Debate: "How low should LDL cholesterol be lowered?" Viewpoint: "It doesn't need to be very low"

Lipid Target in Very High-Risk Cardiovascular Patients: Lesson from PCSK9 Monoclonal Antibodies

The role of low-density lipoproteins (LDLs) as a major risk factor for cardiovascular disease has been demonstrated by several epidemiological studies. The molecular basis for LDLs in atherosclerotic plaque formation and progression is not completely unraveled yet. Pharmacological modulation of plasma LDL-C concentrations and randomized clinical trials addressing the impact of lipid-lowering interventions on cardiovascular outcome have clearly shown that reducing plasma LDL-C concentrations results in a significant decrease in major cardiovascular events. For many years, statins have represented the most powerful pharmacological agents available to lower plasma LDL-C concentrations. In clinical trials, it has been shown that the greater the reduction in plasma LDL-C concentrations, the lower the rate of major cardiovascular events, especially in high-risk patients, because of multiple risk factors and recurrent events. However, in a substantial number of patients, the recommended LDL target is difficult to achieve because of different factors: genetic background (familial hypercholesterolemia), side effects (statin intolerance), or high baseline plasma LDL-C concentrations. In the last decade, our understanding of the molecular mechanisms involved in LDL metabolism has progressed significantly and the key role of proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged. This protein is an enzyme able to bind the LDL receptors (LDL-R) on hepatocytes, favoring their degradation. Blocking PCSK9 represents an intriguing new therapeutic approach to decrease plasma LDL-C concentrations, which in recent studies has been demonstrated to also result in a significant reduction in major cardiovascular events.

The impact of long-term growth hormone treatment on metabolic parameters in Japanese patients with short stature born small for gestational age

BACKGROUND/AIMS

An examination of the effects of up to 260 weeks of growth hormone (GH) therapy on metabolic parameters in Japanese children born small for gestational age (SGA).

METHODS

Data were analysed from a 156-week extension of a 104-week multicentre, randomised, double-blind, parallel-group trial. Sixty-five children born SGA (age 3-<8 years) received 33 μg/kg/day (n = 31, 64.5% male) or 67 μg/kg/day (n = 34, 58.8% male) GH for 260 weeks. Changes in metabolic parameters - glucose, insulin, total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol - were recorded. Alterations in weight, body mass index standard deviation score (BMI SDS) and vital signs were also evaluated.

RESULTS

Over 260 weeks of GH treatment, a positive correlation between Δheight SDS and Δinsulin-like growth factor-I SDS was observed. Insulin and glucose levels were generally unaffected. Favourable changes in lipid profiles were recorded, which were maintained for the study duration. No adverse alterations in weight, BMI SDS or vital signs were noted.

CONCLUSION

Long-term, continuous GH treatment in children born SGA appears to be efficacious, associated with potential benefits for several metabolic parameters and associated with no long-term safety concerns.

Apolipoprotein B knockdown by AAV-delivered shRNA lowers plasma cholesterol in mice

Serum low-density lipoprotein cholesterol (LDL-C) levels are proportionate to the risk of atherosclerotic cardiovascular disease. In order to reduce serum total cholesterol and LDL-C levels in mice, RNA interference (RNAi) was used to inhibit expression of the structural protein of LDL-C, apolipoprotein B100 (ApoB). We developed and screened 19 short hairpin RNAs (shRNAs) targeting conserved sequences in human, mouse, and macaque ApoB mRNAs (shApoB) and subsequently narrowed our focus to one candidate for in vivo testing. Self-complementary adeno-associated virus serotype 8 (scAAV8) was used for long-term transduction of murine liver with shApoB. A strong dose-dependent knockdown of ApoB mRNA and protein was observed, which correlated with a reduction in total cholesterol levels, without obvious signs of toxicity. Furthermore, shApoB was found to specifically reduce LDL-C in diet-induced dyslipidemic mice, whereas high-density lipoprotein cholesterol (HDL-C) remained unaffected. Finally, elevated lipid accumulation was shown in murine liver transduced with shApoB, a known phenotypic side effect of lowering ApoB levels. These results demonstrate a robust dose-dependent knockdown of ApoB by AAV-delivered shRNA in murine liver, thus providing an excellent candidate for development of RNAi-based gene therapy for the treatment of hypercholesterolemia.

Reduction in low-density lipoprotein cholesterol levels during statin therapy is associated with a reduced incidence of advanced colon polyps

BACKGROUND

Elevated serum cholesterol levels may stimulate proliferation in adenomatous polyps (AP). Our aim was to determine how a reduction of low-density lipoprotein (LDL) cholesterol levels in patients taking statins influences the incidence of APs.

METHODS

We performed a retrospective study of patients taking statins who were found to have > or =1 APs on an index colonoscopy, and who also had a follow-up colonoscopy within 3 to 5 years. Patients were divided into 2 groups: (1) those with > or =30% reduction in LDL levels and (2) those with < 30% reduction in LDL levels during the interval between colonoscopies. Univariate and multivariate analysis were evaluated for their association with advanced APs.

RESULTS

We identified 231 patients. Univariate analysis showed that patients with > or =30% LDL reduction had fewer mean total numbers of APs (2.6 versus 3.3, P = 0.02), fewer advanced APs (14% versus 26%, P = 0.04), and smaller APs (5 mm versus 6.1 mm, P = 0.01) than those with <30% reduction in LDL. Multiple logistic regression analysis confirmed that > or =30% LDL reduction was associated with smaller APs (P < 0.01). Subjects with > or =30% LDL reduction also had a 53% reduced incidence of advanced APs (OR, 0.47; CI, 0.22-0.96; P < 0.05). These findings remained significant even when adjusted for nonsteroidal antiinflammatory drug use, age, family history of APs, and body mass index.

CONCLUSIONS

A reduction in LDL levels of > or=30% during a 3- to 5-year period of statin therapy was associated with a 53% reduction in the incidence of advanced APs, even after adjustment for other known polyp risk factors.

Thinking intelligently about therapy of atherosclerosis

Atherosclerosis is a very complex disease. Although it is thought that hyperlipidemia, dyslipidemia, and other conditions such as high blood pressure are mainly responsible for the development of atherosclerosis, many other factors such as endothelial dysfunction and inflammation play a significant role in its pathology. The clinicians should be aware of all the contributing factors to optimize the therapy for atherosclerosis. A combination of lifestyle modification, nutritional measures, and pharmacological intervention with statins or fibrates would achieve good results if the treatment of atherosclerosis were pursued vigorously. In the presence of hypertension, the use of angiotensin-converting enzyme inhibitors and calcium channel blockers would be more appropriate.