Urine and plasma concentrations of amino acids and plasma vitamin status differ, and are differently affected by salmon intake, in obese Zucker fa/fa rats with impaired kidney function and in Long-Evans rats with healthy kidneys

Abstract

Kidney function affects amino acid metabolism and vitamin status. The aims of the present study were to investigate urine and plasma concentrations of amino acids as well as plasma vitamin status in rats with impaired renal function (Zucker fa/fa rats) and in rats with normal kidney function (Long-Evans rats), and to explore the effects of salmon intake on these parameters and potential biomarkers of salmon intake in both rat strains. Male rats were fed diets with casein as sole protein source (control diet) or 25 % protein from baked salmon and 75 % casein for 4 weeks. Urine concentrations of markers of renal function and most amino acids and plasma concentrations of most vitamins were higher, and plasma concentrations of several amino acids including arginine, total glutathione and most tryptophan metabolites were lower in Zucker fa/fa rats compared with Long-Evans rats fed the control diet. Concentrations of kidney function markers were lower after salmon intake only in Zucker fa/fa rats. A trend towards lower urine concentrations of amino acids was seen in both rat strains fed the salmon diet, but this was more pronounced in Long-Evans rats and did not reflect the dietary amino acid content. Urine 1-methylhistidine, 3-methylhistidine, trimethylamineoxide and creatine concentrations, and plasma 1-methylhistidine and creatine concentrations were higher after salmon intake in both rat strains. To conclude, concentrations of amino acids in urine and plasma as well as vitamin status were different in Zucker fa/fa and Long-Evans rats, and the effects of salmon intake differed by rat strain for some of these parameters.

Effects of intact and hydrolysed blue whiting proteins on blood pressure and markers of kidney function in obese Zucker fa/fa rats

“…Also, no difference was seen between the groups for urine creatinine concentration. Urine concentrations (relative to creatinine) of total protein and cystatin C were abnormally high and comparable to concentrations previously seen in obese Zucker fa/fa rats with prominent hyperperfusion damage in podocytes [25,40], but concentrations were similar in all groups (Table 5). Urine carbamide and uric acid concentrations were also abnormally high; however, the carbamide concentration was lower in all blue whiting protein-fed groups compared to the control group and uric acid concentration was lower in the BW-HA-fed rats, but similar in BW-WM and BW-HP-fed rats when compared to controls.…”

“…Proteinuria develops in the obese Zucker fa/fa rat already at around age 10 weeks [45] and decreased renal function is seen in obese Zucker fa/fa rats at around 12 weeks age [46], thus elevated urine concentrations (relative to creatinine) of total protein, free proteinogenic amino acids, cystatin C, carbamide and uric acid could be expected. Indeed, when compared to previous findings in male obese Zucker fa/fa rats [20,25,40], the urine concentrations of total protein, free proteinogenic amino acids, cystatin C, carbamide, uric acid and ammonium were abnormally high in all experimental groups with no difference between control group and blue whiting protein-fed groups, thus indicating renal dysfunction in all groups. Amino acids filtered by the glomeruli will normally be reabsorbed by the tubules and are therefore not excreted in urine [47], and the presence of proteins and amino acids in urine is amongst the earliest sign of almost all renal diseases in both humans and animals [48][49][50].…”

Metabolic Status of Lean and Obese Zucker Rats Based on Untargeted and Targeted Metabolomics Analysis of Serum

“…Despite the existing published reports regarding metabolic status in Zucker rats [ 33 , 34 ], an untargeted metabolomics approach was never explored, in spite of its potential. Our data that averaged untargeted metabolomics analyses of serum from Zucker rats show that lean (L) and obese (O) rats have substantially different metabolic imprints for the 50 metabolites selected for analysis.…”