Depression gets old fast: do stress and depression accelerate cell aging?

Depression and risk of developing dementia

Depression is highly common throughout the life course and dementia is common in late life. Depression has been linked with dementia, and growing evidence implies that the timing of depression may be important in defining the nature of this association. In particular, earlier-life depression (or depressive symptoms) has consistently been associated with a more than twofold increase in dementia risk. By contrast, studies of late-life depression and dementia risk have been conflicting; most support an association, yet the nature of this association (for example, if depression is a prodrome or consequence of, or risk factor for dementia) remains unclear. The likely biological mechanisms linking depression to dementia include vascular disease, alterations in glucocorticoid steroid levels and hippocampal atrophy, increased deposition of amyloid-β plaques, inflammatory changes, and deficits of nerve growth factors. Treatment strategies for depression could interfere with these pathways and alter the risk of dementia. Given the projected increase in dementia incidence in the coming decades, understanding whether treatment for depression alone, or combined with other regimens, improves cognition is of critical importance. In this Review, we summarize and analyze current evidence linking late-life and earlier-life depression and dementia, and discuss the primary underlying mechanisms and implications for treatment.

Circulating levels of brain-derived neurotrophic factor: correlation with mood, cognition and motor function

Brain-derived neurotrophic factor (BDNF) is the most widely distributed neurotrophin in the CNS, where it plays several pivotal roles in synaptic plasticity and neuronal survival. As a consequence, BDNF has become a key target in the physiopathology of several neurological and psychiatric diseases. Recent studies have consistently reported altered levels of BDNF in the circulation (i.e., serum or plasma) of patients with major depression, bipolar disorder, Alzheimer's disease, Huntington's disease and Parkinson's disease. Correlations between serum BDNF levels and affective, cognitive and motor symptoms have also been described. BDNF appears to be an unspecific biomarker of neuropsychiatric disorders characterized by neurodegenerative changes.

Physical exercise alleviates debilities of normal aging and Alzheimer's disease

Both healthy aging and the pathologic incidence of disorders associated with aging involve an array of debilities. Physical exercise harnesses implicit and inherent biologic characteristics amenable to the putative interventional influences under clinical, institutional or laboratory conditions. The neurodegenerative and pathophysiologic progressions that constitute Alzheimer's disease (AD), amnestic mild cognitive impairment (aMCI), normal aging, and different animal models of AD have shown the existence of several putative mechanisms. A large variety of moderating factors have demonstrated that the ever-proliferating plethora of neurotrophic factors, neurogenesis as observed through generality of expression and neuronal arborization. The insistent efficacy of brain vascular angiogenesis may delay also the comorbid incidence of depressive disorders with dementia pathology. The pathogenesis of aging may be contained by selective treatments: these diverse conditions, linked to the basis of the aging concept, have been shown, to greater or lesser extents, to respond to a variety of scheduled applications of physical exercise. The range of reports that provide accounts of the mechanisms mediating the positive progressive response to exercise intervention is far-ranging; these studies indicate that subtle changes at molecular, neuronal, vascular and epigenetic levels may exert notable consequence at functional expression and, perhaps most essentially, offer convincing expectancy of significant benefits.

Leukocyte telomere length in major depression: correlations with chronicity, inflammation and oxidative stress--preliminary findings

BACKGROUND

Depression is associated with an unusually high rate of aging-related illnesses and early mortality. One aspect of "accelerated aging" in depression may be shortened leukocyte telomeres. When telomeres critically shorten, as often occurs with repeated mitoses or in response to oxidation and inflammation, cells may die. Indeed, leukocyte telomere shortening predicts early mortality and medical illnesses in non-depressed populations. We sought to determine if leukocyte telomeres are shortened in Major Depressive Disorder (MDD), whether this is a function of lifetime depression exposure and whether this is related to putative mediators, oxidation and inflammation.

METHODOLOGY

Leukocyte telomere length was compared between 18 unmedicated MDD subjects and 17 controls and was correlated with lifetime depression chronicity and peripheral markers of oxidation (F2-isoprostane/Vitamin C ratio) and inflammation (IL-6). Analyses were controlled for age and sex.

PRINCIPAL FINDINGS

The depressed group, as a whole, did not differ from the controls in telomere length. However, telomere length was significantly inversely correlated with lifetime depression exposure, even after controlling for age (p<0.05). Average telomere length in the depressed subjects who were above the median of lifetime depression exposure (≥9.2 years' cumulative duration) was 281 base pairs shorter than that in controls (p<0.05), corresponding to approximately seven years of "accelerated cell aging." Telomere length was inversely correlated with oxidative stress in the depressed subjects (p<0.01) and in the controls (p<0.05) and with inflammation in the depressed subjects (p<0.05).

CONCLUSIONS

These preliminary data indicate that accelerated aging at the level of leukocyte telomeres is proportional to lifetime exposure to MDD. This might be related to cumulative exposure to oxidative stress and inflammation in MDD. This suggest that telomere shortening does not antedate depression and is not an intrinsic feature. Rather, telomere shortening may progress in proportion to lifetime depression exposure.

EEG frontal asymmetry in the depressed and remitted elderly: is it related to the trait or to the state of depression?

BACKGROUND

Over the last 30 years, frontal EEG asymmetry has been investigated with regards to the study of emotion, motivation, and psychopathology.

METHOD

We analyzed the frontal alpha asymmetry, depressive symptoms with a Beck Depression Inventory (BDI) and quality of life with a Short Form Health Survey-36® (SF-36®) in depressed (n=12), remitted (n=8) and non-depressed (n=7) elderly subjects. We also evaluated the correlation between the frontal EEG asymmetry and physical and mental aspects of SF-36®.

RESULTS

The groups showed no difference regarding the frontal alpha asymmetry (F=0.37; p=0.69). Moreover, there was no significant correlation between frontal asymmetry and quality of life (mental and physical aspects).

CONCLUSION

The results showed no evidence of a relationship between frontal asymmetry, quality of life and depression in the elderly. Future studies on frontal asymmetry should carefully consider the effects of age.

Telomere length of patients with major depression is shortened but independent from therapy and severity of the disease

BACKGROUND

Shortened telomere length has been observed in a variety of diseases. Our objective was to analyze mean telomere length of patients with major depressive disorder. A key question was whether telomere length varies in different groups of depressive patients.

METHODS

We obtained blood samples from patients with major depressive disorder (n = 54) and healthy subjects (n = 20). We isolated genomic DNA and measured mean telomere length using telomere restriction fragments and Southern blotting. We grouped patients according to the therapy they received including total antidepressant dose.

RESULTS

Mean telomere length of the entire patient group (7.20 ± 0.61 kb) was significantly shorter than in the control group (7.55 ± 0.54 kb). We observed no significant difference in telomere length among the different patient groups, but each of these patient groups had significantly shorter telomeres than the healthy subjects. Further analysis revealed no significant association between telomere length and illness duration and between telomere length and the severity of depression, as determined by the Hamilton score.

CONCLUSION

These results provide further evidence that major depressive disorder is associated with shortened telomeres. However, differences in the applied therapy, the duration of illness, or the severity of depression do not seem to have any influence on telomere length.

Developmental dioxin exposure of either parent is associated with an increased risk of preterm birth in adult mice

We have previously described diminished uterine progesterone response and increased uterine sensitivity to inflammation in adult female mice with a history of developmental exposure to TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin). Since parturition in mammals is an inflammatory process mediated in part by a decline in progesterone action, toxicant-mediated disruption of progesterone receptor (PR) expression at the maternal-fetal interface would likely impact the timing of birth. Therefore, in the current study, we examined pregnancy outcomes in adult female mice with a similar in utero exposure to TCDD. We also examined the impact of in utero TCDD exposure of male mice on pregnancy outcomes in unexposed females since the placenta, a largely paternally derived organ, plays a major role in the timing of normal parturition via inflammatory signaling. Our studies indicate that developmental exposure of either parent to TCDD is associated with preterm birth in a subsequent adult pregnancy due to altered PR expression and placental inflammation.

Ageing and neurodegenerative diseases

Ageing, which all creatures must encounter, is a challenge to every living organism. In the human body, it is estimated that cell division and metabolism occurs exuberantly until about 25 years of age. Beyond this age, subsidiary products of metabolism and cell damage accumulate, and the phenotypes of ageing appear, causing disease formation. Among these age-related diseases, neurodegenerative diseases have drawn a lot of attention due to their irreversibility, lack of effective treatment, and accompanied social and economical burdens. In seeking to ameliorate ageing and age-related diseases, the search for anti-ageing drugs has been of much interest. Numerous studies have shown that the plant polyphenol, resveratrol (3,5,4'-trihydroxystilbene), extends the lifespan of several species, prevents age-related diseases, and possesses anti-inflammatory, and anti-cancer properties. The beneficial effects of resveratrol are believed to be associated with the activation of a longevity gene, SirT1. In this review, we discuss the pathogenesis of age-related neurodegenerative diseases including Alzheimer's disease, Parkinson's disease and cerebrovascular disease. The therapeutic potential of resveratrol, diet and the roles of stem cell therapy are discussed to provide a better understanding of the ageing mystery.

Metabolic syndrome in severe mental disorders

The concept of metabolic syndrome in psychiatry provides a united front for confronting a series of metabolic changes that are predictive of cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM), which are highly prevalent in severe mental disorders (SMDs), such as schizophrenia, bipolar disorders, and severe depression. This review attempts to answer the following questions: (1) Is there evidence of significantly increased risk of metabolic syndrome in SMDs? (2) How is this evidence explained by stress theory and functional polymorphism? (3) What role can psychopharmacology and psychosocial therapies play in minimizing the problem? We have done a historical review using related literature from Medline. Compared with the general population, metabolic syndrome is two to three times more common in SMDs. The evidence for this predates the era of antipsychotic drugs. Altered glucose metabolism and dyslipidemia seem to be integral to SMDs. However, major psychotropic drugs are associated with metabolic syndrome, because of their activity at the appetite-stimulating receptors. SMDs seem to trigger a pathogenic cycle that fuels metabolic syndrome. To explain these findings, a neural diathesis-stress model has been proposed. Furthermore, candidate genes associated with receptors for weight gain are implicated. Using metformin (≥750 mg/day) may significantly reduce metabolic risks, and the data support consideration of this intervention for psychiatric patients taking antipsychotics. The obstacles to the implementation of the available guidelines for monitoring metabolic effects and changing unhelpful lifestyles need to be overcome by making monitoring mandatory and integration of physical exercise into routine care. Drug development and genotyping for the risk factors are future solutions.