Effects of single housing on behavior, corticosterone level and body weight in male and female mice.

BACKGROUND: Experimental mice are often single-housed either for an individual analysis (feeding behavior, imaging, calorimetry) or as a stress paradigm (social isolation) in translational biomedical research. Reports of the influence of single housing in rodents are conflicting and may depend on age and duration of isolation. Sex is often not included as a factor. In this study we investigated the effects of 4-week single housing in male and female mice on behavior, body weight, and serum corticosterone levels. RESULTS: Behavioral tests showed no effect on anhedonia and stress coping, anxiety and motor exploration. Social avoidance occurred in both males and females. Regarding physiological effects, single housing did not induce changes in serum corticosterone levels, but reduced body weight gain. CONCLUSIONS: While some mouse studies of chronic social isolation reported depression-related disturbances, our data suggest that single housing might be not necessarily be too stressful. This is important for animal welfare regulations and experiments in life science research.

Sex-specific differences in metabolic hormone and adipose tissue dynamics induced by moderate low-carbohydrate and ketogenic diet.

Low-carbohydrates diets are increasingly used to treat obesity and metabolic disorders. A very low-carbohydrate, ketogenic diet is hard to follow and, due to the very high fat content, linked to severe side effects, like hyperlipidemia and atherogenesis. Therefore, a less restrictive, unsaturated fat-based low-carbohydrate diet appears as a promising alternative. Since neither sex differences, nor their effect on specific metabolic hormones and adipose tissue compartments have been investigated thoroughly in these diets, we aimed to analyze their dynamics and metabolic factors in mice. We found a significant sexual dimorphism with decreased body weight and subcutaneous fat only in males on ketogenic diet, while diminished insulin, elevated ghrelin and FGF-21 were present with a differential time course in both sexes. The non-ketogenic moderate low-carbohydrate diet increased body weight and perigonadal fat in females, but induced leptin elevation in males. Both diets enhanced transiently TNFɑ only in males and had no impact on behavior. Altogether, these results reveal complex sex-dependent effect of dietary interventions, indicating unexpectedly females as more prone to unfavorable metabolic effects of low-carbohydrate diets.

Ketogenic diet for mood disorders from animal models to clinical application.

Mood disorders such as major depressive disorder (MDD) and bipolar disorder (BD) are often resistant to current pharmacological treatment. Therefore, various alternative therapeutic approaches including diets are, therefore, under investigation. Ketogenic diet (KD) is effective for treatment-resistant epilepsy and metabolic diseases, however, only a few clinical studies suggest its beneficial effect also for mental disorders. Animal models are a useful tool to uncover the underlying mechanisms of therapeutic effects. Women have a twice-higher prevalence of mood disorders but very little is known about sex differences in nutritional psychiatry. In this review, we aim to summarize current knowledge of the sex-specific effects of KD in mood disorders. Ketone bodies improve mitochondrial functions and suppress oxidative stress, inducing neuroprotective and anti-inflammatory effects which are both beneficial for mental health. Limited data also suggest KD-induced improvement of monoaminergic circuits and hypothalamus-pituitary-adrenal axis-the key pathophysiological pathways of mood disorders. Gut microbiome is an important mediator of the beneficial and detrimental effects of diet on brain functioning and mental health. Gut microbiota composition is affected in mood disorders but its role in the therapeutic effects of different diets, including KD, remains poorly understood. Still little is known about sex differences in the effects of KD on mental health as well as on metabolism and body weight. Some animal studies used both sexes but did not find differences in behavior, body weight loss or gut microbiota composition. More studies, both on a preclinical and clinical level, are needed to better understand sex-specific effects of KD on mental health.