Functional consequences of brain exposure to saturated fatty acids: From energy metabolism and insulin resistance to neuronal damage

Ndufs4 knockout mice with isolated complex I deficiency engage a futile adaptive brain response

Paediatric Leigh syndrome (LS) is an early-onset and fatal neurodegenerative disorder lacking treatment options. LS is frequently caused by mutations in the NDUFS4 gene, encoding an accessory subunit of mitochondrial complex I (CI), the first complex of the oxidative phosphorylation (OXPHOS) system. Whole-body Ndufs4 knockout (KO) mice (WB-KO mice) are widely used to study isolated CI deficiency, LS pathology and interventions. These animals develop a brain-specific phenotype via an incompletely understood pathomechanism. Here we performed a quantitative analysis of the sub-brain proteome in six-weeks old WB-KO mice vs. wildtype mice. Brain regions comprised of a brain slice (BrSl), cerebellum (CB), cerebral cortex (CC), hippocampus (HC), inferior colliculus (IC), and superior colliculus (SC). Proteome analysis demonstrated similarities between CC/HC, and between IC/SC, whereas BrSl and CB differed from these two groups and each other. All brain regions displayed greatly reduced levels of two CI structural subunits (NDUFS4, NDUFA12) and an increased level of the CI assembly factor NDUFAF2. The level of CI-Q module subunits was significantly more reduced in IC/SC than in BrSl/CB/CC/HC, whereas other OXPHOS complex levels were not reduced. Gene ontology and pathway analysis demonstrated specific and common proteome changes between brain regions. Across brain regions, upregulation of cold-shock-associated proteins, mitochondrial fatty acid (FA) oxidation and synthesis (mtFAS) were the most prominent. FA-related pathways were predominantly upregulated in CB and HC. Based upon these results, we argue that stimulation of these pathways is futile and pro-pathological and discuss alternative strategies for therapeutic intervention in LS. SIGNIFICANCE: The Ndufs4 knockout mouse model is currently the most relevant and most widely used animal model to study the brain-linked pathophysiology of human Leigh Syndrome (LS) and intervention strategies. We demonstrate that the Ndufs4 knockout brain engages futile and pro-pathological responses. These responses explain both negative and positive outcomes of intervention studies in Leigh Syndrome mice and patients, thereby guiding novel intervention opportunities.

Laminaria japonica Polysaccharide Regulates Fatty Hepatosis Through Bile Acids and Gut Microbiota in Diabetes Rat

In this study, we examined the effect of Laminaria japonica polysaccharide (fucoidan) on the regulation of lipid metabolism. A rat model of diabetes mellitus (DM) was established by a high-sugar and high-fat diet combined with streptozotocin. Changes in the rats' body weight and blood glucose level during the experiment were recorded. Before the end of the experiment, an automatic biochemical analyzer was used to detect the fasting blood glucose (FBG), lipid content in serum, and insulin content, and calculate the insulin resistance index. Oil red O staining was used to detect lipid deposition in the liver. H&E staining, Masson staining, and PASM staining were used to observe the pathological structural changes in the liver. 16 s RNA sequencing and targeted metabolomics were used to detect intestinal microbiota and bile acid content. The results showed that fucoidan was able to inhibit weight loss in the DM rats and reduce the content of triglycerides (TG), cholesterol (TC), and low-density lipoprotein (LDL-C) in serum. Oil red O staining showed a decrease in liver fat accumulation after fucoidan treatment. 16 s RNA sequencing demonstrated that fucoidan increased the abundance of Bacteroidia, Campylobacteria, Clostridia, Gammaproteobacteria, Negativicutes, and Verrucomicrobi. Fucoidan also increased the secretion of secondary bile acids (Nor-DCA, TLCA, β-UDCA) and alleviated lipid metabolism disorders. The expression of α-SMA was inhibited by fucoidan, whereas the expression of FXR and TGR5 was promoted. Fucoidan shows good activity in regulating lipid metabolism by regulating the expression of FXR and TGR5 and acting on the intestinal flora-bile acid axis.

Metabolic Syndrome and Biotherapeutic Activity of Dairy (Cow and Buffalo) Milk Proteins and Peptides: Fast Food-Induced Obesity Perspective-A Narrative Review

Metabolic syndrome (MS) is defined by the outcome of interconnected metabolic factors that directly increase the prevalence of obesity and other metabolic diseases. Currently, obesity is considered one of the most relevant topics of discussion because an epidemic heave of the incidence of obesity in both developing and underdeveloped countries has been reached. According to the World Obesity Atlas 2023 report, 38% of the world population are presently either obese or overweight. One of the causes of obesity is an imbalance of energy intake and energy expenditure, where nutritional imbalance due to consumption of high-calorie fast foods play a pivotal role. The dynamic interactions among different risk factors of obesity are highly complex; however, the underpinnings of hyperglycemia and dyslipidemia for obesity incidence are recognized. Fast foods, primarily composed of soluble carbohydrates, non-nutritive artificial sweeteners, saturated fats, and complexes of macronutrients (protein-carbohydrate, starch-lipid, starch-lipid-protein) provide high metabolic calories. Several experimental studies have pointed out that dairy proteins and peptides may modulate the activities of risk factors of obesity. To justify the results precisely, peptides from dairy milk proteins were synthesized under in vitro conditions and their contributions to biomarkers of obesity were assessed. Comprehensive information about the impact of proteins and peptides from dairy milks on fast food-induced obesity is presented in this narrative review article.

Correlation of the Serum Fatty Acids with Cognitive Function: An NHANES 2011-2014 and Multivariate Mendelian Randomization Analysis

Background

The relationship between serum fatty acids and cognitive function has been the subject of extensive study.

Objective

To analyze the relationship between serum fatty acids composition and cognitive function by NHANES database and multivariate Mendelian randomization (MR) analysis.

Methods

A sub-cohort of 1,339 individuals with serum fatty acids and Digit Symbol Substitution Test (DSST) examinations from the 2011-2014 wave of the NHANES were analyzed using fully adjusted multiple linear regression models for associations between serum hydrolyzed fatty acid levels and cognitive function. Univariable and multivariable MR was used to analyze the correlation between 98 exposures related to serum fatty acids and cognitive function. Results from different database sources were combined using meta-analysis.

Results

The fully adjusted regression analysis showed that linoleic acid (LA), Omega 6, fatty acids (FAs), and LA/FAs were positively correlated with DSST. 27 exposures were included for univariate MR analysis. Ultimately, only 2 traits had IVW test p-values ranging between 0.0019 and 0.05, both of which were LA/FAs. The meta-analysis of univariate MR revealed that LA/FAs was positively associated with cognitive function (β: 0.040, 95% CI = 0.013-0.067, p = 0.0041). In multivariate MR analysis, after adjusting for education, ischemic stroke, and age, LA/FAs was positively independently associated with cognitive function (IVW β: 0.049, 95% CI = 0.021-0.077, p = 0.0006). The results of MVMR are well in line with the univariate results.

Conclusions

Both the Cross-sectional observational analyses and MR-based studies supported a suggestive causal relationship between the serum ratio of Linoleic acid in fatty acids and cognitive function.

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.

Sphingolipid metabolism in brain insulin resistance and neurological diseases

Sphingolipids, as members of the large lipid family, are important components of plasma membrane. Sphingolipids participate in biological signal transduction to regulate various important physiological processes such as cell growth, apoptosis, senescence, and differentiation. Numerous studies have demonstrated that sphingolipids are strongly associated with glucose metabolism and insulin resistance. Insulin resistance, including peripheral insulin resistance and brain insulin resistance, is closely related to the occurrence and development of many metabolic diseases. In addition to metabolic diseases, like type 2 diabetes, brain insulin resistance is also involved in the progression of neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. However, the specific mechanism of sphingolipids in brain insulin resistance has not been systematically summarized. This article reviews the involvement of sphingolipids in brain insulin resistance, highlighting the role and molecular biological mechanism of sphingolipid metabolism in cognitive dysfunctions and neuropathological abnormalities of the brain.

Detrimental consequences of tebuconazole on redox homeostasis and fatty acid profile of honeybee brain

Excessive use of azole fungicides in agriculture poses a potential threat to honeybees and other pollinator insects; however, the detailed effects of these molecules remain largely unclear. Hence, in the present study it was aimed to investigate the acute sublethal effects of tebuconazole on the redox homeostasis and fatty acid composition in the brain of honeybees. Our findings demonstrate that tebuconazole decreased total antioxidant capacity, the ratio of reduced to oxidized glutathione and disturbed the function of key antioxidant defense enzymes along with the induction of lipid peroxidation indicated by increased malondialdehyde levels, while it also altered the fatty acid profile of the brain. The present study highlights the negative impact of tebuconazole on honeybees and contributes to the understanding of potential consequences related to azole exposure on pollinator insects' health, such as the occurrence of colony collapse disorder.