**1. Introduction**

Cardiovascular disease (CVD) is one of the foremost causes of mortality and is a major contributor to morbidity for individuals with diabetes. Lipids abnormalities play an important role in raising the cardiovascular risk in diabetic and obese individuals. The main components of dyslipidemia in diabetes and metabolic syndrome is documented as small, dense lowdensity lipoprotein (LDL-cholesterol), the elevation in remnant triglyceride-rich lipoprotein particles, and the low high-density lipoprotein (HDL-cholesterol), which have very powerful atherogenic components.

Diabetes and chronic diseases such as chronic kidney diseases (CKD) were assessed as highrisk for cardiovascular risks by JNC-7, JSH-2009, the Adult Treatment Program III (ATP III)., therefore those conditions require more aggressive control of hypertension and dyslipidemia. [1, 2, 3, 4]. The American Heart Association (AHA) and the American College of Cardiology (ACC) recommended the following four groups of patients should be treated by statins; (1) patients with cardiovascular disease including angina, a previous heart attack or stroke, or other related condition; (2) patients with an LDL cholesterol ≥190 mg/dL; (3) patients with type 2 diabetes aged between 40 and 75 years. They reported that (4) patients with an estimated 10 year risk of cardiovascular diseases including a heart attack or stroke or developing other form of cardiovascular disease of ≥7.5% aged between 40 and 75 years. In addition, both Adult Treatment Program (ATP III) [3] and the American Diabetes Association (ADA) [4] guidelines have identified low-density lipoprotein cholesterol and the first priority of lipid lowering. There is strong evidence from landmark secondary prevention studies, that LDL cholesterol lowering in patients with diabetes leads to significant clinical benefits. Therefore, the benefit of statins on type 2 diabetes has been confirmed. [5]

Assellberg *et al.* [6] found 4 polymorphisms for HDL-cholesterol, 6 polymorphisms of LDLcholesterol, 10 for total cholesterol, and 4 polymorphisms for triglycerides might be responsible

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for these lipids' parameters phenotypes in the investigation using 2,000 genes.Genome-wide association studies (GWASs) have shown strong relationships between genetric polymor‐ phisms and lipids levels. Dyslipidemia may have, at least partly, determined genetic back‐ grounds, and understanding the heritability of dyslipidemia may help to control dyslipidemia.

Dyslipidemia is known as one of the important causes for the atherogenic changes in cardio‐ vascular system, and results in very severe cardiovascular risk. Therefore, diabetes patients with dyslipidemia have much higher prevalence of mortality and morbidity of cardiovascular risks compared to diabetes patients without dyslipidemia. However, there have been a lot of discussions, especially required statins on type 2 diabetes, because statins increase the risk of new-onset type 2 diabetes mellitus [7-9]. Very recent genetic meta-analysis suggested that the increased risk of type 2 diabetes noted with statins is at least partially explained by 3-hy‐ droxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase or HMGCR) inhibition [10].

The statins work in the liver to prevent the formation of cholesterol. This class of drugs are most effective at lowering the LDL- cholesterol, but also have modest effects on lowering triglycerides and raising HDL- cholesterol. There are several large cohort studies investigating the effects of statins on cardiovascular risks such as the Scandinavian Simvastatin Survival Study (4S) [11] and the Cholesterol and Recurrent Events (CARE) [12, 13] trial, however, the results are discordant. Some studies showed the drugs to reduce a patient's risk of cardiac events and stroke, outside of their ability to lower cholesterol levels. On the other hand, the statins are known as their side effects including elevation in glucose levels, which is well documented as one of the risk factors for ischemic heart diseases. A number of investigations have shown that people on a high-dose regimen of the cholesterol drug atorvastatin and other cholesterol-lowering drugs may have a slightly increased risk of developing type 2 diabetes, particularly if they have several of the classic diabetes risk factors. Therefore, the American Heart Association (AHA) /The American College of Cardiology (ACC) stated separately the guideline on dyslipidemia in 2013 [14].

This chapter will review *i)* at first, dyslipidemia as a risk factor for cardiovascular diseases, and then *ii)* the benefits and demerits for dyslipidemia treatments in type 2 diabetes using statins based on the data in several large cohort studies. *iii)* Furthermore, the discrepancy, statins can improve dyslipidemia but cannot prevent the new onset of type 2 diabetes, will be discussed.
