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Lifestyle and vascular risk effects on MRI-based biomarkers of Alzheimer's disease: a cross-sectional study of middle-aged adults from the broader New York City area.
Mosconi, L, Walters, M, Sterling, J, Quinn, C, McHugh, P, Andrews, RE, Matthews, DC, Ganzer, C, Osorio, RS, Isaacson, RS, et al
BMJ open. 2018;8(3):e019362
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Alzheimer’s disease (AD) is the most common form of dementia, affecting nearly 34 million people worldwide. It has been estimated that one in every three cases of AD may be attributable to diet and lifestyle factors. The aim of this study was to investigate the effects of lifestyle and vascular-related risk factors for AD. Researchers studied the brain scans of 116 healthy adults aged 30-60 years. They collected information on factors related to lifestyle, such as diet, physical activity and intellectual enrichment. They also looked at markers for vascular risk such as body mass index (BMI), cholesterol and homocysteine, as well as cognitive function. The researchers found that a Mediterranean-style diet and good insulin sensitivity were both associated with a healthier brain structure. A better score for intellectual enrichment and lower BMI were both associated with better cognition. They concluded that adopting a Mediterranean-style diet and maintaining a healthy weight might reduce the risk of developing AD.
Abstract
OBJECTIVE To investigate the effects of lifestyle and vascular-related risk factors for Alzheimer's disease (AD) on in vivo MRI-based brain atrophy in asymptomatic young to middle-aged adults. DESIGN Cross-sectional, observational. SETTING Broader New York City area. Two research centres affiliated with the Alzheimer's disease Core Center at New York University School of Medicine. PARTICIPANTS We studied 116 cognitively normal healthy research participants aged 30-60 years, who completed a three-dimensional T1-weighted volumetric MRI and had lifestyle (diet, physical activity and intellectual enrichment), vascular risk (overweight, hypertension, insulin resistance, elevated cholesterol and homocysteine) and cognition (memory, executive function, language) data. Estimates of cortical thickness for entorhinal (EC), posterior cingulate, orbitofrontal, inferior and middle temporal cortex were obtained by use of automated segmentation tools. We applied confirmatory factor analysis and structural equation modelling to evaluate the associations between lifestyle, vascular risk, brain and cognition. RESULTS Adherence to a Mediterranean-style diet (MeDi) and insulin sensitivity were both positively associated with MRI-based cortical thickness (diet: βs≥0.26, insulin sensitivity βs≥0.58, P≤0.008). After accounting for vascular risk, EC in turn explained variance in memory (P≤0.001). None of the other lifestyle and vascular risk variables were associated with brain thickness. In addition, the path associations between intellectual enrichment and better cognition were significant (βs≥0.25 P≤0.001), as were those between overweight and lower cognition (βs≥-0.22, P≤0.01). CONCLUSIONS In cognitively normal middle-aged adults, MeDi and insulin sensitivity explained cortical thickness in key brain regions for AD, and EC thickness predicted memory performance in turn. Intellectual activity and overweight were associated with cognitive performance through different pathways. Our findings support further investigation of lifestyle and vascular risk factor modification against brain ageing and AD. More studies with larger samples are needed to replicate these research findings in more diverse, community-based settings.
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Effects of dietary glycemic index on brain regions related to reward and craving in men.
Lennerz, BS, Alsop, DC, Holsen, LM, Stern, E, Rojas, R, Ebbeling, CB, Goldstein, JM, Ludwig, DS
The American journal of clinical nutrition. 2013;98(3):641-7
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Clinical studies using functional brain imaging have found increased activity in the nucleus accumbens (thought to play a central role in reward and cravings) in obese subjects after viewing or eating highly palatable, calorific food. Additionally, studies have shown that striatal dopamine receptor activity was lower for obese subjects, suggesting that overeating may compensate for lower dopamine activity in these people. This study compared the brain activity following a high GI or a low GI meal, focusing on the areas of the brain that are responsible for eating behaviour, reward and addiction. Subjects were healthy overweight or obese men. The findings showed that compared to low GI meals, a high GI meal increased self-reported hunger, stimulated brain regions associated with reward and cravings, and decreased blood glucose (which could increase hunger and the hedonistic value of food).
Abstract
BACKGROUND Qualitative aspects of diet influence eating behavior, but the physiologic mechanisms for these calorie-independent effects remain speculative. OBJECTIVE We examined effects of the glycemic index (GI) on brain activity in the late postprandial period after a typical intermeal interval. DESIGN With the use of a randomized, blinded, crossover design, 12 overweight or obese men aged 18-35 y consumed high- and low-GI meals controlled for calories, macronutrients, and palatability on 2 occasions. The primary outcome was cerebral blood flow as a measure of resting brain activity, which was assessed by using arterial spin-labeling functional magnetic resonance imaging 4 h after test meals. We hypothesized that brain activity would be greater after the high-GI meal in prespecified regions involved in eating behavior, reward, and craving. RESULTS Incremental venous plasma glucose (2-h area under the curve) was 2.4-fold greater after the high- than the low-GI meal (P = 0.0001). Plasma glucose was lower (mean ± SE: 4.7 ± 0.14 compared with 5.3 ± 0.16 mmol/L; P = 0.005) and reported hunger was greater (P = 0.04) 4 h after the high- than the low-GI meal. At this time, the high-GI meal elicited greater brain activity centered in the right nucleus accumbens (a prespecified area; P = 0.0006 with adjustment for multiple comparisons) that spread to other areas of the right striatum and to the olfactory area. CONCLUSIONS Compared with an isocaloric low-GI meal, a high-GI meal decreased plasma glucose, increased hunger, and selectively stimulated brain regions associated with reward and craving in the late postprandial period, which is a time with special significance to eating behavior at the next meal. This trial was registered at clinicaltrials.gov as NCT01064778.