Dodecanedioic acid overcomes metabolic inflexibility in type 2 diabetic subjects.

Metabolically healthy skeletal muscle possesses the ability to switch easily between glucose and fat oxidation in response to homeostatic signals. In type 2 diabetes mellitus and obesity, the skeletal muscle shows a great reduction in this metabolic flexibility. A substrate like dodecanedioic acid (C-12), able to increase skeletal muscle glycogen stores via succinyl-CoA formation, might both postpone the fatigue and increase fatty acid utilization, since it does not affect insulin secretion. In healthy volunteers and in type 2 diabetic subjects, the effect of an oral C-12 load was compared with a glucose or water load during prolonged, moderate-intensity, physical exercise. C-12 metabolism was analyzed by a mathematical model. After C-12, diabetics were able to complete the 2 h of exercise. Nonesterified fatty acids increased both during and after the exercise in the C-12 session. C-12 oxidation provided 14% of total energy expenditure, and the sum of C-12 plus lipids oxidized after the C-12 meal was significantly greater than lipids oxidized after the glucose meal (P < 0.025). The fraction of C-12 that entered the central compartment was 47% of that ingested. During the first phase of the exercise ( approximately 60 min), the mean C-12 clearance from the central compartment toward tissues was 2.57 and 1.30 l/min during the second phase of the exercise. In conclusion, C-12 seems to be a suitable energy substrate during exercise, since it reduces muscle fatigue, is rapidly oxidized, and does not stimulate insulin secretion, which implies that lipolysis is not inhibited as reported after glucose ingestion.

Low 25-hydroxyvitamin D does not affect insulin sensitivity in obesity after bariatric surgery.

OBJECTIVE: A positive correlation between levels of 25-hydroxyvitamin D [25(OH)D] and insulin sensitivity has been shown in healthy subjects. We aimed to test the hypothesis that concentration of 25(OH)D influences insulin sensitivity in obesity before and after weight loss. RESEARCH METHODS AND PROCEDURES: We investigated the relation between serum 25(OH)D and insulin sensitivity (estimated by euglycemic-hyperinsulinemic clamp) in 116 obese women (BMI > or = 40 kg/m2) evaluated before and 5 and 10 years after biliopancreatic diversion (BPD). Body composition was estimated by the isotope dilution method. RESULTS: Prevalence of hypovitaminosis D was 76% in the obese status and 91% and 89% at 5 and 10 years after BPD, respectively, despite ergocalciferol supplementation. 25(OH)D concentration decreased from 39.2 +/- 22.3 in obesity (p = 0.0001) to 27.4 +/- 16.4 and 25.1 +/- 13.9 nM 5 and 10 years after BPD, respectively. Whole-body glucose uptake increased from 24.27 +/- 4.44 at the baseline to 57.29 +/- 11.56 and 57.71 +/- 8.41 mumol/kg(fat free mass) per minute 5 and 10 years after BPD, respectively (p = 0.0001). Predictor of 25(OH)D was fat mass (R2 = 0.26, p = 0.0001 in obesity; R2 = 0.20, p = 0.02 after BPD). Parathormone correlated with fat mass (R2 = 0.19; p = 0.0001) and BMI (R2 = 0.053; p = 0.01) and inversely with M value (R2 = 0.16; p = 0.0001), but only in obese subjects. DISCUSSION: A high prevalence of hypovitaminosis D was observed in morbid obesity both before and after BPD. Low 25(OH)D did not necessarily imply increased insulin resistance after BPD, a condition where, probably, more powerful determinants of insulin sensitivity overcome the low circulating 25(OH)D levels. However, the present data cannot exclude some kind of influence of vitamin D status on glucose and insulin metabolism.

Effects of binge eating behavior on fuel oxidation and body composition.

OBJECTIVE: To investigate energy expenditure and glucose metabolism after a standard oral glucose load (75 g) in 8 normal weight bulimic women and 8 normal weight control women and to evaluate the relative endocrine implication. DESIGN: Serum glucose and insulin were measured both in basal conditions and after the glucose load; a basal endocrine assessment and body composition was evaluated and glucose induced thermogenesis (GIT) was calculated during 300 min following the glucose load. RESULTS: Serum glucose levels were significantly lower in bulimics both in fasting and in post-prandial state. Insulin levels were similar in bulimic and control women before and after the glucose load. FSH, leptin and free urinary cortisol (FUC) were all within the normal ranges, but significantly lower in bulimic patients compared with controls (p < 0.001). Fat mass (FM) and Fat-free mass (FFM) were reduced in bulimic patients, even if they normalized after correction per body weight. Resting energy expenditure (REE) was similar in the two groups even after FFM normalization, while GIT was lower in bulimic patients and it was strongly related to free urinary chortisol. Glucose oxidation was higher in fasting state and post glucose load, while lipid oxidation was strongly reduced. CONCLUSION: An energy preservation mechanism seems to be the key element for normal-weight bulimic patients' metabolism, consisting in leptin levels and GIT reduction, and lipid oxidation inhibition.

beta-cell function in morbidly obese subjects during free living: long-term effects of weight loss.

Insulin hypersecretion and insulin resistance are physiologically linked features of obesity. We tested whether extreme hypersecretion impairs beta-cell function under free-living conditions and whether major weight loss modifies insulin hypersecretion, insulin sensitivity, and beta-cell function. Plasma glucose, C-peptide, and free fatty acid concentrations were measured at hourly intervals during 24 h of normal life (including calorie-standardized meals) in 20 morbidly obese nondiabetic patients (BMI 48.4 +/- 1.7 kg/m2) and 7 nonobese age- and sex-matched control subjects; 8 of the obese patients were restudied 6 months and 2 years following biliopancreatic diversion. Insulin secretion was reconstructed from C-peptide levels by deconvolution and related to concurrent glucose levels through a mathematical model incorporating key features of beta-cell function: rate sensitivity, beta-cell glucose sensitivity, and potentiation. Insulin sensitivity (by the euglycemic insulin clamp technique) was reduced by 50% in obese subjects (23.1 +/- 2.5 of obese subjects vs. 52.9 +/- 4.9 micromol.min(-1) . kg(FFM)(-1) of control subjects, means +/- SE, P = 0.0004) as was mean 24-h insulin clearance (median 809 [interquartile range 451] vs. 1,553 [520] ml.min(-1) . m(-2), P < 0.001) due to a 50% reduction in hepatic insulin extraction (P < 0.01). Over 24 h, insulin secretion was doubled in obese subjects (468 nmol [202] in obese subjects vs. 235 [85] of control subjects, P=0.0002). Despite the hypersecretion, beta-cell glucose sensitivity, rate sensitivity, and potentiation were similar in obese and control subjects. Six months postoperatively (weight loss = 33 +/- 3 kg), both insulin hypersecretion (282 nmol [213]) and insulin sensitivity (51.6 +/- 3.7 micromol.min(-1).kg(FFM)(-1)) were normalized. At 2 years (weight loss = 50 +/- 8 kg), insulin sensitivity was supernormal (68.7 +/- 3.3 micromol.min(-1).kg(FFM)(-1)) and insulin secretion was lower than normal (167 nmol [37]) (both P < 0.05 vs. control subjects). In conclusion, severe uncomplicated obesity is characterized by gross insulin hypersecretion and insulin resistance, but the dynamic aspects of beta-cell function are intact. Malabsorptive bariatric surgery corrects both the insulin hypersecretion and the insulin resistance at a time when BMI is still high. With continued weight loss over a 2-year period, moderately obese subjects become supersensitive to insulin and, correspondingly, insulin hyposecretors.

Reduced plasma ghrelin concentration in celiac disease after gluten-free diet treatment.

OBJECTIVE: Celiac disease (CD) is characterized by malabsorption, weight loss and increased energy expenditure. The aim of this study was to investigate the relationship between circulating ghrelin and leptin, which are produced at gastrointestinal level and are involved in energy balance regulation, and changes in body composition and energy metabolism in CD patients before and after gluten-free diet (GFD)-induced restoration of the intestinal mucosa. MATERIAL AND METHODS: Body composition (by dual-energy X-ray absorptiometry), resting metabolic rate and substrate oxidation rates (by indirect calorimetry) were assessed in 18 adult women with the classic form of CD (age 31.4 +/- 7.8 years, body mass index (BMI) 20.6 +/- 2.1 kg/m2) before and at least 2 years after GFD treatment and in 22 age-matched healthy women (age 33.1 +/- 7.2 years, BMI 22.9 +/- 2.1 kg/m2). Plasma leptin and ghrelin concentrations were assessed by the ELISA and RIA procedures, respectively. RESULTS: Fat-free mass was reduced before and after GFD compared to control subjects (p < 0.01), while fat mass increased after treatment (p < 0.01). Plasma leptin concentration was similar between groups and correlated only with BMI (r = 0.84; p < 0.0001) and percentage body fat (r = 0.86; p < 0.0001). Circulating ghrelin levels (pg/ml) were similar between untreated patients and control subjects, but decreased after GFD treatment (untreated CD: 282.6 +/- 55.5 versus treated 109.2 +/- 49.9; p < 0.0001 and versus control subjects 262.2 +/- 30.0; p < 0.0001) and were negatively correlated with BMI in CD patients (r = -0.32; p < 0.01). CONCLUSIONS: The low plasma ghrelin concentration found in CD patients after GFD treatment could only be partially explained by the slight increase in body-weight and fat mass. Further studies are needed to better ascertain the role played by an incomplete functional or quantitative recovery of ghrelin-producing cells in CD.

Leptin pulsatility in formerly obese women.

Plasma leptin and growth hormone (GH) profile and pulsatility have been studied in morbidly obese subjects before and 14 months after bilio-pancreatic diversion (BPD), a bariatric technique producing massive lipid malabsorption. The maximum leptin diurnal variation (acrophase) decreased (10.27+/-1.70 vs. 22.60+/-2.79 ng x ml(-1); P=0.001), while its pulsatility index (PI) increased (1.084+/-0.005 vs. 1.050+/-0.004 ng x ml(-1) x min(-1); P=0.02) after BPD. Plasma GH acrophase increased (P=0.0001) from 0.91+/-0.20 to 4.58+/-0.80 microg x l(-1) x min(-1) after BPD as well as GH PI (1.70+/-0.13 vs. 1.20+/-0.04 microg x l(-1) x min(-1); P=0.024). Whole-body glucose uptake (M), assessed by euglycemic-hyperinsulinemic clamp, almost doubled after BPD (from 0.274+/-0.022 to 0.573+/-0.027 mmol x kgFFM(-1) x min(-1); P<0.0001), while 24 h lipid oxidation was significantly (P<0.0001) reduced (131.94+/-35.58 vs. 44.56+/-15.10 g). However, the average lipid oxidation was 97.2+/-3.1% (P<0.01) of the metabolizable lipid intake after the bariatric operation, while it was 69.2+/-8.5% before. After the operation, skeletal muscle ACC2 mRNA decreased (P<0.0001) from 452.82+/-76.35 to 182.45+/-40.69% of cyclophilin mRNA as did the malonyl-CoA (from 0.28+/-0.02 to 0.16+/-0.01 nmol x g(-1); P<0.0001). Leptin changes negatively correlated with M changes (R2=0.69, P<0.001). In a stepwise regression (R2=0.87, P=0.0055), only changes in 24 h free fatty acids (B=0.105+/-0.018, P=0.002) and glucose/insulin ratio (B=0.247+/-0.081, P=0.029) were the best predictors of leptin variations. In conclusion, the reversion of insulin resistance after BPD might allow reversal of leptin resistance, restoration of leptin pulsatility, and consequent inhibition of ACC2 mRNA expression, translating to a reduced synthesis of malonyl-CoA, which, in turn, results in increased fatty acid oxidation. Finally, since leptin inhibits GH secretion, a reduction of circulating leptin levels might have produced an increase in GH secretion, as observed in our series.

Ghrelin does not influence gastric emptying in obese subjects.

OBJECTIVE: To evaluate the relationship between fasting plasma concentrations of ghrelin and gastric emptying in obese individuals compared with lean subjects. RESEARCH METHODS AND PROCEDURES: We included 20 obese patients (9 men and 11 women, BMI > 30 kg/m2) and 16 nonobese control subjects (7 men and 9 women, BMI < or = 25 kg/m2). Gastric emptying of solids (egg sandwich labeled with radionuclide) was measured at 120 minutes with (99m)Tc-single photon emission computed tomography imaging. Ghrelin and leptin were analyzed by radioimmunoassay and ELISA methods, respectively. RESULTS: The gastric half-emptying time was similar in obese men and women (67.8 +/- 14.79 vs. 66.6 +/- 13.56 minutes) but significantly shorter (p < 0.001) than in the control population (men: 88.09 +/- 11.72 minutes; women: 97.25 +/- 10.31 minutes). Ghrelin levels were significantly lower in obese subjects (131.37 +/- 47.67 vs. 306.3 +/- 45.52 pg/mL; p < 0.0001 in men and 162.13 +/- 32.95 vs. 272.8 +/- 47.77 pg/mL; p < 0.0001 in women). A negative correlation between gastric emptying and fasting ghrelin levels was observed only in lean subjects (y = -0.2391x + 157.9; R2 = 0.95). Also, in the lean group, ghrelin was the only significant independent determinant of gastric emptying, explaining 98% of the variance (adjusted R2) in a multiple regression analysis. DISCUSSION: This report shows that, in humans, gastric emptying is faster in obese subjects than in lean controls and that, whereas ghrelin is the best determinant of gastric kinetics in healthy controls, this action is lost in obesity.

Changes in fat mass influence SREBP-1c and UCP-2 gene expression in formerly obese subjects.

OBJECTIVE: To investigate the effect of fat mass (FM) reduction on adipose tissue gene expression in terms of lipid synthesis [sterol regulatory binding protein 1c (SREBP-1c)] and lipid oxidation [uncoupling protein 2 (UCP-2)] 2 years after lipid malabsorption and to assess the influence of lipid malabsorption on fat-free mass (FFM) maintenance evaluating the expression of genes related to glycolysis [hexokinase (HKII)] and glucose storage [glycogen synthase (GS)]. RESEARCH METHOD AND PROCEDURES: SREBP-1c, UCP-2, HKII, and GS mRNA expression were studied by reverse transcriptase-competitive polymerase chain reaction in 10 massively obese subjects before and 2 years after bilio-pancreatic diversion (BPD). Body composition was assessed by isotopic dilution method and insulin sensitivity by euglycemic-hyperinsulinemic clamp. RESULTS: FM decrease was approximately 60%, whereas FFM remained at normal physiological levels. In adipose tissue, SREBP-1c mRNA reduction (-39%, p < 0.005) was related only to FM changes after BPD, and UCP-2 decrease (-37%, p < 0.05) was dependent on free fatty acid (FFA) changes. No significant variations were observed in HKII and GS gene expression in skeletal muscle. DISCUSSION: Lipid malabsorption induced by BPD altered the expression of genes involved in glucose and lipid metabolism, with different consequences on FM and FFM. The degree of FM loss seems to interfere with SREBP-1c gene suppression to preserve an adequate amount of fat storage, in accordance with the thrifty genotype hypothesis. The reduction of FFAs induced by BPD acts in inhibiting FFA transportation to the mitochondria (UCP-2), contributing to the decreased lipid oxidation inside the adipose tissue.

The ingestion of saturated fatty acid triacylglycerols acutely affects insulin secretion and insulin sensitivity in human subjects.

To assess the effects of acute dietary saturated fat intake on glucose-induced insulin secretion rate (ISR), measured by the C-peptide deconvolution method, and on insulin clearance and sensitivity, five obese and five normal-weight women (controls) were studied after either a 100 g oral butter load or a 100 ml water load. At 120 min after the oral load a hyperglycaemic clamp was performed over 180 min. A dramatic increase of ISR occurred after butter compared with the water challenge in the controls (1305.6 (SE 124.1) v. 616.1 (SE 52.5) pmol/min; P<0.01) and to a lesser degree in the obese subjects (1975.0 (SE 44.1) v. 1417.5 (se 56.0) pmol/min; P<0.05). Insulin sensitivity was impaired after butter (0.60 x 10(-2) (SE 0.11 x 10(-2)) v. 2.26 x 10(-2) (SE 0.32 x 10(-2)) ml/min per kg FFM per (pmol/l); P<0.01) in the controls but not in the obese group. Insulin clearance during the clamp was reduced after butter compared with after the water load only in the controls (0.89 (SE 0.22) v. 1.70 (SE 0.15) litres/min; P<0.01). The data are consistent with the hypothesis that acute excess lipid availability may lead to a compensatory elevation in glucose-induced insulin secretion as a result of the decline in insulin sensitivity and a reduced insulin clearance.

Hypocalcemia complicating near-total thyroidectomy in patients with coexisting lipid malabsorption due to biliopancreatic diversion.

BACKGROUND: Patients who have undergone biliopancreatic diversion (BPD) show a high incidence of mild hypocalcemia, which may become symptomatic and life-treating after an extensive thyroid operation. METHODS: 4 cases are reported of women who had undergone BPD, who subsequently underwent near-total thyroidectomy for extensive multinodular goiter. RESULTS: The first patient developed severe symptomatic hypocalcemia with malnutrition in the long-term, that required elongation of the common limb of the BPD. The second and third patients developed severe symptomatic hypocalcemia immediately after the thyroidectomy. In the fourth patient, preventive and continuing intravenous administration of calcium gluconate was started in the early hours after the thyroidectomy and allowed a safe and fast discharge home. CONCLUSION: In patients who are candidates for both thyroid and bariatric surgery, surgeons should carefully evaluate the opportunity to perform the thyroidectomy first. BPD patients who later undergo thyroidectomy should be perioperatively routinely treated with intravenous calcium and, whenever appropriate, intravenous vitamin D, to allow a safe and rapid discharge.

Lowered tumor necrosis factor receptors, but not increased insulin sensitivity, with infliximab.

OBJECTIVES: To verify whether Infliximab could modify insulin sensitivity and TNF-alpha and GLUT4 mRNA expression in muscle and adipose tissue of morbidly obese subjects. Soluble TNF receptors I and II (TNFR-I and TNFR-II) were also assayed. RESEARCH METHODS AND PROCEDURES: Six obese subjects were investigated before and 2 weeks after a single intravenous administration of 5 mg/kg Infliximab; insulin sensitivity was evaluated by euglycemic hyperinsulinemic clamp, and TNF-alpha and GLUT4 mRNA expression were assessed by reverse-transcriptase polymerase chain reaction on muscle and adipose tissue. TNF-alpha, TNFR-I, and TNFR-II were determined using the ELISA technique. RESULTS: Infliximab infusion did not affect fasting plasma insulin or fasting plasma glucose levels; whole body glucose uptake did not change significantly. TNF-alpha and GLUT4 mRNA did not show any significant change in muscle or adipose tissue. Serum TNF-alpha was undetectable before and after treatment, whereas TNFR-I and TNFR-II concentrations significantly decreased (p < 0.01). DISCUSSION: An explanation for the absence of effect of Infliximab on insulin resistance in morbidly obese subjects may be the paracrine way of action of this cytokine. Because Infliximab is predominantly distributed within the vascular compartment, its effectiveness in penetrating muscle and adipose tissue is potentially low. The significant decrease of TNFR-I and TNFR-II might be ascribed to a targeted effect of Infliximab on the immune system.

Restoration of adiponectin pulsatility in severely obese subjects after weight loss.

Diurnal variations of adiponectin levels have been studied in normal-weight men and in diabetic and nondiabetic obese subjects, but no data have been reported in obese subjects after weight loss. We collected blood samples at 1-h intervals over 24 h from seven severely obese subjects before and after massive weight loss consequent to surgical operation (bilio-pancreatic diversion [BPD]) to measure adiponectin, insulin, glucose, and cortisol levels. Insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp (M value). Studies of diurnal variations and pulsatility of adiponectin, insulin, and cortisol were performed. The pulsatility index (PI) of adiponectin increased after BPD from 0.04 to 0.11 microg/min (P = 0.01). Insulin PI significantly increased after the operation (1.50 vs. 1.08 pmol.l(-1).min(-1), P = 0.01), while cortisol PI did not significantly change. The adiponectin clearance rate changed from 0.001 +/- 10(-4).min(-1) before BPD to 0.004 +/- 8. 10(-4).min(-1) after BPD (P = 0.03). Insulin clearance increased from 0.006 +/- 6. 10(-4).min(-1) before BPD to 0.009 +/- 4.10(-4). min(-1) after BPD (P = 0.02). The M value doubled after surgery (27.08 +/- 8.5 vs. 53.34 +/- 9.3 micromol.kg(FFM)(-1).min(-1); P < 0.001) becoming similar to the values currently reported for normal-weight subjects. In conclusion, in formerly severely obese subjects, weight loss paired with the reversibility of insulin resistance restores homeostatic control of the adiponectin secretion, contributing to the reduction of cardiovascular risk already described in these patients.

Insulin clearance in obesity.

Insulin uptake and degradation is a complex and not yet completely understood process involving not only insulin sensitive tissues. The most important degradative system is insulin degrading enzyme which is a highly conserved metalloendopeptidase requiring Zn(++) for its proteolytic action, although protein disulfide isomerase and cathepsin D are also involved in insulin metabolism. The liver and the kidney are the principal sites for insulin clearance. In obese subjects with hyperinsulinemia and high levels of free fatty acids, insulin hepatic clearance is impaired, while the glomerular filtration rate, renal plasma flow and albumin excretion are increased, suggesting a state of renal vasodilatation leading to an abnormally transmitted arterial pressure to the glomerular capillaries through a dilated afferent arteriole. Insulin can be cleared also by muscle, adipocytes, gastrointestinal cells, fibroblasts, monocytes and lymphocytes which contain insulin receptors and internalization and regulation mechanism for insulin metabolism.

Decreased muscle acetyl-coenzyme A carboxylase 2 mRNA and insulin resistance in formerly obese subjects.

OBJECTIVE: A relationship between free fatty acids, intramuscular triglycerides (TG(M)s), and insulin resistance is widely accepted. The intracellular level of malonyl-coenzyme A (CoA) was suggested to be the possible link. Acetyl-CoA carboxylase (ACC) is a key enzyme in fatty acid metabolism, catalyzing the synthesis of malonyl-CoA, a fatty acid acyl-chain elongation unit, from acetyl-CoA. We assessed ACC2 mRNA expression variations in skeletal muscle of subjects who have undergone biliopancreatic diversion (BPD) operation. BPD, in fact inducing a massive lipid malabsorption, leads to a reversion of insulin resistance. RESEARCH METHODS AND PROCEDURES: Twelve obese women (BMI > 40 kg/m(2)) were enrolled in the study. Body composition, euglycemic-hyperinsulinemic clamp, and muscle biopsies for lipid analysis and reverse transcription-competitive polymerase chain reaction were performed before and 3 years after BPD. RESULTS: The average weight loss was around 37%. A significant inverse linear relation was observed between glucose uptake and TG(M) (y = -5.62x - 142.82, R(2) = 0.50, p = 0.01). The reduced amount of ACC2 mRNA directly correlated with both TG(M) (y = 2.11x +69.85, R(2) = 0.70, p = 0.01) and fasting insulin (y = 1.49x + 57.17, R(2) = 0.69, p < 0.01) concentrations. DISCUSSION: In conclusion, down-regulation of ACC2 mRNA, induced by the lowering of plasma insulin concentration, is related to improvement of insulin sensitivity. We hypothesize that reduced amount of malonyl-CoA, consequent to reduced ACC2 mRNA, enhancing fatty acid oxidation, causes lowering of the intramyocitic triglyceride depot.

Decreased uncoupling protein expression and intramyocytic triglyceride depletion in formerly obese subjects.

OBJECTIVE: To examine the muscular uncoupling protein expression 2 (UCP2) and UCP3 gene expression in morbid obese subjects before and after bariatric surgery [bilio-pancreatic diversion (BPD)]. RESEARCH METHODS AND PROCEDURES: Eleven obese subjects (BMI = 49 +/- 2 kg/m(2)) were studied before BPD and 24 months after BPD. Skeletal muscle UCP2 and UCP3 mRNA was measured using reverse transcriptase-competitive polymerase chain reaction and UCP3 protein by Western blotting. Intramyocytic triglycerides were quantified by high-performance liquid chromatography. Twenty-four-hour energy expenditure and respiratory quotient (RQ) were measured in a respiratory chamber. RESULTS: After BPD, the average weight loss was approximately 38%. Nonprotein RQ was increased in the postobese subjects (0.73 +/- 0.00 vs. 0.83 +/- 0.02, p < 0.001). The intramyocytic triglyceride level dropped (3.66 +/- 0.16 to 1.60 +/- 0.29 mg/100 mg of fresh tissue, p < 0.0001) after BPD. Expression of UCP2 and UCP3 mRNA was significantly reduced (from 35.9 +/- 6.1% to 18.6 +/- 4.5% of cyclophilin, p = 0.02; from 60.2 +/- 14.0% to 33.4 +/- 8.5%, p = 0.03; respectively). UCP3 protein content was also significantly reduced (272.19 +/- 84.13 vs. 175.78 +/- 60.31, AU, p = 0.04). A multiple regression analysis (R(2) = 0.90) showed that IMTG levels (p = 0.007) represented the most powerful independent variable for predicting UCP3 variation. DISCUSSION: The strong correlation of UCP expression and decrease in IMTG levels suggests that triglyceride content plays an even more important role in the regulation of UCP gene expression than the circulating levels of free fatty acids or the achieved degree of weight loss.

Bioimpedance analysis: a useful technique for assessing appendicular lean soft tissue mass and distribution.

The present study was aimed at evaluating the feasibility and reliability of lower limb skeletal muscle (SM) mass estimates obtained by bioimpedance analysis (BIA). BIA estimates were compared with the estimates obtained by dual-energy X-ray absorptiometry (DXA). Ten normal weight and 10 obese women had BIA and DXA evaluations. Lower limb SM mass was then derived from DXA appendicular lean soft tissue estimates. Lower limb SM mass and SM distribution were also estimated from BIA modeling that fits measured resistance values along the leg. SM mass (mean +/- SD) was 5.8 +/- 1.0 kg by BIA vs. 5.8 +/- 1.1 kg by DXA in normal weight subjects and 7.2 +/- 1.4 kg by BIA vs. 7.2 +/- 1.2 kg by DXA in obese subjects. Mean +/- SD of the absolute value of the relative error was 7.0 +/- 3.4 and 5.9 +/- 3.4% in the two groups, respectively. Similar results were obtained by using five resistance values for the analysis. In conclusion, the proposed BIA model provides an adequate means of evaluating appendicular SM mass.

Reduced PDK4 expression associates with increased insulin sensitivity in postobese patients.

OBJECTIVE: The aim of this study was to verify whether changes in PDK4 mRNA expression in skeletal muscle in formerly obese subjects who underwent malabsorptive bariatric surgery [bilio-pancreatic diversion (BPD)] might be related to insulin sensitivity improvement, and if these possible modifications might correlate with a reduction of the intramyocytic lipid level. RESEARCH METHODS AND PROCEDURES: Six obese women (body mass index 46.6 +/- 8.2 kg/m(2)) were enrolled in the study. Body composition, euglycemic-hyperinsulinemic clamp and muscle biopsies for skeletal muscle lipid analysis, and semiquantitative reverse transcriptase-polymerase chain reaction were performed before and 3 years after BPD. RESULTS: The average weight loss observed after surgery was approximately 42%. Increased glucose uptake was accompanied by a significant decrease of PDK4 mRNA (R(2) = 0.71, p < 0.001). The amounts of intramyocytic triglycerides correlate directly with PDK4 mRNA (R(2) = 0.87, p = 0.005) and inversely with glucose uptake values (R(2) = 0.75, p < 0.001). DISCUSSION: Our results support the concept that a reduced tissue availability of fatty acids consequent to a massive lipid malabsorption influences glucose metabolism acting through the regulation of PDH complex. In fact, as shown in animals, a higher level of FFA availability is likely to induce overexpression of PDK4 also in humans.

Lowering of circulating free-fatty acids levels and reduced expression of leptin in white adipose tissue in postobesity status.

BACKGROUND: Our aim was to investigate the regulation of the gene expression of leptin in subcutaneous adipose tissue biopsies in morbid obesity before and after biliopancreatic diversion (BPD). METHODS: Longitudinal study in morbidly obese subjects investigated twice: before and 6 months after BPD. Fourteen morbidly obese women, 37+/-13 years old and with a body mass index of 51.6+/-8.2 kg/m2, were studied before and 6 months after BPD (40.6+/-8.0 kg/m2). Using reverse transcriptase polymerase chain reaction analysis, the mRNA expression of leptin was investigated in adipose tissue. Plasma leptin was measured by radioimmunoassay; plasma insulin was measured by microparticle enzyme immunoassay. Free fatty acids (FFA) were measured using a colorimetric kit. RESULTS: A significant decrease in leptin mRNA level was observed in comparison with pretreatment in BPD patients (59+/-34 vs 143+/-85 arbitrary units, P<0.01). A strict relationship between adipose tissue leptin mRNA and plasma leptin either before (R2=0.80, P<0.0001) or after BPD (R2=0.86, P<0.0001) and between plasma FFA concentration and insulin either before (R2=0.65, P<0.001) or after BPD (R2=0.92, P<0.0001) was observed. Finally, a significant correlation was found between changes in FFA and insulin (R2=0.64, P<0.001), insulin and leptin (R2=0.88, P<0.0001), and insulin and leptin mRNA (R2=0.83, P<0.0001). CONCLUSION: These data demonstrate a high correlation between leptin mRNA expression in adipose tissue and plasma leptin in postobese subjects after BPD. The significant relationship between both leptin mRNA and plasma leptin with insulin suggests that circulating insulin might regulate leptin expression. It might be hypothesized that plasma FFA concentration can act on the insulin secretion and subsequently on the leptin secretory pathway.

Insulin resistance in morbid obesity: reversal with intramyocellular fat depletion.

Obesity is a frequent cause of insulin resistance and poses a major risk for diabetes. Abnormal fat deposition within skeletal muscle has been identified as a mechanism of obesity-associated insulin resistance. We tested the hypothesis that dietary lipid deprivation may selectively deplete intramyocellular lipids, thereby reversing insulin resistance. Whole-body insulin sensitivity (by the insulin clamp technique), intramyocellular lipids (by quantitative histochemistry on quadriceps muscle biopsies), muscle insulin action (as the expression of Glut4 glucose transporters), and postprandial lipemia were measured in 20 morbidly obese patients (BMI = 49 +/- 8 [mean +/- SD] kg x m(-2)) and 7 nonobese control subjects. Patients were restudied 6 months later after biliopancreatic diversion (BPD; n = 8), an operation that induces predominant lipid malabsorption, or hypocaloric diet (n = 9). At 6 months, BPD had caused the loss of 33 +/- 10 kg through lipid malabsorption (documented by a flat postprandial triglyceride profile). Despite an attained BMI still in the obese range (39 +/- 8 kg x m(-2)), insulin resistance (23 +/- 3 micromol/min per kg of fat-free mass; P < 0.001 vs. 53 +/- 13 of control subjects) was fully reversed (52 +/- 11 micromol/min per kg of fat-free mass; NS versus control subjects). In parallel with this change, intramyocellular-but not perivascular or interfibrillar-lipid accumulation decreased (1.63 +/- 1.06 to 0.22 +/- 0.44 score units; P < 0.01; NS vs. 0.07 +/- 0.19 of control subjects), Glut4 expression was restored, and circulating leptin concentrations were normalized. In the diet group, a weight loss of 14 +/- 12 kg was accompanied by very modest changes in insulin sensitivity and intramyocellular lipid contents. We conclude that lipid deprivation selectively depletes intramyocellular lipid stores and induces a normal metabolic state (in terms of insulin-mediated whole-body glucose disposal, intracellular insulin signaling, and circulating leptin levels) despite a persistent excess of total body fat mass.