Cardiac phenotype in familial partial lipodystrophy

OBJECTIVES

LMNA variants have been previously associated with cardiac abnormalities independent of lipodystrophy. We aimed to assess cardiac impact of familial partial lipodystrophy (FPLD) to understand the role of laminopathy in cardiac manifestations.

STUDY DESIGN

Retrospective cohort study.

METHODS

Clinical data from 122 patients (age range: 13-77, 101 females) with FPLD were analysed. Mature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with an LMNA variant were studied as proof-of-concept for future studies.

RESULTS

Subjects with LMNA variants had a higher prevalence of overall cardiac events than others. The likelihood of having an arrhythmia was significantly higher in patients with LMNA variants (OR: 3.77, 95% CI: 1.45-9.83). These patients were at higher risk for atrial fibrillation or flutter (OR: 5.78, 95% CI: 1.04-32.16). The time to the first arrhythmia was significantly shorter in the LMNA group, with a higher HR of 3.52 (95% CI: 1.34-9.27). Non-codon 482 LMNA variants were more likely to be associated with cardiac events (vs. 482 LMNA: OR: 4.74, 95% CI: 1.41-15.98 for arrhythmia; OR: 17.67, 95% CI: 2.45-127.68 for atrial fibrillation or flutter; OR: 5.71, 95% CI: 1.37-23.76 for conduction disease). LMNA mutant hiPSC-CMs showed a higher frequency of spontaneous activity and shorter action potential duration. Functional syncytia of hiPSC-CMs displayed several rhythm alterations such as early afterdepolarizations, spontaneous quiescence and spontaneous tachyarrhythmia, and significantly slower recovery in chronotropic changes induced by isoproterenol exposure.

CONCLUSIONS

Our results highlight the need for vigilant cardiac monitoring in FPLD, especially in patients with LMNA variants who have an increased risk of developing cardiac arrhythmias. In addition, hiPSC-CMs can be studied to understand the basic mechanisms for the arrhythmias in patients with lipodystrophy to understand the impact of specific mutations.

Insulin secretion-sensitivity index-2 could be a novel marker in the identification of the role of pancreatic iron deposition on beta-cell function in thalassemia major

The purpose of this study is to evaluate the impact of insulin secretion-sensitivity index-2 (ISSI-2) in the identification of the role of pancreatic iron deposition on beta-cell function in thalassemia major. Tissue iron stores were measured with magnetic resonance imaging (MRI) in the liver (R2), pancreas (R2*), and heart (T2*). ISSI-2 was assessed as a novel oral glucose tolerance test-based measure of beta-cell function. Also, the Stumvoll index showing the insulin sensitivity and Stumvoll index estimating first and second phase insulin secretion were calculated. Fourteen of the 51 Thalassemia Major patients, aged 8-34 (mean 21.1 ± 7.2) years-old, had either an impaired glucose tolerance test (n = 9, 17.6%) or diabetes mellitus (n = 5, 9.8%)-referred to as the glucose dysregulation (GD) group. The median serum ferritin and the mean liver R2 and cardiac T2* values were not significantly different between the GD and normal glucose tolerance (NGT, n = 37) groups whereas pancreas R2* was significantly higher in the GD group compared to the NGT group (p = 0.004). Patients with GD showed significantly lower ISSI-2 index (p < 0.001) as well as the Stumvoll index and Stumvoll first and second phase indices compared to those with NGT (p < 0.001). All patients with GD displayed a pancreas R2* >50 Hz and ISSI-2 <2. In conclusion, Pancreas R2* MRI combined with ISSI-2 index may be valuable parameters to identify patients at the highest risk for developing glucose dysregulation.

A new type of familial partial lipodystrophy: distinctive fat distribution and proteinuria

PURPOSE

To describe an interesting subtype of familial partial lipodystrophy (FPLD).

METHODS

The phenotype of this distinctive FPLD subtype was studied in three Turkish female siblings.

RESULTS

Mutation testing was negative for the genes associated with lipodystrophy syndromes. In MRI studies, fat loss was prominent in the posterior aspects of the proximal lower limbs, whilst some fat was preserved in the anterior, medial and lateral aspects. Remarkably, fat tissue was preserved in the distal part of the limbs. Local fat accumulation was observed in the mons pubis area. Asymmetrical fat loss was also remarkable in the upper extremities. All three patients had severe insulin resistance associated with diabetes mellitus, acanthosis nigricans, hypertriglyceridemia and hepatic steatosis. Abnormal amounts of proteinuria were detected in all three subjects. Renal biopsy showed mild tubular atrophy, interstitial fibrosis, irregular thickening and wrinkling of glomerular basal membranes, small areas of segmental sclerosis and pedicel effacement.

CONCLUSIONS

We reported a form of FPLD characterized by a striking pattern of highly selective partial fat loss and proteinuria.

The effect of long-term nicotine exposure on bone mineral density and oxidative stress in female Swiss Albino rats

PURPOSE

To evaluate the effect of long-term low or high-dose nicotine exposure on bone mass via measuring bone mineral density (BMD) and oxidant-antioxidant status markers.

METHODS

Thirty-five female Swiss Albino rats weighing 70 ± 10 g were divided as the control group (n = 12), low-dose nicotine group (n = 12) and high-dose nicotine group (n = 11). While the control group was given only normal drinking water, the low-dose nicotine group had 0.4 mg/kg per day and the high-dose nicotine group, 6.0 mg/kg per day of nicotine added to their water for the period of 1 year. BMD was determined with X-ray absorptiometry of lumbar vertebra, corpus femoris, proximal and distal femur. To evaluate oxidant-antioxidant status malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activities were determined.

RESULTS

When comparing the nicotine groups and controls, neither BMD nor oxidant-antioxidant status markers showed any statistically significant difference. In comparison to the controls, 12 months of high-dose oral nicotine exposure did not have a significant effect on BMD and low-dose nicotine exposure led to a statistically insignificant increase in BMD.

CONCLUSIONS

Contrary to common belief, the results of this study show that nicotine is not responsible for the decrease in BMD leading to osteoporosis frequently seen in smokers. However, there is a need to explore the other harmful materials in tobacco which may be responsible for the alterations seen in BMD of smokers.