Short-term Regulation of Visfatin Release in vivo by Oral Lipid Ingestion and in vitro by Fatty Acid Stimulation

Abstract

Visfatin represents a new adipokine secreted by visceral adipose tissue and possibly regulating insulin sensitivity. Data on the regulation of visfatin are sparse and contradictory. Our study investigates the regulation of serum visfatin concentrations in healthy and non-diabetic subjects in response to the ingestion of a newly developed oral lipid solution (OLI) in vivo. Furthermore, the effects of a broad spectrum of fatty acids on adipocytic visfatin release were investigated in vitro.100 (42 male and 58 female) healthy volunteers were included in the study. Anthropometric and laboratory parameters (lipoproteins, glucose, insulin, C-peptide) were measured after an overnight fast at 0 h and 2 h, 4 h, and 6 h after OLI. 3T3-L1 preadipocytes were differentiated into mature adipocytes and stimulated with increasing doses of 10 different fatty acids, and the release of visfatin into the supernatants was measured by ELISA.Serum triglycerides significantly rose after OLI. This was accompanied by a significant decrease of glucose, insulin and C-peptide. Serum visfatin levels significantly decreased after OLI. Fasting visfatin levels were negatively correlated with fasting glucose levels. Of the 5 saturated fatty acids tested, only palmitic acid exerted significant effects by strongly downregulating visfatin release by about 66%. The mono-unsaturated fatty acids palmitoleic acid and oleic acid exerted opposite effects decreasing/increasing visfatin release, respectively. Both of the poly-unsaturated fatty acids linoleic acid and arachidonic acid decreased visfatin release.Oral lipid ingestion is a physiological regulator of systemic visfatin release. Fatty acids differentially regulate visfatin release in vitro.

Serum Progranulin Concentrations are not Responsive During Oral Lipid Tolerance Test and Oral Glucose Tolerance Test

“…As previously published [13,14], the study cohort A (OLTT, oral lipid tolerance test) and cohort B (OGTT, oral glucose tolerance test) were examined at the University Hospital of Regensburg, Germany. The study was approved by the local ethical committee and all participants gave their informed consent.…”

“…The study was approved by the local ethical committee and all participants gave their informed consent. Both cohorts consisted of 100 healthy volunteers and have been characterized recently by our group with respect to the regulation of the adipokine visfatin [13,14]. Cohort A [13] consisted of 58 females and 42 males.…”

“…Cohort A [13] consisted of 58 females and 42 males. Study cohort B [14] consisted of 64 females and 36 males. Exclusion criteria were a positive history of any kind of acute or chronic illness, evidence of acute or chronic infection within 10 days prior to the OLTT or OGTT, age < 18 years or > 55 years, and any kind of medication except oral contraceptives.…”

“…Patients history concerning type 2 diabetes and cardiovascular diseases as well as habits such as smoking and hormonal contraception were documented. • ▶ Table 1 summarizes the characteristics of both study populations as published earlier in detail [13,14].…”

“…As published recently by our group [14], we used a novel solution that was completely free of proteins and carbohydrates but contains all fatty acid species (saturated, mono-unsaturated and The pilot studies with these 2 study populations were published earlier and focused on serum visfatin concentrations [13,14]. For illustration of the present data on progranulin, baseline, and anthropometric parameters of the cohorts are given as published earlier in detail [13,14] …”