Effect of buformin on splanchnic carbohydrate and substrate metabolism in healthy man

The effect of buformin (100 mg b.i.d. for 5 days) on carbohydrate metabolism, both splanchnic glucose output (SGO) and net substrate exchange were studied in 6 healthy male volunteers in the basal state and following glucose ingestion (100 g). Control studies without buformin were also performed in 5 men. Splanchnic glucose and substrate exchange was determined by means of the hepatic venous catheter technique. SGO was 154 ± 18 (SEM) mg/min in the postabsorptive state and increased 33.3 ± 2.8 g above the basal level during the 150 min period following glucose ingestion. Buformin administration did not alter basal SGO (157 ± 26 mg/min), nor the splanchnic exchange of pyruvate, alanine, glycerol, OH-butyrate and acetoacetate. Splanchnic lactate balance was altered by buformin and net lactate output occurred. Following glucose ingestion the rise in splanchnic lactate output was increased, whereas no change in SGO ($\text{32.9 ± 3.5 g}\text{150 min}$) and splanchnic exchange of the other substrates was observed. The increase in arterial blood glucose concentration following oral glucose loading was reduced by buformin pretreatment (p < 0.0005). The insulin production rate (basal, 16 ± 2 mU/min; following oral glucose, $\text{13 ± 2 U}\text{150 min}$) as calculated from C-peptide release from the splanchnic area was unchanged by buformin. Except for a marked rise in splanchnic lactate production, buformin did not alter splanchnic carbohydrate metabolism after orally ingested glucose in healthy man. The diminished increase in arterial blood glucose concentration associated with unaltered insulin production suggests that buformin facilitates glucose utilization by peripheral tissues.     

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.     

Fasting metabolism in infants: II. The effect of severe undernutrition and infusion of alanine on glucose production estimated with U-13C-glucose

Gluconeogenesis was estimated in fasting infants by dilution of stable isotopic glucose after completion of glycogen oxidation. The effect of availability of gluconeogenic substrates was compared before and after dietary treatment of severe malnutrition and after infusion of excess alanine. Five infants were each studied in two nutritional states. Total glucose production was measured by constant i.v. infusion of uniformly labeled ¹³C-glucose and determination of the ¹³C content of plasma glucose isolated as gluconic acid. A comparison was made with possible sources of net glucose production calculated from simultaneous determinations of respiratory oxygen consumption and carbon dioxide production and urinary nitrogen excretion. Observed average rates of total fasting glucose production under these conditions were 2.8 mg/kg min (range 1.9–4.1) in the malnourished infants, and 2.7 mg/kg min (range 2.4–3.1) in the recovered infants. Average glucose concentration at the same time was $\text{37 mg}\text{100 ml}$ and $\text{42 mg}\text{100 ml}$, respectively. Oxidation of glycogen could have accounted for 7% of total glucose production in either case. Available glycerol from fat oxidation could have accounted for 18% of glucose production in the malnourished subjects and 22% after recovery. Available gluconeogenic amino acids from protein could have contributed 9% and 21% of total glucose production, respectively. The remaining major source of glucose unaccounted for in both cases is attributed to lactate, pyruvate, and alanine recycled via the Cori cycle with loss of ¹³C. It can be calculated that about 90% of carbon flux through oxaloacetate under these conditions was derived from fatty acids, accounting for the lose of ¹³C.Following measurement of endogenous glucose production, alanine was infused intravenously, 4 mg/kg min, for an additional 3 hr, resulting in a 15-fold increase in plasma alanine. There was an initial increase in glucose concentration, with an estimated initial rate of increase of the glucose pool of approximately 1 mg/kg min due to both increased inflow and decreased outflow, the proportions of which were quite variable in different subjects. Final average increase in glucose concentration was $\text{30 mg}\text{100 ml}$, and both inflow and outflow finally increased approximately 1 mg/kg min. The increase in glucose production was half as great as would have been possible from the increased rate of urea production. There were no significant differences between the malnourished and recovered children. It is concluded that following glycogenolysis the major source of gluconeogenesis in these fasting infants was recycled products of glycolysis. The large decrease in availability of gluconeogenic amino acids associated with severe undernutrition did not result in significantly decreased glucose production or hypoglycemia, because amino acids accounted for a relatively small fraction of total gluconeogenesis. The initial increase in glucose concentration after infusion of alanine was not consistently due to increased gluconeogenesis. The relatively small increase in rate of glucose production after increasing alanine and the similarity between the two groups indicates that the maximum possible rate of gluconeogenesis was not much greater than availability of endogenous substrates.     

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.     

Muscle nitrogen metabolism in chronic hepatic insufficiency.

Whole blood arterio-venous (A-V) differences for ammonia (NH3) and amino acids were determined across the forearm in 14 patients with decompensated alcoholic cirrhosis and hyperammonemia. NH3 was extracted by the forearm in all patients; however, the fractional extraction of NH3 was significantly less in five individuals with gross muscle wasting (13.3% versus 25.3%). There was neither a significant uptake nor release of NH3 in normal control subjects. The arterial concentrations of 12 out of 20 amino acids were strikingly diminished in the patient group. In contrast to normal subjects, in whom the release of alanine exceeds that of glutamine, the A-V difference for glutamine in the patients was threefold greater than that for alanine. The A-V differences for all other amino acids were not significantly different from zero. The results suggest that (1) muscle plays an important role in disposing of NH3 in patients with hepatic insufficiency and (2) a major fraction of NH3 taken up by muscle is released as glutamine.     

Physiologic responses to epinephrine infusion: The basis for a new stress test for coronary artery disease

Since many patients with chest pain cannot exercise adequately, an alternative stress would be useful to evaluate coronary reserve. We studied the physiologic responses to epinephrine to assess its potential. We report on 39 patients with chest pain. Doses from 0.03 to 0.30 μg/kg/min were administered intravenously. Heart rate increased from 72 ± 10 to 86 ± 12 bpm (mean ± SD), systolic blood pressure (BP) from 122 ± 20 to 158 ± 18 mm Hg (increased afterload), and rate-pressure product/100 from 88 ± 21 to 133 ± 18. Rate-corrected pre-ejection period decreased from 141 ± 23 to 92 ± 14 msec and $\text{LVET}\text{PEP}$ ratio from 0.41 ± 0.1 to 0.24 ± 0.05 (increased contractility). Increased afterload and contractility increased myocardial oxygen demand. Simultaneously diastolic time and BP decreased, reducing myocardial blood supply. The endocardial viability ratio fell from 1.27 ± 0.3 to 0.80 ± 0.2. These data suggest that epinephrine infusion would be a useful stress test for coronary disease and are supported by a sensitivity of 87% and specificity of 100% in 23 patients with known coronary anatomy.     

The effect of diabetes and the redox potential on amino acid content and release by isolated rat hemidiaphragms

The free amino acid content of diaphragm muscles of control and diabetic rats was studied 5 days after the injection of streptozotocin. Muscles were prepared for analysis either immediately after sacrifice or following incubation in balanced salt solution containing 5.5 mM glucose, with or without an electron acceptor, 0.02 mM methylene blue. Diaphragms of diabetic rats contained significantly more free taurine, glutamate, and branched chain amino acids than the controls at sacrifice, and significantly less glutamine, serine, asparagine, lysine, arginine, histidine, threonine, citrulline, and carnosine. Alanine decreased in plasma of diabetic rats but not in diaphragms before incubation. Hemidiaphragms of diabetic rats produced less alanine and more glutamate during incubation than controls. After incubation they contained less than half as much alanine and glutamine and twice as much glutamate than the controls, having released approximately 40% less alanine and 25% more glutamate into the medium than the controls. Glutamine release was not significantly different between the two groups. Methylene blue increased the free alanine content in the tissue water as well as alanine release by control and by diabetic muscles; the glutamate content of muscles decreased concomitantly. The effects of methylene blue were greater in the diabetic group. Branched chain amino acid release by diabetic muscles decreased during incubation with methylene blue. Muscles of diabetic rats contained more α-ketoglutarate than the controls after incubation with or without methylene blue. Methylene blue increased the α-ketoglutarate content of muscles and its release into the medium, the effect being greater in diabetics than in controls. Hemidiaphragms from diabetic rats released less pyruvate during incubation than controls, while lactate release by the two groups was not significantly different. Incubation with methylene blue caused a marked increase in pyruvate release by diabetic muscles, and a lesser stimulation in controls; lactate release increased in both groups. After incubation the lactate/pyruvate ratio in muscles was lower in the methylene blue treated group. The in vitro effect of 0.02 mM phenazine methosulfate on alanine production was similar to that of methylene blue. The data is compatible with the hypothesis that the $\text{NADH}\text{NAD}$ ratio may exert a restraining effect on alanine production and release by muscle. The progressive increase in this ratio may play a role in the eventual deceleration of gluconeogenesis during a prolonged fast and may restrain this process in uncompensated diabetes.     

Evidence for a physiologic role of pancreatic glucagon in human glucose homeostasis: Studies with somatostatin

To study the role of glucagon in human glucose homeostasis, experimental glucagon deficiency was produced by infusing somatostatin (i.v. 250 μg bolus, followed by infusion of 500 μg/hr) in six normal subjects and in two hypophysectomized patients—an insulin-dependent diabetic and a nondiabetic. In normal subjects, somatostatin lowered plasma glucagon from a mean (± SE) basal level of 85 ± 15 to 33 ± 10 pg/ml, p < 0.001. Concurrently, plasma glucose fell from $\text{90 ± 2 to 73 ± 3 mg}\text{100 ml}$, p < 0.001. Serum insulin and growth hormone fell slightly during somatostatin infusion, while plasma free fatty acids rose. In both hypophysectomized patients, somatostatin lowered plasma glucagon and glucose levels. In all subjects, after stopping somatostatin infusions, plasma glucagon and glucose returned promptly to control values, while serum growth hormone did not change. In additional in vitro studies, somatostatin (1 μg/ml) had no effect on muscle glucose uptake. Since it is known that somatostatin has no direct effect on hepatic glucose production, these results suggest that the fall in plasma glucose during somatostatin infusion resulted from inhibition of glucagon secretion, thus providing evidence that this hormone plays a physiologic role in the maintenance of fasting euglycemia in man.     

Regulation of pool sizes and turnover rates of amino acids in humans: 15N-glycine and 15N-alanine single-dose experiments using gas chromatography—Mass spectrometry analysis

Gas chromatography—mass spectrometry (GCMS) of plasma amino acid derivatives has been used to determine directly the ¹⁵N-enrichment of plasma glycine and alanine in ten volunteers at various metabolic states. Isotope-enrichment time-decay curves of plasma glycine and alanine, following a single intravenous dose of ¹⁵N-glycine or ¹⁵N-L-alanine were obtained and provide an estimate of the extracellular compartment. Relatively narrow ranges were obtained for the glycine pool ($\text{7.7–11.8 μ}\text{mole}\text{100 g}\text{body wt}$), rate constants of transport (3.7–4.2 hr^?1) and flux ($\text{28–43 μ}\text{mole hr}{}^{\mathrm{?1}}\text{100 g}\text{body wt}$) in the postabsorptive state. In postprandial humans, pool sizes showed only a modest variation whereas the rate constants of transport of glycine and alanine were significantly lower. The plasma ¹⁵N-glycine and ¹⁵N-alanine isotope-enrichment time-decay curves over the first hour following a single i.v. dose of ¹⁵N-amino acid represent mostly the hepatic uptake of glycine and alanine from the extracellular pool. The results presented in this study establish the stable isotope GCMS method as a more accurate, more convenient, and safe alternative to the use of radioactive labeled amino acids in studies of amino acid metabolism in human subjects.     

Splanchnic, renal, and muscle clearance of alanylglutamine in man and organ fluxes of alanine and glutamine when infused in free and peptide forms

The present study was designed to investigate organ metabolism of intravenously (IV) infused (100 mumol.h-1.kg-1) alanylglutamine and its amino acid constituents in a group of healthy subjects. The dipeptide clearance (mumol/min) by kidney (51 +/- 3) was significantly (P less than .01) greater than the clearance by either splanchnic organs (19 +/- 6) or skeletal muscle (21 +/- 8). Infusion of alanylglutamine significantly (P less than .01) increased arterial plasma concentrations of free alanine (260 +/- 31 v 330 +/- 38 mumol/L) and free glutamine (620 +/- 66 v 764 +/- 65 mumol/L) when compared with the baseline period. Concurrently, splanchnic uptake of alanine and glutamine increased and muscle release of alanine ceased. However, muscle release of glutamine remained unaffected. Renal balances of alanine and glutamine changed from neutral to negative (net release) and from positive (net uptake) to neutral, respectively. Infusion of a corresponding mixture of alanine and glutamine had similar effects on arterial plasma concentrations and splanchnic and muscle balances of alanine and glutamine, but had no effect on renal balances of these amino acids. From these studies in man, we conclude that kidney predominates over other organs in clearance of alanylglutamine from plasma and that this may account for the different effect of infusion of alanine and glutamine in free and peptide forms on renal fluxes of these amino acids.     

Abnormal prolactin responsivity to dopaminergic suppression in hyperprolactinemic patients

Previous in vivo studies have shown that the constant infusion of dopamine suppresses prolactin (PRL) levels to within the normal range in a variety of hyperprolactinemic states, but there are no data on the relative suppressibility of the lactotroph in patients with hyperprolactinemia or on their metabolism of dopamine. Consequently, six patients with elevated PRL levels received a dopamine infusion of 4 μg/kg/min to study PRL clearance while another eight patients underwent a graded infusion at rates of 0, 1, 2 and 4 μg/kg/min to test PRL suppressibility. In four patients of the latter group an 8 μg/kg/min infusion rate was added. Healthy volunteer control subjects underwent comparable studies. PRL was measured by radioimmunoassay and dopamine by radioenzymatic techniques.The absolute PRL levels at each infusion rate were greater in the patients than in the control subjects. During the 4 μg/kg/min infusion rate, the respective PRL concentrations were 8.2 ± 1.8 and 2.0 ±0.1 ng/ml, (p < 0.001), despite higher dopamine levels in the patients (45.5 ± 6.7 versus 33.5 ± 3.8 ng/ml, p < 0.05). Neither increasing the infusion rate to 8 μg/kg/min nor prolonging the 4 μg/kg/min infusion for 6 hours decreased PRL levels further (9.6 ± 3.3 and 10.8 ± 2.5 ng/ml, respectively). Relative PRL resistance to dopamine in the hyperprolactinemic patients was demonstrated by (1) a significantly more shallow slope of the regression line of PRL versus dopamine concentrations and (2) the concentration of dopamine causing 50 percent PRL suppression (14.7 versus 6.8 ng/ml, p < 0.02). PRL metabolism was not disordered in the patients with elevated PRL levels, since the half-life ($\text{t}\text{1}\text{2}$) of the early phase of PRL clearance during their prolonged 4 μg/kg/min dopamine infusion was similar to that present in the control subjects (58.5 ± 5.9 versus 53.7 ± 9.4 min). Thus, these data demonstrate both an absolute and relative lactotroph refractoriness to dopamine in hyperprolactinemic states and suggest that there remains either a dopamine-resistant cell population, and/or continued PRL release from an enlarged cell mass, despite maximal inhibitory dopamine concentrations.     

Plasma levels of colchicine after oral administration of a single dose

Plasma colchicine levels have been measured serially after the oral administration of 1.0 mg of the drug to ten volunteer subjects. Peak colchicine concentrations averaged $\text{0.323 ± 0.173 μ}\text{g}\text{100}\text{ml}$. Two populations were evident within the group, one with highest concentrations $\text{1}\text{2}\text{hr}$ after administration, and a second with highest concentrations 2 hr after administration of colchicine by mouth.     

Effect of intraarterial infusion of the ketoanalogue of leucine on amino acid release by forearm muscle

α-Ketoanalogues of most essential amino acids can be converted to the corresponding amino acids in man and appear to be useful dietary supplements in protein-intolerant patients. Recently, the branchedchain amino acids, especially leucine, have been found to promote protein synthesis in isolated muscle. The present studies were designed to assess the capacity of skeletal muscle to aminate the keto-analogue of leucine and determine if the metabolism of the ketoacid promotes protein synthesis. Six normal postabsorptive males received a 30-min brachial intraarterial infusion of ketoleucine (34.4 μmoles/min). Changes in ipsilateral muscle balance were estimated from whole blood concentrations and flow for 1 hr. Brachial arterial blood ketoleucine concentration increased by an average of 1.02 mM. In a single passage across forearm muscle, 52% of the ketoacid was extracted. Leucine was the only amino acid released in increased amounts, accounting for 31% of ketoleucine extracted. The remainder was apparently oxidized. No one donor capable of supplying all the nitrogen needed for leucine production could be identified, but significant reductions in the release of alanine, glycine, and histidine, and changes from release to uptake of valine and isoleucine, suggest possible contributions from these amino acids. Glutamine-asparagine release did not change. Lysine, tyrosine, and phenylalanine balances were also unchanged, suggesting no anabolic effect of ketoleucine on muscle protein under these conditions. The results demonstrate rapid transamination and utilization of ketoleucine by skeletal muscle in postabsorptive man.     

Protective effects of regulatory amino acids on ischaemia-reperfusion injury in the isolated perfused rat liver

Objective. Some amino acids (AAs) display potent regulatory activities on cell metabolism, including via anti-oxidative defences. The aim of this study was to evaluate the protective effect of these AAs on warm ischaemia-reperfusion (I/R) injury in the isolated perfused rat liver.

Material and methods. Livers from fasted male Sprague-Dawley rats were isolated and perfused without (control group) or with (AP group) a mixture of regulatory AAs (glutamine, histidine, leucine, methionine, proline, phenylalanine, tryptophan and alanine). After 45 min of perfusion, warm ischaemia was induced for 45 min by clamping the portal vein catheter; thereafter, reperfusion was performed for 30 min.

Results. TNF-α production was significantly lower in the AP group during reperfusion (Control: 39±7 versus AP: 16±2 pg min^?1 g^?1, p<0.05), and lactate dehydrogenase (LDH) release decreased significantly during the last 15 min of reperfusion (Control: 0.13±0.03 versus AP: 0.04±0.02 IU min^?1 g^?1, p<0.05), despite similar levels of oxidative stress. The addition of regulatory AAs was not associated with variations in portal flow, bile flow, hepatic glucose or urea metabolism. However, significant changes in intrahepatic glutamine (Control: 1.4±0.2 versus AP: 2.6±0.5 µmol g^?1, p<0.05) together with higher glutamate release in the AP group (Control: 10.2±5.4 versus AP: 42.6±10.9 nmol min^?1 g^?1, p<0.05) indicated modifications in nitrogen metabolism.

Conclusions. Taken together, the lower TNF-α production, suggesting decreased inflammatory response, the decrease in LDH release in the AP group, demonstrating a better preservation of liver viability, and the increase in hepatic glutamine indicate that AAs play an important role in the liver's response to I/R.     

Relationship of serum gastrin to parathyroid hormone secretion in sheep

The influence of hypergastrinemia on secretion of parathyroid hormone (PTH) was studied in sheep. Synthetic human gastrin I, 4–9 μg/kg/hr, was infused for 1 hr into fasted, unanesthetized sheep. Blood was obtained at 15-min intervals before, during, and after infusion of gastrin from an indwelling arterial catheter. Blood pH, serum total calcium and circulating gastrin and PTH (radioimmunoassay) were determined. Despite the fact that gastrin infusion resulted in marked hypergastrinemia and in a small but statistically significant decrease in total serum calcium concentration (mean change in serum calcium $\text{0.28}\text{mg}\text{100}\text{ml}$), P < 0.005), PTH concentrations after gastrin infusions (34 ± 5 μl-eq/ml) did not change from basal (35 ± 6 μl-eq/ml). These studies do not substantiate the suggestion that acute hypergastrinemia, directly or indirectly, results in the release of PTH.     

Effect of hyperammonemia on leucine and protein metabolism in rats

The cause of muscle wasting and decreased plasma levels of branched chain amino acids (BCAA), valine, leucine, and isoleucine in liver cirrhosis is obscure. Here we have evaluated the effect of hyperammonemia. Rats were infused with either an ammonium acetate/bicarbonate mixture, a sodium acetate/bicarbonate mixture, or saline for 320 minutes. The parameters of leucine and protein metabolism were evaluated in the whole body and in several tissues using a primed constant intravenous infusion of L-[1-14C]leucine. Ammonium infusion caused an increase in ammonia and glutamine levels in plasma, a decrease in BCAA and alanine in plasma and skeletal muscle, a significant decrease in whole-body proteolysis and protein synthesis, and an increase in leucine oxidized fraction. A significant decrease in protein synthesis after ammonium infusion was observed in skeletal muscle while a nonsignificant effect was observed in liver, gut, heart, spleen, and kidneys. We conclude that the decrease in plasma BCAA after ammonia infusion is associated with decreased proteolysis and increased leucine oxidized fraction.     

Number and size of myocytes and amount of interstitial space in the ventricular septum and in the left ventricular free wall in hypertrophic cardiomyopathy

The wall thickness of the myocardium depends on 3 variables: the number of muscle layers, the mean size of myocytes and the percent area of interstitial space. To clarify the pathogenesis of asymmetric septal hypertrophy (ASH) in hypertrophic cardiomyopathy (HC), these 3 variables and wall thickness were measured in the ventricular septum (VS) and in the left ventricular (LV) posterior wall. The $\text{VS}\text{LV}$ ratio of wall thickness was correlated with the $\text{VS}\text{LV}$ ratios of the 3 variables in the hearts of 10 patients in HC with ASH and in 37 control patients without ASH (25 with no cardiac disease and 12 with systemic hypertension). The $\text{VS}\text{LV}$ ratios (mean ± standard deviation) in hearts with HC were 1.6 ± 0.2 for wall thickness, 1.8 ± 0.3 for the number of transmural muscle layers, 0.9 ± 0.1 for mean size of myocytes and 1.1 ± 0.1 for percent area of transmural interstitial space. The $\text{VS}\text{LV}$ ratios in control hearts were 1.0 ± 0.1 for wall thickness, 1.0 ± 0.1 for number of transmural muscle layers, 1.0 ± 0.1 for mean size of myocytes and 1.0 ± 0.1 for percent area of interstitial space. The $\text{VS}\text{LV}$ ratios of wall thickness and transmural muscle layers correlated well. In hearts with ASH in HC, the number of muscle layers was greater in the VS (630 ± 80) and smaller in the LV free wall (360 ± 70) than in the control hearts (500 ± 60 and 480 ± 50, respectively). Thus, the pathogenetic factor of ASH in HC is an increased $\text{VS}\text{LV}$ ratio of the number of muscle layers, and the degree of ASH is determined by the combined abnormalities in the numbers of transmural muscle layers in the VS and the LV free wall.     

Effect of dichloroacetate on gluconeogenesis in vivo in the presence of a fixed gluconeogenic substrate supply to the liver

Administration of dichloroacetate (DCA) to conscious 48 h fasted dogs causes a reduction in the conversion of circulating alanine and lactate to glucose coincident with both a reduction in the load of alanine and lactate delivered to the liver and a decrease in the plasma insulin-glucagon ($\text{I}\text{G}$) molar ratio. To determine whether DCA inhibits gluconeogenesis independent of its effect on alanine and lactate levels, the drug was infused concurrently with alanine and lactate in order to fix the load of these gluconeogenic precursors reaching the liver. When the circulating levels of alanine and lactate were fixed, DCA increased the net hepatic uptake of alanine markedly (98 ± 26%) but increased lactate uptake only slightly (8 ± 7%). However, the fraction of these gluconeogenic precursors which were converted to ¹⁴C-glucose decreased. Since the net effect of these changes was to increase the overall conversion of alanine and lactate to glucose, it is evident that the increase in precursor uptake overrode the inhibition of the gluconeogenic process per se. This increase in hepatic precursor uptake may have been due to DCA stimulation of pyruvate dehydrogenase activity or the observed decline in the $\text{I}\text{G}$ molar ratio. The observed increase in overall glucose production (33 ± 10%) was probably attributable to the increase in gluconeogenesis as well as an increase in glycogenolysis since 48 h fasted dogs still have some hepatic glycogen (15 mg/gm). By overcoming the peripheral effects of DCA on gluconeogenic precursor supply it becomes evident that DCA has: (1) a direct inhibitory action on intrahepatic gluconeogenesis, and (2) an effect on the pancreas which by virtue of a change in the $\text{I}\text{G}$ molar ratio may offset the direct intrahepatic effect of the drug.     

A comparison of methods of assessment of body composition including neutron activation analysis of total body nitrogen

Fourteen healthy men underwent determinations of total body nitrogen (TBN) by prompt gamma neutron activation analysis and total body potassium (TBK) by whole body counting to estimate the muscle and nonmuscle components of the fat-free body mass (FFBM) and their protein contents. Comparison of FFBM estimated from TBN and TBK (60.6 ± 6.9 kg, mean ± SD), densitometry (62.3 ± 7.1 kg), TBK alone (62.2 ± 8.0 kg), and TBW (63.9 ± 7.8 kg) showed no differences among the techniques. Similarly, there were neither differences in fat mass nor percent body fat among the methods. Analysis of the chemical composition of FFBM of this group showed $\text{TBK}\text{FFBM}\text{= 62.6 ± 2.3 mEq/kg}$, $\text{TBW}\text{FFBM}\text{= 74.6 ± 0.2\%}$, $\text{TBN}\text{FFBM}\text{= 32.74 ± 1.09 g/kg}$, protein/FFBM = 20.5 ± 0.7%. The calculated mineral content of the FFBM was 6.4%. These values are strikingly similar to the values calculated by direct chemical analysis. It was concluded that the combined TBN-TBK method is a valid technique for estimating body composition in man.     

Branched chain amino acids activate messenger ribonucleic acid translation regulatory proteins in human skeletal muscle, and glucocorticoids blunt this action

Branched chain amino acids (BCAA) are particularly effective anabolic agents. Recent in vitro studies suggest that amino acids, particularly leucine, activate a signaling pathway that enhances messenger ribonucleic acid translation and protein synthesis. The physiological relevance of these findings to normal human physiology is uncertain. We examined the effects of BCAA on the phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (eIF4E-BP1) and ribosomal protein S6 kinase (p70(S6K)) in skeletal muscle of seven healthy volunteers. We simultaneously examined whether BCAA affect urinary nitrogen excretion and forearm skeletal muscle protein turnover and whether the catabolic action of glucocorticoids could be mediated in part by inhibition of the action of BCAA on the protein synthetic apparatus. BCAA infusion decreased urinary nitrogen excretion (P < 0.02), whole body phenylalanine flux (P < 0.02), plasma phenylalanine concentration (P < 0.001), and improved forearm phenylalanine balance (P = 0.03). BCAA also increased the phosphorylation of both eIF4E-BP1 (P < 0.02) and p70(S6K) (P < 0.03), consistent with an action to activate the protein synthetic apparatus. Dexamethasone increased plasma phenylalanine concentration (P < 0.001), prevented the BCAA-induced anabolic shift in forearm protein balance, and inhibited their action on the phosphorylation of p70(S6K). We conclude that in human skeletal muscle BCAA act directly as nutrient signals to activate messenger ribonucleic acid translation and potentiate protein synthesis. Glucocorticoids interfere with this action, and that may be part of the mechanism by which they promote net protein catabolism in muscle.