Type 2 diabetes, obesity, and risk of amyotrophic lateral sclerosis: A population-based cohort study

Novel Leptin-Based Therapeutic Strategies to Limit Synaptic Dysfunction in Alzheimer's Disease

Accumulation of hyper-phosphorylated tau and amyloid beta (Aβ) are key pathological hallmarks of Alzheimer's disease (AD). Increasing evidence indicates that in the early pre-clinical stages of AD, phosphorylation and build-up of tau drives impairments in hippocampal excitatory synaptic function, which ultimately leads to cognitive deficits. Consequently, limiting tau-related synaptic abnormalities may have beneficial effects in AD. There is now significant evidence that the hippocampus is an important brain target for the endocrine hormone leptin and that leptin has pro-cognitive properties, as activation of synaptic leptin receptors markedly influences higher cognitive processes including learning and memory. Clinical studies have identified a link between the circulating leptin levels and the risk of AD, such that AD risk is elevated when leptin levels fall outwith the physiological range. This has fuelled interest in targeting the leptin system therapeutically. Accumulating evidence supports this possibility, as numerous studies have shown that leptin has protective effects in a variety of models of AD. Recent findings have demonstrated that leptin has beneficial effects in the preclinical stages of AD, as leptin prevents the early synaptic impairments driven by tau protein and amyloid β. Here we review recent findings that implicate the leptin system as a potential novel therapeutic target in AD.

Metformin ameliorates mitochondrial damage induced by C9orf72 poly(GR) via upregulating AKT phosphorylation

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are devastating neurodegenerative diseases with no effective cure. GGGGCC repeat expansion in C9orf72 is the most common genetic cause of both ALS and FTD. A key pathological feature of C9orf72 related ALS/FTD is the presence of abnormal dipeptide repeat proteins translated from GGGGCC repeat expansion, including poly Glycine-Arginine (GR). In this study, we observed that (GR)50 conferred significant mitochondria damage and cytotoxicity. Metformin, the most widely used clinical drug, successfully relieved (GR)50 induced mitochondrial damage and inhibited (GR)50 related cytotoxicity. Further research revealed metformin effectively restored mitochondrial function by upregulating AKT phosphorylation in (GR)50 expressed cells. Taken together, our results indicated restoring mitochondrial function with metformin may be a rational therapeutic strategy to reduce poly(GR) toxicity in C9orf72 ALS/FTD patients.

Mitochondria-associated membrane collapse impairs TBK1-mediated proteostatic stress response in ALS

The organelle contact site of the endoplasmic reticulum and mitochondria, known as the mitochondria-associated membrane (MAM), is a multifunctional microdomain in cellular homeostasis. We previously reported that MAM disruption is a common pathological feature in amyotrophic lateral sclerosis (ALS); however, the precise role of MAM in ALS was uncovered. Here, we show that the MAM is essential for TANK-binding kinase 1 (TBK1) activation under proteostatic stress conditions. A MAM-specific E3 ubiquitin ligase, autocrine motility factor receptor, ubiquitinated nascent proteins to activate TBK1 at the MAM, which results in ribosomal protein degradation. MAM or TBK1 deficiency under proteostatic stress conditions resulted in increased cellular vulnerability in vitro and motor impairment in vivo. Thus, MAM disruption exacerbates proteostatic stress via TBK1 inactivation in ALS. Our study has revealed a proteostatic mechanism mediated by the MAM-TBK1 axis, highlighting the physiological importance of the organelle contact sites.

Type 2 diabetes, obesity, and risk of amyotrophic lateral sclerosis: A population-based cohort study

BACKGROUND

Type 2 diabetes and obesity may be inversely associated with amyotrophic lateral sclerosis (ALS), but the evidence is controversial.

METHODS

Using Danish, nationwide registries (1980-2016), we identified patients with a diagnosis of type 2 diabetes (N = 295,653) and patients with a diagnosis of obesity (N = 312,108). Patients were matched (1:3) to persons from the general population on birth year and sex. We computed incidence rates and Cox regression derived hazard ratios (HRs) of a diagnosis of ALS. In multivariable analyses, HRs were controlled for sex, birth year, calendar year, and comorbidities.

RESULTS

We observed 168 incident cases of ALS (0.7 [95% confidence interval (CI): 0.6-0.8] per 10,000 person-years) among patients with type 2 diabetes and 859 incident cases of ALS (0.9 [95% CI: 0.9-1.0] per 10,000 person-years) among matched comparators. The adjusted HR was 0.87 (95% CI: 0.72-1.04). The association was present among men (adjusted HR: 0.78 [95% CI: 0.62-0.99]) but not women (adjusted HR: 1.03 [95% CI: 0.78-1.37]), and among those aged ≥60 years (adjusted HR: 0.75 [95% CI: 0.59-0.96]) but not younger. We observed 111 ALS events (0.4 [95% CI: 0.4-0.5] per 10,000 person-years) among obesity patients and 431 ALS events (0.5 [95% CI: 0.5-0.6] per 10,000 person-years) among comparators. The adjusted HR was 0.88 (95% CI: 0.70-1.11).

CONCLUSIONS

Diagnoses of type 2 diabetes and obesity were associated with a reduced rate of ALS compared with general population comparators, particularly among men and patients aged 60 years or above. However, absolute rate differences were small.