Taste and smell dysfunction in clinical populations

Alfaro Leiva, Raul Andres

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https://hdl.handle.net/2142/115705 Copy

Description

Title

Taste and smell dysfunction in clinical populations

Author(s)

Alfaro Leiva, Raul Andres

Issue Date

2022-04-20

Director of Research (if dissertation) or Advisor (if thesis)

Pepino, Yanina

Doctoral Committee Chair(s)

Madak-Erdogan, Zeynep

Committee Member(s)

• Cadwallader, Keith R
• Parker, Anna Arthur

Department of Study

Food Science & Human Nutrition

Discipline

Food Science & Human Nutrition

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Taste
• Smell
• Psychophysics
• Clinical

Abstract

The senses of taste and smell serve as sensors of molecules in foods, beverages, and the environment. The sense of taste can recognize non-volatiles through receptors located in the tongue, oral cavity, and pharynx. The perceptions elicited by taste sensing include sweet, salty, sour, bitter, and umami, which are the 5 recognized basic tastes. The sense of smell can recognize volatiles that in a combinatorial fashion elicit perceptions of thousands of odor objects. The importance of the sense of taste and smell include modulating food intake, regulating metabolism, indicating progression of neurodegenerative diseases, and ensuring safety by detecting hazardous substances and environments. Despite the importance of the senses of taste and smell, many clinicians fail to quantitively assess taste and smell dysfunctions and pinpoint the etiology of a patient’s complaints regarding disturbances to their taste and smell function. There are many challenges that arise when evaluating taste and smell function in the clinical setting. The peripheral and central components of the taste and smell organs not only work independently from each other but also integrate to form the perception of flavor which hinders clinician’s ability to pinpoint whether a taste or smell dysfunction underlies a patient’s complaint, especially when only evaluating taste or smell in isolation. However, isolating taste and smell can also reveal specific impairments in their normal function. Consequently, because of these challenges, diverse clinical populations carry the burden of uncharacterized and unresolved taste and smell dysfunctions. This dissertation aims to explore taste and smell dysfunctions in two clinical populations with uncharacterized and unresolved taste and smell dysfunctions: head and neck squamous cell carcinoma (HNSCC) survivors and patients with Wolfram Syndrome. HNSCC survivors complain of persisting taste and smell dysfunction long after radiation therapy has been completed. Wolfram syndrome is a rare genetic disease that causes vision and hearing loss but smell and taste loss have not been studied in this disease. The overall objective of this dissertation is to determine presence and extent of unresolved and uncharacterized taste and smell dysfunctions in these two clinical populations using a comprehensive set of validated psychophysical methodologies that evaluate both taste and smell function. We tested three major hypotheses based on the limitations and gaps in knowledge regarding the taste and smell function of HNSCC survivors and patients with Wolfram Syndrome. Hypothesis 1: Radiation therapy for the treatment of HNSCC is associated with long-term (or chronic) alterations of taste and smell function. Hypothesis 2: Wolfram syndrome is associated with smell and taste dysfunction. Hypothesis 3: Odor-induced taste enhancement is affected in Wolfram syndrome. To test our hypothesis, we took advantage of collaborations with Dr. Hershey in Washington University School of Medicine and Dr. Arthur at Carle Foundation Hospital, and we recruited groups of participants from the targeted clinical populations of HNSCC survivors and patients with Wolfram syndrome. Additionally, we locally recruited some of the sex and age equivalent healthy control groups to compare against these two clinical populations of interest. We used a series of validated psychophysical tests that evaluate the conscious perception of a stimulus. For taste tests we included measurements of regional (isolating tip of the tongue using a cotton swab) and whole mouth taste intensity, odor-induced taste enhancement using nose clip and no nose clip conditions, and taste identification. As stimuli, we included sucrose for sweetness, citric acid for sourness/bitterness, sodium chloride for saltiness and caffeine and quinine for bitterness. Additionally, we used familiar aromas to assess odor- induced taste enhancement. Strawberry extract was added to sucrose, lemon extract to citric acid, sodium chloride was prepared in vegetable broth, and caffeine from instant coffee. For smell tests, we used n-butanol detection thresholds to assess smell sensitivity function (Sniffin’ Sticks), and the University of Pennsylvania Smell Identification Test (UPSIT) to assess smell identification function. Our results found for Hypothesis 1: HNSCC survivors experienced subtle differences in taste perception in the long term compared with the healthy control group. Regarding smell, differences between HNSCC survivors and healthy control group were almost negligible and limited to a weaker perception of the smell of coffee in HNSCC survivors. Hypothesis 2: Wolfram syndrome is associated with olfactory dysfunction, and such olfactory impairment is qualitative (i.e., decreased ability for smell identification) and not due to olfactory insensitivity or secondary to having insulin-dependent diabetes. Finally, our findings also suggest that, in contrast to the sense of smell (and vision and audition); the sense of taste is overall well conserved in individuals with Wolfram syndrome. Hypothesis 3: Despite having severe impairments in smell identification, retronasal odor-induced taste enhancement appears normal in patients with Wolfram syndrome. Additionally, patients with Wolfram syndrome had a reduced olfactory sensitivity and a weaker perceived smell intensity when savoring solutions prepared with lemon extract, vegetable broth and coffee. Regarding gustatory function, as we found before, participants with Wolfram syndrome were not different than the healthy controls when tasting different taste qualities in the whole mouth while wearing nose clips. Our findings uncover the presence of taste and smell dysfunctions in both HNSCC survivors and patients with Wolfram Syndrome. HNSCC survivors have a very subtle regional impairment of taste function that persists long after radiation therapy and could possibly explain complaints of these patients. These subtle-regional taste impairments may not be the sole source of HNSCC survivor’s complaints and future research avenues should additionally explore the phenomenon of burning mouth syndrome, metallic taste, and texture alterations in HNSCC survivors. We also characterized smell identification and sensitivity dysfunction in Wolfram syndrome, a progressive neurodegenerative disorder. Despite a striking smell identification impairment, taste-smell interactions, specifically odor-induced taste enhancement, is still preserved in Wolfram syndrome patients. These research findings highlight the importance of using a comprehensive set of validated methodologies that quantify taste and smell function, to be able to pinpoint subtle or complex alterations in taste and smell function in clinical populations.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Raul Alfaro Leiva

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