A review of observational studies on the relationship between cholesterol and coronary heart disease

Genetics of Lipid and Lipoprotein Disorders and Traits

PURPOSE OF REVIEW

Plasma lipids, namely cholesterol and triglyceride, and lipoproteins, such as low-density lipoprotein (LDL) and high-density lipoprotein, serve numerous physiological roles. Perturbed levels of these traits underlie monogenic dyslipidemias, a diverse group of multisystem disorders. We are on the verge of having a relatively complete picture of the human dyslipidemias and their components.

RECENT FINDINGS

Recent advances in genetics of plasma lipids and lipoproteins include the following: (1) expanding the range of genes causing monogenic dyslipidemias, particularly elevated LDL cholesterol; (2) appreciating the role of polygenic effects in such traits as familial hypercholesterolemia and combined hyperlipidemia; (3) accumulating a list of common variants that determine plasma lipids and lipoproteins; (4) applying exome sequencing to identify collections of rare variants determining plasma lipids and lipoproteins that via Mendelian randomization have also implicated gene products such as NPC1L1, APOC3, LDLR, APOA5, and ANGPTL4 as causal for atherosclerotic cardiovascular disease; and (5) using naturally occurring genetic variation to identify new drug targets, including inhibitors of apolipoprotein (apo) C-III, apo(a), ANGPTL3, and ANGPTL4.

SUMMARY

Here, we compile this disparate range of data linking human genetic variation to plasma lipids and lipoproteins, providing a "one stop shop" for the interested reader.

Cigarette smoking and periodontitis: methodology to assess the strength of evidence in support of a causal association

Identification of the cause of the development and progression of periodontitis has received extensive attention, with notable advances over the past decade in clinical, microbiological, immunological, biochemical, and behavioral knowledge. However, it is still largely unknown which factors lead to the conversion of non-destructive forms of periodontal disease into destructive forms and disease progression. Chronic adult periodontitis is believed to be influenced by an interaction of host defense and environmental factors. Although these variables have been studied extensively, no study has employed randomized controlled prospective human or randomized controlled community intervention designs, methodologies necessary to prove a variable to be a cause of periodontitis. Owing to the absence of literature employing rigorous experimental design, this article assesses systematically observational, cross-sectional and longitudinal studies to examine the potential causal association between cigarette smoking and periodontitis. The methodology of Sir Bradford Hill's criteria for causation was used as the framework. Results suggest that cigarette smoking is causally associated with periodontitis. That is, cigarette smoking is consistently associated with an increased prevalence/severity of periodontitis and is suspected on theoretical grounds of playing a causal role. Hill's criteria provide a useful methodology to better understand the pathogenesis of periodontal diseases and may be applied to study the pathogenesis of other dental diseases as well.

Fluvastatin for dyslipoproteinemia, with or without concomitant chronic renal insufficiency

Renal insufficiency is frequently associated with both quantitative and qualitative abnormalities in lipid and hemorheologic profiles. Although this may lead to increased risk of cardiovascular disease, a number of studies have also shown dyslipidemia to be a significant risk factor for the progression of renal insufficiency in human chronic renal disease. This double-blind, placebo-controlled trial aimed to assess the effect of fluvastatin, a synthetic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on these parameters in dyslipidemic patients with or without chronic renal insufficiency. After a 6-week placebo run-in, 42 patients who had been previously stratified into 2 groups on the basis of creatinine clearance levels (0.5-1.0 mL/sec or > 1.0-1.5 mL/sec) were randomized to treatment with fluvastatin (40 mg daily) or matching placebo. Significant differences (on analysis of variance with repeated measures) were seen between fluvastatin and placebo treatment groups for changes in total cholesterol (-15% vs 1%, respectively; p < 0.001), low density lipoprotein cholesterol (LDL-C; -21% vs -5%; p < 0.001), very low density lipoprotein cholesterol (-14% vs 14%; p = 0.017), very low density lipoprotein triglycerides (-1% vs 29%; p = 0.014) and total triglycerides (-7% vs 24%; p < 0.001). These effects on cholesterol levels were reflected in a significant decrease in apolipoprotein B levels with fluvastatin therapy (p < 0.001). Apolipoprotein A-I levels increased (p = 0.054) despite no significant change in the levels of high density lipoprotein cholesterol. Response to therapy did not differ between the 2 renal function groups for any of the lipid, lipoprotein, and apolipoprotein variables. Hemorheologic parameters were not altered with fluvastatin therapy, regardless of renal function.(ABSTRACT TRUNCATED AT 250 WORDS)