Summary Decreased growth hormone (GH) and thyroid hormone (TH) signaling are associated with longevity and metabolic fitness. The mechanisms underlying these benefits are poorly understood, but may overlap with those of dietary restriction (DR), which imparts similar benefits. Recently we discovered that hydrogen sulfide (H2S) is increased upon DR and plays an essential role in mediating DR benefits across evolutionary boundaries. Here we found increased hepatic H2S production in long-lived mouse strains of reduced GH and/or TH action, and in a cell-autonomous manner upon serum withdrawal in vitro. Negative regulation of hepatic H2S production by GH and TH was additive and occurred via distinct mechanisms, namely direct transcriptional repression of the H2S-producing enzyme cystathionine γ-lyase (CGL) by TH, and substrate-level control of H2S production by GH. Mice lacking CGL failed to downregulate systemic T4 metabolism and circulating IGF-1, revealing an essential role for H2S in the regulation of key longevity-associated hormones.

New Findings What is the central question of this study?Does glucocorticoid excess disrupt brown adipose tissue (BAT) phenotype and function? What is the main finding and its importance?Glucocorticoid excess induced an extensive remodelling of interscapular BAT, resulting in a white‐like phenotype in association with metabolic disturbances. Glucocorticoids might be an important modulator of BAT physiology and BAT may have a role in pathophysiology of metabolic disturbances induced by glucocorticoid excess. Abstract In mammals, brown adipose tissue (BAT) is centrally involved in energy metabolism. To test the hypothesis that glucocorticoid excess disrupts BAT phenotype and function, male Wistar rats were treated with corticosterone in drinking water for 21 days. To confirm induction of glucocorticoid excess and metabolic disturbances, adrenal weight, corticotrophin releasing hormone mRNA levels and corticosterone serum levels were measured and a glucose tolerance test and serum triacylglycerol analyses were performed. Adipose tissue deposits were excised, weighed and evaluated by a set of biochemical, histological and molecular procedures, including thin‐layer chromatography, histochemistry, immunohistochemistry, quantitative real‐time polymerase chain reaction, high‐resolution oxygraphy, ATP synthesis and enzymatic activity measurements. The approach was successful in induction of glucocorticoid excess and metabolic disturbances. Lower body weight and increased adiposity were observed in corticosterone‐treated rats. Interscapular brown adipose tissue (iBAT) showed higher sensitivity to glucocorticoids than other fat deposits. The treatment induced lipid accumulation, unilocular rearrangement, increased collagen content and decreased innervation in iBAT. Furthermore, expression of Prdm16 (P < 0.05), Ucp1 (P <0.05) and Slc7a10 (P <0.05) mRNA decreased, while expression of Fasn (P <0.05) and Lep (P <0.05) mRNA increased in brown adipose tissue. Also, the levels of UCP1 diminished (P <0.001, 2.5‐fold). Finally, lower oxygen consumption (P <0.05), ATP synthesis (P <0.05) and mitochondrial content (P <0.05) were observed in iBAT of glucocorticoid‐treated rats. Glucocorticoid excess induced an extensive remodelling of interscapular brown adipose tissue, resulting in a white‐like phenotype in association with metabolic disturbances.

Life expectancy in most developed countries has been rising over the last century. In the UK alone, there are around 12 million people over 65 years old and centenarians have increased by 85% in the past 15 years. As a result of our ageing population, which is due mainly to improvements in medical treatments, public health, improved housing and lifestyle choices, there is an associated increase in prevalence of pathological conditions, such as metabolic disorders, type 2 diabetes (T2D), cardiovascular and neurodegenerative diseases, many types of cancer and others. Statistics suggest that nearly 54% of elderly people in the UK live with at least two chronic conditions, revealing the urgency for identifying interventions that can prevent and/or treat such disorders. Nonpharmacological, dietary interventions such as caloric restriction (CR) and methionine restriction (MR) have revealed promising outcomes in increasing longevity and preventing and/or reversing the development of ageing-associated disorders. In this review, we discuss the evidence and mechanisms that are involved in these processes. FGF21 and H 2 S are important molecules involved in the effects of CR and MR in the extension of life span. Their role is also associated with the prevention of metabolic and cognitive disorders, highlighting these interventions as promising modulators for improvement of health span.

We evaluated the effects of hypo- and hyperthyroid statuses during the initial phase of skeletal muscle regeneration in rats. To induce hypo- or hyperthyroidism, adult male Wistar rats were treated with methimazole (0.03%) or T4 (10 μg/100 g), respectively, for 10 days. Three days before sacrifice, a crush injury was produced in the solear muscles of one half of the animals, while the other half remained intact. T3, T4, TSH, and leptin serum levels were not affected by the injury. Serum T3 and T4 levels were significantly increased in hyperthyroid and hyper-injury animals. Hypothyroidism was confirmed by the significant increase in serum TSH levels in hypothyroid and hypo-injury animals. Injury increased cell infiltration and macrophage accumulation especially in hyperthyroid animals. Both type 2 and type 3 deiodinases were induced by lesion, and the opposite occurred with the type 1 isoform, at least in the control and hyperthyroid groups. Injury increased both MyoD and myogenin expression in all the studied groups, but only MyoD expression was increased by thyroidal status only at the protein level. We conclude that thyroid hormones modulate skeletal muscle regeneration possibly by regulating the inflammatory process, as well as MyoD and myogenin expression in the injured tissue.

In recent years, the use of insufficiently characterised control subjects has been a contributing factor to increasing irreproducibility in different areas of biomedical research including neuroscience and metabolism. There is now a growing awareness of phenotypic differences between the metabolic profiles of C57BL/6 substrains which are commonly used as control animals.We here investigated baseline metabolic characteristics such as glucose regulation, fasted serum insulin levels and hepatic insulin signalling in five different C57BL/6 sub-strains (N, J, JOla, JRcc) of both sexes, obtained from two commercial vendors Charles River Laboratories (Crl) and Envigo (Env).Our results indicated systematic and tissue-specific differences between substrains, modulated by both vendor and sex in all parameters investigated, not necessarily mediated by the presence of theNntmutation. Not only were there differences between 6J and 6N as expected, all three 6J sub-strains exhibited different profiles, even from the same breeder. Two distinct metabolic profiles were identified, one in which low insulin levels resulted in impaired glucose clearance (6JCrl; both sexes) and the other, where sustained elevations in fasted basal insulin levels led to glucose intolerance (male 6JRccEnv). Further, 6JRccEnv displayed sex differences in both glucose clearance and hepatic insulin signalling markers. In comparison, the two 6N substrains of either sex, irrespective of vendor, did not exhibit considerable differences, with 6NCrl animals presenting a good choice as a healthy baseline ‘control’ for many types of experiments.Overall, our data emphasise the importance of selecting and characterising control subjects regarding background, sex, and supplier to ensure proper experimental outcomes in biomedical research.

In recent years, insufficiently characterised controls have been a contributing factor to irreproducibility in biomedical research including neuroscience and metabolism. There is now a growing awareness of phenotypic differences between the C57BL/6 substrains which are commonly used as control animals. We here investigated baseline metabolic characteristics such as glucose regulation, fasted serum insulin levels and hepatic insulin signalling in five different C57BL/6 substrains (N, J, JOla, JRcc) of both sexes, obtained from two commercial vendors, Charles River Laboratories (Crl) and Envigo (Env). Our results indicate systematic and tissue-specific differences between substrains, affected by both vendor and sex, in all parameters investigated, and not necessarily mediated by the presence of the NntC57BL/6J mutation. Not only were there differences between 6J and 6N as expected, all three 6J substrains exhibited different profiles, even from the same breeder. Two distinct metabolic profiles were identified, one in which low insulin levels resulted in impaired glucose clearance (6JCrl; both sexes) and the other, where sustained elevations in fasted basal insulin levels led to glucose intolerance (male 6JRccEnv). Further, 6JRccEnv displayed sex differences in both glucose clearance and hepatic insulin signalling markers. In comparison, the two 6N substrains of either sex, irrespective of vendor, did not exhibit considerable differences, with 6NCrl animals presenting a good choice as a healthy baseline ‘control’ for many types of experiments. Overall, our data emphasise the importance of selecting and characterising control subjects regarding background, sex, and supplier to ensure proper experimental outcomes in biomedical research.