Canine cognitive dysfunction (CCD) is a common neurobehavioral syndrome in aged dogs, especially in Japanese dog breeds such as Shiba. Polyunsaturated fatty acids (PUFA), including arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), are constituents of biological membranes and nervous tissue. EPA and DHA can be synthesized from alpha-linolenic acid (ALA), but the conversion rate is lower in both humans and dogs, making them prone to deficiency. In humans, it has been reported that high erythrocyte long chain omega-3 fatty acid (FA) levels appear to be associated with better cognitive function later in life and lower risk of cognitive decline. On the other hand, the activity of desaturase (delta-5 desaturase and delta-6 desaturase), which metabolizes EPA and DHA from precursors, has been reported to be lower in Japanese than in Westerners, possibly due to dietary culture as Japanese have historically ingested EPA and DHA directly from seafood. We hypothesized that Japanese dogs share historically similar diets with Japanese and may have a lower desaturase activity compared with Western dogs. The aim of this pilot study was to investigate the composition of FAs in the erythrocyte membrane and plasma, and to evaluate desaturase activity in Japanese dogs and non-Asian dogs.
Prospective study. Twenty-five Shiba dogs without CCD and 57 non-Asian dogs without CCD were used. The FAs (omega-3 PUFA, omega-6 PUFA, monounsaturated PUFA, and saturated PUFA) composition of the erythrocyte membrane and plasma were measured from blood samples using gas chromatography. The difference between Shiba dogs and non-Asian dogs was evaluated using the Wilcoxson rank-sum test.
Shiba dogs had a significantly lower composition (%) of EPA (median: 1.09, range: 0-2.43), DHA (median: 1.15, range: 0-4.12) and total omega-3 FA (median: 3.22, range: 0.48-7.10) in erythrocyte membranes compared with non-Asian dogs (median: 1.20, range: 0.40-2.12; median: 1.51, range: 0-2.56; median: 4.03, range: 1.31-7.08) (p = 0.0055; 0.0379; 0.0419).
These findings might suggest that Shiba dogs have lower desaturase activity than non-Asian dogs. The high incidence of CCD in Shiba dogs may be associated with the low composition of omega-3 FAs in erythrocyte membrane. Studies on FAs using dogs with a unified diet are required to clarify the metabolic difference between Japanese dogs and non-Asian dogs, and to elucidate the association between FAs and CCD.
Dr. Go Togawa received his veterinary degree from the Azabu University, Japan in 2015. During his undergraduate study, he developed a strong interest in small animal neurology. After graduation, he started combined PhD and clinical training course in small animal neurology at the Azabu University, Japan. His research interest includes degenerative myelopathy, canine idiopathic epilepsy and canine cognitive dysfunction.
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