Oral Presentation Australian & New Zealand Obesity Society 2015 Annual Scientific Meeting

Dietary acid load, metabolic acidosis and insulin resistance - lessons from cross-sectional and overfeeding studies in humans (#27)

Rebecca S Williams 1 2 , Daniel L Chen 1 , Leonie K Heilbronn 3 , Jerry R Greenfield 1 4 5 , Dorit Samocha-Bonet 1 5
  1. Diabetes & Metabolism Division, The Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  2. The University of Sydney, Sydney, NSW, Australia
  3. Discipline of Medicine, University of Adelaide, Adelaide, SA, Australia
  4. Department of Endocrinology and Diabetes Centre, St Vincent's Hospital, Sydney, NSW, Australia
  5. Faculty of Medicine, The University of New South Wales, Sydney, NSW, Australia

Western diets rich in animal protein and poor in fruit and vegetables increase the body acid load, a predictor of type 2 diabetes risk. The relationships between dietary acid load, body acid/base balance and insulin resistance remain unclear. The objective of this study was to evaluate the association between dietary acid load, body acid/base balance and insulin resistance at baseline and following a short-term overfeeding in healthy individuals. Insulin sensitivity was measured by euglycaemic-hyperinsulinaemic clamp in healthy individuals (n=104, 49 men). Plasma lactate, an indicator of metabolic acidosis, was measured and acid load scores (potential renal acid load [PRAL] and net endogenous acid production [NEAP]) were derived from diet diaries. The cohort was grouped into lean and overweight/obese and the latter was further classified as insulin-sensitive (Obsen) and insulin-resistant (Obres) based on glucose infusion rate (GIR, top tertile vs. bottom 2 tertiles) during the clamp. A subset of 40 individuals underwent a 28-day overfeeding intervention (+1250 kcal/day) and studies were repeated. Obsen and Obres were matched for adiposity (BMI and fat mass, both P=1). Fasting plasma lactate was higher in Obres (0.78 [0.63-1.14] mmol/L) compared with both lean (0.71 [0.44-0.90] mmol/L, P=0.02) and Obsen (0.67 [0.56-0.79] mmol/L, P=0.04), and not different between lean and Obsen (P=0.9). Overfeeding was characterised by an increase in dietary acid load scores PRAL (P=0.003) and NEAP (P=0.05), a reduction in GIR (P=0.03) and an increase in fasting plasma lactate (P=0.02). The change in lactate was inversely associated with the change in GIR (r=-0.36, P=0.03). In conclusion, mild metabolic acidosis, measured by plasma lactate, aligns with insulin resistance independent of obesity and is induced by short-term increases in energy and dietary acid load in healthy humans. Further studies are required to determine whether buffering mild metabolic acidosis improves insulin resistance and reduces diabetes risk.