Adiponectin Paradox in Alzheimer's Disease; Relevance to Amyloidogenic Evolvability?

Reevaluating Adiponectin's impact on obesity hypertension: a Chinese case-control study

BACKGROUND

Obesity and hypertension are major risk factors for cardiovascular diseases that affect millions of people worldwide. Both conditions are associated with chronic low-grade inflammation, which is mediated by adipokines such as adiponectin. Adiponectin is the most abundant adipokine that has a beneficial impact on metabolic and vascular biology, while high serum concentrations are associated with some syndromes. This "adiponectin paradox" still needs to be clarified in obesity-associated hypertension. The aim of this study was to investigate how adiponectin affects blood pressure, inflammation, and metabolic function in obesity hypertension using a Chinese adult case-control study.

METHODS

A case-control study that had finished recruiting 153 subjects divided as four characteristic groups. Adiponectin serum levels were tested by ELISA in these subjects among these four characteristic Chinese adult physical examination groups. Waist circumference (WC), body mass index (BMI), systolic blood pressure (SB), diastolic blood pressure (DB), and other clinical laboratory data were collected. Analyzation of correlations between the research index and differences between groups was done by SPSS.

RESULTS

Serum adiponectin levels in the| normal healthy group (NH group) were significantly higher than those in the newly diagnosed untreated just-obesity group (JO group), and negatively correlated with the visceral adiposity index. With multiple linear egression analysis, it was found that, for serum adiponectin, gender, serum albumin (ALB), alanine aminotransferase (ALT) and high-density lipoprotein cholesterol (HDLC) were the significant independent correlates, and for SB, age and HDLC were the significant independent correlates, and for DB, alkaline phosphatase (ALP) was the significant independent correlate. The other variables did not reach significance in the model.

CONCLUSIONS

Our study reveals that adiponectin's role in obesity-hypertension is multifaceted and is influenced by the systemic metabolic homeostasis signaling axis. In obesity-related hypertension, compensatory effects, adiponectin resistance, and reduced adiponectin clearance from impaired kidneys and liver all contribute to the "adiponectin paradox".

Cognitive impairment in patients with heart failure: molecular mechanism and therapy

Heart failure (HF) is associated with multiple organ dysfunction and many comorbidities. Its incidence is high among the elderly and is a major health burden worldwide. Cognitive impairment (CI) is highly prevalent in older patients with HF, which is an abnormality in one or more of the items of cognition, attention, memory, language, psychomotor function, and visual spatial acuity. Studies have shown that the incidence of CI in HF patients is between 13 and 54%, and patients with both conditions have poor self-care ability and prognosis, as well as increased mortality rates. However, the mechanisms of CI development in HF patients are still unclear. In this review, we describe the epidemiology and risk factors as well as measures of improving CI in HF patients. We update the latest pathophysiological mechanisms related to the neurocognitive changes in HF patients, expounding on the mechanisms associated with the development of CI in HF patients.

Reconsideration of Alzheimer's Disease Therapy from a Viewpoint of Amyloidogenic Evolvability

 Presuming that Alzheimer's disease (AD) might represent an antagonistic pleiotropic phenomenon derived from the evolvability of multiple amyloidogenic proteins, targeting such proteins simultaneously could enhance therapeutic efficacy. Furthermore, considering that amyloid-β (Aβ) immunotherapies during reproductive life stage might adversely decrease Aβ evolvability in an offspring's brain, the disease-modifying Aβ immunotherapies should be limited to post-reproductive time in lifespan. Thus, current Aβ immunotherapy strategies should be revised accordingly. Given that the "adiponectin paradox" might underlie both amyloidosis and cognitive dysfunction in aging brain, blocking activin signaling situated downstream of the adiponectin paradox might be an alternative strategy to prevent AD.

Mitochondria targeting drugs for neurodegenerative diseases—design, mechanism and application

Neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD) are a heterogeneous group of disorders characterized by progressive degeneration of neurons. NDDs threaten the lives of millions of people worldwide and regretfully remain incurable. It is well accepted that dysfunction of mitochondria underlies the pathogenesis of NDDs. Dysfunction of mitochondria results in energy depletion, oxidative stress, calcium overloading, caspases activation, which dominates the neuronal death of NDDs. Therefore, mitochondria are the preferred target for intervention of NDDs. So far various mitochondria-targeting drugs have been developed and delightfully some of them demonstrate promising outcome, though there are still some obstacles such as targeting specificity, delivery capacity hindering the drugs development. In present review, we will elaborately address 1) the strategy to design mitochondria targeting drugs, 2) the rescue mechanism of respective mitochondria targeting drugs, 3) how to evaluate the therapeutic effect. Hopefully this review will provide comprehensive knowledge for understanding how to develop more effective drugs for the treatment of NDDs.

APOE Polymorphism and Endocrine Functions in Subjects with Morbid Obesity Undergoing Bariatric Surgery

BACKGROUND

Obesity is an interplay between genes and the environment, including lifestyle. The genetics of obesity is insufficiently understood. Apolipoprotein E (APOE) genetic polymorphism has been associated with a wide range of disorders. Knowing that some APOE alleles are associated with obesity and endocrine disorders that are common in obesity, the present study aimed at exploring associations between APOE polymorphisms and endocrine functions in subjects with obesity undergoing bariatric surgery.

METHODS

Analyses of hormones in blood collected before and one year after bariatric surgery were examined. The APOE alleles were grouped as follows: E2 = ε2ε2 + ε2ε3; E3 = ε3ε3 + ε2ε4; E4 = ε3ε4 + ε4ε4. The APOE groups were analysed as nominal and ordered groups (E2-E3-E4) with a linear mixed model to predict the hormonal effects of the groups.

RESULTS

Forty-nine women (79%) and thirteen (21%) men with a mean age of 47.7 (SD 8.5) years were included in the study. The adiponectin level was significantly lower (p < 0.05) in the E2 group compared with the E4 group. Adiponectin and cortisol were positively and negatively associated, respectively, with the ordered APOE groups.

CONCLUSIONS

The ordered APOE groups E2-E3-E4 were significantly associated with high and low levels of adiponectin and cortisol, respectively. The findings indicate APOE-mediated effects on body weight and metabolic functions in subjects with morbid obesity.

An Explanation for the Adiponectin Paradox

The adipokine adiponectin improves insulin sensitivity. Functional signal transduction of adiponectin requires at least one of the receptors AdipoR1 or AdipoR2, but additionally the glycosyl phosphatidylinositol-anchored molecule, T-cadherin. Overnutrition causes a reduction in adiponectin synthesis and an increase in the circulating levels of the enzyme glycosyl phosphatidylinositol-phospholipase D (GPI-PLD). GPI-PLD promotes the hydrolysis of T-cadherin. The functional consequence of T-cadherin hydrolysis is a reduction in adiponectin sequestration by responsive tissues, an augmentation of adiponectin levels in circulation and a (further) reduction in signal transduction. This process creates the paradoxical situation that adiponectin levels are augmented, whereas the adiponectin signal transduction and insulin sensitivity remain strongly impaired. Although both hypoadiponectinemia and hyperadiponectinemia reflect a situation of insulin resistance, the treatments are likely to be different.

Metabolic determinants of Alzheimer's disease: A focus on thermoregulation

Alzheimer's disease (AD) is a complex age-related neurodegenerative disease, associated with central and peripheral metabolic anomalies, such as impaired glucose utilization and insulin resistance. These observations led to a considerable interest not only in lifestyle-related interventions, but also in repurposing insulin and other anti-diabetic drugs to prevent or treat dementia. Body temperature is the oldest known metabolic readout and mechanisms underlying its maintenance fail in the elderly, when the incidence of AD rises. This raises the possibility that an age-associated thermoregulatory deficit contributes to energy failure underlying AD pathogenesis. Brown adipose tissue (BAT) plays a central role in thermogenesis and maintenance of body temperature. In recent years, the modulation of BAT activity has been increasingly demonstrated to regulate energy expenditure, insulin sensitivity and glucose utilization, which could also provide benefits for AD. Here, we review the evidence linking thermoregulation, BAT and insulin-related metabolic defects with AD, and we propose mechanisms through which correcting thermoregulatory impairments could slow the progression and delay the onset of AD.

Therapeutic Potential of α-Synuclein Evolvability for Autosomal Recessive Parkinson's Disease

The majority of Parkinson's disease (PD) is sporadic in elderly and is characterized by α-synuclein (αS) aggregation and other alterations involving mitochondria, ubiquitin-proteasome, and autophagy. The remaining are familial PD associated with gene mutations of either autosomal dominant or recessive inheritances. However, the former ones are similar to sporadic PD, and the latter ones are accompanied by impaired mitophagy during the reproductive stage. Since no radical therapies are available for PD, the objective of this paper is to discuss a mechanistic role for amyloidogenic evolvability, a putative physiological function of αS, among PD subtypes, and the potential relevance to therapy. Presumably, αS evolvability might benefit familial PD due to autosomal dominant genes and also sporadic PD during reproduction, which may manifest as neurodegenerative diseases through antagonistic pleiotropy mechanism in aging. Indeed, there are some reports describing that αS prevents apoptosis and mitochondrial alteration under the oxidative stress conditions, notwithstanding myriads of papers on the neuropathology of αS. Importantly, β-synuclein (βS), the nonamyloidogenic homologue of αS, might buffer against evolvability of αS protofibrils associated with neurotoxicity. Finally, it is intriguing to predict that increased αS evolvability through suppression of βS expression might protect against autosomal recessive PD. Collectively, further studies are warranted to better understand αS evolvability in PD pathogenesis, leading to rational therapy development.

Adiponectin: a pleiotropic hormone with multifaceted roles

Adipose tissue mostly composed of different types of fat is one of the largest endocrine organs in the body playing multiple intricate roles including but not limited to energy storage, metabolic homeostasis, generation of heat, participation in immune functions and secretion of a number of biologically active factors known as adipokines. The most abundant of them is adiponectin. This adipocite-derived hormone exerts pleiotropic actions and exhibits insulin-sensitizing, antidiabetic, anti-obesogenic, anti-inflammatory, antiatherogenic, cardio- and neuroprotective properties. Contrariwise to its protective effects against various pathological events in different cell types, adiponectin may have links to several systemic diseases and malignances. Reduction in adiponectin levels has an implication in COVID-19-associated respiratory failure, which is attributed mainly to a phenomenon called 'adiponectin paradox'. Ample evidence about multiple functions of adiponectin in the body was obtained from animal, mostly rodent studies. Our succinct review is entirely about multifaceted roles of adiponectin and mechanisms of its action in different physiological and pathological states.

The value of adiponectin-resistin (AR) index in newly diagnosed obesity hypertension: a case control study among Chinese adult

OBJECTIVE

To explore the role of adiponectin-resistin (AR) index as a better indicator of obesity-related hypertension.

METHOD(S)

This study continued a case control study that had finished recruiting 153 subjects divided as four characteristic groups. Fasting serum resistin levels (FSR) and Fasting serum adiponectin levels (FSA) were tested by ELISA. And, other related anthropometric clinical and metabolic data were collected. Analyzation on correlations between research index and differences between groups were done by SPSS. AR index's performance was also validated by the receiver operating characteristic (ROC) curves, the net reclassification improvement (NRI), and the integrated discrimination improvement (IDI).

RESULT(S)

The AR index was defined as 1+ log₁₀(R₀)-log₁₀(A₀). AUC of the AR index was 0.660 and NRI and IDI indicated AR index outperformed FSA alone. AR index statistically significantly negatively correlated with SB and DB and positively with ALB and SCR. AR index was statistically significantly different between the NH group and OH group and more specific than FSR alone as a biomarker of obesity-related hypertension.

CONCLUSION(S)

The AR index was more strongly associated with increased risk of obesity-related hypertension than the solely index of FSR or FSA and was useful for early diagnosis of obesity-related hypertension.

Adiponectin: a potential target for obesity-associated Alzheimer's disease

Obesity and dementia are two growing problems worldwide. Obesity act as a crucial risk factor for various diseases including Alzheimer's disease (AD). Several preclinical studies showed that middle-age obesity can be act as a possible feature of mild cognitive impairment in later years. Some studies have also demonstrated that a high-fat diet causes AD pathology, including extracellular amyloid-beta accumulation, hyperphosphorylation of tau, and cognition impairment. The correlation and molecular mechanism related to obesity-associated AD needs to be better evaluated. Presently, obesity results in an altered expression of several hormones, growth factors, and adipokines. Multiple signaling pathways such as leptin, insulin, adiponectin, and glutamate are involved to regulate vital functions in the brain and act as neuroprotective mediators for AD in a normal state. In obesity, altered adiponectin (APN) level and its associated downstream pathway could result in multiple signaling pathway disruption. Presently, Adiponectin and its inducers or agonist are considered as potential therapeutics for obesity-associated AD. This review mainly focuses on the pleiotropic effects of adiponectin and its potential to treat obesity-associated AD.

What Are the Clinical and Systemic Results of Periodontitis Treatment in Obese Individuals?

Purpose of Review

Periodontitis and obesity are characterized by a dysregulated inflammatory state. Obese individuals have a higher chance of presenting periodontitis. Clinical studies in different populations demonstrate that individuals with obesity have worse periodontal conditions. This current review aims to explore recent literature to understand what the impacts of obesity on periodontal treatment outcomes are and to learn whether periodontal treatment can improve systemic biomarkers in obese individuals.

Recent Findings

Short- and long-term evaluations demonstrated that non-surgical periodontal treatment could improve clinical parameters in obese individuals, represented as the reduction in mean probing depth, sites with probing depth ≥ 4 mm, and extension of bleeding on probing. However, obese individuals may have less clinical improvement when compared to normal-weight individuals with a similar periodontal profile. Additionally, periodontal treatment may contribute to a reduction in systemic levels of retinol-binding protein 4 and leptin, while promoting an increase in systemic levels of adiponectin.

Summary

Overall, obese individuals with periodontitis can significantly benefit from non-surgical periodontal treatment. However, clinical improvements seem to be less prominent in obese individuals with periodontitis compared to non-obese individuals with similar periodontal status. Nevertheless, periodontal treatment may impact significantly on the reduction of several biochemical biomarkers of obesity with or without weight reduction. Further investigations are needed to improve our comprehension of the mechanisms underlying those findings.

Adiponectin Paradox as a Therapeutic Target in Alzheimer's Disease

Despite the apparent neurotoxicity of amyloid-β (Aβ), recent clinical trials of Aβ immunotherapy have not shown any clinical benefit in Alzheimer’s disease (AD). Given this, clarification of the next generation therapeutic strategy in AD is warranted. Hypothetically, adiponectin might be involved in promoting amyloidogenic evolvability in reproduction, which may result in the adiponectin paradox through antagonistic pleiotropy mechanism in aging, leading to AD. Accordingly, preventing the adiponectin paradox by suppressing adiponectin signaling might prove therapeutic in AD.

Adiponectin-mimetic novel nonapeptide rescues aberrant neuronal metabolic-associated memory deficits in Alzheimer's disease

Background

Recently, we and other researchers reported that brain metabolic disorders are implicated in Alzheimer’s disease (AD), a progressive, devastating and incurable neurodegenerative disease. Hence, novel therapeutic approaches are urgently needed to explore potential and novel therapeutic targets/agents for the treatment of AD. The neuronal adiponectin receptor 1 (AdipoR1) is an emerging potential target for intervention in metabolic-associated AD. We aimed to validate this hypothesis and explore in-depth the therapeutic effects of an osmotin-derived adiponectin-mimetic novel nonapeptide (Os-pep) on metabolic-associated AD.

Methods

We used an Os-pep dosage regimen (5 μg/g, i.p., on alternating days for 45 days) for APP/PS1 in amyloid β oligomer-injected, transgenic adiponectin knockout (Adipo−/−) and AdipoR1 knockdown mice. After behavioral studies, brain tissues were subjected to biochemical and immunohistochemical analyses. In separate cohorts of mice, electrophysiolocal and Golgi staining experiments were performed. To validate the in vivo studies, we used human APP Swedish (swe)/Indiana (ind)-overexpressing neuroblastoma SH-SY5Y cells, which were subjected to knockdown of AdipoR1 and APMK with siRNAs, treated with Os-pep and other conditions as per the mechanistic approach, and we proceeded to perform further biochemical analyses.

Results

Our in vitro and in vivo results show that Os-pep has good safety and neuroprotection profiles and crosses the blood-brain barrier. We found reduced levels of neuronal AdipoR1 in human AD brain tissue. Os-pep stimulates AdipoR1 and its downstream target, AMP-activated protein kinase (AMPK) signaling, in AD and Adipo−/− mice. Mechanistically, in all of the in vivo and in vitro studies, Os-pep rescued aberrant neuronal metabolism by reducing neuronal insulin resistance and activated downstream insulin signaling through regulation of AdipoR1/AMPK signaling to consequently improve the memory functions of the AD and Adipo−/− mice, which was associated with improved synaptic function and long-term potentiation via an AdipoR1-dependent mechanism.

Conclusion

Our findings show that Os-pep activates AdipoR1/AMPK signaling and regulates neuronal insulin resistance and insulin signaling, which subsequently rescues memory deficits in AD and adiponectin-deficient models. Taken together, the results indicate that Os-pep, as an adiponectin-mimetic novel nonapeptide, is a valuable and promising potential therapeutic candidate to treat aberrant brain metabolism associated with AD and other neurodegenerative diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13024-021-00445-4.

Diabetes, inflammation, and the adiponectin paradox: Therapeutic targets in SARS-CoV-2

Aging and pre-existing conditions in older patients increase severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) severity and its complications, although the causes remain unclear. Apart from acute pulmonary syndrome, Coronavirus 2019 (COVID-19) can increasingly induce chronic conditions. Importantly, SARS-CoV-2 triggers de novo type 2 diabetes mellitus (T2DM) linked to age-associated cardiovascular disease (CVD), cancers, and neurodegeneration. Mechanistically, SARS-CoV-2 induces inflammation, possibly through damage-associated molecular pattern (DAMP) signaling and ‘cytokine storm,’ causing insulin resistance and the adiponectin (APN) paradox, a phenomenon linking metabolic dysfunction to chronic disease. Accordingly, preventing the APN paradox by suppressing APN-related inflammatory signaling might prove beneficial. A better understanding could uncover novel therapies for SARS-CoV-2 and its chronic disorders.

Adiponectin paradox as a therapeutic target of the cancer evolvability in aging

Recent study suggests that protofibril-formation of amyloidogenic proteins (APs) might be involved in evolvability, an epigenetic inheritance of multiple stresses, in various biological systems. In cancer, evolvability of multiple APs, such as p53, γ-synuclein and the members of the calcitonin family of peptides, might be involved in various features, including increased cell proliferation, metastasis and medical treatment resistance. In this context, the objective of this paper is to explore the potential therapeutic benefits of reduced APs evolvability against cancer. Notably, the same APs are involved in the pathogenesis of neurodegenerative disease and cancer. Given the unsatisfactory outcomes of recent clinical trial of Aβ immunotherapy in Alzheimer's disease, it is possible that suppressing the aggregation of individual APs might also be not effective in cancer. As such, we highlight the adiponectin (APN) paradox that might be positioned upstream of AP aggregation in both neurodegenerative disease and cancer, as a common therapeutic target in both disease types. Provided that the APN paradox due to APN resistance under the diabetic conditions might promote AP aggregation, suppressing the APN paradox combined with antidiabetic treatments might be effective for the therapy of both neurodegenerative disease and cancer.

Possible Role of Activin in the Adiponectin Paradox-Induced Progress of Alzheimer's Disease

Accumulating evidence suggests that the adiponectin (APN) paradox might be involved in promoting aging-associated chronic diseases such as Alzheimer's disease (AD). In human brain, APN regulation of the evolvability of amyloidogenic proteins (APs), including amyloid-β (Aβ) and tau, in developmental/reproductive stages, might be paradoxically manifest as APN stimulation of AD through antagonistic pleiotropy in aging. The unique mechanisms underlying APN activity remain unclear, a better understanding of which might provide clues for AD therapy. In this paper, we discuss the possible relevance of activin, a member of transforming growth factor β (TGFβ) superfamily of peptides, to antagonistic pleiotropy effects of APN. Notably, activin, a multiple regulator of cell proliferation and differentiation, as well as an endocrine modulator in reproduction and an organizer in early development, might promote aging-associated disorders, such as inflammation and cancer. Indeed, serum activin, but not serum TGFβ increases during aging. Also, activin/TGFβ signal through type II and type I receptors, both of which are transmembrane serine/threonine kinases, and the serine/threonine phosphorylation of APs, including Aβ42 serine 8 and αS serine 129, may confer pathological significance in neurodegenerative diseases. Moreover, activin expression is induced by APN in monocytes and hepatocytes, suggesting that activin might be situated downstream of the APN paradox. Finally, a meta-analysis of genome-wide association studies demonstrated that two SNPs relevant to the activin/TGFβ receptor signaling pathways conferred risk for major aging-associated disease. Collectively, activin might be involved in the APN paradox of AD and could be a significant therapeutic target.

Connecting Alzheimer's Disease With Diabetes Mellitus Through Amyloidogenic Evolvability

Type 2 diabetes mellitus (T2DM) has been clearlylinked to oxidative stress and amylin amyloidosis in pancreatic β-cells. Yet despite extensive investigation, the biological significance of this is not fully understood. Recently, we proposed that Alzheimer's disease (AD)-relevant amyloidogenic proteins (APs), such as amyloid-β (Aβ) and tau, might be involved in evolvability against diverse stressors in the brain. Given the analogous cellular stress environments shared by both T2DM and AD, the objective of this study is to explore T2DM pathogenesis from the viewpoint of amyloidogenic evolvability. Similar to AD-related APs, protofibrillar amylin might confer resistance against the multiple stressors in β-cells and be transmitted to offspring to deliver stress information, in the absence of which, type 1 DM (T1DM) in offspring might develop. On the contrary, T2DM may be manifested through an antagonistic pleiotropy mechanism during parental aging. Such evolvability-associated processes might be affected by parental diabetic conditions, including T1DM and T2DM. Furthermore, the T2DM-mediated increase in AD risk during aging might be attributed to an interaction of amylin with AD-related APs through evolvability, in which amylin protofibrillar formation presumably caused by adiponectin (APN) resistance could increase protofibril formation of AD-related APs in evolvability and subsequently lead to T2DM promotion of AD through antagonistic pleiotropy in aging. This suggests that targeting APN combined with an anti-T2DM agent might be therapeutic against neurodegeneration. Collectively, T1DM and T2DM might be linked through amylin evolvability, and a better understanding of amyloidogenic evolvability might also reveal clues to therapeutic interventions for AD comorbid with T2DM.

Insights Into the Controversial Aspects of Adiponectin in Cardiometabolic Disorders

In 2016, the World Health Organization estimated that more than 1.9 billion adults were overweight or obese. This impressive number shows that weight excess is pandemic. Overweight and obesity are closely associated with a high risk of comorbidities, such as insulin resistance and its most important outcomes, including metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. Adiponectin has emerged as a salutary adipocytokine, with insulin-sensitizing, anti-inflammatory, and cardiovascular protective properties. However, under metabolically unfavorable conditions, visceral adipose tissue-derived inflammatory cytokines might reduce the transcription of the adiponectin gene and consequently its circulating levels. Low circulating levels of adiponectin are negatively associated with various conditions, such as insulin resistance, type 2 diabetes mellitus, metabolic syndrome, and cardiovascular disease. In contrast, several recent clinical trials and meta-analyses have reported high circulating adiponectin levels positively associated with cardiovascular mortality and all-cause mortality. These results are biologically intriguing and counterintuitive, and came to be termed "the adiponectin paradox". Adiponectin paradox is frequently associated with adiponectin resistance, a concept related with the downregulation of adiponectin receptors in insulin-resistant states. We review this contradiction between the apparent role of adiponectin as a health promoter and the recent evidence from Mendelian randomization studies indicating that circulating adiponectin levels are an unexpected predictor of increased morbidity and mortality rates in several clinical conditions. We also critically review the therapeutic perspective of synthetic peptide adiponectin receptors agonist that has been postulated as a promising alternative for the treatment of metabolic syndrome and type 2 diabetes mellitus.

Plasma levels of adipokines in patients with Alzheimer's disease - where is the "breaking point" in Alzheimer's disease pathogenesis?

Peripheral insulin resistance is associated with decreasing adiponectin and increasing leptin plasma levels, and also with cognitive decline. The effects of adipokines on brain function have been published from both animal and human studies. In particular, the influence of leptin and adiponectin on the development of Alzheimer's disease (AD) has been extensively investigated. However, the association between adipsin and AD is as yet unknown. In 37 patients with AD and 65 controls that followed the same study protocol, we tested whether adiponectin, leptin, and adipsin could be used as biomarkers in the early stages of AD. In contrast with conclusions of cognition studies in insulin resistant states, our study found a correlation of impaired neuropsychological performance with increasing adiponectin and decreasing leptin in AD patients. Nevertheless, no significant differences between patients and controls were found. AD women had significantly increased adipsin compared to controls, and there was a positive correlation of adipsin with age and disease duration. Although adipokines do not appear to be suitable biomarkers for early AD diagnosis, they certainly play a role in the pathogenesis of AD. Further studies will be needed to explain the cause of the adipokine "breaking point" that leads to the pathogenesis of overt AD.

mTOR Mysteries: Nuances and Questions About the Mechanistic Target of Rapamycin in Neurodegeneration

The mechanistic target of rapamycin protein complex, mTORC1, has received attention in recent years for its role in aging and neurodegenerative diseases, such as Alzheimer's disease. Numerous excellent reviews have been written on the pathways and drug targeting of this keystone regulator of metabolism. However, none have specifically highlighted several important nuances of mTOR regulation as relates to neurodegeneration. Herein, we focus on six such nuances/open questions: (1) "Antagonistic pleiotropy" - Should we weigh the beneficial anabolic functions of mTORC1 against its harmful inhibition of autophagy? (2) "Early/late-stage specificity" - Does the relative importance of these neuroprotective/neurotoxic actions change as a disease progresses? (3) "Regional specificity" - Does mTOR signaling respond differently to the same interventions in different brain regions? (4) "Disease specificity" - Could the same intervention to inhibit mTORC1 help in one disease and cause harm in another disease? (5) "Personalized therapy" - Might genetically-informed personalized therapies that inhibit particular nodes in the mTORC1 regulatory network be more effective than generalized therapies? (6) "Lifestyle interventions" - Could specific diets, micronutrients, or exercise alter mTORC1 signaling to prevent or improve the progression neurodegenerative diseases? This manuscript is devoted to discussing recent research findings that offer insights into these gaps in the literature, with the aim of inspiring further inquiry.