Abnormalities of plasma
lipid and
lipoprotein concentrations are common in both
insulin-dependent (
IDDM) and non-
insulin-dependent (
NIDDM)
diabetes mellitus. In general, individuals with
IDDM who are untreated or inadequately treated have elevations in both postprandial and fasting
triglyceride levels in association with reduced activity of
lipoprotein lipase.
Low-density lipoprotein (
LDL) cholesterol levels can rise when
insulin deficiency impacts on
LDL-receptor function. When patients with
IDDM are treated and plasma
glucose levels well controlled, plasma
very-low-density lipoprotein (
VLDL) triglyceride and
LDL cholesterol levels are usually normal. In addition, plasma
high-density lipoprotein (
HDL) cholesterol levels are normal or elevated in well-controlled
IDDM subjects. In
NIDDM, increased
VLDL triglyceride and reduced
HDL cholesterol concentrations are common and are only partially related to
glycemic control. Overproduction of VLDL leads to
hypertriglyceridemia, which can be exacerbated if
lipoprotein lipase activity is also reduced. The regulation of
LDL levels is complex; catabolism can be reduced if significant
insulin deficiency exists or increased if significant
hypertriglyceridemia is present. The reduced levels of
HDL cholesterol in
NIDDM appear to be related to increased exchange of HDL
cholesteryl esters for VLDL
triglycerides, although other mechanisms may exist. The roles of
insulin resistance,
obesity, and independently inherited abnormalities of
lipoprotein metabolism in the etiology of
dyslipidemia of
NIDDM are complex and require further investigation. Finally, the effects of diabetes on glycosylation of
apoproteins; on other
lipid enzymes, particularly hepatic
triglyceride lipase; on
lipoprotein surface
lipids; and on hepatic uptake of remnants have only just begun to be defined. In view of the marked increase in atherosclerotic
cardiovascular disease in individuals with
diabetes mellitus, prompt attention to and aggressive
therapy for
dyslipidemia should be a central component of care for these patients.