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In humans, social participation and integration wane with advanced age, a pattern hypothesized to stem from cognitive or physical decrements. Similar age-related decreases in social participation have been observed in several nonhuman primate species. Here, we investigated cross-sectional age-related associations between social interactions, activity patterns, and cognitive function in 25 group-living female vervets (a.k.a. African green monkeys, Chlorocebus sabaeus) aged 8–29 years. Time spent in affiliative behavior decreased with age, and time spent alone correspondingly increased. Furthermore, time spent grooming others decreased with age, but the amount of grooming received did not. The number of social partners to whom individuals directed grooming also decreased with age. Grooming patterns mirrored physical activity levels, which also decreased with age. The relationship between age and grooming time was mediated, in part, by cognitive performance. Specifically, executive function significantly mediated age’s effect on time spent in grooming interactions. In contrast, we did not find evidence that physical performance mediated age-related variation in social participation. Taken together, our results suggest that aging female vervets were not socially excluded but decreasingly engaged in social behavior, and that cognitive deficits may underlie this relationship.

•What is the primary question addressed by this study?Do clinical characteristics of participants in the ADMET 2 trial predict better response to methylphenidate for the treatment of apathy in Alzheimer's disease?•What is the main finding of this study?Participants without anxiety or agitation, who were younger, taking a cholinesterase inhibitor, with 73–80 mm Hg diastolic blood pressure, having low functional capacity, were found to respond better to methylphenidate. Combining these characteristics in a multivariate model provided individualized prediction of treatment response.•What is the meaning of the finding?These clinical characteristics may affect the efficacy of methylphenidate in treating apathy, and may help clinicians identify patients most likely to respond to treatment.

Cellular senescence contributes to Alzheimer’s disease (AD) pathogenesis. An open-label, proof-of-concept, phase I clinical trial of orally delivered senolytic therapy, dasatinib (D) and quercetin (Q), was conducted in early-stage symptomatic patients with AD to assess central nervous system (CNS) penetrance, safety, feasibility and efficacy. Five participants (mean age = 76 + 5 years; 40% female) completed the 12-week pilot study. D and Q levels in blood increased in all participants (12.7–73.5 ng ml−1for D and 3.29–26.3 ng ml−1for Q). In cerebrospinal fluid (CSF), D levels were detected in four participants (80%) ranging from 0.281 to 0.536 ml−1with a CSF to plasma ratio of 0.422–0.919%; Q was not detected. The treatment was well-tolerated, with no early discontinuation. Secondary cognitive and neuroimaging endpoints did not significantly differ from baseline to post-treatment further supporting a favorable safety profile. CSF levels of interleukin-6 (IL-6) and glial fibrillary acidic protein (GFAP) increased (t(4) = 3.913, P= 0.008 and t(4) = 3.354, P= 0.028, respectively) with trending decreases in senescence-related cytokines and chemokines, and a trend toward higher Aβ42 levels (t(4) = −2.338, P= 0.079). In summary, CNS penetrance of D was observed with outcomes supporting safety, tolerability and feasibility in patients with AD. Biomarker data provided mechanistic insights of senolytic effects that need to be confirmed in fully powered, placebo-controlled studies. ClinicalTrials.gov identifier: NCT04063124.

OBJECTIVE To determine acute effects of intranasal insulin on regional cerebral perfusion and cognition in older adults with type 2 diabetes mellitus (DM). RESEARCH DESIGN AND METHODS This was a [...]

OBJECTIVE--Impaired insulin sensitivity is linked to cognitive deficits and reduced brain size. However, it is not yet known whether insulin sensitivity involves regional changes in gray matter volume. Against this [...]

OBJECTIVE--Severe hypoglycemia may impair medial temporal-mediated cognitive skills, such as the ability to recall past events explicitly (delayed declarative memory). The objective of this study was to determine whether delayed [...]

We tested the hypothesis that as few as two weekly brief episodes of superimposed hypoglycemia (i.e., doubling the average frequency of symptomatic hypoglycemia) would reduce physiological and behavioral defenses against [...]

To test the hypothesis that glycemic thresholds for hypoglycemic cognitive dysfunction, like those for neuroendocrine responses to and symptoms of hypoglycemia, shift to lower plasma glucose concentrations after recent antecedent [...]

IMPORTANCE: Apathy, characterized by diminished will or initiative and one of the most prevalent neuropsychiatric symptoms in individuals with Alzheimer disease, is associated with significant caregiver burden, excess disability, increased medical costs, and mortality. OBJECTIVE: To measure whether methylphenidate compared with placebo decreases the severity of apathy in individuals with Alzheimer disease. DESIGN, SETTING, AND PARTICIPANTS: This multicenter randomized placebo-controlled clinical trial was conducted from August 2016 to July 2020 in 9 US clinics and 1 Canadian clinic specializing in dementia care. A total of 307 potential participants were screened. Of those, 52 did not pass screening and 55 were not eligible. Participants with Alzheimer disease, mild to moderate cognitive impairment, and frequent and/or severe apathy as measured by the Neuropsychiatric Inventory (NPI) were included. INTERVENTIONS: Ten milligrams of methylphenidate, twice daily, vs matching placebo. MAIN OUTCOMES AND MEASURES: The coprimary outcomes included (1) change from baseline to 6 months in the NPI apathy subscale or (2) improved rating on the Alzheimer’s Disease Cooperative Study Clinical Global Impression of Change. Other outcomes include safety, change in cognition, and quality of life. RESULTS: Of 200 participants, 99 were assigned to methylphenidate and 101 to placebo. The median (interquartile range) age of study participants was 76 (71-81) years; 68 (34%) were female and 131 (66%) were male. A larger decrease was found from baseline to 6 months in the NPI apathy score in those receiving methylphenidate compared with placebo (mean difference, −1.25; 95% CI, −2.03 to −0.47; P = .002). The largest decrease in the NPI apathy score was observed in the first 100 days, with a significant hazard ratio for the proportion of participants with no apathy symptoms receiving methylphenidate compared with placebo (hazard ratio, 2.16; 95% CI, 1.19-3.91; P = .01). At 6 months, the odds ratio of having an improved rating on the Alzheimer’s Disease Cooperative Study Clinical Global Impression of Change for methylphenidate compared with placebo was 1.90 (95% CI, 0.95-3.84; P = .07). The difference in mean change from baseline to 6 months estimated using a longitudinal model was 1.43 (95% CI, 1.00-2.04; P = .048). Cognitive measures and quality of life were not significantly different between groups. Of the 17 serious adverse events that occurred during the study, none were related to the study drug. No significant differences in the safety profile were noted between treatment groups. CONCLUSIONS AND RELEVANCE: This study found methylphenidate to be a safe and efficacious medication to use in the treatment of apathy in Alzheimer disease. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02346201

The effect of hyperglycemia on hormone levels, metabolite levels, and memory performance was examined in 22 subjects with very mild and mild probable dementia of the Alzheimer type (DAT) and in 12 normal elderly adults. Subjects were tested in 3 plasma glucose conditions (fasting baseline, 175 mg/dl, and 225 mg/dl) at initial and 18-month follow-up sessions. Initially, adults with very mild DAT showed memory facilitation and elevations in plasma insulin in the 225-mg/dl glucose condition relative to baseline. At follow-up, very mild DAT patients whose dementia had progressed showed significant decreases in insulin and hyperglycemic memory facilitation. Changes in basal insulin and cortisol levels over time were correlated with memory changes for DAT subjects. These results suggest that glucoregulatory abnormalities may contribute to the pathophysiology of DAT.

We sought 1) to determine which symptoms of hypoglycemia are reproducible, 2) to pharmacologically distinguish neurogenic (autonomic) from neuroglycopenic symptoms, and 3) to test the hypothesis that awareness of hypoglycemia [...]

Dual declines in gait speed and cognitive performance are associated with increased risk of developing dementia. Characterizing the patterns of such impairments therefore is paramount to distinguishing healthy from pathological aging. Nonhuman primates such as vervet/African green monkeys (Chlorocebus aethiops sabaeus) are important models of human neurocognitive aging, yet the trajectory of dual decline has not been characterized. We therefore (1) assessed whether cognitive and physical performance (i.e., gait speed) are lower in older aged animals; (2) explored the relationship between performance in a novel task of executive function (Wake Forest Maze Task—WFMT) and a well-established assessment of working memory (delayed response task—DR task); and (3) examined the association between baseline gait speed with executive function and working memory at 1-year follow-up. We found (1) physical and cognitive declines with age; (2) strong agreement between performance in the novel WFMT and DR task; and (3) that slow gait is associated with poor cognitive performance in both domains. Our results suggest that older aged vervets exhibit a coordinated suite of traits consistent with human aging and that slow gait may be a biomarker of cognitive decline. This integrative approach provides evidence that gait speed and cognitive function differ across the lifespan in female vervet monkeys, which advances them as a model that could be used to dissect relationships between trajectories of dual decline over time.

•This study operationalized the diagnostic criteria for apathy (DCA) into a clinical rated questionnaire and validated it against the Neuropsychiatric Inventory-apathy (NPI-apathy) subscale; it also compared the DCA and NPI-apathy subscale to the Dementia Apathy Interview Rating (DAIR) scale.•The NPI apathy subscale selects patients likely to meet DCA. The DCA was highly concordant with other measures used for the assessment of apathy.•The strong concordance between the DCA, NPI-apathy, and DAIR suggests that these instruments are measuring a similar conceptualization of apathy.

IMPORTANCE: Compared with non-Hispanic White individuals, African American individuals from the same community are approximately twice as likely to develop Alzheimer disease. Despite this disparity, the largest Alzheimer disease genome-wide association studies to date have been conducted in non-Hispanic White individuals. In the largest association analyses of Alzheimer disease in African American individuals, ABCA7, TREM2, and an intergenic locus at 5q35 were previously implicated. OBJECTIVE: To identify additional risk loci in African American individuals by increasing the sample size and using the African Genome Resource panel. DESIGN, SETTING, AND PARTICIPANTS: This genome-wide association meta-analysis used case-control and family-based data sets from the Alzheimer Disease Genetics Consortium. There were multiple recruitment sites throughout the United States that included individuals with Alzheimer disease and controls of African American ancestry. Analysis began October 2018 and ended September 2019. MAIN OUTCOMES AND MEASURES: Diagnosis of Alzheimer disease. RESULTS: A total of 2784 individuals with Alzheimer disease (1944 female [69.8%]) and 5222 controls (3743 female [71.7%]) were analyzed (mean [SD] age at last evaluation, 74.2 [13.6] years). Associations with 4 novel common loci centered near the intracellular glycoprotein trafficking gene EDEM1 (3p26; P = 8.9 × 10−7), near the immune response gene ALCAM (3q13; P = 9.3 × 10−7), within GPC6 (13q31; P = 4.1 × 10−7), a gene critical for recruitment of glutamatergic receptors to the neuronal membrane, and within VRK3 (19q13.33; P = 3.5 × 10−7), a gene involved in glutamate neurotoxicity, were identified. In addition, several loci associated with rare variants, including a genome-wide significant intergenic locus near IGF1R at 15q26 (P = 1.7 × 10−9) and 6 additional loci with suggestive significance (P ≤ 5 × 10−7) such as API5 at 11p12 (P = 8.8 × 10−8) and RBFOX1 at 16p13 (P = 5.4 × 10−7) were identified. Gene expression data from brain tissue demonstrate association of ALCAM, ARAP1, GPC6, and RBFOX1 with brain β-amyloid load. Of 25 known loci associated with Alzheimer disease in non-Hispanic White individuals, only APOE, ABCA7, TREM2, BIN1, CD2AP, FERMT2, and WWOX were implicated at a nominal significance level or stronger in African American individuals. Pathway analyses strongly support the notion that immunity, lipid processing, and intracellular trafficking pathways underlying Alzheimer disease in African American individuals overlap with those observed in non-Hispanic White individuals. A new pathway emerging from these analyses is the kidney system, suggesting a novel mechanism for Alzheimer disease that needs further exploration. CONCLUSIONS AND RELEVANCE: While the major pathways involved in Alzheimer disease etiology in African American individuals are similar to those in non-Hispanic White individuals, the disease-associated loci within these pathways differ.

IMPORTANCE: Insulin modulates aspects of brain function relevant to Alzheimer disease and can be delivered to the brain using intranasal devices. To date, the use of intranasal insulin to treat persons with mild cognitive impairment and Alzheimer’s disease dementia remains to be examined in a multi-site trial. OBJECTIVE: To examine the feasibility, safety, and efficacy of intranasal insulin for the treatment of persons with mild cognitive impairment and Alzheimer disease dementia in a phase 2/3 multisite clinical trial. DESIGN, SETTING, AND PARTICIPANTS: A randomized (1:1) double-blind clinical trial was conducted between 2014 and 2018. Participants received 40 IU of insulin or placebo for 12 months during the blinded phase, which was followed by a 6-month open-label extension phase. The clinical trial was conducted at 27 sites of the Alzheimer’s Therapeutic Research Institute. A total of 432 adults were screened, and 144 adults were excluded. Inclusion criteria included adults aged 55 to 85 years with a diagnosis of amnestic mild cognitive impairment or Alzheimer disease (based on National Institute on Aging–Alzheimer Association criteria), a score of 20 or higher on the Mini-Mental State Examination, a clinical dementia rating of 0.5 or 1.0, and a delayed logical memory score within a specified range. A total of 289 participants were randomized. Among the first 49 participants, the first device (device 1) used to administer intranasal insulin treatment had inconsistent reliability. A new device (device 2) was used for the remaining 240 participants, who were designated the primary intention-to-treat population. Data were analyzed from August 2018 to March 2019. INTERVENTIONS: Participants received 40 IU of insulin (Humulin-RU-100; Lilly) or placebo (diluent) daily for 12 months (blinded phase) followed by a 6-month open-label extension phase. Insulin was administered with 2 intranasal delivery devices. MAIN OUTCOMES AND MEASURES: The primary outcome (mean score change on the Alzheimer Disease Assessment Scale–cognitive subscale 12) was evaluated at 3-month intervals. Secondary clinical outcomes were assessed at 6-month intervals. Cerebrospinal fluid collection and magnetic resonance imaging scans occurred at baseline and 12 months. RESULTS: A total of 289 participants (155 men [54.6%]; mean [SD] age, 70.9 [7.1] years) were randomized. Of those, 260 participants completed the blinded phase, and 240 participants completed the open-label extension phase. For the first 49 participants, the first device used to administer treatment had inconsistent reliability. A second device was used for the remaining 240 participants (123 men [51.3%]; mean [SD] age, 70.8 [7.1] years), who were designated the primary intention-to-treat population. No differences were observed between treatment arms for the primary outcome (mean score change on ADAS-cog-12 from baseline to month 12) in the device 2 ITT cohort (0.0258 points; 95% CI, −1.771 to 1.822 points; P = .98) or for the other clinical or cerebrospinal fluid outcomes in the primary (second device) intention-to-treat analysis. No clinically important adverse events were associated with treatment. CONCLUSIONS AND RELEVANCE: In this study, no cognitive or functional benefits were observed with intranasal insulin treatment over a 12-month period among the primary intention-to-treat cohort. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01767909

Alzheimer's disease (AD) is a continuum with neuropathologies manifesting years before clinical symptoms; thus, AD research is attempting to identify more disease-modifying approaches to test treatments administered before full disease expression. Designing such trials in cognitively normal elderly individuals poses unique challenges.

Both subjective cognitive decline (SCD) and a family history of Alzheimer’s disease (AD) portend risk of brain abnormalities and progression to dementia. Posterior default mode network (pDMN) connectivity is altered early in the course of AD. It is unclear whether SCD predicts similar outcomes in cognitively normal individuals with a family history of AD.

Considerable overlap has been identified in the risk factors, comorbidities and putative pathophysiological mechanisms of Alzheimer disease and related dementias (ADRDs) and type 2 diabetes mellitus (T2DM), two of the most pressing epidemics of our time. Much is known about the biology of each condition, but whether T2DM and ADRDs are parallel phenomena arising from coincidental roots in ageing or synergistic diseases linked by vicious pathophysiological cycles remains unclear. Insulin resistance is a core feature of T2DM and is emerging as a potentially important feature of ADRDs. Here, we review key observations and experimental data on insulin signalling in the brain, highlighting its actions in neurons and glia. In addition, we define the concept of 'brain insulin resistance' and review the growing, although still inconsistent, literature concerning cognitive impairment and neuropathological abnormalities in T2DM, obesity and insulin resistance. Lastly, we review evidence of intrinsic brain insulin resistance in ADRDs. By expanding our understanding of the overlapping mechanisms of these conditions, we hope to accelerate the rational development of preventive, disease-modifying and symptomatic treatments for cognitive dysfunction in T2DM and ADRDs alike.

Both type 1 and type 2 diabetes adversely affect the microvasculature in multiple organs. Our understanding of the genesis of this injury and of potential interventions to prevent, limit, or reverse injury/dysfunction is continuously evolving. This statement reviews biochemical/cellular pathways involved in facilitating and abrogating microvascular injury. The statement summarizes the types of injury/dysfunction that occur in the three classical diabetes microvascular target tissues, the eye, the kidney, and the peripheral nervous system; the statement also reviews information on the effects of diabetes and insulin resistance on the microvasculature of skin, brain, adipose tissue, and cardiac and skeletal muscle. Despite extensive and intensive research, it is disappointing that microvascular complications of diabetes continue to compromise the quantity and quality of life for patients with diabetes. Hopefully, by understanding and building on current research findings, we will discover new approaches for prevention and treatment that will be effective for future generations.

Type 2 diabetes, impaired glucose tolerance (IGT), and associated hyperinsulinemia increase the risk for impaired verbal memory (1-3). In rodents, insulin resistance adversely affects brain structures that support memory (4). [...]

Cognitive impairment in older individuals is a complex trait that in population-based studies most commonly derives from an individually varying mixture of Alzheimer disease, Lewy body disease, and vascular brain injury. We investigated the molecular composition of synaptic particles from three sources: consecutive rapid autopsy brains from the Adult Changes in Thought Study, a population-based cohort; four aged nonhuman primate brains optimally processed for molecular investigation; and targeted replacement transgenic mice homozygous for APOEε4. Our major goal was to characterize the molecular composition of human synaptic particles in regions of striatum and prefrontal cortex. We performed flow cytometry to measure six markers of synaptic subtypes, as well as amyloid β 42 and paired helical filament tau. Our results showed selective degeneration of dopaminergic terminals throughout the striatum in individuals with Lewy body disease, and serotonergic degeneration in human ventromedial caudate nucleus from individuals with an APOEε4 allele. Similar results were seen in mouse caudate nucleus homozygous for APOEε4 via targeted replacement. Together, extension of these clinical, pathologic, and genetic associations from tissue to the synaptic compartment of cerebral cortex and striatum strongly supports our approach for accurately observing the molecular composition of human synapses by flow cytometry.

The translation of promising preclinical treatments into effective drugs for Alzheimer's disease (AD) has been challenging. One of the most potent risk factors for sporadic AD is carrier status of the epsilon 4 allele of the apolipoprotein E gene (E4). E4 carriers show a differential response to several therapies which are being investigated as AD treatments, including acetylcholinesterase inhibitors and therapeutics with vascular and metabolic targets. The differential treatment responses of E4 carriers may partially explain why some treatments show a null effect in clinical trials. Understanding the reasons behind these responses is not only important for clinical practice, but may also help us elucidate mechanisms for this neurodegenerative disease.

IMPORTANCE Sporadic Alzheimer disease (AD) is caused in part by decreased clearance of the β-amyloid (Aβ) peptide breakdown products. Lipid-depleted (LD) apolipoproteins are less effective at binding and clearing Aβ, and LD Aβ peptides are more toxic to neurons. However, not much is known about the lipid states of these proteins in human cerebrospinal fluid. OBJECTIVE To characterize the lipidation states of Aβ peptides and apolipoprotein E in the cerebrospinal fluid in adults with respect to cognitive diagnosis and APOE ε4 allele carrier status and after a dietary intervention. DESIGN Randomized clinical trial. SETTING Veterans Affairs Medical Center clinical research unit. PARTICIPANTS Twenty older adults with normal cognition (mean [SD] age, 69 [7] years) and 27 with amnestic mild cognitive impairment (67 [6] years). INTERVENTIONS Randomization to a diet high in saturated fat content and with a high glycemic index (High diet; 45% of energy from fat [>25% saturated fat], 35%-40% from carbohydrates with a mean glycemic index >70, and 15%-20% from protein) or a diet low in saturated fat content and with a low glycemic index (Low diet; 25% of energy from fat [<7% saturated fat], 55%-60% from carbohydrates with a mean glycemic index <55, and 15%-20% from protein). MAIN OUTCOMES AND MEASURES Lipid-depleted Aβ42 and Aβ40 and apolipoprotein E in cerebrospinal fluid. RESULTS Baseline levels of LD Aβ were greater for adults with mild cognitive impairment compared with adults with normal cognition (LD Aβ42, P = .05; LD Aβ40, P = .01). These findings were magnified in adults with mild cognitive impairment and the ε4 allele, who had higher LD apolipoprotein E levels irrespective of cognitive diagnosis (P < .001). The Low diet tended to decrease LD Aβ levels, whereas the High diet increased these fractions (LD Aβ42, P = .01; LD Aβ40, P = .15). Changes in LD Aβ levels with the Low diet negatively correlated with changes in cerebrospinal fluid levels of insulin (LD Aβ42 and insulin, r = −0.68 [P = .01]; LD Aβ40 and insulin, r = −0.78 [P = .002]). CONCLUSIONS AND RELEVANCE The lipidation states of apolipoproteins and Aβ peptides in the brain differ depending on APOE genotype and cognitive diagnosis. Concentrations can be modulated by diet. These findings may provide insight into the mechanisms through which apolipoprotein E4 and unhealthy diets impart risk for developing AD.

IMPORTANCE Growth hormone–releasing hormone (GHRH) has been previously shown to have cognition-enhancing effects. The role of neurotransmitter changes, measured by proton magnetic resonance spectroscopy, may inform the mechanisms for this response. OBJECTIVE To examine the neurochemical effects of GHRH in a subset of participants from the parent trial. DESIGN Randomized, double-blind, placebo-controlled substudy of a larger trial. SETTING Clinical research unit at the University of Washington School of Medicine. PARTICIPANTS Thirty adults (17 with mild cognitive impairment [MCI]), ranging in age from 55 to 87 years, were enrolled and successfully completed the study. INTERVENTIONS Participants self-administered daily subcutaneous injections of tesamorelin (Theratechnologies Inc), a stabilized analogue of human GHRH (1 mg/d), or placebo 30 minutes before bedtime for 20 weeks. At baseline and weeks 10 and 20, participants underwent brain magnetic resonance imaging and spectroscopy protocols and cognitive testing and provided blood samples after fasting. Participants also underwent glucose tolerance tests before and after intervention. MAIN OUTCOMES AND MEASURES Brain levels of glutamate, inhibitory transmitters γ-aminobutyric acid (GABA) and N-acetylaspartylglutamate (NAAG), and myo-inositol (MI), an osmolyte linked to Alzheimer disease in humans, were measured in three 2 × 2 × 2-cm3 left-sided brain regions (dorsolateral frontal, posterior cingulate, and posterior parietal). Glutamate, GABA, and MI levels were expressed as ratios to creatine plus phosphocreatine, and NAAG was expressed as a ratio to N-acetylaspartate. RESULTS After 20 weeks of GHRH administration, GABA levels were increased in all brain regions (P < .04), NAAG levels were increased (P = .03) in the dorsolateral frontal cortex, and MI levels were decreased in the posterior cingulate (P = .002). These effects were similar in adults with MCI and older adults with normal cognitive function. No changes in the brain levels of glutamate were observed. In the posterior cingulate, treatment-related changes in serum insulin-like growth factor 1 were positively correlated with changes in GABA (r = 0.47; P = .001) and tended to be negatively correlated with MI (r = −0.34; P = .06). Consistent with the results of the parent trial, a favorable treatment effect on cognition was observed in substudy participants (P = .03). No significant associations were observed between treatment-related changes in neurochemical and cognitive outcomes. Glucose homeostasis in the periphery was not reliably affected by GHRH administration and did not account for treatment neurochemical effects. CONCLUSIONS Twenty weeks of GHRH administration increased GABA levels in all 3 brain regions, increased NAAG levels in the frontal cortex, and decreased MI levels in the posterior cingulate. To our knowledge, this is the first evidence that 20 weeks of somatotropic supplementation modulates inhibitory neurotransmitter and brain metabolite levels in a clinical trial, and it provides preliminary support for one possible mechanism to explain favorable GHRH effects on cognition in adults with MCI and in healthy older adults. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00257712.

BACKGROUND Growth hormone–releasing hormone (GHRH), growth hormone, and insulinlike growth factor 1 have potent effects on brain function, their levels decrease with advancing age, and they likely play a role in the pathogenesis of Alzheimer disease. Previously, we reported favorable cognitive effects of short-term GHRH administration in healthy older adults and provided preliminary evidence to suggest a similar benefit in adults with mild cognitive impairment (MCI). OBJECTIVE To examine the effects of GHRH on cognitive function in healthy older adults and in adults with MCI. DESIGN Randomized, double-blind, placebo-controlled trial. SETTING Clinical Research Center, University of Washington School of Medicine in Seattle. PARTICIPANTS A total of 152 adults (66 with MCI) ranging in age from 55 to 87 years (mean age, 68 years); 137 adults (76 healthy participants and 61 participants with MCI) successfully completed the study. INTERVENTION Participants self-administered daily subcutaneous injections of tesamorelin (Theratechnologies Inc), a stabilized analog of human GHRH (1 mg/d), or placebo 30 minutes before bedtime for 20 weeks. At baseline, at weeks 10 and 20 of treatment, and after a 10-week washout (week 30), blood samples were collected, and parallel versions of a cognitive battery were administered. Before and after the 20-week intervention, participants completed an oral glucose tolerance test and a dual-energy x-ray absorptiometry scan to measure body composition. MAIN OUTCOME MEASURES Primary cognitive outcomes were analyzed using analysis of variance and included 3 composites reflecting executive function, verbal memory, and visual memory. Executive function was assessed with Stroop Color-Word Interference, Task Switching, the Self-Ordered Pointing Test, and Word Fluency, verbal memory was assessed with Story Recall and the Hopkins Verbal Learning Test, and visual memory was assessed with the Visual-Spatial Learning Test and Delayed Match-to-Sample. RESULTS The intent-to-treat analysis indicated a favorable effect of GHRH on cognition (P = .03), which was comparable in adults with MCI and healthy older adults. The completer analysis showed a similar pattern, with a more robust GHRH effect (P = .002). Subsequent analyses indicated a positive GHRH effect on executive function (P = .005) and a trend showing a similar treatment-related benefit in verbal memory (P = .08). Treatment with GHRH increased insulinlike growth factor 1 levels by 117% (P < .001), which remained within the physiological range, and reduced percent body fat by 7.4% (P < .001). Treatment with GHRH increased fasting insulin levels within the normal range by 35% in adults with MCI (P < .001) but not in healthy adults. Adverse events were mild and were reported by 68% of GHRH-treated adults and 36% of those who received placebo. CONCLUSIONS Twenty weeks of GHRH administration had favorable effects on cognition in both adults with MCI and healthy older adults. Longer-duration treatment trials are needed to further examine the therapeutic potential of GHRH administration on brain health during normal aging and “pathological aging.” TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00257712

OBJECTIVE To examine the effects of intranasal insulin administration on cognition, function, cerebral glucose metabolism, and cerebrospinal fluid biomarkers in adults with amnestic mild cognitive impairment or Alzheimer disease (AD). DESIGN Randomized, double-blind, placebo-controlled trial. SETTING Clinical research unit of a Veterans Affairs medical center. PARTICIPANTS The intent-to-treat sample consisted of 104 adults with amnestic mild cognitive impairment (n = 64) or mild to moderate AD (n = 40). INTERVENTION Participants received placebo (n = 30), 20 IU of insulin (n = 36), or 40 IU of insulin (n = 38) for 4 months, administered with a nasal drug delivery device (Kurve Technology, Bothell, Washington). MAIN OUTCOME MEASURES Primary measures consisted of delayed story recall score and the Dementia Severity Rating Scale score, and secondary measures included the Alzheimer Disease's Assessment Scale–cognitive subscale (ADAS-cog) score and the Alzheimer's Disease Cooperative Study–activities of daily living (ADCS-ADL) scale. A subset of participants underwent lumbar puncture (n = 23) and positron emission tomography with fludeoxyglucose F 18 (n = 40) before and after treatment. RESULTS Outcome measures were analyzed using repeated-measures analysis of covariance. Treatment with 20 IU of insulin improved delayed memory (P < .05), and both doses of insulin (20 and 40 IU) preserved caregiver-rated functional ability (P < .01). Both insulin doses also preserved general cognition as assessed by the ADAS-cog score for younger participants and functional abilities as assessed by the ADCS-ADL scale for adults with AD (P < .05). Cerebrospinal fluid biomarkers did not change for insulin-treated participants as a group, but, in exploratory analyses, changes in memory and function were associated with changes in the Aβ42 level and in the tau protein–to–Aβ42 ratio in cerebrospinal fluid. Placebo-assigned participants showed decreased fludeoxyglucose F 18 uptake in the parietotemporal, frontal, precuneus, and cuneus regions and insulin-minimized progression. No treatment-related severe adverse events occurred. CONCLUSIONS These results support longer trials of intranasal insulin therapy for patients with amnestic mild cognitive impairment and patients with AD. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00438568

OBJECTIVE To compare the effects of a 4-week high–saturated fat/high–glycemic index (HIGH) diet with a low–saturated fat/low–glycemic index (LOW) diet on insulin and lipid metabolism, cerebrospinal fluid (CSF) markers of Alzheimer disease, and cognition for healthy adults and adults with amnestic mild cognitive impairment (aMCI). DESIGN Randomized controlled trial. SETTING Veterans Affairs Medical Center clinical research unit. PARTICIPANTS Forty-nine older adults (20 healthy adults with a mean [SD] age of 69.3 [7.4] years and 29 adults with aMCI with a mean [SD] age of 67.6 [6.8] years). INTERVENTION Participants received the HIGH diet (fat, 45% [saturated fat, > 25%]; carbohydrates, 35%-40% [glycemic index, > 70]; and protein, 15%-20%) or the LOW diet (fat, 25%; [saturated fat, < 7%]; carbohydrates, 55%-60% [glycemic index, < 55]; and protein, 15%-20%) for 4 weeks. Cognitive tests, an oral glucose tolerance test, and lumbar puncture were conducted at baseline and during the fourth week of the diet. MAIN OUTCOME MEASURES The CSF concentrations of β-amyloid (Aβ42 and Aβ40), tau protein, insulin, F2-isoprostanes, and apolipoprotein E, plasma lipids and insulin, and measures of cognition. RESULTS For the aMCI group, the LOW diet increased CSF Aβ42 concentrations, contrary to the pathologic pattern of lowered CSF Aβ42 typically observed in Alzheimer disease. The LOW diet had the opposite effect for healthy adults, ie, decreasing CSF Aβ42, whereas the HIGH diet increased CSF Aβ42. The CSF apolipoprotein E concentration was increased by the LOW diet and decreased by the HIGH diet for both groups. For the aMCI group, the CSF insulin concentration increased with the LOW diet, but the HIGH diet lowered the CSF insulin concentration for healthy adults. The HIGH diet increased and the LOW diet decreased plasma lipids, insulin, and CSF F2-isoprostane concentrations. Delayed visual memory improved for both groups after completion of 4 weeks of the LOW diet. CONCLUSION Our results suggest that diet may be a powerful environmental factor that modulates Alzheimer disease risk through its effects on central nervous system concentrations of Aβ42, lipoproteins, oxidative stress, and insulin.Arch Neurol. 2011;68(6):743-752--

OBJECTIVES To examine the effects of aerobic exercise on cognition and other biomarkers associated with Alzheimer disease pathology for older adults with mild cognitive impairment, and assess the role of sex as a predictor of response. DESIGN Six-month, randomized, controlled, clinical trial. SETTING Veterans Affairs Puget Sound Health Care System clinical research unit. PARTICIPANTS Thirty-three adults (17 women) with amnestic mild cognitive impairment ranging in age from 55 to 85 years (mean age, 70 years). INTERVENTION Participants were randomized either to a high-intensity aerobic exercise or stretching control group. The aerobic group exercised under the supervision of a fitness trainer at 75% to 85% of heart rate reserve for 45 to 60 min/d, 4 d/wk for 6 months. The control group carried out supervised stretching activities according to the same schedule but maintained their heart rate at or below 50% of their heart rate reserve. Before and after the study, glucometabolic and treadmill tests were performed and fat distribution was assessed using dual-energy x-ray absorptiometry. At baseline, month 3, and month 6, blood was collected for assay and cognitive tests were administered. MAIN OUTCOME MEASURES Performance measures on Symbol-Digit Modalities, Verbal Fluency, Stroop, Trails B, Task Switching, Story Recall, and List Learning. Fasting plasma levels of insulin, cortisol, brain-derived neurotrophic factor, insulinlike growth factor-I, and β-amyloids 40 and 42. RESULTS Six months of high-intensity aerobic exercise had sex-specific effects on cognition, glucose metabolism, and hypothalamic-pituitary-adrenal axis and trophic activity despite comparable gains in cardiorespiratory fitness and body fat reduction. For women, aerobic exercise improved performance on multiple tests of executive function, increased glucose disposal during the metabolic clamp, and reduced fasting plasma levels of insulin, cortisol, and brain-derived neurotrophic factor. For men, aerobic exercise increased plasma levels of insulinlike growth factor I and had a favorable effect only on Trails B performance. CONCLUSIONS This study provides support, using rigorous controlled methodology, for a potent nonpharmacologic intervention that improves executive control processes for older women at high risk of cognitive decline. Moreover, our results suggest that a sex bias in cognitive response may relate to sex-based differences in glucometabolic and hypothalamic-pituitary-adrenal axis responses to aerobic exercise.Arch Neurol. 2010;67(1):71-79--

In recent years a rapidly increasing number of studies has focused on the relationship between dementia and metabolic disorders such as diabetes, obesity, hypertension, and dyslipidemia. Etiological heterogeneity and comorbidity pose challenges for determining relationships among metabolic disorders. The independent and interactive effects of brain vascular injury and classic pathological agents such as β-amyloid have also proved difficult to distinguish in human patients, blurring the lines between Alzheimer disease and vascular dementia. This review highlights recent work aimed at identifying convergent mechanisms such as insulin resistance that may underlie comorbid metabolic disorders and thereby increase dementia risk. Identification of such convergent factors will not only provide important insight into the causes and interdependencies of late-life dementias but will also inspire novel strategies for treating and preventing these disorders.Arch Neurol. 2009;66(3):300-305--

Insulin modulates cognition and other aspects of normal brain function. Insulin resistance is characterized by chronic peripheral insulin elevations, and it is accompanied by reduced brain insulin levels and insulin activity. Obesity, type 2 diabetes mellitus and hypertension are strongly associated with insulin resistance. In addition, insulin resistance increases the risk of age-related memory impairment and Alzheimers disease. Possible mechanisms through which these risks are increased include the effects of peripheral hyperinsulinemia on memory, CNS inflammation, and regulation of the -amyloid peptide. We have shown that raising plasma insulin in humans to levels that characterize patients with insulin resistance increases the levels of A and inflammatory agents in brain. These convergent effects may impair memory and induce AD pathology. Therapeutic strategies focused on preventing or correcting insulin abnormalities may thus benefit a subset of adults with age-related memory impairment and AD.

Aβ is the major component of amyloid plaques characterizing Alzheimer's disease (AD). Aβ accumulation can be affected by numerous factors including increased rates of production and/or impaired clearance. Insulin-degrading enzyme (IDE) has been implicated as a candidate enzyme responsible for the degradation and clearance of Aβ in the brain. We have previously shown that AD patients exhibit abnormalities in insulin metabolism that are associated with apoliprotein E (APOE) status. The possible association of IDE with AD, as well as the link between APOE status and insulin metabolism, led us to examine the expression of IDE in AD. We report that hippocampal IDE protein is reduced by approximately 50% in ε4+ AD patients compared to ε4− patients and controls. The allele-specific decrease of IDE in ε4+ AD patients is not associated with neuronal loss since neuron-specific enolase levels were comparable between the AD groups, regardless of APOE status. Hippocampal IDE mRNA levels were also reduced in AD patients with the ε4 allele compared to AD and normal subjects without the ε4 allele. These findings show that reduced IDE expression is associated with a significant risk factor for AD and suggest that IDE may interact with APOE status to affect Aβ metabolism.

The presence of cocaine during the prenatal period disrupts the development of neural systems involved in mediating visual attention; therefore, it is possible that prenatal cocaine exposure results in impairments in visual attention in early childhood. In the current study we hypothesized that preschool children with prenatal cocaine exposure would exhibit difficulties in the disengagement operation of visual attention and in sustaining attention, particularly for targets presented in the right visual field. Fourteen cocaine-exposed children and 20 control children between 14 and 60 months of age were assessed on measures of visual attention, cognition, and behavior. Cocaine-exposed children had slower reaction times on disengagement trials in the second half of our attention task, supporting our hypotheses that impairments in disengagement and sustained attention are associated with prenatal cocaine exposure. There was a trend for slower reaction times to targets presented in the right visual field, but not to targets presented in the left visual field. Cocaine-exposed children also exhibited greater difficulties in behavioral regulation. Overall, our findings suggest that children with prenatal cocaine exposure demonstrate specific impairments in visual attention and behavioral regulation. (JINS, 2002, 8, 12–21.)

Inhibition of return is a bias in attention that reduces the likelihood of returning attention to previously viewed locations. This attention bias develops during the first 6 months of life and is putatively mediated by midbrain structures. The present study evaluated the effects of perinatal lesions on the development of inhibition of return. Thirty-three children with perinatal injury resulting in spastic diplegic cerebral palsy were grouped based on magnetic resonance exams. Children with anterior (n = 5), posterior (n = 12), diffuse (n = 8), or no apparent (n = 8) lesions were compared with a group of age-matched children without neurologic injury (n = 39) on an orienting task designed to elicit inhibition of return. Short-delay trials demonstrated grossly intact facilitation of attention for all groups. Long-delay trials that produced inhibition of return in the control and posterior injury groups indicated a disruption of inhibition of return in the groups with anterior and diffuse lesions. The findings are consistent with previous reports that anterior regions are important for the developing attention system, and that bilateral injury can result in unilateral disruption of visual attention. (JINS, 2001, 7, 275–284.)

Higher fasting plasma insulin levels and reduced CSF-to-plasma insulin-ratios, suggestive of insulin resistance, have been observed in patients with Alzheimer's disease (AD) who do not possess an apolipoprotein E (ApoE)-4 allele. Insulin has also been implicated in processing of ?-amyloid and amyloid precursor protein (APP). We examined the effects of intravenous insulin administration while maintaining euglycemia on insulin-mediated glucose disposal, memory, and plasma APP in patients with AD and normal adults of varying ApoE genotypes. AD subjects without an 4 allele had significantly lower insulin-mediated glucose disposal rates than did AD patients with an 4 allele ( p< 0.03 ) or than did normal adults without an 4 allele ( p< 0.02 ). AD subjects without an 4 allele also showed significant memory facilitation with insulin administration ( p< 0.04 ), whereas the AD-4 group did not. Insulin reduced APP levels for AD patients without an ApoE 4 allele, but raised APP for AD patients with an ApoE H4 allele These results document ApoE-related differences in insulin metabolism in AD that may relate to disease pathogenesis.

N-methyl-D-aspartate (NMDA) glutamate receptor antagonists are reported to induce schizophrenia-like symptoms in humans, including cognitive impairments. Shortcomings of most previous investigations include failure to maintain steady-state infusion conditions, test multiple doses and/or measure antagonist plasma concentrations. This double-blind, placebo-controlled, randomized, within-subjects comparison of three fixed subanesthetic, steady-state doses of intravenous ketamine in healthy males (n = 15) demonstrated dose-dependent increases in Brief Psychiatric Rating Scale positive (F[3,42] = 21.84; p< 0.0001) and negative symptoms (F[3,42] = 2.89; p= 0.047), and Scale for the Assessment of Negative Symptoms (SANS) total scores (F[3,42] = 10.55; p< 0.0001). Ketamine also produced a robust dose-dependent decrease in verbal declarative memory performance (F[3,41] = 5.11; p= 0.004), and preliminary evidence for a similar dose-dependent decrease in nonverbal declarative memory, occurring at or below plasma concentrations producing other symptoms. Increasing NMDA receptor hypofunction is associated with early occurring memory impairments followed by other schizophrenia-like symptoms.

Recent studies indicate that the neural systems underlying the development of visual attention may differ from the systems subserving attention in adulthood. Our study examined the effects of early brain injury on attentional operations. A covert orienting task (Posner, Cohen, & Rafal, 1982) was administered to 29 children with sickle cell anemia (SCA), 17 of whom had experienced stroke (6 bifrontal and 11 diffuse), and 20 siblings without SCA. Children with bifrontal injury showed lateralized impairment in early-stage attentional processing, consisting of faster reaction times to targets in the left visual field that were preceded by invalid cues. These results were similar to findings in a previous study of children with bifrontal perinatal injury (Craft, White, & Park, 1994). In contrast, children with diffuse lesions showed exaggerated increases in reaction time for invalidly cued targets in both visual fields. The performance of SCA children without strokes was similar to that of sibling control subjects. The results indicate that anterior brain regions play an important role in the development of attentional operations throughout childhood.

Previous studies have reported that developmental disruption of dopaminergic systems results in lateralized deficits in visual attention (Posner et al., 1991; Craft et al., 1992). Infants who were prenatally exposed to cocaine were hypothesized to have increased reaction times to targets in the right visual field on measures of visual attention compared with infants who were not exposed to cocaine. Seventeen children without prenatal exposure to cocaine and 14 children who were exposed to cocaine (age range from 8–40 months) completed a visual attention task, the Mental Development Index of the Bayley Scales of Infant Development, Second Edition; and the Preschool Language Scale, Third Edition. Cocaine-exposed children were slower to orient to stimuli in the right visual field after repeated trials, especially after attention was first cued to the left visual field. They were also less likely to orient to the right when given a choice. Results suggest that the left hemisphere visual attention system is disproportionately affected by prenatal exposure to cocaine. (JINS, 1997, 3, 237–245.)

Glucose utilization appears to play a role in memory, and patients with Senile Dementia of the Alzheimer Type (SDAT) show particular abnormalities of the glucose system. The present study examined the effects of glucose administration on memory in subjects with mild SDAT and age- matched controls. SDAT subjects demonstrated greater overall increases in blood glucose levels following glucose administration. Normal subjects whose blood glucose levels returned to near baseline following glucose administration showed facilitated memory performance, whereas SDAT subjects whose blood glucose levels remained elevated showed significant improvement following glucose administration. The results suggest that impaired glucose regulation contributes to memory impairment in SDAT.

Phenylketonuria (PKU) is a genetic disorder of amino acid metabolism that is associated with brain catecholamine depletion and deficient myelination. Although neuropsychological deficits have been documented in children with early-treated PKU (ETPKU), no study to date has examined possible effects of impaired myelination in this population. In the present study, interhemispheric transfer time was assessed for 14 children with ETPKU, 22 children with attention deficit-hyperactivity disorder, and 48 normal children, using a manual reaction time paradigm previously validated with callosal agenesis patients (Milner, 1982). Children with ETPKU demonstrated slowed interhemispheric transfer from the left to the right hemisphere as compared with the two other groups. The magnitude of slowing was correlated with age and phenylalanine levels at birth. Results support the hypothesis that abnormal myelination disrupts the development of interhemispheric connections in ETPKU, and suggest that left hemisphere projections may be particularly susceptible to such disruption.

Previous studies of the neuropsychological consequences of insulin dependent diabetes mellitus (IDDM) have had mixed and often contradictory results, possibly due to the heterogeneity of the samples and neuropsychological measures, and a lack of specific hypotheses. In order to address this problem, we focused on the effect of severe hypoglycemia on memory functioning in a relatively homogeneous sample of childhood-onset IDDM patients. Given the deleterious effects of hypoglycemia on medial temporal lobe structures (e.g., hippocampus) and the relationship between medial temporal damage and declarative memory functioning, we hypothesized that those patients who had experienced severe hypoglycemia would demonstrate impaired declarative memory and spared nondeclarative memory functioning. Results of the study were generally consistent with this hypothesis, although some impact of hypoglycemia was observed on perceptual priming ability. (JINS, 1997, 3, 509–520.)

Patients with Alzheimer's disease (AD) have elevations of fasting plasma insulin that are hypothesized to be associated with disrupted brain insulin metabolism. We examined paired fasted plasma and CSF insulin levels in 25 patients with AD and 14 healthy age-matched adults and determined whether insulin levels were related to severity of dementia and apolipoprotein E-4 homozygosity, a known genetic risk factor for AD. The AD patients had lower CSF insulin, higher plasma insulin, and a reduced CSF-to-plasma insulin ratio when compared with healthy adults. The differences were greater for patients with more advanced AD. Patients who were not apolipoprotein E-4 homozygotes had higher plasma insulin levels and reduced CSF-to-plasma ratios, whereas 4 homozygotes with AD had normal values. Both plasma and CSF insulin levels are abnormal in AD, and there are metabolic differences among apolipoprotein E genotypes.

The neural systems underlying visual attention have been well-documented in adults through studies examining the effects of brain lesions on specific attentional operations (Posner, Cohen, & Rafal, 1982). The questions of how this attentional system develops and how it is affected by disruption during development are only beginning to be addressed. In the present study, a covert orienting task (Posner et al., 1982) was administered to 33 children with bilateral perinatal injury to anterior, posterior, or diffuse brain regions and 36 normal children to determine the effects of such injury on visual attention. Children with bilateral anterior lesions showed lateralized impairment indicating compromise of left hemisphere early attentional processes. In contrast, children with posterior lesions that typically disrupt attention in adults showed only general slowing, with no differences in right or left visual field performance or deficits in specific attentional operations. These results suggest that anterior brain regions play an important role in the development of visual attention, and that left hemisphere attentional processes are particularly affected by disruption of anterior function.

CT measurements of right and left occipital length and width were correlated with eye dominance for 14 men and 27 women. Female subjects demonstrated little relationship between eye dominance and occipital measurements. For male subjects, however, right eye dominance was significantly correlated with increased lengths and widths for both right and left hemispheres on CT slices W, SM, and SM +1, which contain a large proportion of visual cortex and visual association areas. These data suggest that eye dominance is related to occipital morphology for men.

Insulin-degrading enzyme (IDE) has been identified as a candidate protease in the clearance of amyloid-β (Aβ) peptides from the brain. IDE activity and binding to insulin are known to be inhibited by glucocorticoids in vitro. In Alzheimer disease (AD), both a decrease in IDE levels and an increase in peripheral glucocorticoid levels have been documented. Our study investigated the effects of glucocorticoid treatment on IDE expression in vivo in 12 nonhuman primates (Macaca nemestrina). Year-long, high-dose exposure to the glucocorticoid cortisol (hydrocortisone acetate) was associated with reduced IDE protein levels in the inferior frontal cortex and reduced IDE mRNA levels in the dentate gyrus of the hippocampus. We assessed Aβ40 and Aβ42 levels by ELISA in the brain and in plasma, total plaque burden by immunohistochemistry, and relative Aβ1-40 and Aβ1-42 levels in the brain by mass spectrometry. Glucocorticoid treatment increased Aβ42 relative to Aβ40 levels without a change in overall plaque burden within the brain, while Aβ42 levels were decreased in plasma. These findings support the notion that glucocorticoids regulate IDE and provide a mechanism whereby increased glucocorticoid levels may contribute to AD pathology.