How to configure ExtJS 4 Store (proxy and reader) to read metadata

My question is how to get metadata besides totalRecords, in my case it is version, code, searchquery (please look at json).

{
"result": {
    "version":"1",
    "code":"200",
    "searchquery": "false",
    "totalRecords": "2",
    "account":[
            {
                "lastname": "Ivanoff", 
                "firstname": "Ivan", 
                "accountId":"1"
            },
            {
                "lastname": "Smirnoff", 
                "firstname": "Ivan", 
                "accountId":"2"
            }
        ]
}

}

Here is my model:

Ext.define("test.Account", {
    extend: "Ext.data.Model",
    fields: [
        {name: 'accountId', type: 'string'},
        {name: 'lastname', type: 'string'},
        {name: 'firstname', type: 'string'}    
    ]
});

And store:

Ext.define("test.TestStore", {
    extend: "Ext.data.Store",
    model: "test.Account",
    proxy: {
        type: "ajax",
        url: "users.json",  
        reader: {
            type    : 'json',
            root    : 'result.account',
            totalProperty: "result.totalRecords"
        }
    },

    listeners: {
        load: function(store, records, success) {
            console.log("Load: success " + success);     
        }
    }
});

Using this store I am able to load records (account) and cannot find any methods to access rest of the fields.

Thank you in advance.