trimethyllysine and Body-Weight

We tested the hypothesis that transcription of novel organic cation transporters (OCTNs) is directly regulated by peroxisome proliferator-activated receptor (PPAR)-alpha. Therefore, wild-type mice and mice deficient in PPAR alpha (PPAR alpha-/-) were treated with the PPAR alpha agonist WY 14,643. Wild-type mice treated with WY 14,643 had a greater abundance of OCTN2 mRNA in their liver, muscle, kidney, and small intestine and a greater abundance of OCTN3 mRNA in kidney and small intestine than did untreated wild-type mice (P < 0.05). Moreover, wild-type mice treated with WY 14,643 had greater mRNA abundances of enzymes involved in hepatic carnitine synthesis (4-N-trimethylaminobutyraldehyde dehydrogenase, gamma-butyrobetaine dioxygenase) and increased carnitine concentrations in liver and muscle than did untreated wild-type mice (P < 0.05). Untreated PPAR alpha-/- mice had a lower abundance of OCTN2 mRNA in liver, kidney, and small intestine and lower carnitine concentrations in plasma, liver, and kidney than did untreated wild-type mice (P < 0.05). In PPAR alpha-/- mice, treatment with WY 14,643 did not influence mRNA abundance of OCTN2 and OCTN3 and carnitine concentrations in all tissues analyzed. The abundance of OCTN1 mRNA in all the tissues analyzed was not changed by treatment with WY 14,643 in wild-type or PPAR alpha-/- mice. In conclusion, this study shows that transcriptional upregulation of OCTN2 and OCTN3 in tissues and of enzymes involved in hepatic carnitine biosynthesis are mediated by PPAR alpha. It also shows that PPAR alpha mediates changes of whole-body carnitine homeostasis in mice by upregulation of carnitine transporters and enzymes involved in carnitine synthesis.

Topics: Animals; Betaine; Body Weight; Carnitine; Liver; Lysine; Male; Membrane Proteins; Mice; Mice, Knockout; Organ Size; Organ Specificity; Organic Cation Transport Proteins; PPAR alpha; RNA, Messenger; Solute Carrier Family 22 Member 5; Transcription, Genetic; Up-Regulation

Rates of carnitine biosynthesis in mammals depend on the availability of substrates and the activity of enzymes subserving the pathway. This study was undertaken to test the hypothesis that the availability of epsilon-N-trimethyllysine is rate-limiting for synthesis of carnitine in the growing rat and to evaluate diet as a source of this precursor for carnitine biosynthesis. Rats apparently absorbed greater than 90% of a tracer dose of [methyl-3H]epsilon-N-trimethyllysine, and approximately 30% of that was incorporated into tissues as [3H]carnitine. Rats given oral supplements of epsilon-N-trimethyllysine (0.5-20 mg/d), but no dietary carnitine, excreted more carnitine than control animals receiving no dietary epsilon-N-trimethyllysine or carnitine. Rates of carnitine excretion increased in a dose-dependent manner. Tissue and serum levels of carnitine also increased with dietary epsilon-N-trimethyllysine supplementation. There was no evidence that the capacity for carnitine biosynthesis was saturated even at the highest level of oral epsilon-N-trimethyllysine supplementation. Common dietary proteins (casein, soy protein and wheat gluten) were found to be poor sources of epsilon-N-trimethyllysine for carnitine biosynthesis. The results of this study indicate that the availability of epsilon-N-trimethyllysine limits the rate of carnitine biosynthesis in the growing rat.

Topics: Administration, Oral; Animals; Biological Availability; Body Weight; Carnitine; Injections, Intravenous; Lysine; Male; Mixed Function Oxygenases; Organ Size; Rats; Rats, Inbred Strains; Tissue Distribution; Tritium

Trimethyllysine residues in peptide linkage, precursors of carnitine biosynthesis, were measured in fed and 3-day fasted rats. Whole-body peptide-linked trimethyllysine in fasted rats was significantly less than in fed rats when expressed per initial body weight (17.8 vs 24.8 mumol/100 g initial body weight). Skeletal muscle had the highest peptide-linked trimethyllysine content (2.5 nmol/mg protein), followed by heart (1.9 nmol/mg protein). The content in kidney, liver and small intestine were similar, but less than in heart. Of the eight tissues tested, the brain had the only significant increase with fasting. The hepatic peptide-linked trimethyllysine in fasted rats was significantly decreased when expressed per milligram DNA. The study shows a commensurate loss of peptide-linked trimethyllysine accompanying protein loss during fasting. The study also shows that muscle contains over 65% of the whole-body peptide-linked trimethyllysine, and as such is a major reservoir of precursor for carnitine biosynthesis.

Topics: Animals; Body Weight; Brain; Carnitine; Lysine; Male; Muscles; Peptides; Rats; Rats, Inbred Strains; Starvation; Tissue Distribution

The effects of ascorbate deficiency on carnitine biosynthesis was investigated in young male guinea pigs. Liver and kidney carnitine levels were not affected by the deficiency, but scorbutic animals had 50% less carnitine in heart and skeletal muscle than control animals. Labeled carnitine precursors, 6-N-tri-methyl-L-lysine and 4-N-trimethylaminobutyrate, both of which require ascorbate for their enzymatic hydroxylation, were injected into the vena cava of control, pair-fed and scorbutic animals. The distribution of isotope in compounds present in the liver and kidney after 1 h was determined. The uptake of trimethyllysine by the liver was less than 2% in 1 h, while the kidney took up approx. 20% of the 14C. Control and pair-fed animals converted trimethyllysine to kidney trimethylaminobutyrate 8--10 times as well as did scorbutic animals. Trimethylaminobutyrate hydroxylase, present in the liver but almost absent from the kidney, converted nearly all of substrate taken up by the liver to carnitine in both the scorbutic and control animals.

Topics: Animals; Ascorbic Acid Deficiency; Body Weight; Carnitine; gamma-Aminobutyric Acid; Guinea Pigs; Kidney; Liver; Lysine; Male; Muscles; Myocardium; Organ Size

Growth assays using mice on synthetic amino acid diets showed that substituting epsilon-N-methyl-L-lysine, epsilon-N-dimethyl-L-lysine and epsilon-N-trimethyl-L-lysine for lysine resulted in relative replacement values about 1/12, 1/20 and 1/25, respectively, of that obtained with the standard lysine diet. Similar studies showed that the alpha-N-acetyl-L-lysine is not utilized by mice and that the relative the replacement value of epsilon-N-acetyl-L-lysine was about 3% of that of lysine. Analogous substitution of D-lysine and the lysine sulfur-containing analog, S-(2-aminoethyl)-L-cysteine, for lysine resulted in weight losses during the feeding period. The results are discussed with reference to factors that are expected to influence the biological utilization f lysine analogs and derivatives.

Topics: Animals; Biological Assay; Biological Availability; Body Weight; Cysteine; Dietary Proteins; Lysine; Mice; Structure-Activity Relationship