Effect of Pioglitazone on Cardiometabolic Risk in Patients With Obstructive Sleep Apnea.

Prevalence of insulin resistance is increased in patients with obstructive sleep apnea (OSA). Because insulin resistance is an independent predictor of cardiovascular disease (CVD), this study was initiated to see if pioglitazone administration would improve insulin sensitivity and thereby decrease risk of CVD in overweight/obese, nondiabetic, insulin-resistant patients with untreated OSA. Patients (n = 30) were administered pioglitazone (45 mg/day) for 8 weeks, and measurements were made before and after intervention of insulin action (insulin-mediated glucose uptake by the insulin suppression test), C-reactive protein, lipid/lipoprotein profile, and gene expression profile of periumbilical subcutaneous fat tissue. Insulin sensitivity increased 31% (p <0.001) among pioglitazone-treated subjects, associated with a decrease in C-reactive protein concentration (p ≤0.001), a decrease in plasma triglyceride, and increase in high-density lipoprotein cholesterol concentrations (p ≤0.001), accompanied by significant changes in apolipoprotein A1 and B concentrations and lipoprotein subclasses known to decrease CVD risk. In addition, subcutaneous adipose tissue gene expression profile showed a 1.6-fold (p <0.01) increase in GLUT4 expression and decreased expression in 5 of 9 inflammatory genes (p <0.05). In conclusion, enhanced insulin sensitivity can significantly decrease multiple cardiometabolic risk factors in patients with untreated OSA, consistent with the view that coexisting insulin resistance plays an important role in the association between OSA and increased risk of CVD.

Does enhanced insulin sensitivity improve sleep measures in patients with obstructive sleep apnea: a randomized, placebo-controlled pilot study.

BACKGROUND: High fasting insulin levels have been reported to predict development of observed apneas, suggesting that insulin resistance may contribute to the pathogenesis of obstructive sleep apnea (OSA). The aim of this study was to determine whether enhancing insulin sensitivity in individuals with OSA would improve sleep measures. PATIENTS/METHODS: Insulin-resistant, nondiabetic individuals with untreated OSA were randomized (2:1) to pioglitazone (45 mg/day) or placebo for eight weeks in this single-blind study. All individuals had repeat measurements pertaining to sleep (overnight polysomnography and functional outcomes of sleep questionnaire) and insulin action (insulin suppression test). RESULTS: A total of 45 overweight/obese men and women with moderate/severe OSA were randomized to pioglitazone (n = 30) or placebo (n = 15). Although insulin sensitivity increased 31% among pioglitazone-treated compared with no change among individuals receiving placebo (p <0.001 for between-group difference), no improvement in quantitative or qualitative sleep measurements was observed. CONCLUSIONS: Pioglitazone administration increased insulin sensitivity in otherwise untreated individuals with OSA, without any change in polysomnographic sleep measures over an eight-week period. These findings do not support a causal role for insulin resistance in the pathogenesis of OSA.

Salsalate-induced changes in lipid, lipoprotein, and apoprotein concentrations in overweight or obese, insulin-resistant, nondiabetic individuals.

BACKGROUND AND OBJECTIVE: Although salsalate administration consistently lowers plasma triglyceride concentrations in patients with type II diabetes, prediabetes, and/or insulin resistance, changes in low-density lipoprotein cholesterol (LDL-C) concentrations have been inconsistent; varying from no change to a significant increase. To evaluate the clinical relevance of this discordance in more detail, we directly measured LDL-C and obtained a comprehensive assessment of changes in lipid, lipoprotein, and apoprotein concentrations associated with salsalate use in insulin-resistant individuals, overweight or obese, but without diabetes, using vertical auto profile method. METHODS: A single-blind, randomized, placebo-controlled study was performed in volunteers who were overweight or obese, without diabetes, and insulin resistant on the basis of their steady-state plasma glucose concentration during an insulin suppression test. Participants were randomized 2:1 to receive salsalate 3.5 g/d (n = 27) or placebo (n = 14) for 4 weeks. Comprehensive lipid, lipoprotein, and apoprotein analysis by vertical auto profile was obtained after an overnight fast, before and after study intervention. RESULTS: There was no change in directly measured LDL-C concentration in salsalate-treated individuals. However, salsalate administration was associated with various changes considered to decrease atherogenicity; including decreases in triglyceride and total very low-density lipoprotein cholesterol (VLDL-C) concentrations, a shift from small denser LDL lipoproteins toward larger, more buoyant LDL particles, decreases in VLDL(1+2)-C and LDL(4)-C, and nonsignificant decreases in non-high-density lipoprotein cholesterol and apolipoprotein B. No significant changes occurred in the placebo-treated group. CONCLUSIONS: Atherogenicity of the lipid, lipoprotein, and apoprotein profile of insulin-resistant individuals who were overweight or obese improved significantly in association with salsalate treatment. The clinical importance of this finding awaits further study.

Circulating microRNA-320a and microRNA-486 predict thiazolidinedione response: Moving towards precision health for diabetes prevention.

INTRODUCTION: The aims of this study were to compare microRNA (miR) expression between individuals with and without insulin resistance and to determine whether miRs predict response to thiazolidinedione treatment. MATERIALS AND METHODS: In a sample of 93 healthy adults, insulin resistance was defined as steady state plasma glucose (SSPG)≥180 mg/dL and insulin sensitive as <120 mg/dL. Response to thiazolidinedione therapy was defined as ≥10% decrease in SSPG. We selected a panel of microRNAs based on prior evidence for a role in insulin or glucose metabolism. Fold change and Wilcoxon rank sum tests were calculated for the 25 miRs measured. RESULTS: At baseline, 81% (n=75) of participants were insulin resistant. Five miRs were differentially expressed between the insulin resistant and sensitive groups: miR-193b (1.45 fold change (FC)), miR-22-3p (1.15 FC), miR-320a (1.36 FC), miR-375 (0.59 FC), and miR-486 (1.21 FC) (all p<0.05). In the subset who were insulin resistant at baseline and received thiazolidinediones (n=47), 77% (n=36) showed improved insulin sensitivity. Six miRs were differentially expressed between responders compared to non-responders: miR-20b-5p (1.20 FC), miR-21-5p, (0.92 FC), miR-214-3p (1.13 FC), miR-22-3p (1.14 FC), miR-320a (0.98 FC), and miR-486-5p (1.25 FC) (all p<0.05). DISCUSSION: This study is the first to report miRs associated with response to a pharmacologic intervention for insulin resistance. MiR-320a and miR-486-5p identified responders to thiazolidinedione therapy among the insulin resistant group.

Usefulness of fetuin-A to predict risk for cardiovascular disease among patients with obstructive sleep apnea.

Patients with obstructive sleep apnea (OSA) are at increased risk for cardiovascular diseases (CVDs). Fetuin-A, a novel hepatokine, has been associated with the metabolic syndrome (MetS), insulin resistance, and type 2 diabetes mellitus, all of which are highly prevalent in patients with OSA and associated with increased CVD risk. The goal of this study was to determine whether fetuin-A could be involved in the pathogenesis of CVD risk in patients with OSA, through relations of fetuin-A with MetS components and/or insulin resistance. Overweight or obese, nondiabetic volunteers (n = 120) were diagnosed with OSA by in-laboratory nocturnal polysomnography. Steady-state plasma glucose concentrations derived during the insulin suppression test were used to quantify insulin-mediated glucose uptake; higher steady-state plasma glucose concentrations indicated greater insulin resistance. Fasting plasma fetuin-A and lipoprotein concentrations were measured. Whereas neither the prevalence of MetS nor the number of MetS components was associated with tertiles of fetuin-A concentrations, the lipoprotein components of MetS, triglycerides and high-density lipoprotein cholesterol, increased (p <0.01) and decreased (p <0.05), respectively, across fetuin-A tertiles. Additionally, comprehensive lipoprotein analysis revealed that very low density lipoprotein (VLDL) particles and VLDL subfractions (VLDL1+2 and VLDL3) were increased across fetuin-A tertiles. In contrast, neither insulin resistance nor sleep measurements related to OSA were found to be modified by fetuin-A concentrations. In conclusion, abnormalities of lipoprotein metabolism, but not MetS or insulin resistance per se, may represent a mechanism by which fetuin-A contributes to increased CVD risk in patients with OSA.

Abnormalities of lipoprotein concentrations in obstructive sleep apnea are related to insulin resistance.

STUDY OBJECTIVE: Prevalence of cardiovascular disease (CVD) is increased in patients with obstructive sleep apnea (OSA), possibly related to dyslipidemia in these individuals. Insulin resistance is also common in OSA, but its contribution to dyslipidemia of OSA is unclear. The study's aim was to define the relationships among abnormalities of lipoprotein metabolism, clinical measures of OSA, and insulin resistance. DESIGN: Cross-sectional study. OSA severity was defined by the apnea-hypopnea index (AHI) during polysomnography. Hypoxia measures were expressed as minimum and mean oxygen saturation, and the oxygen desaturation index. Insulin resistance was quantified by determining steady-state plasma glucose (SSPG) concentrations during the insulin suppression test. Fasting plasma lipid/lipoprotein evaluation was performed by vertical auto profile methodology. SETTING: Academic medical center. PARTICIPANTS: 107 nondiabetic, overweight/obese adults. MEASUREMENTS AND RESULTS: Lipoprotein particles did not correlate with AHI or any hypoxia measures, nor were there differences noted by categories of OSA severity. By contrast, even after adjustment for age, sex, and BMI, SSPG was positively correlated with triglycerides (r = 0.30, P < 0.01), very low density lipoprotein (VLDL) and its subclasses (VLDL1+2) (r = 0.21-0.23, P < 0.05), and low density lipoprotein subclass 4 (LDL4) (r = 0.30, P < 0.01). SSPG was negatively correlated with high density lipoprotein (HDL) (r = -0.38, P < 0.001) and its subclasses (HDL2 and HDL3) (r = -0.32, -0.43, P < 0.01), and apolipoprotein A1 (r = -0.33, P < 0.01). Linear trends of these lipoprotein concentrations across SSPG tertiles were also significant. CONCLUSIONS: Pro-atherogenic lipoprotein abnormalities in obstructive sleep apnea (OSA) are related to insulin resistance, but not to OSA severity or degree of hypoxia. Insulin resistance may represent the link between OSA-related dyslipidemia and increased cardiovascular disease risk.

Effect of salsalate on insulin action, secretion, and clearance in nondiabetic, insulin-resistant individuals: a randomized, placebo-controlled study.

OBJECTIVE: Salsalate treatment has been shown to improve glucose homeostasis, but the mechanism remains unclear. The aim of this study was to evaluate the effect of salsalate treatment on insulin action, secretion, and clearance rate in nondiabetic individuals with insulin resistance. RESEARCH DESIGN AND METHODS: This was a randomized (2:1), single-blind, placebo-controlled study of salsalate (3.5 g daily for 4 weeks) in nondiabetic individuals with insulin resistance. All individuals had measurement of glucose tolerance (75-g oral glucose tolerance test), steady-state plasma glucose (SSPG; insulin suppression test), and insulin secretion and clearance rate (graded-glucose infusion test) before and after treatment. RESULTS: Forty-one individuals were randomized to salsalate (n = 27) and placebo (n = 14). One individual from each group discontinued the study. Salsalate improved fasting (% mean change -7% [95% CI -10 to -14] vs. 1% [-3 to 5], P = 0.005) but not postprandial glucose concentration compared with placebo. Salsalate also lowered fasting triglyceride concentration (-25% [-34 to -15] vs. -6% [-26 to 14], P = 0.04). Salsalate had no effect on SSPG concentration or insulin secretion rate but significantly decreased insulin clearance rate compared with placebo (-23% [-30 to -16] vs. 3% [-10 to 15], P < 0.001). Salsalate was well tolerated, but four individuals needed a dose reduction due to symptoms. CONCLUSIONS: Salsalate treatment in nondiabetic, insulin-resistant individuals improved fasting, but not postprandial, glucose and triglyceride concentration. These improvements were associated with a decrease in insulin clearance rate without change in insulin action or insulin secretion.

Pancreatic beta cell function following liraglutide-augmented weight loss in individuals with prediabetes: analysis of a randomised, placebo-controlled study.

AIMS/HYPOTHESIS: Liraglutide can modulate insulin secretion by directly stimulating beta cells or indirectly through weight loss and enhanced insulin sensitivity. Recently, we showed that liraglutide treatment in overweight individuals with prediabetes (impaired fasting glucose and/or impaired glucose tolerance) led to greater weight loss (-7.7% vs -3.9%) and improvement in insulin resistance compared with placebo. The current study evaluates the effects on beta cell function of weight loss augmented by liraglutide compared with weight loss alone. METHODS: This was a parallel, randomised study conducted in a single academic centre. Both participants and study administrators were blinded to treatment assignment. Individuals who were 40-70 years old, overweight (BMI 27-40 kg/m(2)) and with prediabetes were randomised (via a computerised system) to receive liraglutide (n = 35) or matching placebo (n = 33), and 49 participants were analysed. All were instructed to follow an energy-restricted diet. Primary outcome was insulin secretory function, which was evaluated in response to graded infusions of glucose and day-long mixed meals. RESULTS: Liraglutide treatment (n = 24) significantly (p ≤ 0.03) increased the insulin secretion rate (% mean change [95% CI]; 21% [12, 31] vs -4% [-11, 3]) and pancreatic beta cell sensitivity to intravenous glucose (229% [161, 276] vs -0.5% (-15, 14]), and decreased insulin clearance rate (-3.5% [-11, 4] vs 8.2 [0.2, 16]) as compared with placebo (n = 25). The liraglutide-treated group also had significantly (p ≤ 0.03) lower day-long glucose (-8.2% [-11, -6] vs -0.1 [-3, 2]) and NEFA concentrations (-14 [-20, -8] vs -2.1 [-10, 6]) following mixed meals, whereas day-long insulin concentrations did not significantly differ as compared with placebo. In a multivariate regression analysis, weight loss was associated with a decrease in insulin secretion rate and day-long glucose and insulin concentrations in the placebo group (p ≤ 0.05), but there was no association with weight loss in the liraglutide group. The most common side effect of liraglutide was nausea. CONCLUSIONS/INTERPRETATION: A direct stimulatory effect on beta cell function was the predominant change in liraglutide-augmented weight loss. These changes appear to be independent of weight loss. TRIAL REGISTRATION: ClinicalTrials.gov NCT01784965 FUNDING: The study was funded by the ADA.

Benefits of liraglutide treatment in overweight and obese older individuals with prediabetes.

OBJECTIVE: The aim was to evaluate the ability of liraglutide to augment weight loss and improve insulin resistance, cardiovascular disease (CVD) risk factors, and inflammation in a high-risk population for type 2 diabetes (T2DM) and CVD. RESEARCH DESIGN AND METHODS: We randomized 68 older individuals (mean age, 58±8 years) with overweight/obesity and prediabetes to this double-blind study of liraglutide 1.8 mg versus placebo for 14 weeks. All subjects were advised to decrease calorie intake by 500 kcal/day. Peripheral insulin resistance was quantified by measuring the steady-state plasma glucose (SSPG) concentration during the insulin suppression test. Traditional CVD risk factors and inflammatory markers also were assessed. RESULTS: Eleven out of 35 individuals (31%) assigned to liraglutide discontinued the study compared with 6 out of 33 (18%) assigned to placebo (P=0.26). Subjects who continued to use liraglutide (n=24) lost twice as much weight as those using placebo (n=27; 6.8 vs. 3.3 kg; P<0.001). Liraglutide-treated subjects also had a significant improvement in SSPG concentration (-3.2 vs. 0.2 mmol/L; P<0.001) and significantly (P≤0.04) greater lowering of systolic blood pressure (-8.1 vs. -2.6 mmHg), fasting glucose (-0.5 vs. 0 mmol/L), and triglyceride (-0.4 vs. -0.1 mmol/L) concentration. Inflammatory markers did not differ between the two groups, but pulse increased after liraglutide treatment (6.4 vs. -0.9 bpm; P=0.001). CONCLUSIONS: The addition of liraglutide to calorie restriction significantly augmented weight loss and improved insulin resistance, systolic blood pressure, glucose, and triglyceride concentration in this population at high risk for development of T2DM and CVD.