Graphical AbstractHighlights d Mice lacking gut microbiota have impaired UCP1-dependent thermogenesis in cold d These effects are replicated in germ-free mice treated with CL-316243 d IL-4 has no differential effect on energy metabolism in either control or ABX mice d Gavage of ABX mice with butyrate partially rescues the effects on BAT recruitment SUMMARYThe relation between gut microbiota and the host has been suggested to benefit metabolic homeostasis. Brown adipose tissue (BAT) and beige adipocytes facilitate thermogenesis to maintain host core body temperature during cold exposure. However, the potential impact of gut microbiota on the thermogenic process is confused. Here, we evaluated how BAT and white adipose tissue (WAT) responded to temperature challenges in mice lacking gut microbiota. We found that microbiota depletion via treatment with different cocktails of antibiotics (ABX) or in germfree (GF) mice impaired the thermogenic capacity of BAT by blunting the increase in the expression of uncoupling protein 1 (UCP1) and reducing the browning process of WAT. Gavage of the bacterial metabolite butyrate increased the thermogenic capacity of ABX-treated mice, reversing the deficit. Our results indicate that gut microbiota contributes to upregulated thermogenesis in the cold environment and that this may be partially mediated via butyrate.

Sulfidation has gained increasing interest in recent years for improving the sequestration of contaminants by zerovalent iron (ZVI). In view of the bright prospects of the sulfidated ZVI (S-ZVI), this review comprehensively summarized the latest developments in sulfidation of ZVI, particularly that of nanoscale ZVI (S-nZVI). The milestones in development of S-ZVI technology including its background, enlightenment, synthesis, characterization, water remediation and treatment, etc., are summarized. Under most circumstances, sulfidation can enhance the sequestration of various organic compounds and metal(loid)s by ZVI to various extents. In particular, the reactivity of S-ZVI toward contaminants is strongly dependent on S/Fe molar ratio, sulfidation method, and solution chemistry. Additionally, sulfidation can improve the selectivity of ZVI toward targeted contaminant over water under anaerobic conditions. The mechanisms of sulfidation-induced improvement in contaminants sequestration by ZVI are also summarized. Finally, this review identifies the current knowledge gaps and future research needs of S-ZVI for environmental application.

SUMMARY Lactation is the most energetically expensive period for mammals and is associated with increased metabolism and energy intake, but decreased thermogenic capacity. It is well known that small mammals increase both food intake and thermogenesis in the cold. The present study aimed to examine whether Brandt's voles Lasiopodomys brandtii could adjust energy intake and thermogenesis to accommodate simultaneous lactation and cold exposure. The voles were placed into two temperature treatments: warm(23±1°C) and cold (5±1°C). Animals at each temperature treatment were further divided into two groups: non-reproductive (NR) and lactating females. We found that lactating voles at peak lactation in the cold enhanced food intake by 2.6 g day–1 compared with those in the warm, and increased uncoupling protein 1 (UCP1) content in brown adipose tissue (BAT), to the same level as the cold-exposed NR females. Serum leptin levels decreased significantly during lactation and were positively correlated with body mass and fat mass. After correcting for the effects of body mass,residual serum leptin was negatively correlated with residual gross energy intake and residual RMR. In addition, residual serum leptin levels were positively correlated with UCP1 contents in the warm, but not in the cold. Together, these data suggest that lactating voles can increase thermogenic capacity and energy intake to meet the high energetic costs of simultaneous lactation and cold exposure. Further, serum leptin appears to be involved in the energy intake regulation and thermoregulation, but the thermoregulation in the cold may be mainly mediated by other factors.

When zerovalent iron (ZVI) is used in reductive removal of contaminants from industrial wastewater, where dissolved oxygen (DO) competes with target contaminant for the electrons donated by ZVI, both the reactivity and the electron selectivity (ES) of ZVI toward target contaminant are critical. Thus, the reactivity and ES of two sulfidated ZVI (S-ZVI) samples, synthesized by ball-milling with elemental sulfur (S-ZVI) and reacting with NaS (S-ZVI), toward Cr(VI) under aerobic conditions were investigated. Sulfidation appreciably increased the reactivity of ZVI and the ratio of the rate constants for Cr(VI) removal by S-ZVI or S-ZVI to their counterparts without sulfur fell in the range of 1.4-29.9. ES of S-ZVI and S-ZVI toward Cr(VI) were determined to be 14.6% and 13.3%, which were 10.7- and 7.5-fold greater than that without sulfidation, respectively. This was mainly ascribed to the greater improving effect of sulfidation on the reduction rate of Cr(VI) than that of DO by ZVI. The improving effects of sulfidation on the performance of ZVI were mainly due to the following mechanisms: sulfidation increased the specific surface area of ZVI, the FeS layer facilitated the enrichment of Cr(VI) anions on S-ZVI surface because of its anions selective property and favored the electron transfer from Fe core to Cr(VI) at the surface because of its role as efficient electron conductor.

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Huddling as social thermoregulatory behavior is commonly used by small mammals to reduce heat loss and energy expenditure in the cold. Our study aimed to determine the effect of huddling behavior on energy conservation, thermogenesis, core body temperature (Tb) regulation and body composition in Brandt's voles (Lasiopodomys brandtii). Adult captive-bred female Brandt's voles (n = 124) (~50 g) in 31 cages with 4 individuals each were exposed to cool (23 ± 1°C) and cold (4 ± 1°C) ambient temperatures (Ta) and were allowed to huddle or were physically separated. The cold huddling (Cold-H) groups significantly reduced food intake by 29% and saved digestible energy 156.99 kJ/day compared with cold separated groups (Cold-S); in cool huddling groups (Cool-H) the reduction in food intake was 26% and digestible energy was saved by 105.19 kJ/day in comparison to the separated groups (Cool-S). Resting metabolic rate (RMR) of huddling groups was 35.7 and 37.2% lower than in separated groups at cold and cool Tas, respectively. Maximum non-shivering thermogenesis (NSTmax) of huddling voles was not affected by Ta, but in Cold-S voles it was significantly increased in comparison to Cool-S. Huddling groups decreased wet thermal conductance by 39% compared with separated groups in the cold, but not in the cool Ta. Unexpectedly, huddling voles significantly decreased Tb by 0.25 – 0.50°C at each Ta. Nevertheless, activity of Cold-H voles was higher than in Cold-S voles. Thus, huddling is energetically highly effective because of reduced metabolic rate, thermogenic capacity and relaxed Tb regulation despite the increase of activity. Therefore, Brandt's voles can remain active and maintain their body condition without increased energetic costs during cold exposure. This study highlights the ecological significance of huddling behavior for maintenance of individual fitness at low costs, and thus survival of population during severe winter in small mammals.

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Although quantum dot (QD)-induced toxicity occurs due to free radicals, generation of oxidative stress mediated by reactive oxygen species (ROS) formation is considered an important mechanism. However, free radical mechanisms are essentially difficult to elucidate at the molecular level because most biologically relevant free radicals are highly reactive and short-lived, making them difficult to directly detect, especially in vivo. Antioxidants play an important role in preventing or, in most cases, limiting the damage caused by ROS. Healthy people and animals possess many endogenous antioxidative substances that scavenge free radicals in vivo to maintain the redox balance and genome integrity. The antioxidant capacity of an organism is highly important but seldom studied. In this study, the dose and time effects of CdTe QDs on the antioxidant capacities of the liver and kidneys were investigated in mice using the electron paramagnetic resonance (EPR) spin-trapping technique. We found that the liver and kidneys of healthy mice contain specific antioxidant capacities that scavenge ·OH and ·O 2 − . Furthermore, oxidative stress markers (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx], glutathione [GSH] and malondialdehyde [MDA]) were examined. In dose course studies, the free radical scavenging efficiencies of the liver and kidneys were found to gradually decrease with increasing concentration of CdTe QD exposure. The activities and levels of SOD, CAT, GPx and MDA were observed to increase in treated groups, whereas those of GSH were reduced. The time course studies revealed that the QD-induced antioxidant efficiency reduction was time dependent with GSH decrease and could recover after a period of time. These experimental results offer new information on QD toxicity in vivo. Specifically, CdTe QDs can deplete GSH to reduce the elimination ability of the liver and kidneys for ·OH and ·O 2 − , thus inducing oxidative damage to tissues.