The fatty acid desaturation index of blood lipids, as a biomarker of hepatic stearoyl-CoA desaturase expression, is a predictive factor of breast cancer risk

Associated factors of estimated desaturase activity in the EPIC-Potsdam study

BACKGROUND AND AIMS

Altered activity of desaturase enzymes may be involved in the development of metabolic diseases like type 2-diabetes. Desaturase activities might be modifiable by diet and lifestyle-related factors, but no study has systematically investigated such factors so far. We aimed to evaluate the association of demographic, anthropometric, dietary and lifestyle characteristics with estimated Δ5-, Δ6- and Δ9-desaturase activity.

METHODS AND RESULTS

A subsample (n = 1782) of the EPIC-Potsdam study was used for a cross-sectional analysis, involving men and women, mainly aged 35-65 years. Fatty acid (FA) product-to-precursor ratios, derived from the FA composition of erythrocyte membrane phospholipids, were used to estimate desaturase activities. Multiple linear regression models were used with estimated Δ5-, Δ6- and Δ9-desaturase activity as outcome and demographic (age, sex), anthropometric (BMI, WHR), dietary intake (FAs, carbohydrates) and lifestyle (physical activity, smoking, alcohol consumption) factors as exposure variables. Alcohol intake was positively associated with estimated Δ6- (explained variance in desaturase activity: 1.52%) and estimated Δ9-desaturase activity (explained variance: 5.53%). BMI and WHR showed a weak inverse association with estimated Δ5-desaturase activity (explained variance: BMI: 1.07%; WHR: 1.02%) and weak positive associations with estimated Δ6-(explained variance: BMI: 1.17%; WHR: 1.19%) and estimated Δ9-desaturase activities (explained variance: BMI: 0.70%; WHR: 0.96%). Age, sex, physical activity, smoking and dietary factors were only weakly associated with the estimated desaturase activities.

CONCLUSION

Our findings suggest that alcohol intake as well as obesity measures are associated with the FA ratios reflecting desaturase activity.

Erythrocyte membrane fatty acid composition is related to overloaded plasma ferritin in Chinese males with angiographic coronary artery disease

Not only is iron deficiency an abnormal iron status, but iron overload is also harmful for human health. It has been reported that overloaded iron stores are positively associated with increased coronary artery disease (CAD) risk, which is called the "iron-heart hypothesis". Previous studies evaluating the relationships between fatty acids (FAs) and body iron status only focused on participants with iron deficiency. However, whether FA composition is related to overloaded iron remains unclear. Therefore, this study was designed to investigate the relationships between erythrocyte membrane FA (Ery-FA) composition and overloaded body iron status as measured by plasma ferritin levels in Chinese CAD patients. A total of 446 subjects with angiographically identified CAD (mean age 63.1 years, 76.9% males) were recruited in a hospital between 2009 and 2010. Ery-FAs were measured by gas chromatography and the activities of FA desaturases, which are involved in the de novo synthesis of unsaturated FAs, were evaluated by using FA product-to-precursor ratios. Results showed that the average iron status was a bit overloaded in the population (median ferritin levels of 234.1 ng mL(-1) and 40.4% males of overload). Moreover, in males, saturated FAs (SFAs) were positively correlated (22 : 0, r = 0.182, p = 0.001; 24 : 0, r = 0.214, p < 0.001), whereas monounsaturated FAs (MUFAs) and n-6 polyunsaturated FAs (PUFAs) were negatively correlated (18 : 1n-9, r = -0.120, p = 0.028; 18 : 2n-6, r = -0.216, p < 0.001) with plasma ferritin levels. A negative correlation (r < 0, p < 0.05) between stearoyl-CoA desaturase (SCD) activity and ferritin levels was also found in males. However, all the significant associations above were not observed in females. In conclusion, the Ery-FA composition was related to overloaded plasma ferritin levels only in Chinese males with angiographic CAD, which might be linked to the change of SCD activity. The results may contribute to the understanding of the mechanism of the iron-heart hypothesis.

Cancer death is related to high palmitoleic acid in serum and to polymorphisms in the SCD-1 gene in healthy Swedish men

BACKGROUND

A high proportion of monounsaturated fatty acids (MUFAs) or a high ratio of MUFAs to saturated fatty acids in plasma, reflecting a high activity of the lipogenic enzyme stearoyl-CoA desaturase-1 (SCD-1), has been shown to be related to cancer death and incidence in some studies.

OBJECTIVES

The objective was to study whether the serum cholesteryl ester proportion of palmitoleic acid [16:1n-7 (16:1ω-3)] and the ratio of palmitoleic to palmitic acid (16:1n-7/16:0), as an estimation of the activity of SCD-1, are related to cancer death and to investigate whether polymorphisms in the SCD-1 gene are related to cancer mortality.

DESIGN

A community-based cohort of 50-y-old men was followed for a maximum of >40 y. Survival analysis was used to relate fatty acid composition in serum, analyzed at baseline by gas-liquid chromatography (n = 1981), and single nucleotide polymorphisms in the SCD-1 gene (n = 986) to cancer death. A 7-d dietary record was completed at age 70 y (n = 880).

RESULTS

The proportions of 16:1n-7 and the ratio of 16:1n-7 to 16:0 were associated with cancer mortality during follow-up in a comparison of the highest with the lowest quartile of 16:1n-7 (adjusted HR: 1.37; 95% CI: 1.04, 1.82). Inherited variance of the SCD-1 gene seemed to be related to cancer death, especially among men with a low proportion of PUFA in the diet in a comparison of the highest with the lowest weighted genetic risk score (HR: 2.14; 95% CI: 1.13, 4.04).

CONCLUSION

The findings are compatible with the hypothesis that there is an association between endogenously synthesized MUFAs and cancer death.

Prospective associations between plasma saturated, monounsaturated and polyunsaturated fatty acids and overall and breast cancer risk - modulation by antioxidants: a nested case-control study

BACKGROUND

Mechanistic data suggest that different types of fatty acids play a role in carcinogenesis and that antioxidants may modulate this relationship but epidemiologic evidence is lacking. Our aim was to investigate the association between plasma saturated, monounsaturated and polyunsaturated fatty acids (SFAs, MUFAs and PUFAs) and overall and breast cancer risk and to evaluate the potential modulatory effect of an antioxidant supplementation on these relationships.

METHODS

A nested case-control study included all first incident cancer cases diagnosed in the SU.VI.MAX study between 1994 and 2002 (n=250 cases, one matched control/case). Participants to the SU.VI.MAX randomized controlled trial received either vitamin/mineral antioxidants or placebo during this intervention period. Baseline fatty acid composition of plasma total lipids was measured by gas chromatography. Conditional logistic regression was performed overall and stratified by intervention group.

RESULTS

Dihomo-γ-linolenic acid (Ptrend=0.002), the dihomo-γ-linolenic/linoleic acids ratio (Ptrend=0.001), mead acid (Ptrend=0.0004), and palmitoleic acid (Ptrend=0.02) were inversely associated with overall cancer risk. The arachidonic/dihomo-γ-linolenic acids ratio (Ptrend=0.02) and linoleic acid (Ptrend=0.02) were directly associated with overall cancer risk. Similar results were observed for breast cancer specifically. In stratified analyses, associations were only observed in the placebo group. Notably, total PUFAs were directly associated with overall (Ptrend=0.02) and breast cancer risk in the placebo group only.

CONCLUSION

Specific SFAs, MUFAs and PUFAs were prospectively differentially associated with cancer risk. In addition, this study suggests that antioxidants may modulate these associations by counteracting the potential effects of these fatty acids on carcinogenesis.

Opportunities and challenges in developing stearoyl-coenzyme A desaturase-1 inhibitors as novel therapeutics for human disease

This review provides an overview of stearoyl-coenzyme A desaturase-1 (SCD1) as a novel therapeutic target for metabolic disorders and other indications. Target validation is reviewed, and limitations due to incomplete knowledge of the relevant biological systems are described. Assay development, particularly for high throughput screening, and characterization of SCD1 inhibition are summarized. The progress and evolution in medicinal chemistry are discussed, specifically focusing on key attributes of the most advanced SCD1 inhibitors described in the primary literature and in patent applications. This work culminated in numerous companies identifying potent selective inhibitors, some of which progressed to early clinical development. The status of current SCD1 drug discovery programs is reviewed. Challenges are discussed, and potential new directions are indicated.

Nutrition and breast cancer

Breast cancer incidence is rising worldwide with an increase in aggressive neoplasias in young women. Suspected factors responsible for the global increase include lifestyle changes, notably diet. Currently accepted risk factors directly linked to diet are greater body weight and alcohol consumption. Weight gain in adulthood is associated with increased risk of breast cancer in post-menopausal women, suggesting that weight gain before and around menopausal age may be determinant for breast cancer development among postmenopausal women. Numerous studies also show an impact of specific diets and nutrients - fatty acids, carbohydrates, vitamins B, D, carotenoids, phytoestrogens, fiber - on breast cancer risk, and evidence supports a mechanistic basis for an influence of specific nutrients. However, these studies are plagued with conflicting results. In this review, a new examination of the relationship between nutrition and breast cancer is proposed in light of recent epidemiological studies. Successful development of breast cancer prevention strategies will require identification of biological markers of dietary exposure, and to coordinate worldwide research to discern the effects of diet.

Omega-3 fatty acids for the prevention of breast cancer: an update and state of the science

The quantity and makeup of dietary fat intake are known to impact human health. Use of Omega-3 (ω-3) polyunsaturated fatty acid (PUFA) supplements has gained increasing attention for a variety of purported health benefits, including cancer prevention. Preclinical evidence has been encouraging and recent studies have expanded our understanding of the mechanisms by which ω-3 PUFAs may protect against breast cancer. However, epidemiologic studies have yielded mixed results. Recent population studies have attempted to delineate factors that may influence the effects of ω-3 PUFAs such as total fat intake and the ratio of ω-3 to ω-6 PUFA intake. Several clinical trials, including some currently ongoing, are investigating novel strategies that favorably alter endogenous fatty acid profiles in an effort to develop clinically feasible prevention methods. Identification of well-defined subpopulations that are most likely to benefit from a targeted prevention approach will likely be crucial in this effort.

Positive feedback loop and synergistic effects between hypoxia-inducible factor-2α and stearoyl-CoA desaturase-1 promote tumorigenesis in clear cell renal cell carcinoma

Adapting to hypoxic stress is pivotal in tumor progression and determining tumor malignancy. The transcriptional factor hypoxia-inducible factor (HIF) is crucial in modulating tumorous hypoxic responses through altering cell energy metabolism, which includes the modification of glucose and lipid metabolism-associated gene expression. Stearoyl-CoA desaturase-1 (SCD1) is the main isoform of SCDs, the rate-limiting enzymes in the biosynthesis of monounsaturated fatty acids from saturated fatty acids, which is extensively activated in cancer progression. In this study, we found that SCD1 and HIF-2α were overexpressed in human clear cell renal cell carcinoma (ccRCC) tissues and ccRCC cell lines, and were upregulated in the 786-0 ccRCC cell line under hypoxia. Knockdown of SCD1 or HIF-2α impacted the other's expression. Enhancing SCD1 resulted in HIF-2α upregulation, which could be blocked by inhibiting the PI3K/Akt pathway. Deficiency of SCD1 or HIF-2α in 768-0 cells led to apoptosis, less colony formation ability, and decreased cell migration. More obvious effects were observed in 786-0 cells with double SCD1 and HIF-2α knockdown. These results indicate a PI3K/Akt-mediated loop between SCD1 and HIF-2α that mutually enhances their protein levels. Both SCD1 and HIF-2α are critical to promoting tumorigenesis by synergistically acting on maintaining cell survival, triggering cell migration, and enhancing the colony formation ability of cancer cells.

New insights into the health effects of dietary saturated and omega-6 and omega-3 polyunsaturated fatty acids

Cardiovascular diseases and cancers are leading causes of morbidity and mortality. Reducing dietary saturated fat and replacing it with polyunsaturated fat is still the main dietary strategy to prevent cardiovascular diseases, although major flaws have been reported in the analyses supporting this approach. Recent studies introducing the concept of myocardial preconditioning have opened new avenues to understand the complex interplay between the various lipids and the risk of cardiovascular diseases. The optimal dietary fat profile includes a low intake of both saturated and omega-6 fatty acids and a moderate intake of omega-3 fatty acids. This profile is quite similar to the Mediterranean diet. On the other hand, recent studies have found a positive association between omega-6 and breast cancer risk. In contrast, omega-3 fatty acids do have anticancer properties. It has been shown that certain (Mediterranean) polyphenols significantly increase the endogenous synthesis of omega-3 whereas high intake of omega-6 decreases it. Finally, epidemiological studies suggest that a high omega-3 to omega-6 ratio may be the optimal strategy to decrease breast cancer risk. Thus, the present high intake of omega-6 in many countries is definitely not the optimal strategy to prevent cardiovascular disease and cancers. A moderate intake of plant and marine omega-3 in the context of the traditional Mediterranean diet (low in saturated and omega-6 fatty acids but high in plant monounsaturated fat) appears to be the best approach to reduce the risk of both cardiovascular diseases and cancers, in particular breast cancer.

Subcutaneous adipose tissue fatty acid desaturation in adults with and without rare adipose disorders

Background

Elevated stearoyl-CoA desaturase activity has been described in obese states, with an increased desaturation index (DI) suggesting enhanced lipogenesis. Differences in the DI among various phenotypes of abnormal adiposity have not been studied. Abnormal accumulation of subcutaneous adipose tissue occurs in rare adipose disorders (RADs) including Dercum's disease (DD), multiple symmetric lipomatosis (MSL), and familial multiple lipomatosis (FML). Examining the DI in subcutaneous fat of people with DD, MSL and FML may provide information on adipose tissue fatty acid metabolism in these disorders. The aims of this pilot study were: 1) to determine if differences in adipose tissue DIs are present among RADs, and 2) to determine if the DIs correlate to clinical or biochemical parameters.

Methods

Subcutaneous adipose tissue was obtained from human participants with DD (n = 6), MSL (n = 5), FML (n = 8) and obese Controls (n = 6). Fatty acid composition was determined by gas chromatography/mass spectrometry. The DIs (palmitoleic/palmitic, oleic/stearic, vaccenic/stearic ratios) were calculated from the gas chromatogram peak intensities. SCD1 gene expression was determined. Spearman's correlations between the DIs and available clinical or biochemical data were performed.

Results

In DD subjects, the vaccenic/stearic index was lower (p < 0.05) in comparison to Controls. Percent of total of the saturated fatty acid myristic acid was higher in DD compared with Controls and FML. Percent of monounsaturated vaccenic acid in DD trended lower when compared with Controls, and was decreased in comparison to FML. In MSL, total percent of the polyunsaturated fatty acids was significantly lower than in the Control group (p < 0.05). In the total cohort of subjects, the palmitoleic/palmitic and oleic/stearic DIs positively correlated with age, BMI, and percent body fat.

Conclusions

The positive associations between the DIs and measures of adiposity (BMI and percent body fat) support increased desaturase activity in obesity. The lower vaccenic/stearic DI in DD SAT compared with Controls suggests presence of other factors involved in fat accumulation in addition to lifestyle. Other mechanisms driving fat accumulation in DD such as inflammation or lymphatic dysfunction should be investigated.

Plasma phospholipid fatty acid concentrations and risk of gastric adenocarcinomas in the European Prospective Investigation into Cancer and Nutrition (EPIC-EURGAST)

BACKGROUND

Epidemiologic data suggest that diet is a risk factor in the etiology of gastric cancer. However, the role of dietary fatty acids, a modifiable risk factor, remains relatively unexplored.

OBJECTIVE

The objective of this study was to determine the association of plasma phospholipid fatty acid concentrations, as biomarkers of exogenous and endogenously derived fatty acids, with the risk of gastric adenocarcinoma in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition-Europe Gastric Cancer (EPIC-EURGAST).

DESIGN

Fatty acids were measured by gas chromatography in prediagnostic plasma phospholipids from 238 cases matched to 626 controls by age, sex, study center, and date of blood donation. Conditional logistic regression models adjusted for Helicobacter pylori infection status, BMI, smoking, physical activity, education, and energy intake were used to estimate relative cancer risks.

RESULTS

Positive risk associations for gastric cancer were observed in the highest compared with the lowest quartiles of plasma oleic acid (OR: 1.72; 95% CI: 1.01, 2.94), di-homo-γ-linolenic acid (OR: 1.92; 95% CI: 1.10, 3.35), α-linolenic acid (OR: 3.20; 95% CI: 1.70, 6.06), and the ratio of MUFAs to saturated fatty acids, as an indicator of stearoyl-CoA desaturase-1 enzyme activity (OR: 1.40; 95% CI: 0.81, 2.43). An inverse risk association was observed with the ratio of linoleic to α-linolenic acid (OR: 0.37; 95% CI: 0.20, 0.66).

CONCLUSION

These data suggest that a specific prediagnostic plasma phospholipid fatty acid profile, characterized mainly by high concentrations of oleic acid, α-linolenic acid, and di-homo-γ-linolenic acid, which presumably reflect both a complex dietary pattern and altered fatty acid metabolism, may be related to increased gastric cancer risk.

Roles of StearoylCoA Desaturase-1 in the Regulation of Cancer Cell Growth, Survival and Tumorigenesis

The development and maintenance of defining features of cancer, such as unremitting cell proliferation, evasion of programmed cell death, and the capacity for colonizing local tissues and distant organs, demand a massive production of structural, signaling and energy-storing lipid biomolecules of appropriate fatty acid composition. Due to constitutive activation of fatty acid biosynthesis, cancer cell lipids are enriched with saturated (SFA) and, in particular, monounsaturated fatty acids (MUFA), which are generated by StearoylCoA desaturase-1, the main enzyme that transforms SFA into MUFA. An increasing number of experimental and epidemiological studies suggest that high levels of SCD1 activity is a major factor in establishing the biochemical and metabolic perturbations that favors the oncogenic process. This review examines evidence that suggests the critical implication of SCD1 in the modulation of multiple biological mechanisms, specifically lipid biosynthesis and proliferation and survival signaling pathways that contribute to the development and progression of cancer.