The Potential of Carnosine Supplementation in Optimising Cardiometabolic Health in Patients With Prediabetes and Type 2 Diabetes: a Randomsied, Double-blinded, Placebo-controlled Trial

Type 2 diabetes is a major public health problem worldwide. Obesity itself markedly increases the risk of type 2 diabetes (DM2), which now affects every second obese person. With 60% of adult Australians overweight or obese and 25% of Australians aged over 25 years having prediabetes or diabetes, the quality-of-life and cost impact is inescapable. In Australia, direct healthcare costs for DM2 are currently estimated as $1.1 billion annually, with the prospect of doubling by 2025. Obesity and DM2 dramatically increase the risk of cardiovascular disease (CVD) with ~80% of individuals with both obesity and DM2 develop CVD. The annual healthcare costs for CVD in Australia now amount to $7.7 billion; and the total aggregated costs, including loss of income, are much higher again. Treating DM2 and CVD is expensive and often unsatisfactory. Weight loss and exercise are the mainstay of prevention and therapy but they are difficult and costly to achieve on a large scale; hence the DM2 epidemic continues unabated. Therefore, interventions at low cost and easy to implement at the population level is urgently required.

Neurodegenerative diseases often occurs in people with DM2, and DM2 is in turn associated with increased risk of cognitive decline. Neurodegenerative diseases such as Alzheimer's disease are also associated with metabolic impairment. They share many common pathogenic features with DM2 such as insulin resistance, chronic low-grade inflammation, vascular disease, oxidative stress and accumulation of advanced glycation endproducts (AGEs). Progression of these diseases over years-decades is also worsened by a sedentary life-style. Therefore not surprisingly, regular physical activity is beneficial in those patients, likely due to improvement of neurological, motor and cardiometabolic profile. However, it is difficult and costly to achieve on a large scale, and thus, safe and low-cost strategies are needed.

Type 2 diabetes is associated with increased amounts of ectopic fat depots in muscle including intramyocellular lipids (IMCL), and adipocytes located between muscle groups (inter-muscular) and also between muscle fascicles (intramuscular). Both IMCL and intra- and inter-muscular adipose tissue (IMAT) may deleteriously effect muscle metabolism and insulin sensitivity through increased local secretion of pro-inflammatory adipokines, and inter-muscular fat may additionally impair insulin action through reductions in blood flow to muscle.

Could carnosine be that strategy? Strong molecular and animal data (>2000 papers) suggests that it has great potential, with all the relevant properties. Carnosine, is present in several tissues including muscle and brain, easily crosses the blood-brain barrier, and extensive animal data show that carnosine has chelating properties and modulates glucose metabolism, advanced glycation, pro-inflammatory and pro-oxidative states, as well as motor functions and neurotransmission. A promising further use may derive from its effect on cardiometabolic health and neuroprotection. Current research, confined to animal studies, supports carnosine supple¬ment¬ation for preventing and treating obesity, DM2, CVD, and neurodegenerative diseases - by virtue of its anti-inflammatory, antioxidative, anti-glycating and chelating effects. Our team's novel pilot studies provide the first human cross-sectional and interventional metabolic data, and demonstrate relationships among carnosine, obesity, insulin resistance, and dyslipidaemia. Previous clinical trials also showed that supplementation of carnosine for 2-3 months improved cognitive performance in healthy individuals and patients with neurodegenerative diseases. However, none of them showed its effect in patient with type 2 diabetes and explored the effects of change in cardiometabolic outcomes on cognitive function.

Apart from its excellent side-effect profile, carnosine is cheap and safe (it is an over-the-counter dietary supplement), making it prima facie ideal for widespread, low cost use. Robust human research is now urgently needed to test the therapeutic potential of carnosine in improving cardiometabolic profile and cognitive function, and study the mechanisms involved.