Pediatric thiamine deficiency disorders in high-income countries between 2000 and 2020: a clinical reappraisal

Often thought to be a nutritional issue limited to low- and middle-income countries (LMICs), pediatric thiamine deficiency (PTD) is perceived as being eradicated or anecdotal in high-income countries (HICs). In HICs, classic beriberi cases in breastfed infants by thiamine-deficient mothers living in disadvantaged socioeconomic conditions are thought to be rare. This study aims to assess PTD in HICs in the 21st century. Literature searches were conducted to identify case reports of PTD observed in HICs and published between 2000 and 2020. The analyzed variables were age, country, underlying conditions, clinical manifestations of PTD, and response to thiamine supplementation. One hundred and ten articles were identified, totaling 389 PTD cases that were classified into four age groups: neonates, infants, children, and adolescents. Eleven categories of PTD-predisposing factors were identified, including genetic causes, lifestyle (diabetes, obesity, and excessive consumption of sweetened beverages), eating disorders, cancer, gastrointestinal disorders/surgeries, critical illness, and artificial nutrition. TD-associated hyperlactatemia and Wernicke encephalopathy were the most frequent clinical manifestations. The circumstances surrounding PTD in HICs differ from classic PTD observed in LMICs and this study delineates its mutiple predisposing factors. Further studies are required to estimate its magnitude. Awareness is of utmost importance in clinical practice.

Selenium and RNA Virus Interactions: Potential Implications for SARS-CoV-2 Infection (COVID-19)

SARS-CoV-2 is an RNA virus responsible for the COVID-19 pandemic that already claimed more than 340,000 lives worldwide as of May 23, 2020, the majority of which are elderly. Selenium (Se), a natural trace element, has a key and complex role in the immune system. It is well-documented that Se deficiency is associated with higher susceptibility to RNA viral infections and more severe disease outcome. In this article, we firstly present evidence on how Se deficiency promotes mutations, replication and virulence of RNA viruses. Next, we review how Se might be beneficial via restoration of host antioxidant capacity, reduction of apoptosis and endothelial cell damages as well as platelet aggregation. It also appears that low Se status is a common finding in conditions considered at risk of severe COVID-19, especially in the elderly. Finally, we present a rationale for Se use at different stages of COVID-19. Se has been overlooked but may have a significant place in COVID-19 spectrum management, particularly in vulnerable elderly, and might represent a game changer in the global response to COVID-19.

Selenium and RNA Virus Interactions: Potential Implications for SARS-CoV-2 Infection (COVID-19)

SARS-CoV-2 is an RNA virus responsible for the COVID-19 pandemic that already claimed more than 340,000 lives worldwide as of May 23, 2020, the majority of which are elderly. Selenium (Se), a natural trace element, has a key and complex role in the immune system. It is well-documented that Se deficiency is associated with higher susceptibility to RNA viral infections and more severe disease outcome. In this article, we firstly present evidence on how Se deficiency promotes mutations, replication and virulence of RNA viruses. Next, we review how Se might be beneficial via restoration of host antioxidant capacity, reduction of apoptosis and endothelial cell damages as well as platelet aggregation. It also appears that low Se status is a common finding in conditions considered at risk of severe COVID-19, especially in the elderly. Finally, we present a rationale for Se use at different stages of COVID-19. Se has been overlooked but may have a significant place in COVID-19 spectrum management, particularly in vulnerable elderly, and might represent a game changer in the global response to COVID-19.

Selenium and RNA Virus Interactions: Potential Implications for SARS-CoV-2 Infection (COVID-19)

SARS-CoV-2 is an RNA virus responsible for the COVID-19 pandemic that already claimed more than 340,000 lives worldwide as of May 23, 2020, the majority of which are elderly. Selenium (Se), a natural trace element, has a key and complex role in the immune system. It is well-documented that Se deficiency is associated with higher susceptibility to RNA viral infections and more severe disease outcome. In this article, we firstly present evidence on how Se deficiency promotes mutations, replication and virulence of RNA viruses. Next, we review how Se might be beneficial via restoration of host antioxidant capacity, reduction of apoptosis and endothelial cell damages as well as platelet aggregation. It also appears that low Se status is a common finding in conditions considered at risk of severe COVID-19, especially in the elderly. Finally, we present a rationale for Se use at different stages of COVID-19. Se has been overlooked but may have a significant place in COVID-19 spectrum management, particularly in vulnerable elderly, and might represent a game changer in the global response to COVID-19.

Thiamine Deficiency in Tropical Pediatrics: New Insights into a Neglected but Vital Metabolic Challenge

In humans, thiamine is a micronutrient prone to depletion that may result in severe clinical abnormalities. This narrative review summarizes current knowledge on thiamine deficiency (TD) and bridges the gap between pathophysiology and clinical presentation by integrating thiamine metabolism at subcellular level with its function to vital organs. The broad clinical spectrum of TD is outlined, with emphasis on conditions encountered in tropical pediatric practice. In particular, TD is associated with type B lactic acidosis and classic forms of beriberi in children, but it is often unrecognized. Other severe acute conditions are associated with hypermetabolism, inducing a functional TD. The crucial role of thiamine in infant cognitive development is also highlighted in this review, along with analysis of the potential impact of TD in refeeding syndrome during severe acute malnutrition (SAM). This review aims to increase clinical awareness of TD in tropical settings where access to diagnostic tests is poor, and advocates for an early therapeutic thiamine challenge in resource-limited settings. Moreover, it provides evidence for thiamine as treatment in critical conditions requiring metabolic resuscitation, and gives rationale to the consideration of increased thiamine supplementation in therapeutic foods for malnourished children.

Impact of HIV-1 genetic diversity on plasma HIV-1 RNA Quantification: usefulness of the Agence Nationale de Recherches sur le SIDA second-generation long terminal repeat-based real-time reverse transcriptase polymerase chain reaction test

The high genetic diversity of HIV-1 has a major impact on the quantification of plasma HIV-1 RNA, representing an increasingly difficult challenge. A total of 898 plasma specimens positive for HIV-1 RNA by commercial assays (Amplicor v1.5; Roche Diagnostic Systems, Alameda, CA or Versant v3.0; Bayer Diagnostics, Emeryville, CA) were tested using the Agence Nationale de Recherches sur le SIDA second-generation (G2) real-time reverse transcriptase polymerase chain reaction (RT-PCR) test: 518 samples containing HIV-1 of known subtype, including 88 from 2 subtype panels and 430 harboring B (n = 266) and non-B (n = 164) group M HIV-1 subtypes from patients followed up in 2002 through 2005 at Necker Hospital (Paris, France), and 380 samples from 10 different countries (Argentina, Cambodia, Cameroon, Central African Republic, France, Ivory Coast, Madagascar, Morocco, Thailand, and Zimbabwe). HIV-1 RNA values obtained by G2 real-time PCR were highly correlated with those obtained by the Amplicor v1.5 for B and non-B subtypes (R = 0.892 and 0.892, respectively) and for samples from diverse countries (R = 0.867 and 0.893 for real-time PCR vs. Amplicor v1.5 and real-time PCR vs. Versant v3.0, respectively). Approximately 30% of specimens harboring non-B subtypes were underquantified by at least -0.51 log10 in Amplicor v1.5 versus 5% underquantified in G2 real-time PCR. Discrepant results were also obtained with subtype B samples (14% underquantified by Amplicor v1.5 vs. 7% by G2 real-time PCR). Similar percentages were observed when comparing results obtained with the G2 real-time PCR assay with those obtained using the Versant assay. Addressing HIV-1 diversity, continual monitoring of HIV-1 RNA assays, together with molecular epidemiology studies, is required to improve the accuracy of all HIV RNA assays.

Taurine kinetics assessed using [1,2-13C2]taurine in healthy adult humans

To assess the dynamics of taurine metabolism in vivo, two sets of studies were carried out in healthy volunteers. First, pilot studies were carried in a single human subject to determine the time course of plasma and whole blood isotope enrichment over the course of an 8-h, unprimed continuous infusion of [1,2-(13)C(2)]taurine. Second, five healthy adult males received two tracer infusions on separate days and in randomized order: 1) a 6-h continuous infusion of [1,2-(13)C(2)]taurine (3.1 +/- 0.2 micromol x kg(-1) x h(-1)) and 2) a bolus injection of [(13)C(2)]taurine (3.0 +/- 0.1 micromol/kg). Isotope enrichments in plasma and whole blood taurine were determined by gas chromatography-mass spectrometry. The pilot experiments allowed us to establish that steady-state isotope enrichment was reached in plasma and whole blood by the 5th h of tracer infusion. The plateau enrichment reached in whole blood was lower than that obtained in plasma taurine (P < 0.02). In the second set of studies, the appearance rate (R(a)) of plasma taurine, determined from continuous infusion studies was 31.8 +/- 3.1 micromol x kg(-1) x h(-1). After a bolus injection of tracer, the enrichment decay over the subsequent 2 h was best fitted by a two-exponential curve. Taurine R(a) was approximately 85% higher when determined using the bolus injection technique compared with continuous infusion of tracer. We conclude that 1) taurine R(a) into plasma is very low in healthy postabsorptive humans, and, due to taurine compartmentation between the extra- and intracellular milieus, may represent only interorgan taurine transfer and merely a small fraction of whole body taurine turnover; and 2) the bolus injection technique may overestimate taurine appearance into plasma. Further studies are warranted to determine whether alterations in bile taurine dynamics affect taurine R(a).

Lipodystrophic syndromes and hyperlipidemia in a cohort of HIV-1-infected patients receiving triple combination antiretroviral therapy with a protease inhibitor

OBJECTIVES

To assess the frequency and features of lipodystrophic syndromes in HIV-1-infected patients receiving highly active antiretroviral therapy (HAART) with a protease inhibitor (PI), and examine whether clinical and biologic abnormalities are always associated in these conditions.

METHODS

Retrospective-prospective single-center observational study of 175 patients. Comparisons for continuous variables by t-test and paired t-test, and Kaplan-Meier analysis of time to onset of lipodystrophy were performed.

RESULTS

In all, 51 patients (29%) had morphologic changes, after a mean HAART duration of 20.0 +/- 6.1 months, and were categorized into pure lipoatrophy (n = 16), mixed syndrome (truncal fat accumulation and face or limb lipoatrophy) (n = 30) or pure truncal fat accumulation (n = 5). Because of the small number, the latter group was not analyzed statistically. No differences were found among patients with lipoatrophy, mixed syndrome, or no lipodystrophy, in terms of gender, CD4 count, and HIV RNA plasma load at time of HAART initiation, nor in response to treatment. Patients with a mixed syndrome were older. Patients with lipoatrophy had longer duration of HIV disease, pre-HAART exposure to nucleoside analog therapy, and HAART. Baseline and pre-HAART fasting triglyceride levels were higher in patients who developed lipoatrophy, whereas weight and fasting cholesterol were higher in patients who developed a mixed syndrome. After 12 and 24 months on HAART, triglycerides and cholesterol rose significantly in all patients, independently of lipodystrophy, whereas these parameters were not increased during nucleoside analog therapy.

CONCLUSIONS

Nucleoside analog exposure appears as a risk factor for lipoatrophy. Age and nutritional status (reflected by baseline weight, triglycerides and cholesterol) may influence the evolution to lipoatrophy or a mixed syndrome. Hyperlipidemia is observed in the absence of lipodystrophy and depends on PI exposure.

Impact of emerging technologies and regulations on the role of POCT

Point-of-care testing (POCT) can be introduced by laboratory directors or clinicians in response to the need for rapid results to guide treatment. The professional responsibility for ensuring reliable and accurate results is well-defined in some countries such as France, but the role and responsibility of the laboratory is less clear in many other places. When point-of-care instrument technology and the intrinsic design of the device leads to device-specific parameters or analytical differences from laboratory-based equipment, there is a risk of misinterpretation and erroneous treatment decisions. Laboratory staffs are more often aware of the interaction of analytical technology and result interpretation than clinicians, making it more rational to involve the laboratory in the selection of point-of-care equipment, procedures, and therapeutic decisions based on the results. The design control and risk-analysis provisions of emerging regulations such as the EU in vitro diagnostic medical device (IVD) can be interpreted as engaging the manufacturer's responsibility, even when the equipment is functioning according to specification. This is especially true of device-specific parameters in which cross-calibration or traceability to a reference material or method is not possible. This is a further argument for involvement of the laboratory in the selection and implementation of point-of-care testing devices.

Duodenal vs. gastric administration of labeled leucine for the study of splanchnic metabolism in humans

Low-rate (6 ml/h) intragastric infusion of stable, isotope-labeled amino acids is commonly used to assess the splanchnic handling of amino acids in humans. However, when used in the postabsorptive state, this method yields unreliable plasma isotopic enrichments, with a coefficient of variation >10%. In this metabolic condition, we confirmed in six subjects that an intragastric infusion of L-[(2)H(3)]leucine at 6 ml/h yields an unreliable isotopic steady state in plasma amino acids with a coefficient of variation of 43 +/- 12% (mean +/- SD). In five additional subjects, we assessed the effects of 1) increasing the rate of delivery of a leucine tracer in an isotonic plasmalike solution at 240 ml/h into the gastric site, and 2) changing the site of infusion from gastric to duodenal with this same high rate of delivery. In contrast to the gastric route, and regardless of the rate of delivery, only the intraduodenal route allowed 1) isotopic plasma steady state (i.e., coefficients of variation were <10%: 5 +/- 3%), and 2) reproducible leucine extraction coefficients (22 +/- 5%). We conclude that an infusion site that bypasses the gastric emptying process, i.e., the duodenal route, along with delivery of a plasmalike solution, is necessary to reach isotopic steady state in plasma when labeled leucine is infused into the gastrointestinal tract in the postabsorptive state.

Insulin secretion and sensitivity in children on cyclic total parenteral nutrition

BACKGROUND

Some children receiving total parenteral nutrition (TPN) have abnormal glucose tolerance.

METHODS

Insulin secretion and sensitivity were studied in 12 patients, aged 5.7 to 19.4 years, receiving cyclic nocturnal TPN. Insulin secretion was measured during an IV glucose tolerance test (IVGTT; 0.5 g/kg) followed by a hyperglycemic clamp (plasma glucose at 10 mmol/L). Insulin sensitivity was assessed by hyperinsulinemic euglycemic clamp (insulin infusion = 1 mU/kg/min).

RESULTS

Patients with normal glucose tolerance receiving TPN had an insulin response to IVGTT similar to that of normal children of the same age. Insulin levels of TPN patients were higher than those in healthy young adults during the hyperglycemic clamp. Whole body glucose disposal was greater in younger than in older children (range, 7.1 to 25.2 mg/kg/min), and this inverse correlation with age was statistically significant (p < .01). Two patients with abnormal glucose tolerance showed a decreased capacity to release insulin, whereas insulin sensitivity was unchanged in one of these two patients. Two patients treated with prednisone or octreotide had insulin levels similar to those of normal TPN children.

CONCLUSIONS

The insulin response to sustained hyperglycemia was stronger in children with normal glucose tolerance on cyclic TPN. Patients with a limited capacity to release insulin, either constitutional or acquired, may not be able to produce enough insulin in these conditions and develop glucose intolerance during TPN. Insulin sensitivity was not a key factor in the alteration of glucose tolerance.

Insulin responses to intravenous glucose, intravenous arginine and a hyperglycaemic clamp in ICA-positive subjects with different degrees of glucose tolerance

The relationship between altered insulin secretion and impaired glucose tolerance was studied in 32 non-obese subjects aged 14-49 years with islet-cell antibodies (ICA) and fasting blood glucose below 7.9 mmol/l, using oral (OGTT) and intravenous (IVGTT) glucose tolerance tests. Glucose tolerance was normal in 19 subjects, impaired (IGT) in 4 and satisfied diabetic criteria in 9. Fifteen of these subjects and 8 ICA-negative controls also underwent a hyperglycaemic clamp (10 mmol/l) and a glucose-potentiated IV arginine bolus. Acute insulin response to IVGTT and insulin and C-peptide responses to the hyperglycaemic clamp and the arginine bolus were dramatically lower (p < 0.001) in diabetic and IGT subjects than in ICA-positive patients with normal glucose tolerance and control subjects. Insulin responses to the three tests were inversely correlated with plasma glucose levels and the area under the curve of OGTT. The correlations between the degree of glucose tolerance and insulin responses to IVGTT, the hyperglycaemic clamp and the arginine bolus were virtually identical. It is concluded that insulin responses to the three stimuli were severely altered in ICA-positive patients with impaired glucose tolerance or asymptomatic diabetes, normal in normotolerant ICA-positive subjects, and correlated with glucose tolerance.

Assessment of insulin sensitivity in glucokinase-deficient subjects

The chronic hyperglycaemia of glucokinase-deficient diabetes results from a glucose-sensing defect in pancreatic beta cells and abnormal hepatic glucose phosphorylation. We have evaluated the contribution of insulin resistance to this form of chronic hyperglycaemia. Insulin sensitivity, assessed by the homeostasis model assessment (HOMA) method in 35 kindreds with glucokinase mutations, was found to be significantly decreased in 125 glucokinase-deficient subjects as compared to 141 unaffected first-degree relatives. Logistic regression analysis showed that in glucokinase-deficient subjects a decrease in insulin sensitivity was associated with deterioration of the glucose tolerance status. A euglycaemic hyperinsulinaemic clamp was performed in 14 glucokinase-deficient subjects and 12 unrelated control subjects. In six patients and six control subjects the clamp was coupled to dideutero-glucose infusion to measure glucose turnover. Average glucose infusion rates (GIR) at 1 and 5 mU.kg body weight.min-1 insulin infusion rates were significantly lower in (the glucokinase-deficient) patients than in control subjects. Although heterogeneous results were observed, in 8 out of the 14 patients GIRs throughout the experiment were lower than 1 SD below the mean of the control subjects. Hepatic glucose production at 1 mU.kg body weight-1.min-1 insulin-infusion rate was significantly higher in patients than in control subjects. In conclusion, insulin resistance correlates with the deterioration of glucose tolerance and contributes to the hyperglycaemia of glucokinase-deficient diabetes. Taken together, our results are most consistent with insulin resistance being considered secondary to the chronic hyperglycaemia and/or hypoinsulinaemia of glucokinase-deficiency. Insulin resistance might also result from interactions between the unbalanced glucose metabolism and susceptibility gene(s) to low insulin sensitivity likely to be present in this population.

Cyclosporin A does not delay insulin dependency in asymptomatic IDDM patients

OBJECTIVE

To measure the effects of cyclosporin A (CyA) with no insulin therapy on glucose tolerance and beta-cell function in the preclinical phase of insulin-dependent diabetes mellitus (IDDM).

RESEARCH DESIGN AND METHODS

beta-cell responses to the intravenous glucose tolerance test (IVGTT), hyperglycemic clamp, intravenous arginine, and intravenous glucagon were evaluated before and after a 6-month course of CyA in seven patients (mean age 19.6 years) with asymptomatic IDDM.

RESULTS

Initial insulin secretory responses were severely decreased when the patients were compared with eight healthy control subjects: IVGTT (1 + 3 min): 106 +/- 16 vs. 884 +/- 190 pmol/l (P < 0.001); hyperglycemic clamp: 102 +/- 16 vs. 310 +/- 42 pmol/l (P < 0.001); intravenous arginine: 346 +/- 72 vs. 1104 +/- 168 pmol/l (P < 0.01); and intravenous glucagon: 170 +/- 37 vs. 247 +/- 35 pmol/l (NS). The beta-cell responses remained markedly abnormal after 6 months of CyA, although the response to intravenous glucose and oral glucose tolerance tests improved in three subjects. All the patients became insulin-dependent after 5-36 months.

CONCLUSIONS

CyA alone is not a suitable treatment for asymptomatic IDDM. Earlier identification of subjects with substantial beta-cell secretory capacity and newer nontoxic intervention strategies are required for the prevention of IDDM.

Insulin responses to intravenous glucose and the hyperglycemic clamp in cystic fibrosis patients with different degrees of glucose tolerance

The relationship between altered insulin secretion and impaired glucose tolerance was studied in 32 cystic fibrosis patients, 16 men and 16 women, aged 8-26 y, using oral and i.v. glucose tolerance tests and a hyperglycemic glucose clamp (10 mmol/L). Seven of these subjects were already being treated with insulin; seven had fasting blood glucose levels below 7.2 mmol/L but satisfied diabetic criteria at the oral glucose tolerance test; glucose tolerance was impaired in 13 subjects and normal in five. The insulin responses to the two i.v. glucose stimuli were inversely correlated with the plasma glucose levels (60 and 120 min) and the area under the curve of the oral glucose tolerance test. However, the acute insulin response to i.v. glucose was severely altered in patients with impaired glucose tolerance, whereas plasma insulin levels during the hyperglycemic clamp did not differ from those of healthy subjects. The responses to the two stimuli were dramatically low in the diabetic patients. These results suggest that cystic fibrosis patients with normal or impaired glucose tolerance retain their capacity to secrete insulin. Alterations in the acute phase of glucose-stimulated insulin secretion seem to be principally responsible for the early impairment in glucose tolerance.

The development of hyperglycaemia in patients with insulin-resistant generalized lipoatrophic syndromes

Insulin resistance is present in patients suffering from lipoatrophic syndromes long before the onset of diabetes mellitus. Thus, the decreased peripheral glucose disposal may not be the only mechanism of hyperglycaemia. The kinetic parameters of glucose homeostasis were evaluated in six young females aged 15, 16, 18, 19 and 24 years with generalized lipoatrophy; one patient was studied both at 12 and 15 years. Insulin resistance was evaluated in vivo by the hyperinsulinaemic euglycaemic clamp (3-4 insulin infusion rates from 1 to 100 mU/kg.min). All patients showed a rightward shift of the dose-response curve, indicating decreased insulin sensitivity. In two patients, maximal glucose disposal was moderately decreased, while in five patients it was dramatically reduced (3.6-6.9 mg/kg.min). Fasting plasma glucose was variable (4.3-18.3 mmol/l) and did not correlate with peripheral glucose disposal rates. Hepatic glucose production, measured by infusion of [6,6-2H] glucose, varied from 1.7 to 8.3 mg/kg.min and was significantly correlated with fasting plasma glucose. The overproduction of glucose despite basal hyperinsulinism suggested hepatic insulin resistance, which was confirmed by the abnormal response to constant unlabelled glucose infusion (2 mg/kg.min) in five patients. In conclusion, impaired glucose tolerance seems to develop in generalized lipoatrophy with aggravated peripheral insulin resistance. The present data show that fasting hyperglycaemia is mainly the consequence of increased hepatic glucose production.

Insulin resistance and excess weight in adolescent insulin-dependent diabetic girls

Insulin dependent diabetic adolescent girls show a tendency towards excess weight. The relationship between insulin resistance and body mass index (BMI) was investigated in 23 Type 1 adolescents aged 13-20 yr. These patients body mass indexes spanned from 19.8 to 30.5. Excess weight was evaluated using Z-scores, corrected for age with reference to french standards. 9 patients with a Z-score greater than 2 were considered as obese. Insulin sensibility was measured using the hyperinsulinaemic euglycaemic clamp (insulin infusion rate, 1 mU kg-1 min-1). The mean glucose infusion rate during the clamp was low in the diabetic girls (2.29 +/- 1.35 mg kg-1 min-1), confirming the existence of insulin resistance. However, the degree of insulin resistance was not correlated with the excess in weight (glucose infusion rate, 2.23 +/- 1.24 vs 2.33 +/- 1.46 mg kg-1 min-1 in the obese and the non-obese patients, respectively). None of the factors which influence on insulin sensitivity could explain this lack of correlation, the obese patients showing greater daily insulin doses (1.36 +/- 0.22 vs 1.22 +/- 0.25 unit kg-1 day-1) and worse metabolic control (Hba1C, 10.9 +/- 1.4 vs 10.2 +/- 2.0%). Insulin resistance was significantly correlated with free fatty acid levels during the clamp.

Primary pancreatic beta-cell secretory defect caused by mutations in glucokinase gene in kindreds of maturity onset diabetes of the young

Maturity-onset diabetes of the young (MODY), characterised by non-insulin-dependent diabetes mellitus (NIDDM) with an early age of onset, is a genetically heterogeneous disorder. In most MODY kindreds described in France, chronic hyperglycaemia is caused by mutations in the gene encoding pancreatic beta-cell and liver glucokinase (GCK). We here report the beta-cell secretory profiles of nine patients from four GCK-linked MODY kindreds. First-phase insulin secretion assessed by an intravenous glucose test was comparable in patients and seven controls. However, beta-cell secretory response to continuous glucose stimulus during a hyperglycaemic glucose clamp was significantly reduced: mean plasma insulin values of 12 (SD 7) vs 40 (11) mU/l (p = 0.0001) and mean plasma C-peptide values 1.20 (0.30) vs 2.61 (0.37) (p = 0.0001). This secretory profile is different from those for NIDDM with late age of onset or MODY not linked to GCK. Fasting plasma insulin and C-peptide in patients were inappropriately low in relation to concomitant plasma glucose level. Furthermore, during a hyperinsulinaemic euglycaemic clamp, endogenous insulin secretion at euglycaemia (5 mmol/l) was suppressed in patients but not in controls. These results suggest that mutant GCK may lead to chronic hyperglycaemia by raising the threshold of circulating glucose level which induces insulin secretion. These data provide the first demonstration of a primary pancreatic secretory defect associated with a form of NIDDM.

[Determination of pH in the body: methodologic review]

The maintenance of a defined free H+ concentration within narrow limits is a prerequisite and feature of living organisms. In recent years the different disciplines of biological science have made considerable progress in the elucidation of the mechanisms involved in pH homeostasis. Recent advances have occurred also in the field of pH measurement. This review focuses mainly on the modern instruments for pH and blood gas analysis. The techniques of intracellular pH currently in general use are described together with some of the techniques for determination of pH in subcellular compartments.