Gut microbiota link dietary fiber intake and short-chain fatty acid metabolism with eating behavior.

The gut microbiome has been speculated to modulate feeding behavior through multiple factors, including short-chain fatty acids (SCFA). Evidence on this relationship in humans is however lacking. We aimed to explore if specific bacterial genera relate to eating behavior, diet, and SCFA in adults. Moreover, we tested whether eating-related microbiota relate to treatment success in patients after Roux-en-Y gastric bypass (RYGB). Anthropometrics, dietary fiber intake, eating behavior, 16S-rRNA-derived microbiota, and fecal and serum SCFA were correlated in young overweight adults (n = 27 (9 F), 21-36 years, BMI 25-31 kg/m2). Correlated genera were compared in RYGB (n = 23 (16 F), 41-70 years, BMI 25-62 kg/m2) and control patients (n = 17 (11 F), 26-69 years, BMI 25-48 kg/m2). In young adults, 7 bacteria genera, i.e., Alistipes, Blautia, Clostridiales cluster XVIII, Gemmiger, Roseburia, Ruminococcus, and Streptococcus, correlated with healthier eating behavior, while 5 genera, i.e., Clostridiales cluster IV and XIVb, Collinsella, Fusicatenibacter, and Parabacteroides, correlated with unhealthier eating (all | r | > 0.4, FDR-corrected p < 0.05). Some of these genera including Parabacteroides related to fiber intake and SCFA, and to weight status and treatment response in overweight/obese patients. In this exploratory analysis, specific bacterial genera, particularly Parabacteroides, were associated with weight status and eating behavior in two small, independent and well-characterized cross-sectional samples. These preliminary findings suggest two groups of presumably beneficial and unfavorable genera that relate to eating behavior and weight status, and indicate that dietary fiber and SCFA metabolism may modify these relationships. Larger interventional studies are needed to distinguish correlation from causation.

Genetic correlations and genome-wide associations of cortical structure in general population samples of 22,824 adults.

Cortical thickness, surface area and volumes vary with age and cognitive function, and in neurological and psychiatric diseases. Here we report heritability, genetic correlations and genome-wide associations of these cortical measures across the whole cortex, and in 34 anatomically predefined regions. Our discovery sample comprises 22,824 individuals from 20 cohorts within the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium and the UK Biobank. We identify genetic heterogeneity between cortical measures and brain regions, and 160 genome-wide significant associations pointing to wnt/ß-catenin, TGF-ß and sonic hedgehog pathways. There is enrichment for genes involved in anthropometric traits, hindbrain development, vascular and neurodegenerative disease and psychiatric conditions. These data are a rich resource for studies of the biological mechanisms behind cortical development and aging.

The effects of plant-based diets on the body and the brain: a systematic review.

Western societies notice an increasing interest in plant-based eating patterns such as vegetarian and vegan, yet potential effects on the body and brain are a matter of debate. Therefore, we systematically reviewed existing human interventional studies on putative effects of a plant-based diet on the metabolism and cognition, and what is known about the underlying mechanisms. Using the search terms "plant-based OR vegan OR vegetarian AND diet AND intervention" in PubMed filtered for clinical trials in humans retrieved 205 studies out of which 27, plus an additional search extending the selection to another five studies, were eligible for inclusion based on three independent ratings. We found robust evidence for short- to moderate-term beneficial effects of plant-based diets versus conventional diets (duration ≤ 24 months) on weight status, energy metabolism and systemic inflammation in healthy participants, obese and type-2 diabetes patients. Initial experimental studies proposed novel microbiome-related pathways, by which plant-based diets modulate the gut microbiome towards a favorable diversity of bacteria species, yet a functional "bottom up" signaling of plant-based diet-induced microbial changes remains highly speculative. In addition, little is known, based on interventional studies about cognitive effects linked to plant-based diets. Thus, a causal impact of plant-based diets on cognitive functions, mental and neurological health and respective underlying mechanisms has yet to be demonstrated. In sum, the increasing interest for plant-based diets raises the opportunity for developing novel preventive and therapeutic strategies against obesity, eating disorders and related comorbidities. Still, putative effects of plant-based diets on brain health and cognitive functions as well as the underlying mechanisms remain largely unexplored and new studies need to address these questions.