively preserved. However, hypothalamic insulin signaling and hypophagia were drastically impaired. These findings suggest that impairment of hypothalamic insulin actions by HS-LP feeding was not related to tissue FA composition.

Sex-Specific Effects of Diets High in Unsaturated Fatty Acids on Spatial Learning and Memory in Guinea Pigs

Unsaturated fatty acids (UFAs), including omega-3, omega-6 polyunsaturated and omega-9 monounsaturated fatty acids, are essential components and modulators of neuromembranes and may affect various aspects of physiology and cognition. UFAs are suggested to positively affect spatial learning and memory and also to diminish the negative consequences of physiological stress on cognitive abilities. Due to pronounced sex differences in neurophysiological functions, we hypothesize that these UFA-related effects might differ between male and female individuals. We therefore determined the effects of dietary UFAs on cognitive performances in a radial-Y-maze in male and female guinea pigs in relation to saliva cortisol concentrations, a marker for physiological stress. Animals were assigned to four treatment groups and maintained on diets enriched in either chia seeds (omega-3), walnuts (omega-6), or peanuts (omega-9), or a control diet. Female learning abilities throughout a three-day learning phase were positively affected by omega-3 and omega-9, as determined by a decreasing latency to pass the test and the number of conducted errors, while males generally showed distinct learning abilities, irrespective of the diet. A sex difference in learning performances was found in the control group, with males outperforming females, which was not detected in the UFA-supplemented groups. This was paralleled by significantly increased saliva cortisol concentrations in males throughout the cognition test compared to females. Three days after this learning phase, UFA-supplemented males and all females showed unchanged performances, while control males showed an increased latency and therefore an impaired performance. These results were corroborated by pronounced differences in the plasma UFA-status, corresponding to the different dietary treatments. Our findings indicate sex-specific effects of dietary UFAs, apparently enhancing spatial learning abilities only in females and protecting males from long-term memory impairment, while male learning abilities seem to be more strongly affected by an acute physiological stress response to the maze task.

Weight-sparing effect of insulin detemir: a consequence of central nervous system-mediated reduced energy intake?

Insulin therapy is often associated with adverse weight gain. This is attributable, at least in part, to changes in energy balance and insulin's anabolic effects. Adverse weight gain increases the risk of poor macrovascular outcomes in people with diabetes and should therefore be mitigated if possible. Clinical studies have shown that insulin detemir, a basal insulin analogue, exerts a unique weight-sparing effect compared with other basal insulins. To understand this property, several hypotheses have been proposed. These explore the interplay of efferent and afferent signals between the muscles, brain, liver, renal and adipose tissues in response to insulin detemir and comparator basal insulins. The following models have been proposed: insulin detemir may reduce food intake through direct or indirect effects on the central nervous system (CNS); it may have favourable actions on hepatic glucose metabolism through a selective effect on the liver, or it may influence fluid homeostasis through renal effects. Studies have consistently shown that insulin detemir reduces energy intake, and moreover, it is clear that this shift in energy balance is not a consequence of reduced hypoglycaemia. CNS effects may be mediated by direct action, by indirect stimulation by peripheral mediators and/or via a more physiological counter-regulatory response to insulin through restoration of the hepatic-peripheral insulin gradient. Although the precise mechanism remains unclear, it is likely that the weight-sparing effect of insulin detemir can be explained by a combination of mechanisms. The evidence for each hypothesis is considered in this review.

Lipidomic evidence that lowering the typical dietary palmitate to oleate ratio in humans decreases the leukocyte production of proinflammatory cytokines and muscle expression of redox-sensitive genes

We recently reported that lowering the high, habitual palmitic acid (PA) intake in ovulating women improved insulin sensitivity and both inflammatory and oxidative stress. In vitro studies indicate that PA can activate both cell membrane toll-like receptor-4 and the intracellular nucleotide oligomerization domain-like receptor protein (NLRP3). To gain further insight into the relevance to human metabolic disease of dietary PA, we studied healthy, lean and obese adults enrolled in a randomized, crossover trial comparing 3-week, high-PA (HPA) and low-PA/high-oleic-acid (HOA) diets. After each diet, both hepatic and peripheral insulin sensitivities were measured, and we assessed cytokine concentrations in plasma and in supernatants derived from lipopolysaccharide-stimulated peripheral blood mononuclear cells (PBMCs) as well as proinflammatory gene expression in skeletal muscle. Insulin sensitivity was unaffected by diet. Plasma concentration of tumor necrosis factor-α was higher during the HPA diet. Lowering the habitually high PA intake by feeding the HOA diet resulted in lower secretion of interleukin (IL)-1β, IL-18, IL-10, and tumor necrosis factor-α by PBMCs, as well as lower relative mRNA expression of cJun and NLRP3 in muscle. Principal components analysis of 156 total variables coupled to analysis of covariance indicated that the mechanistic pathway for the differential dietary effects on PBMCs involved changes in the PA/OA ratio of tissue lipids. Our results indicate that lowering the dietary and tissue lipid PA/OA ratio resulted in lower leukocyte production of proinflammatory cytokines and muscle expression of redox-sensitive genes, but the relevance to diabetes risk is uncertain.

The brain response to peripheral insulin declines with age: a contribution of the blood-brain barrier?

Objectives

It is a matter of debate whether impaired insulin action originates from a defect at the neural level or impaired transport of the hormone into the brain. In this study, we aimed to investigate the effect of aging on insulin concentrations in the periphery and the central nervous system as well as its impact on insulin-dependent brain activity.

Methods

Insulin, glucose and albumin concentrations were determined in 160 paired human serum and cerebrospinal fluid (CSF) samples. Additionally, insulin was applied in young and aged mice by subcutaneous injection or intracerebroventricularly to circumvent the blood-brain barrier. Insulin action and cortical activity were assessed by Western blotting and electrocorticography radiotelemetric measurements.

Results

In humans, CSF glucose and insulin concentrations were tightly correlated with the respective serum/plasma concentrations. The CSF/serum ratio for insulin was reduced in older subjects while the CSF/serum ratio for albumin increased with age like for most other proteins. Western blot analysis in murine whole brain lysates revealed impaired phosphorylation of AKT (P-AKT) in aged mice following peripheral insulin stimulation whereas P-AKT was comparable to levels in young mice after intracerebroventricular insulin application. As readout for insulin action in the brain, insulin-mediated cortical brain activity instantly increased in young mice subcutaneously injected with insulin but was significantly reduced and delayed in aged mice during the treatment period. When insulin was applied intracerebroventricularly into aged animals, brain activity was readily improved.

Conclusions

This study discloses age-dependent changes in insulin CSF/serum ratios in humans. In the elderly, cerebral insulin resistance might be partially attributed to an impaired transport of insulin into the central nervous system.

Effects of diets high in unsaturated Fatty acids on socially induced stress responses in Guinea pigs

Unsaturated fatty acids (UFAs), such as omega-3 and omega-6 poly- and omega-9 monounsaturated fatty acids are important nutrients and major components of neuronal cell membranes. They play a major role in modulating brain functions and physiology and may therefore diminish behavioral and physiological stress reactions in corroboration with decreased cortisol concentrations. Functionally, cortisol itself can modulate several behaviors and also the fatty acid metabolism in the long term. But only little is known about the behavioral and physiological influences of dietary UFAs in a social group, where individuals are regularly exposed to stressful situations. Therefore, the aim of this study was to determine the effects of dietary UFAs on saliva cortisol concentrations and behavioral responses in socially confronted guinea pigs. Three groups of animals were additionally supplemented with 500 mg chia seeds (high in omega-3), walnuts (high in omega-6), or peanuts (high in omega-9) per kg bodyweight each day and compared to a control group. During social confrontation saliva cortisol concentrations significantly increased in all groups, which was accompanied by a loss in bodyweight. However, cortisol levels remained lower in the chia and walnut groups compared to controls. Additionally, the walnut group displayed significantly increased locomotion, while no differences between groups were detected in socio-positive, sexual, or aggressive behaviors. Total plasma omega-3, omega-6, and omega-9 fatty acids were significantly increased in the corresponding groups, due to the dietary supplementations. However, a significant decrease in plasma omega-3 and an increase in plasma n-6 fatty acids were detected in the chia group when comparing the measurements before and after social confrontation. We conclude that both omega-3 and omega-6 polyunsaturated fatty acids can diminish behavioral and physiological stress responses to the social environment, enabling individuals to cope with social stressors, but at the expense of plasma derived omega-3 fatty acids.

Cinnamon extract improves insulin sensitivity in the brain and lowers liver fat in mouse models of obesity

Objectives

Treatment of diabetic subjects with cinnamon demonstrated an improvement in blood glucose concentrations and insulin sensitivity but the underlying mechanisms remained unclear. This work intends to elucidate the impact of cinnamon effects on the brain by using isolated astrocytes, and an obese and diabetic mouse model.

Methods

Cinnamon components (eugenol, cinnamaldehyde) were added to astrocytes and liver cells to measure insulin signaling and glycogen synthesis. Ob/ob mice were supplemented with extract from cinnamomum zeylanicum for 6 weeks and cortical brain activity, locomotion and energy expenditure were evaluated. Insulin action was determined in brain and liver tissues.

Results

Treatment of primary astrocytes with eugenol promoted glycogen synthesis, whereas the effect of cinnamaldehyde was attenuated. In terms of brain function in vivo, cinnamon extract improved insulin sensitivity and brain activity in ob/ob mice, and the insulin-stimulated locomotor activity was improved. In addition, fasting blood glucose levels and glucose tolerance were greatly improved in ob/ob mice due to cinnamon extracts, while insulin secretion was unaltered. This corresponded with lower triglyceride and increased liver glycogen content and improved insulin action in liver tissues. In vitro, Fao cells exposed to cinnamon exhibited no change in insulin action.

Conclusions

Together, cinnamon extract improved insulin action in the brain as well as brain activity and locomotion. This specific effect may represent an important central feature of cinnamon in improving insulin action in the brain, and mediates metabolic alterations in the periphery to decrease liver fat and improve glucose homeostasis.

Clinical Implications of Impaired Sleep

Despite its pervasiveness in primary care, deficient sleep often is underappreciated as a cue to other health risks. Accordingly, this review discusses contemporary evidence-based perspectives on impaired sleep and its associations with other lifestyle medicine concerns, including obesity, cardiovascular conditions, psychological problems, and health-compromising habits. The potential clinical benefits of promoting sleep health also will be considered.

Maternal fatty acids in pregnancy, FADS polymorphisms, and child intelligence quotient at 8 y of age

BACKGROUND

Brain tissue is selectively enriched with highly unsaturated fatty acids (FAs). Altering the maternal FA status in pregnancy may improve fetal neural development with lasting consequences for child development.

OBJECTIVE

We explored whether maternal FAs in erythrocytes, either measured directly or indirectly by maternal FADS genetic variants, are associated with child intelligence quotient (IQ).

DESIGN

Linear regression analyses, adjusted for 18 confounders, were used to investigate the associations in 2839 mother-child pairs from the population-based Avon Longitudinal Study of Parents and Children cohort.

RESULTS

Low levels of arachidonic acid (20:4n-6) were associated with lower performance IQ (-2.0 points; 95% CI: -3.5, -0.6 points; P = 0.007, increased R² = 0.27%), high levels of osbond acid (22:5n-6) were associated with verbal IQ (-1.8 points; 95% CI: -3.2, -0.4 points; P = 0.014, R² = 0.20%), and high levels of adrenic acid (22:4n-6) were associated with verbal IQ (-1.7 points; 95% CI:-3.1, -0.3 points; P = 0.016, R² = 0.19%). There was some evidence to support a negative association of low docosahexaenoic acid (DHA; 22:6n-3) with full-scale IQ (R² = 0.15%). Novel weak associations were also observed for low levels of osbond acid (R² ≤ 0.29%) and FADS variants with opposite effects for intron variants and variants in the promoter region such as rs3834458 (R² ≤ 0.38%).

CONCLUSIONS

These results support the positive role of maternal arachidonic acid and DHA on fetal neural development, although the effects on child IQ by 8 y of age were small (0.1 SD), with other factors contributing more substantially. The endogenous synthesis of these FAs by FADS genes, especially FADS2, may also be important. The replication of these results is recommended.

Impaired glucose tolerance in rats fed low-carbohydrate, high-fat diets

Moderate low-carbohydrate/high-fat (LC-HF) diets are widely used to induce weight loss in overweight subjects, whereas extreme ketogenic LC-HF diets are used to treat neurological disorders like pediatric epilepsy. Usage of LC-HF diets for improvement of glucose metabolism is highly controversial; some studies suggest that LC-HF diets ameliorate glucose tolerance, whereas other investigations could not identify positive effects of these diets or reported impaired insulin sensitivity. Here, we investigate the effects of LC-HF diets on glucose and insulin metabolism in a well-characterized animal model. Male rats were fed isoenergetic or hypocaloric amounts of standard control diet, a high-protein "Atkins-style" LC-HF diet, or a low-protein, ketogenic, LC-HF diet. Both LC-HF diets induced lower fasting glucose and insulin levels associated with lower pancreatic β-cell volumes. However, dynamic challenge tests (oral and intraperitoneal glucose tolerance tests, insulin-tolerance tests, and hyperinsulinemic euglycemic clamps) revealed that LC-HF pair-fed rats exhibited impaired glucose tolerance and impaired hepatic and peripheral tissue insulin sensitivity, the latter potentially being mediated by elevated intramyocellular lipids. Adjusting visceral fat mass in LC-HF groups to that of controls by reducing the intake of LC-HF diets to 80% of the pair-fed groups did not prevent glucose intolerance. Taken together, these data show that lack of dietary carbohydrates leads to glucose intolerance and insulin resistance in rats despite causing a reduction in fasting glucose and insulin concentrations. Our results argue against a beneficial effect of LC-HF diets on glucose and insulin metabolism, at least under physiological conditions. Therefore, use of LC-HF diets for weight loss or other therapeutic purposes should be balanced against potentially harmful metabolic side effects.

Mediterranean diet habits in older individuals: associations with cognitive functioning and brain volumes

To examine the association between dietary habits, cognitive functioning and brain volumes in older individuals, data from 194 cognitively healthy individuals who participated in the Prospective Investigation of the Vasculature in Uppsala Seniors cohort were used. At age 70, participants kept diaries of their food intake for 1week. These records were used to calculate a Mediterranean diet (MeDi) score (comprising dietary habits traditionally found in Mediterranean countries, e.g. high intake of fruits and low intake of meat), with higher scores indicating more pronounced MeDi-like dietary habits. Five years later, participants' cognitive capabilities were examined by the seven minute screening (7MS) (a cognitive test battery used by clinicians to screen for dementia), and their brain volumes were measured by volumetric magnetic resonance imaging. Multivariate linear regression analyses were constructed to examine the association between the total MeDi score and cognitive functioning and brain volumes. In addition, possible associations between MeDi's eight dietary features and cognitive functioning and brain volumes were investigated. From the eight dietary features included in the MeDi score, pertaining to a low consumption of meat and meat products was linked to a better performance on the 7MS test (P=0.001) and greater total brain volume (i.e. the sum of white and gray matter, P=0.03) when controlling for potential confounders (e.g. BMI) in the analysis. Integrating all dietary features into the total MeDi score explained less variance in cognitive functioning and brain volumes than its single dietary component meat intake. These observational findings suggest that keeping to a low meat intake could prove to be an impact-driven public health policy to support healthy cognitive aging, when confirmed by longitudinal studies. Further, they suggest that the MeDi score is a construct that may mask possible associations of single MeDi features with brain health domains in elderly populations.

Fatting the brain: a brief of recent research

Fatty acids are of paramount importance to all cells, since they provide energy, function as signaling molecules, and sustain structural integrity of cellular membranes. In the nervous system, where fatty acids are found in huge amounts, they participate in its development and maintenance throughout life. Growing evidence strongly indicates that fatty acids in their own right are also implicated in pathological conditions, including neurodegenerative diseases, mental disorders, stroke, and trauma. In this review, we focus on recent studies that demonstrate the relationships between fatty acids and function and dysfunction of the nervous system. Fatty acids stimulate gene expression and neuronal activity, boost synaptogenesis and neurogenesis, and prevent neuroinflammation and apoptosis. By doing so, they promote brain development, ameliorate cognitive functions, serve as anti-depressants and anti-convulsants, bestow protection against traumatic insults, and enhance repairing processes. On the other hand, unbalance between different fatty acid families or excess of some of them generate deleterious side effects, which limit the translatability of successful results in experimental settings into effective therapeutic strategies for humans. Despite these constraints, there exists realistic evidence to consider that nutritional therapies based on fatty acids can be of benefit to several currently incurable nervous system diseases.

Is obesity a brain disease?

That the brain is involved in the pathogenesis and perpetuation of obesity is broadly self-intuitive, but traditional evaluation of this relationship has focused on psychological and environment-dependent issues, often referred to as the "it's all in the head" axiom. Here we review evidence that excessive nutrition or caloric flux, regardless of its primary trigger, elicits a biological trap which imprints aberrant energy control circuits that tend to worsen with the accumulation of body fat. Structural and functional changes in the brain can be recognized, such as hypothalamic inflammation and gliosis, reduction in brain volume, reduced regional blood flow or diminished hippocampal size. Such induced changes collectively translate into a vicious cycle of deranged metabolic control and cognitive deficits, some of which can be traced back even to childhood or adolescence. Much like other components of the obese state, brain disease is inseparable from obesity itself and requires better recognition to allow future therapeutic targeting.

Substituting dietary monounsaturated fat for saturated fat is associated with increased daily physical activity and resting energy expenditure and with changes in mood

BACKGROUND

The Western diet increases risk of metabolic disease.

OBJECTIVE

We determined whether lowering the ratio of saturated fatty acids to monounsaturated fatty acids in the Western diet would affect physical activity and energy expenditure.

DESIGN

With the use of a balanced design, 2 cohorts of 18 and 14 young adults were enrolled in separate randomized, double-masked, crossover trials that compared a 3-wk high-palmitic acid diet (HPA; similar to the Western diet fat composition) to a low-palmitic acid and high-oleic acid diet (HOA; similar to the Mediterranean diet fat composition). All foods were provided by the investigators, and the palmitic acid (PA):oleic acid (OA) ratio was manipulated by adding different oil blends to the same foods. In both cohorts, we assessed physical activity (monitored continuously by using accelerometry) and resting energy expenditure (REE). To gain insight into a possible mood disturbance that might explain changes in physical activity, the Profile of Mood States (POMS) was administered in cohort 2.

RESULTS

Physical activity was higher during the HOA than during the HPA in 15 of 17 subjects in cohort 1 (P = 0.008) (mean: 12% higher; P = 0.003) and in 12 of 12 subjects in the second, confirmatory cohort (P = 0.005) (mean: 15% higher; P = 0.003). When the HOA was compared with the HPA, REE measured during the fed state was 3% higher for cohort 1 (P < 0.01), and REE was 4.5% higher in the fasted state for cohort 2 (P = 0.04). POMS testing showed that the anger-hostility score was significantly higher during the HPA (P = 0.007).

CONCLUSIONS

The replacement of dietary PA with OA was associated with increased physical activity and REE and less anger. Besides presumed effects on mitochondrial function (increased REE), the dietary PA:OA ratio appears to affect behavior. The second cohort was derived from a study that was registered at clinicaltrials.gov as R01DK082803.