Effect of dietary oils on peripheral neuropathy-related endpoints in dietary obese rats

Figures & data

Table 1 Effect of dietary oils on weight gain, diet consumption, nonfasting blood glucose, and serum-free fatty acid, triglyceride, cholesterol, and TBARS in DIO Sprague-Dawley rats

Determination	Control (9)	DIO (11)	DIO+olive oil (9)	DIO+safflower oil (9)	DIO+flaxseed oil (9)	DIO+evening primrose oil (8)	DIO+menhaden oil (9)
Start weight (g)	351±4	336±5	343±5	344±4	341±3	352±4	334±5
Weight at treatment (g)	465±11	530±8*	536±9*	533±10*	544±9*	536±8*	541±9*
End weight (g)	530±18	647±27*	682±21*	693±13*	706±14*	668±12*	645±14*
Diet consumed (g/kg body wt/day)	43±1	28±1*	29±1*	29±1*	30±1^Citation1	28±1*	29±1*
Blood glucose (mg/dL)	161±12	162±14	162±4	158±7	155±6	169±7	147±7
Free fatty acid (mmol/L)	0.23±0.06	0.48±0.09*	0.42±0.05*	0.55±0.12*	0.60±0.08*	0.53±0.13*	0.32±0.05
Triglyceride (mg/mL)	36±3	48±6	75±8*	48±7	60±8	56±3*	35±6
Cholesterol (mg/mL)	1.7±0.2	2.0±0.1	1.9±0.1	1.8±0.2	2.2±0.4	2.0±0.2	1.2±0.4
TBARS (mg/mL)	0.59±0.09	0.88±0.05*	0.69±0.06	0.69±0.06	0.78±0.06	0.47±0.15	0.57±0.11

Notes: Data are presented as the mean ± standard error of mean.

* p<0.05 compared to control. Parentheses indicate the number of experimental animals.

Abbreviations: TBARS, thiobarbituric acid substances; DIO, diet-induced obese; wt, weight.

Figure 1 Effect of dietary oils on motor and sensory nerve conduction velocity in DIO Sprague-Dawley rats.

Notes: Motor and sensory nerve conduction velocities were examined as described in the “Materials and methods” section. Data are presented as the mean±standard error of mean in m/s. The number of rats in each group was the same as shown in Table 1. *p<0.05 compared to control rats; ⁺p<0.05 compared to DIO rats.
Abbreviations: MNCV, motor nerve conduction velocity; SNCV, sensory nerve conduction velocity; DIO, diet-induced obese; OO, olive oil; SO, safflower oil; FO, flaxseed oil; EPO, evening primrose oil; MO, menhaden oil.

Figure 2 Effect of dietary oils on intraepidermal nerve fiber density and thermal nociception in DIO Sprague-Dawley rats.

Notes: Intraepidermal nerve fiber density and thermal nociception were examined as described in the “Materials and methods” section. Data are presented as the mean±standard error of mean for intraepidermal nerve fiber profiles per mm and thermal nociception in seconds. The number of rats in each group was the same as shown in Table 1. *p<0.05 compared to control rats; ⁺p<0.05 compared to DIO rats.
Abbreviations: IENF, intraepidermal nerve fiber density; DIO, diet-induced obese; OO, olive oil; SO, safflower oil; FO, flaxseed oil; EPO, evening primrose oil; MO, menhaden oil.

Figure 3 Effect of dietary oils on cornea nerve fiber length and cornea sensitivity in DIO Sprague-Dawley rats.

Notes: Innervation of the subepithelial layer of the cornea and corneal sensitivity were determined by using corneal confocal microscopy and Cochet–Bonnet filament esthesiometer, respectively, as described in the “Materials and methods” section. The number of rats in each group was the same as shown in Table 1. Data are presented as the mean±standard error of mean for innervation of the cornea in mm/mm² and for corneal sensitivity in centimeters. *p<0.05 compared to control rats; ⁺p<0.05 compared to DIO rats.
Abbreviations: DIO, diet-induced obese; OO, olive oil; SO, safflower oil; FO, flaxseed oil; EPO, evening primrose oil; MO, menhaden oil.

Figure 4 Effect of dietary oils on vascular relaxation by acetylcholine in epineurial arterioles of the sciatic nerve in DIO Sprague-Dawley rats.

Notes: Pressurized arterioles (40 mm Hg and ranging from 60 to 100 µm luminal diameters) were constricted with phenylephrine (30%–50%) and incremental doses of acetylcholine were added to the bathing solution while recording steady state vessel diameter. The number of rats in each group was the same as shown in Table 1. Data are presented as the mean of % relaxation±standard error of mean. *p<0.05 compared to control rats; ⁺p<0.05 compared to DIO rats.
Abbreviation: DIO, diet-induced obese.

Figure S1 Effect of dietary oils on glucose clearance in DIO Sprague-Dawley rats.

Notes: Rats were fed a standard or high-fat diet for 16 weeks. Afterward, 50% kcal derived from lard in the high-fat diet was replaced with olive oil, safflower oil, flaxseed oil, evening primrose oil, or menhaden oil. Rats were maintained on these diets as well as on standard and high-fat diets for an additional 32 weeks. Glucose utilization was determined as described in the “Materials and methods” section. Data are presented as the mean±standard error of mean in mg/dL. The area under the curve was significantly different (p<0.05) for high-fat-fed rats and high-fat-fed rats treated with olive oil, safflower oil, or menhaden oil versus control. The number of rats in each group was the same as shown in Table 1.
Abbreviation: DIO, diet-induced obese.

Table S1 Fatty acid % composition of diets

Diet	16:0	18:0	18:1	18:2	18:3 (n-6)	18:3 (n-3)	20:5	22:6
Control	21±3.0	7.3±1.2	30.4±4.0	31.7±5.1	2.8±0.6	<1	<1	<1
High fat	16.8±2.2	10.8±1.3	41.2±5.6	26.9±2.8	2.3±0.3	<1	<1	<1
Olive oil	14.9±2.4	5.4±0.7	49.7±6.3	21.3±3.0	2.0±0.1	<1	<1	<1
Safflower oil	12.3±0.7*	6.0±0.5	24.9±3.4	54.3±4.3*,+	<1*,+	<1	<1	<1
Flaxseed oil	11.1±1.0*,+	6.2±1.0	27.0±2.8	23.6±3.4	<1*,+	31.0±3.3*,+	<1	<1
Evening primrose oil	11.6±1.7*,+	6.0±0.7	20.7±2.4	52.5±4.0*,+	5.4±0.8	<1	<1	<1
Menhaden oil	18.7±0.9	7.1±0.6	22.6±2.6	16.0±0.9	<1*,+	2.0±0.1	9.5±1.0*,+	6.9±0.4*,+

Notes: Data are presented as the mean of three determinations ± standard error of mean.

* p<0.05 compared to control;

+ p<0.05 compared to high fat.

Table S2 Effect of dietary lipids on fatty acid % composition of serum measured by gas chromatography

Diet	16:0	18:0	18:1	18:2	18:3 (n-6)	18:3 (n-3)	20:4	20:5	22:6
Control (9)	23.1±1.7	17.2±1.2	10.2±0.5	13.8±0.7	0.6±0.5	0.4±0.1	18.9±2.0	0.7±0.2	3.1±0.5
High fat (11)	19.4±0.6	21.5±0.6	8.4±0.5	16.4±0.5	0.3±0.1	0.4±0.1	21.0±0.9	0.4±0.1	3.2±0.3
High fat+olive oil (8)	19.1±0.7*	20.9±0.6	11.1±0.6+	13.4±1.0	0.1±0.0	0.3±0.0	21.3±1.0	0.5±0.1	4.7±0.7
High fat+safflower oil (9)	18.3±0.5*	22.3±0.7	5.9±0.3*,+	17.7±0.8*	0.3±0.1	0.8±0.4	21.4±1.1	0.6±0.3	3.0±0.3
High fat+flaxseed oil (8)	19.3±0.5*	20.9±0.9	7.8±1.1	17.3±0.6	0.2±0.1	2.5±0.8*,+	15.5±0.1+	1.9±0.1+	4.9±0.4
High fat+evening primrose oil (7)	17.9±0.7*	22.1±1.2	5.1±0.3*,+	17.5±0.8	0.7±0.1+	0.6±0.3	22.3±1.2	0.5±0.1	3.0±0.6
High fat+menhaden oil (8)	22.5±0.7+	19.9±0.5	6.8±0.4	14.4±0.5	ND	0.4±0.1	11.9±0.4*,+	4.4±0.4*,+	7.6±0.6*,+

Notes: Data are presented as the mean±standard error of mean.

* p<0.05 compared to control;

+ p<0.05 compared to high fat. The number of animals in each group is shown in parenthesis.

Abbreviation: ND, not detected.

Table S3 Effect of dietary lipids on fatty acid % composition of liver measured by gas chromatography

Diet	16:0	18:0	18:1	18:2	18:3 (n-6)	18:3 (n-3)	20:4	20:5	22:6
Control (9)	17.1±4.3	15.4±1.9	12.7±2.0	11.9±0.5	0.3±0.1	0.2±0.1	21.6±2.3	0.2±0.1	6.8±0.3
High fat (10)	18.3±0.3	19.0±1.3	12.9±15.0	15.0±0.8	0.4±0.1	0.4±0.1	20.4±1.1	0.3±0.1	5.5±0.4
High fat+olive oil (9)	14.6±2.4	19.5±0.7	14.9±1.6	12.1±1.0	0.3±0.1	0.2±0.1	23.8±0.4	0.2±0.1	6.9±0.5
High fat+safflower oil (9)	15.3±0.7	18.7±0.5	8.9±0.4	19.0±1.3*,+	0.7±0.2	0.3±0.1	23.3±1.1	0.3±0.1	5.2±0.3
High fat+flaxseed oil (9)	17.8±0.3	16.2±2.0	11.1±0.8	15.0±0.4	0.3±0.1	4.3±0.6*,+	14.8±1.1*,+	3.5±0.6*,+	7.0±0.7
High fat+evening primrose oil (8)	15.8±0.7	20.3±0.7*	7.2±0.4	17.4±1.0*	0.7±0.1	0.5±0.2	26.0±0.7+	0.4±0.2	4.1±0.2*
High fat+menhaden oil (9)	18.7±0.9	17.4±0.6	8.4±0.6	13.6±0.3	0.3±0.2	0.5±0.1	14.3±0.8*,+	5.2±0.5*,+	13.0±0.4*,+

Notes: Data are presented as the mean±standard error of mean.

* p<0.05 compared to control;

+ p<0.05 compared to high fat. The number of animals in each group is shown in parenthesis.

Table S4 Fatty acid unsaturation indices of liver and serum measured by gas chromatography

Diet	Liver	Serum
Control	1.75±0.06	1.51±0.08
High fat	1.71±0.04	1.56±0.04
High fat+olive oil	1.87±0.03+	1.63±0.05
High fat+safflower oil	1.83±0.03	1.59±0.03
High fat+evening primrose oil	1.85±0.02	1.63±0.04
High fat+flaxseed oil	1.87±0.04+	1.62±0.04
High fat+menhaden oil	2.16±0.03*,+	1.65±0.05

Notes: Data are presented as the mean±standard error of mean.

* p<0.05 compared to control;

+ p<0.05 compared to high fat.

Table S5 Ratio of n-6 to n-3 fatty acids of liver and serum measured by gas chromatography

Diet	Liver	Serum
Control	4.39±0.27	7.02±0.71
High fat	5.07±0.23	8.35±0.74
High fat+olive oil	4.49±0.37	6.27±0.78
High fat+safflower oil	6.80±0.48*,+	9.49±1.15
High fat+evening primrose oil	8.09±0.45*,+	9.60±1.38
High fat+flaxseed oil	1.87±0.11*,+	3.40±0.38*,+
High fat+menhaden oil	1.39±0.10*,+	1.96±0.11*,+

Notes: Data are presented as the mean±standard error of mean.

* p<0.05 compared to control;

+ p<0.05 compared to high fat.

Cortez M Singleton JR Smith AG Glucose intolerance, metabolic syndrome, and neuropathy Handb Clin Neurol 2014 126 109 122 25410218

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