Cigarette smoking is a major risk factor for gastrointestinal disorders, such as peptic ulcer, Crohn’s disease (CD), and several cancers. The mechanisms proposed to explain the role of smoking in these disorders include mucosal damage, changes in gut irrigation, and impaired mucosal immune response. Paradoxically, cigarette smoking is a protective factor for the development and progression of ulcerative colitis (UC). UC and CD represent the two most important conditions of inflammatory bowel diseases, and share several clinical features. The opposite effects of smoking on these two conditions have been a topic of great interest in the last 30 years, and has not yet been clarified. In this review, we summarize the most important and well-understood effects of smoking in the gastrointestinal tract; and particularly, in intestinal inflammation, discussing available studies that have addressed the causes that would explain the opposite effects of smoking in CD and UC.

Objective: Infants born from overweight and obese mothers with glucose-controlled gestational diabetes (GDM) tend to be large-for-gestational age (LGA). It is hypothesized that this is due to an excessive rise in maternal triglyceride levels. Methods: Two-hundred and seventy nine singleton GDM pregnancies were divided into three groups according to prepregnancy BMI: normal weight (BMI 5 20-24.9; n 5 128), overweight (BMI 5 25-29.9; n 5 105), and obese (BMI 30; n 5 46). Individual z-scores (ZS) of maternal triglycerides and of newborn weight (NWZS) were calculated as deviations from published 50th percentiles. Mean z-scores (MZS) were the average of triglyceride ZSs. MZS of triglycerides, HbA1c and NWZS were compared. Variables are expressed as mean 6 SD. Results: In the three groups respectively: LGA (%) 5 10.1%, 19.0% and 30.4% (P 5 0.015). Birth weight (g) 5 3274.2 6 501.3, 3342.4 6 620.2 and 3366.36644.7 (R SPEARMAN 5 0.111, P 5 0.027). HbA1c (%) 5 5.2 6 0.39, 5.3 6 0.50 and 5.4 6 0.47 (P 5 NS). Triglyceride MZS 5 1.20 6 1.13, 1.52 6 1.37 and 1.62 6 1.42 (R SPEARMAN 5 0.116, P 5 0.024). Correlations between triglyceride MZS and NWZS were, respectively: r 5 0.12 (P 5 NS), r 5 0.42 (P <0.001), and r 5 0.47 (P < 0.001). Conclusions: In overweight and obese GDM mothers, maternal triglycerides are partially responsible for LGA infants despite good maternal glucose control during pregnancy.

Heme Oxygenase 1 (HMOX1) is an enzyme that catalyzes the reaction that degrades the heme group contained in several important proteins, such as hemoglobin, myoglobin, and cytochrome p450. The enzymatic reaction catalyzed by HMOX1 generates Fe2+, biliverdin and CO. It has been shown that HMOX1 activity and the by-product CO can downmodulate the damaging immune response in several models of intestinal inflammation as a result of pharmacological induction of HMOX1 expression and the administration of non-toxic amounts of CO. Inflammatory Bowel Diseases, which includes Crohn's Disease (CD) and Ulcerative Colitis (UC), are one of the most studied ailments associated to HMOX1 effects. However, microbiota imbalances and infections are also important factors influencing the occurrence of acute and chronic intestinal inflammation, where HMOX1 activity may play a major role. As part of this article we discuss the immune modulatory capacity of HMOX1 during IBD, as well during the infections and interactions with the microbiota that contribute to this inflammatory disease.