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Ethiopathogeny of Familial Partial Lipodystrophy

Goal: Search for new genes related to familial partial Lipodystrophy and its pathogenetical mechanisms.

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David Araujo-Vilar
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An abnormal distribution of fatty tissues associated with certain tissue disorders is driven by disrupted fat cell differentiation. Type 2 familial partial lipodystrophy (FPLD2) is a genetic condition that results in fat being lost from the limbs and accumulating in the face and neck. Giovanna Lattanzi at the National Research Council of Italy in Bologna and co-workers found that fat cell (adipocyte) precursors did not clearly differentiate into either of the two main fatty tissue types, brown or white, in FPLD2 patients. White adipocyte precursors exhibited impaired lipid formation and abnormal levels of brown tissue markers. Conversely, brown adipocyte precursors showed high lipid levels and increased autophagy, a natural process involving degradation and recycling of cellular components. The neck is normally where brown fat accumulates, but FPLD2 patients had adipocytes there displaying white fat characteristics.
David Araujo-Vilar
added 2 research items
Laminopathies are genetic disorders associated with alterations in nuclear envelope proteins, known as lamins. The LMNA gene encodes lamins A and C, and LMNA mutations have been linked to diseases involving fat (type 2 familial partial lipodystrophy [FPLD2]), muscle (type 2 Emery-Dreifuss muscular dystrophy [EDMD2], type 1B limb-girdle muscular dystrophy [LGMD1B], and dilated cardiomyopathy), nerves (type 2B1 Charcot-Marie-Tooth disease), and premature aging syndromes. Moreover, overlapping syndromes have been reported. This study aimed to determine the genetic basis of an overlapping syndrome in a patient with heart disease, myopathy, and features of lipodystrophy, combined with severe metabolic syndrome. We evaluated a 54-year-old woman with rheumatoid arthritis, chronic hypercortisolism (endogenous and exogenous), and a history of cured adrenal Cushing syndrome. The patient presented with a complex disorder, including metabolic syndrome associated with mild partial lipodystrophy (Köbberling-like); mild hypertrophic cardiomyopathy, with Wolff-Parkinson- White syndrome and atrial fibrillation; and limb-girdle inflammatory myopathy. Mutational analysis of the LMNA gene showed a heterozygous c.1634G>A (p.R545H) variant in exon 10 of LMNA. This variant has previously been independently associated with FPLD2, EDMD2, LGMD1B, and heart disease. We describe a new, LMNA-associated, complex overlapping syndrome in which fat, muscle, and cardiac disturbances are related to a p.R545H variant.
David Araujo-Vilar
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The objective of our research was to identify the mathematical model that would best define the relationship between obesity, insulin resistance (IR), and beta-cell function. Eighty-seven healthy subjects with a wide range of body mass index (BMI) were studied. Insulin sensitivity (IS) was calculated using Bergman's minimal model. Acute insulin response (AIRg) was calculated as the secretion of insulin during the first 10 minutes following a glucose bolus. IS x AIRg was used as an index of insulin-mediated glucose uptake (IMGU). The relationships among BMI, IS, fasting plasma insulin (FPI), and AIRg were studied in linear relationship terms and in terms of the hyperbolic function. Where the best fit was linear, the Jones and Molitoris method was used to investigate whether the 2-line fit was significantly better. The division of the population into BMI quartiles shows that from the third quartile, IS (12.4 +/- 6.0 v 11.0 +/- 6.4 v 4.8 +/- 1.8 v 3.2 +/- 2.0 E-5 min(-1)[pmol/L](-1), P < .01) diminishes. Nevertheless, a plateau was established between the last 3 quartiles for IS x AIRg. AIRg related to BMI via a breakpoint of 29.3 kg . m(-2). The best fits for both the BMI/IS and BMI/FPI relationships were hyperbolic. Our data indicate that obesity represents a continuum of IR, with severity increasing as BMI increases. Nevertheless, above a value of 29 kg . m(-2) and despite great increases in adiposity, IS tends to descend slowly. Moreover, there seems to be an IMGU threshold at a BMI value of approximately 27 kg . m(-2), above which an increase in adiposity leads to a greater fall in IS x AIRg. Furthermore, this threshold also appears to affect pancreatic response to a glucose stimulus.
David Araujo-Vilar
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Purpose: The purpose of this study is to summarize the effectiveness and safety of metreleptin in patients with congenital or acquired generalized lipodystrophy. Methods: Patients (n = 66) aged ≥6 months had lipodystrophy, low circulating leptin, and ≥1 metabolic abnormality (diabetes mellitus, insulin resistance, or hypertriglyceridemia). Metreleptin dose (once or twice daily) was titrated to a mean dose of 0.10 mg/kg/day with a maximum of 0.24 mg/kg/day. Means and changes from baseline to month 12 were assessed for glycated hemoglobin (HbA1c), fasting triglycerides (TGs), and fasting plasma glucose (FPG). Additional assessments included the proportions of patients achieving target decreases in HbA1c or fasting TGs at months 4, 12, and 36, medication changes, and estimates of liver size. Treatment-emergent adverse events (TEAEs) were recorded. Results: Significant mean reductions from baseline were seen at month 12 for HbA1c (-2.2%, n = 59) and FPG (-3.0 mmol/L, n = 59) and mean percent change in fasting TGs (-32.1%, n = 57) (all p ≤ 0.001). Reductions from baseline over time in these parameters were also significant at month 36 (all p < 0.001, n = 14). At month 4, 34.8% of patients had a ≥1% reduction in HbA1c and 62.5% had a ≥30% reduction in fasting TGs; at month 12, 80% of patients had a ≥1% decrease in HbA1c or ≥30% decrease in TGs, and 66% had a decrease of ≥2% in HbA1c or ≥40% decrease in TGs. Of those on medications, 41%, 22%, and 24% discontinued insulin, oral antidiabetic medications, or lipid-lowering medications, respectively. Mean decrease in liver volume at month 12 was 33.8% (p < 0.001, n = 12). Most TEAEs were of mild/moderate severity. Conclusions: In patients with generalized lipodystrophy, long-term treatment with metreleptin was well tolerated and resulted in sustained improvements in hypertriglyceridemia, glycemic control, and liver volume.
David Araujo-Vilar
added a research item
The nuclear lamina is a complex reticular structure that covers the inner face of the nucleus membrane in metazoan cells. It is mainly formed by intermediate filaments called lamins, and exerts essential functions to maintain the cellular viability. Lamin A/C provides mechanical steadiness to the nucleus and regulates genetic machinery. Laminopathies are tissue-specific or systemic disorders caused by variants in LMNA gene (primary laminopathies) or in other genes encoding proteins which are playing some role in prelamin A maturation or in lamin A/C function (secondary laminopathies). Those disorders in which adipose tissue is affected are called laminopathic lipodystrophies and include type 2 familial partial lipodystrophy and certain premature aging syndromes. This work summarizes the main clinical features of these syndromes, their associated comorbidities and the clues for the differential diagnosis with other lipodystrophic disorders.
David Araujo-Vilar
added 2 research items
Ageing is thought to be a polygenic and stochastic process in which multiple mechanisms operate at the same time. At the level of the individual organism ageing is associated with a progressive deterioration of health and quality of life, sharing common features such as: alopecia and grey hair, loss of audition, macular degeneration, neurodegeneration, cardiovascular diseases, osteoporosis, cataract formation, type-2 diabetes, lipodystrophies; a generally increased susceptibility to infection, autoimmune disorders and diseases such as cancer; and an impaired ability to cope with stress. Recent studies of mechanisms involved in the ageing process are contributing to the identification of genes involved in longevity. Monogenic heritable disorders causing premature ageing, and animal models have contributed to the understanding of some of the characteristic organism-level features associated with human ageing. Werner syndrome and Hutchinson-Gilford progeria syndrome are the best characterized human disorders. Werner syndrome patients have a median life expectancy of 47 years with clinical conditions from the second decade of life. Hutchinson-Gilford progeria syndrome patients die at a median age of 11-13 years with clinical conditions appearing soon after birth. In both syndromes, alterations in specific genes have been identified, with mutations in the WRN and LMNA genes respectively being the most closely associated with each syndrome. Results from molecular studies strongly suggest an increase in DNA damage and cell senescence as the underlying mechanism of pathological premature ageing in these two human syndromes. The same general mechanism has also been observed in human cells undergoing the normal ageing process. In the present article the molecular mechanisms currently proposed for explaining these two syndromes, which may also partly explain the normal ageing process, are reviewed.
Context: Steroid 11beta-hydroxylase (CYP11B1) deficiency (11OHD) is the second most common form of congenital adrenal hyperplasia (CAH). Cases of nonclassic 11OHD are rare compared with the incidence of nonclassic 21-hydroxylase deficiency. Objective: The aim of the study was to analyze the functional consequences of seven novel CYP11B1 mutations (p.M88I, p.W116G, p.P159L, p.A165D, p.K254_A259del, p.R366C, p.T401A) found in three patients with classic 11OHD, two patients with nonclassic 11OHD, and three heterozygous carriers for CYP11B1 mutations. Methods: We conducted functional studies employing a COS7 cell in vitro expression system comparing wild-type (WT) and mutant CYP11B1 activity. Mutants were examined in a computational three-dimensional model of the CYP11B1 protein. Results: All mutations (p.W116G, p.A165D, p.K254_A259del) found in patients with classic 11OHD have absent or very little 11beta-hydroxylase activity relative to WT. The mutations detected in patients with nonclassic 11OHD showed partial functional impairment, with one patient being homozygous (p.P159L; 25% of WT) and the other patient compound heterozygous for a novel mild p.M88I (40% of WT) and the known severe p.R383Q mutation. The two mutations detected in heterozygous carriers (p.R366C, p.T401A) also reduced CYP11B1 activity by 23 to 37%, respectively. Conclusion: Functional analysis results allow for the classification of novel CYP11B1 mutations as causative for classic and nonclassic 11OHD, respectively. Four partially inactivating mutations are predicted to result in nonclassic 11OHD. These findings double the number of mild CYP11B1 mutations previously described as associated with mild 11OHD. Our data are important to predict phenotypic expression and provide important information for clinical and genetic counseling in 11OHD.
David Araujo-Vilar
added 2 research items
Beradinelli-Seip congenital generalized lipodystrophy is a rare autosomal recessive disorder characterized by near-complete absence of adipose tissue, Herculean appearance, insulin resistance, hypoleptinaemia and diabetes mellitus. The aim of this study was to investigate the in vitro effects of pioglitazone on the expression of genes involved in adipogenesis in fibroblasts from a patient with this condition due to a seipin mutation. Primary cultures of fibroblasts from the skin of the patient were obtained. Fibroblasts were treated with classic adipose differentiation medium, with and without pioglitazone. Several adipogenes were evaluated by real-time reverse transcriptase-polymerase chain reaction and western blotting. Intracellular localization of prelamin A was studied by immunofluorescence microscopy. The expression of the adipogenic genes PPARG, LPL, LEP and SLC2A4 was reduced in lipodystrophic fibroblasts, while treatment with pioglitazone increased the expression of these genes. Moreover, and unexpectedly, we found an accumulation of farnesylated prelamin A in lipodystrophic fibroblasts. The process of adipocyte differentiation is compromised in patients with Beradinelli-Seip congenital lipodystrophy owing to diminished expression of the regulatory genes involved, which pioglitazone treatment partially rescues. Prelamin A accumulation establishes a link with other types of familial lipodystrophies, as familial partial lipodystrophy.
Familial partial lipodystrophy of the Dunnigan type (FPLD2) presents with a decrease of subcutaneous adipose tissue (SAT) in the limbs and trunk. As thyroid hormones (TH) play an important role in adipogenesis, we studied if SAT from subjects with FPLD2 have changes in the gene expression levels of monocarboxylate transporter 8 (MCT8), a TH transporter, and TH nuclear receptors and in iodothyronine deiodinases (DIOs) expression and activities that could affect TH bioavailability and action in white adipose tissue. Seven subjects with FPLD2 and 10 healthy controls were studied. Two biopsies of SAT were obtained from each subject, one near the umbilicus and the other from the thigh. Expression of MCT8, DIO2, DIO3, THRA1, THRB1, and RXRG mRNAs were quantified by real-time polymerase chain reaction. DIO1 and DIO2 activities in adipose tissue homogenates were determined. Serum thyroid-stimulating hormone and TH levels were measured by chemiluminescence. Subjects with FPLD2 had lower levels of MCT8 mRNA expression in the thigh than in the abdomen SAT, and lower than in the abdomen and thigh SAT from control subjects. FPLD2 subjects also had higher DIO2 expression and activity in the thigh than in the abdomen SAT and higher than in controls. Thigh SAT from subjects with FPLD2 has lower expression of MCT8 and higher DIO2 expression and activity than abdominal SAT, suggesting that changes in local TH metabolism may occur in areas with lipoatrophy. DIO2 expression and activity in SAT suggest that DIO2 can regulate the metabolism and action of TH in human white adipose tissue.
David Araujo-Vilar
added a research item
Objective: Type 1 and type 2 familial partial lipodystrophies (FPLD) are characterized by the loss or increase of subcutaneous fat in certain body regions, as well as metabolic disorders. Higher muscle volume and mass have also been described. However, so far, possible bone involvement has not been studied. The aim of this study was to evaluate bone mineral density (BMD) in patients with type 1 and type 2 FPLD. Methods: A total of 143 women were selected and distributed into three groups (17 women with FPLD2, 82 women with FPLD1 and 44 non-lipodystrophic obese female controls). A thorough history and physical examination were carried out on all subjects, as well as the measurement of anthropometric features. BMD along with fat and fat-free mass (FFM) were determined by DXA (dual-energy X-ray absorptiometry). Statistical analyses, primarily using the χ(2) , ANOVA and ANCOVA tests, were performed, using age, height, fat and FFM as covariables. Results: After eliminating the possible influences of age, height, fat and FFM, we observed that there were no significant differences in total BMD between patients with FPLD and the control group, showing total BMD values of 1.092 ± 0.037 g/cm(2) in the FPLD2 group, 1.158 ± 0.013 g/cm(2) in the FPLD1 group and 1.173 ± 0.018 g/cm(2) in the control group (p = 0.194). Similarly, no significant differences were found in segmental BMD. Conclusions: Unlike in other types of laminopathy in which bone is affected, in the case of FPLD there are no differences in BMD compared to non-lipodystrophic subjects. This article is protected by copyright. All rights reserved.
David Araujo-Vilar
added 7 research items
Familial partial lipodystrophy are Mendelian disorders involving abnormal body fat distribution and insulin resistance. The current classification includes the Köbberling syndrome (type 1 familial partial lipodystrophy), characterized by fat loss in the lower limbs and abnormal fat accumulation in other areas. Type 1 familial partial lipodystrophy appears to be heritable, but little is known about it, including putative contributing mutations. We aimed to characterize this syndrome better by evaluating a group of women with phenotypic features of type 1 familial partial lipodystrophy. This is a case-controlled study in which 98 women with type 1 familial partial lipodystrophy that lacked classical mutations known to cause familial partial lipodystrophy were compared with 60 women without lipodystrophy and 25 patients with type 2 familial partial lipodystrophy (Dunnigan disease). Clinical course, body composition by dual-energy X-ray absorptiometry, HbA1c, lipid profile, insulin, leptin and family history were evaluated in all of the participants. Analyses of receiver-operating characteristic curve were performed for type 1 familial partial lipodystrophy diagnosis, comparing different truncal/limbs ratios. Among patients with type 1 familial partial lipodystrophy, 68 % developed recognizable lipodystrophy before adolescence, and most displayed an autosomal-dominant pattern (86 %). Women with type 1 familial partial lipodystrophy had less lower-limb adipose tissue than women without lipodystrophy, but significantly more than patients with Dunnigan disease. Moreover, metabolic disturbances occurred more frequently in the type 1 familial partial lipodystrophy group (81 %) than in the non-lipodystrophic group (30 %, p<0.05). The severity of metabolic disturbances was inversely proportional to the percentage of fat in the lower extremities and directly proportional to the amount of visceral adipose tissue. Metabolic profiles were worse in type 1 familial partial lipodystrophy than in Dunnigan disease. According to the receiver-operating characteristic curve analysis, the best ratio was subscapular/calf skinfolds (KöB index), with a cut-off value of 3.477 (sensitivity: 89 %; specificity: 84 %). Type 1 familial partial lipodystrophy was an early-onset, autosomal-dominant lipodystrophy, characterized by fat loss in the lower limbs and abnormal fat accumulation in the abdominal visceral region, associated to insulin resistance and metabolic disorders. A KöB index >3.477 is highly suggestive of this syndrome.
A variety of missense mutations in LMNA (the gene for lamin C and prelamin A) cause familial partial lipodystrophy (FPLD), a disease associated with reduced adipose tissue, particularly in the limbs. Several studies have reported that fibroblasts from FPLD subjects have an accumulation of prelamin A. Those findings were intriguing but also perplexing because many of the LMNA missense mutations associated with lipodystrophy are located in sequences distant from the sequences required for the farnesylation of prelamin A and ZMPSTE24-mediated conversion of prelamin A to mature lamin A. Here, we revisited the issue of prelamin A accumulation in the setting of FPLD mutations. We used western blots with lamin A/C antibodies and prelamin A–specific monoclonal antibodies to assess prelamin A levels in wild-type fibroblasts and fibroblasts carrying LMNA mutations associated with lipodystrophy (R482W, I299V, C591F, T528M). None of the mutant fibroblasts exhibited an accumulation of prelamin A. Also, the amount of prelamin A accumulation in response to lopinavir (an inhibitor of ZMPSTE24) was similar in wild-type and mutant fibroblasts. Thus, the LMNA lipodystrophy mutations that we examined did not lead to prelamin A accumulation, nor did they render those cells more susceptible to prelamin A accumulation when ZMPSTE24 was inhibited by lopinavir.
David Araujo-Vilar
added a research item
Phenotypic features appeared after puberty in female, but not male subjects with familial partial lipodystrophy (FPLD). We have studied anthropometrical, clinical, and metabolic gender differences in a Spanish family with FPLD resulting from a lamin A/C gene mutation, R482W. Genetic studies were carried out on 14 members of the family. In eleven heterozygous mutation carriers (6 men, 5 women), body composition was evaluated by bioelectric impedance analysis, skin-fold measurements were taken, and lipid profiles were drawn. Moreover, plasma glucose, insulin, and leptin were determined, and insulin resistance and beta cell response were evaluated using HOMA. Ten healthy women and 10 healthy men matched for age and body mass index were used as control group. Body composition was similar in these patients to normal people. However, skin-folds of extremities were thinner in FPLD women compared with those of control subjects, but not in men. The affected women, but not men, showed hypoleptinaemia, insulin resistance, and beta-cell hyperresponse compared with unaffected women. The lipid profile was normal in the young patients, irrespective of sex. Type 2 diabetes mellitus and hypertriglyceridaemia were detected in old and overweight patients only. In conclusion, molecular diagnosis allows us to demonstrate that women with FPLD present both adipose tissue and biochemical abnormalities early in life, and this did not happen in affected men.
David Araujo-Vilar
added 3 research items
Lipodystrophies are rare diseases which affect adipose tissue, usually metabolically active tissue, both subcutaneous and visceral, and which are characterized by fat loss. This loss of fat can affect almost the entire body, as in generalized lipodystrophies, or only part of the body, as in partial and localized lipodystrophies. The causes of lipodystrophies can be genetic or acquired, and the latter usually have an immunological basis. Lipodystrophies are frequently associated with a series of metabolic complications such as insulin resistance, hypertriglyceridemia, low HDLcholesterol and hypoleptinemia, which are usually related to the extent of fat loss. Acanthosis nigricans, hepatic steatosis and polycystic ovaries are also frequently associated. The aim of this review is to describe the clinical features and diagnostic criteria of the different types of lipodystrophies, as well as to provide further information on their molecular bases.
Lipodystrophies are a heterogeneous group of diseases characterized by abnormal fat distribution. Familial partial lipodystrophy 2 (FPLD2) is due to mutations in the LMNA gene. Previous studies have suggested that LMNA mutations 5' to the nuclear localization signal (NLS) are more likely to underlie laminopathies with cardiac or skeletal muscle involvement, while mutations 3' to the NLS are more likely to underlie lipodystrophy and progeroid syndromes. To study the clinical and molecular features of a subject with FPLD. We carried out mutational analysis of LMNA gene in a woman with FPLD phenotype and in her relatives. Insulin resistance was evaluated by minimal model. Body composition was evaluated by dual-energy X-ray absorptiometry (DEXA). Echocardiography was done in affected subjects. 3T3-L1 preadipocytes were transfected with wild-type or mutant prelamin A constructs. In transfected cells, lamin A was detected using a Cy3-conjugated monoclonal anti-FLAG antibody. The patient showed atypical fat distribution, insulin resistance, severe aortic stenosis and hypertrophic cardiomyopathy. She has an affected 11-year-old son, not yet lipodystrophic but with an incipient aortic disease. LMNA sequencing showed that mother and son were both heterozygous for a novel c.1772G > T missense mutation in exon 11, which causes the substitution of the cysteine at residue 591 by a phenylalanine (C591F). In mouse preadipocytes transfected with the mutant human LMNA gene, the mutant lamin A isoform was mislocated in the nucleus. This patient shows a novel clinical form of FPLD2, due to a mutation affecting lamin A only, with cardiac involvement.
Type 2 familial partial lipodystrophy (FPLD2) is characterised by loss of fat in the limbs and buttocks and results from mutations in the LMNA gene. To evaluate the role of several genes involved in adipogenesis in order to better understand the underlying mechanisms of regional loss of subcutaneous adipose tissue (scAT) in patients with FPLD2. In total, 7 patients with FPLD2 and 10 healthy control participants were studied. A minimal model was used to calculate the insulin sensitivity (IS). scAT was obtained from abdomen and thigh by biopsy. Relative gene expression was quantified by real-time reverse transcription PCR in a thermal cycler. Prelamin A western blot analysis was carried out on scAT and prelamin A nuclear localisation was determined using immunofluorescence. Adipocyte nuclei were examined by electron microscopy. Patients with FPLD2 were found to have significantly lower IS. The expression of LMNA was similar in both groups. The expression of PPARG2, RB1, CCND3 and LPL in thigh but not in abdomen scAT was significantly reduced (67%, 25%, 38% and 66% respectively) in patients with FPLD2. Significantly higher levels of prelamin A were found in peripheral scAT of patients with FPLD2. Defects in the peripheral heterochromatin and a nuclear fibrous dense lamina were present in the adipocytes of patients with FPLD2. In FPLD2 participants, prelamin A accumulation in peripheral scAT is associated with a reduced expression of several genes involved in adipogenesis, which could perturb the balance between proliferation and differentiation in adipocytes, leading to less efficient tissue regeneration.
David Araujo-Vilar
added a research item
Type 2 familial partial lipodystrophy (FPLD2) is a rare adipose tissue (AT) disease caused by mutations in LMNA, in which lipomas appear occasionally. In this study, we aimed to histologically characterize FPLD2-associated lipomatosis and study the expression of genes and proteins involved in cell cycle control, mitochondrial function, inflammation and adipogenesis. One lipoma and perilipoma fat from each of four subjects with FPLD2 and 10 control subjects were analysed by optical microscopy. The presence of inflammatory cells was evaluated by immunohistochemistry. Real-time RT-PCR and Western blot were used to evaluate gene and protein levels. Adipocytes from lipodystrophic patients were significantly larger than those of controls, in both the lipomas and perilipoma fat. Lipodystrophic AT exhibited CD68(+) macrophages and CD3(+) lymphocytes infiltration. TP53 expression was reduced in all types of lipomas. At protein level, C/EBPβ, p53 and pRb were severely disturbed in both lipodystrophic lipomas and perilipoma fat coming from lipoatrophic areas, whereas the expression of CEBPα was normal. Mitochondrial function genes were less expressed in lipoatrophic fat. In both lipomas and perilipoma fat from lipoatrophic areas, the expression of adipogenes was lower than controls. Even in lipomas, the adipogenic machinery is impaired in lipodystrophic fat coming from lipoatrophic regions in FPLD2, although the histological phenotype is near-normal, exhibiting low-grade inflammatory features. Our results suggest that the p53 pathway and some adipogenic proteins, such as CEBPα, could contribute to the maintenance of this near normal phenotype in the remnant AT present in these patients.
David Araujo-Vilar
added a project goal
Search for new genes related to familial partial Lipodystrophy and its pathogenetical mechanisms.