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Khan S, Gutierrez JA, Chapurin N, Nguyen SA, Soler ZM, Schlosser RJ. The impact of race on olfaction: A systematic review and meta-analysis. Int Forum Allergy Rhinol 2023; 13:2063-2072. [PMID: 37183309 DOI: 10.1002/alr.23184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/24/2023] [Accepted: 05/11/2023] [Indexed: 05/16/2023]
Abstract
BACKGROUND Many studies have identified a higher degree of Olfactory Dysfunction (OD) in Black patients compared to White patients. This study aims to analyze olfactory outcomes in different races. METHODS The PubMed, Scopus, and CINAHL databases were searched from inception to September 5, 2022, for English-language articles documenting self-reported and psychophysical OD stratified by race. A meta-analysis of proportions, comparison of weighted proportions, and comparison of means were performed in MedCalc 20.218. In the quantitative analysis, 79,297 patients were included, comprising 79.3% Whites, 16.1% Blacks, and 4.6% Hispanics. RESULTS A total of 14 studies were meta-analyzed. The prevalence of self-reported OD in Hispanic, White, and Black patients was 19.5% (95% CI, 16.6% to 22.6%), 17.2% (95% CI, 10.5% to 25.0%), and 13.9% (95% CI, 9.3% to 19.2%), respectively (p < 0.0007). The prevalence of psychophysical OD in Black, White, and Hispanic patients was 30.3% (95% CI, 24.2% to 36.9%), 24.2% (95% CI, 20.1% to 28.5%), and 18.4% (95% CI, 16.3% to 20.7%), respectively (p < 0.0001). Blacks reported a greater extent of unrecognized OD compared to Whites, with a difference of 16.5% (95% CI, 15.0% to 17.9%) versus 5.8% (95% CI, 3.4% to 8.0%), respectively (p < 0.0001). Hispanic rates of self-reported OD and psychophysical OD were not statistically different. CONCLUSIONS Our findings suggest that Blacks have the highest rate of psychophysical OD and are more likely to underreport their awareness compared to Whites.
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Affiliation(s)
- Sofia Khan
- Department of Otolaryngology-Head and Neck Surgery, Division of Rhinology and Endoscopic Skull Base Surgery, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Jorge A Gutierrez
- Department of Otolaryngology-Head and Neck Surgery, Division of Rhinology and Endoscopic Skull Base Surgery, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Nikita Chapurin
- Department of Otolaryngology-Head and Neck Surgery, Division of Rhinology and Endoscopic Skull Base Surgery, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Shaun A Nguyen
- Department of Otolaryngology-Head and Neck Surgery, Division of Rhinology and Endoscopic Skull Base Surgery, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Zachary M Soler
- Department of Otolaryngology-Head and Neck Surgery, Division of Rhinology and Endoscopic Skull Base Surgery, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Rodney J Schlosser
- Department of Otolaryngology-Head and Neck Surgery, Division of Rhinology and Endoscopic Skull Base Surgery, Medical University of South Carolina, Charleston, South Carolina, USA
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AlBilasi TM, Alanazi RM, AlDhawi LF, Albathi AA. Outcome and Safety of Insulin in the Management of Smell Loss: A Systematic Review. EAR, NOSE & THROAT JOURNAL 2023:1455613231201028. [PMID: 37776014 DOI: 10.1177/01455613231201028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2023] Open
Abstract
Background: Olfactory dysfunction can negatively impact the quality of life and increase the risk of danger from warning odors. Various factors can cause olfactory dysfunction, including COVID-19 infection, which has increased anosmia cases. No medications are approved; however, recent studies have suggested that intranasal insulin could effectively treat olfactory dysfunction. Aim: To comprehensively evaluate the effectiveness and safety of intranasal insulin in treating olfactory dysfunction. Materials and Methods: PubMed, Google Scholar, and CENTRAL databases were searched using specific keywords, and the outputs were screened using the Rayyan AI system. Original research articles published without time frame limitations that reported the relevant outcomes were included. The reviewers performed the screening and data extraction, and any disagreements were resolved by a third senior author. Results: This systematic review identified 66 references from 3 databases, with 45 articles meeting the criteria for review after duplicates were removed. Six articles met the inclusion criteria and were selected, including 177 subjects. The selected studies consisted of various study designs, including pilot studies, placebo-controlled trials, crossover studies, and randomized clinical trials. The findings showed that intranasal insulin therapy had beneficial effects on olfactory function. Specifically, improvements were observed in olfactory detection and discrimination in patients with post-COVID-19 anosmia, olfactory threshold performance in healthy participants, and odor identification in hyposmic patients. However, there were variations in the observed effects based on different doses of insulin administered and gender differences. It also shows that using insulin provides good outcomes. Using it intranasally was safe and did not cause any complications. Conclusion: Intranasal insulin has shown promising results as a potentially safe treatment for olfactory dysfunction. Studies suggest that it can improve olfactory thresholds. Further studies are needed to investigate optimal doses and potential gender differences in response.
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Affiliation(s)
- Thamer M AlBilasi
- Department of Otolaryngology - Head & Neck Surgery (ORL-H&N), Prince Sultan Military Medical City (PSMMC), Riyadh, Saudi Arabia
| | - Rawan Mahmoud Alanazi
- A Medical Student College of Medicine, Dar Al Uloom University, Riyadh, Saudi Arabia
| | - Lama F AlDhawi
- A Medical Student at Al-Maarefa University College of Medicine, Riyadh, Saudi Arabia
| | - Abeer Ali Albathi
- Department of Otolaryngology - Head & Neck Surgery (ORL-H&N), Prince Sultan Military Medical City (PSMMC), Riyadh, Saudi Arabia
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Schumann K, Rodriguez-Raecke R, Sijben R, Freiherr J. Elevated Insulin Levels Engage the Salience Network during Multisensory Perception. Neuroendocrinology 2023; 114:90-106. [PMID: 37634508 DOI: 10.1159/000533663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 08/14/2023] [Indexed: 08/29/2023]
Abstract
INTRODUCTION Brain insulin reactivity has been reported in connection with systematic energy metabolism, enhancement in cognition, olfactory sensitivity, and neuroendocrine circuits. High receptor densities exist in regions important for sensory processing. The main aim of the study was to examine whether intranasal insulin would modulate the activity of areas in charge of olfactory-visual integration. METHODS As approach, a placebo-controlled double-blind within crossover design was chosen. The experiments were conducted in a research unit of a university hospital. On separate mornings, twenty-six healthy normal-weight males aged between 19 and 31 years received either 40 IU intranasal insulin or placebo vehicle. Subsequently, they underwent 65 min of functional magnetic resonance imaging whilst performing an odor identification task. Functional brain activations of olfactory, visual, and multisensory integration as well as insulin versus placebo were assessed. Regarding the odor identification task, reaction time, accuracy, pleasantness, and intensity measurements were taken to examine the role of integration and treatment. Blood samples were drawn to control for peripheral hormone concentrations. RESULTS Intranasal insulin administration during olfactory-visual stimulation revealed strong bilateral engagement of frontoinsular cortices, anterior cingulate, prefrontal cortex, mediodorsal thalamus, striatal, and hippocampal regions (p ≤ 0.001 familywise error [FWE] corrected). In addition, the integration contrast showed increased activity in left intraparietal sulcus, left inferior frontal gyrus, left superior frontal gyrus, and left middle frontal gyrus (p ≤ 0.013 FWE corrected). CONCLUSIONS Intranasal insulin application in lean men led to enhanced activation in multisensory olfactory-visual integration sites and salience hubs which indicates stimuli valuation modulation. This effect can serve as a basis for understanding the connection of intracerebral insulin and olfactory-visual processing.
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Affiliation(s)
- Katja Schumann
- Diagnostic and Interventional Neuroradiology, RWTH Aachen University, Aachen, Germany
| | - Rea Rodriguez-Raecke
- Diagnostic and Interventional Neuroradiology, RWTH Aachen University, Aachen, Germany
- Brain Imaging Facility, Interdisciplinary Center for Clinical Research, RWTH Aachen University, Aachen, Germany
| | - Rik Sijben
- Brain Imaging Facility, Interdisciplinary Center for Clinical Research, RWTH Aachen University, Aachen, Germany
| | - Jessica Freiherr
- Department of Psychiatry and Psychotherapy, Friedrich-Alexander, University Erlangen-Nürnberg, Erlangen, Germany
- Fraunhofer Institute for Process Engineering and Packaging IVV, Freising, Germany
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Bloody olfaction? Confounding associations of sex and age on the influence of blood parameters and body weight on odor identification performance in healthy adults. Physiol Behav 2022; 254:113907. [PMID: 35817126 DOI: 10.1016/j.physbeh.2022.113907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 07/04/2022] [Accepted: 07/07/2022] [Indexed: 11/20/2022]
Abstract
Olfactory function and nutrition are closely related and may influence each other via metabolic parameters. However, the relationship between nutritional blood parameters and olfactory performance is still unclear. Inconclusive findings exist for specific blood parameters. In this extensive analysis, we examined the relationship between olfactory performance, measured with MONEX-40, as well as intensity and pleasantness ratings with 38 metabolic blood parameters, age, sex, and the anthropometric measurements body mass index (BMI) and body fat percentage (BFP). Therefore, we included data of 418 healthy, well-phenotyped Caucasians of the Enable cohort. We replicated age-dependent olfactory identification scores (p < 0.001) and found slight evidence for a body fat dependence measured with BFP (BF10 = 10.466). We further identified a sex difference only in middle-aged adults (p < 0.001) that could be explained by environmental factors. Several blood parameters correlated significantly with the MONEX-40 score (p < 0.05 - p < 0.001). However, these effects diminished after adjusting for sex and age (p > 0.9) that were identified as confounders. The same applies for BFP. In addition, no parameters were identified to correlate significantly with perceived olfactory intensity or pleasantness score if controlled for sex and age (p > 0.08). Our results suggest that metabolic blood parameters are not related to olfactory identification performance in a relevant manner and highlight the importance of controlling for sex and age in chemosensory research.
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Intranasal insulin and orexins to treat age-related cognitive decline. Physiol Behav 2021; 234:113370. [PMID: 33621561 DOI: 10.1016/j.physbeh.2021.113370] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 02/19/2021] [Indexed: 02/06/2023]
Abstract
The intranasal (IN) administration of neuropeptides, such as insulin and orexins, has been suggested as a treatment strategy for age-related cognitive decline (ARCD). Because dysfunctional neuropeptide signaling is an observed characteristic of ARCD, it has been suggested that IN delivery of insulin and/or orexins may restore endogenous peptide signaling and thereby preserve cognition. IN administration is particularly alluring as it is a relatively non-invasive method that directly targets peptides to the brain. Several laboratories have examined the behavioral effects of IN insulin in young, aged, and cognitively impaired rodents and humans. These studies demonstrated improved performance on various cognitive tasks following IN insulin administration. Fewer laboratories have assessed the effects of IN orexins; however, this peptide also holds promise as an effective treatment for ARCD through the activation of the cholinergic system and/or the reduction of neuroinflammation. Here, we provide a brief overview of the advantages of IN administration and the delivery pathway, then summarize the current literature on IN insulin and orexins. Additional preclinical studies will be useful to ultimately uncover the mechanisms underlying the pro-cognitive effects of IN insulin and orexins, whereas future clinical studies will aid in the determination of the most efficacious dose and dosing paradigm. Eventually, IN insulin and/or orexin administration may be a widely used treatment strategy in the clinic for ARCD.
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Abstract
The intranasal (IN) route enables the delivery of insulin to the central nervous system in the relative absence of systemic uptake and related peripheral side effects. Intranasally administered insulin is assumed to travel along olfactory and adjacent pathways and has been shown to rapidly accumulate in cerebrospinal fluid, indicating efficient transport to the brain. Two decades of studies in healthy humans and patients have demonstrated that IN insulin exerts functional effects on metabolism, such as reductions in food intake and body weight and improvements of glucose homeostasis, as well as cognition, ie, enhancements of memory performance both in healthy individuals and patients with mild cognitive impairment or Alzheimer's disease; these studies moreover indicate a favourable safety profile of the acute and repeated use of IN insulin. Emerging findings suggest that IN insulin also modulates neuroendocrine activity, sleep-related mechanisms, sensory perception and mood. Some, but not all studies point to sex differences in the response to IN insulin that need to be further investigated along with the impact of age. "Brain insulin resistance" is an evolving concept that posits impairments in central nervous insulin signalling as a pathophysiological factor in metabolic and cognitive disorders such as obesity, type 2 diabetes and Alzheimer's disease, and, notably, a target of interventions that rely on IN insulin. Still, the negative outcomes of longer-term IN insulin trials in individuals with obesity or Alzheimer's disease highlight the need for conceptual as well as methodological advances to translate the promising results of proof-of-concept experiments and pilot clinical trials into the successful clinical application of IN insulin.
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Affiliation(s)
- Manfred Hallschmid
- Institute of Medical Psychology and Behavioural Neurobiology, University of Tübingen, Tübingen, Germany
- German Centre for Diabetes Research (DZD), Tübingen, Germany
- Institute for Diabetes Research and Metabolic Diseases, Helmholtz Centre Munich at the University of Tübingen, Tübingen, Germany
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Abstract
Brain insulin signaling contributes to memory function and might be a viable target in the prevention and treatment of memory impairments including Alzheimer's disease. This short narrative review explores the potential of central nervous system (CNS) insulin administration via the intranasal pathway to improve memory performance in health and disease, with a focus on the most recent results. Proof-of-concept studies and (pilot) clinical trials in individuals with mild cognitive impairment or Alzheimer's disease indicate that acute and prolonged intranasal insulin administration enhances memory performance, and suggest that brain insulin resistance is a pathophysiological factor in Alzheimer's disease with or without concomitant metabolic dysfunction. Intranasally administered insulin is assumed to trigger improvements in synaptic plasticity and regional glucose uptake as well as alleviations of Alzheimer's disease neuropathology; additional contributions of changes in hypothalamus-pituitary-adrenocortical axis activity and sleep-related mechanisms are discussed. While intranasal insulin delivery has been conclusively demonstrated to be effective and safe, the recent outcomes of large-scale clinical studies underline the need for further investigations, which might also yield new insights into sex differences in the response to intranasal insulin and contribute to the optimization of delivery devices to grasp the full potential of intranasal insulin for Alzheimer's disease.
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Affiliation(s)
- Manfred Hallschmid
- Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Otfried-Müller-Str. 25, 72076, Tübingen, Germany.
- German Center for Diabetes Research (DZD), Tübingen, Germany.
- Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen, Tübingen, Germany.
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Trevino JT, Quispe RC, Khan F, Novak V. Non-Invasive Strategies for Nose-to-Brain Drug Delivery. JOURNAL OF CLINICAL TRIALS 2020; 10:439. [PMID: 33505777 PMCID: PMC7836101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Intranasal drug administration is a promising method for delivering drugs directly to the brain. Animal studies have described pathways and potential brain targets, but nose-to-brain delivery and treatment efficacy in humans remains debated. We describe the proposed pathways and barriers for nose-to-brain drug delivery in humans, drug properties that influence central nervous system delivery, clinically tested methods to enhance absorption, and the devices used in clinical trials. This review compiles the available evidence for nose-to-brain drug delivery in humans and summarizes the factors involved in nose-to-brain drug delivery.
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Affiliation(s)
- J T Trevino
- Department of Neurology, SAFE Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - R C Quispe
- Department of Neurology, SAFE Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - F Khan
- Department of Neurology, SAFE Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
| | - V Novak
- Department of Neurology, SAFE Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
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