Does the insulin-like growth factor system interact with prostaglandins and proinflammatory cytokines during neurodegeneration?

Phenomenological and biological correlates of improved cognitive function in hospitalized elderly medical inpatients

Deterioration of cognitive ability is a recognized outcome following acute illness in older patients. Levels of circulating cytokines and APOE genotype have both been linked with acute illness-related cognitive decline. In this observational longitudinal study, consecutive admissions to an elderly medical unit of patients aged ≥70 years were assessed within 3 days and re-assessed twice weekly with a range of scales assessing cognitive function, functional status and illness severity. Cytokines and APOE genotype were measured in a subsample. Improvement was defined as either a 20% or three points increase in mini mental state examination (MMSE). From the 142 participants 55 (39%) experienced cognitive improvement, of which 30 (54.5%) had delirium while 25 had non-delirious acute cognitive disorder. Using bivariate statistics, subjects with more severe acute illness, lower insulin-like growth factor-I (IGF-I) levels and more severe delirium were more likely to experience a ≥20% improvement in MMSE scores. When the criterion of cognitive improvement was a 3 point improvement in MMSE, those with more severe delirium, females and older were more likely to be improved. Longitudinal analysis using any criterion of improvement indicated that improvement was significantly (p<.05) predicted by higher levels of IGF-I, lower levels of IL-1 (alpha and beta), lack of APOE epsilon 4 allele, and female gender. In conclusion, cognitive recovery during admission is not exclusively linked to delirium status, but reflects a range of factors. The character and relevance of non-delirious acute cognitive disorder warrants further study.

Insulin-like growth factor I and the pathogenesis of delirium: a review of current evidence

Delirium is a frequent complication in medically ill elderly patients that is associated with serious adverse outcomes including increased mortality. Delirium risk is linked to older age, dementia, and illness that involves activation of inflammatory responses. IGF-I is increasingly postulated as a key link between environmental influences on body metabolism with a range of neuronal activities and has been described as the master regulator of the connection between brain and bodily well-being. The relationships between IGF-I and ageing, cognitive impairment and inflammatory illness further support a possible role in delirium pathogenesis. Five studies of IGF-I in delirium were identified by a systematic review. These conflicting findings, with three of the five studies indicating an association between IGF-1 and delirium occurrence, may relate to the considerable methodological differences in these studies. The relevance of IGF-I and related factors to delirium pathogenesis can be clarified by future studies which account for these issues and other confounding factors. Such work can inform therapeutic trials of IGF-I and/or growth hormone administration.

Neuroinflammation, COX-2, and ALS—a dual role?

Although the root cause of many neurodegenerative diseases is unknown, neuroinflammation may play a key role in these types of disease, including amyotrophic lateral sclerosis (ALS). In the context of neurodegeneration, it is unclear if the disease is propagated through inflammation, or whether in contrast, evidence of inflammation reflects an attempt to protect against further cellular injury. Inflammatory pathways involving the cyclooxygenase (COX) enzymes and subsequent generation of prostaglandins are potential target sites for treatments to halt the progression of ALS. In the CNS, COX enzymes are localized to neurons, astrocytes, and microglia and can be induced under various conditions. In addition, there appears to be a dual role for the prostaglandin products of COX enzymes in the nervous system. Some prostaglandins promote the survival of neurons, while others promote apoptosis. In this review, the pathways of COX activity and prostaglandin production form the center of the debate regarding the dual nature of neuroinflammation. We will also discuss how this duality may affect future treatments for neurodegenerative diseases such as ALS.

Differential absorption and distribution of epidermal growth factor and insulin-like growth factor in diabetic NOD mice

Previous studies have shown that absorption of growth factors occurs through the gastrointestinal tract and the oral cavity. The non-obese diabetic (NOD) mouse, a model for spontaneous development of type 1 insulin-dependent diabetes (IDDM), was evaluated for the absorption and systemic distribution of growth factors. Radiolabeled epidermal growth factor (EGF) and insulin-like growth factor, type I (IGF-I), were administered by gavage into the stomach or by lozenge into the sublingual vasculature of either diabetic or nondiabetic mice. After a time-dependent uptake, the levels of absorption and distribution through the tissues were measured. A similar time course of EGF absorption following gavage administration was determined for NOD and C57BL/6 mice, with a maximum tissue distribution by 30-min post infusion. Diabetic NOD mice showed similar levels of IGF uptake and tissue distribution compared with nondiabetic NOD and normal healthy C57BL/6 mice, whether administered by gavage or sublingual lozenge. On the other hand, gavage uptake and tissue distribution of EGF was significantly higher in diabetic mice when compared to sublingual administration in nondiabetic NOD or C57BL/6 healthy control mice. These findings suggest that the overall potential uptake and distribution of saliva-derived growth factors in systemic wound-healing processes is retained with diabetes onset, and may offer a new avenue to treating this complication of diabetes.