Rats made cirrhotic by chronic CCl4 treatment still exhibit anticipatory activity to a restricted feeding schedule

The ameliorative effects of Lactobacillus coagulans and Lactobacillus casei probiotics on CCl4-induced testicular toxicity based on biochemical, histological and molecular analyses in rat

Probiotics are commonly present in foods and role as dietary adjuncts and alternatives to pharmacological products in many medical fields. The aim of this study was to investigate the effects of Lactobacillus coagulans and Lactobacillus casei probiotics on carbon tetrachloride (CCl₄ )-induced reproductive injury and sperm toxicity in rats. Thirty-two Wistar rats were divided into four groups as follows: sham, CCl₄ (2 ml/kg), L. casei probiotic + 2 ml/kg CCl₄ and L. coagulans probiotic + 2 ml/kg CCl₄ . On the 36th day after the intervention, serum levels of follicle-stimulating hormone (FSH), luteinising hormone (LH) and total testosterone (T), as well as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, were measured. Testicular malondialdehyde (MDA) level, the expressions of apoptosis-related genes (Bcl-2 and Bax), Bax/Bcl-2 ratio, histomorphometric indices such as tubular differentiation index (TDI), repopulation index (RI), spermiogenesis index (SPI) and sperm parameters were evaluated. L. casei and L. coagulans probiotics improved the levels of reproductive hormones and antioxidant capacity in rats. Both the probiotics, especially L. casei, increased the rate spermatogenesis which accompanied with significant increments in testicular TDI, RI and SPI. Furthermore, both probiotics down-regulated Bax and up-regulated Bcl-2, following by decreased Bax/Bcl-2 ratio. Our key findings indicated that L. casei and L. coagulans have protective effects against CCl₄ -induced testicular toxicity.

Neural Mechanisms of Circadian Regulation of Natural and Drug Reward

Circadian rhythms are endogenously generated near 24-hour variations of physiological and behavioral functions. In humans, disruptions to the circadian system are associated with negative health outcomes, including metabolic, immune, and psychiatric diseases, such as addiction. Animal models suggest bidirectional relationships between the circadian system and drugs of abuse, whereby desynchrony, misalignment, or disruption may promote vulnerability to drug use and the transition to addiction, while exposure to drugs of abuse may entrain, disrupt, or perturb the circadian timing system. Recent evidence suggests natural (i.e., food) and drug rewards may influence overlapping neural circuitry, and the circadian system may modulate the physiological and behavioral responses to these stimuli. Environmental disruptions, such as shifting schedules or shorter/longer days, influence food and drug intake, and certain mutations of circadian genes that control cellular rhythms are associated with altered behavioral reward. We highlight the more recent findings associating circadian rhythms to reward function, linking environmental and genetic evidence to natural and drug reward and related neural circuitry.

Sucrose modifies c-fos mRNA expression in the brain of rats maintained on feeding schedules

Food intake is regulated according to circadian activity, metabolic needs and the hedonic value of food. Rodents placed on a fixed feeding schedule show behavioral and physiological anticipation of mealtime referred to as food-anticipatory activity (FAA). FAA is driven by the food-entrainable oscillator (FEO), whose anatomical substrate is not yet known. Recent data have shown that restricted feeding schedules for regular chow and daily limited access to palatable food in free-feeding rats activate distinct brain regions during FAA. The combination of a deprivation regimen and scheduled access to palatable food may give rise to a more global anticipatory mechanism because the temporal cycles of energy balance would be strongly modulated by the incentive properties of palatable food; however, the neuronal response to this combined treatment is not yet known. The present study investigated how adding palatable sucrose to feeding schedules affects the pattern of brain c-fos mRNA expression during FAA (0-3 h) and 1 h following feeding. The rats maintained on scheduled chow access increased their daily chow intake, while the rats maintained on scheduled sucrose and chow mainly increased their daily sucrose intake. Adding sucrose to scheduled feeding displaced c-fos mRNA expression from the dorsomedial and paraventricular hypothalamic nuclei and posterior lateral hypothalamus (LH) to the prefrontal cortex, lateral septum, nucleus accumbens and anterior LH. During refeeding, the rats on scheduled sucrose demonstrated higher activation of the nucleus of the solitary tract. The present results suggest that palatable sucrose combined with restricted feeding schedules activate a distinct neuronal network compared to neuronal activation produced by scheduled access to regular chow. These data provide evidence that the brain may contain different food-oscillatory systems and that food palatability may shift the neuronal activity from the medial hypothalamus to the limbic and reward-related areas even at the negative metabolic state.

Peripheral oscillators: the driving force for food-anticipatory activity

Food-anticipatory activity (FAA) and especially the food-entrained oscillator (FEO) have driven many scientists to seek their mechanisms and locations. Starting our research on FAA we, possibly like many other scientists, were convinced that clock genes held the key to the location and the underlying mechanisms for FAA. In this review, which is aimed especially at discussing the contribution of the peripheral oscillators, we have put together the accumulating evidence that the clock gene machinery as we know it today is not sufficient to explain food entrainment. We discuss the contribution of three types of oscillating processes: (i) within the suprachiasmatic nucleus (SCN), neurons capable of maintaining a 24-h oscillation in electrical activity driven by a set of clock genes; (ii) oscillations in metabolic genes and clock genes in other parts of the brain and in peripheral organs driven by the SCN or by food, which damp out after a few cycles; (iii) an FEO which, we propose, is a system built up of different oscillatory processes and consisting of an as-yet-unidentified network of central and peripheral structures. In view of the evidence that clock genes and metabolic oscillations are not essential for the persistence of FAA we propose that food entrainment is initiated by a repeated metabolic state of scarcity that drives an oscillating network of brain nuclei in interaction with peripheral oscillators. This complex may constitute the proposed FEO and is distributed in our peripheral organs as well as within the central nervous system.

"Feeding time" for the brain: a matter of clocks

Circadian clocks are autonomous time-keeping mechanisms that allow living organisms to predict and adapt to environmental rhythms of light, temperature and food availability. At the molecular level, circadian clocks use clock and clock-controlled genes to generate rhythmicity and distribute temporal signals. In mammals, synchronization of the master circadian clock located in the suprachiasmatic nuclei of the hypothalamus is accomplished mainly by light stimuli. Meal time, that can be experimentally modulated by temporal restricted feeding, is a potent synchronizer for peripheral oscillators with no clear synchronizing influence on the suprachiasmatic clock. Furthermore, food-restricted animals are able to predict meal time, as revealed by anticipatory bouts of locomotor activity, body temperature and plasma corticosterone. These food anticipatory rhythms have long been thought to be under the control of a food-entrainable clock (FEC). Analysis of clock mutant mice has highlighted the relevance of some, but not all of the clock genes for food-entrainable clockwork. Mutations of Clock or Per1 do not impair expression of food anticipatory components, suggesting that these clock genes are not essential for food-entrainable oscillations. By contrast, mice mutant for Npas2 or deficient for Cry1 and Cry2 show more or less altered responses to restricted feeding conditions. Moreover, a lack of food anticipation is specifically associated with a mutation of Per2, demonstrating the critical involvement of this gene in the anticipation of meal time. The actual location of the FEC is not yet clearly defined. Nevertheless, current knowledge of the putative brain regions involved in food-entrainable oscillations is discussed. We also describe several neurochemical pathways, including orexinergic and noradrenergic, likely to participate in conveying inputs to and outputs from the FEC to control anticipatory processes.

Metabolic adaptations of liver mitochondria during restricted feeding schedules

Food anticipatory activity (FAA) is an output of the food-entrained oscillator (FEO), a conspicuous biological clock that expresses when experimental animals are under a restricted food schedule (RFS). We have shown that the liver is entrained by RFS and exhibits an anticipatory response before meal time in its oxidative and energetic state. The present study was designed to determine the mitochondrial oxidative and phosphorylating capacity in the liver of rats under RFS to further support the biochemical anticipatory role that this organ plays during the food entrainment (9). Metabolic and functional parameters of liver mitochondria were characterized before (0800 h), during (1100 h), and after (1400 h) FAA. The main results were as follows. First, there was an enhancement during FAA (1100 h) in 1) oxidative capacity (site I of the electron transport chain), 2) phosphorylating ability (estimated by ATP synthesis), and 3) activities of NADH shuttles. Second, after rats were fed (1400 h), the phosphorylating capacity remained high, but this was not the case for the respiratory control ratio for site I. Finally, in the three experimental conditions before, during, and after FAA, an increment was detected in the H(+) electrochemical potential, due to an elevation in mitochondrial membrane potential, and in mitochondrial yield. Most of the changes in mitochondrial properties related to RFS were also present when results were compared with those from the 24-h fasted group. In conclusion, the results support the notion that a distinctive rheostatic state is installed in the metabolic activity of the liver when FEO is being expressed.

c-Fos expression in hypothalamic nuclei of food-entrained rats

The present study aimed to identify the hypothalamic nuclei involved with food entrainment by using c-Fos-like immunoreactivity (c-Fos-IR) as a marker of functional activation. We studied rats entrained 3 wk to restricted feeding schedules (RF), their ad libitum (AL) controls, and the persistence of c-Fos-IR temporal patterns in entrained-fasted rats. In addition, we included 22-h fasting and 22-h fasting-refeeding groups as controls of fasting and refeeding acute effects. Diurnal patterns of c-Fos-IR were observed in the tuberomammilar nucleus (TM) and suprachiasmatic nucleus (SCN) in AL rats. In all nuclei, except the SCN and ventromedial nucleus (VMH), restricted feeding schedules imposed a temporal pattern of increased c-Fos-IR around mealtime. An increase in c-Fos-IR before and after meal time was observed in dorsomedial nucleus (DMH), lateral nucleus (LH), perifornical area (PeF), and TM, and a marked increase was observed in the paraventricular nucleus (PVN) after feeding. Food-entrained c-Fos-IR patterns persisted after 3 days in fasting in DMH, LH, and PeF. Present data suggest that FEO might not rely on a single nucleus and rather may be a distributed system constituted of interacting nuclei in which the PVN is mainly involved with the response to signals elicited by food ingestion and, therefore, with the entraining pathway. We can suggest that the PeF and TM may be involved with the arousal state during food anticipation and the DMH and LH with the time-keeping mechanism of FEO or its output.