Ting Yu Amelia Yam

Dysregulated insulin signaling in the brain has been linked to cognitive impairment and dementia. Insulin-like growth factor 1 (IGF-1) is a peptide growth hormone crucial for neurogenesis and neuroprotection. Findings regarding potential involvement of IGF-1 in dementia have been conflicting, and the status of IGF-1 in clinical cohorts with Alzheimer’s disease (AD) and concomitant cerebrovascular disease (CeVD) burden is unknown. A Singapore-based memory clinic cohort consisting of 46 non-cognitively impaired (NCI), 101 with cognitive impairment, no dementia (CIND) and 81 AD dementia subjects underwent plasma IGF-1 measurements and neuroimaging assessments for association analyses of peripheral IGF-1 with regional brain volumes, as well as with neuroimaging CeVD markers (lacunes, cerebral microbleeds, white matter hyperintensities). Plasma IGF-1 levels were significantly lower in AD compared to NCI and CIND participants (both p < 0.001). Plasma IGF-1 was significantly associated with smaller hippocampal (p = 0.035), amygdala (p = 0.024), parietal lobe (p = 0.029), and frontal lobe (p = 0.002) volumes. In contrast, plasma IGF-1 did not associate with CeVD markers after covariate adjustments. Our findings suggest that plasma IGF-1 may be a blood-based biomarker for reduced brain volumes, while having no direct role in CeVD pathophysiology.

Dysregulated insulin signaling in brain has been linked to cognitive impairment and dementia. Insulin-like growth factor-1 (IGF-1) is a peptide growth hormone crucial for neurogenesis and neuroprotection. Findings regarding potential involvement of IGF-1 in dementia have been conflicting, and the status of IGF-1 in clinical cohorts with Alzheimer’s disease (AD) and concomitant cerebrovascular disease (CeVD) burden is unknown. A Singapore-based memory clinic cohort consisting of 46 non-cognitively impaired (NCI), 101 with cognitive impairment, no dementia (CIND) and 81 AD dementia subjects underwent plasma IGF-1 measurements and neuroimaging assessments for association analyses of peripheral IGF-1 with regional brain volumes, as well as with neuroimaging CeVD markers (lacunes, cerebral microbleeds, white matter hyperintensities). Plasma IGF-1 levels were significantly lower in AD compared to NCI and CIND participants (both p < 0.001). Plasma IGF-1 was significantly associated with smaller hippocampal (p = 0.035), amygdala (p = 0.024), parietal lobe (p = 0.029), and frontal lobe (p = 0.002) volumes. In contrast, plasma IGF-1 did not associate with CeVD markers after covariate adjustments. Our findings suggest that plasma IGF-1 may be a specific blood-based biomarker for neurodegeneration, while having no direct role in CeVD pathophysiology.

INTRODUCTION: While elevated blood glial fibrillary acidic protein (GFAP) has been associated with brain amyloid pathology, whether this association occurs in populations with high cerebral small vessel disease (CSVD) concomitance remains unclear.METHODS: Using a Singapore‐based cohort of cognitively impaired subjects, we assessed associations between plasma GFAP and neuroimaging measures of brain amyloid and CSVD, including white matter hyperintensities (WMH). We also examined the diagnostic performance of plasma GFAP in detecting brain amyloid beta positivity (Aβ+).RESULTS: When stratified by WMH status, elevated brain amyloid was associated with higher plasma GFAP only in the WMH– group (β = 0.383; P < 0.001). The diagnostic performance of plasma GFAP in identifying Aβ+ was significantly higher in the WMH– group (area under the curve [AUC] = 0.896) than in the WMH+ group (AUC = 0.712, P = 0.008).DISCUSSION: The biomarker utility of plasma GFAP in detecting brain amyloid pathology is dependent on the severity of concomitant WMH.Highlight: Glial fibrillary acidic protein (GFAP)’s association with brain amyloid is unclear in populations with high cerebral small vessel disease (CSVD). Plasma GFAP was measured in a cohort with CSVD and brain amyloid. Plasma GFAP was better in detecting amyloid in patients with low CSVD versus high CSVD. Biomarker utility of GFAP in detecting brain amyloid depends on the severity of CSVD.

Ototoxicity is a major adverse effect of platinum-based chemotherapeutics and currently, there remains a lack of United States Food and Drug Administration-approved therapies to prevent or treat this problem. In our study, we examined the role of the sphingosine 1-phosphate receptor 2 (S1P₂) in attenuating cisplatin-induced ototoxicity in several different animal models and cell lines. We found that ototoxicity in S1P₂ knockout mice is dependent on reactive oxygen species (ROS) production and that S1P₂ receptor activation with a specific agonist, CYM-5478, significantly attenuates cisplatin-induced defects, including hair cell degeneration in zebrafish and prolonged auditory brainstem response latency in rats. We also evaluated the cytoprotective effect of CYM-5478 across different cell lines and showed that CYM-5478 protects neural-derived cell lines but not breast cancer cells against cisplatin toxicity. We show that this selective protection of CYM-5478 is due to its differential effects on key regulators of apoptosis between neural cells and breast cancer cells. Overall, our study suggests that targeting the S1P₂ receptor represents a promising therapeutic approach for the treatment of cisplatin-induced ototoxicity in cancer patients.