Physiological Role of Orexin/Hypocretin in the Human Body in Motivated Behavior: A Comprehensive Review

Influence of Intermittent Fasting on Body Composition, Physical Performance, and the Orexinergic System in Postmenopausal Women: A Pilot Study

Objective: This study aims to evaluate the effects of different nutritional strategies, specifically intermittent fasting (IF) combined with high-intensity interval training (HIIT) versus a low-calorie diet (LCD), on body composition, physical performance, and the orexinergic system in postmenopausal women. Methods: A randomized controlled trial involving thirty postmenopausal women (mean age 57.50 ± 6.50 years) was conducted over eight weeks, comparing the two dietary approaches alongside an 8-week HIIT program. Body composition was assessed using bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DEXA). Performance metrics included handgrip strength and the 6-min walking test (6MWT). Salivary samples were analyzed for Orexin-A (OX-A) levels pre- and post-intervention. Results: Significant improvements in health metrics, such as heart rate (HR) and endurance, were found, with mean HR changes showing a significant difference (F = 5.943, p = 0.033) between the groups at T1. Orexin-A levels reflected significant metabolic regulation shifts in relation to other variables, showing a change from baseline to post-intervention values at T1 (F = 10,931, p = 0.033). Flexibility (sit and reach) significantly improved by 6% (p < 0.05), as well as VO2 max (10%, p < 0.05), both highlighted as key predictors of overall health outcomes. Additionally, Cohen's d analyses indicated that the dietary groups exhibited notable differences in endurance, with the LCD group showing a Cohen's d of -0.90, suggesting a large effect size compared with the control group. Conclusions: The combination of IF and HIIT is an effective nutritional strategy for enhancing body composition and physical performance in postmenopausal women, potentially mediated by changes in the orexinergic system. Further research is warranted to explore long-term effects and underlying mechanisms.

Drinking severity mediates the relationship between hypothalamic connectivity and rule-breaking/intrusive behavior differently in young women and men: an exploratory study

Background

The hypothalamus is a key hub of the neural circuits of motivated behavior. Alcohol misuse may lead to hypothalamic dysfunction. Here, we investigated how resting-state hypothalamic functional connectivities are altered in association with the severity of drinking and clinical comorbidities and how men and women differ in this association.

Methods

We employed the data of the Human Connectome Project. A total of 870 subjects were included in data analyses. The severity of alcohol use was quantified for individual subjects with the first principal component (PC1) identified from principal component analyses of all drinking measures. Rule-breaking and intrusive scores were evaluated with the Achenbach Adult Self-Report Scale. We performed a whole-brain regression of hypothalamic connectivities on drinking PC1 in all subjects and men/women separately and evaluated the results at a corrected threshold.

Results

Higher drinking PC1 was associated with greater hypothalamic connectivity with the paracentral lobule (PCL). Hypothalamic PCL connectivity was positively correlated with rule-breaking score in men (r=0.152, P=0.002) but not in women. In women but not men, hypothalamic connectivity with the left temporo-parietal junction (LTPJ) was negatively correlated with drinking PC1 (r=-0.246, P<0.001) and with intrusiveness score (r=-0.127, P=0.006). Mediation analyses showed that drinking PC1 mediated the relationship between hypothalamic PCL connectivity and rule-breaking score in men and between hypothalamic LTPJ connectivity and intrusiveness score bidirectionally in women.

Conclusions

We characterized sex-specific hypothalamic connectivities in link with the severity of alcohol misuse and its comorbidities. These findings extend the literature by elucidating the potential impact of problem drinking on the motivation circuits.

Understanding zebrafish sleep and wakefulness physiology as an experimental model for biomedical research

Sleep is a globally observable fact, or period of reversible distracted rest, that can be distinguished from arousal by various behavioral criteria. Although the function of sleep is an evolutionarily conserved behavior, its mechanism is not yet clear. The zebrafish (Danio rerio) has become a valuable model for neurobehavioral studies such as studying learning, memory, anxiety, and depression. It is characterized by a sleep-like state and circadian rhythm, making it comparable to mammals. Zebrafish are a good model for behavioral studies because they share genetic similarities with humans. A number of neurotransmitters are involved in sleep and wakefulness. There is a binding between melatonin and the hypocretin system present in zebrafish. The full understanding of sleep and wakefulness physiology in zebrafish is still unclear among researchers. Therefore, to make a clear understanding of the sleep/wake cycle in zebrafish, this article covers the mechanism involved behind it, and the role of the neuromodulator system followed by the mechanism of the HPA axis.