Local overexpression of V1a-vasopressin receptor enhances regeneration in tumor necrosis factor-induced muscle atrophy

Water deprivation induces a systemic procatabolic state that differentially affects oxidative and glycolytic skeletal muscles in male mice

Dehydration, characterized by the loss of total body water and/or electrolytes due to diseases or inadequate fluid intake, is prevalent globally but often underestimated. Its contribution to long-term chronic diseases and sarcopenia is recognized, yet the mechanisms involved in systemic and muscle protein metabolism during dehydration remain unclear. This study investigated metabolic adaptations in a 36-h water deprivation (WD) model of mice. Male C57BL/6 mice underwent 36-h WD or pair-feeding at rest, with assessments of motor skills along with biochemical and metabolic parameters. Dehydration was confirmed by hypernatremia, body mass loss, hyporexia, and increased activity of vasopressinergic and oxytocinergic neurons compared with controls. These results were associated with liver mass loss, decreased glycemia, and increased cholesterolemia. In addition, increased V̇o2 and a decreased respiratory exchange ratio indicated reduced carbohydrate consumption and potentially increased protein use during dehydration. Thus, skeletal muscle protein metabolism was evaluated due to its high protein content. In the oxidative muscles of the WD group, total and proteasomal proteolysis increased, which was associated with decreased Akt-mediated intracellular signaling. Interestingly, there was an increase in fiber cross-sectional area, likely due to higher muscle water content caused by increased intracellular osmolality induced by protein catabolism products. Conversely, no changes were observed in protein turnover or water content in glycolytic muscles. These findings suggest that short-term WD imposes a procatabolic state, depleting protein content in skeletal muscle. However, skeletal muscle may respond differently to dehydration based on its phenotype and might adapt for a limited time.NEW & NOTEWORTHY This study investigated the effects of WD on mouse homeostasis, focusing on energy substrates and skeletal muscle protein metabolism. Our findings revealed a shift toward reduced dependence on carbohydrate degradation and increased reliance on lipid oxidation, or even protein oxidation, as energy sources, since we observed increased proteolysis in one muscle phenotype. Despite body mass loss, soleus and EDL muscle masses were differently affected. These results indicate the procatabolic potential of short-term WD in mice.

Increased copeptin may reflect vasopressin-related metabolic changes after bariatric surgery

OBJECTIVE

Mechanisms underlying metabolic improvement following metabolic and bariatric surgery (MBS) may provide insight into novel therapies. Vasopressin improves body composition and protects against hypoglycemia. Associations of copeptin, a stable cleavage product of vasopressin, with BMI and insulin resistance suggest an adaptive increase in vasopressin to counteract metabolic disruption. To our knowledge, no study has investigated copeptin before and after MBS in humans. This study's aim was to investigate copeptin changes following MBS and associations with metabolic parameters.

METHODS

This was a 12-month longitudinal study of 64 youth (78% female; mean age 18.7 [SD 2.8] y) with obesity (mean BMI 45.6 [SD 6.8] kg/m2) undergoing MBS (n = 34) or nonsurgical (NS) lifestyle management (n = 30). Fasting copeptin, hemoglobin A1c (HbA1c), homeostatic model assessment for insulin resistance (HOMA-IR), body composition, and resting energy expenditure (REE) were assessed.

RESULTS

Over 12 months, copeptin increased more (time-by-treatment p = 0.017) whereas HbA1c and adiposity decreased more after MBS than NS (ps ≤ 0.036). Copeptin changes correlated negatively with percentage fat mass and REE changes (rho ≤ -0.29; ps ≤ 0.025) in the whole group, and they correlated positively with HbA1c and HOMA-IR (rho ≥ 0.41; false discovery rate-adjusted p = 0.05) and negatively with REE changes (rho = -0.55; false discovery rate-adjusted p = 0.036) in the MBS group.

CONCLUSIONS

Increases in copeptin after weight loss in MBS compared with NS were associated with lower REE and higher HbA1c/HOMA-IR values. Vasopressin may contribute to MBS-related metabolic modifications.

Taurine Administration Counteracts Aging-Associated Impingement of Skeletal Muscle Regeneration by Reducing Inflammation and Oxidative Stress

Sarcopenia, which occurs during aging, is characterized by the gradual loss of skeletal muscle mass and function, resulting in a functional decline in physical abilities. Several factors contribute to the onset of sarcopenia, including reduced regenerative capacity, chronic low-grade inflammation, mitochondrial dysfunction, and increased oxidative stress, leading to the activation of catabolic pathways. Physical activity and adequate protein intake are considered effective strategies able to reduce the incidence and severity of sarcopenia by exerting beneficial effects in improving the muscular anabolic response during aging. Taurine is a non-essential amino acid that is highly expressed in mammalian tissues and, particularly, in skeletal muscle where it is involved in the regulation of biological processes and where it acts as an antioxidant and anti-inflammatory factor. Here, we evaluated whether taurine administration in old mice counteracts the physiopathological effects of aging in skeletal muscle. We showed that, in injured muscle, taurine enhances the regenerative process by downregulating the inflammatory response and preserving muscle fiber integrity. Moreover, taurine attenuates ROS production in aged muscles by maintaining a proper cellular redox balance, acting as an antioxidant molecule. Although further studies are needed to better elucidate the molecular mechanisms responsible for the beneficial effect of taurine on skeletal muscle homeostasis, these data demonstrate that taurine administration ameliorates the microenvironment allowing an efficient regenerative process and attenuation of the catabolic pathways related to the onset of sarcopenia.

Characterization of stress response involved in chicken myopathy

Myopathies (Woody Breast (WB) and White Striping (WS)) of broiler chickens have been correlated with fast growth. Recent studies reported that localized hypoxia and metabolic impairment may involve in these myopathies of birds. In order to better understand the stress response mechanisms affecting myopathies of broilers, the aim of this study was to examine effects of WB and both WB/WS on stress hormone corticosterone (CORT) levels and expressional changes of stress response genes including glucocorticoid (GC) receptor (GR), 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1), DNA methylation regulators (DNMTs), and arginine vasotocin receptor 1a and 1b (V1aR, V1bR). Results of radioimmunoassay showed that CORT levels of WB and WB/WS birds were significantly higher compared to Con (p < 0.05), however, the combination of WB/WS was not significantly higher than WB birds, implying that the effects of WB and WS on CORT are not synergistic. Hepatic GR expression of both WB and WB/WS birds were significantly higher compared to Con (p < 0.05). However, GR expression levels in breast muscle of both WB and WB/WS birds were decreased compared to Con (p < 0.05). Hepatic 11β-HSD1 expression was increased only in WB/WS birds compared to Con birds with no significant difference between Con and WB birds. 11β-HSD1 expression was decreased and increased in WB and WB/WS birds compared to Con, respectively, in breast muscle (p < 0.05). DNMT1 expression was significantly decreased in both muscle and liver of WB birds, and in muscle of WB/WS birds, but not in liver of WB/WS birds, indicating differential effects of WS on the epigenetical stress response of muscle and liver compared to WB. V1aR expression was significantly increased in muscle of WB birds, and in liver of WB/WS birds compared to Con birds (p < 0.05). V1bR was not changed in muscle and liver of WB birds compared to Con birds. Taken together, results suggest that GC-induced myopathies occur in fast-growing broiler chickens and circulating CORT level might be a significant biochemical marker of myopathies (WB and WS) of birds. In addition, chronic stress responses in breast muscle and tissue-specific epigenetic changes of stress response genes by DNMTs may play a critical role in the occurrence of myopathies.

Neurohypophyseal hormones and skeletal muscle: a tale of two faces

The neurohypophyseal hormones vasopressin and oxytocin were invested, in recent years, with novel functions upon striated muscle, regulating its differentiation, trophism, and homeostasis. Recent studies highlight that these hormones not only target skeletal muscle but represent novel myokines. We discuss the possibility of exploiting the muscle hypertrophying activity of oxytocin to revert muscle atrophy, including cancer cachexia muscle wasting. Furthermore, the role of oxytocin in cardiac homeostasis and the possible role of cardiac atrophy as a concause of death in cachectic patients is discussed.

Thyroid Hormone Protects from Fasting-Induced Skeletal Muscle Atrophy by Promoting Metabolic Adaptation

Thyroid hormones regulate a wide range of cellular responses, via non-genomic and genomic actions, depending on cell-specific thyroid hormone transporters, co-repressors, or co-activators. Skeletal muscle has been identified as a direct target of thyroid hormone T3, where it regulates stem cell proliferation and differentiation, as well as myofiber metabolism. However, the effects of T3 in muscle-wasting conditions have not been yet addressed. Being T3 primarily responsible for the regulation of metabolism, we challenged mice with fasting and found that T3 counteracted starvation-induced muscle atrophy. Interestingly, T3 did not prevent the activation of the main catabolic pathways, i.e., the ubiquitin-proteasome or the autophagy-lysosomal systems, nor did it stimulate de novo muscle synthesis in starved muscles. Transcriptome analyses revealed that T3 mainly affected the metabolic processes in starved muscle. Further analyses of myofiber metabolism revealed that T3 prevented the starvation-mediated metabolic shift, thus preserving skeletal muscle mass. Our study elucidated new T3 functions in regulating skeletal muscle homeostasis and metabolism in pathological conditions, opening to new potential therapeutic approaches for the treatment of skeletal muscle atrophy.

Oxytocin and Vasopressin Systems in Obesity and Metabolic Health: Mechanisms and Perspectives

PURPOSE OF REVIEW

The neurohypophysial endocrine system is identified here as a potential target for therapeutic interventions toward improving obesity-related metabolic dysfunction, given its coinciding pleiotropic effects on psychological, neurological and metabolic systems that are disrupted in obesity.

RECENT FINDINGS

Copeptin, the C-terminal portion of the precursor of arginine-vasopressin, is positively associated with body mass index and risk of type 2 diabetes. Plasma oxytocin is decreased in obesity and several other conditions of abnormal glucose homeostasis. Recent data also show non-classical tissues, such as myocytes, hepatocytes and β-cells, exhibit responses to oxytocin and vasopressin receptor binding that may contribute to alterations in metabolic function. The modulation of anorexigenic and orexigenic pathways appears to be the dominant mechanism underlying the effects of oxytocin and vasopressin on body weight regulation; however, there are apparent limitations associated with their use in direct pharmacological applications. A clearer picture of their wider physiological effects is needed before either system can be considered for therapeutic use.

Inhibition of Phosphoinositide 3-Kinase/Protein Kinase B Signaling Hampers the Vasopressin-dependent Stimulation of Myogenic Differentiation

Arginine-vasopressin (AVP) promotes muscle differentiation, hypertrophy, and regeneration through the combined activation of the calcineurin and Calcium/Calmodulin-dependent Protein Kinase (CaMK) pathways. The AVP system is impaired in several neuromuscular diseases, suggesting that AVP may act as a physiological factor in skeletal muscle. Since the Phosphoinositide 3-kinases/Protein Kinase B/mammalian Target Of Rapamycin (PI3K/Akt/mTOR) signaling plays a significant role in regulating muscle mass, we evaluated its role in the AVP myogenic effect. In L6 cells AKT1 expression was knocked down, and the AVP-dependent expression of mTOR and Forkhead box O3 (FoxO) was analyzed by Western blotting. The effect of the PI3K inhibitor LY294002 was evaluated by cellular and molecular techniques. Akt knockdown hampered the AVP-dependent mTOR expression while increased the levels of FoxO transcription factor. LY294002 treatment inhibited the AVP-dependent expression of Myocyte Enhancer Factor-2 (MEF2) and myogenin and prevented the nuclear translocation of MEF2. LY294002 also repressed the AVP-dependent nuclear export of histone deacetylase 4 (HDAC4) interfering with the formation of multifactorial complexes on the myogenin promoter. We demonstrate that the PI3K/Akt pathway is essential for the full myogenic effect of AVP and that, by targeting this pathway, one may highlight novel strategies to counteract muscle wasting in aging or neuromuscular disorders.