A High-Fat Western Diet Attenuates Intestinal Changes in Mice with DSS-Induced Low-Grade Inflammation

Upregulation of inflammatory genes and pathways links obesity to severe COVID-19

Obesity is a risk factor for developing severe COVID-19. However, the mechanism underlying obesity-accelerated COVID-19 remains unclear. Here, we report results from a study in which 2-3-month-old K18-hACE2 (K18) mice were fed a western high-fat diet (WD) or normal chow (NC) over 3 months before intranasal infection with a sublethal dose of SARS-CoV2 WA1 (a strain ancestral to the Wuhan variant). After infection, the WD-fed K18 mice lost significantly more body weight and had more severe lung inflammation than normal chow (NC)-fed mice. Bulk RNA-seq analysis of lungs and adipose tissue revealed a diverse landscape of various immune cells, inflammatory markers, and pathways upregulated in the infected WD-fed K18 mice when compared with the infected NC-fed control mice. The transcript levels of IL-6, an important marker of COVID-19 disease severity, were upregulated in the lung at 6-9 days post-infection in the WD-fed mice when compared to NC-fed mice. Transcriptome analysis of the lung and adipose tissue obtained from deceased COVID-19 patients found that the obese patients had an increase in the expression of genes and the activation of pathways associated with inflammation as compared to normal-weight patients (n = 2). The K18 mouse model and human COVID-19 patient data support a link between inflammation and an obesity-accelerated COVID-19 disease phenotype. These results also indicate that obesity-accelerated severe COVID-19 caused by SARS-CoV-2 WA1 infection in the K18 mouse model would be a suitable model for dissecting the cellular and molecular mechanisms underlying pathogenesis.

Navigating nonalcoholic fatty liver disease (NAFLD): Exploring the roles of estrogens, pharmacological and medical interventions, and life style

The pursuit of studying this subject is driven by the urgency to address the increasing global prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD) and its profound health implications. NAFLD represents a significant public health concern due to its association with metabolic disorders, cardiovascular complications, and the potential progression to more severe conditions like non-alcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Liver estrogen signaling is important for maintaining liver function, and loss of estrogens increases the likelihood of NAFLD in postmenopausal women. Understanding the multifaceted mechanisms underlying NAFLD pathogenesis, its varied treatment strategies, and their effectiveness is crucial for devising comprehensive and targeted interventions. By unraveling the intricate interplay between genetics, lifestyle, hormonal regulation, and gut microbiota, we can unlock insights into risk stratification, early detection, and personalized therapeutic approaches. Furthermore, investigating the emerging pharmaceutical interventions and dietary modifications offers the potential to revolutionize disease management. This review reinforces the role of collaboration in refining NAFLD comprehension, unveiling novel therapeutic pathways, and ultimately improving patient outcomes for this intricate hepatic condition.

Intestinal Inflammation and Regeneration-Interdigitating Processes Controlled by Dietary Lipids in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a disease of chronic inflammatory conditions of the intestinal tract due to disturbance of the inflammation and immune system. Symptoms of IBD include abdominal pain, diarrhea, bleeding, reduced weight, and fatigue. In IBD, the immune system attacks the intestinal tract's inner wall, causing chronic inflammation and tissue damage. In particular, interlukin-6 and interlukin-17 act on immune cells, including T cells and macrophages, to amplify the immune responses so that tissue damage and morphological changes occur. Of note, excessive calorie intake and obesity also affect the immune system due to inflammation caused by lipotoxicity and changes in lipids supply. Similarly, individuals with IBD have alterations in liver function after sustained high-fat diet feeding. In addition, excess dietary fat intake, along with alterations in primary and secondary bile acids in the colon, can affect the onset and progression of IBD because inflammatory cytokines contribute to insulin resistance; the factors include the release of inflammatory cytokines, oxidative stress, and changes in intestinal microflora, which may also contribute to disease progression. However, interfering with de novo fatty acid synthase by deleting the enzyme acetyl-CoA-carboxylase 1 in intestinal epithelial cells (IEC) leads to the deficiency of epithelial crypt structures and tissue regeneration, which seems to be due to Lgr5+ intestinal stem cell function. Thus, conflicting reports exist regarding high-fat diet effects on IBD animal models. This review will focus on the pathological basis of the link between dietary lipids intake and IBD and will cover the currently available pharmacological approaches.

High-fat diet promotes the effect of fructo-oligosaccharides on the colonic luminal environment, including alkaline phosphatase activity in rats

We recently reported that fermentable nondigestible carbohydrates such as oligosaccharides, commonly increase colonic alkaline phosphatase (ALP) activity and the gene expression of Alpi-1, coding for rat intestinal alkaline phosphatase-I isozyme in rats and that the effect of oligosaccharides on colonic ALP activity is affected by the quality of dietary fats. We hypothesized that the amount of dietary fat would modulate the effect of oligosaccharides on colonic ALP and luminal environment in rats. In experiment 1, male Sprague-Dawley rats were fed a low-fat (LF, 5% lard) or high-fat (HF, 30% lard) diet with or without 4% fructo-oligosaccharides (FOS). In experiment 2, they were fed a 2.5%, 7%, 20%, or 40% fat (lard) diet with 4% FOS for 2 weeks. Dietary FOS in the HF diet (HF-FOS) significantly increased ALP activity in the colon and cecal digesta and colonic expression of Alpi-1, but not in the LF diet with FOS groups (LF-FOS). In comparison to the LF-FOS group, the increases in fecal mucins, Lactobacillus ratio, as well as cecal n-butyrate, and the decrease in fecal Clostridium coccoides, were more pronounced in the HF-FOS group. Compared with the 2.5% or 7% fat + FOS diet, the 20% fat + FOS diet significantly increased colonic ALP activity, Alpi-1 expression, and fecal mucins. These factors did not differ significantly between 20% and 40% fat + FOS diets. To exert the maximum effect of FOS on the colonic luminal environment, including ALP activity in rats, significantly more fat may be required than that contained present a LF diet.

Preventive Effects of Long-Term Intake of Plant Oils With Different Linoleic Acid/Alpha-Linolenic Acid Ratios on Acute Colitis Mouse Model

Objective

To investigate the preventive effects of plant oils with different linoleic acid/alpha-linolenic acid (LA/ALA) ratios against colitis symptoms, and dysbiosis of gut microbiota in acute colitis mouse model.

Methods

Sixty male C57BL/6 mice were assigned into six groups (n = 10): three groups were fed low-fat diets with low, medium, and high LA/ALA ratios; and three groups were fed with high-fat diets with low, medium, and high LA/ALA ratios. After 3 months of diet, the mice were exposed to dextran sodium sulfate solution to induce acute colitis. The severity of colitis was estimated by disease activity index (DAI) and histopathological examination. 16S rRNA gene sequencing was used for the analysis of gut microbiota.

Results

Plant oils with a lower LA/ALA ratio showed higher alleviating effects on the symptoms of colitis, which were accompanied by the better prebiotic characteristics manifested as effectively inhibiting the abnormal expansion of phylum Proteobacteria and genus Escherichia-Shigella in the gut microbiota of colitis mouse models.

Conclusion

A potential IBD prevention strategy of reducing the LA/ALA ratio in the daily consumed plant oils was proposed in this study. Furthermore, based on the optimized LA/ALA ratio, this preventive effect might not be weakened by the high intake of plant oils.