Background & Aims: Expression of mucin MUC2, the structural component of the colonic mucus layer, is lowered in inflammatory bowel disease. Our aim was to obtain insight in the role of Muc2 in epithelial protection. Methods: Muc2 knockout (Muc2^−/−) and Muc2 heterozygous (Muc2^+/−) mice were characterized and challenged by a colitis-inducing agent, dextran sulfate sodium (DSS). We monitored clinical symptoms, intestinal morphology, and differences in intestine-specific protein and messenger RNA levels. Results: The Muc2^−/− mice showed clinical signs of colitis (as of 5 weeks), aggravating as the mice aged. Microscopic analysis of the colon of Muc2^−/− mice showed mucosal thickening, increased proliferation, and superficial erosions. Colonic goblet cells in the Muc2^−/− mice were negative for Muc2, but trefoil factor 3 was still detectable. In Muc2^−/− mice, transient de novo expression of Muc6 messenger RNA was observed in the distal colon. On day 2 of DSS treatment, the histologic damage was more severe in Muc2^+/− versus wild-type (Muc2^+/+) mice, but the disease activity index was not yet different. By day 7, the disease activity index and histologic score were significantly elevated in Muc2^+/− versus Muc2^+/+ mice. The disease activity index of the Muc2^−/− mice was higher (versus both Muc2^+/+ and Muc2^+/− mice) throughout DSS treatment. The histologic damage in the DSS-treated Muc2^−/− mice was different compared with Muc2^+/+ and Muc2^+/− mice, with many crypt abscesses instead of mucosal ulcerations. Conclusions: This study shows that Muc2 deficiency leads to inflammation of the colon and contributes to the onset and perpetuation of experimental colitis.

Objective: Peroxisome proliferator-activated receptor γ (PPAR γ) is the molecular target for thiazolidinediones (TZDs), a class of synthetic antidiabetic agents. However, the naturally occurring agonists of PPARs remain largely unknown. Punicic acid (PUA) is a conjugated linolenic acid isomer found in pomegrante. The objective of this study was to test the hypothesis that PUA activates PPAR γ and thereby ameliorates glucose homeostasis and obesity-related inflammation. Methods: The ability of PUA to modulate PPAR reporter activity was determined in 3T3-L1 pre-adipocytes. A cell-free assay was used to measure PUA's binding to the ligand-binding domain (LBD) of human PPAR γ. The preventive actions of PUA were investigated using genetically obese db/db mice and a model of diet-induced obesity in PPAR γ-expressing and tissue-specific PPAR γ null mice. Expression of PPAR α, γ, PPAR-responsive genes and TNF-α was measured in tissues controlling glucose homeostasis. Results: PUA caused a dose-dependent increase PPAR α and γ reporter activity in 3T3-L1 cells and bound although weakly to the LBD of human PPAR γ. Dietary PUA decreased fasting plasma glucose concentrations, improved the glucose-normalizing ability, suppressed NF-κB activation, TNF-α expression and upregulated PPAR α- and γ-responsive genes in skeletal muscle and adipose tissue. Loss of PPAR γ impaired the ability of dietary PUA to improve glucose homeostasis and suppress inflammation. Conclusions: Our studies demonstrate that PUA binds and robustly activates PPAR γ, increases PPAR γ-responsive gene expression and the loss of PPAR γ in immune cells impairs its ability to ameliorate diabetes and inflammation.

Rotavirus is the most important cause of infantile gastroenteritis. Since in vivo mucosal responses to a rotavirus infection thus far have not been extensively studied, we related viral replication in the murine small intestine to alterations in mucosal structure, epithelial cell homeostasis, cellular kinetics, and differentiation. Seven-day-old suckling BALB/c mice were inoculated with 2 × 10⁴focus-forming units of murine rotavirus and were compared to mock-infected controls. Diarrheal illness and viral shedding were recorded, and small intestinal tissue was evaluated for rotavirus (NSP4 and structural proteins)- and enterocyte-specific (lactase, SGLT1, and L-FABP) mRNA and protein expression. Morphology, apoptosis, proliferation, and migration were evaluated (immuno)histochemically. Diarrhea was observed from days 1 to 5 postinfection, and viral shedding was observed from days 1 to 10. Two peaks of rotavirus replication were observed at 1 and 4 days postinfection. Histological changes were characterized by the accumulation of vacuolated enterocytes. Strikingly, the number of vacuolated cells exceeded the number of cells in which viral replication was detectable. Apoptosis and proliferation were increased from days 1 to 7, resulting in villous atrophy. Epithelial cell turnover was significantly higher (<4 days) than that observed in controls (7 days). Since epithelial renewal occurred within 4 days, the second peak of viral replication was most likely caused by infection of newly synthesized cells. Expression of enterocyte-specific genes was downregulated in infected cells at mRNA and protein levels starting as early as 6 h after infection. In conclusion, we show for the first time that rotavirus infection induces apoptosis in vivo, an increase in epithelial cell turnover, and a shutoff of gene expression in enterocytes showing viral replication. The shutoff of enterocyte-specific gene expression, together with the loss of mature enterocytes through apoptosis and the replacement of these cells by less differentiated dividing cells, likely leads to a defective absorptive function of the intestinal epithelium, which contributes to rotavirus pathogenesis.

Long-term supplementation with conjugated linoleic acid (CLA) reduces body fat mass (BFM) and increases or maintains lean body mass (LBM). However, the regional effect of CLA was not studied. The study aimed to evaluate the effect of CLA per region and safety in healthy, overweight and obese adults. A total of 118 subjects (BMI: 28–32 kg/m²) were included in a double blind, placebo-controlled trial. Subjects were randomised into two groups supplemented with either 3·4 g/d CLA or placebo for 6 months. CLA significantly decreased BFM at month 3 (Δ = − 0·9 %, P = 0·016) and at month 6 (Δ = − 3·4 %, P = 0·043) compared with placebo. The reduction in fat mass was located mostly in the legs (Δ = − 0·8 kg, P < 0·001), and in women (Δ = − 1·3 kg, P = 0·046) with BMI >30 kg/m² (Δ = − 1·9 kg, P = 0·011), compared with placebo. The waist–hip ratio decreased significantly (P = 0·043) compared with placebo. LBM increased (Δ = +0·5 kg, P = 0·049) within the CLA group. Bone mineral content was not affected (P = 0·70). All changes were independent of diet and physical exercise. Safety parameters including blood lipids, inflammatory and diabetogenic markers remained within the normal range. Adverse events did not differ between the groups. It is concluded that supplementation with CLA in healthy, overweight and obese adults decreases BFM in specific regions and is well tolerated.