Predictive value of early decreased plasma ghrelin level for three-month cognitive deterioration in patients with mild traumatic brain injury

Proteomic discovery of prognostic protein biomarkers for persisting problems after mild traumatic brain injury

Some individuals with mild traumatic brain injury (mTBI), also known as concussion, have neuropsychiatric and physical problems that last longer than a few months. Symptoms following mTBI are not only impacted by the kind and severity of the injury but also by the post-injury experience and the individual's responses to it, making the persistence of mTBI particularly difficult to predict. We aimed to identify prognostic blood-based protein biomarkers predicting 6-month outcomes, in light of the clinical course after the injury, in a longitudinal mTBI cohort (N = 42). Among 420 target proteins quantified by multiple-reaction monitoring-mass spectrometry assays of blood samples, 31, 43, and 15 proteins were significantly associated with the poor recovery of neuropsychological symptoms at < 72 h, 1 week, and 1 month after the injury, respectively. Sequential associations among clinical assessments (depressive symptoms and cognitive function) affecting the 6-month outcomes were evaluated. Then, candidate biomarker proteins indirectly affecting the outcome via neuropsychological symptoms were identified. Using the identified proteins, prognostic models that can predict the 6-month outcome of mTBI were developed. These protein biomarkers established in the context of the clinical course of mTBI may have potential for clinical application.

Results of scoping review do not support mild traumatic brain injury being associated with a high incidence of chronic cognitive impairment: Commentary on McInnes et al. 2017

A recently published review of 45 studies concluded that approximately half of individuals who sustain a single mild traumatic brain injury (MTBI) experience long-term cognitive impairment (McInnes et al. Mild Traumatic Brain Injury (mTBI) and chronic cognitive impairment: A scoping review. PLoS ONE 2017;12:e0174847). Stratified by age, they reported that 50% of children and 58% of adults showed some form of cognitive impairment. We contend that the McInnes et al. review used a definition of "cognitive impairment" that was idiosyncratic, not applicable to individual patients or subjects, inconsistent with how cognitive impairment is defined in clinical practice and research, and resulted in a large number of false positive cases of cognitive impairment. For example, if a study reported a statistically significant difference on a single cognitive test, the authors concluded that every subject with a MTBI in that study was cognitively impaired-an approach that cannot be justified statistically or psychometrically. The authors concluded that impairment was present in various cognitive domains, such as attention, memory, and executive functioning, but they did not analyze or report the results from any of these specific cognitive domains. Moreover, their analyses and conclusions regarding many published studies contradicted the interpretations provided by the original authors of those studies. We re-reviewed all 45 studies and extracted the main conclusions from each. We conclude that a single MTBI is not associated with a high incidence of chronic cognitive impairment.

Ghrelin and Neurodegenerative Disorders-a Review

Ghrelin, the endogenous ligand of the growth hormone secretagogue receptor 1a (GHS-R1a), is a gut-derived, orexigenic peptide hormone that primarily regulates growth hormone secretion, food intake, and energy homeostasis. With the wide expression of GHS-R1a in extra-hypothalamic regions, the physiological role of ghrelin is more extensive than solely its involvement in metabolic function. Ghrelin has been shown to be involved in numerous higher brain functions, such as memory, reward, mood, and sleep. Some of these functions are disrupted in neurodegenerative disorders, including Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD). This link between ghrelin and these neurodegenerative diseases is supported by numerous studies. This review aims to provide a comprehensive overview of the most recent evidence of the novel neuromodulatory role of ghrelin in PD, AD, and HD. Moreover, the changes in circulating and/or central ghrelin levels that are associated with disease progression are also postulated to be a biomarker for clinical diagnosis and therapy.

Central acylated ghrelin improves memory function and hippocampal AMPK activation and partly reverses the impairment of energy and glucose metabolism in rats infused with β-amyloid

Ghrelin is a gastric hormone released during the fasting state that targets the hypothalamus where it induces hunger; however, emerging evidence suggests it may also affect memory function. We examined the effect of central acylated-ghrelin and DES-acetylated ghrelin (native ghrelin) on memory function and glucose metabolism in an experimentally induced Alzheimer's disease (AD) rat model. AD rats were divided into 3 groups and Non-AD rats were used as a normal-control group. Each rat in the AD groups had intracerebroventricular (ICV) infusion of β-amyloid (25-35; 16.8nmol/day) into the lateral ventricle for 3 days, and then the pumps were changed to infuse either acylated-ghrelin (0.2nmol/h; AD-G), DES-acylated ghrelin (0.2nmol/h; AD-DES-G), or saline (control; AD-C) for 3 weeks. The Non-AD group had ICV infusion of β-amyloid (35-25) which does not deposit in the hippocampus. During the next 3 weeks memory function, food intake, body weight gain, body fat composition, and glucose metabolism were measured. AD-C exhibited greater β-amyloid deposition compared to Non-AD-C, and AD-G suppressed the increased β-amyloid deposition and potentiated the phosphorylation AMPK. In addition, AD-G increased the phosphorylation GSK and decreased the phosphorylation of Tau in comparison to AD-C and AD-DES-G. Cognitive function, measured by passive avoidance and water maze tests, was much lower in AD-C than Non-AD-C whereas AD-G but not AD-DES-G prevented the decrease (p<0.021). Body weight gain was lower in AD-C group than Non-AD-C group without changing epididymal fat mass. AD-G reversed the decrease in body weight which was due to increased energy intake and decreased energy expenditure. The AD-G group exhibited a decrease in the second part of serum glucose levels during an oral glucose tolerance test (OGTT) compared to the AD-C and AD-DES-G group (p<0.009). However, area under the curve of insulin during the first part of OGTT was higher in AD-DES-G than other groups, whereas during the second part it was suppressed in AD-G as much as Non-AD. In conclusion, central acylated ghrelin in rats prevented the deterioration of memory function, and energy and glucose metabolisms were partially improved, possibly due to less β-amyloid accumulation. This research suggests that interventions such as intermittent fasting to facilitate sustained elevations of acyl-ghrelin should be investigated for cognitive and metabolic benefits, especially in person with early symptoms of memory impairment.