Our objectives in this study were as follows: 1) to determine the rate of creatine accretion by the neonatal piglet; 2) identify the sources of this creatine; 3) measure the activities of the enzymes of creatine synthesis; and 4) to estimate the burden that endogenous creatine synthesis places on the metabolism of the 3 amino acids required for this synthesis: glycine, arginine, and methionine. We found that piglets acquire 12.5 mmol of total creatine (creatine plus creatine phosphate) between 4 and 11 d of age. As much as one-quarter of creatine accretion in neonatal piglets may be provided by sow milk and three-quarters by de novo synthesis by piglets. This rate of creatine synthesis makes very large demands on arginine and methionine metabolism, although the magnitude of the demand depends on the rate of remethylation of homocysteine and of reamidination of ornithine. Of the 2 enzymes of creatine synthesis, we found high activity of l-arginine:glycine amidinotransferase in piglet kidneys and pancreas and of guanidinoacetate methyltransferase in piglet livers. Piglet livers also had appreciable activities of methionine adenosyltransferase, which synthesizes S-adenosylmethionine, and of betaine:homocysteine methyltransferase, methionine synthase, and methylene tetrahydrofolate reductase, which are required for the remethylation of homocysteine to methionine. Creatine synthesis is a quantitatively major metabolic process in piglets.

of cyclooxygenase isoform activity and prostanoid production in normal and diseased Han:SPRD-cy rat kidneys. Am J Physiol Renal Physiol 290: F897-F904, 2006. First published October 18, 2005 doi:10.1152/ajprenal.00332.2005.-Renal prostanoids are important regulators of normal renal function and maintenance of renal homeostasis. In diseased kidneys, renal cylooxygenase (COX) expression and prostanoid formation are altered. With the use of the Han:Sprague-Dawley-cy rat, the aim of this study was to determine the relative contribution of renal COX isoforms (protein, gene expression, and activity) on renal prostanoid production [thromboxane B 2 (TXB2, stable metabolite of TXA2), prostaglandin E2 (PGE2), and 6-keto-prostaglandin F1␣ (6-keto-PGF1␣, stable metabolite of PGI 2)] in normal and diseased kidneys. In diseased kidneys, COX-1-immunoreactive protein and mRNA levels were higher and COX-2 levels were lower compared with normal kidneys. In contrast, COX activities were higher in diseased compared with normal kidneys for both COX-1 [0.05 Ϯ 0.02 vs. 0.45 Ϯ 0.11 ng prostanoids ⅐ min Ϫ1 ⅐ mg protein Ϫ1 (P Ͻ 0.001)] and COX-2 [0.64 Ϯ 0.10 vs. 2.32 Ϯ 0.22 ng prostanoids ⅐ min Ϫ1 ⅐ mg protein Ϫ1 (P Ͻ 0.001)]. As the relative difference in activity was greater for COX-1, the ratio of COX-1/COX-2 was higher in diseased compared with normal kidneys, although the predominant activity was still due to the COX-2 isoform in both genotypes. Endogenous and steady-state in vitro levels of prostanoids were ϳ2-10 times higher in diseased compared with normal kidneys. The differences between normal and diseased kidney prostanoids were in the order of TXB 2 Ͼ 6-keto-PGF 1␣ Ͼ PGE2, as determined by higher renal prostanoid levels and COX activity ratios of TXB 2/6-keto-PGF1␣, TXB2/PGE2, and 6-keto-PGF 1␣/PGE2. This specificity in both the COX isoform type and for the prostanoids produced has implications for normal and diseased kidneys in treatments involving selective inhibition of COX isoforms. thromboxane; prostaglandin CYCLOOXYGENASE (COX

Conjugated linoleic acid (CLA) slows the progression of disease in models of chronic kidney disease. Because obesity is associated with nephropathy and increased renal cyclooxygenase (COX) levels, the effects of dietary CLA on kidney function, morphology, and COX protein levels in the kidneys of young obese (fa/fa) Zucker rats, a model of metabolic syndrome, were examined. In study 1, 6-wk-old fa/fa and lean Zucker rats were given a mixture of CLA isomers (1.5% CLA, wt:wt) or the control diet (CTL) with no CLA for 8 wk. To examine specific isomer effects, study 2 used the same model with the following diets: 0.4% (g/g) cis-9, trans-11 (c9,t11) CLA; 0.4% trans-10, cis-12 (t10,c12) CLA; a combination of these 2 isomers (0.4% each); or CTL diets with no CLA. In study 1, fa/fa rats given the CLA mixture had 11% smaller kidney weights and 28% smaller glomeruli, and feed intake and body weight did not differ from the CTL rats. In study 2, diet also did not affect body weights, but fa/fa rats given a diet containing t10,c12 CLA had 7% lower kidney weights, 20% smaller glomeruli, and 39% lower COX-2 protein levels than CTL rats. In conclusion, dietary t10,c12 CLA reduces the enlargement of glomeruli in young obesity-associated nephropathy and is associated with lower protein levels of renal COX-2. Long-term studies with CLA supplementation are required to determine whether these changes would lead to reduction in development of renal disease associated with obesity.

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