Monika Karczewska-Kupczewska

Profiling of Circulating MicroRNAs Reveals Common MicroRNAs Linked to Type 2 Diabetes That Change With Insulin Sensitization

OBJECTIVE This study sought to identify the profile of circulating microRNAs (miRNAs) in type 2 diabetes (T2D) and its response to changes in insulin sensitivity. RESEARCH DESIGN AND METHODS The circulating miRNA profile was assessed in a pilot study of 12 men: 6 with normal glucose tolerance (NGT) and 6 T2D patients. The association of 10 circulating miRNAs with T2D was cross-sectionally validated in an extended sample of 45 NGT vs. 48 T2D subjects (65 nonobese and 28 obese men) and longitudinally in 35 T2D patients who were recruited in a randomized, double-blinded, and placebo-controlled 3-month trial of metformin treatment. Circulating miRNAs were also measured in seven healthy volunteers before and after a 6-h hyperinsulinemic-euglycemic clamp and insulin plus intralipid/heparin infusion. RESULTS Cross-sectional studies disclosed a marked increase of miR-140-5p, miR-142-3p, and miR-222 and decreased miR-423-5p, miR-125b, miR-192, miR-195, miR-130b, miR-532-5p, and miR-126 in T2D patients. Multiple linear regression analyses revealed that miR-140-5p and miR-423-5p contributed independently to explain 49.5% (P < 0.0001) of fasting glucose variance after controlling for confounders. A discriminant function of four miRNAs (miR-140-5p, miR-423-5p, miR-195, and miR-126) was specific for T2D with an accuracy of 89.2% (P < 0.0001). Metformin (but not placebo) led to significant changes in circulating miR-192 (49.5%; P = 0.022), miR-140-5p (−15.8%; P = 0.004), and miR-222 (−47.2%; P = 0.03), in parallel to decreased fasting glucose and HbA1c. Furthermore, while insulin infusion during clamp decreased miR-222 (−62%; P = 0.002), the intralipid/heparin mixture increased circulating miR-222 (163%; P = 0.015) and miR-140-5p (67.5%; P = 0.05). CONCLUSIONS This study depicts the close association between variations in circulating miRNAs and T2D and their potential relevance in insulin sensitivity.

Insulin resistance, serum adiponectin, and proinflammatory markers in young subjects with the metabolic syndrome

Insulin resistance is the underlying metabolic abnormality in the metabolic syndrome. The low-grade chronic inflammation may be associated with metabolic risk factors and atherogenesis. The aim of our study was to establish the link between the metabolic syndrome, as defined by the National Cholesterol Education Program (NCEP) criteria, and insulin sensitivity, serum adiponectin, and parameters of chronic inflammation in young subjects. The group of 223 subjects (mean age, 25.86 +/- 5.49 years; body mass index, 28.04 +/- 6.91 kg/m2) was studied. Oral glucose tolerance test, euglycemic hyperinsulinemic clamp, and estimation of serum adiponectin and proinflammatory factors were performed. The NCEP-defined metabolic syndrome was present in 49 subjects (21.97%). The higher the number of NCEP criteria fulfilled was, the bigger were the decrease in insulin sensitivity (P < .0001) and adiponectin (P < .0001) and the increase in fasting and postload insulin (both Ps < .0001), C-reactive protein (P < .0001), interleukin 18 (P < .0001), interleukin 6 (P < .0001), and soluble tumor necrosis factor-alpha receptors sTNFR1 (P < .0001) and sTNFR2 (P < .0001) observed. Multiple regression analysis revealed that adiponectin and inflammatory factors predicted NCEP score independent of insulin sensitivity (all adjusted beta values between .16 and .32, all Ps < .01). Young subjects with metabolic syndrome demonstrate an increased inflammatory response and lower adiponectin concentration.

Serum Retinol Binding Protein 4 Is Related to Insulin Resistance and Nonoxidative Glucose Metabolism in Lean and Obese Women with Normal Glucose Tolerance

CONTEXT Retinol-binding protein (RBP) 4 is secreted by adipose tissue and is postulated to be a determinant of insulin sensitivity. The mechanisms of RBP4 insulin desensitizing action remain unclear. OBJECTIVE The aim of the present study was to estimate the relationships between serum RBP4 concentration with insulin sensitivity and oxidative and nonoxidative glucose metabolism in lean and obese women. DESIGN AND PARTICIPANTS The study group consisted of 67 women with normal glucose tolerance, 27 lean and 40 overweight or obese. Insulin sensitivity was estimated with the euglycemic hyperinsulinemic clamp. Glucose and lipid oxidation was measured with indirect calorimetry in the basal state and during the last 30 min of the clamp. Nonoxidative glucose metabolism was calculated in insulin-stimulated conditions by subtracting glucose oxidation from total glucose metabolism. RESULTS There was no difference in serum RBP4 concentration between lean and obese women. Serum RBP4 was inversely related to insulin sensitivity and nonoxidative glucose metabolism in the entire group (r = -0.36, P =0.003 in both cases) and within the subgroups of lean (r = -0.41, P =0.034 and r = -0.41, P =0.031) and obese women (r = -0.41, P =0.009 and r = -0.40, P =0.01, respectively). These relationships were independent of potential confounding factors. RBP4 levels were not associated with oxidative metabolism of glucose or lipid. CONCLUSIONS Our data indicate that serum RBP4 is related to decreased insulin sensitivity, mostly through its association with nonoxidative glucose metabolism.

Autophagy-regulating TP53INP2 mediates muscle wasting and is repressed in diabetes

A precise balance between protein degradation and synthesis is essential to preserve skeletal muscle mass. Here, we found that TP53INP2, a homolog of the Drosophila melanogaster DOR protein that regulates autophagy in cellular models, has a direct impact on skeletal muscle mass in vivo. Using different transgenic mouse models, we demonstrated that muscle-specific overexpression of Tp53inp2 reduced muscle mass, while deletion of Tp53inp2 resulted in muscle hypertrophy. TP53INP2 activated basal autophagy in skeletal muscle and sustained p62-independent autophagic degradation of ubiquitinated proteins. Animals with muscle-specific overexpression of Tp53inp2 exhibited enhanced muscle wasting in streptozotocin-induced diabetes that was dependent on autophagy; however, TP53INP2 ablation mitigated experimental diabetes-associated muscle loss. The overexpression or absence of TP53INP2 did not affect muscle wasting in response to denervation, a condition in which autophagy is blocked, further indicating that TP53INP2 alters muscle mass by activating autophagy. Moreover, TP53INP2 expression was markedly repressed in muscle from patients with type 2 diabetes and in murine models of diabetes. Our results indicate that TP53INP2 negatively regulates skeletal muscle mass through activation of autophagy. Furthermore, we propose that TP53INP2 repression is part of an adaptive mechanism aimed at preserving muscle mass under conditions in which insulin action is deficient.

Circulating Brain-Derived Neurotrophic Factor Concentration Is Downregulated by Intralipid/Heparin Infusion or High-Fat Meal in Young Healthy Male Subjects

OBJECTIVE Insulin resistance and type 2 diabetes are associated with an increased risk of neurodegenerative diseases. Brain-derived neurotrophic factor (BDNF) regulates neuronal differentiation and synaptic plasticity, and its decreased levels are supposed to play a role in the pathogenesis of Alzheimer’s disease and other disorders. The aim of the current study was to estimate the effects of hyperinsulinemia and serum free fatty acids (FFA) elevation on circulating BDNF concentration in humans. RESEARCH DESIGN AND METHODS We studied 18 healthy male subjects (mean age 25.6 ± 3.0 years; mean BMI 26.6 ± 4.8 kg/m2). Serum and plasma BDNF concentration was measured in the baseline state and in the 120 and 360 min of euglycemic hyperinsulinemic clamp with or without intralipid/heparin infusion. Furthermore, plasma BDNF was measured in 20 male subjects (mean age 22.7 ± 2.3 years; mean BMI 24.9 ± 1.5 kg/m2) 360 min after a high-fat meal. RESULTS Insulin sensitivity was reduced by ∼40% after 6 h of intralipid/heparin infusion (P < 0.001). During both clamps, serum and plasma BDNF followed the same pattern. Hyperinsulinemia had no effect on circulating BDNF. Raising FFA had no effect on circulating BDNF in 120 min; however, it resulted in a significant decrease by 43% in serum and by 35% in plasma BDNF after 360 min (P = 0.005 and 0.006, respectively). High-fat meal also resulted in a decrease by 27.8% in plasma BDNF (P = 0.04). CONCLUSIONS Our data show that raising FFA decreases circulating BDNF. This might indicate a potential link between FFA-induced insulin resistance and neurodegenerative disorders.

Increased suppression of serum ghrelin concentration by hyperinsulinemia in women with anorexia nervosa

CONTEXT Ghrelin is a peptide secreted mainly by the stomach, which has the ability to stimulate appetite and food intake. Serum ghrelin concentration decreases rapidly after a meal, probably because of the concurrent increase in serum insulin. Anorexia nervosa (AN) is an eating disorder, which is characterized by high serum ghrelin concentration; however, the regulation of circulating ghrelin by insulin in this disorder remains unclear. OBJECTIVE To estimate serum ghrelin concentration in the fasting state and after hyperinsulinemia in women with AN. DESIGN AND PARTICIPANTS We examined 19 women with AN, 26 lean healthy women, and 25 women who were overweight or obese. Serum ghrelin concentration was measured in the fasting state and after euglycemic hyperinsulinemic clamp. RESULTS Insulin sensitivity was similar in AN and normal-weight women, and was markedly decreased in the obese subjects. In the fasting state, serum ghrelin was higher in AN group than in other groups (normal-weight, P=0.017; obese, P=0.0001) and in normal-weight women than in obese women (P=0.044). Hyperinsulinemia resulted in a marked decrease in serum ghrelin in AN (P<0.0001) and normal-weight women (P=0.002). The fall in serum ghrelin was higher in AN group than in other groups (normal-weight, P=0.0008; obese, P=0.0001), and was related to insulin sensitivity (r=0.24, P<0.05). In multiple regression analysis, only fasting serum ghrelin and the presence of AN were independent predictors of this fall. CONCLUSIONS Women with AN have an increased suppression of serum ghrelin by hyperinsulinemia. This phenomenon might lead to an increased and more rapid feeling of satiety in AN.

The FTO gene modifies weight, fat mass and insulin sensitivity in women with polycystic ovary syndrome, where its role may be larger than in other phenotypes.

AIM Genome-wide association studies have shown that variation in the FTO gene predisposes to obesity and related traits that are common features of polycystic ovary syndrome (PCOS). The aim of the present study was to assess the effect of FTO variation on obesity, insulin sensitivity, and metabolic and hormonal profiles in PCOS. METHODS We examined 136 PCOS women (mean body mass index [BMI]: 28.28+/-6.95kg/m(2), mean age: 25.36+/-5.48 years). Anthropometric measurement, euglycaemic-hyperinsulinaemic clamp and oral glucose tolerance tests and sex hormone assessments were performed. The study group was genotyped for the FTO rs9939609 polymorphism. RESULTS BMI (29.0+/-6.9kg/m(2) vs 26.1+/-6.8kg/m(2); P=0.023), body weight (80.1+/-20.7kg vs 72.6+/-20.2kg; P=0.048), fat mass (29.7+/-1 6.6kg vs 24.6+/-17.7kg; P=0.045) and waist circumference (89.8+/-16.7cm vs 83.2+/-17.1cm; P=0.028) were higher in carriers of at least one copy of the A allele. Differences in these parameters were more significant when comparing AA and TT homozygotes. Women with the AA genotype also had decreased insulin sensitivity (P=0.025) and follicle-stimulating hormone (P=0.036). In logistic-regression analyses, the association of the FTO gene polymorphism with insulin sensitivity was no longer significant when BMI was included in the model. CONCLUSION Variation in the FTO gene modifies weight, adiposity and other measures of obesity and insulin sensitivity in PCOS. The examined FTO gene variant appears to have a greater impact on obesity and related traits in PCOS than in other phenotypes. The effect on insulin sensitivity appears to be secondary to its influence on obesity and body fat.

Insulin sensitivity, metabolic flexibility, and serum adiponectin concentration in women with anorexia nervosa

Anorexia nervosa (AN) is an eating disorder resulting in sustained low weight and marked decrease in fat mass. The lack of adipose tissue observed in lipodystrophies is accompanied by insulin resistance. It remains unclear if the same phenomenon would be present in AN. The objective of the study was to estimate insulin sensitivity, oxidative and nonoxidative glucose metabolism in insulin-stimulated conditions, metabolic flexibility, and serum adiponectin concentration in women with AN. We examined 21 women with AN and 24 healthy normal-weight female controls. Euglycemic hyperinsulinemic clamp, indirect calorimetry, and the measurement of serum adiponectin concentration were performed in all the subjects. We did not observe differences in insulin sensitivity, oxidative and nonoxidative glucose metabolism in insulin-stimulated conditions, and metabolic flexibility between AN and control subjects. Serum adiponectin was higher in AN women in comparison with control group (P = .002). Women with AN have normal insulin sensitivity because of the preserved response of glucose oxidation, nonoxidative glucose metabolism in response to insulin, and normal metabolic flexibility. High adiponectin concentration and normal insulin sensitivity in anorectic women suggest that in AN the adipocytes are still capable of functioning at the level that is sufficient to prevent the metabolic consequences.

Serum Soluble Glycoprotein 130 Concentration Is Inversely Related to Insulin Sensitivity in Women With Polycystic Ovary Syndrome

OBJECTIVE Insulin resistance might play a role in the pathogenesis of polycystic ovarian syndrome (PCOS). The family of glycoprotein 130 (gp130) cytokines could influence insulin action. One of these cytokines is interleukin (IL)-6, which exerts a short-term insulin-sensitizing effect, whereas in a long-term period, it might induce insulin resistance. Some other gp130 activators are supposed to have beneficial metabolic effects. Gp130 is present in the circulation in the soluble form (sgp130), which inhibits intracellular gp130 signaling. The aim of the present study was to estimate the relation between sgp130 and insulin sensitivity in women with PCOS. RESEARCH DESIGN AND METHODS We studied 78 women with PCOS (35 lean and 43 obese) and 34 healthy women (18 lean and 16 obese). The euglycemic-hyperinsulinemic clamp and the measurements of serum sgp130, IL-6, soluble IL-6 receptor (sIL-6R), and sex hormones were performed. RESULTS Both obesity and PCOS were characterized by an increased sgp130 (P < 0.0001 and P = 0.0002, respectively). sIL-6R concentration was lower (P = 0.0036) in women with PCOS independently of obesity. Serum sgp130 was negatively correlated with insulin sensitivity when control and PCOS women were analyzed together (r = −0.36, P < 0.0001) and in the PCOS subjects separately (r = −0.34, P = 0.002). In multiple regression analysis, this correlation was significant after adjustment for BMI, waist, percent of body fat, postload glucose and insulin, triglycerides, and high-sensitive C-reactive protein. CONCLUSIONS Serum sgp130 is inversely and independently associated with insulin sensitivity in women with PCOS. An increased serum sgp130 in obesity and PCOS suggests an inhibition of intracellular gp130 signaling in insulin-resistant conditions.

Decreased serum brain-derived neurotrophic factor concentration in young nonobese subjects with low insulin sensitivity

OBJECTIVE Insulin resistance and type 2 diabetes are associated with an increased risk of neurodegenerative diseases. Decreased brain-derived neurotrophic factor (BDNF) levels might play a role in the pathogenesis of neuropsychiatric disorders. The aim of our study was to estimate serum BDNF concentration in nonobese women divided into subgroups according to their insulin sensitivity. DESIGN AND METHODS We studied 46 young, healthy, nonobese women. Insulin sensitivity was estimated with the euglycemic-hyperinsulinemic clamp technique. Then, participants were divided into subgroups of high (mean, 12.79±2.01mg/kg fat-free mass/min) and low insulin sensitivity (mean, 7.33±1.66mg/kg fat-free mass/min). RESULTS We observed decreased serum BDNF concentration in women with low insulin sensitivity in comparison to high insulin sensitivity group (3306.11±603.10 vs 4141.91±755.37pg/mL, p=0.001). Serum BDNF was positively related to insulin sensitivity (r=0.43, p=0.003). This correlation remained significant after adjustment for other estimated parameters. CONCLUSIONS Serum BDNF is decreased in young nonobese women with low insulin sensitivity. Early detection and prevention of insulin resistance might be useful in the prevention of neurodegenerative disorders.