The optimal therapeutic irisin dose intervention in animal model: A systematic review

[Exercise promotes irisin expression to ameliorate renal injury in type 2 diabetic rats]

OBJECTIVE

To investigate the role of irisin in exercise-induced improvement of renal function in type 2 diabetic rats.

METHODS

Forty male SD rats aged 4-6 weeks were randomized into normal control group, type 2 diabetes mellitus model group, diabetic exercise (DE) group and diabetic irisin (DI) group (n=8). The rats in DE group were trained with treadmill running for 8 weeks, and those in DI group were given scheduled irisin injections for 8 weeks. After the treatments, blood biochemical parameters of the rats were examined, and renal histopathology was observed with HE, Masson and PAS staining. Western blotting was used to detect the protein expression levels in the rats'kidneys.

RESULTS

The diabetic rats showed significantly increased levels of fasting insulin, total cholesterol, triglyceride, serum creatinine and blood urea nitrogen with lowered serum irisin level (all P < 0.05). Compared with those in DM group, total cholesterol, triglyceride, serum creatinine and blood urea nitrogen levels were decreased and serum irisin levels were increased in both DE and DI groups (all P < 0.05). The rats in DM group showed obvious structural disorders and collagen fiber deposition in the kidneys, which were significantly improved in DE group and DI group. Both regular exercises and irisin injections significantly ameliorated the reduction of FNDC5, LC3-II/I, Atg7, Beclin-1, p-AMPK, AMPK and SIRT1 protein expressions and lowered of p62 protein expression in the kidneys of the diabetic rats (all P < 0.05).

CONCLUSION

Both exercise and exogenous irisin treatment improve nephropathy in type 2 diabetic rats possibly due to irisin-mediated activation of the AMPK/SIRT1 pathway in the kidneys to promote renal autophagy.

Irisin reduces orthodontic tooth movement in rats by promoting the osteogenic potential in the periodontal ligament

OBJECTIVES

Positive effects of irisin on osteogenic differentiation of periodontal ligament (PDL) cells have been identified previously, this study aims to examine its effect on orthodontic tooth movement (OTM) in vivo.

MATERIALS AND METHODS

The maxillary right first molars of male Wistar rats (n = 21) were moved mesially for 14 days, with submucosal injection of two dosages of irisin (0.1 or 1 μg) or phosphate-buffered saline (control) every third day. OTM was recorded by feeler gauge and micro-computed tomography (μCT). Alveolar bone and root volume were analysed using μCT, and plasma irisin levels by ELISA. Histological characteristics of PDL tissues were examined, and the expression of collagen type I, periostin, osteocalcin (OCN), von Willebrand factor (vWF) and fibronectin type III domain-containing protein 5 (FNDC5) in PDL was evaluated by immunofluorescence staining.

RESULTS

Repeated 1 μg irisin injections suppressed OTM on days 6, 9, and 12. No significant differences were observed in OTM in the 0.1 μg irisin group, or in bone morphometric parameters, root volume or plasma irisin, compared to control. Resorption lacunae and hyalinization were found at the PDL-bone interface on the compression side in the control, whereas they were scarce after irisin administration. The expression of collagen type I, periostin, OCN, vWF, and FNDC5 in PDL was enhanced by irisin administration.

LIMITATIONS

The feeler gauge method may overestimate OTM.

CONCLUSIONS

Submucosal irisin injection reduced OTM by enhancing osteogenic potential of PDL, and this effect was more significant on the compression side.

Move Your Body toward Healthy Aging: Potential Neuroprotective Mechanisms of Irisin in Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia in older adults, having a significant global burden and increasing prevalence. Current treatments for AD only provide symptomatic relief and do not cure the disease. Physical activity has been extensively studied as a potential preventive measure against cognitive decline and AD. Recent research has identified a hormone called irisin, which is produced during exercise, that has shown promising effects on cognitive function. Irisin acts on the brain by promoting neuroprotection by enhancing the growth and survival of neurons. It also plays a role in metabolism, energy regulation, and glucose homeostasis. Furthermore, irisin has been found to modulate autophagy, which is a cellular process involved in the clearance of protein aggregates, which are a hallmark of AD. Additionally, irisin has been shown to protect against cell death, apoptosis, oxidative stress, and neuroinflammation, all of which are implicated in AD pathogenesis. However, further research is needed to fully understand the mechanisms and therapeutic potential of irisin in AD. Despite the current gaps in knowledge, irisin holds promise as a potential therapeutic target for slowing cognitive decline and improving quality of life in AD patients.

Impact of Sustained Exogenous Irisin Myokine Administration on Muscle and Myocyte Integrity in Sprague Dawley Rats

Irisin is an exercise-induced myokine implicated as a fundamental mediator of physical activity benefits. The aim of the present study was to investigate the role of the chronic administration model of irisin on the physiological and molecular status of skeletal muscle. A total of 20 female Sprague Dawley rats (250 ± 40 g) were implanted with an irisin-loaded osmotic pump (5 µg/kg/day) for 42 days; in addition, 3 females received a single subcutaneous injection of irisin (5 µg/kg). On a weekly basis for six weeks, animals were weighed and blood samples were collected. After 42 days, hind muscle biopsies were collected for histology and gene analysis. Serum irisin, clinical biochemistry, and histopathology were quantified and evaluated. Genes encoding for different physiological muscle activities, such as oxidative stress, fatty acid metabolism, muscle hypertrophy, mitochondrial fusion, and aging were assayed. The results showed a significant reduction in body weight percentage and creatine kinase level without affecting the morphological characteristics of skeletal muscle. Significant changes were noted in genes involved in muscle physiological activity, growth, and aging, as well as genes encoding for the antioxidant system, fatty acid oxidation processes, and mitochondrial fusion. In conclusion, exogenous irisin can induce the same physiological and molecular mechanisms that might be induced by exercise.

The Role of Interventional Irisin on Heart Molecular Physiology

Irisin, encoded by the FNDC5 (fibronectin type III domain containing 5) gene, is a novel myokine that has been implicated as an essential mediator of exercise benefits. Effects of irisin on heart physiology is still ambiguous. This study aimed to evaluate the impact of exogenous administration of irisin on heart physiology and the pharmacokinetic profile of pump-administered irisin. To do so, Sprague Dawley rats were implanted with an irisin-loaded osmotic pump (5 μg/kg/day) for 42 days, and other animals were administered with single bolus subcutaneous injections of irisin (5 µg/kg). Body weights and blood samples were collected weekly for 42 days for serum irisin quantification and histopathology. Clinical biochemistry analyses were performed. Heart mRNA expression was assessed in 26 selected genes. Chronic interventional exogenous irisin significantly reduced body weight without affecting the heart myocyte size and significantly reduced creatine kinase enzyme level. Blood CBC, serum biochemistry, and heart morphology were normal. Gene expression of FNCD5, Raf1, CPT1, IGF-1, and CALCIN, encoding for heart physiology, increased while PGC1, Nox4, and Mfn1 significantly decreased. Nevertheless, irisin increased the expression of cardioprotective genes and inhibited some genes that harm heart physiology. Administration of irisin promotes myocardial functions and could be translated into clinical settings after preclinical profiling.

Irisin reduces the abnormal reproductive and metabolic phenotypes of PCOS by regulating the activity of brown adipose tissue in mice

Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disease in women, with clinical manifestations of anovulation and hyperandrogenaemia. The treatment of PCOS mainly focuses on improving clinical symptoms, such as insulin sensitivity or menstrual disorder, through drug treatment. However, due to the pathogenesis diversity of PCOS, there is still a lack of effective treatment in clinics. Metabolic disorder is the key factor in the occurrence of PCOS. Brown adipose tissue (BAT) is a special adipose tissue in the human body that can participate in metabolic balance by improving heat production. BAT has been demonstrated to be an important substance involved in the metabolic disorder of PCOS. Although increasing evidence indicates that BAT transplantation can improve the symptoms of PCOS, it is difficult to achieve BAT transplantation at present due to technical limitations. Stimulation of BAT activation by exogenous substances may be an effective alternative therapy for PCOS. In this study, we investigated the effects of Irisin on dehydroepiandrosterone (DHEA)-induced PCOS in mice and evaluated the effect of Irisin on serum hormone levels and changes in body temperature, body weight and ovarian morphology. In our study, we found that Irisin can enhance the thermogenesis and insulin sensitivity of PCOS mice by activating the function of BAT. In addition, Irisin treatment can correct the menstrual cycle of PCOS mice, improve the serum steroid hormone disorder status, and reduce the formation of ovarian cystic follicles. In conclusion, our results showed that Irisin treatment significantly improved the metabolic disorder of PCOS and may provide a new and alternative therapy for the treatment of this pathology.