Klotho protein concentrations as a function of sex, APOE, family history or Alzheimer’s disease biomarker status in an at‐risk cohort

Abstract

AbstractBackgroundThe KLOTHO gene encodes for a longevity and neuroprotective klotho hormone. The non‐human animal literature suggests that higher levels of klotho promote resilience against Alzheimer’s disease (AD)‐related neuropathology. Human carriers of the functionally advantageous KLOTHO KL‐VS variant have higher serum klotho levels and show attenuation of proteins involved in AD‐related neuropathology (β‐amyloid (Aβ) and tau). How klotho protein relates to AD neuropathology or risk factors (APOE gene, family history, sex) is less well understood.MethodThe sample consists of 318 middle‐aged and older, cognitively normal adults (MeanAge(SD) = 63.8(6.66); range = 44‐80; 65% female) from the Wisconsin Registry for Alzheimer’s Prevention and the Wisconsin Alzheimer’s Disease Research Center studies. Stratifications of the sample into positive vs. negative AD biomarker status were made using local reference cutpoints measured via cerebrospinal fluid (CSF: Aβ40, Aβ42, total tau, phosphorylated tau, and their respective ratios to Aβ42) or positron emission tomography (PET; β‐amyloid: 11C‐Pittsburgh compound B(PiB); tau: 18F‐MK‐6240). We examined whether baseline serum klotho protein concentrations differed based on AD biomarker status (whether positive (i.e., abnormal) for β‐amyloid or tau) or characteristics related to AD risk.ResultThere were no significant differences in baseline serum klotho concentrations between those considered positive vs. negative for β‐amyloid or tau whether by CSF or PET (P’s>0.19). Females (844 pg/mL) compared to males (765 pg/mL) had significantly higher serum klotho concentrations (F (1,317) = 7.37; P = 0.007). No differences were observed based on APOE4 status or parental AD history (P’s>0.31).ConclusionWe confirm sex‐dependent difference in serum klotho favoring females. No significant differences in serum klotho protein concentrations were observed based on APOE4, AD family history or AD biomarker status (+/‐) in our cohort of middle‐aged and older, cognitively normal adults, albeit enriched for AD risk. While this may seem in contrast to a recent case‐control study (Grøntvedt, 2022) suggesting that klotho protein is associated with β‐amyloid and tau burden and clinical stages of AD, that study measured circulating klotho in plasma and included participants with MCI and AD diagnoses. Our results add to the growing KLOTHO literature and highlight the need for better understanding of the underlying mechanisms for its effects.