Implication of metabolomic profiles to wide thermoneutral zone in Mongolian gerbils (Meriones unguiculatus)

Higher Concentration of Dietary Selenium, Zinc, and Copper Complex Reduces Heat Stress-Associated Oxidative Stress and Metabolic Alteration in the Blood of Holstein and Jersey Steers

This study investigated the influence of high concentrations of dietary minerals on reducing heat stress (HS)-associated oxidative stress and metabolic alterations in the blood of Holstein and Jersey steers. Holstein steers and Jersey steers were separately maintained under a 3 × 3 Latin square design during the summer conditions. For each trial, the treatments included Control (Con; fed basal TMR without additional mineral supplementation), NM (NRC recommended mineral supplementation group; [basal TMR + (Se 0.1 ppm + Zn 30 ppm + Cu 10 ppm) as DM basis]), and HM (higher than NRC recommended mineral supplementation group; [basal TMR + (Se 3.5 ppm + Zn 350 ppm + Cu 28 ppm) as DM basis]). Blood samples were collected at the end of each 20-day feeding trial. In both breeds, a higher superoxide dismutase concentration (U/mL) along with lower HSP27 (μg/L) and HSP70 (μg/L) concentrations were observed in both mineral-supplemented groups compared to the Con group (p < 0.05). The HM group had significantly higher lactic acid levels in Jersey steers (p < 0.05), and tended to have higher alanine levels in Holstein steers (p = 0.051). Based on star pattern recognition analysis, the levels of succinic acid, malic acid, γ-linolenic acid, 13-methyltetradecanoic acid, and tyrosine decreased, whereas palmitoleic acid increased with increasing mineral concentrations in both breeds. Different treatment groups of both breeds were separated according to the VIP scores of the top 15 metabolites through PLS−DA analysis; however, their metabolic trend was mostly associated with the glucose homeostasis. Overall, the results suggested that supplementation with a higher-than-recommended concentration of dietary minerals rich in organic Se, as was the case in the HM group, would help to prevent HS-associated oxidative stress and metabolic alterations in Holstein and Jersey steers.

High Ambient Temperature Aggravates Experimental Autoimmune Uveitis Symptoms

Whether ambient temperature influences immune responses leading to uveitis is unknown. We thus tested whether ambient temperature affects the symptoms of experimental autoimmune uveitis (EAU) in mice and investigated possible mechanisms. C57BL/6 mice were kept at a normal (22°C) or high temperature (30°C) housing conditions for 2 weeks and were then immunized with human interphotoreceptor retinoid-binding protein (IRBP651–670) peptide to induce EAU. Histological changes were monitored to evaluate the severity of uveitis. Frequency of Th1 cells and Th17 cells was measured by flow cytometry (FCM). The expression of IFN-γ and IL-17A mRNA was measured by real-time qPCR. The generation of neutrophil extracellular traps (NETs) was quantified by enzyme-linked immunosorbent assay (ELISA). Differential metabolites in the plasma of the mice kept in the aforementioned two ambient temperatures were measured via ultra-high-performance liquid chromatography triple quadrupole mass spectrometry quadrupole time of flight mass spectrometry (UHPLC-QQQ/MS). The differential metabolites identified were used to evaluate their effects on differentiation of Th1 and Th17 cells and generation of NETs in vitro. The results showed that EAU mice kept at high temperature experienced a more severe histopathological manifestation of uveitis than mice kept at a normal temperature. A significantly increased frequency of Th1 and Th17 cells in association with an upregulated expression of IFN-γ and IL-17A mRNA was observed in the splenic lymphocytes and retinas of EAU mice in high temperature. The expression of NETs as evidenced by myeloperoxidase (MPO) and neutrophil elastase (NE), was significantly elevated in serum and supernatants of neutrophils from EAU mice kept at high temperature compared to the normal temperature group. The metabolites in the plasma from EAU mice, fumaric acid and succinic acid, were markedly increased in the high temperature group and could induce the generation of NETs via the NADPH oxidase-dependent pathway, but did not influence the frequency of Th1 and Th17 cells. Our findings suggest that an increased ambient temperature is a risk factor for the development of uveitis. This is associated with the induction of Th1 and Th17 cells as well as the generation of NETs which could be mediated by the NADPH oxidase-dependent pathway.

HSP70 plays a role in the defense of acute and chronic heat stress in Mongolian gerbils (Meriones unguiculatus)

Mongolian gerbils (Meriones unguiculatus) show a wide thermal neutral zone (TNZ, 26.5-38.9 °C). Whether heat shock proteins (HSPs) are involved in thermal tolerance for gerbils has still been unknown. We investigated the effects of acute and chronic high temperature within and above TNZ on the expressions of HSP70 and HSP90 and oxidative status in Mongolian gerbils, to test the hypothesis that the gerbils need increase the expression in HSPs to defense the acute and chronic heat stress. In experiment I, 50 Mongolian gerbils were exposed to 23 °C, 27 °C, 37 °C, 40 °C and 43.5 °C for 80 min respectively, and then sacrificed 12 h after treatment. HSP70 expression in the liver increased at 40 °C compared to that at 23 °C, but did not change after 27 °C, 37 °C or 43.5 °C exposure. There were no differences in HSP90 expression, oxidative stress parameters such as malonaldehyde (MDA) and hydrogen peroxide (H₂O₂), or antioxidant parameters such as superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in the liver. HSP70 and HSP90 expression both in the heart and brain showed no differences among groups. In experiment II, another set of 30 gerbils were acclimated to 23 °C, 27 °C and 37 °C for 21 days, respectively. During chronic acclimation, HSP70 expression increased and H₂O₂ level decreased in the liver in 37 °C group compared to other two groups. Both H₂O₂ and SOD in the brain decreased in 37 °C group, but there were no differences in HSP70, MDA or T-AOC in the brain. These data indicate that Mongolian gerbils can maintain basal levels of HSPs after acute exposure to temperatures within the wide TNZ, but rely on increased HSP70 in the liver to protect from heat damage at temperatures above TNZ and during chronic heat acclimation. The increased HSP70 expression in the liver may contribute to keeping from heat damage in desert rodents.

Brown adipose tissue plays thermoregulatory role within the thermoneutral zone in Mongolian gerbils (Meriones unguiculatus)

Brown adipose tissue (BAT) plays an important role in thermoregulation and many metabolic processes in small mammals, especially in cold adaptation. However, in warm adaptation, ambient temperature cannot directly activate BAT by sympathetic nervous system. Mongolian gerbils exhibit a wider thermoneutral zone (26.5-38.9 °C). We hypothesized that BAT atrophied near the lower critical temperature and further atrophied near the upper critical temperature. Male gerbils were acclimated to 23 °C, 27 °C or 37 °C, respectively, for 3 weeks. Results showed that regulatory non-shivering thermogenesis did not change in gerbils acclimated to 27 °C compared with 23 °C group, whereas it was reduced by 43.5% in gerbils acclimated to 37 °C. Bigger lipid droplet in BAT was observed in gerbils acclimated to 27 °C and 37 °C compared with 23 °C group, while the expression of uncoupling protein 1 and tyrosine hydroxylase was only reduced in gerbils acclimated to 37 °C. Further, thermoneutral acclimation did not change BAT thermogenesis by down-regulation of peroxisome proliferator-activated receptor gamma coactivator-1α, PR domain containing 16, peroxisome proliferator-activated receptor-α or peroxisome proliferator activated receptor-γ gene expression in BAT. In addition, body temperature was reduced in gerbils acclimated to 37 °C compared with 23 °C group, which was associated with a decreased resting metabolic rate and regulatory non-shivering thermogenesis. In conclusion, BAT does not atrophy near the lower critical temperature, whereas it atrophies near the upper critical temperature, suggesting that BAT may play thermoregulatory role within the TNZ in Mongolian gerbils.

Metabolomics Profiling of Serum and Urine in Three Beef Cattle Breeds Revealed Different Levels of Tolerance to Heat Stress

This study was to determine differences in the global metabolic profiles of serum and urine of Xuanhan yellow cattle, Simmental crossbred cattle (Simmental × Xuanhan yellow cattle), and cattle-yaks (Jersey × Maiwa yak) under heat stress (temperature-humidity index remained above 80 for 1 week). A total of 55 different metabolites associated with the three breeds were identified in the serum and urine samples by gas chromatography-mass spectrometry. The metabolic adaptations to heat stress are heterogeneous. Cattle-yaks mobilize a greater amount of body protein to release glucogenic amino acids to supply energy, whereas the tricarboxylic acid cycle is inhibited. Simmental crossbred cattle mobilize a greater amount of body fat to use free fatty acids as an energy source. In comparison with Simmental crossbred cattle and cattle-yaks, Xuanhan yellow cattle have higher glycolytic activity and possess a stronger antioxidant defense system and are, in conclusion, more adapted to hot and humid environments.