Evaluation of the effect of N-acetyl-glucosamine administration on biomarkers for cartilage metabolism in healthy individuals without symptoms of arthritis: A randomized double-blind placebo-controlled clinical study.

The present study aimed to evaluate the effect of N-acetyl-glucosamine (GlcNAc) on the joint health of healthy individuals without arthritic symptoms. A randomized double-blind placebo-controlled clinical trial was performed to investigate the effect of oral administration of a GlcNAc-containing test supplement (low dose, 500 mg/day and high dose, 1,000 mg/day) on cartilage metabolism in healthy individuals with a mean age of 48.6±1.3 years (range, 23-64 years) by analyzing the ratio of type II collagen degradation to type II collagen synthesis using type II collagen degradation (C2C) and synthesis (PIICP) markers. The results indicated that the changes in C2C/PIICP ratios from the baseline were suppressed in the treated with low and high doses of GlcNAc, compared with the placebo group at week 16 during intervention. To further elucidate the effect of GlcNAc, subjects with impaired cartilage metabolism were evaluated. Notably, the changes in the C2C/PIICP ratios were markedly suppressed in the groups treated with low and high doses of GlcNAc at week 16. Finally, to exclude the effect of heavy body weight on joint loading, subjects weighing <70 kg with impaired cartilage metabolism were analyzed. Notably, the changes in the C2C/PIICP ratios were suppressed in the groups treated with low and high doses of GlcNAc at weeks 12 and 16. No test supplement-related adverse events were observed during or following the intervention. Together, these observations suggest that oral administration of GlcNAc at doses of 500 mg and 1,000 mg/day exhibits a chondroprotective effect on healthy individuals by reducing the C2C/PIICP ratio (relatively decreasing type II collagen degradation and increasing type II collagen synthesis) without any apparent adverse effects.

Vascular effects and safety of supplementation with shark liver oil in middle-aged and elderly males.

Shark liver oil (SLO) has long been used as a traditional health food, with a particular benefit for vascular health, in Japan. The aim of this study was to assess the effect of dietary supplementation with SLO on arterial stiffness and peripheral microvascular function in otherwise healthy middle-aged and older males with slightly increased arterial stiffness. A randomized, double-blind, placebo-controlled, parallel study design was used to assign 41 healthy males with a mean age of 59.0±4.0 years (range, 45-69 years) to either SLO (n=21) or placebo (n=20) treatment for eight weeks. The effects on arterial stiffness and peripheral microvascular function were assessed by the cardio-ankle vascular index (CAVI) and by measurement of hand blood flow to cutaneous tissues using a laser Doppler perfusion imaging (LDPI) technique, respectively. Although the magnitude of the changes in the CAVI value during the eight-week intervention for the SLO group did not significantly differ from that for the placebo group, the changes in the CAVI value for the former group were significantly associated (r=0.575, P<0.01) with age. It was also found that the LDPI values at week 8 were significantly lowered (P<0.05) compared with the baseline values in the placebo group, while no change was observed in the SLO group, resulting in a significant difference in the changes between the two groups (P=0.002). Neither SLO supplementation-related adverse side-effects nor any abnormal changes in routine laboratory tests, including lipid profiles and anthropometric and haemodynamic parameters, were observed throughout the intervention. SLO may have the potential to safely improve vascular health in middle-aged and elderly males.

Effects of Orally Administered Pyrroloquinoline Quinone Disodium Salt on Dry Skin Conditions in Mice and Healthy Female Subjects.

Pyrroloquinoline quinone (PQQ) is a coenzyme involved in the redox-cycling system. The supplemental use of PQQ has been examined based on its properties as an antioxidant and redox modulator. Although an animal study on deficiency of PQQ suggested that PQQ contributes to skin conditions, its efficacy in humans has not been reported. The present study aimed to investigate the effects of orally administered PQQ on skin moisture, viscoelasticity, and transepidermal water loss (TEWL) both in dry skin mouse models and in healthy female subjects with a subjective symptom of dry skin. In our dry skin mouse model study, oral intake of PQQ (0.0089%, w/w, in the diet for 6 wk) significantly decreased the number of mast cells in the dermis and the number of CD3⁺ T-cells in the epidermis. In our human study, oral intake of PQQ (20 mg/d for 8 wk) significantly inhibited the increase in TEWL on the forearm. Finally, subject questionnaires showed positive impressions for the improvement of skin conditions. These results suggest that oral intake of PQQ improves skin conditions both in female subjects with dry skin and in mice with a compromised skin barrier function.