Pretreated Glehnia littoralis Extract Prevents Neuronal Death Following Transient Global Cerebral Ischemia through Increases of Superoxide Dismutase 1 and Brain-derived Neurotrophic Factor Expressions in the Gerbil Hippocampal Cornu Ammonis 1 Area

Glehnia littoralis Fr. Schmidtex Miq.: A systematic review on ethnopharmacology, chemical composition, pharmacology and quality control

ETHNOPHARMACOLOGICAL RELEVANCE

Glehnia littoralis Fr. Schmidtex Miq. is a well-known perennial herb that is used in traditional medicine in China, Japan and Korea. G. littoralis has the effects of treating the lungs with heat, nourishing yin and blood, and acting as an expectorant. Traditional Chinese medicine (TCM) prescriptions containing G. littoralis have various clinical applications, such as clearing heat, relieving coughs, treating hepatic fibrosis, resolving phlegm, and treating esophagitis.

AIM OF THE REVIEW

This paper aims to provide a comprehensive and productive review of G. littoralis, mainly including traditional application, ethnopharmacology, chemical composition, pharmacological activities, and quality control.

MATERIALS AND METHODS

Literature search was conducted through the Web of Science, ScienceDirect, Springer Link, PubMed, Baidu Scholar, CNKI, and WanFang DATA by using the keywords "Glehnia littoralis", "Radix Glehniae", "Bei Shashen", "Clinical application", "Chemical composition", "Quality control" and "pharmacological action". In addition, information was collected from relevant ancient books, reviews, and documents (1980-2022).

RESULTS

G. littoralis is a traditional Chinese herbal medicine with great clinical value and rich resources. More than 186 components, including coumarins, lignans, polyacetylenes, organic acids, flavonoids, and terpenoids, have been isolated and identified from G. littoralis. The pharmacological activities of more than half of these chemicals are yet unknown. Polyacetylenes and coumarins are the most important bioactive compounds responsible for pharmacological activities, such as antiproliferative, anti-oxidation, anti-inflammatory, antibacterial, antitussive, immune regulation and analgesic. In this study, the progress in chemical analysis of G. littoralis, including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (MS), and HPLC-MS, were summarized.

CONCLUSION

In this paper reviewed the previous literature regarding ethnopharmacological, phytochemical, pharmacological, and quality evaluation of the processing of G. littoralis was reviewed, providing potential reference information for future investigation and clinical applications. However, research on the relationship between chemical constituents and traditional uses of G. littoralis is lacking, and the comprehensive pharmacological effects and mechanisms of G. littoralis require further detailed exploration. In addition, an efficient method for chemical profiling is still unavailable to obtain potent bioactive markers for quality control. Perfect quality standards, which are also the basis for further drug development of G. littoralis, are urgently needed to ensure its quality and clinical application.

The Impact of Cerebral Ischemia on Antioxidant Enzymes Activity and Neuronal Damage in the Hippocampus

Cerebral ischemia and subsequent reperfusion, leading to reduced blood supply to specific brain areas, remain significant contributors to neurological damage, disability, and mortality. Among the vulnerable regions, the subcortical areas, including the hippocampus, are particularly susceptible to ischemia-induced injuries, with the extent of damage influenced by the different stages of ischemia. Neural tissue undergoes various changes and damage due to intricate biochemical reactions involving free radicals, oxidative stress, inflammatory responses, and glutamate toxicity. The consequences of these processes can result in irreversible harm. Notably, free radicals play a pivotal role in the neuropathological mechanisms following ischemia, contributing to oxidative stress. Therefore, the function of antioxidant enzymes after ischemia becomes crucial in preventing hippocampal damage caused by oxidative stress. This study explores hippocampal neuronal damage and enzymatic antioxidant activity during ischemia and reperfusion's early and late stages.

Standardized extract of Glehnia Littoralis abrogates memory impairment and neuroinflammation by regulation of CREB/BDNF and NF-κB/MAPK signaling in scopolamine-induced amnesic mice model

Mild cognitive impairment is a typical symptom of early Alzheimer's disease (AD). Glehnia littoralis (G. littoralis), a medicinal halophyte plant commonly used to treat strokes, has been shown to possess some therapeutic qualities. In this study, we investigated the neuroprotective and anti-neuroinflammatory effects of a 50% ethanol extract of G. littoralis (GLE) on lipopolysccharide (LPS)-stimulated BV-2 cells and scopolamine-induced amnesic mice. In the in vitro study, GLE treatment (100, 200, and 400 µg/mL) markedly attenuated the translocation of NF-κB to the nucleus concomitantly with the significant mitigation of the LPS-induced production of inflammatory mediators, including NO, iNOS, COX-2, IL-6, and TNF-α. In addition, the GLE treatment suppressed the phosphorylation of MAPK signaling in the LPS-stimulated BV-2 cells. In the in vivo study, mice were orally administered with the GLE (50, 100, and 200 mg/kg) for 14 days, and cognitive loss was induced via the intraperitoneal injection of scopolamine (1 mg/kg) from 8 to 14 days. We found that GLE treatment ameliorated memory impairment and simultaneously improved memory function in the scopolamine-induced amnesic mice. Correspondingly, GLE treatment significantly decreased the AChE level and upregulated the protein expression of neuroprotective markers, such as BDNF and CREB, as well as Nrf2/HO-1 and decreased the levels of iNOS and COX-2 in the hippocampus and cortex. Furthermore, GLE treatment attenuated the increased phosphorylation of NF-κB/MAPK signaling in the hippocampus and cortex. These results suggest that GLE has a potential neuroprotective activity that may ameliorate learning and memory impairment by regulating AChE activity, promoting CREB/BDNF signaling, and inhibiting NF-κB/MAPK signaling and neuroinflammation.

Cu,Zn-Superoxide Dismutase has Minimal Effects Against Cuprizone-Induced Demyelination, Microglial Activation, and Neurogenesis Defects in the C57BL/6 Mouse Hippocampus

Cuprizone causes consistent demyelination and oligodendrocyte damage in the mouse brain. Cu,Zn-superoxide dismutase 1 (SOD1) has neuroprotective potential against various neurological disorders, such as transient cerebral ischemia and traumatic brain injury. In this study, we investigated whether SOD1 has neuroprotective effects against cuprizone-induced demyelination and adult hippocampal neurogenesis in C57BL/6 mice, using the PEP-1-SOD1 fusion protein to facilitate the delivery of SOD1 protein into hippocampal neurons. Eight weeks feeding of cuprizone-supplemented (0.2%) diets caused a significant decrease in myelin basic protein (MBP) expression in the stratum lacunosum-moleculare of the CA1 region, the polymorphic layer of the dentate gyrus, and the corpus callosum, while ionized calcium-binding adapter molecule 1 (Iba-1)-immunoreactive microglia showed activated and phagocytic phenotypes. In addition, cuprizone treatment reduced proliferating cells and neuroblasts as shown using Ki67 and doublecortin immunostaining. Treatment with PEP-1-SOD1 to normal mice did not show any significant changes in MBP expression and Iba-1-immunoreactive microglia. However, Ki67-positive proliferating cells and doublecortin-immunoreactive neuroblasts were significantly decreased. Simultaneous treatment with PEP-1-SOD1 and cuprizone-supplemented diets did not ameliorate the MBP reduction in these regions, but mitigated the increase of Iba-1 immunoreactivity in the corpus callosum and alleviated the reduction of MBP in corpus callosum and proliferating cells, not neuroblasts, in the dentate gyrus. In conclusion, PEP-1-SOD1 treatment only has partial effects to reduce cuprizone-induced demyelination and microglial activation in the hippocampus and corpus callosum and has minimal effects on proliferating cells in the dentate gyrus.

Treatment of rat brain ischemia model by NSCs-polymer scaffold transplantation

Neural stem cells (NSCs) transplantation is a promising therapeutic strategy for ischemic stroke. However, significant cell death after transplantation greatly limits its effectiveness. Poly (trimethylene carbonate)15-F127-poly (trimethylene carbonate)15 (PTMC15-F127-PTMC15, PFP) is a biodegradable thermo-sensitive hydrogel biomaterial, which can control drug release and provide permissive substrates for donor NSCs. In our study, we seeded NSCs into PFP polymer scaffold loaded with three neurotrophic factors, including brain-derived neurotrophic factor, nerve growth factor, and Neurotrophin-3. And then we transplanted this NSCs-polymer scaffold in rat brains 14 days after middle cerebral artery occlusion. ELISA assay showed that PFP polymer scaffold sustained releasing three neurotrophic factors for at least 14 days. Western Blot and fluorescence immunostaining revealed that NSCs-polymer scaffold transplantation significantly reduced apoptosis of ischemic penumbra and promoted differentiation of the transplanted NSCs into mature neurons. Furthermore, infarct size was reduced, and neurological performance of the animals were improved by the transplanted NSCs-polymer scaffold. These results demonstrate that PFP polymer scaffold loaded with neurotrophic factors can enhance the effectiveness of stem cell transplantation therapy, which provides a new way for cell transplantation therapy in ischemic stroke.

Trends in Gliosis in Obesity, and the Role of Antioxidants as a Therapeutic Alternative

Obesity remains a global health problem. Chronic low-grade inflammation in this pathology has been related to comorbidities such as cognitive alterations that, in the long term, can lead to neurodegenerative diseases. Neuroinflammation or gliosis in patients with obesity and type 2 diabetes mellitus has been related to the effect of adipokines, high lipid levels and glucose, which increase the production of free radicals. Cerebral gliosis can be a risk factor for developing neurodegenerative diseases, and antioxidants could be an alternative for the prevention and treatment of neural comorbidities in obese patients.

AIM

Identify the immunological and oxidative stress mechanisms that produce gliosis in patients with obesity and propose antioxidants as an alternative to reducing neuroinflammation.

METHOD

Advanced searches were performed in scientific databases: PubMed, ProQuest, EBSCO, and the Science Citation index for research on the physiopathology of gliosis in obese patients and for the possible role of antioxidants in its management.

CONCLUSION

Patients with obesity can develop neuroinflammation, conditioned by various adipokines, excess lipids and glucose, which results in an increase in free radicals that must be neutralized with antioxidants to reduce gliosis and the risk of long-term neurodegeneration.

Properties of the Novel Chinese Herbal Medicine Formula Qu Du Qiang Fei I Hao Fang Warrant Further Research to Determine Its Clinical Efficacy in COVID-19 Treatment

Introduction: COVID-19, the infectious disease induced by the virus severe acute respiratory syndrome-related coronavirus-2, has caused increasing global health concerns, and novel strategies to prevent or ameliorate the condition are needed. Traditional Chinese Medicine (TCM) herbal formulas have been used in the treatment of epidemics in China for over 2000 years. This study investigated the therapeutic effects of Qu Du Qiang Fei I Hao Fang (QDQF1) "Eliminating Virus and Strengthening Lung-No.1 Formula," in the treatment and prevention of COVID-19. QDQF1 consists of Shēng Huáng Qí, Běi Shā Shēn, Chuān Jié Gěng, Zhì Fáng Fēng, Qīng Lián Qiáo, Jīn Yín Huā, Bǎn Lán Gēn, Chǎo Cāng Zhú, Zǐ Huā Dì Dīng, and Shēng gān căo. Materials and Methods: A literature survey was performed by conducting systematic electronic searches in PubMed, Science Direct, Google Scholar, and in books. Results: Each herb in this formula has long been used to treat various diseases due to their pharmacologic, antiviral, anti-inflammatory, and antimicrobial effects that inhibit microbial adherence to mucosal or epithelial surfaces, inhibit endotoxin shock, and selectively inhibit microbial growth. Conclusion: The herbs chosen for the QDQF1 formula have been historically paired, and cast a wide net over the potential COVID-19 symptomatology. Their combined functions provide comprehensive and balanced therapeutics from both TCM and allopathic perspectives. Individual herbs and herbal combinations are analyzed for their applicability to pertinent TCM patterns of COVID-19 presentations, including heat and cold patterns, damp and phlegm syndromes, toxicity, and deficiency patterns. A further study in a randomized, double-blind, and placebo-controlled trial of QDQF1 is recommended to assess its therapeutic efficacy in the treatment of COVID-19.

Experimental pretreatment with YES-10®, a plant extract rich in scutellarin and chlorogenic acid, protects hippocampal neurons from ischemia/reperfusion injury via antioxidant role

Erigeron annuus (L.) PERS. (EALP) and Clematis mandshurica RUPR. (CMR) have been used in traditional remedies due to their medicinal effects. Recently, we reported that pretreatment with 200 mg/kg of YES-10^® (a combination of extracts from leaves of EALP and CMR) displayed neuroprotective effects against brain ischemia and reperfusion injury. The present study analyzed the major ingredients of YES-10^® and investigated whether neuroprotection from YES-10^® was dependent upon antioxidant effects in the cornu ammonis 1 (CA1) field in the gerbil hippocampus, after transient forebrain ischemia for 5 min. YES-10^® was demonstrated to predominantly contain scutellarin and chlorogenic acid. Pretreatment with YES-10^® significantly increased protein levels and the immunoreactivity of copper/zinc-superoxide dismutase (SOD1) and manganese-superoxide dismutase (SOD2) was in the pyramidal neurons of the hippocampal CA1 field when these were examined prior to transient ischemia induction. The increased SODs in CA1 pyramidal neurons following YES-10^® treatment were maintained after ischemic injury. In this case, the CA1 pyramidal neurons were protected from ischemia-reperfusion injury. Oxidative stress was significantly attenuated in the CA1 pyramidal neurons, and this was determined by 4-hydroxy-2-nonenal immunohistochemistry and dihydroethidium histofluorescence staining. Taken together, the results indicated that YES-10^® significantly attenuated transient ischemia-induced oxidative stress and may be utilized for developing a protective agent against ischemic insults.

Long-term use of combined conventional medicine and Chinese herbal medicine decreases the mortality risk of patients with lung cancer

BACKGROUND

We explored the effect of Chinese herbal medicine (CHM) on the long-term survival of lung cancer patients and hazard ratio (HR) and to analyse CHM herbs and formulas for lung cancer treatment.

METHODS

We conducted a retrospective cohort study on diagnosed lung cancer patients in 2003-2016 from Taipei and Dalin Tzu Chi General Hospital Cancer Registry Database and from outpatient database from Chinese Medicine and Conventional Medicine Department. We categorised the patients into CHM user and CHM nonuser groups according to the CHM consumption time. After passing the proportional hazard assumption, we used the Cox PH model to calculate the groups' survival hazard ratio (HR) and examine the statistical difference and effect of CHM on lung cancer survival.

RESULTS

We classified 2557 lung cancer patients into 1643 CHM nonusers and 228 CHM users. The CHM users had lower mortality than the CHM nonusers. With the multivariable Cox model, we observed that the CHM use was associated with 35% lower risk of mortality (adjusted HR: 0.65; 95% confidence interval: 0.51-0.76). Continuous CHM use of >180 days may further lessen the mortality risk by 64%. Finally, eight herbs and two formulas could significantly lower the mortality. After pairing the eight herbs for analysis, seven combinations could reduce the mortality better than only using one herb.

CONCLUSION

CHM users had significantly lower mortality than CHM nonusers. The longer the CHM use, the more the mortality HR declined. Glehnia littoralisF. Schmidt ex Miq., Polyporus umbellatus(Pers.) Fries and Trichosanthes kirilowii Maxim. possess a highly substantial anticancer activity compared with other herbs.

YES-10, A Combination of Extracts from Clematis mandshurica RUPR. and Erigeron annuus (L.) PERS., Prevents Ischemic Brain Injury in A Gerbil Model of Transient Forebrain Ischemia

: Clematis mandshurica RUPR. (CMR) and Erigeron annuus (L.) PERS. (EALP) have pharmacological effects including anti-inflammatory activity and been used in traditional medicines in Asia. However, neuroprotective effects of CMR and/or EALP extracts against brain ischemic insults have never been addressed. Thus, the aim of this study was to examine neuroprotective effects of YES-10, a combination of extracts from CMR and EALP (combination ratio, 1:1), in the hippocampus following ischemia/reperfusion in gerbils. Protection of neurons was investigated by cresyl violet staining, fluoro-jade B histofluorescence staining and immunohistochemistry for neuronal nuclei. In addition, attenuation of gliosis was studied by immunohistochemistry for astrocytic and microglial markers. Treatments with 50 or 100 mg/kg YES-10 failed to protect neurons in the hippocampus after ischemia/reperfusion injury. However, administration of 200 mg/kg YES-10 protected neurons from ischemia/reperfusion injury and attenuated reactive gliosis. These findings strongly suggest that a combination of extracts from CMR and EALP can be used as a prevention approach/drug against brain ischemic damage.

Pretreatment of Populus tomentiglandulosa protects hippocampal CA1 pyramidal neurons from ischemia-reperfusion injury in gerbils via increasing SODs expressions and maintaining BDNF and IGF-I expressions

To examine the effects of Populus tomentiglandulosa (PT) extract on the expressions of antioxidant enzymes and neurotrophic factors in the cornu ammonis 1 (CA1) region of the hippocampus at 5 min after inducing transient global cerebral ischemia (TGCI) in gerbils, TGCI was induced by occlusion of common carotid arteries for 5 min. Before ischemic surgery, 200 mg·kg^-1 PT extract was orally administrated once daily for 7 d. We performed neuronal nuclear antigen immunohistochemistry and Fluoro-Jade B staining. Furthermore, we determined in situ production of superoxide anion radical, expression levels of SOD1 and SOD2 as antioxidant enzymes and brain-derived neurotrophic factor (BDNF) and insulin-like growth factor I (IGF-I) as neurotrophic factors. Pretreatment with 200 mg·kg^-1 PT extract prevented neuronal death (loss). Furthermore, pretreatment with 200 mg·kg^-1 PT extract significantly inhibited the production of superoxide anion radical, increased expressions of SODs and maintained expressions of BDNF and IGF-I. Such increased expressions of SODs were maintained in the neurons after IRI. In summary, pretreated PT extract can significantly increase levels of SODs and protect the neurons against TGCI, suggesting that PT can be a useful natural agent to protect against TGCI.

Neuroprotective Secondary Metabolite Produced by an Endophytic Fungus, Neosartorya fischeri JS0553, Isolated from Glehnia littoralis

Roots of Glehnia littoralis have been used to heal stroke as a traditional medicine. Even though many studies on this plant have been conducted, the secondary metabolites produced by its endophytes and their bioactivities have not been investigated thus far. Therefore, a new meroditerpenoid named sartorypyrone E (1) and eight known compounds (2-9) were isolated from extracts of cultured Neosartorya fischeri JS0553, an endophyte of G. littoralis. The isolated metabolites were identified using spectroscopic methods and chemical reaction, based on a comparison to literature data. Relative and absolute stereochemistries of compound 1 were also elucidated. To identify the protective effects of isolated compounds (1-9) in HT22 cells against glutamate-induced cytotoxicity, we assessed inhibition of cell death, intracellular reactive oxygen species (ROS) accumulation, and calcium ion (Ca²⁺) influx. Among the isolates, compound 8, identified as fischerin, showed significant neuroprotective activity on glutamate-mediated HT22 cell death through inhibition of ROS, Ca²⁺ influx, and phosphorylation of mitogen-activated protein kinase, including c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p38. The results suggested that the metabolites produced by the endophyte N. fischeri JS0553 might be related to the neuroprotective activity of its host plant, G. littoralis.

Pretreated Oenanthe Javanica extract increases anti-inflammatory cytokines, attenuates gliosis, and protects hippocampal neurons following transient global cerebral ischemia in gerbils

Recently, we have reported that Oenanthe javanica extract (OJE) displays strong neuroprotective effect against ischemic damage after transient global cerebral ischemia. However, neuroprotective mechanisms of OJE have not been fully identified. Thus, this study investigated the neuroprotection of OJE in the hippocampal CA1 area and its anti-inflammatory activity in gerbils subjected to 5 minutes of transient global cerebral ischemia. We treated the animals by intragastrical injection of OJE (100 and 200 mg/kg) once daily for 1 week prior to transient global cerebral ischemia. Neuroprotection of OJE was observed by immunohistochemistry for neuronal nuclear antigen and histofluorescence staining for Fluoro-Jade B. Immunohistochemistry of glial fibrillary acidic protein and ionized calcium-binding adapter molecule 1 was done for astrocytosis and microgliosis, respectively. To investigate the neuroprotective mechanisms of OJE, we performed immunohistochemistry of tumor necrosis factor-alpha and interleukin-2 for pro-inflammatory function and interleukin-4 and interleukin-13 for anti-inflammatory function. When we treated the animals by intragastrical administration of 200 mg/kg of OJE, hippocampal CA1 pyramidal neurons were protected from transient global cerebral ischemia and cerebral ischemia-induced gliosis was inhibited in the ischemic hippocampal CA1 area. We also found that interleukin-4 and -13 immunoreactivities were significantly increased in pyramidal neurons of the ischemic CA1 area after OJE pretreatment, and the increased immunoreactivities were sustained in the CA1 pyramidal neurons after transient global cerebral ischemia. However, OJE pretreatment did not increase interleukin-2 and tumor necrosis factor-alpha immunoreactivities in the CA1 pyramidal neurons. Our findings suggest that pretreatment with OJE can protect neurons and attenuate gliosis from transient global cerebral ischemia via increasing expressions of interleukin-4 and -13. The experimental plan of this study was reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) in Kangwon National University (approval No. KW-160802-1) on August 10, 2016.

Glehnia littoralis Extract Promotes Neurogenesis in the Hippocampal Dentate Gyrus of the Adult Mouse through Increasing Expressions of Brain-Derived Neurotrophic Factor and Tropomyosin-Related Kinase B

Background:

Glehnia littoralis has been used for traditional Asian medicine, which has diverse therapeutic activities. However, studies regarding neurogenic effects of G. littoralis have not yet been considered. Therefore, in this study, we examined effects of G. littoralis extract on cell proliferation, neuroblast differentiation, and the maturation of newborn neurons in the hippocampus of adult mice.

Methods:

A total of 39 male ICR mice (12 weeks old) were randomly assigned to vehicle-treated and 100 and 200 mg/kg G. littoralis extract-treated groups (n = 13 in each group). Vehicle and G. littoralis extract were orally administrated for 28 days. To examine neurogenic effects of G. littoralis extract, we performed immunohistochemistry for 5-bromo-2-deoxyuridine (BrdU, an indicator for cell proliferation) and doublecortin (DCX, an immature neuronal marker) and double immunofluorescence staining for BrdU and neuronal nuclear antigen (NeuN, a mature neuronal marker). In addition, we examined expressional changes of brain-derived neurotrophic factor (BDNF) and its major receptor tropomyosin-related kinase B (TrkB) using Western blotting analysis.

Results:

Treatment with 200 mg/kg, not 100 mg/kg, significantly increased number of BrdU-immunoreactive (⁺) and DCX⁺ cells (48.0 ± 3.1 and 72.0 ± 3.8 cells/section, respectively) in the subgranular zone (SGZ) of the dentate gyrus (DG) and BrdU⁺/NeuN⁺ cells (17.0 ± 1.5 cells/section) in the granule cell layer as well as in the SGZ. In addition, protein levels of BDNF and TrkB (about 232% and 244% of the vehicle-treated group, respectively) were significantly increased in the DG of the mice treated with 200 mg/kg of G. littoralis extract.

Conclusion:

G. littoralis extract promots cell proliferation, neuroblast differentiation, and neuronal maturation in the hippocampal DG, and neurogenic effects might be closely related to increases of BDNF and TrkB proteins by G. littoralis extract treatment.

Age‑dependent decreases in insulin‑like growth factor‑I and its receptor expressions in the gerbil olfactory bulb

Insulin-like growth factor-I (IGF-I) is a multifunctional protein present in the central nervous system. A number of previous studies have revealed alterations in IGF-I and its receptor (IGF-IR) expression in various regions of the brain. However, there are few reports on age-dependent alterations in IGF-I and IGF-IR expressions in the olfactory bulb, which contains the secondary neurons of the olfactory system. The present study examined the cellular morphology in the olfactory bulb by using cresyl violet (CV) staining at postnatal month (PM) 3 in the young group, PM 6 in the adult group and PM 24 in the aged group in gerbils. In addition, detailed examinations were performed of the protein levels and immunoreactivities of IGF-I and IGF-IR in the olfactory bulb in each group. There were no significant changes in the cellular morphology between the three groups. The protein levels and immunoreactivities of the IGF-I and IGF-IR were the highest in the young group and they decreased with age. He protein levels and immunoreactivities of the IGF-I and IGF-IR were the lowest in the aged group. In brief, our results indicate that IGF-I and IGF-IR expressions are strong in young olfactory bulbs and significantly reduced in aged olfactory bulbs. In conclusion, subsequent decreases in IGF-I and IGF-IR expression with age may be associated with olfactory decline. Further studies are required to investigate the roles of IFG-I and IGF-IR in disorders of the olfactory system.