Aldo V. Greco

Evidence of Plasma CoQ10‐Lowering Effect by HMG‐CoA Reductase Inhibitors: A Double‐Blind, Placebo‐Controlled Study

Inhibitors of HMG‐CoA reductase are new safe and effective cholesterol‐lowering agents. Elevation of alanine‐amino transferase (ALT) and aspartate‐amino transferase (AST) has been described in a few cases and a myopathy with elevation of creatinine kinase (CK) has been reported rarely. The inhibition of HMG‐CoA reductase affects also the biosynthesis of ubiquinone (CoQ10). We studied two groups of five healthy volunteers treated with 20 mg/day of pravastatin (Squibb, Italy) or simvastatin (MSD) for a month. Then we treated 30 hypercholesterolemic patients in a double‐blind controlled study with pravastatin, simvastatin (20 mg/day), or placebo for 3 months. At the beginning, and 3 months thereafter we measured plasma total cholesterol, CoQ10, ALT, AST, CK, and other parameters (urea, creatinine, uric acid, total bilirubin, gamma GT, total protein). Significant changes in the healthy volunteer group were detected for total cholesterol and CoQ10 levels, which underwent about a 40% reduction after the treatment. The same extent of reduction, compared with placebo was measured in hypercholesterolemic patients treated with pravastatin or simvastatin. Our data show that the treatment with HMG‐CoA reductase inhibitors lowers both total cholesterol and CoQ10 plasma levels in normal volunteers and in hypercholesterolemic patients. CoQ10 is essential for the production of energy and also has antioxidative properties. A diminution of CoQ10 availability may be the cause of membrane alteration with consequent cellular damage.

Genetic epidemiology of cholesterol cholelithiasis among Chilean Hispanics, Amerindians, and Maoris

BACKGROUND & AIMS The etiology of cholesterol gallstones is multifactorial, with interactions of genes and the environment. The hypothesis that aborigine cholesterol lithogenic genes are widely spread among Chileans, a population with a high prevalence of gallstones, was tested. METHODS Medical history and anthropometric measurements were obtained and abdominal ultrasonography was performed in 182 Mapuche Indians, 225 Maoris of Easter Island, and 1584 Hispanics. Blood groups, DNA, lipids, and glucose were analyzed. The Amerindian Admixture Index and mitochondrial DNA (mtDNA) assessed the ethnicity and degree of racial admixture. RESULTS Amerindian Admixture Index was 0.8 in Mapuches and 0.4 in Hispanics. All Mapuches, 88% of Hispanics, but none of Maoris had Amerindian mtDNA haplotypes. Age- and sex-adjusted global prevalence of gallstone disease was higher in Mapuches (35%) than in Hispanics (27%) and Maoris (21%). Compared with Hispanics, the youngest group of Mapuches had the greatest corrected risk of gallstones: odds ratios of 6.0 in women and 2.3 in men. In contrast, the gallstone risk in Maoris was lower compared with Hispanics: odds ratios of 0.6 for women and 0.5 for men. CONCLUSIONS Cholesterol lithogenic genes appear widely spread among Chilean Indians and Hispanics. They could determine the early formation of gallstones and explain the high prevalence of gallbladder diseases among some South American populations.

Insulin Resistance Directly Correlates With Increased Saturated Fatty Acids in Skeletal Muscle Triglycerides

A close relationship between elevated plasma free fatty acid (FFA) levels and insulin resistance is commonly reported in obese subjects. The aim of the present study was to evaluate the role of intramuscular triglyceride (mTG) and FFA levels in insulin sensitivity in 30 nondiabetic normal-weight or obese subjects (18 with body mass index [BMI] = 21.8 +/- 3.3 kg/m2 and 12 with BMI = 34.6 +/- 2.7 kg/m2) who underwent minor abdominal surgery. Body composition was estimated by isotopic dilution, substrate oxidation by indirect calorimetry, and whole-body glucose uptake by euglycemic-hyperinsulinemic clamp (EHC). Glucose uptake (M) value negatively correlated with the MTG level (R2 = -.56, P < .0001), which was increased in obese patients (11.6 +/- 2.2 v 6.2 +/- 1.4 micromol/g wet weight muscle tissue, P < .0001). The TG fatty acid profile was significantly different in the 2 groups: an increased concentration of saturated fat was present in obese patients (unsaturated to saturated ratio, 1.89 +/- 0.40 v2.19 +/- 0.07, P < .0001). Stepwise linear regression analysis of total mTGs and palmitic and oleic fractions on the M value showed that only TGs and palmitic acid were significantly related to glucose uptake (R2 = .66, P < .0001). Furthermore, among the other anthropometric variables, only the BMI was significantly correlated with MTGs (R2 = .71, P < .0001). In conclusion, not only the MTG concentration but also the FFA pattern seems to affect insulin-mediated glucose uptake. A pivotal role might be played by a high saturated fatty acid content in the TGs.

Reversibility of insulin resistance in obese diabetic patients: role of plasma lipids

Summary The aim of the present study was to measure whole body glucose uptake (M) and oxidation rate by euglycaemic hyperinsulinaemic clamp and indirect calorimetry in 7 morbidly obese subjects (BMI > 40 kg/m2) at three time points: before bilio-pancreatic diversion (BPD) surgery (Ob); 3 months after surgery (POI); and after reaching stable body weight, at least 2 years after surgery (POII). A group of 7 control subjects (C), matched groupwise for sex, age and BMI with POII patients, was also studied. The M value at POI was significantly higher than at Ob (49.12 ± 8.57 vs 18.14 ± 8.57 μmol · kg−1· min−1). No statistical difference was observed between the POII and C groups. Similarly, glucose oxidation rate was significantly increased at POI with respect to Ob (24.2 ± 7.23 vs 9.42 ± 3.91 μmol · kg−1· min−1) and was not significantly different between POII and C. Basal levels of non-esterified fatty acids (NEFA) decreased significantly both from Ob to POI and from POI to POII (1517.1 ± 223.9 vs 1039.6 ± 283.4 vs 616.0 ± 77.6 μmol · l−1). The same applied to basal plasma triglycerides (2.07 ± 0.77 vs 1.36 ± 0.49 vs 0.80 ± 0.19 g · l−1). Weight decreased mainly in the late postoperative period (POI to POII 124.28 ± 11.22 to 69.71 ± 11.78, 83 % of total decrement), rather than in the early postoperative period (Ob to POI 135.25 ± 14.99 to 124.28 ± 11.22 kg, 17 % of total decrement). We also report the clinical case of a young woman of normal weight, who underwent BPD for chylomicronaemia (secondary to familial lipoprotein lipase deficiency), whose M value, plasma insulin and blood glucose levels were normalized upon normalization of serum NEFA and triglyceride levels as determined by the therapeutic lipid malabsorption. In conclusion, in obese diabetic patients lipid malabsorption induced by BPD causes a definite enhancement of insulin sensitivity and glucose tolerance. This improvement in metabolism is noticeable before the surgery has major effects on body weight. These observations suggest that lowered plasma lipids, rather than weight loss per se, are the cause of the reversibility of insulin resistance. [Diabetologia (1997) 40: 599–605]

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.

L-Carnitine Improves Glucose Disposal in Type 2 Diabetic Patients

OBJECTIVE Aim of the present study is to evaluate the effects of L-carnitine on insulin-mediated glucose uptake and oxidation in type II diabetic patients and compare the results with those in healthy controls. DESIGN Fifteen type II diabetic patients and 20 healthy volunteers underwent a short-term (2 hours) euglycemic hyperinsulinemic clamp with simultaneous constant infusion of L-carnitine (0.28 micromole/kg bw/minute) or saline solution. Respiratory gas exchange was measured by an open-circuit ventilated hood system. Plasma glucose, insulin, non-esterified fatty acids (NEFA) and lactate levels were analyzed. Nitrogen urinary excretion was calculated to evaluate protein oxidation. RESULTS Whole body glucose uptake was significantly (p<0.001) higher with L-carnitine than with saline solution in the two groups investigated (48.66+/-4.73 without carnitine and 52.75+/-5.19 micromoles/kg(ffm)/minute with carnitine in healthy controls, and 35.90+/-5.00 vs. 38.90+/-5.16 micromoles/kg(ffm)/minute in diabetic patients). Glucose oxidation significantly increased only in the diabetic group (17.61+/-3.33 vs. 16.45+/-2.95 micromoles/kg(ffm)/minute, p<0.001). On the contrary, glucose storage increased in both groups (controls: 26.36+/-3.25 vs. 22.79+/-3.46 micromoles/kg(ffm)/minute, p<0.001; diabetics: 21.28+/-3.18 vs. 19.66+/-3.04 micromoles/kg(ffm)/minute, p<0.001). In type II diabetic patients, plasma lactate significantly decreased during L-carnitine infusion compared to saline, going from the basal period to the end-clamp period (0.028+/-0.0191 without carnitine and 0.0759+/-0.0329 with carnitine, p<0.0003). CONCLUSIONS L-carnitine constant infusion improves insulin sensitivity in insulin resistant diabetic patients; a significant effect on whole body insulin-mediated glucose uptake is also observed in normal subjects. In diabetics, glucose, taken up by the tissues, appears to be promptly utilized as fuel since glucose oxidation is increased during L-carnitine administration. The significantly reduced plasma levels of lactate suggest that this effect might be exerted through the activation of pyruvate dehydrogenase, whose activity is depressed in the insulin resistant status.

Nonselective Loss of Contrast Sensitivity in Visual System Testing in Early Type I Diabetes

Objective Psychophysical methods in patients with diabetes mellitus reveal deficits of central or foveal vision. Our aim was to evaluate the contrast-sensitivity thresholds in 24 insulin-dependent (type I) diabetic patients with a short disease duration and without retinopathy, taking into account metabolic control. Research Design and Methods The control group consisted of age-matched nondiabetic subjects. None had visual or systemic symptoms. Contrast sensitivity measured at eight different spatial frequencies to sinusoidal bar patterns of 0.6–12.2 cycles/deg can detect functional defects in the spatially sensitive retinal ganglion cells or in higher visual pathways. We performed two different temporal types of contrast-sensitivity testing, dynamic (8 Hz) and static (0 Hz). Results Significant losses with dynamic contrast-sensitivity test at all but the highest spatial frequencies (i.e., 12.2 cycles/deg) were shown, whereas there was significant attenuation of contrast sensitivity at five spatial frequencies (1.0, 1.4, 2.2, 7.1, and 9.6 cycles/deg) in the static mode. Grating losses (<2SD of control means) of contrast sensitivity were found in 33.3% (dynamic) and in 72.9% (static) of eyes of diabetic patients. HbA1c values were positively correlated at variable spatial frequencies (1.0, 1.4, and 2.2 cycles/deg for dynamic test and 0.6, 1.0, 1.4, 2.2, 4.8, and 7.1 cycles/deg for static test). Conclusions Our results suggest an early, generally nonselective neuronal damage of visual pathways that occurs before the onset of clinically detectable retinopathy. The visual deficit may be related directly to the effects of diabetes; repetitive minor hypoglycemic insults may contribute more than a marked hyperglycemic condition to the mechanisms underlying physiological changes along the optic nerve.

Insulin and glucagon concentrations in portal and peripheral veins in patients with hepatic cirrhosis

SummaryThe portal vein was catheterized via the umbilical vein under local anaesthesia in 10 non-diabetic subjects about to undergo exploratory laparotomy and in 8 patients with liver cirrhosis. Immunoreactive insulin (IRI) and glucagon (IRG) were assayed in portal and peripheral blood before and during IV infusion of glucose (0.33 g/kg) or arginine (25 g). Basal peripheral plasma (IRI) levels were raised in cirrhotic patients (19±2 versus 10±1 μU/ml; P<0.001). Basal portal insulin values, however, did not differ in the two groups. After glucose cirrhotic patients had higher peripheral insulin concentrations, compared to controls, significant at 45 and 60 minutes. In contrast portal insulin levels were higher in controls than in cirrhotics by 1 minute (403±43 versus 158±38 μU/ml; P<0.001) and remained so for the 60 minutes of study. Similarly, after arginine cirrhotics had significantly higher peripheral insulin concentrations and lower portal concentrations than controls. Peak portal vein insulin levels were delayed in cirrhotics (168±16 μU/ml at 3 min) compared with controls (413±25 μU/ml at 1 min). In the basal state both portal and peripheral glucagon levels were higher in cirrhotics than control subjects. Unlike in controls, IV glucose did not suppress glucagon secretion in cirrhotic patients. Peripheral plasma glucagon concentrations after arginine were also consistently higher in cirrhotics than controls, but unlike insulin portal venous glucagon levels were also raised (1800±360 pg/ml, cirrhotics; 960±87 pg/ml, controls; P<0.001; 1 min after arginine infusion). We conclude that insulin secretion is decreased in liver cirrhosis and that the peripheral hyperinsulinaemia observed reflects diminished hormone metabolism. The high plasma glucagon levels observed in cirrhotic patients are the result of pancreatic hypersecretion of glucagon.

Skeletal muscle triglycerides lowering is associated with net improvement of insulin sensitivity, TNF-alpha reduction and GLUT4 expression enhancement.

AIMS/HYPOTHESIS: The aim of the present study was to investigate the relationship between intramyocytic triglycerides levels, muscle TNF-α and GLUT4 expression and insulin resistance.METHODS: Insulin sensitivity was studied in 14 severely obese women (BMI>40 kg/m2), before and 6 months after low-dietary intake or bariatric malabsorptive surgery (bilio-pancreatic diversion, BPD), by the euglycaemic hyperinsulinaemic clamp technique, while the amount of intramyocytic triglycerides was chemically measured in needle muscle biopsies. Using reverse transcriptase‐polymerase chain reaction analysis, the muscle mRNA expression of TNF-α and GLUT4 was also investigated.RESULTS: The weight loss after surgery was 25.98±5.81 kg (P<0.001), while that obtained with the diet was 5.07±5.99 kg (P=NS). Marked decrease in TNF-α mRNA levels (76.67±12.59 to 14.01±5.21 AU, P<0.001) were observed in comparison with pre-treatment, whereas GLUT4 was significantly increased (62.25±11.77–124.25±21.01 AU, P<0.001) only in BPD patients. Increased glucose uptake (M) was accompanied by a significant decrease of TNF-α mRNA (76.67±12.59–14.01±5.21 AU, P<0.01) and an increase of GLUT4. The amounts of TNF-α mRNAs in skeletal muscle correlated inversely with GLUT4 mRNAs and directly with intramyocytic triglycerides levels. In a step-down regression analysis (r2=0.95) TNFα mRNA (P=0.0014), muscular TG levels (P=0.018), and GLUT4 mRNA (P=0.028) resulted to be the most powerful independent variables for predicting M values.CONCLUSION/INTERPRETATION: These findings suggest that insulin resistance in morbidly obese patients is positively associated to the intramyocytic triglycerides content and to TNF-α gene expression and inversely correlated to GLUT4 expression.

Body composition and energy expenditure after weight loss following bariatric surgery

Objectives: To assess the effectiveness of biliopancreatic diversion (BPD) in the treatment of morbid obesity and to evaluate how the procedure affects body weight. Subjects: Fourteen morbidly obese subjects studied before and 30 months after BPD and fifteen healthy volunteers matched for age, sex and height (controls). Methods: Comparison of the following parameters were made in the study groups before surgery and 30 months after BPD and with those of the controls group: fat mass, fat-free mass, non-protein substrate oxidation, basal metabolic rate, plasma glucose, insulin and free fatty acid concentrations. Results: Obese subjects lost 60.38±10.71 kg of weight during 18 months following surgery and then remained stable for another 12 months, when this study was performed. Weight loss was substantially due to a loss of fat mass (FM: 60.13±13.01 kg before and 19.02±8.61 kg after BPD; p<0.001). FM were not statistically different between post-obese subjects and controls; however, post-obese patients retained significantly more fat free mass (FFM) than controls. Subsequently, basal metabolic rates of post-obese subjects were higher than those of the control group (p<0.05). Fasting non-protein respiratory quotient (npRQ) was significantly lower before BPD than 30 months after the surgery (0.798±0.04 vs. 0.90±0.048, p<0.001), suggesting that, while obese, patients oxidized more lipids than carbohydrates. Moreover, fasting and two-hour plasma glucose and insulin concentrations decreased significantly after BPD to values comparable to those of the control group. Conclusion: Weight loss in obese patients after BPD is mainly due to lipid malabsorption, but increased energy expenditure associated with retaining a high FFM in physically active post-obese subjects may also play a role, enabling them to maintain long-term reduced body weights.