Liver lipid alterations in rats fed arginine deficient diets

Gut Microbiome Critically Impacts PCB-induced Changes in Metabolic Fingerprints and the Hepatic Transcriptome in Mice

Polychlorinated biphenyls (PCBs) are ubiquitously detected and have been linked to metabolic diseases. Gut microbiome is recognized as a critical regulator of disease susceptibility; however, little is known how PCBs and gut microbiome interact to modulate hepatic xenobiotic and intermediary metabolism. We hypothesized the gut microbiome regulates PCB-mediated changes in the metabolic fingerprints and hepatic transcriptome. Ninety-day-old female conventional and germ-free mice were orally exposed to the Fox River Mixture (synthetic PCB mixture, 6 or 30 mg/kg) or corn oil (vehicle control, 10 ml/kg), once daily for 3 consecutive days. RNA-seq was conducted in liver, and endogenous metabolites were measured in liver and serum by LC-MS. Prototypical target genes of aryl hydrocarbon receptor, pregnane X receptor, and constitutive androstane receptor were more readily upregulated by PCBs in conventional conditions, indicating PCBs, to the hepatic transcriptome, act partly through the gut microbiome. In a gut microbiome-dependent manner, xenobiotic, and steroid metabolism pathways were upregulated, whereas response to misfolded proteins-related pathways was downregulated by PCBs. At the high PCB dose, NADP, and arginine appear to interact with drug-metabolizing enzymes (ie, Cyp1-3 family), which are highly correlated with Ruminiclostridium and Roseburia, providing a novel explanation of gut-liver interaction from PCB-exposure. Utilizing the Library of Integrated Network-based Cellular Signatures L1000 database, therapeutics targeting anti-inflammatory and endoplasmic reticulum stress pathways are predicted to be remedies that can mitigate PCB toxicity. Our findings demonstrate that habitation of the gut microbiota drives PCB-mediated hepatic responses. Our study adds knowledge of physiological response differences from PCB exposure and considerations for further investigations for gut microbiome-dependent therapeutics.

The orotic acid concentration in the blood, milk, and urine of dairy cows fed with urea supplemented diet

The experiment was performed on 4 cows Black and White, 550-650 kg of body weight, before and during 100 days after parturition. Two cows were fed with control and the next two with urea supplemented diet (urea-N constituting about 20% of total N in ration, 13% c.p. in DM). In cows fed with urea supplemented diet the considerable but unequal increase of urinary orotic acid excretion (particularly evident in first 30 days of lactation) was observed. There was however no influence of urea ration on the level of orotic acid in milk. The average orotic acid level in blood plasma (1.14 +/- 0.71 mumol X l-1 and 0.94 +/- 0.22 mumol X l-1 for control and urea fed cow respectively) established 0.01 and 0.001 of the average orotic acid concentration in urine and milk, respectively. Feeding with urea ration did not affect the level of orotic and UMP but increased the uridine concentration in blood plasma. During the parturition the lowest level of orotic acid in blood plasma, milk and urine was observed.

Effect of dietary factors on the responses of chicks to corticosterone injections

Corticosterone-injected chicks fed on a diet based on sorghum gained less weight and accumulated more hepatic fat than chicks treated similarly and fed on a diet based on maize. The retention of nitrogen and dry matter and the apparent metabolisable energy of these diets were not affected by type of grain, either in corticosterone-injected or in untreated birds. A slight methionine deficiency in the maize diet resulted in an additional increase in the concentration of hepatic lipids in corticosterone-injected chicks. However, hepatic lipid concentration was not affected by either a deficiency or an excess of methionine in the diet based on sorghum. The dietary fat concentration of isocaloric and isonitrogenous diets and the energy concentration of diets containing similar energy-to-protein ratios did not affect the response of the chicks to corticosterone. There was a negative correlation between the relative weight gain of corticosterone-treated chicks and the relative hepatic fat content. The latter was positively correlated with relative abdominal fat pad size.

Effects on liver and serum lipids of dietary supplements of methionine and excess lysine given to previously-starved rats

The addition of lysine hydrochloride (50 g/kg) to a diet supplemented with methionine (3 g/kg) had no effect on liver lipids when rats (Wistar and Sprague-Dawley) were fed ad lib. for 14 d. However, refeeding a diet supplemented with methionine and excess lysine hydrochloride to previously-starved rats (Wistar) for 6, 7 or 9 d, but not 3 or 4 d, resulted in liver lipid accumulation, mainly triglycerides, which was prevented by the addition of arginine, citrulline, ornithine, adenine, allopurinol or maize oil, but not by guanine, cytosine, thymine or uracil. The addition of lysine hydrochloride to a methionine-supplemented diet resulted in reduced serum triglyceride levels after refeeding for 3 or 4 d and reduced serum cholesterol levels after refeeding for 3, 4 or 6 d. Serum lipids were unaffected by refeeding the diets for 7 or 9 d. Since hepatic lipid accumulation was preceded by the decline in the level of serum triglycerides, one of the factors responsible for lipid accumulation in the liver might be reduced transport of triglycerides from the liver into the blood. When adenine and allopurinol were added to the diet supplemented with methionine and lysine hydrochloride refed for 4 d, there was an increase in serum triglycerides. However, when this diet was refed for 7 d, with the addition of arginine, citrulline, guanine, pyrimidine bases, allopurinol or maize oil, no effects on serum cholesterol and triglyceride levels were observed.

Alterations in liver nucleic acids and nucleotides in arginine deficient rats

Dietary arginine deficiency is associated with retarded growth and depressed feed intake. Nucleic acid biosynthesis as indicated by the incorporation of [6-14C]-orotic acid and [32P]-orthophosphate was significantly depressed in rats fed an arginine deficient diet. The activities of the pyrimidine enzymes, aspartate transcarbamylase (ATC) and dihydroorotate dehydrogenase (DHODH) were significantly increased in rats fed an arginine deficient diet. ATC and DHODH activities in rats fed the arginine deficient diet returned to control activities after 3 wk of feeding. Orotidine 5' phosphate decarboxylase and orotate phosphoribosyl transferase activities were not affected by dietary arginine availability. In the rat fed an arginine deficient diet there was an increase in total liver pyrimidine nucleotides and a decrease in the total purine nucleotides. Significant alterations in the individual liver nucleotides were also observed. Incubation of various tissues obtained from rats fed an arginine deficient diet or a complete diet with glutamine (5mM) revealed that the liver is the major site of orotic acid synthesis. Orotic acid production in liver slices using glutamine as the nitrogen source was significantly greater in rats fed an arginine deficient diet compared to controls. The orotic aciduria occurring in rats fed an arginine deficient diet is associated with increased synthesis and decreased utilization of pyrimidines.

High performance reversed phase chromatography of cholesterol and cholesteryl esters of human plasma lipoproteins

Cholesterol and cholesteryl esters were separated according to their carbon number and number of double bonds by high performance reversed-phase chromatography (HPRC) using acetonitrile/chloroform/methanol (1:1:1, v/v) as a mobile phase. It was found that within the same equivalent carbon number (ECN) category, cholesteryl esters with the highest number of double bonds eluted ahead of those with a lower number of double bonds, and with the cis isomers eluting ahead of their trans partners. Thus, cholesteryl oleate (C27-18:1c) elutes ahead of cholesteryl palmitate (C27-16:0) and ahead of cholesteryl elaidate (C27-18:1t). Human lipoprotein, as well as rat liver cholesteryl esters, were separated using this technique.

Fatty liver of growing rats fed excess lysine and its prevention by adenine or allopurinol

Weanling male Sprague-Dawley rats were fed ad libitum 15% casein diets with and without 5.0% lysine-HCI, 0.25% adenine sulfate or 0.1% allopurinol for 2 weeks. Addition of lysine alone depressed 2-week growth from 94 to 65 g increased average daily urinary orotic acid excretion from 0.39 to 1.77 mg and increased the percentage of total liver lipids from 3.6 to 11.2. Adenine or allopurinol did not change growth but markedly enhanced lysine-induced orotic aciduria and completely prevented lysine-induced fatty livers. Reports by other show that adenine and allopurinol also prevent fatty livers or rats fed arginine-free diets or excess orotic acid. The authors conclude that lysine-induced orotic aciduria results from arginine deficiency caused by antagonism of arginine function by lysine, and that lysine-induced fatty liver probably results from a lesion identical to that produced by feeding excess orotic acid.