Gut metabolic changes during pregnancy reveal the importance of gastrointestinal region in sample collection.

INTRODUCTION: Studies of gastrointestinal physiology and the gut microbiome often consider the influence of intestinal region on experimental endpoints. However, this same consideration is not often applied to the gut metabolome. Understanding the contribution of gut regionality may be critically important to the rapidly changing metabolic environments, such as during pregnancy. OBJECTIVES: We sought to characterize the difference in the gut metabolome in pregnant mice stratified by region-comparing the small intestine, cecum, and feces. Pre-pregnancy feces were collected to understand the influence of pregnancy on the fecal metabolome. METHODS: Feces were collected from CD-1 female mice before breeding. On gestation day (GD) 18, gut contents were collected from the small intestine, cecum, and descending colon. Metabolites were analyzed with LC-MS/MS using the Biocrates MetaboINDICATOR™ MxP® Quant 500 kit. RESULTS: Of the 104 small molecule metabolites meeting analysis criteria, we found that 84 (81%) were differentially abundant based on gut region. The most significant regional comparison observed was between the cecum and small intestines, with 52 (50%) differentially abundant metabolites. Pregnancy itself altered 41 (39.4%) fecal small molecule metabolites. CONCLUSIONS: The regional variation observed in the gut metabolome are likely due to the microbial and physiological differences between the different parts of the intestines. Additionally, pregnancy impacts the fecal metabolome, which may be due to evolving needs of both the dam and fetus.

Prenatal ozone exposure programs a sexually dimorphic susceptibility to high-fat diet in adolescent Long Evans rats.

Altered fetal growth, which can occur due to environmental stressors during pregnancy, may program a susceptibility to metabolic disease. Gestational exposure to the air pollutant ozone is associated with fetal growth restriction in humans and rodents. However, the impact of this early life ozone exposure on offspring metabolic risk has not yet been investigated. In this study, fetal growth restriction was induced by maternal inhalation of 0.8 ppm ozone on gestation days 5 and 6 (4 hr/day) in Long Evans rats. To uncover any metabolic inflexibility, or an impaired ability to respond to a high-fat diet (HFD), a subset of peri-adolescent male and female offspring from filtered air or ozone exposed dams were fed HFD (45% kcal from fat) for 3 days. By 6 weeks of age, male and female offspring from ozone-exposed dams were heavier than offspring from air controls. Furthermore, offspring from ozone-exposed dams had greater daily caloric consumption and reduced metabolic rate when fed HFD. In addition to energy imbalance, HFD-fed male offspring from ozone-exposed dams had dyslipidemia and increased adiposity, which was not evident in females. HFD consumption in males resulted in the activation of the protective 5'AMP-activated protein kinase (AMPKα) and sirtuin 1 (SIRT1) pathways in the liver, regardless of maternal exposure. Unlike males, ozone-exposed female offspring failed to activate these pathways, retaining hepatic triglycerides following HFD consumption that resulted in increased inflammatory gene expression and reduced insulin signaling genes. Taken together, maternal ozone exposure in early pregnancy programs impaired metabolic flexibility in offspring, which may increase susceptibility to obesity in males and hepatic dysfunction in females.

Episodic ozone exposure in Long-Evans rats has limited effects on cauda sperm motility and non-coding RNA populations.

Epidemiological evidence suggests the potential for air pollutants to induce male reproductive toxicity. In experimental studies, exposure to ozone during sensitive windows in the sperm lifecycle has been associated with impaired sperm motility. Subsequently, we sought to investigate the effects of episodic exposure to ozone during sperm maturation in the rat. Long-Evans rats were exposed to either filtered air or ozone (0.4 or 0.8 ppm) for five non-consecutive days over two weeks. Ozone exposure did not impact male reproductive organ weights or sperm motility ∼24 hours following the final exposure. Furthermore, circulating sex hormones remained unchanged despite increased T3 and T4 in the 0.8 ppm group. While there was indication of altered adrenergic signaling attributable to ozone exposure in the testis, there were minimal impacts on small non-coding RNAs detected in cauda sperm. Only two piwi-interacting RNAs (piRNAs) were altered in the mature sperm of ozone-exposed rats (piR-rno-346434 and piR-rno-227431). Data across all rats were next analyzed to identify any non-coding RNAs that may be correlated with reduced sperm motility. A total of 7 microRNAs (miRNAs), 8 RNA fragments, and 1682 piRNAs correlated well with sperm motility. Utilizing our exposure paradigm herein, we were unable to substantiate the relationship between ozone exposure during maturation with sperm motility. However, these approaches served to identify a suite of non-coding RNAs that were associated with sperm motility in rats. With additional investigation, these RNAs may prove to have functional roles in the acquisition of motility or be unique biomarkers for male reproductive toxicity.