Glucagon-like peptide-1 receptor agonist stimulates mitochondrial bioenergetics in human adipocytes

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) are relatively new pharmacological agents used to normalize glucose level in type 2 diabetes. Recently, GLP-1RAs have been approved for the treatment of obesity to reduce body weight in non-diabetic patients. The extra-pancre-atic effects of GLP-1RAs, as well as their molecular mechanism of action, are still poorly understood. Thus this study was aimed to verify the hypothesis that the mechanism of action of the GLP-1RAs involves mitochondria and that GLP-1RAs administration can improve mitochondrial functions. For this purpose, preadipocytes CHUBS7 were differentiated to mature adipocytes and then stimulated with GLP-1RA, exendin-4 at 100 nM for 24 h. Oxygen consumption rates, mitochondrial membrane potential, intracellular ATP (adenosine triphosphate) level, SIRT1 and SIRT3 gene expression and the histone deacetylases' activity were measured. Exendin-4 was found to uncouple mitochondrial electron transport from ATP synthesis, slightly decreasing mitochondrial membrane potential in mature adipocytes. Routine respiration and uncoupled oxy- gen consumption rates were higher in exendin-4 treated adipocytes than in the non-treated cells. The ATP level remained unchanged. Exendin-4 enhanced SIRT1 and SIRT3 genes expression. Histone deacetylases' activity in the nuclear fraction was not affected by exendin-4, although the activity of class III histone deacetylases was increased. All of the effects on mitochondrial bioenergetics induced by exendin-4 were abolished by addition of glucagon-like peptide 1 receptor antagonist. In conclusion, exendin-4 activates the sirtuin pathway and increases energy expenditure in human adipocytes. Our results suggest another mechanism that may be responsible for body weight reduction observed in patients using GLP-1RAs

High fat mixed meal tolerance test leads to suppression of osteocalcin decrease in obese insulin resistant subjects compared to healthy adults

Nutrients influence bone turnover. Carboxylated osteocalcin (Gla-OC) participates in bone formation whereas its undercarboxylated form (Glu-OC) acts as a hormone in glucose metabolism. The aim of the study was to determine the responses of Gla-OC, Glu-OC, and total-OC (calculated as the sum of Gla-OC and Glu-OC) to a high fat mixed meal tolerance test (HFMTT) in non-obese (body mass index (BMI) < 30 kg/m2, n = 24) and obese subjects (30 < BMI < 40 kg/m2, n = 70) (both sexes, aged 25⁻65 years). Serum Gla-OC and Glu-OC were measured at baseline as well as at 2 and 6 h during a HFMTT by enzyme-linked immunosorbent assay (ELISA). Baseline Gla-OC, Glu-OC, and total-OC levels were lower in obese individuals compared to non-obese participants (p = 0.037, p = 0.016 and p = 0.005, respectively). The decrease in Gla-OC and total-OC, but not in Glu-OC, concentrations during the HFMTT was suppressed in obese, but not in non-obese controls (p < 0.05, p < 0.01, p = 0.08, respectively). Subjects with the highest homeostatic model assessment for insulin resistance (HOMA-IR) index values had a less pronounced decrease in total-OC compared to patients with values of HOMA-IR index in the 1st quartile (p < 0.05). Net incremental area under Gla-OC inversely correlated with adiponectin (rho = −0.35, p = 0.001). Increase in insulin sensitivity and adiponectin level in obese subjects could beneficially influence postprandial bone turnover expressed by osteocalcin concentration

Epigenetic regulation of processes related to high level of fibroblast growth factor 21 in obese subjects

We hypothesised that epigenetics may play an important role in mediating fibroblast growth factor 21 (FGF21) resistance in obesity. We aimed to evaluate DNA methylation changes and miRNA pattern in obese subjects associated with high serum FGF21 levels. The study included 136 participants with BMI 27–45 kg/m2. Fasting FGF21, glucose, insulin, GIP, lipids, adipokines, miokines and cytokines were measured and compared in high serum FGF21 (n = 68) group to low FGF21 (n = 68) group. Human DNA Methylation Microarrays were analysed in leukocytes from each group (n = 16). Expression of miRNAs was evaluated using quantitative PCR-TLDA. The study identified differentially methylated genes in pathways related to glucose transport, insulin secretion and signalling, lipid transport and cellular metabolism, response to nutrient levels, thermogenesis, browning of adipose tissue and bone mineralisation. Additionally, it detected transcription factor genes regulating FGF21 and fibroblast growth factor receptor and vascular endothelial growth factor receptor pathways regulation. Increased expression of hsa-miR-875-5p and decreased expression of hsa-miR-133a-3p, hsa-miR-185-5p and hsa-miR-200c-3p were found in the group with high serum FGF21. These changes were associated with high FGF21, VEGF and low adiponectin serum levels. Our results point to a significant role of the epigenetic regulation of genes involved in metabolic pathways related to FGF21 action

Carboxylated and undercarboxylated osteocalcin in metabolic complications of human obesity and prediabetes

Background Carboxylated osteocalcin (Gla‐OC) participates in bone remodeling, whereas the undercarboxylated form (Glu‐OC) takes part in energy metabolism. This study was undertaken to compare the blood levels of Glu‐OC and Gla‐OC in nonobese, healthy obese, and prediabetic volunteers and correlate it with the metabolic markers of insulin resistance and early markers of inflammation. Methods Nonobese (body mass index [BMI] <30 kg/m2 ; n = 34) and obese subjects (30 <BMI <40 kg/m2 ; n = 98), both sexes, aged 25 to 65 years, were divided into healthy control, normal weight subjects, healthy obese, and obese with biochemical markers of prediabetes. The subgroups with obesity and low or high Gla‐OC or Glu‐OC were also considered for statistical analysis. After 2 weeks of diet standardization, venous blood was sampled for the determination of Gla‐OC, Glu‐OC, lipid profile, parameters of inflammation (hsCRP, interleukin 6, sE‐selectin, sPECAM‐1, and monocyte chemoattractant protein 1), and adipokines (leptin, adiponectin, visfatin, and resistin). Results Gla‐OC in obese patients was significantly lower compared to nonobese ones (11.36 ± 0.39 vs 12.69 ± 0.90 ng/mL, P = .048) and weakly correlated with hsCRP (r = −0.18, P = .042), visfatin concentration (r = −0.19, P = .033), and BMI (r = −0.17, P = .047). Glu‐OC was negatively associated with fasting insulin levels (r = −0.18, P = .049) and reduced in prediabetic individuals compared with healthy obese volunteers (3.04 ± 0.28 vs 4.48 ± 0.57, P = .025). Conclusions Decreased blood concentration of Glu‐OC may be a selective early symptom of insulin resistance in obesity, whereas the decreased level of Gla‐OC seems to be associated with the appearance of early markers of low grade inflammation accompanying obesity

Doświadczanie stresu przez osoby z otyłością - badania własne

WSTĘP. Stres może być czynnikiem wywołującym potrzebę jedzenia, a jedzenie ze względu na swoją dostępność jest prostym sposobem zmniejszenia napięcia. Celem badań jest analiza doświadczania stresu przez osoby z otyłością. MATERIAŁ I METODY. Badaniem objęto 117 pacjentów leczonych z powodu otyłości (śr. wieku: 50 lat, śr. BMI = 34,5) oraz 107 osób w grupie kontrolnej. Badani wypełniali Kwestionariusz Oceny Stresu analizujący sytuacyjną i dyspozycyjną ocenę stresu. WYNIKI. W grupie badanej sytuacja leczenia (sytuacyjna ocena stresu) jest postrzegana jako bardziej zagrażająca (12,2 vs. 6,7; p < 0,000) i krzywdząca (5,9 vs. 3,3; p < 0,000), stanowiąca większe wyzwanie do aktywności (9,5 vs. 7,6; p < 0,000), lecz z małymi szansami na zmianę (4,0 vs. 8,2; p < 0,000) w porównaniu z grupą kontrolną. Podobnie, w zakresie oceniania różnych trudnych sytuacji, osoby otyłe bardziej postrzegają je jako zagrażające (11,9 vs. 7,2; p < 0,000), krzywdzące (6,3 vs. 4,6; p < 0,000) i mniej optymistyczne (4,4 vs. 6,1; p < 0,000) niż grupa kontrolna. WNIOSKI. W doświadczaniu sytuacji stresu osoby otyłe są bardzo obciążone psychicznie, a jedzenie może być formą zmniejszenia napięcia. Dlatego programy leczenia otyłości powinny mieć charakter kompleksowej terapii, uwzględniającej kształtowanie umiejętności efektywnego radzenia sobie ze stresem

DNA methylation microarrays identify epigenetically regulated lipid related genes in obese patients with hypercholesterolemia

Background: Epigenetics can contribute to lipid disorders in obesity. The DNA methylation pattern can be the cause or consequence of high blood lipids. The aim of the study was to investigate the DNA methylation profile in peripheral leukocytes associated with elevated LDL-cholesterol level in overweight and obese individuals.Methods: To identify the differentially methylated genes, genome-wide DNA methylation microarray analysis was performed in leukocytes of obese individuals with high LDL-cholesterol (LDL-CH, ≥ 3.4 mmol/L) versus control obese individuals with LDL-CH, < 3.4 mmol/L. Biochemical tests such as serum glucose, total cholesterol, HDL cholesterol, triglycerides, insulin, leptin, adiponectin, FGF19, FGF21, GIP and total plasma fatty acids content have been determined. Oral glucose and lipid tolerance tests were also performed. Human DNA Methylation Microarray (from Agilent Technologies) containing 27,627 probes for CpG islands was used for screening of DNA methylation status in 10 selected samples. Unpaired t-test and Mann–Whitney U-test were used for biochemical and anthropometric parameters statistics. For microarrays analysis, fold of change was calculated comparing hypercholesterolemic vs control group. The q-value threshold was calculated using moderated Student's t-test followed by Benjamini–Hochberg multiple test correction FDR.Results: In this preliminary study we identified 190 lipid related CpG loci differentially methylated in hypercholesterolemic versus control individuals. Analysis of DNA methylation profiles revealed several loci engaged in plasma lipoprotein formation and metabolism, cholesterol efflux and reverse transport, triglycerides degradation and fatty acids transport and β-oxidation. Hypermethylation of CpG loci located in promoters of genes regulating cholesterol metabolism: PCSK9, LRP1, ABCG1, ANGPTL4, SREBF1 and NR1H2 in hypercholesterolemic patients has been found. Novel epigenetically regulated CpG sites include ABCG4, ANGPTL4, AP2A2, AP2M1, AP2S1, CLTC, FGF19, FGF1R, HDLBP, LIPA, LMF1, LRP5, LSR, NR1H2 and ZDHHC8 genes. Conclusions: Our results indicate that obese individuals with hypercholesterolemia present specific DNA methylation profile in genes related to lipids transport and metabolism. Detailed knowledge of epigenetic regulation of genes, important for lipid disorders in obesity, underlies the possibility to influence target genes by changing diet and lifestyle, as DNA methylation is reversible and depends on environmental factors. These findings give rise for further studies on factors that targets methylation of revealed genes