Reduced levels of serum FGF19 and impaired expression of receptors for endocrine FGFs in adipose tissue from HIV-infected patients

Levels of β-klotho determine the thermogenic responsiveness of adipose tissues: involvement of the autocrine action of FGF21

Fibroblast growth factor-21 (FGF21) is a hormonal regulator of metabolism; it promotes glucose oxidation and the thermogenic capacity of adipose tissues. The levels of β-klotho (KLB), the co-receptor required for FGF21 action, are decreased in brown (BAT) and white (WAT) adipose tissues during obesity, diabetes, and lipodystrophy. Reduced β-klotho levels have been proposed to account for FGF21 resistance in these conditions. In this study, we explored whether downregulation of β-klotho affects metabolic regulation and the thermogenic responsiveness of adipose tissues using mice with total (KLB-KO) or partial (KLB-heterozygotes) ablation of β-klotho. We herein show that KLB gene dosage was inversely associated with adiposity in mice. Upon cold exposure, impaired browning of subcutaneous WAT and milder alterations in BAT were associated with reduced KLB gene dosage in mice. Cultured brown and beige adipocytes from mice with total or partial ablation of the KLB gene showed reduced thermogenic responsiveness to β3-adrenergic activation by treatment with CL316,243, indicating that these effects were cell-autonomous. Deficiency in FGF21 mimicked the KLB-reduction-induced impairment of thermogenic responsiveness in brown and beige adipocytes. These results indicate that the levels of KLB in adipose tissues determine their thermogenic capacity to respond to cold and/or adrenergic stimuli. Moreover, an autocrine action of FGF21 in brown and beige adipocytes may account for the ability of the KLB level to influence thermogenic responsiveness.NEW & NOTEWORTHY Reduced levels of KLB (the obligatory FGF21 co-receptor), as occurring in obesity and type 2 diabetes, reduce the thermogenic responsiveness of adipose tissues in cold-exposed mice. Impaired response to β3-adrenergic activation in brown and beige adipocytes with reduced KLB occurs in a cell-autonomous manner involving an autocrine action of FGF21.

FGF21 and its Relationship with Inflammatory and Metabolic Parameters in HIV Patients after Antiretroviral Treatment

BACKGROUND

Fibroblast Growth Factor 21 (FGF21) serum levels are associated with insulin resistance and metabolic syndrome in HIV patients.

OBJECTIVE

To quantify FGF21 levels in HIV patients using antiretroviral therapy (ART) and to analyze a possible association between serum FGF21 levels and lipid profile, levels of proinflammatory cytokines, and atherogenic risk factors.

MATERIALS AND METHODS

Twenty patients with HIV infection, who received ART in a scheme consisting of Tenofovir/Emtricitabine+Lopinavir/Ritonavir, were enrolled in this study. The serum levels of FGF21, inflammatory parameters (IL-6 and IL-1β), glucose, cholesterol, triglycerides, and insulin were determined at baseline and after 36 weeks of treatment. The homeostatic model assessment for insulin resistance (HOMA-IR) and the atherogenic risk factor were also calculated.

RESULTS

After 36 weeks, serum FGF21 levels decreased significantly (p=0.011), whereas IL-6 levels (r=0.821, p=0.0001) and the CD4+ T cell count (r=0.446, p=0.048), showed a positive correlation with the decrease in FGF21 levels. There was an increase in total cholesterol (r=-0.483, p=0.031), LDL (r=-0.496, p=0.026), VLDL (r=-0.320, p=0.045), and the atherogenic index factor (r=-0.539, p=0.014), these values showed a negative correlation with FGF21 levels.

CONCLUSION

The decrease of serum FGF21 levels due to ART is associated with the alteration in lipid profile and an increased risk for cardiovascular diseases. These variations are predictors of inflammatory status in HIV patients using antiretroviral therapy.

Klotho-HIV and Oxidative Stress: The Role of Klotho in Cardiovascular Disease Under HIV Infection-A Review

Combined antiretroviral therapy has improved quality and life expectancy of people living with human immunodeficiency virus (HIV). However, this therapy increases oxidative stress (OS), which in turn causes alterations in lipid and carbon metabolism, kidney disease, liver cirrhosis, and increased risk of cardiovascular disease. The Klotho gene has been implicated in cardiovascular risk increase. Klotho protein expression at X level decreases the risk of heart disease. HIV-positive people usually present low plasma levels of Klotho; thus, contributing to some extent to an increase in cardiovascular risk for these types of patients, mostly by favoring atherosclerosis. Therefore, our aim is to provide an overview of the effect of OS on Klotho protein and its consequent cardiometabolic alterations in HIV-positive patients on antiretroviral therapy.

Cardiovascular risk factors among Ghanaian patients with HIV: A cross-sectional study

BACKGROUND

Cardiovascular disease (CVD) poses a significant cause of morbidity and mortality among people living with human immunodeficiency virus (HIV). However, data are limited on CVD risk burden among HIV patients in Ghana. We describe the age- and sex-adjusted prevalence of CVD risk factors among HIV patients in Ghana.

METHODS

From January 2013 to May 2014, we identified eligible HIV patients 18 years and older, as well as uninfected adult blood donors presenting to the Komfo Anokye Teaching Hospital as controls. Using a standardized protocol, we collected demographic, clinical, laboratory, and electrocardiographic data. We created multivariable logistic regression models to compare the prevalence of abnormal risk factors between the two groups.

RESULTS

We recruited 345 patients with HIV (n = 173 on HAART, n = 172 not on HAART) and 161 uninfected adult blood donors. Patients with HIV were older (mean [SD] age: 41 [11] vs 32 [11] years) and were more likely to be female (72% vs 28%) than blood donors. Among patients on HAART, median (interquartile range) treatment duration was 17 (4-52) months. The prevalence of hypertension, hypercholesterolemia, and diabetes mellitus among HIV patients was 9%, 29%, and 5%, respectively, compared with 5%, 15%, and 0.6% among uninfected blood donors. Smoking was the least prevalent CVD risk factor (1%-2%). After adjustment for age, sex, and body mass index, HIV patients had a 10-fold higher odds of prevalent diabetes compared with controls, (adjusted OR = 10.3 [95% CI: 1.2, 86.7]).

CONCLUSION

CVD risk factors are common among HIV patients in Ghana, demonstrating the urgent need for creation and implementation of strategic CVD interventions.

Association of Fibroblast Growth Factor-23 (FGF-23) With Incident Frailty in HIV-Infected and HIV-Uninfected Individuals

BACKGROUND

In the Multicenter AIDS Cohort Study, we examined whether fibroblast growth factor-23 (FGF-23), a bone-derived phosphaturic hormone involved in bone metabolism, is associated with incident frailty. Furthermore, we examined whether this association differs by HIV serostatus and race.

METHODS

Of 715 men assessed for frailty and selected for FGF-23 measurements using stored blood samples (2007-2011), 512 men were nonfrail at/before the baseline visit. Frailty was defined by the presence of ≥3 of the following on 2 consecutive 6-month visits within 1 year: unintentional weight loss ≥10 pounds, weakness, slowness, low energy, and low physical activity. We determined the association of FGF-23 levels with incident frailty using proportional hazards models adjusting for sociodemographics, comorbidities, and kidney function.

RESULTS

Sixty-five percent were HIV-infected; 29% were black. Median baseline FGF-23 levels were lower in HIV-infected vs. HIV-uninfected men (33.7 vs. 39.9 rU/mL, P = 0.006) but similar by race. During a median follow-up of 6.6 years, 32 men developed frailty; they had higher baseline FGF-23 levels vs. men who remained nonfrail (45 vs. 36 rU/mL, P = 0.02). FGF-23 (per doubling) was associated with a 1.63-fold risk of frailty [95% confidence interval (CI): 1.19 to 2.23]; results did not differ by HIV serostatus. Conversely, FGF-23 was associated with a 2.72-fold risk of frailty among blacks (95% CI: 1.51 to 4.91) but had minimal association among nonblacks (hazard ratio = 1.26, 95% CI: 0.77 to 2.05; p-interaction = 0.024).

CONCLUSIONS

Among men with or at-risk of HIV infection, higher FGF-23 was associated with greater risk of frailty, particularly in blacks. The mechanisms by which FGF-23 may contribute to frailty warrant further study.

Changing concepts of HIV infection and renal disease

PURPOSE OF REVIEW

Human immunodeficiency virus (HIV)-associated nephropathy (HIVAN) was identified as the major renal manifestation of HIV infection early in the HIV epidemic. However, HIV infection now is associated with a different spectrum of renal lesions leading to chronic kidney disease. This review examines the changes in kidney injury occurring in the current HIV era and the factors involved in this transformation of disease expression.

RECENT FINDINGS

The incidence of HIVAN and opportunistic infections in HIV-infected individuals has declined in concert with the use of effective combination antiretroviral agents. Chronic kidney disease has become more prevalent as patients infected with HIV are living longer and developing non-HIV-associated diseases such as hypertension and diabetes. Additionally, noncollapsing focal and segmental glomerulosclerosis, co-infection with hepatitis C, HIV-associated immune complex kidney disease, HIV-related accelerated aging, and antiretroviral therapies contribute to progressive loss of renal function.

SUMMARY

HIV infection is now associated with a variety of renal lesions causing chronic kidney disease, not all of which are virally induced. It is important to determine the cause of renal functional decline in an HIV-infected patient, as this will impact patient management and prognosis.

Aging is associated with increased FGF21 levels but unaltered FGF21 responsiveness in adipose tissue

Fibroblast growth factor 21 (FGF21) has been proposed to be an antiaging hormone on the basis of experimental studies in rodent models. However, circulating FGF21 levels are increased with aging in rodents and humans. Moreover, despite the metabolic health‐promoting effects of FGF21, the levels of this hormone are increased under conditions such as obesity and diabetes, an apparent incongruity that has been attributed to altered tissue responsiveness to FGF21. Here, we investigated serum FGF21 levels and expression of genes encoding components of the FGF21‐response molecular machinery in adipose tissue from healthy elderly individuals (≥70 years old) and young controls. Serum FGF21 levels were increased in elderly individuals and were positively correlated with insulinemia and HOMA‐IR, indices of mildly deteriorated glucose homeostasis. Levels of β‐Klotho, the coreceptor required for cellular responsiveness to FGF21, were increased in subcutaneous adipose tissue from elderly individuals relative to those from young controls, whereas FGF receptor‐1 levels were unaltered. Moreover, total ERK1/2 protein levels were decreased in elderly individuals in association with an increase in the ERK1/2 phosphorylation ratio relative to young controls. Adipose explants from aged and young mice respond similarly to FGF21 “ex vivo”. Thus, in contrast to what is observed in obesity and diabetes, high levels of FGF21 in healthy aging are not associated with repressed FGF21‐responsiveness machinery in adipose tissue. The lack of evidence for impaired FGF21 responsiveness in adipose tissue establishes a distinction between alterations in the FGF21 endocrine system in aging and chronic metabolic pathologies.

Reciprocal Effects of Antiretroviral Drugs Used To Treat HIV Infection on the Fibroblast Growth Factor 21/β-Klotho System

Following antiretroviral therapy, HIV-infected patients show increased circulating levels of the antidiabetic hormone fibroblast growth factor 21 (FGF21). In contrast, the expression of the FGF21-obligatory coreceptor β-Klotho (KLB) is reduced in target tissues. This situation is comparable to the FGF21 resistance status observed in obesity and type 2 diabetes. Here, we performed the first systematic study of the effects of distinct members of different antiretroviral drug classes on the FGF21/KLB system in human hepatic, adipose, and skeletal muscle cells. Most protease inhibitors and the nonnucleoside reverse transcriptase inhibitor efavirenz induced FGF21 gene expression. Neither nucleoside reverse transcriptase inhibitors nor the viral entry inhibitor maraviroc had any effect. Among the integrase inhibitors, elvitegravir significantly induced FGF21 expression, whereas raltegravir had minor effects only in adipose cells. In human hepatocytes and adipocytes, known target cells of FGF21 action, efavirenz, elvitegravir, and the lopinavir-ritonavir combination exerted inhibitory effects on KLB gene expression. Drug treatments that elicited FGF21 induction/KLB repression were those found to induce endoplasmic reticulum (ER) stress and oxidative stress. Notably, the pharmacological agents thapsigargin and tunicamycin, which induce these stress pathways, mimicked the effects of drug treatments. Moreover, pharmacological inhibitors of either ER or oxidative stress significantly impaired lopinavir–ritonavir-induced regulation of FGF21, but not KLB. In conclusion, the present in vitro screen study identifies the antiretroviral drugs that affect FGF21/KLB expression in human cells. The present results could have important implications for the management of comorbidities resulting from side effects of specific antiretroviral drugs for the treatment of HIV-infected patients.

High FGF21 levels are associated with altered bone homeostasis in HIV-1-infected patients

BACKGROUND

Fibroblast growth factor-21 (FGF21) has emerged as an important regulator of glucose, lipid, and body weight homeostasis. However, recent experimental studies have reported that increased FGF21 levels may lead to bone loss.

OBJECTIVE

To assess the relationship of serum FGF21 levels and altered bone homeostasis in HIV-1-infected patients.

DESIGN

Cross-sectional study of 137 HIV-1-infected patients and 35 healthy controls conducted at the Hospital de la Santa Creu i Sant Pau, Barcelona. Among HIV-1-infected patients, 35 were untreated (naïve), 43 were treated with antiretrovirals (HIV-1/ART) with no lipodystrophy, and 59 patients were HIV-1/ART and experienced lipodystrophy. Bone mineral density (BMD) and content (BMC) were assessed using dual-energy X-ray absorptiometry. Serum levels of FGF21, receptor activator of nuclear factor (NF)-KB ligand (RANKL), and C-telopeptide of type-I collagen (CTX-1) were measured by enzyme-linked immunosorbent assays. Serum levels of osteocalcin, osteoprotegerin, leptin, tumor necrosis factor-α, interleukin-6, interleukin-8, and monocyte chemoattractant protein-1 were determined using an antibody-linked, fluorescently labeled microsphere bead-based multiplex analysis system.

RESULTS

Alterations in bone parameters and bone homeostasis marker levels were consistent with higher turnover and bone loss in HIV-1 infected patients. FGF21 correlated negatively with BMD and BMC. FGF21 correlated positively with serum levels of osteoprotegerin and CTX-1, as well as with the CTX-1/osteocalcin ratio.

CONCLUSIONS

Elevated FGF21 levels are associated with poor bone homeostasis in HIV-1-infected patients. Increases in FGF21 serum level may be an indicator not only of metabolic derangement but it may also serve as a biomarker of altered bone homeostasis in HIV-1 infected patients.

FGFs: crucial factors that regulate tumour initiation and progression

Fibroblast growth factors (FGFs) are crucial signalling molecules involved in normal cell growth, differentiation and proliferation. Over the past few decades, a large body of research has illustrated effects of individual FGFs on tumour initiation and progression. Tumour development is commonly accompanied with generation of new blood and lymph vessels, which support enhanced cell proliferation. Moreover, acquisition of tumour cells of the epithelial-mesenchymal transition (EMT) phenotype, enhances tumour cell migration and invasion potentials, crucial steps in tumour metastasis. This review summarizes recent findings concerning roles of FGFs in angiogenesis, lymphangiogenesis and EMT.

Fibroblast growth factor-21, energy balance and obesity

Fibroblast growth factor (FGF)-21 is an endocrine member of the FGF family with healthy effects on glucose and lipid metabolism. FGF21 reduces glycemia and lipidemia in rodent models of obesity and type 2 diabetes. In addition to its effects improving insulin sensitivity, FGF21 causes weight loss by increasing energy expenditure. Activation of the thermogenic activity of brown adipose tissue and promotion of the appearance of the so-called beige/brite type of brown adipocytes in white fat are considered the main mechanisms underlying the leaning effects of FGF21. Paradoxically, however, obesity in rodents and humans is characterized by high levels of FGF21 in the blood. Some degree of resistance to the actions of FGF21 has been proposed as part of the endocrine alterations in obesity. The resistance in adipose tissue from obese rodents and patients is likely attributable to abnormally low levels of the FGF co-receptor β-Klotho, required for FGF21 cellular action. However, native FGF21 and FGF21 derivatives retain their healthy metabolic and weight-loss effects when used as pharmacological agents to treat obese rodents and humans. FGF21 derivatives or molecules mimicking FGF21 action appear to be interesting candidates for the development of novel anti-obesity drugs designed to increase energy expenditure.

Circulating fibroblast growth factor 23 (FGF23) levels are associated with metabolic disturbances and fat distribution but not cardiovascular risk in HIV-infected patients

OBJECTIVES

Dyslipidaemia, insulin resistance, metabolic syndrome and HIV/HAART-associated lipodystrophy syndrome (HALS) are common comorbidities in HIV-1-infected patients, which may increase cardiovascular risk. Fibroblast growth factor 23 (FGF23) is a bone-derived hormone with effects on metabolism and phosphate homeostasis. The aim of this study was to determine the relationship between FGF23 levels, metabolic alterations, fat distribution and cardiovascular risk.

METHODS

This was a cross-sectional study. Serum FGF23 levels were analysed in 152 patients and 34 healthy control individuals. Patients belonged to three groups: HIV-1-infected, antiretroviral-treated patients who have developed HALS (n = 60); HIV-1-infected, antiretroviral-treated patients without HALS (n = 43); and untreated (naive) HIV-1-infected patients (n = 49). Serum FGF23 levels were compared with lipid and glucose homeostasis parameters, fat distribution and cardiovascular risk.

RESULTS

Serum FGF23 levels were increased in HIV-1-infected patients, but the increase was most marked in those with HALS. FGF23 levels showed a strong positive correlation with age, indicators of dyslipidaemia (LDL cholesterol, polyunsaturated fatty acids and monounsaturated fatty acids), HALS parameters (trunk/appendicular fat ratio), insulin resistance (fasting insulin and homeostasis model assessment of insulin resistance) and C-reactive protein. FGF23 levels correlated with cardiovascular risk but correlation was lost after age adjustment.

CONCLUSIONS

FGF23 levels are increased in HIV-1-infected patients, especially in those with HALS, and this increase is associated with dyslipidaemia, insulin resistance, metabolic syndrome, fat distribution and parameters of inflammation. FGF23 is not associated with cardiovascular risk when age is taken into account.

Opposite alterations in FGF21 and FGF19 levels and disturbed expression of the receptor machinery for endocrine FGFs in obese patients

OBJECTIVE

Fibroblast growth factor (FGF)-21, and possibly FGF19, protect against type 2 diabetes mellitus (T2DM) and obesity in rodents. We investigated the circulating levels of FGF21 and FGF19 in obese patients with varying degrees of abnormal glucose homeostasis, and we determined gene expression for FGF receptors (FGFR1-4) and the co-receptor β-Klotho, in liver and adipose tissues.

SUBJECTS AND METHODS

We analyzed 35 lean healthy (71% men) and 61 obese patients (49% men, median body mass index (BMI): 40.5 kg m(-2), interquartile range: 34.7-46.2). Among obese patients, 36 were normoglycemic, 15 showed impaired glucose tolerance and 10 had T2DM. Biopsies from liver and visceral and subcutaneous fat from a subset of obese patients and controls were analyzed. FGF19 and FGF21 levels were measured using enzyme-linked immunosorbent assay, and tissue mRNA and protein levels by reverse transcription-polymerase chain reaction and immunoblotting.

RESULTS

FGF21 serum levels were significantly increased in obese patients compared with controls (P<0.001), whereas FGF19 levels were decreased (P < 0.001). FGF21 levels were positively correlated with homeostasis model assessment of insulin resistance (P = 0.0002, r = 0.37) and insulin (P = 0.001, r = 0.32), whereas FGF19 levels were negatively correlated (P = 0.007, r = -0.27; P=0.003, r = -0.28; respectively). After adjusting for BMI, the correlations of FGF21 and FGF19 levels with indicators of abnormal glucose homeostasis were not significant. In obese patients, the hepatic expression of FGF21 was increased. (P = 0.04). β-Klotho transcript levels in visceral fat (P = 0.002) and β-Klotho protein levels in subcutaneous (P = 0.03) and visceral fat (P = 0.04) were significantly reduced in obese patients, whereas hepatic levels for β-Klotho (P = 0.03), FGFR1 (P = 0.04) and FGFR3 (P = 0.001) transcripts were significantly increased.

CONCLUSIONS

Obesity is characterized by reciprocal alterations in FGF19 (decrease) and FGF21 (increase) levels. Although worsened in diabetic obese patients, obesity itself appears as the predominant determinant of the abnormalities in FGF21 and FGF19 levels. Opposite changes in β-Klotho expression in fat and liver indicate potential tissue-specific alterations in the responsiveness to endocrine FGFs in obesity.

Fibroblast growth factor-21 is expressed in neonatal and pheochromocytoma-induced adult human brown adipose tissue

OBJECTIVE

In rodents, brown (BAT) and white (WAT) adipose tissues are targets and expression sites for fibroblast growth factor-21 (FGF21). In contrast, human WAT expresses negligible levels of FGF21. We examined FGF21 expression in human BAT samples, including the induced BAT found in adult patients with pheochromocytoma, and interscapular and visceral BAT from newborns.

METHODS

The expression of FGF21 and uncoupling protein-1 (UCP1, a brown adipocyte marker), was determined by quantitative real-time-PCR and immunoblotting. The transcript levels of marker genes for developmentally-programmed BAT (zinc-finger-protein of the cerebellum-1, ZIC1) and inducible-BAT (cluster of differentiation-137, CD137) were also determined.

RESULTS

FGF21 and UCP1 are significantly expressed in visceral adipose tissue from pheochromocytoma patients, but not in visceral fat from healthy individuals. In neonates, FGF21 and UCP1 are both expressed in visceral and interscapular fat, and their expression levels show a significant positive correlation. Marker gene expression profiles suggest that inducible BAT is present in visceral fat from pheochromocytoma patients and neonates, whereas developmentally-programmed BAT is present in neonatal interscapular fat.

CONCLUSIONS

Human BAT, but not WAT, expresses FGF21. The expression of FGF21 is especially high in inducible, also called beige/brite, neonatal BAT, but it is also found in the interscapular, developmentally-programmed, BAT of neonates.

Metabolic disease in HIV infection

The treatment of metabolic disease is becoming an increasingly important component of the long-term management of patients with well controlled HIV on antiretroviral therapy (ART). Metabolic diseases probably develop at the intersection of traditional risk factors (such as obesity, tobacco use, and genetic predisposition) and HIV-specific and ART-specific contributors (including chronic inflammation and immune activation). This Review discusses present knowledge on adipose tissue dysfunction, insulin-glucose homoeostasis, lipid disturbances, and cardiovascular disease risk in people with HIV on ART. Although new antiretroviral drugs are believed to induce fewer short-term metabolic perturbations than do older drugs, the long-term effects of these drugs are not fully understood. Additionally, patients remain at increased risk of cardiovascular disease and other metabolic comorbidities. Research and treatment should focus on selection of ART that is both virologically effective and has minimum metabolic effects, minimisation of traditional risk factors for metabolic disease, and development of novel therapies to treat metabolic disease in patients with HIV, including use of anti-inflammatory and immunomodulatory drugs.

Serum concentrations of fibroblast growth factors 19 and 21 in women with gestational diabetes mellitus: association with insulin resistance, adiponectin, and polycystic ovary syndrome history

BACKGROUND

Fibroblast growth factor 19 (FGF19) and FGF21 are considered to be novel adipokines that improve glucose tolerance and insulin sensitivity. In the current study, we investigated serum FGF19 and FGF21 levels in patients with gestational diabetes mellitus (GDM) and explored their relationships with anthropometric and endocrine parameters.

METHOD

Serum FGF19 and FGF21 levels were determined by enzyme-linked immunosorbent assay (ELISA) in patients with GDM (n = 30) and healthy pregnant controls (n = 60) matched for maternal and gestational age. Serum FGF19 and FGF21 levels were correlated with anthropometric, metabolic, and endocrine parameters.

RESULTS

Circulating levels of FGF19 were significantly reduced in patients with GDM relative to healthy pregnant subjects, whereas FGF21 levels were increased in GDM patients. Serum FGF19 levels independently and inversely correlated with insulin resistance (increased homeostasis model assessment of insulin resistance, HOMA-IR) and were positively related to serum adiponectin in both groups. In contrast, serum FGF21 levels independently and positively correlated with insulin resistance and serum triglycerides and were inversely related to serum adiponectin. In addition, in the combined population of both groups, those women with preconception polycystic ovary syndrome (PCOS) history had the lowest levels of FGF19, which were significantly lower than those in GDM patients without PCOS history and those in controls without PCOS history.

CONCLUSIONS

Circulating FGF19 levels are reduced in GDM patients, in contrast with FGF21 levels. Both serum FGF19 and FGF21 levels are strongly related to insulin resistance and serum levels of adiponectin. Considering the different situation between FGF19 and FGF21, we suggest that reduced serum FGF19 levels could be involved in the pathophysiology of GDM, while increased serum FGF21 levels could be in a compensatory response to this disease.

Expression of fibroblast growth factor-21 in muscle is associated with lipodystrophy, insulin resistance and lipid disturbances in patients with HIV

Background

Fibroblast growth factor (FGF)-21 is a novel regulator of glucose and lipid metabolism. Recently, increased FGF-21 mRNA expression in muscle was found in patients with type 2 diabetes, but the role for FGF-21 in muscle is not well understood. Patients with HIV-infection and lipodystrophy are characterised by various degree of lipid-driven insulin resistance. We hypothesized that muscle FGF-21 mRNA would be altered in HIV patients with lipodystrophy.

Design

Twenty-five HIV-infected men with lipodystrophy (LD) and 15 age-matched healthy controls, received an oral glucose tolerance test and a euglycemic-hyperinsulinemic clamp (50 mU/m2/min) combined with 6,6-H₂ glucose infusion. Muscle biopsies were obtained and FGF-21 mRNA and glycogen synthase (GS) activity were measured.

Results

Subjects with HIV were insulin resistant compared with non-HIV subjects. Compared to controls, HIV subjects demonstrated a twofold increase of plasma FGF-21 from 70.4±56.8 pg/ml vs 109.1±71.8 pg/ml, respectively (p = 0.04) and an eight-fold increase in muscular FGF-21 mRNA expression (p = 0.001). Muscle FGF-21 mRNA correlated inversely with the rate of disappearance of glucose during insulin clamp (r = −0.54, p = 0.0009), and the GS fractional velocity in muscle (r = −0.39, p = 0.03), and directly with fasting insulin (r = 0.50, p = 0.0022), HOMA-IR (r = 0.47, p = 0.004), triglycerides (r = 0.60. P = 0.0001), waist-to-hip ratio (r = 0.51, p = 0.0001) and limb fat mass (−0.46, p = 0.004), but not to plasma FGF-21.

Conclusion

FGF-21 mRNA is increased in skeletal muscle in HIV patients and correlates to whole-body (primarily reflecting muscle) insulin resistance, but not to plasma FGF-21. Those findings add to the evidence that FGF-21 is a myokine and may suggest that muscle FGF-21 is working in a local manner.