Supplementation of Sulfur-Containing Amino Acids or Essential Amino Acids Does Not Reverse the Hepatic Lipid-Lowering Effect of a Protein-Rich Insect Meal in Obese Zucker Rats

The present study tested the hypothesis that the liver lipid-lowering effect of insect meal (IM) is caused by its low methionine concentration. A total of fifty, male obese Zucker rats were randomly assigned to five groups of 10 rats each (casein (C), IM, IM + Met, IM + Cys, and IM + EAA). While group C received a diet with casein, the IM-fed groups received a diet with IM as the protein source. In groups IM + Met, IM + Cys and IM + EAA, the diets were additionally supplemented with methionine, cysteine and essential amino acids (EAA), respectively. Hepatic concentrations of triacylglycerols and cholesterol, and hepatic mRNA levels and activities of lipogenic and cholesterogenic enzymes were markedly lower in the IM-fed groups than in group C (p < 0.05). All of these parameters either did not differ across the IM-fed groups or were only slightly higher in groups IM + Met, IM + Cys and IM+EAA than in the group IM. In conclusion, the results indicate that a difference in the amino acid composition between IM and casein, a low concentration of methionine in IM and a reduced cysteine synthesis secondary to a decreased methionine availability resulting from feeding IM are not causative for the lipid-lowering effect of IM.

Maternal betaine status, but not that of choline or methionine, is inversely associated with infant birth weight

Maternal one-carbon metabolism during pregnancy is crucial for fetal development and programming by DNA methylation. However, evidence on one-carbon biomarkers other than folate is lacking. We, therefore, investigated whether maternal plasma methyl donors, that is, choline, betaine and methionine, are associated with birth outcomes. Blood samples were obtained from 115 women during gestation (median 26·3 weeks, 90 % range 22·7–33·0 weeks). Plasma choline, betaine, methionine and dimethylglycine were measured using HPLC-tandem MS. Multivariate linear and logistic regression models were used to estimate the association between plasma biomarkers and birth weight, birth length, the risk of small-for-gestational-age and large-for-gestational-age (LGA). Higher level of maternal betaine was associated with lower birth weight (–130·3 (95 % CI –244·8, –15·9) per 1 sd increment for log-transformed betaine). Higher maternal methionine was associated with lower risk of LGA, and adjusted OR, with 95 % CI for 1 sd increase in methionine concentration was 0·44 (95 % CI 0·21, 0·89). Stratified analyses according to infant sex or maternal plasma homocysteine status showed that reduction in birth weight in relation to maternal betaine was only limited to male infants or to who had higher maternal homocysteine status (≥5·1 µmol/l). Higher maternal betaine status was associated with reduced birth weight. Maternal methionine was inversely associated with LGA risk. These findings are needed to be replicated in future larger studies.

Methionine concentration in the pre-starter diet: its effect on broiler breast muscle development

The effect of feeding diets of variable methionine concentration on breast muscle development was assessed in Ross 308 broiler chicks. Four isonitrogenous and isoenergetic starter diets were formulated to contain 7.8, 5.9, 4.6, and 3.4 g methionine/kg diet, and were provided for the first 7 days post-hatch. At 7 days of age all birds were placed on an industry standard starter diet with 5.9 g methionine/kg diet until 14 days, and then provided standard broiler grower (until 28 days) and finisher (until 42 days) diets. Birds were weighed periodically throughout the study and feed intake and feed conversion ratio were determined. Ten birds per treatment were sacrificed and weighed on 0, 1, 4, 7, 14, 21, 28, 35, and 42 days. The pectoralis major (breast muscle) was then removed from the carcass and weighed. Samples of breast muscle were collected for genetic and histological analysis. Expression of the myogenic marker genes, myogenic differentiation factor 1 and myogenin, which regulate satellite cell activity, and the adipogenic marker gene, peroxisome proliferator-activated receptor gamma (PPARγ), was measured. Histological assessment of breast muscle morphology and fat deposition morphology was also performed. No effect of dietary treatment was observed on body or breast muscle weight, feed intake or feed conversion ratio. Marker gene expression was also similar in all treatment groups, except for PPARγ. Significantly higher expression of PPARγ was observed at 0 days in the 5.9 g methionine/kg diet treatment, before dietary treatments were provided. Expression of PPARγ did not differ among treatment groups on any subsequent day. Methionine dietary treatment had no effect on the morphological structure of the breast muscle, or intramuscular fat deposition. These results suggest that under the conditions of this study, satellite cell activity in the early post-hatch chick, and subsequent muscle development, were not responsive to the variable methionine manipulations tested in the pre-starter period.