Evaluation of circulating irisin levels in healthy young individuals after a single 100,000IU vitamin D dose

The impact of vitamin D on type 2 diabetes management: boosting PTP1B gene expression and physical activity benefits in rats

BACKGROUND

The protein tyrosine phosphatase 1B (PTP1B) plays a crucial role in the development of insulin resistance. Aerobic training (AT) and vitamin D (Vit D) supplementation have been shown to individually improve glucose tolerance and diabetes-related factors. However, the impact of their combined effect on PTP1B gene expression and serum irisin in the visceral adipose tissue remains unknown. This study aims to investigate whether 8 weeks of combined AT with Vit D supplementation can improve the expression of PTP1B in adipose tissue and serum irisin in obese rats with type 2 diabetes (T2D).

METHODS

Fifty male Wistar rats were divided into two groups: diabetic (n = 40) and non-diabetic (ND; n = 10). The diabetic rats were further divided into four groups: aerobic training with vitamin D supplementation (D + AT + Vit D; n = 10), aerobic training only (D + AT; n = 10), vitamin D supplementation only (D + Vit D; n = 10), and control (D + C; n = 10). The D + Vit D and D + AT + Vit D groups received 5000 IU of vitamin D via injection once a week, while the D + AT and D + C groups received sesame oil. Diabetes was induced in all groups except the nondiabetic group by intraperitoneal (IP) injection of streptozotocin. At the end of the intervention, blood and adipose tissue samples were collected, and RNA was extracted from adipose tissue for real-time PCR analysis of PPTP1B gene expression.

RESULTS

There was an increase in serum Vit D and irisin levels and a decrease in HOMA-IR and PTP1B gene expression in the diabetic rat model treated with D + AT and injected with 50,000 IU/kg/week of Vit D. Comparatively, when treated with D + AT + Vit D, the downregulation of PTP1B was significantly higher (p = 0.049; p = 0.004), and there was a significant increase in irisin (p = 0.010; p = 0.001).

CONCLUSION

The present study shows that the combined AT and Vit D supplementation positively impacts the expression of PTP1B in adipose tissue and serum irisin in rats with T2D. These findings suggest that combining AT with Vit D supplementation can provide a new and effective strategy to improve glucose tolerance and diabetes-related factors in individuals with T2D by regulating the expression of PTP1B in adipose tissue and promoting the synthesis of beneficial irisin protein.

Irisin and Secondary Osteoporosis in Humans

Irisin is a peptide secreted by skeletal muscle following exercise that plays an important role in bone metabolism. Numerous experiments in vitro and in mouse models have shown that the administration of recombinant irisin promotes osteogenesis, protects osteocytes from dexamethasone-induced apoptosis, prevents disuse-induced loss of bone and muscle mass, and accelerates fracture healing. Although some aspects still need to be elucidated, such as the dose- and frequency-dependent effects of irisin in cell cultures and mouse models, ample clinical evidence is emerging to support its physiological relevance on bone in humans. A reduction in serum irisin levels, associated with an increased risk of osteoporosis and bone fractures, was observed in postmenopausal women and in both men and women during aging, Recently, cohort studies of subjects with secondary osteoporosis showed that these patients have lower circulating levels of irisin, suggesting that this myokine could be a novel marker to monitor bone quality in this disease. Although there are still few studies, this review discusses the emerging data that are highlighting the involvement of irisin in some diseases that cause secondary osteoporosis.

Diagnosis and management of vitamin D deficiency in the Gulf Cooperative Council (GCC) countries: an expert consensus summary statement from the GCC vitamin D advisory board

OBJECTIVE

A summary of recommendations is given within the Gulf Cooperation Council (GCC) setting on the assessment and management of vitamin D deficiency in the region.

METHODS

An assembly of 11 regional experts gathered to formulate an all-inclusive approach to vitamin D deficiency within GCC.

RESULTS AND CONCLUSION

Several gaps were identified before regional guidelines could be developed. These include adequacy and standardization of vitamin D testing, frequency of repeated testing and reference ranges, distinguishing prevention from the treatment of vitamin D deficiency, quality assurance of vitamin D products sold within GCC including contents and origins of products, and cut-points for vitamin D levels in local populations. A platform is created that can be further developed for overall regional implementation.

Vitamin D supplementation improves SIRT1, Irisin, and glucose indices in overweight or obese type 2 diabetic patients: a double-blind randomized placebo-controlled clinical trial

BACKGROUND

Vitamin D (VD) may increase sirtuin 1 (SIRT1) and subsequently PPAR-γ coactivator 1α (PGC-1α) and irisin levels and these improvements may reduce insulin resistance (IR). The aim was to assess the effects of vitamin D supplementation on SIRT1, irisin, and IR in overweight/obese type 2 diabetes (T2D) patients.

METHODS

Ninety T2D males and females were recruited as a clinical trial study (mean of age and body mass index (BMI) of intervention and placebo groups were 50.05 ± 10.17 and 50.36 ± 10.2 yrs. and 31.37 ± 3.4 and 30.43 ± 3.2 kg/m², respectively). The inclusion criteria were T2D, VD deficient, BMI > 25 kg/m², and serum HbA1c < 8.5%. The exclusion criteria were using vitamin and mineral supplements, having any acute disease, recent modifying dose or type of drugs. The supplementation was 50,000 IU/week VD or placebo for 8 weeks. The demographic characteristics, anthropometrics, dietary intakes and physical activity status, sun exposure status, fasting blood sugar (FBS) and insulin, glycosylated hemoglobin (HbA1c), irisin, SIRT1, 25-hydroxy D3 (25(OH)VD), homeostasis model assessment of insulin resistance (HOMA-IR), and quantitative insulin sensitivity check index (QUICKI) were determined. The significant P-value was ≤0.05.

RESULTS

The increase of serum VD, SIRT1, and irisin in the intervention group was significant (p < 0.001). HbA1c was decreased significantly by 1%. The changes in the other glucose indices (FBS, insulin, and IR) were non-significant.

CONCLUSIONS

VD supplementation may improve T2D by decreasing HbA1c and increasing SIRT1 and irisin in VD deficient T2D patients. Further trials are suggested.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials, IRCT201604202365N11. Registered 21/08/2016, http://en.irct.ir/trial/2019.

Upregulation of FNDC5 gene expression in C2C12 cells after single and combined treatments of resveratrol and ATRA

Background

Irisin is a newly discovered myokine that secreted from skeletal muscle cells. Several studies showed that irisin involves in thermogenesis and increases the expression of browning markers such as uncoupling protein-1 that in turns induces the conversion of white adipose tissue to brown fat. Resveratrol (Res) and all-trans retinoic acid (ATRA) can also upregulate the expression of thermogenesis genes. In the present study, the effects of single and combined treatments of Res and ATRA on fibronectin type III domain containing 5 (FNDC5) gene expression was explored.

Methods

The mouse myoblasts, C2C12 cells, were seeded in 6-well plastic plates and cultured in DMEM media. After differentiation, in a pilot study, C2C12 myotubes were treated with different concentrations of Res and ATRA for 12 h. The best result was obtained by treatment of 1and 25 μM of Res and 1 μM of ATRA. Then the main study was continued by single and combined treatment of these compounds at chosen concentration. After treatments, total RNA was extracted from C2C12 cells. Complementary DNA (cDNA) was generated by the cDNA synthesis kit and FNDC5 mRNA expression was evaluated by the real-time PCR method.

Results

The FNDC5 gene expression in C2C12 myotubes of alone-treated with 1 μM, 25 μM Res and 10 μM ATRA did not change compared to vehicle group. However, in combination-treated the expression of FNDC5 gene was significantly increased compared to vehicle group.

Conclusion

This is the first evidence that Res and ATRA can regulate FNDC5 gene expression in C2C12 myotubes. More investigations are necessary to explore the therapeutic effects of these nutrients in obesity, diabetes, cardiac and neurovascular disease.

Irisin Maternal Plasma and Cord Blood Levels in Mothers with Spontaneous Preterm and Term Delivery

Irisin, an adipomyokine identified in 2012, has been investigated in association with common pregnancy complications, including gestational diabetes mellitus, preeclampsia, and intrauterine growth restriction. The objective of this study is to examine the potential role of irisin in preterm birth (PTB) by comparing its level between mothers with term and preterm labor. Maternal peripheral blood and cord blood samples were collected from 30 mothers who delivered prematurely and from 35 mothers who delivered at term. Irisin concentrations were measured in all samples using ELISA, and four common single nucleotide polymorphisms in the irisin gene were determined (rs16835198, rs726344, rs3480, and rs1746661). Univariable and multivariable regression modeling was applied to evaluate maternal and cord blood irisin concentrations in relation to preterm/term labor. Irisin concentration in umbilical cord blood was found to be associated with PTB in the univariable model (p = 0.046). On the other hand, no differences in maternal blood irisin levels between mothers with preterm and term deliveries were established. To the best of our knowledge, this is the first study determining irisin levels in term and preterm deliveries in maternal peripheral blood and umbilical cord blood. Our study shows a possible association between cord blood irisin concentration and PTB occurrence.