Western Diet can Impair Odor-related Learning and Olfactory Memory

Problems with the sense of smell seem to be an early indicator of cognitive decline in people with type 2 diabetes. However, it's unknown whether diet and obesity play a role in who develops these symptoms. Now, a new study published in the journal Chemical Neuroscience found that mice fed on moderate-fat, high-sugar chow simulating a Western diet showed a faster deterioration in their ability to learn and remember new odors. Few people with type 2 diabetes (T2D) show olfactory dysfunction, including detecting, discriminating, or recalling odors, or even a complete loss of smell. These symptoms are strongly linked to cognitive impairment, and evidence hints they could be an early indicator of the condition in T2D people.

Obesity, the leading risk factor for T2D, has also been linked with olfactory dysfunction. Still, the impact of obesity on the sense of smell, specifically in these patients, is unclear, as studies have produced contradictory results.

It's also unclear whether specific nutrients in the diet, such as fat and sugar, alter the sense of smell. To find out more, Grazyna Lietzau, Cesare Patrone, and colleagues wanted to examine the effects of two diets on various olfactory functions in mice: a moderate-fat, high-sugar diet and a high-fat, moderate-sugar diet (HFD) (alike Western diet, WD). In mice, both diets cause T2D and obesity-like features.

At one, three, and eight months, the research team performed tests to assess various olfactory functions in the mice. By 8 months, both the HFD- and WD-fed mice had diminished odor detection, odor-related learning, and olfactory memory than the control group mice. However, the WD-fed mice had a faster deterioration in the latter two abilities, showing olfactory dysfunction as early as three months after beginning the diet.

These findings indicate that high dietary sugar content, rather than hyperglycemia or weight gain, is associated with early deterioration of olfactory functions tied to learning and memory, the experts say.

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Source-Medindia