Methylprednisolone therapy in deceased donors reduces inflammation in the donor liver and improves outcome after liver transplantation: a prospective randomized controlled trial.

OBJECTIVE: To investigate potential beneficial effects of donor treatment with methylprednisolone on organ function and outcome after liver transplantation. SUMMARY BACKGROUND DATA: It is proven experimentally and clinically that the brain death of the donor leads to increased levels of inflammatory cytokines and is followed by an intensified ischemia/reperfusion injury after organ transplantation. In experiments, donor treatment with steroids successfully diminished these effects and led to better organ function after transplantation. METHODS: To investigate whether methylprednisolone treatment of the deceased donor is applicable to attenuate brain death-associated damage in clinical liver transplantation we conducted a prospective randomized treatment-versus-control study in 100 deceased donors. Donor treatment (n = 50) consisted of 250 mg methylprednisolone at the time of consent for organ donation and a subsequent infusion of 100 mg/h until recovery of organs. A liver biopsy was taken immediately after laparotomy and blood samples were obtained after brain death diagnosis and before organ recovery. Cytokines were assessed by real-time reverse transcriptase-polymerase chain reaction. Soluble serum cytokines were measured by cytometric bead array system. RESULTS: After methylprednisolone treatment, steroid plasma levels were significantly higher (P < 0.05), and a significant decrease in soluble interleukins, monocyte chemotactic protein-1, interleukin-2, interleukin-6, tumor necrosis factor-alpha, and inducible protein-10 was observed. Methylprednisolone treatment resulted in a significant downregulation of intercellular adhesion molecule-1, tumor necrosis factor-alpha, major histocompatibility complex class II, Fas-ligand, inducible protein-10, and CD68 intragraft mRNA expression. Significantly ameliorated ischemia/reperfusion injury in the posttransplant course was accompanied by a decreased incidence of acute rejection. CONCLUSIONS: Our present study verifies the protective effect of methylprednisolone treatment in deceased donor liver transplantation, suggesting it as a potential therapeutical approach.

Brain death activates donor organs and is associated with a worse I/R injury after liver transplantation.

The majority of transplants are derived from donors who suffered from brain injury. There is evidence that brain death causes inflammatory changes in the donor. To define the impact of brain death, we evaluated the gene expression of cytokines in human brain dead and ideal living donors and compared these data to organ function following transplantation. Hepatic tissues from brain dead (n = 32) and living donors (n = 26) were collected at the time of donor laparotomy. Additional biopsies were performed before organ preservation, at the time of transplantation and one hour after reperfusion. Cytokines were assessed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and cytometric bead array. Additionally, immunohistological analysis of tissue specimens was performed. Inflammatory cytokines including IL-6, IL-10, TNF-alpha, TGF-beta and MIP-1alpha were significantly higher in brain dead donors immediately after laparotomy compared to living donors. Cellular infiltrates significantly increased in parallel to the soluble cytokines IL-6 and IL-10. Enhanced immune activation in brain dead donors was reflected by a deteriorated I/R injury proven by elevated alanin-amino-transferase (ALT), aspartat-amino-transferase (AST) and bilirubin levels, increased rates of acute rejection and primary nonfunction. Based on our clinical data, we demonstrate that brain death and the events that precede it are associated with a significant upregulation of inflammatory cytokines and lead to a worse ischemia/reperfusion injury after transplantation.

Pathogenesis and treatment of diabetic vascular disease - illustrated by two cases.

This publication is a summary of the presentations given at the First JIM Grand Round held at the Sahlgrenska University Hospital on 15 March 2006. The Grand Round was based on two case reports; a patient with type 2 diabetes and pronounced macrovascular disease and another patient with early microvascular disease combined with the macrovascular complications. The pathogenesis of the vascular complications and the current treatment regimens were discussed in relation to the history and examinations performed in these patients.

Routine screening of donor hearts by coronary angiography is feasible.

BACKGROUND: Because of the shortage of donor hearts, the criteria for acceptance have been considerably extended. Meanwhile every fourth heart donor in Europe is over 50 years old. As we have previously demonstrated, transmission of preexisting coronary atherosclerosis (CAS) by means of transplantation is not rare. Transmitted CAS results in a 2- to 3-fold increased risk for early graft failure after heart transplantation (HTX). Nevertheless, in most cases donor angiograms are not considered feasible. METHODS: In May 2003 in the northeast region of the Deutsche Stiftung Organtransplantation (DSO-NO), we introduced the guideline that every donor over 40 years old must be screened by angiography. RESULTS: Up to May 2003, fewer than 5% of donors had been screened by angiography; this situation is the rule in most Eurotransplant regions at present. Since May 2003 in the DSO-NO region, 85% of all donors over 40 years old were screened by angiography. Seventy percent of all donor hospitals--offering 90% of all donors--had an angiography facility. The additional costs of approximately euro 800 per donor angiogram were compensated by fewer fruitless airplane missions when CAS was diagnosed by the surgeon on the spot, which cost on average about euro 5,000 each. In conclusion, from a logistical as well as from a financial point of view, almost comprehensive angiographic donor screening is feasible. It reduces the risk of a recipient suffering from early graft failure.

Does contrast medium administration in organ donors affect early kidney graft function?

Since the upper age for organ donors has been raised, a higher incidence of preexistent organ damage and functional impairment is to be expected. Coronary artery sclerosis increases with age. It can only be diagnosed with certainty by coronary angiography. Since contrast medium administration may cause renal damage when risk factors are present, this study sought to establish whether angiography negatively influenced the early postoperative function of kidney grafts. We compared the clinical courses of 36 recipients of kidneys from donors in whom coronary angiography or levography had been performed with 36 recipients of kidneys from donors who had not been subjected to contrast medium. The results showed that the administration of contrast medium had no influence on renal function at 3 or 6 months after transplantation. In conclusion, fears that donor kidneys might be harmed by contrast medium appeared to therefore be unfounded.

Significant reduction of proinflammatory cytokines by treatment of the brain-dead donor.

INTRODUCTION: Experimental studies suggest that brain death in the donor has a significant impact on graft quality; however, there are no data correlating organ-specific cytokine expression and the corresponding serum protein levels in human organ donors. Furthermore, it is unknown whether donor treatment can reduce the up-regulation of proinflammatory cytokines and thereby optimize organ quality. METHODS: We investigated the expression pattern of cytokines comparing serum (n = 53) and tissue expression (n = 25) in brain-dead human donors. The controls were living donors (n = 25). Additionally 41 deceased donors were treated with steroids before organ harvest (250 mg initial, afterward 100 mg/h until laparotomy). Hepatic tissue samples were obtained immediately after donor laparotomy to assess transcription rates of tissue cytokines (IL-6, IL-10, CD3, TGFb, TNFa, BAG, HO-1, Mipla) by RT-PCR. Serum samples were obtained after declaration of brain death and before laparotomy. RESULTS: Transcription of proinflammatory cytokines was significantly increased in brain-dead compared to living donor grafts (P < .005). Donor treatment with steroids led to significantly decreased tissue and serum expression of proinflammatory cytokines (P < .01), which were comparable to living donors. Tissue levels of cytokines (IL-6, IL-10) correlated strongly with serum levels of the corresponding proteins. CONCLUSIONS: Serum protein levels of proinflammatory cytokines proffer a valuable, easy accessible marker to define the immunological status of a graft. Our data suggest a beneficial effect of anti-inflammatory treatment of brain-dead organ donors.

Reduced expression of PGC-1 and insulin-signaling molecules in adipose tissue is associated with insulin resistance.

Peroxisome proliferator-activated receptor gamma (PPAR gamma) co-activator 1 (PGC-1) regulates glucose metabolism and energy expenditure and, thus, potentially insulin sensitivity. We examined the expression of PGC-1, PPAR gamma, insulin receptor substrate-1 (IRS-1), glucose transporter isoform-4 (GLUT-4), and mitochondrial uncoupling protein-1 (UCP-1) in adipose tissue and skeletal muscle from non-obese, non-diabetic insulin-resistant, and insulin-sensitive individuals. PGC-1, both mRNA and protein, was expressed in human adipose tissue and the expression was significantly reduced in insulin-resistant subjects. The expression of PGC-1 correlated with the mRNA levels of IRS-1, GLUT-4, and UCP-1 in adipose tissue. Furthermore, the adipose tissue expression of PGC-1 and IRS-1 correlated with insulin action in vivo. In contrast, no differential expression of PGC-1, GLUT-4, or IRS-1 was found in the skeletal muscle of insulin-resistant vs insulin-sensitive subjects. The findings suggest that PGC-1 may be involved in the differential gene expression and regulation between adipose tissue and skeletal muscle. The combined reduction of PGC-1 and insulin signaling molecules in adipose tissue implicates adipose tissue dysfunction which, in turn, can impair the systemic insulin response in the insulin-resistant subjects.

Tactile directional sensibility and diabetic neuropathy.

Five different procedures used to diagnose neuropathy were compared in a "blind" study with diabetic patients. The aim was to evaluate tests of tactile directional sensibility. Three matched groups were examined, two groups with type I diabetes, either with or without suspected neuropathy, and one of healthy controls. Testing consisted of: (1) examination by a specialist in neurology, (2) electrophysiologic measurement of nerve conduction velocity and determination of cool sensitivity, and (3) determination of directional sensibility in two stages, with categorical and quantitative techniques. Abnormal test results were obtained for both groups of diabetic patients. Quantitatively measured directional sensibility had the highest sensitivity (89%) and specificity (85%) when calculated for patients who had received a diagnosis of neuropathy from the neurologist, despite one case of abnormal directional sensibility among the healthy controls. Conduction velocity testing was almost comparably sensitive (80%) and cool sensitivity, comparably specific (85%) when calculated in the same manner.

Impaired phosphorylation and insulin-stimulated translocation to the plasma membrane of protein kinase B/Akt in adipocytes from Type II diabetic subjects.

AIMS/HYPOTHESIS: To examine protein kinase B/Akt distribution and phosphorylation in response to insulin in different subcellular fractions of human fat cells from healthy subjects and subjects with Type II (non-insulin-dependent) diabetes mellitus. METHODS: We prepared subcellular fractions of plasma membranes (PM), low density microsomes and cytosol and examined gene and protein expression as well as serine and threonine phosphorylation in response to insulin. RESULTS: Protein kinase B/Akt mRNA as well as total protein kinase B/Akt protein in whole-cell lysate and cytosol were similar in both groups. Insulin increased protein kinase B/Akt translocation to the the plasma membrane about twofold [(p < 0.03) in non-diabetic cells but this effect was impaired in diabetic cells (approximately 30%; p > 0.1)]. In both groups, protein kinase B/Akt threonine phosphorylation considerably increased in low density microsomes and cytosol whereas serine phosphorylation was predominant in the plasma membrane. Phosphatidylinositol-dependent kinase 1, which partially activates and phosphorylates protein kinase B/Akt on the specific threonine site, was predominant in cytosol but it was also recovered in low density microsomes. Serine phosphorylation in response to insulin was considerably reduced (50-70 %; p < 0.05) in diabetic cells but threonine phosphorylation was less reduced (approximately 20%). Wortmannin inhibited these effects of insulin supporting a role for PI3-kinase activation. CONCLUSION/INTERPRETATION: Insulin stimulates a differential subcellular pattern of phosphorylation of protein kinase B/Akt. Furthermore, insulin-stimulated translocation of protein kinase B/Akt to the plasma membrane, where serine phosphorylation and full activation occurs, is impaired in Type II diabetes. Threonine phosphorylation was much less reduced. This discrepancy may be related to differential activation of phosphatidylinositol 3-kinase in the different subcellular compartments and phosphatidylinositol-dependent kinase 1 having high affinity for phosphatidylinositol phosphate 3.

Impaired glucose transport and protein kinase B activation by insulin, but not okadaic acid, in adipocytes from subjects with Type II diabetes mellitus.

AIMS/HYPOTHESIS: To study the effects of insulin and okadaic acid, a serine/threonine phosphatase inhibitor which does not increase PI3-kinase activity, on the rate of glucose transport and protein kinase B activation in adipocytes from healthy subjects and subjects with Type II (non-insulin-dependent) diabetes mellitus. METHODS: Adipocytes were incubated with or without insulin or okadaic acid or both and glucose transport, protein kinase B activity, phosphorylation and protein expression measured. RESULTS: Insulin and okadaic acid alone increased glucose uptake to a similar degree in adipocytes from healthy subjects and, when combined, exerted a partial additive effect. The effect of insulin was reduced by about 60% in adipocytes from Type II diabetic patients, whereas the effect of okadaic acid was essentially unchanged and no further increase was seen when okadaic acid and insulin were combined. Okadaic acid increased protein kinase B activity to a greater extent (two to threefold) than insulin but only slightly increased the serine phosphorylation of protein kinase B. Adipocytes from Type II diabetic subjects exhibited both an impaired sensitivity as well as a reduced total serine phosphorylation and activation of protein kinase B in response to insulin but protein kinase B activity in response to okadaic acid was intact. CONCLUSION/INTERPRETATION: These results show that the ability of insulin to increase glucose transport and activate protein kinase B is reduced in fat cells from Type II diabetic subjects. Protein kinase B can, however, be activated by agents like okadaic acid which bypass the upstream defects in the insulin signalling pathway in Type II diabetic cells and, thus, increase glucose uptake.

Bedtime uncooked cornstarch supplement prevents nocturnal hypoglycaemia in intensively treated type 1 diabetes subjects.

OBJECTIVES: The present study tests two interrelated hypotheses: (1) that bedtime ingestion of uncooked cornstarch exerts a lower and delayed nocturnal blood glucose peak compared with a conventional snack; (2) that bedtime carbohydrate supplement, administered as uncooked cornstarch, prevents nocturnal hypoglycaemia without altering metabolic control in intensively treated type 1 diabetes (IDDM) patients. DESIGN AND SUBJECTS: The above hypotheses were tested separately (1) by pooling and analysing data from two overnight studies of comparable groups of patients with non-insulin dependent diabetes mellitus (NIDDM) (14 and 10 patients, respectively), and (2) by a double-blind, randomized 4-week cross-over study in 12 intensively treated IDDM patients. SETTING: Sahlgrenska University Hospital, Göteborg. Sweden. INTERVENTIONS: (1) Ingestion of uncooked cornstarch and wholemeal bread (0.6 g of carbohydrates kg-1 body weight) and carbohydrate-free placebo at 22.00 h. (2) Intake of uncooked cornstarch (0.3 g kg-1 body weight) and carbohydrate-free placebo at 23.00 h. MAIN OUTCOME MEASURES: (1) Nocturnal glucose and insulin levels; (2) frequency of self-estimated hypoglycaemia (blood glucose [BG] levels < 3.0 mmol L-1) at 03.00 h, HbA1c and fasting lipids. RESULTS: Bedtime uncooked cornstarch ingestion led to a lower (2.9 +/- 0.5 vs. 5.2 +/- 0.6 mM, P = 0.01) and delayed (4.3 +/- 0.6 vs. 2.0 +/- 0.0 h, P < 0.01) BG peak, compared with a conventional snack, in NIDDM patients. Four weeks of bedtime uncooked cornstarch supplement, as compared with placebo, led to a 70% reduction in the frequency of self-estimated hypoglycaemia at 03.00 h (P < 0.05), without affecting HbA1c or fasting lipids in IDDM patients. CONCLUSIONS: Uncooked cornstarch, ingested at bedtime, mimicked the nocturnal glucose utilization profile following insulin replacement, with a peak in blood glucose after 4 h. In IDDM patients, bedtime uncooked cornstarch supplement diminished the number of self-estimated hypoglycaemic episodes, without adversely affecting HbA1c and lipid levels. Hence, bedtime uncooked cornstarch ingestion may be feasible to prevent a mid-nocturnal glycaemic decline following insulin replacement in IDDM and, based on the nocturnal blood glucose profile, may also be preferable compared with conventional snacks.

Insulin signaling and action in fat cells: associations with insulin resistance and type 2 diabetes.

Adipose tissue only accounts for a relatively small proportion (< 10%) of the peripheral glucose utilization in response to insulin. However, the fat cells may still play an important role in insulin resistance and Syndrome X through, for instance, its endocrine functions (production of leptin, TNF alpha, PAI-1, etc.) and involvement in lipid metabolism (FFA release and hydrolysis of triglycerides). The fat cells are also highly sensitive to insulin and may thus be used to elucidate molecular mechanisms for insulin resistance in man. Examinations of the intracellular signaling mechanisms for insulin in fat cells from individuals with Type 2 diabetes revealed markedly lower insulin-stimulated PI3-kinase activity. This was due to a pronounced reduction in the cellular expression of the docking protein, IRS 1, whereas expression of IRS 2 was normal. However, IRS 2-associated PI3-kinase activity was only approximately one-third of that found to be associated with IRS 1 in normal cells. Downstream activation and serine phosphorylation of PKB/Akt by insulin were also markedly reduced in Type 2 diabetes. Furthermore, the dose-response curve for this effect of insulin was similar to that for glucose transport in both normal and Type 2 diabetic cells. Thus, these data show that both PI3-kinase and PKB activation by insulin are markedly reduced in Type 2 diabetes. We also examined whether an attenuated activation of PI3-kinase by insulin can be seen in non-diabetic insulin-resistant states. Approximately 30% of healthy subjects with at least two first-degree relatives with Type 2 diabetes exhibited perturbations in IRS-1 expression and signaling. These individuals were characterized by insulin resistance as well as other markers of Syndrome X. Thus, impaired IRS-1 expression and downstream signaling events in fat cells in response to insulin are associated with insulin resistance and Syndrome X.

Insulin receptor substrate (IRS) 1 is reduced and IRS-2 is the main docking protein for phosphatidylinositol 3-kinase in adipocytes from subjects with non-insulin-dependent diabetes mellitus.

The large docking protein IRS-1 is a major substrate for the insulin receptor and other tyrosine kinases. It plays a key role in eliciting many of insulin's actions, including binding and activation of phosphatidylinositol (PI) 3-kinase and the subsequent increase in glucose transport. Gene disruption of IRS-1 in mice is associated with an impaired insulin-stimulated glucose disposal in vivo and glucose transport in vitro, but the survival of the animals and residual insulin sensitivity is dependent on the presence of the alternative docking protein IRS-2. We examined the expression and function of IRS-1 and IRS-2 in adipocytes from healthy and diabetic individuals. Cells from subjects with non-insulin-dependent diabetes mellitus (NIDDM), but not with insulin-dependent diabetes mellitus, had an impaired insulin effect and a marked reduction (70 +/- 6%) in the expression of IRS-1 protein, whereas IRS-2 was unchanged. In normal cells, IRS-1 was the main docking protein for the binding and activation of insulin-stimulated PI 3-kinase; IRS-2 was also functional but required a higher insulin concentration for a similar binding and activation of PI 3-kinase. In contrast in NIDDM cells with a low IRS-1 content, IRS-2 became the main docking protein. These findings may provide important reasons for the insulin resistance in NIDDM.

Insulin promotes and cyclic adenosine 3',5'-monophosphate impairs functional insertion of insulin receptors in the plasma membrane of rat adipocytes: evidence for opposing effects of tyrosine and serine/threonine phosphorylation.

The aim of the present study was to elucidate events in the plasma membrane (PM) associated with the previously described effect of insulin to rapidly enhance the number of cell surface insulin binding sites in rat adipocytes. [125I]insulin was cross-linked to cell surface insulin receptors of intact cells that had been preincubated with or without insulin. Subsequently prepared PM displayed a approximately 3-fold increase in bound [125I]insulin when cells had been pretreated with 6 nM insulin for 20 min compared to membranes from control cells, and SDS-PAGE with autoradiography showed that this occurred at the insulin receptor alpha-subunit. The magnitude of the effect was similar to that found for insulin binding to intact cells that had been preincubated with insulin. In contrast, the insulin binding capacity in the PM was not affected by prior treatment of cells with insulin when assessed with the addition of [125I]insulin directly to solubilized PM; this suggests an unchanged total number of PM receptors. Thus, the enhancement of cell surface insulin binding capacity produced by insulin is not due to the translocation of receptors, but instead appears to be confined to receptors already present in the PM. The addition of phospholipase C (from Clostridium perfringens), which cleaves PM phospholipids, mimicked the effect of insulin to enhance cell surface binding in adipocytes, and this suggests a pool of cryptic PM receptors. Both the nonmetabolizable cAMP analog N6-monobutyryl cAMP (N6-mbcAMP) and the serine/threonine phosphatase inhibitor okadaic acid abolished the effect of concomitant insulin treatment to increase binding capacity. In contrast, the tyrosine phosphatase inhibitor vanadate increased insulin binding even in the presence of okadaic acid or N6-mbcAMP. The effect of N6-mbcAMP to impair cell surface insulin binding was also evident in the presence of a peptide derived from the major histocompatibility complex type I that effectively impairs receptor internalization, but the amount of PM receptors assessed by immunoblot was unaltered. Taken together, the data suggest that insulin exposure leads to the uncovering of cryptic receptors associated with the PM. It is also suggested that tyrosine phosphorylation promotes this process, whereas enhanced serine phosphorylation, e.g. produced by cAMP, impairs the functional insertion of the receptors, rendering them unable to bind insulin.

A stable peroxovanadium compound with insulin-like action in human fat cells.

Aqueous solutions of peroxovanadium (pV) compounds are potent insulin-mimics in various types of cell. Since chemical instability is a problem with these agents, we studied the insulin-like action in human fat cells of a stable pV complex, bpV(pic). It enhanced 14C-U-glucose uptake in a dose-dependent manner by approximately twofold which was slightly less than the effect of insulin (approximately threefold). The pV complex did not alter cell-surface insulin binding and submaximal concentrations did not influence cellular sensitivity to insulin action on glucose uptake. The bpV(pic) inhibited the lipolytic effect of isoprenaline to the same extent as insulin; however, when the cGMP-inhibitable low-K(m) phosphodiesterase (cGI-PDE) was blocked with the specific inhibitor OPC 3911, the antilipolytic effect of insulin, but not that of bpV(pic), was completely prevented. Moreover, when lipolysis was stimulated by the non-hydrolysable cAMP analogue N6-monobutyryl cAMP, bpV(pic), in contrast to insulin, maintained an antilipolytic effect. These findings indicate that bpV(pic) exerts its antilipolytic effect not only through cGI-PDE activation, similar to the effect of insulin, but also by means of other mechanisms. The tyrosine kinase activity of insulin receptors from human placenta was not altered by the pV compound itself, whereas bpV(pic) clearly enhanced insulin-stimulated activity. In contrast, in situ tyrosine phosphorylation of the insulin receptor beta-subunit as well as that of several other proteins was clearly increased in cells which were treated with bpV(pic), whereas vanadate only amplified insulin-stimulated tyrosine phosphorylation. In conclusion, bpV(pic) exerts powerful insulin-like effects in human fat cells and may be a new and potentially useful agent in the management of insulin-resistant states.

The cGMP-inhibitable phosphodiesterase modulates glucose transport activation by insulin.

To assess the role of the cGMP-inhibitable phosphodiesterase (cGI-PDE) in the action of insulin on glucose transport, adipocytes from young, lean rats were preincubated for 20 min at 37 degrees C with and without OPC 3911, a specific inhibitor of cGI-PDE, and 3-O-methylglucose uptake was measured. Insulin-stimulated glucose transport was impaired by OPC 3911 (approximately 15%) and this impairment became more pronounced in the presence of the degradable cAMP-analogue 8-bromo-cAMP (approximately 45%). This analogue alone did not significantly decrease glucose transport. Furthermore, insulin sensitivity was impaired by the combination of OPC 3911 and 8-bromo-cAMP. Maximal insulin-stimulated glucose transport in adipocytes from aging, obese rats was affected similarly by OPC 3911 and 8-bromo-cAMP, suggesting that cGI-PDE activity is not markedly altered in this insulin-resistant state. In conclusion, cGI-PDE exerts a modulating effect on the stimulatory action of insulin on glucose transport. This effect is particularly pronounced when the cellular cAMP levels are elevated.

Cellular cyclic AMP levels modulate insulin sensitivity and responsiveness--evidence against a significant role of Gi in insulin signal transduction.

Treating rats with pertussis toxin (PTX) both elevated the adipocyte cAMP levels and impaired sensitivity and responsiveness to the antilipolytic effect of insulin in the presence of different beta-adrenergic agonists. However, in the presence of a fixed medium concentration of the degradable cAMP analogue, 8-bromo-cAMP, the effect of insulin was similar in PTX- and control cells. Elevating the cAMP levels in control cells either through different concentrations of the cAMP analogue or addition of adenosine deaminase impaired both insulin sensitivity and responsiveness to a similar extent as that seen in PTX-treated cells. The antilipolytic effect of insulin was exerted through the activation of the cGMP-inhibitable phosphodiesterase (cGI-PDE) as it was dose-dependently impaired by the specific cGI-PDE inhibitor OPC 3911. The results show the importance of the cellular cAMP levels in modulating insulin sensitivity and action. Gi plays a minor role, if any, for the signal transduction of the antilipolytic effect of insulin.