Insulin-like growth factor-1 and progression of motor symptoms in early, drug-naïve Parkinson's disease

Association between serum IGF‑1 levels and non-motor symptoms in Parkinson's disease

AIMS

We aimed to measure serum insulin-like growth factor 1 (IGF-1) levels in Parkinson's disease (PD) patients and assess their correlation with non-motor symptoms (NMS).

BACKGROUND

Emerging evidence suggests that abnormal levels of IGF-1 play a crucial role in the development of PD.

OBJECTIVE

Further systematic research is needed to explore the potential roles of abnormal IGF-1 levels in NMS of PD.

METHODS

The study enrolled a total of 129 PD patients and 130 healthy controls (HCs). Within the PD cohort, 74 patients were classified as being in the early stage, while 55 were in the moderate stage.

RESULTS

This study found no significant difference in serum IGF-1 levels between PD patients and HC. Further analysis revealed no significant difference in IGF-1 levels between early-stage PD and those in the moderate stages. Linear regression analysis indicated a significant association between serum IGF-1 levels and Nonmotor Symptom Scale (NMSS) scores in PD patients. Linear regression analysis revealed significant correlations between serum IGF-1 levels and general cognitive function, information processing speed, and executive function in PD patients. Furthermore, lower serum IGF-1 levels were associated with fatigue in PD patients.

CONCLUSIONS

In summary, our study suggests a potential association between serum IGF-1 levels and specific NMS in patients with PD. These findings highlight the importance of long-term follow-up studies to determine whether serum biomarkers can serve as valuable tools for early detection of NMS in PD.

Physical activity and neurotrophic factors as potential drivers of neuroplasticity in Parkinson's Disease: A systematic review and meta-analysis

Parkinson's disease (PD) is a neurodegenerative disorder, characterized by motor and non-motor symptoms, that still lacks of a disease-modifying treatment. Consistent evidence proved the benefits of physical therapy on motor and non-motor symptoms in PD patients, leading the scientific community to propose physical activity as disease-modifying therapy for PD and suggesting the involvement of neurotrophic factors (NFs) as key mediators of neuroplasticity. However, the lack of standardized exercise training and methodological flaws of clinical trials have limited the evidence demonstrating the exercise-induced changes in serum and plasma neurotrophic factors concentration. A systematic search, covering 20 years of research in this field and including randomized and non-randomized controlled trials (RCTs and non-RCTs), which reported changes in serum and plasma NFs after a specific intervention, were reviewed. Pooled effect sizes (p-ESs) and 95% confidence intervals (95%CIs) were calculated using a random effects model with R software. A total of 18 articles, of which exercise programs of interventions were codified in terms of type, intensity and duration adopting a standardisation methodology, were included in the systematic review. Six papers, describing the effect of different training programs on BDNF and IGF-1 levels, were included and independently analysed in two meta-analyses. Quantitative analysis for BDNF indicated a statistically significant improvement in serum concentration of PD patients (MD: 5.99 ng/mL; 95%IC: 0.15 -11.83; I2 = 77%) performing physical activity compared with control conditions in RCTs. Preliminary evidence supported the hypothesis that a moderate intensity aerobic exercise (MIAE) would be necessary to induce the changes in NFs. However, sensitivity analysis of meta-analysis and the few studies included in subgroup analysis did not support these results. Alongside, meta-analysis followed by sensitivity analysis revealed a potential change in serum IGF-1 (MD: 33.47 ng/mL; 95%IC: 8.09-58.85) in PD patients performing physical activity with respect controls in RCT studies. Considering the limited evidence to support or refute the increase in NFs levels in PD patients performing physical activity, there is a need to develop a rigorous controlled randomized trial, with standardization for loading intensity of physical activity, greater sample size, and a correct stratification of PD patients to establish a well-defined correlation between physical activity and NFs levels.

Effects of rasagiline combined with levodopa and benserazide hydrochloride on motor function and homocysteine and IGF-1 levels in elderly patients with Parkinson's disease

BACKGROUND

During the course of their illness, people with Parkinson's disease may see changes in their insulin-like growth factor (IGF-1) and serum homocysteine (Hcy) indices. In this study, patients with intermediate to severe Parkinson's disease were examined for how Resagiline and levodopa and benserazide hydrochloride affected their motor performance, serum levels of homocysteine (Hcy), and insulin-like growth factor (IGF-1).

METHODS

From June 2020 to December 2021, a total of 100+ cases of Parkinson's patients over 60 years old in the middle and late stages of Parkinson's were seen in the outpatient and inpatient departments of the Third People's Hospital of Chengdu City and had a detailed observation record, and according to the inclusion criteria, the patients who met the criteria were randomly grouped into a clinical observation group and a control group. The subjects in the control group received only levodopa and benserazide hydrochloride treatment, while the observation group was treated with Resagiline in combination with the clinical control group. The total treatment observation period was 1 year for both groups, and the motor function and serum Hcy and IGF-1 indexes of both groups were compared after the end of treatment.

RESULTS

We randomly and evenly grouped 64 patients who met the requirements of the inclusion criteria into a clinical observation group and a control group, each with 32 patients, from among 168 patients over 60 years of age with detailed observation records in the middle and late stages of Parkinson's. After the 1-year observation period, we found that the total effective rate after treatment in the clinical observation group (93.75%) and significantly higher than that in the control group (68.75%) (P < 0.05); after 1 year of treatment, the UPDRS score decreased in both groups, and the observation group was significantly lower than the control group (P < 0.05); after treatment, serum Hcy decreased and IGF-1 increased in both groups, and the observation group was higher than the control group mean values (P < 0.05).

CONCLUSIONS

In patients with Parkinson's disease who are in the middle and late stages of the disease, the administration of Resagiline combined with levodopa and benserazide hydrochloride can significantly lower the body's serum Hcy level, significantly raise IGF-1 levels, and significantly improve motor function in patients with Parkinson's disease. It can also have significant therapeutic effects.

Cyclic Glycine-Proline (cGP) Normalises Insulin-Like Growth Factor-1 (IGF-1) Function: Clinical Significance in the Ageing Brain and in Age-Related Neurological Conditions

Insulin-like growth factor-1 (IGF-1) function declines with age and is associated with brain ageing and the progression of age-related neurological conditions. The reversible binding of IGF-1 to IGF binding protein (IGFBP)-3 regulates the amount of bioavailable, functional IGF-1 in circulation. Cyclic glycine-proline (cGP), a metabolite from the binding site of IGF-1, retains its affinity for IGFBP-3 and competes against IGF-1 for IGFBP-3 binding. Thus, cGP and IGFBP-3 collectively regulate the bioavailability of IGF-1. The molar ratio of cGP/IGF-1 represents the amount of bioavailable and functional IGF-1 in circulation. The cGP/IGF-1 molar ratio is low in patients with age-related conditions, including hypertension, stroke, and neurological disorders with cognitive impairment. Stroke patients with a higher cGP/IGF-1 molar ratio have more favourable clinical outcomes. The elderly with more cGP have better memory retention. An increase in the cGP/IGF-1 molar ratio with age is associated with normal cognition, whereas a decrease in this ratio with age is associated with dementia in Parkinson disease. In addition, cGP administration reduces systolic blood pressure, improves memory, and aids in stroke recovery. These clinical and experimental observations demonstrate the role of cGP in regulating IGF-1 function and its potential clinical applications in age-related brain diseases as a plasma biomarker for-and an intervention to improve-IGF-1 function.

Risk of Neurodegenerative Diseases in Patients With Acromegaly: A Cohort Study

BACKGROUND AND OBJECTIVES

A few recent studies have reported an association between insulin-like growth factor-1 (IGF-1) and neurodegenerative disease, but there was no report on any association between acromegaly and neurodegenerative disease. We investigated whether the risk of Alzheimer disease (AD), Parkinson disease, and other neurodegenerative diseases was increased among patients with acromegaly using nationwide data of Korea.

METHODS

We studied the association between acromegaly and Parkinson disease and dementia in 1,611 patients with acromegaly and controls (age-matched and sex-matched 8,055 participants with no diagnosis of acromegaly) from the National Health Insurance System database between 2006 and 2016 with a mean follow-up period of 7.34 years. Cox proportional hazards regression analysis was used to assess the risk of all outcomes in patients with acromegaly compared with controls with adjusting for age, sex, household income, place, type 2 diabetes, hypertension, and dyslipidemia.

RESULTS

The average age of the patients with acromegaly and the controls was 54.16 years (40.4% men). The incidence rate of Parkinson disease in patients with acromegaly (1.54 per 1,000 person-years) was significantly higher than that in the control group (0.55 per 1,000 person-years) (log-rank test p = 0.001). Acromegaly was associated with a higher risk of Parkinson disease (hazard ratio [HR] = 2.609, 95% CI: 1.410-2.609) than the control. In addition, acromegaly was associated with a higher risk of all-cause dementia (HR = 2.299, 95% CI: 1.362-3.881), Alzheimer disease (HR = 2.228, 95% CI: 1.191-4.168), and non-AD dementia (HR = 6.553, 95% CI: 1.754-24.482) than the control during the first 3 years after diagnosis and treatment. In subgroup analysis, diabetes was associated with higher risk of all-cause dementia (P for interaction = 0.028) in patients with acromegaly compared with controls.

DISCUSSION

Our study results suggest that acromegaly is associated with neurodegenerative disease. Further study is needed on the association between IGF-1/growth hormone level and neurodegenerative disease.

Neuroprotective effects of insulin-like growth factor-2 in 6-hydroxydopamine-induced cellular and mouse models of Parkinson's disease

Skin-derived precursor Schwann cells have been reported to play a protective role in the central nervous system. The neuroprotective effects of skin-derived precursor Schwann cells may be attributable to the release of growth factors that nourish host cells. In this study, we first established a cellular model of Parkinson's disease using 6-hydroxydopamine. When SH-SY5Y cells were pretreated with conditioned medium from skin-derived precursor Schwann cells, their activity was greatly increased. The addition of insulin-like growth factor-2 neutralizing antibody markedly attenuated the neuroprotective effects of skin-derived precursor Schwann cells. We also found that insulin-like growth factor-2 levels in the peripheral blood were greatly increased in patients with Parkinson's disease and in a mouse model of Parkinson's disease. Next, we pretreated cell models of Parkinson's disease with insulin-like growth factor-2 and administered insulin-like growth factor-2 intranasally to a mouse model of Parkinson's disease induced by 6-hydroxydopamine and found that the level of tyrosine hydroxylase, a marker of dopamine neurons, was markedly restored, α-synuclein aggregation decreased, and insulin-like growth factor-2 receptor down-regulation was alleviated. Finally, in vitro experiments showed that insulin-like growth factor-2 activated the phosphatidylinositol 3 kinase (PI3K)/AKT pathway. These findings suggest that the neuroprotective effects of skin-derived precursor Schwann cells on the central nervous system were achieved through insulin-like growth factor-2, and that insulin-like growth factor-2 may play a neuroprotective role through the insulin-like growth factor-2 receptor/PI3K/AKT pathway. Therefore, insulin-like growth factor-2 may be an useful target for Parkinson's disease treatment.

Insulin-like growth factor in Parkinson's disease is related to nonmotor symptoms and the volume of specific brain areas

BACKGROUND

Insulin-like growth factor 1 (IGF-1) plays a protective role in Parkinson's disease (PD). To date, studies on the relationship between plasma IGF-1 levels and nonmotor symptoms and brain gray matter volume in PD patients have been rare.

METHODS

A Siemens automatic chemical analyzer was used to determine plasma IGF-1 levels in 55 healthy controls and 119 PD patients, including those at the early (n = 67) and middle-late (n = 52) stages of the disease. Evaluation of motor symptoms and nonmotor symptoms in PD patients was assessed by the associated scales. Image acquisition in 65 PD patients was performed using a Siemens MAGNETOM Prisma 3 T magnetic resonance imaging (MRI) scanner.

RESULTS

Plasma IGF-1 levels in early-stage PD patients were higher than those in healthy controls, and plasma IGF-1 levels in early-stage PD patients were higher than those in middle-late-stage PD patients. Plasma IGF-1 levels were significantly negatively correlated with anxiety, depression and cognitive dysfunction. Receiver operating characteristic (ROC) curve assessment confirmed that plasma IGF-1 levels had good predictive accuracy for PD with anxiety, depression and cognitive dysfunction. Furthermore, plasma IGF-1 levels were significantly positively correlated with volumes in the insula, caudate and anterior cingulate.

CONCLUSIONS

This study shows that plasma IGF-1 levels were correlated with the nonmotor symptoms of anxiety, depression and cognitive dysfunction and the volume in specific brain areas. This is the first report examining the relationships between plasma IGF-1 and clinical manifestations and imaging features in PD patients.

Diabetes mellitus and Parkinson's disease: dangerous liaisons between insulin and dopamine

The relationship between diabetes mellitus and Parkinson's disease has been described in several epidemiological studies over the 1960s to date. Molecular studies have shown the possible functional link between insulin and dopamine, as there is strong evidence demonstrating the action of dopamine in pancreatic islets, as well as the insulin effects on feeding and cognition through central nervous system mechanism, largely independent of glucose utilization. Therapies used for the treatment of type 2 diabetes mellitus appear to be promising candidates for symptomatic and/or disease-modifying action in neurodegenerative diseases including Parkinson's disease, while an old dopamine agonist, bromocriptine, has been repositioned for the type 2 diabetes mellitus treatment. This review will aim at reappraising the different studies that have highlighted the dangerous liaisons between diabetes mellitus and Parkinson's disease.

A Sensor-Based Perspective in Early-Stage Parkinson's Disease: Current State and the Need for Machine Learning Processes

Parkinson's disease (PD) is a progressive neurodegenerative disorder associated with dysfunction of dopaminergic neurons in the brain, lack of dopamine and the formation of abnormal Lewy body protein particles. PD is an idiopathic disease of the nervous system, characterized by motor and nonmotor manifestations without a discrete onset of symptoms until a substantial loss of neurons has already occurred, enabling early diagnosis very challenging. Sensor-based platforms have gained much attention in clinical practice screening various biological signals simultaneously and allowing researchers to quickly receive a huge number of biomarkers for diagnostic and prognostic purposes. The integration of machine learning into medical systems provides the potential for optimization of data collection, disease prediction through classification of symptoms and can strongly support data-driven clinical decisions. This work attempts to examine some of the facts and current situation of sensor-based approaches in PD diagnosis and discusses ensemble techniques using sensor-based data for developing machine learning models for personalized risk prediction. Additionally, a biosensing platform combined with clinical data processing and appropriate software is proposed in order to implement a complete diagnostic system for PD monitoring.

Impaired brain insulin signalling in Parkinson's disease

AIMS

Brain insulin resistance (i.e., decreased insulin/insulin-like growth factor-1 [IGF-1] signalling) may play a role in the pathophysiology of Parkinson's disease (PD), and several anti-diabetic drugs have entred clinical development to evaluate their potential disease-modifying properties in PD. A measure of insulin resistance is the amount of the downstream messenger insulin receptor substrate-1 that is phosphorylated at serine residues 312 (IRS-1pS312) or 616 (IRS-1pS616). We assessed IRS-1pS312 and IRS-1pS616 expression in post-mortem brain tissue of PD patients and a preclinical rat model based on viral-mediated expression of A53T mutated human α-synuclein (AAV2/9-h-α-synA53T).

METHODS

IRS-1pS312 and IRS-1pS616 staining intensity were determined by immunofluorescence in both neurons and glial cells in the substantia nigra pars compacta (SNc) and putamen of PD patients and controls without known brain disease. We further explored a possible relation between α-synuclein aggregates and brain insulin resistance in PD patients. Both insulin resistance markers were also measured in the SNc and striatum of AAV2/9-h-α-synA53T rats.

RESULTS

We found higher IRS-1pS312 staining intensity in nigral dopaminergic neurons and a trend for higher IRS-1pS312 staining intensity in putaminal neurons of PD patients. We observed no differences for IRS-1pS616 staining intensity in neurons or IRS-1pS312 staining intensity in glial cells. IRS-1pS312 showed high co-localisation within the core of nigral Lewy bodies. Like PD patients, AAV2/9-h-α-synA53T rats showed higher IRS-1pS312 staining intensity in the SNc and striatum than controls, whereas IRS-1pS616 was not different between groups.

CONCLUSIONS

Our results provide evidence for brain insulin resistance in PD and support the rationale for repurposing anti-diabetic drugs for PD treatment.

Enhancement of Biological Properties of Blackcurrants by Lactic Acid Fermentation and Incorporation into Yogurt: A Review

Blackcurrants (BC) and yogurt are known to possess several health benefits. The objective of this review was to compile the latest information on the effect of lactic acid fermentation on BC and their incorporation into yogurt, including the impact of this combination on chemical composition, sensory aspects, and health attributes of the blend. Google Scholar, Scopus, and PubMed were used to research the most recent literature on BC juice, the whole BC berry, and yogurt. Health benefits were assessed from human and animal studies within the last 5 years. The results suggest that BC have several health promoting compounds that ameliorate some neurological disorders and improve exercise recovery. Yogurt contains compounds that can be used to manage diseases such as type 2 diabetes (T2D) and irritable bowel disease (IBD). Fermenting BC with lactic acid bacteria (LAB) and its incorporation into yogurt products increases the polyphenol and antioxidant capacity of BC, creating a blend of prebiotics and probiotics compounds with enhanced benefits. More research is needed in the area of lactic acid fermentation of berries in general, especially BC.

Is insulin-like growth factor-1 involved in Parkinson's disease development?

Parkinson's disease (PD) is a neurodegenerative disorder that results in the death of dopaminergic neurons within the substantia nigra pars compacta and the reduction in dopaminergic control over striatal output neurons, leading to a movement disorder most commonly characterized by akinesia or bradykinesia, rigidity and tremor. Also, PD is less frequently depicted by sensory symptoms (pain and tingling), hyposmia, sleep alterations, depression and anxiety, and abnormal executive and working memory related functions. On the other hand, insulin-like growth factor 1 (IGF-1) is an endocrine, paracrine and autocrine hormone with several functions including tissue growth and development, insulin-like activity, proliferation, pro-survival, anti-aging, antioxidant and neuroprotection, among others. Herein this review tries to summarize all experimental and clinical data to understand the pathophysiology and development of PD, as well as its clear association with IGF-1, supported by several lines of evidence: (1) IGF-1 decreases with age, while aging is the major risk for PD establishment and development; (2) numerous basic and translational data have appointed direct protective and homeostasis IGF-1 roles in all brain cells; (3) estrogens seem to confer women strong protection to PD via IGF-1; and (4) clinical correlations in PD cohorts have confirmed elevated IGF-1 levels at the onset of the disease, suggesting an ongoing compensatory or "fight-to-injury" mechanism.

New markers in Parkinson's disease

Parkinson's disease (PD) is a chronic, debilitating neurodegenerative disorder characterized clinically by a variety of progressive motor and nonmotor symptoms. Currently, there is a dearth of diagnostic tools available to predict, diagnose or mitigate disease risk or progression, leading to a challenging dilemma within the healthcare management system. The search for a reliable biomarker for PD that reflects underlying pathology is a high priority in PD research. Currently, there is no reliable single biomarker predictive of risk for motor and cognitive decline, and there have been few longitudinal studies of temporal progression. A combination of multiple biomarkers might facilitate earlier diagnosis and more accurate prognosis in PD. In this review, we focus on the recent developments of serial biomarkers for PD from a variety of clinical, biochemical, genetic and neuroimaging perspectives.

Serum insulin-like growth factor-1 levels in neurodegenerative diseases

BACKGROUND

We investigated serum insulin-like growth factor (IGF)-1 levels in patients with neurodegenerative diseases and correlated these levels with clinical parameters.

METHODS

One hundred and fifty-six patients with neurodegenerative diseases were included in this study, and serum IGF-1 levels were determined.

RESULTS

Serum IGF-1 levels (mean ± standard error) were not significantly different among the patients with different neurodegenerative diseases: Parkinson's disease (PD; n = 73), 112.1 ± 5.1 ng/mL; progressive supranuclear palsy (n = 15), 102.9 ± 8.3 ng/mL; multiple system atrophy (n = 22), 103.1 ± 37.6 ng/mL; Alzheimer's disease (AD; n = 18), 102.2 ± 9.4 ng/mL; amyotrophic lateral sclerosis (n = 6), 105.5 ± 27.4 ng/mL; dementia with Lewy bodies (n = 14), 82.4 ± 7.4 ng/mL; frontotemporal dementia (n = 6), 90.0 ± 17.0 ng/mL; and corticobasal syndrome (n = 2), 118.0 ± 14.0 ng/mL. In patients with PD, serum IGF-1 levels were negatively correlated with age and modified Rankin scale (mRS) scores and positively correlated with the striatal dopamine transporter-specific binding ratio and the frontal assessment battery score. In patients with AD, serum IGF-1 levels were negatively correlated with age, disease duration, and mRS scores.

CONCLUSION

We found correlations of serum IGF-1 levels with frontal lobe and striatal dopaminergic function and disability in PD patients and with disability in AD patients. The usefulness of measuring serum IGF-1 levels for monitoring disease progression in neurodegenerative diseases requires further studies.

Altered Brain Expression of Insulin and Insulin-Like Growth Factors in Frontotemporal Lobar Degeneration: Another Degenerative Disease Linked to Dysregulation of Insulin Metabolic Pathways

BACKGROUND

Frontotemporal lobar degeneration (FTLD) is the third most common dementing neurodegenerative disease with nearly 80% having no known etiology.

OBJECTIVE

Growing evidence that neurodegeneration can be linked to dysregulated metabolism prompted us to measure a panel of trophic factors, receptors, and molecules that modulate brain metabolic function in FTLD.

METHODS

Postmortem frontal (Brodmann's area [BA]8/9 and BA24) and temporal (BA38) lobe homogenates were used to measure immunoreactivity to Tau, phosphorylated tau (pTau), ubiquitin, 4-hydroxynonenal (HNE), transforming growth factor-beta 1 (TGF-β1) and its receptor (TGF-β1R), brain-derived neurotrophic factor (BDNF), nerve growth factor, neurotrophin-3, neurotrophin-4, tropomyosin receptor kinase, and insulin and insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-2 (IGF-2) and their receptors by direct-binding enzyme-linked immunosorbent assay.

RESULTS

FTLD brains had significantly elevated pTau, ubiquitin, TGF-β1, and HNE immunoreactivity relative to control. In addition, BDNF and neurotrophin-4 were respectively reduced in BA8/9 and BA38, while neurotrophin-3 and nerve growth factor were upregulated in BA38, and tropomyosin receptor kinase was elevated in BA24. Lastly, insulin and insulin receptor expressions were elevated in the frontal lobe, IGF-1 was increased in BA24, IGF-1R was upregulated in all three brain regions, and IGF-2 receptor was reduced in BA24 and BA38.

CONCLUSIONS

Aberrantly increased levels of pTau, ubiquitin, HNE, and TGF-β1, marking neurodegeneration, oxidative stress, and neuroinflammation, overlap with altered expression of insulin/IGF signaling ligand and receptors in frontal and temporal lobe regions targeted by FTLD. Dysregulation of insulin-IGF signaling networks could account for brain hypometabolism and several characteristic neuropathologic features that characterize FTLD but overlap with Alzheimer's disease, Parkinson's disease, and Dementia with Lewy Body Disease.

Biomarkers in Neurodegenerative Diseases

The past decade has seen tremendous efforts in biomarker discovery and validation for neurodegenerative diseases. The source and type of biomarkers has continued to grow for central nervous system diseases, from biofluid-based biomarkers (blood or cerebrospinal fluid (CSF)), to nucleic acids, tissue, and imaging. While DNA remains a predominant biomarker used to identify familial forms of neurodegenerative diseases, various types of RNA have more recently been linked to familial and sporadic forms of neurodegenerative diseases during the past few years. Imaging approaches continue to evolve and are making major contributions to target engagement and early diagnostic biomarkers. Incorporation of biomarkers into drug development and clinical trials for neurodegenerative diseases promises to aid in the development and demonstration of target engagement and drug efficacy for neurologic disorders. This review will focus on recent advancements in developing biomarkers for clinical utility in Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS).

40 YEARS of IGF1: IGF1: the Jekyll and Hyde of the aging brain

The insulin-like growth factor 1 (IGF1) signaling pathway has emerged as a major regulator of the aging process, from rodents to humans. However, given the pleiotropic actions of IGF1, its role in the aging brain remains complex and controversial. While IGF1 is clearly essential for normal development of the central nervous system, conflicting evidence has emerged from preclinical and human studies regarding its relationship to cognitive function, as well as cerebrovascular and neurodegenerative disorders. This review delves into the current state of the evidence examining the role of IGF1 in the aging brain, encompassing preclinical and clinical studies. A broad examination of the data indicates that IGF1 may indeed play opposing roles in the aging brain, depending on the underlying pathology and context. Some evidence suggests that in the setting of neurodegenerative diseases that manifest with abnormal protein deposition in the brain, such as Alzheimer's disease, reducing IGF1 signaling may serve a protective role by slowing disease progression and augmenting clearance of pathologic proteins to maintain cellular homeostasis. In contrast, inducing IGF1 deficiency has also been implicated in dysregulated function of cognition and the neurovascular system, suggesting that some IGF1 signaling may be necessary for normal brain function. Furthermore, states of acute neuronal injury, which necessitate growth, repair and survival signals to persevere, typically demonstrate salutary effects of IGF1 in that context. Appreciating the dual, at times opposing 'Dr Jekyll' and 'Mr Hyde' characteristics of IGF1 in the aging brain, will bring us closer to understanding its impact and devising more targeted IGF1-related interventions.

Supplementation of Blackcurrant Anthocyanins Increased Cyclic Glycine-Proline in the Cerebrospinal Fluid of Parkinson Patients: Potential Treatment to Improve Insulin-Like Growth Factor-1 Function

Background: Insulin-like growth factor-1 (IGF-1) function is impaired in Parkinson disease. Cyclic glycine-proline (cGP), a metabolite of IGF-1, is neuroprotective through improving IGF-1 function. Parkinson disease patients score lower on Hospital-associated Anxiety and Depression Scale after supplementing blackcurrant anthocyanins (BCA), which may be associated with IGF-1 function. We evaluated the changes of cGP and IGF-1 before and after the supplementation. Methods: Plasma and cerebrospinal fluid (CSF) were collected from 11 male patients before and after 28 day supplementation of BCA. The concentrations of IGF-1, IGF binding protein (IGFBP)-3, and cGP were measured using ELISA and HPLC-MS assays. The presence of cGP in the BCA was evaluated. Results: cGP presented in the BCA. BCA supplementation increased the concentration of cGP (p < 0.01), but not IGF-1 and IGFBP-3 in the CSF. CSF concentration of cGP was correlated with plasma concentration of cGP (R = 0.68, p = 0.01) and cGP/IGF-1 molar ratio (R = 0.66, p = 0.01). The CSF/plasma ratio was high in cGP and low in IGF-1 and IGFBP-3. Conclusion: cGP is a natural nutrient to the BCA. The increased CSF cGP in Parkinson disease patients may result from the central uptake of plasma cGP. Given neurotrophic function, oral availability, and effective central uptake of cGP, the BCA has the potential to be developed to treat neurological conditions with IGF-1 deficiency.

Serum Insulin-Like Growth Factor-1 in Parkinson's Disease; Study of Cerebrospinal Fluid Biomarkers and White Matter Microstructure

Background: Growing evidence shows that impaired signaling of Insulin-like Growth Factor-1 (IGF-1) is associated with neurodegenerative disorders, such as Parkinson's disease (PD). However, there is still controversy regarding its proinflammatory or neuroprotective function. In an attempt to elucidate the contribution of IGF-1 in PD, we aimed to discover the relation between serum IGF-1 levels in drug-naïve early PD patients and cerebrospinal fluid (CSF) biomarkers as well as microstructural changes in brain white matter. Methods: The association between quartiles of serum IGF-1 levels and CSF biomarkers (α-synuclein, dopamine, amyloid-β_1-42, total tau, and phosphorylated tau) was investigated using adjusted regression models in 404 drug-naïve early PD patients with only mild motor manifestations and 188 age- and sex-matched healthy controls (HC) enrolled in the Parkinson's Progression Markers Initiative (PPMI). By using region of interest analysis and connectometry approach, we tracked the white matter microstructural integrity and diffusivity patterns in a subgroup of study participants with available diffusion MRI data to investigate the association between subcomponents of neural pathways with serum IGF-1 levels. Results: PD patients had higher levels of IGF-1 compared to HC, although not statistically significant (mean difference: 3.60, P = 0.44). However, after adjustment for possible confounders and correction for False Discovery Rate (FDR), IGF-1 was negatively correlated with CSF α-synuclein, total and phosphorylated tau levels only in PD subjects. The imaging analysis proved a significant negative correlation (FDR corrected P-value = 0.013) between continuous levels of serum IGF-1 in patients with PD and the connectivity, but not integrity, in following fibers while controlling for age, sex, body mass index, depressive symptoms, education years, cognitive status and disease duration: middle cerebellar peduncle, cingulum, genu and splenium of the corpus callosum. No significant association was found between brain white matter microstructral measures or CSF markers of healthy controls and levels of IGF-1. Conclusion: Altered connectivity in specific white matter structures, mainly involved in cognitive and motor deterioration, in association with higher serum IGF-1 levels might propose IGF-1 as a potential associate of worse outcome in response to higher burden of α-synucleinopathy and tauopathy in PD.

Association of IGF1 gene polymorphism with Parkinson's disease in a Han Chinese population

BACKGROUND

Accumulating evidence suggests that insulin-like growth factor 1 (IGF1) plays an important role in Parkinson's disease (PD) pathogenesis. However, it is not clear whether IGF1 polymorphism contributes to PD risk.

METHODS

We performed a case-control study in a Han Chinese population that included 512 sporadic PD cases and 535 matched controls. All participants were genotyped for rs972936 using the Sequenom MassARRAY iPLEX platform. Serum IGF1 levels of 61 de novo, drug-naïve PD patients and 55 age- and sex-matched controls were also measured using an enzyme-linked immunosorbent assay.

RESULTS

Genotype frequency of rs972936-CC was significantly associated with an increased PD risk (p = 0.009), especially in males (p = 0.024) and late-onset patients (p = 0.013). Serum IGF1 levels were significantly increased in de novo, drug-naïve PD patients compared to controls (p = 0.036), although they were not correlated with motor dysfunction in PD patients (p = 0.220).

CONCLUSIONS

The present study shows that rs972936 polymorphism may increase susceptibility to PD, especially in males and late-onset patients. Furthermore, high serum IGF1 levels may be a potential diagnostic biomarker for PD in the Han Chinese population, although they do not correlate with a more severe motor dysfunction.

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.

Manganese and the Insulin-IGF Signaling Network in Huntington's Disease and Other Neurodegenerative Disorders

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease resulting in motor impairment and death in patients. Recently, several studies have demonstrated insulin or insulin-like growth factor (IGF) treatment in models of HD, resulting in potent amelioration of HD phenotypes via modulation of the PI3K/AKT/mTOR pathways. Administration of IGF and insulin can rescue microtubule transport, metabolic function, and autophagy defects, resulting in clearance of Huntingtin (HTT) aggregates, restoration of mitochondrial function, amelioration of motor abnormalities, and enhanced survival. Manganese (Mn) is an essential metal to all biological systems but, in excess, can be toxic. Interestingly, several studies have revealed the insulin-mimetic effects of Mn-demonstrating Mn can activate several of the same metabolic kinases and increase peripheral and neuronal insulin and IGF-1 levels in rodent models. Separate studies have shown mouse and human striatal neuroprogenitor cell (NPC) models exhibit a deficit in cellular Mn uptake, indicative of a Mn deficiency. Furthermore, evidence from the literature reveals a striking overlap between cellular consequences of Mn deficiency (i.e., impaired function of Mn-dependent enzymes) and known HD endophenotypes including excitotoxicity, increased reactive oxygen species (ROS) accumulation, and decreased mitochondrial function. Here we review published evidence supporting a hypothesis that (1) the potent effect of IGF or insulin treatment on HD models, (2) the insulin-mimetic effects of Mn, and (3) the newly discovered Mn-dependent perturbations in HD may all be functionally related. Together, this review will present the intriguing possibility that intricate regulatory cross-talk exists between Mn biology and/or toxicology and the insulin/IGF signaling pathways which may be deeply connected to HD pathology and, perhaps, other neurodegenerative diseases (NDDs) and other neuropathological conditions.

Role of metabolism in neurodegenerative disorders

Along with the increase in life expectancy over the last century, the prevalence of age-related disorders, such as neurodegenerative diseases continues to rise. This is the case of Alzheimer's, Parkinson's, Huntington's diseases and Multiple sclerosis, which are chronic disorders characterized by neuronal loss in motor, sensory or cognitive systems. Accumulating evidence has suggested the presence of a strong correlation between metabolic changes and neurodegeneration. Indeed epidemiologic studies have shown strong associations between obesity, metabolic dysfunction, and neurodegeneration, while animal models have provided insights into the complex relationships between these conditions. In this context, hormones such as leptin, ghrelin, insulin and IGF-1 seem to play a key role in the regulation of neuronal damage, toxic insults and several other neurodegenerative processes. This review aims to presenting the most recent evidence supporting the crosstalk linking energy metabolism and neurodegeneration, and will focus on metabolic manipulation as a possible therapeutic tool in the prevention and treatment of neurodegenerative diseases.

Phenome-based gene discovery provides information about Parkinson's disease drug targets

BACKGROUND

Parkinson disease (PD) is a severe neurodegenerative disease without curative drugs. The highly complex and heterogeneous disease mechanisms are still unclear. Detecting novel PD associated genes not only contributes in revealing the disease pathogenesis, but also facilitates discovering new targets for drugs.

METHODS

We propose a phenome-based gene prediction strategy to identify disease-associated genes for PD. We integrated multiple disease phenotype networks, a gene functional relationship network, and known PD genes to predict novel candidate genes. Then we investigated the translational potential of the predicted genes in drug discovery.

RESULTS

In a cross validation analysis, the average rank for 15 known PD genes is within top 0.8 %. We also tested the algorithm with an independent validation set of 669 PD-associated genes detected by genome-wide association studies. The top ranked genes predicted by our approach are enriched for these validation genes. In addition, our approach prioritized the target genes for FDA-approved PD drugs and the drugs that have been tested for PD in clinical trials. Pathway analysis shows that the prioritized drug target genes are closely associated with PD pathogenesis. The result provides empirical evidence that our computational gene prediction approach identifies novel candidate genes for PD, and has the potential to lead to rapid drug discovery.

Insulin-Like Growth Factor 1 (IGF-1) in Parkinson's Disease: Potential as Trait-, Progression- and Prediction Marker and Confounding Factors

INTRODUCTION

Biomarkers indicating trait, progression and prediction of pathology and symptoms in Parkinson's disease (PD) often lack specificity or reliability. Investigating biomarker variance between individuals and over time and the effect of confounding factors is essential for the evaluation of biomarkers in PD, such as insulin-like growth factor 1 (IGF-1).

MATERIALS AND METHODS

IGF-1 serum levels were investigated in up to 8 biannual visits in 37 PD patients and 22 healthy controls (HC) in the longitudinal MODEP study. IGF-1 baseline levels and annual changes in IGF-1 were compared between PD patients and HC while accounting for baseline disease duration (19 early stage: ≤3.5 years; 18 moderate stage: >4 years), age, sex, body mass index (BMI) and common medical factors putatively modulating IGF-1. In addition, associations of baseline IGF-1 with annual changes of motor, cognitive and depressive symptoms and medication dose were investigated.

RESULTS

PD patients in moderate (130±26 ng/mL; p = .004), but not early stages (115±19, p>.1), showed significantly increased baseline IGF-1 levels compared with HC (106±24 ng/mL; p = .017). Age had a significant negative correlation with IGF-1 levels in HC (r = -.47, p = .028) and no correlation in PD patients (r = -.06, p>.1). BMI was negatively correlated in the overall group (r = -.28, p = .034). The annual changes in IGF-1 did not differ significantly between groups and were not correlated with disease duration. Baseline IGF-1 levels were not associated with annual changes of clinical parameters.

DISCUSSION

Elevated IGF-1 in serum might differentiate between patients in moderate PD stages and HC. However, the value of serum IGF-1 as a trait-, progression- and prediction marker in PD is limited as IGF-1 showed large inter- and intraindividual variability and may be modulated by several confounders.

Serum Insulin-Like Growth Factor-1 in Patients with De Novo, Drug Naïve Parkinson's Disease: A Meta-Analysis

Objective

Insulin-like growth factor-1 (IGF-1) is reported to be neuroprotective in the setting of Parkinson’s disease (PD), and there is increasing interest in the possible association of serum IGF-1 levels with PD patients, but with conflicting results. Therefore, we conducted a meta-analysis to evaluate the association of serum IGF-1 levels in de novo, drug naïve PD patients compared with healthy controls.

Methods

Pubmed, ISI Web of Science, OVID, EMBASE, and Cochrane library databases from 1966 to October 2014 were utilized to identify candidate studies using Medical Subjective Headings without language restriction. A random-effects model was chosen, with subgroup analysis and sensitivity analysis conducted to reveal underlying heterogeneity among the included studies.

Results

In this meta-analysis, we found that PD patients had higher serum IGF-1 levels compared with healthy controls (summary mean difference [MD] = 17.75, 95%CI = 6.01, 29.48). Subgroup analysis demonstrated that the source of heterogeneity was population differences within the total group. Sensitivity analysis showed that the combined MD was consistent at any time omitting any one study.

Conclusions

The results of this meta-analysis demonstrate that serum IGF-1 levels were significantly higher in de novo, drug-naïve PD patients compared with healthy controls. Nevertheless, additional endeavors are required to further explore the association between serum IGF-1 levels and diagnosis, prognosis and early therapy for PD.

Blood Biomarkers Associated with Cognitive Decline in Early Stage and Drug-Naive Parkinson's Disease Patients

Early diagnosis of Parkinson's disease (PD) continues to be a major challenge in the field. The lack of a robust biomarker to detect early stage PD patients has considerably slowed the progress toward the development of potential therapeutic agents. We have previously evaluated several RNA biomarkers in whole blood from participants enrolled in two independent clinical studies. In these studies, PD patients were medicated, thus, expression of these biomarkers in de novo patients remains unknown. To this end, we tested ten RNA biomarkers in blood samples from 99 untreated PD patients and 101 HC nested in the cross-sectional Parkinson's Progression Markers Initiative by quantitative real-time PCR. One biomarker out of ten, COPZ1 trended toward significance (nominal p = 0.009) when adjusting for age, sex, and educational level. Further, COPZ1, EFTUD2 and PTBP1 mRNAs correlated with clinical features in PD patients including the Hoehn and Yahr scale, Movement Disorder Society revision of Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and Montreal Cognitive Assessment (MoCA) score. Levels of EFTUD2 and PTBP1 were significantly higher in cognitively normal PD patients (PD-CN) compared to cognitively impaired PD patients (PD-MCI). Interestingly, blood glucose levels were significantly higher in PD and PD-MCI patients (≥ 100 mg/dL, pre-diabetes) compared to HC. Collectively, we report the association of three RNA biomarkers, COPZ1, EFTUD2 and PTBP1 with clinical features including cognitive decline in early drug-naïve PD patients. Further, our results show that drug-naïve PD and PD-MCI patients have glucose levels characteristic of pre-diabetes patients, suggesting that impaired glucose metabolism is an early event in PD. Evaluation of these potential biomarkers in a larger longitudinal study is warranted.

Gut-brain connection: The neuroprotective effects of the anti-diabetic drug liraglutide

Long-acting glucagon-like peptide-1 (GLP-1) analogues marketed for type 2 diabetes (T2D) treatment have been showing positive and protective effects in several different tissues, including pancreas, heart or even brain. This gut secreted hormone plays a potent insulinotropic activity and an important role in maintaining glucose homeostasis. Furthermore, growing evidences suggest the occurrence of several commonalities between T2D and neurodegenerative diseases, insulin resistance being pointed as a main cause for cognitive decline and increased risk to develop dementia. In this regard, it has also been suggested that stimulation of brain insulin signaling may have a protective role against cognitive deficits. As GLP-1 receptors (GLP-1R) are expressed throughout the central nervous system and GLP-1 may cross the blood-brain-barrier, an emerging hypothesis suggests that they may be promising therapeutic targets against brain dysfunctional insulin signaling-related pathologies. Importantly, GLP-1 actions depend not only on the direct effect mediated by its receptor activation, but also on the gut-brain axis involving an exchange of signals between both tissues via the vagal nerve, thereby regulating numerous physiological functions (e.g., energy homeostasis, glucose-dependent insulin secretion, as well as appetite and weight control). Amongst the incretin/GLP-1 mimetics class of anti-T2D drugs with an increasingly described neuroprotective potential, the already marketed liraglutide emerged as a GLP-1R agonist highly resistant to dipeptidyl peptidase-4 degradation (thereby having an increased half-life) and whose systemic GLP-1R activity is comparable to that of native GLP-1. Importantly, several preclinical studies showed anti-apoptotic, anti-inflammatory, anti-oxidant and neuroprotective effects of liraglutide against T2D, stroke and Alzheimer disease (AD), whereas several clinical trials, demonstrated some surprising benefits of liraglutide on weight loss, microglia inhibition, behavior and cognition, and in AD biomarkers. Herein, we discuss the GLP-1 action through the gut-brain axis, the hormone’s regulation of some autonomic functions and liraglutide’s neuroprotective potential.

Meta-analyses of seven GIGYF2 polymorphisms with Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder that affects ~2% of the global population aged ≥65 years. Grb10-interacting GYF protein-2 (GIGYF2) can influence the development of PD through the regulation of insulin-like growth factor-1. The aim of the present meta-analysis study was to establish the contribution of GIGYF2 polymorphisms to PD. The study was conducted based on nine eligible studies consisting of 7,246 PD patients and 7,544 healthy controls. The results indicated that the GIGYF2 C.3630A>G polymorphism increased the risk of PD by 37% [P=0.008; odds ratio (OR), 1.37; 95% confidence interval (CI), 1.08-1.73] and that the GIGYF2 C.167G>A polymorphism was significantly associated with PD (P=0.003; OR, 3.67; 95% CI, 1.56-8.68). The meta-analyses of the other five GIGYF2 polymorphisms (C.1378C>A, C.1554G>A, C.2940A>G, C.1370C>A and C.3651G>A) did not reveal any significant associations. The present meta-analyses of the GIGYF2 genetic polymorphisms may provide a comprehensive overview of this PD candidate gene for future studies.

Mechanisms of action of brain insulin against neurodegenerative diseases

Insulin, a pancreatic hormone, is best known for its peripheral effects on the metabolism of glucose, fats and proteins. There is a growing body of evidence linking insulin action in the brain to neurodegenerative diseases. Insulin present in central nervous system is a regulator of central glucose metabolism nevertheless this glucoregulation is not the main function of insulin in the brain. Brain is known to be specifically vulnerable to oxidative products relative to other organs and altered brain insulin signaling may cause or promote neurodegenerative diseases which invalidates and reduces the quality of life. Insulin located within the brain is mostly of pancreatic origin or is produced in the brain itself crosses the blood-brain barrier and enters the brain via a receptor-mediated active transport system. Brain Insulin, insulin receptor and insulin receptor substrate-mediated signaling pathways play important roles in the regulation of peripheral metabolism, feeding behavior, memory and maintenance of neural functions such as neuronal growth and differentiation, neuromodulation and neuroprotection. In the present review, we would like to summarize the novel biological and pathophysiological roles of neuronal insulin in neurodegenerative diseases and describe the main signaling pathways in use for therapeutic strategies in the use of insulin to the cerebral tissues and their biological applications to neurodegenerative diseases.

Maternal exposure to bisphenol A may increase the risks of Parkinson's disease through down-regulation of fetal IGF-1 expression

So far, the pathogenesis of Parkinson's disease (PD) remains unclear. Current studies implicate environmental toxins may be potential causes of fetal origin of PD. BPA is a member of the family of estrogenic chemicals existing widely in environment. Significant evidences from animal experimentation have demonstrated that BPA interfere with fetal neurodevelopment. Based on previous reports and our research on EB derived from hESCs, we speculate that maternal exposure to low-dose BPA during gestational period may decrease IGF-1 expression, thus hinder the development of fetal DA neurons, and finally increase the risks of fetal origin of PD. Our hypothesis may shed new light on the pathogenesis of PD and lead to potential preventive treatments.