Introduction

Plasmalogens (Pls) are ether-type phospholipids with vinyl-ether linkages and are widely distributed in the animal body. Pls have antioxidant properties, and the reduction of plasmalogen in plasma has been observed in diseases associated with oxidative stress, such as Alzheimer's disease (Goodenowe et al., J. Lipid. Res. 2007) and atherosclerosis (M. Nishimukai et al., Clin Chim Acta. 2014), suggesting that the ingestion of Pls may induce ameliorative effects. However, there is little structure-function information, such as whether different fatty acids bound to Pls affect the physiological functions of Pls.

Aims & Methods

Therefore, we investigated the effects of enteral administration of bacterial Pls to rats (N. Sato et al., Front. Cell Dev. Biol., 2022), focusing on the fact that bacterial Pls from Selenomonas ruminantium contains shorter even-chain fatty acids than Pls from animal sources (T. Watanabe et al., J. Gen. Appl. Microbiol., 1982). In this study, the absorption kinetics of microbial Pls bound to shorter odd-chain fatty acids (carbons 13, 15, and 17) than animal Pls were investigated in the rat small intestine. Our ultimate goal in this study is to elucidate the physiological structure-function relationship of Pls in humans by approaching the absorption mechanism of Pls in the small intestine. Male Wistar/ST rats, 9 weeks of age, were fed a standard diet (AIN 93G formula) for a 3-day acclimation period. A vinyl catheter and a silicone catheter were then implanted in the thoracic lymphatic duct for lymphatic fluid collection and in the duodenum for enteral administration, respectively. After lymph collection for 30 min (initial lymph) on the day after indwelling catheter implantation, the rats were administered 1 mL of emulsified lipid solution of lipids containing PlsEtn extracted from bacteria. Lymph was collected from the thoracic duct lymph over the next 7 hours after the administration of the test solution. Each lymph fluid before and after lipid administration was analyzed for molecular species of Pls in the lymph fluid using LC-MS/MS after lipid extraction was performed.

Results

Bacterial Pls derived from S. ruminantium, cultured in a medium including lactic acid as a carbon source, consisted of ethanolamine Pls (PlsEtn) with odd hydrocarbon chains, as 15:1 or 17:1, at sn-1 and sn-2 positions. At the sn-1 position of PlsEtn released into the lymph fluid, odd hydrocarbon chains specific to microbial Pls were bound, whereas at the sn-2 position of PlsEtn, 20:4 fatty acids were mainly bound, just as when Pls from microorganisms with short, even-chain fatty acids were administered. In PlsEtn with a 15-carbon hydrocarbon chain bound at the sn-1 position, 22:6 fatty acids were mainly bound at the sn-2 position.

Conclusion

These results suggest that bacterial Pls to which odd-chain fatty acids are bound are absorbed into the body while maintaining the characteristic structure of odd hydrocarbon chains at the sn-1 position. However, it has been suggested that the fatty acids derived from bacterial PlsEtn are barely bound at the sn-2 position and undergo a conformational change similar to that of animal PlsEtn, i.e., 20:4 and 22:6 re-esterification. This finding leads not only to the elucidation of the selectivity and specificity of lipid biosynthesis in the gastrointestinal tract, but also to the effective utilization of bacterial resources as food.

Introduction

Short-chain fatty acids (SCFA), primarily acetate, propionate, and butyrate, are microbial metabolites associated with various metabolic health benefits. In the human colon, SCFA are produced through the fermentation of dietary fibers and absorbed by colonocytes, which use them as energy source. In contrast, fermented foods contain SCFA which are absorbed in the small intestine. Unlike colonocytes, enterocytes do not primarily use SCFA as energy source and therefore we hypothesized that a greater proportion of SCFA would reach the systemic circulation following SCFA absorption in the small intestine compared to the colon. In addition, SCFA also stimulate enteroendocrine L-cells to release glucagon-like peptide 1 (GLP-1) and peptide YY (PYY), which regulate appetite and the glucose homeostasis. Given the higher density of L-cells in the colon, we further hypothesized that colonic SCFA administration would result in greater gut hormone secretion.

Aims & Methods

These hypotheses were evaluated in a randomized, crossover study involving healthy participants. SCFA (230 mmol; Ac:Pr:Bu 6:2:2) were administered either to the small intestine (visit 1) or the colon (visit 2) using targeted delivery capsules. A third study visit with placebo capsules was included to account for the GLP-1 and PYY release induced by meal consumption. On each visit, participants ingested one of the capsule types during a standardized breakfast. Blood samples were collected at regular timepoints for 8 hours to assess SCFA, GLP-1, PYY, glucose, and c-peptide concentrations. At each timepoint, appetite was rated using a 100 mm visual analogue scale (VAS). Data were analyzed using linear mixed models with capsule type, time and their interaction as fixed effects and subject as random effect. When significant effects were detected, planned contrasts were conducted with Bonferroni adjustment for multiple comparisons.

Results

Twenty-eight healthy subjects (11 males,17 females; age 23 ± 4 years; BMI 22 ± 2 kg/m²) completed all study visits. Small intestinal SCFA delivery led to higher circulating SCFA concentrations than colonic delivery (mean & 95% CI iAUC , acetate: 379 [258-501] µM.h vs. 19.1 [-65-103] µM.h, p_adj < 0.0001; propionate: 24.6 [19.7-29.6] µM.h vs. 6.62[3.66-9.58] µM.h, p_adj < 0.0001; butyrate: 9.92 [6.92-12.9] µM.h vs. 2.71 [1.35-4.06] µM.h, p_adj < 0.0001). SCFA administration in both delivery sites increased GLP-1 and PYY release compared to placebo (p_adj < 0.0001). Furthermore, PYY release was higher following colonic compared to small intestinal SCFA delivery (β = 0.109, SE = 0.0173, t(1395) = 6.332, p_adj < 0.001), whereas GLP-1 release did not differ between these two delivery sites (β = 0.0448, SE = 0.0195, t(1395) = 2.302, p_adj = 0.0645). Despite increased hormone release, glucose homeostasis remained unaffected. However, SCFA administration influenced subjective appetite. Small intestinal SCFA administration reduced hunger and prospective food consumption, and increased fullness and satiation (p_adj < 0.01) compared to placebo. Colonic delivery also increased satiation and reduced prospective consumption (p_adj <0.05).

Conclusion

In conclusion, SCFA administration in the small intestine resulted in higher circulating SCFA concentrations, whereas colonic SCFA delivery more effectively stimulated PYY release. These findings highlight the importance of intestinal absorption site in determining the metabolic effects of SCFA.

Introduction

Dietary fatty acids impact the fatty acid profile of cell membranes and act as a source of fatty acids for many key physiological pathways. Overconsumption of n-6 polyunsaturated fatty acids (PUFAs) with low intake of n-3 PUFAs is associated with the pathogenesis of inflammatory-driven diet-related chronic diseases, including CD. Derivatives of n-6 PUFAs, such as arachidonic acid (AA) are involved in the proinflammatory cascade, whereas the n-3 PUFAs (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) maintain anti-inflammatory homeostasis. Considering that fatty acids in the cell membrane may be relevant to inflammation, we examined how changing the fatty acid composition of the diet would alter the erythrocyte cell membrane's (EM) fatty acid profile in adult patients with mild-moderate luminal CD following the CD Therapeutic Dietary Intervention (CD-TDI).

Aims & Methods

This is a sub-study (n=24, 46% female, median age 43(31-54)) of an ongoing RCT designed to determine the effectiveness of the CD-TDI to induce clinical and biomarker remission in patients with CD. We examined how the fatty acid profile of the EM changes in adults with mild-moderate luminal CD (n=13) that follow the CD-TDI or their habitual diet (HD) (n=11) for 13 weeks. The CD-TDI is a whole-food diet which incorporates principles of the Mediterranean diet, with one strategy being to shift the fatty acid profile by limiting dietary sources of n-6 PUFA, increasing dietary sources of n-3 PUFA and monounsaturated fatty acids (MUFA). The HD did not change their dietary intake. Blood samples were collected at Week 0 (W0) and Week 13 (W13) and analyzed for EM fatty acid composition. Fatty acids were extracted using a combined extraction and methylation protocol with direct-injection gas chromatography to quantify long-chain fatty acids from the EM. Dietary intake was evaluated using the ASA 24-hour Dietary Assessment Tool^®.

Results

Diet analysis comparing intakes from W0 to W13 revealed a significant reduction in AA intake (p=0.05) with a trend for increased intake of n-3 PUFA from DHA (p=0.07). The HD group had a significantly higher intake of AA (p=0.03), with no other dietary changes in fatty acid intakes observed within or between groups. In the EM of the CD-TDI group, within-group differences at W13 showed a lower percentage of arachidonic acid (n-6 PUFA) (0.3±0.3% vs. 0.1±0.1%, p=0.03), a significant increase in oleic acid (MUFA) (12±2.3% vs 13±2.2% p=0.02) and a trend for higher DHA (n-3 PUFA) (2.9±0.9% vs. 3.4±0.9%; p=0.08). No significant differences within groups were observed in the HD at W0 and W13. Between-group differences at W13 demonstrated that the CD-TDI group had a significantly higher mean percentage of total EM n-3 PUFAs than the HD (4.4% vs. 3.2%; p=0.005). At week 13 a higher EM PUFA balance (EPA+DHA/n-6 PUFA) was observed between groups (CDI:15±3.1% vs HD:11±2.1%; p=0.002). PUFA balance was inversely correlated to the change in the intestinal biomarker fecal calprotectin at W13 in the CDI-group (r2=0.634; p=0.03).

Conclusion

The CD-TDI altered the fatty acid profile of the EM in patients with mild-moderately active CD. Within the EM, the CD-TDI group demonstrated significant reductions in the proinflammatory mediatory AA while increasing oleic acid, total n-3 PUFA, leading to a higher PUFA balance which correlated with intestinal biomarkers of mucosal inflammation. More research is needed to fully understand the relationship between EM and gut inflammation to determine the underlying mechanisms involved.

Introduction

Diagnostics of enteropathy with membrane digestion disturbance (EMDD) is based on the evaluation of carbohydrase activity in duodenal mucosa (DM). There is no information about diagnostic value of ileum mucosa (IM) carbohydrases.
Study objective. Assess the diagnostic value of carbohydrases activity in mucous membrane of duodenum and distal ileum in patients with EMDD and irritable bowel syndrome (IBS).

Aims & Methods

The study includes 12 patients with EMDD, 16 patients with IBS and 12 relatively healthy persons (control group). Study design included analysis of food tolerance and evaluation of activity of sucrase (S), glucoamylase (GA), maltase (М) and lactase (L) in mucous membrane of duodenum and ileum based on the method of Dahlquist with N.I.Belostotsky modification. Microsoft Office Excel and STATISTICA 10.0 were used for statistical evaluation of material. Mann-Whitney criterion was used to evaluate the differences between quantitative parameters. The differences were considered to be significant at p <0.05. Control group was used for comparison.

Results

Ratio of carbohydrase activity in duodenum and ileum in control group and patients with IBS and EMDD.

In control group the carbohydrases activity in duodenum mucosa was not significantly statistically different from the one in ileum mucosa.
In patients with IBS glucoamylase and maltase activity parameters in IM were significantly different from activity in DM, which can be interpreted as functional inequality of enzyme activity of various departments of small intestine.
In patients with EMDD GA level in ileum mucosa is 5.2 times higher, maltase level is 3.8 times higher and sucrose level is 2 times higher than duodenum enzyme levels, which demonstrates the possibility of formation of compensatory reaction of adaptive shift type towards distal segments of small intestine, initially described by A.M. Ugolev et al. in 1985

Conclusion

Enzyme activity distribution along small intestine is an adaptor function of its segments. Our study confirmed the need and promising outlook of further investigations in terms of evaluation of proximo-distal gradients of enzyme activity to study compensatory reactions which can be fulfilled by distal segment of small intestine in case of duodenum damage.
The evaluation of carbohydrase activity in ileum mucosa provides additional opportunities for diagnostics of EMDD and its differentiation from IBS, which can be used to improve therapeutic approaches.

Introduction

The aging with weight gain induces pathological changes in the liver, exacerbating non-alcoholic fatty liver disease (NAFLD). In the reproductive age, NAFLD is more prevalent and severe in males, however, NAFLD occurs at a higher rate among postmenopausal females. The liver and small bowel are closely interrelated through enterohepatic circulation, such that damage to the small bowel can significantly impact hepatic function. In small intestine, the expression of tight junction protein (TJP) in nearly associated with the development of NAFLD. The aim of this study was to investigate the effects of age and sex on hepatic steatosis and the small bowel under conditions of a high fructose, high-fat diet (HFHFD) in rats.

Aims & Methods

6-week-old male and female F344 rats divided into control and HFHFD groups, along with 2-year-old F344 rats. Over an 8-week period, the high fat diet (Raonbio, 60 kcal% fat) provided twice weekly and high fructose water (20%) gave once weekly for HFHFD groups. After 8 weeks, all animals were sacrificed, and both liver and small intestinal tissue were collected. All tissue samples were subjected to hematoxylin and eosin staining for histological analysis. RNA extraction from the jejunum mucosa was followed by qRT-PCR analysis to assess claudin-2 (cldn-2, one of TJP) gene expression.

Results

The body weight change (%) and the hepatic steatosis scores were significantly higher in the HFHFD groups compared to both male and female control groups (Table). Histological scores of old rat HFHFD groups were significantly higher than those of 6 week HFHFD groups, regardless of sex (Table). In terms of histological inflammation scores of old control group small bowel were higher than those of 6 week control group regardless of sex (Table). The jejunum villus/crypt ratio of 6-week-old rats significantly decreased only among males (Table). In contrast, in the 2-year-old groups, the villus/crypt ratio resulted in a reduction only among females and the mRNA expression of cldn-2 observed in females with significant elevation (Table).

		Weight	Steatosis score	Inflammation score			Jejunum villus/crypt length ratio	Cldn-2 mRNA expression
				Duodenum	Jejunum	Ileum
Male	6-week Con vs. 6-week HFHFD	increase (p = 0.006)	increase (p = 0.003)	increase (p = 0.072)	increase (p = 0.026)	increase (p = 0.049)	decrease (p = 0.072)	-
	2-year Con vs. 2-year HFHFD	increase (p = 0.006)	increase (p = 0.002)	-	increase (p = 0.015)	-	-	-
	6-week Con vs. 2-year Con	-	-	increase (p = 0.005)	-	increase (p = 0.022)	-	-
	6-week HFHFD vs. 2-year HFHFD	-	increase (p = 0.007)	-	-	-	-	-
Female	6-week Con vs. 6-week HFHFD	increase (p = 0.004)	increase (p = 0.002)	-	increase (p = 0.007)	increase (p = 0.104)	-	increase (p = 0.056)
	2-year Con vs. 2-year HFHFD	increase (p = 0.004)	increase (p = 0.002)	-	-	-	decrease (p = 0.076)	increase (p = 0.005)
	6-week Con vs. 2-year Con	-	-	increase (p = 0.007)	increase (p = 0.002)	increase (p = 0.002)	-	-
	6-week HFHFD vs. 2-year HFHFD	-	increase (p = 0.011)	-	-	-	-	-

Con, control; HFHFD, high fructose high fat diet; Cldn-2, Claudin-2; vs., versus

Conclusion

Our data showed that high fructose, high-fat diet induced hepatic steatosis and inflammation of small bowel, especially in old rats. This indicates that NAFLD is related with damage of small bowel brush border membrane. The upregulated gene expression of cldn-2 (p = 0.005) and the decreased tendency of jejunum villus/crypt ratio (p = 0.076) in the aged females rats suggests a potential role of TJP in advancing NAFLD in postmenopausal females.

References

Lee, Sun Min, et al. "Microbial changes and host response in F344 rat colon depending on sex and age following a high-fat diet." Frontiers in microbiology 9 (2018): 386521.
He, Yongyuan, et al. "Emerging role of aging in the progression of NAFLD to HCC." Ageing Research Reviews 84 (2023): 101833.
Hollander, Daniel, and Jonathan D. Kaunitz. "The “leaky gut”: tight junctions but loose associations?." Digestive diseases and sciences 65.5 (2020): 1277-1287.
Ahmad, Rizwan, et al. "Obesity-induces organ and tissue specific tight junction restructuring and barrier deregulation by claudin switching." Scientific reports 7.1 (2017): 1-16.
Zhou, Xiaoqiong, et al. "Gut microbiota induces hepatic steatosis by modulating the T cells balance in high fructose diet mice." Scientific Reports 13.1 (2023): 6701.
Amasheh, Salah, et al. "Claudin-2 expression induces cation-selective channels in tight junctions of epithelial cells." Journal of cell science 115.24 (2002): 4969-4976.
Lonardo, Amedeo, et al. "Sex differences in nonalcoholic fatty liver disease: state of the art and identification of research gaps." Hepatology 70.4 (2019): 1457-1469.

Introduction

Nutritional factors are increasingly recognized as key modulators of intestinal inflammation and fibrosis, offering new therapeutic angles in IBD management. Among dietary components, medium-chain fatty acids (MCFAs) have drawn attention for their bioactive properties. Lauric acid (LA), MCFA with anti-inflammatory properties, has an unclear role in IBD, particularly within a fibrotic context. LA interacts with G protein-coupled receptor 84 (GPR84), which is notably elevated in UC¹

Aims & Methods

This study evaluated the effects of lauric acid (0, 50, 100, and 250 µM) on human intestinal fibroblasts (HSIF) and colonic epithelial cells (CoEpi) under basal and pro-fibrotic conditions induced by TGFβ1 (10 ng/mL). Fibrotic gene expression was assessed by PCR—HSIF: COL1A1, COL3A1, COL4A1, ACTA2, FN1, TGFβ, GPR84; CoEpi: SNAI1/2, CDH1, COL1A1, FNDC4, VIM, GPR84. Protein levels of GPR84, FNDC5, COL1A1, αSMA, and FGFR2 in HSIF were measured via Western blot. Data were expressed as fold change (mean ± SEM) relative to 0 µM LA and analyzed using ANOVA or Kruskal-Wallis tests, depending on normality (*P < 0.05 vs. 0 µM LA; **P < 0.01 vs. 0 µM LA; #P < 0.05 vs. 0 µM LA + TGFβ1; ##P < 0.01 vs. 0 µM LA + TGFβ1).

Results

Under basal conditions, lauric acid (LA) significantly decreased the mRNA expression of fibrosis-related genes in HSIF, including COL1A1 (250 µM: 0.2 ± 0.07**) and COL3A1 (50 µM: 0.4 ± 0.1**), as well as ACTA2 (100 µM: 0.1 ± 0.1**). These anti-fibrotic effects were maintained or enhanced under TGFβ1 stimulation, particularly at lower LA doses—e.g., COL1A1 (50 µM: 1.1 ± 0.15##), COL3A1 (50 µM: 0.24 ± 0.1#), COL4A1 (250 µM: 0.6 ± 0.1#), and ACTA2 (100 µM: 0.7 ± 0.4#). Under fibrotic conditions, LA also significantly reduced the protein expression of COL1A1 (250 µM: 0.4 ± 0.17##) and αSMA (250 µM: 0.9 ± 0.14#). LA increased GPR84 mRNA expression in HSIF under both basal (250 µM: 1167 ± 646*) and fibrotic (250 µM: 1048 ± 505##) conditions, without affecting fibronectin or TGFβ levels.
In CoEpi cells, LA promoted epithelial-mesenchymal transition (EMT) markers in both basal and TGFβ1-stimulated states. This included upregulation of VIMENTIN (250 µM: 3.9 ± 0.6*; with TGFβ1: 6.4 ± 1.5#), SNAI2 (250 µM: 3.4 ± 0.5*; with TGFβ1: 3.9 ± 0.5##), and FIBRONECTIN (250 µM: 2.6 ± 0.5*; with TGFβ1: 4.4 ± 0.8##), alongside a decrease in E-CADHERIN (250 µM: 0.5 ± 0.08*; with TGFβ1: 0.35 ± 0.07#). GPR84 mRNA expression also increased significantly in CoEpi cells under both conditions (basal: 6.9 ± 1.5**; pro-fibrotic: 5.1 ± 1.0##). No changes were observed in COL1A1 or SNAI1 expression.

Conclusion

Lauric acid plays a dual, context-dependent role in intestinal fibrosis. It reduces fibrotic markers in fibroblasts, suggesting therapeutic potential, but promotes EMT in epithelial cells, which may contribute to fibrosis progression. These opposing effects, possibly mediated by GPR84, highlight lauric acid as both a friend and foe in gut health—supporting the need for further investigation before considering it as a dietary intervention in IBD.

References

Bauset C, Carda-Diéguez M, Cejudo-Garcés A, Buetas E, Seco-Cervera M, Macias-Ceja DC, Navarro-Vicente F, Esplugues JV, Calatayud S, Mira Á, Ortiz-Masiá D, Barrachina MD, Cosín-Roger J. A disturbed metabolite-GPCR axis is associated with microbial dysbiosis in IBD patients: Potential role of GPR109A in macrophages. Biochim Biophys Acta Mol Basis Dis. 2024 Dec;1870(8):167489. doi: 10.1016/j.bbadis.2024.167489. Epub 2024 Sep 2. PMID: 39233260