Treatment of liver fibrosis is very limited as there is currently no effective anti-fibrotic therapy. Spirulina platensis (SP) is a blue-green alga that is widely supplemented in healthy foods. The objective of this study was to determine whether SP supplementation can prevent obesity-induced liver fibrosis in vivo. Male C57BL/6J mice were randomly assigned to a low-fat or a high-fat (HF)/high-sucrose/high-cholesterol diet or an HF diet supplemented with 2·5 % SP (w/w) (HF/SP) for 16 or 20 weeks. There were no significant differences in body weight, activity, energy expenditure, serum lipids or glucose tolerance between mice on HF and HF/SP diets. However, plasma alanine aminotransferase level was significantly reduced by SP at 16 weeks. Expression of fibrotic markers and trichrome stains showed no differences between HF and HF/SP. Splenocytes isolated from HF/SP fed mice had lower inflammatory gene expression and cytokine secretion compared with splenocytes from HF-fed mice. SP supplementation did not attenuate HF-induced liver fibrosis. However, the expression and secretion of inflammatory genes in splenocytes were significantly reduced by SP supplementation, demonstrating the anti-inflammatory effects of SP in vivo. Although SP did not show appreciable effect on the prevention of liver fibrosis in this mouse model, it may be beneficial for other inflammatory conditions.

Increasing attention has been paid to Spirulina for its potential clinical uses. The present study investigated the protection by dietary Spirulina platensis against d-galactosamine (d-GalN)- and acetaminophen (APAP)-induced hepatitis in ICR mice. Mice in each group (n 6) were fed with a standard diet (American Institute of Nutrition (AIN)-93G), a positive control diet containing 0·5 % butylated hydroxytoluene (BHT), or a diet containing 3, 6 or 9 % S. platensis for 1 week. On the last day the mice were treated with d-GalN (300 mg/kg body weight, intraperitoneally) or APAP (150 mg/kg body weight, intraperitoneally) and 24 h later the mice were killed. The doses of both 6 and 9 % S. platensis were found to significantly alleviate the increase of serum glutamate oxaloacetoacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) activities in d-GalN- or APAP-intoxicated mice. The observation was very similar to that of the positive control groups. Two more experiments were carried out to investigate the involvement of thiobarbituric acid-reactive substances (TBARS) and IL-18 in the suppression of 6 % S. platensis on d-GalN- and APAP-induced hepatitis. The significant increase of GOT and GPT activities was found to be accompanied with the elevation of hepatic TBARS level, IL-18 mRNA expression and serum IL-18 concentration, and was significantly alleviated by supplementation with 6 % S. platensis in diets. These results showed that dietary S. platensis could provide a significant protection against d-GalN- and APAP-induced liver injuries, and IL-18 and lipid peroxidation might be involved in the protective influence of S. platensis.

The requirements for efficient utilization of high light fluxes in cultures of Spirulina platensis have previously been elucidated. The most important of these was a short light-path coupled with a highly turbulent flow, facilitating ultrahigh cell densities (i.e. above 100 mg chl l−1). The present study shows that for each irradiance there is an optimal culture density, defined as the concentration that yields the highest output rate of cell mass under the prevailing conditions. In ultrahigh cell density cultures, a linear relationship was observed between the output rate and the irradiance, up to a photon flux density (PFD) of 2500 μmol m−2 s−1. Using a total PFD of 8000 μmol m−2 s−1, a maximal output rate of 16.8 g dry weight m−2 s−1 was obtained, which is the highest reported for a culture of photoautotrophic microorganisms exposed to direct beam radiation. Testing the effect of reduction in light-path on productivity, output rate per unit volume increased 50-fold as the light-path was reduced 27-fold, i.e. from 200 mm to 7.5 mm. Likewise, the output rate calculated on an areal basis was almost doubled, increasing from 2.5 to 4.6 g m−2 s−1, and the specific growth rate increased c. 20% as the light-path was reduced to 7.5 mm. The very significant effect of the length of the light-path on enhancing the output rate is interpreted as resulting from improvement in the light regime to which the individual cells are exposed, as reflected in the frequency and overall characteristics of the light–dark cycles.