Undenatured type II collagen protects against collagen-induced arthritis by restoring gut-joint homeostasis and immunity

Oral administration of harmless antigens can induce suppression of reactive immune responses, a process that capitalises on the ability of the gastrointestinal tract to tolerate exposure to food and commensal microbiome without triggering inflammatory responses. Repeating exposure to type II collagen induces oral tolerance and inhibits induction of arthritis, a chronic inflammatory joint condition. Although some mechanisms underlying oral tolerance are described, how dysregulation of gut immune networks impacts on inflammation of distant tissues like the joints is unclear. We used undenatured type II collagen in a prophylactic regime -7.33 mg/kg three times/week- to describe the mechanisms associated with protective oral immune-therapy (OIT) in gut and joint during experimental Collagen-Induced Arthritis (CIA). OIT reduced disease incidence to 50%, with reduced expression of IL-17 and IL-22 in the joints of asymptomatic mice. Moreover, whilst the gut tissue of arthritic mice shows substantial damage and activation of tissue-specific immune networks, oral administration of undenatured type II collagen protects against gut pathology in all mice, symptomatic and asymptomatic, rewiring IL-17/IL-22 networks. Furthermore, gut fucosylation and microbiome composition were also modulated. These results corroborate the relevance of the gut-joint axis in arthritis, showing novel regulatory mechanisms linked to therapeutic OIT in joint disease

Possible Role of Intestinal Fatty Acid Oxidation in the Eating-Inhibitory Effect of the PPAR-alpha Agonist Wy-14643 in High-Fat Diet Fed Rats

PPAR-α plays a key role in lipid metabolism; it enhances fatty acid oxidation (FAO) and ketogenesis. Pharmacological PPAR-α activation improves insulin sensitivity and reduces food intake, but its mechanisms of action remain unknown. We here report that intraperitoneal (IP) administration of the PPAR-α agonist Wy-14643 (40 mg/kg BW) reduced food intake in adult male rats fed a high-fat diet (HFD, 49% of the energy) mainly through an increase in the latency to eat after injection, and without inducing a conditioned taste avoidance. Also, IP administered Wy-14643 caused an acute (the first 60 min) decrease in the respiratory quotient (RQ) and an increase in hepatic portal vein β-hydroxybutyrate level (at 35 min) without affecting plasma non-esterified fatty acids. Given the known stimulatory effect of PPAR-α on FAO and ketogenesis, we measured the protein expression level of carnitine palmitoyltransferase-1 (CPT 1A) and mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMG-CoAS2), two key enzymes for FAO and ketogenesis, respectively, in liver, duodenum and jejunum. Wy-14643 induced a significant increase in the expression of CPT 1A in the jejunum and duodenum and of HMG-CoAS2 in the jejunum, but neither CPT 1A nor HMG-CoAS2 expression was increased in the liver. The induction of CPT 1A and HMG-CoAS2 expression was associated with a decrease in the lipid droplet content selectively in the jejunum. Our findings indicate that Wy-14643 stimulates FAO and ketogenesis in the intestine, in particular in the jejunum, rather than in the liver, thus supporting the hypothesis that PPAR-α activation inhibits eating by stimulating intestinal FAO.ISSN:1932-620

The CCK(-like) receptor in the animal kingdom: functions, evolution and structures.

In this review, the cholecystokinin (CCK)(-like) receptors throughout the animal kingdom are compared on the level of physiological functions, evolutionary basis and molecular structure. In vertebrates, the CCK receptor is an important member of the G-protein coupled receptors as it is involved in the regulation of many physiological functions like satiety, gastrointestinal motility, gastric acid secretion, gall bladder contraction, pancreatic secretion, panic, anxiety and memory and learning processes. A homolog for this receptor is also found in nematodes and arthropods, called CK receptor and sulfakinin (SK) receptor, respectively. These receptors seem to have evolved from a common ancestor which is probably still closely related to the nematode CK receptor. The SK receptor is more closely related to the CCK receptor and seems to have similar functions. A molecular 3D-model for the CCK receptor type 1 has been built together with the docking of the natural ligands for the CCK and SK receptors in the CCK receptor type 1. These molecular models can help to study ligand-receptor interactions, that can in turn be useful in the development of new CCK(-like) receptor agonists and antagonists with beneficial health effects in humans or potential for pest control

Effect of intraperitoneally (IP) injected Wy-14643 on meal pattern.

<p>IP administered Wy-14643 (40 mg/kg/ml) on meal patterns in ad libitum HFD-fed rats (n = 23). Wy-14643 increased the latency of the first meal (<b>A</b>) and decreased the second meal size (<b>E</b>), but did not significantly affect first meal size and duration (<b>B</b>, <b>C</b>), intermeal interval (<b>D</b>) and second meal duration (<b>F</b>). Data for first meal size are presented as median with percentiles and were analyzed with Wilcoxon Signed Ranks Test. Results for the other parameters (latency to eat, first meal duration, second meal size and duration) are presented as means ± SEM and were analyzed using a paired <i>t</i>-test. ** Significant difference (<i>P</i> < 0.01) compared to vehicle.</p

Effect of intraperitoneally (IP) injected Wy-14643 on food intake.

<p>(<b>A</b>) IP injected Wy-14643 (10, 20, 40 or 80 mg/kg/ml) dose-dependently reduced cumulative food intake (FI) in ad libitum HFD-fed rats (n=23). * Less than vehicle (<i>P</i> < 0.05), ** less than vehicle (<i>P</i> < 0.01), Mann-Whitney U test. (<b>B</b>) IP administered Wy-14643 (40 mg/kg/ml, n=10) did not reduce saccharin solution intake (% of total fluid intake) vs. water in a two-bottle preference test, whereas LiCl (60 mg/kg in 9.4 ml/kg H₂O, n = 3) did. The height of each bar represents the median and the top and bottom of each bar shows 75th and 25th percentile respectively. * Significantly different from vehicle (<i>P</i> = 0.05).</p

Effect of intraperitoneal (IP) administration of Wy-14643 on the protein expression pattern.

<p>Carnitine palmitoyltransferase 1A (CPT 1A) (top), mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMG-CoAS2) (bottom) and β-actin in the liver (A), the duodenum (B) and the jejunum (C) were analyzed by Western blotting 1h after IP administration of Wy-14643 (40 mg/kg/ml). Panels below the graphs show representative blots; upper panels show quantification of protein levels after normalization to β-actin. Data are presented relative to the vehicle (100%) and each bar represent median with 25th/75th percentiles (* <i>P</i><0.05; Mann-Whitney U test).</p

Effect of intraperitoneal (IP) administration of Wy-14643 on energy homeostasis.

<p>Respiratory quotient (<b>A</b>), spontaneous locomotor activity (<b>B</b>), energy expenditure and body temperature (<b>C</b>, <b>D</b>) were assessed during 12 h following IP administration of Wy-14643 (40 mg/kg/ml). * and** significantly different from vehicle (*<i>P</i> < 0.05, **<i>P</i> < 0.01; Wilcoxon Signed Ranks Test, data presented as median with 25th/75th percentiles.</p

Effects of intraperitoneal (IP) administration of Wy-14643 on lipid droplets.

<p>The picture shows a representative photographic representation of lipid droplets (green) within the cytosol (pink) of the intestinal mucosa of the jejunum (<b>A</b>) of a rat treated with IP Wy-14643 (40 mg/kg/ml, right) or vehicle (1 ml/kg, DMSO: saline 70:30, left) (Color: blue = nuclei). Each bar represent median with 25th/75th percentiles of 19 rat of the number of lipid droplets (<b>B</b>) within the cytosol [cytosol expressed as area per pixel (px²)] and the area occupied by lipid droplets (<b>C</b>) of the liver and intestinal mucosa in percent. * Significantly different from vehicle (<i>P</i>< 0.05).</p

Effects of intraperitoneal (IP) administration of Wy-14643 on plasma metabolites.

<p>β-hydroxybutyrate (BHB) (<b>A</b>) and non-esterified fatty acids (NEFA) (<b>B</b>) levels were assessed 45 min before (baseline), 35 and 70 min after treatment (Wy-14643, 40 mg/kg/ml) and 3g HFD test meal. ** Significant difference compared to vehicle (<i>P</i> < 0.01; Wilcoxon Signed Ranks Test, data are presented as median with 25th/75th percentiles.</p