The aim of this study is to determine whether carnosine supplementation in overweight/obese individuals can improve insulin secretion and/or insulin resistance by decreasing sub clinical inflammation. The investigators hypothesise that carnosine supplementation will reduce type 2 diabetes and cardiovascular risk factors by lowering chronic low-grade inflammation (CLI), oxidative stress, advanced glycation end products (AGEs), and advanced lipoxidation end products (ALEs). Aim :To determine the capacity of carnosine supplementation to decrease major risk factors for type 2 diabetes and cardiovascular disease and identify metabolic pathways involved, specifically by: 1. Reducing diabetes risk (insulin sensitivity; secretory function and glucose tolerance) 2. Improving cardiovascular risk factors (lipids; arterial (aortic) stiffness; central blood pressure (cBP); endothelial function). 3. Decreasing the CLI, oxidative stress, AGEs, and ALEs, and increase detoxification of reactive carbonyl species (RCSs).
Cardiovascular risk factors including type 2 diabetes underpin a major threat to the globe and result in a heavy health and financial burden across the healthcare system. Treating type 2 diabetes and cardiovascular disease is expensive and often unsatisfactory. Current medications bring unwanted side effects, and often merely delay rather than prevent type 2 diabetes complications and cardiovascular disease. As a further concern, the micro- and macrovascular complications of type 2 diabetes often start developing before actual diagnosis. Diabetes prevention and treatment through weight loss and exercise programs is a difficult and costly public health measure, leaving the tidal wave of type 2 diabetes to swell even more. An alternative is urgently needed: a low-cost safe approach, easy to implement at population level. Could carnosine be that alternative? The evidence suggests carnosine has significant metabolic impact and presents such an alternative. A naturally occurring dipeptide, carnosine is already emerging as a human therapy in exercise physiology, heart failure, cataract prevention and treatment, neurology, and psychiatry. A promising further use may derive from its effect on cardiovascular risk factors. Metabolic research, though confined to animal studies, strongly suggests that carnosine supplementation aids the prevention and treatment of obesity, type 2 diabetes, and cardiovascular disease - by virtue of its anti-inflammatory, antioxidative, and anti-glycating effects. The investigators conducted the first pilot data in human and demonstrate relationships among carnosine, obesity, insulin resistance, and dyslipidemia. Put briefly, the pilot weighs strongly in favour of carnosine as a means of reducing cardiovascular risk in humans. Too good to be true? Apart from its excellent side-effect profile, carnosine is inexpensive and seemingly safe (available as an over-the-counter food additive), making it prima facie ideal for population use. In this setting research is now urgently needed - to test the significant metabolic potential of carnosine to address a major health problem. The investigators propose a comprehensive double-blind placebo-controlled human trial to investigate the effects of carnosine supplementation on cardiovascular risk factors. If the investigators demonstrate a role in reducing risk factors for type 2 diabetes and cardiovascular disease in overweight and obese non-diabetic humans, the public health implications will be revolutionary, offering the world a genuine low cost, accessible, intervention to curtail the advance of obesity, type 2 diabetes, and cardiovascular disease.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
QUADRUPLE
Enrollment
84
Monash Centre for Health Research and Implementation
Melbourne, Victoria, Australia
RECRUITINGChange in insulin sensitivity measured by euglycaemic glucose clamp
The clamp will be used to measure insulin sensitivity. The clamp is initiated by an intravenous bolus injection of insulin (9milliUnit/kg). Insulin is then constantly infused at a rate of 40 milliUnit.m-2.min-1 for 120 min into an arm vein, whilst glucose is variably infused to maintain euglycaemia. Plasma glucose values will be monitored every 5 minutes during the clamp and the variable infusion rate of glucose is adjusted to maintain blood glucose at a constant value of 5mmol/L.
Time frame: From baseline to 14 weeks
Change in markers of endothelial dysfunction
This is done using non-invasive peripheral arterial tomography (PAT; endothelium-dependent digital pulse amplitude testing (EndoPAT), Itamar Medical Ltd, Israel), which records continuous plethysmo¬graphic signals of the finger arterial pulse wave. Finger plethysmographic probes are placed on each index finger; and after a 5 min equilib¬ration period, a blood pressure cuff on the non-dominant arm is inflated to 60 mmHg above systolic for 5 min and then deflated to induce reactive hyperaemia. Measurements of post-occlusion changes (reactive hyperaemia PAT: RH-PAT) are continued for 10 min. Results are normalised to the non-occluded arm, compensating for potential systemic changes (RH-PAT ratio).
Time frame: From baseline to 14 weeks
Change in Acute Insulin Secretory Response - Intravenous Glucose Tolerance Test
This will be measured in response to 25g intravenous glucose and calculated as the average incremental plasma insulin level from the third to the fifth minute after the glucose bolus.
Time frame: From baseline to 14 weeks
Change in Resting systolic and diastolic blood pressure
Resting systolic and diastolic blood pressure and pulse rate will be measured using an automated oscillometric measurement system (Dinamap, USA) after a 30 minute rest.
Time frame: From baseline to 14 weeks
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