Almantas Maleckas

Prof. Dr. Almantas Maleckas


Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 December 2016 in Gland Surgery
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AMAlmantas Maleckas
Almantas Maleckas
RGRita Gudaitytė
Rita Gudaitytė
RPRūta Petereit
Rūta Petereit
LVLinas Venclauskas
Linas Venclauskas
DVDžilda Veličkienė
Džilda Veličkienė
Roux-en-Y gastric bypass (RYGB) is one of the most common operations performed for the patients with morbid obesity. Weight regain (WR) is a complication that may decrease efficiency of the surgical treatment and demand further interventions. Different factors including lifestyle, mental health, hormonal/metabolic and surgical plays role in WR after RYGB. Various treatment options have been proposed for WR. Conservative treatment is less effective than surgery. Endoscopic refashioning of gastric pouch/stoma fails to achieve sustainable weight loss. Surgical reduction of pouch has acceptable short-term results, but WR after 3 years is substantial. Banded gastric bypass achieves good short-term results, but long-term follow-up data are needed. Distalization of RYGB has a high risk of protein calorie malnutrition (PCM) and conversion to BP diversion (BPD)/duodenal switch (DS) is a technically demanding procedure. Both procedures achieve sustainable long-term weight loss. More studies are needed to explore long-term results of various surgical interventions for WR after RYGB.

20 December 2017 in Obesity Surgery
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Journal Article
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VWVille Raymond Wallenius
Ville Raymond Wallenius
EDEveline Dirinck
Eveline Dirinck
LFLars Fändriks
Lars Fändriks
AMAlmantas Maleckas
Almantas Maleckas
Carel W. Le RouxCarel W. Le Roux
Carel W. Le Roux
ATAnders Thorell
Anders Thorell
Background Roux-en-Y gastric bypass (LRYGB) has weight-independent effects on glycemia in obese type 2 diabetic patients, whereas sleeve gastrectomy (LSG) is less well characterized. This study aims to compare early weight-independent and later weight-dependent glycemic effects of LRYGB and LSG. Methods Eighteen LRYGB and 15 LSG patients were included in the study. Glucose, insulin, GLP-1, and GIP levels were monitored during a modified 30 g oral glucose tolerance test before surgery and 2 days, 3 weeks, and 12 months after surgery. Patients self-monitored glucose levels 2 weeks before and after surgery. Results Postoperative fasting blood glucose decreased similarly in both groups (LRYGB vs. SG; baseline—8.1 ± 0.6 vs. 8.2 ± 0.4 mmol/l, 2 days—7.8 ± 0.5 vs. 7.4 ± 0.3 mmol/l, 3 weeks—6.6 ± 0.4 vs. 6.6 ± 0.3 mmol/l, respectively, P < 0.01 vs. baseline for both groups; 12 months—6.6 ± 0.4 vs. 5.9 ± 0.4, respectively, P < 0.05 for LRYGB and P < 0.001 for LSG vs. baseline, P = ns between the groups at all times). LSG, but not LRYGB, showed increased peak insulin levels 2 days postoperatively (mean ± SEM; LSG + 58 ± 14%, P < 0.01; LRYGB − 8 ± 17%, P = ns). GLP-1 levels increased similarly at 2 days, but were higher in LRYGB at 3 weeks (AUC; 7525 ± 1258 vs. 4779 ± 712 pmol × min, respectively, P < 0.05). GIP levels did not differ. Body mass index (BMI) decreased more after LRYGB than LSG (− 10.1 ± 0.9 vs. − 7.9 ± 0.5 kg/m2, respectively, P < 0.05). Conclusion LRYGB and LSG show very similar effects on glycemic control, despite lower GLP-1 levels and inferior BMI decrease after LSG.

26 January 2015 in Scandinavian Journal of Surgery
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Journal Article
Open access
AMAlmantas Maleckas
Almantas Maleckas
LVL. Venclauskas
L. Venclauskas
VWVille Raymond Wallenius
Ville Raymond Wallenius
HLH. Lönroth
H. Lönroth
LFL. Fändriks
L. Fändriks
Background and Aims: The prevalence of diabetes is increasing worldwide, and most of the cases are type 2 diabetes mellitus. The relationship between type 2 diabetes mellitus and obesity is well established, and surgical treatment is widely used for obese patients with type 2 diabetes mellitus. The aim was to present current knowledge about the possible mechanisms responsible for glucose control after surgical procedures and to review the surgical treatment results. Material and Methods: Medical literature was searched for the articles presenting the impact of surgical treatment on glycemic control, long-term results, and possible mechanisms of action among obese individuals with type 2 diabetes mellitus. Results: Remission of type 2 diabetes mellitus after bariatric surgery depends on the definition of the remission used. Complete remission rate after surgery with the new criteria is lower than was considered before. Randomized controlled studies demonstrate that surgery is superior to best medical treatment for the patients with type 2 diabetes mellitus. The recurrence of type 2 diabetes mellitus after bariatric surgery is observed in up to 40% of cases with ≥5 years of follow-up. Despite the recurrence of type 2 diabetes mellitus in this group, better glycemic control and lower risk of macrovascular complications are present. Incretin effects on glycemic control after bariatric surgery are well described, but the role of other possible mechanisms (bile acids, microbiota, intestinal gluconeogenesis) in humans is unclear. Conclusion: Surgery is an effective treatment of type 2 diabetes mellitus in obese patients. The most optimal surgical procedure for the treatment of obese patients with type 2 diabetes mellitus is still to be established. More research is needed to explore the mechanisms of glycemic control after bariatric surgery.

1 November 2021 in Free Radical Biology and Medicine
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Journal Article
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BCBarbara Choromańska
Barbara Choromańska
Piotr MyśliwiecPiotr Myśliwiec
Piotr Myśliwiec
JDJacek Dadan
Jacek Dadan
AMAlmantas Maleckas
Almantas Maleckas
Anna ZalewskaAnna Zalewska
Anna Zalewska
Mateusz MaciejczykMateusz Maciejczyk
Mateusz Maciejczyk
Obesity is a chronic disease of complex etiology. Recent evidence suggests that obesity is caused by inflammation of adipose tissue leading to metabolic disorders, cardiovascular disease and cancer. This is the first study to evaluated the effects of age and gender on redox homeostasis, glutathione metabolism, and oxidative damage to plasma/serum lipids and proteins in morbidly obese patients. The study included 120 (60 men and 60 women) morbidly obese patients with class 3 obesity (BMI > 40 kg/m2), classified into three groups depending on age: 20-39 years (n = 20), 40-59 years (n = 20) and 60 years or older (n = 20). The number of patients was calculated a priori based on our previous experiment. We observed a reduction in serum activity of antioxidant enzymes (↓SOD) and plasma concentration of non-enzymatic antioxidants (↓GSH) in obese patients compared to the lean controls, which further decreased with age. Redox status (↑TAC, ↑TOS and ↓OSI) in morbidly obese men and women was shifted towards oxidation. Moreover, lipid (↑MDA and ↑LOOH) and protein (↑AOPP, ↑AGE and ↑Amadori products) damage products of oxidation and nitrosylation/nitration (↑total NO, ↑S-nitrosothiols, ↑peroxynitrite and ↑nitrotyrosine) were elevated in both genders of morbidly obese patients and were higher in the elderly. Interestingly, the concentrations of oxidative and nitrosative stress markers were generally higher in obese men compared to obese women at the same age. Summarizing, we showed that the total antioxidant/oxidant potential of obese patients is significantly increased and shifted towards oxidation. Obese patients have increased lipid and protein oxidation, glycation and nitration as compared to the lean controls. Disturbances in redox homeostasis increase with age in obese patients. Oxidative and nitrosative stress are more intense in men than in women at the same age.

26 November 2014 in BMC Surgery
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AMAntanas Mickevicius
Antanas Mickevicius
PIPovilas Ignatavicius
Povilas Ignatavicius
RMRytis Markelis
Rytis Markelis
APAudrius Parseliunas
Audrius Parseliunas
DBDainora Butkute
Dainora Butkute
Zilvinas DambrauskasZilvinas Dambrauskas
Zilvinas Dambrauskas
A steady decline in gastric cancer mortality rate over the last few decades is observed in Western Europe. However it is still not clear if this trend applies to Eastern Europe where high incidence rate of gastric cancer is observed. This was a retrospective non-randomized, single center, cohort study. During the study period 557 consecutive patients diagnosed with gastric cancer in which curative operation was performed met the inclusion criteria. The study population was divided into two groups according to two equal time periods: 01-01-1994 – 31-12-2000 (Group I – 273 patients) and 01-01-2001 – 31-12-2007 (Group II – 284 patients). Primary (five-year survival rate) and secondary (postoperative complications, 30-day mortality rate and length of hospital stay) endpoints were evaluated and compared. Rate of postoperative complications was similar between the groups, except for Grade III (Clavien-Dindo grading system for the classification of surgical complications) complications that were observed at significantly lower rates in Group II (26 (9.5%) vs. 11 (3.9%), p = 0.02). Length of hospital stay was significantly (p = 0.001) shorter (22.6 ± 28.9 vs. 16.2 ± 17.01 days) and 30-day mortality was significantly (p = 0.02) lower (15 (5.5%) vs. 4 (1.4%)) in Group II. Similar rates of gastric cancer related mortality were observed in both groups (92.3% vs. 90.7%). However survival analysis revealed significantly (p = 0.02) better overall 5-year survival rate in Group II (35.6%, 101 of 284) than in Group I (23.4%, 64 of 273). There was no difference in 5-year survival rate when comparing different TNM stages. Gastric cancer treatment results remain poor despite decreasing early postoperative mortality rates, shortening hospital stay and improved overall survival over the time. Prognosis of treatment of gastric cancer depends mainly on the stage of the disease. Absence of screening programs and lack of clinical symptoms in early stages of gastric cancer lead to circumstances when most of the patients presenting with advanced stage of the disease can expect a median survival of less than 30 months even after surgery with curative intent.

11 October 2021 in Medicina
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KMKajus Merkevičius
Kajus Merkevičius
RKRičardas Kundelis
Ričardas Kundelis
AMAlmantas Maleckas
Almantas Maleckas
DVDzilda Velickiene
Dzilda Velickiene
Background and objectives: Although the role of the gut microbiome in type 2 diabetes (T2D) pathophysiology is evident, current systematic reviews and meta-analyses analyzing T2D treatment mainly focus on metabolic outcomes. The objective of this study is to evaluate the microbiome and metabolic changes after different types of treatment in T2D patients. Materials and Methods: A systematic search of PubMed, Wiley online library, Science Direct, and Cochrane library electronic databases was performed. Randomized controlled clinical trials published in the last five years that included T2D subjects and evaluated the composition of the gut microbiome alongside metabolic outcomes before and after conventional or alternative glucose lowering therapy were selected. Microbiome changes were evaluated alongside metabolic outcomes in terms of bacteria taxonomic hierarchy, intestinal flora biodiversity, and applied intervention. Results: A total of 16 eligible studies involving 1301 participants were reviewed. Four trials investigated oral glucose-lowering treatment, three studies implemented bariatric surgery, and the rest analyzed probiotic, prebiotic, or synbiotic effects. The most common alterations were increased abundance of Firmicutes and Proteobacteria parallel to improved glycemic control. Bariatric surgery, especially Roux-en-Y gastric bypass, led to the highest variety of changed bacteria phyla. Lower diversity post-treatment was the most significant biodiversity result, which was present with improved glycemic control. Conclusions: Anti-diabetic treatment induced the growth of depleted bacteria. A gut microbiome similar to healthy individuals was achieved during some trials. Further research must explore the most effective strategies to promote beneficial bacteria, lower diversity, and eventually reach a non-T2D microbiome.