Andrews, James C.

Abstract Objective Pulsatile insulin secretion is impaired in diseases such as type 2 diabetes that are characterized by insulin resistance. This has led to the suggestion that changes in insulin pulsatility directly impair insulin signaling. We sought to examine the effects of pulse characteristics on insulin action in humans, hypothesizing that a decrease in pulse amplitude or frequency is associated with impaired hepatic insulin action. Methods We studied 29 nondiabetic subjects on two occasions. On 1 occasion, hepatic and peripheral insulin action was measured using a euglycemic clamp. The deuterated water method was used to estimate the contribution of gluconeogenesis to endogenous glucose production. On a separate study day, we utilized nonparametric stochastic deconvolution of frequently sampled peripheral C-peptide concentrations during fasting to reconstruct portal insulin secretion. In addition to measuring basal and pulsatile insulin secretion, we used approximate entropy to measure orderliness and Fourier transform to measure the average, and the dispersion of, insulin pulse frequencies. Results In univariate analysis, basal insulin secretion (R2 = 0.16) and insulin pulse amplitude (R2 = 0.09) correlated weakly with insulin-induced suppression of gluconeogenesis. However, after adjustment for age, sex, and weight, these associations were no longer significant. The other pulse characteristics also did not correlate with the ability of insulin to suppress endogenous glucose production (and gluconeogenesis) or to stimulate glucose disappearance. Conclusions Overall, our data demonstrate that insulin pulse characteristics, considered independently of other factors, do not correlate with measures of hepatic and peripheral insulin sensitivity in nondiabetic humans.

BACKGROUND Metabolic disorders such as type 2 diabetes have been associated with a decrease in insulin pulse frequency and amplitude. We hypothesized that the T allele at rs7903146 in TCF7L2, previously associated with β cell dysfunction, would be associated with changes in these insulin pulse characteristics. METHODS Twenty-nine nondiabetic subjects (age 46 ± 2, BMI 28 ± 1 kg/m 2 ) participated in this study. Of these, 16 were homozygous for the C allele at rs7903146 and 13 were homozygous for the T allele. Deconvolution of peripheral C-peptide concentrations allowed the reconstruction of portal insulin secretion over time. These data were used for subsequent analyses. Pulse orderliness was assessed by approximate entropy (ApEn), and the dispersion of insulin pulses was measured by a frequency dispersion index (FDI) after a Fast Fourier Transform (FFT) of individual insulin secretion rates. RESULTS During fasting conditions, the CC genotype group exhibited decreased pulse disorderliness compared with the TT genotype group (1.10 ± 0.03 vs. 1.19 ± 0.04, P = 0.03). FDI decreased in response to hyperglycemia in the CC genotype group, perhaps reflecting less entrainment of insulin secretion during fasting. CONCLUSION Diabetes-associated variation in TCF7L2 is associated with decreased orderliness and pulse dispersion, unchanged by hyperglycemia. Quantification of ApEn and FDI could represent novel markers of β cell health. FUNDING This work was funded by US NIH (DK78646, DK116231), University of Padova research grant CPDA145405, and Mayo Clinic General Clinical Research Center (UL1 TR000135).

The characteristics of pulsatile insulin secretion are important determinants of type 2 diabetes pathophysiology, but they are understudied due to the difficulties in measuring pulsatile insulin secretion noninvasively. Deconvolution of either peripheral C-peptide or insulin concentrations offers an appealing alternative to hepatic vein catheterization. However, to do so, there are a series of methodological challenges to overcome. C-peptide has a relatively long half-life and accumulates in the circulation. On the other hand, peripheral insulin concentrations reflect relatively fast clearance and hepatic extraction as it leaves the portal circulation to enter the systemic circulation. We propose a method based on nonparametric stochastic deconvolution of C-peptide concentrations, using individually determined C-peptide kinetics, to overcome these limitations. The use of C-peptide (instead of insulin) concentrations allows estimation of portal (and not post-hepatic) insulin pulses, whereas nonparametric stochastic deconvolution allows evaluation of pulsatile signals without any a priori assumptions of pulse shape and occurrence. The only assumption required is the degree of smoothness of the (unknown) secretion rate. We tested this method first on simulated data and then on 29 nondiabetic subjects studied during euglycemia and hyperglycemia and compared our estimates with the profiles obtained from hepatic vein insulin concentrations. This method produced satisfactory results both in the ability to fit the data and in providing reliable estimates of pulsatile secretion, in agreement with hepatic vein measurements. In conclusion, the proposed method enables reliable and noninvasive measurement of pulsatile insulin secretion. Future studies will be needed to validate this method in people with type 2 diabetes.

AbstractBackgroundIn patients with persistent (P‐PHPT) or recurrent (R‐PHPT) primary hyperparathyroidism, preoperative localization is important. Selective parathyroid hormone venous sampling (sPVS) is an invasive technique that can be used to regionalize and/or lateralize the source of PHPT when noninvasive imaging studies are nonlocalizing. The aim of the present study was to assess the role of sPVS in the preoperative evaluation of patients with P‐PHPT or R‐PHPT and negative, equivocal, or discordant noninvasive imaging localization.MethodsAfter IRB‐approval a retrospective review of all patients with P‐PHPT or R‐PHPT and nonlocalizing noninvasive imaging that underwent sPVS from 2000 to 2014 was performed. The location of the source of PHPT at sPVS was predicted by a parathyroid hormone (PTH) gradient and compared to the surgical, pathology, and biochemical follow‐up data as the gold standard. Sensitivity and positive predictive value (PPV) were calculated.ResultsOf 30 patients who underwent sPVS, 12 patients did not undergo surgical exploration due to negative or non‐localizing PTH gradient (n = 8) or opted for medical management (n = 4). Of the 18 patients who underwent surgical exploration, 17 (94 %) had a positive PTH gradient and pathologic parathyroid tissue identified at surgery. Sensitivity and PPV of sPVS were 93 and 77 %, respectively, for all surgical cases, 86 and 60.0 % for cervical cases (n = 11), and 100 and 100 % for mediastinal cases (n = 7). Sixteen patients (89 %) were surgically cured.ConclusionsIn patients with P‐PHPT or R‐PHPT and nonlocalizing imaging studies, sPVS is a sensitive test for localizing the source of PHPT when a positive PTH gradient is present.

Treatment options for refractory hepatic encephalopathy (HE) are limited. Patients who fail medical management may harbor large portosystemic shunts (PSSs) which are possible therapeutic targets. This study aims to describe patient selection, effectiveness, and safety of percutaneous PSS embolization in those with medically refractory HE. A retrospective evaluation of consecutive adult patients with medically refractory HE referred for PSS embolization at a tertiary center was performed (2003‐2015). Patient data collected included the type of HE, medications, Model for End‐Stage Liver Disease (MELD) score, shunt type, embolization approach, and materials used. Outcomes of interest were immediate (7 days), intermediate (1‐4 months), and longer‐term (6‐12 months) effectiveness and periprocedural safety. Effectiveness was determined based on changes in hospitalization frequency, HE medications, and symptoms. Twenty‐five patients with large PSS were evaluated for shunt embolization. Five were excluded due to high MELD scores (n = 1), comorbid conditions (n = 1), or technical considerations (n = 3). Of 20 patients who underwent embolization, 13 had persistent and 7 had recurrent HE; 100% (20/20) achieved immediate improvement. Durable benefit was achieved in 100% (18/18) and 92% (11/12) at 1‐4 and 6‐12 months, respectively. The majority (67%; 8/12) were free from HE‐related hospitalizations over 1 year; 10% developed procedural complications, and all resolved. Six developed new or worsening ascites. In conclusion, PSS embolization is a safe and effective treatment strategy that should be considered for select patients with medically refractory HE. Liver Transplantation 22 723–731 2016 AASLD.

Transarterial chemoembolization (TACE) is a common treatment for patients with hepatocellular carcinoma (HCC) who are awaiting liver transplantation (LT). The aim of this study was to assess the impact of multiple TACE treatments on tumor necrosis, tumor recurrence, and survival in these patients. A retrospective analysis was performed for 104 consecutive patients undergoing LT for HCC from January 2002 to December 2009 who were treated with TACE before LT. The number of TACE treatments was not associated with tumor necrosis in the explant. After a median follow‐up of 69 months (range = 0‐123 months), 14 of the 104 patients (13%) developed recurrent HCC after LT. Recurrence had a significant relationship with a short interval between the diagnosis of HCC and LT (≤6 months) in univariate and multivariate analyses [P = 0.029, odds ratio (OR) = 19.2]. Patients subjected to a single TACE treatment were more likely to experience recurrence, although this finding was not confirmed in the multivariate analysis. No significant relationship was observed between tumor necrosis in the explant and recurrence. The mean overall survival was 102.8 months (95% confidence interval = 94.9‐110.8 months) with 1‐, 3‐, and 5‐year survival rates of 91%, 89%, and 84% respectively. In the univariate survival analysis, the presence of ascites before TACE, a waiting time ≤ 9 months, and tumor characteristics at the pathological examination were statistically associated with shorter survival. In the multivariate analysis, only vascular invasion (P < 0.001, OR = 7.99) remained independently associated with shorter survival. The number of TACE treatments was not associated with survival. In conclusion, multiple TACE treatments were not associated with a higher risk of recurrence or shorter survival. Continued use of TACE should be considered as indicated if the patient and lesions are suitable for retreatment. A shorter waiting time before LT is related to an increased risk of recurrence and decreased survival after LT for HCC. These data could reflect the presence of more aggressive tumor biology and may be useful for guiding organ allocation policy to consider a minimum observation period before LT for regions with shorter wait times. Liver Transpl 21:248‐257, 2015. © 2014 AASLD.