Fasting hyperglycemia contributes disproportionately to nonenzymatic glycosylation and the microvascular complications of type 2 diabetes. However, little is known about the regulation of glucose concentrations in the fasting state relative to what is known about the postprandial state. The proposed experiment is part of a series of experiments designed to establish how glucagon and insulin interact with their receptors to control fasting glucose in health and in prediabetes.

The interaction between α-cell and β-cell function to regulate fasting glucose is incompletely understood. This is an important gap in our knowledge as fasting glucose contributes disproportionately to HbA1c and the microvascular complications of type 2 diabetes (T2DM). The regulation of fasting glucose in health and disease is relatively understudied.

Insulin and glucagon should regulate glucose reciprocally through direct interaction; insulin restrains α-cell secretion while glucagon directly stimulates β-cell secretion. In addition, there are indirect interactions via changes in glucose. Glucagon increases endogenous glucose production (EGP) increasing glucose (and insulin secretion). Conversely, insulin stimulates glucose disappearance (Rd) and suppresses EGP, lowering glucose (and stimulating glucagon).

However, this does not appear to occur uniformly in prediabetes. For example, in impaired fasting glucose (IFG), glucagon secretion rate (GSR) is inappropriate for the prevailing glucose. This is not accompanied by reciprocal changes in insulin secretion rate (ISR). Variability in the hepatic response to glucagon and to insulin further compound the dysregulation of fasting glucose. The net effect of these variables is unknown. This experiment is intended to test the hypothesis that impaired glucagon-induced insulin secretion contributes to fasting hyperglycemia in IFG.

Inclusion Criteria:

• Individuals with normal or impaired fasting glucose and normal or impaired glucose tolerance

Exclusion Criteria:

• HbA1c less than 6.5%
• Use of any glucose-lowering agents including metformin or sulfonylureas.
• For female subjects: positive pregnancy test at the time of enrollment or study
• History of prior upper abdominal surgery such as adjustable gastric banding, pyloroplasty and vagotomy.
• Active systemic illness or malignancy.
• Symptomatic macrovascular or microvascular disease.

In addition to the patient-level data, the metadata, data dictionary, statistical analysis plan, and final protocol will be shared. The sharing of the data dictionary, statistical analysis plan and final protocol with amendments will enable researchers to understand how the data was collected and to correctly interpret the data for future secondary analysis. We plan to share datasets resulting from the proposed studies in Vivli, a non-profit institution that supports the Vivli repository.

The data shared will be archived and available on the platform for request by researchers for a minimum of 10 years after contribution. Data will be made accessible no later than the time of our associated publication or the end of the grant period (whichever comes first). On an ongoing basis, Vivli evaluates its data holdings regarding maintaining access and reserves the right to discontinue the distribution of a data collections when deemed appropriate. When materials are deaccessioned, the data are no longer publicly accessible at Vivli, they may still be preserved in Vivli's storage vault. Because digital files are assigned a persistent digital object identifier (DOI), the study description is still available to view, but is not searchable through Vivli.

The data being shared is human data from clinical trials and therefore a higher level of protection is required. Access to this data will be controlled by a managed access process whereby access is provided only after approval. Data will be controlled access with the General Research Use Data Use Limitation, as allowed by the informed consent and the institutional certification.