The Concept of CMR

Insulin resistance

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Figure 1: Number of metabolic syndrome abnormalities by NCEP-ATP III clinical criteria, diabetes and prevalent CVD and hazard ratios of 10-year risk of fatal and non-fatal CVD

Figure 1: Number of metabolic syndrome abnormalities by NCEP-ATP III clinical criteria, diabetes and prevalent CVD and hazard ratios of 10-year risk of fatal and non-fatal CVD

Some investigators argue that it is not the metabolic syndrome that is responsible for increasing CVD risk, but rather insulin resistance state per se (11). Several clinical criteria and cut-off values have been proposed to identify individuals with the metabolic syndrome and each has a different relationship to insulin resistance. A prospective analysis has demonstrated that insulin resistance substantially increases diabetes or CVD risk in people with the metabolic syndrome, but in the general population, risk prediction in the presence of the metabolic syndrome is similar whether or not insulin resistance is accounted for (12). The Hoorn study (13) found that the metabolic syndrome increased CVD risk roughly twofold. This study also revealed that men with the metabolic syndrome—according to National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III) clinical criteria—had similar CVD risk as men with diabetes but less risk than men with prevalent CVD (Figure 1). However, metabolic syndrome criteria that included information on fasting insulin levels were no better predictors of CVD risk than those that did not take this insulin resistance marker into account. Similarly, results from the IRAS (14) revealed that there is no need to measure plasma glucose-insulin levels through oral glucose tolerance testing or insulin resistance measures in order to predict diabetes risk. It is sufficient to identify the metabolic syndrome using NCEP-ATP III or International Diabetes Federation (IDF) clinical criteria. In contrast, data from the Framingham Offspring Study (15) revealed that plasma glucose-insulin levels measured after an oral glucose tolerance test could increase CVD risk beyond that of the metabolic syndrome. However, indirect measures of insulin resistance—such as the homeostasis model assessment formula (HOMA-IR) requiring only fasting glucose and insulin measurements—could not improve prediction of diabetes risk.

Legend: Bars show age-adjusted hazard ratios for 0 (reference category), 1, 2, and ≥ 3 metabolic syndrome abnormalities by NCEP-ATP III clinical criteria, baseline type 2 diabetes, and baseline prevalent CVD status.

Reference

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11. Reaven GM. The metabolic syndrome: is this diagnosis necessary? Am J Clin Nutr 2006; 83: 1237-47.

12. Meigs JB, Rutter MK, Sullivan LM, et al. Impact of Insulin Resistance on Risk of Type 2 Diabetes and Cardiovascular Disease in People with Metabolic Syndrome. Diabetes Care 2007; 30: 1219-25.

13. Dekker JM, Girman C, Rhodes T, et al. Metabolic syndrome and 10-year cardiovascular disease risk in the Hoorn Study. Circulation 2005; 112: 666-73.

14. Hanley AJ, Karter AJ, Williams K, et al. Prediction of type 2 diabetes mellitus with alternative definitions of the metabolic syndrome: the Insulin Resistance Atherosclerosis Study. Circulation 2005; 112: 3713-21.

15. Rutter MK, Meigs JB, Sullivan LM, et al. Insulin resistance, the metabolic syndrome, and incident cardiovascular events in the Framingham Offspring Study. Diabetes 2005; 54: 3252-7.

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