Context There is evidence demonstrating variation in insulin sensitivity across the menstrual cycle. However, to date, research has yielded inconsistent results. Objective This study investigated variation in insulin sensitivity across the menstrual cycle and associations with BMI, physical activity and cardiorespiratory fitness. Design Data from 1906 premenopausal women in NHANES cycles 1999-2006 were analysed. Main outcome measures Menstrual cycle day was assessed using questionnaire responses recording days since last period. Rhythmic variation of plasma glucose, triglyceride and insulin, homeostatic model of insulin resistance (HOMA-IR) and adipose tissue insulin resistance index (ADIPO-IR) across the menstrual cycle were analysed using cosinor rhythmometry. Participants were assigned low or high categories of BMI, physical activity and cardiorespiratory fitness and category membership included in cosinor models as covariates. Results Rhythmicity was demonstrated by a significant cosine fit for glucose (p= 0.014) but not triglyceride (p= 0.369), insulin (p= 0.470), HOMA-IR (p=0.461) and ADIPO-IR (p= 0.335). When covariates were included, rhythmicity was observed when adjusting for: 1. BMI: glucose (p< 0.001), triglyceride (p< 0.001), insulin (p< 0.001), HOMA-IR (p< 0.001) and ADIPO-IR (p< 0.001); 2. Physical activity: glucose (p< 0.001), triglyceride (p= 0.006) and ADIPO-IR (p= 0.038); 3. Cardiorespiratory fitness: triglyceride (p= 0.041), insulin (p= 0.002), HOMA-IR (p= 0.004) and ADIPO-IR (p= 0.004). Triglyceride amplitude, but not acrophase, was greater in the high physical activity category compared to low (p=0.018). Conclusions Rhythmicity in insulin sensitivity and associated metabolites across the menstrual cycle are modified by BMI, physical activity and cardiorespiratory fitness.

Cyclical changes in hormone profiles across the menstrual cycle are associated with alterations in metabolic control. MicroRNAs (miRNA) contribute to regulating metabolic control, including adipose tissue metabolism. How fluctuations in hormonal profiles across the menstrual cycle affect adipose tissue miRNA expression remain unknown. Eleven healthy, regularly menstruating females underwent four sampling visits across their menstrual cycle. Subcutaneous abdominal adipose tissue and venous blood samples were collected each at sampling visit. Luteinizing hormone (LH) tests, calendar counting, and serum hormone concentrations were used to determine menstrual cycle phases: early-follicular (EF); late-follicular (LF); post-ovulatory (PO) and mid-luteal (ML). Serum follicle-stimulating hormone, LH, estrogen, progesterone and testosterone were determined using multiplex magnetic bead panels and enzyme-linked immunosorbent assays. Global adipose tissue miRNA expression levels were determined via microarray in a subset of participants (N=8) and 17 candidate miRNAs validated by RT-qPCR in the whole cohort (N=11). Global analysis of adipose tissue miRNA expression identified 33 miRNAs significantly altered across the menstrual cycle; however, no significant differences remained after correcting for multiple testing (p>0.05). RT-qPCR analysis of candidate miRNAs revealed miR-497-5p expression was significantly altered across the menstrual cycle (np2=0.18, p=0.03); however, post-hoc tests did not reveal any significant differences between menstrual cycle phases (p> 0.05). miR-30c-5p associated with testosterone concentration (R2=0.13, p=0.033). These pilot data indicate differences in adipose tissue miRNAs in healthy women across the menstrual cycle and a weak association with ovarian hormones. Further research in larger sample sizes is required to confirm regulation of miRNA expression across the menstrual cycle.

and associated video demonstrate a percutaneous biopsy technique to obtain samples of subcutaneous adipose tissue from areas surrounding the umbilicus. This method is a low-risk and efficient way to investigate a range of parameters (e.g., gene or protein expression, enzyme activity, lipid content) within adipose tissue. ABSTRACT:Studies on adipose tissue are useful in understanding metabolic and other conditions. Human subcutaneous adipose tissue is accessible. With appropriate training and strict adherence to aseptic technique, subcutaneous adipose samples can be safely and efficiently obtained in a nonclinical setting by researchers. Following the administration of local anesthetic lateral to the umbilicus, a 14 G needle attached to a 5 or 10 mL syringe is inserted through the skin into the subcutaneous tissue. Under suction, the syringe is moved in a reciprocating, slicing motion to isolate fragments of adipose tissue. Withdrawing the plunger is enough to ensure that adipose tissue fragments are aspirated through the needle into the syringe. A single biopsy can collect about 200 mg of tissue. This biopsy technique is very safe for both participants and research staff. Following the biopsy, participants can resume most everyday activities, although they should avoid swimming and overly strenuous activities for 48 h to avoid excessive bleeding. Participants can safely undergo 2 biopsies within a single day, meaning that the technique can be applied in before-after acute intervention studies. INTRODUCTION:Adipose tissue can provide useful information on the metabolic function of humans. Human subcutaneous adipose tissue is readily accessible. A technique for subcutaneous adipose tissue

Objective: Cell-free microRNAs (cf-miRNAs) are secreted from cells and transported via the blood to exert their effect on target tissues. Numerous pathophysiological adaptations, including exercise, alter cf-miRNA levels. The aim of the systematic review was to investigate the cf-miRNA response to an acute bout of exercise and to interpret it using a robust correlated and hierarchical effects (CHE) meta-analysis. Design: The systematic review was registered in PROSPERO (CRD42021256303). A CHE meta-analysis was used to compare the changes in cf-miRNA levels and the influence of exercise modality. An exploratory machine-learning-based approach was used to capture influential moderators. Data sources: Primary studies were retrieved from PubMed and SPORTDiscus (09.03.2022). Relative changes in cf-miRNA expression in response to exercise were computed for each study. The ROBINS-I, GRADE and AMSTAR2 tools were used to assess evidence certainty and risk of bias. Eligibility criteria: Thirty-six studies including an acute exercise intervention in N=880 healthy males and females aged 18-45yrs met the eligibility criteria. Results: Muscle enriched cf-miR-1 (N=320), cf-miR-133a (N=195) and cf-miR-133b (N=132) levels increased 1-2hr (cf-miR1: FC = 2.72, 95% CI= 1.5-4.0; cf-miR133a: FC = 2.10, 95% CI = 1.6-2.6; cf-miR-133b: FC = 2.39, 95% CI = 1.2-3.6) and 24 hr post-exercise (cf-miR1: FC = 2.25, 95% CI= 1.3-3.2; cf-miR133a: FC = 1.81, 95% CI = 1.4-2.2; cf-miR-133b: FC = 1.99, 95% CI = 1.2-2.8). Conclusion: Acute exercise triggers temporal and modality specific responses in cf-miRNAs. levels. Influential moderators included sample size, collection time point, exercise modality, age and the use of various technical quality controls.