Isoform-specific dysregulation of AMP-activated protein kinase signaling in a non-human primate model of Alzheimer's disease.

AMP-activated protein kinase (AMPK) is a molecular sensor that is critical for the maintenance of cellular energy homeostasis, disruption of which has been indicated in multiple neurodegenerative diseases including Alzheimer's disease (AD). Mammalian AMPK is a heterotrimeric complex and its enzymatic α subunit exists in two isoforms: AMPKα1 and AMPKα2. Here we took advantage of a recently characterized non-human primate (NHP) model with sporadic AD-like neuropathology to explore potential relationships between AMPK signaling and AD-like neuropathology. Subjects were nine female vervet monkeys aged 19.5 to 23.4 years old. Subjects were classified into three groups, control lacking AD pathology (n = 3), moderate AD pathology (n = 3), and more severe AD Pathology (n = 3). We found increased activity (assessed by phosphorylation) of AMPKα2 in hippocampi of NHP with AD-like neuropathology, compared to the subjects without AD pathology, with no alterations of AMPKα1 activity. Across all subjects, CSF Abeta42 was inversely associated with cerebral amyloid plaque density. Further, Aß plaque burden is correlated with levels of either soluble or insoluble brain Aß measurement. Unbiased mass spectrometry based proteomics studies combined with bioinformatics analysis revealed that many of the dysregulated proteins characteristic of AD neuropathology are associated with AMPK signaling. Our findings on the AMPK molecular signaling cascades provide further support for use of the NHP model to investigate new therapeutic strategies and development of novel biomarkers for Alzheimer's disease.

Diet, psychosocial stress, and Alzheimer's disease-related neuroanatomy in female nonhuman primates.

INTRODUCTION: Associations between diet, psychosocial stress, and neurodegenerative disease, including Alzheimer's disease (AD), have been reported, but causal relationships are difficult to determine in human studies. METHODS: We used structural magnetic resonance imaging in a well-validated non-human primate model of AD-like neuropathology to examine the longitudinal effects of diet (Mediterranean vs Western) and social subordination stress on brain anatomy, including global volumes, cortical thicknesses and volumes, and 20 individual regions of interest (ROIs). RESULTS: Western diet resulted in greater cortical thicknesses, total brain volumes, and gray matter, and diminished cerebrospinal fluid and white matter volumes. Socially stressed subordinates had smaller whole brain volumes but larger ROIs relevant to AD than dominants. DISCUSSION: The observation of increased size of AD-related brain areas is consistent with similar reports of mid-life volume increases predicting increased AD risk later in life. While the biological mechanisms underlying the findings require future investigation, these observations suggest that Western diet and psychosocial stress instigate pathologic changes that increase risk of AD-associated neuropathology, whereas the Mediterranean diet may protect the brain.

Differential effects of western versus mediterranean diets and psychosocial stress on ovarian function in female monkeys (Macaca fascicularis).

Ovarian dysfunction increases risk for chronic diseases of aging including cardiovascular disease, depression, cognitive impairment, as well as bone and muscle loss which promote frailty. Psychosocial stress can disrupt ovarian function, and recent observations suggest that consumption of a Western Diet may also. Determination of causal relationships among diet, psychosocial stress, and ovarian physiology is difficult in humans. Long-tailed (a.k.a. cynomolgus) macaques (Macaca fascicularis) are an excellent translational model for the study of diet and psychosocial effects on ovarian physiology and aging-related processes. They have 28-day menstrual cycles with hormonal fluctuations like those of women, and similar physiologic responses to alterations and/or cessation of cyclicity. We examined ovarian function in 38 middle-aged socially housed females fed either a Western or Mediterranean diet for 31 months (≈ a 9-year period for humans). During the last year, we examined cycle length and peak progesterone per cycle using blood sampling (3/week) and vaginal swabbing for menses (6/week). Repeated measures analysis revealed a circannual pattern consistent with increased menstrual cycle disturbance during the late Summer and early Fall (F(11,348)= 4.05 p < 0.001). In addition, both Western diet (F(1,34)= 3.99; p = 0.05) and the stress of low social status (F(1,34)= 3.99; p = 0.04) reduced mean progesterone levels. Thus, on average, subordinates in the Western group had the lowest average progesterone levels (10.02 ng/pl). Compared to Western diets, Mediterranean diets exhibited protective effects via menstrual cycle regularity. For dominant monkeys, consuming Mediterranean diets resulted in significantly greater likelihood of having regular menstrual cycles. Mediterranean diets also protected individuals from shorter than normal menstrual cycles. The relationships between diet and menstrual regularity were partially mediated by both adrenal reactivity and social isolation. This study demonstrates the additive negative effects of poor diet and psychosocial stress on ovarian physiology in mid-life and lays the groundwork for future investigations to uncover their impact on metabolic signatures of accelerated aging. The results also suggest that - compared to Western-style diets - a Mediterranean diet may exert a protective influence against ovarian dysfunction and its pathologic sequelae.

Diet, obesity, and the gut microbiome as determinants modulating metabolic outcomes in a non-human primate model.

BACKGROUND: The objective of this study was to increase understanding of the complex interactions between diet, obesity, and the gut microbiome of adult female non-human primates (NHPs). Subjects consumed either a Western (n=15) or Mediterranean (n=14) diet designed to represent human dietary patterns for 31 months. Body composition was determined using CT, fecal samples were collected, and shotgun metagenomic sequencing was performed. Gut microbiome results were grouped by diet and adiposity. RESULTS: Diet was the main contributor to gut microbiome bacterial diversity. Adiposity within each diet was associated with subtle shifts in the proportional abundance of several taxa. Mediterranean diet-fed NHPs with lower body fat had a greater proportion of Lactobacillus animalis than their higher body fat counterparts. Higher body fat Western diet-fed NHPs had more Ruminococcus champaneliensis and less Bacteroides uniformis than their low body fat counterparts. Western diet-fed NHPs had significantly higher levels of Prevotella copri than Mediterranean diet NHPs. Western diet-fed subjects were stratified by P. copri abundance (P. copriHIGH versus P. copriLOW), which was not associated with adiposity. Overall, Western diet-fed animals in the P. copriHIGH group showed greater proportional abundance of B. ovatus, B. faecis, P. stercorea, P. brevis, and Faecalibacterium prausnitzii than those in the Western P. copriLOW group. Western diet P. copriLOW subjects had a greater proportion of Eubacterium siraeum. E. siraeum negatively correlated with P. copri proportional abundance regardless of dietary consumption. In the Western diet group, Shannon diversity was significantly higher in P. copriLOW when compared to P. copriHIGH subjects. Furthermore, gut E. siraeum abundance positively correlated with HDL plasma cholesterol indicating that those in the P. copriLOW population may represent a more metabolically healthy population. Untargeted metabolomics on urine and plasma from Western diet-fed P. copriHIGH and P. copriLOW subjects suggest early kidney dysfunction in Western diet-fed P. copriHIGH subjects. CONCLUSIONS: In summary, the data indicate diet to be the major influencer of gut bacterial diversity. However, diet and adiposity must be considered together when analyzing changes in abundance of specific bacterial taxa. Interestingly, P. copri appears to mediate metabolic dysfunction in Western diet-fed NHPs. Video abstract.

Whole Body Irradiation Induces Diabetes and Adipose Insulin Resistance in Nonhuman Primates.

PURPOSE: Diabetes mellitus is a delayed effect of radiation exposure in human and nonhuman primates. Diabetes mellitus is characterized by peripheral tissue insulin resistance, and as a result, irradiation exposure may cause important changes in insulin-sensitive tissues such as muscle and adipose. METHODS AND MATERIALS: We prospectively investigated changes in response to irradiation (4 Gy whole body exposure) in 16 male rhesus macaques. We evaluated changes in body composition and glycemic control for 2 years. Insulin responsiveness, lipolysis, inflammation, and fibrosis were evaluated at study end. RESULTS: Irradiated animals accumulate less fat and significantly increased percent glycation of hemoglobin A1c over time, such that 40% of irradiated monkeys had values that define them as diabetic at 2 years. Subcutaneous (SQ) adipose tissue was insulin resistant, as evidenced by reduced phosphorylation of the insulin receptor substrate-1 in response to insulin challenge and had increased basal lipolysis despite comparable insulin exposures to control animals. Irradiated SQ adipose tissue had more macrophage infiltration and adipocytes were larger. The observed hypertrophy was associated with decreased glycemic control and macrophage infiltration correlated with decreased adiponectin, signifying that inflammation is associated with worsening health. No evidence of SQ adipose fibrosis was detected. CONCLUSIONS: Our study is the first to prospectively illustrate that sublethal irradiation exposures directly propagate metabolic disease in the absence of obesity in nonhuman primates and implicate SQ adipose dysfunction as a target tissue.

Mediterranean diet, stress resilience, and aging in nonhuman primates.

Persistent psychological stress increases the risk of many chronic diseases of aging. Little progress has been made to effectively reduce stress responses or mitigate stress effects suggesting a need for better understanding of factors that influence stress responses. Limited evidence suggests that diet may be a factor in modifying the effects of stress. However, long-term studies of diet effects on stress reactive systems are not available, and controlled randomized clinical trials are difficult and costly. Here we report the outcomes of a controlled, randomized preclinical trial of the effects of long-term consumption (31 months, ~ equivalent to 9 human years) of Western versus Mediterranean - like diets on behavioral and physiological responses to acute (brief social separation) and chronic (social subordination) psychosocial stress in 38 adult, socially-housed, female cynomolgus macaques. Compared to animals fed a Western diet, those fed the Mediterranean diet exhibited enhanced stress resilience as indicated by lower sympathetic activity, brisker and more overt heart rate responses to acute stress, more rapid recovery, and lower cortisol responses to acute psychological stress and adrenocorticotropin (ACTH) challenge. Furthermore, age-related increases in sympathetic activity and cortisol responses to stress were delayed by the Mediterranean diet. Population level diet modification in humans has been shown to be feasible. Our findings suggest that population-wide adoption of a Mediterranean-like diet pattern may provide a cost-effective intervention on psychological stress and promote healthy aging with the potential for widespread efficacy.

Advanced maternal age impacts physiologic adaptations to pregnancy in vervet monkeys.

The trend to delay pregnancy in the USA has resulted in the number of advanced maternal age (AMA) pregnancies to also increase. In humans, AMA is associated with a variety of pregnancy-related pathologies such as preeclampsia (PE). While AMA is known to be a factor which contributes to the development of pregnancy-induced diseases, the molecular and cellular mechanisms giving rise to this phenomenon are still very limited. This is due in part to lack of a preclinical model which has physiologic relevance to human pregnancy while also allowing control of environmental and genetic variability inherent in human studies. To determine potential physiologic relevance of the vervet/African green monkey (Chlorocebus aethiops sabaeus) as a preclinical model to study the effects of AMA on adaptations to pregnancy, thirteen age-diverse pregnant vervet monkeys (3-16 years old) were utilized to measure third trimester blood pressure (BP), complete blood count, iron measurements, and hormone levels. Significant associations were observed between third trimester diastolic BP and maternal age. Furthermore, the presence of leukocytosis with enhanced circulating neutrophils was observed in AMA mothers compared to younger mothers. Moreover, we observed a negative relationship between maternal age and estradiol, progesterone, and cortisol levels. Finally, offspring born to AMA mothers displayed a postnatal growth retardation phenotype. These studies demonstrate physiologic impairment in the adaptation to pregnancy in AMA vervet/African green monkeys. Our data indicate that the vervet/African green monkey may serve as a useful preclinical model and tool for deciphering pathological mediators of maternal disease in AMA pregnancy.

Mediterranean versus Western Diet Effects on Caloric Intake, Obesity, Metabolism, and Hepatosteatosis in Nonhuman Primates.

OBJECTIVE: This study aimed to determine the effects of humanlike Western and Mediterranean diets on caloric intake, obesity, metabolism, and hepatosteatosis in an established nonhuman primate model of obesity, cardiometabolic syndrome, type 2 diabetes, and atherosclerosis. METHODS: A 38-month, randomized, preclinical, nonhuman primate primary prevention trial of 38 socially housed, middle-aged adult females was conducted. The monkeys were characterized during a 7-month baseline phase while consuming chow and then randomized to either Western or Mediterranean diets; the groups were balanced on baseline characteristics. Western and Mediterranean diets were formulated to closely reflect human diets, matched on macronutrient content, with protein and fat derived largely from animal sources in the Western diet and plant sources in the Mediterranean diet. Food consumption, activity levels, energy expenditure, body composition, carbohydrate metabolism, and hepatosteatosis were measured during baseline and treatment phases. RESULTS: The Western diet increased caloric intake for the first 6 months and body fat, activity, energy expenditure, insulin resistance, and hepatosteatosis after 2.5 years, whereas the Mediterranean diet reduced triglyceride levels. CONCLUSIONS: This is the first report of differential caloric intake and obesity with long-term consumption of a Western versus Mediterranean diet under controlled experimental conditions and the first experimental evidence that a Mediterranean diet protects against hepatosteatosis compared with a Western diet.

Consumption of Mediterranean versus Western Diet Leads to Distinct Mammary Gland Microbiome Populations.

Recent identification of a mammary gland-specific microbiome led to studies investigating bacteria populations in breast cancer. Malignant breast tumors have lower Lactobacillus abundance compared with benign lesions, implicating Lactobacillus as a negative regulator of breast cancer. Diet is a main determinant of gut microbial diversity. Whether diet affects breast microbiome populations is unknown. In a non-human primate model, we found that consumption of a Western or Mediterranean diet modulated mammary gland microbiota and metabolite profiles. Mediterranean diet consumption led to increased mammary gland Lactobacillus abundance compared with Western diet-fed monkeys. Moreover, mammary glands from Mediterranean diet-fed monkeys had higher levels of bile acid metabolites and increased bacterial-processed bioactive compounds. These data suggest that diet directly influences microbiome populations outside the intestinal tract in distal sites such as the mammary gland. Our study demonstrates that diet affects the mammary gland microbiome, establishing an alternative mechanistic pathway for breast cancer prevention.

Relationships of depressive behavior and sertraline treatment with walking speed and activity in older female nonhuman primates.

Depression is the most common mental health problem in aging persons and is a leading risk factor for physical disability, especially in women. Though antidepressant drugs such as serotonin reuptake inhibitors (SSRI) are commonly prescribed, epidemiological evidence reveals mixed effects of long-term antidepressant use on physical function and activity, possibly depending on depressive status. The purpose of this preclinical trial was to determine the relationships of depressive behavior and the potential for an SSRI treatment to modulate walking speed and activity patterns in older adult female cynomolgus monkeys (Macaca fascicularis). We evaluated the effects of depression and a commonly prescribed SSRI, sertraline HCl (20 mg/kg/day p.o.), on (a) walking speed, (b) accelerometry-derived activity (counts) and sedentariness (daytime 60-s sedentary epochs), and (c) observed locomotor and sedentary behaviors (% time) in adult female depressed and nondepressed monkeys (n = 42; 17.2 ± 1.8 years) during an 18 month pre-treatment phase and an 18 month treatment phase using a longitudinal, stratified placebo-control study design. Monkeys that were depressed prior to treatment (19/42) subsequently had slower walking speeds (F D [1, 38] = 4.14; p ≤ 0.05) and tended to be more sedentary during the daytime (F D [1, 38] = 3.63; p ≤ 0.06). Sertraline did not affect depressive behaviors, walking speed, accelerometry-derived physical activity or sedentariness, or time observed in total locomotor or sedentary behavior (all p > 0.10). This study provides the first experimental demonstration of relationships between nonhuman primate behavioral depression and walking speed, activity, and sedentariness and provides evidence for a lack of an effect of SSRI treatment on these phenotypes.

Microbial translocation and skeletal muscle in young and old vervet monkeys.

Intestinal barrier dysfunction leads to microbial translocation (MT) and inflammation in vertebrate and invertebrate animal models. Age is recently recognized as a factor leading to MT, and in some human and animal model studies, MT was associated with physical function. We evaluated sarcopenia, inflammation, MT biomarkers, and muscle insulin sensitivity in healthy female vervet monkeys (6-27 years old). Monkeys were fed consistent diets and had large and varied environments to facilitate physical activity, and stable social conditions. Aging led to sarcopenia as indicated by reduced walking speeds and muscle mass, but general metabolic health was similar in older monkeys (n = 25) as compared to younger ones (n = 26). When older monkeys were physically active, their MT burden approximated that in young monkeys; however, when older monkeys were sedentary, MT burden was dramatically increased. MT levels were positively associated with inflammatory burden and negatively associated with skeletal muscle insulin sensitivity. Time spent being active was positively associated with insulin sensitivity as expected, but this relationship was specifically modified by the individual monkey's MT, not inflammatory burden. Our data supports clinical observations that MT interacts with physical function as a factor in healthy aging.

Long term sertraline effects on neural structures in depressed and nondepressed adult female nonhuman primates.

BACKGROUND: Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed for mood and other disorders. However, their neural effects are difficult to study due to patient compliance and drug history variability, and rarely studied in those prescribed SSRIs for non-mood disorders. Here we evaluated SSRI effects on neural volumetrics in depressed and nondepressed monkeys. METHODS: 42 socially-housed cynomolgus monkeys were randomized to treatment balanced on pretreatment depressive behavior and body weight. Monkeys were trained for oral administration of placebo or 20 mg/kg sertraline HCl daily for 18 months and depressive and anxious behavior recorded. Volumes of neural regions of interest in depression were measured in magnetic resonance images and analyzed by 2 (depressed, nondepressed)×2 (placebo, sertraline) ANOVA. RESULTS: Sertraline reduced anxiety (p=0.04) but not depressive behavior (p=0.43). Left Brodmann's Area (BA) 32 was smaller in depressed than nondepressed monkeys (main effect of depression: p<0.05). Sertraline and depression status interacted to affect volumes of left Anterior Cingulate Cortex (ACC), left BA24, right hippocampus (HC), and right anterior HC (sertraline×depression interactions: all p's<0.05). In the Placebo group, depressed monkeys had smaller right anterior HC and left ACC than nondepressed monkeys. In nondepressed monkeys, sertraline reduced right HC volume, especially right anterior HC volume. In depressed monkeys sertraline increased left ACC volume. In nondepressed monkeys, sertraline reduced left BA24 volumes resulting in smaller BA24 volumes in nondepressed than sertraline-treated depressed monkeys. CONCLUSIONS: These observations suggest that SSRIs may differentially affect neural structures in depressed and nondepressed individuals.