Body mass index and the risk of Parkinson disease

Energy intake and exercise as determinants of brain health and vulnerability to injury and disease

Evolution favored individuals with superior cognitive and physical abilities under conditions of limited food sources, and brain function can therefore be optimized by intermittent dietary energy restriction (ER) and exercise. Such energetic challenges engage adaptive cellular stress-response signaling pathways in neurons involving neurotrophic factors, protein chaperones, DNA-repair proteins, autophagy, and mitochondrial biogenesis. By suppressing adaptive cellular stress responses, overeating and a sedentary lifestyle may increase the risk of Alzheimer's and Parkinson's diseases, stroke, and depression. Intense concerted efforts of governments, families, schools, and physicians will be required to successfully implement brain-healthy lifestyles that incorporate ER and exercise.

Fat-free body mass but not fat mass is associated with reduced gray matter volume of cortical brain regions implicated in autonomic and homeostatic regulation

Obesity has been associated with alterations of both functional and structural aspects of the human central nervous system. In obese individuals both fat mass (FM; primarily consisting of adipose tissue) and fat-free mass (FFM; all non-adipose tissues) are increased and it remains unknown whether these compartments have separate effects on human brain morphology. We used voxel-based morphometry to investigate the relationships between measures of body composition and regional gray matter volume (GMV) in 76 healthy adults with a wide range of adiposity (24 F/52 M; age 32.1 ± 8.8 years; percentage of body fat [PFAT%] 25.5 ± 10.9%; BMI 29.8 ± 8.9). Fat-free mass index (FFMI kg × m(-2)) showed negative associations in bilateral temporal regions, the bilateral medial and caudolateral OFC, and the left insula. Fat mass index (FMI kg × m(-2)) showed similar, but less extensive negative associations within temporal cortical regions and the left caudolateral orbitofrontal cortex (OFC). In addition, negative associations were seen for FMI with GMV of the cerebellum. Associations of FFMI with temporal and medial orbitofrontal GMV appeared to be independent of adiposity. No associations were seen between measures of adiposity (i.e. FM and PFAT) and GMV when adjusted for FFM. The majority of regions that we find associated with FFM have been implicated in the regulation of eating behavior and show extensive projections to central autonomic and homeostatic core structures. These data indicate that not adipose tissue or relative adiposity itself, but obesity related increases in absolute tissue mass and particularly FFM may have a more predominant effect on the human brain. This might be explained by the high metabolic demand of FFM and related increases in total energy needs.

Body mass index and the risk of dementia among Louisiana low income diabetic patients

Background

The association between obesity and dementia risk remains debatable and no studies have assessed this association among diabetic patients. The aim of our study was to investigate the association between body mass index (BMI) and dementia risk among middle and low income diabetic patients.

Methodology/Principal Findings

The sample included 44,660 diabetic patients (19,618 white and 25,042 African American) 30 to 96 years of age without a history of dementia in the Louisiana State University Hospital-Based Longitudinal Study. During a mean follow-up period of 3.9 years, 388 subjects developed incident dementia. The age- and sex-adjusted hazards ratios (HRs) for incident dementia at different levels of BMI (≤25, 25–26.9, 27–29.9, 30–34.9, and ≥35 kg/m²) were 1.00, 0.53 (95% CI 0.34–0.83), 0.29 (0.18–0.45), 0.37 (0.25–0.56), and 0.31 (0.21–0.48) (P_trend<0.001) in white diabetic patients, and 1.00, 1.00 (95% CI 0.62–1.63), 0.62 (0.39–0.98), 0.56 (0.36–0.86), and 0.65 (0.43–1.01) (P_trend = 0.029) in African American diabetic patients. Further adjustment for other confounding factors affected the results only slightly. There was a significant interaction between race and BMI on dementia risk (χ² = 5.52, 1df, p<0.025), such that the association was stronger in white patients. In stratified analyses, the multivariate-adjusted inverse association between BMI and risk of dementia was present in subjects aged 55–64 years, 65–74 years, and ≥75 years, in men and women, in non-smokers and smokers, and in subjects with different types of health insurance.

Conclusions/Significance

Higher baseline BMI was associated with a lower risk of dementia among diabetic patients, and this association was stronger among white than among African American diabetic patients.

Dietary energy intake modifies brainstem autonomic dysfunction caused by mutant α-synuclein

Parkinson's disease (PD) patients often exhibit impaired regulation of heart rate by the autonomic nervous system (ANS) that may precede motor symptoms in many cases. Results of autopsy studies suggest that brainstem pathology, including the accumulation of α-synuclein, precedes damage to dopaminergic neurons in the substantia nigra in PD. However, the molecular and cellular mechanisms responsible for the early dysfunction of brainstem autonomic neurons are unknown. Here we report that mice expressing a mutant form of α-synuclein that causes familial PD exhibit aberrant autonomic control of the heart characterized by elevated resting heart rate and an impaired cardiovascular stress response, associated with reduced parasympathetic activity and accumulation of α-synuclein in the brainstem. These ANS abnormalities occur early in the disease process. Adverse effects of α-synuclein on the control of heart rate are exacerbated by a high energy diet and ameliorated by intermittent energy restriction. Our findings establish a mouse model of early dysregulation of brainstem control of the cardiovascular system in PD, and further suggest the potential for energy restriction to attenuate ANS dysfunction, particularly in overweight individuals.

Metabolic markers or conditions preceding Parkinson's disease: a case-control study

Several metabolic markers or conditions have been explored as possible risk or protective factors for Parkinson's disease (PD); however, results remain conflicting. We further investigated these associations using a case-control study design. We used the medical records-linkage system of the Rochester Epidemiology Project to identify 196 subjects who developed PD in Olmsted County, Minnesota, from 1976 through 1995. Each incident case was matched by age (±1 year) and sex to a general population control. We reviewed the complete medical records of cases and controls in the medical records-linkage system to abstract information about body mass index (BMI), cholesterol level, hypertension, and diabetes mellitus preceding the onset of PD (or the index year). There were no significant differences between cases and controls for the metabolic markers or conditions investigated. No significant associations were found using 2 cutoffs for BMI level (BMI ≥ 25 or BMI ≥ 30 kg/m(2) ) and 3 cutoffs for cholesterol levels (>200, >250, or >300 mg/dL). Neither a diagnosis of hypertension or the documented use of antihypertensive medications was significantly associated with the subsequent risk of PD (odds ratio [OR], 1.00; 95% confidence interval [CI], 0.65-1.54; P = .99) nor was a diagnosis of diabetes mellitus or the use of glucose-lowering medications (OR, 0.77; 95% CI, 0.37-1.57; P = .47). Our study, based on historical information from a records-linkage system, does not support an association between BMI, cholesterol level, hypertension, or diabetes mellitus with later development of PD.

Food reward functions as affected by obesity and bariatric surgery

Roux-en-Y gastric bypass surgery (RYGB) remains to be the most effective long-term treatment for obesity and its associated comorbidities, but the specific mechanisms involved remain elusive. Because RYGB patients appear to no longer be preoccupied with thoughts about food and are satisfied with much smaller meals and calorically dilute foods, brain reward mechanisms could be involved. Just as obesity can produce maladaptive alterations in reward functions, reversal of obesity by RYGB could normalize these changes or even further reset the food reward system through changes in gut hormone secretion, aversive conditioning and/or secondary effects of weight loss. Future studies with longitudinal assessments of reward behaviors and their underlying neural circuits before and after surgery will be necessary to uncover the specific mechanisms involved. Such new insights could be the base for future 'knifeless' pharmacological and behavioral approaches to obesity.

High-fat diet exacerbates MPTP-induced dopaminergic degeneration in mice

The identification of modifiable nutritional risk factors is highly relevant to the development of preventive strategies for neurodegenerative disorders including Parkinson's disease (PD). In this study, adult C57BL/6 mice were fed either a control (CD-12%kcal) or a high-fat diet (HFD-60%kcal) for 8 weeks prior to MPTP exposure, a toxin which recreates a number of pathological features of PD. HFD-fed mice significantly gained weight (+41%), developed insulin resistance and a systemic immune response characterized by an increase in circulating leukocytes and plasmatic cytokines/chemokines (interleukin-1α, MCP-1, MIP-1α). As expected, the MPTP treatment produced nigral dopaminergic degeneration as evidenced by the loss of striatal dopamine and the decreased number of nigral tyrosine hydroxylase (TH)- and dopamine transporter-expressing neurons (23% and 25%, respectively). However, exposure to HFD exacerbated the effects of MPTP on striatal TH (23%) and dopamine levels (32%), indicating that diet-induced obesity is associated with a reduced capacity of nigral dopaminergic terminals to cope with MPTP-induced neurotoxicity. Since high-fat consumption is commonplace in our modern society, dietary fat intake may represent an important modifiable risk factor for PD.

Does vigorous exercise have a neuroprotective effect in Parkinson disease?

Parkinson disease (PD) is progressive, with dementia and medication-refractory motor problems common reasons for late-stage nursing-home placement. Increasing evidence suggests that ongoing vigorous exercise/physical fitness may favorably influence this progression. Parkinsonian animal models reveal exercise-related protection from dopaminergic neurotoxins, apparently mediated by brain neurotrophic factors and neuroplasticity (predicted from in vitro studies). Similarly, exercise consistently improves cognition in animals, also linked to enhanced neuroplasticity and increased neurotrophic factor expression. In these animal models, immobilization has the opposite effect. Brain-derived neurotrophic factor (BDNF) may mediate at least some of this exercise benefit. In humans, exercise increases serum BDNF, and this is known to cross the blood-brain barrier. PD risk in humans is significantly reduced by midlife exercise, documented in large prospective studies. No studies have addressed whether exercise influences dementia risk in PD, but exercised patients with PD improve cognitive scores. Among seniors in general, exercise or physical fitness has not only been associated with better cognitive scores, but midlife exercise significantly reduces the later risk of both dementia and mild cognitive impairment. Finally, numerous studies in seniors with and without dementia have reported increased cerebral gray matter volumes associated with physical fitness or exercise. These findings have several implications for PD clinicians. (1) Ongoing vigorous exercise and physical fitness should be highly encouraged. (2) PD physical therapy programs should include structured, graduated fitness instruction and guidance for deconditioned patients with PD. (3) Levodopa and other forms of dopamine replenishment therapy should be utilized to achieve the maximum capability and motivation for patients to maintain fitness.

Does vigorous exercise have a neuroprotective effect in Parkinson disease?

Parkinson disease (PD) is progressive, with dementia and medication-refractory motor problems common reasons for late-stage nursing-home placement. Increasing evidence suggests that ongoing vigorous exercise/physical fitness may favorably influence this progression. Parkinsonian animal models reveal exercise-related protection from dopaminergic neurotoxins, apparently mediated by brain neurotrophic factors and neuroplasticity (predicted from in vitro studies). Similarly, exercise consistently improves cognition in animals, also linked to enhanced neuroplasticity and increased neurotrophic factor expression. In these animal models, immobilization has the opposite effect. Brain-derived neurotrophic factor (BDNF) may mediate at least some of this exercise benefit. In humans, exercise increases serum BDNF, and this is known to cross the blood-brain barrier. PD risk in humans is significantly reduced by midlife exercise, documented in large prospective studies. No studies have addressed whether exercise influences dementia risk in PD, but exercised patients with PD improve cognitive scores. Among seniors in general, exercise or physical fitness has not only been associated with better cognitive scores, but midlife exercise significantly reduces the later risk of both dementia and mild cognitive impairment. Finally, numerous studies in seniors with and without dementia have reported increased cerebral gray matter volumes associated with physical fitness or exercise. These findings have several implications for PD clinicians. (1) Ongoing vigorous exercise and physical fitness should be highly encouraged. (2) PD physical therapy programs should include structured, graduated fitness instruction and guidance for deconditioned patients with PD. (3) Levodopa and other forms of dopamine replenishment therapy should be utilized to achieve the maximum capability and motivation for patients to maintain fitness.

Obesity, diabetes, and risk of Parkinson's disease

The aim of this work was to investigate whether obesity and diabetes are related to risk of Parkinson's disease. We prospectively followed 147,096 participants in the Cancer Prevention Study II Nutrition Cohort from 1992 to 2005. Participants provided information on anthropometric variables and medical history at baseline and on waist circumference in 1997. Incident cases of Parkinson's disease (n = 656) were confirmed by treating neurologists and medical record review. Relative risks were estimated using proportional hazards models, adjusting for age, gender, smoking, and other risk factors. Neither body mass index nor waist circumference significantly predicted Parkinson's disease risk. Relative risk comparing individuals with a baseline body mass index of ≥ 30 to those with a body mass index <23 was 1.00 (95% confidence interval: 0.75, 1.34; P trend: 0.79), and that comparing individuals with a waist circumference in the top category (≥ 40.3 inches in men and ≥ 35 inches in women) to those in the bottom category (<34.5 inches in men and <28 inches in women) was 1.35 (95% confidence interval: 0.95, 1.93; P trend: 0.08). History of diabetes was not significantly associated with Parkinson's disease risk (combined relative risks = 0.88; 95% confidence interval: 0.62, 1.25; P heterogeneity = 0.96). In addition, neither body mass index at age 18 nor changes in weight between age 18 and baseline were significantly associated with Parkinson's disease risk. The results did not differ significantly by gender. Our results do not provide evidence for a relationship between body mass index, weight change, waist circumference, or baseline diabetes and risk of Parkinson's disease.

Insulin resistance impairs nigrostriatal dopamine function

Clinical studies have indicated a link between Parkinson's disease (PD) and Type 2 Diabetes. Although preclinical studies have examined the effect of high-fat feeding on dopamine function in brain reward pathways, the effect of diet on neurotransmission in the nigrostriatal pathway, which is affected in PD and parkinsonism, is less clear. We hypothesized that a high-fat diet, which models early-stage Type 2 Diabetes, would disrupt nigrostriatal dopamine function in young adult Fischer 344 rats. Rats were fed a high fat diet (60% calories from fat) or a normal chow diet for 12 weeks. High fat-fed animals were insulin resistant compared to chow-fed controls. Potassium-evoked dopamine release and dopamine clearance were measured in the striatum using in vivo electrochemistry. Dopamine release was attenuated and dopamine clearance was diminished in the high-fat diet group compared to chow-fed rats. Magnetic resonance imaging indicated increased iron deposition in the substantia nigra of the high fat group. This finding was supported by alterations in the expression of several proteins involved in iron metabolism in the substantia nigra in this group compared to chow-fed animals. The diet-induced systemic and basal ganglia-specific changes may play a role in the observed impairment of nigrostriatal dopamine function.

Association of Blood Pressure and Hypertension With the Risk of Parkinson Disease

Cardiovascular risk factors, such as diabetes mellitus and central obesity, have been associated with Parkinson disease (PD), but data on blood pressure and PD are lacking. We sought to examine the association of blood pressure and hypertension with the risk of PD among men and women. This study consisted of 7 surveys (1972–2002) on representative samples of the general population in Finland (National FINRISK Study). A total number of 59 540 participants (age 25 to 74 years; 51.8% women) who were free of PD and stroke at baseline were prospectively followed until December 31, 2006, to identify incident PD cases using the National Social Insurance Register database. Cox proportional hazards models were constructed to estimate the hazard ratio of PD associated with blood pressure. During a mean follow-up period of 18.8 years (SD: 10.2 years), 423 men and 371 women were ascertained to have developed PD. In women, compared with normotensive subjects (<130/80 mm Hg), the multivariable-adjusted hazard ratios of PD associated with high-normal blood pressure (130 to 139/80 to 89 mm Hg) and hypertension (≥140/90 mm Hg or use of antihypertensive agents) were 1.63 (95% CI: 1.07 to 2.47) and 1.62 (95% CI: 1.09 to 2.42). There was no significant association between blood pressure and PD risk in men. The multivariable-adjusted hazard ratios of PD associated with use of antihypertensive agents were 1.08 (95% CI: 0.79 to 1.48) in men and 1.03 (95% CI: 0.76 to 1.38) in women. This study suggests that, in women, above-optimal blood pressure, including high-normal blood pressure and hypertension, is associated with an increased risk of PD. Optimal control of blood pressure in women may reduce the incidence of PD.

Food reward, hyperphagia, and obesity

Given the unabated obesity problem, there is increasing appreciation of expressions like "my eyes are bigger than my stomach," and recent studies in rodents and humans suggest that dysregulated brain reward pathways may be contributing not only to drug addiction but also to increased intake of palatable foods and ultimately obesity. After describing recent progress in revealing the neural pathways and mechanisms underlying food reward and the attribution of incentive salience by internal state signals, we analyze the potentially circular relationship between palatable food intake, hyperphagia, and obesity. Are there preexisting individual differences in reward functions at an early age, and could they be responsible for development of obesity later in life? Does repeated exposure to palatable foods set off a cascade of sensitization as in drug and alcohol addiction? Are reward functions altered by secondary effects of the obese state, such as increased signaling through inflammatory, oxidative, and mitochondrial stress pathways? Answering these questions will significantly impact prevention and treatment of obesity and its ensuing comorbidities as well as eating disorders and drug and alcohol addiction.

Epidemiology and etiology of Parkinson's disease: a review of the evidence

The etiology of Parkinson's disease (PD) is not well understood but likely to involve both genetic and environmental factors. Incidence and prevalence estimates vary to a large extent-at least partly due to methodological differences between studies-but are consistently higher in men than in women. Several genes that cause familial as well as sporadic PD have been identified and familial aggregation studies support a genetic component. Despite a vast literature on lifestyle and environmental possible risk or protection factors, consistent findings are few. There is compelling evidence for protective effects of smoking and coffee, but the biologic mechanisms for these possibly causal relations are poorly understood. Uric acid also seems to be associated with lower PD risk. Evidence that one or several pesticides increase PD risk is suggestive but further research is needed to identify specific compounds that may play a causal role. Evidence is limited on the role of metals, other chemicals and magnetic fields. Important methodological limitations include crude classification of exposure, low frequency and intensity of exposure, inadequate sample size, potential for confounding, retrospective study designs and lack of consistent diagnostic criteria for PD. Studies that assessed possible shared etiological components between PD and other diseases show that REM sleep behavior disorder and mental illness increase PD risk and that PD patients have lower cancer risk, but methodological concerns exist. Future epidemiologic studies of PD should be large, include detailed quantifications of exposure, and collect information on environmental exposures as well as genetic polymorphisms.

GPA protects the nigrostriatal dopamine system by enhancing mitochondrial function

Guanidinopropionic acid (GPA) increases AMPK activity, mitochondrial function and biogenesis in muscle and improves physiological function, for example during aging. Mitochondrial dysfunction is a major contributor to the pathogenesis of Parkinson's disease. Here we tested whether GPA prevents neurodegeneration of the nigrostriatal dopamine system in MPTP-treated mice. Mice were fed a diet of 1% GPA or normal chow for 4 weeks and then treated with either MPTP or saline. Indices of nigrostriatal function were examined by HPLC, immunohistochemistry, stereology, electron microscopy and mitochondrial respiration. MPTP intoxication decreased TH neurons in the SNpc of normal chow-fed mice; however GPA-fed mice remarkably exhibited no loss of TH neurons in the SNpc. MPTP caused a decrease in striatal dopamine of both normal chow- and GPA-fed mice, although this effect was significantly attenuated in GPA-fed mice. GPA-fed mice showed increased AMPK activity, mitochondrial respiration and mitochondrial number in nigrostriatal TH neurons, suggesting that the neuroprotective effects of GPA involved AMPK-dependent increases in mitochondrial function and biogenesis. MPTP treatment produced a decrease in mitochondrial number and volume in normal chow-fed mice but not GPA-fed mice. Our results show the neuroprotective properties of GPA in a mouse model of Parkinson's disease are partially mediated by AMPK and mitochondrial function. Mitochondrial dysfunction is a common problem in neurodegeneration and thus GPA may slow disease progression in other models of neurodegeneration.

Neurodegeneration in an animal model of Parkinson's disease is exacerbated by a high-fat diet

Despite numerous clinical studies supporting a link between type 2 diabetes (T2D) and Parkinson's disease (PD), the clinical literature remains equivocal. We, therefore, sought to address the relationship between insulin resistance and nigrostriatal dopamine (DA) in a preclinical animal model. High-fat feeding in rodents is an established model of insulin resistance, characterized by increased adiposity, systemic oxidative stress, and hyperglycemia. We subjected rats to a normal chow or high-fat diet for 5 wk before infusing 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle. Our goal was to determine whether a high-fat diet and the resulting peripheral insulin resistance would exacerbate 6-OHDA-induced nigrostriatal DA depletion. Prior to 6-OHDA infusion, animals on the high-fat diet exhibited greater body weight, increased adiposity, and impaired glucose tolerance. Two weeks after 6-OHDA, locomotor activity was tested, and brain and muscle tissue was harvested. Locomotor activity did not differ between the groups nor did cholesterol levels or measures of muscle atrophy. High-fat-fed animals exhibited higher homeostatic model assessment of insulin resistance (HOMA-IR) values and attenuated insulin-stimulated glucose uptake in fast-twitch muscle, indicating decreased insulin sensitivity. Animals in the high-fat group also exhibited greater DA depletion in the substantia nigra and the striatum, which correlated with HOMA-IR and adiposity. Decreased phosphorylation of HSP27 and degradation of IκBα in the substantia nigra indicate increased tissue oxidative stress. These findings support the hypothesis that a diet high in fat and the resulting insulin resistance may lower the threshold for developing PD, at least following DA-specific toxin exposure.

Physical activities and future risk of Parkinson disease

OBJECTIVE

To prospectively investigate the relationship between physical activity and Parkinson disease (PD).

METHODS

We evaluated physical activity in relation to PD among 213,701 participants of the NIH-AARP Diet and Health Study cohort. Physical activities over 4 periods (ages 15-18, 19-29, and 35-39, and in the past 10 years) were noted in 1996-1997, and physician-diagnosed PD was reported on the 2004-2006 follow-up questionnaire. Only cases diagnosed after 2000 (n = 767) were included in the analyses.

RESULTS

Higher levels of moderate to vigorous activities at ages 35-39 or in the past 10 years as reported in 1996-1997 were associated with lower PD occurrence after 2000 with significant dose-response relationships. The multivariate odds ratios (OR) between the highest vs the lowest levels were 0.62 (95% CI confidence interval [CI] 0.48-0.81, p for trend 0.005) for ages 35-39 and 0.65 (95% CI 0.51-0.83, p for trend 0.0001) for in the past 10 years. Further analyses showed that individuals with consistent and frequent participation in moderate to vigorous activities in both periods had approximately a 40% lower risk than those who were inactive in both periods. Moderate to vigorous activities at earlier ages or light activities were not associated with PD. Finally, the association between higher moderate to vigorous physical activities and lower PD risk was demonstrated in a metaanalysis of prospective studies.

CONCLUSIONS

Although we cannot exclude the possibility that less participation in physical activity is an early marker of PD, epidemiologic evidence suggests that moderate to vigorous exercise may protect against PD.

Non-motor extranigral signs and symptoms in Parkinson's disease

Clinical symptoms in Parkinson's disease (PD) comprise both motor and non-motor symptoms. In this disease, synucleinopathic-induced, nigral dopamine deficiency-related dysfunction of the basal ganglia is held responsible for the characteristic levodopa-responsive motor signs and symptoms (bradykinesia, hypokinesia, rigidity), known as parkinsonism and essential for clinical diagnosis in PD, as well as subtle motivational and cognitive dysfunctions. Some motor symptoms, such as tremor and postural instability, and most non-motor symptoms, however, are not fully levodopa-responsive, and suggested to manifest extranigral pathology. These symptoms include autonomic, sleep, sensory and neuropsychiatric symptoms, which in some cases may precede the first signs of motor parkinsonism, closely correlating with the progression of Lewy body pathology in PD. The recognition and treatment of these mostly under-recognized and under-treated symptoms is important, as these symptoms might have more impact on the quality of life in PD patients as compared to motor parkinsonism. On top of this, recognition of these manifestations in the prodromal phase of motor PD is critical to early diagnosis and treatment, as disease-modifying drugs, once identified, should be initiated as soon as possible, preferably in this premotor phase of the disease. On top of this, (non)motor extranigral symptoms in PD might also be of iatrogenic origin, whether directly as indirectly. During conventional, oral, dopaminomimetic treatment, the progressive loss of striatal dopaminergic nerve endings with the loss of cerebral dopamine storage capacity, renders the cerebral dopamine level fully dependent of the plasma levodopa levels, thus changing dopaminergic receptor stimulation from continuous to a more pulsatile pattern. Supposedly due to this process, neuroplastic changes in (sub)cortical dopaminergic pathways might cause therapeutic response fluctuations: motor and nonmotor fluctuations with anxiety- and panic-attacks and/or mood swings, dyskinesias and punding. Finally, dopaminomimetic pharmacotherapy may also induce extranigral non-motor drug-related direct adverse effects, such as impulse control disorders. In this article, non-motor signs and symptoms of extranigral PD-related pathology will be discussed, as well as the (suggested) criteria for diagnosis and treatment. Of course, also the recognition of the signs and symptoms of the prodromal (premotor) phase, suggestive for the presence of the PD, will be discussed. Iatrogenic non-motor symptoms, though, will not be further discussed.

The role of gut hormones and the hypothalamus in appetite regulation

The World Health Organisation has estimated that by 2015 approximately 2.3 billion adults will be overweight and more than 700 million obese. Obesity is associated with an increased risk of diabetes, cardiovascular events, stroke and cancer. The hypothalamus is a crucial region for integrating signals from central and peripheral pathways and plays a major role in appetite regulation. In addition, there are reciprocal connections with the brainstem and higher cortical centres. In the arcuate nucleus of the hypothalamus, there are two major neuronal populations which stimulate or inhibit food intake and influence energy homeostasis. Within the brainstem, the dorsal vagal complex plays a role in the interpretation and relaying of peripheral signals. Gut hormones act peripherally to modulate digestion and absorption of nutrients. However, they also act as neurotransmitters within the central nervous system to control food intake. Peptide YY, pancreatic polypeptide, glucagon-like peptide-1 and oxyntomodulin suppress appetite, whilst ghrelin increases appetite through afferent vagal fibres to the caudal brainstem or directly to the hypothalamus. A better understanding of the role of these gut hormones may offer the opportunity to develop successful treatments for obesity. Here we review the current understanding of the role of gut hormones and the hypothalamus on food intake and body weight control.

Ghrelin promotes and protects nigrostriatal dopamine function via a UCP2-dependent mitochondrial mechanism

Ghrelin targets the hypothalamus to regulate food intake and adiposity. Endogenous ghrelin receptors [growth hormone secretagogue receptor (GHSR)] are also present in extrahypothalamic sites where they promote circuit activity associated with learning and memory, and reward seeking behavior. Here, we show that the substantia nigra pars compacta (SNpc), a brain region where dopamine (DA) cell degeneration leads to Parkinson's disease (PD), expresses GHSR. Ghrelin binds to SNpc cells, electrically activates SNpc DA neurons, increases tyrosine hydroxylase mRNA and increases DA concentration in the dorsal striatum. Exogenous ghrelin administration decreased SNpc DA cell loss and restricted striatal dopamine loss after 1-methyl-4-phenyl-1,2,5,6 tetrahydropyridine (MPTP) treatment. Genetic ablation of ghrelin or the ghrelin receptor (GHSR) increased SNpc DA cell loss and lowered striatal dopamine levels after MPTP treatment, an effect that was reversed by selective reactivation of GHSR in catecholaminergic neurons. Ghrelin-induced neuroprotection was dependent on the mitochondrial redox state via uncoupling protein 2 (UCP2)-dependent alterations in mitochondrial respiration, reactive oxygen species production, and biogenesis. Together, our data reveal that peripheral ghrelin plays an important role in the maintenance and protection of normal nigrostriatal dopamine function by activating UCP2-dependent mitochondrial mechanisms. These studies support ghrelin as a novel therapeutic strategy to combat neurodegeneration, loss of appetite and body weight associated with PD. Finally, we discuss the potential implications of these studies on the link between obesity and neurodegeneration.

Total cholesterol and the risk of Parkinson's disease: a review for some new findings

The studies on the association between serum cholesterol level and the risks of neurodegenerative diseases risk are debated. Some prospective studies have found that high serum cholesterol may increase the risks of dementia/Alzheimer's disease and ischemic stroke. However, other studies have found no association or a decreased risk of hemorrhagic stroke with increasing levels of serum total cholesterol. Little is known about the association between serum total cholesterol or a history of hypercholesterolemia and Parkinson's disease (PD) risk. Only a few case-control studies and four prospective epidemiological studies have examined this association, but the results are inconsistent. An inverse association between serum total cholesterol and the risk of PD has been found in one prospective study; however, no significant association is reported in the case-control studies and other two prospective studies. Recently, one large prospective study from Finland suggests that high total cholesterol at baseline is associated with an increased risk of PD. Further studies, especially large clinical trials, are needed.

A timeline for Parkinson's disease

It is reasonably well established that prior to the motor phase of classical Parkinson's disease (PD) there is a prodromal period of several years duration. Once typical motor features appear, the disease continues up to 20 years depending on multiple variables. The clinical features of the prodromal and motor phases may be correlated with pathological changes in the central and autonomic nervous systems to allow a sequential plan of disease progression. We present a 'best guess' for a typical individual presenting with PD in their sixties and speculate that the disease will last approximately 40 years from the earliest non-motor features to death. Appreciation of this concept may allow better strategies for slowing or halting disease progression.

Dietary intake in adults at risk for Huntington disease: analysis of PHAROS research participants

OBJECTIVE

To examine caloric intake, dietary composition, and body mass index (BMI) in participants in the Prospective Huntington At Risk Observational Study (PHAROS).

METHODS

Caloric intake and macronutrient composition were measured using the National Cancer Institute Food Frequency Questionnaire (FFQ) in 652 participants at risk for Huntington disease (HD) who did not meet clinical criteria for HD. Logistic regression was used to examine the relationship between macronutrients, BMI, caloric intake, and genetic status (CAG <37 vs CAG > or =37), adjusting for age, gender, and education. Linear regression was used to determine the relationship between caloric intake, BMI, and CAG repeat length.

RESULTS

A total of 435 participants with CAG <37 and 217 with CAG > or =37 completed the FFQ. Individuals in the CAG > or =37 group had a twofold odds of being represented in the second, third, or fourth quartile of caloric intake compared to the lowest quartile adjusted for age, gender, education, and BMI. This relationship was attenuated in the highest quartile when additionally adjusted for total motor score. In subjects with CAG > or =37, higher caloric intake, but not BMI, was associated with both higher CAG repeat length (adjusted regression coefficient = 0.26, p = 0.032) and 5-year probability of onset of HD (adjusted regression coefficient = 0.024; p = 0.013). Adjusted analyses showed no differences in macronutrient composition between groups.

CONCLUSIONS

Increased caloric intake may be necessary to maintain body mass index in clinically unaffected individuals with CAG repeat length > or =37. This may be related to increased energy expenditure due to subtle motor impairment or a hypermetabolic state.

Obesity and restless legs syndrome in men and women

BACKGROUND

Obesity and restless legs syndrome (RLS) are both associated with hypofunction of dopamine in the CNS. We therefore examined whether individuals who are obese have an increased risk of RLS in two ongoing US cohorts, the Nurses' Health Study II and the Health Professional Follow-up Study.

METHODS

We included 65,554 women and 23,119 men free of diabetes, arthritis, and pregnancy in the current analyses. Information on RLS was assessed using a set of standardized questions. Participants were considered to have RLS if they met four RLS diagnostic criteria recommended by the International RLS Study Group and had restless legs > or =5 times/month. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression models adjusting for age, smoking, use of antidepressant, phobic anxiety score, and other covariates. Log ORs from the two cohorts were pooled by a fixed-effects model.

RESULTS

There were 6.4% of women and 4.1% of men who were considered to have RLS. Multivariate adjusted ORs for RLS were 1.42 (95% CI: 1.3, 1.6; p trend <0.0001) for participants with body mass index (BMI) >30 vs <23 kg/m(2) and 1.60 (95% CI: 1.5, 1.8; p trend <0.0001) for highest vs lowest waist circumference quintiles. Greater BMI in early adulthood (age 18-21 years) and weight gain were also associated with a higher prevalence of RLS (p trend <0.01 for both).

CONCLUSIONS

Both overall and abdominal adiposity are associated with increased likelihoods of having restless legs syndrome (RLS). Further prospective studies are warranted to clarify causative association between obesity and risk of developing RLS.

A diet for dopaminergic neurons?

Parkinson's disease (PD) is the second most common neurodegenerative disease, which unfortunately is still fatal. Since the discovery of dopamine (DA) neuronal cell loss within the substantia nigra in PD, the past decades have seen the understanding of the pathophysiological mechanisms underlying the degenerative process advance at a very impressive rate. Nevertheless, there is at present no cure for PD. Although there are no proven therapies for prevention, a large body of evidence from animal studies has highlighted the paramount role of dietary factors in counteracting DA degeneration. Consistently, associations between the risk of developing PD and the intake of nutrients, individual foods, and dietary patterns have been recently shown. Therefore, promoting healthy lifestyle choices such as a Mediterranean diet might be the key to reducing the risk of PD.

Meeting report: consensus statement-Parkinson's disease and the environment: collaborative on health and the environment and Parkinson's Action Network (CHE PAN) conference 26-28 June 2007

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disorder. People with PD, their families, scientists, health care providers, and the general public are increasingly interested in identifying environmental contributors to PD risk.

METHODS

In June 2007, a multidisciplinary group of experts gathered in Sunnyvale, California, USA, to assess what is known about the contribution of environmental factors to PD.

RESULTS

We describe the conclusions around which they came to consensus with respect to environmental contributors to PD risk. We conclude with a brief summary of research needs.

CONCLUSIONS

PD is a complex disorder, and multiple different pathogenic pathways and mechanisms can ultimately lead to PD. Within the individual there are many determinants of PD risk, and within populations, the causes of PD are heterogeneous. Although rare recognized genetic mutations are sufficient to cause PD, these account for < 10% of PD in the U.S. population, and incomplete penetrance suggests that environmental factors may be involved. Indeed, interplay among environmental factors and genetic makeup likely influences the risk of developing PD. There is a need for further understanding of how risk factors interact, and studying PD is likely to increase understanding of other neurodegenerative disorders.

Parkinson disease: primacy of age as a risk factor for mitochondrial dysfunction

In 1983, it was reported that certain drug users with a history of exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a contaminant of an illicitly produced meperidine analogue, developed an irreversible syndrome resembling idiopathic Parkinson disease (PD). Soon thereafter, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine's active metabolite, 1-methyl-4-phenylpyridine, was shown to be a complex I inhibitor. Activity of complex I (the point of entry for most electrons that traverse the mitochondrial electron transport chain) has been found to be impaired in the substantia nigra pars compacta and also in other brain tissues in PD patients. In 2006, high temporal and spatial resolution phosphorous functional magnetic resonance spectroscopy was used to demonstrate that, in 20 PD patients, mitochondrial dysfunction extended to the visual cortex. Epidemiologic studies have implicated a number of apparently disparate exogenous factors in the causation of PD. For example, exposure to certain pesticides and herbicides (many known to inhibit electron transport chain activity) increases PD risk. Parkinson disease risk can be doubled, tripled, or more in individuals with repeated head injuries. Over time, PD risk is almost doubled in men and women with prior type 2 diabetes mellitus. Nevertheless, despite evidence that certain exogenous and/or developmental factors play a role in causation of PD, their potential effect on PD incidence is greatly overshadowed by that of advancing age. In 1 prospective study, PD incidence rate in subjects at least 85 years old was about 14 times that observed in subjects aged 56 to 65 years. The dramatic effect of aging on PD risk may be explained in part by the fact that mitochondrial DNA deletions are abundant and cause functional impairment in aged human substantia nigra pars compacta neurons. High levels of these mutations are associated with electron transport chain deficiency, a situation that favors increased oxidative damage, Lewy body formation, and apoptotic cell death. Systematic study of the effects of putative risk factors in animal models of parkinsonism may be expected to improve our understanding of PD's complex pathogenesis.

Diabetes in patients with idiopathic Parkinson's disease

OBJECTIVE

Previous observational studies reported inconsistent results on the association between diabetes and Parkinson's disease, and data on the risk of developing incident diabetes in relation to Parkinson's disease are scarce. We aimed at comparing the diabetes prevalence between patients with or without Parkinson's disease and at exploring the risk of developing incident diabetes associated with Parkinson's disease.

RESEARCH DESIGN AND METHODS

We used the U.K.-based General Practice Research Database (GPRD) to 1) compare the diabetes prevalence between Parkinson's disease cases and a matched comparison group free of Parkinson's disease between 1994 and 2005 and to 2) conduct a follow-up study with a nested case-control analysis to quantify the risk of developing new-onset diabetes in association with Parkinson's disease.

RESULTS

The diabetes prevalence was similar in patients with and without Parkinson's disease (adjusted odds ratio [OR] 0.95 [95% CI 0.80-1.14]). In the cohort analysis (incidence rate ratio [IRR] 0.55 [95% CI 0.38-0.81]) and in the nested case-control analysis (adjusted OR 0.53 [95% CI 0.33-0.87]), the risk of developing diabetes was lower in patients with Parkinson's disease than in subjects without. The adjusted OR for patients with Parkinson's disease who were current levodopa users of five or more prescriptions was 0.22 (0.10-0.48) and was 1.11 (0.50-2.45) for Parkinson's disease patients not using levodopa.

CONCLUSIONS

In this observational study, diabetes prevalence was closely similar between patients with Parkinson's disease and subjects without. The risk of developing incident diabetes was lower for patients with Parkinson's disease than for patients without, a finding that was limited to Parkinson's disease patients who were using levodopa.

Increased resting-state functional connectivity in obese adolescents; a magnetoencephalographic pilot study

BACKGROUND

Obesity is not only associated with metabolic abnormalities, but also with cognitive dysfunction and changes in the central nervous system. The present pilot study was carried out to investigate functional connectivity in obese and non-obese adolescents using magnetoencephalography (MEG).

METHODOLOGY/PRINCIPAL FINDINGS

Magnetoencephalographic recordings were performed in 11 obese (mean BMI 38.8+/-4.6 kg/m(2)) and 8 lean (mean BMI 21.0+/-1.5 kg/m(2)) female adolescents (age 12-19 years) during an eyes-closed resting-state condition. From these recordings, the synchronization likelihood (SL), a common method that estimates both linear and non-linear interdependencies between MEG signals, was calculated within and between brain regions, and within standard frequency bands (delta, theta, alpha1, alpha2, beta and gamma). The obese adolescents had increased synchronization in delta (0.5-4 Hz) and beta (13-30 Hz) frequency bands compared to lean controls (P(delta total) = 0.001; P(beta total) = 0.002).

CONCLUSIONS/SIGNIFICANCE

This study identified increased resting-state functional connectivity in severe obese adolescents. Considering the importance of functional coupling between brain areas for cognitive functioning, the present findings strengthen the hypothesis that obesity may have a major impact on human brain function. The cause of the observed excessive synchronization is unknown, but might be related to disturbed motivational pathways, the recently demonstrated increase in white matter volume in obese subjects or altered metabolic processes like hyperinsulinemia. The question arises whether the changes in brain structure and communication are a dynamic process due to weight gain and whether these effects are reversible or not.

Diet, urate, and Parkinson's disease risk in men

The authors examined whether a diet that increases plasma urate level is also related to reduced risk of Parkinson's disease (PD). The study population comprised 47,406 men in the Health Professionals Follow-up Study. The potential effect of diet on plasma urate level was estimated by regressing plasma urate on intakes of selected foods and nutrients in a subsample of 1,387 men. Coefficients of this regression model were then used to calculate a dietary urate index for all cohort participants. Multivariate relative risks of PD were estimated by means of Cox proportional hazards models. After 14 years of follow-up (1986-2000), the authors documented 248 incident cases of PD. A higher dietary urate index was associated with a lower risk of PD (top quintile vs. bottom: relative risk = 0.47, p-trend = 0.0008), after adjustment for age, smoking, caffeine intake, and other potential confounders. This association remained strong and significant after further adjustment for each component of the index individually (p-trend < 0.02 for each). These data support urate as a potentially protective factor in PD and suggest that dietary changes expected to increase plasma urate level may contribute to lower risk of PD. These potential benefits, however, should be weighed against expected adverse effects on risk of gout and other chronic diseases.

Impact of psychiatric disorders on Parkinson's disease : a nationwide follow-up study from Sweden

OBJECTIVES

To analyze whether hospitalization for a psychiatric disorder predicts Parkinson's disease (PD) in men and women in different age groups after accounting for socioeconomic status and geographical region.

METHODS

Data from the MigMed database were used to identify all people in Sweden hospitalized for psychiatric disorder and PD during the study period (1987 to 2001). Standardized incidence ratios (SIRs) with 95% confidence intervals (CI) for PD were calculated among those with and without hospitalization for psychiatric disorder.

RESULTS

There were 1876 cases of PD among those with psychiatric disorder during the study period. The risk of developing PD was strongest among those under age 50; the SIR was 11.56 (95% CI 9.15-14.41). The risk was attenuated with increasing age in both men and women. There were similar risk patterns in all subtypes of psychiatric disorders in PD patients. The overall risk of PD among people with psychiatric disorders was higher for women than men.

CONCLUSIONS

A psychiatric disorder is an appreciable risk factor for the development of PD, particularly in people under age 50. The association between PD and psychiatric disorders should be taken into account by clinicians and health care providers.

Type 2 diabetes and the risk of Parkinson's disease

OBJECTIVE

To evaluate whether type 2 diabetes at baseline is a risk factor for Parkinson's disease.

RESEARCH DESIGN AND METHODS

We prospectively followed 51,552 Finnish men and women 25-74 years of age without a history of Parkinson's disease at baseline. History of diabetes and other study parameters were determined at baseline using standardized measurements. Ascertainment of the Parkinson's disease status was based on the nationwide Social Insurance Institution's drug register data. Hazard ratios of incident Parkinson's disease associated with the history of type 2 diabetes were estimated.

RESULTS

During a mean follow-up period of 18.0 years, 324 men and 309 women developed incident Parkinson's disease. Age- and study year-adjusted hazard ratios of incident Parkinson's disease among subjects with type 2 diabetes, compared with those without it, were 1.80 (95% CI 1.03-3.15) in men, 1.93 (1.05-3.53) in women, and 1.85 (1.23-2.80) in men and women combined (adjusted also for sex). Further adjustment for BMI, systolic blood pressure, total cholesterol, education, leisure-time physical activity, smoking, alcohol drinking, and coffee and tea consumption affected the results only slightly. The multivariate adjusted association between type 2 diabetes and the risk of Parkinson's disease was also confirmed in stratified subgroup analysis.

CONCLUSIONS

These data suggest that type 2 diabetes is associated with an increased risk of Parkinson's disease. Surveillance bias might account for higher rates in diabetes. The mechanism behind this association between diabetes and Parkinson's disease is not known.

Coffee and tea consumption and the risk of Parkinson's disease

Several prospective studies have assessed the association between coffee consumption and Parkinson's disease (PD) risk, but the results are inconsistent. We examined the association of coffee and tea consumption with the risk of incident PD among 29,335 Finnish subjects aged 25 to 74 years without a history of PD at baseline. During a mean follow-up of 12.9 years, 102 men and 98 women developed an incident PD. The multivariate-adjusted (age, body mass index, systolic blood pressure, total cholesterol, education, leisure-time physical activity, smoking, alcohol and tea consumption, and history of diabetes) hazard ratios (HRs) of PD associated with the amount of coffee consumed daily (0, 1-4, and > or = 5 cups) were 1.00, 0.55, and 0.41 (P for trend = 0.063) in men, 1.00, 0.50, and 0.39 (P for trend = 0.073) in women, and 1.00, 0.53, and 0.40 (P for trend = 0.005) in men and women combined (adjusted also for sex), respectively. In both sexes combined, the multivariate-adjusted HRs of PD for subjects drinking > or = 3 cups of tea daily compared with tea nondrinkers was 0.41 (95% CI 0.20-0.83). These results suggest that coffee drinking is associated with a lower risk of PD. More tea drinking is associated with a lower risk of PD.