Association of fat mass profile with natriuretic peptide receptor alpha in subcutaneous adipose tissue of medication-free healthy men: A cross-sectional study

Background: Atrial natriuretic peptide increases lipolysis in human adipocytes by binding to natriuretic peptide receptor-A (NPRA). The aim of the current study was to examine the associations of NPRA mRNA of subcutaneous adipose tissue with fat mass, fat-free mass, body mass index (BMI) and arterial blood pressure in medication-free healthy men. Method: Thirty-two volunteers [age (years): 36.06±7.36, BMI: 27.60±4.63 (kg/m2)] underwent assessments of body height/weight, % fat mass, fat-free mass (kg), blood pressure, and a subcutaneous adipose tissue biopsy via a surgical technique. Results: We found that NPRA mRNA was negatively associated with % fat mass (r=-0.40, R2=0.16, p=0.03) and BMI (r=-0.45, R2=0.20, p=0.01). Cohen’s f2 effect size analyses showed a small effect size between NPRA mRNA and BMI (f2=0.25). One-way analysis of variance with Bonferroni post-hoc tests showed a tendency for mean differences of NPRA mRNA across BMI categories (p=0.06). This was confirmed by Cohen’s d effect size analyses revealing a large effect size of NPRA mRNA between obese individuals (BMI≥30 kg/m2) and either normal weight (BMI=19-25 kg/m2; d=0.94) or overweight (BMI=25-30 kg/m2; d=1.12) individuals. Conclusions: NPRA mRNA is negatively associated with % fat mass and BMI in medication-free healthy men, suggesting a possible role of NPRA in the control of fat mass accumulatio

Thermogenic capacity of human white-fat: the actual picture

Presented at the 9th Greek Conference of Biochemistry and Physiology of Exercise, Thessaloniki, Greece, 18–20 October 2019Cold exposure and exercise may increase thermogenic capacity of white adipose tissue (WAT), which could subsequently enhance energy expenditure and body weight loss. We aimed to identify possible alterations in uncoupling protein 1 (UCP1)—the main biomarker of thermogenic activation—in human WAT due to both cold exposure and exercise, as well as the link between environmental temperature and thermogenic capacity of human WAT. MATERIAL & METHOD: We conducted four human experimental studies and two systematic reviews and meta-analyses—PROSPERO registration CRD42019120116, CRD42019120213. RESULTS: UCP1 mRNA was higher in winter than in summer [t(30) = 2.232, p = 0.03] in human WAT and our meta-analysis showed a main effect of cold exposure on human UCP1 mRNA [standard mean difference (Std-md) = 1.81, confidence interval (CI) = 0.50–3.13, p = 0.007]. However, UCP1 mRNA/protein expressions displayed no associations with %fat mass or BMI (p > 0.05, Cohen’s f2 < 0.20). Both a 2-hour cooling and a non-cooling protocol preceding the positron emission tomography/computed tomography (PET/CT) measurements revealed no association between environmental temperature and standardised uptake value (SUVmax) of human WAT, as well as no mean differences in SUVmax-WAT-activity between winter and summer. An 8-week exercise program had no effect on UCP1 of human WAT or on body composition. Our meta-analysis also revealed: (a) no effect of chronic exercise on human UCP1 mRNA, (b) a main effect of chronic exercise on UCP1 protein concentrations (Std-md = 0.59, CI = 0.03–1.16, p = 0.04) and UCP1 mRNA (Std-md = 1.76, CI = 0.48–3.04, p = 0.007) in WAT of normal diet animals, c) a main effect of chronic exercise on UCP1 mRNA (Std-md = 2.94, CI = 0.24–5.65, p = 0.03) and UCP1 protein concentrations (Std-md = 2.06, CI = 0.07–4.05, p = 0.04) of high-fat diet animals. CONCLUSIONS: Cold exposure represents a main stimulus for increased thermogenic capacity in human white adipocytes; however, this may have no impact on body weight loss. Chronic exercise may represent no major stimulus for UCP1 induced in human white adipocytes, while in animals it increases UCP1 gene independently of their diet. Therefore, evidence from animal studies regarding UCP1 gene activation in white adipocytes may not be applicable in humans. Finally, the identification of human WAT thermogenic capacity via PET/CT examination may be optimal with both a cooling and a non-cooling protocol.Published onlin

Electrical pulse stimulation of cultured cells as a method for mimicking exercise: A systematic review, meta-regression and meta-analysis- Raw Data for Meta-analysis and Metaregression

We performed meta-analyses to calculate the differences between control (non-stimulated) and EPS-stimulated cells for the biological indices having enough data for such an analysis. In cases of not reported values, we used WebPlotDigitizer (v4.5,2021) to extract the information from the given graphs.In cases where the number of studies was not identified, we assumed that they were conducted in triplicates and in cases of a range of number of studies, we used the mean. Since different methods and scales were utilized in the eligible studies, we used standardized mean differences (SMDs) instead of absolute mean differences to standardize our findings to uniform scale. Missing SDs were imputed using the average coefficient of variation from all complete cases. </p

Μελέτη των παραγόντων και των σηματοδοτικών μονοπατιών που ενέχονται στη φαιοποίηση του λευκού λιπώδους ιστού και στην επίδραση της άσκησης στο λιπώδη ιστό

Metabolic diseases and related pathologies have been associated with adiposity and relatively recently genetic traits have been identified to have a specific link between white adipose tissue (WAT), cardiovascular disease, body mass index (BMI)-adjusted type 2 diabetes (T2D) and dyslipidemia. Brown adipose tissue (BAT) and beige adipocytes have been identified as major players in the battle against obesity and metabolic disorders. The main protein expressed in BAT and beige adipocytes is UCP1 and an unanswered question is which is the contribution of UCP1 single nucleotide polymorphisms (SNPs) to susceptibility for cardiometabolic pathologies (CMP) and how their involvement in specific risk factors for these conditions varies across populations. Therefore I investigated the impact of UCP1 SNPs A-3826G, A-1766G, Ala64Thr and A-112C across Armenia, Greece, Poland, Russia and United Kingdom. In Armenia, GA genotype and A allele of Ala64Thr displayed ~2-fold higher risk for CMP compared to GG genotype and G allele, respectively (p<0.05). In Greece, A allele of Ala64Thr decreased risk of CMP by 39%. Healthy individuals with A-3826G GG genotype and carriers of mutant allele of A-112C and Ala64Thr had higher body mass index compared to those carrying other alleles. Heterozygosity of A-112C and Ala64Thr SNPs was related to lower WHR in CMP individuals compared to wild type homozygotes (p<0.05). Concluding, the studied SNPs could be associated with the most common CMP and their risk factors in some populations. Apart from UCP1 genetic profile in different populations and species, UCP1 expression is affected by external factors such as exercise, thus the effect of exercise on the formation of beige adipocytes has produced controversial results in human studies. My aim was to research- via an in vitro model of co-culturing of C2C12 myotubes and 3T3-L1 adipocytes under the stimuli of electrical pulse stimulation (EPS) mimicking muscle contraction- the impact of the the direct crosstalk between adipocytes and stimulated muscle cells. When EPS was applied, the t co-culturing led to increases in UCP1 (p = 0.044; d = 1.29) and IL-6 (p = 0.097; d = 1.13) protein expression in the 3T3-L1 adipocytes. In vitro co-culturing of C2C12 myotubes and 3T3-L1 adipocytes under the stimuli of EPS leads to increased expression of thermogenic proteins. I detected changes in the expression pattern of proteins related to browning of adipose tissue, supporting the use of this in vitro model to study the crosstalk between adipocytes and contracting muscle. Although, exercise benefits a wide spectrum of diseases and affects most tissues and organs, as proven by my previous study, many aspects of its underlying mechanistic effects remain unsolved. In vitro exercise, mimicking neuronal signals leading to muscle contraction, can be a valuable tool to address this issue. I performed a systematic review and metanalysis for relevant studies assessing in vitro exercise using electrical pulse stimulation to mimic exercise. I observed variability among existing protocols of in vitro exercise and heterogeneity among protocols of the same type of exercise. The analyses showed that biological indices in vitro followed the patterns of in vivo exercise, and that these effects were correlated with the duration of stimulation, leading to the conclusion that in vitro exercise follows motifs of exercise in humans, allowing biological parameters, such as the aforementioned, to be valuable tools in defining the types of in vitro exercise.Τα μεταβολικά νοσήματα και οι συναφείς παθολογίες έχουν συσχετιστεί με το λιπώδη ιστό και σχετικά πρόσφατα εντοπίστηκαν γενετικά χαρακτηριστικά που έχουν ειδική σχέση μεταξύ του λευκού λιπώδους ιστού (ΛΛΙ), των καρδιαγγειακών νοσημάτων, του διαβήτη τύπου 2 (ΔΤ2) και της δυσλιπιδαιμίας, προσαρμοσμένου στο δείκτη μάζας σώματος (ΔΜΣ). Ο καφέ λιπώδης ιστός (ΚΛΙ) και τα μπεζ λιποκύτταρα έχουν αναγνωριστεί ως σημαντικοί παράγοντες στη μάχη κατά της παχυσαρκίας και των μεταβολικών διαταραχών. Η κύρια πρωτεΐνη που εκφράζεται στο ΚΛΙ και στα μπεζ λιποκύτταρα είναι η UCP1 και ένα αναπάντητο ερώτημα είναι ποια είναι η συμβολή των μονονουκλεοτιδικών πολυμορφισμών (SNPs) της UCP1 στις καρδιομεταβολικές παθολογίες (ΚΜΠ) και πώς η συμβολή τους σε συγκεκριμένους παράγοντες κινδύνου για αυτές ποικίλλει μεταξύ των πληθυσμών. Ως εκ τούτου, διερεύνησα την επίδραση των UCP1 SNPs A-3826G, A-1766G, Ala64Thr και A-112C στην Αρμενία, την Ελλάδα, την Πολωνία, τη Ρωσία και το Ηνωμένο Βασίλειο. Στην Αρμενία, ο γονότυπος GA και το αλληλόμορφο A του Ala64Thr εμφάνισαν ~2 φορές υψηλότερο κίνδυνο για ΚΜΠ σε σύγκριση με τον γονότυπο GG και το αλληλόμορφο G, αντίστοιχα (p<0,05). Στην Ελλάδα, το αλληλόμορφο Α του Ala64Thr μείωσε τον κίνδυνο εμφάνισης ΚΜΠ κατά 39%. Τα υγιή άτομα με γονότυπο A-3826G GG και οι φορείς των μεταλλαγμένων αλληλόμορφων A-112C και Ala64Thr είχαν υψηλότερο δείκτη μάζας σώματος σε σύγκριση με εκείνους που έφεραν άλλα αλληλόμορφα. Η ετεροζυγωτία των SNPs A-112C και Ala64Thr σχετιζόταν με χαμηλότερο WHR σε άτομα με ΚΜΠ σε σύγκριση με τους ομοζυγώτες φυσιολογικού γονότυπου (p<0,05). Συμπερασματικά, τα SNPs που μελετήθηκαν θα μπορούσαν να συσχετιστούν με τις πιο συχνές ΚΜΠ και τους παράγοντες κινδύνου τους σε ορισμένους πληθυσμούς. Εκτός όμως, από το γενετικό προφίλ της UCP1 σε διαφορετικούς πληθυσμούς και είδη, η έκφραση της UCP1 επηρεάζεται από εξωτερικούς παράγοντες, όπως η άσκηση, η επίδραση της οποίας στο σχηματισμό μπεζ λιποκυττάρων είναι αμφιλεγόμενη με βάση μελέτες σε ανθρώπους. Σκοπός μου ήταν να ερευνήσω- μέσω ενός in vitro μοντέλου συγκαλλιέργειας μυοκυττάρων C2C12 και λιποκυττάρων 3T3-L1 υπό το ερέθίσμα της ηλεκτρικής παλμικής διέγερσης (EPS) που μιμείται τη μυϊκή συστολή- την άμεση αλληλεπίδραση μεταξύ λιποκυττάρων και διεγερμένων μυϊκών κυττάρων. Όταν εφαρμόστηκε EPS, στη συγκαλλιέργεια αυξήθηκε η έκφραση των πρωτεϊνών UCP1 (p = 0,044- d = 1,29) και IL-6 (p = 0,097- d = 1,13) στα λιποκύτταρα 3T3-L1, δηλαδή η in vitro συγκαλλιέργεια μυοκυττάρων C2C12 και λιποκυττάρων 3T3-L1 υπό του EPS οδηγεί σε αυξημένη έκφραση θερμογόνων πρωτεϊνών. Οι αλλαγές στο πρότυπο έκφρασης πρωτεϊνών που σχετίζονται με τη φαιοποίηση του λιπώδους ιστού, υποστηρίζουν τη χρήση αυτού του in vitro μοντέλου. Παρόλο που η άσκηση ωφελεί ένα ευρύ φάσμα ασθενειών και επηρεάζει τους περισσότερους ιστούς και όργανα, όπως αποδείχθηκε από την προηγούμενη μελέτη μου, πολλές πτυχές των υποκείμενων μηχανιστικών επιδράσεών της παραμένουν άλυτες. Η άσκηση in vitro, που μιμείται τα νευρικά σήματα που οδηγούν σε μυϊκή συστολή, μπορεί να αποτελέσει πολύτιμο εργαλείο έρευνας. Διεξήγαγα μια συστηματική ανασκόπηση και μετ-ανάλυση για σχετικές μελέτες που αξιολογούν την άσκηση in vitro με τη χρήση ηλεκτρικών παλμών και παρατήρησα ποικιλομορφία μεταξύ των υφιστάμενων πρωτοκόλλων άσκησης in vitro και ετερογένεια μεταξύ πρωτοκόλλων του ίδιου τύπου άσκησης. Οι αναλύσεις έδειξαν ότι οι βιολογικοί δείκτες in vitro ακολουθούσαν τα μοτίβα της άσκησης in vivo και ότι τα αποτελέσματα αυτά συσχετίζονταν με τη διάρκεια της διέγερσης, οδηγώντας στο συμπέρασμα ότι η άσκηση in vitro ακολουθεί μοτίβα της άσκησης στον άνθρωπο, επιτρέποντας σε βιολογικές παραμέτρους, να αποτελέσουν πολύτιμα εργαλεία για τον καθορισμό των τύπων άσκησης in vitro

Characteristics of the Protocols Used in Electrical Pulse Stimulation of Cultured Cells for Mimicking In Vivo Exercise: A Systematic Review, Meta-Analysis, and Meta-Regression

While exercise benefits a wide spectrum of diseases and affects most tissues and organs, many aspects of its underlying mechanistic effects remain unsolved. In vitro exercise, mimicking neuronal signals leading to muscle contraction in vitro, can be a valuable tool to address this issue. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for this systematic review and meta-analysis, we searched EMBASE and PubMed (from database inception to 4 February 2022) for relevant studies assessing in vitro exercise using electrical pulse stimulation to mimic exercise. Meta-analyses of mean differences and meta-regression analyses were conducted. Of 985 reports identified, 41 were eligible for analysis. We observed variability among existing protocols of in vitro exercise and heterogeneity among protocols of the same type of exercise. Our analyses showed that AMPK, Akt, IL-6, and PGC1a levels and glucose uptake increased in stimulated compared to non-stimulated cells, following the patterns of in vivo exercise, and that these effects correlated with the duration of stimulation. We conclude that in vitro exercise follows motifs of exercise in humans, allowing biological parameters, such as the aforementioned, to be valuable tools in defining the types of in vitro exercise. It might be useful in transferring obtained knowledge to human research

Effects of In Vitro Muscle Contraction on Thermogenic Protein Levels in Co-Cultured Adipocytes

The crosstalk between the exercising muscle and the adipose tissue, mediated by myokines and metabolites, derived from both tissues during exercise has created a controversy between animal and human studies with respect to the impact of exercise on the browning process. The aim of this study was to investigate whether co-culturing of C2C12 myotubes and 3T3-L1 adipocytes under the stimuli of electrical pulse stimulation (EPS) mimicking muscle contraction can impact the expression of UCP1, PGC-1a, and IL-6 in adipocytes, therefore providing evidence on the direct crosstalk between adipocytes and stimulated muscle cells. In the co-cultured C2C12 cells, EPS increased the expression of PGC-1a (p = 0.129; d = 0.73) and IL-6 (p = 0.09; d = 1.13) protein levels. When EPS was applied, we found that co-culturing led to increases in UCP1 (p = 0.044; d = 1.29) and IL-6 (p = 0.097; d = 1.13) protein expression in the 3T3-L1 adipocytes. The expression of PGC-1a increased by EPS but was not significantly elevated after co-culturing (p = 0.448; d = 0.08). In vitro co-culturing of C2C12 myotubes and 3T3-L1 adipocytes under the stimuli of EPS leads to increased expression of thermogenic proteins. These findings indicate changes in the expression pattern of proteins related to browning of adipose tissue, supporting the use of this in vitro model to study the crosstalk between adipocytes and contracting muscle

Implication of Irisin in Different Types of Cancer: A Systematic Review and Meta-Analysis

Cancer is a set of diseases characterized by several hallmark properties, such as increased angiogenesis, proliferation, invasion, and metastasis. The increased angiogenic activity constantly supplies the tumors with nutrients and a plethora of cytokines to ensure cell survival. Along these cytokines is a newly discovered protein, called irisin, which is released into the circulation after physical exercise. Irisin is the product of fibronectin type III domain-containing protein 5 (FNDC5) proteolytic cleavage. Recently it has been the topic of investigation in several types of cancer. In this study, we conducted a systematic review and meta-analysis to investigate its implication in different types of cancer. Our results suggest that irisin expression is decreased in cancer patients, thus it can be used as a valid biomarker for the diagnosis of several types of cancer. In addition, our results indicate that irisin may have an important role in tumor progression and metastasis since it is involved in multiple signaling pathways that promote cell proliferation and migration

Cell survival during complete nutrient deprivation depends on lipid droplet-fueled beta-oxidation of fatty acids

Cells exposed to stress of different origins synthesize triacylglycerols and generate lipid droplets (LD), but the physiological relevance of this response is uncertain. Using complete nutrient deprivation of cells in culture as a simple model of stress, we have addressed whether LD biogenesis has a protective role in cells committed to die. Complete nutrient deprivation induced the biogenesis of LD in human LN18 glioblastoma and HeLa cells and also in CHO and rat primary astrocytes. In all cell types, death was associated with LD depletion and was accelerated by blocking LD biogenesis after pharmacological inhibition of Group IVA phospholipase A2 (cPLA2α) or down-regulation of ceramide kinase. Nutrient deprivation also induced β-oxidation of fatty acids that was sensitive to cPLA2α inhibition, and cell survival in these conditions became strictly dependent on fatty acid catabolism. These results show that, during nutrient deprivation, cell viability is sustained by β-oxidation of fatty acids that requires biogenesis and mobilization of LD

Cell survival during complete nutrient deprivation depends on lipid droplet-fueled beta-oxidation of fatty acids

Cells exposed to stress of different origins synthesize triacylglycerols and generate lipid droplets (LD), but the physiological relevance of this response is uncertain. Using complete nutrient deprivation of cells in culture as a simple model of stress, we have addressed whether LD biogenesis has a protective role in cells committed to die. Complete nutrient deprivation induced the biogenesis of LD in human LN18 glioblastoma and HeLa cells and also in CHO and rat primary astrocytes. In all cell types, death was associated with LD depletion and was accelerated by blocking LD biogenesis after pharmacological inhibition of Group IVA phospholipase A2 (cPLA2α) or down-regulation of ceramide kinase. Nutrient deprivation also induced β-oxidation of fatty acids that was sensitive to cPLA2α inhibition, and cell survival in these conditions became strictly dependent on fatty acid catabolism. These results show that, during nutrient deprivation, cell viability is sustained by β-oxidation of fatty acids that requires biogenesis and mobilization of LD

Association of fat mass profile with natriuretic peptide receptor alpha in subcutaneous adipose tissue of medication-free healthy men: A cross-sectional study [version 2; referees: 2 approved]

Background: Atrial natriuretic peptide increases lipolysis in human adipocytes by binding to natriuretic peptide receptor-A (NPRA). The aim of the current study was to examine the associations of NPRA mRNA of subcutaneous adipose tissue with fat mass, fat-free mass, body mass index (BMI) and arterial blood pressure in medication-free healthy men. Method: Thirty-two volunteers [age (years): 36.06±7.36, BMI: 27.60±4.63 (kg/m2)] underwent assessments of body height/weight, % fat mass, fat-free mass (kg), blood pressure, and a subcutaneous adipose tissue biopsy via a surgical technique. Results: We found that NPRA mRNA was negatively associated with % fat mass (r=-0.40, R2=0.16, p=0.03) and BMI (r=-0.45, R2=0.20, p=0.01). Cohen’s f2 effect size analyses showed a small effect size between NPRA mRNA and BMI (f2=0.25). One-way analysis of variance with Bonferroni post-hoc tests showed a tendency for mean differences of NPRA mRNA across BMI categories (p=0.06). This was confirmed by Cohen’s d effect size analyses revealing a large effect size of NPRA mRNA between obese individuals (BMI≥30 kg/m2) and either normal weight (BMI=19-25 kg/m2; d=0.94) or overweight (BMI=25-30 kg/m2; d=1.12) individuals. Conclusions: NPRA mRNA is negatively associated with % fat mass and BMI in medication-free healthy men, suggesting a possible role of NPRA in the control of fat mass accumulation