IR, syndrome X and the metabolic syndrome are all one and the same names for people who have problems with insulin production. The condition arises when the cells are no longer able to respond to the action of insulin in transporting glucose from the bloodstream into the body’s tissues. It is as if the cell membranes cannot hear the “knocking” of this hormone on their door. As a consequence, the pancreas produces more insulin in the hope that a louder “knock” will allow the glucose to enter the cell. The increased insulin output initially overcomes the problem and mobilizes the glucose. However as time goes by, the increased insulin is no longer effective in transporting the glucose into the cells. The pancreas then starts to produce super physiologic doses of insulin, eventually burning itself out. Without insulin to keep glucose in check, blood sugar levels increase leading to the development of T2DM. Inflammation and oxidation are also implicated in the pathophysiology of T2DM and cardiovascular disease. It is no surprise then that four out of the five criteria for diagnosing IR are characterized by oxidative stress (obesity, hyperglycaemia, high blood pressure, increased triglycerides and low HDL cholesterol levels).1 Elevated levels of pro-inflammatory cytokines such as tumour necrosis factor and interleukin-6 have been observed in T2DM and explain in part, the increased propensity to atherosclerosis in these individuals.2
While the cause of IR is multifactorial, lifestyle factors appear to have a profound effect on blood sugar regulation and may well be the triggering factor in genetically susceptible individuals. In fact, the Diabetes Prevention Program Research Group went so far as to say that lifestyle intervention can prevent or delay T2DM in high risk persons.3 Lack of exercise, central adiposity and a diet high in saturated fats and low in fibre are some of the key lifestyle characteristics associated with increased risk of T2DM
The prevalence of IR and T2DM has risen dramatically in the New Zealand population, reaching epidemic proportions. 2004 statistics show the prevalence of diabetes to be 8% in women and 10% in men >45 years of age. The incidence of IR is much higher – an estimated 37% of the total population. Of great concern is the fact that IR is now high in young adults (25-39 years). As IR is a precursor to T2DM, the statistics predict a pattern of diabetes occurring at a much younger age.5 Estimated medical costs relating to T2DM in New Zealand are projected to reach one billion by the year 2021.