Free insulin-like growth factor-I and cognitive function in older persons living in community

Cognitive function and skeletal size and mineral density at age 6-7 years: Findings from the Southampton Women's Survey

INTRODUCTION

Poor cognitive function and osteoporosis commonly co-exist in later life. In women, this is often attributed to post-menopausal estrogen loss. However, a common early life origin for these conditions and the associations between cognitive function and bone mineral density (BMD) in childhood have not previously been explored. We examined these relationships at age 6-7 years in the Southampton Women's Survey (SWS) mother-offspring cohort.

METHODS

Child occipitofrontal circumference (OFC), a proxy for brain volume, intelligence quotient (IQ) [Wechsler Abbreviated Scale of Intelligence] and visual recognition and working memory [CANTAB® Delayed Matching to Sample (DMS) and Spatial Span Length (SSP), respectively] were assessed. Whole-body-less-head (WBLH) and lumbar spine dual-energy X-ray absorptiometry [Hologic Discovery] (DXA) were performed to measure bone area (BA), bone mineral content (BMC), BMD and bone mineral apparent density (BMAD). Linear regression was used to examine associations between age and sex standardized variables (β represent standard deviation (SD) difference per SD of cognitive function).

RESULTS

DXA was performed in 1331 children (mean (SD) age 6.8 (0.33) years, 51.5 % male), with OFC, IQ, DMS and SSP assessed in 1250, 551, 490 and 460, respectively. OFC (β = 0.25 SD/SD, 95%CI 0.20,0.30), IQ (β = 0.11 SD/SD, 95%CI 0.02,0.19), and DMS (β = 0.11, SD/SD, 95%CI 0.01,0.20) were positively associated with WBLH BA, with similar associations for lumbar spine BA. OFC and DMS were also positively associated with WBLH BMC, but only OFC was associated with BMD (WBLH: β = 0.38 SD/SD, 95%CI 0.33,0.43; LS: β = 0.19 SD/SD, 95%CI 0.13,0.24).

CONCLUSION

Childhood brain volume was positively associated with measures of skeletal size and BMD, whereas IQ and memory were associated only with skeletal size. These findings suggest that common early life determinants for skeletal growth and BMD and cognitive function should be explored to identify potential early-life approaches to preventing osteoporosis and cognitive decline.

Association between serum insulin-like growth factor 1 levels and the improvements of cognitive impairments in a subgroup of schizophrenia: Preliminary findings

BACKGROUND

Numerous studies have implicated abnormal insulin-like growth factor 1 (IGF-1) in the pathophysiology of schizophrenia, but findings have been inconsistent.

METHODS

We conducted a meta-analysis to compare IGF-1 levels in schizophrenia patients with healthy controls and explored factors contributing to variability between estimates. In an independent sample (58 chronic schizophrenia patients and 30 healthy controls), we investigated differences in IGF-1 levels among schizophrenia subgroups with distinct cognitive profiles, identified using k-means clustering based on five cognitive domains from The Repeatable Battery for the Assessment of Neuropsychological Status. Associations between serum IGF-1 levels and clinical and neurocognitive improvements were also examined.

RESULTS

The meta-analysis revealed significantly lower serum IGF-1 levels in schizophrenia patients compared to healthy controls, albeit with high heterogeneity. Medication status, BMI, and severity of negative symptoms were identified as potential contributors to this heterogeneity. In our independent study, antipsychotic treatment led to a significant increase in IGF-1 levels, and lower pre-treatment serum IGF-1 levels correlated with greater improvement in cognitive deficits, particularly in a subgroup with more severe cognitive symptoms.

CONCLUSIONS

Our findings support the "IGF-1 deficiency hypothesis" in the pathogenesis of schizophrenia. Further research is crucial to elucidate the role of IGF-1 in the cognitive impairments associated with schizophrenia.

Alterations in brain structure and function associated with pediatric growth hormone deficiency: A multi-modal magnetic resonance imaging study

Introduction

Pediatric growth hormone deficiency (GHD) is a disease resulting from impaired growth hormone/insulin-like growth factor-1 (IGF-1) axis but the effects of GHD on children's cognitive function, brain structure and brain function were not yet fully illustrated.

Methods

Full Wechsler Intelligence Scales for Children, structural imaging, diffusion tensor imaging, and resting-state functional magnetic resonance imaging were assessed in 11 children with GHD and 10 matched healthy controls.

Results

(1) The GHD group showed moderate cognitive impairment, and a positive correlation existed between IGF-1 levels and cognitive indices. (2) Mean diffusivity was significantly increased in both corticospinal tracts in GHD group. (3) There were significant positive correlations between IGF-1 levels and volume metrics of left thalamus, left pallidum and right putamen but a negative correlation between IGF-1 levels and cortical thickness of the occipital lobe. And IGF-1 levels negatively correlated with fractional anisotropy in the superior longitudinal fasciculus and right corticospinal tract. (4) Regional homogeneity (ReHo) in the left hippocampus/parahippocampal gyrus was negatively correlated with IGF-1 levels; the amplitude of low-frequency fluctuation (ALFF) and ReHo in the paracentral lobe, postcentral gyrus and precentral gyrus were also negatively correlated with IGF-1 levels, in which region ALFF fully mediates the effect of IGF-1 on working memory index.

Conclusion

Multiple subcortical, cortical structures, and regional neural activities might be influenced by serum IGF-1 levels. Thereinto, ALFF in the paracentral lobe, postcentral gyrus and precentral gyrus fully mediates the effect of IGF-1 on the working memory index.

Insulin-like growth factor I sensitization rejuvenates sleep patterns in old mice

Sleep disturbances are common during aging. Compared to young animals, old mice show altered sleep structure, with changes in both slow and fast electrocorticographic (ECoG) activity and fewer transitions between sleep and wake stages. Insulin-like growth factor I (IGF-I), which is involved in adaptive changes during aging, was previously shown to increase ECoG activity in young mice and monkeys. Furthermore, IGF-I shapes sleep architecture by modulating the activity of mouse orexin neurons in the lateral hypothalamus (LH). We now report that both ECoG activation and excitation of orexin neurons by systemic IGF-I are abrogated in old mice. Moreover, orthodromical responses of LH neurons are facilitated by either systemic or local IGF-I in young mice, but not in old ones. As orexin neurons of old mice show dysregulated IGF-I receptor (IGF-IR) expression, suggesting disturbed IGF-I sensitivity, we treated old mice with AIK3a305, a novel IGF-IR sensitizer, and observed restored responses to IGF-I and rejuvenation of sleep patterns. Thus, disturbed sleep structure in aging mice may be related to impaired IGF-I signaling onto orexin neurons, reflecting a broader loss of IGF-I activity in the aged mouse brain.

Neuroprotective Biomarkers and Cognitive Function in a Long-Term Prospective Population-based Study of Aging US Adults

BACKGROUND

Relationships between brain-derived neurotrophic factor (BDNF), insulin-like growth factor (IGF-1), aldosterone, and cognition in aging were evaluated in the population-based Epidemiology of Hearing Loss Study (1993 to present).

METHODS

Beginning in 1998 to 2000, cognitive impairment was assessed by report of physician diagnoses and the Mini-Mental State Examination. In 2009 to 2010 and 2013 to 2016, information was collected on diagnosis of mild cognitive impairment/dementia. Decline in cognitive function was assessed by principal component analysis from additional tests administered during 2009 to 2010 and 2013 to 2016. BDNF, IGF-1, and aldosterone were measured in serum collected in 1998 to 2000.

RESULTS

There were 1970 participants (mean age=66.9 y; 59.1% female) without cognitive impairment at baseline. Among women, low BDNF was associated with 16-year incident cognitive impairment [hazard ratio=1.76; 95% confidence interval (CI)=1.04, 2.98]. Among men, increasing IGF-1 was associated with decreased risk [per SD: relative risk (RR)=0.57; 95% CI=0.35, 0.92], whereas increasing aldosterone levels were associated with increased risk (per SD: RR=1.28; 95% CI=1.01, 1.62) for 5-year incident mild cognitive impairment/dementia. Overall, low BDNF was associated with increased risk (RR=1.52; 95% CI=1.02, 2.26) for 5-year cognitive decline.

CONCLUSION

Low levels of serum BDNF and IGF-1 were associated with poorer cognition during aging. There may be differential biomarker effects by sex.

Effects of β-carotene intake on the risk of fracture: a Bayesian meta-analysis

Background

Epidemiological studies examining the association between β-carotene intake and risk of fracture have reported inconsistent findings. We conducted a meta-analysis to investigate the association between β-carotene intake and risk of fracture.

Methods

We systematically searched PubMed, EMBASE and Cochrane library databases for relevant articles that were published until December 2019. We also identified studies from reference lists of articles identified from the clinical databases. The frequentist and Bayesian random-effects model was used to synthesize data.

Results

Nine studies with a total of 190,545 men and women, with an average age of 59.8 years, were included in this meta-analysis. For β-carotene intake (1.76–14.30 mg/day), the pooled risk ratio (RR) of any fracture was 0.67 (95% Credible Interval (CrI): 0.51–0.82; heterogeneity: P = 0.66, I² = 0.00%) and 0.63 (95%CrI: 0.44–0. 82) for hip fracture. By study design, the pooled RRs were 0.55 (95% CrI: 0.14–0.96) for case-control studies and 0.82 (95% CrI: 0.58–0.99) for cohort studies. By geographic region, the pooled RRs were 0.58 (95% CrI: 0.28–0.89), 0.86 (95% CrI: 0.35–0.1.37), and 0.91(95% CrI: 0.75–1.00) for studies conducted in China, the United States, and Europe, respectively. By sex, the pooled RRs were 0.88 (95% CrI: 0.73–0.99) for males and 0.76 (95% CrI, 0.44–1.07) for females. There was a 95% probability that β-carotene intake reduces risk of hip fracture and any type of fracture by more than 20%.

Conclusions

The present meta-analysis suggests that β-carotene intake was inversely associated with fracture risk, which was consistently observed for case-control and cohort studies. Randomized controlled trials are warranted to confirm this relationship.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-020-03733-0.

Insulin-like growth factor 1 signaling in motor neuron and polyglutamine diseases: From molecular pathogenesis to therapeutic perspectives

The pleiotropic peptide insulin-like growth factor 1 (IGF-I) regulates human body homeostasis and cell growth. IGF-I activates two major signaling pathways, namely phosphoinositide-3-kinase (PI3K)/protein kinase B (PKB/Akt) and Ras/extracellular signal-regulated kinase (ERK), which contribute to brain development, metabolism and function as well as to neuronal maintenance and survival. In this review, we discuss the general and tissue-specific effects of the IGF-I pathways. In addition, we present a comprehensive overview examining the role of IGF-I in neurodegenerative diseases, such as spinal and muscular atrophy, amyotrophic lateral sclerosis, and polyglutamine diseases. In each disease, we analyze the disturbances of the IGF-I pathway, the modification of the disease protein by IGF-I signaling, and the therapeutic strategies based on the use of IGF-I developed to date. Lastly, we highlight present and future considerations in the use of IGF-I for the treatment of these disorders.

Metabolic and Neurocognitive Changes Following Lifestyle Modification: Examination of Biomarkers from the ENLIGHTEN Randomized Clinical Trial

BACKGROUND

Previous studies have demonstrated that aerobic exercise (AE) and the Dietary Approaches to Stop Hypertension (DASH) diet can improve neurocognition. However, the mechanisms by which lifestyle improves neurocognition have not been widely studied. We examined the associations between changes in metabolic, neurotrophic, and inflammatory biomarkers with executive functioning among participants from the Exercise and Nutritional Interventions for Neurocognitive Health Enhancement (ENLIGHTEN) trial.

OBJECTIVE

To examine the association between changes in metabolic function and neurocognition among older adults with cognitive impairment, but without dementia (CIND) participating in a comprehensive lifestyle intervention.

METHODS

ENLIGHTEN participants were randomized using a 2×2 factorial design to receive AE, DASH, both AE+DASH, or a health education control condition (HE) for six months. Metabolic biomarkers included insulin resistance (homeostatic model assessment [HOMA-IR]), leptin, and insulin-like growth factor (IGF-1); neurotrophic biomarkers included brain derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF); and inflammatory biomarkers included interleukin-6 (IL-6) and C-Reactive Protein (CRP).

RESULTS

Participants included 132 sedentary older adults (mean age = 65 [SD = 7]) with CIND. Results demonstrated that both AE (d = 0.48, p = 0.015) and DASH improved metabolic function (d = 0.37, p = 0.039), without comparable improvements in neurotrophic or inflammatory biomarkers. Greater improvements in metabolic function, including reduced HOMA-IR (B = -2.3 [-4.3, -0.2], p = 0.033) and increased IGF-1 (B = 3.4 [1.2, 5.7], p = 0.004), associated with increases in Executive Function.

CONCLUSION

Changes in neurocognition after lifestyle modification are associated with improved metabolic function.

The role of exercise in the reversal of IGF-1 deficiencies in microvascular rarefaction and hypertension

Hypertension has been linked with peripheral and central reductions in vascular density, and with devastating effects on brain function. However, the underlying mechanisms in the relationship between blood pressure and cognitive impairment have yet to be fully elucidated. Here, we review compelling evidence from two lines of inquiry: one that links microvascular rarefaction with insulin-like growth factor 1 (IGF-1) deficiencies, and another which posits that vascular dysfunction precedes hypertension. Based on the findings from experimental and clinical studies, we propose that these lines of evidence converge, and suggest that age-related declines in IGF-1 concentrations precede microvascular rarefaction, initiate an increase in vascular resistance, and therefore are causally linked to onset of hypertension. Physical exercise provides a relevant model for supporting our premise, given the well-established effects of exercise in attenuating vascular dysfunction, hypertension, IGF-1 deficiency, and cognitive decline. We highlight here the role of exercise-induced increases in blood flow in improving vascular integrity and enhancing angiogenesis via the actions of IGF-1, resulting in reversal of rarefaction and hypertension, and enhancement of cerebral blood flow and cognition.

The Link Between Tau and Insulin Signaling: Implications for Alzheimer's Disease and Other Tauopathies

The microtubule-associated protein tau (MAPT) is mainly identified as a tubulin binding protein essential for microtubule dynamics and assembly and for neurite outgrowth. However, several other possible functions for Tau remains to be investigated. Insulin signaling is important for synaptic plasticity and memory formation and therefore is essential for proper brain function. Tau has recently been characterized as an important regulator of insulin signaling, with evidence linking Tau to brain and peripheral insulin resistance and beta cell dysfunction. In line with this notion, the hypothesis of Tau pathology as a key trigger of impaired insulin sensitivity and secretion has emerged. Conversely, insulin resistance can also favor Tau dysfunction, resulting in a vicious cycle of these events. In this review article, we discuss recent evidence linking Tau pathology, insulin resistance and insulin deficiency. We further highlight the deleterious consequences of Tau pathology-induced insulin resistance to the brain and/or peripheral tissues, suggesting that these are key events mediating cognitive decline in Alzheimer’s disease (AD) and other tauopathies.

Association Between Insulin Resistance, Plasma Leptin, and Neurocognition in Vascular Cognitive Impairment

BACKGROUND

Greater body weight has been associated impairments in neurocognition and greater dementia risk, although the mechanisms linking weight and neurocognition have yet to be adequately delineated.

OBJECTIVE

To examine metabolic mechanisms underlying the association between obesity and neurocognition.

METHODS

We conducted a secondary analysis of weight, neurocognition, and the potentially mediating role of metabolic and inflammatory biomarkers among 160 participants from the ENLIGHTEN trial of vascular cognitive impairment, no dementia (CIND). Neurocognition was assessed using a 45-minute assessment battery assessing Executive Function, Verbal and Visual Memory. We considered three metabolic biomarkers: insulin resistance (homeostatic model assessment [HOMA-IR]), plasma leptin, and insulin-like growth factor (IGF-1). Inflammation was assessed using C-reactive protein. Multiple regression analyses were used.

RESULTS

Participants included 160 sedentary older adults with CIND. Participants tended to be overweight or obese (mean BMI = 32.5 [SD = 4.8]). Women exhibited higher BMI (p = 0.043), CRP (p < 0.001), and leptin (p < 0.001) compared with men. Higher BMI levels were associated with worse performance on measures of Executive Function (β= -0.16, p = 0.024) and Verbal Memory (β= -0.16, p = 0.030), but not Visual Memory (β= 0.05, p = 0.500). Worse metabolic biomarker profiles also were associated with lower Executive Function (β= -0.12, p = 0.050). Mediation analyses suggested leptin was a plausible candidate as a mediator between BMI and Executive Function.

CONCLUSIONS

In overweight and obese adults with vascular CIND, the association between greater weight and poorer executive function may be mediated by higher leptin resistance.

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.

The association between peripheral total IGF-1, IGFBP-3, and IGF-1/IGFBP-3 and functional and cognitive outcomes in the Mayo Clinic Study of Aging

Levels of insulin-like growth factor (IGF)-1, IGF-binding protein (IGFBP)-3, and their ratio in the blood may be useful for monitoring those at risk of cognitive and functional decline. However, the association between IGF measures and functional and cognitive outcomes has been mixed, and the associations may vary by sex. The present study investigated the cross-sectional, sex-specific associations between serum measures total IGF-1, IGFBP-3, and the IGF-1/IGFBP-3 ratio, gait speed, and cognition in 1320 cognitively unimpaired participants aged 50-95 years enrolled in the Mayo Clinic Study of Aging. We used multivariable linear regression models to determine the association between IGF measures and gait speed or cognitive test performance by sex. IGF measures were not associated with cognitive or functional performance among men. Among women, higher levels of log total IGF-1 and IGFBP-3 were associated with better performance in attention, visuospatial, and global cognitive domains, independent of the gait speed. These findings suggest that among women, IGF measures are associated with cognition, and these associations are independent of function.

Higher dietary carotenoid intake associated with lower risk of hip fracture in middle-aged and elderly Chinese: A matched case-control study

BACKGROUND

Mechanism studies have suggested that carotenoids may benefit bone health due to their antioxidant properties, but epidemiological data on their effects on risk of hip fracture are sparse.

PURPOSE

To explore the relationships between dietary total and specific carotenoids and the risk of hip fracture in a middle-aged and elderly Chinese population.

DESIGN

A case-control study of 1070 patients with hip fractures (diagnosed within 2 weeks) aged 55-80 years and 1070 age- (within 3 years) and gender-matched controls was conducted in Guangdong, China between 2009 and 2015. Information on dietary carotenoid intake was assessed using a 79-item food frequency questionnaire administered in face-to-face interviews, and general information was collected using structured questionnaires. The univariate and multivariate conditional logistic regression models were applied to analyze the associations.

MAIN RESULTS

Higher intakes of both total and some specific carotenoids (including β-carotene, β-cryptoxanthin and lutein/zeaxanthin) were significantly associated with a lower risk of hip fracture (all p trends <0.01). Compared with the lowest quartile of carotenoids, the multivariate-adjusted odds ratios and 95% confidential intervals of the highest quartile were 0.44 (0.29, 0.68) (total carotenoids), 0.50 (0.29, 0.69) (β-carotene), 0.55 (0.38, 0.80) (β-cryptoxanthin) and 0.40 (0.27, 0.59) (lutein/zeaxanthin), respectively. There were no statistically significant associations between α-carotene and lycopene intakes and hip fracture risk after adjustment for various confounding variables.

CONCLUSION

These results suggest that the consumption of carotenoids may be protective against hip fracture in middle-aged and elderly Chinese adults.

Association between Cognition and Serum Insulin-Like Growth Factor-1 in Middle-Aged & Older Men: An 8 Year Follow-Up Study

Low levels of insulin-like growth factor-1 (IGF-1), an essential neurotrophic factor, have been associated with worse cognitive function in older adults. However, few studies have assessed the prospective association of serum IGF-1 with cognitive function. We aimed to determine the association between serum IGF-1 on concurrent and prospective cognitive function in a population sample of men aged 40–80 years. Blood samples were assessed for IGF-1 levels at baseline and neuropsychological assessments were performed at baseline (n = 400) and at follow-up after a mean duration of 8.3 years (n = 286). Linear regression analyses were carried out to determine the associations between quintiles of IGF-1 and cognitive function at the baseline and follow-up visits. Results showed that those in the top quintile of IGF-1 had lower processing capacity and global cognition scores at follow-up after controlling for cognitive function at baseline and other confounding factors. Additional analyses exploring associations with IGF-1 separately in middle-aged and older participants, and with quartiles of IGF-1 produced similar results. In those older than 60 years, high IGF-1 levels were also associated with lower baseline processing capacity. These results suggest that high IGF-1 levels are associated with worse long-term cognition in men. Together with past studies, we suggest that both, high and low levels of IGF-1 may be associated with poor cognitive function and that optimum levels of IGF-1 (quintile 2 and 3 in current study) may be associated with better cognitive function.

Insulin-like growth factor-1 and insulin-like growth factor binding protein 3 and risk of postoperative cognitive dysfunction

Insulin-like growth factor (IGF)-1 is implicated in learning and memory. Experimental studies have suggested that the IGF-1 system is beneficial in cognition, especially in Alzheimer’s disease (AD), by opposing Aβ amyloid processing and hyperphosphorylated tau toxicity. Low IGF-I and insulin-like growth factor binding protein (IGFBP)-3 serum levels are significantly associated with AD. To assess the relationship between circulating IGF-I and IGFBP3 levels and change of postoperative cognition. The study was performed in patients scheduled for elective head and neck carcinoma surgery under general anesthesia. On the day before the operation and postoperative days 1, 3 and 7, mini-mental state examination (MMSE) was performed by the same doctor, and blood samples were collected at 08:00 h after overnight fasting. The circulating levels of IGF-1 and IGFBP3 were measured by enzyme-linked immunosorbent assay. One hundred and two patients completed all four MMSE tests and forty-four of them completed all the four blood samples collection. Postoperative circulating IGF-1 level, ratio of IGF-1/IGFBP3 and MMSE score significantly decreased, whereas IGFBP3 level significantly increased compared with preoperative values in total patients. The change trends of circulating IGF-1 level and MMSE score were similar. Preoperative circulating IGF-1 level, ratio and MMSE score were significantly lower in POCD group compared to non-POCD group. There was no significant difference in preoperative level of circulating IGFBP3 between the two groups. Preoperative circulating IGF-1 level was negatively correlated with age and positively with MMSE. Logistic regression analysis revealed that lower preoperative IGF-1 level and elderly patients increased the odds of POCD. Down-regulation of circulating IGF-1 level may be involved in the mechanism of postoperative cognitive dysfunction. Older patients had lower circulating IGF-1 levels and were more susceptible to POCD.

Comparison of the effects of resveratrol and caloric restriction on learning and memory in juvenile C57BL/6J mice

OBJECTIVES

Both caloric restriction (CR) and resveratrol (RSV) have been shown to improve learning and memory, but their potential effects in juvenile animals were unknown. Here, we evaluated the effects of RSV and CR on learning and memory function in juvenile mice and investigated potential molecular mechanisms.

METHODS

Six-week-old C57BL/6J mice were assigned to one of three different dietary groups: normal control (stock diet) (n=12), CR diet (30% caloric reduction diet) (n=12), and RSV diet (stock diet supplemented with 18.6 mg/kg RSV) (n=12), for 6 months. Body weight and blood glucose were measured every 4 weeks. Serum cholesterol and serum triglyceride levels were examined using biochemical methods. Serum insulin and insulin-like growth factor 1 (IGF-1) levels were evaluated using enzyme linked immunosorbant assay (ELISA), and protein expression of silent mating type information regulation 2 homology 1 (SIRT1), p53, p16, peroxisome proliferator-activated receptor γ (PPARγ), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), phosphorylated-cAMP response element-binding protein (p-CREB), and IGF-1 were examined with immunohistochemistry.

RESULTS

Although long-term CR diet did not alter physiological conditions in juvenile mice relative to control, RSV supplementation slightly elevated blood glucose, serum triglyceride, and serum insulin levels. Both CR and RSV improved learning and memory function, although the effect of CR was significantly greater. Both CR and RSV downregulated p53 and upregulated IGF-1 in hippocampal CA1 region of mice.

CONCLUSION

We demonstrate that CR and RSV may improve learning and memory by downregulating p53 and upregulating IGF-1 in hippocampal CA1 region of juvenile mice.

Efficient Expression of Igf-1 from Lentiviral Vectors Protects In Vitro but Does Not Mediate Behavioral Recovery of a Parkinsonian Lesion in Rats

Gene therapy approaches delivering neurotrophic factors have offered promising results in both preclinical and clinical trials of Parkinson's disease (PD). However, failure of glial cell line-derived neurotrophic factor in phase 2 clinical trials has sparked a search for other trophic factors that may retain efficacy in the clinic. Direct protein injections of one such factor, insulin-like growth factor (IGF)-1, in a rodent model of PD has demonstrated impressive protection of dopaminergic neurons against 6-hydroxydopamine (6-OHDA) toxicity. However, protein infusion is associated with surgical risks, pump failure, and significant costs. We therefore used lentiviral vectors to deliver Igf-1, with a particular focus on the novel integration-deficient lentiviral vectors (IDLVs). A neuron-specific promoter, from the human synapsin 1 gene, excellent for gene expression from IDLVs, was additionally used to enhance Igf-1 expression. An investigation of neurotrophic effects on primary rat neuronal cultures demonstrated that neurons transduced with IDLV-Igf-1 vectors had complete protection on withdrawal of exogenous trophic support. Striatal transduction of such vectors into 6-OHDA-lesioned rats, however, provided neither protection of dopaminergic substantia nigra neurons nor improvement of animal behavior.

Mind over hormones: sex differences in associations of well-being with IGF-I, IGFBP-3 and physical activity in the KORA-Age study

OBJECTIVES

A ssociations between well-being, serum levels of insulin-like growth factor 1 (IGF-I), and its primary binding protein IGFBP-3, were examined in an epidemiologic study. The influence of physical activity on the effect of hormones on well-being was considered.

METHODS

Cross-sectional data from participants of the KORA-Age study (n=985, age 64-93) was analyzed in sex-specific multivariable regressions of well-being (World Health Organization (WHO) -5) or ill-being (geriatric depression scale (GDS) -15). Models were adjusted for age, physical activity, sleep, BMI, smoking, and cognition. Adjusted WHO-5 means demonstrated the interaction between hormone quintiles with physical activity.

RESULTS

Full models indicated that increased IGFBP-3 positively associated with well-being in women (β estimate=0.14, standard error (SE)=0.06) and less so in men (β=0.11, SE=0.07). IGF-I associated positively with depression (β=0.11, SE=0.06) and negatively with well-being (β=-0.11, SE=0.06) in women. Similar but not statistically discernable effects were observed in men. Adjusted mean WHO-5 scores illustrated the positive effect of physical activity and IGFBP-3 on well-being in women only.

CONCLUSIONS

Opposite and independent associations of IGF-I and IGFBP-3 on well-being observed in women suggests neuroprotective effects of IGFBP-3 in age.

Effects of aquatic exercise and CES treatment on the changes of cognitive function, BDNF, IGF-1, and VEGF of persons with intellectual disabilities

[Purpose]

The purpose of this study was to investigate the effects of aquatic exercise and CES treatment on the cognitive function by using K-WAB and BDNF, IGF-1, and VEGF of persons with intellectual disabilities.

[Methods]

All subjects were 15 male with intellectual disabilities who were participating in the aquatic training program and CES treatment during 12 weeks at rehabilitation center. The subjects were divided into control group, exercise group, and exercise+CES group. Blood samples for BDNF, IGF-1, and VEGF were taken from brachial vein at rest between before and after treatment.

[Results]

The results are summarized as follows: Cognitive function level increased significantly in the exercise+CES group compared to those in the exercise and control group. The changes of blood IGF-1 concentration were no significant difference among groups. The changes of blood BDNF and VEGF concentration were significantly increased in exercise group and exercise+CES group than control group. However, blood BDNF and VEGF concentration were significantly difference between exercise group and exercise+CES group.

[Conclusion]

In conclusion, it can be concluded that CES treatment with exercise can amend cognitive function of persons with intellectual disabilities more effectively and increase of BDNF and VEGF by exercise can explain the cognitive function improvement of persons with intellectual disabilities.

Factors affecting employment among informal caregivers assisting people with multiple sclerosis

The objective of this study was to identify characteristics of informal caregivers, caregiving, and the people with multiple sclerosis (MS) receiving assistance that are associated with reduced caregiver employment. Data were collected during telephone interviews with 530 MS caregivers, including 215 employed caregivers, with these survey data analyzed using logistic regression. Poorer cognitive ability by the care recipient to make decisions about daily tasks and more caregiving hours per week predicted reduced caregiver employment. Better physical health domains of caregiver quality of life were associated with significantly lower odds of reduced employment. Health professionals treating informal caregivers, as well as those treating people with MS, need to be aware of respite, support, and intervention programs available to MS caregivers and refer them to these programs, which could reduce the negative impact of caregiving on employment.

The Association between IGF-1 Polymorphisms, IGF-1 Serum Levels, and Cognitive Functions in Healthy Adults: The Amsterdam Growth and Health Longitudinal Study

Several studies have demonstrated an association between polymorphisms in the insulin-like growth factor-1 (IGF-1) gene and IGF-1 serum levels. IGF-1 levels have been associated with cognitive functioning in older persons and growth hormone deficient patients. The present study investigates whether IGF-1 polymorphisms, IGF-1 levels, and cognition are interconnected in healthy adults. Data of 277 participants (mean age: 42.4 years) of the Amsterdam Growth and Health Longitudinal Study on IGF-1 promoter polymorphisms, IGF-1 serum level, spatial working memory (SWM), paired associate learning (PAL), and IQ tests were analyzed. (M)ANOVAs were applied to confirm the associations between IGF-1 polymorphisms and IGF-1 levels and between IGF-1 levels and cognition. Three groups were distinguished based on specific IGF-1 polymorphism alleles: a homozygote 192 bp/192 bp genotype, a heterozygote 192 bp/x genotype, and a noncarrier x/x genotype. Although different IGF-1 levels were found for the three genotypes, performance on all cognitive tasks and IQ measures was similar. Despite the associations between IGF-1 polymorphisms and IGF-1 levels, no association was found between cognition and IGF-1 levels. It seems that IGF-1 does not play a role in the cognitive performance of healthy middle-aged adults. Possible, IGF-1 fulfills a more developmental and protective role in cognition which becomes apparent during childhood, old-age, or disease.

Xanthoceraside attenuates learning and memory deficits via improving insulin signaling in STZ-induced AD rats

Xanthoceraside, a triterpenoid saponin extracted from the fruit husks of Xanthoceras sorbifolia Bunge, has been shown to reverse the cognitive deficits observed in several Alzheimer's disease (AD) animal models. Increasing evidence suggests the involvement of the insulin signaling pathway in neurodegenerative disorders such as AD. Thus, we used an AD animal model of cognitive impairment induced by the intracerebroventricular (ICV) injection of streptozotocin (STZ) to test the effects of xanthoceraside on behavioral impairments and insulin signaling mechanisms. In our present study, memory impairment was assessed using the Morris water maze test. The expression of IR, IGF-1R and Raf-1/ERK/CREB was tested by western blotting. The STZ group showed memory deficits in the Morris water maze test and significant decreases in IR and IGF-1R protein levels in the hippocampus. Xanthoceraside treatment significantly rescued memory deficits, as well as IR and IGF-1R protein expression levels. STZ inhibited the Ras/ERK signaling cascade and decreased the phosphorylation of CREB; these effects were also attenuated by xanthoceraside treatment. These results suggest the potential use of xanthoceraside for the treatment of neurodegenerative disorders in which brain insulin signaling may be involved.

Biochemical markers of aging for longitudinal studies in humans

Much progress has been made in the past decades in unraveling the mechanisms that are responsible for aging. The discovery that particular gene mutations in experimental species such as yeast, flies, and nematodes are associated with longevity has led to many important insights into pathways that regulate aging processes. However, extrapolating laboratory findings in experimental species to knowledge that is valid for the complexity of human physiology remains a major challenge. Apart from the restricted experimental possibilities, studying aging in humans is further complicated by the development of various age-related diseases. The availability of a set of biomarkers that really reflect underlying aging processes would be of much value in disentangling age-associated pathology from specific aging mechanisms. In this review, we survey the literature to identify promising biochemical markers of aging, with a particular focus on using them in longitudinal studies of aging in humans that entail repeated measurements on easily obtainable material, such as blood samples. Our search strategy was a 2-pronged approach, one focused on general mechanisms of aging and one including studies on clinical biomarkers of age-related diseases.

Insulin-like growth factor-I and insulin-like growth factor binding protein-3 in Alzheimer's disease

CONTEXT

Few large studies have been conducted to assess the relationship between circulating IGF and late-life cognition.

OBJECTIVE

The aim of the study was to assess the relationship between IGF-I and IGF binding protein-3 (IGFBP-3) serum levels and cognitive impairment, including Alzheimer's disease (AD).

METHODS

In this multicentric cross-sectional study, 694 elderly subjects (218 men, 476 women; 78.6 ± 6.7 yr old) were included; 481 had memory complaints and were diagnosed, after comprehensive cognitive assessment, with AD (n = 224) or mild cognitive impairment (MCI) (n = 257). The control group was comprised of 213 subjects without memory complaint and with normal cognition (recruited among patients' caregivers). IGF-I and IGFBP-3 serum levels were determined by ELISA.

RESULTS

IGF-I and IGFBP-3 serum levels were significantly associated with cognitive status in men (IGF-I, 137 ± 69 ng/ml for AD vs. 178 ± 88 ng/ml for MCI and 172 ± 91 ng/ml for controls, P = 0.01; IGFBP-3, 3675 ± 1542 ng/ml for AD vs. 4143 ± 1828 ng/ml for MCI and 4488 ± 1893 ng/ml for controls, P = 0.04). In women, IGFBP-3 was significantly associated with cognitive status (3781 ± 1351 ng/ml for AD vs. 4190 ± 1408 ng/ml for MCI and 4390 ± 1552 ng/ml for controls; P < 0.001), but no significant differences between groups for IGF-I occurred. After adjustment for confounding variables (age, educational level, body mass index, diabetes, apolipoprotein E ε4 status), logistic regression indicated that IGF-I [odds ratio (95% confidence interval) = 0.48 (0.26-0.88)] and IGFBP-3 [odds ratio (95% confidence interval) = 0.71 (0.52-0.97)] serum levels were independently associated with AD in men, but not in women.

CONCLUSIONS

We report a significant association between low IGF-I and IGFBP-3 serum levels and AD in men, but not in women.

Hormone replacement therapy and physical function in healthy older men. Time to talk hormones?

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

Down-regulation of IGF-1/IGF-1R in hippocampus of rats with vascular dementia

Insulin-like growth factor-1 (IGF-1) has been demonstrated to have neuroprotective effects, but little is known concerning its role in vascular dementia (VaD). This study aimed to evaluate expression of IGF-1 signaling in hippocampus in rat model of VaD, and probe the underlying mechanisms. Permanent occlusion of bilateral common carotid arteries (2-VO) was used as VaD model. Learning and memory functions were declined significantly in 2-VO rats, and these impairments were further deteriorated with the prolongation of 2-VO treatment. IGF-1, IGF-1 receptor (IGF-1R), total Akt and phosphorylated Akt (p-Akt) were all measured at 1, 2 and 4 months following 2-VO injury. Compared with controls, IGF-1, IGF-1 mRNA and p-Akt expression were significantly decreased in hippocampus of 2-VO rats. However, changes of IGF-1R and total Akt levels were not significant. These results suggest that down-regulation of IGF-1 and p-Akt may contribute to the impairments of learning and memory functions after 2-VO. IGF-1/IGF-1R signaling system may involved in the onset and development of VaD.

Insulin-like growth factor-1 and delirium in critically ill mechanically ventilated patients: a preliminary investigation

BACKGROUND

Delirium occurs frequently in the intensive care unit (ICU), but its pathophysiology is still unclear. Low levels of insulin-like growth factor 1 (IGF-1), a hormone with neuroprotective properties, have been associated with delirium in some non-ICU studies, but this relationship has not been examined in the ICU. We sought to test the hypothesis that low IGF-1 concentrations are associated with delirium during critical illness.

METHODS

Mechanically ventilated medical ICU patients were prospectively enrolled, and blood was collected after enrollment for measurement of IGF-1 using radioimmunometric assay. Delirium and coma were identified daily using the Confusion Assessment Method for the ICU and the Richmond Agitation-Sedation Scale, respectively. The association between IGF-1 and delirium was evaluated with logistic regression. In addition, the association between IGF-1 and duration of normal mental state, measured as days alive without delirium or coma, was assessed using multiple linear regression.

RESULTS

Among 110 patients, the median age was 65 years (IQR, 52-75) and APACHE II was 27 (IQR, 22 -32). IGF-1 levels were not a risk factor for delirium on the day after IGF-1 measurement (p = 0.97), at which time 65% of the assessable patients were delirious. No significant association was found between IGF-1 levels and duration of normal mental state (p = 0.23).

CONCLUSIONS

This pilot study, the first to investigate IGF-1 and delirium in critically ill patients, found no association between IGF-1 and delirium. Future studies including serial measurements of IGF-1 and IGF-1 binding proteins are needed to determine whether this hormone has a role in delirium during critical illness.

Resveratrol improves cognitive function in mice by increasing production of insulin-like growth factor-I in the hippocampus

We examined whether resveratrol increases insulin-like growth factor-I (IGF-I) production in the hippocampus by stimulating sensory neurons in the gastrointestinal tract, thereby improving cognitive function in mice. Resveratrol increased calcitonin gene-related peptide (CGRP) release from dorsal root ganglion (DRG) neurons isolated from wild-type (WT) mice. Increases in tissue levels of CGRP, IGF-I, and IGF-I mRNA and immunohistochemical expression of IGF-I were observed in the hippocampus at 3 weeks after oral administration of resveratrol in WT mice. Significant enhancement of angiogenesis and neurogenesis was observed in the dentate gyrus of the hippocampus in these animals (P<.01). Improvement of spatial learning in the Morris water maze was observed in WT mice after administration of resveratrol. None of the effects of resveratrol observed in WT mice were seen after resveratrol administration in CGRP-knockout (CGRP(-/-)) mice. Although red wine containing 20 mg/L of resveratrol produced effects similar to those of resveratrol administrationl in WT mice, neither red wine containing 3.1 mg/L of resveratrol nor white wine exhibited such effects in WT mice. Resveratrol was undetectable in the hippocampus of WT mice administered resveratrol and red wine containing 20 mg/L of resveratrol. These observations strongly suggest that resveratrol increases hippocampal IGF-I production via sensory neuron stimulation in the gastrointestinal tract, thereby improving cognitive function in mice.

Exercise and Cognitive Function: Can Working Out Train the Brain, Too?

Studies exploring the relationship between physical activity, fitness, and cognitive function vary across the lifespan in terms of both their number and the apparent strength of the associations. Studies of children are relatively few in number but generally show a positive association between physical activity and cognitive function. Studies of younger adults are even more scarce; findings are equivocal and do not support the hypothesis that greater physical activity or fitness benefits cognitive function. Studies of older adults suggest that greater physical activity and fitness may improve or at least maintain cognitive function. Increasing physical activity may improve cognitive function, especially executive function in elderly persons. A veritable handful of studies suggest that long-term strength training may have cognitive benefits for elderly persons. Regular exercise and greater aerobic fitness are associated with greater brain volume, improved neurophysiological responses to stimuli as measured by electroencephalography (EEG), and higher levels of growth factors that promote growth of brain tissue, neurogenesis, and angiogenesis. However, the findings are not unequivocal (EEG), often based on animal studies (growth factors), and the physiological significance is not well understood. Therefore, while promising, much work remains to validate these findings in humans and to determine their physiological significance for brain health and function. Current evidence does not support the cardiovascular fitness hypothesis and suggests that the neural activity during exercise itself may initiate changes in the brain, independent of the nature of the exercise. More studies are needed to establish a causal relationship, not merely associations, between exercise and cognitive function. These studies need to better quantify physical activity. Likewise, more work is needed to determine the mechanisms by which exercise alters brain function.

Insulin-like growth factor-1 (IGF-1): relation with cognitive functioning and neuroimaging marker of brain damage in a sample of hypertensive elderly subjects

IGF-1 decline has been related to age-dependent cognitive impairment and dementia. No study examined IGF-1 levels in subjects with a risk factor for brain damage such as hypertension. We investigated the relationship between IGF-1, cognitive functioning and neuroimaging in a sample of 75 hypertensive elderly subjects aged > 65. Cognitive performance were tested by mini mental state examination (MMSE), Cambridge cognitive examination (CAMDEX-R), and the frontal assessment battery (FAB). Among other indices, free IGF-1 in serum was assayed. The radial width of the temporal horn (rWTH) evaluates medial cerebral temporal lobe atrophy. Significant correlations between IGF-1 levels and both total and sub-domain scores of cognition were found. IGF-1 level was significantly lower in cognitively declined group. The lowest IGF-1 -percentile subgroup was significantly cognitively impaired. A statistically non-significant, but lower IGF-1 level was found in the sub-sample with pathologically wider rWTH. Levels of IGF-1 below 79.4 microg/l are associated with cognitive decline, whereas a level above 118 microg/l seems to be a marker of normal cognitive performance. A decreasing of IGF-1 related to a widening of the rWTH suggests an involvement of this hormone in hippocampus atrophy.

Cilostazol improves cognitive function in mice by increasing the production of insulin-like growth factor-I in the hippocampus

Insulin-like growth factor I (IGF-I) exerts beneficial effects on cognitive function by inducing angiogenesis and neurogenesis in the hippocampus. We demonstrated that stimulation of sensory neurons in the gastrointestinal tract increased IGF-I production in the hippocampus, and thereby improved cognitive function in mice. Since cAMP plays a critical role in stimulation of sensory neurons, the type III phosphodiesterase (PDE3) inhibitor cilostazol might increase IGF-I production in the hippocampus by stimulating sensory neurons and thus improve cognitive function in mice. We tested this hypothesis in the present study. Cilostazol increased the release of calcitonin gene-related peptide (CGRP) and levels of cAMP in dorsal root ganglion (DRG) neurons isolated from wild-type (WT) mice. Tissue levels of cAMP in the DRG and hippocampus and those of CGRP, IGF-I, and IGF-I mRNA in the hippocampus were increased after 4-week oral administration of cilostazol to WT mice. Levels of expression of c-fos in the spinal dorsal horns, parabrachial nuclei, the solitary tract nucleus, and the hippocampus were also increased in these animals. Significant enhancement of angiogenesis and neurogenesis was observed in the dentate gyrus of the hippocampus after cilostazol administration in WT mice. Significant improvement of spatial learning was also observed in WT mice administered cilostazol. However, none of these effects in WT mice were observed in CGRP-knockout mice. These observations suggest that cilostazol may improve cognitive function in mice by increasing the hippocampal production of IGF-I through stimulation of sensory neurons.

Circulating insulin-like growth factor I and cognitive function: neuromodulation throughout the lifespan

Insulin-like growth factor I (IGF-I) is central to the somatotropic (growth hormone) axis. It promotes tissue growth and continues to have anabolic effects in adulthood. Accumulating evidence from the last decade, however, reveals that circulating levels of IGF-I also significantly affects cognitive brain function. Specifically, the decline of serum IGF-I might be associated with the age-related cognitive decline in elderly people. Moreover, psychiatric and neurological conditions characterized by cognitive impairment may be characterized by altered levels of IGF-I. Some evidence is emerging that interventions that target the GH/IGF-I axis may improve cognitive functioning, at least in deficient states. As there is evidence linking high serum IGF-I levels with cancer risk, these interventions should be carefully evaluated. On a cellular and molecular level, IGF-I may be a crucial component of neural homeostasis since disturbed IGF-I input is inevitably linked to perturbed function. Consistent with this, all nerve cells are potential targets of IGF-I actions, including neurons, glia, endothelial, epithelial, and perivascular cells. Indeed, many key cellular processes in the brain are affected by IGF-I's neurotrophic and modulatory actions. We review the regulation by IGF-I of neurotransmission and neuronal plasticity and conclude that serum IGF-I is an important mediator of neuronal growth, survival and function throughout the lifespan. The role of IGF-I in synaptic plasticity render its neurotrophic potential a key target for remediating the cognitive impairment associated with a range of neurological conditions.

Stimulation of sensory neurons improves cognitive function by promoting the hippocampal production of insulin-like growth factor-I in mice

Calcitonin gene-related peptide (CGRP) increases the production of insulin-like growth factor-I (IGF-I) in the mouse brain. IGF-I exerts beneficial effects on the cognitive function by increasing synaptic transmission and by inducing angiogenesis and neurogenesis in the hippocampus. In the current study, we examined whether stimulation of sensory neurons by capsaicin improved the cognitive function by increasing the production of IGF-I in the hippocampus using wild-type (WT) and CGRP-knockout (CGRP-/-) mice. Significant increases of the hippocampal tissue levels of CGRP, IGF-I, and IGF-I messenger RNA (mRNA) were observed after capsaicin administration in WT mice (P < 0.01) but not in CGRP-/- mice. Increase in the expression of c-fos was also observed in the spinal dorsal horn, the parabrachial nuclei, and the hippocampus after capsaicin administration in WT mice but not in CGRP-/- mice. Significant enhancement of angiogenesis and neurogenesis was observed in the dentate gyrus of the hippocampus after capsaicin administration in WT mice (P < 0.01) but not in CGRP-/- mice. Although capsaicin administration improved spatial learning in WT mice, no such effect was observed in CGRP-/- mice. Capsaicin-induced improvement of the spatial learning was reversed by administration of an anti-IGF-I antibody and by that of a CGRP receptor antagonist CGRP (8-37) in WT mice. The administration of IGF-I improved the spatial learning in both WT and CGRP-/- mice. These observations strongly suggest that the stimulation of sensory neurons by capsaicin might increase IGF-I production via increasing the hippocampal tissue CGRP levels, and it may thereby promote angiogenesis and neurogenesis to produce improvement of the cognitive function in mice.

Preliminary investigation of plasma levels of sex hormones and human growth factor(s), and P300 latency as correlates to cognitive decline as a function of gender

Background

Aging is marked by declines in levels of many sex hormones and growth factors, as well as in cognitive function. The P300 event-related potential has been established as a predictor of cognitive decline. We decided to determine if this measure, as well as 2 standard tests of memory and attention, may be correlated with serum levels of sex hormones and growth factors, and if there are any generalizations that could be made based on these parameters and the aging process.

Findings

In this large clinically based preliminary study several sex-stratified associations between hormone levels and cognition were observed, including (1) for males aged 30 to 49, both IGF-1 and IGFBP-3 significantly associated negatively with prolonged P300 latency; (2) for males aged 30 to 49, the spearman correlation between prolonged P300 latency and low free testosterone was significant; (3) for males aged 60 to 69, there was a significant negative correlation between P300 latency and DHEA levels; (4) for females aged 50 to 59 IGFBP-3 significantly associated negatively with prolonged P300 latency; (5) for females at all age periods, estrogen and progesterone were uncorrelated with P300 latency; and (6) for females aged 40 to 69, there was significant negative correlation between DHEA levels and P300 latency. Moreover there were no statistically significant correlations between any hormone and Wechsler Memory Scale-III (WMS-111). However, in females, there was a significant positive correlation between estrogen levels and the number of Attention Deficit Disorder (ADD) complaints.

Conclusion

Given certain caveats including confounding factors involving psychiatric and other chronic diseases as well as medications, the results may still have important value. If these results could be confirmed in a more rigorously controlled investigation, it may have important value in the diagnosis, prevention and treatment of cognitive impairments and decline.

Protective effect of total carotenoid and lycopene intake on the risk of hip fracture: a 17-year follow-up from the Framingham Osteoporosis Study

In vitro and in vivo studies suggest that carotenoids may inhibit bone resorption, yet no previous study has examined individual carotenoid intake (other than beta-carotene) and the risk of fracture. We evaluated associations of total and individual carotenoid intake (alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, lutein + zeaxanthin) with incident hip fracture and nonvertebral osteoporotic fracture. Three hundred seventy men and 576 women (mean age, 75 +/- 5 yr) from the Framingham Osteoporosis Study completed a food frequency questionnaire (FFQ) in 1988-1989 and were followed for hip fracture until 2005 and nonvertebral fracture until 2003. Tertiles of carotenoid intake were created from estimates obtained using the Willett FFQ adjusting for total energy (residual method). HRs were estimated using Cox-proportional hazards regression, adjusting for sex, age, body mass index, height, total energy, calcium and vitamin D intake, physical activity, alcohol, smoking, multivitamin use, and current estrogen use. A total of 100 hip fractures occurred over 17 yr of follow-up. Subjects in the highest tertile of total carotenoid intake had lower risk of hip fracture (p = 0.02). Subjects with higher lycopene intake had lower risk of hip fracture (p =0.01) and nonvertebral fracture (p = 0.02). A weak protective trend was observed for total beta-carotene for hip fracture alone, but associations did not reach statistical significance (p = 0.10). No significant associations were observed with alpha-carotene, beta-cryptoxanthin, or lutein + zeaxanthin. These results suggest a protective role of several carotenoids for bone health in older adults.

Donepezil improves cognitive function in mice by increasing the production of insulin-like growth factor-I in the hippocampus

Insulin-like growth factor-I (IGF-I) exerts beneficial effects on cognitive function. The selective acetylcholinesterase inhibitor donepezil increases serum IGF-I levels in elderly subjects. Because stimulation of sensory neurons induces IGF-I production by releasing calcitonin gene-related peptide (CGRP) in the mouse brain, we hypothesized that donepezil increases IGF-I production by sensory neuron stimulation to improve the cognitive function in mice. Donepezil, but not tacrine, increased the CGRP release from dorsal root ganglion neurons isolated from wild-type (WT) mice. Pretreatment with the protein kinase A inhibitor KT5720 [(9S,10S,12R)-2,3,9,10,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg: 3',2',1'-kl]pyrrolo[3,4-i][1,6]-benzo-diazocine-10-carboxylic acid hexyl ester] reversed the effects induced by donepezil. Increase in tissue levels of CGRP, IGF-I, and IGF-I mRNA in the hippocampus was observed at 4 weeks after oral administration of donepezil in WT mice. In these animals, c-fos expression in spinal dorsal horns, parabrachial nuclei, the solitary tract nucleus, and the hippocampus was increased. Enhancement in angiogenesis and neurogenesis was observed in the dentate gyrus of the hippocampus of WT mice after donepezil administration. Improvement of spatial learning was observed in WT mice after donepezil administration. Oral administration of tacrine for 4 weeks produced none of the aforementioned effects induced by donepezil in WT mice. However, none of the effects observed in WT mice was seen after donepezil administration in CGRP-knockout mice and WT mice subjected to functional denervation. These observations suggest that donepezil may improve cognitive function in mice by increasing the hippocampal production of IGF-I through sensory neuron stimulation. These effects of donepezil may not be dependent on its acetylcholinesterase inhibitory activity.

Use of serum insulin-like growth factor-I levels to predict psychiatric non-response to donepezil in patients with Alzheimer's disease

OBJECTIVE

Insulin-like growth factor-I (IGF-I) deficiency may be involved in cognitive deficits seen with aging and in neurodegenerative diseases such as Alzheimer's disease (AD). This study was aimed at investigating whether non-responder to donepezil could be predicted using decreased serum levels of IGF-I in AD patients.

DESIGN

This study involved 106 elderly subjects: 50 patients with AD and 56 age-matched controls without dementia. In patients with AD, donepezil was given orally 3 mg/day for 4 weeks and 5 mg/day for another 12 weeks. AD patients were divided into responders and non-responders based on the changes in mini-mental state examination (MMSE) scores before and 16 weeks after treatment with donepezil. Serum levels of IGF-I and atherogenic biomarkers were determined.

RESULTS

Before treatment with donepezil, there was a significant positive correlation between serum IGF-I levels and the MMSE scores in all subjects. Serum IGF-I levels and the MMSE scores were significantly lower in AD patients than in non-demented controls and were the lowest in non-responders to donepezil. Atherogenic biomarkers (LDL cholesterol, triglycerides, lipoprotein(a), lipid peroxide, apolipoprotein E, and glucose levels) did not differ significantly among these groups. On multiple logistic regression, non-responders to donepezil showed decreased serum IGF-I levels <110 ng/ml and MMSE scores <15 points before treatment.

CONCLUSIONS

These findings suggest that decreased levels of serum IGF-I combined with MMSE scores before treatment could predict non-responders to donepezil among AD patients, which may be a simple and practical method for selecting patients expected to show a response to treatment.