Precision xtra blood

Nutritional ketosis was determined via circulating glucose (mg/dL) and ketone body (β-hydroxybutyrate; BHB; mmol/L)) concentration using the Precision Xtra blood monitoring system (Abbott Diabetes Care, Inc, Alameda, CA, USA). These values were utilized to calculate a glucose ketone index (GKI), in which lower values indicate a higher level of nutritional ketosis, using the formula: $\frac{\raisebox{1ex}{$glucose \left(\frac{\mathrm{mg}}{\mathrm{dL}}\right)$}\!\left/ \!\raisebox{-1ex}{$18.016$}\right.}{BHB \left(\frac{\mathrm{mmol}}{L}\right)}$ .

β-hydroxybutyrate (BHB; mmol; L), the prominent ketone body in the blood, and glucose levels (mg; dL) were determined using the Precision Xtra blood monitoring system (Abbott Diabetes Care, Inc., Alameda, CA, United States). Rats were briefly restrained and received a small nick to the tail using a sterile scalpel blade to obtain blood for monitoring glucose and ketone body levels. Measurements were taken 1 h after eating each week for the first 3 weeks of dietary intervention. Following confirmation of nutritional ketosis throughout the first 3 weeks, weekly blood draws were stopped to prevent undue stress to the animals. However, intermittent testing continued between weeks 4–29 to ensure sustained ketosis.

Ketone and glucose levels were assessed in urine or blood as indicated in the figure legend using a Precision Xtra blood glucose and ketone monitoring system (Abbott Diabetes Care Inc., Alameda, CA, USA). For urine samples, mice were gently restrained at the neck and urine collected. For blood samples, mice were anesthetized with isoflurane and blood collected from the inferior vena cava and assayed for ketone and glucose levels with a Precision Xtra meter. Low off-scale glucose meter readings were adjusted to 20 mg/dL. High off-scale glucose meter readings were adjusted to 500 mg/dL. High off-scale ketone meter readings were adjusted to 8.0 mmol/L. Blood samples were collected during the light phase after 4 h fasting.