Comparative analysis of the influence of a high-fat/high-carbohydrate diet on the level of anxiety and neuromotor and cognitive functions in Wistar and DAT-KO rats

Toxicological Characteristics of Bacterial Nanocellulose in an In Vivo Experiment-Part 1: The Systemic Effects

Bacterial nanocellulose (BNC) is being considered as a potential replacement for microcrystalline cellulose as a food additive and a source of dietary fiber due to its unique properties. However, studies on the risks of consuming BNC in food are limited, and it is not yet approved for use in food in the US, EU, and Russia.

AIM

This study aims to perform a toxicological and hygienic assessment of the safety of BNC in a subacute 8-week administration in rats.

METHODS

BNC was administered to male Wistar rats in doses of 0, 1.0, 10.0, and 100 mg/kg body weight for 8 weeks. Various parameters such as anxiety levels, cognitive function, organ masses, blood serum and liver biochemistry, oxidative stress markers, vitamin levels, antioxidant gene expression, and liver and kidney histology were evaluated.

RESULTS

Low and medium doses of BNC increased anxiety levels and liver glutathione, while high doses led to elevated LDL cholesterol, creatinine, and uric acid levels. Liver tissue showed signs of degeneration at high doses. BNC did not significantly affect vitamin levels.

CONCLUSION

The adverse effects of BNC are either not dose-dependent or fall within normal physiological ranges. Any effects on rats are likely due to micronutrient deficiencies or impacts on intestinal microbiota.

Patterns of ethanol intake in male rats with partial dopamine transporter deficiency

Mesolimbic dopamine signaling plays a major role in alcohol and substance use disorders as well as comorbidities such as anxiety and depression. Growing evidence suggests that alcohol drinking is modulated by the function of the dopamine transporter (DAT), which tightly regulates extracellular dopamine concentrations. Adult male rats on a Wistar Han background (DAT+/+) and rats with a partial DAT deletion (DAT+/-) were used in this study. First, using fast-scan cyclic voltammetry in brain slices containing the nucleus accumbens core from ethanol-naïve subjects, we measured greater evoked dopamine concentrations and slower dopamine reuptake in DAT+/- rats, consistent with increased dopamine signaling. Next, we measured ethanol drinking using the intermittent access two-bottle choice paradigm (20% v/v ethanol vs. water) across 5 weeks. DAT+/- rats voluntarily consumed less ethanol during its initial availability (the first 30 min), especially after longer periods of deprivation. In addition, DAT+/- males consumed less ethanol that was adulterated with the bitter tastant quinine. These findings suggest that partial DAT blockade and concomitant increase in brain dopamine levels has potential to reduce drinking and ameliorate alcohol use disorder (AUD).

Antioxidant system alterations and physiological characteristics of neonatal and juvenile DAT-KO rats

Dopamine transporter knockout (DAT-KO) rats represent a valuable rodent model for studying the molecular and phenotypical outcomes of the effects of excessive dopamine accumulation in the synaptic cleft and the prolonged action of dopamine on neurons. Animals with DAT deficiency are characterized by hyperactivity, stereotypy, cognitive deficits, and impairments in behavioral and biochemical indicators. Several key pathophysiological mechanisms are known to be common to psychiatric, neurodegenerative, metabolic, and other diseases. Among these mechanisms, oxidative stress systems play a particularly important role. One of the main antioxidant systems in the brain is glutathione: specifically, glutathione S-transferase, glutathione reductase, and catalase play a significant role in the regulation of vital oxidative processes, and their dysfunction has been shown in Parkinson's disease, Alzheimer's disease, and other neurodegenerative diseases. The current study aimed to analyze the dynamics of the activity levels of glutathione reductase and glutathione S-transferase in erythrocytes, as well as catalase in the blood plasma, of DAT-deficient, homo- and heterozygous, neonatal and juvenile rats (both male and female). Their behavioral and physiological parameters were evaluated at the age of 1.5 months. For the first time, changes in physiological and biochemical parameters were shown in DAT-KO rats at 1.5 months of postnatal life. The key role of glutathione S-transferase, glutathione reductase, and catalase in the regulation of oxidative stress in DAT-KO rats at the 5th week of life was demonstrated. A positive effect of a slightly increased dopamine level on memory function was shown in DAT-heterozygous animals.

Toward assessing the role of dietary fatty acids in lamb's neurological and cognitive development

Understanding and measuring sheep cognition and behavior can provide us with measures to safeguard the welfare of these animals in production systems. Optimal neurological and cognitive development of lambs is important to equip individuals with the ability to better cope with environmental stressors. However, this development can be affected by nutrition with a special role from long-chain fatty acid supply from the dam to the fetus or in lamb's early life. Neurological development in lambs takes place primarily during the first two trimesters of gestation. Through late fetal and early postnatal life, the lamb brain has a high level of cholesterol synthesis. This rate declines rapidly at weaning and remains low throughout adulthood. The main polyunsaturated fatty acids (PUFA) in the brain are ω-6 arachidonic acid and ω-3 docosahexaenoic acid (DHA), which are elements of plasma membranes' phospholipids in neuronal cells. DHA is essential for keeping membrane integrity and is vital for normal development of the central nervous system (CNS), and its insufficiency can damage cerebral functions and the development of cognitive capacities. In sheep, there is evidence that supplying PUFA during gestation or after birth may be beneficial to lamb productive performance and expression of species-specific behaviors. The objective of this perspective is to discuss concepts of ruminant behavior and nutrition and reflect on future research directions that could help to improve our knowledge on how dietary fatty acids (FA) relate to optimal neurological and cognitive development in sheep.

Anxiolytic and Antioxidant Effect of Phytoecdysteroids and Polyphenols from Chenopodium quinoa on an In Vivo Restraint Stress Model

The variety of stressful conditions in daily human activity requires nutritional support with safe, specialized food products containing functional food ingredients (FFIs) enriched with biologically active plant substances with proven adaptogenic properties. In this in vivo study, by evaluating a set of physiological parameters and biochemical markers, we investigated the effectiveness of the developed FFIs from Chenopodium quinoa grains in stress conditions induced by daily episodes of immobilization for 36 days. The results of the evaluation of the anxiety-like functions, locomotor, and search activity of rats in the "open field" and "elevated plus maze" tests demonstrated the ability of FFIs to reduce stressful behavior induced by immobilization. The improvement in the long-term memory of animals treated with FFIs was noted in the passive avoidance test. Together with the hypolipidemic effect and compensation of transaminase levels, FFIs normalized the excretion of catecholamines in the urine and reduced the levels of malondialdehyde to values of the control group. According to the results of the assessment of FFI acute oral toxicity, the LD₅₀ value exceeded 5000 mg/kg of body weight, which categorizes the FFIs under hazard class 5-substances with low hazard. The conducted experiment demonstrated the effectiveness of nutritional support with FFIs on the selected stress model. The positive safety profile of FFIs makes them reasonable to study on other stress models and to conduct clinical testing as part of specialized food products in various categories of people exposed to chronic stress.

Dopamine, Erectile Function and Male Sexual Behavior from the Past to the Present: A Review

Early and recent studies show that dopamine through its neuronal systems and receptor subtypes plays different roles in the control of male sexual behavior. These studies show that (i) the mesolimbic/mesocortical dopaminergic system plays a key role in the preparatory phase of sexual behavior, e.g., in sexual arousal, motivation and reward, whereas the nigrostriatal system controls the sensory-motor coordination necessary for copulation, (ii) the incertohypothalamic system is involved in the consummatory aspects of sexual behavior (penile erection and copulation), but evidence for its role in sexual motivation is also available, (iii) the pro-sexual effects of dopamine occur in concert with neural systems interconnecting the hypothalamus and preoptic area with the spinal cord, ventral tegmental area and other limbic brain areas and (iv) D₂ and D₄ receptors play a major role in the pro-sexual effects of dopamine. Despite some controversy, increases or decreases, respectively, of brain dopamine activity induced by drugs or that occur physiologically, usually improves or worsens, respectively, sexual activity. These findings suggest that an altered central dopaminergic tone plays a role in mental pathologies characterized by aberrant sexual behavior, and that pro-erectile D₄ receptor agonists may be considered a new strategy for the treatment of erectile dysfunction in men.

Comprehensive assessment of the effectiveness of l-carnitine and transresveratrol in rats with diet-induced obesity

OBJECTIVES

Transresveratrol (Res) and l-carnitine (l-Car) are proposed to alleviate metabolic and immune disorders and increase physical activity in obese individuals. This study aims to estimate the effect of Res and l-Car in rats with diet-induced obesity.

METHODS

Male Wistar rats were fed a diet with excess fat and fructose (high-fat high-carbohydrate diet [HFCD]) supplemented with Res and l-Car at doses of 25 and 300 mg/kg of body weight, respectively, for 63 d. An assessment of grip strength, behavioral reactions, as well as biochemical, morphological, and immunological parameters, was performed.

RESULTS

Res supplementation did not affect energy consumption, but l-Car increased when animals had free access to feed. Body weight gains were the highest in animals fed the HFCD, lowest in rats receiving the control balanced diet, and intermediate in animals receiving Res and l-Car. Feeding with Res and l-Car canceled the decrease in long-term memory in rats fed the HFCD, as well as reduced anxiety and increased mobility. With both supplements, bilirubin, triglycerides, and low-density lipoprotein levels in the blood plasma returned to normal values, but only l-Car increased the ratio of aspartic and alanine transaminases. In addition, l-Car lowered the levels of leptin and ghrelin and increased transforming growth factor beta 1 in the blood plasma, and consumption of Res was accompanied by a decrease in interleukin-17A and increase in interferon gamma in spleen lysates. Moreover, l-Car reduced the number of cells with lipid inclusions in the liver.

CONCLUSIONS

The consumption of Res and l-Car leads to a significant reduction in dyslipidemia and inflammation with potentially favorable changes in behavioral responses.

Adaptogenic Properties of a Phytoecdysteroid-Rich Extract from the Leaves of Spinacia oleracea L

Increasing the ability of the human body to adapt in conditions of physical or emotional stress is promising from the standpoint of the use of preventive nutrition containing functional food ingredients (FFI) with proven effectiveness in complex physiological in vivo studies. In this work, we developed FFI from spinach leaves (Spinacia oleracea L.) with a high content of polyphenols and adaptogens-phytoecdysteroids. Using in vivo models of increased physical activity and immobilization-induced emotional stress, we evaluated the nonspecific resistance of rats in response to the addition of the developed FFI to the diet. In the acute toxicity experiment, we found no signs of FFI toxicity up to 5000 mg/kg body weight. As a result of the daily 26-day consumption of FFI, we observed an anxiolytic effect in physiological studies. FFI prevented an increase in the content of biogenic amines in the blood, the main markers of the stress system, and had a positive effect on the lipid metabolism of the rats. The obtained results demonstrate a "smoothing" effect on the body's reaction in response to induced stress conditions.

Effects of Tyrosine and Tryptophan Supplements on the Vital Indicators in Mice Differently Prone to Diet-Induced Obesity

We studied the effects of the addition of large neutral amino acids, such as tyrosine (Tyr) and tryptophan (Trp), in mice DBA/2J and tetrahybrid mice DBCB receiving a high-fat, high-carbohydrate diet (HFCD) for 65 days. The locomotor activity, anxiety, muscle tone, mass of internal organs, liver morphology, adipokines, cytokines, and biochemical indices of animals were assessed. The Tyr supplementation potentiated increased anxiety in EPM and contributed to a muscle tone increase, a decrease in the AST/ALT ratio, and an increase in protein anabolism in both mice strains. Tyr contributed to a decrease in liver fatty degeneration and ALT reduction only in DBCB that were sensitive to the development of obesity. The addition of Trp caused an increase in muscle tone and potentiated an increase in anxiety with age in animals of both genotypes. Trp had toxic effects on the livers of mice, which was manifested in increased fatty degeneration in DBCB, edema, and the appearance of micronuclei in DBA/2J. The main identified effects of Tyr on mice are considered in the light of its modulating effect on the dopamine neurotransmitter metabolism, while for the Trp supplement, effects were presumably associated with the synthesis of its toxic metabolites by representatives of the intestinal microflora.

Effects of Tyrosine and Tryptophan in Rats with Diet-Induced Obesity

Amino acids tyrosine (Tyr) and tryptophan (Trp) play a significant role in the regulation of energy metabolism, locomotor activity, and eating behavior. We studied the possibility of modulating these processes in obesity by increasing the pool of Tyr and Trp in the experimental diet. As a model of obesity, we used Wistar rats fed a diet with an excess specific energy value (HFCD) for 64 days. Trp led to a normalization of the rats’ body weight almost to the control level, but increased anxiety-like behavior and decreased long-term memory. The consumption of amino acids resulted in increased grip strength and impairment of short-term memory. The locomotor activity of animals decreased with age as a result of Tyr consumption, while Trp, on the contrary, prevented this. The Tyr supplementation led to the normalization of triglycerides and LDL. In the spleen cell lysates, amino acids suppressed the production of proinflammatory cytokines. The liver tissue morphology showed that the consumption of Tyr noticeably weakened the signs of fatty degeneration. The addition of Trp, on the contrary, led to an unfavorable effect, consisting of the appearance of a high number of large rounded fatty vacuoles. The data obtained indicate a more pronounced anti-inflammatory effect of Tyr as compared to Trp.

Effect of resveratrol on behavioral, biochemical, and immunological parameters of DBA/2J and tetrahybrid DBCB mice receiving diet with excess fat and fructose

Polyphenolic biologically active substances (BAS) including resveratrol (R) can exert beneficial effects on fat accumulation, blood pressure, glycemia, insulin sensitivity, and plasma lipid profile in patients with obesity, and associated diseases. The study aimed to determine the effect of R at a dose of 25 mg/kg body weight on the DBA/2J and DBCB mice with diet-induced obesity followed by the consumption high-fat high-carbohydrate diet (HFCD). Behavioral reactions (elevated plus maze [EPM]) and muscle tone (the strength of the forepaw grip) were tested, and plasma biochemical and immunological parameters were assessed. In the repeated EPM test, anxiety increased only in DBCB mice during the second trial. In DBCB mice treated with HFCD, the muscle tone decreased with the second trial; however, this effect was not observed in the background of R consumption. R decreased the level of triglycerides, diminished the activities of alanine and asparagine aminotransferases, which were elevated upon HFCD consumption. Ghrelin level increased after R consumption in mice of both genotypes. The leptin to ghrelin ratio was reduced in DBCB mice receiving R. Consumption of R increased IL-3 and IL-10 levels in both DBA/2J and DBCB mice. IL-12p70 level increased in DBCB mice in response to R. R addition to HFCD reduced several symptoms of dyslipidemia in highly sensitive tetrahybrid mice. The results obtained indicate the importance of a personalized (depending on the genotype) approach when any R prescription, among other BAS and dietary factors, are used in diet therapy for patients with low, moderate and high-risk obesity.

Altered Sexual Behavior in Dopamine Transporter (DAT) Knockout Male Rats: A Behavioral, Neurochemical and Intracerebral Microdialysis Study

Central dopamine plays a key role in sexual behavior. Recently, a Dopamine Transporter knockout (DAT KO) rat has been developed, which displays several behavioral dysfunctions that have been related to increased extracellular dopamine levels and altered dopamine turnover secondary to DAT gene silencing. This prompted us to characterize the sexual behavior of these DAT KO rats and their heterozygote (HET) and wild type (WT) counterparts in classical copulatory tests with a sexually receptive female rat and to verify if and how the acquisition of sexual experience changes along five copulatory tests in these rat lines. Extracellular dopamine and glutamic acid concentrations were also measured in the dialysate obtained by intracerebral microdialysis from the nucleus accumbens (Acb) shell of DAT KO, HET and WT rats, which underwent five copulatory tests, when put in the presence of an inaccessible sexually receptive female rat and when copulation was allowed. Markers of neurotropism (BDNF, trkB), neural activation (Δ-FosB), functional (Arc and PSA-NCAM) and structural synaptic plasticity (synaptophysin, syntaxin-3, PSD-95) were also measured in the ventral tegmental area (VTA), Acb (shell and core) and medial prefrontal cortex (mPFC) by Western Blot assays. The results indicate that the sexual behavior of DAT KO vs. HET and WT rats shows peculiar differences, mainly due to a more rapid acquisition of stable sexual activity levels and to higher levels of sexual motivation and activity. These differences occurred with differential changes in dopamine and glutamic acid concentrations in Acb dialysates during sexual behavior, with lower increases of dopamine and glutamic acid in DAT KO vs. WT and HET rats, and a lower expression of the markers investigated, mainly in the mPFC, in DAT KO vs. WT rats. Together these findings confirm a key role of dopamine in sexual behavior and provide evidence that the permanently high levels of dopamine triggered by DAT gene silencing cause alterations in both the frontocortical glutamatergic neurons projecting to the Acb and VTA and in the mesolimbic dopaminergic neurons, leading to specific brain regional changes in trophic support and neuroplastic processes, which may have a role in the sexual behavior differences found among the three rat genotypes.