Awareness of lipid guideline recommendations for high-risk patients amongst primary care physicians in Canada

Background

Lipid guidelines for cardiovascular (CV) risk reduction have evolved in recent years, particularly since the introduction of PCSK9 inhibitors. In many jurisdictions, CV risk management is provided by primary care physicians (PCPs). We surveyed Canadian PCPs regarding their awareness and implementation of the 2021 Canadian Cardiovascular Society (CCS) lipid guideline recommendations for patients following an acute coronary syndrome (ACS) or for those with diabetes but without CV disease.

Methods and results

From a national database of PCPs with interest and/or experience in CV medicine, we invited PCPs to complete a survey regarding lipid management in high-risk patients. A committee of PCPs and specialists with lipid expertise including several co-authors of the 2021 CCS lipid guidelines had designed the survey to probe awareness and practice patterns. A total of 203 PCPs from across Canada completed the survey between January and March 2022. 23.6% of respondents had previously prescribed a PCSK9 inhibitor. Almost all (96.5%) PCPs concurred that a post-ACS patient should be seen by their PCP within 4 weeks of hospital discharge (79.3% within 2 weeks). Almost half (45.3%) responded that discharge summaries provided inadequate information relevant for PCPs, and 43% felt that lipid management post-ACS was the primary responsibility of specialists. More than half (56%) articulated challenges when seeing a post-ACS patient, related to inadequate discharge information, complexities of polypharmacy and duration of therapies, and managing perceived or real statin intolerance. 62% correctly identified the LDL-C intensification threshold of 1.8 mmol/L in post-ACS patients, while 79% considered that PCSK9 inhibitors were indicated only for those patients who were already receiving statins plus ezetimibe or had substantially elevated LDL-C levels. 55.2% were able to correctly identify clinical features associated with greatest absolute benefit of PCSK9 inhibitors in post-ACS patients. For patients with diabetes but without ASCVD, 80% of PCPs incorrectly believed that PCSK9 inhibitors were indicated for LDL-C levels above threshold despite statin therapy, and only 42% correctly identified the LDL-C threshold for treatment intensification of 2.0 mmol/L.

Conclusion

While PCPs are aware of the urgency regarding lipid management in post-ACS patients, many encounter challenges after hospital discharge, frequently deferring lipid management to specialists. Thus, almost one year following publication of the 2021 CCS lipid guidelines, substantial knowledge gaps remain regarding intensification thresholds and treatment options for patients post-ACS or for those with diabetes. Innovative and effective knowledge translation programs are urgently required.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Amgen Canada

RNAi inhibition of angiopoietin-like protein 3 (ANGPTL3) with ARO-ANG3 mimics the lipid and lipoprotein profile of familial combined hypolipidemia

Background

Elevated LDL-C and triglyceride rich lipoproteins (TRLs) are independent risk factors for cardiovascular disease (CVD). Genetic deficiency of angiopoietin-like protein 3 (ANGPTL3) is associated with reduced circulating levels of LDL-C, triglycerides (TGs), VLDL-C, HDL-C and reduced CVD risk, with no described adverse phenotype. ARO-ANG3 is a RNA interference drug designed to silence expression of ANGPTL3. Single doses of ARO-ANG3 have been shown to reduce ANGPTL3, TGs, VLDL-C and LDL-C in healthy volunteers (HVs, AHA 2019). We report the effects of multiple doses of ARO-ANG3 in HVs with a focus on the duration of action.

Methods

ARO-ANG3 was administered subcutaneously to HVs on days 1 and 29 at doses of 100, 200 or 300 mg (n=4 per group). Measured parameters included ANGPTL3, LDL-C, TGs, VLDL-C and HDL-C. Follow up is ongoing.

Results

All HVs have received both doses and follow-up is currently through week 16 (12 weeks after second dose). Mean nadir for ANGPTL3 levels occurred 2 weeks after the second dose (−83–93%) with minimal change for 200 and 300 mg but 16% recovery for 100 mg at week 16. Mean TGs and VLDL-C reached nadir earlier (3 wks, −61–65%) without apparent dose response and minimal change for any dose at wk 16. LDL-C nadir occurred 4–6 wks after the second dose (−45–54%), again with minimal evidence for dose response or change through wk 16. HDL-C was reduced 14–37% at wk 16. ARO-ANG3 was well tolerated without serious or severe adverse events or dropouts related to drug. The most common adverse events have been headache and upper respiratory infections.

Conclusions

Genetic deficiency of ANGPTL3 is a cause of familial combined hypolipemia and is associated with a decreased risk of CVD. Using RNAi to selectively suppress ANGPTL3 production reproduces these genetic effects with a duration of at least 12 weeks following a second dose and with good tolerability over 16 wks. ANGPTL3 inhibition results in lowering of LDL-C and TRLs which may confer protection against CVD in patients with atherogenic mixed dyslipidemia.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Arrowhead Pharmaceuticals

RNA interference targeting apolipoprotein C-III with ARO-APOC3 in healthy volunteers mimics lipid and lipoprotein findings seen in subjects with inherited apolipoprotein C-III deficiency

Background

Individuals with triglycerides (TGs) ≥1,000 mg/dL (11.1 mmol/L) are at increased risk of acute pancreatitis. Genetic studies indicate that individuals with apolipoprotein C-3 (APOC3) loss-of-function mutations have low TGs, reduced cardiovascular risk and no observed adverse phenotype. RNA interference (RNAi) with ARO-APOC3 has shown deep and durable knockdown (KD) of APOC3 after single doses in healthy volunteers (HVs, presented at AHA 2019) with good tolerability. We report here initial results using multiple doses of ARO-APOC3 to silence APOC3 expression in HVs.

Methods

ARO-APOC3 was administered subcutaneously to HVs on days 1 and 29 at doses of 10, 25 or 50 mg (n=4 per group). Measured parameters included plasma concentrations of APOC3, LDL-C, TGs, VLDL-C and HDL-C.

Results

All HVs have received both doses and follow-up for most parameters is available through week (wk) 14 (10 wks after second dose) for the 10 and 25 mg doses and through wk 10 for 50 mg. Mean nadir for APOC3 levels occurred at wk 3 for 10 mg (−73%) and remained similar at wk 10 (−66%), at wk 6 for 25 mg (−90%) with no change at wk 10 and at wk 2 for 50 mg (−94%) unchanged at wk 8. TGs fell faster in the 50 mg group (wk 1: 10 mg −41%; 25 mg −47%; 50 mg −72%). By wk 6 the 25 and 50 mg results were similar (−68% and −74%, respectively) and remained similar through wk 14. 10 mg was less active with a nadir of −56% and mean reductions between 42% and 56% post-nadir. VLDL-C values mirrored TGs. LDL-C reductions were more modest and did not manifest a dose response. Mean nadirs (−23–26%) occurred 4–6 wks after the first dose, again with minimal change through 10–14 wks of follow-up. Consistent with genetic studies, HDL-C increased to a maximum at approximately wk 8 (10 mg +42%, 25 mg +48%, 50 mg +84%). ARO-APOC3 was well tolerated without serious or severe adverse events or dropouts related to drug. The most common adverse events were mild injection site AEs and headache.

Conclusions

Genetic deficiency of APOC3 is associated with substantial reductions in TGs, VLDL-C and increases in HDL-C without an adverse phenotype. Using RNAi to selectively suppress APOC3 production mimics these lipid and lipoprotein effects, with a duration of at least 10 weeks following a second dose and with good tolerability over 16 wks using doses ranging from 10 to 50 mg. Investigation of optimal dosing regimen is ongoing, especially with respect to dosing interval. This therapeutic approach has potential for treating patients with chylomicronemia at risk of pancreatitis.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Arrowhead Pharmaceuticals

A genome-wide linkage scan for familial partial lipodystrophy susceptibility genes in a German kindreds

Background: In Dunnigan-type familial partial lipodystrophy (FPLD) patients are born with normal fat distribution, but subcutaneous fat from extremities and gluteal regions are lost during puberty. The abnormal fat distribution leads to the development of metabolic syndrome (MetS), a cluster of phenotypes including hyperglycemia, dyslipidemia, hypertension, and visceral obesity. The study of FPLD as a monogenic model of MetS may uncover genetic risk factors of the common MetS which affects ~30% of adult North Americans. Two molecular forms of FPLD have been identified including FPLD2, resulting from heterozygous mutations in the LMNA gene, and FPLD3, resulting from both heterozygous dominant negative and haploinsufficiency mutations in the PPARG gene. However, many patients with clinically diagnosed FPLD have no mutation in either LMNA or PPARG, suggesting the involvement of additional genes in FPLD etiology. Methods: Here, we report the results of an Affymetrix 10K GeneChip microarray genome-wide linkage analysis study of a German kindred displaying the FPLD phenotype and no known lipodystrophy-causing mutations. Results: The investigation identified three chromosomal loci, namely 1q, 3p, and 9q, with non-parametric logarithm of odds (NPL) scores >2.7. While not meeting the criteria for genome-wide significance, it is interesting to note that the 1q and 3p peaks contain the LMNA and PPARG genes respectively. Conclusions: Three possible conclusions can be drawn from these results: 1) the peaks identified are spurious findings, 2) additional genes physically close to LMNA, PPARG, or within 9q, are involved in FPLD etiology, or 3) alternative disease causing mechanisms not identified by standard exon sequencing approaches, such as promoter mutations, alternative splicing, or epigenetics, are also responsible for FPLD.

Utility of a lung biopsy for the diagnosis of idiopathic pulmonary fibrosis

It is not known if a surgical lung biopsy is necessary in all patients for the diagnosis of idiopathic pulmonary fibrosis (IPF). We conducted a blinded, prospective study at eight referring centers. Initially, cases were evaluated by clinical history and examination, transbronchial biopsy, and high-resolution lung computed tomography scans. Pulmonologists at the referring centers then assessed their certainty of the diagnosis of IPF and provided an overall diagnosis, before surgical lung biopsy. The lung biopsies were reviewed by a pathology core and 54 of 91 patients received a pathologic diagnosis of IPF. The positive predictive value of a confident (certain) clinical diagnosis of IPF by the referring centers was 80%. The positive predictive value of a confident clinical diagnosis was higher, when the cases were reviewed by a core of pulmonologists (87%) or radiologists (96%). Lung biopsy was most important for diagnosis in those patients with an uncertain diagnosis and those thought unlikely to have IPF. These studies suggest that clinical and radiologic data that result in a confident diagnosis of IPF by an experienced pulmonologist or radiologist are sufficient to obviate the need for a lung biopsy. Lung biopsy is most helpful when clinical and radiologic data result in an uncertain diagnosis or when patients are thought not to have IPF.

Substance P (NK1)- and neurokinin A (NK2)-receptor gene expression in inflammatory airway diseases

The tachykinin neuropeptides substance P and neurokinin (NK) A have been postulated to participate in the inflammatory reaction in airways of smokers and asthmatics. We have examined the hypothesis that the expression of one or more of the three cloned tachykinin receptors (NK1, NK2, and NK3) is increased in inflammatory airway disorders, which could result in augmentation of the effect of released tachykinin neuropeptides. NK1 receptor and NK2 receptor but not NK3-receptor mRNA were detected by ribonuclease protection assay in RNA from both cartilaginous and membranous bronchi and subpleural lung. In lung samples containing membranous airways, NK2-receptor mRNA expression was increased fourfold in asthmatics compared with nonsmoking controls, whereas NK1-receptor mRNA levels were similar in the two groups. NK1- and NK2-receptor mRNA expression was increased twofold in smokers without airflow obstruction compared with nonsmokers, whereas NK1-receptor mRNA expression was significantly lower in patients with chronic obstructive pulmonary disease compared with smoking controls. In situ hybridization indicated NK1-receptor mRNA was expressed in submucosal glands and airway epithelial cells, whereas NK2-receptor and NK3-receptor mRNA were not detected. These observations have implications for the pathophysiology and treatment of both asthma and tobacco smoke-induced airway inflammation.

Comparative efficacy and safety of pravastatin, nicotinic acid and the two combined in patients with hypercholesterolemia

In a comparative study, 158 patients with type IIa or IIb primary hypercholesterolemia received either placebo, nicotinic acid extended-release capsules (0.5 to 1.0 g twice daily), pravastatin (40 mg at bedtime), or the combination for a short-term, 8-week period. A long-term, 88-week phase followed in which the addition of other lipid-lowering agents was permitted. During the short-term phase, low-density lipoprotein cholesterol levels were lower, in relation to baseline, with nicotinic acid treatment (-21%) than with placebo (P < or = 0.05), with pravastatin (-33%) than with either placebo (p < or = 0.001) or nicotinic acid (p < or = 0.05) and with combination therapy (-49%) than with the other 3 treatments (p < or = 0.05) at all weeks measured. At week 8, high-density lipoprotein cholesterol levels were increased, in relation to placebo, by nicotinic acid treatment (12%; p < or = 0.05), pravastatin therapy (13%; p < or = 0.01) and combination therapy (16%; p < or = 0.01). Adverse events were less frequent in the pravastatin and placebo groups (p < or = 0.05). In comparison with placebo, treatment with nicotinic acid resulted in significant increases in aspartate and alanine aminotransferase. The placebo and pravastatin groups did not differ significantly regarding adverse events or laboratory parameters. Similar results were observed in the long-term phase. Therefore, pravastatin is very effective and well tolerated in the treatment of type IIa or IIb primary hypercholesterolemia, and is superior to nicotinic acid in both efficacy and adverse event profile.(ABSTRACT TRUNCATED AT 250 WORDS)

Upper gastrointestinal bleeding due to superior mesenteric artery to duodenum fistula: rare complication of metastatic lung carcinoma

Although metastases from primary carcinoma of the lung to the small intestine appear to be more common than previously suspected, they rarely produce symptoms. Such metastases may present as bowel perforations. Overt gastrointestinal bleeding has been described only as a prelude to perforation. We describe the case of a 55-yr-old man with carcinoma of the lung that had metastasized to the brain and to the third part of the duodenum. The duodenal metastasis presented with massive upper gastrointestinal hemorrhage. The metastasis was seen to be actively bleeding at endoscopy, and a direct fistula from a branch of the superior mesenteric artery to the third part of the duodenum was shown angiographically. Arterial invasion and destruction by tumor was confirmed at postmortem examination. This complication of metastatic carcinoma of the lung has not been previously described in the English literature.

Lipoprotein lipase deficiency resulting from a nonsense mutation in exon 3 of the lipoprotein lipase gene

In DNA from a male patient of German and Polish ancestry who has lipoprotein lipase deficiency, sequencing of all nine exons and intron-exon boundaries corresponding to the coding region of the lipoprotein lipase gene detected a C----T transition leading to the substitution of a stop signal for the codon that normally determines a glutamine at position 106 of the mature enzyme. Hybridization with allele-specific oligonucleotides at this position established that the patient was homozygous for this mutation. This mutation must lead to the synthesis of a sharply truncated protein, accounting for the enzymatic deficiency noted in the patient.

Missense mutation (Gly----Glu188) of human lipoprotein lipase imparting functional deficiency

Cloning and sequencing of lipoprotein lipase (LPL) cDNA prepared from the adipose tissue of a patient with classical LPL deficiency revealed a G to A transition at nucleotide 818 in all sequenced clones, leading to the substitution of glutamic acid for glycine at residue 188 of the mature protein. Hybridization of genomic DNA with allele-specific oligonucleotides confirmed that the patient was homozygous for this mutation and revealed that carrier status for this mutation among relatives of the patient was significantly associated with hypertriglyceridemia. Assay of the patient's plasma for immunoreactive enzyme and activity demonstrated the presence of a circulating inactive enzyme protein, the concentration of which was further increased by injection of heparin. The mutant sequence was produced by oligonucleotide-directed mutagenesis, and both normal and mutant sequences were cloned into the expression vector pSVL and transfected into COS-1 cells. The normal sequence led to the in vitro expression of an enzyme that bound to heparin-Sepharose and had a specific catalytic activity similar to that of normal postheparin plasma enzyme. By contrast, the mutant enzyme expressed in vitro was catalytically inactive and displayed a lower affinity for heparin than the normal enzyme. We conclude that this single amino acid substitution leads to the in vivo expression of an inactive enzyme accounting for the manifestations of LPL deficiency noted in the patient.

Tridimensional ultrastructure of glomerular capillary endothelium revealed by high-resolution scanning electron microscopy

Recent advances in specimen preparation techniques and scanning electron microscope (SEM) design have permitted ultrastructural examination of the glomerular capillary wall in three dimensions using high-resolution scanning electron microscopy (HRSEM). Specimens in which the cytosol and cytoskeleton have been extracted, but cell membranes nuclear structures and organelles left in place, were studied using a Hitachi SEM with a resolution of approximately 3 nm. Each HRSEM micrograph displayed a depth of field and information content equivalent to 15-30 consecutive, ultrathin, transmission electron microscope (TEM) sections viewed simultaneously in perfect serial alignment. The results have confirmed previous ultrastructural observations obtained by use of TEM and, in addition, have revealed new ultrastructural features of the normal rat glomerulus. A morphometric analysis of glomerular endothelium carried out using the HRSEM micrographs revealed that the endothelial cell processes, which lie between the fenestrae, are nearly circular in cross section and that they, as well as the fenestrae, have a diameter of approximately 60 nm. The potential functional role of the fenestrae in controlling access to the underlying basement membrane requires further study.

Bradykinin stimulates a rise in cytosolic calcium in renal glomerular mesangial cells via a pertussis toxin insensitive pathway

Bradykinin elicits a complex response in the renal glomerulus which includes a reduction in the glomerular capillary ultrafiltration coefficient. To elucidate the biochemical mechanism of this response, we investigated calcium signalling in rat renal glomerular mesangial cells in culture using the calcium-sensitive fluorescent dye, Indo-1. Bradykinin was found to cause a concentration-dependent transient rise in cytosolic free calcium followed by a sustained slower secondary rise. The bradykinin response persisted with acute removal of extracellular calcium using EGTA, indicating that calcium entry from outside the cell did not mediate this primary response. Prolonged exposure to EGTA, which reduced intracellular stores, eliminated the calcium response to bradykinin but not to vasopressin, indicating differential sensitivity to intracellular calcium stores of these two hormonal responses. In agreement, prior stimulation with vasopressin significantly attenuated the response to bradykinin, but the converse did not occur. Aluminum fluoride and pertussis toxin were used to investigate the possible involvement of a guanyl nucleotide regulatory protein in signal transduction. Aluminum fluoride induced a transient rise in cytosolic calcium that was abrogated by prior exposure of the cells to pertussis toxin. This demonstrates the effectiveness of pertussis toxin and the presence of a calcium-signalling pathway susceptible to pertussis toxin in these cells. In contrast, the responses to bradykinin and vasopressin were unaffected by pertussis toxin. We conclude that bradykinin stimulates release of calcium from intracellular stores in glomerular mesangial cells via a pertussis toxin insensitive pathway. This mesangial response provides a direct biochemical basis for the bradykinin-induced fall in glomerular capillary ultrafiltration coefficient which has been observed in vivo.