Substitution of high-dose sucrose with fructose in high-fat diets resulted in higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine and phenylalanine, and higher urine concentrations of arginine and citrulline.

High fructose intake has been shown to increase circulating alanine transaminase in humans, which could reflect damage to the liver by fructose but could also be linked to higher level of transamination of amino acids in liver. Therefore, we hypothesized that a diet with high content of fructose would affect the amino acid composition in rat plasma and urine differently from a diet with high sucrose content. Because high intake of sucrose and fructose is often accompanied with high intake of saturated fat in the Western-style diet, we wanted to compare the effects of high fructose/sucrose in diets with normal or high content of coconut oil on individual free amino acids plasma and urine. Male Wistar rats were fed diets with normal (10 wt%) or high (40 wt%) content of sucrose or fructose, with normal or high fat content (7 or 22 wt%) and 20 wt% protein (casein). Rats fed high-fructose high-fat diet had higher plasma concentrations of aspartic acid, cystine, glutamic acid, ornithine, and phenylalanine and higher urine concentrations of arginine and citrulline when compared to rats fed high-sucrose high-fat diet. Substituting normal content of sucrose with fructose in the diets had little impact on amino acids in plasma and urine. Serum concentrations of alanine transaminase, aspartate transaminase, and creatinine, and urine cystatin C and T cell immunoglobulin mucin-1 concentrations were comparable between the groups and within normal ranges. To conclude, substituting high-dose sucrose with high-dose fructose in high-fat diets affected amino acid compositions in plasma and urine.

Intake of farmed Atlantic salmon fed soybean oil increases hepatic levels of arachidonic acid-derived oxylipins and ceramides in mice.

Introduction of vegetable ingredients in fish feed has affected the fatty acid composition in farmed Atlantic salmon (Salmo salar L). Here we investigated how changes in fish feed affected the metabolism of mice fed diets containing fillets from such farmed salmon. We demonstrate that replacement of fish oil with rapeseed oil or soybean oil in fish feed had distinct spillover effects in mice fed western diets containing the salmon. A reduced ratio of n-3/n-6 polyunsaturated fatty acids in the fish feed, reflected in the salmon, and hence also in the mice diets, led to a selectively increased abundance of arachidonic acid in the phospholipid pool in the livers of the mice. This was accompanied by increased levels of hepatic ceramides and arachidonic acid-derived pro-inflammatory mediators and a reduced abundance of oxylipins derived from eicosapentaenoic acid and docosahexaenoic acid. These changes were associated with increased whole body insulin resistance and hepatic steatosis. Our data suggest that an increased ratio between n-6 and n-3-derived oxylipins may underlie the observed marked metabolic differences between mice fed the different types of farmed salmon. These findings underpin the need for carefully considering the type of oil used for feed production in relation to salmon farming.

A mixture of cod and scallop protein reduces adiposity and improves glucose tolerance in high-fat fed male C57BL/6J mice.

Low-protein and high-protein diets regulate energy metabolism in animals and humans. To evaluate whether different dietary protein sources modulate energy balance when ingested at average levels obesity-prone male C57BL/6J mice were pair-fed high-fat diets (67 energy percent fat, 18 energy percent sucrose and 15 energy percent protein) with either casein, chicken filet or a mixture of cod and scallop (1:1 on amino acid content) as protein sources. At equal energy intake, casein and cod/scallop fed mice had lower feed efficiency than chicken fed mice, which translated into reduced adipose tissue masses after seven weeks of feeding. Chicken fed mice had elevated hepatic triglyceride relative to casein and cod/scallop fed mice and elevated 4 h fasted plasma cholesterol concentrations compared to low-fat and casein fed mice. In casein fed mice the reduced adiposity was likely related to the observed three percent lower apparent fat digestibility compared to low-fat, chicken and cod/scallop fed mice. After six weeks of feeding an oral glucose tolerance test revealed that despite their lean phenotype, casein fed mice had reduced glucose tolerance compared to low-fat, chicken and cod/scallop fed mice. In a separate set of mice, effects on metabolism were evaluated by indirect calorimetry before onset of diet-induced obesity. Spontaneous locomotor activity decreased in casein and chicken fed mice when shifting from low-fat to high-fat diets, but cod/scallop feeding tended (P = 0.06) to attenuate this decrease. Moreover, at this shift, energy expenditure decreased in all groups, but was decreased to a greater extent in casein fed than in cod/scallop fed mice, indicating that protein sources regulated energy expenditure differently. In conclusion, protein from different sources modulates energy balance in C57BL/6J mice when given at normal levels. Ingestion of a cod/scallop-mixture prevented diet-induced obesity compared to intake of chicken filet and preserved glucose tolerance compared to casein intake.