Effect of oral alanine on blood beta-hydroxybutyrate and plasma glucose, insulin, free fatty acids, and growth hormone in normal and diabetic subjects

Blood beta-hydroxybutyrate and plasma free fatty acids, glucose, insulin, and growth hormone responses were measured following oral 1-alanine in doses of 0.5 or 0.1 g/kg. In normal and untreated adult diabetic subjects beta-hydroxybutyrate decreased 59%–84% (high dose) and 34%–47% (low dose). This reduction occurred in two phases, the first corresponding to a rise in plasma insulin (high and low dose) and the second corresponding to a fall in free fatty acids (with high dose only). In long-term insulin-treated diabetics made ketotic by withdrawal of insulin, the first phase was still clearly demonstrable, suggesting that alanine is capable of inhibiting ketosis by some extrainsulin mechanism. In these subjects, alanine produced a rise in free fatty acids as beta-hydroxybutyrate fell. Plasma glucose remained stable in normal and untreated diabetics, but rose significantly in insulin-dependent diabetics. Alanine also produced a delayed release of growth hormone starting at 90 min in normals and insulin-dependent diabetics. This release appeared to correlate with and was likely due to a preceding fall in free fatty acids.     

Effect of somatostatin on blood glucose, plasma growth hormone, insulin, and free fatty acids in normal subjects and acromegalic patients

Synthetic growth-hormone-release inhibitory hormone (GRIH, somatostatin) infused in seven acromegalics significantly lowered plasma growth hormone (GH) and immunoreactive insulin (IRI) levels, did not have any effect on blood glucose, and significantly increased plasma free fatty acids (FFA). Somatostatin, when infused in three normal subjects during an arginine test, inhibited plasma GH and IRI responses. Hypoglycemia-induced GH release was also blocked by somatostatin in two normal subjects thus tested.     

Blood pressure crisis following withdrawal of clonidine (Catapres, Catapresan), with special reference to arterial and urinary catecholamine levels, and suggestions for acute management

In five patients with severe essential hypertension, placebo was substituted after 24 to 48 months of treatment with clonidine and a diuretic. In the present study, four of the patients developed a marked blood pressure rise following withdrawal of clonidine which was rapidly reversed by intravenous administration of propranolol 0.2 mg. per kilogram of body weight and phentolamine 20 to 30 mg. The fifth patient was pretreated with reserpine 2.0 mg. intramuscularly for three days prior to withdrawal of clonidine, and the blood pressure rise which he experienced was far less impressive. All patients experienced similar “withdrawal” symptoms, consisting of headaches, insomnia, restlessness, tremor, and nausea.Catecholamines were determined in arterial blood and urine, before and during the overshoot. They revealed a marked increase, particularly in the urine samples, consistent with the appearance of a hyperadrenergic state.     

Ontogeny of embryonic chicken lung: effects of pituitary gland, corticosterone, and other hormones upon pulmonary growth and synthesis of surfactant phospholipids

The actions of hormones on growth, cellular proliferation, and on synthetic rates of the major surfactant phospholipids, phosphatidylcholine (PC) and disaturated PC (DSPC), were studied in the lung of the chick embryo. Particular emphasis was placed on the effects of hypophysectomy, pituitary transplantation, and treatment with corticosterone (CORT). One study was concerned with hydrocortisone (HYCORT), estrogen (E2), thyroxine (T4), ovine prolactin (oPRL), and insulin. Hypophysectomy interfered with the normal gain in protein, the progressive dehydration of the embryonic lung, and also caused a reduction in the number of pulmonary cells on Days 16 and 18 of incubation. Absence of the pituitary gland diminished pulmonary PC by Day 16. Transplantation of one pituitary gland or exogenous CORT partially restored pulmonary phospholipid and PC (normalized per wet weight) in hypophysectomized (hypox) embryos. Transplantation also restored relative protein content in lungs of hypox individuals. Beyond this, transplantation was generally ineffective in reversing deficits of hypox individuals. All concentrations of CORT administered (30-100-300 micrograms) reduced the rate of pulmonary cell division. The highest dose was toxic as judged by its capacity to cause cellular death. Treatment of intact chicken embryos with CORT or E2 for two days stimulated incorporation of [14C]choline into PC and DSPC (the most surface-active component of PC) in the lungs of Day 17 embryos. CORT, but not E2, stimulated DSPC synthesis when treatment was increased to 3 days. Other hormones tested (T4, oPRL, insulin, and HYCORT) had no effect upon the rate of incorporation of [14C]choline into PC or DSPC. These results indicate that during ontogeny the avian lung becomes sensitive to CORT, and possibly E2, prior to 16 days of incubation. CORT, in particular, acts both to trigger the prehatching stimulation of surfactant phospholipid synthesis, especially the vital DSPC fraction, and to slow the rate of pulmonary cellular division coincident with biochemical differentiation of the surfactant system.     

Regulation of vascular tone,molecular mechanisms

The goal of this survey was to review briefly the molecular mechanisms that regulate vascular smooth muscle function. Components of the machinery involved in the contraction and relaxation of vascular smooth muscle include the following.Contractile proteins. The force generated by vascular smooth muscle is the result of thin (actin) and thick (myosin) filaments being pulled by one another so that the cell tends to shorten. The processes by which this intereaction is regulated are a matter of some debate. However, most observations indicate that the process that initiates contraction is a calcium-dependent phosphorylation of the myosin light chain.Cellular sites for the regulation of myoplasmic calcium concentration. The final event that initiates the contractile process is an increase in the intracellular concentration of ionized calcium. Cellular sites that may contribute to the raising and lowering of ionized calcium include the following: (A) cell membrane, (B) sarcoplasmic reticulum, and (C) mitochondria.Membrane electrical events. The electrical state of the cell membrane influences contractile responses of vascular smooth muscle. Over the physiologic range, an elevation in the membrane potential has a reciprocal influence on muscle excitability. The membrane potential is the sum of the diffusion potentials and the electrogenic pump.Excitation-contraction coupling. The excitatory events of the cell membrane (changes in membrane potential and the generation of action potentials) are coupled to the interaction of the contractile proteins by an increase in myoplasmic ionized calcium.Cyclic nucleotides and calcium. Cyclic AMP and cyclic GMP may link contraction and relaxation to the release and uptake of activator calcium by subcellular organelles. These nucleotides also influence the level of phosphorylation of the myosin light chain.Energy metabolism and hypoxia. The chemical energy source for cellular processes in vascular smooth muscle is ATP. Vascular tone, or maintenance of a contractile force, in this muscle is a relatively efficient process that may reflect a special noncycling link between myosin and actin. Current evidence suggests that hypoxic conditions influence vascular tone by altering the activity of the electrogenic sodium pump.This listing of statements is by no means the final word in molecular mechanisms that govern vascular tone. Indeed, vascular smooth muscle remains to be a constant source of surprises for the interested investigator.     

Insulin, growth hormone, and glucagon in prediabetes mellitus — A review

Insulin, growth hormone, and glucagon responses have been extensively studied in “prediabetic” man by a variety of perturbations. Insulin responses have been reported to be high, normal, or low. Growth hormone levels appear generally to be high. Glucagon levels have received only scant attention, but the available information suggests an enhanced response. It appears that a better definition of the prediabetic state is required in addition to techniques that can adequately quantify both secretion and clearance rates of these hormones.     

Brain tryptophan, plasma free tryptophan and distribution of plasma neutral amino acids.

Although rat brain tryptophan is strikingly elevated following portacaval shunt, plasma total tryptophan is unchanged and plasma free tryptophan is not elevated to the same degree as brain tryptophan. Investigation of the concentrations of the neutral amino acids (phenylalanine, tyrosine, methionine, threonine, leucine, isoleucine, and valine) revealed that their distribution and the sum of their concentrations were altered following portacaval shunt, and that this pattern was similar to that seen in humans with cirrhosis of the liver. It is suggested that both the elevation in plasma free tryptophan and the decrease in the competing neutral amino acids, act together to increase the transport of tryptophan into brain when portal blood is diverted around the liver. The implications of these findings in therapy of hepatic coma is discussed.     

Precursors of plasma triglyceride fatty acids in obesity

The contribution of plasma free fatty acids (FFA) and blood glucose to the production of endogenous plasma triglyceride fatty acid (TGFA) has been studies in 13 post-absorptive human subjets who were selected on the basis of obesity, hypertriglyceridemia or both. Tracer doses of palmitic acid-9,10^?3H were given as priming injections followed by constant infusions for 9 hr to ensure that the ratio of specific activities, VLDL-TGFA/plasma FFA, reached a constant level. Once constant, this ratio provides an estimate of the proprotion of the endogenous TGFA derived from ciruculating FFA. In five lean subjects this ratio was 80%–100%, while in eight obese subjects the range was 22%–64%. Overall there was a highly significant negative correlation between the equilibrated specific activity ratios and the degree of obesity. In six subjects, three lean and three overweight, infusions of ¹⁴C-U-glucose were also given. Glucose carbon was readily incorporated into triglyceride glycorol, but there was minimal incorporation of glucose into TGFA, confirming that lipogenesis is negligible in the postabsorptive state and suggesting that the additional source of fatty acids for plasma TGFA production in the overweight subjects is likely to be stored hepatic triglyceride.     

Suppression of insulin secretion by protein deprivation in obesity.

The effect of low protein diets on insulin levels was studied in 17 obese, nondiabetic hyperinsulinemic subjects. Their mean weight was 271% of ideal weight. Nine patients were fed a weight-maintaining 3700-calorie diet for 14 days; this diet contained 398 g carbohydrate and 170 g protein. The patients were then fed an isocaloric diet containing only 6 g protein and 587 g carbohydrate for 14 more days. Mean basal insulin levels decreased from 50.4 to 34.7 μU/ml. This decrease was accompanied by a significant decrease in mean plasma glucose. In seven patients who were fed the low-protein diet after a 4-day period of total fast, the low-protein diet prevented the recovery of basal insulin levels decreased during fasting. These findings were in contrast to the apparent recovery of basal insulin levels observed when the control rather than the low-protein diet was refed in 4 patients following a fast. The suppression of basal insulin levels by protein deprivation was not correlated with changes in plasma glucose, glucagon, urinary 17-hydroxycorticoids, or body weight. Although urinary 17-hydroxycorticoids and free cortisol decreased significantly on protein-restricted diets, treatment with cortisol did not prevent the effect of protein deprivation on basal insulin and glucose levels. Plasma levels of branched chain amino acids (valine, leucine, and isoleucine) decreased in parallel to insulin levels on the isocaloric low-protein diets. We conclude that protein-restricted diets can decrease basal plasma insulin levels in obesity even in the presence of sufficient calories to maintain weight and high carbohydrate content. Of the factors investigated that may account for this phenomenon, it is unlikely that glucagon, glucose, or cortisol play a direct role. It is possible that protein as well as carbohydrate plays a role in the development of hyperinsulinemia and insulin resistance in obesity.     

Effect of exercise on splanchnic exchange of free fatty acids

Splanchnic exchange of free fatty acids (FFA) was studied in seven healthy male subjects at rest and during bicycle exercise at 700–900 kg-m/min following arterial and hepatic venous catheterization. The arterial-hepatic venous (A-HV) FFA difference correlated significantly with arterial FFA both at rest and during exercise. The regression lines for rest and exercise differed significantly, indicating an increased release of FFA from the extrahepatic splanchnic area during exercise. The A-HV FFA difference did not differ significantly from zero during exercise and correlated negatively to the arterial lactate level. A net release of FFA from the splanchnic area was observed under extreme exercise condition with low FFA levels and arterial lactate above 5 mmole/liter. It is concluded that the net splanchnic FFA uptake is reduced during exercise permitting a redistribution of the body's FFA turnover towards greater FFA utilization by muscle.     

Effect of clofibrate on arginine-stimulated glucagon and insulin secretion in man

Insulin and glucagon have been reported to have opposing effects upon the mechanisms regulating serum triglyceride concentration. Glucagon in excess of insulin will lower serum lipids in man. In the present studies, we have examined the possibility that a change in glucagon and insulin regulation might contribute to the hypolipemic action of the drug clofibrate. Control insulin and glucagon secretion were evaluated in 24 normal subjects by intravenous arginine infusion, which resulted in a prompt rise in both serum immunoreactive insulin and glucagon concentration. During the maximum rise in concentration of these hormones, plasma triglyceride concentration was acutely reduced from basal levels of $\text{104 ± 6}\text{mg}\text{100}\text{ml}$ to $\text{75 ± 5}\text{mg}\text{100}\text{ml}$ (p ≤ 0.001). Following 7 days of clofibrate therapy, basal plasma triglyceride concentration attained a new mean level of $\text{78 ± 5}\text{mg}\text{100}\text{ml}$, while basal insulin and glucagon concentrations remained unchanged. However, arginine infusion now resulted in a reduction of the insulin secretory response to 56% of the preclofibrate studies with an associated normal glucagon secretory response. Serum triglyceride concentration was further reduced during arginine infusion to $\text{46 ± 3}\text{mg}\text{100}\text{ml}$, demonstrating this minimum level as maximum plasma glucagon levels were attained, representing an excess of this hormone relative to the reduced insulin concentration. These observations are consistent with an effect of clofibrate on the hormonal regulation of triglyceride physiology in man. Glucose tolerance was unimpaired by clofibrate therapy in these normal subjects, in spite of an apparent reduction in glucose-stimulated insulin secretion.     

Virilizing syndrome associated with an adrenal cortical adenoma secreting predominantly testosterone.

A 22 year old woman had virilization and mild Cushing's syndrome. Serum testosterone levels were high (3.2 ng/ml), urinary 17-ketosteroid levels slightly elevated (17.5 mg/d) and plasma cortisol at 16:00 hours normal (7.2 μg/dl). Basal level of cortisol secretion was normal but with evidence of autonomy. An abnormal adrenal scan led to an adrenal venogram showing a tumor image in the left adrenal gland. Selective adrenal venous catheterization indicated that the tumor was secreting testosterone and cortisol; left/right adrenal venous values were $\text{53.5}\text{3.7}$ ng/ml for testosterone and $\text{92.8}\text{13.6}$ μg/dl for cortisol. Testosterone levels did not rise with human chorionic gonadotropin (hCG). The basal serum level of Δ₄ androstenedione was at the upper limit of normal and of 17 α-hydroxyprogesterone high. The patient underwent surgical removal of a well circumscribed, 19 g left adrenal adenoma. Values for serum testosterone, DHEA-S and 17β-estradiol (E₂) decreased markedly postoperatively. The in vivo biochemical findings were corroborated in vitro by incubation of tumor tissue slices and nontumorous adrenal cortex. The tumor was capable of secreting testosterone, cortisol, DHEA and E₂, but the capacity was greatest for testosterone, DHEA and E₂. Analysis of tissue homogenates also revealed the presence of testosterone, cortisol, DHEA and E₂. The pattern of steroid production suggests partial 21-hydroxylase deficiency and enhanced 17β-reductase activity.     

Metabolic adaptation with physical training: 14C-acetate incorporation into tissue lipids

Forty-eight rats were fed ad libitum, fasted 24 hr, rested 48 hr, and injected i.p. with 40 μCi of ¹⁴C-acetate/100 g body weight. Twenty-four rats had followed a progressive physical training program for 12 wk and 24 rats acted as their controls. Following this injection, the rats were sequentially sacrificed at 5-, 10-, 15-, and 20-min intervals and total cholesterol (TC), free cholesterol (FC), and triglyceride (TG) specific activity and concentrations were measured from serum, liver, triceps, and heart tissue. Curves relating specific activity to the time point data were fitted by the method of least squares. Comparison of these curves revealed that serum, liver, and triceps TC and FC specific activity were significantly higher in the trained rats. In contrast, corresponding TC and FC concentrations for these three tissues varied. Liver TC level was significantly less for the trained group, probably due to a reduction in the esterified moiety, since liver FC measures were unchanged. Training resulted in significantly lower TC concentrations in the selected tissues studied even though specific activity curves appeared similar for both groups. Our conclusions are that lipid metabolic adaptation; studied in vivo, occurs in tissues with training, but that these adaptations are not uniform across tissues, lipid moieties, or measurement parameters.     

Effects of dibutyryl adenosine 3',5'-monophosphate on hepatic metabolism of free fatty acids.

The effects of dibutyryl cyclic adenosine 3',5'-monophosphate (Bu2cAMP) on metabolism of free fatty acids by perfused livers from normal fed male rats were investigated. In one group of experiments, Bu2cAMP was added to the medium and infused at a constant rate to maintain concentrations of 0, 0.4, 1.0, 4.0, or 10. 0 X 10(-5) M nucleotide in the perfusate plasma, assuming the nucleotide was not metabolized by the liver. Oleic acid was infused as the complex with albumin at the rate of 124.3 mumoles/hr. Uptake of free fatty acid by the liver was identical in all groups. Production of ketone bodies, however, increased, and output of triglyceride decreased with increasing concentration of Bu2cAMP. The nucleotide also stimulated output of glucose. Maximal effects were observed when the concentration of Bu2cAMP was approximately 2-3 X 10(-5) M. The output of very low density lipoproteins, as judged by flotation in the zonal ultracentrifuge, was also diminshed by the nucleotide. In other experiments, 1-14C-oleate was infused (120.8 mumoles/hr) along with 2 X 10(-5) M Bu2cAMP, and the disposition of 14C into CO2, ketone bodies, and esterified lipids was evaluated. Bu2cAMP depressed the proportion of 1-14C-oleate converted to triglyceride and increased the fraction converted to ketone bodies and CO2. Not only was ketogenesis stimulated, but a larger proportion of the ketone bodies was derived from exogenous fatty acid.     

Influence of prostaglandins on plasma glucagon levels in the rat.

The effect of PGE1and PGA1 intravenous infusion (2/mug/min) on plasma glucose and glucagon levels was investigated in normal, sympathectomized and propranolol-treated rats. PGE1 infusion significantly increased glucose and glucagon levels, while PGA1 had no effect. Since the dose of PGE1 used in this study was able to reduce the arterial blood pressure by about 20%, the possibility that PGE1 acted indirectly through a reflex sympathetic overactivity was tested. The increases in plasma glucagon induced by PGE1 occurred also in sympathectomized or in beta-blocked animals. Thus, it was possible to exclude a sympathetic mediation or a direct stimulation of pancreatic beta-receptors as a likely mechanism of PGE1 action.     

Effect of glucagon on amino acid and nitrogen metabolism in fasting man

The infusion of small amounts of glucagon into fasting subjects has been reported to paradoxically decrease urinary urea nitrogen excretion. The mechanism and tissues by which this apparent protein sparing was accomplished was examined in the current study by infusing glucagon ($\text{0.1 mg}\text{24 hr × 4}\text{days}$) into subjects who had fasted for 5–6 wk. It was found that circulating levels of alanine and glutamine declined while urinary urea nitrogen excretion decreased and ammonia nitrogen excretion increased. These findings suggested that hepatic gluconeogenesis had been diminished while renal ammoniagenesis and gluconeogenesis had increased. The further finding of a significant prolongation of the $\text{t}\text{,}\text{1}\text{2}$ of ¹⁴C-lalanine (U) 24 hr after the start of the infusion appeared to substantiate this diminution in hepatic gluconeogenesis. In addition, while serum insulin levels had declined significantly by the end of the infusion, circulating levels of the branched-chain amino acids had increased. It was concluded that the infusion of small amounts of glucagon may have resulted in a diminution of portal glucagon levels, which in turn resulted in a decrease in hepatic gluconeogenesis and, directly or indirectly, a compensatory increase in renal ammoniagenesis and gluconeogenesis. The coincidental decline in alamine and the increase in levels of the branched-chain amino acids suggest that the infused glucagon had affected peripheral amino acid metabolism as well.     

Plasma levels of free polyunsaturated fatty acids in patients with ischemic heart disease

The concentrations of individual free fatty acids in plasma were determined in a group of patients who had suffered a myocardial infarction and in control subjects. The patients had lower concentrations of free octadecatrienoic and arachidonic acids and a higher concentration of eicosatrienoic acid, compared to the controls. The relationships between the concentrations of these fatty acids suggest that both trienoic acids belong to the linoleic acid series of polyunsaturated fatty acids. The changes in the concentrations of polyunsaturated free fatty acids are compatible with a block in the conversion of eicosatrienoic to arachidonic acid in the subjects with clinical atherosclerotic disease. Long-term tolbutamide treatment had no significant effect on the plasma concentrations of free polyunsaturated fatty acids in postinfarction patients.     

Influence of acetylsalicylic acid on plasma glucose, insulin, glucagon, and growth hormone levels following tolbutamide stimulation in man.

The effects of acetylsalicylic acid (ASA), a known inhibitor of prostaglandin (PG) synthesis, on plasma glucose, insulin, glucagon and growth hormone (GH) responses to tolbutamide were examined in ten normal volunteers. Treatment with 3.2 g ASA daily for 3 days caused a significant reduction in basal plasma glucose levels (p less than 0.05); by contrast, basal insulin rose from 23 +/- 2 to 31 +/- 2 microU/ml (p less than 0.01). No significant changes in the basal concentrations of glucagon and GH were found after ASA. Insulin response to tolbutamide was significantly augmented after ASA (p less than 0.01) while GH response to hypoglycemia was reduced (p less than 0.05). The pattern of plasma glucose and glucagon was not significantly modified by the treatment. Since ASA seems to have an action opposite to PGE on insulin and GH secretion, it is possible that the ASA may work through inhibition of PG synthesis.     

Pseudomonas aeruginosa endocarditis in drug addicts

Six intravenous heroin users with P. endocarditis were seen between 1970 and 1972. Five out of six (83 per cent) had tricuspid valvulitis. Fever and a significant murmur were found in all cases, a subacute presentation and splenomegaly were found in 83 per cent, and chest pain with cavitating infiltrates on x-ray was observed in 67 per cent. Three patients died of infection. Three patients survived; one was cured with medical therapy alone, and two required surgical removal of the infected valve as well. The success of surgical ablation of the tricuspid valve in these patients is encouraging, particularly in view of their poor response before surgery to combinations of antibiotics with proved in vitro efficacy. Prior bacteremia with more virulent organisms may be important in the pathogenesis of endocarditis with Pseudomonas.