Low high-density lipoprotein cholesterol level is a significant risk factor for development of type 2 diabetes: Data from the Hawaii-Los Angeles-Hiroshima study

Aims/IntroductionA low level of high-density lipoprotein cholesterol (HDLC) is a common feature of metabolic syndrome. We have reported that Japanese-Americans who share a virtually identical genetic makeup with native Japanese, but who have lived Westernized lifestyles for decades, have lower HDLC levels and a high prevalence of type2 diabetes compared with native Japanese. However, the impact of low HDLC level on type2 diabetes is unclear. The aims of the present study were to evaluate whether serum HDLC level was associated with development of type2 diabetes and if the effect might be modified by lifestyle. Materials and MethodsWe examined 1,133 non-diabetic Japanese-Americans and 1,072 non-diabetic Japanese, who underwent the 75-g oral glucose tolerance test (OGTT) and were followed for an average of 8.8 and 7.0years, respectively. We analyzed whether serum HDLC level is a risk factor for development of type2 diabetes based on the Cox proportional hazards model. ResultsAfter adjustment for age and sex, hazard ratios for development of type2 diabetes per unit of serum HDLC level (mmol/L) were 0.292 (95% confidence interval [CI] 0.186-0.458, P<0.0001) among Japanese-Americans and 0.551 (95% CI 0.375-0.88, P=0.0023) among native Japanese. Comparable hazard ratios after further adjustment for category of OGTT and body mass index were 0.981 (95% CI 0.970-0.993, P=0.0018) and 0.991 (95% CI 0.980-1.002, P=0.112), respectively. ConclusionsHDLC level was associated with development of type2 diabetes in both Japanese-Americans and native Japanese. However, these results suggest that the impact of high-density lipoprotein on glucose metabolism might be affected by lifestyle.