Long-term outcomes of liver transplantation for homozygous familial hypercholesterolaemia in Australia and New Zealand

BACKGROUND AND AIMS

Homozygous familial hypercholesterolaemia (FH) causes severe cardiovascular disease from childhood. Conventional drug therapy is usually ineffective; lipoprotein apheresis (LA) is often required. Liver transplantation (LT) can correct the metabolic defect but is considered a treatment of last resort. Newer drugs including lomitapide and evinacumab might reduce the need for apheresis and LT. We sought to determine the long-term outcomes following LT in Australia and New Zealand.

METHODS

We analysed demographic, biochemical and clinical data from all patients in Australia and New Zealand who have received LT for homozygous FH, identified from the Australia and New Zealand Liver and Intestinal Transplant Registry.

RESULTS

Nine patients (five female; one deceased; seven aged between 3 and 6 years at the time of LT and two aged 22 and 26 years) were identified. Mean follow-up was 14.1 years (range 4-27). Baseline LDL-cholesterol off all treatment was 23 ± 4.1 mmol/L. Mean LDL-cholesterol on medical therapy (including maximal statin therapy in all patients, ezetimibe in three and LA in five) was 11 ± 5.7 mmol/L (p < 0.001). After LT, mean LDL-cholesterol was 2.6 ± 0.9 mmol/L (p = 0.004) with three patients remaining on statin therapy and none on LA. One patient died from acute myocardial infarction (AMI) three years after LT. Two patients required aortic valve replacement, more than 10 years after LT. The remaining six patients were asymptomatic after eight to 21 years of follow-up. No significant adverse events associated with immunosuppression were reported.

CONCLUSIONS

LT for homozygous FH was highly effective in achieving substantial long-term reduction in LDL-cholesterol concentrations in all nine patients. LT remains an option for severe cases of homozygous FH where drug therapy combined with apheresis is ineffective or unfeasible.

The adrenal vein sampling outcomes study (AVOS): success rates following adrenalectomy for unilateral primary aldosteronism

The objective was to determine the clinical and biochemical success rates and assess the nature of follow-up after adrenalectomy in patients with unilateral primary aldosteronism (PA), subtyped by adrenal vein sampling (AVS) in West Australia (WA) using the Primary Aldosteronism Surgical Outcome (PASO) criteria. Clinical and biochemical outcomes were retrospectively evaluated in patients with unilateral PA who underwent adrenalectomy according to AVS between September 2017 and September 2020. Pre- and post-surgical data were collected using a standardised questionnaire, review of clinic letters and examination of private and public pathology results and radiological reports. Follow-up data were available for 47 patients post-adrenalectomy; biochemical outcome data were available for 37 patients, clinical outcome data for 40 patients, with 30 patients having both outcomes available. Final assessment was performed between 0 to 3 months in 23/37 (62.2%) patients with biochemical outcomes, 15/40 (37.5%) with clinical outcomes, and 17/30 (56.7%) with both clinical and biochemical outcomes. Complete biochemical success was achieved in 83.8% (31/37) of patients, with 26.7% (8/30) obtaining both complete clinical and biochemical success. Complete clinical success was achieved in 35.0% (14/40) of patients, with 47.5% (19/40) obtaining partial clinical success. Overall, 93.6% (44/47) of patients derived benefit from adrenalectomy. The outcomes of adrenalectomy for unilateral PA in Western Australian using standardised PASO criteria demonstrate highly comparable clinical and biochemical success rates to international data. However, further standardisation of post-operative follow-up care needs to be implemented to ensure the recommended repeat follow-up assessment criteria are collected.

Detecting patients with Cushing's syndrome: The importance of initial test selection

BACKGROUND AND OBJECTIVES

The recommended initial tests for suspected Cushing's syndrome are late-night salivary cortisol (LNSC), 24-hour urinary free cortisol (UFC) and the 1 mg overnight dexamethasone suppression test (ONDST). These tests have higher sensitivity and specificity than serum cortisol. The aim of this study was to determine the relative frequency of these requested tests in primary care.

METHOD

Initial test selection for investigation of Cushing's syndrome was audited by reviewing pathology request forms for cortisol tests made to a major community-based laboratory in 2019. Those with hypertension or adrenal incidentaloma as the documented indication for testing were included.

RESULTS

In 214 of 272 cases (78.7%; 95% confidence interval: 73.2%, 83.3%) initial testing was by measurement of serum cortisol alone.

DISCUSSION

The relatively infrequent selection of the higher sensitivity tests (ONDST, UFC and LNSC) for investigation of suspected Cushing's syndrome signifies a risk of delayed or missed diagnosis, with important implications for morbidity and mortality.

Approach to the diagnosis of secondary hypertension in adults

Presentations that should raise suspicion of secondary hypertension include early-onset, severe or resistant hypertension. A suggestive family history or clinical clues can point to a specific secondary cause. The most common causes and associations are renal disease, primary aldosteronism and obstructive sleep apnoea. Medicines, illicit substances and alcohol may also be responsible. The assessment of patients begins with history taking and examination, to look for clinical clues. Laboratory tests include electrolytes, urea, creatinine and the aldosterone:renin ratio, urinalysis and the urine albumin:creatinine ratio. Abnormal results should prompt further investigation. Initial testing for primary aldosteronism is best done before starting potentially interfering antihypertensive drugs. If the patient is already taking interfering antihypertensive drugs that cannot be stopped, the interpretation of the aldosterone:renin ratio must consider the presence of those drugs. Specialist advice can be sought if needed.

Contemporary perspectives on the genetics and clinical use of lipoprotein(a) in preventive cardiology

PURPOSE OF REVIEW

The pathogenicity of lipoprotein(a) [Lp(a)] as a risk factor for atherosclerotic cardiovascular disease (ASCVD) is well evidenced and recognized by international consensus-based guidelines. However, the measurement of Lp(a) is not routine clinical practice. Therapeutic agents targeting Lp(a) are now progressing through randomised clinical trials, and it is timely for clinicians to familiarize themselves with this complex and enigmatic lipoprotein particle.

RECENT FINDINGS

Recent developments in the understanding of genetic influences on the structure, plasma concentration and atherogenicity of Lp(a) have contextualized its clinical relevance. Mendelian randomization studies have enabled estimation of the contribution of Lp(a) to ASCVD risk. Genotyping individual patients with respect to Lp(a)-raising single nucleotide polymorphisms predicts ASCVD, but has not yet been shown to add value beyond the measurement of Lp(a) plasma concentrations, which should be done by Lp(a) isoform-independent assays capable of reporting in molar concentrations. Contemporary gene-silencing technology underpins small interfering RNA and antisense oligonucleotides, which are emerging as the leading Lp(a)-lowering therapeutic agents. The degree of Lp(a)-lowering required to achieve meaningful reductions in ASCVD risk has been estimated by Mendelian randomization, providing conceptual support.

SUMMARY

Measurement of Lp(a) in the clinical setting contributes to the assessment of ASCVD risk, and will become more important with the advent of specific Lp(a)-lowering therapies. Knowledge of an individual patient's genetic predisposition to increased Lp(a) appears to impart little or not additional clinical value beyond Lp(a) particle concentration.

Lipoprotein apheresis and PCSK9 inhibitors for severe familial hypercholesterolaemia: Experience from Australia and New Zealand

INTRODUCTION

Severe familial hypercholesterolaemia (FH) causes premature disability and death due to atherosclerotic cardiovascular disease and is refractory to standard lipid-lowering therapies. Lipoprotein apheresis (LA) has long been a standard of care for patients with severe FH, but is invasive, expensive and time-consuming for patients and their caregivers. Newer drug therapies, including the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, may reduce the need for LA.

MATERIALS AND METHODS

We audited the records of 16 patients (eight homozygous, eight heterozygous) treated with LA in Australia and New Zealand, 14 of whom subsequently commenced PCSK9 inhibitor therapy. LA was performed by cascade filtration in all centres.

RESULTS

LDL-cholesterol was acutely lowered by 69 ± 7% in patients with homozygous FH and by 72 ± 9% in those with heterozygous FH, representing time-averaged reductions of 36 ± 12% and 34 ± 5%, respectively. LA was well-tolerated, and patients reported comparable quality of life to population and disease-related norms. After commencement of PCSK9 inhibitors, four of seven patients with homozygous FH had meaningful biochemical responses, with a reduction in the frequency of LA permitted in one patient and complete cessation in another. Four of seven patients with heterozygous FH were able to be managed without LA after commencing PCSK9 inhibitors.

CONCLUSION

While PCSK9 inhibitors have reduced the need for LA, some patients with severe FH continue to require LA, and will require it for the foreseeable future. However, emerging therapies, including angiopoetin-like 3 inhibitors, may further reduce the need for LA.

Widening the spectrum of genetic testing in familial hypercholesterolaemia: Will it translate into better patient and population outcomes?

Familial hypercholesterolaemia (FH) is caused by pathogenic variants in LDLR, APOB or PCSK9. Impaired low-density lipoprotein (LDL) receptor function leads to decreased LDL catabolism and premature atherosclerotic cardiovascular disease (ASCVD). Thousands of LDLR variants are known, but assignation of pathogenicity requires accurate phenotyping, family studies and assessment of LDL receptor function. Precise, genetic diagnosis of FH using targeted next generation sequencing allows for optimal treatment, distinguishing FH from pathogenically distinct disorders requiring different treatment. Polygenic hypercholesterolaemia resulting from an accumulation of LDL cholesterol-raising single nucleotide polymorphisms (SNPs) could also be suspected by this approach. Similarly, ASCVD risk could be estimated by broader sequencing of cholesterol and non-cholesterol-related genes. Both of these areas require further research. The clinical management of FH, focusing on the primary or secondary prevention of ASCVD, has been boosted by PCSK9 inhibitor therapy. The efficacy of PCSK9 inhibitors in homozygous FH may be partly predicted by the LDLR variants. While expanded genetic testing in FH is clinically useful in providing an accurate diagnosis and enabling cost-effective testing of relatives, further research is needed to establish its value in improving clinical outcomes.

Pharmacokinetics of flucloxacillin during prolonged intermittent renal replacement therapy in a 76-year-old man

Prolonged intermittent renal replacement therapy (PIRRT) use has been increasing in critically ill patients with kidney dysfunction. PIRRT can affect the pharmacokinetics of many drugs, although no data is available to guide flucloxacillin dosing in this clinical scenario. Herein, we describe the pharmacokinetics of flucloxacillin, given at 1 g every 4 h during PIRRT, in a 76-year-old, critically ill patient with a methicillin-susceptible Staphylococcus aureus (MSSA) prosthetic joint infection complicated by bacteraemia. Blood samples were taken over 2 days including during a 9-h PIRRT session. A two-compartment model was developed to describe differences in clearance of flucloxacillin during PIRRT and off-PIRRT (9.45 vs. 6.89 L/h). A flucloxacillin dose of 1 g every 4 h during PIRRT therapy appeared to attain adequate exposures for MSSA sepsis in this patient, however higher doses may be required for infection sites with poor drug penetration.

Pharmacokinetics of Benzylpenicillin (Penicillin G) during Prolonged Intermittent Renal Replacement Therapy

Prolonged intermittent renal replacement therapy (PIRRT) is an increasingly adopted method of renal replacement in critically ill patients. Like continuous renal replacement therapy, PIRRT can alter the pharmacokinetics (PK) of many drugs. In this setting, dosing data for antibiotics like benzylpenicillin are lacking. In order to enable clinicians to prescribe benzylpenicillin safely and effectively, knowledge of the effects of PIRRT on the plasma PK of benzylpenicillin is required. Herein, we describe the PK of benzylpenicillin in 2 critically ill patients on PIRRT for the treatment of penicillin-susceptible Staphylococcus aureus bacteremia complicated by infective endocarditis. Blood samples were taken for each patient taken over dosing periods during PIRRT and off PIRRT. Two-compartment PK models described significant differences in the mean clearance of benzylpenicillin with and without PIRRT (6.61 vs. 3.04 L/h respectively). We would suggest a benzylpenicillin dose of 1,800 mg (3 million units) every 6-h during PIRRT therapy as sufficient to attain PK/pharmacodynamic target.

Clinical guidance on the contemporary use of proprotein convertase subtilisin/kexin type 9 monoclonal antibodies

There is now significant evidence for the benefits of lowering low-density lipoprotein cholesterol (LDL-c) to reduce the risk of atherosclerotic cardiovascular disease (ASCVD). Although statins are the most widely prescribed lipid-lowering therapy that effectively lower LDL-c, especially in combination with ezetimibe, some patients require adjunctive therapy to further lower LDL-c and mitigate attendant risk of ASCVD. The gap can be filled by proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies whose use is currently supported by two recent cardiovascular outcome studies and new treatment guidelines. We provide an overview of extant studies investigating PCSK9 monoclonal antibodies in various patient populations, an update of the guidelines regarding their use and a case-based discussion.

The challenge of improving the diagnostic yield from metanephrine testing in suspected phaeochromocytoma and paraganglioma

Background

Plasma-free metanephrines (PFM) or urinary fractionated metanephrines (UFM) are the preferred biochemical tests for the diagnosis of phaeochromocytoma and paraganglioma (PPGL). Borderline increased results should be followed up to either exclude or confirm diagnosis.

Methods

We extracted all PFM and UFM results reported by our laboratory over a six-month period from the laboratory information system. We categorized patients with borderline increased results according to whether follow-up testing had been performed as suggested in the initial laboratory report. Questionnaires were then sent to all requesting doctors and medical notes reviewed where available.

Results

Two hundred and four patients with borderline increased PFM or UFM were identified. Sixty-five (38.5%) of 169 patients with borderline increased PFM had a repeat test out of which 36 were normal and 29 did not normalize. Of 35 patients with borderline increased UFM, 17 (48.6%) had subsequent PFM measurement, out of which 15 were normal. Questionnaires were returned to 106 (52%) patients. Of these, the most frequent indication for testing was hypertension ( n = 50); 15 patients had an incidental adrenal mass and two of these patients were diagnosed with a phaeochromocytoma.

Conclusion

Only 38% of patients with borderline increased PFM had a repeat PFM measurement. This was not significantly higher when compared with the 28% in a previous audit that we reported in 2010 ( P = 0.10). Forty-nine per cent of patients with a borderline increased UFM had a repeat UFM or PFM measurement. There remains a substantial possibility of missed detection of PPGL.

Improved technical success and radiation safety of adrenal vein sampling using rapid, semi-quantitative point-of-care cortisol measurement

Objective

Primary aldosteronism is a curable cause of hypertension which can be treated surgically or medically depending on the findings of adrenal vein sampling studies. Adrenal vein sampling studies are technically demanding with a high failure rate in many centres. The use of intraprocedural cortisol measurement could improve the success rates of adrenal vein sampling but may be impracticable due to cost and effects on procedural duration.

Design

Retrospective review of the results of adrenal vein sampling procedures since commencement of point-of-care cortisol measurement using a novel single-use semi-quantitative measuring device for cortisol, the adrenal vein sampling Accuracy Kit. Measurements: Success rate and complications of adrenal vein sampling procedures before and after use of the adrenal vein sampling Accuracy Kit. Routine use of the adrenal vein sampling Accuracy Kit device for intraprocedural measurement of cortisol commenced in 2016.

Results

Technical success rate of adrenal vein sampling increased from 63% of 99 procedures to 90% of 48 procedures ( P = 0.0007) after implementation of the adrenal vein sampling Accuracy Kit. Failure of right adrenal vein cannulation was the main reason for an unsuccessful study. Radiation dose decreased from 34.2 Gy.cm2 (interquartile range, 15.8–85.9) to 15.7 Gy.cm2 (6.9–47.3) ( P = 0.009). No complications were noted, and implementation costs were minimal.

Conclusions

Point-of-care cortisol measurement during adrenal vein sampling improved cannulation success rates and reduced radiation exposure. The use of the adrenal vein sampling Accuracy Kit is now standard practice at our centre.

PCSK9 in context: A contemporary review of an important biological target for the prevention and treatment of atherosclerotic cardiovascular disease

The identification of the critical role of proprotein convertase subtilisin/kexin type 9 (PCSK9) has rapidly led to the development of PCSK9 inhibition with monoclonal antibodies (mAbs). PCSK9 mAbs are already in limited clinical use and are the subject of major cardiovascular outcomes trials, which, if universally positive, could see much wider clinical application of these agents. Patients with familial hypercholesterolaemia are the most obvious candidates for these drugs, but other patients with elevated cardiovascular risk, statin intolerance or hyperlipoproteinaemia(a) may also benefit. PCSK9 mAbs, administered once or twice monthly, reduce LDL cholesterol levels by 50% to 70%, and appear to be safe and acceptable to patients over at least 2 years of treatment; however, treatment-emergent adverse effects are not always identified in clinical trials, as well-evidenced by statin myopathy. Inclisiran is a promising RNA-based therapy that promotes the degradation of PCSK9 mRNA transcripts and has similar efficacy to mAbs, but with a much longer duration of action. The cost-effectiveness and long-term safety of therapies targeted at inhibiting PCSK9 remain to be demonstrated if they are to be used widely in coronary prevention.

Isolated brachydactyly type E and idiopathic pancreatitis in a patient presenting to a lipid disorders clinic

An 18-year-old female tertiary student was referred to a lipid clinic with hypertriglyceridaemia discovered after presentation with acute pancreatitis. The patient's only medication was l-thyroxine for treatment of hypothyroidism. She was overweight, normotensive, with unremarkable facies. However, she had hypermobile hand joints and brachydactyly resulting in loss of left 3-5 and right 4 and 5 knuckle definitions. Radiography revealed shortening of metacarpals 3-5 on the left and 4 and 5 on the right. Her mother had similar skeletal changes, consistent with a dominant mode of inheritance. Abnormally short digits involving the metacarpals, classified as brachydactyly type E, can be isolated or occur as part of a syndrome. Turner syndrome, Albright hereditary osteodystrophy, hypertension with brachydactyly, chromosome 2q37 microdeletion and PTHLH mutations were excluded following clinical, biochemical and genetic testing. No specific treatment was required. Genetic testing for isolated and syndromic forms of brachydactyly facilitates family screening and prepregnancy counselling.

Anacetrapib for the treatment of dyslipidaemia: the last bastion of the cholesteryl ester transfer protein inhibitors?

INTRODUCTION

Inhibition of cholesteryl ester transfer protein (CETP) has emerged as a potential way to decrease cardiovascular risk by raising high density lipoprotein (HDL) cholesterol and lowering low density lipoprotein (LDL) cholesterol concentrations. However, high profile withdrawals of several CETP inhibitors have cast doubt over this hypothesis. Despite this concern, anacetrapib appears to be safe, well-tolerated and delivers a substantial increases in HDL cholesterol and reductions in LDL cholesterol as monotherapy and when combined with a statin.

AREAS COVERED

We discuss the role of CETP and HDL cholesterol as therapeutic targets, describe the pharmacokinetics and pharmacodynamics of anacetrapib, as well as report on the recent clinical trials.

EXPERT OPINION

The focus of CETP inhibition has shifted from HDL cholesterol-raising to LDL cholesterol-lowering. Although anacetrapib appears to be safe and is effective in altering lipid-related biochemical parameters of interest, its effect on cardiovascular outcomes remains unknown. Extrapolation of LDL cholesterol lowering to improved cardiovascular outcomes is not possible, because LDL and HDL functionality in the setting of anacetrapib treatment is unclear. The results of the phase III REVEAL randomised controlled trial will be critical for anacetrapib to establish a place in clinical care.

Liver transplantation for the treatment of homozygous familial hypercholesterolaemia in an era of emerging lipid-lowering therapies

Homozygous familial hypercholesterolaemia (FH) causes severe premature coronary artery disease because of very high levels of low density lipoprotein (LDL)-cholesterol. Standard lipid-lowering drugs and LDL-apheresis may not be sufficiently effective. Liver transplantation replaces defective LDL receptors and vastly improves the lipid profile, and we present the first report of an Australian adult to receive this treatment. Emerging drug treatments for FH may be alternatives to LDL-apheresis and transplantation, but long-term safety and efficacy data are lacking for all of these options.

Lipoprotein apheresis and new therapies for severe familial hypercholesterolemia in adults and children

Familial hypercholesterolemia (FH), the most common and severe monogenic form of hypercholesterolemia, is an autosomal co-dominant disease characterized by an increased plasma low density lipoprotein (LDL)-cholesterol concentration and premature coronary heart disease (CHD). The clinical phenotype depends on the gene involved and severity of mutation (or mutations) present. Patients with homozygous or compound heterozygous FH have severe hypercholesterolemia (LDL-cholesterol >13 mmol/L) due to a gene dosing effect and without treatment have accelerated atherosclerotic CHD from birth, and frequently die of CHD before age 30. Cholesterol-lowering therapies have been shown to reduce both mortality and major adverse cardiovascular events in individuals with FH. Lipoprotein apheresis concomitant with lipid-lowering therapy is the treatment of choice for homozygous FH. This article describes the rationale and role of lipoprotein apheresis in the treatment of severe FH and outlines the recent advances in new pharmacotherapies for this condition.

An uncommon Essex-Lopresti fracture dislocation with radial displacement in distal direction: diagnosis and surgical treatment of a rare case

Essex-Lopresti injuries are rare and present a clinical challenge. Incomplete diagnosis and treatment can lead to long-term instability, pain and functional impairment. We report on a clinical case of proximal radioulnar joint (PRUJ) and distal radioulnar joint (DRUJ) dislocation with unusual distal radial displacement and associated radial head shear fracture. The case was managed with closed reduction of the PRUJ and DRUJ followed by open reduction and fixation of the radial head. A high index of suspicion with thorough examination of the elbow, forearm and wrist and comprehensive imaging was important in reaching a complete diagnosis for appropriate treatment. Anatomical reduction of the PRUJ and DRUJ is essential to achieve optimal functional outcomes. Six months following the injury the patient made a satisfactory recovery with full range of movement; however, she continued to have mild to moderate general and moderate work-related disability.

Characterization of cytosolic glutathione peroxidase and phospholipid-hydroperoxide glutathione peroxidase genes in rainbow trout (Oncorhynchus mykiss) and their modulation by in vitro selenium exposure

Selenium (Se) is an oligonutrient with both essential biological functions and recognized harmful effects. As the selenocysteine (SeCys) amino acid, selenium is integrated in several Se-containing proteins (selenoproteins), many of which are fundamental for cell homeostasis. Nevertheless, selenium may exert toxic effects at levels marginally above those required, mainly through the generation of reactive oxygen species (ROS). The selenium chemical speciation can strongly affect the bioavailability of this metal and its impact on metabolism, dictating the levels that can be beneficial or detrimental towards an organism. Glutathione peroxidase (GPxs) is the largest and the most studied selenoprotein family. Cytosolic glutathione peroxidase (cGPx, GPx1) and phospholipid hydroperoxide glutathione peroxidase (PHGPx, GPx4) are widely distributed throughout tissues, and play a pivotal role in regulating the oxidative status in the cell. In this study we have cloned GPx1 and GPx4 genes in rainbow trout (Oncorhynchus mykiss). The constitutive mRNA expression of these GPx genes was examined in 18 trout tissues and their responsiveness to Se availability was analysed using a rainbow trout liver cell line (RTL). An inorganic (sodium selenite, Na2SeO3) and organic (selenocysteine, Cys-Se-Se-Cys) selenocompound have been used as Se sources. GPx1 activity was also tested to verify the impact of transcript changes on the enzymatic function of these molecules. To understand if the results obtained from the transcript expression analysis were due to Se bioavailability or generation of ROS, the cytoxicity of the two selenocompounds was tested by measuring the impact of Se on cell membrane integrity. Lastly, Se availability was quantified by mass spectrophotometry to determine the amount of Se in the cell culture media, the Se background due to the foetal calf serum supplement and the contribution from the two selenocompounds used in the treatments. Three isoforms of genes for both GPx1 (GPx1a, 1b1 and 1b2) and GPx4 (GPx4a1, a2 and b) have been identified. The discovery of a third gene encoding for GPx1 and GPx4 hints that salmonids may have the biggest selenoproteome amongst all vertebrates. Transcripts of GPx4 genes were more highly expressed in most tissues examined in vivo (except blood, head kidney and spleen), whereas those of the GPx1 genes were more responsive to selenium exposure in vitro, especially to the organic form. Interestingly, GPx1a was the most sensitive to selenium availability in non stressful conditions, whereas GPx1b1 and GPx1b2 were highly induced by exposure to selenium levels that had some toxic effects on the cells. Although the different concentrations tested of the two selenocompounds modulate GPx1 transcript expression to various degrees, no significant change of GPx1 enzymatic activity was detectable. Our results lead us to conclude that trout GPx1 transcripts expression level may represent a sensitive biomarker for selenium intake, helping to evaluate if selenium concentration and chemical speciation impact on cell homeostasis.

Circadian desynchrony and metabolic dysfunction; did light pollution make us fat?

Circadian rhythms are daily oscillations in physiology and behaviour that recur with a period of 24h, and that are entrained by the daily photoperiod. The cycle of sunrise and sunset provided a reliable time cue for many thousands of years, until the advent of artificial lighting disrupted the entrainment of human circadian rhythms to the solar photoperiod. Circadian desynchrony (CD) occurs when endogenous rhythms become misaligned with daily photoperiodic cycles, and this condition is facilitated by artificial lighting. This review examines the hypothesis that chronic CD that has accompanied the availability of electric lighting in the developed world induces a metabolic and behavioural phenotype that is predisposed to the development of obesity. The evidence to support this hypothesis is based on epidemiological data showing coincidence between the appearance of obesity and the availability of artificial light, both geographically, and historically. This association links CD to obesity in humans, and is corroborated by experimental studies that demonstrate that CD can induce obesity and metabolic dysfunction in humans and in rodents. This association between CD and obesity has far reaching implications for human health, lifestyle and work practices. Attention to the rhythmicity of daily sleep, exercise, work and feeding schedules could be beneficial in targeting or reversing the modern human predisposition to obesity.

The influence of renal threshold on the interpretation of urine tests for glucose in diabetic patients

A knowledge of the renal threshold for glucose is important in the interpretation of urine tests in diabetes. We describe a simple method for determining renal threshold from blood and urine tests performed by the patients themselves. In a group of 65 insulin-dependent diabetic patients there was a wide variation in renal threshold, with a mean of 130 mg/dl (range 54-180 mg/dl). Threshold tended to rise with age, and it is suggested that the higher the renal threshold, the higher is the mean blood glucose achieved by the patient (r = 0.50, P = < 0.001). The change in blood glucose required to convert urine tests from 0% to 2% is very variable and ranged from 36 to 288 mg/dl (mean 110 mg/dl). The simple method that we describe may improve understanding of the significance of urine test results without the necessity for hospital admission.

Diabetic autonomic neuropathy. The diagnostic value of heart rate monitoring

The use of heart rate monitoring in the diagnosis of diabetic autonomic neuropathy, and its value in observing the natural history of this disorder, has been assessed. Two tests were used: measurement of heart rate variation during deep breathing and of heart rate change on standing up. Two hundred and eighty seven diabetics aged between 20 and 49 years were studied, and 21 of them were observed repeatedly over 3 to 5 years. Heart rate variation (HRV) on deep breathing proved to be the more sensitive diagnostic index of autonomic neuropathy and was abnormal or borderline in 62 of 64 patients with established autonomic symptoms. Autonomic abnormalities were also detected in some diabetics without autonomic symptoms especially in those with peripheral neuropathy, 30% of whom had abnormal HRV on deep breathing. Abnormal tests appeared to represent permanent autonomic damage and may be present for years without the development of autonomic symptoms, occasionally (7%) preceding any other manifestation of diabetic neuropathy. Serial observations of HRV on deep breathing over 3 to 5 years showed little change, although overall there was a small deterioration of autonomic function, with a decrease of HRV score of 1.0 per year. The tests used are simple, and provide quantitative bedside measurements of autonomic function. When heart rate variation is normal, autonomic neuropathy is virtually excluded.

Sickle cell trait and diabetic retinopathy

The presence of sickle cell trait and the prevalence and severity of retinopathy were assessed in 124 Negro diabetics. Sickle cell trait had no adverse effect on diabetic retinopathy.

Cardiorespiratory arrest and diabetic autonomic neuropathy

Twelve cardiorespiratory arrests in eight neuropathy are reported. Only one patient died at the time, but two others subsequently died suddenly at home. There was no evidence of myocardial infarction, cardiac arrhythmia, or hypoglycaemia at the time of arrest. In most of the episodes there was some interference with respiration, either by anaesthesia, drugs, or bronchopneumonia. Five of the episodes occured during or immediately after anaesthesia. It is suggested that the arrests were caused by defective respiratory rather than cardiovascular reflexes. Cardiorespiratory arrest appears to be a specific feature of diabetic autonomic neuropathy and may contribute to the mortality of this condition.

Recessive inheritance of diabetes: the syndrome of diabetes insipidus, diabetes mellitus, optic atrophy and deafness

A few rare syndromes have been delineated in which diabetes mellitus is inherited in association with other conditions. This paper describes five patients, including four siblings in one family, who have diabetes insipidus, diabetes mellitus, optic atrophy and deafness (the DIDMOAD syndrome). The parents of both families are normal but are first cousins. All the patients have insulin-dependent diabetes mellitus with a typical juvenile-onset. The onset of diabetes insipidus was insidious and the symptoms could easily have been ascribed to poor control of diabetes mellitus. The importance of diagnosing diabetes insipidus is that all these patients had dilatation of the urinary tract varying from mild hydroureter to severe hydronephrosis and this improved with treatment of the diabetes insipidus. It is suggested that patients with diabetes mellitus and optic atrophy should have regular screening tests for diabetes insipidus since it is likely that they represent cases of the full syndrome with incomplete clinical expression. The occurrence of this rare syndrome in four siblings of unaffected parents indicates that the syndrome is due to a recessive gene, but the pathogenesis is unknown.

Cardiovascular effects of insulin

Insulin increased the heart rates of seven diabetics with normal cardiovascular reflexes. This effect, which was not due to hypoglycaemia, was greater in the upright than in the supine position and was produced by as little as one unit given intravenously. This increase in heart rate may be a compensatory response to maintain cardiac output.

Provocation of postural hypotension by insulin in diabetic autonomic neuropathy

The effect of insulin administration on blood pressure has been investigated in eight diabetes with autonomic neuropathy. Systolic and diastolic pressures fell considerably after insulin in all of them. This effect was aggravated by tilting to the vertical position. Five patients fainted when upright with systolic blood pressures less than 50 mm. Hg. This hypotensive effect of insulin occurs whether it is administered intravenously, intramuscularly, or subcutaneously. The onset of the effect is almost immediate after intravenous insulin, is progressive, and may last for several hours. It coincides with a falling blood glucose level and occurs before hypoglycemic levels are reached, and it may be present when the blood glucose level is still elevated. Diurnal variations of postural hypotension have been recorded in some patients, the standing blood pressure falling with the onset of insulin action and rising again as the latter declines. Some of our patients were unable to differentiate between symptoms of hypoglycemia and hypotension. Postural hypotension may account for some episodes of sudden loss of consciousness without warning, usually attributed to hypoglycemia.

Disappearing diabetes

For five years a nurse was treated for diabetes mellitus. She was found to have tampered with her blood and urine tests and later was believed to have fabricated her condition from the outset.

Treatment of diabetic coma with continuous low-dose infusion of insulin

Thirty-eight patients in diabetic coma from four different centres were treated with a continuous low-dose intravenous infusion of insulin at an average dose of 7.2 IU/hr. All patients recovered rapidly except for one profoundly shocked patient who died. The mean fall in plasma glucose was 58% four hours after the start of insulin. Blood ketone bodies and plasma free fatty acids showed a similar response. There was no significant difference in plasma glucose response according to severity of acidosis or previous treatment with insulin. Hypokalaemia was uncommon. In the treatment of diabetic coma this technique has proved simple, safe, and effective.