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Objective: Non-shivering thermogenesis (NST) mediated by uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) can be activated via the adrenergic system in response to cold or diet, contributing to both thermal and energy homeostasis. Other mechanisms, including metabolism of skeletal muscle, may also be involved in NST. However, relative contribution of these energy dissipating pathways and their adaptability remain a matter of long-standing controversy. Methods: We used warm-acclimated (30 °C) mice to characterize the effect of an up to 7-day cold acclimation (6 °C; CA) on thermoregulatory thermogenesis, comparing inbred mice with a genetic background conferring resistance (A/J) or susceptibility (C57BL/6 J) to obesity. Results: Both warm-acclimated C57BL/6 J and A/J mice exhibited similar cold endurance, assessed as a capability to maintain core body temperature during acute exposure to cold, which improved in response to CA, resulting in comparable cold endurance and similar induction of UCP1 protein in BAT of mice of both genotypes. Despite this, adrenergic NST in BAT was induced only in C57BL/6 J, not in A/J mice subjected to CA. Cold tolerance phenotype of A/J mice subjected to CA was not based on increased shivering, improved insulation, or changes in physical activity. On the contrary, lipidomic, proteomic and gene expression analyses along with palmitoyl carnitine oxidation and cytochrome c oxidase activity revealed induction of lipid oxidation exclusively in skeletal muscle of A/J mice subjected to CA. These changes appear to be related to skeletal muscle NST, mediated by sarcolipin-induced uncoupling of sarco(endo)plasmic reticulum calcium ATPase pump activity and accentuated by changes in mitochondrial respiratory chain supercomplexes assembly. Conclusions: Our results suggest that NST in skeletal muscle could be adaptively augmented in the face of insufficient adrenergic NST in BAT, depending on the genetic background of the mice. It may provide both protection from cold and resistance to obesity, more effectively than BAT.

Objective: Administration of FGF21 to mice reduces body weight and increases body temperature. The increase in body temperature is generally interpreted as hyperthermia, i.e. a condition secondary to the increase in energy expenditure (heat production). Here, we examine an alternative hypothesis: that FGF21 has a direct pyrexic effect, i.e. FGF21 increases body temperature independently of any effect on energy expenditure. Methods: We studied the effects of FGF21 treatment on body temperature and energy expenditure in high-fat-diet-fed and chow-fed mice exposed acutely to various ambient temperatures, in high-fat diet-fed mice housed at 30 °C (i.e. at thermoneutrality), and in mice lacking uncoupling protein 1 (UCP1). Results: In every model studied, FGF21 increased body temperature, but energy expenditure was increased only in some models. The effect of FGF21 on body temperature was more (not less, as expected in hyperthermia) pronounced at lower ambient temperatures. Effects on body temperature and energy expenditure were temporally distinct (daytime versus nighttime). FGF21 enhanced UCP1 protein content in brown adipose tissue (BAT); there was no measurable UCP1 protein in inguinal brite/beige adipose tissue. FGF21 increased energy expenditure through adrenergic stimulation of BAT. In mice lacking UCP1, FGF21 did not increase energy expenditure but increased body temperature by reducing heat loss, e.g. a reduced tail surface temperature. Conclusion: The effect of FGF21 on body temperature is independent of UCP1 and can be achieved in the absence of any change in energy expenditure. Since elevated body temperature is a primary effect of FGF21 and can be achieved without increasing energy expenditure, only limited body weight-lowering effects of FGF21 may be expected.

The Special Nature Reserve, a part of the nature “Meadows of Great Bustard” (MGB), is a protected area with an extremely rare and sensitive ecosystem. The MGB spreads in the northeast of Vojvodina in Serbia. The natural potentials of MGB, in addition to diverse flora and fauna, are symbolized by a jeopardized species of bird called the Great Bustard (Otis tarda). Only a few specimens of this species live in this protected area, and they need to be protected. Globally, the Great Bustard is vulnerable species (VU) and a seriously protected species in Serbia. The goal of the research in this paper is to determine whether sustainable tourism affects the satisfaction of residents, using a quantitative method through the Prism of Sustainability (PoS) research model, which includes the technique of surveying respondents (residents). In this part of Vojvodina lives a population that has specific social characteristics. The cultural legacy, customs of this part of Banat, way of treating nature, local crafts, and local events stand out among those characteristics. The favorable geographical position of MGB, the proximity of Romania and Hungary, and good traffic connections with numerous cities in Serbia and the region represent significant potential for tourism development. The natural motives of MGB and ecological interests should be a priority in planning and developing tourism. A nature-based tourism destination can be formed by combining natural and social motives. The main forms of tourism, important for the development of this area, are ecotourism, scientific research tourism, and birdwatching tourism in the MGB. The significant results of the research are those that point out that the respondents rated ecological and socio-cultural sustainability as the most important. Also, these two dimensions have the greatest impact on sustainable tourism in the MGB. After the conducted research, it can be concluded that the residents are satisfied with sustainable tourism, i.e., sustainable tourism significantly affects the satisfaction of residents.

Surčin represents the youngest Belgrade municipality which, due to the richness of its natural and cultural resources, as well as favourable traffic and geographical position, features the overall tourist offer of Belgrade as an interesting excursion tourist destination. Day trips, excursion tours, cruises, short thematic sightseeing tours are only part of the excursion tourism product of Surčin municipality. Following the global trends in the tourist market and activating the tourist offer of marginal urban municipalities contribute to the development of Belgrade urban tourism through the enrichment of the tourist offer and innovation of contents of the local and foreign visitors stay. The aim of this paper is to point out the excursion tourism product of Surčin municipality as a contribution to the development of Belgrade urban tourism. The methods used in the work include office and field research using the survey.