Effects of Nonpurified and Choline Supplemented or Nonsupplemented Purified Diets on Hepatic Steatosis and Methionine Metabolism in C3H Mice

Hepatic oxylipin profiles in mouse models of Wilson disease: New insights into early hepatic manifestations

Hepatic inflammation is commonly identified in Wilson disease (WD), a genetic disease of hepatic and brain copper accumulation. Copper accumulation is associated with increased oxidative stress and reactive oxygen species generation which may result in non-enzymatic oxidation of membrane-bound polyunsaturated fatty acids (PUFA). PUFA can be oxidized enzymatically via lipoxygenases (LOX), cyclooxygenases (COX), and cytochrome P450 monooxygenases (CYP). Products of PUFA oxidation are collectively known as oxylipins (OXL) and are bioactive lipids that modulate hepatic inflammation. We examined hepatic OXL profiles at early stages of WD in two mouse models, the toxic milk mouse from The Jackson Laboratory (tx-j) and the Atp7b knockout on a C57Bl/6 background (Atp7b-/-B6). Targeted lipidomic analysis performed by ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry showed that in both tx-j and Atp7b-/-B6 mice, hepatic OXL profiles were altered with higher thromboxane and prostaglandins levels. The levels of oxidative stress marker, 9-HETE were increased more markedly in tx-j mice. However, both genotypes showed upregulated transcript levels of many genes related to oxidative stress and inflammation. Both genotypes showed higher prostaglandins, thromboxin along with higher PUFA-derived alcohols, diols, and ketones with altered epoxides; the expression of Alox5 was upregulated and many CYP-related genes were dysregulated. Pathway analyses show dysregulation in arachidonic acid and linoleic acid metabolism characterizes mice with WD. Our findings indicate alterations in hepatic PUFA metabolism in early-stage WD and suggest the upregulation of both, non-enzymatic ROS-dependent and enzymatic PUFA oxidation, which could have implications for hepatic manifestations in WD and represent potential targets for future therapies.

Addition of Soluble Fiber in Low-Fat Purified Diets Maintains Cecal and Colonic Morphology, Modulates Bacterial Populations and Predicted Functions, and Improves Glucose Tolerance Compared with Traditional AIN Diets in Male Mice

Background

Purified diets (PDs) contain refined ingredients with one main nutrient, allowing for greater control relative to grain-based diets (GBDs), which contain unrefined grains and animal byproducts. Traditional PDs like the American Institute of Nutrition (AIN)-76A (76A) and AIN-93G (93G) can negatively impact metabolic and gut health when fed long term, in part due to lower total fiber, no soluble fiber, and higher sucrose content.

Objective

Two studies were conducted to determine how PDs with reduced sucrose and increased fiber (soluble and insoluble) influence metabolic and gut health in mice compared with traditional AIN PDs or GBDs.

Methods

In study 1, C57Bl/6N mice (n = 75) consumed a GBD [LabDiet 5002 (5002)], 76A, 93G, or 2 PDs with reduced sucrose and higher fiber for 88 d. Body composition and metabolic parameters were assessed. In study 2, C57Bl/6N mice (n = 54) consumed either 2 GBDs (LabDiet 5001 or 5002) or PDs with different types/levels of fiber for 14 d. Microbiome alterations and predicted functional metagenomic changes were measured.

Results

The PD with 75 g cellulose and 25 g inulin per 4084 kcals marginally influenced body weight and adiposity, but improved glucose tolerance relative to 93G (P = 0.0131) and 76A (P = 0.0014). Cecal and colonic weights were lower in mice fed cellulose-based PDs compared with those fed GBDs and soluble-fiber PDs. Soluble-fiber PDs reduced alpha diversity and showed similar beta diversity, which differed from cellulose-based PDs and GBDs. Certain genera associated with improved gut health such as Bifidobacteria and Akkermansia were significantly elevated by soluble-fiber PDs (P ≤ 0.01). Metabolic pathways related to carbohydrate and fatty acid metabolism were affected by PDs.

Conclusions

PDs formulated with lower sucrose and increased fiber content, particularly soluble fiber, blunted elevations in metabolic parameters and favorably impacted the microbiota and metagenome in C57BL/6N mice.

Sex-specific effects of neonatal oral sucrose treatment on growth and liver choline and glucocorticoid metabolism in adulthood

Hospitalized preterm infants experience painful medical procedures. Oral sucrose is the nonpharmacological standard of care for minor procedural pain relief. Infants are treated with numerous doses of sucrose, raising concerns about potential long-term effects. The objective of this study was to determine the long-term effects of neonatal oral sucrose treatment on growth and liver metabolism in a mouse model. Neonatal female and male mice were randomly assigned to one of two oral treatments (n = 7-10 mice/group/sex): sterile water or sucrose. Pups were treated 10 times/day for the first 6 days of life with 0.2 mg/g body wt of respective treatments (24% solution; 1-4 μL/dose) to mimic what is given to preterm infants. Mice were weaned at age 3 wk onto a control diet and fed until age 16 wk. Sucrose-treated female and male mice gained less weight during the treatment period and were smaller at weaning than water-treated mice (P ≤ 0.05); no effect of sucrose treatment on body weight was observed at adulthood. However, adult sucrose-treated female mice had smaller tibias and lower serum insulin-like growth factor-1 than adult water-treated female mice (P ≤ 0.05); these effects were not observed in males. Lower liver S-adenosylmethionine, phosphocholine, and glycerophosphocholine were observed in adult sucrose-treated compared with water-treated female and male mice (P ≤ 0.05). Sucrose-treated female, but not male, mice had lower liver free choline and higher liver betaine compared with water-treated female mice (P < 0.01). Our findings suggest that repeated neonatal sucrose treatment has long-term sex-specific effects on growth and liver methionine and choline metabolism.

Preclinical Models of Altered Early Life Nutrition and Development of Reproductive Disorders in Female Offspring

Early epidemiology studies in humans have and continue to offer valuable insight into the Developmental Origins of Health and Disease (DOHaD) hypothesis, which emphasises the importance of early-life nutritional and environmental changes on the increased risk of metabolic and reproductive disease in later life. Human studies are limited and constrained by a range of factors which do not apply to preclinical research. Animal models therefore offer a unique opportunity to fully investigate the mechanisms associated with developmental programming, helping to elucidate the developmental processes which influence reproductive diseases, and highlight potential biomarkers which can be translated back to the human condition. This review covers the use and limitations of a number of animal models frequently utilised in developmental programming investigations, with an emphasis on dietary manipulations which can lead to reproductive dysfunction in offspring.