Steatosi epatica non alcolica e diabete mellito tipo 2: studio dell'associazione tra grado di steatosi, fattori metabolici e alterazioni vascolari

NAFLD (non alcoholic fatty liver disease) is defined by the presence of hepatic steatosis not associated with a significant alcohol intake nor to the assumption of specific drugs. It is frequently associated with diabetes, obesity and metabolic syndrome. Many authors support the concept that NAFLD is the hepatic manifestation of the metabolic syndrome, and that the insulin-resistance is the common soil in the pathogenesis. Although the natural history of this disease seems to be benign, an evolution toward steatohepatitis and cirrhosis, and a link between NAFLD and cardiovascular (clinical and subclinical) diseases, have been demonstrated. The objectives of this research were to evaluate prevalence and degree of steatosis in patients with type 2 diabetes and the metabolic syndrome (defined by ATP III criteria); to search for metabolic factors which are predictive for the degree of steatosis, and to evaluate the possible link between hepatic steatosis and anatomic vasculopathy (intima-media thickness – IMT and carotid plaques) and endothelial function (flow mediated dilation - FMD). An observational study was performed among 60 type 2 diabetic patients (M/F 25/35) with metabolic syndrome afferent to our Diabetes Center. Steatosis was evaluated by means of semi-quantitative ecography (4 grades) as well as by an “objective quantitative” method based on the determination of liver/kidney ratio (6 grades). The presence of carotid plaques and the IMT measurement were evaluated by means of ecocolordoppler of the supra-aortic arteries. The endothelial function was evaluated by means of ecography as the vasodilatation induced by ischemia in the brachial artery (FMD). We measured anthropometric variables (body mass index, waist circumference), metabolic parameters (lipids, HbA1c, HOMA), inflammation markers (hs-PCR, IL-6, TNFα), thrombogenic factors (fibrinogen) and an adipokine (leptin). We applied a statistical program (Ordered Probit) to evaluated the probability to predict the degree of steatosis by the combination of metabolic parameters. The prevalence of steatosis was 88% (33% mild steatosis, 33% moderate e 22% severe). IMT was 0.88 ± 0.23mm; 63% of patients had carotid plaques. FMD (calculated in 45 patients) was reduced with respect to normal values (5.02 ± 1.81%). We demonstrated a correlation between the degree of steatosis and BMI, waist, the number of metabolic syndrome’s factors, sex, diastolic pressure, insulinemia, HOMA, Hb1Ac, HDL-cholesterol (inverse), hs-PCR, fibrinogen, leptin. We didn’t demonstrate any correlation between steatosis, and medium and maximum IMT, the presence of carotid plaques and FMD. With multiple regression analysis HOMA and BMI levels were indipendent factors which predict hepatic steatosis (p 0.033). Using the combination of HbA1c, waist and insulinemia, a prediction of the exact grade of steatosis (± one steatosis grade) (evaluated by ecography) was obtained in 96.5% of cases. This study confirms that, in this population of diabetic patients with metabolic myndrome, NAFLD can be considered the hepatic manifestation of the syndrome since it correlates with HOMA and obesity. A high prevalence of increased IMT and of presence of carotid plaques, as well as a reduced FMD compared to general population, are also demonstrated, although they are not apparently linked with steatosis.La steatosi epatica non alcolica (NAFLD) si definisce come la presenza di steatosi epatica in soggetti con modesto o assente consumo di alcol e mancata assunzione/esposizione a determinati farmaci o sostanze; è frequentemente associata al diabete, all’obesità e alla sindrome metabolica, tanto da essere considerata da molti autori come la manifestazione epatica della sindrome metabolica, avendo come fattore patogenetico comune l’insulino-resistenza. La storia naturale della NAFLD sembra benigna anche se può evolvere in steatoepatite e in cirrosi ed è stata dimostrata una correlazione tra NAFLD e patologie cardiovascolari (cliniche e subcliniche). Lo scopo dello studio è stato di valutare la prevalenza ed il grado di steatosi epatica in un gruppo di pazienti affetti da diabete mellito tipo 2 e sindrome metabolica (definita in base ai criteri dell’ATP III), di ricercare i fattori metabolici predittivi del grado di steatosi e di valutare l’eventuale relazione esistente tra steatosi epatica e vasculopatia anatomica (spessore medio-intimale carotideo [IMT] e placche carotidee) e funzionale (dilatazione flusso mediata [FMD]). E’ stato eseguito uno studio osservazionale su 60 pazienti (M/F 25/35) affetti da diabete mellito di tipo 2 e sindrome metabolica afferenti al nostro servizio di Diabetologia. La presenza di steatosi è stata valutata mediante ultrasonografia sia con metodica soggettiva semiquantitativa (4 gradi) sia con metodica oggettiva quantitativa mediante la determinazione del rapporto fegato/rene (6 gradi). La ricerca di placche aterosclerotiche carotidee e la misurazione dell’IMT sono stati eseguiti con ecocolordoppler dei tronchi sovraaortici; la funzione endoteliale è stata valutata mediante ultrasonografia con valutazione della vasodilatazione indotta dall’ischemia a livello dell’arteria brachiale (FMD). Sono stati misurati i parametri antropometrici (indice di massa corporea e circonferenza addominale), metabolici (assetto lipidico, HbA1c, HOMA), citochine infiammatorie (hs-PCR, IL-6, TNFα), fattori trombogenici (fibrinogeno) e adipochine (leptina). E’ stato utilizzato inoltre un programma statistico (Ordered Probit) in cui associando alcuni parametri metabolici viene predetta la probabilità del soggetto di appartenere ad una determinata classe di steatosi. La prevalenza di steatosi è risultata dell’88% (33% steatosi lieve, 33% moderata e 22% grave); l’IMT medio pari a 0.88 ± 0.23 mm; il 63% dei pazienti presentavano placche carotidee; l’FMD (calcolato su 45 pazienti) è risultato ridotto e pari a 5.02 ± 1.81%. Dividendo i pazienti per classi di steatosi abbiamo evidenziato una correlazione tra steatosi e BMI, circonferenza addominale, numero dei fattori della sindrome metabolica, sesso, pressione diastolica, insulinemia, HOMA, HbA1c, colesterolo-HDL (inversa), hs-PCR, fibrinogeno e log leptinemia. Non abbiamo dimostrato invece alcuna correlazione tra grado di steatosi e IMT medio o massimo, presenza di placche aterosclerotiche e valore di FMD. Con il modello di regressione multipla HOMA e waist sono risultati fattori indipendenti che influenzano il grado di steatosi epatica (p 0.033). Associando HbA1c, waist, insulinemia il modello statistico Ordered Probit mi predice il grado esatto o con un errore di un grado di steatosi soggettiva (valutato all’ecografia) nel 96,5% dei casi. Questo studio conferma che nei nostri pazienti diabetici con sindrome metabolica la NAFLD correla strettamente con obesità e insulino-resistenza, può essere quindi considerata la manifestazione epatica della sindrome metabolica. E’ stata dimostrata un’elevata prevalenza di aumentato IMT e di placche carotidee, così come di riduzione dell’FMD rispetto alla popolazione generale, sebbene non sembra esservi correlazione con la steatosi epatica

Effects of insulin on methionine and homocysteine kinetics in type 2 diabetes with nephropathy

Although hyperhomocysteinemia, an independent cardiovascular risk factor, is common in type 2 diabetes with nephropathy, the mechanism(s) of this alteration is not known. In healthy humans, hyperinsulinemia, increases methionine transmethylation, homocysteine transsulfuration, and clearance. No such data exist in type 2 diabetes either in the fasting state or in response to hyperinsulinemia. To this purpose, seven male type 2 diabetic patients with albuminuria (1.2 +/- 0.4 g/day, three with mild to moderate renal insufficiency) and seven matched control subjects were infused for 6 h with (L)-[methyl-H-2(3), 1-C-13]methionine. Methionine flux, transmethylation, and disposal into proteins as well as homocysteine remethylation, transsulfuration, and clearance were determined before and after euglycemic hyperinsulinemia (similar to 1,000 pmol/l). In type 2 diabetic subjects, homocysteine concentration was twofold greater (P 50% and from similar to 40 to > 100%, respectively; P < 0.05) than in control subjects. The insulin-induced increments of methionine transmethylation, homocysteine transsulfuration, and clearance were markedly reduced in type 2 diabetic subjects (by more than threefold, P < 0.05 or less vs. control subjects). In contrast, methionine methyl and carbon flux were not increased in the patients. In conclusion, pathways of homocysteine disposal are impaired in type 2 diabetes with nephropathy, both in postabsorptive and insulin-stimulated states, possibly accounting for the hyperhomocysteinemia of this condition

No association between the degree of liver steatosis and early signs of vasculopathy in T2DM.

Non alcoholic fatty liver disease (NAFLD) is both an independent and an associated risk factor for cardiovascular (CV) disease in the general population [1]. Whereas the association between NAFLD, and early signs of vasculopathy, such as an increased intima-media thickness (IMT) and a decreased flow-mediated vasodilation (FMD), has been reported in the general population, such an association in type 2 diabetes mellitus (T2DM) is controversial. In T2DM patients with NAFLD FMD was decreased [2], whereas IMT was not different, with respect to patients without liver steatosis [3]. Should a (causative) relationship between hepatic steatosis and early signs of vasculopathy exists, the degree of liver fat should be associated with a worse endothelial function and morphology. However, despite the bulk of data generated on this complex association, insufficient reports exist on T2DM. To this aim, we measured the extent of liver fat, average IMT, the presence and type of carotid plaques, and FMD, in sixty consecutive T2DM patients largely affected by features of the MS. Liver steatosis, IMT, and presence and types of carotid plaques, were evaluated by ultrasonography (using an HDI 5000 Philips Medical Systems apparatus, Bothell, WA, USA), with a broad-band width phased array transducer (2–5 MHz). Steatosis was divided into four classes following the traditional US classification (class 0: absence; classes 1–3: increasing degrees, of steatosis) [4]. IMT was assessed using standard procedures [5]. FMD was evaluated in 45 patients using an internationally validated approach [6]. Only six patients were current smokers, and seven had a positive history for CV disease (five for ischemic heart disease, and two for cerebrovascular disease). No subject was positive for hepatitis C virus infection. The overall prevalence of steatosis was 88% (34% mild, 34% moderate e 20% severe). Average IMT was 0.88 ± 0.03 mm (Mean ± SE), significantly greater (p < 0.0001) than the mean value of a healthy, age- and sex matched population at our Institution (0.72 ± 0.03 mm). Fifty-eight percent of patients had carotid plaques. Average FMD in the patients (5.02 ± 0.81%) was lower (p < 0.001) than the normal values of healthy, age- and sex matched individuals from our Institution (6.56 ± 0.60%). Nevertheless, there was no difference, among the four classes of steatosis, in either FMD (class 0: 5.10 ± 0.89%; class 1: 4.97 ± 0.46%; class 2: 4.73 ± 0.40%; class 3: 5.25 ± 0.17%) (p = 0.543 by ANOVA), average IMT (0.82 ± 0.08; 0.93 ± 0.05; 0.85 ± 0.05; and 0.85 ± 0.06 mm, respectively; p = 0.760 by ANOVA), or the prevalence of carotid plaques (43; 70; 60 and 69% respectively, p = 0.644). In conclusion, in T2DM patients largely exhibiting features of the MS, the degree of liver steatosis is not associated with early signs of (sub)clinical atherosclerosis and altered vascular function. These data question the role of liver fat as a direct determinant of early signs of vasculopathy in T2DM. Alternatively, it is possible that the burden of cardiovascular risk factors already present in these T2DM patients, obscure the possible contribution given by the degree of steatosis, on early signs of arteriosclerosis

Decreased Homocysteine Trans-Sulfuration in Hypertension With Hyperhomocysteinemia: Relationship With Insulin Resistance

Homocysteine is an independent cardiovascular risk factor and is elevated in essential hypertension. Insulin stimulates homocysteine catabolism in healthy individuals. However, the mechanisms of hyperhomocysteinemia and its relationship with insulin resistance in essential hypertension are unknown

Insulin on methionine and homocysteine kinetics in healthy humans: plasma vs. intracellular models

Methionine is a sulfur-containing amino acid that is reversibly converted into homocysteine. Homocysteine is an independent cardiovascular risk factor frequently associated with the insulin resistance syndrome. The effects of insulin on methionine and homocysteine kinetics in vivo are not known. Six middle-aged male volunteers were infused with L-[methyl-H-2(3), 1-C-13]methionine before (for 3 h) and after (for 3 additional hours) an euglycemic hyperinsulinemic (150 mU/l) clamp. Steady-state methionine and homocysteine kinetics were determined using either plasma (i.e., those of methionine) or intracellular (i.e., those of plasma homocysteine) enrichments. By use of plasma enrichments, insulin decreased methionine rate of appearance (R-a; both methyl- and carbon R-a) by 25% (P < 0.003 vs. basal) and methionine disposal into proteins by 50% (P < 0.0005), whereas it increased homocysteine clearance by similar to 70% (P < 0.025). With intracellular enrichments, insulin increased all kinetic rates, mainly because homocysteine enrichment decreased by similar to 40% (P < 0.001). In particular, transmethylation increased sixfold (P < 0.02), transsulfuration fourfold (P = 0.01), remethylation eightfold (P < 0.025), and clearance eightfold (P < 0.004). In summary, 1) physiological hyperinsulinemia stimulated homocysteine metabolic clearance irrespective of the model used; and 2) divergent changes in plasma methionine and homocysteine enrichments were observed after hyperinsulinemia, resulting in different changes in methionine and homocysteine kinetics. In conclusion, insulin increases homocysteine clearance in vivo and may thus prevent homocysteine accumulation in body fluids. Use of plasma homocysteine as a surrogate of intracellular methionine enrichment, after acute perturbations such as insulin infusion, needs to be critically reassessed

Effects of insulin on methionine and homocysteine kinetics in type 2 diabetes with nephropathy

Although hyperhomocysteinemia, an independent cardiovascular risk factor, is common in type 2 diabetes with nephropathy, the mechanism(s) of this alteration is not known. In healthy humans, hyperinsulinemia, increases methionine transmethylation, homocysteine transsulfuration, and clearance. No such data exist in type 2 diabetes either in the fasting state or in response to hyperinsulinemia. To this purpose, seven male type 2 diabetic patients with albuminuria (1.2 +/- 0.4 g/day, three with mild to moderate renal insufficiency) and seven matched control subjects were infused for 6 h with (L)-[methyl-H-2(3), 1-C-13]methionine. Methionine flux, transmethylation, and disposal into proteins as well as homocysteine remethylation, transsulfuration, and clearance were determined before and after euglycemic hyperinsulinemia (similar to 1,000 pmol/l). In type 2 diabetic subjects, homocysteine concentration was twofold greater (P 50% and from similar to 40 to > 100%, respectively; P < 0.05) than in control subjects. The insulin-induced increments of methionine transmethylation, homocysteine transsulfuration, and clearance were markedly reduced in type 2 diabetic subjects (by more than threefold, P < 0.05 or less vs. control subjects). In contrast, methionine methyl and carbon flux were not increased in the patients. In conclusion, pathways of homocysteine disposal are impaired in type 2 diabetes with nephropathy, both in postabsorptive and insulin-stimulated states, possibly accounting for the hyperhomocysteinemia of this condition