Gain-of-Function Claims for Type-2-Diabetes-Associated Coding Variants in SLC16A11 Are Not Supported by the Experimental Data

Human genetic variants in SLC16A11 are associated with increased risk of type 2 diabetes (T2D). We previously identified two distinct mechanisms through which co-inherited T2D-risk coding and non-coding variants disrupt SLC16A11 expression and activity, thus implicating reduced SLC16A11 function as the disease-relevant direction of effect. In a recent publication, Zhao et al. (2019a) argue that human SLC16A11 coding variants confer gain of function, basing their conclusions on phenotypic changes observed following overexpression of mutant murine Slc16a11. However, data necessary to demonstrate gain-of-function activity are not reported. Furthermore, several fundamental flaws in their experimental system-including inaccurate modeling of the human variant haplotype and expression conditions that are not physiologically relevant-prevent conclusions about T2D-risk variant effects on human physiology. This Matters Arising paper is in response to Zhao et al. (2019a), published in Cell Reports. See also the response by Zhao et al. (2019b) in this issue of Cell Reports.

Zinc transporter 10 (ZnT10)-dependent extrusion of cellular Mn2+ is driven by an active Ca2+-coupled exchange

Manganese (Mn²⁺) is extruded from the cell by the zinc transporter 10 (ZnT10). Loss of ZnT10 expression caused by autosomal mutations in the ZnT10 gene leads to hypermanganesemia in multiple organs. Here, combining fluorescent monitoring of cation influx in HEK293-T cells expressing human ZnT10 with molecular modeling of ZnT10 cation selectivity, we show that ZnT10 is exploiting the transmembrane Ca²⁺ inward gradient for active cellular exchange of Mn²⁺ In analyzing ZnT10 activity we used the ability of Fura-2 to spectrally distinguish between Mn²⁺ and Ca²⁺ fluxes. We found that (a) application of Mn²⁺-containing Ca²⁺-free solution to ZnT10-expressing cells triggers an influx of Mn²⁺, (b) reintroduction of Ca²⁺ leads to cellular Mn²⁺ extrusion against an inward Mn²⁺ gradient, and (c) the cellular transport of Mn²⁺ by ZnT10 is coupled to a reciprocal movement of Ca²⁺ Remarkably, replacing a single asparagine residue in ZnT10 (Asp-43) with threonine (ZnT10 N43T) converted the Mn²⁺/Ca²⁺ exchange to an uncoupled channel mode, permeable to both Ca²⁺ and Mn²⁺ The findings in our study identify the first ion transporter that uses the Ca²⁺ gradient for active counter-ion exchange. They highlight a remarkable versatility in metal selectivity and mode of transport controlled by the tetrahedral metal transport site of ZnT proteins.

Type 2 Diabetes Variants Disrupt Function of SLC16A11 through Two Distinct Mechanisms

Type 2 diabetes (T2D) affects Latinos at twice the rate seen in populations of European descent. We recently identified a risk haplotype spanning SLC16A11 that explains ∼20% of the increased T2D prevalence in Mexico. Here, through genetic fine-mapping, we define a set of tightly linked variants likely to contain the causal allele(s). We show that variants on the T2D-associated haplotype have two distinct effects: (1) decreasing SLC16A11 expression in liver and (2) disrupting a key interaction with basigin, thereby reducing cell-surface localization. Both independent mechanisms reduce SLC16A11 function and suggest SLC16A11 is the causal gene at this locus. To gain insight into how SLC16A11 disruption impacts T2D risk, we demonstrate that SLC16A11 is a proton-coupled monocarboxylate transporter and that genetic perturbation of SLC16A11 induces changes in fatty acid and lipid metabolism that are associated with increased T2D risk. Our findings suggest that increasing SLC16A11 function could be therapeutically beneficial for T2D. VIDEO ABSTRACT.

[On the legalization debate of non-medical cannabis consumption : Position paper of the German Association for Psychiatry, Psychotherapy and Psychosomatics]

Calls are increasing for the legalization of cannabis. Some legal experts, various politicians, political parties and associations are demanding a change in drug policy. The legalization debate is lively and receiving wide coverage in the media. The German Association for Psychiatry, Psychotherapy and Psychosomatics (DGPPN) comments on the most important questions from a medical scientific perspective: can cannabis consumption trigger mental illnesses, what consequences would legalization have for the healthcare system and where is more research needed?

[Psychiatric comorbidities with tobacco-related disorders]

The coincidence of tobacco smoking and psychiatric disorders is of great epidemiological and therapeutic importance. Tobacco smoking by people with mental disorders leads to disproportionately high somatic health risks, an adverse clinical course, poorer clinical outcomes and reduced quality of life (QoL). The etiological causes of the high comorbidity between smoking and mental disorders are still unclear: currently, tobacco smoking is discussed as being either the consequence or contributory cause of psychological disorders or both disorders share common antecedents and interactions. Psychiatric patients are motivated to quit and smoking cessation is not generally less effective with smokers with mental disorders than with mentally healthy individuals. Specific smoking cessation programs in the inpatient and outpatient settings are time-consuming and complex but effective. Within the framework of the current S3 guidelines the international evidence has been updated and transformed into treatment guidelines following an elaborate consensus process. Basically the same interventional measures should be used as with mentally healthy individuals; however, smokers with a psychological comorbidity often need more intensive adjuvant psychotherapeutic interventions and often need pharmaceutical support, (bupropion, varenicline and nicotine replacement therapy). Due to the overall unsatisfactory findings the treatment guidelines are partially based on clinical consensus decisions. In this field, a considerable need for research has been determined.

[Cannabis--Position Paper of the German Respiratory Society (DGP)]

In this position paper, the adverse health effects of cannabis are reviewed based on the existing scientific literature; in addition possible symptom-relieving effects on some diseases are depicted. In Germany, cannabis is the most widely used illicit drug. Approximately 600,000 adult persons show abusive or addictive cannabis consumption. In 12 to 17 year old adolescents, cannabis use increased from 2011 to 2014 from 2.8 to 6.4%, and the frequency of regular use from 0.2 to 1.5%. Currently, handling of cannabinoids is much debated in politics as well as in general public. Health aspects have to be incorporated into this debate. Besides analysing mental and neurological side effects, this position paper will mainly focus on the influences on the bronchopulmonary and cardiovascular system. There is strong evidence for the induction of chronic bronchitis. Allergic reactions including asthma are known, too. Associations with other diseases like pulmonary emphysema, lung cancer and pneumonia are not sufficiently proven, however cannot be excluded either. In connection with the use of cannabis cardiovascular events such as coronary syndromes, peripheral vascular diseases and cerebral complications have been noted. Often, the evidence is insufficient due to various reasons; most notably, the overlapping effects of tobacco and cannabis use can frequently not be separated adequately. Empirically, early beginning, high-dosed, long-lasting and regular cannabis consumption increase the risk of various psychological and physical impairments and negatively affect age-based development. Concerns therefore relate especially to children and adolescents. There is only little scientific evidence for medical benefits through cannabis as a remedy; systematic research of good quality, in particular prospective, randomised, placebo-controlled double-blinded studies are rare. The medical societies signing this position paper conclude that cannabis consumption is linked to adverse health effects which have to be taken into consideration in the debate about the social attitude towards cannabinoids. The societies agree that many aspects regarding health effects of cannabis are still uncertain and need clarification, preferably through research provided by controlled studies.

[Methodology of the S3 guidelines on alcohol and tobacco-related disorders]

BACKGROUND

From 2010 until 2015 two interdisciplinary evidence-based guidelines were developed to summarize the current knowledge regarding screening, diagnostics and treatment of alcohol and tobacco-related disorders.

METHODS

Both guidelines were prepared under the auspices of the German Society for Psychiatry, Psychotherapy and Psychosomatics (Deutsche Gesellschaft für Psychiatrie, Psychotherapie, Psychosomatik und Nervenheilkunde, DGPPN) and the German Society for Addiction Research and Therapy (Deutsche Gesellschaft für Suchtforschung und -therapie, DG-Sucht). To meet the methodological criteria for the highest quality guidelines (S3 criteria) as defined by the Association of the Scientific Medical Societies in Germany (Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften, AWMF) the following criteria were realized: (1) a systematic search, selection and appraisal of the international literature, (2) a structured process to reach consensus and (3) inclusion of all relevant representatives of future guideline users.

RESULTS

More than 60 clinical experts and researchers analyzed the scientific literature. In total 41 international and national guidelines (23 for alcohol and 18 for tobacco) were used. Moreover, 83 systematic Cochrane reviews (alcohol 28, tobacco 55) and 5863 articles (alcohol 2213, tobacco 3650) were analyzed. A total of 7 expert groups formulated 174 recommendations for the screening, diagnosis and treatment of alcohol-related disorders. Six expert groups created 81 recommendations for the screening, diagnosis and treatment of tobacco-related disorders. Approximately 50 scientific associations, professional organizations, patient and family initiatives, as well as representatives of the healthcare system formed a consensus group. In seven 1 and 2-day conferences, all clinical recommendations were discussed and approved by this group. Both guidelines will be revised on a regular basis to guarantee that the clinical recommendations are kept up to date.

CONCLUSIONS

Both systematically developed, evidence-based treatment guidelines are comprehensive instruments to provide orientation and assist the decision-making process for physicians, psychologists and other therapists as well as patients and their families in the diagnosis and treatment of alcohol and tobacco use related disorders.

Efficacy of a targeted cognitive-behavioral treatment program for cannabis use disorders (CANDIS)

AIMS

To examine the efficacy, 3- and 6-month follow-up effects of a psychological treatment for older adolescents and adults with DSM-IV cannabis use disorders. The program was tailored to the needs of this patient population.

EXPERIMENTAL PROCEDURES

A randomized controlled clinical trial of 122 patients aged 16 to 44 years with DSM-IV cannabis dependence as the main substance use diagnosis was conducted. Patients were randomly assigned to either Active Treatment (AT, n = 90) or a Delayed Treatment Control group (DTC, n = 32). Treatment consisted of 10 sessions of therapy, detailed in a strictly enforced manual. Assessments were conducted at baseline, during each therapy session, at post treatment and at follow-up assessments at 3 and 6 months.

RESULTS

The treatment retention rate was 88%. Abstinence was achieved in 49% of AT patients and in 13% of those in DTC (p < 0.001; intend-to-treat (ITT) analysis). Further, AT patients improved significantly (p < = 0.001) in the frequency of cannabis use per week, addiction severity, number of disability days, and overall level of psychopathology. Program effects were maintained over a 3-month- (abstinence rate: 51%) and 6-month follow-up (45%) period.

CONCLUSION

The treatment program is effective in obtaining abstinence as well as reducing cannabis use and improves the associated social and mental health burden.

Identification of the Zn2+ binding site and mode of operation of a mammalian Zn2+ transporter

Vesicular zinc transporters (ZnTs) play a critical role in regulating Zn2+ homeostasis in various cellular compartments and are linked to major diseases ranging from Alzheimer disease to diabetes. Despite their importance, the intracellular localization of ZnTs poses a major challenge for establishing the mechanisms by which they function and the identity of their ion binding sites. Here, we combine fluorescence-based functional analysis and structural modeling aimed at elucidating these functional aspects. Expression of ZnT5 was followed by both accelerated removal of Zn2+ from the cytoplasm and its increased vesicular sequestration. Further, activity of this zinc transport was coupled to alkalinization of the trans-Golgi network. Finally, structural modeling of ZnT5, based on the x-ray structure of the bacterial metal transporter YiiP, identified four residues that can potentially form the zinc binding site on ZnT5. Consistent with this model, replacement of these residues, Asp599 and His451, with alanine was sufficient to block Zn2+ transport. These findings indicate, for the first time, that Zn2+ transport mediated by a mammalian ZnT is catalyzed by H+/Zn2+ exchange and identify the zinc binding site of ZnT proteins essential for zinc transport.

The German monitoring and reporting system for the treatment of substance-related problems: a national system on the basis of aggregated data

The German treatment monitoring and reporting system EBIS for out-patient centres treating clients with substance-related problems and disorders was set up in 1980. A parallel system for in-patient treatment was added in 1993 under the name of SEDOS. Together they are based nation-wide on more than 600 specialised treatment centres which collect diagnosis- and treatment-related data as well as information on socio-economic and family background. As part of the data relate to the end of treatment, also evaluative elements are included. In EBIS and SEDOS, aggregated data are the basis of the national and regional statistics produced, which offers a very high level of data protection for the clients treated. The revision of the national system implementing the Treatment Demand Indicator Protocol as the European Monitoring Centre for Drugs and Drug Addiction standard has already been started.