Midlife cancer/diabetes and risk of dementia and mild cognitive impairment: A population-based prospective cohort study in Japan

Palmitate and glucose increase amyloid precursor protein in extracellular vesicles: Missing link between metabolic syndrome and Alzheimer's disease

The metabolic syndrome (MetS) and Alzheimer's disease share several pathological features, including insulin resistance, abnormal protein processing, mitochondrial dysfunction and elevated inflammation and oxidative stress. The MetS constitutes elevated fasting glucose, obesity, dyslipidaemia and hypertension and increases the risk of developing Alzheimer's disease, but the precise mechanism remains elusive. Insulin resistance, which develops from a diet rich in sugars and saturated fatty acids, such as palmitate, is shared by the MetS and Alzheimer's disease. Extracellular vesicles (EVs) are also a point of convergence, with altered dynamics in both the MetS and Alzheimer's disease. However, the role of palmitate- and glucose-induced insulin resistance in the brain and its potential link through EVs to Alzheimer's disease is unknown. We demonstrate that palmitate and high glucose induce insulin resistance and amyloid precursor protein phosphorylation in primary rat embryonic cortical neurons and human cortical stem cells. Palmitate also triggers insulin resistance in oligodendrocytes, the supportive glia of the brain. Palmitate and glucose enhance amyloid precursor protein secretion from cortical neurons via EVs, which induce tau phosphorylation when added to naïve neurons. Additionally, EVs from palmitate-treated oligodendrocytes enhance insulin resistance in recipient neurons. Overall, our findings suggest a novel theory underlying the increased risk of Alzheimer's disease in MetS mediated by EVs, which spread Alzheimer's pathology and insulin resistance.

A combination of midlife diabetes mellitus and the apolipoprotein E ε4 allele increase risk for cognitive decline

BACKGROUND

It has been suggested that diabetes mellitus (DM) and the apolipoprotein E (APOE) ε4 allele (APOE4) increase the risk for Alzheimer's disease (AD) and cognitive decline. However, the evidence is sparse. We explored whether APOE4 status modulated the effects of midlife and late-life DM on global cognition of non-demented older adults.

METHODS

In all, 176 non-demented adults (age 65-90 years) were enrolled. All the participants underwent comprehensive clinical assessments including midlife and late-life DM evaluation and APOE genotyping. The global cognitive performance index was assessed by the total score (TS) of the Consortium to Establish a Registry for Alzheimer's Disease neuropsychological battery.

RESULTS

We found a significant midlife DM × APOE4 interaction effect on the global cognitive performance. Subgroup analyses indicated that an association between midlife DM and decreased global cognitive performance was apparent only in older adults who were APOE4-positive, and not in those with APOE4-negative.

CONCLUSION

Our findings from non-demented older adults suggest that midlife DM increases the risk for AD and cognitive decline, and this risk is modulated by APOE4 status. To prevent AD and cognitive decline, physicians should check for the possible coexistence of midlife DM and APOE4-positive status.

Diabetes and dementia: Clinical perspective, innovation, knowledge gaps

The world faces a pandemic-level prevalence of type 2 diabetes. In parallel with this massive burden of metabolic disease is the growing prevalence of dementia as the population ages. The two health issues are intertwined. The Lancet Commission on dementia prevention, intervention, and care was convened to tackle the growing global concern of dementia by identifying risk factors. It concluded, along with other studies, that diabetes as well as obesity and the metabolic syndrome more broadly, which are frequently comorbid, raise the risk of developing dementia. Type 2 diabetes is a modifiable risk factor; however, it is uncertain whether anti-diabetic drugs mitigate risk of developing dementia. Reasons are manifold but constitute a critical knowledge gap in the field. This review outlines studies of type 2 diabetes on risk of dementia, illustrating key concepts. Moreover, it identifies knowledge gaps, reviews strategies to help fill these gaps, and concludes with a series of recommendations to mitigate risk and advance understanding of type 2 diabetes and dementia.

Prevalence of self-reported memory problems in adults with type 2 diabetes mellitus and cancer in the USA

PURPOSE

To determine the prevalence of memory problems in individuals with or without a history of DM and cancer and assess possible compounding effects of these diseases on self-reported memory problems (SRMP).

METHODS

We used data from the 2009-2018 National Health and Nutrition Examination Survey. We conducted logistic regression analyses to determine the associations among DM, cancer, and SRMP, adjusting for age, sex, race/ethnicity, education, and poverty level. We examined the interaction effects of comorbid DM and cancer on SRMP. We compared participants with both DM and cancer to those with cancer only and to those with no DM or cancer.

RESULTS

We included 26,842 adults ≥ 20 years old (N = 3374 with DM, N = 23,468 without DM) and 51.87% female. There were 10,434 Whites, 5730 Blacks, 6795 Hispanics, and 3883 other races/multiracial. More individuals with DM reported memory problems than those without DM (p < 0.0001). More individuals with cancer reported memory problems than those without cancer (p < 0.0001). Of those with both DM and cancer, 14.19% reported memory problems. More individuals with DM had cancer than those without DM (p < 0.0001). Of those with both diseases, 55.75% had DM before the cancer diagnosis. DM (odds ratio[OR] = 1.87, 95%CI, 1.55-2.26) and cancer (OR = 1.81, 95%CI, 1.43-2.30) predicted SRMP. The interaction between DM and cancer was significant, and the likelihood of having both diseases compared to having neither DM nor cancer was OR = 2.09, 95%CI, 1.41 - 3.11.

CONCLUSION

Strategies to mitigate SRMP in individuals with comorbid DM and cancer history should consider the impact of both diseases.