Warm-blooded animals such as birds and mammals are able to protect stable body temperature due to various thermogenic mechanisms. These processes can be facultative (occurring only under specific conditions, such as acute cold) and adaptive (adjusting their capacity according to long-term needs). They can represent a substantial part of overall energy expenditure and, therefore, affect energy balance. Classical mechanisms of facultative thermogenesis include shivering of skeletal muscles and (in mammals) non-shivering thermogenesis (NST) in brown adipose tissue (BAT), which depends on uncoupling protein 1 (UCP1). Existence of several alternative thermogenic mechanisms has been suggested. However, their relative contribution to overall heat production and the extent to which they are adaptive and facultative still needs to be better defined. Here we focus on comparison of NST in BAT with thermogenesis in skeletal muscles, including shivering and NST. We present indications that muscle NST may be adaptive but not facultative, unlike UCP1-dependent NST. Due to its slow regulation and low energy efficiency, reflecting in part the anatomical location, induction of muscle NST may counteract development of obesity more effectively than UCP1-dependent thermogenesis in BAT.

• MeSH
• chvění * fyziologie   MeSH
• energetický metabolismus fyziologie   MeSH
• fyziologická adaptace * fyziologie   MeSH
• hnědá tuková tkáň * metabolismus   MeSH
• kosterní svaly * metabolismus   MeSH
• lidé MeSH
• obezita * metabolismus   patofyziologie   MeSH
• termogeneze * fyziologie   MeSH
• uncoupling protein 1 metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• uncoupling protein 1 MeSH

OBJECTIVE: The possibility to counteract the development of obesity in humans by recruiting brown or brite/beige adipose tissue (and thus UCP1) has attracted much attention. Here we examine if a diet that can activate diet-induced thermogenesis can exploit pre-enhanced amounts of UCP1 to counteract the development of diet-induced obesity. METHODS: To investigate the anti-obesity significance of highly augmented amounts of UCP1 for control of body energy reserves, we physiologically increased total UCP1 amounts by recruitment of brown and brite/beige tissues in mice. We then examined the influence of the augmented UCP1 levels on metabolic parameters when the mice were exposed to a high-fat/high-sucrose diet under thermoneutral conditions. RESULTS: The total UCP1 levels achieved were about 50-fold higher in recruited than in non-recruited mice. Contrary to underlying expectations, in the mice with highly recruited UCP1 and exposed to a high-fat/high-sucrose diet the thermogenic capacity of this UCP1 was completely inactivate. The mice even transiently (in an adipostat-like manner) demonstrated a higher metabolic efficiency and fat gain than did non-recruited mice. This was accomplished without altering energy expenditure or food absorption efficiency. The metabolic efficiency here was indistinguishable from that of mice totally devoid of UCP1. CONCLUSIONS: Although UCP1 protein may be available, it is not inevitably utilized for diet-induced thermogenesis. Thus, although attempts to recruit UCP1 in humans may become successful as such, it is only if constant activation of the UCP1 is also achieved that amelioration of obesity development could be attained.

• Klíčová slova
• Adipostat, Beige adipose tissue, Body weight regulation, Diet-induced thermogenesis, Glucose homeostasis, UCP1,
• MeSH
• béžová tuková tkáň metabolismus   MeSH
• dieta s vysokým obsahem tuků škodlivé účinky   MeSH
• energetický metabolismus MeSH
• hnědá tuková tkáň * metabolismus   MeSH
• lidé MeSH
• myši MeSH
• obezita * metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

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.

• Klíčová slova
• Brown adipose tissue, Mitochondrial supercomplex, Non-shivering thermogenesis, Obesity, Sarcolipin, Skeletal muscle,
• MeSH
• adrenergní látky metabolismus   MeSH
• hnědá tuková tkáň * metabolismus   MeSH
• inbrední kmeny myší MeSH
• kosterní svaly metabolismus   MeSH
• myši inbrední C57BL MeSH
• myši MeSH
• obezita metabolismus   MeSH
• proteomika * MeSH
• termogeneze fyziologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adrenergní látky MeSH

OBJECTIVE: Classical ATP-independent non-shivering thermogenesis enabled by uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) is activated, but not essential for survival, in the cold. It has long been suspected that futile ATP-consuming substrate cycles also contribute to thermogenesis and can partially compensate for the genetic ablation of UCP1 in mouse models. Futile ATP-dependent thermogenesis could thereby enable survival in the cold even when brown fat is less abundant or missing. METHODS: In this study, we explore different potential sources of UCP1-independent thermogenesis and identify a futile ATP-consuming triglyceride/fatty acid cycle as the main contributor to cellular heat production in brown adipocytes lacking UCP1. We uncover the mechanism on a molecular level and pinpoint the key enzymes involved using pharmacological and genetic interference. RESULTS: ATGL is the most important lipase in terms of releasing fatty acids from lipid droplets, while DGAT1 accounts for the majority of fatty acid re-esterification in UCP1-ablated brown adipocytes. Furthermore, we demonstrate that chronic cold exposure causes a pronounced remodeling of adipose tissues and leads to the recruitment of lipid cycling capacity specifically in BAT of UCP1-knockout mice, possibly fueled by fatty acids from white fat. Quantification of triglyceride/fatty acid cycling clearly shows that UCP1-ablated animals significantly increase turnover rates at room temperature and below. CONCLUSION: Our results suggest an important role for futile lipid cycling in adaptive thermogenesis and total energy expenditure.

• Klíčová slova
• Brown adipose tissue, Fatty acids, Futile substrate cycle, Lipolysis, Re-esterification, UCP1-independent thermogenesis,
• MeSH
• adenosintrifosfát metabolismus   MeSH
• hnědá tuková tkáň * metabolismus   MeSH
• mastné kyseliny metabolismus   MeSH
• myši knockoutované MeSH
• myši MeSH
• termogeneze * MeSH
• triglyceridy metabolismus   MeSH
• uncoupling protein 1 genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenosintrifosfát MeSH
• mastné kyseliny MeSH
• triglyceridy MeSH
• Ucp1 protein, mouse MeSH Prohlížeč
• uncoupling protein 1 MeSH

Impaired thermogenesis observed in mice with whole-body ablation of peroxisome proliferator-activated receptor-γ coactivator-1β (PGC-1β; officially known as PPARGC1B) may result from impaired brown fat (brown adipose tissue; BAT) function, but other mechanism(s) could be involved. Here, using adipose-specific PGC-1β knockout mice (PGC-1β-AT-KO mice) we aimed to learn whether specific PGC-1β ablation in adipocytes is sufficient to drive cold sensitivity. Indeed, we found that warm-adapted (30°C) mutant mice were relatively sensitive to acute cold exposure (6°C). When these mice were subjected to cold exposure for 7 days (7-day-CE), adrenergic stimulation of their metabolism was impaired, despite similar levels of thermogenic uncoupling protein 1 in BAT in PGC-1β-AT-KO and wild-type mice. Gene expression in BAT of mutant mice suggested a compensatory increase in lipid metabolism to counteract the thermogenic defect. Interestingly, a reduced number of contacts between mitochondria and lipid droplets associated with low levels of L-form of optic atrophy 1 was found in BAT of PGC-1β-AT-KO mice. These genotypic differences were observed in warm-adapted mutant mice, but they were partially masked by 7-day-CE. Collectively, our results suggest a role for PGC-1β in controlling BAT lipid metabolism and thermogenesis. This article has an associated First Person interview with the first author of the paper.

• Klíčová slova
• Adrenergic control, Lipid metabolism, Mice, OPA1,
• MeSH
• hnědá tuková tkáň * MeSH
• jaderné proteiny metabolismus   MeSH
• lidé MeSH
• myši MeSH
• PPARGC1A metabolismus   MeSH
• proteiny vázající RNA metabolismus   MeSH
• termogeneze genetika   MeSH
• transkripční faktory metabolismus   MeSH
• tukové buňky MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• jaderné proteiny MeSH
• PPARGC1A MeSH
• PPARGC1B protein, human MeSH Prohlížeč
• Ppargc1b protein, mouse MeSH Prohlížeč
• proteiny vázající RNA MeSH
• transkripční faktory MeSH

The possibility to use leptin therapeutically for lowering glucose levels in patients with type 1 diabetes has attracted interest. However, earlier animal models of type 1 diabetes are severely catabolic with very low endogenous leptin levels, unlike most patients with diabetes. Here, we aim to test glucose-lowering effects of leptin in novel, more human-like murine models. We examined the glucose-lowering potential of leptin in diabetic models of two types: streptozotocin-treated mice and mice treated with the insulin receptor antagonist S961. To prevent hypoleptinemia, we used combinations of thermoneutral temperature and high-fat feeding. Leptin fully normalized hyperglycemia in standard chow-fed streptozotocin-treated diabetic mice. However, more humanized physiological conditions (high-fat diets or thermoneutral temperatures) that increased adiposity - and thus also leptin levels - in the diabetic mice abrogated the effects of leptin, i.e., the mice developed leptin resistance also in this respect. The glucose-lowering effect of leptin was not dependent on the presence of the uncoupling protein-1 and was not associated with alterations in plasma insulin, insulin-like growth factor 1, food intake or corticosterone but fully correlated with decreased plasma glucagon levels and gluconeogenesis. An important implication of these observations is that the therapeutic potential of leptin as an additional treatment in patients with type 1 diabetes is probably limited. This is because such patients are treated with insulin and do not display low leptin levels. Thus, the potential for a glucose-lowering effect of leptin would already have been attained with standard insulin therapy, and further effects on blood glucose level through additional leptin cannot be anticipated.

• Klíčová slova
• glucagon, insulin receptor antagonist, leptin, thermoneutrality, type 1 diabetes, uncoupling protein 1,
• MeSH
• bílá tuková tkáň metabolismus   MeSH
• diabetes mellitus 1. typu metabolismus   MeSH
• experimentální diabetes mellitus metabolismus   MeSH
• glukagon metabolismus   MeSH
• glukoneogeneze MeSH
• hnědá tuková tkáň metabolismus   MeSH
• insulinu podobný růstový faktor I metabolismus   MeSH
• inzulin metabolismus   MeSH
• kortikosteron metabolismus   MeSH
• krevní glukóza účinky léků   metabolismus   MeSH
• kyselina pyrohroznová metabolismus   MeSH
• leptin metabolismus   farmakologie   MeSH
• lidé MeSH
• modely nemocí na zvířatech MeSH
• myši knockoutované MeSH
• myši MeSH
• peptidy farmakologie   MeSH
• přijímání potravy MeSH
• receptor inzulinu antagonisté a inhibitory   MeSH
• spotřeba kyslíku MeSH
• transkriptom MeSH
• uncoupling protein 1 genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• glukagon MeSH
• insulin-like growth factor-1, mouse MeSH Prohlížeč
• insulinu podobný růstový faktor I MeSH
• inzulin MeSH
• kortikosteron MeSH
• krevní glukóza MeSH
• kyselina pyrohroznová MeSH
• LEP protein, human MeSH Prohlížeč
• leptin MeSH
• peptidy MeSH
• receptor inzulinu MeSH
• S961 peptide MeSH Prohlížeč
• Ucp1 protein, mouse MeSH Prohlížeč
• uncoupling protein 1 MeSH