Impact of using different biomarkers of liver fibrosis on hepatologic referral of individuals with severe obesity and NAFLD.

PURPOSE: The purpose of this study was to estimate how many individuals with severe obesity and NAFLD should be referred to hepatologists according to the EASL-EASD-EASO guidelines and whether the choice of specific indicators of liver fibrosis would significantly impact the number of referrals. METHODS: This was a single-center retrospective study of 495 individuals with severe obesity screened at our institution between 2012 and 2018 for a bariatric surgery intervention. The guidelines were applied using the NAFLD Liver Fat Score (NLFS) to assess the presence of steatosis and the NAFLD fibrosis score (NFS), Fibrosis-4 (FIB-4) and Hepamet Fibrosis Score (HFS) to assess the risk of advanced fibrosis. RESULTS: Three hundred and seventy-nine patients (76.6%) had evidence of liver steatosis. The application of the guidelines would lead to referral of 66.3% of patients using NFS, 31.7% using FIB-4 and 34.2% using HFS. When referrals due to abnormal liver function tests were excluded, these percentages dropped to 55.8%, 7.3% and 12.1%, respectively. The strongest inter-biomarker agreement was found between FIB-4 and HFS (κ = 0.86, 95% CI 0.815-0.910). CONCLUSION: Strict application of the guidelines in individuals with severe obesity would probably lead to over-referral, although a great variability exists among the different scores.

Bile acid changes after metabolic surgery are linked to improvement in insulin sensitivity.

BACKGROUND: Metabolic surgery is associated with a prompt improvement in insulin resistance, although the mechanism of action remains unknown. The literature on bile acid changes after metabolic surgery is conflicting, and insulin sensitivity is generally assessed by indirect methods. The aim of this study was to investigate the relationship between improvement in insulin sensitivity and concentration of circulating bile acids after biliopancreatic diversion (BPD) and Roux-en-Y gastric bypass (RYGB). METHODS: This was a prospective observational study of nine patients who underwent BPD and six who had RYGB. Inclusion criteria for participation were a BMI in excess of 40 kg/m2 , no previous diagnosis of type 2 diabetes and willingness to participate. Exclusion criteria were major endocrine diseases, malignancies and liver cirrhosis. Follow-up visits were carried out after a mean(s.d.) of 185·3(72·9) days. Fasting plasma bile acids were assessed by ultra-high-performance liquid chromatography coupled with a triple quadrupole mass spectrometer, and insulin sensitivity was measured by means of a hyperinsulinaemic-euglycaemic clamp. RESULTS: A significant increase in all bile acids, as well as an amelioration of insulin sensitivity, was observed after metabolic surgery. An increase in conjugated secondary bile acids was significantly associated with an increase in insulin sensitivity. Only the increase in glycodeoxycholic acid was significantly associated with an increase in insulin sensitivity in analysis of individual conjugated secondary bile acids. CONCLUSION: Glycodeoxycholic acid might drive the improved insulin sensitivity after metabolic surgery.

Aleglitazar, a dual peroxisome proliferator-activated receptor-α/γ agonist, improves insulin sensitivity, glucose control and lipid levels in people with type 2 diabetes: findings from a randomized, double-blind trial.

The present single-centre, randomized, double-blind, placebo-controlled phase II study investigated the effect of the balanced dual peroxisome proliferator-activated receptor-α/γ agonist aleglitazar on whole-body and liver insulin sensitivity, ß-cell function and other components of cardiometabolic syndrome after 16 weeks of treatment in patients with type 2 diabetes inadequately controlled with metformin monotherapy who received once-daily 150 µg aleglitazar or matching placebo as add-on therapy to metformin. Baseline and 16-week assessments included a two-step hyperinsulinaemic-euglycaemic clamp, followed by a hyperglycaemic clamp, as well as evaluation of glycated haemoglobin (HbA1c), lipids and safety variables. The primary endpoint was change in whole-body insulin sensitivity (M-value) from baseline compared with placebo, derived from the second clamp step. M-value improved significantly from baseline with aleglitazar (n = 16) compared with placebo (n = 24; p = 0.05 for difference between arms). We found statistically significant treatment differences with aleglitazar versus placebo in fasting hepatic insulin resistance index (p = 0.01), and in total glucose disposal (p = 0.03) at the second insulin infusion step. Aleglitazar treatment resulted in significant improvements in HbA1c and lipids and was well tolerated.

The effect of muraglitazar on adiponectin signalling, mitochondrial function and fat oxidation genes in human skeletal muscle in vivo.

AIMS: The molecular mechanisms by which muraglitazar (peroxisome proliferator-activated receptor γ/α agonist) improves insulin sensitivity in Type 2 diabetes mellitus are not fully understood. We hypothesized that muraglitazar would increase expression of 5'-monophosphate-activated protein kinase and genes involved in adiponectin signalling, free fatty acid oxidation and mitochondrial function in skeletal muscle. METHODS: Sixteen participants with Type 2 diabetes received muraglitazar, 5 mg/day (n = 12) or placebo (n = 4). Before and after 16 weeks, participants had vastus lateralis muscle biopsy followed by 180 min euglycaemic hyperinsulinaemic clamp. RESULTS: Muraglitazar increased plasma adiponectin (9.0 ± 1.1 to 17.8 ± 1.5 µg/ml, P < 0.05), while no significant change was observed with placebo. After 16 weeks with muraglitazar, fasting plasma glucose declined by 31%, fasting plasma insulin decreased by 44%, insulin-stimulated glucose disposal increased by 81%, HbA1c decreased by 21% and plasma triglyceride decreased by 39% (all P < 0.05). Muraglitazar increased mRNA levels of 5'-monophosphate-activated protein kinase, adiponectin receptor 1, adiponectin receptor 2, peroxisome proliferator-activated receptor gamma coactivator-1 alpha and multiple genes involved in mitochondrial function and fat oxidation. In the placebo group, there were no significant changes in expression of these genes. CONCLUSIONS: Muraglitazar increases plasma adiponectin, stimulates muscle 5'-monophosphate-activated protein kinase expression and increases expression of genes involved in adiponectin signalling, mitochondrial function and fat oxidation. These changes represent important cellular mechanisms by which dual peroxisome proliferator-activated receptor agonists improve skeletal muscle insulin sensitivity.

A direct comparison of long- and short-acting GLP-1 receptor agonists (taspoglutide once weekly and exenatide twice daily) on postprandial metabolism after 24 weeks of treatment.

AIMS: T-emerge 2 was a randomized, open-label, 24-week trial comparing subcutaneous taspoglutide 10 mg weekly (Taspo10), taspoglutide 20 mg weekly (Taspo20; titrated after 4 weeks of Taspo10), with exenatide 10 mcg BID (Exe; after 4 weeks of Exe 5 mcg) in patients inadequately controlled on metformin, a thiazolidinedione, or both. T-emerge 2 showed that once-weekly Taspo provided better glycaemic control than Exe. This report focuses on a subset of T-emerge 2 participants undergoing a standardized liquid meal comparing Taspo to Exe, which has been previously shown to lower postprandial glucose. METHODS: Meal tolerance tests (MTT) were performed at baseline and at week 24 in a subset of Taspo10, Taspo20 and Exe patients (n = 42, 39 and 67, respectively). Blood samples for glucose, insulin, glucagon and C-peptide were obtained before and after (30, 60, 90, 120 and 180 min) ingestion of a standardized liquid meal. RESULTS: The 2-h postprandial, mean 0-3 h and iAUC0-3 h glucose during the MTT was reduced to a similar extent in all groups and the time profile of the postprandial glucose showed a similar pattern. Taspo10 and Taspo20, but not Exe, significantly increased insulin from baseline (both mean and iAUC0-3 h). Although changes from baseline in C-peptide were not significant within any treatment group, the mean change from baseline (both mean 0-3 h and iAUC0-3 h) was significantly increased in Taspo10 vs. Exe. Mean glucagon showed significant decreases in all groups. CONCLUSION: Taspoglutide and Exe improved postprandial glucose tolerance to a similar extent but possibly with different intimate mechanisms.

Direct effect of GLP-1 infusion on endogenous glucose production in humans.

AIMS/HYPOTHESIS: Glucagon-like peptide-1 (GLP-1) lowers glucose levels by potentiating glucose-induced insulin secretion and inhibiting glucagon release. The question of whether GLP-1 exerts direct effects on the liver, independently of the hormonal changes, is controversial. We tested whether an exogenous GLP-1 infusion, designed to achieve physiological postprandial levels, directly affects endogenous glucose production (EGP) under conditions mimicking the fasting state in diabetes. METHODS: In 14 healthy volunteers, we applied the pancreatic clamp technique, whereby plasma insulin and glucagon levels are clamped using somatostatin and hormone replacement. The clamp was applied in paired, 4 h experiments, during which saline (control) or GLP-1(7-37)amide (0.4 pmol min⁻¹ kg⁻¹) was infused. RESULTS: During the control study, plasma insulin and glucagon were maintained at basal levels and plasma C-peptide was suppressed, such that plasma glucose rose to a plateau of ~10.5 mmol/l and tracer-determined EGP increased by ~60%. During GLP-1 infusion at matched plasma glucose levels, the rise of EGP from baseline was fully prevented. Lipolysis (as indexed by NEFA concentrations and tracer-determined glycerol rate of appearance) and substrate utilisation (by indirect calorimetry) were similar between control and GLP-1 infusion. CONCLUSIONS/INTERPRETATION: GLP-1 inhibits EGP under conditions where plasma insulin and glucagon are not allowed to change and glucose concentrations are matched, indicating either a direct effect on hepatocytes or neurally mediated inhibition.

Validation of [18F]fluorodeoxyglucose and positron emission tomography (PET) for the measurement of intestinal metabolism in pigs, and evidence of intestinal insulin resistance in patients with morbid obesity.

AIMS/HYPOTHESIS: The role of the intestine in the pathogenesis of metabolic diseases is gaining much attention. We therefore sought to validate, using an animal model, the use of positron emission tomography (PET) in the estimation of intestinal glucose uptake (GU), and thereafter to test whether intestinal insulin-stimulated GU is altered in morbidly obese compared with healthy human participants. METHODS: In the validation study, pigs were imaged using [(18)F]fluorodeoxyglucose ([(18)F]FDG) and the image-derived data were compared with corresponding ex vivo measurements in tissue samples and with arterial-venous differences in glucose and [(18)F]FDG levels. In the clinical study, GU was measured in different regions of the intestine in lean (n = 8) and morbidly obese (n = 8) humans at baseline and during euglycaemic hyperinsulinaemia. RESULTS: PET- and ex vivo-derived intestinal values were strongly correlated and most of the fluorine-18-derived radioactivity was accumulated in the mucosal layer of the gut wall. In the gut wall of pigs, insulin promoted GU as determined by PET, the arterial-venous balance or autoradiography. In lean human participants, insulin increased GU from the circulation in the duodenum (from 1.3 ± 0.6 to 3.1 ± 1.1 µmol [100 g](-1) min(-1), p < 0.05) and in the jejunum (from 1.1 ± 0.7 to 3.0 ± 1.5 µmol [100 g](-1) min(-1), p < 0.05). Obese participants failed to show any increase in insulin-stimulated GU compared with fasting values (NS). CONCLUSIONS/INTERPRETATION: Intestinal GU can be quantified in vivo by [(18)F]FDG PET. Intestinal insulin resistance occurs in obesity before the deterioration of systemic glucose tolerance.

Plasma sCD36 is associated with markers of atherosclerosis, insulin resistance and fatty liver in a nondiabetic healthy population.

OBJECTIVES: Insulin resistance is associated with increased CD36 expression in a number of tissues. Moreover, excess macrophage CD36 may initiate atherosclerotic lesions. The aim of this study was to determine whether plasma soluble CD36 (sCD36) was associated with insulin resistance, fatty liver and carotid atherosclerosis in nondiabetic subjects. METHODS: In 1296 healthy subjects without diabetes or hypertension recruited from 19 centres in 14 European countries (RISC study), we determined the levels of sCD36, adiponectin, lipids and liver enzymes, insulin sensitivity (M/I) by euglycaemic-hyperinsulinaemic clamp, carotid atherosclerosis as intima-media thickness (IMT) and two estimates of fatty liver, the fatty liver index (FLI) and liver fat percentage (LF%). RESULTS: IMT, FLI, LF%, presence of the metabolic syndrome, impaired glucose regulation, insulin and triglycerides increased across sCD36 quartiles (Q2-Q4), whereas adiponectin and M/I decreased (P ≤ 0.01). sCD36 was lower in women than in men (P = 0.045). Log sCD36 showed a bimodal distribution, and amongst subjects with sCD36 within the log-normal distribution (log-normal population, n = 1029), sCD36 was increased in subjects with impaired glucose regulation (P = 0.045), metabolic syndrome (P = 0.006) or increased likelihood of fatty liver (P < 0.001). sCD36 correlated significantly with insulin, triglycerides, M/I and FLI (P < 0.05) after adjustment for study centre, gender, age, glucose tolerance status, smoking habits and alcohol consumption. In the log-normal population, these relationships were stronger than in the total study population and, additionally, sCD36 was significantly associated with LF% and IMT (P < 0.05). CONCLUSIONS: In this cross-sectional study of nondiabetic subjects, sCD36 was significantly associated with indices of insulin resistance, carotid atherosclerosis and fatty liver. Prospective studies are needed to further evaluate the role of sCD36 in the inter-relationship between atherosclerosis, fatty liver and insulin resistance.

Impact of increased visceral and cardiac fat on cardiometabolic risk and disease.

OBJECTIVE: Previous studies have highlighted the associations between abdominal, cardiac or total fat accumulation and cardiovascular disease. The aim of this study was to investigate the impact of different ectopic fat depots on measurements of metabolic dysfunction and cardiovascular disease risk. METHODS: Using magnetic resonance imaging in 113 subjects, we measured abdominal (visceral and subcutaneous) and cardiac (epicardial and extra-pericardial) fat depots and examined their association with overall (BMI) and abdominal obesity (waist circumference), dyslipidaemia (triglycerides, total and HDL cholesterol), glucose tolerance (by an oral glucose tolerance test) and insulin sensitivity, blood pressure and 10-year coronary heart disease risk by Framingham score. RESULTS: Fat accumulation was proportional to the degree of obesity, with body fat ranging from 14 to 33 kg, visceral fat from 0.8 to 1.8 kg and cardiac fat from 134 to 236 g. Most cardiac fat (70% on average) was extra-pericardial, with a wide variability for both cardiac depots (epicardial: 172-2008 mm(2); extra-pericardial: 100-5056 mm(2)). Only visceral and extra-pericardial fat, but not epicardial or subcutaneous fat, could discriminate between subjects with three or more factors of the metabolic syndrome or medium-to-high coronary heart disease risk score. Controlling for gender and BMI by multivariable analysis, the best marker of reduced insulin sensitivity was visceral fat (partial r = -0.35); extra-pericardial fat was the closest associate of increased blood pressure (partial r = 0.26) and both extra-pericardial and visceral fat clustered with hypertriglyceridaemia (partial r = 0.29 and 0.24; both P < 0.02). CONCLUSION: Increased epicardial fat per se does not necessarily translate into presence or prediction of disease. In contrast, increased deposition of visceral abdominal and extra-pericardial mediastinal fat are both associated with an enhanced cardiovascular disease risk profile.

Relationship between fatty liver and glucose metabolism: a cross-sectional study in 571 obese children.

BACKGROUND AND AIMS: Early onset type 2 diabetes mellitus (T2DM) is associated with obesity, insulin resistance and impaired beta-cell function. Non-alcoholic fatty liver disease (NAFLD) may be an independent risk factor for T2DM. We investigated the relationship between NAFLD and glucose metabolism in a large sample of obese children. METHODS AND RESULTS: A total of 571 obese children (57% males and 43% females) aged 8-18 years were consecutively studied at a tertiary care centre specialised in paediatric obesity. Liver ultrasonography was used to diagnose NAFLD after exclusion of hepatitis B and C and alcohol consumption. Oral-glucose tolerance testing (OGTT) was performed; insulin sensitivity was evaluated by using the insulin sensitivity index (ISI) and beta-cell function by using the ratio between the incremental areas under the curve (AUC) of insulin and glucose (incAUCins/incAUCglu). A total of 41% of the obese children had NAFLD. Impaired glucose tolerance or T2DM was present in 25% of the children with NAFLD versus 8% of those without it (p<0.001). Children with NAFLD had higher body mass index (BMI), fasting glucose, 120-min OGTT glucose, incAUCins/incAUCglu and lower ISI as compared with children without NAFLD (p≤0.002). At bootstrapped multivariable median regression analysis controlling for gender, age, pubertal status and BMI, NAFLD was an independent predictor of 120-min OGTT glucose and ISI, but not of incAUCins/incAUCglu. Similar findings were obtained using continuous liver steatosis as the predictor, instead of dichotomous NAFLD. CONCLUSION: NAFLD was present in 41% of our obese children and was associated with higher insulin resistance, but not with impaired beta-cell function.

Impact of percent body fat on oral glucose tolerance testing: a cross-sectional study in 1512 obese children.

BACKGROUND: Although an association between insulin resistance (IR) and body adiposity has been reported in obese children, this relationship has not been studied as thoroughly as in adults. AIM: We evaluated the association between oral glucose tolerance testing (OGTT) and percent body fat (PBF) in a sample of 1512 obese children followed at a Pediatric Obesity Clinic. SUBJECTS AND METHODS: Six hundred and twenty-eight male and 884 female obese children aged 6 to 18 yr were consecutively enrolled into the study. OGTT was performed with administration of 1.75 g of glucose per kg of body weight (up to 75 g). PBF was estimated through bioelectrical impedance analysis (BIA) using a population- specific formula recently published by our group. Multivariable median regression was used to evaluate the association between 4 outcomes [glucose area under the curve (AUC), insulin AUC, insulin sensitivity index (ISI), and insulinogenic index (IGI)] and gender, age or pubertal status and PBF. RESULTS: Median PBF was 52% (range 26 to 70%). After correction for age and gender, a 10% increase of PBF was associated with a decrease of -0.50 [95% confidence interval (CI): -0.65 to -0.35] units of ISI and an increase of 0.15 units of IGI (95%CI 0.07 to 0.24). CONCLUSIONS: In obese children, PBF is inversely associated with IR and directly associated to ß-cell response as detected by OGTT.

Early and longer term effects of gastric bypass surgery on tissue-specific insulin sensitivity and beta cell function in morbidly obese patients with and without type 2 diabetes.

AIMS/HYPOTHESIS: Bariatric surgery consistently induces remission of type 2 diabetes. We tested whether there are diabetes-specific mechanisms in addition to weight loss. METHODS: We studied 25 morbidly obese patients (BMI 51.7 ± 1.5 kg/m(2) [mean ± SEM]), 13 with non-insulin-treated type 2 diabetes (HbA(1c) 7.1 ± 0.5% [54 ± 5 mmol/mol]), before and at 2 weeks and 1 year after Roux-en-Y gastric bypass (RYGB). Lean (n = 8, BMI 23.0 ± 0.5 kg/m(2)) and obese (n = 14) volunteers who were BMI-matched (36.0 ± 1.2) to RYGB patients at 1 year after surgery served as controls. We measured insulin-stimulated glucose disposal (M) and substrate utilisation (euglycaemic clamp/indirect calorimetry), endogenous glucose production (EGP) by 6,6-[(2)H(2)]glucose, lipolysis (rate of appearance of [(2)H(5)]glycerol) and beta cell function (acute insulin response to i.v. glucose [AIR] as determined by C-peptide deconvolution). RESULTS: At baseline, all obese groups showed typical metabolic abnormalities, with M, glucose oxidation and non-oxidative disposal impaired, and EGP, lipolysis, lipid oxidation and energy expenditure increased. Early after RYGB plasma glucose and insulin levels, and energy expenditure had decreased, while lipid oxidation increased, with M, EGP and AIR unchanged. At 1 year post-RYGB (BMI 34.4 ± 1.1 kg/m(2)), all diabetic patients were off glucose-lowering treatment and mean HbA(1c) was 5.4 ± 0.14% (36 ± 2 mmol/mol) (p = 0.03 vs baseline); AIR also improved significantly. In all RYGB patients, M, substrate oxidation, EGP, energy expenditure and lipolysis improved in proportion to weight loss, and were therefore similar to values in obese controls, but still different from those in lean controls. CONCLUSIONS/INTERPRETATION: In morbidly obese patients, RYGB has metabolic effects on liver, adipose tissue, muscle insulin sensitivity and pattern of substrate utilisation; these effects can be explained by energy intake restriction and weight loss, the former prevailing early after surgery, the latter being dominant in the longer term.

Metabolic effects of muraglitazar in type 2 diabetic subjects.

AIM: To assess the effect of muraglitazar, a dual peroxisome proliferator-activated receptor (PPAR)γ-α agonist, versus placebo on metabolic parameters and body composition in subjects with type 2 diabetes mellitus (T2DM). METHODS: Twenty-seven T2DM subjects received oral glucose tolerance test (OGTT), euglycaemic insulin clamp with deuterated glucose, measurement of total body fat (DEXA), quantitation of muscle/liver (MRS) and abdominal subcutaneous and visceral (MRI) fat, and then were randomized to receive, in addition to diet, muraglitazar (MURA), 5 mg/day, or placebo (PLAC) for 4 months. RESULTS: HbA1c(c) decreased similarly (2.1%) during both MURA and PLAC treatments despite significant weight gain with MURA (+2.5 kg) and weight loss with PLAC (-0.7 kg). Plasma triglyceride, LDL cholesterol, free fatty acid (FFA), hsCRP levels all decreased with MURA while plasma adiponectin and HDL cholesterol increased (p < 0.05-0.001). Total body (muscle), hepatic and adipose tissue sensitivity to insulin and ß cell function all improved with MURA (p < 0.05-0.01). Intramyocellular, hepatic and abdominal visceral fat content decreased, while total body and subcutaneous abdominal fat increased with MURA (p < 0.05-0.01). CONCLUSIONS: Muraglitazar (i) improves glycaemic control by enhancing insulin sensitivity and ß cell function in T2DM subjects, (ii) improves multiple cardiovascular risk factors, (iii) reduces muscle, visceral and hepatic fat content in T2DM subjects. Despite similar reduction in A1c with PLAC/diet, insulin sensitivity and ß cell function did not improve significantly.

Acute effects of gastric bypass versus gastric restrictive surgery on beta-cell function and insulinotropic hormones in severely obese patients with type 2 diabetes.

CONTEXT: Hyperglycemia resolves quickly after bariatric surgery, but the underlying mechanism and the most effective type of surgery remains unclear. OBJECTIVE: To examine glucose metabolism and beta-cell function in patients with type 2 diabetes mellitus (T2DM) after two types of bariatric intervention; Roux-en-Y gastric bypass (RYGB) and gastric restrictive (GR) surgery. DESIGN: Prospective, nonrandomized, repeated-measures, 4-week, longitudinal clinical trial. PATIENTS: In all, 16 T2DM patients (9 males and 7 females, 52+/-14 years, 47+/-9 kg m(-2), HbA1c 7.2+/-1.1%) undergoing either RYGB (N=9) or GR (N=7) surgery. OUTCOME MEASURES: Glucose, insulin secretion, insulin sensitivity at baseline, and 1 and 4 weeks post-surgery, using hyperglycemic clamps and C-peptide modeling kinetics; glucose, insulin secretion and gut-peptide responses to mixed meal tolerance test (MMTT) at baseline and 4 weeks post-surgery. RESULTS: At 1 week post-surgery, both groups experienced a similar weight loss and reduction in fasting glucose (P<0.01). However, insulin sensitivity increased only after RYGB, (P<0.05). At 4 weeks post-surgery, weight loss remained similar for both groups, but fasting glucose was normalized only after RYGB (95+/-3 mg 100 ml(-1)). Insulin sensitivity improved after RYGB (P<0.01) and did not change with GR, whereas the disposition index remained unchanged after RYGB and increased 30% after GR (P=0.10). The MMTT elicited a robust increase in insulin secretion, glucagon-like peptide-1 (GLP-1) levels and beta-cell sensitivity to glucose only after RYGB (P<0.05). CONCLUSION: RYGB provides a more rapid improvement in glucose regulation compared with GR. This improvement is accompanied by enhanced insulin sensitivity and beta-cell responsiveness to glucose, in part because of an incretin effect.

Ectopic fat and cardiovascular disease: what is the link?

AIM: of this paper is to review the recent literature on the relationship between ectopic fat accumulation and cardiovascular disease. DATA SYNTHESIS: Ectopic fat is an important predictor of metabolic (in particular insulin resistance) and cardiovascular disease, carrying more risk than general fat accumulation. Recent studies have shown a link between ectopic fat accumulation, as cardiac (epicardial or intra-myocardial fat) and/or visceral and/or hepatic fat, and development of atherosclerosis, coronary heart disease and hypertension. CONCLUSIONS: Ectopic fat accumulation is not only a marker of cardiometabolic disease, since through the release of adipocitokines, lipotoxic and glucotoxic agents, participates in the crosstalk with insulin-sensitive organs leading to metabolic, cardiac and vascular dysfunctions.

Effect of pioglitazone on the metabolic and hormonal response to a mixed meal in type II diabetes.

We explored the mechanisms by which a 4-month, placebo-controlled pioglitazone treatment (45 mg/day) improves glycemic control in type II diabetic patients (T2D, n=27) using physiological testing (6-h mixed meal) and a triple tracer technique ([6,6-(2)H(2)]glucose infusion, (2)H(2)O and [6-(3)H]glucose ingestion) to measure endogenous glucose production (EGP), gluconeogenesis (GNG), insulin-mediated glucose clearance and beta-cell glucose sensitivity (by c-peptide modeling). Compared to sex/age/weight-matched non-diabetic controls, T2D patients showed inappropriately (for prevailing insulinemia) raised glucose production (1.05[0.53] vs 0.71[0.36]mmol min(-1) kg(ffm)(-1) pM, P=0.03) because of enhanced GNG (73.1+/-2.4 vs 59.5+/-3.6%, P<0.01) persisting throughout the meal, reduced insulin-mediated glucose clearance (6[5] vs 12[13]ml min(-1) kg(ffm)(-1) nM(-1), P<0.005), and impaired beta-cell glucose-sensitivity (27[38] vs 71[37]pmol min(-1) m(-2) mM(-1), P=0.002). Compared to placebo, pioglitazone improved glucose overproduction (P=0.0001), GNG and glucose underutilization (P=0.05) despite lower insulinemia. GNG improvement was quantitatively related to raised adiponectin. beta-cell glucose sensitivity was unchanged. In mild-to-moderate T2D, pioglitazone monotherapy decreased fasting and post-prandial glycemia, principally via inhibition of gluconeogenesis, improved hepatic and peripheral insulin resistance.

Reduction in hematocrit and hemoglobin following pioglitazone treatment is not hemodilutional in Type II diabetes mellitus.

Peripheral edema, mild weight gain, and anemia are often observed in type II diabetic patients treated with thiazolidinediones (TZDs). Small decreases in hemoglobin (Hb) and hematocrit (Hct) appear to be a class effect of TZDs and are generally attributed to fluid retention, although experimental data are lacking. We analyzed 50 patients with type II diabetes mellitus undergoing either placebo or pioglitazone (PIO, 45 mg/day) for 16 weeks. Before and after therapy, we measured Hb/Hct and used (3)H(2)O and bioimpedance to quantitate total body water (TBW), extracellular water, and fat-free mass. The majority (89%) of the increment in body weight was accounted for by increased body fat. Hb and Hct fell significantly in the PIO group (-0.9+/-0.2 g/dl, -2.4+/-0.5%, both P<0.0001), without change in TBW. A decline in white blood cell (-0.8+/-0.1 x 10(3)/mm(3), P<0.0001) and platelet (-15+/-6 x 10(3)/mm(3), P<0.02) counts was seen after PIO. In conclusion, the small decreases in Hb/Hct observed after 16 weeks of PIO treatment cannot be explained by an increase in TBW. Other causes, such a mild marrow suppressive effect, should be explored.

Pathway of free fatty acid oxidation in human subjects. Implications for tracer studies.

To determine the pathway of plasma FFA oxidation and the site(s) of label fixation observed during infusion of FFA tracers, [1-13C]palmitate and [1-14C]acetate were infused intravenously for 3 h in five volunteers. Breath 13CO2 enrichment and 14CO2 specific activity were followed for 6 h to determine the labeled CO2 decay rates. Acetate enters directly into the TCA cycle; hence, if palmitate transits a large lipid pool before oxidation, 13CO2 enrichment (from palmitate) should decay slower than 14CO2 specific activity (from acetate). Breath 13CO2 enrichment and 14CO2 specific activity decayed at a similar rate after stopping the tracer infusions (half-lives of 13CO2 and 14CO2 decay: mean [+/- SE] 106.6 +/- 8.9 min, and 96.9 +/- 6.0 min, respectively, P = NS), which suggests that palmitate enters the TCA cycle directly and that label fixation occurs after citrate synthesis. Significant label fixation was shown in plasma glutamate/glutamine and lactate/pyruvate during infusion of either [1,2-13C]acetate or [U-13C]palmitate, suggesting that TCA cycle exchange reactions are at least partly responsible for label fixation. This was consistent with our finding that the half-lives of 13CO2 enrichment and 14CO2 specific activity decreased significantly during exercise to 14.4 +/- 3 min and 16.8 +/- 1 min, respectively, since exercise significantly increases the rate of the TCA cycle in relation to that of the TCA cycle exchange reactions. We conclude that plasma FFA entering cells destined to be oxidized are directly oxidized and that tracer estimates of plasma FFA oxidation will underestimate the true value unless account is taken of the extent of label fixation.

An extended fatty liver index to predict non-alcoholic fatty liver disease.

BACKGROUND: In clinical practice, there is a strong interest in non-invasive markers of non-alcoholic fatty liver disease (NAFLD). Our hypothesis was that the fold-change in plasma triglycerides (TG) during a 2-h oral glucose tolerance test (fold-change TGOGTT) in concert with blood glucose and lipid parameters, and the rs738409 C>G single nucleotide polymorphism (SNP) in PNPLA3 might improve the power of the widely used fatty liver index (FLI) to predict NAFLD. METHODS: The liver fat content of 330 subjects was quantified by 1H-magnetic resonance spectroscopy. Blood parameters were measured during fasting and after a 2-h OGTT. A subgroup of 213 subjects underwent these measurements before and after 9 months of a lifestyle intervention. RESULTS: The fold-change TGOGTT was closely associated with liver fat content (r=0.51, P<0.0001), but had less power to predict NAFLD (AUROC=0.75) than the FLI (AUROC=0.79). Not only was the fold-change TGOGTT independently associated with liver fat content and NAFLD, but so also were the 2-h blood glucose level and rs738409 C>G SNP in PNPLA3. In fact, a novel index (extended FLI) generated from these and the usual FLI parameters considerably increased its power to predict NAFLD (AUROC=0.79-0.86). The extended FLI also increased the power to predict changes in liver fat content with a lifestyle intervention (n=213; standardized beta coefficient: 0.23-0.29). CONCLUSION: This study has provided novel data confirming that the OGTT-derived fold-change TGOGTT and 2-h glucose level, together with the rs738409 C>G SNP in PNPLA3, allow calculation of an extended FLI that considerably improves its power to predict NAFLD.

Hyperinsulinemia and autonomic nervous system dysfunction in obesity: effects of weight loss.

BACKGROUND: Because hyperinsulinemia acutely stimulates adrenergic activity, it has been postulated that chronic hyperinsulinemia may lead to enhanced sympathetic tone and cardiovascular risk. METHODS AND RESULTS: In 21 obese (body mass index, 35+/-1 kg/m(2)) and 17 lean subjects, we measured resting cardiac output (by 2-dimensional echocardiography), plasma concentrations and timed (diurnal versus nocturnal) urinary excretion of catecholamines, and 24-hour heart rate variability (by spectral analysis of ECG). In the obese versus lean subjects, cardiac output was increased by 22% (P:<0.03), and the nocturnal drop in urinary norepinephrine output was blunted (P:=0.01). Spectral power in the low-frequency range was depressed throughout 24 hours (P:<0.04). During the afternoon and early night, ie, the postprandial phase, high-frequency power was lower, heart rate was higher; and the ratio of low to high frequency, an index of sympathovagal balance, was increased in direct proportion to the degree of hyperinsulinemia independent of body mass index (partial r=0.43, P:=0.01). In 9 obese subjects who lost 10% to 18% of their body weight, cardiac output decreased and low-frequency power returned toward normal (P:<0.05). CONCLUSIONS: In free-living subjects with uncomplicated obesity, chronic hyperinsulinemia is associated with a high-output, low-resistance hemodynamic state, persistent baroreflex downregulation, and episodic (postprandial) sympathetic dominance. Reversal of these changes by weight loss suggests a causal role for insulin.