LONDON (Reuters) - European and U.S. diabetologists called on Tuesday for greater caution in prescribing oral diabetes pills like GlaxoSmithKline Plc’s Avandia, which has been linked to increased heart attack risk. Glaxo’s Avandia has lost ground to Takeda Pharmaceutical Co Ltd’s Actos in recent months, following publication of a U.S. study in May criticizing its safety record. Both drugs belong to a class of medicines known as thiazolidediones.