Effect of biotin treatment on hepatic gene expression in streptozotocin-induced diabetic rats

Biotin Enhances Testosterone Production in Mice and Their Testis-Derived Cells

Late-onset hypogonadism, a male age-related syndrome characterized by a decline in testosterone production in the testes, is commonly treated with testosterone replacement therapy, which has adverse side effects. Therefore, an alternative treatment is highly sought. Supplementation of a high dosage of biotin, a water-soluble vitamin that functions as a coenzyme for carboxylases involved in carbohydrate, lipid, and amino acid metabolism, has been shown to influence testis functions. However, the involvement of biotin in testis steroidogenesis has not been well clarified. In this study, we examined the effect of biotin on testosterone levels in mice and testis-derived cells. In mice, intraperitoneal treatment with biotin (1.5 mg/kg body weight) enhanced testosterone levels in the serum and testes, without elevating serum levels of pituitary luteinizing hormone. To investigate the mechanism in which biotin increased the testosterone level, mice testis-derived I-10 cells were used. The cells treated with biotin increased testosterone production in a dose- and time-dependent manner. Biotin treatment elevated intracellular cyclic adenosine monophosphate levels via adenylate cyclase activation, followed by the activation of protein kinase A and testosterone production. These results suggest that biotin may have the potential to improve age-related male syndromes associated with declining testosterone production.

Nutraceutical Prevention of Diabetic Complications—Focus on Dicarbonyl and Oxidative Stress

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.

Dietary High-Dose Biotin Intake Activates Fat Oxidation and Hepatic Carnitine Palmitoyltransferase in Rat

This study investigated the effects of dietary high-dose biotin intake on fat oxidation in rats using respiratory gas analysis, and evaluated fatty-acid oxidation-related enzyme activities and gene expressions in the liver. Five-week-old male Sprague-Dawley rats were fed a control diet and three biotin-supplemented diets (additive biotin concentration: 0.05%, 0.10%, and 0.20% of diet) for 3 wk. In 2 wk, fat oxidation in the 0.20% biotin-supplemented diet group was higher than that in the 0.05% biotin-supplemented diet group; however, the energy expenditure and carbohydrate oxidation were unchanged between the dietary groups. At the end of 3 wk, body weight and epididymal white adipose tissue weight reduced in the 0.20% biotin diet group, and hepatic triglyceride levels tended to decrease. Additionally, increased plasma adiponectin concentration and hepatic mitochondrial carnitine palmitoyltransferase activity as well as decreased hepatic acetyl-CoA carboxylase 2 gene expression were observed in the 0.20% biotin-supplemented diet group compared with those in the control group. These results provide strong evidence that dietary high-dose biotin intake activated fat oxidation due to the increase in hepatic β-oxidation, which may contribute to the decrease in hepatic triglyceride concentration and white adipose tissue weight.

Role of vitamins in the metabolic syndrome and cardiovascular disease

The prevalence of metabolic syndrome and cardiovascular disease has increased and continues to be the leading cause of mortality worldwide. The etiology of these diseases includes a complex phenotype derived from interactions between genetic, environmental, and nutritional factors. In this regard, it is common to observe vitamin deficiencies in the general population and even more in patients with cardiometabolic diseases due to different factors. Vitamins are essential micronutrients for cellular metabolism and their deficiencies result in diseases. In addition to its role in nutritional functions, increasingly, vitamins are being recognized as modulators of genetics expression and signals transduction, when consumed at pharmacological concentrations. Numerous randomized preclinical and clinical trials have evaluated the use of vitamin supplementation in the prevention and treatment of metabolic syndrome and cardiovascular disease. However, it is controversy regarding its efficacy in the treatment and prevention of these diseases. In this review, we investigated chemical basics, physiological effect and recommended daily intake, problems with deficiency and overdose, preclinical and clinical studies, and mechanisms of action of vitamin supplementation in the treatment and prevention of metabolic syndrome and cardiovascular disease.

Nutritional and medical food therapies for diabetic retinopathy

Diabetic retinopathy (DR) is a form of microangiopathy. Reducing oxidative stress in the mitochondria and cell membranes decreases ischemic injury and end-organ damage to the retina. New approaches are needed, which reduce the risk and improve the outcomes of DR while complementing current therapeutic approaches. Homocysteine (Hcy) elevation and oxidative stress are potential therapeutic targets in DR. Common genetic polymorphisms such as those of methylenetetrahydrofolate reductase (MTHFR), increase Hcy and DR risk and severity. Patients with DR have high incidences of deficiencies of crucial vitamins, minerals, and related compounds, which also lead to elevation of Hcy and oxidative stress. Addressing the effects of the MTHFR polymorphism and addressing comorbid deficiencies and insufficiencies reduce the impact and severity of the disease. This approach provides safe and simple strategies that support conventional care and improve outcomes. Suboptimal vitamin co-factor availability also impairs the release of neurotrophic and neuroprotective growth factors. Collectively, this accounts for variability in presentation and response of DR to conventional therapy. Fortunately, there are straightforward recommendations for addressing these issues and supporting traditional treatment plans. We have reviewed the literature for nutritional interventions that support conventional therapies to reduce disease risk and severity. Optimal combinations of vitamins B1, B2, B6, L-methylfolate, methylcobalamin (B12), C, D, natural vitamin E complex, lutein, zeaxanthin, alpha-lipoic acid, and n-acetylcysteine are identified for protecting the retina and choroid. Certain medical foods have been successfully used as therapy for retinopathy. Recommendations based on this review and our clinical experience are developed for clinicians to use to support conventional therapy for DR. DR from both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) have similar retinal findings and responses to nutritional therapies.

Influence of amide versus ester linkages on the anticancer properties of the new flavone-biotin conjugates

Novel biotinylated C-6 substituted flavones were synthesised by a one-step method that connects biotin to 6-hydroxyflavone and 6-aminoflavone by esterification and amidation of hydroxyl and amino groups, respectively. The obtained compounds, 6-O-biotinylflavone and 6-biotinylamidoflavone, are the bifunctional molecules composed of a flavone moiety as a fluorescent reporter and biotin as a cancer-targeting unit. Antiproliferative activity was evaluated using SRB assays in MCF-7, MCF-10A, HepG2, MDA-MB-231, 4T1, and Balb/3T3 cell lines. In vitro evaluation revealed that compounds with biotin moiety displayed better cell selectivity between the cancer and normal cells than the parental substrates. These results indicate that anticancer effect is not related to the position of biotin moiety, but it is related to the presence of ester or amide bond. 6-O-Biotinylflavone was more active than 6-hydroxyflavone against human breast (MDA-MB-231) and liver (HepG2) cancer cells with IC50 (concentration of tested agent that inhibits proliferation of the cell population by 50%) values equal to 78.5 ± 18.8 μM and 133.2 ± 14.2 μM, respectively. Non biotinylated 6-aminoflavone was more active than 6-biotinylamidoflavone against all tested cell lines, with IC50 values between 34.3 ± 9.1 μM (4T1) and 173.86 ± 24.3 μM (MCF-7).

Mitigating effect of biotin against irradiation-induced cerebral cortical and hippocampal damage in the rat brain tissue

Radiation-induced brain injury is common and mainly occurs in patients receiving radiotherapy for malignant head and neck tumors. The brain is oversensitive to oxidant injury induced by radiation. Biotin is a member of the vitamin B complex family and its deficiency has been associated with neurogenesis impairment in animals and humans. The present study was undertaken to investigate the mitigating effect of biotin on the cerebral cortical and hippocampal damage induced by radiation exposure. Animals were exposed to radiation in the presence or absence of biotin and sacrificed on day 10. The results demonstrated that the administration of biotin 2 mg to irradiated rats had no significant effect on the radiation-induced damage of the cerebral cortex and the hippocampus, while the administration of biotin 6 mg has significantly attenuated oxidative stress in the hippocampus, manifested by a reduction of 4-hydroxynonenal (4HNE), total nitrate/nitrite (NOx), and xanthine oxidase (XO) levels associated with an elevation of glutathione (GSH) content as well as superoxide dismutase (SOD) and catalase (CAT) activities. In addition, biotin decreased the pro-inflammatory cytokines (interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrotic factor alpha (TNF-α)), caspase-3, poly(ADP-ribose) polymerase 1 (PARP1) level, and PARP1 gene expression. Moreover, biotin 6 mg treatment diminished serum S100 protein (S100B) and neuron-specific enolase (NSE) levels. In conclusion, biotin treatment at high dose post-irradiation has efficiently neutralized the effect of free radicals in the hippocampal region of rats. Thus, it could be applicable as a radio-mitigator for reducing or delayed radiation-induced brain injury in patients post-radiotherapy.

Effect of biotin supplementation on fatty acid metabolic pathways in 3T3-L1 adipocytes

Several studies have shown that pharmacological concentrations of biotin decrease serum lipid concentrations and the expression of lipogenic genes. Previous studies on epididymal adipose tissue in mice revealed that 8 weeks of dietary biotin supplementation increased the protein abundance of the active form of AMPK and the inactive forms acetyl CoA carboxylase (ACC)-1 and - 2, and decreased serum free fatty acid concentrations but did not affect lipolysis. These data suggest that pharmacological concentrations of the vitamin might affect fatty acid metabolism. In this work, we investigated the effects of pharmacological biotin concentrations on fatty acid synthesis, oxidation, and uptake in 3T3-L1 adipocytes. Similar to observations in mice, biotin-supplemented 3T3-L1 adipose cells increased the protein abundance of active ^T172 -AMPK and inactive ACC-1 and -2 forms. No changes were observed in the expression of the transcriptional factor PPARα and carnitine-palmitoyltransferase-1 (CPT-1). Radiolabeled assays indicated a decrease in fatty acid synthesis; an increase in fatty acid oxidation and fatty acid incorporation rate into the lipid fraction between control cells and biotin-supplemented cells. The data revealed an increase in the mRNA abundance of the fatty acid transport proteins Fatp1 and Acsl1 but not Cd36 or Fatp4 mRNA. Furthermore, the abundance of glycerol phosphate acyl transferase-3 protein was increased. Triglyceride content was not affected. Lipid droplet numbers showed an increase and their areas were smaller in the biotin-supplemented group. In conclusion, these data indicate that biotin supplementation causes a decrease in fatty acid synthesis and an increase in its oxidation and uptake. © 2018 BioFactors, 45(2):259-270, 2019.

PGC1α regulates ACMSD expression through cooperation with HNF4α

ACMSD is a tryptophan metabolic key enzyme. HNF4α regulates the transcription of some energy-metabolic enzymes by cooperating with PGC1α, a major transcriptional co-regulator involved in energy metabolism. In this study, we investigated the involvement of PGC1α in Acmsd expression through cooperation with HNF4α. Luciferase reporter assay was performed in NIH3T3 cells using a reporter vector containing HNF4α responsive elements in the Acmsd 5' upstream transcriptional regulatory region together with HNF4α and/or PGC1α expression vectors. The Acmsd luciferase reporter activity was greatly elevated by co-overexpression of HNF4α and PGC1α in NIH3T3 cells. Moreover, the expression level of Acmsd mRNA was significantly increased by co-overexpression of HNF4α and PGC1α in primary hepatocytes compared with expression of either HNF4α or PGC1α alone. These results indicate that PGC1α is involved in Acmsd expression through cooperation with HNF4α.

Effects of Biotin Supplementation During the First Week Postweaning Increases Pancreatic Islet Area, Beta-Cell Proportion, Islets Number, and Beta-Cell Proliferation

During maturation, pancreatic islets achieve their full capacity to secrete insulin in response to glucose, undergo morphological changes in which alpha-cells decrease and beta-cell mass increases, and they acquire the normal alpha- and beta-cell proportion changes that are important for islet functions later in life. In rodents, the first week of postweaning is critical for islet maturation. Multiple studies have documented the detrimental effects of several conditions on pancreatic maturation; however, few studies have addressed the use of pharmacological agents to enhance islet maturation. Biotin might have a potential action on islet maturation. Pharmacological concentrations of biotin have been found to modify islet morphology and function. In a previous study, we found that mice fed a biotin-supplemented diet for 8 weeks after weaning showed an increase in basal and glucose stimulated insulin secretion, enlarged islet size, and modified islet structure. In the present study, we investigated the effect of biotin on maturation features during the first week postweaning. Female BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet for 1 week after weaning. Compared with the control, biotin-supplemented mice showed an increase in pancreatic islet number and area in addition to an augmented proportion of beta-cells in the islet. These effects were related to an increase in beta-cell proliferation. No differences were found in insulin secretion, blood glucose concentrations, or serum insulin levels. These results indicate that biotin supplementation is capable of affecting beta-cell proliferation and might be a therapeutic agent for establishing strategies for regenerative medicine.

Neuroprotective potential of high-dose biotin

A recent controlled trial has established that high-dose biotin supplementation - 100 mg, three times daily - has a stabilizing effect on progression of multiple sclerosis (MS). Although this effect has been attributed to an optimization of biotin's essential cofactor role in the brain, a case can be made that direct stimulation of soluble guanylate cyclase (sGC) by pharmacological concentrations of biotin plays a key role in this regard. The utility of high-dose biotin in MS might reflect an anti-inflammatory effect of cGMP on the cerebral microvasculature, as well on oligodendrocyte differentiation and on Schwann cell production of neurotrophic factors thought to have potential for managing MS. But biotin's ability to boost cGMP synthesis in the brain may have broader neuroprotective potential. In many types of neurons and neural cells, cGMP exerts neurotrophic-mimetic effects - entailing activation of the PI3K-Akt and Ras-ERK pathways - that promote neuron survival and plasticity. Hippocampal long term potentiation requires nitric oxide synthesis, which in turn promotes an activating phosphorylation of CREB via a pathway involving cGMP and protein kinase G (PKG). In Alzheimer's disease (AD), amyloid beta suppresses this mechanism by inhibiting sGC activity; agents which exert a countervailing effect by boosting cGMP levels tend to restore effective long-term potentiation in rodent models of AD. Moreover, NO/cGMP suppresses amyloid beta production within the brain by inhibiting expression of amyloid precursor protein and BACE1. In conjunction with cGMP's ability to oppose neuron apoptosis, these effects suggest that high-dose biotin might have potential for the prevention and management of AD. cGMP also promotes neurogenesis, and may lessen stroke risk by impeding atherogenesis and hypertrophic remodeling in the cerebral vasculature. The neuroprotective potential of high-dose biotin likely could be boosted by concurrent administration of brain-permeable phosphodiesterase-5 inhibitors.

Supplementation with Phycocyanobilin, Citrulline, Taurine, and Supranutritional Doses of Folic Acid and Biotin-Potential for Preventing or Slowing the Progression of Diabetic Complications

Oxidative stress, the resulting uncoupling of endothelial nitric oxide synthase (eNOS), and loss of nitric oxide (NO) bioactivity, are key mediators of the vascular and microvascular complications of diabetes. Much of this oxidative stress arises from up-regulated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity. Phycocyanobilin (PhyCB), the light-harvesting chromophore in edible cyanobacteria such as spirulina, is a biliverdin derivative that shares the ability of free bilirubin to inhibit certain isoforms of NADPH oxidase. Epidemiological studies reveal that diabetics with relatively elevated serum bilirubin are less likely to develop coronary disease or microvascular complications; this may reflect the ability of bilirubin to ward off these complications via inhibition of NADPH oxidase. Oral PhyCB may likewise have potential in this regard, and has been shown to protect diabetic mice from glomerulosclerosis. With respect to oxidant-mediated uncoupling of eNOS, high-dose folate can help to reverse this by modulating the oxidation status of the eNOS cofactor tetrahydrobiopterin (BH4). Oxidation of BH4 yields dihydrobiopterin (BH2), which competes with BH4 for binding to eNOS and promotes its uncoupling. The reduced intracellular metabolites of folate have versatile oxidant-scavenging activity that can prevent oxidation of BH4; concurrently, these metabolites promote induction of dihydrofolate reductase, which functions to reconvert BH2 to BH4, and hence alleviate the uncoupling of eNOS. The arginine metabolite asymmetric dimethylarginine (ADMA), typically elevated in diabetics, also uncouples eNOS by competitively inhibiting binding of arginine to eNOS; this effect is exacerbated by the increased expression of arginase that accompanies diabetes. These effects can be countered via supplementation with citrulline, which efficiently enhances tissue levels of arginine. With respect to the loss of NO bioactivity that contributes to diabetic complications, high dose biotin has the potential to "pinch hit" for diminished NO by direct activation of soluble guanylate cyclase (sGC). High-dose biotin also may aid glycemic control via modulatory effects on enzyme induction in hepatocytes and pancreatic beta cells. Taurine, which suppresses diabetic complications in rodents, has the potential to reverse the inactivating impact of oxidative stress on sGC by boosting synthesis of hydrogen sulfide. Hence, it is proposed that concurrent administration of PhyCB, citrulline, taurine, and supranutritional doses of folate and biotin may have considerable potential for prevention and control of diabetic complications. Such a regimen could also be complemented with antioxidants such as lipoic acid, N-acetylcysteine, and melatonin-that boost cellular expression of antioxidant enzymes and glutathione-as well as astaxanthin, zinc, and glycine. The development of appropriate functional foods might make it feasible for patients to use complex nutraceutical regimens of the sort suggested here.

Dietary Biotin Supplementation Modifies Hepatic Morphology without Changes in Liver Toxicity Markers

Pharmacological concentrations of biotin have pleiotropic effects. Several reports have documented that biotin supplementation decreases hyperglycemia. We have shown that a biotin-supplemented diet increased insulin secretion and the mRNA abundance of proteins regulating insulin transcription and secretion. We also found enlarged pancreatic islets and modified islet morphology. Other studies have shown that pharmacological concentrations of biotin modify tissue structure. Although biotin administration is considered safe, little attention has been given to its effect on tissue structure. In this study, we investigated the effect of biotin supplementation on hepatic morphology and liver toxicity markers. Male BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet for 8 weeks. Versus the control mice, biotin-supplemented mice had an altered portal triad with dilated sinusoids, increased vascularity, and bile conducts. Furthermore, we observed an increased proportion of nucleomegaly and binucleated hepatocytes. In spite of the liver morphological changes, no differences were observed in the serum liver damage indicators, oxidative stress markers, or antioxidant enzymes. Our data demonstrate for the first time that biotin supplementation affects liver morphology in normal mice, and that these modifications are not paralleled with damage markers.

In type 1 diabetics, high-dose biotin may compensate for low hepatic insulin exposure, promoting a more normal expression of glycolytic and gluconeogenic enyzymes and thereby aiding glycemic control

In type 1 diabetics, hepatic exposure to insulin is chronically subnormal even in the context of insulin therapy; as a result, expression of glycolytic enzymes is decreased, and that of gluconeogenic enzymes is enhanced, resulting in a physiologically inappropriate elevation of hepatic glucose output. Subnormal expression of glucokinase (GK) is of particular importance in this regard. Possible strategies for correcting this perturbation of hepatic enzyme expression include administration of small molecule allosteric activators of GK, as well as a procedure known as chronic intermittent intravenous insulin therapy (CIIIT); however, side effects accompany the use of GK activators, and CIIIT is time and labor intensive. Alternatively, administration of high-dose biotin has potential for modulating hepatic enzyme expression in a favorable way. Studies in rodents and in cultured hepatocytes demonstrate that, in the context of low insulin exposure, supra-physiological levels of biotin induce increased expression of GK while suppressing that of the key gluconeogenic enzyme phosphoenolpyruvate carboxykinase. These effects may be a downstream consequence of the fact that biotin down-regulates mRNA expression of FOXO1; insulin's antagonism of the activity of this transcription factor is largely responsible for its modulatory impact on hepatic glycolysis and gluconeogenesis. Hence, high-dose biotin may compensate for subnormal insulin exposure by suppressing FOXO1 levels. High-dose biotin also has the potential to oppose hepatic steatosis by down-regulating SREBP-1 expression. Two pilot trials of high-dose biotin (16 or 2mg per day) in type 1 diabetics have yielded promising results. There is also some reason to suspect that high-dose biotin could aid control of diabetic neuropathy and nephropathy via its stimulatory effect on cGMP production. Owing to the safety, good tolerance, moderate expense, and current availability of high-dose biotin, this strategy merits more extensive evaluation in type 1 diabetes.

Vitamins and their derivatives in the prevention and treatment of metabolic syndrome diseases (diabetes),

A cluster of inter-related conditions such as central obesity, dyslipidemia, impaired glucose metabolism, and hypertension is referred to as Metabolic Syndrome, which is a risk factor for the development of type-2 diabetes. The micro- and macro-vascular complications of diabetes contribute to its morbidity and mortality. In addition to its calcitropic effect, vitamin D is a regulator of gene expression as well as cell proliferation and differentiation. Various cross-sectional and longitudinal cohort studies have indicated a beneficial effect from vitamin D supplementation on the development of type-2 diabetes. Binding of retinol-bound retinol-binding protein to a membrane-binding protein suppresses insulin signaling. All-trans retinoic acid, a derivative of vitamin A, reverses these effects, resulting in increased insulin sensitivity, suppression of the phosphoenolpyruvate carboxy kinase (PEPCK) gene, and the induction of the glucokinase gene. Glucokinase and PEPCK are also regulated in opposite directions by the vitamin biotin, acting at the transcriptional level. Biotin also regulates the synthesis of insulin by the islet of Langerhans cells of the pancreas. The increase in advanced glycation end products (AGEs) is implicated in the initiation and progression of diabetes-associated microvascular diseases. Benfotiamine, a derivative of thiamine, and pyridoxamine, a vitamer of vitamin B6, both have anti-AGE properties, making them valuable therapeutic adjuvants in the treatment of diabetic complications. Thus, various vitamins and their derivatives have profound therapeutic potential in the prevention and treatment of type-2 diabetes.

Biotin uptake by mouse and human pancreatic beta cells/islets: a regulated, lipopolysaccharide-sensitive carrier-mediated process

Biotin is essential for the normal function of pancreatic beta cells. These cells obtain biotin from their surroundings via transport across their cell membrane. Little is known about the uptake mechanism involved, how it is regulated, and how it is affected by internal and external factors. We addressed these issues using the mouse-derived pancreatic beta-TC-6 cells and freshly isolated mouse and human primary pancreatic beta cells as models. The results showed biotin uptake by pancreatic beta-TC-6 cells occurs via a Na(+)-dependent, carrier-mediated process, that is sensitive to desthiobiotin, as well as to pantothenic acid and lipoate; the process is also saturable as a function of concentration (apparent Km = 22.24 ± 5.5 μM). These cells express the sodium-dependent multivitamin transporter (SMVT), whose knockdown (with doxycycline-inducible shRNA) led to a sever inhibition in biotin uptake. Similarly, uptake of biotin by mouse and human primary pancreatic islets is Na(+)-dependent and carrier-mediated, and both cell types express SMVT. Biotin uptake by pancreatic beta-TC-6 cells is also adaptively regulated (via transcriptional mechanism) by extracellular substrate level. Chronic treatment of pancreatic beta-TC-6 cells with bacterial lipopolysaccharides (LPS) leads to inhibition in biotin uptake. This inhibition is mediated via a Toll-Like receptor 4-mediated process and involves a decrease in membrane expression of SMVT. These findings show, for the first time, that pancreatic beta cells/islets take up biotin via a specific and regulated carrier-mediated process, and that the process is sensitive to the effect of LPS.

Modulation of the rat hepatic cytochrome P4501A subfamily using biotin supplementation

Studies have found that biotin favors glucose and lipid metabolism, and medications containing biotin have been developed. Despite the use of biotin as a pharmacological agent, few studies have addressed toxicity aspects including the possible interaction with cytochrome P450 enzyme family. This study analyzed the effects of pharmacological doses of biotin on the expression and activity of the cytochrome P4501A subfamily involved in the metabolism of xenobiotics. Wistar rats were treated daily with biotin (2 mg/kg, i.p.), while the control groups were treated with saline. All of the rats were sacrificed by cervical dislocation after 1, 3, 5, or 7 days of treatment. CYP1A1 and CYP1A2 mRNAs were modified by biotin while enzyme activity and protein concentration were not affected. The lack of an effect of biotin on CYP1A activity was confirmed using other experimental strategies, including (i) cotreatment of the animals with biotin and a known CYP1A inducer; (ii) the addition of biotin to the reaction mixtures for the measurement of CYP1A1 and CYP1A2 activities; and (iii) the use of an S9 mixture that was prepared from control and biotin-treated rats to analyze the activation of benzo[a]pyrene (BaP) into mutagenic metabolites using the Ames test. The results suggest that biotin does not influence the CYP1A-mediated metabolism of xenobiotics.

Survey of the effect of biotin on glycemic control and plasma lipid concentrations in type 1 diabetic patients in kermanshah in iran (2008-2009)

OBJECTIVE

Diabetes mellitus is the most common chronic endocrine disease worldwide. Intensive glycemic control plays an important role in decreasing morbidity and mortality rate of the disease. Preclinical studies have shown that biotin has an essential role in regulating blood glucose and serum lipid metabolism. This study aims to evaluate the effect of biotin on glycemic control and plasma lipids concentrations in type 1diabetic patients.

METHODS

This randomized double-blind placebo-controlled clinical trial study was conducted 70 type 1 diabetic patients with an age range 5-25 years old with poorly controlled (glycosylated hemoglobin ≥8%). Subjects were randomly allocated into two groups. In the intervention group biotin (40 microgram/kg) was administered plus daily insulin, while the control group received placebo plus daily insulin regimen for three months. Laboratory tests including glycosylated hemoglobin (HbA1c), fasting blood sugar and plasma lipids were measured at the base and after 3 months.

RESULTS

In this study, seventy patients were evaluated, 35 were allocated to each group. There were no statistically significant differences between age, gender, duration of diabetes, BMI and BP between the two groups (p>0.05). HbA1c in the intervention (biotin) group was 9.84±1.80 at base and after 3 months treatment, it declined to 8.88±1.73 (p<0.001). In the control group HbA1c at base was 9.39±1.58, after 3 months it increased to10.11± 1.68. There were statistically significant differences in the mean of HbA1c in both the biotin and the control groups (p<0.001). FBS in the biotin group at base was 275±65.76 mg/dl and after 3 months it had reduced to 226± 41.31 (p<0.001). There were statistically significant differences in the mean of total cholesterol, low density lipoprotein cholesterol and triglyceride between the two groups at the end of 3 months (p<0.05).

CONCLUSION

Results of this study showed that biotin administration as an adjuvant in addition to insulin regimen can improve glycemic management and decrease plasma lipids concentrations in poorly controlled type 1 diabetic patients.

The hypotriglyceridemic effect of biotin supplementation involves increased levels of cGMP and AMPK activation

In addition to its role as a carboxylase cofactor, biotin modifies gene expression and has manifold effects on systemic processes. Several studies have shown that biotin supplementation reduces hypertriglyceridemia. We have previously reported that this effect is related to decreased expression of lipogenic genes. In the present work, we analyzed signaling pathways and posttranscriptional mechanisms involved in the hypotriglyceridemic effects of biotin. Male BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet (1.76 or 97.7 mg of free biotin/kg diet, respectively for 8 weeks after weaning. The abundance of mature sterol regulatory element-binding protein (SREBP-1c), fatty-acid synthase (FAS), total acetyl-CoA carboxylase-1 (ACC-1) and its phosphorylated form, and AMP-activated protein kinase (AMPK) were evaluated in the liver. We also determined the serum triglyceride concentrations and the hepatic levels of triglycerides and cyclic GMP (cGMP). Compared to the control group, biotin-supplemented mice had lower serum and hepatic triglyceride concentrations. Biotin supplementation increased the levels of cGMP and the phosphorylated forms of AMPK and ACC-1 and decreased the abundance of the mature form of SREBP-1c and FAS. These data provide evidence that the mechanisms by which biotin supplementation reduces lipogenesis involve increased cGMP content and AMPK activation. In turn, these changes lead to augmented ACC-1 phosphorylation and decreased expression of both the mature form of SREBP-1c and FAS. Our results demonstrate for the first time that AMPK is involved in the effects of biotin supplementation and offer new insights into the mechanisms of biotin-mediated hypotriglyceridemic effects.

Effects of biotin supplementation in the diet on insulin secretion, islet gene expression, glucose homeostasis and beta-cell proportion

Besides its role as a carboxylase cofactor, biotin has a wide repertoire of effects on gene expression, development and metabolism. Pharmacological concentrations of biotin enhance insulin secretion and the expression of genes and signaling pathways that favor islet function in vitro. However, the in vivo effects of biotin supplementation on pancreatic islet function are largely unknown. In the present study, we investigated whether in vivo biotin supplementation in the diet has positive effects in rodent pancreatic islets. Male BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet over 8 weeks postweaning and tested for glucose homeostasis, insulin secretion, islet gene expression and pancreatic morphometry. Insulin secretion increased from the islets of biotin-supplemented mice, together with the messenger RNA (mRNA) expression of several transcription factors regulating insulin expression and secretion, including forkhead box A2, pancreatic and duodenal homeobox 1 and hepatocyte nuclear factor 4α. The mRNA abundance of glucokinase, Cacna1d, acetyl-CoA carboxylase, and insulin also increased. Consistent with these effects, glucose tolerance improved, and glucose-stimulated serum insulin levels increased in biotin-supplemented mice, without changes in fasting glucose levels or insulin tolerance. Biotin supplementation augmented the proportion of beta cells by enlarging islet size and, unexpectedly, also increased the percentage of islets with alpha cells at the islet core. mRNA expression of neural cell adhesion molecule 1, an adhesion protein participating in the maintenance of islet architecture, decreased in biotin-supplemented islets. These findings provide, for the first time, insight into how biotin supplementation exerts its effects on function and proportion of beta cells, suggesting a role for biotin in the prevention and treatment of diabetes.

Administration of biotin prevents the development of insulin resistance in the skeletal muscles of Otsuka Long-Evans Tokushima Fatty rats

Otsuka Long-Evans Tokushima Fatty (OLETF) rat is an animal model for type 2 diabetes mellitus. In the present study, we investigated whether pharmacologic doses of biotin have the potential to abate insulin resistance in the skeletal muscles of OLETF rats. OLETF rats (34 weeks of age) were divided into 2 groups and given distilled water (OLETF-control group) or distilled water containing 3.3 mg L(-1) of biotin (OLETF-biotin group) for 8 weeks. At the end of experimental period, the OLETF-control rats developed severe hyperglycemia and hyperinsulinemia, whereas the OLETF-biotin rats showed significantly smaller responses to oral glucose tolerance test than the OLETF-control rats. The glucose uptake in the hind limbs of the rats was significantly higher in the OLETF-biotin group than in the OLETF-control group. Biotin administration increased the glucose transporter type 4 (GLUT4) protein content in the total membrane fraction but had little effect on the GLUT4 content in the plasma membrane fraction. These results indicate that administration of a pharmacological dose of biotin prevents the development of insulin resistance in the skeletal muscles of OLETF rats presumably via an increase in GLUT4 protein expression but not via GLUT4 translocation.

Biological Effects of Pharmacological Concentrations of Biotin

Understanding the molecular mechanisms of vitamins has opened new perspectives regarding the relationship between nutritional signals and biological functions, which, in turn, has led to the development of new therapeutic agents. Although little is known about water-soluble vitamins as genetic modulators, evidence about their effects on gene expression has grown. In the case of biotin, besides its role as a carboxylase prosthetic group, it also affects gene expression and has a wide repertoire of effects on biological functions. Only recently, the role of pharmacological concentrations of biotin on systemic functions has attracted attention, and it is now being reconsidered with the help of new technologies. This novel approach could lead to new perspectives in its use as a therapeutic agent. The present review is focused on the effects of pharmacological concentrations of biotin on several biological functions and on the biotin signaling pathways that participate in gene expression.