A comparative study on the effects of high-fat diet and endurance training on the PGC-1α-FNDC5/irisin pathway in obese and nonobese male C57BL/6 mice

Guanidinoacetic acid ameliorates hepatic steatosis and inflammation and promotes white adipose tissue browning in middle-aged mice with high-fat-diet-induced obesity

Guanidinoacetic acid (GAA) is a naturally occurring amino acid derivative that plays a critical role in energy metabolism. In recent years, a growing body of evidence has emerged supporting the importance of GAA in metabolic dysfunction. Hence, we aimed to investigate the effects of GAA on hepatic and adipose tissue metabolism, as well as systemic inflammatory responses in obese middle-aged mice models and attempted to explore the underlying mechanism. We found that dietary supplementation of GAA inhibited inguinal white adipose tissue (iWAT) hypertrophy in high-fat diet (HFD)-fed mice. In addition, GAA supplementation observably decreased the levels of some systemic inflammatory factors, including IL-4, TNF-α, IL-1β, and IL-6. Intriguingly, GAA supplementation ameliorated hepatic steatosis and lipid deposition in HFD-fed mice, which was revealed by decreased levels of TG, TC, LDL-C, PPARγ, SREBP-1c, FASN, ACC, FABP1, and APOB and increased levels of HDL-C in the liver. Moreover, GAA supplementation increased the expression of browning markers and mitochondrial-related genes in the iWAT. Further investigation showed that dietary GAA promoted the browning of the iWAT via activating the AMPK/Sirt1 signaling pathway and might be associated with futile creatine cycling in obese mice. These results indicate that GAA has the potential to be used as an effective ingredient in dietary interventions and thus may play an important role in ameliorating and preventing HFD-induced obesity and related metabolic diseases.

Cardioprotective Effects of Exercise: The Role of Irisin and Exosome

Exercise is an effective measure for preventing and treating cardiovascular diseases, although the exact molecular mechanism remains unknown. Previous studies have shown that both irisin and exosomes can improve the course of cardiovascular disease independently. Therefore, it is speculated that the cardiovascular protective effect of exercise is also related to its ability to regulate the concentrations of irisin and exosomes in the circulatory system. In this review, the potential synergistic interactions between irisin and exosomes are examined, as well as the underlying mechanisms including the AMPK/PI3K/AKT pathway, the TGFβ1/Smad2/3 pathway, the PI3K/AKT/VEGF pathway, and the PTEN/PINK1/Parkin pathway are examined. This paper provides evidence to propose that exercise promotes the release of exosomes enriched with irisin, miR-486-5p and miR-342-5p from skeletal muscles, which results in the activation protective networks in the cardiovascular system. Moreover, the potential synergistic effect in exosomal cargo can provide new ideas for clinical research of exercise mimics.

Ferulago angulata extract alleviates testicular toxicity in male mice exposed to diazinon and lead

In this study, we investigated the protective effects of Ferulago angulata extract (FAE) against the reproductive toxicants Diazinon (DZN) and Lead (Pb) in mice. These pollutants are known to induce oxidative stress (OS), while FAE acts as a natural antioxidant. Adult male NMRI mice were exposed to DZN, Pb, and DZN+Pb, with or without FAE treatment for six weeks. We evaluated OS markers, testicular histology, and expression of mRNA related to enzymatic antioxidants. Exposure to DZN and Pb led to increased levels of thiobarbituric acid reactive substance (TBARS) and nitric oxide (NO) in the testes, along with a decrease in the total antioxidant capacity (TAC). Furthermore, the mRNA expression of antioxidant enzymes such as superoxide dismutase 1 (SOD1) and glutathione peroxidase 4 (GPX4) was altered. However, when FAE was administered concurrently, it restored the biochemical parameters to normal levels, reduced the toxic effects of DZN and Pb, and provided protection against testicular histopathological injury. These findings suggest that FAE has the potential to serve as a protective agent against oxidative damage caused by contaminants in reproductive organs, specifically in the testes.

The role of the transsulfuration pathway in spermatogenesis of vitamin D deficient mice

Vitamin D deficiency is a global health problem and has been linked to defective spermatogenesis and male infertility. In this study, we aimed to investigate the main enzymes involved in the transsulfuration pathway of 1-carbon metabolism, and spermatogenesis function. Therefore, sixteen male C57 mice were addressed to a control (standard diet) or vitamin D deficient (VDD) diet for 14 weeks. The results show that compared to the standard diet, VDD increased final body weight and reduced sperm quality, caused damage to the testicular structure, and decreased the serum levels of testosterone. In addition, serum concentrations of homocysteine, vitamin B12, and sperm oxidative stress markers increased. In testicular tissues, the CBS and CSE protein levels were down-regulated whereas HO-1 was up-regulated at both mRNA and protein expression levels. Within a mice deprivation model, VDD deeply suppressed testosterone and impaired spermatogenesis with oxidative stress-mediated mechanisms. The effects of the deprivation appeared to be at least in part independent of genomic and receptor-mediated vitamin D actions and suggest a specific impairment of the alternative transsulfuration pathway.

Maresin 1 Exerts a Tissue-Specific Regulation of Adipo-Hepato-Myokines in Diet-Induced Obese Mice and Modulates Adipokine Expression in Cultured Human Adipocytes in Basal and Inflammatory Conditions

This study analyses the effects of Maresin 1 (MaR1), a docosahexaenoic acid (DHA)-derived specialized proresolving lipid mediator with anti-inflammatory and insulin-sensitizing actions, on the expression of adipokines, including adiponectin, leptin, dipeptidyl peptidase 4 (DPP-4), cardiotrophin-1 (CT-1), and irisin (FNDC5), both in vitro and in in vivo models of obesity. The in vivo effects of MaR1 (50 μg/kg, 10 days, oral gavage) were evaluated in epididymal adipose tissue (eWAT), liver and muscle of diet-induced obese (DIO) mice. Moreover, two models of human differentiated primary adipocytes were incubated with MaR1 (1 and 10 nM, 24 h) or with a combination of tumor necrosis factor-α (TNF-α, 100 ng/mL) and MaR1 (1-200 nM, 24 h) and the expression and secretion of adipokines were measured in both models. MaR1-treated DIO mice exhibited an increased expression of adiponectin and Ct-1 in eWAT, increased expression of Fndc5 and Ct-1 in muscle and a decreased expression of hepatic Dpp-4. In human differentiated adipocytes, MaR1 increased the expression of ADIPONECTIN, LEPTIN, DPP4, CT-1 and FNDC5. Moreover, MaR1 counteracted the downregulation of ADIPONECTIN and the upregulation of DPP-4 and LEPTIN observed in adipocytes treated with TNF-α. Differential effects for TNF-α and MaR1 on the expression of CT-1 and FNDC5 were observed between both models of human adipocytes. In conclusion, MaR1 reverses the expression of specific adipomyokines and hepatokines altered in obese mice in a tissue-dependent manner. Moreover, MaR1 regulates the basal expression of adipokines in human adipocytes and counteracts the alterations of adipokines expression induced by TNF-α in vitro. These actions could contribute to the metabolic benefits of this lipid mediator.

Irisin in domestic animals

Irisin is a 112 amino acid peptide hormone cleaved from the fibronectin type III domain-containing protein. Irisin is highly conserved across vertebrates, suggesting evolutionarily conserved common functions among domestic animals. These functions include the browning of white adipose tissue and increased energy expenditure. Irisin has been detected and studied primarily in plasma, serum, and skeletal muscle, but has also been found in adipose tissue, liver, kidney, lungs, cerebrospinal fluid, breast milk, and saliva. This wider tissue presence of irisin suggests additional functions beyond its role as a myokine in regulating energy use. We are beginning to understand irisin in domestic animals. The goal of this review is to provide an up-to-date commentary on irisin structure, tissue distribution, and functions across vertebrates, especially mammals of importance in veterinary medicine. Irisin could be explored as a potential candidate for developing therapeutic agents and biomarkers in domestic animal endocrinology.

High-fat diet and palmitate inhibits FNDC5 expression via AMPK-Zfp57 pathway in mouse muscle cells

Irisin, a muscle-secreted cytokine involved in maintaining glucose homeostasis and improving insulin resistance, is generated from the precursor fibronectin type Ⅲ domain-containing protein 5 (FNDC5) by specific proteases. Zinc-finger protein Zfp57, a transcription factor that maintains the methylation during early embryonic development, is also reported to be associated with diabetes mellitus. However, the association between Zfp57 and FNDC5 is still unclear. In our study, we explored the detailed regulatory effect of Zfp57 on FNDC5 expression. In this study, we found that high-fat diet or saturated fatty acid palmitate increased the Zfp57 expression and decreased FNDC5 expression in muscle tissue or C2C12 myotubes. RNA sequencing analysis disclosed effects of the high-fat diet on genes associated with insulin resistance and the AMP-activated protein kinase (AMPK) signaling pathway in muscle tissue of mice. Chromatin immunoprecipitation experiments revealed that Zfp57 binds the FNDC5 gene promoter at positions -308 to -188. Moreover, Zfp57 overexpression inhibited FNDC5 expression, and Zfp57 knockdown alleviated the inhibitory effect of palmitate on FNDC5 expression in C2C12 myotubes. In addition, in vivo and in vitro studies demonstrated that activation of the AMPK pathway by 5-Aminoimidazole-4-carboxamide riboside (AICAR) or metformin mitigated the inhibitory effect of Zfp57 on FNDC5 expression and improved insulin resistance. These findings collectively suggest that high-fat diet and palmitate inhibit the AMPK pathway to increase Zfp57 expression, which in turn induces FNDC5 inhibition, to further aggravate insulin resistance.

Irisin is an Effector Molecule in Exercise Rehabilitation Following Myocardial Infarction (Review)

Background: Regular exercise is an effective non-pharmacological therapy for treatment and prevention of cardiovascular disease (CVD). The therapeutic benefits of exercise are mediated partly through improved vascular and increase in metabolic health. Release of exercise-responsive myokines, including irisin, is associated with beneficial effects of exercise in CVD patients.

Observations: The present review provides an overview of the role of exercise in cardiac rehabilitation of patients with myocardial infarction (MI). Further, the role of irisin as a motion-responsive molecule in improving vascular and metabolic health is explored. Possible mechanism of cardioprotective effect of irisin-mediated exercise on myocardial infarction are also summarized in this review.

Conclusion and significance of the review: Irisin is associated with reduced inflammation, antioxidant properties, and anti-apoptotic effect, implying that it is a potential key mediator of the beneficial effects of exercise on vascular and metabolic health. The findings show that irisin is a promising therapeutic target for treatment of patients with cardiovascular disease, particularly post-MI. Further research should be conducted to elucidate the potential mechanisms of cardioprotective effects of irisin and explored whether irisin induced by exercise exerts rehabilitation effects post-MI.

Effects of concurrent training on irisin and fibronectin type-III domain containing 5 (FNDC5) expression in visceral adipose tissue in type-2 diabetic rats

CONTEXT

Evidence suggests that myokines could have clinical implications for metabolic diseases such as type-2 diabetes.

OBJECTIVE

We investigated the effects of concurrent training (CT) on irisin and fibronectin type-III domain containing five (FNDC5) expressions in visceral adipose tissue (VAT) in type-2 diabetic rats.

MATERIALS AND METHODS

Eighteen male Wistar rats (ages four to eight weeks) became diabetic using nicotinamide and streptozotocin and were assigned to either a control (CON) or a CT group using a randomised block design. The CT group exercised on a motor-driven treadmill at 60 to 75 per cent of VO_2max (0% grade) for 10-40 min/day (aerobic training) and performed 10 climbs on a 1-meter ladder utilising weighted resistance of 30-100% of body mass (resistance exercise) for 5 days/week over 8 weeks. Forty-eight hours after the last training session, the VAT of rats was removed and washed. FNDC5-relative gene expression and irisin were measured by the reverse transcription polymerase chain reaction (RT-PCR) method and enzyme-linked immunosorbent assay (ELISA) kit. Additionally, insulin resistance and plasma insulin and glucose levels were determined.

RESULTS

Our findings revealed that CT significantly increased FNDC5-relative gene expression in the VAT of type-2 diabetic rats compared to controls. Furthermore, eight weeks of CT improved insulin resistance and insulin and glucose levels but did not significantly alter irisin levels in type-2 diabetic rats.

DISCUSSION AND CONCLUSION

The results of this study demonstrated that CT increased FNDC5 mRNA and improved insulin resistance, insulin, and glucose levels. Also observed were increased trends (non-significant, p = .051) in irisin levels. Hence, CT may play a role in attenuating metabolic disorders such as obesity and type-2 diabetes.

Insulin-Related Liver Pathways and the Therapeutic Effects of Aerobic Training, Green Coffee, and Chlorogenic Acid Supplementation in Prediabetic Mice

Background

The liver controls blood glucose levels via regulation of anabolic (glycogen synthesis and gluconeogenesis) and catabolic (glycolysis and glycogenolysis) processes through activation of the PI3K-AKT signalling pathway. The aim of this study was to assess the effect of aerobic training, green coffee, and chlorogenic acid supplementation on glucose metabolism-regulating pathways in prediabetic mice.

Methods

C57BL/6 mice were exposed to a high-fat diet and physical activity limitation to induce a state of prediabetes. After 12 weeks, mice were fed a high-fat diet compared to the control mice. The prediabetic mice were further treated with either green coffee, chlorogenic acid, or training or combinations of the same for 10 weeks. At the end of the experimental period, metabolic data (FBG, GTT, HOMA for IR, plasma level of insulinfrom systematic, AST, and ALT assessed into blood), histopathologic, and analysis of gene and protein expressions were obtained for target tissues.

Results

Training along with green coffee and chlorogenic acid supplementation improved complications of prediabetes including weight gain and elevated fasting blood glucose and plasma insulin levels. These effects were associated with the changes in mRNA levels of genes important in hepatic glycogen synthesis (GYS2), glucogenesis (PCK and G6PC2), and glycolysis (GK, PK, and PFKL).

Conclusion

The training in conjunction with green coffee or chlorogenic acid is effective in the prevention of prediabetes in mice. As these interventions are relatively inexpensive and safe application to individuals with prediabetes appears warranted.

Associations between rs3480 and rs16835198 gene polymorphisms of FNDC5 with type 2 diabetes mellitus susceptibility: a meta-analysis

BACKGROUND

FNDC5 is a novel and important player in energy regulation related to glucose metabolism and insulin levels. Thus, it may affect the incidence of type 2 diabetes mellitus (T2DM). Nevertheless, the association between FNDC5 single nucleotide polymorphisms (SNPs) and susceptibility to T2DM remains unclear. The aim of this meta-analysis was to explore whether the SNPs, rs3480 and rs16835198, are associated with the risk of T2DM.

METHODS

Studies published before February 1^st, 2022 were screened to identify the included studies. R software was also applied for calculation of odds ratio (OR), 95% confidence interval (95% CI), heterogeneity, and sensitivity analysis.

RESULTS

Seven studies for rs3480 (involving 5475 patients with T2DM and 4855 healthy controls) and five studies for rs16835198 (involving 4217 patients with T2DM and 4019 healthy controls) were included in this meta-analysis. The results revealed a statistically significant association of rs3480 with T2DM under homozygote (GG vs AA: OR = 1.76, 95% CI = 1.31-2.37, P = 0.0002, I² = 59%) genetic model. However, there was no statistically significant correlation between rs16835198 and susceptibility to T2DM under allelic (G vs T: OR = 1.33, 95% CI = 0.94-1.89, P = 0.11, I² = 84%), heterozygote (GT vs TT: OR = 1.17, 95% CI = 0.80-1.69, P = 0.42, I² = 71%), homozygote (GG vs TT: OR = 1.35, 95% CI = 0.95-1.94, P = 0.10, I² = 62%), recessive (GG+GT vs TT: OR = 1.25, 95% CI = 0.88-1.79, P = 0.22, I² = 72%), and dominant (GG vs GT+GG: OR = 1.20, 95% CI = 0.96-1.50, P = 0.11, I² = 46%) genetic models.

CONCLUSIONS

The present meta-analysis revealed that rs3480 in FNDC5 is significantly associated with susceptibility to T2DM, while rs16835198 does not show such an association.

Spontaneous Physical Activity in Obese Condition Favours Antitumour Immunity Leading to Decreased Tumour Growth in a Syngeneic Mouse Model of Carcinogenesis

Simple Summary

With aging, a deterioration of the immune system, termed immunosenescence, leads to a loss of innate and adaptive immunity in terms of number of cells and functionality. This results in an imbalance between pro- and anti-tumour immune response. The aim of the study was to explore the impact of physical activity on the tissue environment in a murine model of breast carcinogenesis. In this model, spontaneous physical activity slows tumour growth by decreasing low-grade inflammation and promotes antitumour immunity.

Abstract

Our goal was to evaluate the effect of spontaneous physical activity on tumour immunity during aging. Elderly (n = 10/group, 33 weeks) ovariectomized C57BL/6J mice fed a hyperlipidic diet were housed in standard (SE) or enriched (EE) environments. After 4 weeks, orthotopic implantation of syngeneic mammary cancer EO771 cells was performed to explore the immune phenotyping in the immune organs and the tumours, as well as the cytokines in the tumour and the plasma. EE lowered circulating myostatin, IL-6 and slowed down tumour growth. Spleen and inguinal lymph node weights reduced in relation to SE. Within the tumours, EE induced a lower content of lymphoid cells with a decrease in Th2, Treg and MDCS; and, conversely, a greater quantity of Tc and TAMs. While no change in tumour NKs cells occurred, granzyme A and B expression increased as did that of perforin 1. Spontaneous physical activity in obese conditions slowed tumour growth by decreasing low-grade inflammation, modulating immune recruitment and efficacy within the tumour.

Dietary Intervention, When Not Associated With Exercise, Upregulates Irisin/FNDC5 While Reducing Visceral Adiposity Markers in Obese Rats

Obesity is an epidemic disease and the expansion of adipose tissue, especially visceral fat, promotes the secretion of factors that lead to comorbidities such as diabetes and cardiovascular diseases. Thus, diet and exercise have been proposed as an intervention to reverse these complications. An adipocytokine, known as irisin, mediates the beneficial effects of exercise. It has been proposed as a therapeutic potential in controlling obesity. In view of the above, this paper attempts to determine the modulation of irisin, visceral adiposity and biochemical markers in response to dietary intervention and aerobic exercise. To do this, 52 diet-induced obese male Wistar rats were divided into the following four groups: high-fat diet and exercise (HFD-Ex); HFD-Sedentary (HFD-Sed); chow-diet and exercise (CD-Exercise); and CD-Sed. The exercise-trained group performed a treadmill protocol for 60 min/day, 3 days/week for 8 weeks. Body mass (BM), body fat (BF), fat mass (FM), and fat-free mass (FFM) were analyzed. Mesenteric (MES), epididymal (EPI), and retroperitoneal (RET) adipose tissue was collected and histological analysis was performed. Biochemical irisin, triglycerides, glucose, insulin and inflammatory markers were determined and, FNDC5 protein expression was analyzed. In this study, the diet was the most important factor in reducing visceral adiposity in the short and long term. Exercise was an important factor in preserving muscle mass and reducing visceral depots after a long term. Moreover, the combination of diet and exercise can enhance these effects. Diet and exercise exclusively were the factors capable of increasing the values of irisin/FNDC5, however it did not bring cumulative effects of both interventions. Prescriptions to enhance the obesity treatments should involve reducing visceral adiposity by reducing the fat content in the diet associated with aerobic exercise.

Fibronectin type III domain-containing 5 in cardiovascular and metabolic diseases: a promising biomarker and therapeutic target

Cardiovascular and metabolic diseases are the leading causes of death and disability worldwide and impose a tremendous socioeconomic burden on individuals as well as the healthcare system. Fibronectin type III domain-containing 5 (FNDC5) is a widely distributed transmembrane glycoprotein that can be proteolytically cleaved and secreted as irisin to regulate glycolipid metabolism and cardiovascular homeostasis. In this review, we present the current knowledge on the predictive and therapeutic role of FNDC5 in a variety of cardiovascular and metabolic diseases, such as hypertension, atherosclerosis, ischemic heart disease, arrhythmia, metabolic cardiomyopathy, cardiac remodeling, heart failure, diabetes mellitus, and obesity.

Aerobic exercise modulates noncoding RNA network upstream of FNDC5 in the Gastrocnemius muscle of high-fat-diet-induced obese mice

The purpose of the study was to determine the influence of aerobic exercise with a fat-rich diet on ncRNAs expression associated with FNDC5 in the Gastrocnemius muscle of the obese mice. Twenty-five male mice were grouped into two categories of normal diet (ND) and high-fat diet (HF) treatments for three months. For the subsequent treatment, HF-fed animals (obese) were proceeded in four groups: HF-Trained (n = 5), HF-Untrained (n = 5), ND-Trained (n = 5), and ND-Untrained (n = 5). Simultaneously, ND fed mice (n = 5) continued receiving normal diet and being untrained. In the training group, exercise was applied using a treadmill for 2 months. The Gastrocnemius muscle was excised for the assessment of FNDC5 mRNA, protein levels, and ncRNAs. Using bioinformatics tools, two potential miRNAs, miR-129-5p and miR-140-5p, and four lncRNAs constructing a network with FNDC5 were identified. Significant decrease was observed in both miR-129-5p and miR-140-5p in the HF-fed mice vs. ND-fed mice (p < 0.01). Significant increase of lncRNAs Meg3, Malat1, Neat1, and Kcnq1ot1 correlating in the network was also detected (p < 0.001 for all lncRNAs) in HF-fed mice and trained mice (p < 0.001 for Neat1, Meg3, and Kcnq1ot1). The present study suggests that an increase in the muscle FNDC5 of the high-fat diet mice is governed by an expression regulation of suggested ncRNAs, which were revealed by bioinformatics study to be involved in the insulin resistance and glucose homeostasis pathways.

MicroRNA-128 inhibits mitochondrial biogenesis and function via targeting PGC1α and NDUFS4

The size and morphology of mitochondria are very heterogeneous and correlates well with their healthy functioning. In many pathological conditions, mitochondrial morphology is altered due to impaired mitochondrial dynamics (a collective term for mitochondrial fusion and fission) and dysfunction. The current study aimed at identifying the role of microRNA-128 (miR-128) in regulating mitochondrial biogenesis. Previously, peroxisome proliferator activator receptor γ coactivator 1α (PGC1α) has been shown to co-activate key intermediates of mitochondrial biogenesis, function, and dynamics; however, the upstream regulatory network remains largely unknown. We, herein using in silico analysis followed by in vitro experiments in C2C12 myoblasts, showed that miR-128 reduces mitochondrial biogenesis by directly targeting PGC1α. The expression of downstream genes, nuclear respiratory factors 1 and 2 (NRF1 and NRF2, respectively), and mitochondrial transcription factor A (TFAM) were decreased in C2C12 myoblasts upon overexpression of miR-128. Also, miR-128 is shown to promote mitochondrial dysfunction by directly targeting NADH Dehydrogenase (Ubiquinone) Fe-S Protein 4 (NDUFS4). The mitochondrial dynamics and morphology were impaired post miR-128 overexpression, as revealed by downregulation of fusion proteins (mitofusin1 and 2, i.e., MFN1 and MFN2, respectively) and upregulation of fission protein (dynamin-related protein 1, i.e., DRP1). Conversely, inhibition of miR-128 expression improved mitochondrial biogenesis, function, and dynamics, as evidenced by increased mitochondrial mass and ATP production after antimiR-128 treatment. Our findings reveal that inhibition of miR-128 can be a new potential target for reversing the effects of metabolic disorders of skeletal muscle as observed during many pathophysiological conditions such as obesity and type II diabetes.

Modulation and bioinformatics screening of hepatic mRNA-lncRNAs (HML) network associated with insulin resistance in prediabetic and exercised mice

Background

Insulin resistance is associated with prediabetes and further progression to type 2 diabetes mellitus (T2DM). This study aims to investigate novel hepatic lncRNAs associated with key genes in insulin resistance in prediabetes.

Methods

In the bioinformatics phase, we have collected screened a pool of lncRNAs and mRNAs according to their potential association to prediabetic condition. We performed pathway analysis of mRNAs, using DAVID tool based on KEGG repository data. Then, we used Python programming language to get a subset of lncRNAs located in 50 kb proximity with high-fat (HF)-responsive mRNAs. In the experimental phase, prediabetic mice model was established by the treatment of HF diets for 12 weeks. After this treatment, HF-fed animals were divided into two groups of endurance exercised or sedentary, both continuing on the HF diet for 8 weeks. Besides, a group of diabetic mice was treated using a HF diet for 8 weeks followed by injection with STZ solution and then a HF diet for another 4 weeks.

Results

We found three genes having paired lncRNAs annotated in insulin resistance pathway. Their hepatic expression levels were altered in prediabetic condition as upregulation of Srebf1 was associated with GM38501, upregulation of Pck1 was associated with Ctcflos and GM36691, downregulation of Cpt1b was associated with GM44502. All of these expression patterns were replicated in diabetic mice, correlated positively with their predicted lncRNAs. Interestingly, exercise reversed their expression patterns.

Conclusions

We suggest that the expression pattern of the hepatic mRNA-lncRNA (HML) network in prediabetic state undergoes similar modification to that of diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00600-0.

Eight Weeks of High-Intensity Interval Static Strength Training Improves Skeletal Muscle Atrophy and Motor Function in Aged Rats via the PGC-1α/FNDC5/UCP1 Pathway

Background

Sarcopenia is a syndrome characterized by the loss of skeletal muscle mass and strength. Most studies have focused on dynamic resistance exercises for preventing muscular decline and maintaining the muscle strength of older individuals. However, this training mode is impractical for older people with osteoarthritis and a limited range of motion. The static strength training mode is more suitable for older people. Therefore, a determination of the effect and mechanism of static strength training on sarcopenia is critical.

Methods

In this study, we developed a training device designed to collect training data and evaluate the effects of static training on the upper limbs of rats. The expression of PGC-1α was locally blocked by injecting a siRNA at the midpoint of the biceps to determine whether PGC-1α signal transduction participates in the effects of high-intensity interval static training on muscle strength. Then, the rat’s motor capacity was measured after static strength training. Immunohistochemistry and Western blotting were applied to determine PGC-1α/FNDC5/UCP1 expression levels in the muscle and adipose tissue. The serum irisin level was also detected using an enzyme-linked immunosorbent assay (ELISA).

Results

Increased levels of serum irisin and local expression of FNDC5, PGC-1α, and UCP1 were observed in the biceps brachii and surrounding fatty tissue after static strength training. Static strength training showed an advantage in reducing body weight and white fat accumulation while increasing the muscle fiber volume, which resulted in a longer training time and shorter rest time.

Conclusion

Overall, these results indicated that high-intensity interval static training prevents skeletal muscle atrophy and improves the motor function of aged rats through the PGC-1α/FNDC5/UCP1 signaling pathway.

Diet-induced obesity in animal models: points to consider and influence on metabolic markers

Overweight and obesity are a worldwide public health problem. Obesity prevalence has increased considerably, which indicates the need for more studies to better understand these diseases and related complications. Diet induced-obesity (DIO) animal models can reproduce human overweight and obesity, and there are many protocols used to lead to excess fat deposition. So, the purpose of this review was to identify the key points for the induction of obesity through diet, as well as identifying which are the necessary endpoints to be achieved when inducing fat gain. For this, we reviewed the literature in the last 6 years, looking for original articles that aimed to induce obesity through the diet. All articles evaluated should have a control group, in order to verify the results found, and had worked with Sprague-Dawley and Wistar rats, or with C57BL-/-6 mice strain. Articles that induced obesity by other methods, such as genetic manipulation, surgery, or drugs were excluded, since our main objective was to identify key points for the induction of obesity through diet. Articles in humans, in cell culture, in non-rodent animals, as well as review articles, articles that did not have obesity induction and book chapters were also excluded. Body weight and fat gain, as well as determinants related to inflammation, hormonal concentration, blood glycemia, lipid profile, and liver health, must be evaluated together to better determination of the development of obesity. In addition, to select the best model in each circumstance, it should be considered that each breed and sex respond differently to diet-induced obesity. The composition of the diet and calorie overconsumption are also relevant to the development of obesity. Finally, it is important that a non-obese control group is included in the experimental design.

The Effect of Irisin as a Metabolic Regulator and Its Therapeutic Potential for Obesity

Obesity is a worldwide health problem due to the imbalance of energy intake and energy expenditure. Irisin, a newly identified exercise-responsive myokine, which is produced by the proteolytic cleavage of fibronectin type III domain-containing protein 5 (FNDC5), has emerged as a promising therapeutic strategy to combat obesity and obesity-related complications. Various studies in mice have shown that irisin could respond to systematic exercise training and promote white-to-brown fat transdifferentiation, but the role and function of irisin in humans are controversial. In this review, we systematically introduced and analyzed the factors that may contribute to these inconsistent results. Furthermore, we also described the potential anti-inflammatory properties of irisin under a variety of inflammatory conditions. Finally, the review discussed the existing unresolved issues and controversies about irisin, including the transcription of the irisin precursor FNDC5 gene in humans, the cleavage site of the yet unknown proteolytic enzyme that cleaves irisin from FNDC5, and the reliability of irisin levels measured with available detection methods.

Associations of Circulating Irisin with FNDC5 Expression in Fat and Muscle in Type 1 and Type 2 Diabetic Mice

Irisin is an exercise-induced myokine, suggested to exert beneficial effects on metabolism. However, the studies on the regulation of irisin secretion and the expression of its precursor FNDC5 have shown conflicting data. The discrepancies among previous correlation studies in humans are related to the heterogeneity of the study population. The fact that irisin is not only a myokine but also an adipokine leads to the further complexity of the role of irisin in metabolic regulation. In this study, we examined the regulation of FNDC5 expression and irisin in circulation in both type 1 and type 2 diabetic mice, and their potential relationships with metabolic parameters. In streptozotocin (STZ)-induced type 1 diabetic mice, high-fat diet (HFD)-induced obese mice and db/db mice, the circulating irisin as well as FNDC5 gene expression in subcutaneous fat was downregulated. Muscle FNDC5 expression was only significantly lower in STZ mice, and epididymal fat FNDC5 expression was unaltered. It is interesting to note that plasma irisin levels correlated positively with subcutaneous fat FNDC5 expression, but not epididymal fat or muscle. Moreover, both irisin levels and subcutaneous fat FNDC5 correlated negatively with markers of insulin resistance. These results suggest a regulatory role for subcutaneous fat-derived FNDC5/irisin in metabolic disease.

Evaluation of vascular endothelial growth factor A and leukemia inhibitory factor expressions at the time of implantation in diabetic rats following treatment with Metformin and Pioglitazone

Background

Implantation requires intimate crosstalk between the embryo and uterus for a successful establishment of pregnancy. Type 2 diabetes mellitus may lead to implantation failure. The effect of diabetes and its therapeutic drugs on implantation is still largely unclear.

Objective

To assess the endometrial expression changes of vascular endothelial growth factor A (VEGFA) and leukemia inhibitory factor (LIF), at the time of implantation in diabetic rats following treatment with Metformin and Pioglitazone.

Materials and Methods

Twenty-eight 6-8-wk-old Wistar female rats weighing 200-250 gr were divided into four groups (n = 7/each). Type 2 diabetes was induced and Metformin and Pioglitazone were applied for 4 wk. The expression of VEGFA and LIF was measured by real-time reverse transcription-polymerase chain reaction and Western blot.

Results

The relative expression of VEGFA transcript was higher in the diabetic (p = 0.02) and Metformin-treated (p = 0.04) rats compared to the control group. Furthermore, the VEGFA transcript level significantly reduced in Pioglitazone-treated diabetic rats (p = 0.03). LIF expression was elevated in the Metformin- and the Pioglitazone-treated rats and reduced in the diabetic group in comparison with the control group. Compared to the diabetic rats, the expression of LIF was significantly elevated in the Metformin- (p = 0.01) and Pioglitazone-treated (p = 0.03) groups.

Conclusion

The expressions of LIF and VEGFA were altered in diabetic rats during implantation which may be associated with diabetic-related infertility. Pioglitazone is able to restore the VEGFA and LIF expressions to their baseline levels more efficiently than Metformin.

Modulation of inter-organ signalling in obese mice by spontaneous physical activity during mammary cancer development

Accumulative evidence links breast cancer development to excess weight and obesity. During obesity, dysregulations of adipose tissue induce an increase in pro-inflammatory adipokine secretions, such as leptin and oestrogen secretions. Furthermore, a raise in oxidative stress, along with a decrease in antioxidant capacity, induces and maintains chronic inflammation, which creates a permissive environment for cancer development. Physical activity is recommended as a non-pharmacological therapy in both obese and cancer situations. Physical activity is associated with a moderation of acute inflammation, higher antioxidant defences and adipokine regulation, linked to a decrease of tumour-cell proliferation. However, the biological mechanisms underlying the relationship between oxidative stress, low-grade inflammation, carcinogenesis, obesity and physical activity are poorly understood. Our study is based on old, ovariectomised mice (C57BL/6J mice, 33 weeks old), fed with a high fat diet which increases adipose tissue favouring overweight and obesity, and housed in either an enriched environment, promoting physical activity and social interactions, or a standard environment constituting close to sedentary conditions. Our model of mammary carcinogenesis allowed for the exploration of tissue secretions and signalling pathway activation as well as the oxidative status in tumours to clarify the mechanisms involved in a multiple factorial analysis of the data set. The multiple factorial analysis demonstrated that the most important variables linked to moderate, spontaneous physical activity were the increase in growth factor (epithelial growth factor (EGF), hepatocyte growth factor (HGF)) and the activation of the signalling pathways (STAT3, c-jun n-terminal kinases (JNK), EKR1/2, nuclear factor-kappa B (NF-κB)) in the gastrocnemius (G). In inguinal adipose tissue, the NF-κB inflammation pathway was activated, increasing the IL-6 content. The adiponectin plasma (P) level increased and presented an inverse correlation with tumour oxidative status. Altogether, these results demonstrated that spontaneous physical activity in obesity conditions could slow down tumour growth through crosstalk between muscle, adipose tissue and tumour. A spontaneous moderate physical activity was able to modify the inter-organ exchange in a paracrine manner. The different tissues changed their signalling pathways and adipokine/cytokine secretions, such as adiponectin and leptin, resulting in a decrease in anti-oxidative response and inflammation in the tumour environment. This model showed that moderate, spontaneous physical activity suppresses tumour growth via a dialogue between the organs close to the tumour.

Effects of short-term exercise on food intake and the expression of appetite-regulating factors in goldfish

In mammals, growing evidence indicates that exercise affects food intake, metabolism and the expression and blood levels of appetite regulators. In this study, we examined the effects of short-term (30 min, at low and high water flow) exercise on food intake, glucose levels and the expressions of appetite regulators in goldfish hypothalamus (irisin, orexin, CART, leptin), intestine (CCK, PYY, proglucagon/GLP-1), muscle (irisin) and liver (leptin), of brain-derived neurotrophic factor (BDNF) in brain, interleukin-6 (IL6) in muscle and hypothalamus, and major metabolic enzymes, the glycolytic enzyme glucokinase (GCK) and its regulatory protein (GCKR) in liver, the lipolytic enzyme lipoprotein lipase in intestine and muscle, and trypsin in intestine. Fish submitted to high flow exercise had a lower post-exercise food intake compared to control fish but no differences were seen in glucose levels between groups. Exercise induced an increase in hypothalamic expression levels of CART, IL6 and BDNF, but not orexin, irisin, CRF, leptin and NPY. High flow exercise induced an increase in intestine CCK, PYY and GLP-1, and muscle irisin and IL-6 expression levels. Exercise had no effects on expression levels of hepatic leptin or any of the metabolic enzymes examined. Our results suggest that, in goldfish, short-term exercise might decrease feeding in part by affecting the expressions of myokines and peripheral, but not central appetite regulators or metabolic enzyme/hormones.

Mitochondrial Uncoupling: A Key Controller of Biological Processes in Physiology and Diseases

Mitochondrial uncoupling can be defined as a dissociation between mitochondrial membrane potential generation and its use for mitochondria-dependent ATP synthesis. Although this process was originally considered a mitochondrial dysfunction, the identification of UCP-1 as an endogenous physiological uncoupling protein suggests that the process could be involved in many other biological processes. In this review, we first compare the mitochondrial uncoupling agents available in term of mechanistic and non-specific effects. Proteins regulating mitochondrial uncoupling, as well as chemical compounds with uncoupling properties are discussed. Second, we summarize the most recent findings linking mitochondrial uncoupling and other cellular or biological processes, such as bulk and specific autophagy, reactive oxygen species production, protein secretion, cell death, physical exercise, metabolic adaptations in adipose tissue, and cell signaling. Finally, we show how mitochondrial uncoupling could be used to treat several human diseases, such as obesity, cardiovascular diseases, or neurological disorders.

Effect of aerobic exercise, low-fat and high-fat diet on the testis tissue and sperm parameters in obese and nonobese mice model

Semen quality and male fertility depend on numerous factors such as age, environment, lifestyle, physical activity, genetic background and occupation. We aimed to access the effect of aerobic exercise, low- and high-fat diet on mice testis tissue, and sperm function. Obese and nonobese male mice C57BL/6 were exposed to high fat (Hf) or low fat (Lf) and/or activity (Exe: exercise or Sed: sedentary). Finally, testicular morphometric characteristics, sperm concentration and motility (light microscopy), sperm morphology (eosin/nigrosin dye), lipid peroxidation (BODIPY C11 Probe), chromatin (acridine orange and chromomycin A3 staining) were compared within obese groups (Hf/Exe, Lf/Exe, Lf/Sed, Hf/Sed) and nonobese groups (Hf/Exe, Lf/Exe, Lf/Sed, Hf/Sed). Both exercise and diet interventions did not show any alteration in testicular morphological characteristics, sperm morphology and DNA fragmentation within both obese and nonobese groups (p > 0.05). Exercise and/or diet resulted in a significant increase in sperm concentration and motility within both groups (p < 0.05). Exercise in both groups leads to high percentage of lipid peroxidation (p < 0.05). Exercise intervention significantly improved sperm protamine deficiency within obese group (p < 0.05). We concluded that exercise intervention was more effective than diet in improvement of sperm function within obese groups.

FNDC5: A novel player in metabolism and metabolic syndrome

Half a decade ago, transmembrane protein fibronectin type III domain-containing protein 5 (FNDC5) was found to be cleaved as a novel myokine irisin, which burst into prominence for browning of white adipose tissue during exercise. However, FNDC5, the precursor of irisin, has been paid relatively little attention compared with irisin despite evidence that FNDC5 is associated with the metabolic syndrome, which accounts for one-fourth of the world's adult population and contributes to diabetes, cardiovascular disease and all-cause mortality. Besides N-terminal and C-terminal sequences, the FNDC5 protein contains an irisin domain and a short transmembrane region. FNDC5 has shown to be widely distribute in different tissues and is highly expressed in heart, brain, liver, and skeletal muscle. Clinical studies have demonstrated that FNDC5 is essential for maintaining metabolic homeostasis and dysregulation of FNDC5 will lead to systemic metabolism imbalance and the onset of metabolic disorders. Growing evidence has suggested that FNDC5 gene polymorphisms are related to health and disease in different human populations. Additionally, FNDC5 has been found relevant to the regulation of metabolism and metabolic syndrome through diverse upstream and downstream signaling pathways in experimental studies. The present review summarizes the characteristics, clinical significance, and molecular mechanisms of FNDC5 in metabolic syndrome and proposes a novel concept that FNDC5 is activated by forming a putative ligand-receptor complex. Knowledge about the role of FNDC5 may be translated into drug development and clinical applications for the treatment of metabolic disorders.

A comparative study on the effects of acute and chronic downhill running vs uphill running exercise on the RNA levels of the skeletal muscles PGC1-α, FNDC5 and the adipose UCP1 in BALB/c mice

The purpose of this study was to investigate the effect of a single bout and 8 weeks of downhill running versus uphill running exercise on expression of PGC1-α, FNDC5 and UCP1 in mice. Forty-eight BALB/c male mice weighing 25-30 g were randomly assigned into 8 groups: 1) acute downhill running (ADR) on a -15° slope; 2) acute uphill running (AUR) on a +15° slope; 3) acute running without inclination (AWI), 4) acute without exercise as control (ACtrl), 5) chronic downhill running (CDR) on a -15° slope; 6) chronic uphill running (CUR) on a +15°slope; 7) chronic running without inclination (CWI), 8) chronic without exercise as control (CCtrl). Twenty four hours after the last training session, the mice were sacrificed and Calf muscles (including soleus and gastrocnemius) and quadriceps muscles (including Rectus femoris and vastus intermedius) were obtained and expression levels of PGC1-α and FNDC5 in crus and quadriceps muscles and UCP1 in visceral and subcutaneous adipose tissues were measured and compared between the groups. PGC-1α and FNDC5 mRNA levels increased after treadmill exercise training in all acute and chronic exercise groups in both skeletal muscle groups. Furthermore mRNA level of UCP1 in subcutaneous adipose tissue but not in visceral adipose tissue increased both after acute and chronic exercise. Collectively, data showed that downhill running exercise to be more effective than other exercises, as downhill running has led to a greater improvement in metabolism may be considered more effective for browning of fat tissue.