Date Published: November 21, 2011
Author(s): Asha A Kulkarni-Almeida, Manoja K Brahma, Prabhu Padmanabhan, Prabhu D Mishra, Rajashri R Parab, Nitin V Gaikwad, Chandni S Thakkar, Pradipta Tokdar, Prafull V Ranadive, Amrutha S Nair, Anagha A Damre, Umakant A Bahirat, Nitin J Deshmukh, Lalit S Doshi, Amol V Dixit, Saji D George, Ram A Vishwakarma, Kumar VS Nemmani, Girish B Mahajan.
Type-2 diabetes is mediated by defects in either insulin secretion or insulin action. In an effort to identify extracts that may stimulate glucose uptake, similar to insulin, a high throughput-screening assay for measuring glucose uptake in skeletal muscle cells was established. During the screening studies to discover novel antidiabetic compounds from microbial resources a Streptomyces strain PM0324667 (MTCC 5543, the Strain accession number at Institute of Microbial Technology, Chandigarh, India), an isolate from arid soil was identified which expressed a secondary metabolite that induced glucose uptake in L6 skeletal muscle cells. By employing bioactivity guided fractionation techniques, a tri-substituted simple aromatic compound with anti-diabetic potential was isolated. It was characterized based on MS and 2D NMR spectral data and identified as NFAT-133 which is a known immunosuppressive agent that inhibits NFAT-dependent transcription in vitro. Our investigations revealed the antidiabetic potential of NFAT-133. The compound induced glucose uptake in differentiated L6 myotubes with an EC50 of 6.3 ± 1.8 μM without activating the peroxisome proliferator-activated receptor-γ. Further, NFAT-133 was also efficacious in vivo in diabetic animals and reduced systemic glucose levels. Thus it is a potential lead compound which can be considered for development as a therapeutic for the treatment of type-2 diabetes. We have reported herewith the isolation of the producer microbe, fermentation, purification, in vitro, and in vivo antidiabetic activity of the compound.
In 2010, the global prevalence of diabetes was estimated to have reached 285 million and it is predicted to reach 438 million in 2030. Available agents provide imperfect control of the disease, and the medical need for better therapies is widely recognized (Norman 2010). About 90% to 95% of patients have non-insulin dependent diabetes mellitus (NIDDM) or type-2 diabetes and the standard therapy for the treatment of NIDDM has its own limitations (Mark 1997). Diet, oral hypoglycaemic drugs and insulin are the standard modes of treatment. However they are unable to achieve relief from diabetes. This leads to acute and chronic complications. Hence major efforts have been directed towards development of oral hypoglycaemic drugs, to identify both novel insulin secretagogues and compounds able to enhance insulin action in target tissues.
Streptomyces pactum was known to produce antitumor compounds like pactamycin (Bhuyan 1962), vasodilating secondary metabolite like actinopyrones A, B and C (Yano et al. 1986), NADH oxidase inhibitors such as piericidin class of compounds (Matsumoto et al. 1987), and polyetheric antibiotics such as lonomycin (Hamill et al. 1989). Similarly Streptomyces parvisporogenes has been reported to synthesize polyenic antifungal agent like Antibiotic PA 616 (Chas 1960) and pepstatin class of compounds which are pepsin inhibitors (Umezawa 1970). There has been no report of NFAT-133 or similar class of compounds isolated from strains of Streptomyces pactum or Streptomyces parvisporogenes to date.
Antihyperglycemic effects of the Streptomycetes compound NFAT-133 has been revealed by in vitro and animal studies.
The authors declare that they have no competing interests.
Microbiology and fermentation: GBM, SDG, RRP, PVR, PT, In vitro screening and analysis: AAK, MKB, PP, CST, ASN, In vivo evaluation: KVN, AAD, UAB, NJD, LSD, AVD, Chemical isolation and structural elucidation: PDM, NVG, RAV