Fasted C-Peptide Distribution and Associated Clinical Factors in Adults With Longstanding Type 1 Diabetes: Analysis of the Canadian Study of Longevity in Type 1 Diabetes

OBJECTIVE

Although insulin production is reportedly retained in many people with longstanding type 1 diabetes (T1D), the magnitude and relevance of connecting peptide (C-peptide) production are uncertain. In this study, we aimed to define fasted C-peptide distributions and associated clinical factors.

METHODS

In a cross-sectional analysis of the Canadian Study of Longevity, fasted serum and urinary C-peptide was measured in 74 patients with longstanding T1D (duration ≥50 years) and 75 age- and sex-matched controls. Extensive phenotyping for complications was performed and patient-reported variables were included. C-peptide distributions were analyzed, and multivariable logistic regression was used to assess the variable association in participants with T1D.

RESULTS

The 74 participants with T1D had a mean age of 66±8 years, a disease duration of 54 (interquartile range 52 to 58) years, and a glycated hemoglobin (A1C) of 7.4%±0.8% (56.8±9.15 mmol/mol). The 75 controls had a mean age of 65±8 years and an A1C of 5.7%±0.4% (38.4±4.05 mmol/mol). Participants with T1D had lower fasted serum C-peptide than controls (0.013±0.022 vs 1.595±1.099 nmol/L, p<0.001). Of the participants with T1D, C-peptide was detectable in 30 of 73 (41%) serum samples, 32 of 74 (43%) urine samples, and 48 of 74 (65%) for either serum or urine. The variables independently associated with detectable serum or urinary C-peptide were lower total daily insulin requirement (odds ratio 2.351 [for 1 lower unit/kg], p=0.013) and lower hypoglycemia worry score (odds ratio 1.059 [for 1 point lower on the worry subscore of the Hypoglycemia Fear Survey], p=0.030).

CONCLUSIONS

Although detectable C-peptide in longstanding diabetes was common, the magnitude of concentration was extremely low when compared with age- and sex-matched controls. Despite minimal detectability, its presence is validated by lower insulin requirements and strongly associated with lower hypoglycemia worry.

Association of Glucagon With Obesity, Glycemic Control and Renal Function in Adults With Type 2 Diabetes Mellitus

OBJECTIVES

In this study, we used a double-antibody sandwich enzyme-linked immunosorbent assay to assess the association between blood glucagon levels and indices of obesity, glycemic control and renal function in patients with type 2 diabetes mellitus (T2DM).

METHODS

This investigation was a cross-sectional study on inpatients with T2DM who had plasma glucagon levels measured during hospitalization. Associations of fasting glucagon levels (G₀), 120-minute postbreakfast plasma glucagon (G₁₂₀), fasting glucagon/C-peptide ratio (G₀/CPR₀) and postbreakfast glucagon/C-peptide ratio (G₁₂₀/CPR₁₂₀) with clinical data were evaluated using multiple regression analysis.

RESULTS

A total of 345 patients were enrolled in the study. G₀, and G₁₂₀ were significantly and positively associated with serum C-peptide levels. Moreover, G₀ and G₁₂₀ were positively associated with waist circumference, and G₀ was negatively associated with duration of diabetes mellitus. Interestingly, both G₀ and G₁₂₀ were negatively associated with the estimated glomerular filtration rate. In addition, G₁₂₀/CPR₁₂₀ was positively associated with duration of diabetes mellitus and glycoalbumin levels.

CONCLUSIONS

The balance between glucagon and insulin secretion is significantly associated with abdominal obesity and important for maintaining glucose homeostasis. Postprandial hyperglucagonemia could also be related to deterioration of renal function.

Effect of dairy and nondairy snacks on postprandial blood glucose regulation in 9-14-year-old children

In adults, dairy consumption improves short-term blood glucose regulation. It is unknown if these short-term benefits extend to children of different weight statuses. The objective of this study was to investigate the effect of a dairy and nondairy snack in both normal-weight (NW) and overweight/obese (OW/OB) children on blood glucose regulation and food intake (FI). In a repeated-measures crossover design, 11 NW and 7 OW/OB children (age: 9-14 years), consumed, in random order, a dairy (Greek yogurt, 198.9 g, 171 kcal, 0 g fat, 17 g protein) or nondairy (mini sandwich-type cookies, 37.5 g, 175 kcal, 7.5 g fat, 1.3 g protein) snack containing 25 g of available carbohydrates. Ad libitum FI was measured 120 min after snack consumption. Blood glucose, insulin, C-peptide, and glucagon-like peptide-1 (GLP-1) were measured at 0 min (before the snack), and at 30, 60, 90, and 120 min after snack consumption. Insulin secretion was calculated from deconvolution of C-peptide. Hepatic insulin extraction was calculated as C-peptide divided by insulin. FI did not differ between snacks (P = 0.55). Mean blood glucose was lower (P < 0.001) and insulin higher (P < 0.0001) in the 120 min after consuming the dairy snack. C-Peptide concentrations (P = 0.75) and insulin secretion (P = 0.37) were not different between snacks. The increase in insulin was explained by reduced hepatic insulin extraction (P < 0.01). Consumption of the dairy snack also increased mean GLP-1 concentrations (P < 0.001). In conclusion, consumption of a dairy snack by NW and OW/OB children results in reduced postprandial blood glucose concentrations and elevated circulating insulin compared with a nondairy snack possibly because of delayed hepatic insulin extraction.