Biomedical subjects

Alan L Miller

Publications and source records attributed to Alan L Miller.

4 recordsLinked to original sources

PubMed2006

The effects of sustained-release-L-arginine formulation on blood pressure and vascular compliance in 29 healthy individuals.

Vascular endothelial function is crucial to cardiovascular function and thus to blood perfusion to the heart and throughout the body. A number of substances are produced and secreted by vascular endothelial cells, the most important of which is nitric oxide, a potent regulator of vascular function. Nitric oxide diffuses from endothelial cells into underlying smooth muscle, causing relaxation, which results in vasodilation. When this process is inhibited or inadequate the arteries cannot dilate as necessary, resulting in hypertonicity and reduced blood flow. Such endothelial dysfunction also causes increased platelet and monocyte adhesiveness and smooth muscle proliferation, processes thought to be at the genesis of atherosclerotic plaque formation. Since L-arginine is the body's only substrate for nitric oxide synthesis, adequate L-arginine must be present for proper nitric oxide production. In this open label trial, a group of 29 asymptomatic individuals were given L-arginine (1,050 mg, as Perfusia-SR, a sustained-release preparation) twice daily (total 2.1 g daily) for one week. Systolic blood pressure was reduced in 62 percent of participants compared to baseline, with a non-significant mean decrease in all patients of 4 mm Hg. Diastolic blood pressure was reduced in 69 percent of participants, with a mean reduction of 3.7 mm Hg (p = 0.005). In the 10 individuals who were borderline or hypertensive (systolic > 130 or diastolic > 85), there was a mean systolic reduction of 11 mm Hg (p = 0.05), while normotensives (n = 19) had a mean systolic decrease of only 0.22 mm Hg. Diastolic blood pressure was decreased a non-significant 4.9 mm Hg in borderline or hypertensives and 4.5 mm Hg in normotensives (p = 0.026). Vascular elasticity relates to endothelial function, and can be measured non-invasively. At baseline and follow-up, vascular compliance was assessed via digital pulse wave analysis (DPA; Meridian Medical). After one week, pulse wave analysis showed a significant increase in large artery compliance (mean 23% improvement; p = 0.02) and a non-significant increase in small artery compliance (mean 23% improvement; p = 0.15). This study demonstrates blood pressure reductions, especially in patients with borderline or frank hypertension, as well as improved vascular compliance - an indicator of improved endothelial function and perfusion - after a one-week trial of sustained-release L-arginine. Poor endothelial function due to inadequate endothelial nitric oxide production is present in hypertension, as well as in numerous other aspects of cardiovascular disease, including angina, erectile dysfunction, cerebrovascular disease, and peripheral vascular disease. This is the first study showing a moderate dose of sustained-release L-arginine can improve endothelial function and blood pressure.

Adult↗

PubMed2005

Epidemiology, etiology, and natural treatment of seasonal affective disorder.

There is much more seasonal difference in higher latitudes than in lower latitudes. In a significant portion of the population of the northern United States, the shorter days of fall and winter precipitate a syndrome that can consist of depression, fatigue, hypersomnolence, hyperphagia, carbohydrate craving, weight gain, and loss of libido. If these symptoms persist in the winter, abate as the days grow longer, and disappear in the summer, the diagnosis of seasonal affective disorder (SAD) can be made. Many hypotheses exist regarding the biochemical mechanisms behind the predisposition toward this disease, including circadian phase shifting, abnormal pineal melatonin secretion, and abnormal serotonin synthesis. Although the mechanism(s) behind this disease is not fully known, one treatment appears to address each of the theories. Light therapy is a natural, non-invasive, effective, well-researched method of treatment for SAD. Various light temperatures and times of administration of light therapy have been studied, and a combination of morning and evening exposure appears to offer the best efficacy. Other natural methods of treatment have been studied, including L-tryptophan, Hypericum perforatum (St. John's wort), and melatonin.

Humans↗

PubMed2003

The methionine-homocysteine cycle and its effects on cognitive diseases.

Homocysteine, a sulfur-containing amino acid, is a metabolite of the essential amino acid methionine, and exists at a critical biochemical intersection in the methionine cycle - between S-adenosylmethionine, the indispensable ubiquitous methyl donor, and vitamins B12 and folic acid. High blood levels of homocysteine signal a breakdown in this vital process, resulting in far-reaching biochemical and life consequences. The link between homocysteine and cardiovascular disease is well established, and decreasing plasma total homocysteine by providing nutritional cofactors for its metabolism has been shown to reduce the risk of cardiovascular events. Information has been emerging regarding a connection between homocysteine metabolism and cognitive function, from mild cognitive decline (age-related memory loss) to vascular dementia and Alzheimer's disease. Significant deficiencies in the homocysteine re-methylation cofactors cobalamin (B12) and folate, as well as the trans-sulfuration cofactor vitamin B6, are commonly seen in the elderly population, with a resultant increase in homocysteine with advancing age. Hyperhomocysteinemia has been shown to be an independent risk factor for cognitive dysfunction. Indirect and direct vascular damage can be caused by homocysteine, which has been implicated in vascular dementia, with an increased risk of multiple brain infarcts and dementia as homocysteine levels rise. A significant correlation has been found between risk of Alzheimer's disease and high plasma levels of homocysteine, as well as low levels of folic acid, and vitamins B6 and B12. All of these disease associations are thought to be interrelated via increased homocysteine and S-adenosylhomocysteine and subsequent hypomethylation of numerous substances, including DNA and proteins, that render vascular structures and neurons more susceptible to damage and apoptosis. Providing the nutritional cofactors for proper functioning of the methionine cycle may improve methylation and protect the brain from damage. Further studies need to be performed to assess whether this will also reduce the risk of cognitive diseases and/or improve cognitive functioning.

Alzheimer Disease↗

PubMed2003

Nutritional support for wound healing.

Healing of wounds, whether from accidental injury or surgical intervention, involves the activity of an intricate network of blood cells, tissue types, cytokines, and growth factors. This results in increased cellular activity, which causes an intensified metabolic demand for nutrients. Nutritional deficiencies can impede wound healing, and several nutritional factors required for wound repair may improve healing time and wound outcome. Vitamin A is required for epithelial and bone formation, cellular differentiation, and immune function. Vitamin C is necessary for collagen formation, proper immune function, and as a tissue antioxidant. Vitamin E is the major lipid-soluble antioxidant in the skin; however, the effect of vitamin E on surgical wounds is inconclusive. Bromelain reduces edema, bruising, pain, and healing time following trauma and surgical procedures. Glucosamine appears to be the rate-limiting substrate for hyaluronic acid production in the wound. Adequate dietary protein is absolutely essential for proper wound healing, and tissue levels of the amino acids arginine and glutamine may influence wound repair and immune function. The botanical medicines Centella asiatica and Aloe vera have been used for decades, both topically and internally, to enhance wound repair, and scientific studies are now beginning to validate efficacy and explore mechanisms of action for these botanicals. To promote wound healing in the shortest time possible, with minimal pain, discomfort, and scarring to the patient, it is important to explore nutritional and botanical influences on wound outcome.

Amino Acids↗