Insulin-like growth factor-I, cognition and brain aging

The somatotroph pituitary gland function in high-aged multimorbid hospitalized patients with IGF-I deficiency

PURPOSE

It is unclear whether the age-related decline in the somatotropic axis stems from a reduced growth hormone (GH) production in the pituitary gland, or from a peripheral origin akin to an acquired GH resistance. With the help of a GHRH/arginine test, high-aged multimorbid hospitalized patients with IGF-I deficiency are to be tested to determine whether there is primarily a pituitary GH deficiency in the sense of a somatopause.

METHODS

Seventeen multimorbid patients (eleven men and six women) with a mean age of 82 years, with IGF-I concentrations below two standard deviations of 30-year-old men and women were identified. Patients suffered from a variety of common age-related stable diseases including coronary artery disease, chronic liver or kidney disease, chronic heart failure as well as acute conditions e.g., urosepsis or endocarditis. To assess the somatotropic axis they underwent a GHRH/arginine test. Results were evaluated using descriptive statistics.

RESULTS

In average, the peak concentration of GH after stimulation was 14.8 µg/L with a range from 2.76 to 47.4 µg/L. Taking into account both, gender and BMI (with a mean of 26.5 kg/m²) for each participant, the pituitary gland was adequately stimulated in 16 out of the 17 patients. No patient reported common side effects related to the GHRH/arginine test.

CONCLUSION

The somatotroph pituitary gland retains its secretory capacity in the advanced aged. Therefore, age does not seem to be the driving pacemaker for the functional decline of the somatotropic axis within the aged population.

Current Challenges in the Development of Platelet-Rich Plasma-Based Therapies

Nowadays, biological therapies are booming and more of these formulations are coming to the market. Platelet-rich plasma, or PRP, is one of the most widely used biological therapies due to its ease of obtention and autologous character. Most of the techniques to obtain PRP are focusing on new processes and methods of optimization. However, not enough consideration is being given to modify the molecular components of PRP to generate more effective formulations with the aim of improving PRP treatments. Therefore, this review covers different novel PRP-obtaining methods that attempt to modify the molecular composition of the plasma.

Endurance Exercise Training Attenuates the Waterpipe Smoke Inhaling-Induced Learning and Memory Impairment in Rats: Role of Neurotrophic Factors and Apoptotic System

INTRODUCTION

The increasing prevalence of waterpipe tobacco smoking (WTS) and its detrimental effects on memory function have been reported. This study was conducted to investigate the effect of moderate-intensity endurance exercise on the detrimental effects of WTS on learning and spatial memory in rats.

AIMS AND METHODS

Animals were divided into the Control group (CTL), the exercise group (Ex) which trained for 8 weeks, the WTS group (Wp) exposed to smoke inhalation (30 minutes per day, 5 days each week, and for 8 weeks), and the group that did exercise training and received waterpipe smoke together (Ex + Wp). Thereafter, learning and spatial memory were assessed by the Morris water maze test and hippocampal molecular measurements were done.

RESULTS

Waterpipe smoke significantly impaired learning and spatial memory, decreased expression of neurotrophic factors IGF-1 and BDNF (p < .01 and p < .05 vs. CTL group, respectively), increased BAX to BCL-2 ratio (p < .001 vs. CTL group) in hippocampal tissue, and increased the percent of damaged neurons in the hippocampal CA1 area (p < .05 vs. CTL group). Combination of exercise training with WTS prevented learning and spatial memory disturbances and recovered expression of neurotrophic factors IGF-1 (p < .05 vs. Wp group), decreased BAX to BCL-2 ratio (p < .001 vs. Wp group), and reduced percentage of damaged neurons (p < .05 vs. Wp group).

CONCLUSIONS

Findings suggest that moderate-intensity endurance exercise training can ameliorate learning and memory impairment caused by waterpipe smoke in rats. This effect partly results from increasing the expression of neurotrophic factors BDNF and IGF-1 and correcting pro/anti-apoptotic proteins balance in the hippocampal tissue.

IMPLICATIONS

The popularity of WTS especially among youth is increasing. We assessed the effect of hookah smoke with/without exercise on learning and memory. Hookah smoke leads to CA1-neural injury and impairs learning and memory in rats. A combination of exercise training with hookah smoke attenuates these complications. This positive effect of exercise is partially mediated by the balancing of brain-derived neurotrophic factor (BDNF) and Insulin-like growth factor-1 (IGF-1) and also the BAX to BCL-2 ratio, a significant predictor of cell susceptibility to apoptosis. Extrapolation of these positive findings to humans needs complementary studies.

Circulating insulin-like growth factor-1 and brain health: Evidence from 369,711 participants in the UK Biobank

BACKGROUND

The effects of insulin-like growth factor-1 (IGF-1) deficiency on cognitive decline have been consistently reported in animal studies, but the relationship between IGF-1 and human brain health remains controversial. Our study aimed to investigate the associations of serum IGF-1 concentrations with some brain-related disorders and neuroimaging features.

METHODS

This prospective study included 369,711 participants (55.8 ± 8.1 years) from the UK biobank who had serum IGF-1 measured and were free from brain-related disorders of interest - dementia, stroke, and Parkinson's disease (PD) - at enrollment (2006-2010). Restricted cubic splines and Cox proportional hazards models were used to detect the associations between IGF-1 concentrations and brain-related diseases. In addition, general linear regressions were applied to explore the relationship between IGF-1 concentrations and neuroimaging features (volumes of white matter, grey matter, and hippocampus and white matter hyperintensity) among a sub-sample of 36,458 participants with magnetic resonance imaging data collected since 2014.

RESULTS

During a median follow-up of 12.6 years, a total of 4,857 dementia, 6,240 stroke, and 2,116 PD cases were documented. The dose-response analyses yielded U-shaped relationships between IGF-1 concentrations and risks of dementia and stroke (P < 0.001 for non-linearity), with the lowest risks at 18 nmol/L and 26 nmol/L, respectively. A positive linear relationship was observed between IGF-1 concentrations and risk of PD (P = 0.163 for non-linearity). Moreover, neuroimaging analyses showed that higher IGF-1 concentrations were associated with greater volumes of white matter (β = 2.98 × 10-4, P < 0.001) and hippocampus (β = 3.37 × 10-4, P = 0.002) and smaller white matter hyperintensity (β = -3.12 × 10-3, P < 0.001).

CONCLUSIONS

Apart from the diverse associations with neuroimaging features, both low and high IGF-1 concentrations are associated with increased risks of dementia and stroke and higher IGF-1 concentrations are linked to a higher risk of PD, highlighting the potential of IGF-1 as a biomarker for risk stratification of brain health.

The Effects of Exercise for Cognitive Function in Older Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Physical exercise can slow down the decline of the cognitive function of the older adults, yet the review evidence is not conclusive. The purpose of this study was to compare the effects of aerobic and resistance training on cognitive ability.

METHODS

A computerized literature search was carried out using PubMed, Cochrane Library, Embase SCOPUS, Web of Science, CNKI (China National Knowledge Infrastructure), Wanfang, and VIP database to identify relevant articles from inception through to 1 October 2022. Based on a preliminary search of the database and the references cited, 10,338 records were identified. For the measured values of the research results, the standardized mean difference (SMD) and 95% confidence interval (CI) were used to synthesize the effect size.

RESULTS

Finally, 10 studies were included in this meta-analysis. Since the outcome indicators of each literature are different in evaluating the old cognitive ability, a subgroup analysis was performed on the included literature. The study of results suggests that aerobic or resistance training interventions significantly improved cognitive ability in older adults compared with control interventions with the Mini-Mental State Examination (MD 2.76; 95% CI 2.52 to 3.00), the Montreal Cognitive Assessment (MD 2.64; 95% CI 2.33 to 2.94), the Wechsler Adult Intelligence Scale (MD 2.86; 95% CI 2.25 to 3.47), the Wechsler Memory Scale (MD 9.33; 95% CI 7.12 to 11.54), the Wisconsin Card Sorting Test (MD 5.31; 95% CI 1.20 to 9.43), the Trail Making Tests (MD -8.94; 95% CI -9.81 to -8.07), and the Stroop Color and Word Test (MD -5.20; 95% CI -7.89 to -2.51).

CONCLUSION

Physical exercise improved the cognitive function of the older adults in all mental states. To improve cognitive ability, this meta-analysis recommended that patients perform at least moderate-intensity aerobic exercise and resistance exercise on as many days as possible in the week to comply with current exercise guidelines while providing evidence for clinicians.

Crosstalk between neurological, cardiovascular, and lifestyle disorders: insulin and lipoproteins in the lead role

Insulin resistance and impaired lipoprotein metabolism contribute to a plethora of metabolic and cardiovascular disorders. These alterations have been extensively linked with poor lifestyle choices, such as consumption of a high-fat diet, smoking, stress, and a redundant lifestyle. Moreover, these are also known to increase the co-morbidity of diseases like Type 2 diabetes mellitus and atherosclerosis. Under normal physiological conditions, insulin and lipoproteins exert a neuroprotective role in the central nervous system. However, the tripping of balance between the periphery and center may alter the normal functioning of the brain and lead to neurological disorders such as Alzheimer's disease, Parkinson's disease, stroke, depression, and multiple sclerosis. These neurological disorders are further characterized by certain behavioral and molecular changes that show consistent overlap with alteration in insulin and lipoprotein signaling pathways. Therefore, targeting these two mechanisms not only reveals a way to manage the co-morbidities associated with the circle of the metabolic, central nervous system, and cardiovascular disorders but also exclusively work as a disease-modifying therapy for neurological disorders. In this review, we summarize the role of insulin resistance and lipoproteins in the progression of various neurological conditions and discuss the therapeutic options currently in the clinical pipeline targeting these two mechanisms; in addition, challenges faced in designing these therapeutic approaches have also been touched upon briefly.

Cognitive Functioning and Cortical Brain Thickness in Acromegaly Patients: A Pilot study

OBJECTIVE

Cognitive effects in acromegaly patients are poorly understood and the mechanisms involved are still unclear. The aim of this study was to evaluate the cognitive function, depression, and quality of life of acromegaly patients treated with pegvisomant versus somatostatin analogues (SRLs) and to analyze the effect of the different treatments on cognition and possible structural brain changes.

METHODS

This cross-sectional study involved 23 acromegaly patients divided into two groups according to treatment modality: One group of 9 patients treated with pegvisomant and another group of 14 patients treated with SRLs. All participants underwent blood analysis, neuropsychological tests, depression tests, quality of life assessment, and 3-Tesla magnetic resonance imaging.

RESULTS

We found no significant differences between groups in the neuropsychological tests, depression or quality of life; nor in the whole-brain cortical thickness. In the SRL group, the volume of the thalamus correlated positively with executive function, a correlation not found in the pegvisomant group. In addition, the pegvisomant group had significantly higher levels of insulin than the SRL group.

CONCLUSIONS

In conclusion, in this pilot study, the type of pharmacological treatment in patients with acromegaly and good glycemic control did not influence the cognitive function and cortical brain thickness. However, pegvisomant could play a neuroprotective role on the thalamus that will have to be demonstrated with larger samples in future studies.

The Impact of Common Epidemiological Factors on Gray and White Matter Volumes in Magnetic Resonance Imaging-Is Prevention of Brain Degeneration Possible?

Introduction: The aim of the study was to evaluate the impact of multiple risk factors (age, diabetes, hypertension, hyperlipidemia, BMI, smoking, alcohol) on the gray and white matter volumes as well as on the burden of white matter hyperintensities (WMH).

Material and Methods: The study group consisted of 554 subjects (age range: 50–69 yrs, F/M: 367/187) recruited from the larger cohort of the Polish fraction of the Prospective Urban Rural Epidemiological (PURE) study. The participants answered questionnaires about their lifestyle, underwent physical and psychological examination (MoCA test), laboratory blood tests followed by brain MRI. Volumetric measurements of the total gray matter (GMvol), total white matter (WMvol) and WHM (WMHvol) normalized to the total intracranial volume were performed using the Computational Anatomy Toolbox 12 (CAT12) and Statistical Parametric Maps 12 (SPM12) based on 3D T1-weighted sequence. The influence of risk factors was assessed using multiple regression analysis before and after correction for multiple comparisons.

Results: Older age was associated with lower GMvol and WMvol, and higher WMHvol (p < 0.001). Smaller GMvol volume was associated with higher WMHvol (p < 0.001). Higher WMHvol was associated with hypertension (p = 0.01) and less significantly with hyperlipidemia (only before correction p = 0.03). Diabetes, abnormal BMI, smoking and alcohol intake did not have any significant impact on GMvol, WMvol or WMHvol (p > 0.05). MoCA score was not influenced by any of the factors.

Conclusions: Gray matter loss is strongly associated with the accumulation of WMH which seems to be potentially preventable by maintaining normal blood pressure and cholesterol levels.

Effects of treadmill exercise and sex hormones on learning, memory and hippocampal brain-derived neurotrophic factor levels in transient congenital hypothyroid rats

Transient thyroid function abnormalities at birth exhibit intellectual developmental and cognitive disorders in adulthood. Given the well-known effects of physical activity and sex hormones on cognitive functions and brain-derived neurotrophic factor (BDNF), the present study examined the effects of treadmill exercise, sex hormones, and the combined treatment on learning and memory and hippocampal BDNF levels in transient congenital hypothyroid rats. To induce hypothyroidism, 6-propyl-2-thiouracil was added to the drinking water from the 6th day of gestation to the 21st postnatal day (PND). From PNDs 28 to 47, female and male pup rats received 17β-estradiol and testosterone, respectively, and about 30 min later, they were forced to run on the treadmill for 30 min once a day. On PNDs 48-55, spatial learning and memory of all rats tested in the water maze, which followed by measurement of BDNF in the hippocampus. Results showed that developmental hypothyroidism induced significant deficits in spatial learning and memory and hippocampal BDNF in both male and female rats. In both male and female hypothyroid rats, exercise and exercise plus sex hormones, but not sex hormones alone alleviated learning and memory deficits and all treatments (exercise, sex hormones, and the combined treatment) increased hippocampal BDNF. These disconnects in the effects of exercise, sex hormones and the combined treatment on behavioral and neurochemical outcomes suggest that a neurochemical mechanism other than hippocampal BDNF might contribute in the ameliorating effects of exercise on learning and memory deficits induced by developmental thyroid hormone insufficiency.

GH Replacement in the Elderly: Is It Worth It?

Growth hormone (GH), once the age of linear growth is completed, continues to play a fundamental role for the human body. In adulthood, GH contributes to regulate muscle, cardiovascular and bone metabolism. The same happens in old age, although there is less data on the effect of GH in the elderly. Regardless the age of onset, a reduced quality of life (QoL), an increased cardiovascular risk and an accelerated age-related decline in physical strength have been demonstrated in the elderly with GH deficiency (EGHD). In adults with GH deficiency (AGHD), recent studies suggest a role of GH replacement therapy (GHrt) in improving lean/fat mass ratio, blood pressure, lipid profile, bone metabolism and QoL. Despite these recent studies, there is still a lack of randomized controlled trials proving these positive effects in EGHD. Moreover, the lack of a long-term positive outcome on mortality, and the cost of GHrt could often impact on treatment decision-making and lead to postpone or avoid the prescription. The aim of this mini-review is to summarize the available data on GHrt in EGHD, in order to highlight its weaknesses and strengths and to provide directions to clinicians that will help in the management of this specific set of patients.

Pituitary adenomas and neuropsychological status: a systematic literature review

Neurocognitive and psychological dysfunctions associated with pituitary adenomas (PAs) are clinically relevant, though probably under-reported. The aim of the current review is to provide an update on neuropsychological status, psychopathology, and perceived quality of life (QoL) in patients with PAs. A systematic research was performed in PubMed and Scopus in order to identify reports on neurocognitive, psychiatric, and psychological disorders in PAs. Prevalence of alterations, QoL evaluation, and used tests were also recorded. PRISMA guidelines were followed. Of 62,448 identified articles, 102 studies were included in the systematic review. The prevalence of neurocognitive dysfunctions was 15-83% in Cushing's Disease (CD), 2-33% in acromegaly, mostly affecting memory and attention. Memory was altered in 22% of nonfunctioning (NF) PAs. Worsened QoL was reported in 40% of CD patients. The prevalence of psychiatric disorders in CD reached 77% and in acromegaly 63%, mostly involving depression, followed by psychosis, and anxiety. The prevalence of psychopathology was up to 83% in CD, and 35% in acromegaly. Postoperative improvement in patients with CD was observed for: learning processes, overall memory, visuospatial skills, and language skills. Short-term memory and psychomotor speed improved in NFPAs. Postoperative improvement of QoL, somatic symptoms, obsessive-compulsive disorder, and coping strategies was seen in CD and acromegaly. Reports after radiotherapy are discordant. There is wide variability in used tests. PAs have been recently shown to be associated with altered neurocognitive and neuropsychological functions, as well as QoL. These data suggest the importance of a multidisciplinary evaluation for an optimal management.

Chronic adult-onset of growth hormone/IGF-I hypersecretion improves cognitive functions and LTP and promotes neuronal differentiation in adult rats

AIM

Besides their metabolic and endocrine functions, the growth hormone (GH) and its mediated factor, the insulin-like growth factor I (IGF-I), have been implicated in different brain functions, including neurogenesis. Long-lasting elevated GH and IGF-I levels result in non-reversible somatic, endocrine and metabolic morbidities. However, the subcutaneous implantation of the GH-secreting (GH-S) GC cell line in rats leads to the controllable over-secretion of GH and elevated IGF-I levels, allowing the experimental study of their short-term effects on brain functions.

METHODS

Adult rats were implanted with GC cells and checked 10 weeks later, when a GH/IGF-I-secreting tumour was already formed.

RESULTS

Tumour-bearing rats acquired different operant conditioning tasks faster and better than controls and tumour-resected groups. They also presented better retentions of long-term memories in the passive avoidance test. Experimentally evoked long-term potentiation (LTP) in the hippocampus was also larger and longer lasting in the tumour bearing than in the other groups. Chronic adult-onset of GH/IGF-I hypersecretion caused an acceleration of early progenitors, facilitating a faster neural differentiation, maturation and integration in the dentate gyrus, and increased the complexity of dendritic arbours and spine density of granule neurons.

CONCLUSION

Thus, adult-onset hypersecretion of GH/IGF-I improves neurocognitive functions, long-term memories, experimental LTP and neural differentiation, migration and maturation.

Effects of aging on the motor, cognitive and affective behaviors, neuroimmune responses and hippocampal gene expression

The known effects of aging on the brain and behavior include impaired cognition, increases in anxiety and depressive-like behaviors, and reduced locomotor activity. Environmental exposures and interventions also influence brain functions during aging. We investigated the effects of normal aging under controlled environmental conditions and in the absence of external interventions on locomotor activity, cognition, anxiety and depressive-like behaviors, immune function and hippocampal gene expression in C57BL/6 mice. Healthy mice at 4, 9, and 14 months of age underwent behavioral testing using an established behavioral battery, followed by cellular and molecular analysis using flow cytometry, immunohistochemistry, and quantitative PCR. We found that 14-month-old mice showed significantly reduced baseline locomotion, increased anxiety, and impaired spatial memory compared to younger counterparts. However, no significant differences were observed for depressive-like behavior in the forced-swim test. Microglia numbers in the dentate gyrus, as well as CD8+ memory T cells increased towards late middle age. Aging processes exerted a significant effect on the expression of 43 genes of interest in the hippocampus. We conclude that aging is associated with specific changes in locomotor activity, cognition, anxiety-like behaviors, neuroimmune responses and hippocampal gene expression.

Intranasal Insulin: a Treatment Strategy for Addiction

Addiction to substances such as alcohol, cocaine, opioids, and methamphetamine poses a continuing clinical and public challenge globally. Despite progress in understanding substance use disorders, challenges remain in their treatment. Some of these challenges include limited ability of therapeutics to reach the brain (blood-brain barrier), adverse systemic side effects of current medications, and importantly key aspects of addiction not addressed by currently available treatments (such as cognitive impairment). Inability to sustain abstinence or seek treatment due to cognitive deficits such as poor decision-making and impulsivity is known to cause poor treatment outcomes. In this review, we provide an evidenced-based rationale for intranasal drug delivery as a viable and safe treatment modality to bypass the blood-brain barrier and target insulin to the brain to improve the treatment of addiction. Intranasal insulin with improvement of brain cell energy and glucose metabolism, stress hormone reduction, and improved monoamine transmission may be an ideal approach for treating multiple domains of addiction including memory and impulsivity. This may provide additional benefits to enhance current treatment approaches.

Disparate Central and Peripheral Effects of Circulating IGF-1 Deficiency on Tissue Mitochondrial Function

Age-related decline in circulating levels of insulin-like growth factor (IGF)-1 is associated with reduced cognitive function, neuronal aging, and neurodegeneration. Decreased mitochondrial function along with increased reactive oxygen species (ROS) and accumulation of damaged macromolecules are hallmarks of cellular aging. Based on numerous studies indicating pleiotropic effects of IGF-1 during aging, we compared the central and peripheral effects of circulating IGF-1 deficiency on tissue mitochondrial function using an inducible liver IGF-1 knockout (LID). Circulating levels of IGF-1 (~ 75%) were depleted in adult male Igf1^f/f mice via AAV-mediated knockdown of hepatic IGF-1 at 5 months of age. Cognitive function was evaluated at 18 months using the radial arm water maze and glucose and insulin tolerance assessed. Mitochondrial function was analyzed in hippocampus, muscle, and visceral fat tissues using high-resolution respirometry O2K as well as redox status and oxidative stress in the cortex. Peripherally, IGF-1 deficiency did not significantly impact muscle mass or mitochondrial function. Aged LID mice were insulin resistant and exhibited ~ 60% less adipose tissue but increased fat mitochondrial respiration (20%). The effects on fat metabolism were attributed to increases in growth hormone. Centrally, IGF-1 deficiency impaired hippocampal-dependent spatial acquisition as well as reversal learning in male mice. Hippocampal mitochondrial OXPHOS coupling efficiency and cortex ATP levels (~ 50%) were decreased and hippocampal oxidative stress (protein carbonylation and F₂-isoprostanes) was increased. These data suggest that IGF-1 is critical for regulating mitochondrial function, redox status, and spatial learning in the central nervous system but has limited impact on peripheral (liver and muscle) metabolism with age. Therefore, IGF-1 deficiency with age may increase sensitivity to damage in the brain and propensity for cognitive deficits. Targeting mitochondrial function in the brain may be an avenue for therapy of age-related impairment of cognitive function. Regulation of mitochondrial function and redox status by IGF-1 is essential to maintain brain function and coordinate hippocampal-dependent spatial learning. While a decline in IGF-1 in the periphery may be beneficial to avert cancer progression, diminished central IGF-1 signaling may mediate, in part, age-related cognitive dysfunction and cognitive pathologies potentially by decreasing mitochondrial function.

Neuroprotective Properties of Linagliptin: Focus on Biochemical Mechanisms in Cerebral Ischemia, Vascular Dysfunction and Certain Neurodegenerative Diseases

Linagliptin is a representative of dipeptidyl peptidase 4 (DPP-4) inhibitors which are registered and used effectively in a treatment of diabetes mellitus type 2. They increase the levels of active forms of endogenous incretins such as GLP-1 and GIP by inhibiting their enzymatic decomposition. Scientific reports suggest beneficial effects of linagliptin administration via immunological and biochemical pathways involved in neuroprotective processes of CNS. Linagliptin’s administration leads to a decrease in the concentration of proinflammatory factors such as: TNF-α, IL-6 and increases the number of anti-inflammatory patrolling monocytes CX3CR1^bright. Significant reduction in Aβ42 level has been associated with the use of linagliptin implying potential application in Alzheimer’s disease. Linagliptin improved vascular functions by increasing production of nitric oxide (NO) and limiting concentration of apolipoprotein B. Linagliptin-induced decrease in macrophages infiltration may provide improvement in atheromatous plaque stabilization. Premedication with linagliptin increases neuron’s survival after stroke and augments neuronal stem cells proliferation. It seems to be connected with SDF-1α/CXCR4 signaling pathway. Linagliptin prevented abnormal proliferation and migration of rat brain microvascular endothelial cells in a state of hypoperfusion via SIRT1/HIF-1α/VEGF pathway. The article presents a summary of the studies assessing neuroprotective properties of linagliptin with special emphasis on cerebral ischemia, vascular dysfunction and neurodegenerative diseases.

Associations between inflammatory and neurological markers with quality of life and well-being in older adults

OBJECTIVES

Stressful experiences, poor self-rated health, and negative emotional states have been implicated with higher levels of inflammatory markers and lower levels of neurotrophic factors in some healthy adults and clinical populations, but these relationships are unclear in the elderly. This study aimed to identify the associations between systemic inflammatory and neurological markers with well-being and health-related quality of life (HR-QoL) in independently living elderly people.

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

A total of 268 men and women aged ≥65 years living independently in retirement communities in Melbourne, Australia.

MEASURES

Questionnaires were used to assess HR-QoL [Short Form (SF)-36 version 2] and well-being (Personal Wellbeing Index). Serum inflammatory cytokines [interleukin (IL)-4, IL-6, IL-1β, IL-8, IL-10, tumor necrosis factor (TNF)-α, and high sensitive C-reactive protein (hs-CRP)] were standardised to Z-scores and used to calculate pro- and anti-inflammatory composite score and an overall composite inflammatory index. Plasma levels of the neurological markers amyloid β (1-40) and amyloid β (1-42), brain derived neurotrophic factor (BDNF), insulin-like growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF), were also assessed.

RESULTS

No significant associations were found between any inflammatory or neurological marker with HR-OoL or well-being, with the exception that lower perceptions of the HR-QoL vitality subscale were associated with higher levels of hs-CRP [unstandardized beta-coefficient (β): -1.50; 95% CI: -2.53, -0.46; P = 0.004] and Z-scores in the pro-inflammatory composite score (β = -2.06; 95% CI: -3.49, -0.62; P = 0.005).

CONCLUSIONS/IMPLICATIONS

In elderly people residing in independent living retirement communities, there was no consistent evidence indicating that circulating inflammatory or neurological markers were associated with the key physical or mental HR-QoL domains or overall well-being. This suggests that these biomarkers may not be effective predictors in relatively healthy communities, and may be more beneficial in frail or clinical populations. Clinical Trials registry: Australian New Zealand Clinical Trials Registry (ACTRN12613001161718). http://www.anzctr.org.au/.

Evaluating the effects of the novel GLP-1 analogue liraglutide in Alzheimer's disease: study protocol for a randomised controlled trial (ELAD study)

BACKGROUND

Liraglutide is a glucagon-like peptide-1 (GLP-1) analogue currently approved for type 2 diabetes and obesity. Preclinical evidence in transgenic models of Alzheimer's disease suggests that liraglutide exerts neuroprotective effects by reducing amyloid oligomers, normalising synaptic plasticity and cerebral glucose uptake, and increasing the proliferation of neuronal progenitor cells. The primary objective of the study is to evaluate the change in cerebral glucose metabolic rate after 12 months of treatment with liraglutide in participants with Alzheimer's disease compared to those who are receiving placebo.

METHODS/DESIGN

ELAD is a 12-month, multi-centre, randomised, double-blind, placebo-controlled, phase IIb trial of liraglutide in participants with mild Alzheimer's dementia. A total of 206 participants will be randomised to receive either liraglutide or placebo as a daily injection for a year. The primary outcome will be the change in cerebral glucose metabolic rate in the cortical regions (hippocampus, medial temporal lobe, and posterior cingulate) from baseline to follow-up in the treatment group compared with the placebo group. The key secondary outcomes are the change from baseline to 12 months in z scores for clinical and cognitive measures (Alzheimer's Disease Assessment Scale-Cognitive Subscale and Executive domain scores of the Neuropsychological Test Battery, Clinical Dementia Rating Sum of Boxes, and Alzheimer's Disease Cooperative Study-Activities of Daily Living) and the incidence and severity of treatment-emergent adverse events or clinically important changes in safety assessments. Other secondary outcomes are 12-month change in magnetic resonance imaging volume, diffusion tensor imaging parameters, reduction in microglial activation in a subgroup of participants, reduction in tau formation and change in amyloid levels in a subgroup of participants measured by tau and amyloid imaging, and changes in composite scores using support machine vector analysis in the treatment group compared with the placebo group.

DISCUSSION

Alzheimer's disease is a leading cause of morbidity worldwide. As available treatments are only symptomatic, the search for disease-modifying therapies is a priority. If the ELAD trial is successful, liraglutide and GLP-1 analogues will represent an important class of compounds to be further evaluated in clinical trials for Alzheimer's treatment.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01843075 . Registration 30 April 2013.

Reduction in IGF1 mRNA in the Human Subependymal Zone During Aging

The cell proliferation marker, Ki67 and the immature neuron marker, doublecortin are both expressed in the major human neurogenic niche, the subependymal zone (SEZ), but expression progressively decreases across the adult lifespan (PMID: 27932973). In contrast, transcript levels of several mitogens (transforming growth factor α, epidermal growth factor and fibroblast growth factor 2) do not decline with age in the human SEZ, suggesting that other growth factors may contribute to the reduced neurogenic potential. While insulin like growth factor 1 (IGF1) regulates neurogenesis throughout aging in the mouse brain, the extent to which IGF1 and IGF family members change with age and relate to adult neurogenesis markers in the human SEZ has not yet been determined. We used quantitative polymerase chain reaction to examine gene expression of seven IGF family members [IGF1, IGF1 receptor, insulin receptor and high-affinity IGF binding proteins (IGFBPs) 2, 3, 4 and 5] in the human SEZ across the adult lifespan (n=50, 21-103 years). We found that only IGF1 expression significantly decreased with increasing age. IGFBP2 and IGFBP4 expression positively correlated with Ki67 mRNA. IGF1 expression positively correlated with doublecortin mRNA, whereas IGFBP2 expression negatively correlated with doublecortin mRNA. Our results suggest IGF family members are local regulators of neurogenesis and indicate that the age-related reduction in IGF1 mRNA may limit new neuron production by restricting neuronal differentiation in the human SEZ.

The Protective and Restorative Effects of Growth Hormone and Insulin-Like Growth Factor-1 on Methadone-Induced Toxicity In Vitro

Evidence to date suggests that opioids such as methadone may be associated with cognitive impairment. Growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are suggested to be neuroprotective and procognitive in the brain and may therefore counteract these effects. This study aims to explore the protective and restorative effects of GH and IGF-1 in methadone-treated cell cultures. Primary cortical cell cultures were harvested from rat fetuses and grown for seven days in vitro. To examine the protective effects, methadone was co-treated with or without GH or IGF-1 for three consecutive days. To examine the restorative effects, methadone was added for the first 24 h, washed, and later treated with GH or IGF-1 for 48 h. At the end of each experiment, mitochondrial function and membrane integrity were evaluated. The results revealed that GH had protective effects in the membrane integrity assay and that both GH and IGF-1 effectively recovered mitochondrial function and membrane integrity in cells pretreated with methadone. The overall conclusion of the present study is that GH, but not IGF-1, protects primary cortical cells against methadone-induced toxicity, and that both GH and IGF-1 have a restorative effect on cells pretreated with methadone.

The effect of resistance training on cognitive function in the older adults: a systematic review of randomized clinical trials

BACKGROUND

Aging is often accompanied by decline in aspects of cognitive function. Cognitive decline has harmful effects on living independence and general health. Resistance training is seen as a promising intervention to prevent or delay cognitive deterioration, yet the evidence from reviews is less consistent.

AIM

To assess the effect of resistance training on cognition in the elderly with and without mild cognitive impairment and to provide an up-to-date overview.

METHODS

A search was conducted using PUBMED, Web of science, MEDLINE, CINAHL, Cochrane Library, EMBASE, Wan Fang, and China National Knowledge Infrastructure. The searches were limited to articles published in English or Chinese from January 2010 to September 2017.

RESULTS

The search returned 2634 records, of which 12 articles were included in the systematic review. Main results showed that resistance training had positive effects on the executive function and global cognitive function of the elderly, and short-term interventions had little positive effect on memory and attention. Secondary results demonstrated that there was a significant benefit of triweekly resistance training in global cognitive function and biweekly in executive function of the elderly.

CONCLUSIONS

Resistance training had positive effects on the executive cognitive ability and global cognitive function among the elderly; however, it had a weak-positive impact on memory. No significant improvement was found in attention. Triweekly resistance training has a better effect on general cognitive ability than biweekly. Further studies are needed focusing on the development and application of resistance training among the elderly.

Insulin-Like Growth Factor Binding Protein 2 Is Associated With Biomarkers of Alzheimer's Disease Pathology and Shows Differential Expression in Transgenic Mice

There is increasing evidence that metabolic dysfunction plays an important role in Alzheimer's disease (AD). Brain insulin resistance and subsequent impairment of insulin and insulin-like growth factor (IGF) signaling are associated with the neurodegenerative and clinical features of AD. Nevertheless, how the brain insulin/IGF signaling system is altered in AD and the effects of these changes on AD pathobiology are not well understood. IGF binding protein 2 (IGFBP-2) is an abundant cerebral IGF signaling protein and there is early evidence suggesting it associates with AD biomarkers. We evaluated the relationship between protein levels of IGFBP-2 with cerebrospinal fluid (CSF) biomarkers and neuroimaging markers of AD progression in 300 individuals from across the AD spectrum. CSF IGFBP-2 levels were correlated with CSF tau levels and brain atrophy in non-hippocampal regions. To further explore the role of IGFBP2 in tau pathobiology, we evaluated the expression of IGFBP2 in different human and mouse brain cell types and brain tissue from two transgenic mouse models: the P301L-tau model of tauopathy and TASTPM model of AD. We observed significant differential expression of IGFBP2 in both transgenic mouse models relative to wild-type mice in cortex but not in hippocampus. In both humans and mice, IGFBP2 is most highly expressed in astrocytes. Taken together, our findings suggest that IGFBP-2 may be linked to tau pathology and provides further evidence for a relationship between metabolic dysregulation and neurodegeneration. Our results also raise the possibility that this relationship may extend beyond neurons.

Physical exercise, IGF-1 and cognition A systematic review of experimental studies in the elderly

One of hypothetical mechanisms related to cognition is exercise-induced IGF-1.

A Putative Mechanism of Age-Related Synaptic Dysfunction Based on the Impact of IGF-1 Receptor Signaling on Synaptic CaMKIIα Phosphorylation

Insulin-like growth factor 1 receptor (IGF-1R) signaling regulates the activity and phosphorylation of downstream kinases linked to inflammation, neurodevelopment, aging and synaptic function. In addition to the control of Ca2+ currents, IGF-1R signaling modulates the activity of calcium-calmodulin-dependent kinase 2 alpha (CaMKIIα) and mitogen activated protein kinase (MAPK/ErK) through multiple signaling pathways. These proteins (CaMKIIα and MAPK) regulate Ca2+ movement and long-term potentiation (LTP). Since IGF-1R controls the synaptic activity of Ca2+, CaMKIIα and MAPK signaling, the possible mechanism through which an age-dependent change in IGF-1R can alter the synaptic expression and phosphorylation of these proteins in aging needs to be investigated. In this study, we evaluated the relationship between an age-dependent change in brain IGF-1R and phosphorylation of CaMKIIα/MAPK. Furthermore, we elucidated possible mechanisms through which dysregulated CaMKIIα/MAPK interaction may be linked to a change in neurotransmitter processing and synaptic function. Male C57BL/6 VGAT-Venus mice at postnatal days 80 (P80), 365 and 730 were used to study age-related neural changes in two brain regions associated with cognitive function: hippocampus and prefrontal cortex (PFC). By means of high throughput confocal imaging and quantitative immunoblotting, we evaluated the distribution and expression of IGF-1, IGF-1R, CaMKIIα, p-CaMKIIα, MAPK and p-MAPK in whole brain lysate, hippocampus and cortex. Furthermore, we compared protein expression patterns and regional changes at P80, P365 and P730. Ultimately, we determined the relative phosphorylation pattern of CaMKIIα and MAPK through quantification of neural p-CaMKIIα and p-MAPK/ErK, and IGF-1R expression for P80, P365 and P730 brain samples. In addition to a change in synaptic function, our results show a decrease in neural IGF-1/IGF-1R expression in whole brain, hippocampus and cortex of aged mice. This was associated with a significant upregulation of phosphorylated neural MAPK (p-MAPK) and decrease in total brain CaMKIIα (i.e., CaMKIIα and p-CaMKIIα) in the aged brain. Taken together, we showed that brain aging is associated with a change in neural IGF-1/IGF-1R expression and may be linked to a change in phosphorylation of synaptic kinases (CaMKIIα and MAPK) that are involved in the modulation of LTP.

Insulin-like Growth Factor 1 (IGF-1) as a marker of cognitive decline in normal ageing: A review

Insulin-like Growth Factor 1 (IGF-1) and its signaling pathway play a primary role in normal growth and ageing, however serum IGF-1 is known to reduce with advancing age. Recent findings suggest IGF-1 is essential for neurogenesis in the adult brain, and this reduction of IGF-1 with ageing may contribute to age-related cognitive decline. Experimental studies have shown manipulation of the GH/GF-1 axis can slow rates of cognitive decline in animals, making IGF-1 a potential biomarker of cognition, and/or its signaling pathway a possible therapeutic target to prevent or slow age-related cognitive decline. A systematic literature review and qualitative narrative summary of current evidence for IGF-1 as a biomarker of cognitive decline in the ageing brain was undertaken. Results indicate IGF-1 concentrations do not confer additional diagnostic information for those with cognitive decline, and routine clinical measurement of IGF-1 is not currently justified. In cases of established cognitive impairment, it remains unclear whether increasing circulating or brain IGF-1 may reverse or slow down the rate of further decline. Advances in neuroimaging, genetics, neuroscience and the availability of large well characterized biobanks will facilitate research exploring the role of IGF-1 in both normal ageing and age-related cognitive decline.

Trajectories of plasma IGF-1, IGFBP-3, and their ratio in the Mayo Clinic Study of Aging

Insulin-like growth factor 1 (IGF-1) has been associated with osteoporosis, cardiovascular disease, cancer, neurodegenerative diseases, and mortality in middle and older aged adults. Cross-sectionally, IGF-1 decreases with age and levels of IGF-1 are markedly different between individuals. However, little is known about intra-individual trajectories of IGF-1. We examined baseline and serial measures of plasma total IGF-1, IGF binding protein (IGFBP)-3, and their ratio, which is a proxy for bioavailable IGF-1, among 1618 adults, aged 50-95, enrolled in the Mayo Clinic Study of Aging. At baseline, IGF-1 and IGFBP-3 were strongly correlated (r = 0.62, p < 0.001). Total IGF-1 and IGFBP-3 decreased across age, while the ratio of IGF-1/IGFBP-3 increased across age. This pattern was consistent across ages at baseline and intra-individually over an average 2.3 years follow-up (range = 10 months-5.6 years). In age-adjusted linear regression models, baseline levels of total IGF-1, IGFBP-3, and IGF-1/IGFBP-3 varied by participant characteristics (sex, BMI, gait speed), medical comorbidities (Charlson comorbidity index score, hypertension, diabetes, and cardiovascular disease), and hormone replacement therapy use in women. High interclass correlation coefficients (ICCs) suggest little intra-individual variability in levels of total IGF-1 (ICC = 0.84), IGFBP-3 (ICC = 0.88), and IGF-1/IGFBP-3 (ICC = 0.81) over time. In mixed effects models that specified age as a time scale, men showed greater decreases in total IGF-1 and IGFBP-3 with age, while more comorbidities and decreasing gait speed were associated with increasing IGFBP-3. In sex-stratified models, trajectories of total IGF-1, IGFBP-3, and IGF-1/IGFBP-3, as a function of participant demographics, health characteristics, and medical conditions, differed between men and women. These results suggest that change in levels of plasma total IGF-1, IGFBP-3, and IGF-1/IGFBP-3 are associated with demographics, health characteristics, and medical conditions, and that the trajectories of change differ by sex. Future research should consider how IGF-1 and IGFBP-3 might be useful in research or clinic, paying particular attention to how sex may impact levels as a function of demographics, health characteristics, and medical conditions.

Evaluation of depressive mood and cognitive functions in patients with acromegaly under somatostatin analogue therapy

AIMS

Acromegaly is caused by a pituitary adenoma that releases excess growth hormone (GH) and a concomitant increase in insulin-like growth factor 1 (IGF-1). Acromegaly results not only in phenotypic changes, but also in neurologic complications as peripheral neuropathy and cognitive dysfunction. This study aimed to compare depressive mood and cognitive function in patients with acromegaly and in healthy controls as well as to determine the factors underlying cognitive dysfunction in the acromegalic patients.

MATERIALS AND METHODS

This study included 42 patients with acromegaly that were receiving somatostatin analogue therapy and 44 healthy controls. Memory, attention, visuospatial function, inhibitory function, abstract thinking, verbal fluency, and depressive mood were measured in the patients and controls.

RESULTS

Patients with acromegaly had lower learning (p = 0.01), planning (p = 0.03), complex attention and inhibitory function (p = 0.04) scores than the controls. There was no significant difference in depressive mood between the patients and controls (p > 0.05). Gamma knife radiosurgery did not negatively affect cognitive function (p > 0.05).

CONCLUSION

The present findings show that acromegaly negatively affects learning, attention, and planning.

Serum IGF-1 is associated with cognitive functions in early, drug-naïve Parkinson's disease

OBJECTIVE

Cognitive deficits are common in Parkinson's disease (PD) since the early stages and many patients eventually develop dementia. Yet, occurrence of dementia in PD is unpredictable. Evidence supports the hypothesis that insulin-like growth factor-1 (IGF-1) is involved in cognitive deficits. Our aim was to evaluate the relationship between serum IGF-1 levels and neuropsychological scores in a large cohort of drug-naïve PD patients during the earliest stages of the disease.

METHODS

Serum IGF-1 levels were determined in 405 early, drug-naïve PD patients and 191 healthy controls (HC) enrolled in the Parkinson's Progression Markers Initiative (PPMI). The association between serum IGF-1 levels and neuropsychological scores was evaluated with linear regression analysis.

RESULTS

IGF-1 levels were similar in PD and HC. In PD patients the lowest IGF-1 quartile was a predictor of lower performances at the Semantic Fluency task (β = -3.46, 95%CI: -5.87 to -1.01, p = 0.005), the Symbol Digit Modalities Score (β = -2.09, 95%CI: -4.02 to -0.15, p = 0.034), and Hopkins Verbal Learning Test Retention (β = -0.05, 95%CI: -0.09 to -0.009, p = 0.019).

CONCLUSIONS

Lower serum IGF-1 levels are associated to poor performances in cognitive tasks assessing executive function, attention and verbal memory in a large cohort of early PD patients. Follow-up studies are warranted to assess if IGF-1 is related to the development of dementia in PD.

Oxygen-sensitive regulation and neuroprotective effects of growth hormone-dependent growth factors during early postnatal development

Perinatal hypoxia severely disrupts metabolic and somatotrophic development, as well as cerebral maturational programs. Hypoxia-inducible transcription factors (HIFs) represent the most important endogenous adaptive mechanisms to hypoxia, activating a broad spectrum of growth factors that contribute to cell survival and energy homeostasis. To analyze effects of systemic hypoxia and growth hormone (GH) therapy (rhGH) on HIF-dependent growth factors during early postnatal development, we compared protein (using ELISA) and mRNA (using quantitative RT PCR) levels of growth factors in plasma and brain between normoxic and hypoxic mice (8% O2, 6 h; postnatal day 7, P7) at P14. Exposure to hypoxia led to reduced body weight ( P < 0.001) and length ( P < 0.04) compared with controls and was associated with significantly reduced plasma levels of mouse GH ( P < 0.01) and IGF-1 ( P < 0.01). RhGH abrogated these hypoxia-induced changes of the GH/IGF-1 axis associated with normalization of weight and length gain until P14 compared with controls. In addition, rhGH treatment increased cerebral IGF-1, IGF-2, IGFBP-2, and erythropoietin mRNA levels, resulting in significantly reduced apoptotic cell death in the hypoxic, developing mouse brain. These data indicate that rhGH may functionally restore hypoxia-induced systemic dysregulation of the GH/IGF-1 axis and induce upregulation of neuroprotective, HIF-dependent growth factors in the hypoxic developing brain.

Beta-hydroxy-beta-methylbutyrate (HMB) ameliorates age-related deficits in water maze performance, especially in male rats

Beta-hydroxy-beta-methylbutyrate (HMB) is commonly supplemented to maintain muscle in elderly and clinical populations and has potential as a nootropic. Previously, we have shown that in both male and female rats, long-term HMB supplementation prevents age-related dendritic shrinkage within the medial prefrontal cortex (mPFC) and improves cognitive flexibility and working memory performance that are both age- and sex-specific. In this study, we further explore the cognitive effects by assessing visuospatial learning and memory with the Morris water maze. Female rats were ovariectomized at 11months of age to model human menopause. At 12months of age, male and female rats received relatively short- or long-term (1- or 7-month) dietary HMB (450mg/kg/dose) supplementation twice a day prior to testing. Spatial reference learning and memory was assessed across four days in the water maze with four trials daily and a probe trial on the last day. Consistent with previous work, there were age-related deficits in water maze performance in both sexes. However, these deficits were ameliorated in HMB-treated males during training and in both sexes during probe trial performance. Thus, HMB supplementation prevented the age-related decrement in water maze performance, especially in male rats.

General health status and intelligence scores of children of mothers with acromegaly do not differ from those of healthy mothers

PURPOSE

To determine the physical status and intelligence scores of children of acromegalic mothers and to compare them with those of children from mothers without acromegaly.

METHODS

Six women with acromegaly who became pregnant under follow-up between 2010 and 2014 and their 16 children (group A) were assessed and compared with 16 children of healthy women (group B) and 15 children of women with prolactinoma (group C). The physical examinations of children were performed by the department of pediatric endocrinology and intelligence quotient (IQ) testing was undertaken by adult and pediatric psychiatry departments, using appropriate scales for their ages.

RESULTS

Six of the 16 children (girls/boys: 7/9) were born after the diagnosis of acromegaly. Five of the 6 pregnancies occured when the patients were taking somatostatin analogs, none continued taking the drugs during pregnancy. The mean IQ of groups A, B, and C were 106.4 ± 12.5, 105.3 ± 12.5, and 103.2 ± 16.1 respectively (p > 0.05). The mean ages, birth percentiles, recent weight and height standard deviation scores were similar between groups (p > 0.05). Two siblings from group A and 1 child from group B were large for gestational age at birth. At recent follow-up, two children from group A were found tall for their age and one from group C was short for his age and was placed under the care of pediatric endocrinology clinic.

CONCLUSIONS

Pregnancies in acromegaly seems to be uneventful and the general health status and IQ scores of children from women with and without acromegaly were found similar.

Exercise-induced neuroprotective effects on neurodegenerative diseases: the key role of trophic factors

Age-related neurodegenerative disorders, like Alzheimer's or Parkinson's disease, are becoming a major issue to public health care. Currently, there is no effective pharmacological treatment to address cognitive impairment in these patients. Here, we aim to explore the role of exercise-induced trophic factor enhancement in the prevention or delay of cognitive decline in patients with neurodegenerative diseases. There is a significant amount of evidence from animal and human studies that links neurodegenerative related cognitive deficits with changes on brain and peripheral trophic factor levels. Several trials with elderly individuals and patients with neurodegenerative diseases report exercise induced cognitive improvements and changes on trophic factor levels including BDNF, IGF-I, among others. Further studies with healthy aging and clinical populations are needed to understand how diverse exercise interventions produce different variations in trophic factor signaling. Genetic profiles and potential confounders regarding trophic factors should also be addressed in future trials.

Voxel-based statistical analysis of brain metabolism in patients with growth hormone deficiency after traumatic brain injury

OBJECTIVE

The aim of this study was to investigate the regional cerebral metabolism related to growth hormone deficiency (GHD) after traumatic brain injury (TBI) using F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) images.

METHODS

Twenty-three patients with diffuse axonal injury following TBI were enrolled. They underwent brain F-18 FDG PET study and an insulin tolerance test (ITT). According to the results of ITT, they were divided into two groups: patients with GHD and subjects with TBI but normal Growth Hormone (GH). Voxel-based statistical analysis was performed and the regional cerebral glucose metabolism shown on F-18 FDG PET from 10 patients with GHD was compared with those from 13 patients without GHD. Analysis was performed using SPM2 to identify regions where decreased changes in regional cerebral glucose metabolism were significantly related to GHD.

RESULTS

Compared with subjects with TBI but normal GH, patients with GHD after TBI showed decreased cerebral glucose metabolism in the Left superior frontal gyrus, Right angular gyrus, Right superior temporal gyrus, Left inferior temporal gyrus, Left anterior and middle cingulate gyrus and Right anterior and middle cingulate gyrus. (p_uncorrected < 0.005).

CONCLUSIONS

The findings are suggestive of the brain region influenced by GHD. These cortical areas are involved in regulation of intellectual function, executive function and working memory.

The Effects of Early Life Lead Exposure on the Expression of Glycogen Synthase Kinase-3β and Insulin-like Growth Factor 1 Receptor in the Hippocampus of Mouse Pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of GSK-3β and IGF1R in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1, 0.5, and 1%, respectively. On the 21st postnatal day, the Pb levels were determined by graphite furnace atomic absorption spectrometry. The expression of GSK-3β and IGF1R in hippocampus was examined by immunohistochemistry and Western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than those of the control group (P < 0.05). Compared with the control group, the expression of GSK-3β was increased in lead-exposed groups (P < 0.05), but the expression of IGF1R was decreased (P < 0.05). The high expression of GSK-3β and low expression of IGF1R in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Aberrant insulin signaling in Alzheimer's disease: current knowledge

Alzheimer's disease (AD) is the most common form of dementia affecting elderly people. AD is a multifaceted pathology characterized by accumulation of extracellular neuritic plaques, intracellular neurofibrillary tangles (NFTs) and neuronal loss mainly in the cortex and hippocampus. AD etiology appears to be linked to a multitude of mechanisms that have not been yet completely elucidated. For long time, it was considered that insulin signaling has only peripheral actions but now it is widely accepted that insulin has neuromodulatory actions in the brain. Insulin signaling is involved in numerous brain functions including cognition and memory that are impaired in AD. Recent studies suggest that AD may be linked to brain insulin resistance and patients with diabetes have an increased risk of developing AD compared to healthy individuals. Indeed insulin resistance, increased inflammation and impaired metabolism are key pathological features of both AD and diabetes. However, the precise mechanisms involved in the development of AD in patients with diabetes are not yet fully understood. In this review we will discuss the role played by aberrant brain insulin signaling in AD. In detail, we will focus on the role of insulin signaling in the deposition of neuritic plaques and intracellular NFTs. Considering that insulin mitigates beta-amyloid deposition and phosphorylation of tau, pharmacological strategies restoring brain insulin signaling, such as intranasal delivery of insulin, could have significant therapeutic potential in AD treatment.

Insulin-like growth factors and related proteins in plasma and cerebrospinal fluids of HIV-positive individuals

Background

Clinically significant dysregulation of the insulin-like growth factor (IGF) family proteins occurs in HIV-infected individuals, but the details including whether the deficiencies in IGFs contribute to CNS dysfunction are unknown.

Methods

We measured the levels of IGF1, IGF2, IGFBP1, IGFBP2, and IGF2 receptor (IGF2R) in matching plasma and cerebrospinal fluid (CSF) samples of 107 HIV+ individuals from CNS HIV Antiretroviral Therapy Effects Research (CHARTER) and analyzed their associations with demographic and disease characteristics, as well as levels of several soluble inflammatory mediators (TNFα, IL-6, IL-10, IL-17, IP-10, MCP-1, and progranulin). We also determined whether IGF1 or IGF2 deficiency is associated with HIV-associated neurocognitive disorder (HAND) and whether the levels of soluble IGF2R (an IGF scavenging receptor, which we also have found to be a cofactor for HIV infection in vitro) correlate with HIV viral load (VL).

Results

There was a positive correlation between the levels of IGF-binding proteins (IGFBPs) and those of inflammatory mediators: between plasma IGFBP1 and IL-17 (β coefficient 0.28, P = 0.009), plasma IGFBP2 and IL-6 (β coefficient 0.209, P = 0.021), CSF IGFBP1 and TNFα (β coefficient 0.394, P < 0.001), and CSF IGFBP2 and TNF-α (β coefficient 0.14, P < 0.001). As IGFBPs limit IGF availability, these results suggest that inflammation is a significant factor that modulates IGF protein expression/availability in the setting of HIV infection. However, there was no significant association between HAND and the reduced levels of plasma IGF1, IGF2, or CSF IGF1, suggesting a limited power of our study. Interestingly, plasma IGF1 was significantly reduced in subjects on non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy (ART) compared to protease inhibitor-based therapy (174.1 ± 59.8 vs. 202.8 ± 47.3 ng/ml, P = 0.008), suggesting a scenario in which ART regimen-related toxicity can contribute to HAND. Plasma IGF2R levels were positively correlated with plasma VL (β coefficient 0.37, P = 0.021) and inversely correlated with current CD4+ T cell counts (β coefficient −0.04, P = 0.021), supporting our previous findings in vitro.

Conclusions

Together, these results strongly implicate (1) an inverse relationship between inflammation and IGF growth factor availability and the contribution of IGF deficiencies to HAND and (2) the role of IGF2R in HIV infection and as a surrogate biomarker for HIV VL.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0288-6) contains supplementary material, which is available to authorized users.

First clinical data of the neuroprotective effects of nasal insulin application in patients with Alzheimer's disease

Previous reviews have outlined the important role of insulin in the brain, and the observation that insulin signaling is desensitized in patients with Alzheimer's disease (AD). Because insulin is used to treat diabetes and insulin desensitization in the periphery, this motivated the design and execution of clinical pilot trials in patients with AD and mild cognitive impairment. Because insulin has powerful effects on blood sugar levels, a new technique was used by which insulin is applied as a spray. This method avoids high levels of insulin in the periphery and makes use of the transport system, via the nasal epithelium, into the brain. First trials in healthy subjects showed improvement in attention and memory tasks, and confirmed the concept that insulin signaling plays an important role in neuronal function and cognition. In a series of small clinical trials in patients with mild cognitive impairment/AD, nasal application of insulin or long-lasting insulin analogs showed improvements in memory tasks, cerebrospinal fluid biomarkers, and in a fluorodeoxyglucose positron emission tomographic study. In a more recent trial, two patient subgroups were identified, in which the insulin-resistant group improved after drug treatment whereas a subgroup that did not show insulin desensitization deteriorated. This highlights the need to conduct additional studies and demonstrates clearly that the hypothesis that insulin signaling plays in important role in cognition and AD has merit, and that this is a worthwhile target that shows great promise for future drug developments that improve insulin signaling. Insulin itself may not be the best choice, and other drugs that have been developed to treat diabetes that do not enhance insulin desensitization may be a better choice.

Differential effects of prenatal stress in female 5-HTT-deficient mice: towards molecular mechanisms of resilience

Prenatal stress (PS) exposure is known to increase the risk of developing emotional disorders like major depression in later life. However, some individuals do not succumb to adversity following developmental stress exposure, a phenomenon referred to as resilience. To date, the molecular mechanisms explaining why some subjects are vulnerable and others more resilient to PS are far from understood. Recently, we have shown that the serotonin transporter (5-HTT) gene may play a modulating role in rendering individuals susceptible or resilient to PS. However, it is not clear which molecular players are mediating the interaction between PS and the 5-Htt genotype in the context of vulnerability and resilience to PS. For this purpose, we performed a microarray study with the help of Affymetrix GeneChip® Mouse Genome 430 2.0 Array, in which we separated wild-type and heterozygous 5-Htt-deficient (5-Htt+/-) PS offspring into susceptible and resilient offspring according to their performance in the forced swim test. Performance-oriented LIMMA analysis on the mRNA expression microarray data was followed by subsequent Spearman's correlation analysis linking the individual qRT-PCR mRNA expression data to various anxiety- and depression-related behavioral and neuroendocrine measures. Results indicate that, amongst others, Fos-induced growth factor (Figf), galanin receptor 3 (Galr3), growth hormone (Gh) and prolactin (Prl) were differentially expressed specifically in resilient offspring when compared to controls, and that the hippocampal expression of these genes showed several strong correlations with various measures of the hypothalamus-pituitary-adrenal axis (re)activity. In conclusion, there seems to be an intricate interplay between the expression of Figf, Galr3, Gh and Prl and neuroendocrine regulation, which may be critical in mediating resilience to PS exposure. More insight into the exact role of these molecular players may significantly enhance the development of new treatment strategies for stress-related emotional disorders.

Recombinant human growth hormone improves cognitive capacity in a pain patient exposed to chronic opioids

During recent decades, the increasing use of opioids for chronic non-cancer pain has raised concerns regarding tolerance, addiction, and importantly cognitive dysfunction. Current research suggests that the somatotrophic axis could play an important role in cognitive function. Administration of growth hormone (GH) to GH-deficient humans and experimental animals has been shown to result in significant improvements in cognitive capacity. In this report, a patient with cognitive disabilities resulting from chronic treatment with opioids for neuropathic pain received recombinant human growth hormone (rhGH) replacement therapy. A 61-year-old man presented with severe cognitive dysfunction after long-term methadone treatment for intercostal neuralgia and was diagnosed with GH insufficiency by GH releasing hormone-arginine testing. The effect of rhGH replacement therapy on his cognitive capacity and quality of life was investigated. The hippocampal volume was measured using magnetic resonance imaging, and the ratios of the major metabolites were calculated using proton magnetic resonance spectroscopy. Cognitive testing revealed significant improvements in visuospatial cognitive function after rhGH. The hippocampal volume remained unchanged. In the right hippocampus, the N-acetylaspartate/creatine ratio (reflecting nerve cell function) was initially low but increased significantly during rhGH treatment, as did subjective cognitive, physical and emotional functioning. This case report indicates that rhGH replacement therapy could improve cognitive behaviour and well-being, as well as hippocampal metabolism and functioning in opioid-treated patients with chronic pain. The idea that GH could affect brain function and repair disabilities induced by long-term exposure to opioid analgesia is supported.

Central effects of GLP-1: new opportunities for treatments of neurodegenerative diseases

The incretin hormone glucagon-like peptide 1 (GLP-1) has many effects in the body. It is best known for the 'incretin effect', facilitating insulin release from the pancreas under hyperglycaemic conditions. Building on this, GLP-1 mimetics have been developed as a treatment for type 2 diabetes. In the course of monitoring of patients, it has become apparent that GLP-1 mimetics have a range of other physiological effects in the body. In preclinical trials, a substantial body of evidence has been built that these mimetics have neuroprotective and anti-inflammatory effects. GLP-1 also has very similar growth-factor-like properties to insulin, which is presumably the underlying basis of the neuroprotective effects. In preclinical studies of Alzheimer's disease (AD), Parkinson's disease (PD), stroke and other neurodegenerative disorders, it has been shown that most GLP-1 mimetics cross the blood-brain barrier and show impressive neuroprotective effects in numerous studies. In animal models of AD, GLP-1 mimetics such as exendin-4, liraglutide and lixisenatide have shown protective effects in the CNS by reducing β-amyloid plaques, preventing loss of synapses and memory impairments, and reducing oxidative stress and the chronic inflammatory response in the brain. In animal models of PD, exendin-4 showed protection of dopaminergic neurons in the substantia nigra and prevention of dopamine loss in the basal ganglia while preserving motor control. These encouraging findings have spawned several clinical trials, some of which have shown encouraging initial results. Therefore, GLP-1 mimetics show great promise as a novel treatment for neurodegenerative conditions.

Changes in cerebrospinal fluid and blood plasma levels of IGF-II and its binding proteins in Alzheimer's disease: an observational study

Background

The Insulin-like Growth Factor (IGF)-related system is implicated in neuroregeneration and cell repair, as well as regulating lifespan. IGF-II, one component of this system, has also been found to affect memory functions in a rat model. In this study we explored changes in the IGF-related system in patients with Alzheimer’s disease (AD), including changes in IGF-II levels.

Methods

We measured blood plasma and cerebrospinal fluid (CSF) levels of IGF-I, IGF-II, IGFBP-2 and IGFBP-3 in 72 healthy controls and 92 patients with AD.

Results

We found significantly lower blood plasma levels of IGF-II and IGFBP-3 in patients with AD, compared with controls. The levels of IGF-II and IGFBP-2 were significantly elevated in the CSF from patients with AD. We also found correlations between established CSF biomarkers for AD (tau and P-tau) and components of the IGF system.

Conclusions

CSF and blood plasma levels of IGF-II and some of its binding proteins are changed in patients with AD. Further investigation into this area may unravel important clues to the nature of this disease.

Associations between depressive symptoms and memory deficits vary as a function of insulin-like growth factor (IGF-1) levels in healthy older adults

OBJECTIVES

Accumulating evidence suggests an adverse association between depressive symptoms and cognition, but a positive association between insulin-like growth factor (IGF)-1 and cognition. The present study examined the influence of IGF-1 in the relationship between depressive symptoms and learning and memory.

METHODS

A cross-sectional study of 94 healthy fit older adults. Blood was collected and plasma IGF-1 was measured. Depressive symptoms were assessed with the Geriatric Depression Scale (GDS), and learning and memory were assessed using the Rey Auditory Verbal Learning Test (AVLT).

RESULTS

Among older adults with lower IGF-1 levels, higher depressive symptoms scores were associated with lower AVLT delayed recall and recognition. Older adults with higher IF-1 levels showed no associations between depressive symptoms and memory.

CONCLUSIONS

The association between depressive symptoms and cognition is stronger among older adults with lower levels of circulating IGF-1. Further validation studies on groups with depression or different stages of cognitive impairment are needed. IGF-1 may be a novel intervention target for slowing cognitive decline in older adults with depressive symptoms.

Insulin, incretins and other growth factors as potential novel treatments for Alzheimer's and Parkinson's diseases

Recently, it has been shown that in patients with AD (Alzheimer's disease) and, to some degree, in patients with PD (Parkinson's disease) insulin signalling is impaired. This finding has initiated a range of research projects that showed remarkable improvements using treatments that initially had been developed to treat diabetes. Pre-clinical studies showed good neuroprotective effects when applying insulin or long-lasting analogues of incretin peptides. In transgenic animal models of AD and PD, analogues of the incretin GLP-1 (glucagon-like peptide 1) prevented neurodegenerative processes and improved neuronal and synaptic functionality in AD and PD. Amyloid plaque load and synaptic loss as well as cognitive impairment had been ameliorated in AD models, and dopaminergic loss of transmission and motor function was reversed in models of PD. On the basis of these promising findings, several clinical trials are being conducted with the first encouraging clinical results being published. In several pilot studies in AD patients, the nasal application of insulin showed encouraging effects on cognition and biomarkers. A pilot study in PD patients testing a GLP-1 receptor agonist that is currently on the market as a treatment for Type 2 diabetes also showed encouraging effects. Several other clinical trials are currently ongoing in AD patients. The present review summarizes the range of neuroprotective effects that these drugs have demonstrated and emphasizes the great promise that this approach has in providing novel treatments that have protective and even restorative properties that no current drug treatment can offer.

The effects of repeat traumatic brain injury on the pituitary in adolescent rats

Adolescents are one of the highest groups at risk for sustaining both traumatic brain injury (TBI) and repeat TBI (RTBI). Consequences of endocrine dysfunction following TBI have been routinely explored in adults, but studies in adolescents are limited, and show an incidence rate of endocrine dysfunction in 16-61% in patients, 1-5 years after injury. Similar to in adults, the most commonly affected axis is growth hormone (GH) and insulin-like growth hormone 1 (IGF-1). Despite TBI being the primary cause of morbidity and mortality among the pediatric population, there are currently no experimental studies specifically addressing the occurrence of pituitary dysfunction in adolescents. The present study investigated whether a sham, single injury or four repeat injuries (24 h interval) delivered to adolescent rats resulted in disruption of the GH/IGF-1 axis. Circulating levels of basal GH and IGF-1 were measured at baseline, 24 h, 72 h, 1 week, and 1 month after injury, and vascular permeability of the pituitary gland was quantified via Evans Blue dye extravasation. Changes in weight and length of animals were measured as a potential consequence of GH and IGF-1 disruption. The results from the current study demonstrate that RTBI results in significant acute and chronic decreases in circulation of GH and IGF-1, reduction in weight gain and growth, and an increase in Evans Blue dye extravasation in the pituitary compared with sham and single injury animals. RTBI causes significant disruption of the GH/IGF-1 axis that may ultimately affect normal cognitive and physical development during adolescence.

Higher serum insulin-like growth factor-1 is associated with better cognitive performance in persons with mild cognitive impairment

BACKGROUND

Serum insulin-like growth factor-1 (IGF-1) is a mitogenic peptide involved in the regulation of cell proliferation, differentiation, and apoptosis in a wide variety of cells and tissues. Recent research suggests higher circulating levels of IGF-1 are associated with better cognitive performance in healthy older adults and in early stages of Alzheimer's disease, although the cognitive profile associated with elevated IGF-1 has not been examined in persons with mild cognitive impairment.

METHODS

Thirty-one participants (age: 83.71 ± 3.59 years; 58% women) with mild cognitive impairment completed neuropsychological testing and 12-hour fasting blood draw to assess serum IGF-1.

RESULTS

Partial correlations between serum IGF-1 and neuropsychological measures were conducted, adjusting for insulin, body mass index, and age. Higher IGF-1-values were associated with better global cognition (Modified Mini Mental State Exam: r = 0.39, P = 0.04) and verbal list learning (Hopkins Verbal Learning Test learning: r = 0.38, P = 0.05), Hopkins Verbal Learning Test free recall (r = 0.41, P = 0.03), and Hopkins Verbal Learning Test recognition discriminability (r = 0.46, P = 0.01). A similar trend emerged for executive function as tested by the Frontal Assessment Battery (r = 0.33, P = 0.09).

CONCLUSION

Results suggest higher levels of serum IGF-1 are associated with better cognitive performance in persons with mild cognitive impairment, particularly on tests of learning and memory. These findings suggest IGF-1 may be neuroprotective not only in healthy older adults, but also in adults in the earliest stages of Alzheimer's disease. Further investigation is needed to clarify the nature of this relationship, particularly prospective studies.