Glucose metabolism in quinine-treated patients with uncomplicated falciparum malaria

Novel natural and synthetic inhibitors of solute carriers SGLT1 and SGLT2

Selective analogs of the natural glycoside phloridzin are marketed drugs that reduce hyperglycemia in diabetes by inhibiting the active sodium glucose cotransporter SGLT2 in the kidneys. In addition, intestinal SGLT1 is now recognized as a target for glycemic control. To expand available type 2 diabetes remedies, we aimed to find novel SGLT1 inhibitors beyond the chemical space of glycosides. We screened a bioactive compound library for SGLT1 inhibitors and tested primary hits and additional structurally similar molecules on SGLT1 and SGLT2 (SGLT1/2). Novel SGLT1/2 inhibitors were discovered in separate chemical clusters of natural and synthetic compounds. These have IC50-values in the 10-100 μmol/L range. The most potent identified novel inhibitors from different chemical clusters are (SGLT1-IC50 Mean ± SD, SGLT2-IC50 Mean ± SD): (+)-pteryxin (12 ± 2 μmol/L, 9 ± 4 μmol/L), (+)-ε-viniferin (58 ± 18 μmol/L, 110 μmol/L), quinidine (62 μmol/L, 56 μmol/L), cloperastine (9 ± 3 μmol/L, 9 ± 7 μmol/L), bepridil (10 ± 5 μmol/L, 14 ± 12 μmol/L), trihexyphenidyl (12 ± 1 μmol/L, 20 ± 13 μmol/L) and bupivacaine (23 ± 14 μmol/L, 43 ± 29 μmol/L). The discovered natural inhibitors may be further investigated as new potential (prophylactic) agents for controlling dietary glucose uptake. The new diverse structure activity data can provide a starting point for the optimization of novel SGLT1/2 inhibitors and support the development of virtual SGLT1/2 inhibitor screening models.

Drug-Induced Endocrine and Metabolic Disorders

Complex interactions exist amongst the various components of the neuroendocrine system in order to maintain homeostasis, energy balance and reproductive function. These components include the hypothalamus-pituitary- adrenal and -gonadal axes, the renin-angiotensin-aldosterone system, the sympathetic nervous system and the pancreatic islets. These hormones, peptides and neurotransmitters act in concert to regulate the functions of many organs, notably the liver, muscles, kidneys, thyroid, bone, adrenal glands, adipocytes, vasculature, intestinal tract and gonads, through many intermediary pathways. Endocrine and metabolic disorders can arise from imbalance amongst numerous hormonal factors. These disturbances may be due to endogenous processes, such as increased secretion of hormones from a tumour, as well as exogenous drug administration. Drugs can cause endocrine abnormalities via different mechanisms, including direct alteration of hormone production, changes in the regulation of the hormonal axis, effects on hormonal transport, binding, and signalling, as well as similar changes to counter-regulatory hormone systems. Furthermore, drugs can affect the evaluation of endocrine parameters by causing interference with diagnostic tests. Common drug-induced endocrine and metabolic disorders include disorders of carbohydrate metabolism, electrolyte and calcium abnormalities, as well as drug-induced thyroid and gonadal disorders. An understanding of the proposed mechanisms of these drug effects and their evaluation and differential diagnosis may allow for more critical interpretation of the clinical observations associated with such disorders, better prediction of drug-induced adverse effects and better choices of and rationales for treatment.

Hypoglycemia in falciparum malaria: is fasting an unrecognized and insufficiently emphasized risk factor?

Hypoglycemia is a frequently encountered complication in falciparum malaria that is usually ascribed to increased glucose use and impaired glucose production caused by the inhibition of gluconeogenesis. Here, in light of recent data showing that glucose production and gluconeogenesis are often increased in falciparum malaria, we review the causes and the risk factors leading to hypoglycemia in malaria. Fasting emerges as an important potential risk factor. Length of fasting should be included in studies on hypoglycemia in malaria. Full recognition of this risk factor for hypoglycemia in malaria could change both advice to the population, especially mothers, and treatment guidelines in the health sector.

Cachexia in malaria and heart failure: therapeutic considerations in clinical practice

Cachexia is an independent prognostic marker of survival in many chronic diseases including heart failure and malaria. Morbidity and mortality from malaria is high in most of the third world where it presents a very challenging public health problem. Malaria may present in the UK as fever in the returning traveller or as fever in overseas visitors. How and why cachexia develops in malaria in a manner similar to the cachexia of chronic heart failure and the treatment strategies that would alter outcomes in both diseases are discussed in this review.

FFAs are not involved in regulation of gluconeogenesis and glycogenolysis in adults with uncomplicated P. falciparum malaria

In normal subjects, elevation of plasma free fatty acid (FFA) levels stimulates gluconeogenesis (GNG) and inhibits glycogenolysis (GLY). In adults with uncomplicated Plasmodium falciparum malaria, GNG is increased and GLY decreased. To test the hypothesis that FFAs are regulators of GNG and GLY in uncomplicated falciparum malaria, we investigated the effect of inhibition of lipolysis by acipimox in 12 patients with uncomplicated falciparum malaria. Six of them were given acipimox, and six served as controls. Also as controls, six matched healthy subjects were studied on two occasions with and without acipimox. After 16 h of fasting, glucose production and GNG were significantly higher in the malaria patients compared with the healthy controls (P = 0.003 and < 0.0001, respectively), whereas GLY was significantly lower (P < 0.001), together with elevated plasma concentrations of cortisol and glucagon. During the study, glucose production in patients declined over time (P < 0.0001), without a statistically significant difference between the acipimox-treated and untreated patients. In controls, however, with acipimox the decline was less outspoken compared with nontreated controls (P = 0.005). GNG was unchanged over time in patients as well as in healthy controls, and no influence of acipimox was found. In patients, GLY declined over time (P < 0.001), without a difference between acipimox-treated and untreated patients. In contrast, in controls treated with acipimox, no change over time was found, which was statistically different from the decline in untreated controls (P = 0.002). In conclusion, in falciparum malaria, FFAs are not involved in regulation of glucose production, nor of GNG or GLY.

Safety evaluation of fixed combination piperaquine plus dihydroartemisinin (Artekin) in Cambodian children and adults with malaria

AIMS

To assess the haemodynamic, electrocardiographic and glycaemic effects of piperaquine-dihydroartemisinin (Artekin) fixed combination therapy in uncomplicated malaria.

METHODS

Sixty-two Cambodians (32 children and 30 adults) with falciparum or vivax malaria were given Artekin given as four age-based oral doses over 32 h. Supine and erect blood pressure, the electrocardiographic QT interval and plasma glucose were measured before treatment and then at regular intervals during a 4-day admission period as part of efficacy and safety monitoring. QT intervals were rate-corrected (QTc) using Bazett's formula.

RESULTS

Artekin therapy was well tolerated and all patients responded to treatment. Average parasite and fever clearance times were 19 and 12 h, respectively. The pretreatment mean fall in systolic blood pressure on standing was 8 +/- 6 mmHg and 6-hourly measurements over 72 h showed no significant change (P = 0.48). There was a significant lengthening of the mean QTc to a maximum of 11 ms(0.5) (95% confidence interval 4-18 ms(0.5)) relative to baseline at 24 h (P = 0.003). The maximal QTc prolongation observed in any patient was 53 ms(0.5). There was a mean 0.4 mmol l(-1) reduction in the post-absorptive plasma glucose during the first 48 h but no episodes of hypoglycaemia (plasma glucose < 3.0 mmol l(-1)) were observed at any time.

CONCLUSIONS

Artekin is safe and effective combination therapy for uncomplicated malaria in children and adults. Although piperaquine is a long half-life drug related to other quinoline compounds including chloroquine and quinine, no clinically significant cardiovascular or metabolic effects were observed.

Non-radioisotopic glucose turnover in children with falciparum malaria and enteric fever

To determine whether glucose turnover is increased in acute falciparum malaria compared to enteric fever in children, steady-state 6,6-D2-glucose turnover was measured in 9 Malaysian children with uncomplicated malaria (6 males and 3 females; median age 10 years, body weight 22 kg) and in 12 with uncomplicated enteric fever (8 males and 4 females; median age 10 years, body weight 24 kg) in acute illness, after quinine (5 malaria patients) and in convalescence. Baseline plasma glucose concentrations in malaria and enteric fever were similar (all values are medians [ranges in brackets]) 5.6 [3.2-11.3] vs. 5.5 [4.2-8.0] mmol/L), as were serum insulin levels (5.6 [0.4-26.5] vs. 6.8 [1.1-22.5] milliunits/L; P > 0.4). Glucose turnover in the malaria patients was higher than in patients with enteric fever (6.27 [2.71-6.87] vs. 5.20 [4.50-6.08] mg/kg.min; P = 0.02) and in convalescence (4.74 [3.35-6.79] mg/kg.min; P = 0.05 vs. acute malaria study), and fell after quinine together with a rise in serum insulin (P = 0.03). Basal plasma lactate concentrations were higher in enteric fever than in malaria (3.4 [1.8-6.4] vs. 0.8 [0.3-3.8] mmol/L; P < 0.0001) and correlated inversely with glucose turnover in this group (rs = -0.60; n = 12; P = 0.02). These data suggest that glucose turnover is 20% greater in malaria than in enteric fever. This might reflect increased non-insulin-mediated glucose uptake in falciparum malaria and/or impaired gluconeogenesis in enteric fever, and may have implications for metabolic complications and their clinical management in both infections.

The biological basis of malarial disease

In this review we summarise the arguments that inflammatory cytokines, triggered by material released from the parasite at schizogony (malarial toxin), might induce the illness and pathology seen in malaria. These pro-inflammatory cytokines can generate inducible nitric oxide synthase and cause nitric oxide to be released, as can low concentrations of malarial toxin itself provided interferon-gamma, which has only low activity in the absence of malarial toxin, is present. We suggest here that recently described hypermetabolic functions of these mediators provide a much more plausible explanation for malarial hyperlactataemia and hypoglycaemia, the chief prognostic indicators in falciparum malaria, than does hypoxia secondary to mechanical blockage of vessels by sequestering parasites, which is the dominant current theory. We also review the arguments that rationalise, through these mediators, the reversibility of the coma of cerebral malaria. Although not yet tested at a cellular level, the proposal that nitric oxide generated in cerebral vascular walls contributes to this coma continues to gather indirect support. In addition, new evidence incriminating nitric oxide in the mechanism of tolerance to endotoxin rationalises the raised nitric oxide generation seen in malarial tolerance.

The relationship between glucose production and plasma glucose concentration in children with falciparum malaria

The pathophysiology of hypoglycaemia in children with acute falciparum malaria, a frequent and serious complication, is unknown due to absence of data on glucose kinetics. We investigated the correlation between basal glucose production and plasma glucose concentration in 20 children (8 girls) with acute, uncomplicated falciparum malaria by infusion of [6,6-2H2]glucose. Median plasma glucose concentration was 4.5 (range 2.1-6.5) mmol/L and the median glucose production 5.0 (range 4.1-8.4) mg/kg/min. There was a positive correlation between basal glucose production and plasma glucose concentration (r = 0.53, P = 0.016). There was no correlation between the rate of glucose production and the plasma concentrations of alanine, lactate, counter-regulatory hormones or cytokines. It was concluded that, in children with acute uncomplicated falciparum malaria, endogenous glucose production is an important determinant of plasma glucose concentration, contrary to previous findings in adults with malaria, in whom peripheral uptake seems to be more important than glucose production in determining plasma glucose concentration.

Reversal of hypoglycaemia in murine malaria by drugs that inhibit insulin secretion

We have investigated the metabolic disturbances in 2 murine models of blood-stage malaria, Plasmodium chabaudi and Plasmodium yoelii. Blood glucose, plasma insulin and parasitaemia were measured in normal and infected mice before and after treatment with diazoxide, adrenaline, Sandostatin and quinine. Severe hypoglycaemia and marked hyperinsulinaemia developed during both infections. A single injection of diazoxide (25 mg/kg i.p.) or adrenaline (0.03 mg s.c.) lowered insulin concentrations in normal mice, reversed the hypoglycaemia in both infections and significantly reduced the hyperinsulinaemia in P. chabaudi-infected mice (P < 0.0001). Higher doses of Sandostatin (500 micrograms/kg s.c.) were required to reverse hypoglycaemia. Quinine (25 mg/kg i.p.) significantly increased blood glucose in normal and infected mice (P < 0.0010 and no hypoglycaemia was observed in mice with normal blood glucose for more than 3 h. This study shows that the major cause of hypoglycaemia in murine malaria is hyperinsulinaemia rather than high consumption of glucose by host and parasites or chemotherapy with quinine, and that hypoglycaemia can be reversed by correcting the hyperinsulinaemia.

The metabolism of platelet-activating factor in severe and cerebral malaria

In order to examine the effects of platelet-activating factor (PAF) in complicated Plasmodium falciparum infections, plasma concentrations of lyso-PAF, stable metabolite and principal precursor of PAF, were measured in 25 Vietnamese adults with severe malaria. The concentration of PAF in the cerebrospinal fluid (CSF) was determined in a sub-group of 23 comatose patients and, together with that of lyso-PAF, in the plasma of 20 patients on recovery of consciousness. The concentration of lyso-PAF in the plasma was depressed on admission to hospital (median [range]; 21 [8-143] vs. 293 [215-410] ng/ml in 10 controls; P < 0.001). There was, however, no change in plasma activity of acetylhydrolase which converts PAF to lyso-PAF (P > 0.01 vs. controls) while simultaneous reduction in the concentration of lipoproteins associated with lyso-PAF were less than those of lyso-PAF per se in the plasma. The plasma concentration of lyso-PAF on admission was associated with parasitaemia and the concentration of serum triglycerides (rs = -0.42, P = 0.04 in each case), the latter being consistent with hepatic effects of PAF reported in previous studies. CSF concentrations of PAF on admission were low (2.3 [0.5-7.7] vs. 0.9 [0-2.5] ng/ml after recovery, P < 0.01) compared with values reported previously in bacterial meningitis. Plasma concentrations of lyso-PAF after recovery lay between admission and control values. While increased availability of PAF may reflect parasite burden and may modulate liver-mediated metabolic disturbances such as hypoglycaemia and lactic acidosis, the role of PAF in cerebral malaria is uncertain.

The effect of plasma free fatty acids and long-chain triglycerides on glucose metabolism in uncomplicated falciparum malaria

To investigate the therapeutic potential of increased plasma free fatty acid (FFA) and triglyceride concentrations in hypoglycaemic patients receiving quinine, 32 untreated Thai adults with uncomplicated falciparum malaria were allocated at random to one of 4 regimens: 2 mg/kg/min dextrose infused over 60 min either alone (group A) or with a prior injection of 5000 units of heparin and simultaneous Intralipid infusion (group C), or 4 min/kg/min dextrose alone (group B) or with heparin and Intralipid (group D). Quinine (10 mg/kg) was also infused over 60 min in all cases. In patients of groups A and C, mean changes in plasma glucose concentrations from the beginning to the end of the infusion were 0.1 (SD 0.8) and 1.0 (SD 0.7) mmol/L respectively (P = 0.015). In groups B and D, plasma glucose increased by 1.8 (SD 1.2) and 2.2 (SD 0.4) mmol/L respectively (P < 0.5). Plasma FFA levels fell by approximately 50% during the infusion in groups A and B but increased by a similar percentage in groups C and D. Despite significant mean increases in plasma insulin during the infusion (from 12.2 milliunits (mu)/L in group A to 38.8 mu/L in group D), no rebound hypoglycaemia was observed in any patient during the ensuing 7 h. These data suggest that the glycaemic response to dextrose given at high rates, which match average glucose utilization in a severely ill patient with malaria, is not augmented by increased plasma FFA and long-chain triglycerides. However, this strategy increases the glycaemic efficacy of lower dextrose infusion rates and the combination could, therefore, reduce the volumes of hypertonic dextrose required to prevent hypoglycaemia in severely ill patients in whom optimal fluid balance is crucial.

The pharmacokinetics and pharmacodynamics of quinine in the diabetic and non-diabetic elderly

1. Quinine is a front-line antimalarial drug but is prescribed most commonly in nonmalarious countries for cramps. Postural hypotension, hearing loss and hyperinsulinaemic hypoglycaemia occur in malaria and overdose but little is known of quinine kinetics and toxicity in the elderly. 2. We studied 12 non-insulin-dependent diabetics and 10 non-diabetic controls aged 51-79 years. Subjects attended on two occasions > 7 days apart. On each test day, subjects were given a 600 Cal meal at 18.00 h (0 h) and, on one occasion, quinine sulphate 600 mg at 22.00 h (4 h). Venous blood samples for glucose, insulin and quinine assay were drawn pre-prandially and then regularly over the next 38 h. Supine and erect blood pressures were taken and audiometry was performed at 4, 6, 8 and 14 h. A one-compartment open pharmacokinetic model was fitted to serum quinine concentrations. 3. Absorption and elimination half-times, volume of distribution and oral clearance of quinine were comparable in the two groups (P > 0.2) and there was a mean absorption lag-time of approximately 1 h. Basal and immediate post-prandial (< 4 h) serum glucose and insulin concentrations on both test days were similar in the diabetics and also in the non-diabetics, but quinine produced a mean reduction in serum glucose of 1.0 mmol l-1 from 3-5 h post-dose in both groups without affecting serum insulin concentrations. Quinine administration did not alter postural blood pressure changes or produce significant hearing loss in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Dichloroacetate for lactic acidosis in severe malaria: a pharmacokinetic and pharmacodynamic assessment

Lactic acidosis and hypoglycemia are potentially lethal complications of falciparum malaria. We have evaluated the pharmacokinetics and pharmacodynamics of dichloroacetate ([DCA], 46 mg/kg infused over 30 minutes), a stimulant of pyruvate dehydrogenase and a potential treatment for lactic acidosis, in 13 patients with severe malaria and compared the physiological and metabolic responses with those of a control group of patients (n = 32) of equivalent disease severity. The mean +/- SD peak postinfusion level of DCA was 78 +/- 23 mg/L, the total apparent volume of distribution was 0.75 +/- 0.35 L/kg, and systemic clearance was 0.32 +/- 0.16 L/kg/h. Geometric mean (range) venous lactate concentrations in control and DCA recipients before treatment were 4.5 (2.1 to 19.5) and 5.5 (2 to 15.4) mmol/L, respectively (P > .1). A single DCA infusion decreased lactate concentrations from baseline by a mean of 27% after 2 hours, 40% after 4 hours, and 41% after 8 hours, compared with decreases of 5%, 6%, and 16%, respectively, in controls (P = .032). These changes were preceded by rapid and marked decreases in pyruvate concentrations. Arterial pH increased from 7.328 to 7.374 (n = 10, P < .02) 2 hours after the infusion. Hypoglycemia was prevented by infusing glucose at 3 mg/kg/min. There was no clinical, electrocardiographic, or laboratory evidence of toxicity. These results suggest that DCA should be investigated further as an adjunctive therapy for severe malaria.

Glycerol metabolism in severe falciparum malaria

Gluconeogenesis and liver blood flow (LBF) in severe falciparum malaria were assessed from the clearance and metabolic response to intravenously administered glycerol (0.3 g/kg) and Indocyanine Green ([ICG] 0.4 mg/kg), respectively. Fasting baseline blood glycerol concentrations (mean +/- SD) were significantly higher in acute malaria (133 +/- 65 mumol/L, n = 14), than in convalescence (65 +/- 31 mumol/L, n = 9, P = .01), but basal triacylglycerol concentrations were similar. Estimated glycerol turnover was also more than twice as high in acute malaria compared with convalescence (1.36 +/- 0.87 v 0.54 +/- 0.15 mumol.min-1.kg-1, P = .015). The increment in plasma glucose (AUC0-55 min) following glycerol infusion was greater during acute malaria compared with convalescence (median [range], +31.6 [-0.9 to +107.6] v +14.5 [-103 to +27.1] mmol.min-L-1, P < .05), but the insulin increments were similar (P = .9), indicating reduced tissue insulin sensitivity. The increment in venous lactate (AUC0-55 min) was higher in severely ill patients (17.2 [-7.8 to +53.4] mmol.min.L-1, n = 10) compared with patients with moderately severe malaria (-3.1 [-8.7 to 3.2] mmol.min-L-1, n = 4, P = .01). LBF estimated from ICG clearance was lower during acute illness than in convalescence (mean +/- SD, 15.5 +/- 2.3 v 18.6 +/- 2.9 mL.min-1.kg-1, P = .007) and correlated inversely with the basal venous lactate concentration (rs = .53, P < .05). LBFs less than 15 mL.min-1.kg-1 were associated with hyperlactatemia, and all four fatal cases had LBFs of less than 12 mL.min-1.kg-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Lactic acidosis and hypoglycaemia in children with severe malaria: pathophysiological and prognostic significance

Serial clinical and metabolic changes were monitored in 115 Gambian children (1.5-12 years old) with severe malaria. Fifty-three children (46%) had cerebral malaria (coma score < or = 2) and 21 (18%) died. Admission geometric mean venous blood lactate concentrations were almost twice as high in fatal cases as in survivors (7.1 mmol/L vs. 3.6 mmol/L; P < 0.001) and were correlated with levels of tumour necrosis factor (r = 0.42, n = 79; P < 0.0001) and interleukin 1-alpha (r = 0.6, n = 34; P < 0.0001). Admission blood venous glucose concentrations were lower in fatal cases than survivors (3.2 mmol/L, vs. 5.8 mmol/L; P < 0.0001). Treatment with quinine was associated with significantly more episodes of post-admission hypoglycaemia when compared with artemether or chloroquine. After treatment, lactate concentrations fell rapidly in survivors but fell only slightly, or rose, in fatal cases. Plasma cytokine levels fluctuated widely after admission. Sustained hyperlactataemia (raised lactate concentrations, 4 h after admission) proved to be the best overall prognostic indicator of outcome in this series. Lactic acidosis is an important cause of death in severe malaria.

Metabolic disturbances in Plasmodium coatneyi-infected rhesus monkeys

To investigate metabolic disturbances in an animal model of human malaria, four rhesus monkeys (Macaca mulatta) were infected with Plasmodium coatneyi, a parasite which induces cytoadherence of infected erythrocytes. When moribund or the parasitaemia had plateaued, the monkeys were sacrificed (3 animals) or treated with chloroquine (1 animal). Blood and cerebrospinal fluid (CSF) were sampled at intervals between inoculation and sacrifice or treatment. Arterial and CSF glucose and lactate rose during infection, indicating evolving insulin resistance. The arteriovenous difference in glucose concentration also increased, consistent with increased glucose consumption by parasitised tissues. Arterial plasma lactate rose but a positive arteriovenous concentration difference suggested tissue lactate uptake. The animal with the highest plasma lactate at sacrifice remained hyperglycaemic but also had the highest CSF lactate, the greatest cerebral sequestration and neurological depression, and biochemical and histological evidence of severe hepatic pathology. Serum cholesterol and corrected serum calcium fell consistently during infection; serum phosphate was also reduced in animals without renal impairment. These preliminary results indicate that lactic acidosis is a late complication of severe malaria and, by implication from this and other studies, hypoglycaemia occurs even later; other metabolic changes during P. coatneyi infection in rhesus monkeys also parallel those of severe falciparum malaria in humans. The model could be used in further studies of malaria-associated metabolic dysfunction and its management.

Platelet-activating factor and lipid metabolism in acute malaria

Platelet-activating factor (PAF) contributes to a range of pathophysiological responses in severe illness. To examine PAF metabolism in acute malaria, venous blood was drawn from 10 untreated adults with falciparum malaria, from 8 with untreated vivax malaria, and from 10 controls. Plasma lyso-PAF, produced from PAF through the enzyme acetylhydrolase (AH), was bioassayed, after acetylation to PAF, by platelet [14C]-serotonin release. AH activity was measured by hydrolysis of [3H]-acetyl-PAF. Amounts of plasma lyso-PAF were lower in falciparum (median [range] 24 [9-221] ng/ml) and vivax (35 [7-236] ng/ml) infected patients than in controls (399 [212-504] ng/ml; P < 0.01), and correlated significantly with serum total and HDL-cholesterol (P < 0.001). Plasma AH activities were similar in the control, falciparum and vivax malaria groups. These data suggest that in malaria plasma lyso-PAF values fall together with other blood lipids, but independently of changes in AH activity. This may reflect a generalised decrease in lipid and phospholipid synthesis. However, the reduction of plasma lyso-PAF concentrations in our patients was much greater than that of serum lipoproteins. This is consistent with conversion of lyso-PAF to PAF or with increased PAF-receptor interactions. These two possibilities would have pathophysiological implications.

Glucose turnover in severe falciparum malaria

To investigate glucose metabolism in acute falciparum malaria, [3-3H]glucose turnover was measured in 18 normoglycemic adult Thais (eight males, 10 females; median age, 28 years) with severe infections. Eleven patients were studied before quinine treatment, 15 while receiving quinine, and 10 during convalescence. In paired studies conducted before and after initial intravenous quinine, plasma glucose level decreased from a median (95% confidence limits) of 5.5 (3.0 to 6.6) to 4.6 (2.5 to 6.1) mmol/L (P < or = .027, n = 8), and plasma insulin level increased 9.3 (-3.2 to 30.0) mU/L (P = .02). Glucose turnover decreased during the 4-hour quinine infusion from 3.04 (2.12 to 4.23) to 1.89 (1.20 to 2.54) mg/kg.min-1 (P < .004), as did the metabolic clearance rate for glucose (2.87 [1.88 to 7.83] to 2.50 [1.43 to 4.55) mL/kg.min-1; P = .008). Glucose turnover and clearance measured both after initial quinine treatment and in convalescence were similar (P = .234 and .344, respectively; n = 7). In the series as a whole, there was an inverse association between pretreatment turnover and the simultaneous plasma glucose level (rs = -.76, P < .01; n = 11), a stronger inverse relationship between glucose clearance and plasma glucose level (rs = -.88, P < .001), and a positive association between pretreatment turnover and oral temperature (rs = .65, P < .025; n = 10). These data suggest that, as in other severe illnesses, glucose turnover is high in untreated patients, but that glycolysis by mature parasite forms may accelerate glucose disposal.(ABSTRACT TRUNCATED AT 250 WORDS)

Alpha 1-acid glycoprotein (orosomucoid) and plasma protein binding of quinine in falciparum malaria

1. Plasma concentrations of alpha 1-acid glycoprotein (AAG) and plasma protein binding of quinine were measured in 97 Thai adults with acute falciparum malaria. There was a linear relationship between log AAG and percentage quinine binding (r = 0.71, P less than 0.001) in vivo, which was similar to that observed in vitro; the slopes and intercepts of the regression lines at AAG concentrations of 1 g l-1 were -8.94 and -8.41, and 7.2% and 10.9%, respectively. 2. Hill plots from these data suggest a single high affinity quinine binding site on each molecule of AAG. 3. Plasma AAG concentrations were consistently raised in acute malaria, and were higher in patients with cerebral malaria [2.03 (0.51) g l-1, mean (s.d.)], and conscious patients with severe malaria [1.93 (0.53) g l-1] than in patients with uncomplicated infections [1.55 (0.58) g l-1], P = 0.008. Plasma protein binding of quinine was correspondingly higher and thus the proportion of free drug was lower in the severe groups; 5.5 (2.4)% compared with 7.2 (1.9)%, P = 0.03. 4. Following recovery from malaria, plasma AAG concentrations fell by an estimated 0.05 g l-1 day-1 to levels that were approximately half (median 45%) the admission value at 28 days. 5. AAG is the principal binding protein for quinine in plasma. Changes in plasma concentrations of this acute phase reactant account for the increased plasma protein binding of quinine in acute malaria.

The metabolic response to rapid intravenous glucose injection in acute falciparum malaria

Because hypoglycaemia is common in severe malaria, intravenous glucose is often given empirically to patients on admission to hospital. To investigate the metabolic response to rapid glucose injection in acute malaria, 50 ml of 50% w/v (25 g) dextrose was given over 5 min to 10 adult patients (7 males, 3 females; mean age 30 years) with acute falciparum malaria. Five patients with severe infections were studied between doses of intravenous quinine; 5 cases were uncomplicated and previously untreated. The patients with severe malaria had lower pre-injection plasma glucose concentrations than patients with uncomplicated infections (mean +/- standard deviation, 4.2 +/- 0.9 vs 5.8 +/- 1.1 mmol/litre, 2P less than 0.015). However, peak glucose concentrations (18.6 +/- 4.8 vs 17.0 +/- 2.4 mmol/litre) and integrated responses (AUC0-245 min) were similar in the groups (2P greater than 0.1 in each case), and pre- and post-injection plasma insulin concentrations and AUC0-245 min values were also not significantly different (2P greater than 0.05 in each case). No 'rebound' hypoglycaemia was observed. The patients with severe malaria had higher peak plasma lactate concentrations than the uncomplicated patients (2.5 +/- 0.7 vs 1.5 +/- 0.9 mmol/litre, 2P less than 0.05), but the highest plasma lactate achieved and the greatest maximum post-injection rise were only 3.8 and 0.8 mmol/litre respectively. The average maximum reduction in plasma potassium after injection was 0.2 mmol/litre at 35 min. These data suggest that injections of hypertonic dextrose given empirically in conventional doses to non-acidotic patients with acute, severe malaria are not harmful, but the metabolic response in patients with an established acidosis remains unknown.