Partial replacement with menhaden oil improves peripheral neuropathy in high-fat-fed low-dose streptozotocin type 2 diabetic rat

Abstract

Aims. To determine the effect of partial replacement of a high-fat diet with menhaden oil on diabetic neuropathy in an animal model of type 2 diabetes. Materials and Methods. High-fat/low-dose streptozotocin diabetic rats were used to examine the influence of replacing 50% of the source of the high-fat diet (lard) with menhaden oil, a natural source of n-3 fatty acids, on diabetic neuropathy. Endpoints included analyses of glucose tolerance, fatty liver disease, serum and liver fatty acid composition, serum lipid and adiponectin levels, motor and sensory nerve conduction velocity, thermal sensitivity and innervation of the hindpaw. Results. Diabetic rats were insulin resistant and menhaden oil did not improve whole animal glucose utilization. Menhaden oil did not improve elevated HbA(1)C levels or serum lipid levels but serum levels of adiponectin were significantly increased and hepatic steatosis was significantly improved. Diabetic rats were thermal hypoalgesic, had reduced motor and sensory nerve conduction velocities and intraepidermal nerve fiber profiles were decreased in the hindpaw and these endpoints were significantly improved with menhaden oil. Conclusions. We found that enrichment of a high-fat diet with menhaden oil improved a number of endpoints associated with diabetic neuropathy.

Figure 1

Effect of treatment of high-fat/streptozotocin diabetic rats with menhaden-oil- (MO-) supplemented diet on fatty liver disease. Fat accumulation by the liver was determined using oil red staining. Representative images are provided and data are presented as the mean ± S.E.M in % of total area. The number of rats in each group was the same as shown in Table 2. *P < 0.05 compared to control rats; ⁺ P < 0.05 compared to diabetic rats.

Figure 2

Effect of treatment of high-fat/streptozotocin diabetic rats with menhaden-oil- (MO-) supplemented diet on glucose tolerance. Glucose tolerance was determined as described in Section 2. Data are presented as the mean ± S.E.M. in mg/dL. The number of rats in each group was the same as shown in Table 2.

Figure 3

Effect of treatment of high-fat/streptozotocin diabetic rats with menhaden-oil- (MO-) supplemented diet on motor and sensory nerve conduction velocity. Motor and sensory nerve conduction velocity was examined as described in Section 2. Data are presented as the mean ± S.E.M. in m/sec. The number of rats in each group was the same as shown in Table 2. *P < 0.05 compared to control rats; ⁺ P < 0.05 compared to diabetic rats.

Figure 4

Effect of treatment of high-fat/streptozotocin diabetic rats with menhaden-oil- (MO-) supplemented diet on thermal nociception and intraepidermal nerve fiber density. Thermal nociception and intraepidermal nerve fiber density was examined as described in Section 2. Data are presented as the mean ± S.E.M. for thermal nociception in sec and intraepidermal nerve fiber profiles per mm. The number of rats in each group was the same as shown in Table 2. *P < 0.05 compared to control rats; ⁺ P < 0.05 compared to diabetic rats.