Using polyphenols as a relevant therapy to diabetes and its complications, a review

Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases is emerging. Bioavailability differs greatly from one polyphenol to another, so that the most abundant polyphenols in our diet are not necessarily those leading to the highest concentrations of active metabolites in target tissues. Mean values for the maximal plasma concentration, the time to reach the maximal plasma concentration, the area under the plasma concentration-time curve, the elimination half-life, and the relative urinary excretion were calculated for 18 major polyphenols. We used data from 97 studies that investigated the kinetics and extent of polyphenol absorption among adults, after ingestion of a single dose of polyphenol provided as pure compound, plant extract, or whole food/beverage. The metabolites present in blood, resulting from digestive and hepatic activity, usually differ from the native compounds. The nature of the known metabolites is described when data are available. The plasma concentrations of total metabolites ranged from 0 to 4 mumol/L with an intake of 50 mg aglycone equivalents, and the relative urinary excretion ranged from 0.3% to 43% of the ingested dose, depending on the polyphenol. Gallic acid and isoflavones are the most well-absorbed polyphenols, followed by catechins, flavanones, and quercetin glucosides, but with different kinetics. The least well-absorbed polyphenols are the proanthocyanidins, the galloylated tea catechins, and the anthocyanins. Data are still too limited for assessment of hydroxycinnamic acids and other polyphenols. These data may be useful for the design and interpretation of intervention studies investigating the health effects of polyphenols.

Background Diabetes prevalence is increasing globally, and Sub-Saharan Africa is no exception. With diverse health challenges, health authorities in Sub-Saharan Africa and international donors need robust data on the epidemiology and impact of diabetes in order to plan and prioritise their health programmes. This paper aims to provide a comprehensive and up-to-date review of the epidemiological trends and public health implications of diabetes in Sub-Saharan Africa. Methods We conducted a systematic literature review of papers published on diabetes in Sub-Saharan Africa 1999-March 2011, providing data on diabetes prevalence, outcomes (chronic complications, infections, and mortality), access to diagnosis and care and economic impact. Results Type 2 diabetes accounts for well over 90% of diabetes in Sub-Saharan Africa, and population prevalence proportions ranged from 1% in rural Uganda to 12% in urban Kenya. Reported type 1 diabetes prevalence was low and ranged from 4 per 100,000 in Mozambique to 12 per 100,000 in Zambia. Gestational diabetes prevalence varied from 0% in Tanzania to 9% in Ethiopia. Proportions of patients with diabetic complications ranged from 7-63% for retinopathy, 27-66% for neuropathy, and 10-83% for microalbuminuria. Diabetes is likely to increase the risk of several important infections in the region, including tuberculosis, pneumonia and sepsis. Meanwhile, antiviral treatment for HIV increases the risk of obesity and insulin resistance. Five-year mortality proportions of patients with diabetes varied from 4-57%. Screening studies identified high proportions (> 40%) with previously undiagnosed diabetes, and low levels of adequate glucose control among previously diagnosed diabetics. Barriers to accessing diagnosis and treatment included a lack of diagnostic tools and glucose monitoring equipment and high cost of diabetes treatment. The total annual cost of diabetes in the region was estimated at US$67.03 billion, or US$8836 per diabetic patient. Conclusion Diabetes exerts a significant burden in the region, and this is expected to increase. Many diabetic patients face significant challenges accessing diagnosis and treatment, which contributes to the high mortality and prevalence of complications observed. The significant interactions between diabetes and important infectious diseases highlight the need and opportunity for health planners to develop integrated responses to communicable and non-communicable diseases.

Glucagon-like peptide 1 (GLP-1) has been proposed as a treatment for type 2 diabetes. We have investigated the long-term effects of continuous administration of this peptide hormone in a 6-week pilot study. 20 patients with type 2 diabetes were alternately assigned continuous subcutaneous infusion of GLP-1 (n=10) or saline (n=10) for 6 weeks. Before (week 0) and at weeks 1 and 6, they underwent beta-cell function tests (hyperglycaemic clamps), 8 h profiles of plasma glucose, insulin, C-peptide, glucagon, and free fatty acids, and appetite and side-effect ratings on 100 mm visual analogue scales; at weeks 0 and 6 they also underwent dexascanning, measurement of insulin sensitivity (hyperinsulinaemic euglycaemic clamps), haemoglobin A(1c), and fructosamine. The primary endpoints were haemoglobin A(1c) concentration, 8-h profile of glucose concentration in plasma, and beta-cell function (defined as the first-phase response to glucose and the maximum insulin secretory capacity of the cell). Analyses were per protocol. One patient assigned saline was excluded because no veins were accessible. In the remaining nine patients in that group, no significant changes were observed except an increase in fructosamine concentration (p=0.0004). In the GLP-1 group, fasting and 8 h mean plasma glucose decreased by 4.3 mmol/L and 5.5 mmol/L (p<0.0001). Haemoglobin A(1c) decreased by 1.3% (p=0.003) and fructosamine fell to normal values (p=0.0002). Fasting and 8 h mean concentrations of free fatty acids decreased by 30% and 23% (p=0.0005 and 0.01, respectively). Gastric emptying was inhibited, bodyweight decreased by 1.9 kg, and appetite was reduced. Both insulin sensitivity and beta-cell function improved (p=0.003 and p=0.003, respectively). No important side-effects were seen. GLP-1 could be a new treatment for type 2 diabetes, though further investigation of the long-term effects of GLP-1 is needed.