Insulin degludec improves long-term glycaemic control similarly to insulin glargine but with fewer hypoglycaemic episodes in patients with advanced type 2 diabetes on basal-bolus insulin therapy.

The aim of the present study was to compare the long-term safety and efficacy of insulin degludec with those of insulin glargine in patients with advanced type 2 diabetes (T2D) over 78 weeks (the 52-week main trial and a 26-week extension). Patients were randomized to once-daily insulin degludec or insulin glargine, with mealtime insulin aspart ± metformin ± pioglitazone, and titrated to pre-breakfast plasma glucose values of 3.9-4.9 mmol/l (70-88 mg/dl). After 78 weeks, the overall rate of hypoglycaemia was 24% lower (p = 0.011) and the rate of nocturnal hypoglycaemia was 31% lower (p = 0.016) with insulin degludec in the extension trial set, while both groups of patients achieved similar glycaemic control. Rates of adverse events and total insulin doses were similar for both groups in the safety analysis set. During 18 months of treatment, insulin degludec + mealtime insulin aspart ± oral antidiabetic drugs in patients with T2D improves glycaemic control similarly, but confers lower risks of overall and nocturnal hypoglycaemia than with insulin glargine treatment.

Treat-to-target trials: uses, interpretation and review of concepts.

Treat-to-target trial designs compare investigational insulins with a standard insulin. Treat-to-target trials force-titrate insulin dosages to achieve a prespecified treatment goal. With comparable glycaemic control, comparisons of safety endpoints such as hypoglycaemia can be made to establish the risk-benefit profile of the new insulin. Glargine versus NPH showed comparable A1C reductions; however, A1C <7% without associated nocturnal hypoglycaemia was reached in more patients on glargine and overall hypoglycaemia was lower. Detemir versus glargine showed non-inferiority between the groups; however, with less weight gain and more injection site reactions with detemir. Detemir/aspart versus glargine/aspart showed non-inferiority between the treatments, however, with less weight gain in the detemir group but comparable risk of hypoglycaemia. Degludec in combination with aspart versus glargine/aspart showed comparable A1C reductions. However, degludec-treated patients had less overall hypoglycaemia and less nocturnal hypoglycaemia. Because insulin titrations are guided by goal attainment with each treatment, treat-to-target trials enable clinicians to determine differences in non-glycaemic treatment effects, such as rates of hypoglycaemia and weight gain, at the same level of glycaemic control.

Will the next generation of basal insulins offer clinical advantages?

The 21st century has seen the arrival of several insulin analogue products and the refinement of insulin regimens, with widespread advocacy of continuous titration algorithms and earlier initiation of supplementary insulin therapy (predominantly using basal insulins) in type 2 diabetes. Nevertheless, many insulin-treated diabetes patients remain in poor glycaemic control. This might reflect insufficient titration effort or lax adherence, but these issues could in some cases result from concerns about hypoglycaemia. Certainly there is scope for improving the pharmacokinetic/pharmacodynamic (PK/PD) profile of basal insulin, and three new products offer this prospect. Insulin degludec, now in clinical use, and PEGylated insulin lispro, in development, have greatly extended action profiles that result from two very different, but unique, mechanisms. With once-daily dosing, these insulins produce stable PK/PD profiles at steady state, associated with a low incidence of hypoglycaemia. The feasibility of varied daily dose timing has also been confirmed with insulin degludec. High strength formulations of insulin glargine and insulin degludec offer the prospect of a reduced injection number/volume in high dose users, and in the case of glargine, the PK/PD profile might also be favourably modified. This review considers critically the clinical evidence and expectations we should have for these new basal insulins.

Methods to enhance delivery of prandial insulin and basal-prandial insulin.

Most physicians are comfortable with initiating basal insulin replacement therapy in their patients with type 2 diabetes who are no longer meeting treatment goals with oral antidiabetic agents. What is more challenging is what to do when treatment goals are no longer being met despite adequate titration of basal insulin. Both fasting plasma glucose and postprandial glucose contribute to hemoglobin A1C levels. Addressing postprandial glucose levels can be accomplished by several approaches. Traditionally this has meant moving to basal bolus insulin, which is considered the gold standard. Premixed insulin may also be used. Data is also emerging for basal "plus" strategies, that is, incremental addition of prandial insulin injections. Newer approaches also reviewed in this article included premixed formulations containing ultra-long acting basal insulin with rapid-acting insulin analogs, inhaled insulin and insulin jet injectors, as well as the use of incretin-based therapies.

Effect of insulin degludec versus sitagliptin in patients with type 2 diabetes uncontrolled on oral antidiabetic agents.

AIM: The efficacy and safety of insulin degludec (IDeg), a new basal insulin with an ultra-long duration of action, was compared to sitagliptin (Sita) in a 26-week, open-label trial. METHODS: Insulin-naïve subjects with type 2 diabetes [n = 458, age: 56 years, diabetes duration: 7.7 years, glycosylated haemoglobin (HbA1c): 8.9% (74 mmol/mol)] were randomized (1 : 1) to once-daily IDeg or Sita (100 mg orally) as add-on to stable treatment with 1 or 2 oral antidiabetic drugs (OADs). RESULTS: Superiority of IDeg to Sita in improving HbA1c and fasting plasma glucose (FPG) was confirmed [estimated treatment difference (ETD) IDeg-Sita for HbA1c: -0.43%-points [95% confidence interval (CI): -0.61; -0.24, p < 0.0001] and for FPG: -2.17 mmol/l (95% CI: -2.59; -1.74, p < 0.0001)]. HbA1c < 7% (<53 mmol/mol) was achieved by 41% (IDeg) versus 28% (Sita) of patients, estimated odds ratio IDeg/Sita: 1.60 (95% CI: 1.04; 2.47, p = 0.034). There was no statistically significant difference in the rate of nocturnal confirmed hypoglycaemia between IDeg and Sita [0.52 vs. 0.30 episodes/patient-year, estimated rate ratio (ERR): IDeg/Sita: 1.93 (95% CI: 0.90; 4.10, p = 0.09)]. Rates of overall confirmed hypoglycaemia were higher with IDeg than with Sita [3.1 vs. 1.3 episodes/patient-year, ERR IDeg/Sita: 3.81 (95% CI: 2.40; 6.05, p < 0.0001)]. IDeg was associated with a greater change in body weight than Sita [ETD IDeg-Sita: 2.75 kg (95% CI: 1.97; 3.54, p < 0.0001)]. The overall rates of adverse events were low and similar for both groups. CONCLUSIONS: In patients unable to achieve good glycaemic control on OAD(s), treatment intensification with IDeg offers an effective, well-tolerated alternative to the addition of a second or third OAD.

Obesity and type 2 diabetes: which patients are at risk?

An estimated 72.5 million American adults are obese, and the growing US obesity epidemic is responsible for substantial increase in morbidity and mortality, as well as increased health care costs. Obesity results from a combination of personal and societal factors, but is often viewed as a character flaw rather than a medical condition. This leads to stigma and discrimination towards obese individuals and decreases the likelihood of effective intervention. Conditions related to obesity are increasingly common, such as metabolic syndrome, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), all of which indicate high risk for type 2 diabetes (T2DM). This paper reviews the progression from obesity to diabetes, identifying physiological changes that occur along this path as well as opportunities for patient identification and disease prevention. Patients with prediabetes (defined as having IFG, IGT or both) and/or metabolic syndrome require interventions designed to preserve insulin sensitivity and ß-cell function, both of which start to deteriorate prior to T2DM diagnosis. Lifestyle modification, including both healthy eating choices and increased physical activity, is essential for weight management and diabetes prevention. Although sustained weight loss is often considered by patients and physicians as being impossible to achieve, effective interventions do exist. Specifically, the Diabetes Prevention Program (DPP) and programs modelled along its parameters have shown repeated successes, even with long-term maintenance. Recent setbacks in the development of medications for weight loss further stress the importance of lifestyle management. By viewing obesity as a metabolic disorder rather than a personal weakness, we can work with patients to address this increasingly prevalent condition and improve long-term health outcomes.

Liraglutide in oral antidiabetic drug combination therapy.

The glucagon-like peptide-1 (GLP-1) receptor agonist liraglutide is indicated as an add-on to oral antidiabetic drug regimens in subjects with type 2 diabetes. Herein, the results of clinical trials assessing the efficacy, safety and tolerability of liraglutide when used in combination with either one or two oral antidiabetic therapies are summarised, then contrasted with the effects of exenatide and dipeptidyl peptidase (DPP-4) inhibitors. GLP-1 receptor agonists lead to effective glycaemic control when used as combination therapy with either one or two oral antidiabetic agents, and may confer overall benefits in weight loss and blood pressure in some subjects. These agents are well tolerated; the most commonly reported adverse effect is mild-to-moderate gastrointestinal symptoms, which are usually transient. Rates of hypoglycaemia in these trials were low, although higher rates were noted when combined with a sulphonylurea. While further study will be required, GLP-1 receptor agonists may offer important advantages over other diabetic therapies, including DPP-4 inhibitors.

Non-glycaemic effects mediated via GLP-1 receptor agonists and the potential for exploiting these for therapeutic benefit: focus on liraglutide.

The glucagon-like peptide-1 receptor agonists (GLP-1 RAs) liraglutide and exenatide can improve glycaemic control by stimulating insulin release through pancreatic ß-cells in a glucose-dependent manner. GLP-1 receptors are not restricted to the pancreas; therefore, GLP-1 RAs cause additional non-glycaemic effects. Preclinical and clinical trial data suggest a multitude of additional beneficial effects related to GLP-1 RA therapy, including improvements in ß-cell function, systolic blood pressure and body weight. These effects are of a particular advantage to patients with type 2 diabetes, as most are affected by ß-cell dysfunction, obesity and hypertension. Transient gastrointestinal adverse events, such as nausea and diarrhoea, are also common. To improve gastrointestinal tolerability, an incremental dosing approach is used with liraglutide and exenatide twice daily. A potential protective role for GLP-1 RAs in the cardiovascular and central nervous systems has been suggested from animal studies and short-term clinical trials. These effects and other safety aspects of GLP-1 therapy are currently being investigated in ongoing long-term clinical studies.

Weight loss with liraglutide, a once-daily human glucagon-like peptide-1 analogue for type 2 diabetes treatment as monotherapy or added to metformin, is primarily as a result of a reduction in fat tissue.

AIM: The effect on body composition of liraglutide, a once-daily human glucagon-like peptide-1 analogue, as monotherapy or added to metformin was examined in patients with type 2 diabetes (T2D). METHODS: These were randomized, double-blind, parallel-group trials of 26 [Liraglutide Effect and Action in Diabetes-2 (LEAD-2)] and 52 weeks (LEAD-3). Patients with T2D, aged 18-80 years, body mass index (BMI) < or =40 kg/m(2) (LEAD-2), < or =45 kg/m(2) (LEAD-3) and HbA1c 7.0-11.0% were included. Patients were randomized to liraglutide 1.8, 1.2 or 0.6 mg/day, placebo or glimepiride 4 mg/day, all combined with metformin 1.5-2 g/day in LEAD-2 and to liraglutide 1.8, 1.2 or glimepiride 8 mg/day in LEAD-3. LEAD-2/3: total lean body tissue, fat tissue and fat percentage were measured. LEAD-2: adipose tissue area and hepatic steatosis were assessed. RESULTS: LEAD-2: fat percentage with liraglutide 1.2 and 1.8 mg/metformin was significantly reduced vs. glimepiride/metformin (p < 0.05) but not vs. placebo. Visceral and subcutaneous adipose tissue areas were reduced from baseline in all liraglutide/metformin arms. Except with liraglutide 0.6 mg/metformin, reductions were significantly different vs. changes seen with glimepiride (p < 0.05) but not with placebo. Liver-to-spleen attenuation ratio increased with liraglutide 1.8 mg/metformin possibly indicating reduced hepatic steatosis. LEAD-3: reductions in fat mass and fat percentage with liraglutide monotherapy were significantly different vs. increases with glimepiride (p < 0.01). CONCLUSION: Liraglutide (monotherapy or added to metformin) significantly reduced fat mass and fat percentage vs. glimepiride in patients with T2D.

Effects of vildagliptin on glucose control in patients with type 2 diabetes inadequately controlled with a sulphonylurea.

AIM: To compare the efficacy and tolerability of vildagliptin vs. placebo in patients with type 2 diabetes mellitus (T2DM) who are inadequately controlled [haemoglobin A(1c) (HbA(1c)) 7.5 to 11%] with prior sulphonylurea (SU) monotherapy. METHODS: This 24-week, multicentre, randomized, double-blind, placebo-controlled study assessed the effects of the dipeptidyl peptidase-4 inhibitor vildagliptin (50 mg given once or twice daily) vs. placebo added to glimepiride (4 mg once daily) in 515 patients with T2DM. Adjusted mean changes from baseline to end-point (AMDelta) in HbA(1c), fasting plasma glucose, fasting lipids and body weight were compared by analysis of covariance. RESULTS: The between-group difference (vildagliptin - placebo) in AMDelta HbA(1c) was -0.6 +/- 0.1% in patients receiving vildagliptin 50 mg daily and -0.7 +/- 0.1% in those receiving 100 mg daily (p < 0.001 vs. placebo for both). Greater efficacy was seen in patients > or =65 years of age (-0.7 +/- 0.1% and -0.8 +/- 0.2% for 50 and 100 mg daily respectively) and in patients with baseline HbA(1c) > 9% (Delta = -1.0 +/- 0.2% and -0.9 +/- 0.2% for 50 and 100 mg daily respectively). Relative to placebo, patients receiving vildagliptin also had improvements in beta-cell function and postprandial glucose, with small changes in fasting lipids and body weight. The incidences of adverse events (AEs) (67.1, 66.3 and 64.2%) and serious AEs (2.9, 2.4 and 5.1%) were similar in patients receiving 50 mg vildagliptin, 100 mg vildagliptin or placebo respectively. The incidence of hypoglycaemic events was low but slightly higher in the group receiving vildagliptin 100 mg (3.6%) than in the group receiving vildagliptin 50 mg (1.2%) or placebo (0.6%). CONCLUSIONS: In patients with T2DM inadequately controlled with prior SU monotherapy, addition of vildagliptin (50 or 100 mg daily) to glimepiride (4 mg once daily) improves glycaemic control and is well tolerated. Addition of vildagliptin 50 mg daily to SU monotherapy may be a particularly attractive therapy in elderly patients.

The impact of streptozotocin-induced diabetes mellitus on cyclic nucleotide regulation of skeletal muscle amino acid metabolism in the rat.

The impact of diabetes on cyclic nucleotide-associated mechanisms regulating skeletal muscle protein and amino acid metabolism was assessed using epitrochlaris preparations from streptozotocin-induced diabetic rats. 1 nM epinephrine inhibited alanine and glutamine release from control preparations, but no inhibition was observed from diabetic preparations with <0.1 mM. 10 nM epinephrine stimulated lactate production from control muscle but stimulation in diabetic preparations was observed only at 0.1 mM. Serotonin inhibited amino acid release and stimulated lactate production equally in control and diabetic muscle. 0.1 mM epinephrine increased cyclic (c)AMP levels by 360% in control muscles, but these levels were increased only 83% in diabetic muscle. Basal-, fluoride-, and serotonin-stimulated adenylyl cyclase activities were equal in membrane preparations of diabetic and control muscle, but epinephrine-stimulated adenylyl cyclase was reduced by 60% in diabetic muscle. Carbamylcholine stimulation of alanine and glutamine release was blunted in diabetic preparations. Carbamylcholine increased cGMP levels in control but not in diabetic muscle. In diabetic muscle, guanylyl cyclase activity was 65% of control and the stimulation of cyclase activity by sodium azide was less in diabetic than control preparations. Added cGMP stimulated alanine and glutamine release from control, but not from diabetic muscle. These data suggest a loss of adrenergic and cholinergic responsiveness in diabetic muscle. Because amino acid release also showed a decreased responsiveness to added cAMP and cGMP, the presence of other derangements in the mechanism(s) of cyclic nucleotide regulation of muscle amino acid metabolism also seems likely.

The regulation of skeletal muscle alanine and glutamine formation and release in experimental chronic uremia in the rat: subsensitivity of adenylate cyclase and amino acid release to epinephrine and serotonin.

The mechanism of the increased alanine and glutamine formation and release from skeletal muscle in experimental uremia was investigated using epitrochlearis preparations from control and chronically uremic rats. In uremic muscle, insensitivity to epinephrine or serotonin suppression of alanine and glutamine release was observed. With control muscles, 1 nm or greater, epinephrine inhibited alanine and glutamine release, whereas with uremic muscles, epinephrine concentrations <1 muM did not alter amino acid release. Decreased alanine and glutamine release with 1 nM serotonin was observed in control muscles, but no inhibition was observed with concentrations <1 muM in uremic muscle. Muscle amino acid levels were the same in control and uremic muscles in the presence or absence of epinephrine or serotonin. The reutilization of released alanine by protein synthesis or oxidation to CO(2) was not differentially affected by epinephrine in uremic muscles as compared with control muscle. Dibutyryl-cAMP inhibited amino acid release equally in uremic and control muscles. Epinephrine or serotonin increased cAMP levels two- to four-fold or more in control than in uremic muscle. Basal- and fluoride-stimulated adenylate cyclase activities were equal in uremic and control muscle homogenates and in membrane fractions, but 10 muM epinephrine-stimulated adenylate cyclase was reduced 30-60% with uremia. At any concentration of epinephrine (0.001-100 muM), the stimulation of membrane adenylate cyclase activity was one- to twofold greater with control membranes than with uremic muscle membranes. With either control or uremic muscle, peak adenylate cyclase activity was observed at 1 muM epinephrine. These data indicate that skeletal muscle in chronic uremia acquires an insensitivity to the metabolic action of epinephrine or serotonin. This insensitivity may be attributable in part to the diminished increments in muscle cAMP levels produced by adrenergic and serotonergic agonists. The decreased cAMP levels may derive in turn from a decreased activity or subsensitization of the agonist-stimulated adenylate cyclase in uremic muscle.

Effects of parathyroid hormone on skeletal muscle protein and amino acid metabolism in the rat.

Because prominent skeletal muscle dysfunction and muscle wasting are seen in both chronic uremia and in primary hyperparathyroidism, and because markedly elevated parathyroid hormone levels occur in both disorders, potential effects of parathyroid hormone on skeletal muscle protein, amino acid, and cyclic nucleotide metabolism were studied in vitro using isolated intact rat epitrochlearis skeletal muscle preparations. Intact bovine parathyroid hormone and the synthetic 1-34 fragment of this hormone stimulated the release of alanine and glutamine from muscle of control but not from chronically uremic animals. This stimulation was dependent upon the concentration of parathyroid hormone added: At 10(5) ng/ml parathyroid hormone increased alanine release 84% and glutamine release 75%. Intracellular levels of alanine and glutamine were not altered by parathyroid hormone. Increasing concentrations of the 1-34 polypeptide decreased [(3)H]leucine incorporation into protein of muscles from both control and uremic animals. Using muscles from animals given a pulse-chase label of [guanido-(14)C]arginine in vivo, parathyroid hormone increased the rate of loss of (14)C label from acid-precipitable protein during incubation and correspondingly increased the rate of appearance of this label in the incubation media. Parathyroid hormone increased muscle cAMP levels by 140% and cGMP levels by 185%, but had no effect on skeletal muscle cyclic nucleotide phosphodiesterase activities as assayed in vitro. Adenylyl cyclase activity in membrane preparations from control but not uremic rats was stimulated by parathyroid hormone in a concentration-dependent fashion. However, no stimulation of guanylyl cyclase activity was noted by parathyroid hormone, although stimulation by sodium azide was present. Incubation of muscles with added parathyroid hormone produced a diminished responsiveness towards epinephrine or serotonin regulation of amino acid release and cAMP formation in the presence compared to the absence of parathyroid hormone. In the absence of parathyroid hormone, detectable inhibition of alanine and glutamine release was produced by 10(-9) M epinephrine, whereas in the presence of parathyroid hormone (1,000 ng/ml) inhibition of alanine and glutamine release required 10(-6) M or greater epinephrine. Resistance to cyclic AMP action as well as inhibition of cyclic AMP formation by parathyroid hormone was found. Preincubation of rat sarcolemma with 1-34 parathyroid hormone produced a decreased activity of the isoproterenol-stimulable adenylyl cyclase activity but there was no apparent change in the concentration of isoproterenol required for one-half maximal and maximal stimulation of the enzyme. These findings suggest that high levels of parathyroid hormone have direct effects on skeletal muscle protein, amino acid, and cyclic nucleotide metabolism in muscle of normal but not uremic animals. Treatment with these high levels of parathyroid hormone in vitro appears to reproduce in normal muscle, the metabolic deficits and loss of hormone responsiveness observed in muscle of chronically uremic animals. It is therefore possible that direct effects of parathyroid hormone on skeletal muscle may account in part for the muscle dysfunction and wasting of primary hyperparathyroidism and chronic uremia.

Skeletal muscle protein and amino acid metabolism in experimental chronic uremia in the rat: accelerated alanine and glutamine formation and release.

The kinetics and factors regulating alanine and glutamine formation and release were investigated in skeletal muscle preparations from control and experimentally uremic rats. These preparations maintained phosphocreatine and ATP levels in vitro which closely approximated levels found in vivo. Alanine and glutamine release from uremic muscle were increased 45.8 and 36.0%, respectively, but tissue levels were unaltered. The increased release of alanine by uremic muscle was not accounted for by decreased rates of medium alanine reutilization via oxidation to CO(2) or incorporation into muscle protein. The maximal capacity of added amino acids such as aspartate, cysteine, leucine, and valine to stimulate net alanine and glutamine formation was the same in uremic and control muscle. Epitrochlearis preparations were partially labeled in vivo with [guanido-(14)C]-arginine. On incubation, preparations from uremic animals showed a 54.6% increase in the rate of loss of (14)C-label in acid precipitable protein. Correspondingly, these same uremic preparations showed a 62.7% increase in (14)C-label appearance in the acid-soluble fraction of muscle and in the incubation media. Insulin decreased alanine and glutamine release to an extent threefold greater in uremic than in control preparations, and increased muscle glucose uptake approximately threefold in all preparations. Although basal rates of [4,5-(3)H]leucine incorporation into protein were decreased 25% in uremic muscles as compared with control muscles, insulin stimulated [(3)H]leucine incorporation nearly equally in both preparations. These data demonstrate increased alanine and glutamine production and release from skeletal muscle of chronically uremic rats. This increase appears to derive in part from an enhancement of net protein degradation which could be caused by an acceleration in the breakdown of one or more groups of muscle proteins, or by an inhibition of protein synthesis, or by both processes. The increased alanine and glutamine formation and release in uremia appears not to result from an insensitivity to insulin action. The implications of these findings for an understanding of the abnormal carbohydrate metabolism of uremia are discussed.

Abnormal carbohydrate metabolism in chronic renal failure. The potential role of accelerated glucose production, increased gluconeogenesis, and impaired glucose disposal.

To delineate the potential role of disordered glucose and glucose-precursor kinetics in the abnormal carbohydrate metabolism of chronic renal failure, alanine and glucose production and utilization and gluconeogenesis from alanine were studied in patients with chronic compensated renal insufficiency and in normal volunteers. With simultaneous primed injection-continuous infusions of radiolabeled alanine and glucose, rates of metabolite turnover and precursor-product interrelationships were calculated from the plateau portion of the appropriate specific activity curves. All subjects were studied in the postabsorption state. In 13 patients with chronic renal failure (creatinine = 10.7+/-1.2 mg/100 ml; mean+/-SEM), glucose turnover was found to be 1,035+/-99.3 mumol/min. This rate was increased 56% (P = 0.003) over that observed in control subjects (664+/-33.5 mumol/min). Alanine turnover was 474+/-96.0 mumol/min in azotemic patients. This rate was 191% greater (P = 0.007) than the rate determined in control subjects (163+/-19.4 mumol/min). Gluconeogenesis from alanine and the percent of glucose production contributed by gluconeogenesis from alanine were increased in patients with chronic renal failure (192% and 169%, respectively) as compared to controls (P < 0.05 for each). Alanine utilization for gluconeogenesis was increased from 40.2+/-3.86 mumol/min in control subjects to 143+/-39.0 mumol/min in azotemic patients (P < 0.05). The percent of alanine utilization accounted for by gluconeogenesis was not altered in chronic renal insufficiency. In nondiabetic azotemic subjects, mean fasting glucose and immunoreactive insulin levels were increased 24.3% (P = 0.005) and 130% (P = 0.046), respectively.These results in patients with chronic renal failure demonstrate (a) increased glucose production and utilization, (b) increased gluconeogenesis from alanine, (c) increased alanine production and utilization, and (d) a relative impairment to glucose disposal. We conclude that chronic azotemia is characterized by increased rates of glucose and glucose precursor flux and by a relative impairment to glucose disposal. These findings may suggest an underlying hepatic and peripheral insensitivity to the metabolic action of insulin in patients with chronic renal insufficiency.

Hepatic ketogenesis and gluconeogenesis in humans.

Splanchnic arterio-hepatic venous differences for a variety of substrates associated with carbohydrate and lipid metabolism were determined simultaneously with hepatic blood flow in five patients after 3 days of starvation. Despite the relative predominance of circulating beta-hydroxybutyrate, the splanchnic productions of both beta-hydroxybutyrate and acetoacetate were approximately equal, totaling 115 g/24 h. This rate of hepatic ketogenesis was as great as that noted previously after 5-6 wk of starvation. Since the degree of hyperketonemia was about threefold greater after 5-6 wk of starvation, it seems likely that the rate of ketone-body removal by peripheral tissues is as important in the development of the increased ketone-body concentrations observed after prolonged starvation as increased hepatic ketone-body production rate. Splanchnic glucose release in this study was 123 g/24 h, which was less than that noted previously after an overnight fast, but was considerably more than that noted during prolonged starvation. Hepatic gluconeogenesis was estimated to be 99 g/24 h, calculated as the sum of lactate, pyruvate, glycerol, and amino acid uptake. This was greater than that observed either after an overnight fast or after prolonged starvation. In addition, a direct relationship between the processes of hepatic ketogenesis and gluconeogenesis was observed.

Glucagon-stimulable adenylyl cyclase in rat liver. Effects of chronic uremia and intermittent glucagon administration.

The effects of chronic uremia and glucagon administration on glucagon-stimulable adenylyl cyclase in rat liver were assessed by determinations of adenylyl cyclase activities, specific iodoglucagon binding, and the activity of the stimulatory regulatory component of adenylyl cyclase. Glucagon-stimulated adenylyl cyclase was reduced in uremia to 75-80% of control levels (P less than 0.05), in the presence or absence of saturating levels of guanosine triphosphate (GTP) and 5'-guanylylimidodiphosphate [GMP-P(NH)P]. Although these changes were accompanied by a concomitant 20% reduction in sodium fluoride-stimulated activity, basal, GTP-, GMP-P(NH)P-, and manganese-dependent adenylyl cyclase activities were unchanged. Using [125I-Tyr10]monoiodoglucagon as a receptor probe, the number of high affinity glucagon-binding sites was reduced 28% (P less than 0.01) in uremic as compared with control liver membranes. However, the affinity of these binding sites was unaltered. The S49 cyc- -reconstituting activity with respect to both GMP-P(NH)P- and isoproterenol plus GTP-stimulable adenylyl cyclase was unaltered in membranes from uremic as compared with control rats. Intermittent glucagon (80-100 micrograms) injections administered at 8-h intervals to normal rats reproduced all of the above described effects of chronic experimental uremia on the adenylyl cyclase system. It is concluded that changes in the hormone-stimulable adenylyl cyclase complex in uremia and with glucagon treatment result primarily from a decrease in the number of hormone-specific receptor sites in hepatic plasma membranes. Since the changes in liver adenylyl cyclase are qualitatively and quantitatively the same in glucagon-treated and uremic rats, it is suggested that these may be the result of the hyperglucagonemia of uremia. Further, the data reveal an unexpected dissociation between guanine nucleotide and sodium fluoride stimulation of adenylyl cyclase. Possible causes for this dissociation based on the known subunit composition of cyclase coupling proteins are discussed.

Glucagon-stimulable adenylyl cyclase in rat liver. The impact of streptozotocin-induced diabetes mellitus.

Glucagon receptor levels, glucagon-stimulated and other forms of adenylyl cyclase activity, and regulatory component activity of adenylyl cyclase were determined in hepatic plasma membranes of rats administered streptozotocin without and with insulin to produce varying degrees of hyperglycemia. Receptor levels were assayed by direct binding of the specific probe [125I-Tyr10]-iodoglucagon; regulatory component activity was assayed by the capacity to reconstitute stimulatory regulation in deficient membranes from cyc- S49 murine lymphoma cells. In rats given 150 mg streptozotocin, glucagon stimulation of adenylyl cyclase as well as basal, sodium fluoride, 5' guanylylimidodiphosphate [GMP-P(NH)P] and Mn-dependent activities were reduced 50%, glucagon receptor levels but not affinity were reduced 67%, and regulatory component activity was decreased 50%. In addition, alpha 1-adrenergic receptors and 5'-nucleotidase were similarly reduced in diabetes. However, specific ouabain-inhibitable Na+, K+, ATPase activity was not altered by streptozotocin treatment. The streptozotocin-induced changes were noted within 24 h and became maximal by 120 h after its administration. All of these decreases were partially reversed by in vivo insulin treatment. DNA, cytochrome c oxidase, glucose-6-phosphatase, and N-acetyl-beta-glucosaminidase content in hepatic plasma membrane preparations were not substantially different in diabetic as compared with control animals. The data demonstrate that glucagon-mediated regulation of cyclic AMP formation is deranged in insulin deficiency owing to a combined decrease in receptors, derangement of the coupling mechanism intervening between receptor and adenylyl cyclase, and possibly, an altered basal effector system. Some of these changes appear to reflect a "desensitization-like" phenomenon which may or may not be attributable to the hyperglucagonemia of diabetes mellitus. There also appears to be a concurrent generalized decrease in several but not all plasma membrane receptor and enzymatic proteins. This may be the result of a number of processes among which is the accelerated proteolysis of uncontrolled diabetes.

The role of adrenergic mechanisms in the substrate and hormonal response to insulin-induced hypoglycemia in man.

Sequential determinations of glucose outflow and inflow, and rates of gluconeogenesis from alanine, before, during and after insulin-induced hypoglycemia were obtained in relation to alterations in circulating epinephrine, norepinephrine, glucagon, cortisol, and growth hormone in six normal subjects. Insulin decreased the mean (+/-SEM) plasma glucose from 89+/-3 to 39+/-2 mg/dl 25 min after injection, but this decline ceased despite serum insulin levels of 153+/-22 mul/ml. Before insulin, glucose inflow and outflow were constant averaging 125.3+/-7.1 mg/kg per h. 15 min after insulin, mean glucose outflow increased threefold, but then decreased at 25 min, reaching a rate 15% less than the preinsulin rate. Glucose inflow decreased 80% 15 min after insulin, but increased at 25 min, reaching a maximum of twice the basal rate. Gluconeogenesis from alanine decreased 68% 15 min after insulin, but returned to preinsulin rates at 25 min, and remained constant for the next 25 min, after which it increased linearly. A fourfold increase in mean plasma epinephrine was found 20 min after insulin, with maximal levels 50 times basal. Plasma norepinephrine concentrations first increased significantly at 25 min after insulin, whereas significantly increased levels of cortisol and glucagon occurred at 30 min, and growth hormone at 40 min after insulin. Thus, insulin-induced hypoglycemia in man results from both a decrease in glucose production and an increase in glucose utilization. Accelerated glycogenolysis produced much of the initial, posthypoglycemic increment in glucose production. The contribution of glycogenolysis decreased with time, while that of gluconeogenesis from alanine increased. Of the hormones studied, only the increments in plasma catecholamines preceded or coincided with the measured increase in glucose production after hypoglycemia. It therefore seems probable that adrenergic mechanisms play a major role in the initiation of counter-regulatory responses to insulin-induced hypoglycemia in man.