Use of fibrates in clinical practice: Queensland Lipid Group consensus recommendations

Altered Peroxisome Proliferator-Activated Receptor Alpha Signaling in Variably Diseased Peripheral Arterial Segments

Objective

Peripheral atherosclerosis that accumulates in the extracranial carotid and lower extremity arteries can lead to significant morbidity and mortality. However, atherosclerotic disease progression is often not homogenous and is accelerated by diabetes. We previously observed increased phospholipid content in minimally (Min)-diseased arterial segments compared to maximally (Max)-diseased segments. Since Peroxisome Proliferator-Activated Receptor alpha (PPARα) is a key regulator of lipid metabolism, we hypothesized that it may have differential expression and signaling in Min vs. Max-diseased peripheral arterial segments.

Methods

Eighteen patients who underwent carotid endarterectomy (CEA), and 34 patients who underwent major lower extremity amputation were prospectively enrolled into a vascular tissue biobank. Min and Max-diseased segments were obtained in real-time from CEA plaque and amputated lower extremity arterial segments. mRNA and protein were isolated from specimens and the relative expression of ppara, and its downstream genes Acyl-CoA Oxidase 1 (acox1) and Carnitine Palmitoyltransferase 1A (cpt1a) were also evaluated. We evaluated gene expression and protein content relative to atherosclerotic disease severity and clinical diabetes status. Gene expression was also evaluated relative to Hemoglobin A1c and serum lipid profiles.

Results

In CEA segments of patients with diabetes, we observed significantly higher ppara and acox1 gene expression (p < 0.01 and p < 0.001 respectively), and higher PPARα protein content (p < 0.05). Hemoglobin A1c significantly correlated with expression of ppara (R² = 0.66, p < 0.001), acox1 (R² = 0.31, p < 0.05), and cpt1a (R² = 0.4, p < 0.05). There was no significant difference in gene expression between Min vs. Max-diseased CEA plaque segments. Conversely, in lower extremity arterial segments of patients with diabetes, we observed significantly lower ppara, acox1, and cpt1a expression (p < 0.05, p < 0.001, and p < 0.0001 respectively). Interestingly, CPT1A content was lower in arterial segments of patients with diabetes (p < 0.05). Hemoglobin A1c and HDL-cholesterol had negative correlations with ppara (R² = 0.44, p < 0.05; R² = 0.42, p < 0.05; respectively).

Conclusion

This study demonstrates the significant differential expression of ppara and its immediate downstream genes in human carotid and lower extremity arteries relative to disease severity and diabetes. These findings highlight that mechanisms that influence atheroprogression in the carotid and lower extremities peripheral arteries are not homogenous and can be impacted by patient diabetes status and serum cholesterol profiles. Further elucidating these differential molecular mechanisms can help improve targeted therapy of atherosclerosis in different peripheral arterial beds.

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.

PPARs: regulators of metabolism and as therapeutic targets in cardiovascular disease. Part II: PPAR-β/δ and PPAR-γ

The PPARs are a subfamily of three ligand-inducible transcription factors, which belong to the superfamily of nuclear hormone receptors. In mammals, the PPAR subfamily consists of three members: PPAR-α, PPAR-β/δ and PPAR-γ. PPARs control the expression of a large number of genes involved in metabolic homeostasis, lipid, glucose and energy metabolism, adipogenesis and inflammation. PPARs regulate a large number of metabolic pathways that are implicated in the pathogenesis of metabolic diseases such as metabolic syndrome, Type 2 diabetes mellitus, nonalcoholic fatty liver disease and cardiovascular disease. The aim of this review is to provide up-to-date information about the biochemical and metabolic actions of PPAR-β/δ and PPAR-γ, the therapeutic potential of their agonists currently under clinical development and the cardiovascular disease outcome of clinical trials of PPAR-γ agonists, pioglitazone and rosiglitazone.

Extreme urinary betaine losses in type 2 diabetes combined with bezafibrate treatment are associated with losses of dimethylglycine and choline but not with increased losses of other osmolytes

PURPOSE

Betaine deficiency is a probable cardiovascular risk factor and a cause of elevated homocysteine. Urinary betaine excretion is increased by fibrate treatment, and is also often elevated in diabetes. Does fibrate further increase betaine excretion in diabetes, and does it affect the plasma concentrations and excretions of related metabolites and of other osmolytes?

METHODS

Samples from a previous study of type 2 diabetes were selected if participants were taking bezafibrate (n = 32). These samples were compared with participants matched for age and gender and not on a fibrate (comparator group, n = 64). Betaine, related metabolites, and osmolytes were measured in plasma and urine samples from these 96 participants.

RESULTS

Median urinary betaine excretion in those on bezafibrate was 5-fold higher than in the comparator group (p < 0.001), itself 3.5-fold higher than the median reported for healthy populations. In the bezafibrate group, median dimethylglycine excretion was higher (9-fold, p < 0.001). Excretions of choline, and of the osmolytes myo-inositol, taurine and glycerophosphorylcholine, were not significantly different between groups. Some participants excreted more betaine than usual dietary intakes. Several betaine fractional clearances were >100 %. Betaine excretion correlated with excretions of the osmolytes myo-inositol and glycerophosphorylcholine, and also with the excretion of choline and N,N-dimethylglycine, but it was inconclusive whether these relationships were affected by bezafibrate therapy.

CONCLUSIONS

Increased urinary betaine excretions in type 2 diabetes are further increased by fibrate treatment, sometimes to more than their dietary intake. Concurrent betaine supplementation may be beneficial.

Fenofibrate causes elevation of betaine excretion but not excretion of other osmolytes by healthy adults

BACKGROUND

Cross-sectional data suggest that bezafibrate increases betaine excretion in dyslipidemic patients.

OBJECTIVE

We aimed to demonstrate that fenofibrate induces increased betaine excretion in normal subjects and explore whether other 1-carbon metabolites and osmolytes are similarly affected.

METHODS

Urine was collected from 26 healthy adults before and after treatment with fenofibrate (145 mg/day for 6 weeks). Excretions of betaine, N,N-dimethylglycine, free choline, myo-inositol, taurine, trimethylamine-N-oxide, carnitine, and acetylcarnitine were measured by liquid chromatography with mass spectrometric detection.

RESULTS

Fenofibrate increased the median betaine excretion from 7.5 to 25.8 mmol/mole creatinine (median increase 3-fold), P < .001. The median increase in N,N-dimethylglycine excretion was 2-fold (P < .001). Median choline excretion increased 12% (significant, P = .029). Participants with higher initial excretions tended to have larger increases (P < .001 in all 3 cases). Fenofibrate did not significantly change the median excretions of myo-inositol, taurine, trimethylamine-N-oxide, and carnitine. The excretion of acetylcarnitine decreased 4-fold on treatment, with no correlation between the baseline and after-treatment excretions. Changes in all urine components tested, except trimethylamine-N-oxide, positively correlated with changes in betaine excretion even when the median excretions before and after were not significantly different.

CONCLUSIONS

Fibrates increase betaine, and to a lesser extent N,N-dimethylglycine and choline, excretion. Other osmolytes are not elevated. Because the increase in betaine excretion depends on the baseline excretion, large increases in excretion in the metabolic syndrome and diabetes (where baseline excretions are high) could be expected. Replacement with betaine supplements may be considered.

PPARα activation can help prevent and treat non-small cell lung cancer

Non-small cell lung cancer (NSCLC) not amenable to surgical resection has a high mortality rate, due to the ineffectiveness and toxicity of chemotherapy. Thus, there remains an urgent need of efficacious drugs that can combat this disease. In this study, we show that targeting the formation of proangiogenic epoxyeicosatrienoic acids (EET) by the cytochrome P450 arachidonic acid epoxygenases (Cyp2c) represents a new and safe mechanism to treat NSCLC growth and progression. In the transgenic murine K-Ras model and human orthotopic models of NSCLC, we found that Cyp2c44 could be downregulated by activating the transcription factor PPARα with the ligands bezafibrate and Wyeth-14,643. Notably, both treatments reduced primary and metastatic NSCLC growth, tumor angiogenesis, endothelial Cyp2c44 expression, and circulating EET levels. These beneficial effects were independent of the time of administration, whether before or after the onset of primary NSCLC, and they persisted after drug withdrawal, suggesting the benefits were durable. Our findings suggest that strategies to downregulate Cyp2c expression and/or its enzymatic activity may provide a safer and effective strategy to treat NSCLC. Moreover, as bezafibrate is a well-tolerated clinically approved drug used for managing lipidemia, our findings provide an immediate cue for clinical studies to evaluate the utility of PPARα ligands as safe agents for the treatment of lung cancer in humans.