The effects of different plasma insulin concentrations on lipolytic and ketogenic responses to epinephrine in normal and type 1 (insulin-dependent) diabetic humans.

This study was performed to verify: (1) the ability of different insulin concentrations to restrict the lipolytic and ketogenic responses to exogenous epinephrine administration; (2) whether the ability of insulin to suppress the lipolytic and ketogenic responses during epinephrine administration is impaired in Type 1 (insulin-dependent) diabetic patients. Each subject was infused on separate occasions with insulin at rates of 0.2, 0.4, and 0.8 mU.kg-1.min-1 while normoglycaemic. To avoid indirect adrenergic effects on endocrine pancreas secretions, the so-called "islet clamp" technique was used. Rates of appearance of palmitic acid, acetoacetate, and 3-hydroxybutyrate were simultaneously measured with an infusion of 13C-labelled homologous tracers. After a baseline observation period epinephrine was exogenously administered at a rate of 16 ng.kg-1.min-1. At low insulin levels (20 microU/ml) the lipolytic response of comparable magnitude was detected in normal and Type 1 diabetic patients. However, the ketogenic response was significantly higher in Type 1 diabetic patients. During epinephrine administration, similar plasma glucose increments were observed in the two groups (from 4.74 +/- 0.53 to 7.16 +/- 0.77 mmol/l (p less than 0.05) in Type 1 diabetic patients and from 4.94 +/- 0.20 to 7.11 +/- 0.38 mmol/l (p less than 0.05) in normal subjects, respectively). At intermediate insulin levels (35 microU/ml) no significant differences were found between Type 1 diabetic patients and normal subjects, whereas plasma glucose levels rose from 4.98 +/- 0.30 to 6.27 +/- 0.66 mmol/l (p less than 0.05) in Type 1 diabetic patients, and from 5.05 +/- 0.13 to 6.61 +/- 0.22 mmol/l (p less than 0.05) in normal subjects. At high insulin levels (70 microU/ml) the lipolytic response was detectable only in Type 1 diabetic patients; the ketogenic response was reduced in both groups. During the third clamp, a significant rise in plasma glucose concentration during epinephrine infusion was observed in both groups. In conclusion this study shows that at low insulin levels Type 1 diabetic patients show an increased ketogenic response to epinephrine, despite their normal nonesterified fatty acid response. Instead, high insulin levels are able to restrict the ketogenic response to epinephrine in both normal and Type 1 diabetic subjects, although there is a still detectable lipolytic response in the latter. In the presence of plasma free insulin levels that completely restrict the ketogenic response in the same group, there is still a distinct glycaemic response. Plasma insulin levels in Type 1 diabetic patients are a major determinant of the metabolic response to epinephrine.

Effects of different insulin administrations on plasma amino acid profile in insulin-dependent diabetic patients.

It has long been recognized that diabetes mellitus is characterized by alterations in amino acid metabolism. Our aim was to evaluate the fasting amino acid concentrations in insulin-dependent diabetic subjects treated with different kinds of insulin therapy and with respect to the resulting different metabolic control. Four groups of patients were studied: Group 1: eight type 1 diabetic patients with two daily insulin injections; Group 2: eight type 1 diabetic patients with continuous subcutaneous insulin infusion; Group 3: five type 1 diabetic patients with continuous intraperitoneal insulin infusion; Group 4: six patients with total pancreatectomy. In all patients fasting amino acid profile was determined. Group 1 was also studied after 24 hr insulin withdrawal and after acute normalization of glycaemia. Our data demonstrated that the patients with a mild hyperglycaemia showed a significant increase in plasma amino acid levels. The continuous subcutaneous or intraperitoneal insulin infusion normalized amino acid profile at the expense of peripheral hyperinsulinemia, suggesting the presence of insulin resistance with regard of amino acid metabolism. The acute normoglycaemia demonstrated that plasma branched chain amino acid levels are more sensitive than plasma glucose to insulin action. Moreover, the amino acid pattern of euglycaemic total pancreatectomized patients suggested that a basal level of glucagon is essential in regulating glycogenic amino acid plasma concentrations.

The medium-term effect of natural or extractive dietary fibres on plasma amino acids and lipids in type 1 diabetics.

We evaluated the effect of a diet rich in natural (NF) or extractive fibres (guar gum) on 12 male IDD (insulin-dependent diabetes) out-patients. The treatment lasted for 2 months. During the first month the patients were on an isocaloric diet containing 30 g of fibres and then they were randomly subdivided into two groups. One group followed an isocaloric diet rich in fibres (70 g/day), the second group an isocaloric diet enriched by guar (9 g of guar added to 30 g of natural fibres/day). Reduced serum levels of HbA1c and several amino acids showed that metabolic control significantly improved under each dietary regimen.

Acetoacetate and 3-hydroxybutyrate kinetics in obese and insulin-dependent diabetic humans.

[3-14C]acetoacetate (AcAc) and beta-[3-14C]hydroxybutyrate (beta-OHB) administration, measurements of labeled AcAc and beta-OHB in blood, and kinetic modeling have been used to investigate ketone body (KB) metabolism in five normal, five obese, and eight insulin-withdrawn diabetic subjects. Diabetic subjects were divided in mildly ketotic (MKD) and highly ketotic (HKD) patients according to beta-OHB blood level. A four-compartmental model successfully described the tracer kinetic data in obese and normal subjects, whereas in diabetic patients a five-compartmental model was necessary. Obese subjects showed a significantly lower (P less than 0.05) KB de novo synthesis (R30 = 159 +/- 54 (SD) mumol X min-1 X m-2) in comparison with normal subjects (282 +/- 93), but the clearance rates of AcAc (PCR1) and beta-OHB (PCR2) were similar in the two groups. R30 was 596 +/- 534 in MKD and 1,278 +/- 445 (P less than 0.01) in HKD. PCR1 was not significantly different both in MKD and HKD in comparison with normal subjects. In contrast PCR2 was markedly reduced in HKD (0 +/- 0 ml X min-1 X m-2) in comparison with MKD (1,031 +/- 615) and normal subjects (782 +/- 278). The percentage distribution of KB among various tissues inside the organism of diabetic subjects is abnormal. Both AcAc and beta-OHB recycling and mean residence time are not normal in HKD. A significant correlation was found between C-peptide and KB production in diabetes. These results suggest that a selective defect of beta-OHB peripheral utilization is important in determining and maintaining severe diabetic ketoacidosis.

Carbohydrate and lipid metabolism in cirrhosis. Evidence that hepatic uptake of gluconeogenic precursors and of free fatty acids depends on effective hepatic flow.

Splanchnic arteriovenous differences for several intermediary metabolites of carbohydrate and lipid metabolism were determined simultaneously with hepatic blood flow in seven normal subjects, eight patients with cirrhosis, and six patients with cirrhosis after surgical portosystemic shunt ( SPSS ) after an overnight fast. Arteriovenous differences in the legs were also determined together with flux measurement. The individual turnover rates of acetoacetate (AcAc) and 3 hydroxybutyrate (beta OHB) were also determined by means of isotopic techniques. Splanchnic gluconeogenic precursors and FFA uptakes were lower in cirrhotic patients with SPSS than in normal subjects (P less than 0.05 and P less than 0.01, respectively). Splanchnic triglyceride output was also lower in cirrhotic patients with SPSS than in normal subjects (P less than 0.01), whereas no significant differences were found for AcAc, beta OHB, and glucose release. In the group of cirrhotic patients without SPSS , those patients with negligible signs of portal systemic shunt and normal splanchnic blood flow had uptake of gluconeogenic precursors and of FFA normal or higher than that of normal subjects, whereas those patients with signs of spontaneous portal systemic shunt behaved like cirrhotic patients with SPSS . Alanine release from the leg was lower in both cirrhotic patient groups. Tracer determined hepatic output of AcAc and beta OHB was higher in cirrhotic patients with SPSS (P less than 0.05). Plasma clearance rates of AcAc and beta OHB were significantly elevated in both cirrhotic patient groups. Close agreement was found between tracer and catheterization techniques in the evaluation of ketone body production in cirrhotic patients with SPSS , whereas in cirrhotic patients without SPSS tracer determined hepatic output was slightly lower, possibly because of extrahepatic splanchnic tissue ketone body uptake. In conclusion, our data in patients with cirrhosis indicate that: 1) splanchnic uptake of gluconeogenic precursors and of FFA was related to the degree of portal systemic shunt, e.g. to the degree of effective hepatic blood flow; 2) liver triglyceride but not ketone body output was decreased by the impaired FFA (and glycerol) liver uptake; 3) the higher circulating levels of gluconeogenic precursors (except alanine) and of FFA appeared at least partially due to lower hepatic removal of these metabolites; and 4) peripheral use of ketone bodies was increased and alanine release from the leg reduced in patients with cirrhosis.

Insulin resistance in Cushing's syndrome.

It is well established that cortisol excess causes insulin resistance in man, but the mechanisms responsible for this insulin resistance are poorly understood. We studied five women with Cushing's syndrome with impaired oral glucose tolerance tests and seven normal subjects, plotting the shape of the insulin-induced disposal dose-response curve obtained by means of the euglycemic clamp procedure during four different plasma insulin plateaus at four infusion rates of 21, 73, 760, and 1200 mU/M2 . min. Glucose disposal (M = mg/M2 . min) was calculated as glucose amount infused to maintain euglycemia. In Cushing's syndrome the dose-response curve was shifted to the right in comparison with normal subjects, with a significantly lower M (337 +/- 35 vs. 657 +/- 76 P less than 0.01) during the highest insulin infusion rate [maximal glucose disposal (MGD)] without any significant difference in the levels of insulin half-maximally effective in the stimulation of glucose utilization. Neither erythrocyte nor monocyte maximum insulin receptor binding were different between the two populations. Four Cushing's syndrome patients were studied again after surgical treatment. A marked improvement of MGD was observed without any significant change in insulin-binding capacity. These results, particularly the marked decrease in MGD, a typical feature of postreceptor defects, indicate that cortisol-induced insulin resistance in man is due to an impairment of peripheral insulin action located beyond the hormone-receptor binding step.

Metabolic effects of moderate alcohol intake with meals in insulin-dependent diabetics controlled by artificial endocrine pancreas (AEP) and in normal subjects.

In order to evaluate the effects of moderate alcohol intake on intermediate metabolites, five normal subjects and five euglycemic insulin-dependent diabetics (IDDM) were administered two different isocaloric diets; in one diet 35% of the caloric intake consisted of red wine. The insulin-dependent diabetics were connected to an artificial endocrine pancreas (AEP), and glucose levels were continuously monitored. Blood lactate, pyruvate, acetoacetate (AcAc), 3-hydroxybutyrate (3-OHB), glycerol, free fatty acids (FFA), and alanine levels were measured over a 15-hour period from 9 AM to 12 PM. The results showed that alcohol intake did not significantly influence the glucose profiles in either group (111 +/- 4 mg/100 ml versus 110 +/- 4 mg/100 ml for IDDM; 72 +/- 2 mg/100 ml versus 82 +/- 3 mg/100 ml for controls, 15-hour mean +/- SEM), but in both groups it induced a marked increased in the levels of lactate (1.115 +/- 0.067 mM/liter with alcohol versus 0.706 +/- 0.031 mM/liter without alcohol for IDDM; 0.847 +/- 0.052 mM/liter with alcohol versus 0.666 +/- 0.035 mM/liter without alcohol for controls), in the lactate/pyruvate ratio (24.04 +/- 2.12 with alcohol versus 11.42 +/- 0.20 without alcohol for IDDM; 20.84 +/- 2.16 with alcohol versus 11.62 +/- 0.27 without alcohol for controls), in the levels of 3-OHB (0.081 +/- 0.007 mM/liter with alcohol versus 0.046 +/- 0.003 mM/liter without alcohol for IDDM; 0.067 +/- 0.007 mM/liter with alcohol versus 0.025 +/- 0.002 mM/liter without alcohol for controls) and in the 3-OHB/AcAc ratio (1.452 +/- 0.153 with alcohol versus 0.599 +/- 0.036 without alcohol for IDDM; 1.723 +/- 0.198 with alcohol versus 0.439 +/- 0.040 without alcohol for controls) because of a more reduced redox state. Alcohol intake during meals depressed alanine concentration, while glycerol levels showed a transient increase. Reduced blood FFA concentrations after alcohol intake were observed only in controls. This study demonstrates that moderate alcohol intake with meals also affects intermediate metabolites despite euglycemia. These effects were similar both in normal subjects and in IDDM, even if the harmful effects of alcohol may be enhanced by poor metabolic control in the latter.

The antiketogenic effect of alanine in normal man: evidence for an alanine-ketone body cycle.

The effect of alanine on ketone body levels, independent of hormonal changes, in normal man has been investigated. Five normal subjects were given somatostatin infusions (200 micrograms/hour) for 3 hr. After 1 hr alanine or isotonic saline was infused for 2 hr. With saline blood beta-hydroxybutyrate and acetoacetate levels rose steadily to a peak of 0.230 plus or minus 0.053 and 0.112 plus or minus 0.023 mmole/l respectively. With alanine beta-hydroxybutyrate and acetoacetate levels plateaued at 0.099 plus or minus 0.020 and 0.055 plus or minus 0.006 mmole/l respectively. Alanine levels reached nearly 1 mmole/l but a significant effect on ketone body levels was apparent at physiologic levels (less than 0.6 mmole/l). Plasma fatty acid and glycerol levels did not change significantly. Insulin C-peptide and glucagon levels were suppressed to a similar extent in both experiments. These results support the view that alanine suppresses ketogenesis in man by a direct hepatic effect independent of insulin and glucagon. It is suggested that this forms part of a negative feedback substrate cycle between alanine and ketone bodies.