Interactions between estradiol, diabetes, and brain aging and the risk for cognitive impairment

Sex steroid and cognitive function among community-dwelling older men with or without vascular risk factors: a cross-sectional study

BACKGROUND

The relationship of testosterone and estradiol concentrations with cognitive function among community-dwelling older men was inconclusive. To examine the association of serum testosterone and estradiol concentrations with cognitive function in older men with or without vascular risk factors (VRFs).

METHODS

This cross-sectional study consisted of 224 community-dwelling men aged 65-90 years in the Songjiang District of Shanghai, China. Serum testosterone and estradiol were measured by electrochemiluminescence immunoassay. The following five factors were defined as VRFs in this study: obesity, history of hypertension, diabetes, stroke, and coronary heart disease. Multivariable linear regression was used to examine the association of testosterone and estradiol with the Mini-Mental State Examination (MMSE) in participants with or without VRF. Restricted cubic spline (RCS) regression was performed to account for the nonlinearity of these associations.

RESULTS

An inverted "U" shaped non-linear relationship was found between testosterone concentration and MMSE score in men with one VRF (P overall =.003, non-linear P =.002). Estradiol showed an inverted "U" shaped non-linear relationship with MMSE score independent of VRFs (men without VRF, P overall =.049, non-linear P =.015; men with one VRF, overall P =.007, non-linear P =.003; men with two or more VRFs, overall P =.009, non-linear P =.005).

CONCLUSION

In older men, an optimal level of sex steroid concentration may be beneficial to cognitive function and the VRFs should be considered when interpreting the relationship between sex steroid and cognitive function.

Brain-derived estrogen: a critical player in maintaining cognitive health of aged female rats, possibly involving GPR30

Brain-derived estrogen is an endogenous neuroprotective agent, whether and how might this protective function with aging, especially postmenopausal drops in circulating estrogen, remain unclear. We herein subjected 6, 14, and 18 Mon female rats to mimic natural aging, and found that estrogen synthesis is more active in the healthy aged brain, as evidenced by the highest levels of mRNA and protein expression of aromatase, the key enzyme of E2 biosynthesis, among the three groups. Aromatase knockout in forebrain neurons (FBN-Aro-/-) impaired hippocampal and cortical neurons, and cognitive function in 18 Mon rats, compared to wild-type controls. Furthermore, estrogen nuclear receptors (ERα/β) displayed opposite changes, with a significant ERα decrease and ERβ increase, while membrane receptor GPR30 expressed stably in hippocampus during aging. Intriguingly, GPR30, but not ERα and ERβ, was decreased by FBN-Aro-/-. The results indicate that GPR30 is more sensitive to brain local E2 synthesis. Our findings provide evidence of a critical role for brain-derived estrogen in maintaining healthy brain function in older individuals, possibly involving GPR30.

Associations Between Midlife Menopausal Hormone Therapy Use, Incident Diabetes, and Late Life Memory in the Wisconsin Longitudinal Study

BACKGROUND

Prior research suggests a link between menopausal hormone therapy (MHT) use, memory function, and diabetes risk. The menopausal transition is a modifiable period to enhance long-term health and cognitive outcomes, although studies have been limited by short follow-up periods precluding a solid understanding of the lasting effects of MHT use on cognition.

OBJECTIVE

We examined the effects of midlife MHT use on subsequent diabetes incidence and late life memory performance in a large, same-aged, population-based cohort. We hypothesized that the beneficial effects of MHT use on late life cognition would be partially mediated by reduced diabetes risk.

METHODS

1,792 women from the Wisconsin Longitudinal Study (WLS) were included in analysis. We employed hierarchical linear regression, Cox regression, and causal mediation models to test the associations between MHT history, diabetes incidence, and late life cognitive performance.

RESULTS

1,088/1,792 women (60.7%) reported a history of midlife MHT use and 220/1,792 (12.3%) reported a history of diabetes. MHT use history was associated with better late life immediate recall (but not delayed recall), as well as a reduced risk of diabetes with protracted time to onset. Causal mediation models suggest that the beneficial effect of midlife MHT use on late life immediate recall were at least partially mediated by diabetes risk.

CONCLUSION

Our data support a beneficial effect of MHT use on late life immediate recall (learning) that was partially mediated by protection against diabetes risk, supporting MHT use in midlife as protective against late life cognitive decline and adverse health outcomes.

Associations between cognitive function and endogenous levels of estradiol and testosterone in adults with type 2 diabetes

AIMS

To assess associations that endogenous estradiol and testosterone levels have with cognitive function in older adults with Type 2 diabetes mellitus (T2DM).

METHODS

We use data from the Look AHEAD clinical trial of behavioral weight loss. Endogenous estradiol and total testosterone levels were determined using stored serum from 996 individuals, mean age 69 years, at two times (averaging 4 years apart) during years 8-18 of follow-up. One to four standardized assessments of attention, executive function, memory, and verbal fluency were collected during this follow-up. Mixed effects models and multiple imputation were used to assess associations that estradiol and total testosterone levels had with body mass index and cognitive function.

RESULTS

Estradiol levels were not associated with cognitive function in either sex. Total testosterone levels were not associated with cognitive function in women, but greater total testosterone levels were associated with better verbal fluency in men (p < 0.001), most strongly among those carrying the APOE-e4 allele (interaction p = 0.02). The weight loss intervention left a legacy of relatively lower cognitive functioning among women, which was not mediated by current levels of sex hormones.

CONCLUSIONS

Behavioral weight loss intervention does not affect cognitive functioning through mechanisms related to estradiol or testosterone.

CLINICALTRIALS

gov Identifier: NCT00017953.

The effect of high intensity interval training with beetroot (Beta vulgaris) juice supplementation on serotonin and dopamine receptors expression, anxiety and depression in middle-aged diabetic rats

Objective

The aim of this study was to evaluate the effect of four weeks of high intensity interval training (HIIT) with beetroot juice supplementation (BJ) on serotonin and dopamine receptors in hippocampal tissue, as well as anxiety and depression in middle-aged diabetic rats.

Materials and Methods

In this experimental study, 28 diabetic female rats (55 mg/kg, induced by streptozotocin) aged 12-14 months, weighing 280-320 g, were divided into (1) diabetic control (DC), (2) BJ, (3) HIIT, and (4) HIIT+BJ groups. Also, 7 healthy rats were included in the healthy control (HC) group to evaluate the effect of diabetes induction on the research variables. HIIT was performed for four weeks, 4 sessions per week (70-95% of maximum speed at high intensities; 50-60% of maximum speed at low intensities). Also, BJ was fed daily to rats at a dose of 10 ml/kg.

Results

Hippocampal expression of dopamine receptor-1 (Dop.R), 5-hydroxytryptamine receptor (5-HT. R), open arm entry percentage (OAE%) and movement rate in the HIIT, BJ and HIIT+BJ groups were significantly higher than the DC group. In the HIIT+BJ group, open arm time percentage (OAT%) was higher than the DC group. Levels of Dop.R gene expression were more affected by HIIT, and levels of 5-HT. R were more affected by BJ supplementation; also, HIIT+BJ had a synergistic effect on reducing anxiety and depression.

Conclusion

Although HIIT was more effective than BJ and HIIT+BJ on Dop.R and BJ supplementation on 5-HT.R and improved anxiety and depression, both of HIIT and BJ were complementary in improving dopamine and serotonin receptor-dependent anxiety and depression and enhanced each other's effects.