Intracellular pH and Na+/H+ antiport activity of cultured skin fibroblasts from diabetics

Increased leucocyte Na+/H+ antiport activity has previously been demonstrated in both hypertensive subjects and Type 1 diabetic patients with nephropathy and may indicate a predisposition to hypertension in such diabetic patients. We have studied intracellular pH and Na+/H+ antiport activity in cultured skin fibroblasts from diabetic patients with and without nephropathy, together with non-diabetic controls to assess if such differences persisted in cultured cells. Fibroblasts from diabetic patients with nephropathy were significantly more alkaline [median (range): 6.90 (6.82 to 7.07)] compared to both normoalbuminuric diabetic patients [6.81 (6.75 to 6.89)] or normal controls [6.82 (6.77 to 6.93)] (P < 0.001 for both). This was associated with a raised Na+/H+ antiport activity in cells from patients with nephropathy when intracellular pH (pHi) was clamped to pH 6.5, without any differences in the maximal transport capacity of the antiport at pHi 6.2. Using both intracellular pH and Na+/H+ antiport activity at pHi 6.5, patients with nephropathy were separated from uncomplicated subjects with a sensitivity of 92% and a specificity of 100%. In conclusion, the raised Na+/H+ antiport activity in cells from patients with diabetic nephropathy persists despite passaging in vitro, thus indicating a heritable component, and results mainly from an increased apparent affinity of the antiport for intracellular H+.

Na+/H+ antiport activity and cell growth in cultured skin fibroblasts of IDDM patients with nephropathy

IDDM patients with incipient and overt nephropathy have been found to exhibit an overactivity of RBC sodium-lithium countertransport. To explore the physiological relevance of this finding, we measured the activity of Na+/H+ antiport in serially passaged cultured skin fibroblasts from IDDM patients with and without nephropathy and from normal, nondiabetic control subjects. Na+/H+ antiport activity (measured as the rate of amiloride-sensitive Na+ influx at pHi = 6.4, extracellular pH = 8.0, and [Na+] = 1 mM) was elevated significantly in IDDM patients with nephropathy compared with IDDM patients without nephropathy and nondiabetic control subjects (13.35 +/- 3.8 vs. 8.54 +/- 2.0 vs. 7.33 +/- 2.3 nmol Na+.mg protein-1.min-1; P less than 0.006 and P less than 0.001, respectively). A kinetic analysis of Na+/H+ antiport activity showed that the raised activity in IDDM patients with nephropathy was caused by an increased Vmax for extracellular Na+. Km values were similar in the three groups. pH-stimulated amiloride-sensitive Na+ influx also was higher under baseline conditions and after serum stimulation in cells from IDDM patients with nephropathy. pHi values were significantly higher, both during active proliferation and after 10-min exposure to serum, in cells from IDDM patients with nephropathy, compared with IDDM patients without nephropathy and nondiabetic control subjects. Serum-stimulated incorporation of [3H]thymidine into DNA was greater in IDDM patients with nephropathy than in the other two groups (35.7 +/- 18.9- vs. 17.4 +/- 7.5- vs. 11.9 +/- 8.7-fold stimulation above baseline; P less than 0.01 for both.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships among natriuresis, atrial natriuretic peptide and insulin in insulin-dependent diabetes

Insulin-dependent diabetic patients have a large exchangeable body sodium pool, secondary to sodium retention. The pathogenesis of impaired natriuresis in insulin dependent diabetes remains to be elucidated. The present study examines the role of hyperinsulinemia, impaired atrial natriuretic release, and resistance to atrial natriuretic peptide action in determining sodium retention in normotensive and hypertensive insulin-dependent diabetic patients. Eight insulin-dependent diabetic patients had significantly higher daily sodium excretion rate (147 +/- 16 mmol/day; mean +/- SE) during conventional insulin treatment (daily plasma glucose: 11.6 +/- 1.2 mmol/liter; daily plasma insulin: 27 +/- 3 microU/ml) than during intensified insulin treatment (daily sodium excretion rate: 91 +/- 12, P less than 0.01; daily plasma glucose: 6.8 +/- 0.7, P less than 0.01; daily plasma insulin: 44 +/- 4, P less than 0.01). Daily sodium excretion rate was also significantly lower (107 +/- 13, P less than 0.01) in the same diabetic patients during intensified insulin treatment along with hyperglycemic clamp (daily plasma glucose: 12.8 +/- 0.3, NS; plasma insulin 48 +/- 4, P less than 0.01). Seven control subjects had lower extracellular liquid volume than eight insulin-dependent diabetic patients (11.0 +/- 0.8 l/1.73 m2 vs. 14.8 +/- 0.9, P less than 0.05) and also had baseline plasma atrial natriuretic peptide concentrations (18 +/- 5 pg/ml vs. 37 +/- 4, P less than 0.05). Atrial natriuretic peptide response to saline challenge was blunted in insulin-dependent diabetic patients when saline was administered on the basis of body surface area (90 mmol/1.73 m2.90 min) but not when administered on the basis of extracellular liquid volume (ECV) (8.2 mmol/liter ECV.90 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Clustering of risk factors in hypertensive insulin-dependent diabetics with high sodium-lithium countertransport

Diabetic nephropathy is more common in patients with a positive family history of hypertension and with elevated red blood cell sodium-lithium countertransport, a marker of risk for essential hypertension. To evaluate whether there is a relationship between this cation transport system and indicators of risk of renal and cardiovascular complications in diabetic patients before the development of clinical proteinuria, we studied 31 type 1 (insulin-dependent) diabetic patients with arterial hypertension, without clinical proteinuria and 12 normotensive normoalbuminuric diabetic patients. Sodium-lithium countertransport activity was significantly higher in hypertensive patients (0.43 +/- 0.03 mmol/l RBC x hr) than in normotensive patients (0.23 +/- 0.03; P less than 0.001). To better explore the nature of the association between this transport system and arterial hypertension, hypertensive patients were divided in two groups, with high (greater than 0.41 mmol/l RBC x hr) or normal (less than 0.41) sodium-lithium countertransport activity. The two groups of hypertensive diabetics were similar in age, sex, body mass index and blood pressure levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin resistance is associated with high sodium-lithium countertransport in essential hypertension

The nature of the association between essential hypertension and insulin resistance remains unknown. We measured plasma glucose and insulin levels after an oral glucose tolerance test (OGTT), as well as insulin sensitivity (using a euglycemic hyperinsulinemic clamp), glucose turnover (Rd; using [6,6-2H2]- and [3-3H]glucose isotopic dilution), and forearm net balance of glucose (using arterial-venous difference) in 22 hypertensive patients with high (H2) red blood cell (RBC) sodium-lithium countertransport (Na(+)-Li+ CT; greater than 0.41 mmol.l RBC-1.h-1), 21 hypertensive patients with normal (H1) Na(+)-Li+ CT, and 22 normotensive controls (C). After OGTT, H2 patients had higher plasma glucose and insulin levels than H1 and C. During euglycemic hyperinsulinemia (approximately 100 microU/ml) Rd was lower in H2 [21.7 +/- 1.4 (SE) mumol.kg-1.min-1] than in H1 (44.3 +/- 2.9; P less than 0.01) and C (48.1 +/- 3.0; P less than 0.01), and an inverse correlation was found between rates of Na(+)-Li+ CT and Rd in H1 and H2 (rs = -0.76; P less than 0.01). Forearm glucose uptake was 40-50% lower in H2 compared with H1 and C (P less than 0.01). Lactate concentration increased more in C (from 511 +/- 24 to 1,207 +/- 69 microM) and in H1 (from 564 +/- 40 to 1,122 +/- 99) than in H2 (from 581 +/- 42 to 950 +/- 102, P less than 0.05 vs. both). Forearm blood flow increased more in C (31%, P less than 0.05) and H1 (22%, P less than 0.05) than in H2 (12%).(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium-lithium countertransport and cardiorenal abnormalities in essential hypertension

The rate of red blood cell sodium-lithium countertransport is elevated only in a subgroup of patients with essential hypertension. We have therefore compared renal and cardiac function and morphology in two groups of hypertensive patients with high (n = 23) or normal (n = 22) sodium-lithium countertransport (mean +/- SEM: 0.61 +/- 0.10 versus 0.29 +/- 0.07 mmol/l red blood cells.hr). The two groups were similar in age, sex distribution, body mass index, smoking habit, duration of hypertension, and actual levels of untreated blood pressure. Hypertensive patients with elevated sodium-lithium countertransport activity showed elevated glomerular filtration rate (118 +/- 2 versus 109 +/- 2 ml/min.1.73 m2; p less than 0.001), albumin excretion rate (23 +/- 3 versus 14 +/- 2 micrograms/min; p less than 0.001), larger kidney volume (250 +/- 15 versus 203 +/- 13 ml.1.73 m2; p less than 0.01), lower lithium clearance rate (26.7 +/- 0.3 versus 28.9 +/- 0.3 ml/min.1.73 m2; p less than 0.01), and higher total body exchangeable sodium (2,716 +/- 33 versus 2,485 +/- 41 mmol.1.73 m2; p less than 0.01). Left ventricular mass index (139 +/- 6 versus 119 +/- 6 g/m2; p less than 0.05), relative wall thickness (0.39 +/- 0.05 versus 0.29 +/- 0.04 cm; p less than 0.001), and left posterior wall plus intraventricular septum thickness (2.02 +/- 0.04 versus 1.76 +/- 0.03 cm; p less than 0.05) were also higher in patients with high sodium-lithium countertransport. Hypertensive patients with normal sodium-lithium countertransport had renal and cardiac parameters similar to those of a normotensive control group (n = 21) except for a higher glomerular filtration rate and left ventricular mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-dependent diabetes mellitus and hypertension

Contrasting results have been reported regarding the prevalence of hypertension in insulin-dependent diabetes mellitus (IDDM), showing a slightly higher or normal percentage of IDDM patients with elevated blood pressure levels than in the general population. Most of the cross-sectional and prospective studies on the prevalence of hypertension in IDDM show an association between microalbuminuria and elevated blood pressure levels. However, it is not clear whether hypertension is simply secondary to kidney damage or whether hypertension occurs with or even before the development of impaired kidney function. Patients with IDDM have a higher exchangeable body Na+ pool. Na+ retention in IDDM is accounted for by several metabolic and hormonal abnormalities such as hyperglycemia, hyperketonemia, hyperinsulinemia, altered secretion, and resistance to atrial natriuretic peptide. High blood pressure appears to be dependent, at least at some phase, on expansion of extracellular fluid volume as a consequence of defects in the renal secretion of Na+ and water. On the other hand, a tendency toward Na+ retention characterizes all patients with IDDM, whereas hypertension develops only in a subgroup of diabetic patients. One possible explanation for these findings is that a genetic predisposition plays a role in creating susceptibility to hypertension and perhaps to diabetic nephropathy independent of diabetes, even if Na+ retention can further deteriorate this susceptibility to hypertension. With regard to this issue, it has recently been suggested that the risk of kidney disease in patients with IDDM is associated with a genetic predisposition to hypertension. Furthermore, diabetic nephropathy occurs in familial clusters, because diabetic siblings of nephropathic diabetic patients show a higher frequency of diabetic nephropathy than the diabetic siblings of nonnephropathic diabetic patients. One of the possible genetic markers that could be useful to identify the diabetic patients with susceptibility to hypertension and diabetic nephropathy is the Na+(-)Li+ countertransport activity in erythrocytes.

Effects of insulin on whole body and forearm leucine and KIC metabolism in type 1 diabetes

To investigate whole body rates of appearance (Ra) and forearm metabolism of leucine and alpha-ketoisocaproate (KIC) in type 1 diabetes, before and after insulin administration, seven diabetic subjects were studied in the postabsorptive state with primed-constant infusions of L-[4,5-3H]leucine and [1-14C]KIC, and forearm arterial deep-venous catheterization. This combined technique allowed the selective quantitation of the two processes regulating forearm leucine and KIC metabolism (release and uptake) that may occur simultaneously. Before insulin (arterial plasma glucose, 284 +/- 24 mg/dl; leucine, 215 +/- 24 mumol/l; KIC, 42 +/- 3 mumol/l) forearm leucine and KIC release exceeded uptake slightly but significantly (P less than 0.05). During a 180-min insulin infusion, arterial glucose (144 +/- 27 mg/dl) and leucine concentrations (130 +/- 15 mumol/l) decreased (P less than 0.05 or less vs. base line) toward normal, whereas KIC did not change (33 +/- 4 mumol/l, NS). However, no net uptake of either leucine or KIC across the forearm was detected at any time point. In contrast, a significant net release of these substrates occurred throughout the insulin infusion. By the end of the hormone administration, whole body leucine and KIC Ra decreased 17 and 33%, respectively (P less than 0.01). However, forearm uptake and release of leucine and KIC did not significantly change with respect to base line. The fraction of whole body leucine released from estimated total muscle mass did not change (54 to 48%, NS) before vs. after insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal, metabolic and hormonal responses to ingestion of animal and vegetable proteins

Renal and hormonal responses were studied in a group of healthy individuals fed, in random order, for three weeks, a vegetable protein diet (N = 10), an animal protein diet (N = 10), or an animal protein diet supplemented with fiber (N = 7), all containing the same amount of total protein (chronic study). In seven additional subjects the acute renal, metabolic and hormonal response to ingestion of a meat or soya load of equivalent total protein content was investigated (acute study). In the chronic study GRF, RPF and fractional clearance of albumin and IgG were significantly higher on the animal than the vegetable protein diets (GFR: 121 +/- 4 vs. 111 +/- 4 ml/min/1.73 m2, P less than 0.001; RPF: 634 +/- 29 vs. 559 +/- 26 ml/min/1.73 m2, P less than 0.001; theta alb: 19.5 +/- 3.1 vs. 10.2 +/- 1.6 x 10(-7), P less than 0.01; theta IgG: 11.6 +/- 3.1 vs. 7.5 +/- 1.7 x 10(-7), P less than 0.05). Renal vascular resistance was lower on the animal than vegetable protein diet (82 +/- 5 vs. 97 +/- 5 mmHg/min/liter; P less than 0.001). Fiber supplementation to APD did not have any effect on the renal variables measured which were indistinguishable from APD. In the acute study, GFR and RPF both rose significantly by approximately 16% (P less than 0.005) and approximately 14% (P less than 0.05), respectively, after the meat load, while RVR fell by approximately 12% (P less than 0.05). There were no significant changes in these parameters following the soya load.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium-lithium countertransport in microalbuminuric insulin-dependent diabetic patients

A familial predisposition to arterial hypertension has recently been suggested as one important component of the susceptibility to diabetic kidney disease. Sodium-lithium countertransport activity, a marker of risk for essential hypertension, has been found to be increased in diabetic patients with overt nephropathy. We have measured red blood cell sodium-lithium counter-transport activity in 36 microalbuminuric insulin-dependent diabetic patients, a group at high risk of progression to clinical nephropathy and cardiovascular disease, and compared it with that of a matched group of 36 normoalbuminuric diabetic patients. Sodium-lithium countertransport was higher in the microalbuminuric (0.43 [95% confidence interval (CI) 0.38-0.47] mmol/l red blood cells [RBC]/hr) than in the normoalbuminuric diabetic patients (0.29 [0.25-0.33] mmol/l RBC/hr, mean difference 0.14 [0.08-0.20]; p less than 0.0001). Microalbuminuric patients had a higher frequency of parental hypertension than normoalbuminuric diabetic patients (56% vs. 28%, p less than 0.05). Sodium-lithium countertransport was related to mean arterial pressure in the microalbuminuric patients (r = 0.54, p less than 0.001) and to daily insulin requirements in both groups (microalbuminuric patients r = 0.39, p less than 0.05; normoalbuminuric patients r = 0.42, p less than 0.01). In a subset of patients in whom lipoproteins were measured, sodium-lithium countertransport activity was related to total and very low density lipoprotein triglycerides (r = 0.41, p less than 0.05 and r = 0.48, p less than 0.05) and to apolipoprotein B (r = 0.56, p less than 0.05), independently of body mass index, albumin excretion rate, glycemic control, and insulin dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial metabolism in insulin-deficient diabetic humans without coronary artery disease

Eleven insulin-dependent diabetes mellitus (IDDM) patients with angiographically normal coronary arteries and a normal hemodynamic response to an echocardiographic-dipyridamole test and 12 normal controls were studied at rest and after atrial pacing simultaneously sampling arterial and coronary sinus blood. In IDDM patients, despite hyperglycemia [10.0 +/- 2.0 (SE) mmol/l], myocardial glucose uptake was slightly lower than in controls. This process was significantly activated in both groups during atrial pacing. The isotopically calculated net flux of lactate across myocardium, in agreement with the net balance value based on unlabeled lactate-pyruvate arteriovenous differences, showed a net uptake in controls (3.5 +/- 0.6 mumol.min-1.1.73 m-2) and a net release in IDDM (12.4 +/- 2.6; P less than 0.01). Atrial pacing stimulated lactate uptake in both groups. Myocardial uptake of ketone bodies was significantly higher in IDDM (37.0 +/- 6.3 mumol.min-1.1.73 m-2) than in controls (10.1 +/- 3.4 mumol.min-1.1.73 m-2; P less than 0.01). Free fatty acid uptake was also significantly greater in IDDM than in controls (44.1 +/- 7.0 vs. 24.1 +/- 5.1 mumol.min-1.1.73 m-2; P less than 0.01). Alanine and branched amino acids were released by diabetic but not by control hearts at rest. The normalization of blood glucose concentrations restored normal patterns of lactate and ketone body kinetics across diabetic myocardium. In conclusion, 1) at rest, myocardial lactate and amino acid uptake is markedly impaired in IDDM without coronary artery disease, and 2) the metabolic abnormalities of the diabetic myocardium are not a primary phenomenon but rather a consequence of hypoinsulinemia and hyperglycemia because insulin administration, resulting in euglycemia, restored normal patterns of cardiac metabolism.

Glucose turnover and recycling in diabetes secondary to total pancreatectomy: effect of glucagon infusion

This study was designed to evaluate whether chronic deficiency of pancreatic glucagon in patients with diabetes secondary to total pancreatectomy (PX) is responsible for the commonly observed increase in blood concentrations of gluconeogenic precursors (alanine, lactate, and pyruvate). Seven PX patients were studied on two different occasions: 1) after an overnight insulin infusion (0.15 mU/kg.min) and 2) after an overnight insulin/glucagon infusion (2 ng/kg.min). Five type 1 diabetic individuals were also studied after a similar overnight insulin infusion. In the morning of each study day, [6-3H]glucose and [1-14C]glucose were rapidly injected for determination of total glucose turnover rate [( 6-3H]glucose) and glucose recycling (difference between [6-3H]glucose and [1-14C]glucose turnover rate). Basal concentrations of hormones, glucose, and intermediary metabolites were measured. After overnight insulin infusion, plasma glucose concentration (3.8 +/- 0.4 vs. 6.8 +/- 1.4 mmol/L), turnover rate (8.4 +/- 1.0 vs. 13.7 +/- 1.9 mumol/kg.min), and percent glucose recycling (5.6 +/- 3.9% vs. 19.0 +/- 3.8%) were significantly lower in PX patients than in type 1 diabetic individuals (P less than 0.05-0.01). On the contrary, blood alanine (459 +/- 93 vs. 263 +/- 28 mumol/L), lactate (1157 +/- 109 vs. 818 +/- 116 mumol/L), and pyruvate (71 +/- 8 vs. 42 +/- 3 mumol/L) were significantly higher than those values in type 1 diabetic patients (P less than 0.05-0.01). Insulin/glucagon infusion increased plasma glucose concentration (8.7 +/- 1.5 mmol/L), total turnover (18.1 +/- 1.7 mumol/kg.min), and percent recycling (20.4 +/- 6.6%) to values similar to those in type 1 diabetic subjects. The change in glucose metabolism was associated with a significant drop in blood concentrations of alanine (179 +/- 24 mumol/L), lactate (611 +/- 25 mumol/L), and pyruvate (30 +/- 3 mumol/L; all P less than 0.05-0.01 vs. insulin infusion alone). In PX patients, the glucose turnover rate was inversely correlated with blood concentrations of both alanine (r = 0.67) and lactate (r = 0.71; P less than 0.01). In conclusion, chronic deficiency of pancreatic glucagon in PX patients 1) is associated with a decreased rate of glucose turnover, 2) causes a marked impairment in glucose recycling (an index of the activity of hepatic gluconeogenesis), and 3) increases blood concentrations of alanine, lactate, and pyruvate. All abnormalities are reversed by glucagon.

Role of insulin and atrial natriuretic peptide in sodium retention in insulin-treated IDDM patients during isotonic volume expansion

Because insulin shows an antinatriuretic effect in healthy humans, insulin therapy resulting in circulating hyperinsulinemia may lead to sodium retention and in turn to hypertension in individuals with insulin-dependent diabetes mellitus (IDDM). Moreover, it has been proved that atrial natriuretic peptide (ANP) plays a major role in modulating natriuresis in humans. This study investigated the relationship between insulin and ANP in modulating sodium metabolism in normotensive and hypertensive IDDM subjects compared with control groups of normotensive and hypertensive nondiabetic subjects. IDDM normotensive and hypertensive subjects had mean +/- SE duration of IDDM of 7 +/- 2 and 8 +/- 2 yr, respectively, and had no clinical features of diabetic nephropathy. All subjects received a saline infusion (2 mmol.kg-1.90 min-1) during euglycemia. IDDM normotensive and hypertensive subjects received a subcutaneous insulin infusion (15 mU.kg-1.h-1), resulting in twofold higher plasma free-insulin levels (16 +/- 2 and 19 +/- 3 microU/ml, respectively) than in nondiabetic normotensive and hypertensive subjects (7 +/- 2 and 8 +/- 2 microU/ml, respectively). During saline challenge, sodium excretion increased by 22 +/- 4% in normotensive and 49 +/- 9% in hypertensive nondiabetic subjects but by only 11 +/- 0.4% in normotensive (P less than 0.01) and 8 +/- 2% in hypertensive (P less than 0.01) IDDM subjects. The impaired natriuretic response to saline challenge was mainly due to greater rates of sodium reabsorption by kidney proximal tubules in IDDM than nondiabetic subjects. At baseline, plasma ANP concentrations were significantly higher in both IDDM groups than in control groups (normotensive IDDM and control subjects: 38 +/- 4 and 19 +/- 2 pg/ml, respectively, P less than 0.01; hypertensive IDDM and control subjects: 45 +/- 6 and 27 +/- 4 pg/ml, respectively, P less than 0.05). After saline challenge, ANP concentrations rose to 39 +/- 4 pg/ml in normotensive and 49 +/- 5 pg/ml in hypertensive control subjects, whereas no significant change above baseline value was seen in IDDM subjects. Both IDDM groups showed a 10-12% greater exchangeable Na+ pool than control subjects regardless of the presence of hypertension. Subcutaneous insulin infusion, resulting in circulating plasma free-insulin levels in normotensive control subjects comparable to those in IDDM patients, inhibited natriuresis, increased proximal tubule sodium reabsorption at the level of the kidney, and inhibited an adequate ANP stimulation by saline challenge. We conclude that hyperinsulinemia leads to increased proximal tubule sodium reabsorption and impaired ANP response during saline administration. Both mechanisms account for sodium retention in normotensive and hypertensive IDDM patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Impaired renal response to a meat meal in insulin-dependent diabetes: role of glucagon and prostaglandins

The renal response to 100 g/1.73 m2 protein load in the form of a meat meal was studied in 19 normal subjects and 35 normoalbuminuric insulin-dependent diabetic patients (IDDs) under conditions of sustained euglycemia. The area under the glomerular filtration rate (GFR) curve rose above base line by 1,904 +/- 292 in normals and 502 +/- 237 ml/1.73 m2 in IDDs (P less than 0.01). The meat meal induced a greater increment in the area under the glucagon curve in normals (14,930 +/- 186 pg.ml-1.min-1) than in IDDs (7,227 +/- 67, P less than 0.01); similarly urinary excretion of prostaglandin E2 and 6-ketoprostaglandin F1 alpha rose by 119 and 98%, respectively, in normals but only by 2% (P less than 0.01 vs. normals) and 10% (P less than 0.01 vs. normals) in IDDs. The fractional albumin clearance rose by 102 and 251% in normals and IDDs, respectively. In five normal subjects indomethacin administration abolished the GFR, glucagon, prostaglandin, and albuminuric response to meat ingestion. Glucagon replacement under indomethacin treatment failed to restore these responses. In five diabetic patients, selected for having a flat glucagon and GFR response to a meat meal, replacement of glucagon to postprandial levels increased urinary vasodilatory prostaglandins and restored a normal GFR response. Thus in normal subjects renal vasodilatory prostaglandins appear to be the final effector of the renal hemodynamic and albuminuric response to a meat meal. The prostaglandin increase is likely to be mediated under physiological conditions by a glucagon rise, which, however, has no effect per se on renal hemodynamics.(ABSTRACT TRUNCATED AT 250 WORDS)

Substrate availability other than glucose in the brain during euglycemia and insulin-induced hypoglycemia in dogs

Alternative substrates other than glucose could be used by the brain. In this study we hypothesized that lactate and ketone bodies can provide a significant portion of oxidative brain substrates in insulin-dependent diabetes mellitus (IDDM). Six control (C) and six insulin-treated streptozotocin diabetic (IDDM) dogs were studied during euglycemia (EU) and acute insulin induced hypoglycemia (HYPO). During EU for similar plasma glucose concentration (5.5 +/- 0.4 v 5.2 +/- 0.2 mmol/L in IDDM dogs showed a higher baseline lactate concentration (1.5 +/- 0.25 v 0.74 +/- 0.10 mmol/L; P less than .05). The ketone body concentrations were also increased in IDDM dogs but this increase was not statistically significant. The brain glucose uptake was 6.9 +/- 0.6 mumol/kg/min in C and 5.4 +/- 0.7 in IDDM. Lactate was released by the brain both in IDDM dogs (11.36 +/- 1.8 mumol/kg/min) and in C dogs (3.87 +/- 0.9; P less than .05). The brain ketones rate of disappearance (Rd) was 0.3 +/- 0.05 mumol/kg/min in IDDM dogs and 0.19 +/- 0.08 in C dogs. During HYPO the glucose uptake across the brain was 2.88 +/- 0.7 mumol/kg/min in IDDM and 3.12 +/- 0.5 in C dogs. We observed an overall brain lactate release (3.21 +/- 1.7 mol/kg/min) in C dogs and a net uptake (13.44 +/- 1.1; P less than .01) in IDDM (P less than .01). The brain ketones Rd was 0.1 +/- 0.2 mumol/kg/min in IDDM and 0.1 +/- 0.1 in C dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic factor in hypertensive and normotensive insulin-dependent diabetics

Since insulin increases renal sodium reabsorption, hyperinsulinaemia in insulin-treated insulin-dependent diabetes mellitus might lead to sodium retention and, in turn, increase atrial natriuretic factor (ANF) values. We investigated ANF levels in insulin-dependent diabetes mellitus with and without hypertension. We infused saline (2 mmol/kg per 90 min) in nine normotensive controls, eight normotensive diabetics, seven hypertensive controls and six hypertensive diabetics during the imposition of a euglycaemic glucose clamp with an artificial pancreas. Baseline ANF values were higher in the normotensive and hypertensive diabetics than in the normotensive and hypertensive controls. During a sodium load the sodium excretion rate increased significantly in controls but not in the diabetic groups. The ANF pattern was similar, values being significantly increased in controls and unchanged in diabetic patients. We conclude that euglycaemic, slightly hyperinsulinaemic, insulin-dependent diabetes mellitus patients with and without hypertension are characterized by higher baseline ANF values and an impaired response to an acute saline load as shown by the sodium excretion rate and the plasma ANF concentration.

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.

Na/H and Li/Na exchange in red blood cells of normotensive and hypertensive patients with insulin dependent diabetes mellitus (IDDM)

It has been shown that red blood cell Li/Na exchange, also called countertransport (Li/Na CTT) is increased in patients with insulin dependent diabetes mellitus (IDDM) with clinical or subclinical nephropathy and elevated blood pressure. Because recent experimental evidence confirms that red cell Li/Na CTT is a mode of functioning of the Na/H exchange (Na/H CTT), we have measured both transport modes in 23 IDDM (16 hypertensive and seven normotensive) and in eight normotensive controls with normal glucose tolerance. Na/H and Li/Na CTT were significantly increased in hypertensive compared to normotensive diabetics and controls. Na/H CTT was 78 +/- 28 mmol/L cell/h in hypertensive IDDM, 50 +/- 21 in normotensive IDDM, and 55 +/- 24 in the controls. Li/Na CTT was 0.37 +/- 0.13 mmol/L cell/h, 0.27 +/- 0.10, and 0.25 +/- 0.11, respectively. Na/H and Li/Na CTT were significantly correlated (r = .38, P less than .05). The proximal tubule sodium reabsorption, measured as the fractional Li+ reabsorption, was significantly correlated to red cell Na/H CTT (r = .38, n = 29, P less than .05), but not to the Li/Na CTT (r = .21, n = 29). In conclusion this work confirms that Na/H and Li/Na CTT are function modes of the same transporter and that an increased activity of Na/H CTT might play a role in the blood pressure increase in IDDM.

Hyperparathyroidism does not influence the abnormal primary haemostasis in patients with chronic renal failure

Patients with chronic renal failure suffer from secondary hyperparathyroidism and have greatly increased blood concentrations of intact parathyroid hormone (PTH) and PTH fragments. Thus PTH has been regarded in the last few years as a uraemic toxin possibly responsible for many clinical manifestations of the uraemic syndrome including a tendency to prolonged bleeding. Since PTH inhibits platelet aggregation 'in vitro', the possibility that hyperparathyroidism of uraemia plays a role in the pathogenesis of uraemic bleeding has been considered. Clinical data to support this possibility is not available so far. In this study we have correlated the skin bleeding time, the best clinical marker of uraemic bleeding tendency, with serum concentrations of intact PTH or PTH fragments in 40 patients with chronic renal failure undergoing chronic haemodialysis. Since the skin bleeding time is known to be influenced by packed cell volume (PCV), we also considered two distinct groups of uraemic patients on the basis of their PCV values. The results indicated that bleeding time does not correlate with serum concentrations of intact PTH or PTH fragments. Also, no correlation has been found between PTH values and blood concentrations of calcium, phosphorus, magnesium and hydroxyproline. It is concluded that elevated PTH values in renal-failure patients do not contribute to uraemic platelet defect, as reflected by the skin bleeding time.

Kidney hemodynamics after ketone body and amino acid infusion in normal and IDDM subjects

Little information is available on the hemodynamic response (renal reserve) of the diabetic kidney during an acute amino acid infusion, which has been shown to increase glomerular filtration rate (GFR) in normal humans. We recently found that the infusion of ketone bodies is able to raise GFR in both normal subjects and insulin-dependent diabetes mellitus (IDDM) patients. The aim of this study was to evaluate the renal reserve in 15 IDDM patients with a duration of diabetes of greater than 9 yr [8 with albumin excretion rate less than 15 micrograms/min (group 1) and 7 with albumin excretion rate greater than 100 micrograms/min (group 2)] and in 8 normal subjects during amino acid infusion (33 mumol.kg-1.min-1, Travasol 10% wt/vol solution containing 0.154 mM sodium chloride concentration; Travenol, Savage, MD) and during acetoacetic sodium salt (25 mumol.kg-1.min-1) infusion. Blood glucose was clamped at euglycemic levels. The infusion of sodium acetoacetate resulted in a 10- to 15-fold increase in circulating concentrations of ketone bodies, which were similar in magnitude in normal subjects and diabetic patients. The GFR peak increase above baseline after sodium acetoacetate infusion was 28% in normal subjects and 27% in group 1 and 19% in group 2 diabetic patients. The infusion of amino acid solution produced a three- to fivefold increase in plasma concentrations of amino acids in both normal subjects and diabetic patients. The GFR peak increase above baseline after amino acid infusion was significantly lower in diabetic patients (IDDM group 1: 5%, P less than .01; IDDM group 2: 6%, P less than .01) than in normal subjects (38%).(ABSTRACT TRUNCATED AT 250 WORDS)

Porcine and human insulin absorption from subcutaneous tissues in normal and insulin-dependent diabetic subjects: a deconvolution-based approach

The mechanisms of sc insulin absorption are not understood, and models for interpreting in vivo data cannot be developed without gross simplification. To overcome this difficulty we developed a new approach which makes use of deconvolution analysis and does not require any model of the sc tissue. In five normal subjects and seven insulin-dependent diabetic (IDDM) patients endogenous insulin secretion was suppressed by means of a hypoglycemic glucose clamp procedure (approximately 2.8 mmol/L) sustained by a continuous insulin infusion (approximately 4 pmol/min.kg). A bolus injection of insulin (5.4 nmol) was administered iv, and plasma insulin concentrations were measured frequently for 2 h to assess iv insulin kinetics. Insulin then was injected sc in the abdominal region, and plasma insulin concentrations were measured for 8 h. Each subject was studied twice, with porcine and semisynthetic human insulin (Actrapid, Novo). The rate of insulin absorption was reconstructed by deconvolution from the plasma concentrations and iv insulin kinetic data. Linearity of the iv insulin kinetics, essential for deconvolution analysis, was confirmed by a dose-response study in the range of the measured concentrations (150-1800 pmol/L). In most instances, a two-compartment model was adequate to describe the iv response. The mean plasma insulin clearance rates were 15.5 +/- 1.9 (+/- SD) mL/min.kg (porcine) and 17.2 +/- 6.0 (human) in normal subjects and 20.7 +/- 8.8 (porcine) and 20.9 +/- 9.1 (human) in the IDDM patients. The rate of appearance of human insulin from sc tissue was faster than that of porcine insulin in both normal and IDDM subjects, but no significant differences were found in bioavailability, which was 55 +/- 12% (+/- SD; porcine) and 61 +/- 34% (human) in the normal subjects, and 84 +/- 28% (porcine) and 86 +/- 23% (human) in the IDDM patients. The rate of absorption and bioavailability were higher in the IDDM patients than in the normal subjects, a difference possibly related to increased sc blood flow in the IDDM patients. No differences were found with regard to glucose requirement values, normalized to plasma insulin concentrations, in agreement with the finding that the bioavailability of the two insulin species was similar.

Type I insulin-dependent diabetic patients show an impaired renal hemodynamic response to protein intake

Human kidney responds to a meat meal with an increase in glomerular filtration rate (GFR), but the mechanisms regulating kidney hemodynamics following protein intake are poorly understood in Type I insulin-dependent diabetes. In the present study we investigated GFR response to protein intake (600 gr/1.73 m2 meat meal) in nine normal subjects and 21 Type I insulin-dependent diabetic patients with normal albumin excretion rates as well as proximal tubular sodium reabsorption rates and distal sodium delivery (PRNa and DDNa). The same study was reperformed in normal subjects and diabetic patients, with less than a 5 year diabetes duration, following one week of indomethacin treatment. Normal subjects showed a 38% increase in GFR following protein intake, whereas diabetic patients showed a significantly lower response (18%, p less than 0.01). The response of GFR to protein challenge was negatively related to diabetes duration but not to baseline glomerular filtration rate. Indomethacin treatment completely prevented the protein induced GFR increase in normal subjects but not in diabetic patients. Sodium reabsorption rate was increased following protein challenge both at the proximal and distal tubular level, as was net natriuresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Prevalence of microangiopathic complications in hyperglycemia secondary to pancreatic disease

Diabetes secondary to pancreatic disease (PD) represents a useful model for the study of the effects of chronic hyperglycemia on microangiopathic complications in the absence of those genetic factors predisposing to Type I diabetes. Our aim was to evaluate the prevalence of nephropathy and retinopathy in a group of 86 patients with PD. The genetic pattern, assessed by the determination of HLA antigens, was different than in patients with Type I diabetes. A family history of diabetes was present in 53% of the patients. The prevalence of retinopathy was 37%. Eighteen percent of the patients with duration of diabetes less than 10 years showed an albumin excretion rate (AER) greater than 40 mg/24 hr. The prevalence of pathologic microalbuminuria (greater than 40 mg/24 hr) was found in 29% of the patients with duration of diabetes greater than 10 years. The prevalence of pathologic microalbuminuria is related to the duration of diabetes. Both diastolic and systolic blood pressure is positively correlated to albumin excretion rate (p less than 0.02), suggesting a possible role of hypertension in the evolution of nephropathy. Sixty-one percent of the patients with AER greater than 40 mg/24 h had retinopathy, thus confirming the close association between renal and ocular complications. Abnormal microalbuminuria and retinopathy were not influenced by a family history of diabetes. We conclude that the prevalence of microangiopathic complications is similar to that seen in Type I diabetes, and the metabolic abnormalities of diabetes can play a direct role in the development of diabetic microangiopathy.

Glucose and ketone body turnover in carnitine-palmitoyl-transferase deficiency

Most of the patients with carnitine-palmitoyl-transferase deficiency (CPT) show reduced levels of blood ketone bodies in the postabsorptive state. In the present study, we have evaluated ketone body and glucose kinetics in patients with CPT deficiency. Intermediate metabolites of carbohydrate and lipid metabolism have also been studied. Ketone body (KB) turnover was measured by means of sequential intravenous bolus injections of 3-14C acetoacetate and 3-14C D(-) 3-hydroxybutyrate in four patients with liver, platelet, and muscle deficiency of CPT system and in eight normal overnight fasting subjects. 6-3H glucose was also injected, along with 3-14C ketone bodies to measure glucose turnover rate. Three out of four CPT deficiency patients had normal KB turnover, despite a marked reduction in liver CPT activity. Only one subject, with severe defect of CPT activity in liver, showed a significantly reduced, but still present rate of de novo synthesis of acetoacetate and 3-hydroxybutyrate (40 and 51 mumol/m-2/min-1 respectively) in comparison with control subjects (103 +/- 14 and 157 +/- 22 mumol/m-2/min-1). Blood concentrations of dicarboxylic adipic and suberic acids were significantly higher in CPT deficiency patients (0.035 +/- 0.007 and 0.021 +/- 0.005, mmol/L respectively) than in control subjects (0.008 +/- 0.008 and 0.006 +/- 0.003 respectively). Basal glucose turnover was increased in CPT deficiency patients (505 +/- 13 mumol/m-2/min-1) in comparison with normal subjects (433 +/- 18 mumol/m-2/min-1; P less than .01) as well as clearance rates (127 +/- 3 mL/m-2/min-1 and 91 +/- 11 mL/m-2/min-1, respectively; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic control of kidney hemodynamics in normal and insulin-dependent diabetic subjects. Effects of acetoacetic, lactic, and acetic acids

Diabetes mellitus is associated with important changes in renal hemodynamics. The purpose of this study was to determine whether an increase in blood concentration patterns of ketone bodies and lactic acid, organic acids often elevated in poorly controlled insulin-dependent diabetes mellitus (IDDM), could contribute to increase glomerular filtration rate (GFR) and renal plasma flow (RPF) regardless of changes in circulating levels of glucose and insulin. Six IDDM patients and six normal subjects were given a saline infusion (15 mumol.min-1.kg-1) for 2 h, an acetoacetic acid infusion (15 mumol.min-1.kg-1) for another 2 h, and then a saline infusion after an overnight fast during euglycemic insulin-glucose clamp. Acetoacetic acid infusion resulted in an increase of blood ketone bodies in the range of 0.7-1.5 mM from a basal value of 0.1-0.3 mM. GFR was 125 +/- 16 and 136 +/- 17 ml.min-1.1.73 m-2 in normal and IDDM subjects, respectively, during baseline saline infusion and 138 +/- 21 (P less than .01 vs. basal level) and 158 +/- 15 ml.min-1.1.73 m-2 (P less than .001 vs. basal level) during acetoacetic acid infusion. During the last saline infusion, renal hemodynamic patterns decreased again to baseline levels. Another six IDDM patients and six normal subjects were given saline, lactic acid, and saline infusions at the same rates of infusion after an overnight fast during euglycemic insulin-glucose clamp. Lactic acid concentration increased from approximately 0.5-0.8 to 1.0-1.5 mM in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Glomerular filtration rate is increased in man by the infusion of both D,L-3-hydroxybutyric acid and sodium D,L-3-hydroxybutyrate

A high glomerular filtration rate (GFR) is often found early in insulin-dependent diabetes mellitus (IDDM). It has been suggested that high circulating glucose, glucagon, and GH levels could play a role in this increase in GFR. On the other hand, patients with IDDM in poor metabolic control also have high circulating ketone body levels. This study was undertaken to determine whether exogenous D,L-3-hydroxybutyric acid at two infusion rates (40 and 30 mumol kg-1 min-1) for 180 min altered renal plasma flow (RPF), GFR, and the excretion rate of total protein, beta 2-microglobulin, and albumin in 11 normal (N) subjects and 11 IDDM patients in whom euglycemia was achieved and maintained using the insulin-glucose clamp technique. RPF and GFR were measured by a priming-continuous infusion of [125I]hippurate and [51Cr]EDTA, respectively. The 40 mumol kg-1 min-1 D,L-3-hydroxybutyric acid infusion increased RPF and GFR in both N and IDDM subjects. Mean RPF increased from 588 +/- 78 (+/- SD) to 706 +/- 129 mL min-1 1.73 m-2 in N and from 671 +/- 101 to 781 +/- 99 in IDDM. GFR increased from 121 +/- 11 to 151 +/- 15 ml min-1 1.73 m-2 in N and from 136 +/- 11 to 191 +/- 16 in IDDM. The filtration fraction also was significantly higher in IDDM than in N during the D,L-3-hydroxybutyric acid infusion. The 30 mumol kg-1 min-1 D,L-3-hydroxybutyric acid infusion increased RPF and GFR to a somewhat lesser extent in both groups. D,L-3-hydroxybutyric acid infusions increased the tubular reabsorption rate of ketone bodies and sodium. The increase in tubular sodium reabsorption rate was correlated significantly to that in the tubular ketone body reabsorption rate. A significant decrease in urinary pH was found during the D,L-3-hydroxybutyric acid infusion. D,L-3-Hydroxybutyrate sodium salt (30 mumol kg-1 min-1) also was infused in 5 of the 11 diabetic patients. A similar increase in GFR and RPF occurred. Both total protein and beta 2-microglobulin, but not albumin, excretion rates increased during D,L-3-hydroxybutyric acid (40 mumol kg-1 min-1) infusion in N and IDDM subjects. D,L-3-Hydroxybutyric acid infusion did not change plasma glucagon, GH, or renin activity.(ABSTRACT TRUNCATED AT 400 WORDS)

3-Hydroxy-3-methylglutaric, adipic, and 2-oxoglutaric acids measured by HPLC in the plasma from diabetic patients

A method for the measurement of organic acids in human plasma is presented. The analytical procedure consists of plasma protein precipitation with acetonitrile, acid extraction by chromatography through a DEAE-cellulose column eluted with 100 mM perchloric acid, HPLC by cation-exchange column Aminex HPX-87 eluted with 6.5 mM sulfuric acid. Adipic, 3-hydroxy-3-methylglutaric, 2-oxoglutaric, and citric acids were determined in the plasma of diabetic patients. The concentrations of all the measured acids, but particularly those of adipic and 3-hydroxy-3-methylglutaric acids, were significantly higher than those of healthy controls. These results suggest that in diabetics the omega-oxidation of fatty acids is enhanced.

Alcohol impairs insulin sensitivity in normal subjects

The effects of alcohol on insulin action are not yet clearly established. To assess the effects of intravenously administered ethanol on insulin mediated glucose disposal, euglycaemic clamps at 3 different plasma insulin levels and insulin receptor binding studies on circulating monocytes after alcohol infusion were performed. Ethanol infusion leads to a significant reduction of insulin mediated glucose disposal (7.08 +/- 0.4 vs 8.6 +/- 0.6 mg/Kg/min; 9.8 +/- 0.7 vs 13.4 +/- 0.7; 14.7 +/- 0.7 vs 18.1 +/- 0.7 at 33, 73 and 760 mU/m2/min insulin infusion rate respectively). Monocyte insulin-receptor binding was decreased in all the subjects from 30 to 60% after ethanol infusion. These results demonstrate that alcohol can adversely influence the insulin mediated glucose disposal.

Ketone bodies increase glomerular filtration rate in normal man and in patients with type 1 (insulin-dependent) diabetes mellitus

The purpose of this study was to investigate whether the administration of acetoacetic and hydrochloric acids in a group of control and Type 1 (insulin-dependent) diabetic patients influenced renal haemodynamics. Renal plasma flow increased from 657 +/- 88 to 762 +/- 81 ml X min-1. 1.73 m-2 in diabetic patients (p less than 0.01) and from 590 +/- 71 to 691 +/- 135 in control subjects (p less than 0.01). Glomerular filtration rate increased from 135 +/- 9 to 180 +/- 8 ml X min-1. 1.73 m-2 in diabetic patients (p less than 0.001) and from 117 +/- 8 to 145 +/- 7 in control subjects (p less than 0.01). Similar effects on renal haemodynamics, even if less pronounced, were observed with low dose acetoacetic but not with hydrochloric acid infusion. Total protein, beta 2-microglobulin but not albumin excretion rates were increased by acetoacetic acid. We conclude that an acute increase in blood concentration of ketone bodies within the range found in diabetic patients with poor metabolic control increases renal plasma flow and glomerular filtration rate both in control subjects and diabetic patients and causes a tubular proteinuria.

Differential effects of hyperinsulinemia and hyperaminoacidemia on leucine-carbon metabolism in vivo. Evidence for distinct mechanisms in regulation of net amino acid deposition

The effects of physiologic hyperinsulinemia and hyperaminoacidemia, alone or in combination, on leucine kinetics in vivo were studied in postabsorptive healthy subjects with primed-constant infusions of L-[4,5-3H]leucine and [1-14C]alpha-ketoisocaproate (KIC) under euglycemic conditions. Hyperinsulinemia (approximately 100 microU/ml) decreased (P less than 0.05 vs. baseline) steady state Leucine + KIC rates of appearance (Ra) from proteolysis, KIC (approximately leucine-carbon) oxidation, and nonoxidized leucine-carbon flux (leucine----protein). Hyperaminoacidemia (plasma leucine, 210 mumol/liter), with either basal hormone replacement or combined to hyperinsulinemia, resulted in comparable increases in leucine + KIC Ra, KIC oxidation, and leucine----protein (P less than 0.05 vs. baseline). However, endogenous leucine + KIC Ra was suppressed only with the combined infusion. Therefore, on the basis of leucine kinetic data, hyperinsulinemia and hyperaminoacidemia stimulated net protein anabolism in vivo by different mechanisms. Hyperinsulinemia decreased proteolysis but did not stimulate leucine----protein. Hyperaminoacidemia per se stimulated leucine----protein but did not suppress endogenous proteolysis. When combined, they had a cumulative effect on net leucine deposition into body protein.

Effect of metformin on insulin-stimulated glucose turnover and insulin binding to receptors in type II diabetes

Euglycemic insulin glucose-clamp and insulin-binding studies on erythrocytes and monocytes were performed in seven type II (non-insulin-dependent) diabetic subjects before and after 4 wk of metformin treatment (850 mg 3 times/day) and in five obese subjects with normal glucose tolerance. Glucose turnover was also measured at basal insulin concentrations and during hyperinsulinemic euglycemic clamps. During euglycemic insulin-glucose clamps, diabetic subjects showed glucose disposal rates of 3.44 +/- 0.42 and 7.34 +/- 0.34 mg X kg-1 X min-1 (means +/- SD) before metformin at insulin infusion rates of 0.80 and 15.37 mU X kg-1 X min-1, respectively. With the same insulin infusion rates, glucose disposal was 4.94 +/- 0.55 (P less than .01) and 8.99 +/- 0.66 (P less than .01), respectively, after metformin treatment. Glucose disposal rates in normal obese subjects were 5.76 +/- 0.63 (P less than .01) and 10.92 +/- 1.11 (P less than .01) at 0.80 and 15.37 mU X kg-1 X min-1, respectively. Insulin maximum binding to erythrocytes in diabetics was 9.6 +/- 4.2 and 5.8 +/- 2.6 X 10(9) cells (means +/- SD) before and after metformin treatment, respectively (NS). Insulin maximum binding to monocytes in diabetics was 6.2 +/- 2.3 X 10(7) cells before and 5.0 +/- 1.6% after metformin. Hepatic glucose production was higher in the diabetic patients at basal insulin levels, but not at higher insulin concentrations, and was not significantly changed by drug treatment. Basal glucose and insulin concentrations decreased with metformin. Thus, metformin treatment improved glucose disposal rate without significant effect on insulin-binding capacity on circulating cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-response curves of effects of insulin on leucine kinetics in humans

To determine the effects of physiological and pharmacological insulin concentrations on leucine-carbon kinetics in vivo, eight postabsorptive normal volunteers were infused with L-[4,5-3H]leucine and alpha-[1-14C]ketoisocaproate (KIC). Insulin concentrations were sequentially raised from 8 +/- 1 to 43 +/- 6 and 101 +/- 14 and to 1,487 +/- 190 microU/ml, while maintaining euglycemia with adequate glucose infusions. At the end of each 140-min insulin-infusion period, steady-state estimates of leucine and KIC rates of appearance (Ra), KIC (approximately leucine-carbon) oxidation, nonoxidized leucine-carbon flux [an index of leucine incorporation into protein (Leu----P)], and leucine and KIC interconversion rates were obtained. After the three insulin infusions, leucine Ra decreased by a maximum of approximately 20%. KIC Ra decreased by a maximum of approximately 50%. The sum of leucine plus KIC Ra in the basal state was 2.59 +/- 0.24 mumol X kg-1 X min-1 and decreased by approximately 30% at the maximal insulin concentrations. KIC oxidation decreased by a maximum of approximately 65%. Leu----P did not increase after hyperinsulinemia. Interconversion rates were promptly and markedly suppressed by 50-70%. Leucine clearance increased by approximately 120%. We conclude that euglycemic hyperinsulinemia, at physiological and pharmacological concentrations, decreased leucine and KIC concentrations, leucine-carbon turnover and oxidation, and leucine and KIC interconversions in a dose-dependent manner in vivo.

Intermediary metabolite profiles during euglycemic glucose-insulin clamp: effects of ethanol

We evaluated the effects of different doses of i.v. alcohol on tissue insulin sensitivity, by means of insulin-glucose clamp technique, in 10 young healthy men. The most important intermediary metabolites were assayed. Insulin-dependent glucose disposal was impaired at different levels of alcoholemia, probably through an impairment of the glycolytic pathway. Exogenous insulin administration does not restore the more reduced redox state caused by alcohol oxidation. Alcohol does not interfere with the antiketogenic and antilipolytic insulin effects.

Defective suppression by insulin of leucine-carbon appearance and oxidation in type 1, insulin-dependent diabetes mellitus. Evidence for insulin resistance involving glucose and amino acid metabolism

To determine whether a resistance to insulin in type 1, insulin-dependent diabetes mellitus (IDDM) is extended to both glucose and amino acid metabolism, six normal subjects and five patients with IDDM, maintained in euglycemia with intravenous insulin administration, were infused with L-[4,5-3H]leucine (Leu) and [1-14C]alpha ketoisocaproate (KIC). Steady-state rates of leucine-carbon appearance derived from protein breakdown (Leu + KIC Ra) and KIC (approximately leucine) oxidation were determined at basal and during sequential euglycemic, hyperinsulinemic (approximately 40, approximately 90 and approximately 1,300 microU/ml) clamps. In the euglycemic postabsorptive diabetic patients, despite basal hyperinsulinemia (24 +/- 6 microU/ml vs. 9 +/- 1 microU/ml in normals, P less than 0.05), Leu + KIC Ra (2.90 +/- 0.18 mumol/kg X min), and KIC oxidation (0.22 +/- 0.03 mumol/kg X min) were similar to normal values (Leu + KIC Ra = 2.74 +/- 0.25 mumol/kg X min) (oxidation = 0.20 +/- 0.02 mumol/kg X min). During stepwise hyperinsulinemia, Leu + KIC Ra in normals decreased to 2.08 +/- 0.19, to 2.00 +/- 0.17, and to 1.81 +/- 0.16 mumol/kg X min, but only to 2.77 +/- 0.16, to 2.63 +/- 0.16, and to 2.39 +/- 0.08 mumol/kg X min in the diabetic patients (P less than 0.05 or less vs. normals at each clamp step). KIC oxidation decreased in normal subjects to a larger extent than in the diabetic subjects. Glucose disposal was reduced at all insulin levels in the patients. In summary, in IDDM: (a) Peripheral hyperinsulinemia is required to normalize both fasting leucine metabolism and blood glucose concentrations. (b) At euglycemic hyperinsulinemic clamps, lower glucose disposal rates and a defective suppression of leucine-carbon appearance and oxidation were observed. We conclude that in type 1 diabetes a resistance to the metabolic effects of insulin on both glucose and amino acid metabolism is present.

Type I diabetes is characterized by insulin resistance not only with regard to glucose, but also to lipid and amino acid metabolism

Resistance to the metabolic effects of insulin has been reported with regard to glucose disposal in type I diabetic patients (IDDM) even when they were euglycemic. Our aim was to study glucose, lipid, and amino acid metabolism during glucose clamping at multiple levels of insulin in 10 normal (N) and 6 IDDM patients. Blood glucose was maintained constant (4.7 mmol/liter) at three insulin plateaus (160 min each) [42 +/- 6 (SD) 89 +/- 11, and 1255 +/- 185 microU/ml in N and 36 +/- 4, 80 +/- 13, and 1249 +/- 107 microU/liter in IDDM]. Mean glucose disposal was 34 +/- 11, 69 +/- 10, and 84 +/- 22 mumol kg-1 min-1 in N and 16 +/- 5, 40 +/- 18, and 65 +/- 27 in IDDM, respectively. Baseline concentrations of blood lactate, pyruvate, alanine, and branched chain amino acids were 560 +/- 130, 36 +/- 9, 212 +/- 44, and 451 +/- 19 mumol/liter, in N and 793 +/- 179 (P less than 0.05), 45 +/- 14, 195 +/- 50, and 439 +/- 33 in IDDM, respectively. The maximum percent change of lactate during the euglycemic clamp was +147 +/- 23% in N and +75 +/- 15% (P less than 0.05) in IDDM; that of branched chain amino acids was -61 +/- 5% in N and -48 +/- 7% (P less than 0.01) in IDDM. Baseline concentrations of glycerol, FFA, and adipate were 44 +/- 15, 449 +/- 152, and 8 - 8 mumol/liter in N and 39 +/- 14, 473 +/- 44, and 41 +/- 14 (P less than 0.01) in IDDM. The maximum percent change of glycerol during the euglycemic clamp was -50 +/- 8% in N and -16 +/- 8% (P less than 0.01) in IDDM, that of FFA -98 +/- 3% in N and -70 +/- 4% in IDDM (P less than 0.05). No significant differences were found between N and IDDM with regard to blood concentrations of ketone bodies, citrate, ketoglutarate, and hydroxymethylglutaryl coenzyme A both before and during the euglycemic clamp. The lactate percent increase was significantly correlated to glucose disposal rate (P less than 0.001). The lactate turnover rate increased during the euglycemic clamp and was lower in IDDM than in N. We conclude that during euglycemic-multiple insulin clamp studies the greater lactate increase suggests that the flux of glycolysis is higher in N than in IDDM, tricarboxylic acid concentrations are comparable in N and IDDM, and FFA, glycerol, and branched chain amino acid decreases were less in IDDM than in N, suggesting that IDDM patients are resistant to insulin with regard to lipid and protein metabolism. The higher adipate basal values demonstrate enhanced omega-oxidation in IDDM.

Hormonal and metabolic profiles in patients with alcohol-induced, mixed hypertriglyceridemia before and after abstinence from ethanol and before and after a lipid-lowering diet

The diurnal variation of intermediary metabolites and hormones was determined, as 24-h profiles, in a group of subjects with mixed hypertriglyceridemia while consuming a diet with excess alcohol and caloric intake (Hyp-I) or after a hypotriglyceridemic diet (Hyp-II), and in normal controls. Alcohol was excluded from the hypotriglyceridemic diet and on the days of the study. Hyp-I subjects showed higher 24-h levels of plasma triglyceride, glucose, insulin, lactate, pyruvate, free fatty acid and glycerol. After the hypotriglyceridemic diet the levels of pyruvate, free-fatty acids and glycerol in plasma were normalized, while triglyceride, insulin and glucose concentrations were significantly reduced but remained still higher than in controls. The elevated lactate concentration in Hyp-I subjects were unaffected by the diet. In Hyp-I subjects free-fatty acids and glycerol levels were not suppressed following the meal, in contrast to controls. After the diet this defect in the suppression of endogenous lipolysis was only partially reversed in Hyp-II subjects. Plasma alanine, total ketone body and glucagon concentrations were unaffected. In conclusion, in mixed hypertriglyceridemia high lactate concentration and a defect in the suppression of endogenous lipolysis after a meal could represent a factor enhancing triglyceride production.

Ketone body metabolism in normal and diabetic human skeletal muscle

Although the liver is considered the major source of ketone bodies (KB) in humans, these compounds may also be formed by nonhepatic tissues. To study this aspect further, 3-[14C]hydroxybutyrate (BOH) or [3-14C]acetoacetate (AcAc) were constantly infused after a priming dose and contemporaneous arterial and venous samples were taken at splanchnic, heart, kidney, and leg sites in eight normal subjects (N) undergoing diagnostic catheterization and at the forearm site in five normal and six ketotic diabetic (D) subjects. After 70 min of infusion, tracer and tracee levels of AcAc and BOH reached a steady state in the artery and vein in both normal and diabetic subjects. The venous-arterial (V-A) difference at the forearm step for cold KB was negligible both in normal and diabetic subjects, whereas for labeled KB it was approximately 10-fold higher in diabetic subjects (V-A AcAc, -31 +/- 7 and -270 +/- 34 dpm/ml in N and D, respectively; V-A BOH, -38 +/- 6 and -344 +/- 126 dpm/ml in N and D, respectively). We assumed that the V-A difference in tracer concentration was consistent with dilution of the tracer by newly synthesized tracee inside the muscle and calculated that the forearm muscle produces KB at a rate of 16.2 +/- 3.3 mumol/min in D and 0.9 +/- 0.9 mumol/min in N. These findings can be accounted for by the hypothesis that the disappearance flux of KB from circulation was replaced by an equivalent flux of KB entering the vein at the muscle step in D but not in N. Moreover, in N KB were not only produced but also utilized by the splanchnic area (39 +/- 9 mumol/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Hyperalaninaemia is an early feature of diabetes secondary to total pancreatectomy

High levels of gluconeogenic precursors have been reported in patients with long-term diabetes secondary to total pancreatectomy. In the present study, blood concentrations of alanine, lactate and pyruvate were measured in six patients undergoing total pancreatectomy and in nine control subjects undergoing major abdominal surgery. To exclude the simple effect of lack of insulin and hyperglycaemia in the development of hyperalaninaemia following total pancreatectomy, three pancreatectomized patients and five control subjects underwent surgical operation while connected to an artificial pancreas. Blood concentration of alanine was constant in the control subjects during surgery (182 +/- 20 and 243 +/- 31 mumol/l with and without the artificial pancreas, respectively). In pancreatectomized patients basal blood alanine levels were similar to those in control subjects. Blood alanine level rose quickly after removal of the pancreas from 182 +/- 24 to 285 +/- 15 mumol/1 (p less than 0.05) in the patients connected to the artificial pancreas, and from 198 +/- 17 to 395 +/- 47 mumol/1 (p less than 0.05) in patients undergoing total pancreatectomy without artificial pancreas. These values were higher than those observed in the control subjects at the end of the operation (192 +/- 22 and 230 +/- 45 mumol/l with and without artificial pancreas, respectively.) Basal and intraoperative blood concentrations of lactate and pyruvate were similar in pancreatectomized patients and control subjects.

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.

Effect of streptozotocin in a case of glucagon-secreting malignant islets-cell tumor

A case of a 65-year-old woman with a pancreatic tumor secreting insulin, glucagon, and associated with high PTH levels and hypercalcemia is reported. The patient underwent two Streptozotocin (STZ) treatments (1 g iv/week for 10 weeks) after liver metastases were found. Hormonal and metabolic parameters were monitorized . Before the first STZ treatment insulin levels ranged between 78 and 132 microU/ml. After STZ administration insulin decreased and then remained lower (8-48 microU/ml) until the death of the patient. Pre-treatment glucagon levels ranged between 1.3 and 3.9 ng/ml. STZ induced a decrease of glucagon to 0.5 ng/ml. Glucagon chromatography revealed the prevalence of high molecular weight (greater than 6,000 mol wt) immunoreactive glucagon (0.9 ng/ml) drastically reduced by STZ treatment (0.15 ng/ml). Hypoaminoacidemia was observed before STZ administration, but at the end of the therapy plasma amino acid concentrations were normal. Hypercalcemia too was sensitive to STZ, but not PTH value, which remained high. The second STZ treatment performed a year later was less effective and so a chemotherapeutic protocol was started. Our findings suggest a cytolitic effect of STZ on malignant A-cell, with reduction of glucagon levels and restoration of amino acid metabolism. This effect would be useful for medical treatment of non-operable glucagon secreting tumors.

Insulin-mediated glucose disposal in type I diabetes: evidence for insulin resistance

To clarify whether type I diabetes is characterized by insulin resistance, insulin-mediated glucose metabolism (M; milligrams per kg/min) was estimated by means of the glucose clamp technique in five insulin-dependent diabetic patients and six normal subjects. Three glucose clamps were carried out under different metabolic conditions. Free insulin plateaux were similar during each clamp in both groups. The first clamp was performed in normal subjects after an overnight fast [blood glucose, 80 +/- 3 mg/dl (mean +/- SEM)] and in diabetic patients 18 h after insulin withdrawal (blood glucose, 366 +/- 47 mg/dl). Diabetic patients had a M value (4.25 +/- 0.74) not different from normals (5.38 +/- 0.63; P = NS). The second clamp was done with the same glycemic values (approximately 125 mg/dl) in both groups. M increased to 8.07 +/- 1.06 (P less than 0.01) in the normal subjects and decreased to 2.87 +/- 0.50 (P = NS) in the diabetic patients. The M value in the diabetic patients was lower than that in the normal subjects (P less than 0.05). The third clamp was performed in three diabetic patients after 1 month of treatment with continuous sc insulin infusion. The mean blood glucose level was 88 +/- 6 mg/dl, and M was 3.23 +/- 0.38, significantly lower than that of the normal subjects in the basal state (P less than 0.05). No differences were found in insulin binding to erythrocytes. The mean plasma clearance rate (milliliters per m2/min) of free insulin was the same in both groups (428 +/- 113 in normal subjects and 354 +/- 83 in diabetic patients). Basal endogenous glucose production was higher in the diabetics (3.13 +/- 0.48 mg/kg X min) than in the normal subjects (1.71 +/- 0.57). During the clamp, however, endogenous glucose production was similarly inhibited (approximately 95%) in both groups. Multiple glucose clamp studies were also performed at three different insulin infusion rates (21, 73, and 760 mU/m2 X min, respectively) to generate an insulin-dose response curve for glucose disposal in six diabetic patients treated with continuous sc insulin infusion for at least 6 months. This allowed investigation of the effect of chronic strict insulin therapy leading to normal glucose and intermediary metabolite levels and identification of the cellular mechanism of insulin resistance. A significant reduction of the maximal glucose disposal rate (10.7 +/- 0.5 mg/kg X min) was found in these diabetic patients compared to that in normal subjects (14.9 +/- 1.0; P less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)