Targeting interleukin‐1 for reversing fat browning and muscle wasting in infantile nephropathic cystinosis

Abstract

Background Ctns À/À mice, a mouse model of infantile nephropathic cystinosis, exhibit hypermetabolism with adipose tissue browning and profound muscle wasting. Inflammatory cytokines such as interleukin (IL)-1 trigger inflammatory cascades and may be an important cause for cachexia. We employed genetic and pharmacological approaches to investigate the effects of IL-1 blockade in Ctns À/À mice. Methods We generated Ctns À/À Il1β À/À mice, and we treated Ctns À/À and wild-type control mice with IL-1 receptor antagonist, anakinra (2.5 mg/kg/day, IP) or saline as vehicle for 6 weeks. In each of these mouse lines, we characterized the cachexia phenotype consisting of anorexia, loss of weight, fat mass and lean mass, elevation of metabolic rate, and reduced in vivo muscle function (rotarod activity and grip strength). We quantitated energy homeostasis by measuring the protein content of uncoupling proteins (UCPs) and adenosine triphosphate in adipose tissue and skeletal muscle. We measured skeletal muscle fiber area and intramuscular fatty infiltration. We also studied expression of molecules regulating adipose tissue browning and muscle mass metabolism. Finally, we evaluated the impact of anakinra on the muscle transcriptome in Ctns À/À mice. Results Skeletal muscle expression of IL-1β was significantly elevated in Ctns À/À mice relative to wild-type control mice. Cachexia was completely normalized in Ctns À/À Il1β À/À mice relative to Ctns À/À mice. We showed that anakinra attenuated the cachexia phenotype in Ctns À/À mice. Anakinra normalized UCPs and adenosine triphosphate content of adipose tissue and muscle in Ctns À/À mice. Anakinra attenuated aberrant expression of beige adipose cell biomarkers (UCP-1, CD137, Tmem26, and Tbx1) and molecules implicated in adipocyte tissue browning (Cox2/Pgf2α, Tlr2, Myd88, and Traf6) in inguinal white adipose tissue in Ctns À/À mice. Moreover, anakinra normalized gastrocnemius weight and fiber size and attenuated muscle fat infiltration in Ctns À/À mice. This was accompanied by correction of the increased muscle wasting signalling pathways (increased protein content of ERK1/2, JNK, p38 MAPK, and nuclear factor-κB p65 and mRNA expression of Atrogin-1 and Myostatin) and the decreased myogenesis process (decreased mRNA expression of MyoD and Myogenin) in the gastrocnemius muscle of Ctns À/À mice. Previously, we identified the top 20 differentially expressed skeletal muscle genes in Ctns À/À mice by RNAseq. Aberrant expression of these 20 genes have been implicated in muscle wasting, increased energy expenditure, and lipolysis. We showed that anakinra attenuated 12 of those top 20 differentially expressed muscle genes in Ctns À/À mice. Conclusions Anakinra may provide a targeted novel therapy for patients with infantile nephropathic cystinosis.

Muscle Wasting in Chronic Kidney Disease: Mechanism and Clinical Implications—A Narrative Review

“…Increased levels of systemic inflammatory cytokines, such as interleukin (IL)-1, IL-6, and TNF-α, are well-documented in patients with CKD [ 94 , 123 , 124 ]. Higher baseline IL-1β levels are associated with a more rapid decline in phase angle, an indicator for muscle function, after one-year HD [ 125 ].…”

Nephropathic Cystinosis: Pathogenic Roles of Inflammation and Potential for New Therapies

“…Further supporting a role for inflammasome activation in the pathogenesis of cystinosis in Ctns −/− mice, there was a significant increase in the renal expression of inflammasome-related genes, and an increase in the circulating levels of IL-18 was also observed [ 35 ]. Recently, the increased mRNA and protein levels of IL-1β were also found in the affected skeletal muscles of Ctns −/− mice [ 41 ]. However, to date, it remains to be studied in which cells, in vivo, in the cystinotic kidney and other affected organs, the inflammasome is activated.…”

“…Prencipe et al targeted the activated NLRP3 inflammasome pathway in cystinosis through the cathepsin B inhibitors CA-074Me and diphenyleneiodonium chloride, which decreased the secretion of IL-1β induced by the cystine crystals in the peripheral blood monocytes and suppressing the inflammatory cascade that should follow, thereby paving the way for another mechanism that can be targeted in cystinosis patients [ 18 ]. Cheung et al studied Ctns −/− mice for both the genetic deletion of Il1b as well as treatment with the recombinant IL-1 receptor antagonist (IL-1ra) anakinra, which led to an attenuation of the cachexia phenotype in cystinotic mice, supporting the efficacy of the IL-1 anti-inflammatory-targeted therapy on adipose browning and muscle wasting in nephropathic cystinosis [ 41 ]. Adding to this effect, Gonzalez et al demonstrated significant beneficial actions of the leptin receptor blockade, which is a well-known immunomodulatory cytokine and hormone on the cachexia phenotype in Ctns −/− mice.…”

Muscle and Bone Impairment in Infantile Nephropathic Cystinosis: New Concepts

“…It should be born in mind, that patients with INC displayed elevated levels of Il1β, Il18, and caspase 1 compared to healthy controls, but they also displayed significantly elevated levels of Il18 compared to patients with Familial Mediterranean Fever, a prototypical autoinflammatory disease [ 54 ]. Recently, Cheung et al, demonstrated that by treating Ctns −/− mice with the Il1 receptor antagonist Anakinra they were able to attenuate the cachexia phenotype and correct the abnormal expression of the main biomarkers of beige adipose cells and adipocyte tissue browning, and to attenuate 12 of the 20 main, differentially expressed genes in Ctns −/− mice [ 55 ]. Anakinra treatment also normalized muscle weight and fiber size and decreased infiltration in muscle fat [ 55 ].…”

“…Recently, Cheung et al, demonstrated that by treating Ctns −/− mice with the Il1 receptor antagonist Anakinra they were able to attenuate the cachexia phenotype and correct the abnormal expression of the main biomarkers of beige adipose cells and adipocyte tissue browning, and to attenuate 12 of the 20 main, differentially expressed genes in Ctns −/− mice [ 55 ]. Anakinra treatment also normalized muscle weight and fiber size and decreased infiltration in muscle fat [ 55 ]. These results were close to those observed earlier by the same team using vitamin D [ 51 ], questioning again the role of vitamin D in inflammation regulation.…”