Skeletal muscle-specific over-expression of the nuclear sirtuin SIRT6 blocks cancer-associated cachexia by regulating multiple targets

Serum interferon-gamma-induced protein 10 levels can help predict sarcopenia development in patients with primary hepatocellular carcinoma: A retrospective cohort study

BACKGROUND

Sarcopenia is a prognostic factor in patients with hepatocellular carcinoma (HCC). However, the mechanism underlying sarcopenia development in these patients remains unclear. The chemokine interferon-gamma-induced protein 10/C-X-C motif chemokine ligand 10 (IP-10) has been found to be associated with muscle regeneration or destruction. Thus, we aimed to clarify the role of serum IP-10 levels in predicting sarcopenia development in patients with HCC.

METHODS

This retrospective study enrolled 120 patients with primary HCC whose serum IP-10 levels were measured both at baseline and 1 year after the confirmed diagnosis of HCC. Patients who had sarcopenia at baseline computed tomography imaging were assigned to the Sarco-base group, whereas those in whom sarcopenia was found for the first time after 3 years were assigned to the Sarco-develop group. Those who never met the criteria during the follow-up period were assigned to the Non-Sarco group.

RESULTS

The baseline IP-10 levels were significantly lower in the Sarco-base group compared to the rest (p = 0.016). Conversely baseline IP-10 levels and IP-10 ratio at 1 year were higher in the Sarco-develop group than in the Non-Sarco group (p = 0.0017, p = 0.025). High IP-10 levels at baseline, and high IP-10 ratios at 1 year were independently related factors for sarcopenia development.

CONCLUSIONS

Patients with sarcopenia at baseline more frequently presented with low IP-10 levels than those without. Contrarily, the group without sarcopenia at baseline and with high baseline IP-10 levels and high IP-10 ratios at 1 year were more likely to develop sarcopenia after 3 years. Monitoring of IP-10 levels may enable the identification of groups prone to develop sarcopenia in patients with HCC.

SIRT6 Ameliorates Cancer Cachexia-Associated Adipose Wasting by Suppressing TNFR2 Signalling in Mice

BACKGROUND

Cachexia is a wasting syndrome associated with imbalanced energy metabolism and loss of adipose and muscle tissues and contributes to morbidity and mortality in ageing as well as in patients with severe chronic diseases, including cancer. At present, there are no treatments addressing cachexia that have reached validation to be used in the clinic. In this study, we investigate the protective role of SIRT6, an important regulator of energy homeostasis and health preservation, against Lewis lung carcinoma (LLC)-induced cachexia.

METHODS

SIRT6 levels of serum from gastric cancer patients (n = 22, 65.27 ± 12.50 years old, 40.9% females) and healthy controls (n = 22, 63.50 ± 10.77 years old, 45.4% females) were measured to evaluate the correlation between circulating SIRT6 levels and cancer cachexia development. Ten-week-old SIRT6 transgenic (TG) and wild type (WT) male mice injected with LLC cells (1.5 × 106 per mouse) were used to investigate the protective effects of SIRT6 on cachexia-associated adipose browning and lipolysis and the underlying mechanisms. We explored the effect of SIRT6 on LLC-conditioned medium induced lipolysis in mature adipocytes, differentiated from primary mouse embryonic fibroblasts (MEFs). We evaluated the in vitro effect of a SIRT6 activator by treatment of MDL800.

RESULTS

SIRT6 concentrations were significantly higher in non-cachectic cancer patients (3.41 ± 0.30 ng/mL) compared to cachectic cancer patients (3.20 ± 0.23 ng/mL, p < 0.01), suggesting the negative correlation between SIRT6 level and cachexia in patients with cancer. SIRT6 overexpression significantly ameliorated tumour-induced wasting and energy expenditure in white adipose tissues (eWAT mass loss: 66% in WT vs. 32% in TG; iWAT mass loss: 69% in WT vs. 40% in TG) through suppression of browning and lipolysis. In LLC-induced cachexia, tumour necrosis factor-α receptor 2 (TNFR2) mediated the inhibition of SIRT6 on lipolytic signalling, because the difference in lipolysis between the WT and SIRT6 knockout group was almost eliminated by TNFR2 neutralizing antibody. Increased serum TNFR2 concentration was found in cachectic cancer patients (690.41 pg/mL in non-cachectic vs. 1166.98 pg/mL in cachectic patients, p < 0.05). A selective SIRT6 pharmaceutical activator, MDL800, could completely reverse LLC-induced lipolysis in adipocytes.

CONCLUSION

We found an unexpected beneficial function of SIRT6 in cancer cachexia, demonstrating that increased SIRT6 expression or activity is capable of protecting the host against cachexia-associated tissue wasting, providing a concept of future therapies for cachexia.

Unlocking the Nexus of Sirtuins: A Comprehensive Review of Their Role in Skeletal Muscle Metabolism, Development, and Disorders

The sirtuins constitute a group of histone deacetylases reliant on NAD+ for their activity that have gained recognition for their critical roles as regulators of numerous biological processes. These enzymes have various functions in skeletal muscle biology, including development, metabolism, and the body's response to disease. This comprehensive review seeks to clarify sirtuins' complex role in skeletal muscle metabolism, including glucose uptake, fatty acid oxidation, mitochondrial dynamics, autophagy regulation, and exercise adaptations. It also examines their critical roles in developing skeletal muscle, including myogenesis, the determination of muscle fiber type, regeneration, and hypertrophic responses. Moreover, it sheds light on the therapeutic potential of sirtuins by examining their impact on a range of skeletal muscle disorders. By integrating findings from various studies, this review outlines the context of sirtuin-mediated regulation in skeletal muscle, highlighting their importance and possible consequences for health and disease.

Single nuclei profiling identifies cell specific markers of skeletal muscle aging, frailty, and senescence

Aging is accompanied by a loss of muscle mass and function, termed sarcopenia, which causes numerous morbidities and economic burdens in human populations. Mechanisms implicated in age-related sarcopenia or frailty include inflammation, muscle stem cell depletion, mitochondrial dysfunction, and loss of motor neurons, but whether there are key drivers of sarcopenia are not yet known. To gain deeper insights into age-related muscle loss, we performed transcriptome profiling on lower limb muscle biopsies from 72 young, elderly, and frail human subjects using bulk RNA-seq (N = 72) and single-nuclei RNA-seq (N = 17). This combined approach revealed changes in gene expression that occur with age and frailty in multiple cell types comprising mature skeletal muscle. Notably, we found increased expression of the genes MYH8 and PDK4, and decreased expression of the gene IGFN1, in aged muscle. We validated several key genes changes in fixed human muscle tissue using digital spatial profiling. We also identified a small population of nuclei that express CDKN1A, present only in aged samples, consistent with p21cip1-driven senescence in this subpopulation. Overall, our findings identify unique cellular subpopulations in aged and sarcopenic skeletal muscle, which will facilitate the development of new therapeutic strategies to combat age-related frailty.