Effects of baked and raw salmon fillet on lipids and n-3 PUFAs in serum and tissues in Zucker fa/fa rats​​​​​​​​​​​​​​​​​​​​

Figures & data

Table 1. Composition of diets.​​​​​

g/kg	Baked salmon diet	Raw salmon diet	Control diet
Casein^a	162.2	162.2	216.2
Freeze–dried baked salmon fillet^b	100.0
Freeze–dried raw salmon fillet^b		100.0
Soya oil	70.0	70.0	70.0
Sucrose	90.0	90.0	90.0
Cornstarch	466.0	466.0	512.0
Cellulose	50.0	50.0	50.0
Mineral mix (AIN-93-MX)	35.0	35.0	35.0
Vitamin mix (AIN-93-VX)	10.0	10.0	10.0
L-cysteine	3.0	3.0	3.0
L-methionine	1.6	1.6	1.6
Choline bitartrate^c	2.5	2.5	2.5
Tert-butylhydroquinone	0.014	0.014	0.014
Growth and maintenance supplement^d	10.0	10.0	10.0

^aContains 92.5% crude protein.

^bContains 50% crude protein.

^cContains 41.1 % choline.

^dContains 2.5 g vitamin B₁₂, 2.5 g vitamin K₁ and 995 g sucrose per kg.

Table 2. Contents of indispensable amino acids, the functional amino acid glycine, the conditionally essential amino acid arginine, taurine, ratios of lysine/arginine and methionine/glycine and fatty acids* in the diets (g/kg diet).

g/kg diet	Baked salmon diet	Raw salmon diet	Control diet
Amino acids
Arginine^†	7.9	7.5	6.4
Glycine	5.0	4.8	3.6
Histidine	5.6	5.3	5.1
Isoleucine	10.0	9.4	9.2
Leucine	17.0	17.0	16.0
Lysine	16.0	15.0	14.0
Methionine	7.6	7.1	6.4
Phenylalanine	9.7	9.1	9.1
Threonine	8.0	8.0	7.2
Valine	13.0	12.0	12.0
Taurine	0.1	0.1	ND
Lys/Arg ratio	2.0	2.0	2.2
Met/Gly ratio	1.5	1.5	1.8
Fatty acids
16:0	9.6	9.6	7.5
18:0	3.0	3.0	2.5
18:1 n-9	24.8	26.1	13.9
18:1 n-7	1.6	1.7	0.9
18:2 n-6	34.5	33.9	32.7
18:3 n-3	5.0	5.1	3.9
20:5 n-3	0.5	0.6	ND
22:5 n-3	0.2	0.2	ND
22:6 n-3	1.0	1.1	ND

ND, not detected.

*Only fatty acids found in levels > 0.1 g/kg diet are shown.

†Arginine can be synthesized by the rat, but not in sufficient amounts to meet the demands for normal growth.

Table 3. Body weight at baseline, growth and organ weights relative to body weight at time of euthanasia, energy intake and faecal output one week before euthanasia.

	Baked salmon diet		Raw salmon diet		Control diet		ANOVA
	Mean	SD	Mean	SD	Mean	SD	P
Body weight at baseline (g)	356	13	356	14	357	14	0.98
Body weight at endpoint (g)	541	23	553	27	570	21	0.17
Growth (%)	52	3	48	12	45	11	0.50
Body weight/square body length (without tail) ratio (kg/m^2)	10.1	0.3	9.9	0.4	10.0	0.5	0.78
Liver (g/kg body weight)	36.5	4.8	36.6	3.7	42.9	6.3	0.086
Skeletal muscle (g/kg body weight)	2.9	0.5	3.0	0.5	3.0	0.4	0.83
Epididymal white adipose tissue (g/kg body weight)	31.8	4.6	29.6	4.7	31.3	5.9	0.75
Energy intake (kJ/kg body weight)	1056	142	1194	121	1200	119	0.14
Faecal output (g dry faeces/kg body weight)	3.9	2.0	5.0	1.8	5.9	0.9	0.19

Values are mean and standard deviations, n = 5 in control group, n = 6 in baked salmon group and n = 6 in raw salmon group.

No significant differences were found between groups (p < 0.05; evaluated by one-way ANOVA).

Table 4. Concentrations of serum lipids, bile acids, vitamin D, MG-BSA and CML-BSA.

	Baked salmon diet		Raw salmon diet		Control diet		ANOVA	Post hoc test
	Mean	SD	Mean	SD	Mean	SD	P	P*	P‡	P†
Total cholesterol (mmol/l)	4.9	0.8	5.4	0.8	6.3	0.6	0.022	0.53	0.018	0.13
HDL cholesterol (mmol/l)	2.7	0.2	3.3	1.3	5.3	0.3	0.00039	0.50	0.00039	0.003
LDL cholesterol (mmol/l)	0.9	0.3	1.1	0.4	1.5	0.3	0.0080	0.50	0.0067	0.055
Cholesteryl esters (mmol/l)	3.7	0.5	4.3	1.0	4.9	0.5	0.051
TAG (mmol/l)	4.4	1.5	3.9	0.8	2.3	0.5	0.016	0.68	0.015	0.067
NEFA (mmol/l)	0.8	0.1	0.9	0.1	0.9	0.1	0.60
Bile acids (µmol/l)	15.7	7.0	25.5	17.2	46.0	20.9	0.021	0.54	0.018	0.12
Vitamin D (ng/ml)	28.3	5.3	26.2	7.2	27.4	6.7	0.86
MG-BSA^1 (µg/ml)	4.9	0.6	5.0	0.7	4.4	1.3	0.56
CML-BSA^2 (µg/ml)	2.5	0.7	2.5	0.4	2.7	0.8	0.89

Values are mean and standard deviations, n = 5 in control group, n = 6 in baked salmon group and n = 6 in raw salmon group.

¹Methylglyoxal​​​​​

²Carboxymethyl-lysine

* Baked salmon vs raw salmon.

‡ Baked salmon vs control.

† Raw salmon vs control.

(p < 0.05 were considered significant; evaluated by one-way ANOVA and Tukey HSD post-hoc test).​​​​​

Table 5. Concentrations of lipids in liver and skeletal muscle (thigh), and lipids and bile acids in 24 h faecal output.

	Baked salmon diet		Raw salmon diet		Control diet		ANOVA
	Mean	SD	Mean	SD	Mean	SD	P
Liver
Cholesterol (µmol/g)	7.1	2.3	8.1	1.1	9.3	2.1	0.20
TAG (µmol/g)	125.3	30.3	117.7	39.2	147.1	43.2	0.44
Skeletal muscle
Cholesterol (µmol/g)	1.6	0.1	1.7	0.2	1.6	0.2	0.78
TAG (µmol/g)	17.4	4.5	26.4	15.2	15.7	5.3	0.19
Faeces
Cholesterol(µmol/24 h)	21.0	4.2	23.0	6.8	18.0	5.6	0.37
TAG (µmol/24 h)	2.6	1.3	3.3	2.5	2.3	0.8	0.61
Bile acids (µmol/24 h)	9.1	1.9	10.5	2.3	11.8	2.7	0.20

Values are mean and standard deviations, n = 5 in control group, n = 6 in baked salmon group, and n = 6 in raw salmon group.

No significant differences were found between groups (p < 0.05; evaluated by one-way ANOVA).

Figure 1. Representative images from liver sections showing steatosis in the groups fed with baked salmon diet (A) and raw salmon diet (B) compared to steatosis in the control group (C) (stain hematoxylin-eosin, scale bars 100 micrometer). Insets in the upper right corner display marked-up images for image analysis. The graph shows percentage fat content calculated by image analysis for individual rats.

Table 6. n-3 and n-6 PUFAs in serum, liver, skeletal muscle and epididymal white adipose tissue.

	Baked salmon diet		Raw salmon diet		Control diet		ANOVA	Post-hoc test
g/100 g fatty acids	Mean	SD	Mean	SD	Mean	SD	P	P*	P‡	P†
Serum
18:3 n-3 (ALA)	0.71	0.17	0.81	0.22	0.36	0.05	0.0021	0.54	0.015	0.0020
20:5 n-3 (EPA)	1.40	0.14	1.35	0.22	0.39	0.10	8.6x10^−8	0.86	2.1x10^−7	3.8x10^−7
22:5 n-3 (DPA)	1.19	0.21	1.19	0.28	0.62	0.07	0.00090	1.00	0.0018	0.0020
22:6 n-3 (DHA)	4.55	0.50	4.80	0.57	2.73	0.13	5.3x10^−6	0.61	3.4x10^−5	8.0x10^−6
n-3 PUFA	7.86	0.84	8.18	1.22	4.11	0.13	4.0x10^−6	0.81	1.8x10^−5	7.3x10^−6
18:2 n-6	12.2	0.96	13.4	1.30	10.6	0.32	0.0012	0.13	0.039	0.00087
18:3n-6	0.33	0.04	0.27	0.03	0.32	0.05	0.048	0.047	0.82	0.17
20:3n-6	1.20	0.12	1.12	0.12	0.76	0.12	9.7x10^−5	0.59	0.0010	0.0061
20:4n-6	19.9	3.26	21.1	4.17	31.1	1.84	1.2x10^−5	0.80	0.00019	0.00056
22:4n-6	0.37	0.09	0.33	0.07	0.52	0.02	0.0016	0.60	0.010	0.0016
22:5n-6	0.16	0.04	0.15	0.03	0.51	0.04	9.4x10^−8	0.96	3.5x10^−7	2.6x10^−7
n-6 PUFA	34.2	3.3	36.4	3.4	43.8	2.3	0.00039	0.45	3.7x10^−5	0.0035
n-3/n-6 PUFA ratio	0.23	0.03	0.23	0.05	0.09	0.01	2.1x10^−5	0.98	4.9 x10^−5	6.5x10^−5
Liver
18:3 n-3 (ALA)	0.76	0.20	0.80	0.17	0.35	0.03	0.00062	0.90	0.0021	0.00093
20:5 n-3 (EPA)	0.33	0.14	0.34	0.10	0.05	0.01	0.00066	0.99	0.0016	0.0013
22:5 n-3 (DPA)	0.49	0.18	0.52	0.14	0.18	0.02	0.0019	0.91	0.0057	0.0027
22:6 n-3 (DHA)	2.25	0.74	2.38	0.79	0.94	0.24	0.0056	0.94	0.014	0.0076
n-3 PUFA	3.83	1.09	4.04	1.07	1.52	0.26	0.00090	0.92	0.0028	0.0014
18:2 n-6	9.24	0.99	9.65	1.31	7.08	0.63	0.0026	0.78	0.011	0.0030
18:3 n-6	0.20	0.02	0.17	0.02	0.19	0.02	0.16
20:3 n-6	0.41	0.11	0.42	0.17	0.17	0.05	0.0077	1.00	0.015	0.013
20:4 n-6	3.84	1.62	3.86	1.54	3.20	0.83	0.69
22:4 n-6	0.12	0.03	0.12	0.04	0.12	0.03	1.00
22:5 n-6	0.06	0.02	0.06	0.03	0.15	0.06	0.0021	1.00	0.0042	0.0042
n-6 PUFA	13.9	1.8	14.3	2.5	10.9	1.0	0.026	0.93	0.058	0.030
n-3/n-6 PUFA ratio	0.27	0.05	0.28	0.03	0.14	0.01	9.9x10^−6	0.91	3.7x10^−5	2.0x10^−5
Skeletal muscle
18:3 n-3 (ALA)	0.92	0.15	1.04	0.24	0.71	0.15	0.028	0.50	0.17	0.023
20:5 n-3 (EPA)	0.28	0.06	0.25	0.06	0.12	0.02	0.00022	0.62	2.5x10^−5	0.0013
22:5 n-3 (DPA)	1.80	0.31	1.64	0.58	1.86	0.33	0.69
22:6 n-3 (DHA)	6.16	1.24	5.61	2.26	4.30	0.96	0.19
n-3 PUFA	9.17	1.48	8.55	2.69	6.98	1.17	0.20
18:2 n-6	16.1	1.3	15.4	1.8	16.3	1.9	0.60
20:3 n-6	0.62	0.13	0.53	0.13	0.55	0.10	0.43
20:4 n-6	5.18	0.82	4.20	1.38	7.33	1.49	0.0033	0.39	0.032	0.0027
22:4 n-6	0.34	0.03	0.28	0.07	0.68	0.12	1.7x10^−6	0.47	1.3x10^−5	2.4x10^−6
22:5 n-6	0.29	0.05	0.24	0.08	0.73	0.15	1.3x10^−6	0.66	7.4x10^−6	2.2x10^−6
n-6 PUFA	22.6	2.0	20.7	3.3	25.7	3.6	0.047	0.53	0.24	0.038
n-3/n-6 PUFA ratio	0.40	0.03	0.41	0.07	0.27	0.01	0.00025	1.00	0.00061	0.00056
Adipose tissue
18:3 n-3 (ALA)	1.75	0.09	1.99	0.16	1.50	0.11	5.1x10^−5	0.012	0.012	3.4x10^−5
20:5 n-3 (EPA)	0.13	0.01	0.15	0.02	0.03	0.003	2.0x10^−8	0.20	2.1x10^−7	3.5x10^−8
22:5 n-3 (DPA)	0.28	0.02	0.32	0.03	0.13	0.01	5.5x10^−9	0.027	1.2x10^−7	1.2x10^−8
22:6 n-3 (DHA)	0.46	0.04	0.51	0.06	0.12	0.01	5.0x10^−10	0.062	1.2x10^−8	6.7x10^−9
n-3 PUFA	2.68	0.15	3.05	0.21	1.81	0.13	3.4x10^−8	0.0058	2.0x10^−6	3.2x10^−8
18:2 n-6	15.9	0.7	17.7	1.6	15.9	1.1	0.030	0.048	1.00	0.058
20:3 n-6	0.20	0.02	0.21	0.02	0.16	0.007	0.00082	0.77	0.0035	0.0010
20:4 n-6	0.38	0.05	0.39	0.04	0.43	0.01	0.083	0.89	0.084	0.18
22:4 n-6	0.11	0.02	0.11	0.02	0.15	0.01	0.0019	1.00	0.0036	0.0039
n-6 PUFA	16.7	0.7	18.5	1.6	16.7	1.1	0.036	0.052	1.00	0.072
n-3/n-6 PUFA ratio	0.16	0.006	0.17	0.01	0.11	0.002	2.4x10^−9	0.51	2.1x10^−8	1.1x10^−8

Values are mean and standard deviations, n = 5 in control group, n = 6 in baked salmon group, and n = 6 in raw salmon group.

* Baked salmon vs raw salmon.

‡ Baked salmon vs control.

† Raw salmon vs control.

(p < 0.05 were considered significant; evaluated by one-way ANOVA and Tukey HSD post-hoc test).