Alterations in the metabolomics of sulfur-containing substances in rat kidney by betaine

Ruminal Degradation of Taurine and Its Effects on Rumen Fermentation In Vitro

Taurine accounts for approximately 0.1% of an animal’s body. It cannot be used for protein synthesis but plays a wide range of important roles in the animal body. Taurine does not exist in plants, while mammals can only synthesize 30–40% of the taurine they need. Supplementing taurine to beef cattle may be necessary to improve their nutrient utilization and health status. However, no data are available regarding the metabolism of taurine in the rumen. Two in vitro trials were conducted to investigate the ruminal degradability of taurine and its effects on rumen fermentation. In Trial 1, Tilley and Terry’s in vitro rumen fermentation technique was used for incubation. As treatments, two levels of taurine, i.e., 0 and 10 mg, were added into plastic tubes containing 0.4000 g of feed mixture with a calibrated volume of 50 mL. Three adult cattle fitted with rumen cannulas were used as the donors for rumen fluid. The incubation was carried out at 39 °C for 48 h. The results showed that the taurine degradability increased with incubation time (p < 0.001) while its 2 h-degradability reached 99%. Taurine decreased the 48 h-dry matter degradability (DMD) (p = 0.008) and increased the 24 h- and 48 h-pH (p = 0.005; p = 0.018), respectively. In Trial 2, the Hohenheim gas test was used for incubation. Four levels of taurine, i.e., 0, 5, 10 and 20 mg, were added into glass syringes containing 0.2000 g feed mixture with a calibrated volume of 100 mL as treatments. The rumen fluid donors were the same as in Trial 1. The incubation was carried out at 39 °C for 48 h. The results showed that taurine increased the 48 h-pH (p < 0.001) linearly, decreased the cumulative gas production (p < 0.001) and the total volatile fatty acids (VFA) concentration (p = 0.014), and quadratically affected the ammonia–nitrogen (p < 0.001) and microbial crude protein (MCP) concentrations (p < 0.001). It was concluded that taurine was highly degradable in rumen fermentation. Taurine inhibits ruminal fermentation by decreasing DMD, VFA and gas production while improving MCP synthesis on a dose-dependent basis.

Alleviation of paraquat-induced oxidative lung injury by betaineviaregulation of sulfur-containing amino acid metabolism despite the lack of betaine-homocysteine methyltransferase (BHMT) in the lung

Betaine regulates sulfur-containing amino acid metabolism in the lung despite the lack of BHMT and increases pulmonary antioxidant capacity.

Metabolite and gene expression profiles suggest a putative mechanism through which high dietary carbohydrates reduce the content of hepatic betaine in Megalobrama amblycephala

BACKGROUND

High-carbohydrate diets (HCD) are favoured by the aquaculture industry for economic reasons, but they can produce negative impacts on growth and induce hepatic steatosis. We hypothesised that the mechanism behind this is the reduction of hepatic betaine content.

OBJECTIVE

We further explored this mechanism by supplementing betaine (1%) to the diet of a farmed fish Megalobrama amblycephala.

METHODS

Four diet groups were designed: control (CD, 27.11% carbohydrates), high-carbohydrate (HCD, 36.75% carbohydrates), long-term betaine (LBD, 35.64% carbohydrates) and short-term betaine diet (SBD; 12 weeks HCD + 4 weeks LBD). We analysed growth performance, body composition, liver condition, and expression of genes and profiles of metabolites associated with betaine metabolism.

RESULTS

HCD resulted in poorer growth and liver health (compared to CD), whereas LBD improved these parameters (compared to HCD). HCD induced the expression of genes associated with glucose, serine and cystathionine metabolisms, and (non-significantly, p = .20) a betaine-catabolizing enzyme betaine-homocysteine-methyltransferase; and decreased the content of betaine, methionine, S-adenosylhomocysteine and carnitine. Betaine supplementation (LBD) reversed these patterns, and elevated betaine-homocysteine-methyltransferase, S-adenosylmethionine and S-adenosylhomocysteine (all p ≤ .05).

CONCLUSION

We hypothesise that HCD reduced the content of hepatic betaine by enhancing the activity of metabolic pathways from glucose to homocysteine, reflected in increased glycolysis, serine metabolism, cystathionine metabolism and homocysteine remethylation. Long-term dietary betaine supplementation improved the negative impacts of HCD, inculding growth parameters, body composition, liver condition, and betaine metabolism. However, betaine supplementation may have caused a temporary disruption in the metabolic homeostasis.

Dehomocysteinylation is catalysed by the sirtuin-2-like bacterial lysine deacetylase CobB

Hyperhomocysteinemia, which is characterized by elevated blood levels of the non-protein amino acid homocysteine (Hcy), is an independent risk factor for many diseases, including cardiovascular diseases, neurodegenerative diseases and birth defects. The incorporation of homocysteine into proteins, known as protein N-homocysteinylation, has been considered a major mechanism that contributes to hyperhomocysteinemia. However, the process of dehomocysteinylation, the N-homocysteinylation substrates and the regulatory enzyme(s) remain largely unknown. In this study, we observed that the dehomocysteinylation reaction is a spontaneous process that can be inhibited by blocking -SH groups, which have been demonstrated to be critical for non-enzymatic dehomocysteinylation reactions. We also report that CobB, a known Sir2-like bacterial lysine deacetylase, catalyzes lysine dehomocysteinylation reactions both in vitro and in vivo. Our work provides insight into how this non-enzymatic modification might be removed from affected proteins, supplies potential targets for developing identification methods for N-homocysteine proteins, and identifies CobB as the first prokaryotic dehomocysteinylation enzyme.