Zn(2+)-transporter-8: a dual role in diabetes

Genetic and inflammatory factors underlying gestational diabetes mellitus: a review

Gestational diabetes mellitus (GDM) poses a significant global health concern, impacting both maternal and fetal well-being. Early detection and treatment are imperative to mitigate adverse outcomes during pregnancy. This review delves into the pivotal role of insulin function and the influence of genetic variants, including SLC30A8, CDKAL1, TCF7L2, IRS1, and GCK, in GDM development. These genetic variations affect beta-cell function and insulin activity in crucial tissues, such as muscle, disrupting glucose regulation during pregnancy. We propose a hypothesis that this variation may disrupt zinc transport, consequently impairing insulin production and secretion, thereby contributing to GDM onset. Furthermore, we discussed the involvement of inflammatory pathways, such as TNF-alpha and IL-6, in predisposing individuals to GDM. Genetic modulation of these pathways may exacerbate glucose metabolism dysregulation observed in GDM patients. We also discussed how GDM affects cardiovascular disease (CVD) through a direct correlation between pregnancy and cardiometabolic function, increasing atherosclerosis, decreased vascular function, dyslipidemia, and hypertension in women with GDM history. However, further research is imperative to unravel the intricate interplay between inflammatory pathways, genetics, and GDM. This understanding is pivotal for devising targeted gene therapies and pharmacological interventions to rectify genetic variations in SLC30A8, CDKAL1, TCF7L2, IRS1, GCK, and other pertinent genes. Ultimately, this review offers insights into the pathophysiological mechanisms of GDM, providing a foundation for developing strategies to mitigate its impact.

Diabetes immunity-modulated multifunctional hydrogel with cascade enzyme catalytic activity for bacterial wound treatment

Diabetes immunity-modulated wound treatment in response to the varied microenvironments at different stages remains an urgent challenge. Herein, glucose oxidase (GOx) and quasi-amorphous Fe₂O₃ are co-incorporated into Zn-MOF nanoparticle (F-GZ) for cascade enzyme catalytic activities, where not only the high blood glucose in the wound is consumed via the GOx catalysis, but also the effective anti-bacteria is achieved via the degradedly released Zn²⁺ synergistically with the catalytically produced ·OH during the bacterial infection period with the low pH microenvironment. Simultaneously, the reactive oxygen species scavenging and hypoxia relief is realized via catalyzing H₂O₂ to produce O₂ at the relatively elevated pH environment during the wound recovery period. Subsequently, a multifunctional hydrogel with injectable, self-healing and hemostasis abilities, as well as uniformed F-GZ loading is prepared via the copolymerization reaction. This hydrogel behaves as F-GZ but reduces the toxic effects, which thus accelerates the diabetic wound healing. More importantly, this hydrogel is found to modulate the diabetes immunity possibly mediated via the released Zn²⁺, which thus contributes to the recovered pancreatic islet functions with improved glucose tolerance and increased insulin secretion for enhanced diabetic wound treatments. This work initiates a new strategy for simultaneous diabetic wound management and also suggests a potential way for diabetic immunity modulation.

Zinc supplementation in pre-diabetes mellitus: a systematic review and meta-analysis

INTRODUCTION

Certain pharmacological and lifestyle interventions have been shown to reduce progression of pre-diabetes. We aimed to perform a systematic review and meta-analyses of studies assessing the outcomes of zinc supplementation in individuals with pre-diabetes.

EVIDENCE ACQUISITION

A comprehensive search was conducted in PubMed, SciVerse Scopus and Web of Science databases. Controlled clinical trials in pre-diabetics, on zinc supplement with or without other nutrients, assessing at least one accepted glycaemic parameter as an outcome were deemed eligible.

EVIDENCE SYNTHESIS

Three papers were included in the systematic review and meta analysis, with a total of 265 participants. Duration of zinc supplementation ranged from 6-12 months. The zinc dose ranged from 20-30 mg/day. In the pooled analysis, zinc supplementation significantly reduced FBG both when given alone (-10.86 mg/dL; 95% CI, -14.74 to -6.98; p<0.001) and with other micronutrients (-11.77 mg/dL; p<0.001). Similarly, 2hr-OGTT blood glucose was reduced by 21.08 mg/dL (95% CI, -40.05 to -2.11; p=0.03) in the pooled analysis of studies using zinc alone and in combination with other micronutrients. One study demonstrated a significant reduction of HbA1c by 0.5% with combined supplementation, while another reported a significant reduction in CRP with zinc supplementation. When all trials were considered, TC, HDL-c and HOMA-β showed significant improvement. Zinc supplementation significantly improved the zinc status from baseline.

CONCLUSIONS

Zinc supplementation demonstrated beneficial effects on glycaemic and lipid parameters in individuals with pre-diabetes. It may have the potential to reduce the prevalence of pre-diabetes and control associated morbidity and mortality.

Tropisetron improves pancreas function and increases insulin synthesis and secretion in the STZ-induced diabetic rats: involvement of UCP2/ZnT8 pathway

OBJECTIVES

Diabetes mellitus is one of the most common metabolic diseases. Tropisetron, as a 5-HT3 receptor antagonist, has a considerable role in the inflammation and oxidative stress lowering. This study aimed to investigate the effect of this 5-HT3 receptor antagonist on insulin secretion in male diabetic rats and the possible mechanisms.

METHODS

Animals were divided into five equal groups; the control, tropisetron, diabetes, tropisetron-diabetes and glibenclamide-diabetes (7 in each group). Tropisetron and glibenclamide were administrated for 2 weeks after inducing type 1 diabetes.

KEY FINDINGS

We demonstrated that insulin secretion improved robustly in diabetes-tropisetron compared with the diabetic group. Oxidative stress biomarkers were lower in a diabetes-tropisetron group than in diabetic rats. Simultaneously, tropisetron administration promoted the expression of ZnT8 and GLUT2 and also beta-cell mass in pancreatic tissue, while the expression of uncoupling protein 2 (UCP2) was restrained. The histological evaluation confirmed our results. These effects were equipotent with glibenclamide, indicating that tropisetron can protect islets from the abnormal insulin secretion and morphological changes induced by type 1 diabetes.

CONCLUSIONS

This effect might be partly related to the modulated UCP2/ZnT8 signal pathway and improved oxidative stress-induced damage.

Trace elements in type 2 diabetes mellitus and their association with glycemic control

Background

Alterations in serum levels of trace elements reported in type 2 diabetes mellitus (T2DM) have been linked with induction of T2DM and associated complications.

Objectives

To assess serum levels of copper (Cu), zinc (Zn) and selenium (Se) in T2DM patients with adequate and poor glycemic control.

Patients and methods

This study was performed at King Khalid University Hospital, Riyadh. A total of 100 consenting T2DM patients comprising of 50 patients with glycated hemoglobin (HbA1c) less than 6.5% and 50 patients with HbA1c more than 6.5% along with a group of 50 normal healthy individuals were included in the study. Serum levels of Cu, Zn and Se were measured by inductively coupled plasma-mass spectrometry (ICP-MS) instrument.

Results

Among T2DM patients with HbA1c <6.5%, mean serum Cu levels (13.4+4.3µmol/L) were not different from the controls (14.5+1.92µmol/L) whereas Zn (9.9+2.7µmol/Lvs15+3.2µmol/L;p<0.0001) and Se levels (1+0.2µmol/Lvs1.62+0.2µmol/L; p<0.0004) were lower than the controls. Among T2DM patients with HbA1c >6.5% mean serum Cu (18.1+4.1µmol/Lvs14.5+1.9µmol/L; p<0.0001), Zn (15+3.2µmol/Lvs13.5+1.9µmol/L; p<0.009) and Se (1.62+0.2µmol/Lvs1.17+0.16µmol/L;p<0.0001) were significantly higher than the controls. HbA1c% negatively correlated with HbA1c >6.5% (r = -0.302; p<0.03).

Conclusion

Cu, Zn and Se homeostasis was altered in T2DM patients and varied with glycemic control.

Altered serum Zinc and Copper in Iranian Adults who were of normal weight but metabolically obese

Metabolically obese normal weight (MONW) individuals are potentially at increased risk of developing metabolic syndrome. Serum zinc and copper concentrations were assessed in individuals with MONW to determine whether MONW is associated with altered serum zinc and/or copper status. Normal weight subjects (total n = 2419; 1298 men and 1121 women), were recruited as part of Mashhad Stroke and Heart Association Disorder (MASHAD) Study cohort. They were divided into two groups according to the presence or absence of MetS, defined using IDF criteria. Serum zinc and copper concentrations were determined by atomic absorption. Of the 2419 normal weight adults, 377 had MetS. Of this group, 53.7% and 49.7% had a serum zinc <70 µg/dl (Q1) (p = 0.001) or a serum copper <79 µg/dl (Q1) respectively. Furthermore, 27.3% had a serum copper >131 µg/dl (Q4) (p = 0.034), and 18.8% had a serum zinc >95 µg/dl (Q4). Logistic regression analysis was performed to determine the odds ratio (OR) for an association of serum zinc, copper and zinc to copper ratio with MetS in normal weight subjects. The subjects with a serum zinc >95 µg/dl (Q4) had 0.386 [OR: 0.614(95%CI 0.457–0.823)] lower chance of MetS (p = 0.001) and the subjects with a serum copper >131 (Q4) had OR 1.423 (95% CI: 1.09–1.857) higher chance of MetS (p = 0.009). These data remained significant after adjustment for age and sex, for serum zinc and copper, respectively. Furthermore, our results strongly suggested that zinc and copper were the independent risk factor for metabolic syndrome in normal weight subjects. There is an imbalance between serum copper and zinc concentrations among individuals with MONW when compared with normal BMI individuals without MetS. This may increase the risk of individuals with MONW developing conditions associated with this imbalance, such as diabetes and cardiovascular disease.

Genetic, Functional, and Immunological Study of ZnT8 in Diabetes

Zinc level in the body is finely regulated to maintain cellular function. Dysregulation of zinc metabolism may induce a variety of diseases, e.g., diabetes. Zinc participates in insulin synthesis, storage, and secretion by functioning as a "cellular second messenger" in the insulin signaling pathway and glucose homeostasis. The highest zinc concentration is in the pancreas islets. Zinc accumulation in cell granules is manipulated by ZnT8, a zinc transporter expressed predominately in pancreatic α and β cells. A common ZnT8 gene (SLC30A8) polymorphism increases the risk of type 2 diabetes mellitus (T2DM), and rare mutations may present protective effects. In type 1 diabetes mellitus (T1DM), autoantibodies show specificity for binding two variants of ZnT8 (R or W at amino acid 325) dictated by a polymorphism in SLC30A8. In this review, we summarize the structure, feature, functions, and polymorphisms of ZnT8 along with its association with diabetes and explore future study directions.

Crosstalk between zinc and free fatty acids in plasma

In mammalian blood plasma, serum albumin acts as a transport protein for free fatty acids, other lipids and hydrophobic molecules including neurodegenerative peptides, and essential metal ions such as zinc to allow their systemic distribution. Importantly, binding of these chemically extremely diverse entities is not independent, but linked allosterically. One particularly intriguing allosteric link exists between free fatty acid and zinc binding. Albumin thus mediates crosstalk between energy status/metabolism and organismal zinc handling. In recognition of the fact that even small changes in extracellular zinc concentration and speciation modulate the function of many cell types, the albumin-mediated impact of free fatty acid concentration on zinc distribution may be significant for both normal physiological processes including energy metabolism, insulin activity, heparin neutralisation, blood coagulation, and zinc signalling, and a range of disease states, including metabolic syndrome, cardiovascular disease, myocardial ischemia, diabetes, and thrombosis.

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Serum albumin binds and transports both free fatty acids and Zn²⁺ ions

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Elevated plasma free fatty acids impair Zn²⁺ binding by albumin through an allosteric mechanism

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The resulting changes in plasma zinc speciation are thought to impact blood coagulation and may promote thrombosis

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Increased free Zn²⁺ may lead to enhanced zinc export from plasma and dysregulation of zinc homeostasis in multiple tissues

Zinc supplementation in prediabetes: A randomized double-blind placebo-controlled clinical trial

BACKGROUND

This study evaluated the effects of zinc supplementation on glycemic control, other cardiometabolic and anthropometric parameters, and disease progression in prediabetes.

METHODS

A randomized double-blind placebo-controlled Phase 2 clinical trial was conducted over a 12-month period in 200 subjects (43% male; mean [± SD] age 51.8 ± 7.3 years), randomly assigned (1:  1) to the treatment or control group. The treatment group received zinc (20 mg daily). Subjects were evaluated at baseline and at 1, 3, 6, and 12 months. The primary outcome was the change in glycemic control from baseline. Multiple regression analyses were performed, with change in outcome variables after intervention from baseline used as continuous dependent variables.

RESULTS

In both groups, mean serum zinc concentrations prior to the trial were below normal (15.29-21.41 μmol/L). During the 12-month follow-up, a significantly higher percentage of participants developed type 2 diabetes in the control compared with zinc-treated group (25.0% vs 11.0% respectively; P = 0.016). Fasting plasma glucose (FPG), 2-h glucose levels in the oral glucose tolerance test (OGTT), homeostasis model assessment of insulin resistance (HOMA-IR), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) were significantly lower in the treated group, with significant improvement in β-cell function. In all four regression models, the best predictor of the dependent variables (i.e. change in FPG, 2-h glucose in the OGTT, HOMA-IR, and homeostatic model assessment of β-cell function) was zinc treatment.

CONCLUSIONS

Zinc supplementation reduced blood glucose and insulin resistance while improving β-cell function. Furthermore, supplementation reduced disease progression to diabetes and had beneficial effects on TC and LDL-C.

Trace element status in type 2 diabetes: A meta-analysis

Introduction

Type 2 diabetes is a chronic metabolic disorder that has been associated with alterations in the status of trace elements, including zinc, copper, iron and manganese. However, clinical studies reporting statuses of these trace elements in type 2 diabetes patients compared to controls have shown conflicting results.

Objective

This meta-analysis aimed to summarize the existing literature on the statuses of zinc, copper, iron, and manganese in Type 2 diabetes mellitus patients.

Methods

A literature search of Embase, PubMed, EBSCOHost, ScienceDirect, Scopus, Cochrane library and Web of Science electronic databases was conducted to find studies published from 1970 to November 2016 that compared the trace elements of interest between type 2 diabetic patients and healthy controls. Keywords used were type 2 diabetes, diabetes, hyperglycemia, insulin, glucose, HbA1c, trace elements, micronutrients, zinc, manganese, copper, ceruloplasmin, iron and ferritin. The bias corrected Hedges' g, was utilized as the effect sizes. Due to the biological interaction between trace elements, it is important to collectively evaluate the statuses of these minerals in type 2 diabetes. Thus, the robust variance estimation method was chosen to handle dependency between multiple outcomes.

Results

A total of 52 studies met the inclusion criteria, amounting to 98 effect sizes. Diabetic patients (n=20183) had significantly lower zinc status when compared to controls (effect size = -1.73, p<0.01); whereas copper (effect size = 1.10, p<0.05) and ferritin levels (effect size = 1.05, p<0.01) were significantly higher. Although not significant, ceruloplasmin (effect size = 1.85, p=0.06) and iron (effect size = 1.42, p=0.06) levels were higher, and manganese (effect size = 0.27, p=0.34) was lower in patients.

Conclusion

Results from this meta-analysis indicate lower zinc status accompanied by increased copper and ferritin levels in patients with type 2 diabetes when compared to controls.

Zinc and diabetes mellitus: understanding molecular mechanisms and clinical implications

Background

Diabetes mellitus is a leading cause of morbidity and mortality worldwide. Studies have shown that Zinc has numerous beneficial effects in both type-1 and type-2 diabetes. We aim to evaluate the literature on the mechanisms and molecular level effects of Zinc on glycaemic control, β-cell function, pathogenesis of diabetes and its complications.

Methods

A review of published studies reporting mechanisms of action of Zinc in diabetes was undertaken in PubMed and SciVerse Scopus medical databases using the following search terms in article title, abstract or keywords; (“Zinc” or “Zn”) and (“mechanism” or “mechanism of action” or “action” or “effect” or “pathogenesis” or “pathology” or “physiology” or “metabolism”) and (“diabetes” or “prediabetes” or “sugar” or “glucose” or “insulin”).

Results

The literature search identified the following number of articles in the two databases; PubMed (n = 1799) and SciVerse Scopus (n = 1879). After removing duplicates the total number of articles included in the present review is 111. Our results show that Zinc plays an important role in β-cell function, insulin action, glucose homeostasis and the pathogenesis of diabetes and its complications.

Conclusion

Numerous in-vitro and in-vivo studies have shown that Zinc has beneficial effects in both type-1 and type-2 diabetes. However further randomized double-blinded placebo-controlled clinical trials conducted for an adequate duration, are required to establish therapeutic safety in humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s40199-015-0127-4) contains supplementary material, which is available to authorized users.

Zinc transporters and zinc signaling: new insights into their role in type 2 diabetes

Zinc is an essential trace element that plays a vital role in many biological processes including growth and development, immunity, and metabolism. Recent studies have highlighted zinc's dynamic role as a "cellular second messenger" in the control of insulin signaling and glucose homeostasis. Accordingly, mechanisms that contribute to dysfunctional zinc signaling are suggested to be associated with metabolic disease states including cancer, cardiovascular disease, Alzheimer's disease, and diabetes. The actions of the proteins that control the uptake, storage, and distribution of zinc, the zinc transporters, are under intense investigation due to their emerging role in type 2 diabetes. The synthesis, secretion, and action of insulin are dependent on zinc and the transporters that make this ion available to cellular processes. This suggests that zinc plays a previously unidentified role where changes in zinc status over time may affect insulin activity. This previously unexplored concept would raise a whole new area of research into the pathophysiology of insulin resistance and introduce a new class of drug target with utility for diabetes pharmacotherapy.

The zinc transporter, Slc39a7 (Zip7) is implicated in glycaemic control in skeletal muscle cells

Dysfunctional zinc signaling is implicated in disease processes including cardiovascular disease, Alzheimer's disease and diabetes. Of the twenty-four mammalian zinc transporters, ZIP7 has been identified as an important mediator of the ‘zinc wave’ and in cellular signaling. Utilizing siRNA targeting Zip7 mRNA we have identified that Zip7 regulates glucose metabolism in skeletal muscle cells. An siRNA targeting Zip7 mRNA down regulated Zip7 mRNA 4.6-fold (p = 0.0006) when compared to a scramble control. This was concomitant with a reduction in the expression of genes involved in glucose metabolism including Agl, Dlst, Galm, Gbe1, Idh3g, Pck2, Pgam2, Pgm2, Phkb, Pygm, Tpi1, Gusb and Glut4. Glut4 protein expression was also reduced and insulin-stimulated glycogen synthesis was decreased. This was associated with a reduction in the mRNA expression of Insr, Irs1 and Irs2, and the phosphorylation of Akt. These studies provide a novel role for Zip7 in glucose metabolism in skeletal muscle and highlight the importance of this transporter in contributing to glycaemic control in this tissue.

Zinc transporter 8 autoantibody (ZnT8A) could help differentiate latent autoimmune diabetes in adults (LADA) from phenotypic type 2 diabetes mellitus

BACKGROUND

The ZnT8A is an independent marker for diagnosis of type 1 diabetes mellitus. We investigated the distribution and clinical features of ZnT8A positive latent autoimmune diabetes in adult (LADA) patients to explore the potential diagnostic application.

METHODS

A total of 3062 phenotypic T2DM patients were randomly selected from a national multicenter study - the LADA China Study. Radioligand binding assays were applied to detect the presence of ZnT8A, GADA and IA-2A. HbA1c , fasting C-peptide and serum lipid levels were followed up with ZnT8A positive patients.

RESULTS

The positive prevalence of ZnT8A, GADA and IA-2A in phenotypic T2DM patients was 1.99% (61/3062), 6.43% (197/3062) and 1.96% (60/3062), respectively. The ZnT8A positivity was lower than that of GADA(x²  = 74.8, p < 0.001) but was comparable with that of IA-2A (p > 0.05). The positivity of ZnT8A in IA-2A positive patients was higher than that in GADA positive patients (38.3% vs. 10.7%, x²  = 24.8, p < 0.001). On the basis of GADA and IA-2A positivity, the ZnT8A assay enhanced the diagnostic prevalence of LADA from 7.58 to 8.62%. The LADA patients who were positive for ZnT8A had higher systolic blood pressure when compared with GADA positive cases (p = 0.049) and higher total cholesterol levels when compared with antibody-negative T2DM patients (p = 0.035).

CONCLUSION

The detection of ZnT8A at the basis of GADA and IA-2A can improve diagnostic sensitivity of Chinese LADA.

Zinc transporter expression in zebrafish (Danio rerio) during development

Zinc is a micronutrient important in several biological processes including growth and development. We have limited knowledge on the impact of maternal zinc deficiency on zinc and zinc regulatory mechanisms in the developing embryo due to a lack of in vivo experimental models that allow us to directly study the effects of maternal zinc on embryonic development following implantation. To overcome this barrier, we have proposed to use zebrafish as a model organism to study the impact of zinc during development. The goal of the current study was to profile the mRNA expression of all the known zinc transporter genes in the zebrafish across embryonic and larval development and to quantify the embryonic zinc concentrations at these corresponding developmental time points. The SLC30A zinc transporter family (ZnT) and SLC39A family, Zir-,Irt-like protein (ZIP) zinc transporter proteins were profiled in zebrafish embryos at 0, 2, 6, 12, 24, 48 and 120 h post fertilization to capture expression patterns from a single cell through full development. We observed consistent embryonic zinc levels, but differential expression of several zinc transporters across development. These results suggest that zebrafish is an effective model organism to study the effects of zinc deficiency and further investigation is underway to identify possible molecular pathways that are dysregulated with maternal zinc deficiency.

Zinc and its role in age-related inflammation and immune dysfunction

Zinc is an essential micronutrient required for many cellular processes, especially for the normal development and function of the immune system. Zinc homeostasis and signaling are critical in immune activation, and an imbalance in zinc homeostasis is associated with the development of chronic diseases. Zinc deficiency causes significant impairment in both adaptive and innate immune responses, and promotes systemic inflammation. The elderly are a population particularly susceptible to zinc deficiency. National surveys indicate that a significant portion of the aged population has inadequate zinc intake, and a decline in zinc status is observed with age. There are remarkable similarities between the hallmarks of zinc deficiency and immunological dysfunction in aged individuals. Both zinc deficiency and the aging process are characterized by impaired immune responses and systemic low grade chronic inflammation. It has been hypothesized that age-related zinc deficiency may be an important factor contributing to immune dysfunction and chronic inflammation during the aging process. In this review, we discuss the effects of zinc status on aging, potential molecular and epigenetic mechanisms contributing to age-related decline in zinc status, and the role of zinc in age-related immune dysfunction and chronic inflammation.

GWAS of butyrylcholinesterase activity identifies four novel loci, independent effects within BCHE and secondary associations with metabolic risk factors

Serum butyrylcholinesterase (BCHE) activity is associated with obesity, blood pressure and biomarkers of cardiovascular and diabetes risk. We have conducted a genome-wide association scan to discover genetic variants affecting BCHE activity, and to clarify whether the associations between BCHE activity and cardiometabolic risk factors are caused by variation in BCHE or whether BCHE variation is secondary to the metabolic abnormalities. We measured serum BCHE in adolescents and adults from three cohorts of Australian twin and family studies. The genotypes from ∼2.4 million single-nucleotide polymorphisms (SNPs) were available in 8791 participants with BCHE measurements. We detected significant associations with BCHE activity at three independent groups of SNPs at the BCHE locus (P = 5.8 × 10(-262), 7.8 × 10(-47), 2.9 × 10(-12)) and at four other loci: RNPEP (P = 9.4 × 10(-16)), RAPH1-ABI2 (P = 4.1 × 10(-18)), UGT1A1 (P = 4.0 × 10(-8)) and an intergenic region on chromosome 8 (P = 1.4 × 10(-8)). These loci affecting BCHE activity were not associated with metabolic risk factors. On the other hand, SNPs in genes previously associated with metabolic risk had effects on BCHE activity more often than can be explained by chance. In particular, SNPs within FTO and GCKR were associated with BCHE activity, but their effects were partly mediated by body mass index and triglycerides, respectively. We conclude that variation in BCHE activity is due to multiple variants across the spectrum from uncommon/large effect to common/small effect, and partly results from (rather than causes) metabolic abnormalities.