Serum Irisin Level is Higher and Related with Insulin in Acanthosis Nigricans-related Obesity

The Effects of Obesity, Six Weeks of Aerobic Training, and Cold Water Exposure on the Expression of FNDC5 and UCP1 Genes in Male Wistar Rats

Background

Obesity is a complex disease that has become increasingly prevalent. While obesity itself is not new, its widespread occurrence is a more recent concern. Stimulating brown adipose tissue (BAT) and promoting the browning of white adipose tissue (bWAT) have shown promise as therapeutic targets to increase energy expenditure and counteract weight gain.

Objectives

This study aimed to investigate two main aspects. First, we examined how obesity affects the expression of the fibronectin type-III domain containing 5 (FNDC5) and uncoupling protein 1 (UCP1) genes in male Wistar rats. Second, we assessed the effects of six weeks of aerobic exercise, exposure to cold water, and the combination of both on the expression of the FNDC5 and UCP1 genes in obese male Wistar rats.

Methods

In this experiment, 25 male Wistar rats were randomly assigned to five groups (5 rats per group) after inducing obesity. The groups included: A control group (C), an obesity group (O), an obesity group exposed to cold water (OC), an obesity group engaged in aerobic exercise (OE), and an obesity group exposed to both cold water and aerobic exercise (OCE). The aerobic exercise sessions lasted 30 - 60 minutes, with a speed of 15 - 25 meters per minute. The cold water exposure protocol involved shallow water (2 - 4 cm) with a temperature of 14 - 18°C. The OCE group performed both aerobic and cold water exercises in each session. The expression of the FNDC5 gene in the soleus muscle and the FNDC5 and UCP1 genes in subcutaneous fat was evaluated using Real-Time PCR. All statistical analyses were performed using SPSS software version 16, with a significance level set at P ≤ 0.05.

Results

Obesity significantly increased the expression of the FNDC5 gene (P = 0.008). After six weeks of aerobic exercise (P = 0.016) or cold water exposure (P = 0.016), there was a significant decrease in FNDC5 gene expression. Surprisingly, the combination of both interventions did not result in a significant effect (P = 0.75). On the other hand, none of the interventions-whether aerobic exercise, cold water exposure, or their combination-had a significant effect on the expression of the UCP1 gene (P > 0.05).

Conclusions

The increase in FNDC5 gene expression caused by obesity may serve as a compensatory mechanism to cope with the condition. However, both cold water exposure and aerobic exercise appear to mitigate this increase in FNDC5 gene expression through enhanced thermogenesis.

The role of a recently discovered peptide—irisin—in physiological and pathological processes

Irisin, a cleaved fragment of fibronectin type III domain-containing protein 5 (FNDC5), was originally described as a factor stimulating browning of white adipose tissue, produced during physical exercise by skeletal muscles. However, irisin is not only a new and promising biomarker of metabolism; its expression has been found in a wide variety of tissues and organs such as the peripheral nerves, stomach, pancreas, and skin, and recent data also indicate its role in cancer. Numerous studies focus on the protective role of this protein, which could become an important factor in predicting disease risk, disease prognosis, or possible metastases in cancer patients. Possible use of irisin in therapy is also worth considering. The aim of this paper is to systematize knowledge on the role of irisin in patients and to draw attention to its role in skin diseases including acne vulgaris, psoriasis vulgaris, and hidradenitis suppurativa.

Serum irisin level, insulin resistance, and lipid profiles in patients with hidradenitis suppurativa: a case-control study

Background

Hidradenitis suppurativa is a chronic inflammatory skin disease of terminal follicular acroinfundibulum.

Objectives

This study aimed to evaluate serum irisin, plasma glucose, insulin, and lipid levels in hidradenitis suppurativa, and elucidate possible associations with disease activity, inflammatory, or metabolic parameters.

Methods

This case-control study included 37 patients (M/F: 9/28) and 37 sex-, age- and body mass index -matched healthy controls (M/F: 11/26). Demographic data, Hurley stage of disease, fasting glucose, insulin, total cholesterol, high density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, C-reactive protein levels, erythrocyte sedimentation rate, hematologic parameters, and serum irisin were assessed.

Results

The hidradenitis suppurativa group had significantly higher waist circumference than controls (p < 0.001). Insulin resistance, defined as a homeostatic model assessment for insulin resistance value greater than 2.5, was observed in 45.9% of patients and 8.1% of controls (p = 0.003), whereas metabolic syndrome was observed in 32.4% of patients and 5.4% of controls (p < 0.001). Furthermore, plasma triglycerids, glucose, and insulin levels were significantly higher in the hidradenitis suppurativa (p = 0.013, p = 0.001, and p = 0.004), respectively. Mean irisin level was insignificantly higher in the hidradenitis suppurativa group (37.4 ± 32.6) than in controls (26.2 ± 24.7, p = 0.217).

Study limitation

Physical activity and the exercise levels of participants were not documented.

Conclusion

This study indicates that hidradenitis suppurativa patients have higher serum irisin, fasting plasma glucose, insulin, and triglycerides levels than healthy controls. Thus, the authors suggest that hidradenitis suppurativa patients should be evaluated for insulin resistance and metabolic syndrome, and monitored accordingly.

Relationship between circulating irisin levels and overweight/obesity: A meta-analysis

BACKGROUND

Currently, the findings about irisin as a novel myokine related to obesity are inconsistent in overweight/obese people. To our knowledge, no systematic analysis has been conducted to evaluate the relationship between irisin levels and overweight/obesity.

AIM

To evaluate the association between circulating irisin levels and overweight/obesity.

METHODS

The Cochrane Library, MEDLINE, SCOPUS, and the ISI Web of Science were searched to retrieve all of the studies associated with circulating irisin levels and overweight/obesity. Standard mean difference values and 95% confidence intervals (CI) were estimated and pooled using meta-analysis methodology.

RESULTS

A total of 18 studies were included in our meta-analysis containing 1005 cases and 1242 controls. Our analysis showed that the circulating irisin level in overweight/obese people was higher than that in overall healthy controls (random effects MD = 0.63; 95%CI: 0.22-1.05; P = 0.003). In the subgroup analysis by ethnicity, the irisin level was higher in overweight/obesity people than that in controls in Africa (random effects MD = 3.41; 95%CI: 1.23-5.59; P < 0.05) but not in European, Asian, or American populations. In addition, in a subgroup analysis by age, the results showed that obese children exhibited a higher irisin level than controls (random effects MD = 0.86; 95%CI: 0.28-1.43; P < 0.05).

CONCLUSION

This meta-analysis provides evidence that circulating irisin is higher in obese individuals compared to healthy controls and it is important to identify the relationship between circulating irisin levels and overweight/obesity in predicting overweight/obesity.

Metabolic syndrome and the skin: a more than superficial association. Reviewing the association between skin diseases and metabolic syndrome and a clinical decision algorithm for high risk patients

There is ongoing scientific interest regarding comorbidities associated with the metabolic syndrome (MeTS). MeTS comprises a combination of parameters that predispose individuals to the development of type 2 diabetes and cardiovascular disease (CVD). Three or more of the following criteria are necessary: fasting glucose > 110 mg/dl (5.6 mmol/l), hypertriglyceridemia > 150 mg/dl (1.7 mmol/l), HDL levels < 40 mg/dl (men)/< 50 mg/dl (women), blood pressure > 130/85 mmHg, waist circumference (values for Mediterranean populations > 94 cm (men)/> 89 cm (women). In this review we attempted to summarize relevant data by searching dermatological literature regarding associations between various skin conditions and MeTS. A multitude of studies was retrieved and a further goal of the present article is to present plausible mechanistic connections. The severity of skin conditions like psoriasis has been linked with MeTS. Parameters of MeTS like insulin resistance are present in patients with early onset androgenic alopecia, hidradenitis suppurativa acne and rosacea. Since MeTS can lead to CVD and type 2 diabetes early detection of patients would be very important. Also therapeutic intervention on MeTS could lead to improvement on the severity of skin conditions. This reciprocal relationship between skin diseases and MeTS in our opinion holds great interest for further investigation.

Physiology and role of irisin in glucose homeostasis

Irisin is a myokine that leads to increased energy expenditure by stimulating the 'browning' of white adipose tissue. In the first description of this hormone, increased levels of circulating irisin, which is cleaved from its precursor fibronectin type III domain-containing protein 5, were associated with improved glucose homeostasis by reducing insulin resistance. Consequently, several studies attempted to characterize the role of irisin in glucose regulation, but contradictory results have been reported, and even the existence of this hormone has been questioned. In this Review, we present the current knowledge on the physiology of irisin and its role in glucose homeostasis. We describe the mechanisms involved in the synthesis, secretion, circulation and regulation of irisin, and the controversies regarding the measurement of irisin. We also discuss the direct effects of irisin on glucose regulatory mechanisms in different organs, the indirect effects and interactions with other hormones, and the important open questions with regard to irisin in those organs. Finally, we present the results from animal interventional studies and from human clinical studies investigating the association of irisin with obesity, insulin resistance, type 2 diabetes mellitus and the metabolic syndrome.

Circulating Levels of Irisin in Hypopituitary and Normal Subjects

Context

The recently identified myokine irisin conveys some of the benefits of exercise. Hypopituitarism with adult growth hormone deficiency (HP) is a situation characterized by decreased GH secretion and an altered body composition.

Objective

Our aim was to study the skeletal muscle hormone irisin in HP, and compare the results with a similar group of normal subjects.

Participants and Methods

Seventeen HP patients and fifty-one normal subjects of similar age and sex were studied. The diagnosis of GH deficiency was confirmed by the presence of pituitary disease and a peak GH secretion below 3 μg/L after an insulin tolerance test. The patients were adequately treated for all pituitary hormone deficits, except for GH. Fasting serum irisin was measured with an enzyme immunoassay, and HOMA-IR, QUICKI and HOMA-β were calculated.

Results

Fasting irisin levels (ng/ml) were similar in normal [208.42 (168.44–249.23)] and HP patients [195.13 (178.44–241.44)]. In the control group there were moderate significant positive correlations between irisin and BMI, waist circumference, leptin, fasting insulin, HOMA-IR, HOMA-β, triglycerides, and cholesterol. In the control group there were moderate significant negative correlations between irisin and IGF-I and QUICKI. In the hypopituitary group there were moderate significant positive correlations between irisin and body fat and HOMA-β.

Conclusions

We found similar irisin levels in GH deficiency hypopituitary patients when compared with normal subjects. The correlation between irisin and adiposity related factors suggests that that in the case of this clinical model, irisin is regulated by adiposity and not by GH.