Abstract
Obesity is associated with changes in amino acid metabolism, and studies show that ingestion of fish proteins influence amino acid composition in plasma and urine, in addition to affecting risk factors for metabolic syndrome. Since the majority of fish proteins consumed by humans are as fish fillet, it is of interest to investigate if cod fillet intake affects amino acid composition and metabolic disorders. We hypothesized that a modified AIN-93G diet containing cod fillet would affect amino acid compositions in plasma and urine in obese rats, and also affect risk factors for metabolic syndrome when compared to rats fed a regular AIN-93G diet with casein as the protein source. Obese Zucker fa/fa rats, a rat model of metabolic syndrome, received diets containing 25% protein from lyophilized baked cod fillet and 75% protein from casein (Baked cod diet), or a Control diet with casein for four weeks. The Baked cod diet affected the amino acid composition in plasma, with e.g., lower glycine, histidine, homoarginine, homocysteine, methionine, proline and tyrosine concentrations, but did not affect amino acid concentrations in urine. The concentrations of markers for kidney and liver dysfunction were lower in the Baked cod group, however blood pressure development, fasting and postprandial glucose, and hepatic triacylglycerol concentrations were similar to the Control group. To conclude, substituting 25% of dietary protein with baked cod fillet affected concentrations of some amino acids in plasma and delayed development of kidney and liver dysfunction, but did not affect blood pressure, glucose concentration or fatty liver.
Highlights
The prevalence of obesity continues to rise globally, and this is of major concern since obesity is strongly associated with comorbidities such as hypertension, hypercholesterolemia, hyperlipidemia, fatty liver, type 2 diabetes, renal disease, and cardiovascular diseases [1,2,3,4]
The concentrations of 1methylhistidine, 3-methylhistidine, creatine and TMAO were higher in the Baked cod group compared to the Control group, but otherwise no differences were seen between the groups for concentrations of amino acids and related metabolites in urine (Table 5)
We have previously published that Baked cod group and the Control group were similar with regard to body weight-tosquare body length and weights of selected white adipose tissue depots, liver and thigh muscle relative to body weight at end point, and that the average daily energy intake was similar in the two groups [25]
Summary
The prevalence of obesity continues to rise globally, and this is of major concern since obesity is strongly associated with comorbidities such as hypertension, hypercholesterolemia, hyperlipidemia, fatty liver, type 2 diabetes, renal disease, and cardiovascular diseases [1,2,3,4]. The criteria for metabolic syndrome include abdominal adiposity, reduced high density lipoprotein (HDL) cholesterol, elevated blood pressure and elevated fasting blood glucose. Several factors such as atherogenic dyslipidemia (elevated low density lipoprotein (LDL) cholesterol, reduced HDL cholesterol), elevated liver fat, fasting insulin, glucose after oral glucose tolerance test, and chronic renal disease are listed as important targets for future research on metabolic syndrome [5]. Fish consumption has been associated with reduced risk of coronary heart disease and heart failure [6,7,8,9] and prevalence of type 2 diabetes and metabolic syndrome are low in populations with high fish intake [10,11,12,13]. More research is needed to identify metabolic effects of consumption of lean and fatty fish separately
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