Obesity is characterised by chronic low-grade inflammation, which is a key factor in the development of obesity-related co-morbidities. Intake of n-3 long-chain PUFAs is associated with anti-inflammatory effects. Recent studies suggest that also n-11 long-chain MUFAs may reduce the concentrations of inflammatory markers, possibly by increasing the biosynthesis of EPA. The primary aim was to investigate if diets added herring oil containing cetoleic acid (CA, C22:1n-11) or a CA concentrate (CECO) affected the fatty acid composition in tissues from obese rats with chronic inflammation. Secondary aims included investigating the effects on inflammatory markers. Thirty male obese Zucker fa/fa rats were fed diets containing herring oil (HERO) or a CECO, containing 0·70 or 1·40 wt% CA, respectively, with a comparable content of EPA (0·17 and 0·20 wt%, respectively), or a control diet with soyabean oil for 5 weeks. Data were analysed using one-way ANOVA. CA from HERO and CECO diets were recovered in liver, adipose tissue, muscle and blood cells. The EPA concentration was similar between HERO and CECO groups in tissues, whereas the hepatic concentrations of fatty acid desaturases were lower or similar to Controls. The concentrations of TNFα, matrix metalloproteinase-3, IL6, monocyte chemotactic protein 1 and integrin α M in adipose tissue, and the hepatic concentration of CD68 were lower after CECO intake but were not affected by the HERO diet. To conclude, rats fed the CECO diet had lower concentrations of inflammatory and macrophage infiltration markers, but this effect was probably not mediated through increased EPA biosynthesis.

Accumulation of exogenous fatty acids such as the long-chain n-11 MUFA cetoleic acid (CA, C22:1n-11) may induce functional changes, through direct effects or by affecting the amounts of other fatty acids through changes in catabolic and anabolic processes including desaturation of fatty acids or by other processes. The primary aim of this study was to investigate if dietary CA was absorbed and accumulated in a TAG-rich tissue for storage (white adipose tissue), a stable phospholipid-rich tissue (brain), metabolically active tissues (liver and skeletal muscle) or circulating in the blood (blood cells) and metabolised. Secondary aims included investigating any effects on the levels of EPA and DHA. Eighteen male Zucker diabetic Sprague Dawley (ZDSD) rats were fed diets with herring oil (HERO) containing 0·70 % CA or anchovy oil (ANCO) devoid of CA, or a control diet with soyabean oil for 5 weeks. The HERO and ANCO diets contained 0·35 and 0·37 wt% EPA + DHA, respectively. Data were analysed using one-way ANOVA. CA from dietary HERO was absorbed, and CA and two chain-shortened metabolites were found in blood cells, liver, white adipose tissue (WAT) and muscle, but n-11 MUFAs were not found in the brain. The concentrations of EPA and DHA were similar in liver lipids (TAG, cholesteryl esters and NEFA) as well as in WAT, muscle and brain from rats fed the HERO or ANCO diets. To conclude, CA was taken up by tissues but did not affect levels of EPA and DHA in this diabetic rat model.

Patients with type 2 diabetes have increased risks for dyslipidaemia and subsequently for developing vascular complications. A recent meta-analysis found that cetoleic acid (C22:1n-11) rich fish oils resulted in lower cholesterol concentration in rodents. The aim was to investigate the effect of consuming fish oils with or without cetoleic acid on serum cholesterol concentration in diabetic rats and to elucidate any effects on cholesterol metabolism. Eighteen male Zucker Diabetic Sprague Dawley rats were fed diets containing herring oil (HERO) or anchovy oil (ANCO) or a control diet with soyabean oil for 5 weeks. The HERO diet contained 0·70 % cetoleic acid, with no cetoleic acid in the ANCO diet. The HERO and ANCO diets contained 0·35 and 0·37 wt% EPA + DHA, respectively. Data were analysed using one-way ANOVA. The serum total cholesterol concentration was 14 % lower in the HERO group compared with ANCO and Control groups (P = 0·023). The HERO group had a higher faecal excretion of bile acids (P = 0·0036), but the cholesterol production in the liver, the hepatic secretion of VLDL and the liver’s capacity to take up cholesterol were similar to controls. The ANCO diet did not affect the serum cholesterol concentration, but the hepatic cholesterol biosynthesis, the clearance of lipoprotein cholesterol and the excretion of bile acids in faeces were higher than in the Control group. To conclude, consumption of herring oil, but not of anchovy oil, led to a lower cholesterol concentration in a type 2 diabetes rat model.

Hypercholesterolaemia is a major risk factor for CVD. Fish intake is associated with lower risk of CVD, whereas supplementation with n-3 long-chain PUFA (LC-PUFA) has little effect on the cholesterol concentration. We therefore investigated if cetoleic acid (CA), a long-chain MUFA (LC-MUFA) found especially in pelagic fish species, could lower the circulating total cholesterol (TC) concentration in rodents. A systematic literature search was performed using the databases PubMed, Web of Science and Embase, structured around the population (rodents), intervention (CA-rich fish oils or concentrates), comparator (diets not containing CA) and the primary outcome (circulating TC). Articles were assessed for risk of bias using the SYRCLE’s tool. A meta-analysis was conducted in Review Manager v. 5.4.1 (the Cochrane Collaboration) to determine the effectiveness of consuming diets containing CA-rich fish oils or concentrates on the circulating TC concentration. Twelve articles were included in the systematic review and meta-analysis, with data from 288 rodents. Consumption of CA-rich fish oils and concentrates resulted in a significantly lower circulating TC concentration relative to comparator groups (mean difference −0·65 mmol/l, 95 % CI (−0·93, −0·37), P < 0·00001), with high statistical heterogeneity (I2 = 87 %). The risk of bias is unclear since few of the entries in the SYRCLE’s tool were addressed. To conclude, intake of CA-rich fish oils and concentrates prevents high cholesterol concentration in rodents and should be further investigated as functional dietary ingredients or supplements to reduce the risk for developing CVD in humans.