Phenytoin-induced improvement in muscle cramping and insulin action in three patients with the syndrome of insulin resistance, acanthosis nigricans, and acral hypertrophy

Drug-induced mitochondrial toxicity: Risks of developing glucose handling impairments

Mitochondrial impairment has been associated with the development of insulin resistance, the hallmark of type 2 diabetes mellitus (T2DM). However, the relationship between mitochondrial impairment and insulin resistance is not fully elucidated due to insufficient evidence to support the hypothesis. Insulin resistance and insulin deficiency are both characterised by excessive production of reactive oxygen species and mitochondrial coupling. Compelling evidence states that improving the function of the mitochondria may provide a positive therapeutic tool for improving insulin sensitivity. There has been a rapid increase in reports of the toxic effects of drugs and pollutants on the mitochondria in recent decades, interestingly correlating with an increase in insulin resistance prevalence. A variety of drug classes have been reported to potentially induce toxicity in the mitochondria leading to skeletal muscle, liver, central nervous system, and kidney injury. With the increase in diabetes prevalence and mitochondrial toxicity, it is therefore imperative to understand how mitochondrial toxicological agents can potentially compromise insulin sensitivity. This review article aims to explore and summarise the correlation between potential mitochondrial dysfunction caused by selected pharmacological agents and its effect on insulin signalling and glucose handling. Additionally, this review highlights the necessity for further studies aimed to understand drug-induced mitochondrial toxicity and the development of insulin resistance.

Biallelic POC1A variants cause syndromic severe insulin resistance with muscle cramps

OBJECTIVE

To describe clinical, laboratory, and genetic characteristics of three unrelated cases from Chile, Portugal, and Saudi Arabia with severe insulin resistance, SOFT syndrome, and biallelic pathogenic POC1A variants.

DESIGN

Observational study.

METHODS

Probands' phenotypes, including short stature, dysmorphism, and insulin resistance, were compared with previous reports.

RESULTS

Cases 1 (female) and 3 (male) were homozygous for known pathogenic POC1A variants: c.649C>T, p.(Arg217Trp) and c.241C>T, p.(Arg81*), respectively. Case 2 (male) was compound heterozygous for p.(Arg217Trp) variant and the rare missense variant c.370G>A, p.(Asp124Asn). All three cases exhibited severe insulin resistance, acanthosis nigricans, elevated serum triglycerides and decreased HDL, and fatty liver, resembling three previously reported cases. All three also reported severe muscle cramps. Aggregate analysis of the six known cases with biallelic POC1A variants and insulin resistance showed decreased birth weight and length mean (s.d.): -2.8 (0.9) and -3.7 (0.9) SDS, respectively), severe short stature mean (s.d.) height: -4.9 (1.7) SDS) and moderate microcephaly (mean occipitofrontal circumference -3.0 (range: -4.7 to -1.2)). These findings were similar to those reported for patients with SOFT syndrome without insulin resistance. Muscle biopsy in Case 3 showed features of muscle involvement secondary to a neuropathic process.

CONCLUSIONS

Patients with SOFT syndrome can develop severe dyslipidaemic insulin resistance, independent of the exonic position of the POC1A variant. They also can develop severe muscle cramps. After diagnosis, patients should be regularly screened for insulin resistance and muscle complaints.

Atherogenic Risk Factors among Young Indian Adults with Epilepsy on Treatment with Phenytoin: Need for Novel Therapeutic Strategies

Background

Risk for the development of coronary heart disease and diabetes is found to be more among people with epilepsy especially when on treatment. Redox imbalance contributes to this risk especially in India as it is the diabetic capital of the world with higher prevalence of inflammation.

Objectives

The aim of this study was to evaluate atherogenic risk factors; dyslipidemia, oxidative stress, and systemic inflammation among young Indian adults with epilepsy on treatment with Phenytoin.

Material and Methods

Three groups of age and gender-matched young subjects were recruited. Group 1-Healthy control subjects, Group 2- Newly diagnosed epileptic young adults with recent epileptic seizures, Group 3- Epileptic adults on treatment with Phenytoin for more than 6 months were recruited.

Results

Dyslipidemia was found among the newly diagnosed epileptic subjects in comparison to healthy subjects. The LDL-cholesterol further increased, and HDL-cholesterol further decreased in the third group treated with Phenytoin. Body mass index of these treated epileptic subjects was more in comparison to healthy control. Low-grade inflammation as assessed by hsCRP and oxidative stress were significantly higher among the newly diagnosed epileptic subjects when compared to the healthy controls which further increased on treatment with phenytoin. We found dyslipidemia, oxidative stress, and low-grade inflammation among newly diagnosed epileptic subjects which further increased on treatment with Phenytoin for more than 6 months.

Conclusion

From this study, we conclude that dyslipidemia, oxidative stress and low-grade inflammation are identified among the newly diagnosed young adult Indian epileptic patients. Phenytoin treatment further augmented these complications.

Syndrome of insulin resistance with acanthosis nigricans, acral hypertrophy and muscle cramps in an adolescent - a rare diagnosis revisited

The authors report a 14-y-old boy with insulin resistance, acanthosis nigricans, acral hypertrophy and muscle cramps. While there was a dramatic response of the muscle cramps to phenytoin therapy, some other features of metabolic syndrome did not respond to phenytoin therapy alone.

Design and clinical pilot testing of the model-based dynamic insulin sensitivity and secretion test (DISST)

BACKGROUND

Insulin resistance is a significant risk factor in the pathogenesis of type 2 diabetes. This article presents pilot study results of the dynamic insulin sensitivity and secretion test (DISST), a high-resolution, low-intensity test to diagnose insulin sensitivity (IS) and characterize pancreatic insulin secretion in response to a (small) glucose challenge. This pilot study examines the effect of glucose and insulin dose on the DISST, and tests its repeatability.

METHODS

DISST tests were performed on 16 subjects randomly allocated to low (5 g glucose, 0.5 U insulin), medium (10 g glucose, 1 U insulin) and high dose (20 g glucose, 2 U insulin) protocols. Two or three tests were performed on each subject a few days apart.

RESULTS

Average variability in IS between low and medium dose was 10.3% (p=.50) and between medium and high dose 6.0% (p=.87). Geometric mean variability between tests was 6.0% (multiplicative standard deviation (MSD) 4.9%). Geometric mean variability in first phase endogenous insulin response was 6.8% (MSD 2.2%). Results were most consistent in subjects with low IS.

CONCLUSIONS

These findings suggest that DISST may be an easily performed dynamic test to quantify IS with high resolution, especially among those with reduced IS.

Effects of AEDs on biomarkers in people with epilepsy: CRP, HbA1c and eGFR

The standardised mortality ratio in people with epilepsy is raised to between 2 and 3 compared with the general population. Some biomarker levels, including higher C-reactive protein (CRP), higher glycosylated haemoglobin (HbA1c) and lower estimated glomerular filtration rate (eGFR), are associated with an increase risk of premature mortality. These biomarkers were measured in 125 people with refractory epilepsy to estimate the potential effect of antiepileptic drug (AED) use on these markers. Multiple regression analysis showed that valproate (N=50) use was associated with 55% lower mean CRP concentrations and higher mean eGFR values; and phenytoin (N=32) use with 4% lower mean HbA1c values. These potentially represent health markers improved by AEDs. On the other hand, lamotrigine use (N=48) was associated with 13% lower mean eGFR and this may represent a negative effect on a health marker. These preliminary observations clearly require further controlled studies ideally in people on AED monotherapy.

Acanthosis nigricans

Acanthosis nigricans is a mucocutaneous eruption that occurs in a strikingly exuberant form as a marker for a highly malignant and rapidly fatal internal cancer. Recently, it has been recognized that acanthosis nigricans may also be a relatively common marker for increased long-term risk of the less dramatic but potentially serious systemic disorders associated with insulin resistance and compensatory increased insulin secretion.