To the best our knowledge, this is the first randomized, double-blinded, controlled clinical trial to evaluate the effects of 80 mg/day pyridoxine hydrochloride supplement on anthropometric measurements, body composition, visceral adiposity index, glycemic and lipidemic risk factors and serum levels of leptin and adiponectin in obese and overweight women. The current recommended daily amount (RDA) for B6 is 1.6 mg for adults over 19(27). No adverse effects have been seen from the consumption of B6 food sources. Although some studies have shown severe sensory neuropathy due to treatment with 2–6 g / day pyridoxine hydrochloride (28).The amount of upper limit for this vitamin is 100 mg/day (29).
Results of the present study showed that 8-week consumption of pyridoxine hydrochloride reduced BMI and improved body composition compared with the placebo.
In some studies the effects of pyridoxine on calcium ion signaling have been observed that increases lipolysis and decreases fatty acid synthesis (10–12) Zemel et al (2013) studied the effects of a leucine and pyridoxine-containing nutraceutical on body weight and composition in obese subjects. They recently demonstrated leucine to modulate energy partitioning between adipose tissue and muscle. Further, leucine exhibits a synergy with B6, resulting in reduced adipocyte lipid storage coupled with increased muscle fat oxidation and insulin sensitivity, and reduced oxidative and inflammatory stress (15). They found that this nutraceutical combination improve oxidative capacity and thereby significantly augments weight and fat loss (30). Pyridoxal phosphate inhibits adipocyte Ca2 + influx in vitro, resulting in significant decreases in adipocyte fatty acid synthase expression and activity and corresponding reductions in adipocyte triglyceride content(31) because Ca2 + signaling coordinately stimulates fatty acid synthase activity and inhibits lipolysis in adipocytes(32–36)
Our results showed that pyridoxine hydrochloride had beneficial effects on lipid profile.This effect of vitamin B6 have been shown before (17–19). Pyridoxine supplementation decreased plasma total cholesterol, LDL cholesterol and triglycerides; and reduced HDL cholesterol (17).Also vitamin B6 supplementation was associated with a significant reduction in total cholesterol and HDL cholesterol (18).
We observed significant reduction in fasting insulin and HOMA-IR. In some studies, it has also been shown to decrease fasting blood glucose (13, 22) and insulin resistance (13–16).
Unoki-Kubota et al (2010) examined pyridoxamine supplementation, an inhibitor of (Advanced glycation end products) AGE formation could ameliorate insulin resistance in obese mice with type 2 diabetes. In this study administration of pyridoxamine decreased fasting insulin levels and improved insulin sensitivity in mice (14).
Spellacy et al in 1976 decided to investigate the role of vitamin B6 (pyridoxine) treatment in women with gestational diabetes. This study demonstrated that in one small group treatment with vitamin B6 resulted in an improvement in glucose tolerance and reduced plasma insulin (37). In 2009, Hagiwara et al, conducted a study to investigate the effects of pyridoxamine on glucose intolerance and obesity in mice. It showed that the antioxidative effect of pyridoxamine is associated with improvement of glucose intolerance and obesity in mice fed a high-fat diet. They said that pyridoxamine may be useful in the treatment of the obesity-associated metabolic syndrome(21).Moreover they recently demonstrated the effect of pyridoxamine, an AGE inhibitor, on improvement of glucose intolerance in type 2 diabetes mellitus mice(38).
In our study leptin decreased and adiponectin increased significantly in the pyridoxine hydrochloride group. Maessen et al(2016) reported that pyridoxamine (PM) intervention prevents body weight gain, improves metabolic characteristics (Fasting plasma glucose, cholesterol, insulin, and leptin levels), prevents mild vascular dysfunction and reduces lipid content of liver in (High fat diet)HFD-Induced obese mice. Altogether, these findings highlight the potential of PM to serve as an intervention strategy in obesity (39).
The design of the study, inclusion and exclusion criteria, controlling for covariates, and repeated assessment of dietary components are amongst the strengths of this study. The randomization method distributes fairly the unknown confounding factors between the intervention and control groups. We also used double-blind method to minimize selection and information biases. There are some limitations pertinent to this trial, and we had a few lost to follow‐up that prevented us to do intention‐to‐treat analysis. Further studies with larger sample sizes, longer duration and different dosages of pyridoxine hydrochloride are recommended. Although the participants were asked to maintain their usual diet especially food sources of vitamin B6 during the study, the results may have been affected by unreported or poor compliance. There was not any report of complication or side effect due to intake of hesperidin supplement by the participated patients during the study.