Effects ofdl-2-hydroxy-4-methylthiobutyrate on the first-pass intestinal metabolism of dietary methionine and its extra-intestinal availability

Abstract

The present study was conducted in a one-factorial arrangement to determine the effects of DL-2-hydroxy-4-methylthiobutyrate (DL-HMTB) on the first-pass intestinal metabolism of dietary methionine and its extra-intestinal availability. Barrows (n 6; aged 35 d; weight 8·6 kg), implanted with arterial, portal, mesenteric and gastric catheters, were fed a diet containing DL-methionine (DL-MET) or DL-HMTB once hourly and infused intramesenterically with 1 % p-aminohippurate and intragastrically with [1-13 C]methionine at 7·0 mmol/kg body weight per h. Arterial and portal blood samples were taken at hourly intervals until 6 h of tracer infusion and pigs was then killed for collection of muscle, intestine, liver and kidney samples. The net portal appearance of methionine, expressed as the fraction of ingested directly available L-methionine, was higher (P,0·05) in the DL-HMTB than in the DL-MET diet, and there was no difference (P¼ 0·26) in the fractional portal balance of [1-13 C]methionine between the diets. [1-13 C]methionine enrichment (tracer:tracee ratio; mol/100 mol amino acid) in the jejunum, arterial and portal plasma, liver, kidney and muscle was also not different (P.0·05) between the groups. Over the 6 h period after the start of feeding, the average concentration of citrulline both in the arterial and portal plasma was higher (P,0·05) in the DL-HMTB than in the DL-MET group, and arterial plasma ornithine and taurine concentration was also higher (P,0·05) in the DL-HMTB than in the DL-MET group. However, plasma urea concentration both in the arterial and portal vein was lower (P, 0·05) in the DL-HMTB than in the DL-MET group. These results suggested that the potential difference in the first-pass use of methionine by the intestine between the DL-HMTB and DL-MET diets might affect intestinal and systemic metabolism of other amino acids, which may provide new important insights into nutritional efficiency of different methionine sources.DL-2-Hydroxy-4-methylthiobutyrate: First-pass intestinal metabolism: Extra-intestinal availabilityThe small intestine is a highly differentiated and complex organ, which is not only responsible for the terminal digestion and absorption of nutrients, but also plays an important role in the synthesis, conversion and catabolism of amino acids (1) . Because the apical and basolateral membranes of each enterocyte are chemically, biochemically and physically distinct (2) , an enterocyte can selectively receive nutrients from two sources: the arterial blood across its basolateral membrane and the intestinal lumen across its brush-border membrane. Historically, it is assumed that the primary fate of essential amino acids is to protein synthesis in the target organs; however, intriguing data have demonstrated that catabolism dominates the first-pass utilisation of these amino acids by the gut (3) . Because the extensive catabolism of dietary essential amino acids by the small intestine results in a decrease in their nutritional efficiency (1,3,4) , the question whether the catabolism ...

Effects of Dietary Supplementation of β‐hydroxy‐β‐methylbutyrate on Sow Performance and mRNA Expression of Myogenic Markers in Skeletal Muscle of Neonatal Piglets

“…A total of 20 piglets were slaughtered by anesthetization and bleeding according to the method of Fang et al. (). After death, the abdomen was opened, and the entire intestine was rapidly removed.…”

“…After parturition, one male piglet approaching with average weight was selected from each litter. A total of 20 piglets were slaughtered by anesthetization and bleeding according to the method of Fang et al (2010). After death, the abdomen was opened, and the entire intestine was rapidly removed.…”

Gastrointestinal methionine shuttle: Priority handling of precious goods

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“…A crucial drawback in this scenario is the significant intracellular accumulation of the intermediate metabolite homocysteine, partly, because remethylation of excess homocysteine is strongly inhibited when intracellular Met levels are concurrently high . Thus excess homocysteine finally leaks into the portal and systemic circulation . In contrast to cysteine/cystine, homocysteine has a negative reputation as it contributes to neuronal, endothelial and other dysfunction with consequences for cardiovascular disease and stroke in humans .…”

Gastric digestion of protein through pancreozyme action optimizes intestinal forms for absorption, mucin formation and villus integrity

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