A-18 Early Pattern of Cognitive Changes Associated with Insulin Resistance in a Sample of Young Adults

Objective

Insulin resistance increases the risk of developing type 2 diabetes and subsequently cardiovascular and cerebrovascular disease. It is also linked to neurocognitive disorders and accelerated cognitive aging (Ekblad et al, 2017; Levine, Harrati, & Crimmins, 2018). Using baseline data from a longitudinal study in a sample of 126 cognitively intact adults aged 25–50 years (36.5% males), we assessed cognitive performance in relation to insulin resistance to determine whether an early prodromal pattern of cognitive changes exists prior to advanced metabolic disease.

Methods

Steady state plasma glucose (SSPG) was used to measure insulin resistance. Multivariate regression analyses were conducted using age, years of education, body mass index (BMI), and SSPG as predictors of neuropsychological functioning. In-person and tele-neuropsychological assessment was administered using standard neuropsychological measures.

Results

Higher insulin resistance was associated with significantly worse attention (WAIS-III Digit Span total; B = -0.018, p = 0.03), executive functioning (D-KEFS Color-Word Inhibition/Switching; B = 0.047, p = 0.04) and dominant fine motor abilities (Purdue Pegboard; B = -0.008, p = 0.02). Higher insulin resistance was also associated with trend level worsening of other measures of executive functioning, namely D-KEFS Trails 4 (B = 0.099, p = 0.07) and DKEFS Color-Word Inhibition errors (B = 0.007, p = 0.09).

Conclusions

In young adults, higher insulin resistance was associated with declines in attention, executive functioning, and fine motor abilities. This early pattern of subtle cognitive changes associated with higher insulin resistance seen in this sample of younger adults is consistent with later cognitive declines found in type 2 diabetes and vascular neurocognitive disorder, namely declines in attention, executive functioning, and motor abilities with eventual memory declines in advanced disease.

DIFFERENTIAL EFFECTS OF STATINS ON COGNITION IN WOMEN AT RISK FOR ALZHEIMER’S DISEASE

It is well established that the apolipoprotein epsilon 4 allele (APOE4) and being female are risk factors for late onset Alzheimer’s disease (AD) and declines in verbal learning and memory are early cognitive symptoms of conversion to AD. Because of conflicting findings regarding the effects of statins on cognition, this study examined statin use with respect to verbal learning and memory by APOE4 status in a sample of cognitively unimpaired women at risk for AD. Neuropsychological, statin use, and APOE4 data were utilized as a secondary analysis from an ongoing longitudinal study at the Banner Alzheimer’s Institute in Arizona. Subjects were cognitively unimpaired women aged 47-75 with a family history of probable AD in at least one first-degree relative. Neuropsychological outcome variables included total learning, immediate memory, and delayed memory scores from the Rey Auditory Verbal Learning Test (RAVLT). Statin use was defined by use of a cholesterol lowering drug at study enrollment. APOE4 status was defined by presence of at least one APOE4 allele. Linear regression analyses were conducted to determine existence of interactions between statin use and APOE4 status on cognition. Statistically significant interactions were found between statin use and APOE4 status in RAVLT total learning and immediate memory. Statin use in women APOE4 non-carriers was associated with better verbal learning and immediate memory performances whereas statin use in women APOE4 carriers was associated with worse performances on these same tasks. Conclusions. Findings suggest that sex and APOE4 status may be important factors in consideration of statin use.

Early life adversity blunts responses to pioglitazone in depressed, overweight adults

PURPOSE

Early life adversity is associated with both metabolic impairment and depression in adulthood, as well as with poorer responses to antidepressant medications. It is not yet known whether individual differences in sensitivity to antidiabetic medications could also be related to early life adversity. We examined whether a history of early life adversity affected the observed changes in metabolic function and depressive symptoms in a randomized trial of pioglitazone for augmentation of standard treatments for depression.

PURPOSE

Early life adversity is associated with both metabolic impairment and depression in adulthood, as well as with poorer responses to antidepressant medications. It is not yet known whether individual differences in sensitivity to antidiabetic medications could also be related to early life adversity. We examined whether a history of early life adversity affected the observed changes in metabolic function and depressive symptoms in a randomized trial of pioglitazone for augmentation of standard treatments for depression.

FINDINGS

We found that early life adversity significantly impaired the metabolic response to pioglitazone. Effects on depressive symptoms did not reach significance, but nonetheless suggested that pioglitazone could mitigate the depressant effects of childhood adversity, only among those insulin resistant at baseline.

CONCLUSIONS

We conclude that a history of early life adversity may impair the body's ability to respond to insulin sensitizing pharmacotherapy, and furthermore that its contribution to resistant depression may function in part via the generation of an insulin resistant phenotype.

Cognitive effects of mifepristone in overweight, euthymic adults with depressive disorders

BACKGROUND

Previous studies have shown that individuals with mood disorders have a higher prevalence of both hypercortisolemia and insulin resistance. Insulin resistance is posited to contribute to the cognitive deficits observed in individuals who have depression. However, the mechanistic relationship between cortisol and insulin within the central nervous system remains to be further elucidated. This study aimed to evaluate the effects of the antiglucocorticoid agent, mifepristone, on metabolic function and cognitive performance in individuals receiving treatment for depressive disorders who were euthymic at baseline.

METHODS

Participants were administered a 600 mg/day dose of mifepristone for 28 days. Oral glucose tolerance tests (OGTTs) and cognitive assessments measuring verbal memory and executive functioning were administered at baseline and after 28 days of treatment.

RESULTS

Improvements in attention and verbal learning were associated with reduction of fasting plasma glucose (FPG) in response to mifepristone treatment.

LIMITATIONS

Limitations include the open-label design of this study and a small sample size.

CONCLUSIONS

The findings from this study suggest that improvement in fasting plasma glucose levels, upon administration of mifepristone, is associated with the improvement in early input of verbal information. Further studies are warranted in order to better evaluate the use of mifepristone or other antiglucocorticoid agents in treatment of mood disorders characterized by metabolic dysfunction.

Neural correlates of liraglutide effects in persons at risk for Alzheimer's disease

Insulin resistance (IR) is a metabolic state preceding development of type 2 diabetes (DM2), cardiovascular disease, and neurodegenerative disorders, including Alzheimer's Disease (AD). Liraglutide, a glucagon-like peptide-1 (GLP) agonist, is an insulin-sensitizing agent with neuroprotective properties, as shown in animal studies. The purpose of this double-blinded, placebo-controlled study was to examine the neural effects of administration of liraglutide in cognitively normal late middle-aged individuals with subjective cognitive complaints (half of subjects had family history of AD). Seed-based resting state connectivity using functional magnetic resonance imaging (fMRI) was conducted before and after 12 weeks of liraglutide treatment or placebo. Neuropsychological testing was conducted before and after treatment to determine whether there were any potential behavioral correlates to neural changes.

RESULTS

At baseline (time point 1), higher fasting plasma glucose (FPG) was associated with decreased connectivity between bilateral hippocampal and anterior medial frontal structures. At time point 2, we observed significant improvement in intrinsic connectivity within the default mode network (DMN) in the active group relative to placebo. There were no detectable cognitive differences between study groups after this duration of treatment. To our knowledge, this is the first placebo-controlled study to report neural effects of liraglutide in a middle-aged population with subjective cognitive complaints. Larger and longer duration studies are warranted to determine whether liraglutide has neuroprotective benefits in individuals at risk for AD.

Determinants of cognitive function in individuals with type 2 diabetes mellitus: A meta-analysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with deficits across multiple cognitive domains; however, the determinants of cognitive impairment in T2DM are not well characterized. We aimed to evaluate body mass index (BMI), glycemic control, and T2DM duration as moderators of cognitive dysfunction in T2DM.

METHODS

We conducted a meta-analytic review of the literature reporting data on BMI, hemoglobin A1c (HbA1c), T2DM duration, and validated measures of processing speed (ie, Digit Symbol Substitution Test, Trail Making Test [TMT]-A), verbal learning and memory (ie, Rey Auditory Verbal Learning Test), and working memory/executive function (ie, TMT-B) among individuals with vs without T2DM.

RESULTS

Individuals with T2DM demonstrated deficits across multiple cognitive domains (k = 40; n = 4,252 T2DM; n = 22,322 non-T2DM; effect sizes 0.21 to 0.35). Illness duration and BMI did not significantly moderate measures of cognition; however, higher HbA1c levels were significantly associated with deficits in measures of processing speed (R2 values 0.41 to 0.73, P < .01) and working memory/executive function (R2 = 0.62, P < .001).

CONCLUSIONS

Adults with T2DM exhibited significant deficits across multiple domains of cognitive function. Additionally, we identified an association between poorer glycemic control and cognitive dysfunction. A clinical translation of our findings relates to the reduction in morbidity by improving glycemic control.

Adjuvant pioglitazone for unremitted depression: Clinical correlates of treatment response

Previous studies suggest that insulin-sensitizing agents could play a significant role in the treatment of major depression, particularly depression in patients with documented insulin resistance or those who are resistant to standard psychopharmacological approaches. This study aimed to assess the effects on depressive symptoms with adjuvant treatment with the PPARγ-agonist pioglitazone. Patients (N=37) with non-psychotic, non-remitting depression receiving standard psychiatric regimens for depression were randomized across an insulin sensitivity spectrum in a 12-week double blind, randomized controlled trial of pioglitazone or placebo. Improvement in depression was associated with improvement in glucose metabolism but only in patients with insulin resistance. An age effect was also shown in that response to pioglitazone was more beneficial in younger aged patients. Study findings suggest differential improvement in depression severity according to both glucose metabolic status and level of depression at baseline. A greater understanding of the reciprocal links between depression and IR may lead to a dramatic shift in the way in which depression is conceptualized and treated, with a greater focus on treating and/or preventing metabolic dysfunction.

Cognitive Effects of Hormone Therapy Continuation or Discontinuation in a Sample of Women at Risk for Alzheimer Disease

OBJECTIVE

Use of estrogen-based hormone therapy (HT) as a protection from cognitive decline and Alzheimer disease (AD) is controversial, although cumulative data support HT use when initiated close to menopause onset with estrogen formulations containing 17β-estradiol preferable to conjugated equine estrogen formulations. Little is known regarding specific populations of women who may derive benefit from HT.

METHODS

Women with heightened risk for AD (aged 49-69), all of whom were taking HT for at least 1 year and most of whom initiated HT close to menopause onset, underwent cognitive assessment followed by randomization to continue or discontinue HT. Assessments were repeated at 2 years after randomization.

RESULTS

Women who continued HT performed better on cognitive domains composed of measures of verbal memory and combined attention, working memory, and processing speed measures. Women who used 17β-estradiol versus conjugated equine estrogen, whether randomized to continue or discontinue HT, showed better verbal memory performance at the 2-year follow-up assessment. An interaction was also found with HT randomization and family history of AD in a first-degree relative. All female offspring of patients with AD declined in verbal memory; however, women who continued HT declined less than women who discontinued HT. Women without a first-degree relative with AD showed verbal memory improvement (likely because of practice effects) with continuance and declined with discontinuance of HT.

CONCLUSION

Continuation of HT use appears to protect cognition in women with heightened risk for AD when initiated close to menopause onset.

Association between insulin resistance and cognition in patients with depressive disorders: exploratory analyses into age-specific effects

The current preliminary cross sectional study sought to examine the effects of insulin resistance (IR) and body mass index (BMI) on cognitive performance in adult patients with a history depression, currently not in an acute Major Depressive Episode (MDD). As an exploratory post hoc investigation, special consideration was given to adults <45 years and ≥45 years old. Subjects included men and women ages 19-71 (N = 39) with a history of a non-psychotic, non-melancholic MDD. All subjects underwent an insulin suppression test to determine Steady-State Plasma Glucose (SSPG), a battery of neuropsychological tests, and measurement of BMI. Multiple linear regressions were conducted to determine whether there were differential effects of direct (SSPG) and indirect (BMI) measures on cognition in the whole sample and within dichotomized age groups (<45 and ≥45 years). Preliminary results showed that in the sample as a whole, SSPG was not associated with worse performance on any cognitive variables, while higher BMI was associated with worse dominant hand fine motor skills. Within age groups, differential effects on cognition were found in relation to SSPG and BMI. Higher SSPG was associated with worse cognitive flexibility in the group <45 years, whereas higher BMI was associated with worse estimate of global intelligence in the group ≥45 years. The potential negative impact of IR in younger adults with depression raises concerns regarding the long-term impact on cognition and risk for Alzheimer's disease in undiagnosed younger adults with IR and depression. These negative consequences may not be seen with indirect measures of IR in younger adult populations. Overweight and obesity in older adults with a history of depression appear to have further negative impacts on cognition similar to deficits seen in patients with diabetes.

CLINICALTRIALSGOV IDENTIFIER

Clinical Trial NCT01106313.

Insulin resistance and medial prefrontal gyrus metabolism in women receiving hormone therapy

Insulin resistance (IR) is a putative risk factor for cognitive decline and dementia, and has been shown to impede neuronal glucose metabolism in animal models. This post hoc study focused on metabolic changes in the medial prefrontal region, a brain region exhibiting decline years before documented cognitive changes, relative to high or low IR status in a cohort of postmenopausal women at risk for dementia who were randomized to continue or discontinue existing stable hormone therapy (HT) for 2 years. Subjects were dichotomized into high and low IR groups based on the homeostatic model assessment of insulin resistance, which was within clinically normal limits for the group as a whole at both baseline and 2-year follow-up. Results showed that high and low IR groups showed significant differences in metabolic decline of the medial prefrontal gyrus, regardless of HT randomization group. However, HT randomization was predictive of metabolic decline only in women with low HOMA (homeostatic assessment of insulin resistance). Performance in working memory was consistent with observed metabolic changes. These results suggest IR may be an independent moderator of regional metabolic changes, while protective metabolic effects of HT are most apparent in those at low-end range of IR. If replicated in future studies, these findings will help to better understand the interaction between putative risk and protective factors, and further delineate cohort postmenopausal women who may benefit from HT.

Prospective randomized trial to assess effects of continuing hormone therapy on cerebral function in postmenopausal women at risk for dementia

The objective of this study was to examine the effects of estrogen-based hormone therapy (HT) on regional cerebral metabolism in postmenopausal women (mean age = 58, SD = 5) at risk for development of dementia. The prospective clinical trial design included pre- and post-intervention neuroimaging of women randomized to continue (HT+) or discontinue (HT−) therapy following an average of 10 years of use. The primary outcome measure was change in brain metabolism during the subsequent two years, as assessed with fluorodeoxyglucose-18 positron emission tomography (FDG-PET). Longitudinal FDG-PET data were available for 45 study completers. Results showed that women randomized to continue HT experienced relative preservation of frontal and parietal cortical metabolism, compared with women randomized to discontinue HT. Women who discontinued 17-β estradiol (17βE)-based HT, as well as women who continued conjugated equine estrogen (CEE)-based HT, exhibited significant decline in metabolism of the precuneus/posterior cingulate cortical (PCC) area. Significant decline in PCC metabolism was additionally seen in women taking concurrent progestins (with either 17βE or CEE). Together, these findings suggest that among postmenopausal subjects at risk for developing dementia, regional cerebral cortical metabolism is relatively preserved for at least two years in women randomized to continue HT, compared with women randomized to discontinue HT. In addition, continuing unopposed 17βE therapy is associated specifically with preservation of metabolism in PCC, known to undergo the most significant decline in the earliest stages of Alzheimer's disease.

Trial Registration

ClinicalTrials.govNCT00097058

Topiramate: Effects on cognition in patients with epilepsy, migraine headache and obesity

This paper reviews the clinical implications of topiramate (TPM)-induced cognitive deficits in patients with epilepsy, migraine headache, obesity, and in normal populations, followed by reviews of the literature describing the reversal of such deficits upon medication discontinuation. It also discusses animal investigations of TPM's role of neuroprotection in brain injury. TPM's most intolerable adverse effects (AEs) are on verbal fluency and reaction time, resulting in high discontinuation rates in patients taking it for epilepsy and migraine headache. However, because TPM is so effective in the treatment of epilepsy and migraine headache, its use is expected to continue. There appears to be greater tolerance of TPM's cognitive AEs when it is used in the treatment of obesity, perhaps because of the lower doses required. Research attempting to predict the populations most vulnerable to the cognitive effects caused by TPM is ongoing. Studies suggest that one such population may include patients with a past psychiatric history. Slow titration and administration of the lowest possible doses may decrease risk of cognitive deficits.

Insulin resistance and hippocampal volume in women at risk for Alzheimer's disease

Insulin resistance (IR) is the main pathological condition underlying vascular disorders, such as diabetes and cardiovascular disease, which are well established risk factors for cognitive decline and Alzheimer disease (AD). Hippocampal atrophy has been associated with cognitive decline, but little is known about the influence of IR on hippocampus integrity in non-diabetic, cognitively intact individuals. Herein, 50 women ages 50-65, current users of hormone therapy, underwent magnetic resonance imaging, cognitive testing, and homeostatic assessment of insulin resistance (HOMA-IR), as part of a longitudinal study examining brain structure and function in postmenopausal women at risk for AD. Results demonstrated a significant negative relationship between HOMA-IR and right and total hippocampal volume, overall cognitive performance, and selective tests of verbal and non-verbal memory. The main effect of HOMA-IR on brain structure and cognition was not altered by the presence of APOE-ε4 allele or by reproductive history, such as duration of endogenous and exogenous estrogen exposure. These results suggest that IR in middle-aged individuals at risk for AD may be biomarker for dementia risk.

Cognitive effects of memantine in postmenopausal women at risk of dementia: a pilot study

BACKGROUND

To determine the effects of memantine on cognition in a normal population of postmenopausal women with putative risk factors for Alzheimer's disease (AD) using a built-in control for the genetic risk factor for AD (apoE-epsilon4 status).

METHODS

A prospective, open-label, 6-month pilot medication trial with memantine and follow-up after discontinuance conducted at the Center for Neuroscience in Women's Health, Stanford University School of Medicine. Neuropsychological data were collected on 22 community-dwelling postmenopausal women (11 apoE-epsilon4 carriers and 11 apoE-epsilon4 non-carriers) with at least one putative risk factor for AD.

RESULTS

ApoE-epsilon4 status was not a significant predictor of change in neuropsychological performance. Changes associated with memantine treatment for entire sample included significant declines in some variables associated with verbal learning and memory that improved upon medication withdrawal. A positive medication effect was noted with executive functions and possibly category fluency. Trend-level improvements were seen in motor dexterity of the non-dominant hand and maintained even after drug discontinuance.

CONCLUSIONS

Treatment with memantine appeared to have differential effects on cognitive performance in a population of women with putative risk factors for AD. ApoE-epsilon4 carrier status did not account for observed changes in cognition.

Estrogen and response to sertraline in postmenopausal women with major depressive disorder: a pilot study

OBJECTIVE

Pilot study examining the effects of estrogen therapy (ET) on antidepressant response in postmenopausal women with major depressive disorder (MDD).

METHODS

Twenty-two subjects received sertraline at 50mg/day for one week, with an increase to 100mg/day at week 2 for a 10-week trial. Transdermal estrogen or placebo patches 0.1mg were randomly administered concurrent with the initiation of sertraline treatment. The 21 item Hamilton Depression Rating Scale (HDRS-21) was administered to all patients at baseline and weekly thereafter.

RESULTS

Both groups showed a similar significant reduction in HDRS-21 scores by the end of the study. There was no significant difference between the two treatment groups at the end of the 10-week trial, but the women receiving sertraline with ET showed significantly greater early improvement (weeks 2-4) compared to the women receiving sertraline with placebo.

CONCLUSIONS

Sertraline is an effective antidepressant for postmenopausal women with MDD. ET does not alter the response rate to antidepressant therapy however ET may play a role in accelerating the antidepressant response.

Mood and neuropsychological changes in women with midlife depression treated with escitalopram

OBJECTIVE

This study assessed mood and neuropsychological function in a population of middle-aged women with major depressive disorder treated with escitalopram.

METHODS

Psychometric data measuring severity of depression were collected from 19 women and neuropsychological data were collected from 17 women aged between 45 and 65 years with a Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, diagnosis of major depression in a study in the Behavioral Neuroendocrinology Program at the Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine. All women were treated with escitalopram in an open-label design. Mean age was 55.94 years and mean number of years of education was 16.36 years. Diagnosis of major depressive disorder was assessed with the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, and mood was evaluated with the 21-item Hamilton Depression Rating Scale (HAM-D) at baseline and at weekly follow-ups for 12 weeks. Cognition was assessed at baseline and 3 months after treatment using a neuropsychological test battery, which included an abbreviated measure of Full Scale Intelligence Quotient, measures of attention and processing speed, verbal and nonverbal memory, executive functioning, and verbal fluency. Self-report data were collected on current menopause status and current hormone therapy use in the postmenopausal women. Paired sample t tests were used to analyze the change in total HAM-D scores and neuropsychological variables.

RESULTS

Statistically significant improvements were found in total HAM-D score, Wechsler Memory Scale III Logical Memory 1st Recall, I, and II scores, Wechsler Memory Scale III Visual Reproduction I scores, and Trail Making Test Part B scores. There was a statistically significant decrease in Controlled Oral Word Association Test FAS scores.

CONCLUSIONS

Treatment of depression with escitalopram in a population of middle-aged women was shown to improve mood and cognitive efficiency in complex attention, short- and long-term recall of contextual information, short-term recall of visual information, and cognitive flexibility; however, it was shown to worsen phonemic fluency.