Type 2 diabetes (characterised by impaired glucose control) is increasing in the UK (~3.7 million type 2 diabetics and ~7 million pre-diabetics). This is attributed to lack of physical activity, excess weight and genetic factors. High intensity interval training (HIIT) is a time-efficient exercise regime that improves blood glucose control and may be a useful public health tool. The sirtuins and associated genes involved in producing the chemical, nicotinamide adenine dinucleotide (NAD), required for sirtuin function in the body, are emerging as key players in blood glucose control. This study investigated the interplay between the sirtuin/NAD system and individual variation in insulin sensitivity responses after HIIT. Recreationally active individuals (n=20), not training in a specific sport, 18-35 years, non-smokers, free of cardiovascular, metabolic or haematological disorders were recruited. Body mass, height and fat percentage were measured and oral glucose tolerance tests (OGTT) performed. Each HIIT session consisted of a warm up (3 min at a workload of 50 Watts) followed by 4-6 (building over the first 6 sessions) maximal 30 s sprints at a resistance equivalent to 7.5% of body mass with 3 min unloaded cycling between sets, followed by a cool down (3 min at 50 Watts). Participants performed HIIT three times/week for four weeks. A second OGTT was carried out at least two days after the final training session. Plasma glucose, insulin, lipid profiles and vitamin B3 were measured and insulin sensitivity calculated (Cederholm index). RNA extracted from whole blood collected at baselines (pre and post HIIT) and 60 min post OGTT in PAXgene® blood RNA tubes was assayed for sirtuin and NAD biosynthetic enzyme gene targets using an in-house custom designed assay, the hSIRTNADPlex. The hSIRTNADPlex incorporates 25 gene targets (all 7 mammalian sirtuin genes and 15 enzymes involved in conversion of tryptophan, bioavailable vitamin B3 and metabolic precursors to NAD). NAD/NADP was measured in whole blood. Significant reductions in body weight and body fat post-HIIT were associated with altered lipid profiles, NAD/NADP and regulation of components of the sirtuin/NAD system (NAMPT, CD38 and ABCA1). Improvements in measured metabolic health parameters were achieved in some, but not all, of the young adults tested. Notably, metabolic improvements in response to HIIT were achieved in individuals with poor health parameters measured pre-HIIT. Further investigation of the causes of the marked inter-individual variation in observed responses to HIIT will be critical in formulating optimal public health messages for HIIT and potentially other forms of exercise.
|Publication status||Published - 2016|