The goal of this narrative review is to summarise the current knowledge and limitations related to the anti-inflammatory effects of tomato, tomato-derived products and lycopene in the context of metabolic inflammation associated to cardiometabolic diseases. The potential of tomato and tomato-derived product supplementation is supported by animal and in vitro studies. In addition, intervention studies provide arguments in favour of a limitation of metabolic inflammation. This is also the case for observational studies depicting inverse association between plasma lycopene levels and inflammation. Nevertheless, current data of intervention studies are mixed concerning the anti-inflammatory effect of tomato and tomato-derived products and are not in favour of an anti-inflammatory effect of pure lycopene in humans. From epidemiological to mechanistic studies, this review aims to identify limitations of the current knowledge and gaps that remain to be filled to improve our comprehension in contrasted anti-inflammatory effects of tomato, tomato-derived products and pure lycopene.

The prevalence of type 2 diabetes (T2D) is low in populations with a high fish intake; however prospective studies with fish intake have shown positive, negative or no association between fish intake and the risk for T2D. The aim of this study was to investigate the effects of high intake of lean or fatty fish on glucose tolerance, leucocyte membrane fatty acid composition and leucocyte function in overweight/obese adults. In this randomised clinical trial, sixty-eight healthy overweight/obese participants consumed 750 g/week of either lean or fatty fish as dinners, or were instructed to continue their normal eating habits but to avoid fish intake (control group), for 8 weeks. Energy and macronutrient intake and physical activity were not changed within the groups during the study period. High intake of fatty fish, but not of lean fish, significantly improved glucose regulation 120 min postprandially (P=0·012), but did not affect fasting glucose concentration. A smaller increase in fasting to 120 min postprandial insulin C-peptide concentration was seen after fatty fish intake (P=0·012). Lean fish increased the DHA content in leucocyte membranes (P=0·010), and fatty fish increased the total content of n-3 PUFA (P=0·00016) and reduced the content of n-6 PUFA (P=0·00057) in leucocyte membranes. Lean and fatty fish intake did not affect phagocytosis of bacteria ex vivo. The findings suggest that high intake of fatty fish, but not of lean fish, beneficially affected postprandial glucose regulation in overweight/obese adults, and may therefore prevent or delay the development of T2D in this population.

The effects of Enzamin on obesity-related metabolic disorders in obese db/db mice were examined to explore a novel agent for the prevention of insulin resistance. Db/db mice were treated with water containing Enzamin (0·1 and 1·0 %) for 8 weeks from 6 weeks of age. Enzamin treatment at 1·0 %, but not at 0·1 %, significantly decreased the fasting plasma glucose, serum total cholesterol and TAG levels in db/db mice, without affecting body weight gain and body fat composition. Furthermore, insulin sensitivity and glucose tolerance were improved by the treatment of db/db mice with 1·0 % Enzamin. Immunohistochemical studies and gene expression analysis showed that 1·0 % Enzamin treatment suppressed macrophage accumulation and inflammation in the adipose tissue. In addition, 1·0 % Enzamin treatment increased serum adiponectin in db/db mice. Treatment with 1·0 % Enzamin also significantly suppressed the expression of NADPH oxidase subunits, suggesting an antioxidative effect for Enzamin in the adipose tissue. Furthermore, in vitro experiments demonstrated that the lipopolysaccharide-induced inflammatory reaction was significantly suppressed by Enzamin treatment in macrophages. Enzamin treatment increased the expression of GLUT4 mRNA in muscle, but not GLUT2 mRNA in the liver of db/db mice. Enzamin also increased the mRNA expression of carnitine palmitoyltransferase 1a (CPT1a, muscle isoform) in db/db mice, whereas Enzamin treatment did not affect the mRNA expression of CPT1b (liver isoform) in db/db mice. In conclusion, our data indicate that Enzamin can improve insulin resistance by ameliorating impaired adipocytokine expression, presumably through its anti-inflammatory action, and that Enzamin possesses a potential for preventing the metabolic syndrome.

Inflammation is a hallmark of the metabolic syndrome, which also contributes to a pro-atherogenic state. NF-κB activation, a critical step in regulating inflammatory reactions, can be inhibited by polyphenol (PF) extracts, at least in vitro. In the present study, we set out to study whether a PF-rich extract could attenuate the chronic inflammatory state and/or an acute immune response in vivo in subjects with clustered metabolic risk factors. A commercially available, PF-rich extract (500 mg daily) or placebo was administered for 4 weeks to thirty-four subjects with two or more metabolic risk factors using a randomised, double-blind, cross-over design. During the final study visit, an acute inflammatory challenge (lipopolysaccharide (LPS) 1 ng/kg body weight) was administered to a random subgroup of subjects (PF-rich extract (n 12) and placebo (n 12)). The PF-rich extract modestly reduced the inflammatory chemokines monocyte chemoattractant protein 1 (MCP-1) and macrophage migration inhibitory factor (MIF) (MCP-1 − 6·5 % (PF, median 116 (interquartile range 97–136) pg/ml v. placebo, median 124 (interquartile range 105–153) pg/ml; P < 0·05); MIF − 10·8 % (PF, median 2512 (interquartile range 1898–3972) pg/ml v. placebo, median 2814·5 (interquartile range 2296–3852) pg/ml; P < 0·05); however, other measured markers of inflammation and cardiometabolic disease, such as C-reactive protein, IL-6, HDL-cholesterol, adiponectin and oxidised LDL, remained unaffected. Following the LPS challenge, we found a statistically significant 48 % reduction of MCP-1 production in the PF-rich extract group (n 12) v. placebo (n 12) over 6 h (PF 766 (sd 155) v. placebo 1466 (sd 989) ng/ml; P < 0·05, area under the curve). In conclusion, short-term oral administration of the PF-rich extract caused a modest anti-inflammatory effect in subjects with clustered metabolic risk factors. Further dose-ranging studies are needed to evaluate whether and to what extent PF-rich extracts can be used to reduce the pro-inflammatory state in subjects with metabolic diseases at increased cardiovascular risk.