The effect of gemfibrozil on lipid profile and glucose metabolism in hypertriglyceridaemic well-controlled non-insulin-dependent diabetic patients. For the Gemfibrozil Study Group

We assessed the efficacy of gemfibrozil therapy on lipid profile and glucose metabolism in a large cohort of (type 2) non-insulin-dependent diabetic patients. We enrolled 217 type 2 diabetic patients with plasma triglyceride concentrations equal to or above 2 mmol/l: 110 were randomized to gemfibrozil (600 mg twice daily) and 107 to placebo treatment in a double blind fashion. Each treatment was followed for 20 weeks. To assess postprandial glucose metabolism and insulin secretion, at time 0 and 20 weeks, a standard meal containing 12.5 g of proteins, 40.1 g of carbohydrate, 10 g of lipids was given. No differences in demographic characteristics were observed between patients randomized either to gemfibrozil or to placebo therapy. No differences were observed in total cholesterol and LDL-cholesterol concentration changes between the baseline observations and week 20 of both treatments. At variance, both treatments significantly increased HDL cholesterol. Gemfibrozil treatment significantly decreased plasma triglyceride concentration from 316+/-84 to 214+/-82 mg/dl (P < 0.001), whereas with placebo triglyceride levels increased from 318 + 93 to 380 + 217 mg/dl. No changes were observed in non-esterified fatty acid concentrations or in fasting plasma glucose concentrations, in HbA(1C) values, insulin and C-peptide concentrations. Gemfibrozil treatment: 1) significantly reduces circulating triglyceride concentration; 2) does not significantly affect cholesterol concentration; 3) does not worsen glucose metabolism.

Effect of different times of administration of a single ethanol dose on insulin action, insulin secretion and redox state

AIMS

Ethanol (EtOH) can affect glucose metabolism by altering the redox state, insulin-mediated glucose uptake and insulin secretion. We sought to determine the effects of an acute oral EtOH load on insulin secretion and glucose tolerance and the importance of a different timing of administration relative to a glucose load.

METHODS

Eleven subjects underwent a frequently sampled intravenous glucose tolerance test (FSIGT) on three occasions in random order. In one, EtOH was given 50 min 'before' the FSIGT; on the second, the same amount was administered 6 min after the glucose pulse ('during' study); on the third no EtOH was given.

RESULTS

Blood EtOH peaked at 4.43+/-0.24 mmol/l (mean +/- SD) in the 'during' and 4.16+/-0.31 mmol/l in the 'before' study. No differences were noticed in S(I), the index of insulin sensitivity, or in S(G), the glucose effectiveness, between the 'before', 'during' and control studies. There were no differences in the first-phase insulin secretion between the three studies but a significant increase in the sensitivity to glucose of second-phase dynamic insulin response, phi2, in the 'before' (0.062+/-0.036 pmol x min(-2) x (mg(-1) x dl(-1))(-1)) and 'during' (0.063+/-0.059) studies, compared to the control study (0.017+/-0.010, P<0.05) was observed. No differences were observed in the hepatic extraction of insulin. In the 'before' study, there was a significant decline in NEFA (non-esterified fatty acid) concentration from the baseline (mean 602+/-51 micromol/l) to the O min value (mean 353+/-37, P<0.01). During the FSIGT, the mean plasma NEFA concentration was significantly lower in the 'before' and in the 'during' than in the control study.

CONCLUSION

An acute oral EtOH load does not impair glucose metabolism, at least in part because of an increased second-phase insulin secretion. Since this effect is observed irrespective of whether EtOH is consumed either before or during the glucose load, the existence of a priming effect is questioned.

Glucose metabolic alterations in isolated and perfused rat hepatocytes induced by pancreatic cancer conditioned medium: a low molecular weight factor possibly involved

A serious insulin resistance characterizes pancreatic cancer-associated diabetes mellitus. Elsewhere, we demonstrated that MIA PaCa2 cultured cells secrete a soluble factor responsible for reduced glucose tolerance induced in SCID mice. The intracellular mechanism of insulin resistance was investigated in isolated and perfused rat hepatocytes incubated with MIA PaCa2 conditioned medium. Lactate production was reduced compared to hepatocytes incubated with control medium while 1,2-DAG was increased and PKC was activated in the hepatocytes incubated with MIA PaCa2 conditioned medium. This behavior was not reproduced treating the hepatocytes with the growth factors EGF, interleukin Ibeta, interleukin-6, and TGF-beta1. In an attempt to make a biochemical identification of the hypothesized tumor associated-diabetogenic factors we observed a low molecular weight protein in the conditioned medium, absent in the nonconditioned one, that may be responsible for the described behaviors.

Protein metabolism in glucagonoma

Although protein wasting and reduced amino acid concentrations are common findings in glucagonoma patients, the mechanisms underlying these alterations are unclear. Therefore, we studied basal postabsorptive leucine, phenylalanine and tyrosine turnover following L-[D3]-Leucine, L-[D5]-Phenylalanine and L-[D2]-Tyrosine i.v. infusions in one male and one female patient with glucagonoma, compared with healthy control volunteers. Plasma amino acid concentrations were reduced (-40 to 80%, delta >2 SD vs. control subjects) in both patients. Plasma leucine, phenylalanine and tyrosine rates of appearance in patients with glucagonoma were similar to values in the control subjects, except leucine rate of appearence in the female patient with glucagonoma (+ approximately 30%, delta >2 SD). In contrast, the intracellular leucine rate of appearence, reflecting protein degradation, was considerably increased in both patients (+60-80%, delta >2 SD). Phenylalanine hydroxylation was moderately higher only in the male patient with glucagonoma (+ approximately 30%, delta >2 SD). Leucine, phenylalanine and tyrosine clearances (+100-300%), as well as phenylalanine hydroxylative clearance (+75-100%) were also increased in the patients. In conclusion, whole-body protein breakdown is enhanced in patients with glucagonoma compared with healthy control subjects. Phenylalanine hydroxylative clearance is also higher. Reduced plasma amino acid concentrations are probably due, at least in part, to their increased clearance. These alterations could contribute to the determination of the catabolic state of the glucagonoma syndrome.

Effect of acute ketosis on the endothelial function of type 1 diabetic patients: the role of nitric oxide

In type 1 diabetic patients, acute loss of metabolic control is associated with increased blood flow, which is believed to favor the development of long-term complications. The mechanisms for inappropriate vasodilation are partially understood, but a role of endothelium-derived nitric oxide (NO) production can be postulated. We assessed, in type 1 diabetic patients, the effect of the acute loss of metabolic control and its restoration on forearm endothelial function in 13 type 1 diabetic patients who were studied under conditions of mild ketosis on two different occasions. In study 1, after basal determination, a rapid amelioration of the metabolic picture was obtained by insulin infusion. In study 2, seven type 1 diabetic patients underwent the same experimental procedure, except that fasting plasma glucose was maintained constant throughout. Basal plasma venous concentrations of nitrites/nitrates (NO2- + NO3-) were determined both before and after intravenous insulin infusion. Endothelium-dependent and -independent vasodilation of the brachial artery was assessed by an intra-arterial infusion of N(G)-monomethyl-L-arginine (L-NMMA) and sodium nitroprusside (SNP), respectively. The same parameters were determined in 13 control subjects at baseline conditions and during a hyperinsulinemic-euglycemic glucose clamp. Baseline forearm blood flow (4.89 +/- 0.86 vs. 3.65 +/- 0.59 ml x (100 ml tissue)(-1) x min(-1)) and NO2- + NO3- concentration (30 +/- 8 vs. 24 +/- 3 micromol/l) were higher in type 1 diabetic patients than in control subjects (P < 0.05). Insulin infusion was associated with lower forearm blood flow and plasma (NO2- + NO3-) concentration (P < 0.05), irrespective of the prevailing glucose levels, as compared with patients under ketotic conditions. The responses to L-NMMA were significantly lower in type 1 diabetic patients during euglycemia and hyperglycemic hyperinsulinemia (-11 +/- 5 and -10 +/- 4%, respectively, of the ratio of the infused arm to the control arm) than in control subjects at baseline (-18 +/- 6%, P < 0.05) and during hyperinsulinemia (-32 +/- 11%, P < 0.01). We conclude that the acute loss of metabolic control is associated with a functional disturbance of the endothelial function characterized by hyperemia and increased NO release during ketosis and blunted NO-mediated vasodilatory response during restoration of metabolic control by intravenous insulin. This functional alteration is unlikely to be explained by hyperglycemia itself.

Restoration of early rise in plasma insulin levels improves the glucose tolerance of type 2 diabetic patients

The loss of first-phase insulin secretion is a characteristic feature of type 2 diabetic patients. The fast-acting insulin analog lispro provides a therapeutic tool for assessing the metabolic outcome of restoration of an early rise in plasma insulin levels after the ingestion of an oral glucose load. We studied eight type 2 diabetic patients on two different occasions when they received an oral glucose load (50 g) preceded by either human regular insulin or insulin analog lispro (both 0.075 U/kg lean body mass). Tritiated glucose was infused throughout the studies, and the oral glucose was labeled with [13C6]glucose for monitoring systemic and oral glucose kinetics, respectively. Basal plasma glucose (8.2 +/- 0.9 vs. 7.5 +/- 0.8 mmol/l), insulin (224 +/- 21 vs. 203 +/- 21 pmol/l), and endogenous glucose production (10.4 +/- 1.0 vs. 11.1 +/- 1.1 micromol x kg(-1) x min(-1)) were similar on both occasions. In spite of comparable incremental areas under the curve, the time course of plasma insulin concentration was much different. After injection of regular insulin, plasma insulin peaked at 120 min (368 +/- 42 pmol/l), while with lispro, the peak occurred at 60 min (481 +/- 42 pmol/l). Plasma insulin concentration during the last 3 h of the study, however, was lower with lispro compared with regular insulin. The incremental area under the curve of plasma C-peptide was lower with lispro (0.05 +/- 0.01 vs. 0.13 +/- 0.04 micromol/300 min; P < 0.01). After the ingestion of the oral glucose load, plasma glucose concentration increased by 78% at 80-100 min with regular insulin and by 62% with lispro (P < 0.05) and remained lower for the ensuing 3 h. The incremental area under the curve was 46% lower with lispro (715 +/- 109 vs. 389 +/- 109 pmol/300 min; P < 0.01). There was no difference in the two studies in the rate of appearance of the ingested glucose and in the overall rate of glucose disposal. During the initial 90 min, however, the rate of endogenous glucose production was suppressed in a prompter and more profound manner when lispro was administered (1.39 +/- 0.10 vs. 5.00 +/- 1.22 micromol x kg(-1) x min(-1); P < 0.05), while there was no difference in the late prandial phase. These results show that an early rise in plasma insulin levels after the ingestion of a glucose load is associated with a significant improvement in glucose tolerance due to a prompter, though short-lived, suppression of endogenous glucose production. This amelioration in plasma glucose profile prevents late hyperglycemia and hyperinsulinemia. Therefore, restoration of a more physiologic profile of prandial plasma insulin profile represents a rational approach for treatment of type 2 diabetic patients.

The epidemiology of diabetes mellitus

Insulin-dependent diabetes mellitus (IDDM) develops predominantly in children and young adults, but may appear in all age groups. The incidence of IDDM differs greatly among populations, with Finland and Sardinia showing the greatest incidence rates (approximately 30-35% of cases annually per 100000 children up to age 14 years) and oriental populations showing the lowest rates. IDDM is diagnosed more frequently in the winter months. The major genetic susceptibility to IDDM is linked to the HLA complex on chromosome 6. These genetic backgrounds interact with environmental factors (possibly certain viruses, foods and climate) to initiate the immune-mediated process that leads to beta-cell destruction. Non-insulin dependent diabetes (NIDDM) is the most common form of diabetes. The prevalence of NIDDM varies enormously from population to population. The greatest rates have been found in Pima Indians. The major environmental factors identified as contributing to this form of diabetes are obesity and reduced physical activity. NIDDM shows strong familial aggregation in all populations and is clearly the result of an interaction between genetic susceptibility and environmental factors. Before NIDDM develops, insulin concentrations are high for the degree of glycaemia and of obesity, reflecting the presence of insulin resistance. As insulin resistance worsens, glucose levels increase, with the appearance of glucose intolerance and, finally, of NIDDM, when insulin response cannot compensate for insulin resistance.

Enhanced responsiveness of blood pressure to sodium intake and to angiotensin II is associated with insulin resistance in IDDM patients with microalbuminuria

We assessed blood pressure (BP), body weight, renal hemodynamics, and insulin sensitivity (by euglycemic-hyperinsulinemic clamp) in nine normoalbuminuric and seven microalbuminuric IDDM patients after 6 days on a low-sodium diet (20 mEq) and after 6 days on a high-sodium diet (250 mEq). In microalbuminuric but not in normoalbuminuric IDDM patients, switching from a low to a high-sodium diet was associated with a significant increase in mean BP (from 92 +/- 3 to 101 +/- 4 mmHg; P < 0.001) and in body weight (2.91 +/- 0.63 vs. 1.47 +/- 0.26 kg; P < 0.05). Moreover, under high-sodium conditions, angiotensin II infusion (3 ng x kg(-1) x min(-1)) caused a greater increase in mean BP (14 +/- 2 vs. 7.4 +/- 1 mmHg; P < 0.05) and a smaller reduction in renal plasma flow (-122 +/- 29 vs. -274 +/- 41 ml x min(-1) x 1.73 m2; P < 0.05) in microalbuminuric than in normoalbuminuric IDDM patients. Under low sodium conditions, aldosterone increments after angiotensin II infusion were lower (P < 0.05) in microalbuminuric than in normoalbuminuric IDDM patients. Insulin-mediated glucose disposal was not affected by sodium dietary content, but it was lower in microalbuminuric (P < 0.05) than in normoalbuminuric IDDM patients. The salt-induced changes in mean BP were related to insulin sensitivity (r = -0.78; P < 0.001). In conclusion, in IDDM patients, microalbuminuria is associated with 1) an increased responsiveness of BP to salt intake and angiotensin II, 2) impaired modulation of renal blood flow, and 3) insulin resistance. Therefore, salt sensitivity in IDDM patients clusters with other factors that are likely to play an important role in the pathogenesis of diabetic nephropathy and its cardiovascular complications.

Extreme but asymptomatic hypergastrinemia with gastroparesis in a young woman with insulin dependent diabetes mellitus

Overt diabetic gastroparesis is a rare long-term complication of diabetes, probably resulting from autonomic neuropathy of vagus nerve. It is now clear that neural damage plays a pivotal role in the pathogenesis of the disease. Some studies showed high basal gastrin levels in patients with diabetic gastroparesis, but the clinical meaning of this observation is still unclear. We report the case of a young woman with Insulin Dependent Diabetes Mellitus (IDDM) who was referred to evaluate nausea and vomiting associated to ketoacidosis. Our hypothesis of autonomic neuropathy with gastroparesis was confirmed. We observed a progressive increase in fasting gastrin concentration (20-fold normal values) in the absence of any clinical and laboratory signs of Zollinger-Ellison (ZE) syndrome. The increasing vomiting induced a severe state of cachexia, which required total parenteral nutrition for a long period. All therapeutic approaches were unsuccessful, and the patient rapidly died, suggesting a possible link between the severity of the clinical picture and the gastrin plasma levels.

Forearm nitric oxide balance, vascular relaxation, and glucose metabolism in NIDDM patients

Endothelium-dependent and -independent vascular responses were assessed in 10 NIDDM patients and 6 normal subjects with no evidence of atherosclerotic disease. Changes in forearm blood flow and arteriovenous (AV) serum nitrite/nitrate (NO2-/NO3-) concentrations were measured in response to intra-arterial infusion of acetylcholine (ACh) (7.5, 15, 30 microg/min, endothelium-dependent response) and sodium nitroprusside (SNP) (0.3, 3, 10 microg/min, endothelium-independent response). Insulin sensitivity (determined by minimal model intravenous glucose tolerance test) was lower in NIDDM patients (0.82 +/- 0.20 vs. 2.97 +/- 0.29 10(4) min x microU(-1) x ml(-1); P < 0.01). Baseline forearm blood flow (4.8 +/- 0.3 vs. 4.4 +/- 0.3 ml x 100 ml(-1) tissue x min(-1); NS), mean blood pressure (100 +/- 4 vs. 92 +/- 4 mmHg; NS), and vascular resistance (21 +/- 1 vs. 21 +/- 1 units; NS), as well as their increments during ACh and SNP, infusion were similar in both groups. No difference existed in baseline NO2-/NO3- concentrations (4.09 +/- 0.33 [NIDDM patients] vs. 5.00 +/- 0.48 micromol/l [control subjects]; NS), their forearm net balance (0.31 +/- 0.08 [NIDDM patients] vs. 0.26 +/- 0.08 micromol/l x 100 ml(-1) tissue x min(-1); NS), and baseline forearm glucose uptake. During ACh infusion, both NO2- and NO3- concentrations and net balance significantly increased in both groups, whereas glucose uptake increased only in control subjects. When data from NIDDM and control groups were pooled together, a correlation was found between the forearm AV NO2- and NO3- differences and blood flow (r = 0.494, P = 0.024). On the contrary, no correlation was evident between NO2- and NO3- concentrations or net balance and insulin sensitivity. In summary, 1) no difference existed in basal and ACh-stimulated NO generation and endothelium-dependent relaxation between uncomplicated NIDDM patients and control subjects; 2) in both NIDDM and control groups, forearm NO2- and NO3- net balance following ACh stimulation was related to changes in the forearm blood flow; and 3) ACh-induced increase in forearm blood flow was associated with an increase in glucose uptake only in control subjects but not in NIDDM patients. In conclusion, our results argue against a role of impaired NO generation and blood flow regulation in determining the insulin resistance of uncomplicated NIDDM patients; rather, it supports an independent insulin regulation of hemodynamic and metabolic effects.

Gliclazide potentiates suppression of hepatic glucose production in non-insulin-dependent diabetic patients

The mechanism of the hypoglycemic action of gliclazide was evaluated in 17 diet-treated non-insulin-dependent diabetes mellitus (NIDDM) patients. In study A, five patients received a 240-minute glucose infusion along with [3-3H]glucose infusion. In study B, seven patients received a 240-minute isoglycemic insulin clamp along with [3-3H]glucose infusion. And in study C, five patients received a somatostatin infusion with basal replacing doses of insulin and glucagon. The three studies (A, B, and C) were repeated twice. Gliclazide (240 mg orally) was administered on one occasion, and placebo was given on the second occasion. Basal hepatic glucose production (HGP) and utilization and plasma glucose, insulin, C-peptide, glucagon, and free fatty acid (FFA) concentrations were similar before administration of gliclazide and placebo. In study A, plasma glucose, its incremental area, and HGP were reduced by gliclazide administration (all P < .05), but glucose utilization was not significantly affected. The increase in plasma insulin and C-peptide concentrations was similar with gliclazide and placebo, although the plasma insulin to glucose ratio was increased with gliclazide. HGP decremental area was correlated with the reduction in plasma glucose incremental area (r = -.63, P < .05). In study B, gliclazide administration produced a larger suppression of HGP, but the overall rate of glucose utilization was not different in the two studies. In study C, plasma glucose concentration and HGP progressively decreased in both studies, without a difference between gliclazide and placebo. These results suggest that under conditions of hyperglycemia and hyperinsulinemia gliclazide elicits a larger suppression of HGP.

The role of substrates in the regulation of protein metabolism

Substrates are powerful modulators of amino acid and protein turnover in vivo (Table 4). Intravenous infusions of amino acids exert a protein-anabolic effect, because they directly inhibit endogenous protein degradation and stimulate protein synthesis at the whole-body level. A stimulation of protein synthesis has been observed also at the forearm level. These changes resulted in an improvement of body and tissue protein balance, which is the ultimate goal of any nutritional intervention aimed at preserving body protein stores. In humans acute intravenous infusions of carbohydrates do not appear to affect either protein degradation or leucine oxidation. However, animal studies support the view that glucose availability spares essential amino acids at least in the fetus. The effects of hypercaloric refeeding with high-carbohydrate diets may, however, result in increased protein turnover. Lipids, in the form of long-chain fatty acids, inhibit endogenous protein breakdown and may suppress leucine oxidation in the whole body. They do not affect protein synthesis. In contrast, medium-chain fatty acids apparently increased leucine oxidation, and therefore increased net protein catabolism. Ketone bodies may be anabolic provided that fatty acid concentrations are not concurrently decreased.

Intracellular lactate- and pyruvate-interconversion rates are increased in muscle tissue of non-insulin-dependent diabetic individuals

The contribution of muscle tissues of non-insulin-dependent diabetes mellitus (NIDDM) patients to blood lactate appearance remains undefined. To gain insight on intracellular pyruvate/lactate metabolism, the postabsorptive forearm metabolism of glucose, lactate, FFA, and ketone bodies (KB) was assessed in seven obese non-insulin-dependent diabetic patients (BMI = 28.0 +/- 0.5 kg/m2) and seven control individuals (BMI = 24.8 +/- 0.5 kg/m2) by using arteriovenous balance across forearm tissues along with continuous infusion of [3-13C1]-lactate and indirect calorimetry. Fasting plasma concentrations of glucose (10.0 +/- 0.3 vs. 4.7 +/- 0.2 mmol/liter), insulin (68 +/- 5 vs. 43 +/- 6 pmol/liter), FFA (0.57 +/- 0.02 vs. 0.51 +/- 0.02 mmol/liter), and blood levels of lactate (1.05 +/- 0.04 vs. 0.60 +/- 0.06 mmol/liter), and KB (0.48 +/- 0.04 vs. 0.29 +/- 0.02 mmol/liter) were higher in NIDDM patients (P < 0.01). Forearm glucose uptake was similar in the two groups (10.3 +/- 1.4 vs. 9.6 +/ 1.1 micromol/min/liter of forearm tissue), while KB uptake was twice as much in NIDDM patients as compared to control subjects. Lactate balance was only slightly increased in NIDDM patients (5.6 +/- 1.4 vs. 3.3 +/- 1.0 micromol/min/liter; P = NS). A two-compartment model of lactate and pyruvate kinetics in the forearm tissue was used to dissect out the rates of lactate to pyruvate and pyruvate to lactate interconversions. In spite of minor differences in the lactate balance, a fourfold increase in both lactate- (44.8 +/- 9.0 vs. 12.6 +/- 4.6 micromol/min/liter) and pyruvate-(50.4 +/- 9.8 vs. 16.0 +/- 5.0 micromol/min/liter) interconversion rates (both P < 0.01) were found. Whole body lactate turnover, assessed by using the classic isotope dilution principle, was higher in NIDDM individuals (46 +/- 9 vs. 21 +/- 3 micromol/min/kg; P < 0.01). Insights into the physiological meaning of this parameter were obtained by using a whole body noncompartmental model of lactate/pyruvate kinetics which provides a lower and upper bound for total lactate and pyruvate turnover (NIDDM = 46 +/- 9 vs. 108 +/- 31; controls = 21 +/- 3 - 50 +/-13 micromol/min/kg). In conclusion, in the postabsorptive state, despite a trivial lactate release by muscle, lactate- and pyruvate-interconversion rates are greatly enhanced in NIDDM patients, possibly due to concomitant impairment in the oxidative pathway of glucose metabolism. This finding strongly suggest a major disturbance in intracellular lactate/pyruvate metabolism in NIDDM.

Response of phenylalanine and leucine kinetics to branched chain-enriched amino acids and insulin in patients with cirrhosis

BACKGROUND & AIMS

We tested the effects of branched chain-enriched, aromatic-deficient amino acids with insulin to correct the altered protein turnover as well as phenylalanine (Phe) and leucine (Leu) rate of appearance in compensated cirrhotics and controls.

METHODS

Phe and Leu tracers were infused both before and following intravenous amino acid administration with insulin and euglycemic clamp.

RESULTS

In cirrhosis, fasting whole-body protein synthesis and protein degradation were normal; Phe rate of appearance was greater (P<0.05), whereas Leu rate of appearance/Phe rate of appearance ratio was approximately 35% less than in controls (P<0.001). Following the infusion, protein synthesis did not increase (+1% +/ 5% [NS] vs. +21% +/- 5% [P<0.05] in controls); protein degradation was more suppressed, whereas protein balance increased normally. Total Phe rate of appearance (0.91 +/- 0.13 micromol x kg-1 x min-1) and Leu/Phe disposal ratio (3.53 +/- 0.36) were nearly normalized (fasting controls, 0.68 +/- 0.07 micromol x kg-1 x min-1 and 2.87 +/- 0.14 micromol x kg-1 x min-1, respectively; P>0.05). However, Leu/Phe endogenous rate of appearance ration remained approximately 50% less (1.56 +/- 0.31 vs. 2.87 +/- 0.14; P<0.004) than in controls.

CONCLUSIONS

Following this combined infusion in cirrhosis, net protein deposition increased normally despite a blunted response of protein synthesis. Phe and Leu to Phe peripheral disposal were near normalized; however, the exaggerated endogenous Phe production was not corrected entirely.

Ethanol impairs insulin-mediated glucose uptake by an indirect mechanism

The effect of ethanol (ETOH) on muscle metabolism was assessed in both normal (NC) and noninsulin-dependent (NIDDM) subjects in the basal state and during isoglycemic hyperinsulinemia (450 pmol/L) clamp studies carried out either with systemic (NC, n = 5; NIDDM, n = 5) or intrabrachially (NC, n = 5; NIDDM, n = 5)ETOH infusion. On a repeat study, each subject underwent the same experimental procedures, except that saline was infused instead of ETOH. Systemic ETOH significantly decreased whole body glucose disposal in both NC and NIDDM patients. In NC, ETOH infusion decreased basal forearm glucose uptake (FGU) from 1.22 +/- 0.20 to 0.32 +/- 0.04 mumol/min.100 mL tissue (P < 0.01), whereas in NIDDM, this decrement was not significant (from 0.95 +/- 0.31 to 0.66 +/- 0.23). With saline infusion, hyperinsulinemia significantly stimulated FGU to 4.09 +/- 0.46 mumol/min.100 mL tissue in NC and to 2.50 +/- 0.76 in NIDDM. During ETOH, FGU was depressed by 81% in NC (delta = 3.32 mumol/min.100 mL tissue) and by 48% (P < 0.05) in NIDDM (delta = 1.21 mumol/min.100 mL tissue). Local ETOH infusion did not affect FGU in either NC (1.18 +/- 0.23 vs. 1.1 +/= 0.11 mumol/min.100 mL tissue in the baseline condition and 4.12 +/- 0.65 vs. 3.97 +/- 0.35 in insulin-stimulated conditions) or NIDDM (1.05 +/- 0.29 vs. 1.1 +/- 0.19 mumol/min.100 mL tissue in baseline condition and 2.72 +/- 0.82 vs. 2.83 +/- 0.51 in insulin-stimulated conditions) subjects. With systemic ETOH, but not local infusion, there was a reduction in baseline plasma free fatty acid level and an increase in blood lactate concentration during isoglycemic hyperinsulinemia. In summary, systemic ETOH infusion impairs both whole body and forearm glucose uptake in NC and NIDDM subjects; this effect was more apparent in NC than in NIDDM at both the whole body and forearm level. On the contrary, intrabrachial ETOH infusion did not affect forearm glucose balance in either group. These results suggest that the reduction in muscle glucose disposal associated with increased systemic ETOH concentrations is not caused by a direct ETOH effect on muscle glucose metabolism.

The hemodynamic abnormalities in short-term insulin deficiency: the role of prostaglandin inhibition

It has been suggested that the hemodynamic derangements present in diabetic ketoacidosis are the results not only of profound volume depletion but also of the effects of increased production of vasodilating prostaglandins (PGs), principally PGI2, released by adipose tissue. In animal and in vitro models, prostaglandin synthesis is increased during insulin deficiency. We assessed the effects of short-term ketosis on the metabolic and hemodynamic variables of 10 IDDM patients free from long-term complications and of 9 normal control subjects after a 7-day randomized double-blind indomethacin (INDO) (50 mg q.i.d.) or placebo treatment period. Calf blood flow (CBF), postocclusive reactive hyperemia (PORH), and recovery half-time (an index of overall perfusion) after PORH were measured by plethysmography. Left ventricular and myocardial functions were also studied in each different condition during placebo and INDO treatment in IDDM patients. During placebo treatment, the increase in CBF during ketosis was higher (1.75 +/- 0.29 ml / min / 100 ml muscle) than during INDO (0.85 +/- 0.17 ml / min) / 100 ml muscle; P = 0.007). PORH was similar in baseline conditions, during ketosis, and in recovery in both the placebo and INDO arms. Recovery half-time significantly increased during placebo (10 +/- 2; 200%; P < 0.01) but not during INDO (1 +/- 1; 106%; NS) treatment. In normal control subjects, insulin deficiency did not induce any significant effect on hemodynamic variables. In IDDM patients, during placebo treatment, ketosis increased both the cardiac index (from 3.4 +/- 0.7 to 4.1 +/- 0.81 / min / m; P < 0.01) and the stroke index (from 42 +/- 8 to 49 +/- 7 ml/m2; P < 0.01) without changes in left ventricular ejection fraction but with a significant increase in both left and right ventricular end-diastolic volumes. Metabolic recovery induced a normalization of these parameters. INDO treatment significantly blunted these alterations. In summary, we showed that during acute insulin deficiency, INDO-sensitive mechanisms mediate vascular disturbances. Moreover, INDO treatment was capable of completely preventing the cardiac venous return and the left ventricular alterations. INDO does not interfere with the overall ketogenetic process or with insulin-induced metabolic recovery.

Hyperglucagonemia stimulates phenylalanine oxidation in humans

Glucagon stimulates in vitro liver phenylalanine (Phe) degradation, thus inducing net protein catabolism. Whether these effects occur also in vivo in humans is not known. Therefore, we studied the effects of physiological hyperglucagonemia on Phe rate of appearance (Ra), hydroxylation, and oxidation in seven normal volunteers during infusions of somatostatin with replacement doses of insulin and growth hormone. Steady-state Phe kinetics were evaluated using the L-[1-14C]Phe tracer both at the end of a 3-h basal glucagon replacement period (glucagon concentration: 212 +/- 115 ng/l) and after a 3-h hormone infusion at the rate of approximately 3 ng x kg-1 x min-1 (--> 654 +/- 280 ng/l). Hyperglucagonemia did not change plasma Phe concentration and Ra but increased Phe oxidation by approximately 30% (P < 0.01). Oxidation was also increased by approximately 24% (P < 0.01) using plasma [14C]tyrosine (Tyr) specific activity as a precursor pool. Phe hydroxylation to Tyr estimated by assuming a fixed ratio of Tyr to Phe Ra (0.73) did not change. Nonhydroxylated Phe disposal decreased by approximately 6% (P = 0.08). These data show that in humans in the postabsorptive state, hyperglucagonemia, with near maintenance of basal insulin and growth hormone concentrations, stimulates Phe oxidation but not Phe hydroxylation, suggesting a different regulation of these two Phe catabolic steps. Glucagon may also reduce Phe availability for protein synthesis.

[Lipid peroxidation and LDL modifications in nondiabetic patients with ischemic heart disease: the role of insulin action]

BACKGROUND

Nondiabetic patients with advanced coronary artery disease (CAD) were assessed for lipid peroxidation, LDL modifications and insulin action. Twenty-four patients and 10 normal controls were studied.

METHODS

Insulin tolerance test (Kitt), glucose, insulin lipoproteins, electronegatively charged, modified, low density lipoproteins (LDL-) and the thiobarbituric acid reactivity (TBARS), as an index of lipid peroxidation, were determined.

RESULTS

No difference was observed in insulin action (determined by insulin tolerance test) between patients with CAD (3.31 +/- 0.28%/min; range 0.73-6.13) and normal controls (3.59 +/- 0.42; range 1.76-6.06). The percentage of modified, electronegative LDL (LDL -) was higher in patients with CAD (0.5 +/- 0.48%; range 1.3-9.2) than that of controls (2.80 +/- 0.33; range 1.00-4.00; p = 0.013). TBARS were significantly (P = 0.043) higher in CAD patients (3.49 +/- 0.17 nmol/ml; range 2.4-5.5) than normal controls (1.47 +/- 0.12; range 1.07-2.10). A significantly negative correlation was observed between Kitt and TBARS (r= - 0.48; p = 0.016), and a significant (r = 0.46; p = 0.022) positive correlation was observed between plasma glucose and TBARS. On the contrary no correlation has been observed between LDL- and TBARS.

CONCLUSIONS

We conclude that in patients with advanced coronary artery disease: A) there are increased circulating levels of modified low density lipoprotein; B) there is evidence of increased lipid peroxidation. This latter process is significantly influenced by the degree of insulin action.

High blood ketone body concentration in type 2 non-insulin dependent diabetic patients

To assess the metabolic disturbances, and, in particular, the occurrence of high blood ketone body concentration in post-absorptive Type 2 (non-insulin-dependent) diabetic patients as compared to a matched normal population, a study was carried out in a group of 78 Type 2 diabetic outpatients matched for age and sex and in 78 normal individuals. In all subjects we measured HbA1c, and fasting levels of glucose, FFA, lactate, pyruvate, glycerol, alanine, 3-hydroxybutyrate, acetoacetate, uric acid, total cholesterol, triglycerides, creatinine, growth hormone, cortisol, glucagon, free insulin, and C-peptide. Multistix strips were used for urine ketone determination. As expected HbA1c, and plasma glucose were higher in Type 2 diabetics. This was associated with multiple metabolic disturbances as shown by higher circulating concentrations of FFA, glycerol and gluconeogenic precursors. Similarly, blood levels of ketones (351 +/- 29 vs 159 +/- 15 umol/l; P < 0.0001) were increased, in spite of higher plasma free-insulin (77 +/- 7 vs. 49 +/- 14 pmol/l; p < 0.0001) and C-peptide concentration (0.63 +/- 0.03 vs. 0.46 +/- 0.07 nmol/l; P < 0.05) and no differences in plasma levels of cortisol, and growth hormone. Plasma glucagon levels were higher in Type 2 diabetics. Blood ketone body levels were directly correlated with both plasma glucose and FFA concentrations. These observations clearly show that Type 2 diabetes is a pathologic condition characterised by multiple metabolic disturbances which are fully apparent in the basal state. Furthermore, we emphasise that Type 2 diabetic patients, though not insulin deficient, may present a significant increase in their fasting levels of ketone bodies.

Effect of low-dose ramipril on microalbuminuria in normotensive or mild hypertensive non-insulin-dependent diabetic patients. North-East Italy Microalbuminuria Study Group

Microalbuminuria predicts early mortality and renal disease in non-insulin-dependent diabetic patients. In insulin-dependent diabetic patients, angiotensin converting enzyme inhibition decreases microalbuminuria and retards the progression of renal disease. The aim of this study was to evaluate the effect of low dose ramipril on albumin excretion rate (AER) and blood pressure in non-insulin-dependent diabetic patients with persistent microalbuminuria (AER > 20 < 200 micrograms/min) and normal blood pressure or mild hypertension. The study was a randomized, double-blind, placebo-controlled clinical trial of 6 months duration at 14 hospital-based diabetes centers in northeastern Italy. Blood pressure, plasma glucose, and body weight were determined every month; AER, serum creatinine, glycosylated hemoglobin, and plasma lipids at baseline, after 1 month, and at the end of the study. Of 122 non-insulin-dependent diabetic patients randomly allocated in blocks of four to receive either ramipril (1.25 mg/day) or placebo, 108 (54 in the ramipril group and 54 in the placebo group) completed the study. At baseline, age, duration of diabetes, body mass index, and glycosylated hemoglobin were similar in the two groups and remained unchanged throughout the study. In the placebo group, AER rose from a baseline median of 65 micrograms/min (range 53 to 76, 95% confidence Interval) to 72 micrograms/min (57 to 87) and to 83 micrograms/min (62 to 104) after 1 and 6 months, respectively, but fell from 62 micrograms/min (48 to 76) to 45 micrograms/min (33 to 57) and to 53 micrograms/min (38 to 69), respectively, in the ramipril group, a significant difference between the groups (P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Basal plasma insulin levels exert a qualitative but not quantitative effect on glucose-mediated glucose uptake

We assessed the effect of hyperglycemia on glucose uptake in the presence of normal basal insulin levels or somatostatin-induced hypoinsulinemia in seven normal volunteers during a 200-min hyperglycemic clamp (+ 9 mmol/l) carried out with [3-3H]glucose and indirect calorimetry. Hyperglycemia increased glucose uptake to 22.4 +/- 2.6 and 21.3 +/- 1.6 mumol.kg-1.min-1 with and without insulin replacement, respectively. Normoinsulinemia increased glucose oxidation (delta = + 4.5 +/- 0.6 mumol.kg-1.min-1) and nonoxidative glucose metabolism (delta = + 5.2 +/- 1.7 mumol.kg-1.min-1), whereas with insulinopenia, glucose oxidation did not change (delta = -0.3 +/- 0.6 mumol.kg-1.min-1), and nonoxidative glucose metabolism increased (delta = + 48.7 +/- 0.8 mumol.kg-1.min-1). Nonoxidative glucose metabolism was higher during insulinopenic (13.5 +/- 1.8 mumol.kg-1.min-1) than normoinsulinemic hyperglycemia (9.8 +/- 2.7 mumol.kg-1.min-1; P < 0.01). Plasma FFA concentration and lipid oxidation were higher with insulinopenia. Blood lactate and alanine concentrations were greater with normoinsulinemia.

IN CONCLUSION

1) hyperglycemia promotes glucose uptake by stimulating both nonoxidative and oxidative glucose disposal; 2) the ability of hyperglycemia to enhance total body glucose uptake is similar with and without normoinsulinemia; 3) although acute insulinopenia does not impair the ability of hyperglycemia to stimulate glucose uptake, it plays a critical role in determining the intracellular metabolic fate of glucose taken up in response to hyperglycemia.